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  • oxidation  (49)
  • DSC  (48)
  • Fisheries
  • General Chemistry
  • Theoretical, Physical and Computational Chemistry
  • Springer  (99)
  • 1995-1999  (99)
  • 1945-1949
  • 1940-1944
  • 1996  (99)
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  • 1
    Digitale Medien
    Digitale Medien
    Selective oxidation of secondary amines over titanium silicalite molecular sieves, TS-1 and TS-2 (1996)
    Springer
    Catalysis letters 37 (1996), S. 213-216 
    Details
    ISSN: 1572-879X
    Schlagwort(e): titanium silicalites ; oxidation ; amines ; hydrogen peroxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Titanium silicalite molecular sieves, TS-1 and TS-2 having MFI and MEL structures, respectively, catalyze the oxidation of secondary amines to the corresponding hydroxylamines using hydrogen peroxide as the oxidant. Higher concentrations of H2O2 lead to further oxidation of hydroxylamine to nitrone. Diffuse reflectance spectroscopy shows the formation of a titanium peroxo complex upon addition of hydrogen peroxide to the TS-1 catalyst. The titanium peroxo complex oxidizes the substrate and reforms to a titanyl group.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807756
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  • 2
    Digitale Medien
    Digitale Medien
    Catalytic oxidation of cyclohexene with molecular oxygen by polyoxometalate-intercalated hydrotalcites (1996)
    Springer
    Catalysis letters 40 (1996), S. 43-45 
    Details
    ISSN: 1572-879X
    Schlagwort(e): oxidation ; cyclohexene ; polyoxometalate-intercalated hydrotalcite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Cyclohexene was oxidized with molecular oxygen over transition-metal-substituted polyoxometalate-intercalated hydrotalcites to produce 2-cyclohexene-1-one and 2-cyclohexene-1-ol with high selectivity under mild reaction conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807455
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  • 3
    Digitale Medien
    Digitale Medien
    A broad spectrum catalytic system for removal of toxic organics from water by deep oxidation using dioxygen as the oxidant (1996)
    Springer
    Catalysis letters 40 (1996), S. 95-99 
    Details
    ISSN: 1572-879X
    Schlagwort(e): palladium metal ; oxidation ; toxic organics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In water, metallic palladium was found to catalyze the deep oxidation of a wide variety of functional organics by dioxygen at 80–90°C in the presence of carbon monoxide. Several classes of organic compounds were examined: benzene, phenol and substituted phenols, aliphatic and aromatic halogenated compounds, organophosphorus, and organosulfur compounds. In every case, deep oxidation to carbon monoxide, carbon dioxide, and water occurred in high yields, resulting in up to several hundred turnovers over a 24 h period. Since the heterogeneous catalyst can be removed by simple filtration, simultaneous water purification and contaminant destruction becomes feasible. For those substrates that are insoluble in pure water, a mixture of water and perfluorobutyric acid was successfully employed as the solvent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807463
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  • 4
    Digitale Medien
    Digitale Medien
    Oxidative dehydrogenation of ethane over La1−xSrxFeO3−δ perovskite oxides (1996)
    Springer
    Catalysis letters 38 (1996), S. 189-195 
    Details
    ISSN: 1572-879X
    Schlagwort(e): perovskite ; La1−xSrxFeO3−δ ; dehydrogenation ; oxidation ; ethane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Catalysts of the composition La1−xSrxFeO3−δ, 0⩽x ⩽1, have been tested for the oxidative dehydrogenation of ethane in the temperature range 300–800°C. The catalyst is active above 400°C, giving a maximum yield of 37% ethylene at 650°C. Above 650°C, synthesis gas was formed together with methane, suggesting that the reforming reaction and thermal cracking of ethane took place. The catalytic data are compared to conductivity measurements on the same material, and a good correlation between the activity and p-type conductivity has been found. In the phase diagram for the system LaFeO3-SrFeO3−δ, a phase separation to two types of (La, Sr)FeO3−δ perovskites was observed in the La/Sr binary composition in the temperature range below 800°C. The phase separation can elucidate the dependency of the catalytic activity on its p-type conductivity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00806567
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  • 5
    Digitale Medien
    Digitale Medien
    Inhibition of CO oxidation on hydroxyapatite by tetrachloromethane (1996)
    Springer
    Catalysis letters 39 (1996), S. 205-208 
    Details
    ISSN: 1572-879X
    Schlagwort(e): oxidation ; hydroxyapatite ; carbon monoxide ; inhibition ; tetrachloromethane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The introduction of tetrachloromethane (TCM) into the feedstream of CO and O2 inhibits the formation of CO2 on hydroxyapatite. TCM interacts with the surface of hydroxyapatite to form its chlorinated analogue, chlorapatite, which suppresses the oxidation of CO to CO2. Thus, in the oxidative coupling of methane the beneficial effects of the addition of TCM to the feedstream result, at least in part, from the suppression of the further oxidation of CO.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00805584
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  • 6
    Digitale Medien
    Digitale Medien
    Oxidation of methanol at copper surfaces (1996)
    Springer
    Catalysis letters 37 (1996), S. 79-87 
    Details
    ISSN: 1572-879X
    Schlagwort(e): methanol ; oxidation ; copper ; electron spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The role of preadsorbed oxygen present at Cu(111), Cu(110) and polycrystalline surfaces in the oxidation of methanol has been investigated by X-ray and electron energy loss spectroscopies. In addition to the well established formation of methoxy species and its subsequent decomposition and desorption as formaldehyde, a second reaction pathway to surface formate is present. The latter is temperature dependent being undetectable at 260 K at a polycrystalline surface but occurs at a significant rate at 295 K and above. The limitations of experimental data for methanol oxidation by temperature programmed desorption and molecular beam techniques are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00813523
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  • 7
    Digitale Medien
    Digitale Medien
    Synergistic effects during CO oxidation over mixed oxides. Study of (Fe2O3+SnO2) and (Mn2O3+SnO2) systems (1996)
    Springer
    Catalysis letters 37 (1996), S. 181-185 
    Details
    ISSN: 1572-879X
    Schlagwort(e): synergistic effect ; carbon monoxide ; oxidation ; mixed oxides ; iron oxide ; tin oxide ; manganese oxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Based on the comparative evaluation of the catalytic activity of Fe2O3, Mn2O3 and SnO2 and their mixed oxides (Fe2O3+SnO2) and (Mn2O3+SnO2), it is shown that the system (Mn2O3+SnO2) shows strong synergistic effects during CO oxidation reaction. Such effects are not observed for the analogous system (Fe2O3+SnO2). Based on the calcination and reduction behaviour of these two mixed oxide systems and the redox potentials of the involved cations, the possible reasons for the observance of synergistic effects for the (Mn2O3+SnO2) system are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807751
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  • 8
    Digitale Medien
    Digitale Medien
    Non-uniform surface kinetics with two types of sites: the case of ethanol oxidation on molybdenum oxide (1996)
    Springer
    Catalysis letters 39 (1996), S. 67-71 
    Details
    ISSN: 1572-879X
    Schlagwort(e): non-uniform surface ; kinetics ; ethanol ; oxidation ; molybdenum oxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Temkin's theory of rates of catalytic reactions on non-uniform surfaces is extended to the MoO3-catalyzed oxidation of ethanol to acetaldehyde. Two types of sites are assumed to be present, an oxygen atom site that can be modeled with uniform properties and a metal atom site characterized by non-uniform properties both for ethanol chemisorption to an ethoxide intermediate and the conversion of this intermediate to acetaldehyde. The rate-limiting step is the cleavage of a C-H bond in the absorbed ethoxide intermediate. Non-uniform surface kinetics leads to a kinetic rate expression of the form $$v = kP_{C_2 H_5 OH}^{1 - m} P_{O_2 }^{(1 - m)/4} P_{H_2 O}^{ - (1 - m)/2} $$ . Such a rate expression, withm=0.14, is shown to provide a good fit to kinetic data for the selective oxidation of ethanol on a silica supported molybdenum oxide catalyst.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00813732
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  • 9
    Digitale Medien
    Digitale Medien
    Baeyer-Villiger rearrangement catalysed by titanium silicate molecular sieve (TS-1)/H2O2 system (1996)
    Springer
    Catalysis letters 40 (1996), S. 47-50 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Baeyer-Villiger ; titanium silicate molecular sieve ; oxidation ; rearrangement ; titanium peroxo ; triphase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Titanium silicate molecular sieve TS-1 has been found to be an efficient catalyst for Baeyer-Villiger (BV) oxidation of cyclic and aromatic ketones under triphase conditions (solid catalyst along with two immiscible liquid reactants in the absence of any cosolvent), using dilute H2O2. Reactions studied are the oxidation of cyclohexanone and acetophenone. Whereas in the case of cyclohexane,ε-caprolactone, a BV product along with hydroxy and diketones is formed, in the case of acetophenone, phenyl acetate, a BV product along witho- andp-hydroxyacetophenone is formed. The acidic nature of titanium peroxo species, stabilised by water, is proposed to be responsible for such reactions under triphasic reaction conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807456
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  • 10
    Digitale Medien
    Digitale Medien
    Platinum particle size effect on the oxidative dehydrogenation of aqueous ethanol (1996)
    Springer
    Catalysis letters 36 (1996), S. 31-36 
    Details
    ISSN: 1572-879X
    Schlagwort(e): ethanol ; kinetics ; oxidation ; oxydehydrogenation ; platinum ; structure sensitivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effect of the platinum particle size was investigated for the catalytic oxidative dehydrogenation of aqueous ethanol to ethanal at a temperature of 303 K, an ethanol concentration of 260 mol m−3, a partial oxygen pressure 60 kPa, a pH of 9, and an ethanal and ethanoate concentration of 20 mol m−3. A particle size effect on the turnover frequency was observed but only for particle sizes smaller than 2 nm. Hence, the reaction shows a limited structure sensitivity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807202
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  • 11
    Digitale Medien
    Digitale Medien
    Perfluoroalkylporphyrin complexes as active catalysts for the reaction of isobutane with oxygen and the decomposition of tert-butyl hydroperoxide (1996)
    Springer
    Catalysis letters 36 (1996), S. 69-73 
    Details
    ISSN: 1572-879X
    Schlagwort(e): oxidation ; metalloporphyrins ; hydroperoxide decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A new family of metalloporphyrin complexes having perfluoroalkyl groups in the meso-positions of the ring are active catalysts for the oxidation of isobutane to tert-butyl alcohol, TBA, and for the decomposition of tert-butyl hydroperoxide to TBA. This discovery extends the limited number of meso-substituents that can be used to enhance catalytic activity and fits the postulate that groups that withdraw electrons from the porphyrin periphery give rise to active catalysts for alkane oxidation. The perfluoroalkyl groups also confer oxidative stability, hydrophobicity and lower cost to the catalyst.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807207
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  • 12
    Digitale Medien
    Digitale Medien
    Cubic topology in surfactant and lipid mixtures (1996)
    Springer
    European biophysics journal 24 (1996), S. 293-299 
    Details
    ISSN: 1432-1017
    Schlagwort(e): Phase transition ; NMR ; DSC ; X-ray diffraction ; Bonnet Transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract Ternary systems of palmitoyl-oleoyl-phosphatidylcholine (POPC) and the non-ionic surfactant C12EO2 (di-ethylene-oxide-mono-dodecyl-ether) in water have been studied with optical microscopy, NMR, DSC and X-rays from ambient temperatures to 45 °C. Below 29 °C the system is in the lamellar liquid crystalline state. Between 30 and 32 °C it transforms into a cubic Ia3d structure which converts into the cubic Pn3m phase at 39 °C. The transitions are fully reversible. An epitaxial relationship between all three phases was found, which is an elegant and convenient way to rearrange molecules from lamellar bilayers to a network of curved surfaces. The la3d (Q230) to Pn3m (Q224) transition occurs without measurable enthalpy change. This, together with the metric relation of 1.60 between the cubic lattice constants is strong evidence for a Bonnet transformation, where the structural changes occur without change in curvature. The potential significance of the cubic phases as intermediate structures for biological processes, e. g. transport across a bilayer or fusion of membranes, are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00180370
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  • 13
    Digitale Medien
    Digitale Medien
    Impact of water control projects on fisheries resources in Bangladesh (1996)
    Springer
    Environmental management 20 (1996), S. 523-539 
    Details
    ISSN: 1432-1009
    Schlagwort(e): Water control ; Floodplain ; Fisheries ; Bangladesh ; Chandpur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Bangladesh is a very flat delta built up by the Ganges—Brahmaputra—Meghna/Barak river systems. Because of its geographical location, floods cause huge destruction of lives and properties almost every year. Water control programs have been undertaken to enhance development through mitigating the threat of disasters. This structural approach to flood hazard has severely affected floodplain fisheries that supply the major share of protein to rural Bangladesh, as exemplified by the Chandpur Irrigation Project. Although the regulated environment of the Chandpur project has become favorable for closed-water cultured fish farming, the natural open-water fishery loss has been substantial. Results from research show that fish yields were better under preproject conditions. Under project conditions per capita fish consumption has dropped significantly, and the price of fish has risen beyond the means of the poor people, so that fish protein in the diet of poor people is gradually declining. Bangladesh is planning to expand water control facilities to the remaining flood-prone areas in the next 15–20 years. This will cause further loss of floodplain fisheries. If prices for closed-water fish remain beyond the buying power of the poor, alternative sources of cheap protein will be required.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01474653
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  • 14
    Digitale Medien
    Digitale Medien
    Purification and characterization of fumarase from the syntrophic propionate-oxidizing bacterium strain MPOB (1996)
    Springer
    Archives of microbiology 165 (1996), S. 126-131 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Key words Fumarase ; Syntrophy ; Propionate ; oxidation ; Fumarate fermentation ; Anaerobic oxidation ; Iron-sulfur cluster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Fumarase from the syntrophic propionate-oxidizing bacterium strain MPOB was purified 130-fold under anoxic conditions. The native enzyme had an apparent molecular mass of 114 kDa and was composed of two subunits of 60 kDa. The enzyme exhibited maximum activity at pH 8.5 and approximately 54° C. The K m values for fumarate and l-malate were 0.25 mM and 2.38 mM, respectively. Fumarase was inactivated by oxygen, but the activity could be restored by addition of Fe2+ and β-mercaptoethanol under anoxic conditions. EPR spectroscopy of the purified enzyme revealed the presence of a [3Fe-4S] cluster. Under reducing conditions, only a trace amount of a [4Fe-4S] cluster was detected. Addition of fumarate resulted in a significant increase of this [4Fe-4S] signal. The N-terminal amino acid sequence showed similarity to the sequences of fumarase A and B of Escherichia coli (56%) and fumarase A of Salmonella typhimurium (63%).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002030050307
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  • 15
    Digitale Medien
    Digitale Medien
    Polymerization kinetics of acrylic bone cements by differential scanning calorimetry (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 35-49 
    Details
    ISSN: 1572-8943
    Schlagwort(e): bone cement ; DSC ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Bone cements are widely used for the fixation of metallic prostheses in orthopaedics and to form replacements for skull defects in neurosurgery. Acrylic bone cements are based on a mixture of methyl methacrylate (MMA) and a fine powder of polymethyl methacrylate (PMMA). The polymerization of the bone cement occurs in contact with the bone and the prosthesis which act as the boundaries of a bulk polymerization reactor. The kinetic behaviour of the bone cement plays a fundamental role for the final performance of the implant. In this paper, the isothermal and non-isothermal polymerization behaviour of a commercial bone cement is described. A simple phenomenological model, accounting for the autoacceleration ffect, for a diffusion controlled termination mechanism and for the reaction between inhibitor and initiator, is proposed. The reaction kinetics is analysed by DSC. DSC data are used for the determination of the rates of polymerization under isothermal and non-isothermal conditions. The experimental data are processed to calculate the parameters of the proposed phenomenological kinetic model. The analytical and numerical details related to the integration of the model are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01982684
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  • 16
    Digitale Medien
    Digitale Medien
    Characterizing in situ starch gelatinization (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 181-194 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; gelatinization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Data obtained by dynamic mechanical analysis and DSC analysis of durum wheat dough are presented and discussed. Doughs with water contents ranging from 45 to 55% (w/w) were subjected to sinusoidal shearing by means of a dynamic mechanical spectrometer (Rheometrics, RFS2) equipped with parallel plate geometry, 0.1 strain amplitude and 1 rad/min frequency. The tests were carried on in temperature sweep mode at a heating rate of 2°C min−1. Wheat samples with water contents in the range between 7.5 and 37.5% and doughs with 37.5% moisture content were mixed for different times and subjected to DSC analysis (Perkin-Elmer, DSC-7) at a heating rate of 20°C min−1. Dynamic mechanical analysis revealed that the relationship between the dynamic properties of the dough and the temperature was modified as the water content of the dough increased and was quite different from that for gluten. A similar response was observed in the course of temperature scans made by means of DSC. These experimental findings suggest that the water-starch interaction in the presence of a protein matrix is affected by the availability of water and that the protein system is a competitor with respect to starch.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01982698
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  • 17
    Digitale Medien
    Digitale Medien
    Erfahrungen mit vier Softwarepaketen für Kinetische Auswertungen in der Thermischen Analyse (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 543-557 
    Details
    ISSN: 1572-8943
    Schlagwort(e): compensation effect ; DSC ; kinetics ; TG
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Four computer programs as well as one demo-version for non-linear evaluation of kinetic data in thermal analysis and calorimetry, were presented. The multi-task program TA-kin meets all mathematical requirements for solving the numerical assignments. It is shown that the so-called compensation effect is due to the mathematical structure of the Arrhenius equation. Several applications of TA-kin to a lot of DSC- and TG-measurements and isoperibolic batch experiments as well as adiabatic semi batch experiments realized by precision calorimetry have been discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983996
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  • 18
    Digitale Medien
    Digitale Medien
    Co-curing studies of ethynyl terminated oligoimide and (methyl) nadicimide resins (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 685-695 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; polymers ; resins ; TG
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The paper describes the co-curing studies of ethynyl and ethenyl end-capped imide resins. The effect of composition and chemical structure of ethenyl end-capped resins (nadicimides) on thermal behavior of ethynyl end-capped resins was evaluated using DSC and thermogravimetric analysis. An increase in char yield was observed on co-curing of few resin formulations. A mechanism has been proposed to account for this observation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01981804
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  • 19
    Digitale Medien
    Digitale Medien
    Thermal transitions of cassava starch at intermediate water contents (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1213-1228 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cassava starch ; DSC ; starch thermal properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Order-disorder transitions were investigated in native cassava starch at intermediate moisture contents (35 to 60% wt. water), using Differential Scanning Calorimetry (DSC) and dynamic Wide Angle X-ray Diffractometry (WAXS) with a synchrotron radiation source. The gelatinization of granules occurs as a cooperative process, due to constraints induced in crystallites by the amorphous areas. Variations of water content (water volume fraction from 0.28 to 0.86) and heating rate (0.2–10
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992824
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  • 20
    Digitale Medien
    Digitale Medien
    Isothermal microcalorimetric studies on starch retrogradation (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1179-1200 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; isothermal microcalorimetry ; retrogradation ; starch
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In the present study, isothermal microcalorimetry was introduced as a tool to investigate properties of starch retrogradation during the first 24 h. The study was made on purified amylose and amylopectin from corn, as well as on native starches, such as wheat, potato, maize, waxy maize and amylomaize, differing in their amylose content. The results were obtained in the form ofP-t traces (thermal powervs. time), and integration of these traces gave a net exothermic enthalpy of reaction, caused by the crystallization of amylose and amylopectin. TheP-t traces reflected the quantities of amylose and amylopectin in the starch studied. Depending on the amylose content and the botanical source of the starch, the rate of crystallization of amylose was high and predominated over that of amylopectin during the first 5–10 h. The contribution from amylose crystallization to the measured exothermic enthalpy was very substantial during this period. After ∼10 h, amylose crystallized at a lower constant rate. During the first 24 h, amylopectin crystallized at a low steady rate. The exothermic enthalpies obtained by the isothermal microcalorimetric investigations during the first 24 h of retrogradation were generally low in relation to the endothermic melting enthalpies observed by differential scanning calorimetry (DSC) measurements after 24 h of storage. The discrepancies in enthalpy values between the two methods are discussed in relation to phase separation and the endothermic effects owing to the decrease in polymer-water interactions when polymer-rich regions in the starch gel separate. Besides the exothermic enthalpies obtained, theP-t traces also made it possible to study the initial gelation properties of amylose from different botanical sources. The present study further demonstrated that isothermal microcalorimetry can provide a possible way to investigate the antistaling effect of certain polar lipids, such as sodium dodecylsulphate (SDS) and 1-monolauroyl-rac-glycerol (GML), when added to starches of different botanical origin. The net exothermic heat of reaction for starch retrogradation during the first 24 h was decreased when GML or SDS was added to the starch gels. The recordedP-t traces also showed how the effect of the added lipid influenced different periods during the first 24 h of starch retrogradation, and that the effect depended mainly on the amylose content, the botanical source of the starch, and the type of lipid used. When GML or SDS was added to waxy maize, the isothermal microcalorimetric studies clearly indicated some interaction between amylopectin and the polar lipids. These results concerning the action of anti-staling agents are further discussed in relation to the helical inclusion complexes formed between amylose-polar lipid and amylopectin-polar lipid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992822
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  • 21
    Digitale Medien
    Digitale Medien
    Influence of heating and cooling rates on the glass transition temperature and the fragility parameter of sorbitol and fructose as measured by DSC (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1419-1436 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cooling/heating rate ; DSC ; fragility parameter ; glass transition temperature ; sorbitol-fructose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The glass transition temperatures of sorbitol and fructose were characterized by four points determined on DSC heating thermograms (onset, mid-point, peak and end-point), plus the limit fictive temperature. The variations of these temperature values, observed as functions of cooling and heating rates, were used to determine the fragility parameter, as defined by Angell [1] to characterize the temperature dependence of the dynamic behavior of glass-forming liquids in the temperature range above the glass transition. The apparent activation energy values, determined for the different temperatures studied, were similar for fructose and sorbitol. These values were compared to data obtained from other techniques, such as mechanical spectroscopy. The variations of the apparent activation values, observed in experiments involving cooling and heating at the same rate, slow cooling followed by rate-heating, or rate-cooling followed by fast heating, were explained by aging effects occurring during the heating step.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992837
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  • 22
    Digitale Medien
    Digitale Medien
    Investigation of the complex thermal behavior of fats (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1545-1565 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cocoa butter ; fat crystallization ; DSC ; fat polymorphism ; fat structure ; fats ; lard ; milk fat ; triacylglycerols ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal behavior of three ural fats (displaying very different composition), cocoa butter (CB)2, lard, and a stearin obtained from anhydrous milk-fat (AMF) fractionation, were studied by both DSC and X-ray diffraction as a function of temperature (XRDT). To perform temperature explorations between −30
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992845
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  • 23
    Digitale Medien
    Digitale Medien
    Thermal behaviour of solid complexes of phenoxyalkanoic acids and divalent metals (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 5-14 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cadmium phenoxyacetate ; complexes ; DSC ; mercury(II) phenoxyacetate ; TG
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Solid cadmium and mercury(II) phenoxyacetates were prepared and investigated by DSC and TG techniques. The cadmium salt decomposed in two steps with the loss of 1.5 water molecules at first and the successive formation of CdCO3 as final product. Δdeh H * associated with the loss of one water molecule was compared with the corresponding values obtained for other phenoxyacetates previously studied and the obtained results were discussed. Anhydrous mercury(II) phenoxyacetate gave, on heating, HgCO3 which successively decomposed with the formation of gaseous products and a little amount of solid residue.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979942
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  • 24
    Digitale Medien
    Digitale Medien
    Activation energy of Se2Ge0.2Sb0.8 chalcogenide glass by differential scanning calorimetry (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 177-186 
    Details
    ISSN: 1572-8943
    Schlagwort(e): activation energy ; chalcogenide glass ; DSC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Results of differential scanning calorimetry (DSC) at different heating rates on Se2Ge0.2Sb0.8 chalcogenide glass are reported and discussed. As the heating rate (α) changed, also the glass transition temperature (T g) and onset temperature of crystallization (T c) changed. As the value of the transition activation energyE t changed, the crystallization fraction (χ), heat flow (Δq and the crystallization peak temperature (T p) also changed. The value of the effective activation energy of crystallizationE c was calculated by means of six different methods. The Se2Ge0.2Sb0.8 chalcogenide glass has two crystallization mechanisms, a one-dimensional and an other surface crystallization growth. The average value ofE t for Se2Ge0.2Sb0.8 is equal to 194.95±3.9 kJ·mol−1 and the average value ofE c is equal to 164±3.3 kJ·mol−1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979957
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  • 25
    Digitale Medien
    Digitale Medien
    Thermal study of irradiated polyacetylene films (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 237-243 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; DTG ; polyacetylene films ; TMA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Polyacetylene films irradiated byγ-rays up to 100 MRad were studied by means of TMA, DTG and DSC methods. It is shown that as the irradiation dose increases the concentration of topological branching knots into the polymer chains and theT g values decrease, the total mass loss and the enthalpy of the thermal isomerization reaction also decrease.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979964
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  • 26
    Digitale Medien
    Digitale Medien
    Nucleation and crystallization of polypropylene filled with BaSO4 (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 619-626 
    Details
    ISSN: 1572-8943
    Schlagwort(e): crystallization ; DSC ; filled polypropylene ; nucleation ; structural modification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The influence of high concentration of BaSO4 as nucleating agent on crystallization of fiber-forming polypropylene was studied by DSC. The work presents experimental and calculated values of melting and crystallization enthalpies of filled polypropylene and the influence on the formation of interface interactions between filler and polymers. These results show minimal interactions of components (BaSO4 and polypropylene) under experimental conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02135042
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  • 27
    Digitale Medien
    Digitale Medien
    Thermal analysis of macromolecules (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 643-679 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DDTA ; DSC ; macromolecules
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This review traces the development of thermal analysis over the last 40 years as it was experienced and contributed to by the author. The article touches upon the beginning of calorimetry and thermal analysis of polymers, the development of differential scanning calorimetry (DSC), single run DSC and other special instrumentations, up to the recent addition of modulation to calorimetry. Many new words and phrases have been introduced to the field by the author and his students, leaving a trail of the varied interests one can have over 40 years. It began with “cold crystallization” and most recently the term “oriented, intermediate phase” was coined, creating in-between: “extended chain crystals,” the “irreversible thermodynamics of melting of polymer crystals,” “dynamic differential thermal analysis” (DDTA), “the rule of constant increase ofC p per mobile bead within a molecule at the glass transition temperature,” “superheating of polymer crystals,” “melting kinetics,” “crystallization during polymerization,” the “chain-folding principle, “molecular nucleation,” “rigid amorphous phase,” a “system of classifying molecules,” “macroconformations,” “amorphous defects,” “rules for the entropy of fusion based on molecular shape and flexibility,” “single-molecule single-crystals,” “a system of classifying phases and mesophases,” and “condis phase.”
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983596
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  • 28
    Digitale Medien
    Digitale Medien
    Analysis of mesophase formation in side-chain liquid crystalline polycarbosilanes (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 795-808 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; kinetics ; liquid crystalline polymer ; optical transmittance ; polycarbosilane ; side-chain mesogen ; transition parameters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This paper is concerned with an analysis of the thermodynamics and kinetics of mesophase formation by cooling from the isotropic state of side-chain liquid crystalline polycarbosilanes containing spacers in the range from 3 to 11 CH2-groups. The polymers are characterized by their thermotropic behaviour as far as temperature, enthalpy and entropy of the transitions are concerned. The kinetics was followed by optical and calorimetric methods. Longer spacer length leads to more perfect ordering in the mesophase, higher isotropization temperatures, and lower glass transition temperatures. The Avrami and Ozawa formalism to describe the transition kinetics to the mesophase from the isotropic state cannot be interpreted as the nucleation and growth mechanism known from crystallization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983603
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  • 29
    Digitale Medien
    Digitale Medien
    A DSC study of the effects of sugars on thermal properties of rice starch gels before and after aging (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1201-1212 
    Details
    ISSN: 1572-8943
    Schlagwort(e): aging ; amylopectin ; DSC ; gels ; glass transition ; recrystallization ; retrogradation ; rice starch ; sugars
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermal characterization of gelatinized binary rice starch-water and ternary starch-sugar-water gels before and after aging was carried out using differential scanning calorimetry. The glass transition temperature of the maximally freeze-concentrated solution (T′g) in both fresh and aged gels was observed to decrease progressively with increasing sugar concentration. Aging of the gels generally shiftedT′g to higher temperatures, but had little or no effect on the ice melting peak temperature (T m). The presence of various sugars could either accelerate or retard starch (amylopectin) recrystallization, depending on the type and concentration of sugar, as well as on starch/water ratio. A hypothesis based on the dual antiplasticizing-plasticizing effects of sugars was postulated to explain the observed effects. Of the sugars studied, xylose and fructose appeared to display exceptional retardative and accelerative effects, respectively, on retrogradation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992823
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  • 30
    Digitale Medien
    Digitale Medien
    Effect of hydrothermal treatment on the gelatinisation properties of potato starch as measured by differential scanning calorimetry (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1229-1246 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; gelatinisation ; potato starch
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Gelatinisation temperatures as a function of moisture content were determined for potato starch. The native starch was then hydrothermally treated at a temperature 3% (Kelvin degrees) below the gelatinisation peak temperature and at moisture levels varying from 20 to 67% (by weight). Gelatinisation temperatures, temperature ranges and enthalpy values were affected for all treated samples. However, two sample populations could be distinguished: those samples treated under ‘limited’ moisture conditions and other samples treated in the presence of ‘extragranular’ moisture. A two-step hydrothermal treatment further increased the gelatinisation temperature, but the effect of the second step was small in comparison to that of the first.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992825
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  • 31
    Digitale Medien
    Digitale Medien
    DSC analysis of starch thermal properties related to functionality in low-moisture baked goods (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1299-1314 
    Details
    ISSN: 1572-8943
    Schlagwort(e): baked goods ; cookies ; crackers ; DSC ; pretzels ; starch
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We describe an application of DSC as an analytical ‘fingerprinting’ method that has been used to characterize the thermal properties of wheat starch in low-moisture, wheat-flour-based baked products, including cookies, crackers, and pretzels. This use of DSC has enabled us to relate starch thermal properties, on the one hand, to starch structure, and on the other hand, to starch functionality, in terms of baking performance and finished-product quality.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992829
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  • 32
    Digitale Medien
    Digitale Medien
    Structure and properties of bread dough and crumb (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1339-1360 
    Details
    ISSN: 1572-8943
    Schlagwort(e): bread crumb ; bread dough ; DSC ; hydrocolloid ; mechanical properties ; pentosans ; protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effects of hydrocolloids (guar and locust bean gums), soluble pentosans, and whey proteins on staling of bread crumb were investigated by means of DSC, rheometry, and image analyis. One current hypothesis, that these ingredients would behave as “water binders” and, at least the former two, as anti-staling agents, was indeed confirmed, although this action might be indirect. All the samples considered showed an exothermic DSC peak preceding the endotherm of the amylopectin fusion. According to a previous work, this signal was attributed to a water-dependent cross-linking process that would involve next-neighbouring polymer chains. To check the effect produced by molecular modifications that were expected to increase the water uptake of these ingredients, doughs containing added succinylated pentosans and whey proteins, and a polycarboxylate polymer, PEMULEN TR-1, were examined. These modifications enhanced starch retrogradation and yielded a firmer crumb. It was tentatively concluded that some direct interaction between these modified molecules and the crumb polymers might have taken place. In line with the food polymer science approach, the use of Time-Temperature-Transformation (TTT) diagrams is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992832
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  • 33
    Digitale Medien
    Digitale Medien
    Effects of medium and chemical modification on thermal characteristics of Β-lactoglobulin (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1513-1525 
    Details
    ISSN: 1572-8943
    Schlagwort(e): Β-lactoglobulin ; DSC ; protein modification ; thermal properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal properties of Β-lactoglobulin (Β-LG) were studied by differential scanning calorimetry (DSC) under different medium conditions.pH, neutral salts, protein perturbants, and polyols all affected the DSC characteristics of Β-LG. Acylation with fatty acids also changed the thermal properties, particularly peak width at half-height. The results suggest that the structural stability of Β-LG is controlled by non-covalent forces, particularly electrostatic and hydrophobic interactions. Disulfide bonds did not contribute to the thermal response of Β-LG. Fatty N-acyl-amino acids caused marked increases in thermal stability and decreases in denaturation enthalpy, and additional peaks were observed in the presence of some palmitoyl derivatives.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01992843
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  • 34
    Digitale Medien
    Digitale Medien
    Interpolymer complexes of a new type (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 347-352 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; optical densities ; thermal stability ; three-component interpolymer complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A new type of three-component interpolymer complexes (3IPCM) formed by two similarly charged polyelectrolytes and an oppositely charged low molar mass compound was studied by DSC, NMR and X-ray methods. The low molar mass monobasic compounds in these complexes act as mediators. This type of complexes differs from earlier-obtained 3IPCM, which contained a dibasic low molar mass mediator. The present 3IPCM were obtained from two polymers (polyacrylic acid and sodium polyphosphate) and bases such as 4-vinylpyridine and 2-methyl-5-vinylpyridine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02135012
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  • 35
    Digitale Medien
    Digitale Medien
    Kinetics of curing reaction of a diglycidyl ether of bisphenol A/1,3-bisaminomethyl-cyclohexane (DGEBA/1,3-BAC) epoxy resin system (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 387-395 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cure kinetics ; DSC ; epoxy resins ; gelation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract By employing differential scanning calorimetry (DSC) we have studied the kinetic of the cure reaction for a system containing a diglycidyl ether of bisphenol A (DGEBA) and 1,3-bisaminomethylcyclohexane (1,3-BAC) as a curing agent, using an isothermal approach over the temperature range of 60–110°C. We have determined the reached conversions at several cure temperatures and the reaction rates. The results showed that this cure reaction is autocatalytic. The experimental data were compared with the autocatalytic model proposed by Kamal, which includes two rate constants and two reaction orders. This model gives a good description of cure kinetics up to vitrification point. The activation energies for these rate constants were 44-57 kJ mol−1. From the gel time measurements the value obtained for the overall activation energy was 49.5 kJ mol−1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02135017
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  • 36
    Digitale Medien
    Digitale Medien
    Lifetime prediction of ABS polymers based on thermoanalytical data (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 465-470 
    Details
    ISSN: 1572-8943
    Schlagwort(e): ABS polymer ; DSC ; lifetime estimation ; thermooxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The service life of ABS polymer, stabilized by 2-(3,5-di-tert-butyl-4-hydroxyanilino)-4,6-bis(octylthio)-1,3,5-triazine and containing 50% of a modifying rubber component, was estimated from oxidative induction times measured by DSC in isothermal mode in the temperature interval 140–170°C. The lifetime of ABS powder at the actual temperature of drying was predicted by linear extrapolation according to Arrhenius. However, the extrapolated value was much longer than the real lifetime determined from the long-term oven aging tests at 70 and 90°C, simulating the industrial drying process. The effect of changes in the apparent activation energy of oxidation due to antioxidant consumption during polymer aging is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02135023
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  • 37
    Digitale Medien
    Digitale Medien
    Thermochemical investigation of guest-host interactions in Werner clathrates of type [Ni(4-Etpy)4(NCS)2]·nG (G=naphthalene derivatives) (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 539-548 
    Details
    ISSN: 1572-8943
    Schlagwort(e): complexes ; DSC ; guest-host interactions ; X-ray
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The stoichiometry of thermal decomposition and the thermochemistry were studied for [NiL4(NCS)2] (I) as a host complex, and for its clathrates of type [NiL4(NCS)2]·2G, where L=4-ethylpyridine and guest molecule G=1-methylnaphthalene in clathrate (II), 1-chloronaphthalene in (III) or 1-bromonaphthalene in (IV). For I, the loss of volatile components proceeds in three steps (−2L, −L, −L); the first steps for II–IV also involve the release of G (−2G, −2L). DSC and X-ray powder measurements indicated a phase transition in the host lattice, and allowed differentiation of the escape of G and L molecules. The enthalpy changes give the following sequence of thermodynamic stability for the studied chlathrates: I〉II〉III.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02135033
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  • 38
    Digitale Medien
    Digitale Medien
    Thermal analysis of poly(2-methylpentamethylene terephthalamide) (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 753-771 
    Details
    ISSN: 1572-8943
    Schlagwort(e): crystal-crystal transitions ; crystal forms ; DMA ; DSC ; Nylon M5T ; X-ray
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Poly(2-methylpentamethylene terephthalamide) (Nylon M5T) is a new high temperature aromatic polyamide developed by Hoechst Celanese. In this paper thermal properties of Nylon M5T chips, as well as as-spun and drawn fibers were studied by DSC, DMA, hot stage microscopy and WAXS.T g of the fully amorphous Nylon M5T is 143°C when measured by DSC;T g increases with crystallinity to 151°C. The temperature dependence of the solid and melt specific heat capacities has also been determined. The heat capacity increase at the glass transition of the amorphous polymer is 103.9 J °C−1 mol−1.T g by DMA for the as-spun fiber is 155°C, for a drawn fiber is 180°C. Three secondary transitions were observed by DMA in addition to the glass transition. These correspond to a local mode relaxation of the methylene groups at −120°C, onset of rotation of the amide-groups at −65°C and the onset of the rotation of the phenylenegroups (at 63°C). The crystallinity of Nylon M5T strongly depends on the rate of cooling from the melt. The isothermal crystallization data are melt temperature dependent: two-dimensional crystallization takes place when the samples are crystallized from higher melt temperatures, and this phase changes into a spherulitic structure during cooling to room temperature. Spherulitic crystallization occurs when lower melt temperatures are used. This polymer has three crystal forms as indicated by DSC, DMA and WAXS data. The crystal to crystal transitions are clearly visible when amorphous samples are heated in the DSC, or the DMA curves of as-spun fibers are recorded. It is experimentally shown that a considerable melting of the lower temperature crystal forms takes place during the crystal to crystal transitions. The equilibrium melting point as measured by the Hoffman-Weeks method, has been determined to be 339°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983600
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  • 39
    Digitale Medien
    Digitale Medien
    On the determination of the melting point of semicrystalline polymer by DSC (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 871-878 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; melting point ; polyethylene ; Raman-active longitudinal acoustical mode ; semi-crystalline polymers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This is a study for criteria to judge the melting point of semi-crystalline polymers from the DSC endotherm for polymer melting. Beyond standard indium DSC melting results an evaluation has been made on a series of polyethylenes for which crystal sizes were measured and predicted from Raman LAM analysis. The results confirm the conclusion of Prof. Wunderlich that the DSC content of melting is the proper basis of reporting melting points.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983607
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  • 40
    Digitale Medien
    Digitale Medien
    Modulated temperature DSC measurements relating to the cold crystallization process of poly(ethylene terephtalate) (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 893-903 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cold crystallization ; DSC ; heat capacity ; modulated temperature DSC ; poly(ethylene terephtalate)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The modulated temperature differential scanning calorimetric method (MT-DSC) yields three temperature dependent signals, an underlying heat capacity curve from the underlying heat flow rate (corresponding to the conventional DSC signal), and a complex heat capacity curve with a real part (storage heat capacity) and an imaginary part (loss heat capacity). These curves have been measured in the cold crystallization region for poly(ethylene terephtalate) with a modified Perkin-Elmer DSC-7. The underlying curve shows the well known large exothermic crystallization peak. The storage heat capacity shows a step change which reproduces the change in heat capacity during crystallization. This curve may be used as baseline, to separate the crystallization heat flow rate from the underlying heat flow rate curve. The loss heat capacity curve exhibits a small exothermic peak at the temperature of the step change of the storage curve. It could be caused by changes of the molecular mobility during crystallization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983609
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  • 41
    Digitale Medien
    Digitale Medien
    Thermogravimetric analysis for boiling points and vapour pressure (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1251-1258 
    Details
    ISSN: 1572-8943
    Schlagwort(e): boiling points ; DSC ; TGA ; vapour pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A TGA instrument has been adapted for rapid measurement of boiling points and vapour pressure at temperatures from ambient up to 400°C and pressures from ambient down to 20 mm Hg. Samples were contained in sealed holders having a laser-drilled aperture. Several organic liquids in the 100 to 300 gMW range showed good agreement with reference vapour pressure data. Sample mass, heating rate, and use of inert diluents were important variables affecting accuracy of vapour pressure measurements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979239
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  • 42
    Digitale Medien
    Digitale Medien
    Kinetic analysis of DSC and thermogravimetric data on combustion of lignite (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1657-1669 
    Details
    ISSN: 1572-8943
    Schlagwort(e): activation energy ; combustion ; differential scanning calorimetry ; kinetics ; lignite ; oxidation ; thermogravimetric analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermal analysis increasingly being used to obtain kinetic data relating to sample decomposition. This work involves a comparative study of several methods used to analyse DSC and TG/DTG data obtained on the oxidation of Beypazari lignite. A general computer program was developed and the methods are compared with regard to their accuracy and the ease of interpretation of the kinetics of thermal decomposition. For this study, the ratio method was regarded as the preferred method, because it permits the estimation of reaction order, activation energy and Arrhenius constant simultaneously from a single experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01980771
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  • 43
    Digitale Medien
    Digitale Medien
    Thermodynamic transition properties of highly ordered smectic phases (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 957-973 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; Gibbs energy ; liquid crystalline polyethers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A series of polyethers have been synthesized from 1-(4-hydroxy-4′-biphenyl)-2-(4-hydroxyphenyl)propane and α, Ω-dibromoalkanes having different numbers of methylene units [TPPs]. Both odd- and even-numbered TPPs [TPP(n=odd)s and TPP(n=even)s) exhibit multiple transitions during cooling and heating and they show little supercooling dependence, indicating close-to-equilibrium nature of these transitions. Combining the structural characterization obtainedvia wide angle X-ray diffraction powder and fiber patterns at different temperatures and the morphological observations from microscopy techniques, not only the nematic liquid crystalline phase but also highly ordered smecticF, smectic crystalG andH phases have been identified. The phase diagrams for both TPP(n=odd)s and TPP(n=even)s have been constructed [1–3]. Thermodynamic properties (enthalpy and entropy changes) during these transitions are studied based on differential scanning calorimetry experiments. The contributions of the mesogenic groups and methylene units to each ordering process can be separated and they indicate the characteristics of these processes thereby providing estimations of the transition types.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979442
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  • 44
    Digitale Medien
    Digitale Medien
    Thermal investigation of PEG 4000 — oxazepam binary system (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1743-1753 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; HSM ; oxazepam ; PEG 4000 ; solid dispersion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A thermal study using DSC and Hot Stage Microscopy (HSM) was carried out to investigate the interaction in solid state of the binary system PEG 4000 — oxazepam, and to establish their phase diagram. The eutectic composition, which melting occurs at lower temperature as compared with the pure components, has been determined. The results obtained by DSC and HSM have indicated that PEG 4000 — oxazepam mixtures displays no obvious incompatibilities, and that the system shows a typical eutectic behaviour. However because of the closeness of the melting of PEG 4000 to the eutectic temperature, it was difficult to determine precisely the eutectic composition and temperature on the basis of DSC measurements alone. The use of heats of fusion corresponding to physical mixtures allowed an estimation of the eutectic composition at 6% w/w oxazepam. Additional information of temperature (57.6
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01980920
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  • 45
    Digitale Medien
    Digitale Medien
    étude thermodynamique de certains médicaments (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1755-1758 
    Details
    ISSN: 1572-8943
    Schlagwort(e): combustion calorimetry ; DSC ; sulphamide type compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Two compounds of sulphamide type:p-amino-benzene sulphonamide (I) and 3,4-dimethylisoxazol 5-sulphanylamide (II) were studied by combustion calorimetry and by differential scanning calorimetry (DSC). The enthalpies in solid state at 298,15 K of combustion, δc H m o (I)=-2788,5±1,6 kJ mol−1, δc H m o (II)=-5036±3,8 kJ mol−1 and of formation, δf H m o (I)=-458,3±1,6 kJ mol−1, δfH m o (II)=-180,1±3,8 kJ mol−1 were determined. The thermal effects concerning the melting and phase transition of this compounds were also measured.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01980921
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  • 46
    Digitale Medien
    Digitale Medien
    Application of differential scanning calorimetry in food research and food quality assurance (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1787-1803 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; food components ; food microbiology ; food quality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Differential scanning calorimetry (DSC) is the most widely used thermal analytical technique in food research and it has a great utility in quality assurance of food. Proteins are the most studied food components by thermal analysis including studies on conformation changes of food proteins as affected by various environmental factors, thermal denaturation of tissue proteins, food enzymes and enzyme preparations for the food industry, as well as effects of various additives on their thermal properties. Freezing-induced denaturation of food proteins and the effect of cryoprotectants are also monitored by DSC. Polymer characterization based on DSC of polysaccharides, gelatinization behaviour of starches and interaction of starch with other food components can be determined, and phase transitions during baking processes can be studied by DSC. Studies on crystallization and melting behaviour of fats observed by DSC indicate changes in lipid composition or help characterizing products. Thermal oxidative decomposition of edible oils examined by DSC can be used for predicting oil stability. Using DSC in the freezing range has a great potential for measuring and modelling frozen food thermal properties, and to estimate the state of water in foods and food ingredients. Research in food microbiology utilizes DSC in better understanding thermoadaptive mechanisms or heat killing of food-borne microorganisms. Isothermic microcalorimetric techniques provide informative data regarding microbial growth and microbial metabolism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01980925
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  • 47
    Digitale Medien
    Digitale Medien
    Thermal characterization of polyethylene glycols applied in the pharmaceutical technology using differential scanning calorimetry and hot stage microscopy (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 291-304 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; pharmaceutical technology ; polymer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In the present study, the effect of the molecular weight and thermal treatments on commercial polyethylene glycols (PEG) samples used in the pharmaceutical processing technology, has been analyzed using DSC and HSM. The molecular weight of these polymers range from 1500 to 200000. Thermal investigations on the melting behavior of original PEG samples (as received from the manufacturer) showed only one single melting DSC endotherm effect before 373 K. This fact was associated to the presence of only one type of polymeric chain. Using standard conditions, PEG samples were solidified from the melt at 373 K, either by flash cooling (using liquid nitrogen and an ice bath) and by slow cooling, soaked and by slow cooling at room temperature. They were further studied by DSC. It was found that after cooling, PEG with molecular weight 1500 and 15000 showed DSC thermograms with a single endothermic peak. However, thermograms for PEG 4000 and 6000 produced a splitted melting endotherm. This fact was attributed to the presence of two types of chains, that are the folded and extended chains. Ageing time influences also the shape of the DSC endothermal effects. It was concluded that the endotherms obtained after heating these PEG indicate that the thermal history determine the structure (extended or folded chain type forms) and the degree of crystallinity, as evidenced by changes in heat of fusion values, melting points and structures after crystallization. The relationships between melting enthalpies and melting points, as deduced from DSC diagrams, with molecular weight of the polymers are also presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979969
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  • 48
    Digitale Medien
    Digitale Medien
    Thermal properties of a molecule in a constrained state (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1081-1092 
    Details
    ISSN: 1572-8943
    Schlagwort(e): chemical ionization MS ; constrained dye ; DSC ; dye-amylose inclusion complex ; Tandem MS ; TGA ; Thermal Desorption MS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal properties of a dye molecule (guest) inside the cavity of a host amylose helix were studied by TGA, DSC, and Thermal Desorption MS. The results show that the degradation temperature of dye shifts to a higher temperature by approximately 20°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983622
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  • 49
    Digitale Medien
    Digitale Medien
    Analysis of a symmetric neopolyol ester (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1093-1111 
    Details
    ISSN: 1572-8943
    Schlagwort(e): conformational disorder ; crystal ; DSC ; glass ; glass transition ; heat capacity ; melting transition ; tetra[methyleneoxycarbonyl (2,4,4-trimethyl) pentyl] methane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Quantitative thermal analysis was carried out for tetra[methyleneoxycarbonyl(2,4,4-trimethyl)pentyl]methane. The ester has a glass transition temperature of 219 K and a melting temperature of 304 K. The heat of fusion is 51.3 kJ mol−1, and the increase in heat capacity at the glass transition is 250 J K−1 mol−1. The measured and calculated heat capacities of the solid and liquid states from 130 to 420 K are reported and a discussion of the glass and melting transitions is presented. The computation of the heat capacity made use of the Advanced Thermal Analysis System, ATHAS, using an approximate group-vibration spectrum and a Tarasov treatment of the skeletal vibrations. The experimental and calculated heat capacities of the solid ester were compared over the whole temperature range to detect changes in order and the presence of large-amplitude motion. An addition scheme for heat capacities of this and related esters was developed and used for the extrapolation of the heat capacity of the liquid state for this ester. The liquid heat capacity for the title ester is well represented by 691.1+1.668T [J K−1 mol−1]. A deficit in the entropy and enthalpy of fusion was observed relative to values estimated from empirical addition schemes, but no gradual disordering was noted outside the transition region. The final interpretation of this deficit of conformational entropy needs structure and mobility analysis by solid state13C NMR and X-ray diffraction. These analyses are reported in part II of this investigation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983623
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  • 50
    Digitale Medien
    Digitale Medien
    Analysis of a symmetric neopolyol ester (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1113-1132 
    Details
    ISSN: 1572-8943
    Schlagwort(e): chiral molecule ; conformational disorder and motion ; crystal ; DSC ; heat capacity ; γ-gauche effect ; glass ; glass transition ; melting transition ; molecular mechanics computations ; tetra[methyleneoxycarbonyl (2,4,4-trimethyl) pentyl] methane ; solid state13C NMR ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The symmetric neopolyol ester tetra[methyleneoxycarbonyl(2,4,4-trirnethyl)pentyl]methane (MOCPM) has been studied by variable-temperature solid-state13C NMR and X-ray powder diffraction and compared to molecular mechanics calculations of the molecular structure. Between melting and glass transition temperatures the material is semicrystalline, consisting of two conformationally and motionally distinguishable phases. The more mobile phase is liquid-like and is, thus attributed to an amorphous phase (≈16%). The branches of the molecules in the crystal exhibit two conformationally distinguishable behaviors. In one, the branches are well ordered (≈56%), in the other, the branches are conformationally disordered (≈28%). Different branches of the same molecule may show different conformational order. This unique character of the rigid phase is the reason for the deficit of the entropy of fusion observed earlier by DSC. In the melt, solid state NMR can identify two bonds that are rotationally immobile, even though the molecules as a whole have liquid-like mobility. This partial rigidity of the branches accounts quantitatively for the observed increase in heat capacity at the glass transition. The reason for this unique behavior of MOCPM, a small molecule, is the existence of one chiral centers in each of the four arms of the molecule. A statistical model assuming that at least two of the chiral centers must fit into the order of the crystal can explain the crystallization behavior and would require 12.5% amorphous phase, 28.1% conformational disorder, and 59.4% crystallinity, close to the observed maximum perfection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983624
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  • 51
    Digitale Medien
    Digitale Medien
    Thermoporosimetry (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1177-1189 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; mercury porosimetry ; pore size distribution ; porous glass ; thermoporosimetry ; water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The pore size distributions (PSDs) of microporous glass, which were controlled by acid leaching subsequent to phase separation of CaO-Al2O3-B2O3-SiO2 glass, were determined via both mercury porosimetry and thermoporosimetry (thermal porosimetry). As a result, the pore radii, the cumulative pore volumes, and the surface areas determined via thermoporosimetry were in good agreement with those determined via mercury porosimetry. It was revealed that thermoporosimetry could be applied to pore structure analysis for porous materials having pore sizes at least up to 58 nm in radius.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983628
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  • 52
    Digitale Medien
    Digitale Medien
    Investigation of dehydroxylation of gibbsite into boehmite by DSC analysis (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1339-1347 
    Details
    ISSN: 1572-8943
    Schlagwort(e): boehmite ; DSC ; gibbsite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The dehydroxylation of gibbsite into boehmite was investigated by means of DSC analysis under non-isothermal conditions in the temperature range 453–673 K at heating rates from 2.5 to 20.0 K min−1. Mathematical analysis of the experimental DSC curves revealed the mechanism and kinetics of the gibbsite dehydroxylation process. The kinetic curvesα=f(t) andα=f(T) are sigmoidal in shape; their inflection points and the νm point of the curvesν=f(T) andν=f(T) are interrelated and are defined by the concept of a stationary point. The activation energy for the first stage of gibbsite dehydroxylation in the temperature range 453–673 K is 132.92±8.33–142.26±8.33 kJ mol−1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979247
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  • 53
    Digitale Medien
    Digitale Medien
    Thermal analysis of the polymerization process on the surface of inorganic fillers (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1541-1550 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; FTIR ; grafting ; IDSC ; kinetic parameters ; polymerization ; TG ; thermodynamic parameters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal polymerization of pentabromobenzyl (mono)acrylate (PBB-MA) on the surface of the inorganic fillers Mg(OH)2 and CaCO3 was studied. FTIR spectroscopy and extraction of the polymer in bromobenzene show that polypentabromobenzyl acrylate (PBB-PA) was mostly grafted on the surface of Mg(OH)2. Thermal analysis (TG, DSC, isothermal DSC (IDSC)) demonstrated an increase in polymerization starting temperature, and differences in polymerization enthalpy and apparent activation energy when an inorganic filler is added. These differences depend on the chemical composition of the filler used.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01980760
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  • 54
    Digitale Medien
    Digitale Medien
    Thermoplastic polymers quality control (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 117-121 
    Details
    ISSN: 1572-8943
    Schlagwort(e): baseline ; DSC ; heat of fusion ; polyethylene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A technique is proposed for improving the accuracy of the heat of fusion of semicrystalline polymers by DSC. The results of three commercially available instruments are compared.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01982691
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  • 55
    Digitale Medien
    Digitale Medien
    Characterization of thermomechanical properties in starch and cereal products (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 195-213 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DMA ; DSC ; rheological impacts ; thermomechanical properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermomechanical properties of bread components can be used to characterize various events that have direct rheological impacts. The objective is to observe changes that occur during staling and toughening of a bread or similar products. In this article, characterization of bread polymers, starch and gluten, were examined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01982699
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  • 56
    Digitale Medien
    Digitale Medien
    Measurement of heterogeneously catalyzed gas reactions by DSC (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 445-452 
    Details
    ISSN: 1572-8943
    Schlagwort(e): catalysts ; catalyst activity ; catalyst deactivation ; DSC ; gas reactions ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Gas reactions, catalyzed by solid catalysts, can be measured by DSC. In the experimental set-up an open sample pan with catalyst (powder or pellet) is placed on the sample side of the DSC sensor. The reactive gas mixture flows through the cell and reacts on the catalyst surface. The heat effect, caused by this reaction, results into a DSC signal. The calibration procedure is described for quantitative evaluation of the DSC measurements. For illustration four different reaction systems are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983986
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  • 57
    Digitale Medien
    Digitale Medien
    Internal flexibility of cardiac myosins (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 503-514 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cardiac myosin ; DSC ; flexibility of myosin heads ; spin-labelling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Conventional and saturation transfer electron paramagnetic resonance spectroscopy (EPR and ST EPR) and differential scanning calorimetry (DSC) were used to study the motional dynamics and segmental flexibility of cardiac myosins. Cardiac myosins isolated from bovine and human heart muscle were spin-labelled with isothiocyanate- or maleimide-based probe molecules at the reactive sulfhydryl sites (Cys-697 and Cys-707) of the motor domain. The maleimide probe molecules attached to human cardiac myosin rotated with an effective rotational correlation time of 33 ns which was at least eight times shorter than the rotational correlation time of the same label on skeletal myosin (260 ns). In the presence of MgADP and MgADP plus orthovanadate, flexibility changes in the multisubunit structure of myosins were detected, but this did not lead to changes of the overall rotational property of the myosin heads. Significant difference in the internal flexibility was detected on myosin samples isolated from ischemic tissue, the rotational correlation time decreased to 25 ns. DSC measurements supported the view that addition of nucleotides produced additional loosening in the multisubunit structure of cardiac myosin. It is postulated that there is an intersite communication between the nucleotide binding domain and the 20 kDa subunit where the reactive thiol sites are located.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01983992
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  • 58
    Digitale Medien
    Digitale Medien
    Thermal analysis of hydrated calcium aluminates (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 765-774 
    Details
    ISSN: 1572-8943
    Schlagwort(e): calcium aluminates ; cement ; DSC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Differential scanning calorimeter (DSC) has been used to study the dehydration characteristics of hydrated calcium aluminates such as CA, CA2 and C12A7 where C and A stand for CaO and Al2O3 respectively. Dehydration of CAH10 and C2AH8 (whereH=H2O) occur ∼ at 160–180°C and 200–280°C respectively. These two phases are unstable and ultimately get transformed to AH3 and C3AH6. Dehydration of AH3 and C3AH6 occur between 290 and 350°C and overlap at lower scanning rate. The activation energy for dehydration of the stable AH3 and C2AH6 phases has been found to be 107.16 and 35.58 kJ mol−1 respectively. The compressive strength of the hydrated calcium aluminates has been determined. The result shows that in the case of CA, almost 90% of ultimate strength has been attained in 1 day whereas in CA2, ultimate strength has been attained in 14 days and in C12A7 in 1 day. DSC results have been correlated with the rate of strength developments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01981812
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  • 59
    Digitale Medien
    Digitale Medien
    Caracterisation par analyse calorimetrique differentielle des complexes entre LiAlH4 et les ethers-couronnes 12-C-4, 15-C-5, dicyclohexano-18-C-6 (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 833-846 
    Details
    ISSN: 1572-8943
    Schlagwort(e): crown-ethers (CE) ; 12-C-4 ; 15-C-5 ; DC 18-C-6anti ; DC 18-C-6syn ; DSC ; LiAlH4-CE complexes ; glass-transition ; solvates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal behaviour of complexes [Li+-EC](AlH4)− withEC=12-C-4, 15-C-5, DC 18-C-6 (cis-anti-cis andcis-syn-cis isomers) was investigated by Differential Scanning Calorimetry (DSC). These complexes were prepared as solids from benzene solutions. Pure EC and several solvated species [Li+-EC](AlH4)−·nC6H6 (EC=15-C-5, DC 18-C-6syn) were also studied. DSC has revealed various phenomena. Solid-solid transitions were observed before melting for [Li+-EC](AlH4)− withEC=12-C-4 and 15-C-5. They are probably explained by small molecular modifications strongly dependent on the thermal history of the sample. A glass-transition was found for the pure crown-ether DC 18-C-6anti, the complex [Li+-EC](A1H4)− withEC=DC-18-C-6anti and the two solvates mentioned above.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01981818
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  • 60
    Digitale Medien
    Digitale Medien
    The glass transition (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 887-896 
    Details
    ISSN: 1572-8943
    Schlagwort(e): compensation temperature ; DSC ; fictive temperature ; poly(ethylene terephthalate) ; thermally stimulated depolarization current
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This work deals with a comparison of data obtained from differential scanning calorimetry (DSC) and thermally stimulated depolarization current (TSDC) investigations. Measurements were performed on various poly(ethylene terephthalate) films: a wholly amorphous, a thermally crystallized and drawn samples. For each specimen, the TSDC complex spectra, resolved into elementary ones, led to the determination of the classical compensation temperature (T c ). The glass transition temperature (T g) and the fictive equilibrium temperature (T f) were determined by means of DSC. It appears thatT c is different fromT g and very close toT f.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01981823
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  • 61
    Digitale Medien
    Digitale Medien
    Isothermal melt crystallization kinetics of poly(L-lactic acid) (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 931-939 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; isothermal melt crystallization ; kinetic parameters ; Mathematica® ; new kinetic model ; poly(L-lactic acid)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A DSC study was carried out of the isothermal melt crystallization kinetics of poly(L-lactic acid), PLLA, at 110, 115, 120, 125 and 130
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01979440
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  • 62
    Digitale Medien
    Digitale Medien
    Contribution to the understanding of the parabolic oxidation mechanism of dilute alloys. Part I: Oxides with metal excess or oxygen deficit (1996)
    Springer
    Oxidation of metals 46 (1996), S. 1-17 
    Details
    ISSN: 1573-4889
    Schlagwort(e): dilute alloys ; oxidation ; Wagner-Hauffe rule
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Concerning the parabolic oxidation of alloys with a low content of a different valence element, we show that the Wagner-Hauffe valence approach contains some inaccuracies. This paper is devoted to the growth of an oxide MO with metal excess or oxygen deficit. The analytical processing consists in solving the differential equation connecting the point defect flux to the oxygen pressure. This equation has been solved analytically in the case where the foreign-element concentration is very high compared to that of the point defects in the pure oxide. On this assumption with a lower-valence dopant, as long as the oxide conductivity remains essentially electronic, the oxidation is limited only by the transport of ionic defects across the scale under the electric-potential gradient. Moreover, an increase of the dopant concentration may lead to an oxide exhibiting partial ionic conductivity. Consequently, the parabolic constant variations as a function of the dopant concentration is not monotonic, contrary to results published before. With a higher-valence dopant, the conductivity always remains electronic, and this result agrees with predictions based on the Wagner Hauffe approach, though the demonstrations are fundamentally different.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046881
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  • 63
    Digitale Medien
    Digitale Medien
    Effect of short-circuiting on the oxidation kinetics of copper and its doped varieties in the temperature range of 523–1073 K (1996)
    Springer
    Oxidation of metals 46 (1996), S. 73-107 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; copper ; Li-doped copper ; Cr-doped copper ; short-circuiting ; Mott's parabola ; Wagner's parabola
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The influence of shorting circuitry attachment between metal-oxide and oxideoxygen interfaces on the oxidation kinetics of copper, lithium-doped copper (Li: 400 ppm), and chromium-doped copper (Cr: 12 ppm) have been studied in dry air $$(P_{O_2 } = 21.27kPa)$$ in the temperature range of 523–1073 K. Oxide film or scale growth under short-circuiting as well as under normal oxidation conditions conforms to the parabolic rate law. The oxidation kinetics under short-circuiting resulted in decreased rates for Cu and Li-doped Cu up to a temperature of 773 K, while Cr-doped Cu exhibited an enhancement in rate compared to its normal oxidation in the same temperature range. However, above 873 K, all three systems under shorting circuitry attachment exhibited enhanced rates compared to their normal oxidation rates in conformity to the existing theoretical model. Use of additional resistances in series in the outer short-circuit Pt path have clearly established that below 773 K Mott's fieldinduced migration plays the most important role, while at elevated temperatures Wagner's electrochemical potential-gradient factor acts as the main driving force in the scale-growth process. The results have been interpreted on the basis of average defect concentration, the electrochemical potential gradient, electrical field gradient, and transport coefficient in the Cu2O layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046885
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  • 64
    Digitale Medien
    Digitale Medien
    Effect of Cr, Co, and Ti additions on the high-temperature oxidation behavior of Ni3Al (1996)
    Springer
    Oxidation of metals 46 (1996), S. 109-127 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Ni3Al base alloy ; chromium ; cobalt ; titanium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior of Ni3Al+2.90 wt.% Cr, Ni3Al+3.35 wt% Co, and Ni3Al+2.99 wt.% Ti alloys was studied in 1 atm of air at 1000, 1100, and 1200°C. Isothermal tests revealed parabolic kinetics for all three alloys at all temperatures. Cyclic oxidation for 28 two-hour cycles produced little spallation at 1000°C, but caused partial spallation at 1100°C. Especially, at 1200°C severe spallation in all three alloys was observed. Although additions of Cr, Co, or Ti to Ni3Al alloys slightly increased the isothermal-oxidation resistance, the additions tended to decrease the cyclic-oxidation resistance. The major difference in the oxidation of the three alloys compared with the oxidation of pure Ni3Al alloys was the existence of small α-Al2O3 particles in the middle of the α-Al2O3 scale and the formation of irregularly shaped Kirkendall voids at the alloy-scale interface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046886
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  • 65
    Digitale Medien
    Digitale Medien
    Influence of external mechanical loadings (creep, fatigue) on oxygen diffusion during nickel oxidation (1996)
    Springer
    Oxidation of metals 45 (1996), S. 153-181 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; 18O diffusion ; nickel ; stress effects on diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract This study deals with the influence of various mechanical loadings (fatigue, creep, creep-fatigue) on oxygen diffusion in a particular system, oxidizing nickel. A distinction between the behavior of the oxide layer and underlying nickel was noted during the first step of oxidation at 550°C, in PO 2=1 atm. Mechanical loading causes a decrease of the oxygen mobility through the oxide scale (factor of 103). The oxide thicknesses on nickel undergoing mechanical loadings are different than for an unloaded sample, due to distinct contributions of the oxygen and nickel fluxes in the growing oxide. In the substrate, the ingress of oxygen becomes easier with a constant tensile load (creep). The intergranular-oxygen diffusion coefficient, Di, is increased by a factor of 102 with respect to other samples. In creep, oxygen diffusion takes place along grain boundaries of a structure with smaller grains than in unstrained Ni. A short fatigue period during creep-fatigue decreases the sensitivity of nickel to intergranular-oxygen diffusion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046824
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  • 66
    Digitale Medien
    Digitale Medien
    A study on the oxidation characteristics of cast irons containing aluminum (1996)
    Springer
    Oxidation of metals 45 (1996), S. 109-131 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Fe−Al−C ; Fe−Al−Si−C ; inoculation ; scale ; characterization ; oxidation ; high temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Isothermal-oxidation characteristics of cast irons containing aluminum (5–15% Al) from 700 to 1000°C in air have been studied. In addition to massgain measurements, the morphology and composition of the oxide scales have been examined by SEM-EDX system and XRD analysis. A normal Fe−5Al−C alloy does not develop protective, adherent scales. Even the addition of misch metal and calcium silicide to such an alloy does not improve its oxidation resistance. But aluminum cast iron develops considerable oxidation resistance only when a sufficient quantity of silicon is also present in the alloy. Treatment of the alloy with misch, metal and calcium silicide together assists in protective scale formation. Among the alloys investigated Fe−15Al−Si−C treated with misch metal and calcium silicide shows minimum oxidation at 1000°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046822
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  • 67
    Digitale Medien
    Digitale Medien
    Corrosion of iron in sulfur dioxide at 0.1 MPa (1996)
    Springer
    Oxidation of metals 45 (1996), S. 469-486 
    Details
    ISSN: 1573-4889
    Schlagwort(e): iron ; sulfur dioxide ; oxidation ; tracer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The reaction of iron with sulfur dioxide at 0.1 MPa and 1073 K was studied. The composition and morphology of the scales, transport phenomena occurring in the growing scales, and kinetics of the process were investigated. Scanning electron microscopy and various techniques of X-ray analysis were used. The transport phenomena were studied by marker and by radiotracer techniques. The scales were composed of sulfide and oxides and grew by the outward diffusion of metal. It was concluded that the process initially took place through the reaction of iron with sulfur dioxide molecules. During the next stage of the process the reaction with sulfur dioxide molecules as well as with oxygen molecules is possible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046847
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  • 68
    Digitale Medien
    Digitale Medien
    High-temperature corrosion of Ti and Ti-6Al-4V alloy (1996)
    Springer
    Oxidation of metals 45 (1996), S. 507-527 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; sulfidation ; oxides ; sulfides ; Ti ; Ti-6Al-4V alloy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Pure titanium and Ti-6Al-4V were exposed at 750°C in an H2/H2O/H2S PO 2≈10−18 Pa and PS 2≈10−1 Pa), H2/H2O (PO 2≈10−18 Pa) and air environments for up to 240 hr. The corrosion kinetics, obtained by the discontinuous gravimetric method, showed that the sulfidation/oxidation kinetics were linear for Ti and linear-parabolic for Ti-6Al-4V in the H2/H2O/H2S environment. Both materials obeyed parabolic rate laws in the H2/H2O atmosphere after a transient period, and linear-parabolic rate laws in air. After exposure to the H2/H2O/H2S atmosphere, the titanium specimen displayed a double scale of TiO2 with an intervening TiS2 film between the double-layered scale of TiO2 and the substrate. Ti-6Al-4V also contained a double layer of TiO2 together with a stratum consisting of Al2S3, TiS2 and vanadium sulfide at the junction of the inner TiO2 layer and substrate. Some Al2O3 precipitated in the external portion of the outer TiO2 layer. Following oxidation in the low-PO 2 atmosphere a double-layered oxide of TiO2 scale formed on both Ti and Ti-6Al-4V. The scale on Ti-6Al-4V also contained an α-Al2O3 film situated between the outer and inner (TiO2) layers. For both materials, multilayered-scale formation characterized air oxidation. In detail a multilayered oxide scale of TiO2 formed on the air-oxidized Ti, while a multilayered oxide scale with alternating layers of Al2O3/TiO2 developed on Ti-6Al-4V oxidized in air.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046849
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  • 69
    Digitale Medien
    Digitale Medien
    Mixed oxidant corrosion in nonequilibrium gasifier environments (1996)
    Springer
    Oxidation of metals 45 (1996), S. 487-505 
    Details
    ISSN: 1573-4889
    Schlagwort(e): sulfidation ; oxidation ; gasification ; austenitic steel alloys
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The major use of high-temperature steel alloys in gasifiers is in heat exchangers for cooling hot syngas, consisting mainly of CO and H2 with lesser amounts of H2O and CO2 and minor quantities of H2S and HCl. Metal temperatures range from 250 to 600°C, gas temperatures from 250 to 1200°C. Because of rapid cooling the composition of the gas does not change with temperature. Therefore the gas is not in equilibrium at the metal surface. Calculations show that such gases have lower oxygen and sulfur pressures than equilibrated gases at the same temperature. This makes the results of previous laboratory studies less appropriate for predicting mixed oxidant corrosion in gasifiers. For this reason the present study was carried out using nonequilibrium gas mixtures, similar to gases, produced in entrained-slagging gasifiers. Most corrosion experiments were carried out at 540°C, as this is a common temperature for superheaters and hot-gas cleanup systems. Iron-base model alloys containing 35% Ni, 20% Cr, and various minor alloying additions were studied. Three corrosion regimes were identified over the range of conditions studied, depending on the sulfur-to-oxygen pressure ratio of the gas and the alloy composition. At high PS 2/PO 2 ratios a somewhat protective FeCr2S4 scale formed on all alloys. Below this layer internal oxidation and sulfidation occurred at a slow rate. At lower PS 2/PO 2 ratios nonprotective Fe(Ni, Cr)S external scales formed. These allow rapid internal oxidation of the chromium in the alloy, resulting in high corrosion rates. Under the same conditions very low corrosion rates are obtained when silicon is added to the alloy, because the presence of SiO2 precipitates makes the internal-oxidation layer protective. Thus, the same corrosion model is operative in all three corrosion regimes: external sulfidation of iron and nickel, together with internal oxidation of chromium and other strong-oxide formers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046848
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  • 70
    Digitale Medien
    Digitale Medien
    TEM investigations of the early stages of TiAl oxidation (1996)
    Springer
    Oxidation of metals 46 (1996), S. 255-285 
    Details
    ISSN: 1573-4889
    Schlagwort(e): electron diffraction ; intermetallic ; oxidation ; TEM ; titanium aluminide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The early stages of TiAl oxidation at 900°C and 1000°C in air have been investigated by transmission electron microscopy (TEM). The investigations revealed that at the beginning of oxidation, i.e., after 4 min, TiO2 and Al2O3 grow in a preferential orientation on the γ-TiAl substrate. After 4 h of oxidation an oxide scale structure can already be found similar to that known from long-term oxidation. In addition, besides α-Al2O3, the formation of a second aluminum oxide phase and of titanium nitrides is observed. The processes at the metal-oxide interface of oxidation in the early stages, consisting of a repeated cycle of Al2O3 formation, Al2O3 dissolution, outward migration of Al through the scale, and reprecipitation of Al2O3 in the outer scale, are described by a model. The four stages observed in the kinetics of TiAl oxidation are explained on the basis of the results obtained and the structure of the oxide scale.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01050799
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  • 71
    Digitale Medien
    Digitale Medien
    The corrosion of pure niobium in oxidizing, sulfidizing, and oxidizing-sulfidizing gas mixtures at 600–800°C (1996)
    Springer
    Oxidation of metals 46 (1996), S. 287-297 
    Details
    ISSN: 1573-4889
    Schlagwort(e): pure niobium ; oxidation ; sulfidation ; oxidation-sulfidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The corrosion of pure niobium has been studied at 600–800°C in various environments as part of a study of the corrosion resistance of its alloys with iron, cobalt, and nickel to atmospheres of low-oxygen and/or high-sulfur activities. The results have shown that not only the sulfidation but also the corrosion in mixed atmospheres and particularly the oxidation under low oxygen pressures of pure niobium are quite slow, with kinetics rather similar in the three types of gas mixtures used. The good corrosion resistance of niobium to attack by oxygen under low pressures is quite interesting because this element is corroded very rapidly by oxygen under high oxygen pressures, due to the formation of the nonprotective highest oxide Nb2O5 as a main corrosion product.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01050800
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  • 72
    Digitale Medien
    Digitale Medien
    The oxidation behavior of Fe-20Cr alloy foils in a synthetic exhaust-gas atmosphere (1996)
    Springer
    Oxidation of metals 46 (1996), S. 335-364 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Fe−Cr ; oxidation ; exhaust gas ; oxide adherence ; titanium ; rare earths
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Oxidation tests of rare-earth-modified and Ti-modified Fe−20Cr alloy foils, which are under consideration for catalytic converter supports, were performed in a synthetic exhaust-gas atmosphere (N2+H2O+CO2) between 900°C and 650°C. Between 900°C and 750°C, the rare earths had no effect on oxide growth rates while Ti increased growth rates. Oxide growth rates for the rareearth alloys at 800°C and 750°C are much lower than those found in the literature for oxidation of Fe−Cr alloys or pure Cr in O2-rich atmospheres. The slow growth rates for the rare-earth alloys agree with literature data for oxidation of stainless steels containing 〉20% Cr in wet atmospheres and are caused by growth of an oxide scale only one grain thick. At temperatures ≤700°C, Fe−20Cr alloys grow massive Fe oxides; however, this can be suppressed by adding rare earths or Ti. To ensure good oxide adherence, free sulfur must be eliminated in the alloy by tying it up with a reactive-element addition. Both Ti and the rare earths can be used to tie up S, but the rare earths are more effective. For converter applications, the optimum alloy composition may contain rare earths for good oxide adherence and a small amount of Ti to suppress growth of Fe-rich oxides.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01048635
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  • 73
    Digitale Medien
    Digitale Medien
    Transient oxidation in Fe-Cr-Ni alloys: A Raman-scattering study (1996)
    Springer
    Oxidation of metals 46 (1996), S. 365-381 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; steel ; Raman ; scale ; transient oxides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Using Raman scattering we have investigated the oxidation, in air, of the Fe-Cr-Ni stainless steels Fe-25Cr-20Ni, Fe-25Cr-20Ni-3Zr, and Fe-24Cr-3Zr (wt.%) as a function of temperature in the range 300 to 1000°C. The Raman technique is very sensitive to, and provides a clear identification of, the oxides Fe2O3 and Cr2O3. However, the technique is insensitive to NiO, FeO, and does not give a clear identification of spinels. The Fe−Cr−Ni alloys form chromia scales at temperatures greater than ∼800°C. At lower oxidation temperatures, transient phases are observed. With a 1-h heat treatment at 300°C, we observe the formation of an unidentified scale; we speculate that it is either amorphous or consists of disordered spinel(s). Near 400°C we begin to observe hematite (Fe2O3). The intensity of the Fe2O3 signal increases with temperature to ∼600°C and then decreases, being largely replaced by the signal from Cr2O3. The thickness of the Cr2O3 scale increases with temperature up to ∼1000°C above which spallation becomes apparent. Spinel phases also apparently persist in the scale to 1000°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01048636
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  • 74
    Digitale Medien
    Digitale Medien
    The steady-State corrosion kinetics of two-phase binary alloys forming the most-stable oxide (1996)
    Springer
    Oxidation of metals 46 (1996), S. 383-398 
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    ISSN: 1573-4889
    Schlagwort(e): high temperatures ; binary alloys ; two-phase alloys ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The steady-state kinetics in the high-temperature oxidation of binary A-B alloys containing a mixture of the conjugated solid solutions of B in A (alpha phase) and A in B (beta phase) with exclusive formation of the most-stable oxide BOv have been examined, assuming that the external scale grows on top of a subsurface layer of alpha phase. The results obtained are compared with the corresponding behavior of alloys which are single phase in the whole range of composition. Under identical values of all the parameters involved the concentration of B at the alloy-scale interface is smaller for two-phase than for single-phase alloys under the same concentration of B in the alloy as a result of the restricted flux of B through the alpha-phase layer. As a consequence of this, the two-phase alloys corrode more slowly than single-phase alloys and this difference increases as the solubility of B in the alpha phase decreases. Finally, the simultaneous formation of BOv both externally and as internal oxide is more likely for two-phase than for single-phase materials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01048637
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  • 75
    Digitale Medien
    Digitale Medien
    An analysis of the internal oxidation of binary M-Nb alloys under low oxygen pressures at 600–800°C (1996)
    Springer
    Oxidation of metals 46 (1996), S. 441-463 
    Details
    ISSN: 1573-4889
    Schlagwort(e): niobium alloys ; oxidation ; high temperatures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The corrosion of M−Nb alloys based on iron, cobalt, and nickel and containing 15 and 30 wt% Nb has been studied at 600–800°C under low oxygen pressures (10−24 atm at 600°C and 10−20 atm at 700–800°C). Except for the Co−Nb and Ni−Nb alloys corroded at 800°C, which formed external scales of niobium oxides, corrosion under low O2 pressures produced an internal oxidation of niobium. This attack was much faster than expected on the basis of the classical theory. Furthermore, the distribution of the internal oxide in the alloys containing two metal phases was very close to that of the Nb-rich phase in the original alloys. These kinetic, microstructural, and thermodynamic aspects are examined by taking into account the effects of the limited solubility of niobium in the various base metals and of the two-phase nature of the alloys.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01048640
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  • 76
    Digitale Medien
    Digitale Medien
    The effect of oxygen concentration on the oxidation of low-carbon steel in the temperature range 1000 to 1250°C (1996)
    Springer
    Oxidation of metals 46 (1996), S. 423-440 
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    ISSN: 1573-4889
    Schlagwort(e): oxidation ; scaling ; surface temperature ; heat of reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract This paper describes the oxidation behavior of low-carbon steel samples in binary gas mixtures of oxygen and nitrogen, at oxygen concentrations ranging between 1% and 15% and temperatures ranging between 1000 and 1250°C. Sample weight gains versus time were analyzed, along with measurements and calculations of sample heating rates due to exothermic heat of reaction at the sample surface. It was found that initial rates of oxidation depended on oxygen content in the gasmixture and that these reaction rates were linear up to oxide thicknesses of 0.4 to 0.5 mm. Calculations of linear oxidation rate constants based on equations for mass transport of oxygen in the gas mixture to the sample surface showed good agreement with those measured experimentally, indicating that the initial period of oxidation is controlled by the mass transport of oxygen to the reaction interface. The linear rate constants showed little dependency on temperature, an activation energy of approximately 17kJ/mole being obtained. Measurements of sample surface temperatures have shown that within this linear-oxidation regime, interfacial temperatures of the samples increase with increasing oxygen contents in the gas mixture, owing to exothermic heats of oxidation. Subsequent oxidation kinetics were found to be parabolic. Measured parabolic rates constants were in good agreement with previous investigations, with activation energy values of approximately 127kJ/mole.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01048639
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  • 77
    Digitale Medien
    Digitale Medien
    Effect ofθ-alumina formation on the growth kinetics of alumina-forming superalloys (1996)
    Springer
    Oxidation of metals 46 (1996), S. 465-480 
    Details
    ISSN: 1573-4889
    Schlagwort(e): ODS Alloy ; oxidation ; SIMS ; microstructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Alumina-forming ODS superalloys are excellent oxidation-resistant materials. Their resistance relies upon the establishment of a stable, slow-growing, and adherent α-alumina. In the present investigation, these alloys exhibited unstable and relatively less adherent θ-alumina phase, which increased the oxidation rate in the transient stage and converted into α-alumina in the later part of the exposure. The oxide-growth process was found to depend upon various parameters such as temperature, time, and presence of an active elecment in the superalloy. Characterization carried out by XRD, SEM/EDAX, and AES on oxidized ODS and non-ODS alloys demonstrated a significant influence of the active element, Y, on the transformation of θ- to α-alumina. SIMS analysis of two-stage oxidation at 900°C for two different durations evidently showed that the change in the transport process is due to θ-to-α-alumina transformation. On the basis of these results, a new and consistent mechanism is proposed to explain the influence of θ-alumina and its transformation on growth kinetics and the effect of yttrium on the transformation leading to good scale adherence and oxidation resistance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01048641
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  • 78
    Digitale Medien
    Digitale Medien
    Acid-catalyzed formation of free radicals in the reaction of hydroperoxides with ketones (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 340-345 
    Details
    ISSN: 1573-9171
    Schlagwort(e): oxidation ; acid catalysis ; free radicals ; acetonitrile ; p-toluenesulfonic acid ; tert-butyl hydroperoxide ; cyclohexanone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of formation of free radicals in the cyclohexanone (CH)-tert-butylhydroperoxide (TBHP)-para-toluenesulfonic acid (PTSA) system in acetonitrile was studied. The stoichiometry of the reaction corresponds to the consumption of two TBHP molecules per ketone molecule, whereas the yield of free radicals is -20 % based on the TBHP reacted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01433968
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  • 79
    Digitale Medien
    Digitale Medien
    New heterocyclic system based on vinylsulfonylfluorobenzene and X-ray structural study of this compound (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 414-416 
    Details
    ISSN: 1573-9171
    Schlagwort(e): 1,2,4,5-tetrafluoro-3,6-bis(vinylthio)benzerne ; 1,2,4,5-tetrafluoro-3,6bis(vinylsulfonyl)benzene ; 5,6-difluorobenzo-[a,d]-bis(3,3′-dihydro-1,1′-sulfonylallyl-4,4′-perhydroazine) ; oxidation ; allylamine ; X-ray structural study
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Oxidation of 1,2,4,5-tetrafluoro-3,6-bus (vinylthio)benzene (1) affords 1,2,4,5-tetra fluoro3,6-bis(vinylsulfonyl)benzene (2) in 65 % yield. The reaction of compound 2 with allylamine gives a new heterocyclic compound, 5,6-difluorobenzo-[a,d]-bis(3,3′-dihydro-l,l′-sulfonylallyl-4,4′-perhydroazine) (3). This compound is the product of nucleophilic addition at the vinylsulfonyl group and intramolecular replacement of fluorine atoms of the benzene ring. The structure of compound 3 has been established by X-ray structural study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01433984
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  • 80
    Digitale Medien
    Digitale Medien
    The influence of low-temperature oxidation of active carbons by nitric acid on their physicochemical properties (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1071-1077 
    Details
    ISSN: 1573-9171
    Schlagwort(e): active carbons ; oxidation ; surface chemistry ; n-hexane ; water ; methanol ; adsorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The influence of oxidation by nitric acid on the character of oxygen-containing functional surface groups and porous structure of active carbons is considered. Adsorption properties of the initial and oxidized carbons are studied using adsorption isotherms of vapor of n-hexane and polar substances (water and methanol).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01431592
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  • 81
    Digitale Medien
    Digitale Medien
    Heat release kinetics in the reaction of decane with nitric acid (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1883-1888 
    Details
    ISSN: 1573-9171
    Schlagwort(e): decane ; nitric acid ; nitrogen dioxide ; oxidation ; kinetics ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of the reaction of decane with nitric acid (25.07–75.53 %) at 57.8 to 119 °C in an acid-decane-gas triphasic system was studied. The main contribution to the rate of heat release is made by the oxidation of decane with nitrogen dioxide in the organic phase proceedingvia the mechanism of a degenerate branched-chain reaction. Nitration plays the role of a chain termination reaction. The acid phase is the source of NO2, whose content increases with oxidation. The equilibrium of the nitrogen dioxide distribution in the triphasic system was analyzed. The kinetic law of the reaction, the dependences of the reaction constants of the initial and catalytic stages on temperature and the acid phase composition were determined. The results allow one to calculate the rate of heat release in the decane-HNO3 system under any conditions of the process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01457769
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  • 82
    Digitale Medien
    Digitale Medien
    Phenazinee di-N-oxide radical cation and its reactions with hydrocarbons (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1889-1895 
    Details
    ISSN: 1573-9171
    Schlagwort(e): phenazine di-N-oxide ; radical cation ; hydrocarbons ; oxidation ; mechanism ; O2 effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The absorption spectra of phenazine di-N-oxide radical cation (OPO+·) in dichloromethane were recorded by the spectroelectrochemical method in the range from 300 to 700 nm. The reactions of the electrochemically generated OPO+· withpara-substituted toluenes, ethylbenzene, and cumene were studied. Using differential cyclic voltammetry, relative rate constants of reactions of OPO+· with substrates were determined; their correlations with σ+ para constants of substituents gives p = -2.7, which attests to the nonradical character of the reaction of OPO+· with RH. This conclusion is confirmed by the study of the effect of O2 on oxidation of ethylbenzene and cumene.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01457770
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  • 83
    Digitale Medien
    Digitale Medien
    Interaction of diphenyl sulfide with sulfuryl chloride (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 2668-2669 
    Details
    ISSN: 1573-9171
    Schlagwort(e): diphenyl sulfide ; sulfuryl chloride ; oxidation ; chlorination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The reaction of diphenyl sulfide with sulfuryl chloride was studied. Depending on the reaction conditions, it occurs either as chlorination of the aromatic ring or as oxidation to give sulfoxide.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01431143
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  • 84
    Digitale Medien
    Digitale Medien
    Formation of isomeric iodohydrins from terminal alkenes upon oxidation by a RuCl3-NaIO4 system (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 2813-2815 
    Details
    ISSN: 1573-9171
    Schlagwort(e): alkenes ; catalysis ; oxidation ; iodohydrins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract RuCl3-catalyzed periodate oxidation of alkenes affords isomeric iodohydrins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01430649
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  • 85
    Digitale Medien
    Digitale Medien
    Oxidation of Human Insulin-Like Growth Factor I in Formulation Studies, II. Effects of Oxygen, Visible Light, and Phosphate on Methionine Oxidation in Aqueous Solution and Evaluation of Possible Mechanisms (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 1476-1481 
    Details
    ISSN: 1573-904X
    Schlagwort(e): sulfur ; protein ; oxidation ; chemometrics ; phosphate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The oxidation of methionine in human Insulin-like Growth Factor I (hIGF-I) in aqueous solution was studied with respect to oxygen, visible light and sodium phosphate. Methods. Aqueous solutions of hIGF-I were prepared with different amounts of phosphate and dissolved oxygen. The solutions were stored either in darkness or exposed to artificial visible light. The oxidized hIGF-I was quantified by RP-HPLC. A two level full factorial experimental design, with two levels of each of the three factors studied, was used. Results. Oxidation was found to be positively correlated with light, oxygen content and, interestingly, phosphate. The increasing effect of phosphate on the oxidation appears not to originate from metal contaminants. The influence of both oxygen and phosphate increased with time. The pH dependence of oxidation indicated the formation of a phosphorylated sulfonium ion as an oxidation intermediate. A significant interaction effect between phosphate and visible light suggested participation of radicals. Conclusions. Factorial experiments provide a valuable tool when studying complex mechanisms with interacting factors. The oxidation of methionine in hIGF-I is significantly affected by light but also by the presence of phosphate buffer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1016015226211
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  • 86
    Digitale Medien
    Digitale Medien
    Effects of Polyaminocarboxylate Metal Chelators on Iron-thiolate Induced Oxidation of Methionine- and Histidine-Containing Peptides (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 931-938 
    Details
    ISSN: 1573-904X
    Schlagwort(e): iron ; chelator ; oxidation ; methionine/histidine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. Site-specific protein oxidation induced by prooxidant/metal/ oxygen has been recognized as one of the major degradation pathways of protein pharmaceuticals. Polyaminocarboxylate (PAC) metal chelators are commonly employed to prevent metal-catalyzed oxidation, for they sequester metals. However, studies have indicated that iron chelates may still be catalytically active due to their specific coordination geometry. The purpose of this study was to investigate how PAC chelators affect prooxidant/metal/oxygen-catalyzed oxidation of peptides containing histidine (His) and methionine (Met). Methods. PACs were applied to a model oxidizing system, dithiothreitol/iron/oxygen, which was shown to promote the oxidation of Met to Met sulfoxide in the two model peptides, GGGMGGG and GHGMGGG. Results. PAC chelators did not suppress the peptide oxidation but significantly changed the product pattern. In particular, the yield of Met sulfoxide dropped significantly, while a number of other products emerged, including oxidation products from the N-terminus and His (if present). Overall, the oxidation became rather non-selective in the presence of PACs. The oxidation kinetics were significantly accelerated by nitrilotriacetate (NTA), ethylenediaminediacetate (HDDA), and ethylenediaminetetraacetate (EDTA), but they were slowed down by ethyl-enebis(oxyethylenenitrilo)tetraacetate (EGTA) and diethylenetriaminepentaacetate (DTPA). Meanwhile the PAC chelators were also observed to undergo degradation. Scavengers of hydrogen peroxide or hydroxyl radicals exerted only partial inhibition on the peptide oxidation. Conclusions. The results of this study are rationalized by the abilities of PAC chelators (i) to extract iron from potential binding sites of the peptides to impair site-specific oxidation, and (ii) to promote the formation of ROS different from the species formed at the peptide metal-binding sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1016021716274
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  • 87
    Digitale Medien
    Digitale Medien
    Oxidation of Human Insulin-like Growth Factor I in Formulation Studies: Kinetics of Methionine Oxidation in Aqueous Solution and in Solid State (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 1252-1257 
    Details
    ISSN: 1573-904X
    Schlagwort(e): hIGF-I ; oxidation ; methionine ; HPLC ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The aim of this work was to study the kinetics of oxidation of methionine in human Insulin-like Growth Factor I (hIGF-I)1 in aqueous solution and in the solid state by the aid of quantification of oxygen. Methods. The oxidized form of hIGF-I was characterized by tryptic peptide analysis, RP-HPLC and FAB-MS and quantified by RP-HPLC. The oxygen content was quantified polarographically by a Clark-type electrode. Results. Second-order kinetics with respect to amount of protein and dissolved oxygen was found to be appropriate for the oxidation of methionine in hIGF-I. The rate constants ranged from 1 to 280 M−1 month−l and had an activation energy of 95 (+/−4) kJ/mole. Light exposure, storage temperature and oxygen content were found to have a considerable impact on the oxidation rates. No significant difference in reaction rates was found for the oxidation of hIGF-I in aqueous solution or in the solid state. A method for decreasing the oxygen content in aqueous solution without purging is described. Conclusions. Polarographic quantification of dissolved oxygen makes it possible to establish the kinetics for oxidation of proteins. The oxidation of methionine in hIGF-I appears to follow second-order kinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1016032808039
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  • 88
    Digitale Medien
    Digitale Medien
    Nicanartine Improves in Vitro Resistance of Lipoproteins to Oxidation (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 457-461 
    Details
    ISSN: 1573-904X
    Schlagwort(e): nicanartine ; lipoprotein ; oxidation ; plasma binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The aim of this study is to investigate the plasma protein binding of nicanartine and to measure its antioxidant effect on lipoproteins. Methods. The blood binding was studied with an erythrocyte partitioning method and the lipoprotein oxidation with the conjugated dienes method. Results. Nicanartine was 24.7% LDL (low density lipoprotein)-bound and 29.2% AAG (alphal-acid glycoprotein)-bound. Nicanartine delayed but did not stop the oxidation of the three density classes of lipoprotein HDL (high density lipoprotein), LDL, VLDL (very low density lipoprotein). The addition of AAG to LDL in the conjugated dienes method decreased the nicanartine fraction bound to LDL and decreased its antioxidant effect. The decrease of nicanartine LDL-bound fraction and the decrease in antioxidant effect were not parallel. Conclusions. This suggested that (a) AAG-bound nicanartine dissociated to equilibrate the decrease in LDL-bound nicanartine consummed by oxidation, or (b) the oxidation conditions could involve chemical modifications of nicanartine and therefore modify its affinity for AAG.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1016013130445
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  • 89
    Digitale Medien
    Digitale Medien
    Characterization of a Solid State Reaction Product from a Lyophilized Formulation of a Cyclic Heptapeptide. A Novel Example of an Excipient-Induced Oxidation (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 1811-1814 
    Details
    ISSN: 1573-904X
    Schlagwort(e): peptide stability ; peptide formulation ; oxidation ; fibrinogen receptor antagonist ; mannitol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To elucidate the structure of a degradation product arising from a lyophilized formulation of a cyclic heptapeptide, and to provide a mechanism to account for its formation. Methods. Preparative HPLC was used to isolate the degradate in quantities sufficient for structural studies. A structure assignment was made on the basis of the compounds spectroscopic properties (UV, MS, NMR) and the results of amino acid analysis. Results. The degradate was identified as a benzaldehyde derivative arising from the oxidative deamination of an aminomethyl phenylalanine moiety. The extent of formation of this product is influenced by the amount of mannitol used as an excipient in the formulation. A mechanism is proposed whereby reducing sugar impurities in mannitol act as an oxidizing agent via the intermediacy of Schiff base adducts which subsequently undergo tautomerization and hydrolysis. Conclusions. Reducing sugar impurities in mannitol are responsible for the oxidative degradation of the peptide via a mechanism that involves Schiff base intermediates. This mechanism may be a potential route of degradation of other arylmethyl amines in mannitol-based formulations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1016024923002
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  • 90
    Digitale Medien
    Digitale Medien
    Oxidative Degradation of Antiflammin 2 (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 250-255 
    Details
    ISSN: 1573-904X
    Schlagwort(e): antiflammin 2 ; oxidation ; stability ; degradation ; HPLC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To study the oxidation of the methionine residue of antiflammin 2 (HDMNKVLDL, AF2) as a function of pH, buffer concentration, ionic strength, and temperature using different concentrations of hydrogen peroxide and to determine the accessibility of methionine residue to oxidation. Methods. Reversed-phase high-performance liquid chromatography (RPHPLC) was used as the main analytical method in determining the oxidation rates of AF2. Calibration curves for AF2 and the oxidation product, methionine sulfoxide of AF2 (Met(O)-3-AF2), were constructed for each measurement using standard materials. Fast Atom Bombardment Mass Spectroscopy (FABMS) was used to characterize the product. Results. Met(O)-3-AF2 was the only oxidation product detected at pH 3.0 to 8.0. The oxidation rates were independent of buffer concentrations, ionic strength, and pH from 3.0 to 7.0. However, there was an acceleration of the rates at basic pHs, and small amounts of degradation products other than Met(O)-3-AF2 were observed in this alkaline region. Conclusions. Oxidation of methionine in AF2 does not cause the biological inactivation reported by other laboratories since this drug is relatively stable under neutral conditions in the absence of oxiding agent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1016095131836
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  • 91
    Digitale Medien
    Digitale Medien
    Fish communities in the African Great Lakes (1996)
    Springer
    Environmental biology of fishes 45 (1996), S. 219-235 
    Details
    ISSN: 1573-5133
    Schlagwort(e): Ecology ; Behaviour ; Evolution ; Cichlids ; Fisheries ; Conservation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Ecological conditions in tropical lacustrine systems are considered by focusing on the evolution, maintenance, exploitation and vulnerability of fish communities in the African Great Lakes. The exceptionally high biodiversities in the littoral/sublittoral zones of the very ancient, deep, clear, permanently stratified rift lakes Tanganyika and Malawi, are contrasted with the simpler systems in their pelagic zones, also with biodiversity in the much younger, shallower Victoria, the world's largest tropical lake.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00003090
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  • 92
    Digitale Medien
    Digitale Medien
    Stability of a molybdena-silica catalyst enhanced by water in formaldehyde oxidation (1996)
    Springer
    Reaction kinetics and catalysis letters 58 (1996), S. 323-328 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Formaldehyde ; oxidation ; molybdena ; methanol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A molybdena-silica catalyst showed rapid deactivation in the oxidation of formaldehyde to carbon oxides. The deactivation was greatly retarded by adding water in the feed. Thus, water coproduced in the partial oxidation of methanol to formaldehyde contributes to the relatively stable activity of the molybdena-silica catalyst in the partial oxidation reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02067040
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  • 93
    Digitale Medien
    Digitale Medien
    Oxidative dehydrogenation of propane (1996)
    Springer
    Reaction kinetics and catalysis letters 57 (1996), S. 3-11 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Dehydrogenation ; oxidation ; propane ; propylene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract At temperatures near 650°C and residence times ofca. 3 s, the homogeneous oxidative dehydrogenation (OXD) of propane to propylene and ethylene approached oxygen limiting conditions, even when the reactor was filled with quartz chips. The addition of catalysts that are known to be effective in the OXD of ethane slightly increased the reaction rate, but the selectivities at a given conversion level were the same as those that were achieved in the homogeneous reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02076113
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  • 94
    Digitale Medien
    Digitale Medien
    Fundamental studies on the development of lignin-based adhesives, I. Catalytic demethylation of anisole with molecular oxygen (1996)
    Springer
    Reaction kinetics and catalysis letters 58 (1996), S. 237-242 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Iron porphyrin catalyst ; oxidation ; lignin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In the presence of a catalyst consisting of metal-porphyrin complex and a reductant, anisole was converted into phenol by molecular oxygen at room temperature with a total turnover of the catalyst of about 70 times in 24 h.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02067028
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  • 95
    Digitale Medien
    Digitale Medien
    Reassessment of the roles of the peritrophic envelope and hydrolysis in protecting polyphagous grasshoppers from ingested hydrolyzable tannins (1996)
    Springer
    Journal of chemical ecology 22 (1996), S. 1901-1919 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Orthoptera ; Acrididae ; grasshopper ; Melanoplus sanguinipes ; Phoetaliotes nebrascensis ; peritrophic envelope ; peritrophic membrane ; hydrolyzable tannin ; tannic acid ; oxidation ; hydrolysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We examined several of the mechanisms that have been reported to enable polyphagous grasshoppers (Orthoptera: Acrididae) to tolerate ingested hydrolyzable tannins: hydrolysis, adsorption on the peritrophic envelope, and peritrophic envelope impermeability. None of these mechanisms explain the tolerance ofMelanoplus sanguinipes to ingested tannic acid. In this species, tannin hydrolysis was 12–47% complete, adsorption accounted for less than 1% of the tannic acid contained in the midgut, and the peritrophic envelope was permeated by several gallotannins. The foregut is the main site for the chemical transformation of tannic acid in this species. InPhoetaliotes nebrascensis, hydrolysis was more extensive (82% complete), but the peritrophic envelope was readily permeated by two gallotannins. Oxidizing redox conditions were found in the guts of both species, and ingested tannins were oxidized inM. sanguinipes. We hypothesize that the tolerance of some polyphagous grasshoppers to ingested hydrolyzable tannins may be the consequence of their ability to tolerate the reactive oxygen species generated by polyphenol oxidation, whereas others may rely on rapid and extensive hydrolysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02028511
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  • 96
    Digitale Medien
    Digitale Medien
    The interaction of biliar acids with 2-hydroxypropyl-β-cyclodextrin in solution and in the solid state (1996)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 26 (1996), S. 233-241 
    Details
    ISSN: 1573-1111
    Schlagwort(e): Biliar acid ; 2-hydroxypropyl-β-cyclodextrin ; interaction studies ; IR ; NMR ; DSC ; XRD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The interaction of two biliar acids (chenodeoxycholic acid and cholic acid) with 2-hydroxypropyl-β-cyclodextrin (HPβCD) in solution and in the solid state was studied using different techniques. The formation of an inclusion complex with a 1:1 stoichiometry was suggested by the phase solubility studies. Both differential scanning calorimetry and X-ray diffractometry exhibited the amorphous state of the complex. The inclusion of both biliar acids into the HPβCD cavity was confirmed by the13C-NMR studies. Cholic acid showed a weaker affinity with respect to chenodeoxycholic acid probably owing to the presence of a hydroxyl group onC(12) (12α) close to the complexation site.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01053541
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  • 97
    Digitale Medien
    Digitale Medien
    Organofluorine sulfur-containing compounds (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 153-155 
    Details
    ISSN: 1573-9171
    Schlagwort(e): polyfluorinated thiophenols ; difluorochloromethane ; reactions ; aryldifluoromethyl sulfides ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Polyfluorinated aryldifluoromethyl sulfides have been obtained by treatment of polyfluorinated 4-X-substituted thiophenols with chlorodifluoromethane in an alkaline medium. Reactions of difluoromethylpentafluorophenyl sulfide with H2O2, KMnO4, and HNO3, giving the corresponding sulfoxide and sulfone, were studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01433751
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  • 98
    Digitale Medien
    Digitale Medien
    Study of cool-Dame phenomena during self-ignition of methane-oxygen mixtures (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 2316-2320 
    Details
    ISSN: 1573-9171
    Schlagwort(e): methane ; oxidation ; cool names ; kinetic simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Experimental studies and kinetic simulation have shown that the formation of cool flames is as typical of oxidation of methane as of oxidation of its homologs. Phenomena peculiar to the cool-flame processes in closed systems are observed, namely, the region of a negative temperature coefficient of the reaction, single and double cool-flame flashes, two stage ignition, and light radiation in the range of luminescence of formaldehyde.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01435374
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  • 99
    Digitale Medien
    Digitale Medien
    Oxidation by a “H2O2-vanadium complex-pyrazine-2-carboxylic acid” reagent (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 2386-2388 
    Details
    ISSN: 1573-9171
    Schlagwort(e): metal complex catalysis ; oxidation ; hydrogen peroxide ; vanadium complexes ; alkanes ; activation of the C-H bond
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Lower alkanes (ethane, propane,n-butane,n-pentane) are readily oxidized in acetonitrile solvent by H2O2 with vanadate anion — pyrazine-2-carboxylic acid (PCA), as the catalyst at 75 °C and pressures of −3 atm to produce predominantly or exclusively ketones (aldehydes). Isobutane is transformed selectively intotert-butyl alcohol. The oxidation of cyclohexane at 26 °C in acetone or acetic acid is less efficient than in acetonitrile. The reaction does not occur intert-butyl alcohol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01435388
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