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  • Artikel  (34)
  • Nitrogen fixation
  • kinetics
  • Springer  (24)
  • Wiley-Blackwell  (10)
  • 1995-1999  (34)
  • Maschinenbau  (34)
  • 1
    Digitale Medien
    Digitale Medien
    Degradation of Cellulosic Materials Under the Alkaline Conditions of a Cementitious Repository for Low- and Intermediate-Level Radioactive Waste. II. Degradation Kinetics (1999)
    Springer
    Journal of polymers and the environment 7 (1999), S. 41-51 
    Details
    ISSN: 1572-8900
    Schlagwort(e): Cellulose ; alkaline degradation ; peeling off ; degree of polymerization ; kinetics ; (gluco)isosaccharinic acid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik , Maschinenbau
    Notizen: Abstract The degradation of cellulosic materials, differing mainly in the degree of polymerization and the number of reducing end groups, was studied under the alkaline conditions similar to those existing in a cementitious repository for low- and intermediate-level radioactive waste (pH 13.3, T = 25°C). The kinetics of alkaline degradation (peeling-off reaction) were studied and the data analyzed by the model of Haas et al. [13]. The observed kinetic parameters for the propagation reaction and overall stopping reaction were compared with literature data. Although measured under different experimental conditions, literature data and data from this study show a consistent picture. Differences in the extent of degradation observed for the different cellulosic materials could be satisfactorily explained by differences in reducing end group content and, consequently, by differences in the degrees of polymerization. Besides the number of reducing end groups, the degree of amorphousness also plays an important role. The main degradation products formed under the experimental conditions used are α- and β-(gluco)isosaccharinic acid. This is in agreement with many other studies on alkaline degradation of cellulose. The two isomers are formed in roughly equal amounts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021894102937
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  • 2
    Digitale Medien
    Digitale Medien
    Tetrachlorosilane Consumption in Radio Frequency Glow Discharge (1998)
    Springer
    Plasma chemistry and plasma processing 18 (1998), S. 509-533 
    Details
    ISSN: 1572-8986
    Schlagwort(e): RF SiCl4 discharge ; mass spectrometry ; kinetics ; decomposition ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Time-resolved mass spectrometry was used for analysis of the plasma reactions in radio frequency (RF) SiCl 4 and SiCl 4 −O 2 discharges as functions of starting partial pressure and electrical power. Molecular concentrations of the reactants and products from SiCl 4 alone and with O 2 were obtained from the mass spectra and used for plotting the kinetic curves. The SiCl 4 and O 2 consumption rates were calculated from the kinetic curves and compared with results of theoretical simulation of the reaction. Direct electron impact decomposition was found to be the main pathway for pure SiCl 4 conversion. On the contrary, the consumption of SiCl 4 in the SiCl 4 +O 2 mixtures was largely chemical. The experimental macrokinetics are in agreement with a model in which oxidation is caused by the atomic oxygen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021811316740
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  • 3
    Digitale Medien
    Digitale Medien
    Investigation of the Chemical Action of the Gliding and “Point” Arcs Between the Metallic Electrode and Aqueous Solution (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 53-67 
    Details
    ISSN: 1572-8986
    Schlagwort(e): Arc ; gliding arc ; gas temperature ; electron temperature ; ion composition ; ion bombardment ; liquid electrode ; dye oxidation ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract The plasma–solution interaction processes for gliding and “point” arcs between the aqueous solution surface and the metal electrode in the gas phase are studied. The plasma, liquid, and surface zones are taken into consideration. The electric field strength is measured, and the gas and electron temperatures and ion composition are estimated for the plasma zone. The cathode fall, water vaporization rate, and active species current yield due to the radiation chemistry mechanism are determined for the surface zone. The efficiency of oxidation of iodine ions and organic dyes by different types of discharge in the liquid zone are investigated. The difference in action of the various discharge types may be connected with various influences of the plasma and surface zone on the oxidation processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021803932496
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  • 4
    Digitale Medien
    Digitale Medien
    Kinetics of Solid State Reactions With Fractal Reagent (1998)
    Springer
    Journal of materials synthesis and processing 6 (1998), S. 305-309 
    Details
    ISSN: 1573-4870
    Schlagwort(e): Fractals ; solid state reaction ; kinetics ; nucleation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In the present research we theoretically studied the kinetics of nucleation-limited solid state reactions as influenced by the fractal properties of solid reagent. We consider the model of equal-sized primary particles assembled in fractal cluster. The geometry of such an object is assumed to be described solely by its fractal dimension D and by upper (R max) and lower (R min) cutoffs of fractality further identified with the overall size of the object and the size of the primary particle correspondingly. Depending on the ratio between R max, R min and the radius of the critical nucleus R nucl the following cases are considered: (1) R max ∼ R nucl. In this case the reaction kinetics is described by the equation: α = 1 − B{ln(k′ τ + 1)}D/(D−3), where B, k′ are constants. Numerical solution of this equation gives rise to n-order reaction kinetics with n & 1. (2) R min ≪ R nucl ≪ R max. In this case under certain conditions there can exist non-trivial critical density ρcrit ≠ 0, 1 that favors the formation of the critical nuclei of the new phase. The asymptotic kinetic equation for large times corresponds to n-order reaction with n = (D + 3)/(D + 1). (3) R min ≪ R nucl ∼ R max′. In this case the reaction follows the first-order kinetics with D-dependent rate constant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022643008915
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  • 5
    Digitale Medien
    Digitale Medien
    Oxidation behavior of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy at high temperature in Ar-H2O atmospheres (1997)
    Springer
    Oxidation of metals 47 (1997), S. 411-426 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Incoloy 909 ; superalloy ; scale ; high temperature ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy (Incoloy 909 type alloy), was investigated at temperatures between 1000 K and 1400 K in Ar-(1, 10%)H20 atmosphere using metallographic, electron probe microanalysis, and X-ray diffraction techniques. The oxide scales consist of an external scale and an internal scale which has an intergranular scale (above 1200 K) and an intergranular scale. The oxide phases in each scale are identified asα-Fe2,O3 (below 1200 K) or FeO (above 1300 K) and CoO · Fe2O3 and FeO · Nb2O5, respectively. The morphologies, the oxide phases and the oxidation rates do not depend on the partial pressure of H2O in the range between one and ten percent in Ar gas. The rate constants for the intergranular-scale formation in this alloy are about one-tenth as large as those in Fe-36%Ni alloy reported previously. At all the temperatures the scales grow according to a parabolic rate law and the apparent activation energies for the processes are estimated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02134784
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  • 6
    Digitale Medien
    Digitale Medien
    On the oxidation ofα-Fe andε-Fe2N1−z : I. Oxidation kinetics and microstructural evolution of the oxide and nitride layers (1997)
    Springer
    Oxidation of metals 48 (1997), S. 87-109 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; kinetics ; iron ; iron-nitride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of α-Fe and ɛ-Fe2N1−z at 573 K and 673 K in O2 at 1 atm was investigated by thermogravimetrical analysis, X-ray diffraction, light-optical microscopy, scanning electron microscopy and electron probe X-ray microanalysis. Upon oxidation at 573 K and 673 K, on α-Fe initially α-Fe2O3 develops, whereas on ɛ-Fe2N1−z initially Fe3O4 develops. In an early stage of oxidation the oxidation rate of ɛ-Fe2N1−z appears to be much larger than of α-Fe. This can be attributed largely to an effective surface area available for oxygen uptake, which is much larger for ɛ-Fe2N1−z than for α-Fe due to the porous structure of ɛ-Fe2N1−z as prepared by gaseous nitriding of iron. The development of a magnetite layer in-between the hematite layer and the α-Fe substrate, at a later stage of oxidation, enhances layer-growth kinetics. After 100 min oxidation at 673 K the (parabolic) oxidation rates for α-Fe and ɛ-Fe2N1−z become about equal, indicating that on both substrates the oxide growth is controlled by the same rate limiting step which is attributed to short-circuit diffusion of iron cations. Oxidizing ɛ-Fe2N1−z increases the nitrogen concentration in the remaining ɛ-iron nitride, because the outward flux of iron cations, necessary for oxide growth, leads to an accumulation of nitrogen atoms left behind.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01675263
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  • 7
    Digitale Medien
    Digitale Medien
    Scale formation on γ-TiAl during oxidation at 800 and 900°C in air and in He + 20% O2 (1997)
    Springer
    Oxidation of metals 48 (1997), S. 171-184 
    Details
    ISSN: 1573-4889
    Schlagwort(e): TiAl, corrosion ; high-temperature ; kinetics ; nitrogen dependence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxide scale formation on γ-TiAl at 800 and 900°C was studied using high temperature X-ray diffraction as anin situ-method. The experiments were performed in air and in He with 20 vol.% O2. The formation of alumina in the form of α-Al2O3 and of TiO2 in the form of rutile was observed in both atmospheres and the formation of TiN was detected in air. Depending on the atmosphere the diffraction peaks of two different additional phases were detected, which do not exist in any data base nor in the Ti-Al-O phase diagram. One of them, the Z-phase, appears in He with 20 vol.% O2 and the other, the X-phase, in air. The Zphase was also found at room temperature after oxidation at 900°C in air. The growth of both phases, X and Z, starts immediately with the oxidation process and follows the parabolic rate law.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01675267
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  • 8
    Digitale Medien
    Digitale Medien
    High-temperature oxidation of pure titanium in CO2 and Ar-10%CO2 atmospheres (1997)
    Springer
    Oxidation of metals 48 (1997), S. 289-302 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; titanium ; rutile ; scale ; high temperature ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO2 or Ar-10%CO2. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO2) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01670504
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  • 9
    Digitale Medien
    Digitale Medien
    The Kinetics of Pore Shape Evolution in Alumina (1998)
    Springer
    Journal of materials synthesis and processing 6 (1998), S. 161-167 
    Details
    ISSN: 1573-4870
    Schlagwort(e): Alumina ; surface ; kinetics ; diffusion ; SALK
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The kinetics of shape evolution of a completely faceted crystal/internal void by surface diffusion was modeled. Arrays of micron-sized cavities were generated in sapphire substrates with known surface orientations using microlithography and ion beam etching and converted to internal intragranular pores of nonequilibrium shape by diffusion bonding of the etched substrate to an identical-orientation unetched sapphire substrate. Pore shape evolution rates during high-temperature anneals were monitored and found to be highly sensitive to the orientation of the substrate surface. The observed evolution rates were compared with the predictions of the kinetic model using diffusivity values for alumina that span the range from the highest to the lowest diffusion constants reported in the literature. The comparison suggests that surface-attachment-limited kinetics (SALK) play a major role in surface mass transport on stable low-index planes of alumina.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022665418505
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  • 10
    Digitale Medien
    Digitale Medien
    High-temperature oxidation of tantalum of different purity (1995)
    Springer
    Oxidation of metals 43 (1995), S. 509-526 
    Details
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; kinetics ; tantalum ; oxide ; suboxide ; impurities ; diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The kinetics, structural aspects, and phase morphologies were studied for tantalum oxidation in air from 600 to 1000°C for samples of different purity (99.15%, 99.76%, and 99.95% Ta). Regardless of purity, tantalum oxidation in the temperature range of 600–800°C as a rule is governed by a linear rate law. From 900 to 1000°C the initial-stage oxidation is governed by the parabolic rate law, which changes to the linear rate law with time. TGA, XRD, SEM, and AES methods were used. The, effect of purity on tantalum oxidation was shown to be determined by the mechanism of intermediate-oxide formation. They are TaO z (Ta2O) at 600–800°C and TaO at 900–1000°C. The final product of oxidation was β-Ta2O5.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046896
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  • 11
    Digitale Medien
    Digitale Medien
    Sulfidation behavior of a ferritic commercial alloy in different sulfidizing environments at high temperature (1995)
    Springer
    Oxidation of metals 43 (1995), S. 543-560 
    Details
    ISSN: 1573-4889
    Schlagwort(e): stainless steel ; sulfidation ; hydrogen sulfide ; sulfur vapor ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The sulfidizing behavior of Fe−22Cr−4Al−0.15Zr (wt.%) was studied in two atmospheres: S2 vapor over the range 4.4–25.4 Pa and H2−H2S mixtures corresponding to aP S 2 range 0.2–1.297 Pa in the temperature range 973–1373 K. It was found that the constitution of the gaseous phase is of great importance on the corrosion kinetics and the morphology of the corrosion products. Furthermore, a stratification phenomenon during scale growth was observed during the initial sulfidation stage in H2−H2S mixtures containing a sufficiently high H2S partial pressure. This behavior was not observed during tests in puresulfur vapor.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046898
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  • 12
    Digitale Medien
    Digitale Medien
    Role of interface structure and interfacial defects in oxide scale growth (1995)
    Springer
    Oxidation of metals 44 (1995), S. 63-79 
    Details
    ISSN: 1573-4889
    Schlagwort(e): scale growth ; oxidation mechanism ; kinetics ; scale adherence ; reactive element effect ; intertacial segregation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Recent studies of the structure and dynamics of solid-solid interfaces have provided some understanding about the role of the scale-metal interface in the growth of reaction product scales on pure metals. The action of interfacial defects (misfit dislocations, misorientation dislocations and disconnections) in the creation and annihilation of the point defects suporting the diffusional growth of scales is considered. Anion point defects (vacancies/interstitials) supporting scale growth by anion diffusion are annihilated/created by the climb of misorientation dislocations or disconnections in the scale at the interface. For scale growth by cation diffusion, cation point defects (vacancies/interstitials) can be annihilated/created by the climb of interfacial misfit or misorientation dislocations in the metal. Because of their necessarily high density, in most cases, the dominant climb of misfit dislocations would be favored. The blocking of interfacial reaction steps can be a means to retard the scaling kinetics and to alter the fundamental scaling mode. For instance, the interfacial segregation of large reactive element ions can pin the interface dislocations, an action which poisons the usual interfacial reaction step. Such considerations are consistent with the well-known phenomena ascribed to the reactive element effect (REE).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01046723
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  • 13
    Digitale Medien
    Digitale Medien
    An approximate treatment of the transient state in the corrosion of binary alloys forming the most-stable oxide. Part I: Solid-solution alloys (1997)
    Springer
    Oxidation of metals 47 (1997), S. 91-115 
    Details
    ISSN: 1573-4889
    Schlagwort(e): binary alloys ; oxidation ; transient state ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The initial transient stage in the oxidation of binary alloys forming scales exclusively composed of the most stable oxide is examined by means of a simplified approach which avoids the numerical integration of the diffusion equation for the transport of the metal components in the alloy. At variance with previous solutions to this problem obtained by means of numerical methods, this treatment takes into account also the effect of the gas-scale reaction at the outer surface of the oxide. The concentration of the most-reactive component at the alloy surface changes gradually with time from the initial bulk value towards the corresponding steady-state value without involving any minimum, while the overall rate of the reaction presents a gradual transition from an initial nearly linear towards final parabolic behavior.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01682373
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  • 14
    Digitale Medien
    Digitale Medien
    Global view of microstructural evolution: Energetics, kinetics and dynamical systems (1996)
    Springer
    Acta mechanica Sinica 12 (1996), S. 144-157 
    Details
    ISSN: 1614-3116
    Schlagwort(e): microstructural evolution ; energetics ; kinetics ; dynamic system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract An evolving material structure is in a non-equilibrium state, with free energy expressed by the generalized coordinates. A global approach leads to robust computations for the generalized thermodynamic forces. Those forces drive various kinetic processes, causing dissipation at spots, along curves, surfaces and interfaces, and within volumetric regions. The actual evolution path, and therefore the final equilibrium state, is determined by the energetics and kinetics. A virtual work principle links the free energy landscape and the kinetic processes, and assigns a viscous environment to every point on the landscape. The approach leads to a dynamical system that governs the evolution of generalized coordinates. The microstructural evolution is globally characterized by a basin map in the coordinate space; and by a diversity map and a variety map in the parameter space. The control of basin boundaries raises the issue of energetic and kinetic bifurcations. The variation of basin boundaries under different sets of controlling parameters provides an analytical way to plot the diversity maps of structural evolution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02486793
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  • 15
    Digitale Medien
    Digitale Medien
    Kinetics of vesicle formation (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 303-306 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words Vesicle ; self-assembly ; hydrotrope ; stopped-flow ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  The kinetics of vesicle formation from a hydrotrope (sodium xylenesulfonate) solution of a surfactant (Laureth 4) is studied by the use of a stopped-flow apparatus combined with a dynamic light scattering device to determine vesicle size in the system. The hydrotrope system studied presents a system with a high surfactant solubilization combined with vesicle formation simply by dilution with water. The kinetic results show a single exponential decay time. The kinetic analysis indicates that the vesicles are formed from a molecular solution which resulted from the shear in the stopped-flow device and grow by monomeric association.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050086
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  • 16
    Digitale Medien
    Digitale Medien
    Kinetics of interaction of 3-aminopropyltriethoxysilane with silica gel using elemental analysis and 29Si NMR spectra (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 672-680 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words 3-aminopropyltriethoxy silane ; silica gel ; interaction ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  Three silica gel sample systems, modified with 3-amino-propyltriethoxy silane (APTS), were prepared by sequentially sampling the reaction mixture at various time intervals. The concentrations of 3-aminopropylsilyl groups (APS) bound on the silica surface were determined by elemental analysis. For the same sample systems, 29Si NMR intensities of an (–O)4Si species belonging only to the silica gel particles and corrected by a cross-polarization correction factor were also measured. Both the APS-concentrations and the correc-ted 29Si NMR intensities depended upon reaction time, reflecting the rate of the APTS–silica gel reaction. Kinetic analysis of these data was made by use of the Gauss–Newton method, and the overall reaction was found to consist of three reaction processes (an initial fast reaction, a slower second reaction and a much slower third reaction). In particular, the conversion of (–O)3SiOH to (–O)4Si is predominant in the second reaction process and the pore size of a silica gel particle affects the reaction mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050134
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  • 17
    Digitale Medien
    Digitale Medien
    Dielectric method for detection of phase separation and its kinetics in TMPC/PS blends (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 524-532 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Blends ; tetramethyl polycarbonate ; polystyrene ; LCST ; phase separation ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract A new method for the detection of phase separation and its kinetics through real-time measurements is presented using the dielectric technique. The kinetics of phase separation were determined for a blend of tetramethyl bisphenol-A polycarbonate TMPC and polystyrene PS at different temperatures. The temperature dependence of the rate constant of phase separation was determined. The activation energy of phase separation process is found to be equal to 46 kcal/mole. In addition, it was possible to determine the variation in the composition of the TMPC-rich phase with time. The results obtained were compared with the literature data and were found to be in good agreement.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00658681
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  • 18
    Digitale Medien
    Digitale Medien
    Dynamic measurements of adsorption of hydrolyzed polyacrylamide (HPAM) onto hematite (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 1028-1032 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Hydrolyzed polyacrylamide ; hematite ; adsorption ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The adsorption measurements of hydrolyzed polyacrylamide (HPAM) onto hematite suspension are carried out to study the dynamics of the polymer adsorption onto the suspension particles and to investigate the mode of the polymer adsorption. The polymer is found to show much affinity for the adsorption because of the opposite charges possessed by the polymeric flocculant and the suspension particles. Various adsorption parameters such as adsorption coefficient, the rate constants for the adsorption and desorption, are evaluated with the help of a recently proposed kinetic scheme. It is found that the extent of adsorption and the adsorption rate are adequately affected by increasing the pH of the suspension while, unexpectedly, the adsorption is found to show only a marginal increase on addition of Na2SO4. Both the amount of the adsorbed polymer and the adsorption rate are also found to increase with the degree of hydrolysis of the polyelectrolyte.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00657669
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  • 19
    Digitale Medien
    Digitale Medien
    Solute segregation at grain boundaries (1996)
    Springer
    Interface science 3 (1996), S. 241-267 
    Details
    ISSN: 1573-2746
    Schlagwort(e): grain boundary segregation ; grain boundary cohesion ; fracture ; kinetics ; equilibrium ; anisotropy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract This feature article summarizes the present art and science of grain boundary segregation from the viewpoint of the authors activities in this field. In the part on equilibrium segregation, fundamental effects on grain boundary segregation are discussed such as the nature of the solute/matrix binary system, presence of additional elements, temperature, grain boundary orientation and type of interface. In addition, the predictive capabilities of grain boundary segregation diagrams are outlined. The present models of segregation kinetics are reviewed and discussed in connection with recent experiments. The last part of the paper is focussed on the most important consequences of grain boundary segregation, i.e., grain boundary cohesion and fracture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00194704
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  • 20
    Digitale Medien
    Digitale Medien
    Grain Boundary Migration in Solid State Discontinuous Reactions (1998)
    Springer
    Interface science 6 (1998), S. 113-131 
    Details
    ISSN: 1573-2746
    Schlagwort(e): discontinuous reactions ; discontinuous precipitation ; discontinuous coarsening ; discontinuous dissolution ; grain boundary ; migration ; diffusion ; kinetics ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract Discontinuous reactions are a special class of solid state moving boundary reactions characterized by a discontinuous change in orientation and composition across the migrating reaction front that provides a short circuit path of solute transport. Grain boundary migration in discontinuous reactions is both of technological as well as fundamental interest. In this paper, the initiation/growth mechanism, product morphology, driving force, reaction kinetics, and effect of external parameters on the major discontinuous reactions, namely, discontinuous precipitation, coarsening, dissolution, and diffusion induced grain boundary migration have been discussed. In addition, a number of interesting features about boundary migration in discontinuous reactions has been analyzed. Finally, the scope and necessity of continued research attention in this area have been highlighted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008672705642
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  • 21
    Digitale Medien
    Digitale Medien
    The Compensation Effect in Thermally Activated Interface Processes (1998)
    Springer
    Interface science 6 (1998), S. 267-278 
    Details
    ISSN: 1573-2746
    Schlagwort(e): grain boundaries ; kinetics ; thermal activation ; activation entropy ; activation enthalpy ; compensation effect ; interfaces
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract Extensive experimental evidence is provided for the occurrence of the compensation effect, i.e., the linear dependence of the activation energy on the logarithm of the preexponential factor in interface kinetics, primarily grain boundary migration. It is proposed to attribute the compensation effect to a first order phase transition from the ground state to the activated state during thermal activation. The model is in line with the thermodynamic principles of phase transitions as well as the fundamentals of irreversible thermodynamics. It is capable of accounting for important phenomenological relations of interface kinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008649619917
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  • 22
    Digitale Medien
    Digitale Medien
    Viscosity of Strain Gradient Effects on the Kinetics of Propagating Phase Boundaries in Solids (1997)
    Springer
    Journal of elasticity 46 (1997), S. 53-90 
    Details
    ISSN: 1573-2681
    Schlagwort(e): phase transitions ; kinetics ; traveling waves
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The theory of thermoelastic materials undergoing solid-solid phase transformations requires constitutive information that governs the evolution of a phase boundary. This is known as a kinetic relation which relates a driving traction to the speed of propagation of a phase boundary. The kinetic relation is prescribed in the theory from the onset. Here, though, a special kinetic relation is derived from an augmented theory that includes viscous, strain gradient and heat conduction effects. Based on a special class of solutions, namely travelling waves, the kinetic relation is inherited from the augmented theory as the viscosity, strain gradient and heat conductivity are removed by a suitable limit process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007311302438
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  • 23
    Digitale Medien
    Digitale Medien
    A consideration of curved interfaces in stress-assisted martensite formation (1996)
    Springer
    Journal of elasticity 44 (1996), S. 271-284 
    Details
    ISSN: 1573-2681
    Schlagwort(e): martensite ; kinetics ; driving traction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A purely mechanical, sharp interface model is developed to consider curved interfaces that have been observed between martensite phase variants. The approach is based on a theory of small strains as distinct from small displacement gradients. It admits a realistic characterization of each phase with standard elasticity tensors and allows for inhomogeneous states of strain within each phase including inhomogeneous, finite rotations. The model indicates that any signficant interface curvature must be due to material rotation because interfaces cannot be finitely curved with respect to the material lattice. It is also found that the interface driving traction is not influenced by local lattice rotations unless inertia affects the reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00042136
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  • 24
    Digitale Medien
    Digitale Medien
    Structure‐dependent viscoelastic properties of C9〉‐alkanethiol monolayers (1999)
    Springer
    Tribology letters 7 (1999), S. 67-71 
    Details
    ISSN: 1573-2711
    Schlagwort(e): alkanethiol ; self‐assembled monolayers ; quartz crystal microbalance ; viscoelasticity ; kinetics ; ellipsometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Quartz crystal microbalance techniques and in situ spectroscopic ellipsometry are used to probe the structure‐dependent intrinsic viscoelastic properties of self‐assembled CH3(CH2)8SH alkanethiol monolayers adsorbed from the gas phase onto Au(111)‐textured substrates. Physisorbed molecules, mixed chemisorbed‐fluid/solid phases and solid‐phase domain boundaries make sequentially dominant contributions to the measured energy dissipation in the growing monolayer. Deviations from Langmuir adsorption kinetics reveal a precursor‐mediated adsorption channel. These studies reveal the impact of structural heterogeneity in tribological studies of monolayer lubricants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019117319559
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  • 25
    Digitale Medien
    Digitale Medien
    Curing of novolac-lignocellulosic composites (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 183-189 
    Details
    ISSN: 0959-8103
    Schlagwort(e): curing ; DSC ; FTIR ; kinetics ; novolac ; lignocellulosic materials ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Novalac resin (N) with hexamethylenetetramine (HTA) was cured with biomass (B) or Kraft lignin (KL) or hydroxymethylated Kraft lignin (KLH) or cellulose (CEL). The agricultural/industrial by-product of olive stones was used as biomass. Kraft lignin, hydroxymethylated Kraft lignin and cellulose were isolated from the biomass. The cure was followed by DSC and IR spectroscopy. Based on the IR spectra of cured materials and their characteristic bands, the proportion of N/B = 50/50 was chosen for the preparation of novolac mixtures with other components. Only N-KLH exhibited values of ΔH higher than ΔHm, calculated from the law of mixtures, indicating that KLH participates in the cure reaction. The kinetic parameters E and K0 of the total cure reactions, calculated by DSC scans, increased in the order N 〈 N-KLH 〈 N-B 〈 N-KL 〈 N-CEL. The incorporation of KLH in the mass of N-HTA led to a slight increase in E and k0. On the other hand, KL, CEL and B acted as diluents in the mass of novolac. Generally, the cure of all materials was a first order reaction, indicating that the cure mechanism of novolac remains the same.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1995.210380211
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  • 26
    Digitale Medien
    Digitale Medien
    Mechanism of nickel catalysed dehalogenative step polymerization of aryl dibromidesPresented at ‘MacroAkron '94, 35th IUPAC Symposium on Macromolecules’, Akron, Ohio, 11-15 July 1994. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 37 (1995), S. 171-177 
    Details
    ISSN: 0959-8103
    Schlagwort(e): dehalogenative step polymerization ; nickel catalyst ; kinetics ; reaction mechanism ; poly(N-alkylcarbazolylene)s ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Dehalogenative polycondensation of 3,6-dibromo-N-alkylcarbazoles was catalysed by a Ni(O)-based complex generated in N,N-dimethylacetamide by electroreduction of NiBr2/2,2′-bipyridine. The process involves three different reaction steps, which are successively: electrolysis of Ni(II) to Ni(O); insertion of the latter into a C—Br bond of monomer leading to C—Ni—Br* active species; dehalogenative coupling between active species and monomer yielding oligomers. From the kinetics of electrogeneration of the catalytic system in absence of monomer, a first-order reaction was determined. Insertion and coupling reactions were found to be second-order and comparison of the values of the corresponding rate constants clearly showed that coupling is the rate-determining step of the process. Simultaneous size exclusion chromatography and cyclic voltammetry measurements were carried out in the course of the electrosynthesis of poly(N-alkylcarbazole)s. The change in the molar mass population distribution as a function of electrolysis time revealed a step polymerization process, while showing a termination of the chain growth due to the occurrence of monobrominated species. The study of the effect of the [monomer]/[catalyst] ratio on the molar mass population change indicated that the coupling of active species (Ni(O)-activated monomer) is responsible for the chain growth.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1995.210370304
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  • 27
    Digitale Medien
    Digitale Medien
    p-acetyl benzylidene triphenylarsonium ylide initiated radical terpolymerization of styrene, acrylonitrile and copper acrylate: synthesis, characterization and properties (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 41 (1996), S. 407-412 
    Details
    ISSN: 0959-8103
    Schlagwort(e): terpolymerization ; kinetics ; thermal properties ; arsonium ylide ; styrene ; acrylonitrile ; copper acrylate ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Solution terpolymerization of styrene (Sty), acrylonitrile (AN) and copper acrylate (CuA) has been carried out in dimethylformamide at 90°C for 4 h using p-acetyl benzylidene triphenylarsonium ylide as radical initiator. 1H nuclear magnetic resonance (NMR), IR and elemental analysis have been used to characterized the terpolymer. Analysis of kinetic data indicates the following rate equation: $$R_{\rm p} \propto \left[ {{\rm ylide}} \right]^{0.5} \left[ {{\rm Sty}} \right]\left[ {{\rm AN}} \right]{1 \over {\left[ {{\rm CuA}} \right]}}$$ The overall activation energy is 38 kJ mol-1. The composition of terpolymer calculated from NMR and elemental analysis has been used to evaluate reactivity ratios as r1(Sty) = 5 ± 2 and r2(AN + CuA) = 0.4 ± 0.02 employing the Finemann-Ross method, which confirms its random origin. The terpolymer was thermally stable up to 2007deg;C.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Photopolymerization of carbazolyloxiranes (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 81-85 
    Details
    ISSN: 0959-8103
    Schlagwort(e): photopolymerization ; carbazolyloxiranes ; diaryliodonium salts ; kinetics ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Photopolymerizations of 1-allyloxy-3-(carbazol-9-yl)-2-propanol glycidyl ether and 1-(carbazol-9-yl)-4-oxa-2-pentanol glycidyl ether with diaryliodonium salts in solution and in bulk are reported. These reactions give oligomers of degree of polymerization 4-6. The influence of the functional groups of the monomers on the rate of polymerization, conversion limit and molecular weight is discussed. The effects of photoinitiator and reaction media on these factors have also been studied.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1995.210360111
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  • 29
    Digitale Medien
    Digitale Medien
    Influence of a metallic filler on polyurethane formation (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 40 (1996), S. 1-7 
    Details
    ISSN: 0959-8103
    Schlagwort(e): polyurethane ; network formation ; metallic filler ; viscosity ; kinetics ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The addition of metallic fillers is recognized to impart improvement of acoustic properties to polyurethane-based materials used for marine applications. The system under consideration was obtained by the reaction of a triisocyanateterminated prepolymer with 1,4-butanediol, in the presence of various concentrations of lead powder. With increasing lead content, gelation time is reduced and an Einstein-type law does not apply. The kinetics of the reaction were determined by Fourier transform infrared spectroscopy. Deviation from the classic second order is observed for the filled systems, and the higher the lead content, the more important the deviation is, showing undoubtedly the catalytic effect of the metallic powder.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    Radical polymerization of acrylonitrile initiated by α-picolinium p-chlorophenacylid (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 37 (1995), S. 287-290 
    Details
    ISSN: 0959-8103
    Schlagwort(e): acrylonitrile ; nitrogen-ylid ; kinetics ; polymerization ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The radical polymerization of acrylonitrile (AN) with α-picolinium p-chlorophenacylid (α-PCPY) as initiator using carbon tetrachloride as inert solvent was investigated at 50°C. The polymerization follows ideal kinetics: the exponent values calculated for the initiator and monomer were found to be 0.5 and unity, respectively. A free radical mechanism with bimolecular termination was confirmed by the inhibiting effect of hydroquinone, a radical quencher. The rate of polymerization was a direct function of initiator (α-PCPY) concentraction, monomer (AN) concentration and temperature. The overall activation energy calculated was 56 kJ/mol. The polymerization was favoured by polar solvents and retarded by non-polar solvents.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1995.210370407
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  • 31
    Digitale Medien
    Digitale Medien
    Polymerization of conjugated dienes initiated by soluble organosodium compounds in hydrocarbon solventsPresented at ‘MacroAkron '94, 35th IUPAC Symposium on Macromolecules’, Akron, Ohio, 11-15 July 1994. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 37 (1995), S. 165-169 
    Details
    ISSN: 0959-8103
    Schlagwort(e): anionic polymerization ; chain transfer ; organosodium initiators ; kinetics ; butadiene ; isoprene ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Polymerization of butadiene and isoprene in hydrocarbon solvents initiated by unsolvated organosodium compounds was studied. It was found that the polymer molecular weight and the MWD are determined mainly by chain transfer to solvent and polymer, and no chain transfer to monomer was observed even in the case of isoprene. The overall polymerization rate is proportional to the concentrations of the monomer and the initiator. Apparent chain propagation rate constants were found to be 0.11 litre mol-1 s-1 for butadiene and 0.065 litre mol-1 s-1 for isoprene polymerization in heptane at 30°C. It is suggested that associated (dimeric) forms of polydienylsodium active centres play an important role in chain propagation, being responsible for a stronger chain transfer and a greater 1,2-butadiene, or 3,4-isoprene, unit content than in polymerization with other alkali metals.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1995.210370303
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  • 32
    Digitale Medien
    Digitale Medien
    A systematic approach to the study of multicomponent polymerization kinetics: butyl acrylate/methyl methacrylate/vinyl acetate. III. Emulsion homopolymerization and copolymerization in a pilot plant reactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 37 (1995), S. 235-248 
    Details
    ISSN: 0959-8103
    Schlagwort(e): butyl acrylate ; methyl methacrylate ; vinyl acetate ; pilot plant reactor ; emulsion polymerization ; kinetics ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A systematic study of the terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate (BA/MMA/VAc) is being conducted. In this third stage of the study,Parts 1 and 2: Dubé, M. A. & Penlidis, A., Polymer, 36 (1995) 587. Dubé, M. A. & Penlidis, A., Macromol. Chem. Phys., 196 (1995) 1101. emulsion homopolymerizations and copolymerizations of the monomers comprising the BA/MMA/VAc system were performed in a 5 litre stainless steel pilot plant reactor, mainly for troubleshooting purposes and as a precursor to the detailed terpolymerization experiments to follow.First, a search for a stable emulsion recipe was conducted. At the same time, experimental procedures were established for the 5 litre pilot plant reactor along with product characterization techniques. Finally, selective emulsion homopolymerizations and copolymerizations were run for each of the three monomers and each combination of the three monomers, respectively. The polymers produced were characterized for conversion, composition, molecular weight and particle size.Although the emphasis of the experiments was to establish recipes, techniques, and procedures for emulsions terpolymerization, several useful observations were made regarding the kinetics even from these troubleshooting experiments.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pi.1995.210370401
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  • 33
    Digitale Medien
    Digitale Medien
    Morphology development during the polymerization of styrene within a polyurethane network: Investigations by small-angle X-ray and light scattering (1996)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 7 (1996), S. 295-302 
    Details
    ISSN: 1042-7147
    Schlagwort(e): interpenetrating polymer networks ; kinetics ; phase separation ; X-ray scattering ; light scattering ; polyurethane ; polystyrene ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Phase separation that takes place during the formation of semi-interpenetrating polymer networks based on crosslinked polyurethane and linear polystyrene was studied by small-angle X-ray scattering and light scattering. The kinetics of the chemical reactions was followed by Fourier transform infrared spectroscopy. The occurrence of broad peaks in the X-ray scattering curves was interpreted in terms of distances between the urethane crosslinks. Small modulations on these curves were assigned to sphere-like structures with a diameter of around 5 nm which might be related to the urethane crosslink regions. Small modulations on the light-scattering curves at the beginning of styrene polymerization were assigned to spheres with diameters of around 4.5 μm, which can be related to the polystyrene-rich phase. These modulations disappear with time, which might indicate an increasing polydispersity of the domain sizes. The final morphology was found to depend on the time at which polymerization of styrene is initiated with respect to the time of gelation of polyurethane.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 34
    Digitale Medien
    Digitale Medien
    A review of kinetic studies on the formation of interpenetrating polymer networks (1996)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 7 (1996), S. 221-233 
    Details
    ISSN: 1042-7147
    Schlagwort(e): IPN ; kinetics ; simultaneity ; trommsdorff effect ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Interpenetrating polymer networks (IPNs) are unique alloys of crosslinked polymers. This article reviews the studies on kinetic effects involved in IPN formation. Several investigators have studied the effect of kinetics of curing reactions on the morphology and properties of IPNs. It was found, in general, that the faster the rates of the respective chain extension and crosslinking reactions are and the closer they are to simultaneity, the more homogeneous are the IPNs. Other investigations revealed that the individual components sometimes can polymerize more rapidly in the IPN than alone, due to a “solvent effect” of the IPN. Effects of changing reaction variables, such as NCO/OH ratio, composition activators and temperature were used to study reaction kinetics as well as phase morphology by the Fourier transform infrared technique. Thermochemical techniques have been utilized to study the kinetics of IPN formation which influence phase separation. Small-angle X-ray scattering and small-angle neutron scattering techniques were used to estimate the extent of microheterogeneity of the phase domains in a study of the kinetics of phase separation in the IPNs.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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