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  • Chemistry  (10)
  • 61.16.Di  (2)
  • Chiral separation  (2)
  • plasma  (2)
  • 1990-1994  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Structure of nm-sized InSb clusters formed by spontaneous alloying (1994)
    Springer
    The European physical journal 31 (1994), S. 209-212 
    Details
    ISSN: 1434-6079
    Keywords: 61.16.Di ; 36.40. + d ; 66.30. − h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The alloying behavior of antimony atoms into nm-sized indium clusters has been studied in situ by TEM. When antimony atoms are vapor-deposited onto nm-sized indium clusters, a rapid dissolution of antimony atoms into indium clusters takes place and as a result InSb compound clusters are successfully formed. Such spontaneous alloying occurs even at ambient temperature. InSb clusters thus formed have the wurtzite structure. When these InSb clusters are annealed at 533 K, their structure changes into the sphalerite structure, which is the structure of the equilibrium phase of the bulk In50Sb50. The appearance of wurtzite-type InSb by spontaneous alloying is discussed in terms of ionicity of bonds in InSb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437838
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  • 2
    Electronic Resource
    Electronic Resource
    Cluster-size dependence of alloying behavior in gold clusters (1994)
    Springer
    The European physical journal 31 (1994), S. 131-134 
    Details
    ISSN: 1434-6079
    Keywords: 61.16.Di ; 36.40.+d ; 66.30.−h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Cluster-size dependence of alloying behavior in nm-sized atom clusters has been studied by transmission electron microscopy, using clusters in the Au-Cu system. It was revealed that occurrence of rapid spontaneous alloying becomes more difficult with increasing cluster size. In gold clusters of approximately 4 nm in the mean size, a rapid dissolution of copper atoms took place and homogeneously mixed Au-Cu alloy clusters were formed. In gold clusters of approximately 10 nm in the mean size, rapid alloying of copper took place only at a shell-shaped region beneath the free surface of individual clusters and pure gold was retained at the central region of clusters. In gold clusters of approximately 30 nm in the mean size, no rapid alloying of copper was induced. The ease with which spontaneous alloying takes place is discussed in terms of the lattice softening in atom clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426588
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  • 3
    Electronic Resource
    Electronic Resource
    Fundamental aspect and behavior of saturated fluorocarbons in glow discharge in absence of potential source of hydrogen (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1731-1739 
    Details
    ISSN: 0887-624X
    Keywords: saturated fluorocarbon ; plasma polymerization ; surface fluorination ; ESCA ; sputtering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The glow discharge of a series of saturated fluorocarbons, CnF2n+2 (n = 1, 2, 4, 6, and 8), was studied with glass substrates which do not contain any hydrogen. It was found that the deposition rate was a function of the F/C ratio of the starting fluorocarbons. That is, fluorocarbons with higher F/C ratio, such as CF4 and C2F6, hardly polymerized, while fluorocarbons with lower F/C ratio, such as C8F18, polymerized as well as C2F4. After plasma exposure, the surface of glass substrate was characterized by measurements of water contact angle, water droplet rolling-off angle, and ESCA. Although all saturated fluorocarbon plasmas could alter the surface more hydrophobic than before, the deposited materials from fluorocarbons with higher F/C were not stable. Also, in plasmas with high F/C fluorocarbons, i.e., CF4 and C2F6, sputtering of the electrode material was observed. © 1992 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300826
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  • 4
    Electronic Resource
    Electronic Resource
    Penetration of plasma surface modification. II. CF4 and C2F4 low-temperature cascade arc torch (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1839-1845 
    Details
    ISSN: 0887-624X
    Keywords: plasma ; cascade arc ; surface modification ; fluorination ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The depth of surface modification by low-temperature cascade arc torch is investigated. A stack of 10 sheets of nonwoven fabrics of polyester fibers is exposed to a low-temperature cascade arc torch containing CF4 or C2F4, and the fluorination effect is examined by ESCA. It is shown that interaction of chemically reactive species, created in a low-temperature cascade arc torch, with the surface is not limited to the surface contacted by the torch (flame). The results indicate that the fluorination effect is observed on surfaces which are shadowed from the torch by overlying fibers. The highest degree of fluorination is found on the second layer, rather than on the first layer which the torch contacts directly. No significant differences in the trends of penetration of CF4 and C2F4 treatment through porous samples are observed. However, ESCA data show principal differences in chemical structures of the surfaces treated with CF4 (nonpolymer-forming gas) and C2F4 (polymer-forming gas). These results indicate that chemically reactive species induced by the excited species of argon rather than primary species created by the ionization process seem to play predominant roles in the surface treatment as well as the low-temperature cascade arc torch polymerization of perfluorinated compounds. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321005
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  • 5
    Electronic Resource
    Electronic Resource
    Penetration of plasma surface modification. I. Cf4 and C2F4 glow discharge plasmas (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1829-1837 
    Details
    ISSN: 0887-624X
    Keywords: plasma ; RF glow discharge ; surface modification ; fluorination ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma treatment of a polymeric surface could involve at least three major mechanisms: (1) direct interaction of reactive species in the low-temperature plasma state with the surface (line of sight irradiation effect), and (2) chemical reactions of plasma-induced reactive species with the surface, and (3) reactions among reactive species and the surface (plasma polymerization). The first and the third effects are considered to be limited to the surfaces which directly contact with plasma (glow). The second effect is not limited to the surfaces that contact with plasma state but can penetrate beyond the plasma zone by diffusion. Using an assembly of fibers, of which only the top layer contacts with plasma (glow), the penetration of chemical changes caused by plasma exposure was investigated. Results indicate that the fluorination effect (incorporation of fluorine-containing moieties on the surface of polymeric substrate) penetrates through a considerable thickness of the assembly of fibers, depending on the porosity (gas permeability) of the system. Chemical reactions of plasma-induced (chemically) reactive but nonpolymerizing species with the substrate fibers seems to predominate. The direct interactions of energetic species, such as ions, electrons, and electronically excited species, with polymeric surfaces seems to play relatively minor roles in the plasma treatment investigated. The major role of plasma, in this case, seems to be creating such chemically reactive species. © 1994 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321004
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of plasma polymerized hydrocarbons using CP-MAS 13C-NMR (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1801-1805 
    Details
    ISSN: 0887-624X
    Keywords: Carbon-13 NMR ; plasma polymerization ; thin films ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma polymerized hydrocarbons made from ethane and methane were produced under different reactor conditions and probed by solid-state carbon-13 nuclear magnetic resonance (13C-NMR) with cross-polarization and magic-angle sample spinning. NMR experiments provided structural information about the plasma polymers. The conditions of low power, high hydrocarbon gas flow rate, and no added hydrogen gas appeared to give the highest amount of nonprotonated sp3 hybridized carbons in the films for the reactor design used. The use of methane or ethane as reactor gas did not affect plasma polymer structure significantly.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080291212
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  • 7
    Electronic Resource
    Electronic Resource
    Retention, enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column (1992)
    Springer
    Chromatographia 33 (1992), S. 127-132 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Alpha 1-acid glycoprotein-bonded column ; Propranolol ; Propranolol ester derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an α1-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275892
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  • 8
    Electronic Resource
    Electronic Resource
    Chiral separation of propranolol and its ester derivatives on an ovomucoid-bonded silica: Influence of pH, ionic strength and organic modifier on retention, enantioselectivity and enantiomeric elution order (1990)
    Springer
    Chromatographia 29 (1990), S. 587-592 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ovomucoid-bonded silica ; Chiral separation ; Propranolol ; Propranolol ester derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention, enantioselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propyl,-butyl and-valeryl PP) on an ovomucoid-bonded silica column have been investigated with respect to pH, ionic strength and organic modifier. For these cationic solutes, an increase in the organic modifier content and/or a decrease in the pH result in a decreased retention of both enantiomers. Enantioselectivity of the ester derivatives was higher than of underivated PP. The enantiomeric elution order was (S)/(R) for PP and (R)/(S) for the four ester derivatives, when ethanol or 2-propanol was used as the organic modifier. When methanol or acetonitrile was used as the organic modifier, inversion of the enantiomeric elution order was observed for O-valeryl PP with the use of methanol and for PP and O-propyl PP with acetonitrile. These results suggest that at least two chiral binding- or recognitionsites are present in a protein molecule and/or conformational changes occur in the chiral binding- or recognition-site(s) of the protein molecule bonded to a silica matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02261228
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  • 9
    Electronic Resource
    Electronic Resource
    Polymerization of para-xylylene derivatives. VI. morphology of parylene N and parylene C films investigated by gas transport characteristics (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 545-568 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polychloro-p-xylylene (Parylene C) and poly-p-xylylene (Parylene N) films were synthesized in vacuum with and without the presence of 42 mtorr of argon at various deposition temperatures and three different dimer sublimation rates. Depending on the synthesis conditions, the morphology of the films can vary from a homogeneous (nonporous) structure to a heterogeneous (porous) structure. The transport coefficients of the gases He, O2, N2, and CO2 through these films were measured at 25°C. The transport coefficients for both types of films vary with the deposition temperature and the dimer sublimation rate. The variation, however, cannot be solely explained by the change of crystallinity. Anomalous transport behavior is observed in the homogeneous, as-synthesized polymers of relatively high crystalline content (above 20-30%). In many cases the permeabilities and diffusivities increase despite an increase in crystallinity. The effects of crystallization induced by isothermal and solvent annealing on the transport coefficients of polymers of Parylene C are different from those of Parylene N synthesized with or without argon. The mean pore size and effective porosity of the porous films were calculated from gas permeation data. For Parylene C and Parylene N porous films synthesized without argon, increasing the dimer sublimation rate or decreasing the deposition temperature increases the mean pore size but decreases the effective porosity. For Parylene N porous films synthesized in the presence of argon, increasing the dimer sublimation rate or decreasing the deposition temperature results in a decrease in the mean pore size but an increase in the effective porosity. Overall, no appreciable change in transport coefficients is observed upon addition of an inert gas.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090280409
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  • 10
    Electronic Resource
    Electronic Resource
    Plasma surface treatment on nylon fabrics by fluorocarbon compounds (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 249-264 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Nylon fabrics were treated by low temperature fluorocarbon plasmas. All of the fluorocarbon plasmas applied altered the surface of nylon fabrics to be hydrophobic and water-repellent. The durability of hydrophobicity and water repellency was examined by measurements of the water contact angle, the water droplet rolling-off angle, and the breakthrough water pressure after plasma-treated fabrics were washed. It was found that the structure of starting fluorocarbon and the plasma energy input were important factors in the durability. After washing, surface dynamics were investigated on different drying conditions. It was found that chemical composition and water repellency were dependent on drying conditions because of rotation of hydrophobic segments on the surface of fabrics.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070390205
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