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  • Articles  (42)
  • Chemistry  (40)
  • Analytical Chemistry and Spectroscopy  (17)
  • Chemical Engineering  (3)
  • 78.90.+t  (2)
  • 1990-1994  (42)
  • Physics  (42)
  • 1
    Electronic Resource
    Electronic Resource
    Early stages of laser mixing process in Sb/Ge multilayer thin films (1993)
    Springer
    Applied physics 56 (1993), S. 132-137 
    Details
    ISSN: 1432-0630
    Keywords: 64.75.+g ; 78.90.+t ; 81.40.-z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The onset of mixing at the interfaces between Sb and Ge in thin multilayered films containing two or four layers has been studied. The films were irradiated with nanosecond laser pulses in order to trigger mixing, and in situ reflectivity measurements were used to follow the transformation in real-time. Cross sectional transmission electron microscopy analysis was used to study both the structure and the composition profile before and after irradiation. A threshold irradiation energy exists for the onset of mixing, below which roughening of the interface between the layers is observed, together with recrystallization of the surface Sb layer following melting. The results are consistent with a melting/diffusion process which is inhomogeneously nucleated at the interface between the top Sb and Ge layers. Once mixing is initiated an amorphous Sb-Ge layer of constant thickness is formed, corresponding to mixing along a well defined planar melt front. Voids are observed at the former Sb/Ge interface, which may be related to interfacial stress in the as-grown configuration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00517680
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  • 2
    Electronic Resource
    Electronic Resource
    Structural ripple formation in Ge/Sb multilayers induced by laser irradiation (1994)
    Springer
    Applied physics 58 (1994), S. 197-202 
    Details
    ISSN: 1432-0630
    Keywords: 64.75.+g ; 78.90.+t ; 81.40.−z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Thin multilayer films (Ge/Sb/Ge/Sb/Si substrate) have been irradiated with single nanosecond laser pulses (λ=193 nm). Real-Time Reflectivity (RTR) measurements have been used to follow the transformation in situ and cross-sectional transmission electron microscope analysis was used to study both the microstructure and the composition profile before and after irradiation. Melting and mixing are both found to nucleate at preferential sites in the upper Ge/Sb interface. During this process the film surface topography changes in a way not previously seen, and rippling of the film is observed due to lateral mass flow induced in the Sb layer underneath the surface, most probably arising from volume changes upon melting. For the highest irradiation energy densities, melting of the whole multilayer configuration takes place, the ripples are no longer observed, and following cooling and solidification, a mixed amorphous GeSb film is formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332179
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  • 3
    Electronic Resource
    Electronic Resource
    Non-Newtonian and isothermal analysis of flow of poly(methyl methacrylate) in a model twin screw extruder. Part I (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 986-994 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The flow analysis network (FAN) method was modified to analyze the flow of poly(methyl methacrylate) (PMMA) in a model counter-rotating nonintermeshing screw extruder. The numerical prediction of the pressure profiles was compared with the experimental results. Flow patterns in the screw elements of the model counter-rotating nonintermeshing twin screw extruder were also predicted. A new flow path method was developed to calculate the residence time distribution. This result will be applied to analyze the flow during the reaction in the model twin screw extruder.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341207
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  • 4
    Electronic Resource
    Electronic Resource
    Conformational changes of amorphous poly(ethylene terephthalate) films during uniaxial stretching (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 301-307 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rapid scanning Fourier transform infra-red spectroscopy was used to follow the changes in the population of trans conformers and in the infra-red dichroic functions of the bands characterizing the trans (T) and gauche (G) conformers and the chains in the amorphous regions during stretching of a solution-cast amorphous poly(ethylene terephthalate) (PET) film A in the glassy state (67°C) and in the rubbery state (88°C). Stretching at 67°C showed a yield stress peak followed by strain softening in the stress-strain curve. The population of trans conformers in the amorphous and crystalline regions, Ta + Tc, decreased in the pre-yielding region and then increased continuously after yielding. The T conformers formed during post-yield stretching showed high orientation, while the G conformers remained in low degree of orientation. Stretching at 88°C showed no pronounced yield stress peak in the stress-strain curve, and the population of T conformers did not change until the beginning strain-induced crystallization. A solvent-cast PET film annealed at 67°C for 24 h, the film N, showed a sharp and high yield stress peak in the stress-strain curve, and strain-induced crystallization occurred at lower draw ratio as compared to the film A. The film A showed a non-equilibrium high population of Ta conformers, part of which reverted to G conformers during sub-Tg annealing.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920212
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  • 5
    Electronic Resource
    Electronic Resource
    The thermal deprotection process in an e-beam exposed phenolic-based polymer (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1589-1594 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: In our current work, we have examined the e-beam sensitivity and thermal processing behavior of pure PBOCST [poly(tert-butoxycarbonyloxystyrene)]. An alkali soluble latent image can be generated in the PBOCST by e-beam exposure followed by a post-exposure bake (PEB) at relatively high temperatures (140 to 150°C). Pattern wet development operates on the same basis as a PBOCST/acid generator two component system. Deprotection, accelerated by the exposure, yields alkali soluble areas, while unexposed areas remain insoluble. Sensitivities of 5 to 10°C/cm2 and contrasts of 6 to 10 have been measured. Complete TBOC deprotection results in a film thickness loss of 35 to 40% as CO2 and isobutene are evolved. A laser interferometer/hotplate setup was used to track film thickness with time during the thermal deprotection process. IR analysis confirmed the correlation between conversion and thickness. It was found that a slow initial conversion rate was followed an exponentially steep rise in rate after 50% conversion. Activation energies were on the order of 30 kcal/mol. It was concluded that thermolysis in both exposed and unexposed resist occurred during the PEB, but that the difference in extent of conversion on exposure was sufficient to generate a pattern.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322108
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  • 6
    Electronic Resource
    Electronic Resource
    Non-Newtonian and non-isothermal analysis of flow during polymerization of methyl methacrylate in a model twin screw extruder. Part II (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 995-1004 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The flow analysis network (FAN) method was modified to analyze the flow during polymerization of methyl methacrylate (MMA) in a model counter-rotating nonintermeshing screw extruder. The shear viscosity of the reactive mixture in the twin screw extruder was considered as a mixture of polymer and monomer. Thus, the reaction viscosity of the mixture of polymer and monomer was taken to be an explicit function dependent on the shear rate, temperature, conversion, and molecular weight. A new flow path method was developed to calculate the residence time distribution, which related to the degree of conversion. The numerical prediction of the velocity, temperature, viscosity, and pressure profiles during reaction in the model twin screw extruder is described.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341208
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  • 7
    Electronic Resource
    Electronic Resource
    Percolation effects in degradable polyethylene-starch blends (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 565-579 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The accessibility of starch in polyethylene starch blends was investigated by computer simulation, percolation theory, and acid hydrolysis experiments. The object of this work was to model the bilateral invasion of microbes in polyethylene-starch blends as a function of starch concentration (p), and thickness of the material. It was found that computer simulations in three dimensions were in agreement with both percolation theory and the acid digestion experiments. In computer simulation the accessibility is highly dependent on the percolation threshold concentration (pc), which is 31.17%. Similarly, the accessibility of starch is highly dependent on an apparent percolation threshold near 30% by volume or approximately 40% by weight of starch. At p 〈 pc a small amount of starch is removed from the surfaces only, but at p 〉 pc connected pathways existing throughout the bulk of the material facilitate large amounts of starch extraction. The sharpness of the transition at pc increases with the ratio of sample thickness to starch particle size. The results of this work have application to conduction and reacting systems where one component is dispersed in a matrix of the other.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090290506
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  • 8
    Electronic Resource
    Electronic Resource
    General procedures to determine the composition of commercial, two-part polysulfide aircraft sealants (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2837-2856 
    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: Interpretation of the chemical processes which polysulfide sealants undergo either on storage or when the cured material is subjected to environmental influences requires detailed knowledge of formulations. Procedures have been developed to isolate and identify a range of additives in two-part commercial aircraft sealants of both the dichromate and manganese dioxide cure types. Solvents, curing agent dispersants, and cure rate modifiers were separated chemically and thermal analysis was demonstrated to provide a ready means to estimate carbon in fillers. The phenolic resin adhesion enhancers were conveniently determined using 13C-NMR spectroscopy and could also be identified using size exclusion chromatography. It was shown that virtually no interaction occurred between polysulfide liquid polymers and phenolic resins following aging at 70°C for 7 days. The most appropriate methods for determining curative levels were established and new means of assessing thiol content of the polysulfides by both 13C-NMR and PMR spectroscopy are described. The significance of aspects of the sealant formulations is discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070411126
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  • 9
    Electronic Resource
    Electronic Resource
    Shrinkage force studies of oriented polyethylene terephthalate (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1921-1929 
    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: Shrinkage force measurements on drawn polyethylene terephthalate fibres have been evaluated in terms of the elastic behaviour of a molecular network. It is shown that for low network deformations the classical theory of Kuhn and Grün describes the stress-optical behaviour very well. For high deformations, the recent theory of Edwards and Vilgis has been found to give a satisfactory description of the data. It also provides some tentative insights into the structure of the spun yarns.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420715
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  • 10
    Electronic Resource
    Electronic Resource
    Structural changes on plasma irradiation of ethyl-cyanethyl cellulose as revealed by infrared spectroscopic technique (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 19-22 
    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: Ethyl-cyanethyl cellulose was treated with oxygen plasma using the RF glow discharge technique. Three different plasma-treated samples, including gel fraction, soluble fraction, and newly polymerized product by small moleculars given off by ethyl-cyanethyl cellulose, were obtained. With the infrared spectroscopic technique, the structural differences caused by plasma were studied. The effect of different gas plasma N2, Ar, and O2 on the structure of ethyl-cyanethyl cellulose was also studied.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070430103
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