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  • 1
    Electronic Resource
    Electronic Resource
    Role of Si-H and Si-H2 in the photoluminescence of porous Si (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1099-1101 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: FTIR spectra reported by Brandt et al. [Solid State Commun. 81, 307 (1992)], Tischler et al. [Appl. Phys. Lett. 60, 639 (1992)], and Tsai et al. [Appl. Phys. Lett. 59, 2814 (1991), and 60, 1700 (1992)] have shown the presence of Si-H and Si-H2 lines in porous Si which Canham [Appl. Phys. Lett. 57, 1046 (1990)], Tischler and Tsai have considered essential to the observation of visible photoluminescence (PL). Hydrogen has been ascribed as a surface passivating agent which eliminates nonradiative transitions thus enabling PL to occur. Photo-oxidation has been described as replacing some of the surface passivants with oxygen, generating nonradiative transitions which quench the PL. We have markedly reduced the Si-H and Si-H2 content of anodized samples by treatment with CCl4 vapor. Comparison of the photoluminescent emission and excitation spectra for CCl4 treated and untreated samples show very similar results. Comparison of the FTIR spectra of photo-oxidized samples which exhibit no PL and as-anodized samples show the similar presence of Si-H and Si-H2. These observations suggest that neither Si-H nor Si-H2 is essential for the observation of PL in anodized Si. This result and the similarity in the behavior of porous Si with the polysilynes lead us to concur with Brandt et al. that visible PL in anodized Si is generated by the backbone of a 2D Si polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108754
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  • 2
    Electronic Resource
    Electronic Resource
    Studies of polymer morphology with 13C inversion recovery cross polarization NMR (1989)
    Springer
    Polymer bulletin 21 (1989), S. 229-234 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Inversion recovery cross polarization (IRCP) NMR was used to study the solid state morphologies of plasticized and neat poly(vinyl butyral-co-vinyl alcohol) (PVB), of polyether polyurethane elastomers (PU), and of low density polyethylene (LDPE). IRCP decay data for these polymers were best fit to a biexponential two-component model modulated by T1ϱH relaxation. These results clearly display the two-phase nature of these polymers, as well as the potential applicability of the IRCP technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266178
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  • 3
    Electronic Resource
    Electronic Resource
    A preliminary correlation between macroscopic and microscopic polymer properties: Dynamic storage modulus vs. CPMAS NMR cross polarization rates (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 1717-1725 
    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: A correlation has been established between the dynamic storage modulus (E') and the mean cross polarization time constants 〈TCH〉 for a set of five morphologically diverse polymers, including one at two temperatures and one at two plasticizer concentrations. The correlation is only possible when the TCH values for all of the motional environments within the polymers are considered. An inversion recovery cross polarization (IRCP) NMR technique is used to obtain motional and morphological information from the main chain carbons of each polymer. After comparing simplified correlation functions for the two parameters, an experimental relationship between them is established that suggests that TCH and E' are both modulated by a similar distribution of molecular motions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400926
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  • 4
    Electronic Resource
    Electronic Resource
    Correlations involving modulae and cross-polarization time constants for a series of polyurethane elastomers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 391-398 
    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: Correlations between the macroscopic bulk polymer properties storage modulus (E′) and loss modulus (E″) and the microscopic property of cross-polarization as represented by the time constant TCH have been established for a series of polyurethane elastomers. The dependence of E′, E″, and TCH as a function of molecular weight, rigid domain concentration, and temperature are graphically presented as a series of log plots. An experimental relationship is presented that shows that the distribution of motions of the flexible domains appears to be the major factor in the success of these correlations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450303
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  • 5
    Electronic Resource
    Electronic Resource
    Variable temperature spin-lattice relaxation in the study of the local chain dynamics of polyurethane elastomers (1990)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 28 (1990), S. 301-306 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1990.140281002
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