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  • 1995-1999  (4)
  • 1915-1919
  • Chemistry  (4)
  • Polymer and Materials Science  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Dynamics of semibatch polymerization reactors: II. Pilot-plant study (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 157-165 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A semibatch flow scheduling strategy proposed by Teymour and Ray (1989, 1996) is evaluated for a polymerization reaction conducted in a pilot-plant reactor. The reaction used is the free radical terpolymerization of styrene, α-methyl styrene, and acrylic acid monomers initiated by an organic peroxide initiator and carried out in the presence of a reactive glycol ether solvent. This strategy was tested in both single batch and sequential semibatch modes. The process was shown to produce polymer of constant molecular weight properties and composition as inferred from acid number and monomer conversion measurements. This process could be used for obtaining polymer products from a semibatch reactor that are of comparable quality to CSTR products. Results indicate success of this process at meeting this objective; however, practical considerations relating to agitation and temperature control need to be properly addressed to ensure this success.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430118
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  • 2
    Digitale Medien
    Digitale Medien
    Electron-stimulated desorption total cross-section determination for digermane on Si(100) (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 105-108 
    Details
    ISSN: 0142-2421
    Schlagwort(e): ESD ; Si(100) ; electron-stimulated desorption ; silicon ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: We have studied digermane-covered Si(100) using electron-stimulated desorption (ESD). Estimates are presented for the total H(a) ESD removal cross-section for digermane-exposed Si(100) substrates at 85 K using electrons incident at 150 eV energy. It is found that electron-enhanced deposition of Ge occurs only when physisorbed digermane is present. Auger electron spectroscopy provided the means for determining the relative amounts of germanium adsorbed on the Si(100) surface following digermane exposures, electron irradiation and surface reconstruction. It is found that two coverage regimes are important: initial dosing of digermane on Si(100) at 85 K results in overlayers consisting of both physisorbed digermane and chemisorbed GeHx(a) (x=1, 2 or 3) species; and short anneals to 200 K following exposure of the Si(100) surface at 85 K lead to the presence of only chemisorbed GeHx(a). The two coverage regimes exhibit different ESD behavior. Two kinetic energy distribution (KED) peaks are seen when physisorbed digermane is present, and only one when it is absent. The ESD signal decay curves obtained from the two surfaces are also different: the presence of physisorbed digermane results in a two-component exponential signal decay; the absence of the physisorbed species results in a single-exponential decay. The total H removal cross-section from the physisorbed digermane overlayer was determined to be σ∽1.4×10-15 cm2, while that from Si(100) with only adsorbed GeHx present was found to be σ∽2.6×10-16 cm2. Our results suggest that adsorbed GeHx(a) species remain intact on the surface even when the Si(100) substrate is annealed to 200 K, indicating that hydrogen migration from surface GeHx(a) to Si surface sites does not occur at 200 K. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Atomic level widths for x-ray spectrometry (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 24 (1995), S. 307-319 
    Details
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A self-consistent set of level widths for the K-N7 subshells is assembled using literature experimental data from a variety of spectroscopic methods. In cases where Coster-Kronig processes contribute significantly, the widths differ from the predictions of the atomic single-particle model; in the restricted regions where atomic many-body predictions are available, the agreement is much better. The assembled widths will be useful to Si(Li) spectroscopists who wish to include natural width in the description of spectrometer lineshape; such inclusion will improve accuracy in both fundamental and analytical work. The present database is also of value in identifying where improvements to the currently incomplete knowledge of natural widths are most critical.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/xrs.1300240606
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  • 4
    Digitale Medien
    Digitale Medien
    Effects of low-energy electron irradiation on submonolayer ammonia adsorbed on Pt(111) (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 97-104 
    Details
    ISSN: 0142-2421
    Schlagwort(e): ammonia ; Pt ; adsorption ; electron irradiation ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The effects of electron impact on ammonia-covered Pt(111) have been studied using temperature-programmed desorption (TPD) and electron-stimulated desorption (ESD). For coverages below one monolayer, ammonia adsorbs on the surface in two distinct TPD states: the α-state is broad and desorbs over the temperature range 150-350 K, and the β-state appears as a sharper peak at 150 K. The β-state was seen to be damaged by electron-beam impact much more readily than the α-state, resulting in the formation of atomically adsorbed N on the surface. The mass 28 recombinative nitrogen desorption TPD peak appearing at 550 K exhibited second-order desorption kinetics, further confirming the presence of atomically adsorbed nitrogen. The ESD kinetic energy distributions (KEDs) were obtained for m/e=1 amu, which exhibited broad peaks generally. The H+ KEDs were analyzed using empirical curve fits, with the resulting conclusion that the H+ KEDs contain contributions from at least three different hydrogen-containing surface species. We believe that these three H+ KED peaks are due to ESD from adsorbed NH3, NH2 and H. The ESD cross-section for NH3 removal was measured in three different ways, all of which were found to be in general agreement, and which gave an averaged cross-section value of Qtot=4×10-17 cm2. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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