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  • 1
    Electronic Resource
    Electronic Resource
    Determination of the polarization-depth distribution in poled ferroelectric ceramics using thermal and pressure pulse techniques (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 854-863 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper is the first of a series with the common theme of comparing thermal and acoustic pulse methods of measuring charge or polarization profiles across the thickness of slab-shaped samples that are representative of different types of materials. In this paper, thermal and pressure pulse measurements are reported of the polarization distribution in poled, ferroelectric ceramic samples. The results obtained from both methods are complementary so that there is a benefit to using both. The results also demonstrate that large deviations from uniform polarization can be induced by processing differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351306
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  • 2
    Electronic Resource
    Electronic Resource
    STRUCTURE OF (OC3)Fe(C8H8)Fe(CO)3 (1961)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 83 (1961), S. 489-490 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01463a057
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  • 3
    Electronic Resource
    Electronic Resource
    MOLECULAR STRUCTURE OF C8H8Fe(CO)3 (1961)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 83 (1961), S. 4862-4863 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01484a041
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal pulse study of the electric polarization in a copolymer of vinylidene cyanide and vinyl acetate (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6407-6415 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The polarization induced by thermopoling the alternating vinylidene cyanide/vinyl acetate copolymer has been studied by the thermal pulse technique. The mean polarization over the thickness and its spatial profile were determined as functions of the poling variables: electric field, time, and temperature. Additionally, the thermal stability of the polarization was studied between ambient temperature and the glass-transition temperature of 175 °C. The mean polarization was found to be proportional to the poling field up to the maximum field used of 42 MV/m and to be very stable up to 150 °C. The polarization profiles obtained after poling were found to be highly inhomogeneous, especially for short poling times, indicating positive charge injection from the positive electrode during poling. The polarization distribution continues to evolve after the mean polarization has reached a steady state indicating separate time scales for space-charge migration and dipole reorientation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363639
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  • 5
    Electronic Resource
    Electronic Resource
    Crystal structure of calcium carbonate hexahydrate at about -120.deg. (1970)
    s.l. : American Chemical Society
    Inorganic chemistry 9 (1970), S. 480-486 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic50085a010
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  • 6
    Electronic Resource
    Electronic Resource
    Crystal structures of CaNa2(CO3)2.5H2O, synthetic gaylussite, and CaNa2(CO3)2.2H2O, synthetic pirssonite (1969)
    s.l. : American Chemical Society
    Inorganic chemistry 8 (1969), S. 2093-2103 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic50080a012
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal degradation of poly(methyl methacrylate) at 50°C to 125°C (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 377-393 
    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: Small but significant numbers of chain scissions occur in a commercial poly(methyl methacrylate) sheet exposed to temperatures between 50 and 125°C. The scission rate is initially high and then levels off to a constant rate. The short-time rate of chain scissions is temperature dependent, while the long-time rate of chain scissions appears to be temperature independent. Four possible sources of random chain scission initiation were considered: (1) the presence of unreacted initiators of polymerization, (2) free radicals generated from additives in the commercial film, (3) weak links in the polymer chain, and (4) free radicals generated from the thermal decomposition of an oxidation product of methyl methacrylate (MMA) monomer. The source most consistent with our results is the one involving free radicals generated from the oxidation product of MMA monomer.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070340130
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal degradation study of isotactic polypropylene using factor-jump thermogravimetry (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 1169-1183 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The degradation of isotactic polypropylene in the range 390-465°C was studied using factor-jump thermogravimetry. The degradations were carried out in vacuum and at pressures of 5 and 800 mm Hg of N2, flowing at 100-400 standard mL/s. At 800 mm Hg this corresponds to linear rates of 1-4 mm/s. In vacuum bubbling in the sample caused problems in measuring the rate of weight loss. The apparent activation energy was estimated as 61.5 ± 0.8 kcal/mol (257 ± 3 kJ/mol). In slowly flowing N2 at 800 mm Hg pressure the activation energy was 55.1 ± 0.2 kcal/mol (230 ± 0.8 kJ/mol) for isotactic polypropylene and 51.1 ± 0.5 kcal/mol (214 ± 2 kJ/mol) for a naturally aged sample of atactic polypropylene. For isotactic polypropylene degrading at an external N2 pressure of 5 mm Hg the apparent activation energy was 55.9 ± 0.3 kcal/mol (234 ± 1 kJ/mol). A simplified degradation mechanism was used with estimates of the activation energies of initiation and termination to give an estimate of 29.6 kcal/mol for the ß-scission of tertiary radicals on the polypropylene backbone. Initiation was considered to be backbone scission ß to allyl groups formed in the termination reaction. For initiation by random scission of the polymer backbone, as in the early stages of thermal degradation, an overall activation energy of 72 kcal/mol is proposed. The difference between vacuum and in-N2 activation energies is ascribed to the latent heat contributions of molecules which do not evaporate as soon as they are formed. At these imposed rates of weight loss the average molecular weights of the volatiles in vacuum and in 8 and 800 mm Hg N2 are in the ratios 1-1/2-1/9.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.170200502
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  • 9
    Electronic Resource
    Electronic Resource
    Thermally degrading polyethylene studied by means of factor-jump thermogravimetry (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 1065-1087 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Degradation of polyethylene in both linear (NBS 1475) and branched (NBS 1476) form has been studied in the range 410-475°C using factor-jump thermogravimetry. In vacuum, the rate of weight loss was erratic because of bubbling in the sample. The apparent overall activation energy was determined to be 65.4 ± 0.5 kcal/mol (273 ± 2 kJ/mol). There was no distinguishable difference between linear and branched samples. In slowly flowing N2 at 8 mmHg (1 mmHg = 133 Pa), the overall activation energy was determined to be 64.8 ± 0.3 kcal/mol (271 ± 1 kJ/mol) for linear PE and 64.4 ± 0.2 kcal/mol (269 ± 1 kJ/mol) for a sample of PE with one percent branches. In N2 at 800 mmHg, the values were 62.6 ± 0.5 kcal/mol for linear PE and 61.2 ± 0.6 kcal/mol for the branched sample, the rate of weight loss being smooth in both cases. Changing the linear flow velocities over the range 1-4 mm/sec at 800 mmHg did not affect the results. From the insertion of typical values in the equation relating the overall activation energy for weight loss from linear polyethylene to the activation energies of the component steps, a degradation mechanism involving scission β to allyl groups, with rapid hydrogen abstraction, slower subsequent β scission, and bimolecular termination, is indicated. The activation energy of β scission for secondary alkyl radicals is estimated to be 33 kcal/mol. The reason for the lower activation energies in N2 is related to the effects of preformed molecules. The average molecular weights of the volatiles in vacuum and for 8 and 800 mmHg N2 have been shown to be in the ratios 1 to 1/4 to 1/10, respectively, at these imposed rates of weight loss. The activation energies to use for the initial stage of degradation are 70.6 kcal/mol (295 kJ/mol) in vacuum and 67.8 kcal/mol (284 kJ/mol) at atmospheric pressure.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.170200415
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