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  • 1
    Electronic Resource
    Electronic Resource
    An ac calorimeter for measuring heat capacity of free-standing liquid-crystal films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 415-421 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A unique ac calorimeter for measuring the heat capacity of free-standing liquid-crystal films has been developed. A theory of the measurement method used is presented and the experimental setup is discussed. The calorimeter has been used to study the nature of the smectic-A-hexatic-B transition of several liquid-crystal compounds. The evolution of the heat-capacity anomaly associated with this transition has been studied for films ranging from three to a few thousand smectic layers in thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142136
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  • 2
    Electronic Resource
    Electronic Resource
    Role of hydroxide impurities in the thermoluminescent behavior of lithium fluoride (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 2217-2220 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of OH ion impurities on thermoluminescent sensitivity and supralinearity in LiF:Mg, Ti is analyzed. Available evidence is shown to be consistant with the presence of Ti-OH and Mg-OH complexes. The track interaction model is used to explain the data, with competing centers decreasing sensitivity and supralinearity at high concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334365
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  • 3
    Electronic Resource
    Electronic Resource
    Novel results of extremely thin substrate-free liquid-crystal films obtained from calorimetric and computer simulation studies
    Amsterdam : Elsevier
    Physica A: Statistical Mechanics and its Applications 205 (1994), S. 108-121 
    Details
    ISSN: 0378-4371
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0378-4371(94)90494-4
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  • 4
    Electronic Resource
    Electronic Resource
    Liquid-hexatic phase transitions in single molecular layers of liquid-crystal films (1992)
    [s.l.] : Nature Publishing Group
    Nature 355 (1992), S. 152-154 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Our experimental technique has been reported elsewhere6. Recent improvements have increased the system resolution and stability over wider temperature ranges. Free-standing liquid-crystal films are soap-like films suspended across an aperture (typically 1 cm in diameter)7. Unlike in adsorbed ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/355152a0
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  • 5
    Electronic Resource
    Electronic Resource
    Net shape ceramic microcomponents by modified sol–gel casting (2000)
    Springer
    Microsystem technologies 6 (2000), S. 200-204 
    Details
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract  Development of ceramic microcomponents can open up the current silicon-based MEMS (micro-electro-mechanical systems) technology to new applications, especially for use in high temperature, chemically reactive environments. We report a study of sol–gel technologies applied to the fabrication of microcomponents. Organic/inorganic hybrid materials, particularly silica-based hybrids, were developed by sol–gel processing. A weak silica network was made possible by using acid catalyst, low functionality organic precursor in the sol preparation. Since the weak network has a high tendency to collapse, the result is a denser material. Incorporation of organic ligands modifies the surface chemistry of gel network so that a greater drying stress was developed and a denser hybrid structure was achieved without high temperature treatment. In addition, the incorporation of organic ligands prevented formation of cracks. Nanoscale oxide particles were dispersed and incorporated into the gel network by surface condensation. The incorporation of titania nanoparticles into sols greatly reduced the volume shrinkage of gels and enhanced the mechanical strength of the components. In this work, silica sol was also applied to coat metallic microcomponents and a thin uniform coating was formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005420000051
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  • 6
    Electronic Resource
    Electronic Resource
    Band-edge photoluminescence degradation in GaAs (1991)
    Springer
    Journal of materials science 2 (1991), S. 72-78 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper reports on the degradation of the band-edge photoluminescence (PL) signal seen in various types of GaAs samples during low-power argon laser irradiation. This degradation was observed to take place over a period of minutes and was found to be a function of the position on the wafer as well as the temperature of the wafer and laser power. The decrease in PL intensity did not recover after several hours with the laser off. Surface, thermal and system parameters were eliminated as possible sources of the PL degradation seen. We propose that the observed PL degradation is partly due to a bulk material parameter, and that the method of measuring PL degradation could be used as a more reliable and reproducible method of whole-wafer characterization than the current procedure of mapping PL intensities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694755
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  • 7
    Electronic Resource
    Electronic Resource
    Iron impurities in Si3N4 processing (1985)
    Springer
    Journal of materials science 20 (1985), S. 1807-1814 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The atomic environment of iron impurities is investigated during the processing cycle of reaction-bonding silicon nitride (RBSN). Several analysis techniques are utilized, including X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and electron spin resonance (ESR), to examine iron impurities in the starting silicon powder, in sintered silicon compacts, and in RBSN materials. Results indicate that iron impurities in as-received metallurgical grade silicon powder are incorporated in the silicon bulk as a highly distorted FeSi2 compound. No surface iron or iron-based particulate is observed in the starting material. Upon sintering, the iron environment becomes an ordered FeSi2 structure. In the RBNS material, the FeSi2 structure is again distorted, as observed by both EXAFS and ESR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00555287
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  • 8
    Electronic Resource
    Electronic Resource
    Heat capacity measurements of extremely thin substrate-free liquid-crystal films (1994)
    Springer
    International journal of thermophysics 15 (1994), S. 1189-1197 
    Details
    ISSN: 1572-9567
    Keywords: calorimeter ; density ; film ; heat capacity ; hexatic ; liquid crystal ; smectic-A-hexatic-B transition ; two-dimensional melting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A state-of-the-art calorimetric system has been established. The system enables us to measure simultaneously heat capacity and optical reflectivity of free-standing liquid-crystal films from many hundreds down to only two molecular layers in thickness. Our experimental results on the smectic-A-hexatic-B and smectic-C-smectic-I transitions cannot be described solely in terms of the creation of bond-orientational order, indicating that additional molecular order must be present in the hexatic phases of liquid crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01458827
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of the equilibrium concentration of impurities on the reproducibility of thermoluminescence in MgO (1981)
    Springer
    Journal of materials science 16 (1981), S. 1191-1196 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A study of thermoluminescent (TL) sensitivity and reproducibility is undertaken in crystals of MgO exposed to ultraviolet radiation in the as-received condition, and heat treated in air or in a mixtue of CO/CO2 at either 1000 or 1400° C. The changes in the concentrations of transition metal ions such as Fe3+, Cr3+, Mn2+ and V2+, caused by the heat treatments, are followed using electron spin resonance. It is shown that the equilibrium concentrations of Fe3+ and V2+ ions, which can be altered by heat treatments, play an important role in the reproducibility of the TL in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01033831
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  • 10
    Electronic Resource
    Electronic Resource
    Thermoluminescent mechanisms involving transition metal ion impurities and V-type centres in MgO crystals exposed to ultraviolet radiation (1982)
    Springer
    Journal of materials science 17 (1982), S. 2585-2593 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermoluminescent (TL) mechanisms involving Fe, Cr, Mn and V ions in both divalent and trivalent valence states, and V-type centres were studied in MgO single crystals of varying impurity content after exposure to ultraviolet radiation. Using the ESR technique, it is shown that samples containing primarily divalent impurities show no V-type centres related to the TL mechanism, which is that of charge transfer between the impurities. V-type centres, when present, are seen to be more stable in purer samples than in less pure samples, resulting in a shift of the TL peaks to higher temperatures. The TL mechanism in this case includes charge transfer between V-type centres and the impurities. The supralinear behaviour of TL peak 1 is associated with the R-emission lines of Cr3+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00543891
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