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  • 1
    ISSN: 1432-0630
    Keywords: 72.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Deep-level transient spectroscopy and thermally stimulated capacitance measurements were used to investigate the properties of deep traps in Si-dopedn-Al x Ga1−xAl layers grown by molecular beam epitaxy. Two electron traps at electron emission activation energies of 0.44 and 0.57 eV have been detected. Both traps were studied in detail and found to be the origin of the persistent-photo-conductivity phenomenon in this material. The nature of both traps is the same as of the DX center in liquid phase epitaxial material reported by Lang et al. The electron capture cross-sections areσ n 1 =σ n 2=8.3×10−22cm2 atT=205K. Activation energies ofE σ 1= 0.33eV andE σ 2=0.37eV at temperatures higher than 125 K were determined by DLTS measurements and by direct measurements of the capture transient. In order to allow for the variation of the free-electron concentration during the capture process, a new method for the evaluation of the electron capture crosssection was developed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 7 (1986), S. 803-810 
    ISSN: 1572-9567
    Keywords: composites ; copper ; flash method ; iron ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method for measuring thermal diffusivity in one of the layers of a two-layer composite sample has been described. The heat transfer problem of a two-layer sample associated with pulse thermal diffusivity measurements has been analyzed for two cases: exponential and square-wave pulses. According to our measurements, a triangular heat-pulse function approximates reasonably well the output of the Nd-glass laser. In this paper, an expression is derived for the temperature transient at the rear face of two-layer sample being subjected to a triangular heat-pulse input on the front face. The analytical solution of the problem forms the basis of our method of data reduction. This solution has been programmed for computer processing of the data. The method described here has been successfully tested by limited measurements on copper and iron.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 21 (2000), S. 479-485 
    ISSN: 1572-9567
    Keywords: diamond ; film ; flash method ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper discusses the short-pulse-flash method developed for thermal diffusivity measurements on thin films. Two kinds of CVD diamond film have been prepared, and their thermal diffusivity in the perpendicular direction has been measured with this method. The measurement errors caused by the surface coating are discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-9567
    Keywords: flash method ; thermal contact resistance ; thermal control coatings ; thermal diffusivity ; two-layer composite sample
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal diffusivity of brittle coatings cannot be measured by the flash method directly because of the difficulty of preparing free-standing samples. Adopting the flash method using a two-layer composite sample, it is possible to measure thermal diffusivity if the radiant pulse is well defined and good thermal contact on the interface of the composite sample can be ensured. Using an equilateral trapezoidal pulse of an Nd-glass laser measuring the dimensionless temperature history of the rear face of the sample, we determined the thermal diffusivity of thermal control coatings in the temperature range of 80 to 200°C. The results for different thicknesses of substrate showed that the thermal contact resistance of the interface can be neglected.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 7 (1986), S. 731-742 
    ISSN: 1572-9567
    Keywords: specific heat ; thermal conductivity ; thermal diffusivity ; thermal emissivity ; thermophysical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Various aspects of the importance of thermophysical property (TPP) studies to science and technology in China are discussed. Several stages of the development of experimental principles and equipment are described. Some examples of TPP applications in economic practice are presented. Theoretical and methodological studies in this field are summarized. The presentations are limited mostly to work on solids.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-9567
    Keywords: anisotropic materials ; pyrolytic graphite ; pyrolytic boron nitride ; thermal conductivity ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The laser pulse method can be successfully applied to the measurement of thermal diffusivity of isotropic materials subject to some assumptions. For anisotropic materials, this method is applicable to the measurement of principal thermal diffusivity only on the condition that there is no difference in direction between the principal axis and that of the temperature gradient. After analyzing the heat conduction process in an anisotropic solid, it has been shown that large errors in the measurement of thermal diffusivity would exist if the direction of the principal axis deviates inconspicuously from that of the temperature gradient. The experimental results of thermal diffusivity of highly oriented pyrolytic graphite (HOPG) samples with various deviation angles have been compared with the analytical results. The laser pulse method is not applicable to measurements on semitransparent pyrolytic boron nitride (PBN). We adopted a two-layer composite sample to measure the thermal diffusivity of PBN in the c direction and a particular graphite-PBN composite sample has been prepared which has a very low thermal resistance at the interface. The thermal diffusivity and thermal conductivity of PG (below 2300°C) and PBN (below 1000°C) are given.
    Type of Medium: Electronic Resource
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