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  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3113-3114 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An infrared radiation pyrometer for transient temperature measurement and a photoelectric installation for micrometric length-change measurement were developed. After being heated by a CO2 laser pulse of 0.1 μs, the transient temperature-rise history and length change of thermal expansion of 20–50 μm Al films during tens of microseconds were recorded. Nonsynchronous change of temperature and thermal expansion under transient heating was observed.
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  • 4
    ISSN: 1572-9567
    Keywords: CCD ; contactless ; dilatometer ; foil ; thermal expansion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A contactless, compact, low-cost dilatometer based on a laser-pulse thermal-conductivity apparatus has been developed to measure the linear thermal expansion of foil materials. The two sample-edge images are projected onto the array of a charge-coupled device (CCD). Changes in sample length are determined from measurements of the corresponding displacements of the sample-edge images focused on the CCD. The dilalometer performance was tested by comparing results of measurements of the thermal expansion for pure copper with published data. The linear thermal expansion of an L-16-type foil of 20-μm thickness, which is a candidate material for thermocontrol layers (in engineering), was measured with the apparatus.
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  • 5
    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.
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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.
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  • 7
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The flash method including the single- and double-ended method has gained widespread acceptance for measuring thermal diffusivity of thick foils (in millimeters) as well as thin films (in microns). However when the method is employed, some basic experimental conditions are assumed. In this paper, two of the assumptions, the finite absorption depth effect and the nonlinearity of the detector, are discussed in the situation of thin film samples. For the first one, the deviation of the factor ω1/2 (=π2αt1/2/L2) from 1.37 and the corresponding errors in deriving thermal diffusivity from t1/2 are discussed for various relative absorption depth δ. The result indicates criteria for the method to be available, that is, L(approximately-greater-than)10δ and L(approximately-greater-than)14δ for the double- and the single-ended method. For the second one, by considering the errors in voltage output of a (Hg, Cd)Te IR detector, how the factor ω1/2 deviates from 1.37 and the corresponding errors in thermal diffusivity measurement under various initial temperature conditions are discussed. The results are shown graphically and tabulated. © 1995 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3749-3752 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transient laser pulse has been used to generate nonsynchronous change of temperature rise and thermal expansion in thin films. The transient process of thermal expansion is recorded by a photoelectric high-speed acquisition system. By comparison of the calculated temperature rise and thermal expansion, thermal stress relaxation processes in Al films of 20–50 μm thickness is obtained. This result shows that, for transient heating, thermal stress exists even in the case of uniform temperature distribution and free expansion. And also there is a transient high stress in thin films under high-speed heating.
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