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  • 1
    Electronic Resource
    Electronic Resource
    Thermal conductivity by a pulse-heating method: Theory and experimental apparatus (1990)
    Springer
    International journal of thermophysics 11 (1990), S. 629-641 
    Details
    ISSN: 1572-9567
    Keywords: dynamic measurements ; high temperature ; scanning pyrometry ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new dynamic technique for the measurement of thermal conductivity at high temperatures has been developed at the IMGC. The specimen is brought to high temperatures with a current pulse; during cooling the heat content is dissipated by radiation and by conduction. The differential equation describing this process contains terms related to the heat capacity, the hemispherical total emittance, and the thermal conductivity of the material. If the first two properties are determined using the same specimen during subsecond pulse heating experiments, thermal conductivity may be evaluated by accurate measurements of the round-shaped temperature profiles established on the specimen during cooling. High-speed scanning pyrometry makes possible accurate measurements of temperatures and of temperature derivatives (with respect to space and time), which enables the differential equation describing the power balance at each point of the specimen to be transformed into a linear equation of the unknown thermal conductivity. A large overdetermined system of linear equations is solved by least-squares techniques to obtain thermal conductivity as a function of temperature. The theory underlying the technique is outlined, the experimental apparatus is described, and details of the measurement technique are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01184333
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  • 2
    Electronic Resource
    Electronic Resource
    Differential equations for a dynamic thermal conductivity experiment (1992)
    Springer
    International journal of thermophysics 13 (1992), S. 29-37 
    Details
    ISSN: 1572-9567
    Keywords: dynamic measurements ; high temperature ; scanning pyrometry ; temperature profiles ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The mathematical model that describes a dynamic thermal conductivity experiment is reconsidered by taking into account the role of thermal expansion. Two differential equations are presented that take into account the various physical phenomena occurring in a long thin rod directly heated by a current pulse. One of the two equations keeps variables space and time completely separate and is particularly useful for computer simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503353
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  • 3
    Electronic Resource
    Electronic Resource
    A new dynamic technique for the measurement of hemispherical total emittance (1992)
    Springer
    International journal of thermophysics 13 (1992), S. 17-27 
    Details
    ISSN: 1572-9567
    Keywords: dynamic measurements ; emittance ; high temperature ; scanning pyrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new dynamic technique for the measurement of thermal conductivity under development at the IMGC requires accurate values of heat capacity and of hemispherical total emittance at high temperature. Until recently, these data were provided by subsecond pulse heating experiments performed on the same specimens in the same apparatus. The pulse heating technique is the most accurate method for the determination of heat capacity at high temperatures, but because of various experimental problems, the accuracy of hemispherical total emittance determinations is limited to 5%. A new method for a more accurate determination of hemispherical total emittance is proposed, which uses the same experimental data available from thermal conductivity experiments. An analysis of the temperature profiles measured during the free cooling indicates that regions with high-temperature gradients (toward the ends of the specimen) are the best regions for thermal conductivity measurements, while regions with low-temperature gradients (at the center of the specimen) are the best regions for hemispherical total emittance determinations. The new measurement method and some preliminary results are presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503352
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement of thermophysical properties by a pulse-heating method: Thoriated tungsten in the range 1200 to 3600 K (1994)
    Springer
    International journal of thermophysics 15 (1994), S. 1311-1322 
    Details
    ISSN: 1572-9567
    Keywords: electrical resistivity ; heat capacity ; hemispherical total emissivity ; high temperature ; tungsten ; welding electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thoriated tungsten (tungsten, 98%: thorium oxide. 2 % ) is a widely used electrode material for inert-gas arc-welding. Data for the heat capacity, electrical resistivity. and hemispherical total emissivity of this material are reported for the temperature range 1200–3600 K. A subsecond pulse-heating technique was applied to rod specimens: radiance temperature was measured by high-speed pyrometry. Literature values of the temperature dependence of the normal spectral emissivity of tungsten were used to obtain true temperatures, using the melting point of thoriated tungsten as a calibration point. Reported uncertainties for the properties are 4 % for heat capacity, 1.5 % for electrical resistivity, and 7 % for hemispherical total emissivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01458839
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  • 5
    Electronic Resource
    Electronic Resource
    Thermophysical Properties by a Pulse-Heating Reflectometric Technique: Niobium, 1100 to 2700 K (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1107-1116 
    Details
    ISSN: 1572-9567
    Keywords: electrical resistivity ; heat capacity ; hemispherical total emissivity ; high temperatures ; niobium ; pulse-heating ; refractory metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Pulse-heating experiments were performed on niobium strips, taking the specimens from room temperature to the melting point is less than one second. The normal spectral emissivity of the strips was measured by integrating sphere reflectometry, and, simultaneously, experimental data (radiance temperature, current, voltage drop) for thermophysical properties were collected with sub-millisecond time resolution. The normal spectral emissivity results were used to compute the true temperature of the niobium strips; the heat capacity, electrical resistivity, and hemispherical total emissivity were evaluated in the temperature range 1100 to 2700 K. The results are compared with literature data obtained in pulse-heating experiments. It is concluded that combined measurements of normal spectral emissivity and of thermophysical properties on strip specimens provide results of the same quality as obtained using tubular specimens with a blackbody. The thermophysical property results on niobium also validate the normal spectral emissivity measurements by integrating sphere reflectometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022654804141
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  • 6
    Electronic Resource
    Electronic Resource
    A new technique for the measurement of radiance temperature at the melting point (1993)
    Springer
    International journal of thermophysics 14 (1993), S. 485-494 
    Details
    ISSN: 1572-9567
    Keywords: high-speed pyrometry ; high temperature ; melting ; pulse heating ; radiance temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the radiance temperature of metals at their melting point received wide attention recently on account of controversial results obtained in different laboratories. During further investigations at IMGC, a new technique for radiance temperature measurements at the melting point was perfected, with numerous experiments performed at the melting point of niobium. The new technique consists in bringing the material to the melting point and interrupting the flow of current just before the specimen is destroyed. Using this method the melting plateau may be repeated several times using the same specimen. Repeatibility studies may be performed, and changes in the surface structure of the material may be evaluated. Typical results of this new technique are presented, along with a complete description of this new measurement method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566047
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  • 7
    Electronic Resource
    Electronic Resource
    Physical changes in tungsten and thoriated tungsten electrodes after subsecond heating (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 1037-1045 
    Details
    ISSN: 1572-9567
    Keywords: electron microscopy ; high temperatures ; plasma arc ; pulse heating ; thoria ; thoriated tungsten ; X-ray analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Tungsten and thoriated tungsten rods are commonly used as cathodes for arcs operating in argon. Thoriated tungsten electrodes (2 wt% thorium oxide) have significantly longer lifetimes than pure tungsten electrodes, though the reason for this is not well understood. Samples of both types of electrode were heated to the melting point of tungsten using a Subsecond pulse heating technique. The samples were then examined using electron microscopy and X-ray analysis and the results compared with similar examinations of unheated electrodes. There were definite physical changes apparent in the shape of the thoria particles, but no evidence of any reduction of the thoria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01441992
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  • 8
    Electronic Resource
    Electronic Resource
    Thermophysical properties of thoriated tungsten above 3600 K by a pulse-heating method (1996)
    Springer
    International journal of thermophysics 17 (1996), S. 1025-1036 
    Details
    ISSN: 1572-9567
    Keywords: electrical resistivity ; Frenkel disorder ; heat capacity ; melting point ; thoria ; tungsten ; welding electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thoriated tungsten (tungsten, 98% thorium oxide, 2%) is a widely used electrode material for inert-gas arc-welding. A subsecond pulse-heating technique was applied to rod specimens: radiance temperature was measured by high-speed pyrometry. Literature values of the temperature dependence of the normal spectral emissivity of tungsten were used to obtain true temperatures, with the melting point of thoriated tungsten as a calibration point. Experimental results obtained in the temperature range from 3600 K to the melting point (3693 K) are presented and discussed, along with data obtained during the initial part of the free cooling period. The electrical resistivity results show a regular behavior up to the melting point, indicating that thoria remains an insulator up to 3680 K. During heating, a heat capacity anomaly is found near 3666 K, interpreted as the melting point of thoria. During cooling, two anomalies are found, the first one with a peak near 3660 K and a second one (possibly a Frenkel disorder) with a peak near 3148 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01441991
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  • 9
    Electronic Resource
    Electronic Resource
    Issues and future directions in subsecond thermophysics research (1990)
    Springer
    International journal of thermophysics 11 (1990), S. 819-833 
    Details
    ISSN: 1572-9567
    Keywords: dynamic measurements ; high temperatures ; laser heating ; pulse heating (resistive) ; subsecond thermophysics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The key issues and anticipated future directions in subsecond thermophysics research are presented and discussed. The main emphasis is placed on experimental techniques for measurements of selected thermophysical properties utilizing rapid volume heating (resistive self-heating) and rapid surface heating (laser pulse-heating) methods. The time regime covered is from 1 to 10−12s. Specific research topics and key research areas are identified and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01184348
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of thermal conductivity from temperature profiles (1993)
    Springer
    International journal of thermophysics 14 (1993), S. 525-539 
    Details
    ISSN: 1572-9567
    Keywords: dynamic measurements ; high temperature ; scanning pyrometry ; temperature profiles ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new dynamic technique for the measurement of thermal conductivity is being developed at IMGC. The experiment consists in bringing the specimen to high temperatures with a current pulse and in measuring the temperature profiles during the free cooling period. Different techniques can be used to extract the information on thermal conductivity from the profiles. The numerical computation of thermal conductivity from the experimental temperature profiles in absolute space is possible, but it is difficult and cumbersome because one must know and take into the account the exact position of the infinitesimal elements of the specimen in different profiles. Computations in tube-space (a fictitious space where no thermal expansion occurs) are simpler and lead to less complex numerical computations. Complementary techniques to evaluate thermal conductivity as a function of temperature or at constant temperature are presented with a discussion of advantages and disadvantages of each method. Computer simulations have tested the precision of the complex software. Numerically generated temperature profiles from known thermophysical properties have been obtained and thermal conductivity has been recomputed from the profiles. The relative difference using different computational approaches and different fitting functions is always less than 0.1%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566050
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    Paper (German National Licenses)
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