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1.
The thermal conductivity of molten InSb in the temperature range between 800 and 870 K was measured by the transient hot-wire method using a ceramic probe. The probe was fabricated from a tungsten wire printed on an alumina substrate and coated with a thin alumina layer. The thermal conductivity was found to be about 18 W· m–·K–at the melting point and increased moderately with increasing temperature. The thermal conductivity of alumina used as the substrate for the probe was also measured in the same temperature range.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.On leave from NEC Corporation. 相似文献
2.
Thermal conductivity of pure monoisotopic silicon 总被引:2,自引:0,他引:2
P. G. Klemens 《International Journal of Thermophysics》1981,2(4):323-330
The thermal conductivity of pure monoisotopic silicon is estimated by two methods, which give similar results. One estimate, based on the observed thermal conductivity of monoisotopic germanium, yields a maximum of 66 W · cm–1 · K–1 at 22 K. The other estimate, based on measurements of natural silicon and on the theoretical isotope scattering rate, yields 75 W · cm–1 · K–1 at 22 K, an increase of only 45% over the natural crystal. These values are for crystals of approximately 0.5 cm diameter; smaller crystals yield lower values of the maximum conductivity and smaller isotope effects. Silicon cooled to liquid hydrogen temperature seems promising for high-irradiance laser mirrors. The small gain obtained by using monoisotopic silicon would be substantially greater in cases when the generated phonon distribution is athermal and weighted to higher frequencies. The effective heat transport could then be increased by as much as a factor 60 through the use of monoisotopic silicon. 相似文献
3.
This paper is focused on the pulse transient method. The theory of the method and the measuring regime (time window) are analyzed. The results of the analysis are verified on borosilicate crown glass BK7, which is a candidate for a standard for thermal conductivity. Thermal contact and surface effects affect the length of the time window in which the evaluation procedure is applied. The one-point evaluation technique is compared with the results of the fitting procedure that uses the time window found by difference analysis. The values of the thermal conductivity, thermal diffusivity, and specific heat were found to be 1.05 W· m–1 · K–1, 0.548 × 10–6m – 2 · s–1, and 767 J· kg–1 · K–1, respectively, using the one-point evaluation technique.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1–4, 2002, London, United Kingdom. 相似文献
4.
An apparatus developed for the measurement of thermal conductivity of solids at temperatures from 350 to 1250 K in air, vacuum, or any other controlled atmosphere is described. It is based on the steady-state axial heat flow comparative method and can be used for measurements of conductivities in the range 1 to 100 W·m–1·K–1. New heat source layout gives uniform heat flux across the specimen column, improving the accuracy of the measurements. The specimen stack is fixed in a rigid frame. It incorporates convection current breakers, eliminating thermal insulation of the stack and thereby considerably increasing the ease of specimen mounting. The accuracy of measurements was assessed by measuring the thermal conductivity of approved reference materials and is found to be within ±3%. The results of measurements on nickel of known purity are also presented. Error analysis of the system shows that the determinate error leaving the uncertainty in the thermal conductivity of the reference materials, is less than ±2%. 相似文献
5.
C. E. Hickox D. F. McVey J. B. Miller L. O. Olson A. J. Silva 《International Journal of Thermophysics》1986,7(4):755-764
Results are reported for effective thermal conductivity measurements performed in situ and in core samples of illite marine sediment. The measurements were obtained during a recent oceanographic expedition to a study site in the north central region of the Pacific Ocean. This study was undertaken in support of the U.S. Subseabed Disposal Project, the purpose of which is to investigate the scientific feasibility of using the fine-grained sediments of the sea floor as a repository for high-level nuclear waste. In situ measurements were made and 1.5-m-long hydrostatic piston cores were taken, under remote control, from a platform that was lowered to the sea floor, 5844 m below sea level. The in situ measurement of thermal conductivity was made at a nominal depth of 80 cm below the sediment surface using a specially developed, line-source, needle probe. Thermal conductivity measurements in three piston cores and one box core (obtained several kilometers from the study site) were made on shipboard using a miniature needle probe. The in situ thermal conductivity was approximately 0.91 W · m–1 · K–1. Values determined from the cores were within the range 0.81 to 0.89 W · m–1 · K–1.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A. 相似文献
6.
R. B. Dinwiddie A. J. Whittaker D. G. Onn 《International Journal of Thermophysics》1989,10(5):1075-1084
The thermal transport properties of four commercially available AlN substrates have been investigated using a combination of steady-state and transient techniques. Measurements of thermal conductivity using a guarded longitudinal heat flow apparatus are in good agreement with published room temperature data (in the range 130–170 W · m–1 · K–1). Laser flash diffusivity measurements combined with heat capacity data yielded anomalously low results. This was determined to be an experimental effect for which a method of correction is presented. Low-temperature measurements of thermal conductivity and heat capacity are used to probe the mechanisms that limit the thermal conductivity in AlN.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
7.
A correlation to predict the thermal conductivity of andesitic igneous rocks is developed from measured data on drill cores from wells from the Los Azufres geothermal field, Mexico. The correlation was developed from density, porosity, and thermal conductivity. Seventeen determinations were made on drill cores extracted at varying depths from 12 wells. Thermal conductivity varied from 1.05 to 2.34 W · m–1 · K–1, while bulk density varied from 2050 to 2740 kg · m–3 and grain density varied from 2610 to 2940 kg · m–3. Total porosity varied from 1.9 to 24.7%. Two polynomial regressions, one linear and one quadratic, were tested on the thermal conductivity-times-bulk density product, with total porosity as the independent variable. The correlation coefficients and residual mean square deviations were 0.83 and 0.00491 for the linear fit and 0.87 and 0.00425 for the quadratic model, respectively. For porosities up to about 18%, both models showed very close predictions, but for larger values, the quadratic model appeared to be better and it is recommended for the porosity range from 0 to 25%. Furthermore, density and porosity may be determined from drill cuttings, which are more readily available than cores.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
8.
The thermal conductivity of powder fillings for load-bearing vacuum insulations is investigated. Different opacifiers have been tested in mixtures with perlite powder, precipitated silica, and fumed silica. Using temperature-dependent thermal conductivity measurements, the radiative thermal conductivity and the solid conductivity of the powder samples are separated. Additionally, the influence of the pressure load on the solid conductivity is studied. The thermal conductivities of silica powders with added opacifier powders (carbon black, magnetite, silicon carbide, titanium dioxide) can be as low as 0.003 W·m–1·K–1 if the powder boards are pressed with moderate loads. The use of microporous silica powders as filler materials allows internal gas pressures even beyond 10 hPa with only a moderate increase of the overall conductivity. 相似文献
9.
S. W. Kim H. Yu C. H. Kang S. H. Lee J. C. Kim 《International Journal of Thermophysics》2004,25(5):1505-1517
In order to investigate the photo-induced thermal property changes in chalcogenide thin films, amorphous As
2
S
3 thin film samples, whose thicknesses are 0.5, 1.0, 2.0, and 4.0 m, were prepared on silicon wafers by thermal evaporation. Their thermal conductivity was measured by the 3 method between room temperature and 100 °C. These measurements were repeated after the illumination of an Ar+ laser beam whose photon energy is consistent with the bandgap energy of As
2
S
3, and repeated again for annealed films at 180 °C for 1 h. The result shows that the thermal conductivities of fresh films were 0.14 to 0.27 W·m
–1·K
–1; however, the values increase to 0.28–0.47 W·m
–1·K
–1 after illumination of the sample and decrease to 0.19–0.42 W·m
–1·K
–1 after annealing of the sample. These changes can be explained by the change in microstructure produced from the photo-darkening and thermal annealing. 相似文献
10.
To measure thermal conductivity of materials of low conductivity (0.1 to 1 W·m–1·K–1), a method using a specimen of small size (2×25×25 mm) has been developed. This method applies a well-defined, steady, and uniform heat flux perpendicular to the surface of a small plate sample of polymers or ceramics jointly by means of radiative heat exchange as well as by an areal heater on the sample surface and allows a reasonably rapid (5-min) measurement of thermal conductivity. This method of measuring conductivity is an absolute and direct measurement method which does not need any standard reference materials or information about heat capacity. The principle of the method has been demonstrated by constructing a measurement apparatus and measuring thermal conductivity of a few materials. The thermal conductivities of silicone rubber and Pyrex (Corning 7740) glass measured by the present method between 30 and 90°C are compared with recommended values. 相似文献
11.
This paper presents thermal conductivity measurements of propane over the temperature range of 192–320 K, at pressures to 70 MPa, and densities to 15 mol · L–1, using a transient line-source instrument. The precision and reproducibility of the instrument are within ±0.5%. The measurements are estimated to be accurate to ±1.5%. A correlation of the present data, together with other available data in the range 110–580 K up to 70 MPa, including the anomalous critical region, is presented. This correlation of the over 800 data points is estimated to be accurate within ±7.5%.Nomenclature
a
n, bij, bn, cn
Parameters of regression model
-
C
Euler's constant (=1.781)
-
P
Pressure, MPa (kPa)
-
P
cr
Critical pressure, MPa
-
Q
1
Heat flux per unit length, W · m–1
-
t
time, s
-
T
Temperature, K
-
T
cr
Critical temperature, K
-
T
0
Equilibrium temperature, K
-
T
re
Reference temperature, K
-
T
r
Reduced temperature = T/T
cr
-
T
TP
Triple-point temperature, K
Greek symbols
Thermal diffusivity, m2 · s–1
-
T
i
Temperature corrections, K
-
T
Temperature difference, K
-
T
w
Temperature rise of wire between time t
1 and time t
2, K
-
T
*
Reduced temperature difference (T–T
cr)/Tcr
-
corr
Thermal conductivity value from correlation, W · m–1 · K–1
-
cr
Thermal conductivity anomaly, W · m–1 · K–1
-
e
Excess thermal conductivity, W · m–1 · K–1
-
*
Reduced density difference
-
Thermal conductivity, W–1 · m–1 · K–1, mW · m–1 · K–1
-
bg
Background thermal conductivity, W · m–1 · K–1
-
0
Zero-density thermal conductivity, W · m–1 · K–1
-
Density, mol · L–1
-
cr
Critical density, mol · L–1
-
re
Reference density, mol · L–1
-
r
Reduced density
Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
12.
S. S. Zabrodskii N. V. Antonishin V. S. Nikitin 《Journal of Engineering Physics and Thermophysics》1968,14(5):463-465
The effective thermal conductivity of beds of granular material has been investigated experimentally in the temperature range from 373 to 1200° K at a vacuum of 1·10–4 mm Hg and at atmospheric pressure. 相似文献
13.
The thermal conductivity, , of vitreous boron trioxide was measured, using a hot-wire procedure, from 170 to 570 K and under pressures of up to 1.7 GPa. The thermal conductivity at room temperature and zero pressure was found to be 0.52 W · m–1 · K–1. The values of the logarithmic pressure derivative, g = d(ln )/d(ln ), where is the density, were found to be 1.1 for uncompacted glass and 0.7 for glass compacted to 1.2 GPa. The variation of with temperature at constant density was approximately linear, with a positive slope of 1.38×10–3W·m–1·K–2. 相似文献
14.
A. C. Scott A. I. Johns J. T. R. Watson A. A. Clifford 《International Journal of Thermophysics》1981,2(2):103-114
We have used the transient hot-wire technique to make absolute measurements of the thermal conductivity of dry, CO2-free air in the temperature range from 312 to 373 K and at pressures of up to 24 MPa. The precision of the data is typically ±0.1%, and the overall absolute uncertainty is thought to be less than 0.5%. The data may be expressed, within their uncertainty, by polynomials of second degree in the density. The values at zero-density agree with other reported data to within their combined uncertainties. The excess thermal conductivity as a function of density is found to be independent of the temperature in the experimental range. The excess values at the higher densities are lower than those reported in earlier work.Nomenclature
Thermal conductivity, mW · m–1 · K–1
-
Density, kg · m–3
-
C
p
Specific heat capacity at constant pressure, J · kg–1 · K–1
-
T
Absolute temperature, K
-
q
Heat input per unit wire length, W · m–1
-
t
Time, s
-
K(=/C
p)
Thermal diffusivity, m2 · s–1
-
a
Wire radius, m
-
Euler's constant (=0.5772 )
-
p
c
Critical pressure, MPa
-
T
c
Critical temperature, K
-
c
Critical density, kg · m–3
-
R
Gas constant (=8.314 J · mol–1 · K–1)
-
V
c
Critical volume, m3 · mol–1
-
Z
c(=p
c
V
c/RT
c)
Critical compressibility factor 相似文献
15.
A. Ya. Polishchuk É. É. Shpil'rain I. T. Yakubov 《Journal of Engineering Physics and Thermophysics》1980,38(3):247-250
We give the calculated values of the thermal conductivity and viscosity of lithium vapors (T=800–2000°K, p=3·10–3-3 bar). No experiment was conducted for lithium. A comparison with experiments conducted on sodium and potassium is given.Translated from Inzhernerno-Fizicheskii Zhurnal, Vol. 38, No. 3, pp. 429–433, March, 1980. 相似文献
16.
H. B. Chae K. H. Park D. J. Seong J. C. Kim Y. J. Baik 《International Journal of Thermophysics》1996,17(3):695-703
Diamond films 60 and 170 µm in thickness were grown by PACVD (plasma-assisted chemical vapor deposition) under similar conditions. The thermal diffusivity of these freestanding films was measured between 100 and 300 K using AC calorimetry. Radiation heat loss from the surface was estimated by analyzing both the amplitude and the phase shift of a lock-in amplifier signal. Thermal conductivity was calculated using the specific heat data of natural diamond. At room temperature, the thermal conductivity of the 60 and 170 m films is 9 and 16 W-cm–1. K–1 respectively, which is 40–70% that of natural diamond, The temperature dependence of thermal conductivity of the CVD diamond films is similar to that of natural diamond, Phonon scattering processes are considered using the Debye model, The microsize of the grain boundary has a significant effect on the mean free path of phonons at low temperatures. The grain in CVD diamond film is grown as a columnar structure, Thus, the thicker film has the larger mean grain size and the higher thermal conductivity. Scanning electron microscopy (SEM) and Raman spectroscopy were used to study the microstructure of the CVD diamond films. In this experiment, we evaluated the quality of CVD diamond film of the whole sample by measuring the thermal conductivity.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
17.
Aluminium nitride ceramics with no sintering additives could be densified to close to theoretical density (99.6% theoretical) by pressureless sintering of tape-cast green sheets at 1900 °C for 8 h. The thermal conductivity and bending strength of the specimens were 114 Wm–1 K–1 and 240 MPa, respectively. The effect of Y2O3 additive on sinterability, thermal conductivity and microstructure of aluminium nitride ceramics was investigated. Thermal conductivity increased with increasing amount of Y2O3 additive, sintering temperature and holding time at the sintering temperature. Samples with a thermal conductivity up to 258 Wm–1 K–1 were fabricated by elimination of the grain-boundary phase. 相似文献
18.
This paper decribes the Knudsen-effect errors of the transient line-source method used for accurate measurements of the thermal conductivity and thermal diffusivity of fluids. The analysis demonstrates that the instrument can be used with a good accuracy (>0.5%) to lower densities than previously thought. The principal errors are illustrated by measurements on propane in the temperature range 250–300 K at densities less than 9 kg · m–3. 相似文献
19.
Silica aerogels were synthesized via solvent exchange/surface modification of wet gels from waterglass using IPA/TMCS/n-Hexane solution. The densities, porosities, and specific surface areas of the aerogel were in the range of 0.128–0.153 g/cm3, 93–95%, and 598–795 m2/g, respectively. Aerogel-PVB composites were manufactured by hot pressing. Aerogels were crushed and mixed with PVB. Three mixing methods were performed. The aerogel-PVB composites had densities of 0.19–1.09 g/cm3, and thermal conductivities of 0.03–0.12 W/(m · K). Density and thermal conductivity can be controlled by aerogel volume fraction and the mixing method. The modulus of rupture of aerogel-PVB composites was in the range of 0.15–46.5 MPa. 相似文献
20.
H. M. Roder 《International Journal of Thermophysics》1984,5(4):323-350
The paper presents new experimental measurements of the thermal conductivity of hydrogen. The ortho-para compositions covered are normal, near normal, para, and para-rich. The measurements were made with a transient hot wire apparatus. The temperatures covered the range from 78 to 310 K with pressures to 70 MPa and densities from 0 to a maximum of 40 mol · L–1. For compositions normal and near normal, the isotherms cover the entire range of pressure, and the temperatures are 78, 100, 125, 150, 175, 200, 225, 250, 275, 294, 300, and 310K. The para measurements include eight isotherms at temperatures from 100 to 275 K with intervals of 25 K, pressures to 12 MPa, and densities from 0 to 12 mol · L–1. Three additional isotherms at 150, 250, and 275 K cover para-rich compositions with para percentages varying from 85 to 72%. For these three isotherms the pressures reach 70 MPa and the density a maximum of 30 mol · L–1. The data for all compositions are represented by a single thermal conductivity surface. The data are compared with the experimental measurements of others through the new correlation. The precision (2) of the hydrogen measurements is between 0.5 and 0.8% for wire temperature transients of 4 to 5 K, while the accuracy is estimated to be 1.5%. 相似文献