Platinum Metals Rev., 1965, 9, (2), 60
Thermal Conductivity of Pure Platinum
The thermal conductivity of pure platinum was recently found by Powell and Tye (1) at the National Physical Laboratory, working for the first time on substantial solid specimens, to remain surprisingly constant within 0.5 per cent of 0.73W cm-1°C_1 over the range o to 950°C. Several other investigators have since examined the thermal conductivity of platinum and some of their results were reported at the Thermal Conductivity Conference at the National Physical Laboratory last July.
At first sight the conclusions of Powell and Tye are not fully supported by this further work. Thus K. H. Bode (2) of Physikalische-Technische Bundesanstalt, Braunschweig, obtained a value rising from 0.7025 to 0.7100 between o and 100°C using as test piece a massive cylindrical specimen. The platinum, however, contained 135 to 150 p.p.m. of impurities and its density was only 21.32 g/ml compared with 21. 5, the NPL figure.
J. J. Martin and P. H. Sidles (3) of Iowa State University measured the thermal diffusivity of two specimens, one of high purity (99.999 per cent) and the other less pure (99.9 per cent) at temperatures up to 927°C and from their results calculated values of thermal conductivity. Unexpectedly the purer sample had the lower thermal conductivity at high temperatures. The figures obtained for the purer sample were, however, certainly not constant, being 5 per cent lower at room temperature than the value found by Powell and Tye, and 10 per cent higher at 877°C.
Finally, M. J. Wheeler (4) of the Hirst Research Centre of the General Electric Company Limited, at Wembley, measured thermal diffusivity from 907° to 1477°C using a modulated beam technique. The calculated values of thermal conductivity agree reasonably well with those of Powell and Tye around 1100°C but tend to rise at higher temperatures.
On the whole this new evidence does not seem to be of sufficient weight to overthrow the conclusion of Powell and Tye that the thermal conductivity is sensibly constant from room temperature to around 900°C. On the other hand, it is possible that there may very well be an inflexion around 800 to 900°C, the thermal conductivity tending to rise at higher temperatures.
- 1 Platinum Metals Rev., 1964, 8, 13
- 2 K. H. Bode, PTB-Miueilungen, 1964, 75, (in the Press)
- 3 J. J. Martin and P. H. Sidles, Contribution 1614 from Institute for Atomic Research and Department of Physics, Iowa State University, Ames, Iowa
- 4 M. J. Wheeler, Brit. J. of App. Physics, 1965, 16, (3), 365