Experimental determination of the pressure dependence of the thermal diffusivity of teflon, sodium chloride, quartz, and silica

Abstract

The thermal diffusivity of Teflon, sodium chloride, quartz, and silica glass was measured at 40° C to pressures of 35, 18, 30, and 36 kbar, respectively. A transient line source method was modified for use in a piston‐cylinder high‐pressure cell. Pressure gradients were determined by experiments with bismuth foils. The pressure dependence of the thermal diffusivity at 40°C for the substances studied may be represented as follows (κ in square centimeters per second, P in kilobars): for the low‐pressure phases of Teflon, Teflon I‐II, P < 5.5 kbar, κ = 0.0012 + 3.6 × 10−5P; for the high‐pressure phase, Teflon III, 5.5 kbar < P < 35 kbar, κ = 0.0012 + 8.0 × 10−5 P; for polycrystalline halite, P < 18 kbar, κ = 0.0031 + 9.5 × 10−4 P; for quartz, perpendicular to the c axis, P < 30 kbar, κ = 0.031 + 5.3 × 10−4 P; for silica glass, P < 36 kbar, κ = 0.0068 — 6.7 × 10−6 P. The diffusivity of silica glass decreases with pressure, in contrast to the diffusivity of its crystalline counterpart, quartz, which increases with pressure. In addition to the diffusivity the thermal conductivity of Teflon was determined by measuring the power applied to the heater wire. The thermal conductivity of a Teflon I‐II mixture is approximately constant at 0.0075–0.0078 cal/cm s °K to 5.5 kbar. Above 5.5 kbar the conductivity of Teflon III is given by K = 0.0062 + 4.0 × 10−5P. The specific heat of Teflon decreases with pressure and decreases discontinuously by 15% across the Teflon II‐III phase change, in good agreement with the decrease predicted from thermal expansion and compressibility data.

Microscopic evidence of stishovite generated in low‐pressure shock experiments on porous sandstone: Constraints on its genesis

“…Considering the p ‐ and T ‐dependency of α, no change in the magnitude of order is reported for the present temperature and pressure ranges (Kieffer et al. ; Katsura ; Eriksson et al. ; Gibert and Mainprice ), even if we have to face the melt‐to‐glass transition (Hofmeister and Whittington ).…”

Thermal diffusivity of silica glass at pressures up to 9 GPa

“…He did not observe a pressure dependence of the thermal diffusivity in silica glass. Kieffer et al (1976) also measured thermal diffusivity of silica glass at 310 K and pressures up to 3.5 GPa. Although they reported a negative pressure derivative of thermal diffusivity of silica glass, the absolute value of the pressure derivative was unexpectedly small.…”

“…The pressure range of his measurement was not large enough to detect the pressure dependence of the thermal diffusivity of silica glass. Kieffer et al (1976) measured thermal diffusivity of silica glass at about 310 K and pressured up to 3.5 GPa. As mentioned earlier, although they found a negative pressure derivative of thermal diffusivity of silica glass, its absolute value (6.7…”

“…Conductive heat transfer is believed to be a dominant heat transfer mechanism in subducting slabs so that the measurements of thermal diffusivity and conductivity are fundamental to the comprehension of geophysical processes associated with subduction. So far, high pressure measurements of these heat transfer properties have been made at pressures up to 6 GPa (Fujisawa et al 1968;Yukutake 1974;Kieffer et al 1976;MacPherson and Schloessin 1982;Horai and Susaki 1989). These studies demonstrate that the pressure effects on the heat transfer properties of minerals are relatively large, suggesting that these properties must be measured under high P-T conditions appropriate to the upper mantle.…”

Pressure tuning of the thermal conductivity of the layered muscovite crystal

“…The pressure dependence of the thermal conductivity of solids has been extensively studied at pressures up to Ϸ2 GPa. [10][11][12][13][14] However, much higher pressures, Ϸ20 GPa, are needed to significantly alter the anisotropy of a layered oxide crystal. Studies of ⌳ up to or beyond 20 GPa are rare in the scientific literature and are essentially limited to studies of molecular crystals; 15 and relatively recent work applying the Ångström method within a 5000-ton multianvil apparatus 16 and flash diffusivity within a diamond-anvil cell.…”