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[SIT16-P08] Determination of temperature gradient in the multi-anvil assembly at 2500°C heating temperature based on coesite-stishovite phase transition
Keywords:Temeprature gradient, Multi-anvil, Coesite-stishovite transition
Investigations of the temperature gradient in the high-pressure experimental charges have been conducted extensively since Kushiro [1] developed a tapered-type heater to reduce the temperature gradient in the experimental charge of the piston cylinder high-pressure apparatus [e.g., 2 – 5]. However, the heating temperatures were less than 2000°C in most of those works. On the other hand, the previous works for higher than 2000°C are limited to only the numerical simulation [6]. In this study, at 2500°C heating temperature, we determined the axial temperature gradient in the experimental charge based on the P-T conditions of the SiO2 phase transition between coesite (coe) and stishovite (st) [7]. In this presentation, we also compare those in previous works together with the relationship between the temperature and the distance from the hotspot in the experimental charge.
The experimental procedures in this study were essentially the same as those of Moriguti et al. [8], in which the Kawai-type of multi-anvil apparatus, installed at the Institute for Planetary Material, Okayama University, was used and the experimental cell assembly had a rhenium heater. In this study, SiO2 (99.999%) glass powder was used as the starting material. The separately prepared four samples were compressed at the following press loads, 1.6, 2.0, 2.2, and 2.3 MN (equivalent to 10.4 to 12.6 GPa). And then, the sample was heated at 2500°C for 5 min and was subsequently quenched by shutting off the electric power supply. Phases in the run products were identified using a micro-focused X-ray diffractometry (MF-XRD: Rigaku RINT RAPID II-CMF) with a Cu source. The temperatures at the phase transition of coe-st in the experimental charge were determined using the equation of the phase boundary of coe-st [7]. In this presentation, we also compare those in previous works together with the relationship between the temperature and the distance from the hotspot in the experimental charge.
The temperature gradient along the axis of the furnace which had the hottest point at the center showed a parabolic curve in this study (y = -423.45x2 + 167.40x, r2 = 0.98). This profile of the temperature gradient, the parabolic curve, was consistent with that suggested by Kushiro [1] based on the three measured data in a furnace. In also other previous works in which the straight-wall heater was used, we found that the temperature gradients showed a parabolic profile irrespective of the difference in the materials of the heaters and the surrounding insulators [2, 4, 6, 9].
The temperature gradient in this study was 256 °C/mm, which was the highest compared with those in previous works, 132, 142, and 199 °C/mm obtained from the different heating temperatures, 1500, 1400-1700, and 1975°C, respectively, although the heater materials were different in each, graphite, LaCrO3, and rhenium, respectively [2, 6, 9].
The difference in the temperature gradient would be dominantly due to the difference in the heating temperatures because the systematic increase is observed in the temperature gradients with the increase of the heating temperatures regardless of the differences in the materials of the heaters and the surrounding insulators.
References
[1] Kushiro, I. (1976) Carnegie Inst. Washington Year Book 75, 832-833.
[2] Takahashi, E. et al. (1982) Geophys. Res. Lett. 9, 805-807.
[3] Walter, M.J. et al. (1995) Can. J. Phys. 73, 273-286.
[4] van Westerenen, W. et al. (2003) Geochem. Geophys. Geosys. 4, 1036, doi:10.1029/2002GC000474.
[5] Zarei, A. et al. (2018) High Press. Res. 38, 243-249.
[6] Yoneda, A. et al. (2014) High Press. Res. 34, 392-403.
[7] Zhang, J., Li, B. Utsumi, W. and Lieberman, R.C. (1996) Am. Mineralogist. 23, 1-10.
[8] Moriguti, T. et al. (2022) Am. Mineralogist. 107, 2226-2233.
[9] Gasparik, T. (1989) Contrib Mineral Petrol. 102, 389-405.
The experimental procedures in this study were essentially the same as those of Moriguti et al. [8], in which the Kawai-type of multi-anvil apparatus, installed at the Institute for Planetary Material, Okayama University, was used and the experimental cell assembly had a rhenium heater. In this study, SiO2 (99.999%) glass powder was used as the starting material. The separately prepared four samples were compressed at the following press loads, 1.6, 2.0, 2.2, and 2.3 MN (equivalent to 10.4 to 12.6 GPa). And then, the sample was heated at 2500°C for 5 min and was subsequently quenched by shutting off the electric power supply. Phases in the run products were identified using a micro-focused X-ray diffractometry (MF-XRD: Rigaku RINT RAPID II-CMF) with a Cu source. The temperatures at the phase transition of coe-st in the experimental charge were determined using the equation of the phase boundary of coe-st [7]. In this presentation, we also compare those in previous works together with the relationship between the temperature and the distance from the hotspot in the experimental charge.
The temperature gradient along the axis of the furnace which had the hottest point at the center showed a parabolic curve in this study (y = -423.45x2 + 167.40x, r2 = 0.98). This profile of the temperature gradient, the parabolic curve, was consistent with that suggested by Kushiro [1] based on the three measured data in a furnace. In also other previous works in which the straight-wall heater was used, we found that the temperature gradients showed a parabolic profile irrespective of the difference in the materials of the heaters and the surrounding insulators [2, 4, 6, 9].
The temperature gradient in this study was 256 °C/mm, which was the highest compared with those in previous works, 132, 142, and 199 °C/mm obtained from the different heating temperatures, 1500, 1400-1700, and 1975°C, respectively, although the heater materials were different in each, graphite, LaCrO3, and rhenium, respectively [2, 6, 9].
The difference in the temperature gradient would be dominantly due to the difference in the heating temperatures because the systematic increase is observed in the temperature gradients with the increase of the heating temperatures regardless of the differences in the materials of the heaters and the surrounding insulators.
References
[1] Kushiro, I. (1976) Carnegie Inst. Washington Year Book 75, 832-833.
[2] Takahashi, E. et al. (1982) Geophys. Res. Lett. 9, 805-807.
[3] Walter, M.J. et al. (1995) Can. J. Phys. 73, 273-286.
[4] van Westerenen, W. et al. (2003) Geochem. Geophys. Geosys. 4, 1036, doi:10.1029/2002GC000474.
[5] Zarei, A. et al. (2018) High Press. Res. 38, 243-249.
[6] Yoneda, A. et al. (2014) High Press. Res. 34, 392-403.
[7] Zhang, J., Li, B. Utsumi, W. and Lieberman, R.C. (1996) Am. Mineralogist. 23, 1-10.
[8] Moriguti, T. et al. (2022) Am. Mineralogist. 107, 2226-2233.
[9] Gasparik, T. (1989) Contrib Mineral Petrol. 102, 389-405.