Accurate temperature measurement by temperature field analysis in diamond anvil cell for thermal transport study of matter under high pressures

Abstract

The study on the thermal transport properties of matter under high pressure is important but is hard to fulfill in a diamond anvil cell (DAC) because the accurate measurement of the temperature gradient within the sample of DAC is very difficult. In most cases, the sample temperature can be read accurately from the thermocouples that are directly attached to the lateral edges of diamond anvils because both the sample and diamond anvils can be uniformly heated up to a given temperature. But for the thermal transport property studies in DAC, an artificial temperature distribution along the compression axis is a prerequisite. Obviously, the temperature of the top or bottom surface of the sample cannot be substituted by that of diamond anvils although diamond anvils can be considered as a good medium for heat conduction. With temperature field simulation by finite element analysis, it is found that big measurement errors can occur and are fatal to the correct analysis of thermal transport properties of materials. Thus, a method of combining both the four-thermocouple configuration and temperature field analysis is presented for the accurate temperature distribution measurement in DAC, which is based on the single-function relationship between temperature distribution and sample thermal conductivity.

Magnetic field analysis in a diamond anvil cell for Meissner effect measurement by using the diamond NV – center

“…All the physical and geometrical properties of entities in FEA are input according to the real conditions in experiments. [22] The facet of the diamond anvil is 40 µm in diameter and the magnetic permeability of diamond is approximately 1 H/m. A rhenium gasket is used in simulation, whose size is 6 mm in diameter and 0.25 mm in thickness, and the magnetic permeability is 1 H/m.…”

Investigating the thermal conductivity of materials by analyzing the temperature distribution in diamond anvils cell under high pressure

“…[9][10][11][12][13][14] When a DAC is subjected to high temperatures it can simulate the conditions in the earth's interior in the laboratory, which is of great importance for investigating the thermal properties of minerals and rocks. [15][16][17] However, it is an enormous challenge to characterize the thermophysical properties of the material under test at conditions of extremely high temperature and high pressure (HT-HP). [18] This challenge is even more pronounced in the DAC platform.…”

“…In order to accurately measure the heat transport properties of materials under extreme conditions, innovations have been proposed to measure the steady-state heat conductivity of materials through a DAC. [17] The main idea in this regard was to realize the temperature gradient of samples by directly heating the upper and lower diamond anvils (DAs) in a high-temperature resistant furnace. Therefore, it is essential to calculate the temperature distributions in the sample to study the in situ heat transport properties in the DAC.…”

Effect of deformation of diamond anvil and sample in diamond anvil cell on the thermal conductivity measurement*

“…The designed apparatus is equipped with a vacuum device to realize a stable heat flow field in the DAC. [7] Thermal loads are caused by temperature inhomogeneity in the steady-state heating, and the influence of thermal loads on the structural reliability of DAC and measuring the sample thickness are the main challenges in the early stage of the experiment. [8][9][10] Yue et al in our research group proposed the method of multi-thermocouple in situ temperature measurement combined with the numerical model to simulate the distribution of sample temperature field in DAC by heat conduction, and established a brand-new sample thermal conductivity measurement method.…”

“…[8][9][10] Yue et al in our research group proposed the method of multi-thermocouple in situ temperature measurement combined with the numerical model to simulate the distribution of sample temperature field in DAC by heat conduction, and established a brand-new sample thermal conductivity measurement method. [7] However, the in situ thermal conductivity of samples studied by this method depends on the structural size of the main components of DAC. It is worth noting that at this moment, the stress state and deformation degree of diamond anvils (DAs) and sample under HTHP conditions are not clear.…”