Density measurement of samples under high pressure using synchrotron microtomography and diamond anvil cell techniques

Xianghui Xiao,Luhong Wang,Haozhe Liu,Francesco De Carlo

doi:10.1107/s0909049510008502

Xianghui Xiao, Luhong Wang + Show 2 more

Open Access

https://doi.org/10.1107/s0909049510008502

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Abstract

Accurate mass density information is critical in high-pressure studies of materials. It is, however, very difficult to measure the mass densities of amorphous materials under high pressure with a diamond anvil cell (DAC). Employing tomography to measure mass density of amorphous samples under high pressure in a DAC has recently been reported. In reality, the tomography data of a sample in a DAC suffers from not only noise but also from the missing angle problem owing to the geometry of the DAC. An algorithm that can suppress noise and overcome the missing angle problem has been developed to obtain accurate mass density information from such ill-posed data. The validity of the proposed methods was supported with simulations.

Highlights

Research on the equation of state of materials under highpressure conditions provides important information on the fundamental physical properties of materials, and is a traditionally active area in high-pressure research
Using X-ray scattering and diamond anvil cell (DAC) methods, several cases have been reported by fitting the structural factors of the noncrystalline samples under pressure conditions to estimate the density (Eggert et al, 2002; Shen et al, 2002, 2004)
Synchrotron X-ray absorption methods are widely used by applying the absorption law [I = I0 exp(Àt), where I and I0 are the intensities of the transmitted and incident beams, respectively, and are the mass absorption coefficient and density of the sample, and t is the sample length in the X-ray path] to measure the density of melts under pressure using a large-volume press (Katayama et al, 1993, 1998; Katayama, 1996; Sanloup et al, 2000)

Summary

Introduction

Research on the equation of state of materials under highpressure conditions provides important information on the fundamental physical properties (e.g. density versus pressure) of materials, and is a traditionally active area in high-pressure research. The reason why the calculated mass density of NaCl with Pt as a reference has a good agreement with the real values in the pressure range 0–15 GPa is because the magnitude of (NavagCl À NreaaCl l) À (raevfg À rreefal) is small This makes the approximation in equation (3) more pronounced. Errors contributed from inherent problems in high-pressure DAC experiments, such as pressure gradient, strain and stress states of sample embedded in non-ideal hydrostatic pressure medium, which are very interesting topics and could be approached by other advanced novel techniques like synchrotron X-ray diffraction tomography, are out of the scope of this paper. This suggests a density-fluctuation-driven phase transition from a-Se to m-Se

Conclusions

Findings

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