High-pressure and high-temperature synthesis of rhenium carbide using rhenium and nanoscale amorphous two-dimensional carbon nitride

Nozomu Yasui,Masaya Sougawa,Daisuke Yamazaki,Yohei Kojima,Hiroaki Ohfuji,Kenichi Takarabe,Masaaki Hirai,Shinsuke Kunitsugu,Taku Okada,Kaoru Yamamoto,Rajeev Ahuja

doi:10.1080/23311940.2015.1076702

Nozomu Yasui, Masaya Sougawa + Show 9 more

Open Access

https://doi.org/10.1080/23311940.2015.1076702

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Abstract

Both Re2C and Re2N are ultra incompressible and have a bulk modulus of about 400 GPa. These materials are synthesized under high pressure and high temperature. The synthesis pressures are about 10 GPa or below for Re2C and 20–30 GPa for Re2N. If the synthesis pressure of Re2N was about 10 GPa or below, a large volume high-pressure cell like a multi-anvil apparatus can be used to synthesize Re2N. To realize this, a proper solid nitrogen source is needed instead of liquid or gas nitrogen. We used a precursor of a mixture of rhenium and home-made nanoscale amorphous two-dimensional carbon nitride as a solid nitrogen source. Consequently, the synthesis reaction produced Re2C but not Re2N. We characterized the synthesized Re2C by various techniques including high-pressure x-ray diffraction (XRD). The bulk modulus B0 of the synthesized Re2C under hydrostatic conditions was estimated to be 385.7 ± 18.0 GPa. This value is a little smaller than the previous data. When the pressure medium became non-hydrostatic, the peculiar compression behaviour occurred; the rate of broadening of XRD lines increased and the compression became negligible in the range of a few GPa. The reason for this peculiar behaviour is not known.

Highlights

If a proper solid nitrogen source could be used for synthesizing target nitrogen compounds under high pressure conditions, the synthesis experiment would be easier and faster than when using liquid or gas nitrogen to explore nitride compounds with novel physical properties.High pressure and high temperature synthesis of rhenium carbide was reported 43 years ago by Popova and Boiko, and rhenium carbide and other transition metal carbides were expected to be superhard and have high melting points (Popova & Boiko, 1971)
The whole Pt capsule was covered with epoxy resin and polished with a diamond powder to prepare a cross-sectional surface for microscope observation
After the introduction of epoxy resin, the existence of epoxy resin in the synthesized sample means that the synthesized material includes a gaseous component, and the void was left after the gaseous component went out into the air while grinding

Summary

Introduction

If a proper solid nitrogen source could be used for synthesizing target nitrogen compounds under high pressure conditions, the synthesis experiment would be easier and faster than when using liquid or gas nitrogen to explore nitride compounds with novel physical properties.High pressure and high temperature synthesis of rhenium carbide was reported 43 years ago by Popova and Boiko, and rhenium carbide and other transition metal carbides were expected to be superhard and have high melting points (Popova & Boiko, 1971). We report on the synthesis experiment using the starting material of rhenium and na-2D-C3N4HxOy under high pressure and high temperature.

Results

Conclusion