Maity, Joydeep and Hazra, Biplab and Mallick, Mousumi and Das, Aman Kumar Lal and Show, Bijay Kumar (2025) Advent of low-density superhard orthorhombic diamond based 24 % quartz composite. Journal of Alloys and Compounds, 1036.

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Abstract

A new low-density superhard material is hereby synthesized through a typically adopted low-cost single-step direct reaction synthesis route. The synthesized composite material primarily contains an orthorhombic diamond matrix with 24 vol% of hexagonal SiO2 (quartz) particles. In order to synthesize this material, dried rice husk (source of SiO2) thoroughly mixed with a reactant mixture (consisting of charcoal powder and barium carbonate powder in 4:1 ratio by mass) is isothermally held at 1000°C for 5 h in a closed container. The nascent carbon atoms evolved from the reactant mixture are presumably nucleated on SiO2 particles so as to finally originate a low-density orthorhombic diamond phase without requiring any additional pressure. The evolution of this unique material is substantiated with the thermodynamic feasibility of a highly negative Gibbs free energy change, XRD analysis, FESEM study together with EDS analysis, Raman spectroscopy, X-ray photoelectron spectroscopy and HRTEM analysis together with Electron energy loss spectroscopy. The considerably low density together with three-dimensional structure is attributed to the uniformly distributed vacant lattice sites within the orthorhombic diamond matrix. Furthermore, the superhard characteristic of this material is confirmed with Vickers hardness test. This elucidates a pathway for emergence of a new material possessing significantly high hardness (70 GPa), considerably low density (1.23 g cm−3) and the highest specific hardness (56.91 GPa/g cm−3) among all kinds of known synthesized materials reported so far.

Item Type:	Article
Subjects:	Material Testing
Divisions:	UNSPECIFIED
Depositing User:	Mr. B. R. Panduranga
Date Deposited:	14 Mar 2026 09:41
Last Modified:	14 Mar 2026 09:41
URI:	https://cimfr.csircentral.net/id/eprint/2953

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