# Microstructure and Mechanical Properties of B4C-HfB2-SiC Ceramic Composites Prepared by In Situ Reaction

## TL;DR

Researchers made a new ceramic composite using B4C, HfB2, and SiC, which has excellent mechanical properties and maintains strength at high temperatures.

## Contribution

A novel B4C-HfB2-SiC composite is fabricated via in situ reaction and spark plasma sintering, achieving high density and superior mechanical performance.

## Key findings

- BCHS composites with 15–30 vol.% HfSi2 reached over 98% theoretical density at 1600–1750 °C.
- Maximum hardness, toughness, and flexural strength of 31.3 GPa, 5.6 MPa·m1/2, and 573.9 MPa were achieved with 25 vol.% HfSi2 at 1650 °C.
- Flexural strength remained high at elevated temperatures (540.7 MPa at 400 °C, 586.9 MPa at 800 °C).

## Abstract

B4C-HfB2-SiC (BCHS) ceramic composites were fabricated by in situ reaction with B4C and HfSi2 mixed powders through spark plasma sintering in this work. Effects of sintering temperature and sintering additive (HfSi2) content on the density, microstructure, and mechanical properties of the BCHS specimens were studied. The BCHS composite containing 15–30 vol.% HfSi2 reached over 98% theoretical density in the temperature range of 1600–1750 °C under the pressure of 50 MPa. The Vickers hardness, fracture toughness, and room temperature flexural strength of BCHS sintered at 1650 °C with 25 vol.% HfSi2 reached a maximum value of 31.3 GPa, 5.6 MPa·m1/2, and 573.9 MPa, respectively. The flexural strength was not decreased at elevated temperatures, and the flexural strength at temperatures of 400 °C, 600 °C, and 800 °C was evaluated to be 540.7 MPa, 518.8 MPa, and 586.9 MPa, respectively. Dense B4C-HfB2-SiC composites were fabricated by the spark plasma sintering process. The introduction of HfSi2 can significantly enhance the density and mechanical properties of B4C ceramic.