Exceptional Hardness and Thermal Properties of SiC/(Hf,Ta)C(N)/(B)C Ceramic Composites Derived from Single‐Source Precursor

Abstract

In the present work, monolithic SiC/(Hf0.75Ta0.25)C(N)/(B)C ceramic composites were prepared via spark plasma sintering (SPS) of amorphous SiHfTa(B)CN‐based powders synthesized from single‐source precursors. The as‐sintered ceramic nanocomposites were investigated by XRD, Raman, SEM and TEM in order to study their microstructure and chemical composition. Furthermore, the thermal conductivity, the thermal expansion as well as the hardness and Young’s moduli of the prepared monolithic samples were determined. The incorporation of boron in the system resulted in enhanced densification due to decreased porosity and improved distribution of the individual phases in the composite after sintering. These favourable effects also positively influenced the thermomechanical properties of the composite. The boron‐modified sample displayed a decreased thermal diffusivity and conductivity compared with the boron‐free sample. Additionally, a macro‐hardness obtained by Vickers indentation of 31 GPa was achieved for loads up to 196 N, surpassing the hardness of ultra‐hard materials like silicon carbide, hafnium carbide and tantalum carbide as well as their solid solutions. Young’s moduli of the composites were analyzed to 405 ± 10 GPa and 277.5 ± 41 GPa for the boron‐containing and boron‐free samples, respectively.This article is protected by copyright. All rights reserved.

Hafnium Carbide: Prediction of Crystalline Structures and Investigation of Mechanical Properties

“…Its high melting point, approximately 3900 • C, has attracted interest since a superior level of hardness can be inferred from a high melting point [18]. HfC can form solid solutions with various chemical systems, e.g., with TaC [19], ZrC [20], SiC [21], uranium monocarbide (UC) [22], and more complex ones like (Hf, Ta)C/SiC, and (Hf, Ti)C/SiC [23], SiC/(Hf, Ta)C(N)/(B)C [24], etc.…”