In Situ Growth Behavior of SiC Whiskers with High Aspect Ratio in the Synthesis of ZrB2-SiC Composite Powders

Abstract

Aiming to provide key materials in order to improve the fracture toughness of ZrB2 ceramics, ZrB2-SiC composite powders with in situ grown SiC whiskers were successfully synthesized via a simple molten-salt-assisted ferrous-catalyzed carbothermal reduction method. Thermodynamic calculations on the ZrO2-SiO2-B2O3-C-Fe system were carried out. The effects of heating temperature and ferrous catalyst amount on the growth behavior of SiC whiskers in ZrB2-SiC composite powders were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The results showed that the aspect ratio of SiC whiskers and the relative content of ZrB2 particles increased with increasing heating temperature (1523–1723 K) and a molar ratio of Fe to ZrSiO4 from 0:1 to 0.2:1. Phase-pure ZrB2-SiC composite powders were obtained at 1723 K when the molar ratio of raw materials was 0.2:0.5:1:1.5:8.4 (Fe:NaCl:ZrSiO4:B2O3:C). Single crystalline β-SiC whiskers with a mean diameter of 0.15 μm and an aspect ratio of 70–120 were homogeneously distributed in the final composite powders. A molten-salt-assisted iron-catalyzed vapor–solid mechanism was promoted for the growth mechanism of in situ grown SiC whiskers.

Preparation of In Situ Growth Multiscale β-Sialon Grain-Reinforced Al2O3-Based Composite Ceramic Tool Materials

“…However, ceramic materials are limited by their inherently brittle nature, often resulting in catastrophic failure, restricting their application. The strength and fracture toughness of the composites can be greatly improved by adding elongated grains, whiskers or chopped fibers to the ceramic matrix, such as SiC whiskers and SiC chopped fibers toughening ZrB 2 -based ceramics [ 7 ], ZrB 2 whiskers and elongated grains toughening ZrB 2 –ZrC ceramic tool materials [ 8 , 9 ], TaC whiskers toughening Al 2 O 3 -based composites [ 10 ], elongated β-Si 3 N 4 grain-reinforced Al 2 O 3 -based composites [ 11 ], and elongated β-sialon grain-toughened WC-based cermets [ 12 ], etc. However, directly adding whiskers and elongated grains presents difficulties for dispersion and compaction in the matrix.…”

Fabrication of (SiC-AlN)/ZrB2 Composite with Nano-Micron Hybrid Microstructure via PCS-Derived Ceramics Route

“…In the low-AlN-content region, the grain growth of SiC was curbed by AlN, which can strongly enhance its strength [ 32 , 33 ]. Belonging to an ultra-high temperature ceramic family, ZrB 2 shares the same hexagonal system as AlN, which could potentially increase the high temperature service behavior [ 34 , 35 ].…”