Single-source-precursor synthesis and air-plasma ablation behavior of (Ti,Zr,Hf)C/SiC ceramic nanocomposites at 2200 °C

Abstract

Dense monolithic (Ti,Zr,Hf)C/SiC ceramic nanocomposites with four different molar ratios of metallic elements in the (Ti,Zr,Hf)C phase (i.e., Ti : Zr : Hf = 1 : 1 : 1, 2 : 3 : 5, 2 : 3 : 3, and 1 : 2 : 1) were prepared upon pyrolysis of novel (Ti,Zr,Hf)-containing single-source precursors (SSPs), followed by spark plasma sintering (SPS). A thorough characterization was conducted to elucidate the synthesis of the SSPs, polymer-to-ceramic transformation, chemical/phase compositions, and microstructure of the SiTiZrHfC-based ceramics. The results revealed the feasibility of synthesizing nanocomposites with high (Ti,Zr,Hf)C contents using the SSP method. These nanocomposites were characterized by a unique microstructure with in situ generated (Ti,Zr,Hf)C@C core–shell nanoparticles homogeneously mixed with β-SiC. The ablation behavior of the nanocomposites was evaluated on an air-plasma device for 60 s. Impressively, the nanocomposites exhibited excellent ablation resistance, and the lowest linear ablation rate reached −0.58 μm/s at 2200 °C. Notably, the ablation resistance can be dramatically improved by precisely tailoring the atomic ratios of metal elements within the (Ti,Zr,Hf)C phase via the molecular design of the SSPs. The formation of a multiple-oxide layer with both a high-melting-point phase ((Ti,Zr,Hf)O2) and low-melting-point phases ((Zr,Hf)TiO4) and glassy SiO2, as well as their structure, played a critical role in the enhanced ablation resistance. The uniform distribution of the high-melting-point (Ti,Zr,Hf)O2 nano/microparticles throughout the glassy SiO2 matrix significantly enhanced the viscosity and stability of the oxide layer by the pinning effect, offering superior protection against the ingress of oxygen atoms and excellent resistance to mechanical erosion.

Keywords

• ultrahigh-temperature ceramics (uhtcs)
• multicomponent carbide
• nanocomposites
• ablation behavior
• multiple oxides