Growth and properties of tantalum carbide coatings on graphite by TRD technique

The tantalum carbide-coated graphite material exhibits remarkable chemical stability, corrosion resistance, and heat shock resistance, enabling it to demonstrate excellent stability during the growth of wide bandgap semiconductors. Its application significantly enhances the quality of third-generation semiconductor crystals. Nevertheless, the high cost of this material hinders its widespread utilization in the field of wide bandgap semiconductors. To address this challenge, this study employs the Thermo-reaction deposition and diffusion (TRD) technique to successfully fabricate a tantalum carbide coating on the surface of graphite. Through thermodynamic analysis, this article validate the thermodynamic feasibility of preparing tantalum carbide coatings using the TRD process. To achieve a dense and uniform TaC coating on the graphite surface, we systematically investigate the effects of reducing agent content, reaction temperature, and reaction time on the microstructure of the coating. Experimental research has found that a molar ratio of B4C to Ta2O5 of 1:0.64 optimizes the coating uniformity. Deviations from this ratio, either higher or lower, can lead to coating inhomogeneity or even failure in coating formation. Additionally, this article determine that a reaction temperature range of 1200–1400 °C, coupled with a reaction time not exceeding 6 h, represents the most suitable conditions for preparing TaC coatings on the graphite surface. Finally, to evaluate the practical performance of the coated graphite, this article simulate the corrosive environment encountered during the physical vapor transport method for growing aluminum nitride single crystals. The results demonstrate a significant improvement in the corrosion resistance of the coated graphite. This enhancement is primarily attributed to the formation of a dense TaC coating on the graphite surface, which exhibits remarkable stability at elevated temperatures.