Impact of process parameter on the behavior of pyrocarbon deposition in chemical vapour infiltration (CVI) process

• Published in: Carbon trends 2024-09, Vol.16, p.100380, Article 100380
• Main Authors: Kumar, Dipoo, Painuly, Anil, V, Vinu Viswanath, G, Krishnakumar, Kumar Agarwal, Deepak, Nageswaran, Gomathi
• Format: Article
• Language: English
• Subjects: Carbon-carbon composite; Chemical vapor infiltration (CVI); Pyrocarbon deposition
• ISSN: 2667-0569; 2667-0569
• DOI: 10.1016/j.cartre.2024.100380

•Optimization of process parameters including temperature, pressure, methane, and nitrogen gas flow rates in the chemical vapor deposition process to achieve a high rate of PyC deposition and experimental validation of the same.•Understanding the influence of each CVI process parameter on the rate of PyC deposition and relative mass gain in the CVI process.•Understanding the gas flow behaviour for different sizes and shapes of CVI reactors using dimensionless parameters such as gas residence time, Reynolds number, Schmidt number, Prandtl number, and Peclet number.•Optimum process parameters and dimensionless numbers: Temperature - 1150⁰C, pressure – 100 mbar, methane and nitrogen flow rates - 1 and 0.2 SLPM respectively, gas residence time - 1.2 s, Reynolds number – less than 80, Schmidt number – 6.5-7.5, Prandtl number – 0.017, Peclet number – less than 0.15. Carbon-carbon composite manufactured by deposition of pyrocarbon (PyC) through chemical vapor infiltration (CVI) has the key issue of being process parametric sensitive which necessitates the detailed study of the effect of process parameters on the rate of PyC deposition. Conventional method of studying the parametric effect by changing one variable at a time keeping the other variables constant has a limitation of more number of experiments and missing the interaction effect among the variables. Here, the effect of process parameters including temperature, pressure, methane gas flow rate, and nitrogen gas flow rate on the mass gain and PyC deposition was studied by Taguchi method, a statistical optimization method, which has the advantage of very few experiments performed at specific pairs of process parameters only. The experiments were performed at three levels of the process parameters. Carbon-Carbon composite material is processed through the CVI process where PyC was deposited on porous carbon fiber preforms at various process conditions as per the Taguchi method. The impact of gas residence time, Reynolds number, Prandtl number, and Peclet number were also investigated. It was observed that the CVI process parameters significantly affect the rate of PyC deposition. Optimized CVI process parameters are essential for achieving a high rate of PyC deposition to reduce the processing time. The findings have revealed that a higher PyC deposition rate arises under high temperatures, pressure, methane gas flow rate, and optimal nitrogen gas flow rate. The effect of the critical interaction of the CVI