Effect of the SiCl(4) Flow Rate on SiBN Deposition Kinetics in SiCl(4)-BCl(3)-NH(3)-H(2)-Ar Environment

To improve the thermal and mechanical stability of SiC(f)/SiC or C/SiC composites with SiBN interphase, SiBN coating was deposited by low pressure chemical vapor deposition (LPCVD) using SiCl(4)-BCl(3)-NH(3)-H(2)-Ar gas system. The effect of the SiCl(4) flow rate on deposition kinetics was investigated. Results show that deposition rate increases at first and then decreases with the increase of the SiCl(4) flow rate. The surface of the coating is a uniform cauliflower-like structure at the SiCl(4) flow rate of 10 mL/min and 20 mL/min. The surface is covered with small spherical particles when the flow rate is 30 mL/min. The coatings deposited at various SiCl(4) flow rates are all X-ray amorphous and contain Si, B, N, and O elements. The main bonding states are B-N, Si-N, and N-O. B element and B-N bonding decrease with the increase of SiCl(4) flow rate, while Si element and Si-N bonding increase. The main deposition mechanism refers to two parallel reactions of BCl(3)+NH(3) and SiCl(4)+NH(3). The deposition process is mainly controlled by the reaction of BCl(3)+NH(3).