Petroski Kenneth, Almansour Amjad, Grady Joseph, Suib Steven L
Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States.
NASA Glenn Research Center, Cleveland, Ohio 44135, United States.
ACS Omega. 2020 Sep 15;5(38):24811-24817. doi: 10.1021/acsomega.0c03493. eCollection 2020 Sep 29.
Silicon carbide coated onto Hi-Nicalon Type S fiber is of great interest to the aerospace industry. This work focuses on tuning the reaction parameters of atmospheric pressure SiC CVI using CHSiCl to control the morphology of the coatings produced. Depth of CHSiCl from 1 to 14 cm, temperature from 1000 to 1100 °C, and flow rate of H carrier gas from 5 to 30 SCCM were examined. Coating morphologies ranged from smooth to very nodular, where spherical growths were present along the entire deposition zone. The parameters that yielded a smooth deposition throughout the 20 cm deposition zone were 4-6 cm of CHSiCl depth, 1100 °C, and 10 SCCM of H as a carrier gas. Tensile testing using acoustic emission sensors was performed on SiC/BN/CVI-SiC minicomposites with different coating morphologies. The tensile tests revealed that smooth coatings have better mechanical performance than the nodular coatings; nodular coatings promote premature ultimate brittle failure, while smooth coatings exhibit toughening mechanisms. Smooth coatings had higher average matrix cracking strength (248 MPa) and ultimate tensile strength (541 MPa) than average nodular coating matrix cracking strength (147 MPa) and ultimate strength (226 MPa).
涂覆在Hi-Nicalon Type S纤维上的碳化硅对航空航天工业具有重大意义。这项工作重点在于调整使用CHSiCl进行常压SiC化学气相渗透（CVI）的反应参数，以控制所制备涂层的形态。研究了CHSiCl的深度从1到14厘米、温度从1000到1100℃以及氢气载气流量从5到30标准立方厘米每分钟（SCCM）的情况。涂层形态从光滑到非常结节状不等，在整个沉积区域都存在球形生长物。在整个20厘米沉积区域产生光滑沉积的参数为CHSiCl深度4 - 6厘米、温度1100℃以及作为载气的氢气流量10 SCCM。对具有不同涂层形态的SiC/BN/CVI-SiC微型复合材料进行了使用声发射传感器的拉伸测试。拉伸测试表明，光滑涂层比结节状涂层具有更好的力学性能；结节状涂层会导致过早的最终脆性破坏，而光滑涂层则表现出增韧机制。光滑涂层的平均基体开裂强度（248兆帕）和极限抗拉强度（541兆帕）高于结节状涂层的平均基体开裂强度（147兆帕）和极限强度（226兆帕）。
