大尺寸轻型碳化硅质镜体的制造与材料性能测试

Fabrication and test of large scale light-weight SiC miror

利用凝胶注模(gel-casting)成型工艺制备了620 mm和700 mm×300 mm的碳化硅(SiC)轻型反射镜素坯,经过脱模、干燥、脱脂和反应烧结等工艺,制备了反应烧结SiC(RB-SiC)镜体。镜体经过加工和测试,结果表明:制备的RB-SiC内部结构均匀致密;力学性能和热学性能优异,抗弯强度、断裂韧性和热膨胀系数分别达到了350 MPa、4.1 MPa.m1/2和2.67×10-6/K;镜体经抛光后的表面粗糙度RMS值可优于3 nm,适合用于制备空间用大尺寸轻型反射镜。

The large scale light-weight silicon carbide（SiC） mirror blanks at 4620 mm and 700 mm× 300 mm were prepared with gel-casting method. After drying, burning out the organic elements, infiltrating carbon and reaction-sintering, the reaction-bonded SiC （RB-SiC） mirrors were fabricated. The results of ground mirrors show that the structure of RB-SiC is full solid, and the mechanical and thermal properties of RB-SiC are excellent in bending strength of 350 MPa, fracture toughness of m1/2 and the polls t mirror. coefficient of thermal expansion （CET） of 2.67 ×^10-6/K. The surface roughness hed mirror is better than 3 nm, it is a fine material for the space-borne large scale