增材制造结合反应烧结技术能够制备高度轻量化的碳化硅陶瓷反射镜，针对增材制造技术制备的碳化硅陶瓷存在抗弯强度低、弹性模量低等力学性能差的问题，开展高温氧化提升材料力学性能的研究。对基于增材制造的反应烧结碳化硅陶瓷试样在850 ℃下进行高温氧化处理，研究氧化时间对材料成分及表面缺陷含量的影响，阐明氧化时间对材料性能的提升机制，揭示它对材料性能的影响规律。实验结果表明：当氧化时间为2 h时，材料表面原位生长一层致密的氧化硅膜层，该膜层能够使材料表面缺陷自愈合，有效降低陶瓷材料表面缺陷的含量，此时材料获得最佳的力学性能，抗弯强度和弹性模量分别为263.9 MPa和384.75 GPa，分别提升10.7%和14.4%。该方法具有高效率、低成本和易操作的优势，为增材制造碳化硅陶瓷的性能优化提供理论指导。

Overview: How to further improve the lightweight ratio of high-performance meter-level space mirrors is one of the core issues in the field of large aperture optomechanical structure design. In this paper, a primary mirror blank with a clear aperture of Φ1200 mm was developed for a high-resolution space camera, which achieves the goal of designing area density below 40 kg/m². The SiC mirror blank was manufactured by gel injection molding and reaction sintering process, with the classical back three-point support scheme together with the testing state of the optical axis being horizontally adopted to simplify the supporting structure. Novel lightweight measures such as an alternate arrangement of main and auxiliary stiffeners and the addition of lightweight holes to vertical walls were used inside the semi-closed blank, which further improves the lightweight ratio of space mirrors with the sandwich structure. Distributed datums were proposed to replace the traditional datum setting, which reduces the machining area of datums by more than 80% and improves machining efficiency significantly. A robot arm is used for polishing in optical processing, and the local surface deformation is 47 nm in PV value under the typical polishing pressure of 1.77 kPa, with the mirror surface of 4 mm thick and the spacing between stiffener ribs of 81 mm. A parametric model of the mirror blank was built with shell elements, which contains ten variables including stiffener thickness and blank height, and integrated optimization was carried out so as to determine the optimal combination of structural parameters, using the multi-island genetic algorithm. The final design weight of the mirror blank is 46.9 kg, with corresponding area density of 38.8 kg/m². The RMS value of self-weight deformation of the mirror blank is only 2.87 nm with its optical axis being horizontal, and the free fundamental frequency is 602 Hz, indicating that the mirror blank has good dynamic and static characteristics, which satisfies the design requirements of space cameras. After machining, the measured weight of the mirror blank is 51.3 kg, about 9.4% overweight than the design, and the facesheet is about 1 mm thicker, mainly caused by the inhomogeneity of the molding process. During the centroid position test of the primary mirror blank, the deviation between the measured and theoretical centroid position is about 3.7 mm in the axial direction and 2.0 mm in the radial direction, which can be compensated through adjustment of the supporting structure and has limited influence on the optical performance of mirror assembly. At present, the primary mirror blank has already been polished to RMS λ/8 (λ=632.8 nm) of surface shape accuracy, with no obvious print-through effect observed. The lightweight structure scheme and optimization method of the mirror blank proposed in this paper can provide an important reference for the design of similar space mirrors with the characteristics of large aperture and low areal density.

反应烧结碳化硅（Reaction Bonded SiC， RB-SiC）因具有密度小、导热系数大、热稳定性好等优异性能，被公认为是理想的空间大型反射镜制造材料。然其成形后在表面精密加工过程中易引入加工损伤，故本文开展柔性刻划实验，探究砂带柔性磨削工艺对该材料加工性能的影响。通过刚性/柔性两种接触状态下单颗金刚石磨粒刻划RB-SiC材料的对比实验研究，获得柔性刻划下平均亚表面损伤率为0.677，而刚性刻划下为0.823。基于此，开展不同法向压力、磨粒角度、刻划速度等条件下的正交刻划实验研究，结果表明，法向压力与磨粒角度对材料损伤的影响更为重要；同时，随着法向压力的增大、磨粒角度的减小以及刻划速度的增大，材料损伤程度增加。最后，通过多颗金刚石磨粒刻划实验研究，得出结论：与单颗金刚石磨粒刻划相比，材料表面无严重破碎及损伤，且亚表面损伤层深度小于10 μm。该研究将为砂带柔性磨削加工反应烧结碳化硅材料提供基础指导。