Abstract

A new method is proposed for the engineering of SiC-based ceramic-matrix composite materials strengthened by discrete carbon fibers and single-crystal silicon carbide nanowires. Depending on the macrokinetic characteristics of the combustion process, either diffusion layers, particles of silicon carbide, or silicon carbide nanowires with a diameter of 10–50 nm and a length of 15–20 μm can be formed on the surface of carbon fibers. The sequence of chemical transformations and structure formation in the combustion wave of Si–C–C₂F₄ and Si–C–C₂F₄–Ta mixtures was studied. Silicon carbide nanowires formed in the combustion wave had high crystallinity and a defect-free TaSi₂/SiC interface. The misorientation of the lattices at the interface is about 6%. Nanowires are able to relax the mechanical stresses during growth via the rotation along the growth direction. The optimal combustion temperature for the growth of silicon carbide nanofibers is 1700 K at a ratio of C₂F₄ : C = 2. The lower temperature threshold for the growth of silicon carbide nanowires is caused by a decrease in the yield of reactive fluorides, while the upper-temperature threshold is caused by a failure of the adsorption blocking mechanism on the surface of the nanofibers and the destabilization of the TaSi₂ + Si eutectic droplet. Composites with a SiC–TaSi₂ ceramic matrix and a relative density of 98%, a hardness of 19 GPa, a flexural strength of 420 MPa, and fracture toughness of 12.5 MP m^1/2 were obtained by hot pressing. An increase in the strength of the carbon fiber-matrix interface has manifested in the suppression of carbon fiber pull-out from the matrix.

中文翻译：

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燃烧波现场形成的碳纤维和SiC纳米线离散增强合成陶瓷复合材料的特性

摘要

提出了一种工程化离散碳纤维和单晶碳化硅纳米线增强SiC基陶瓷基复合材料的新方法。根据燃烧过程的宏观动力学特性，可以在碳纤维表面上形成扩散层，碳化硅颗粒或直径为10-50 nm，长度为15-20μm的碳化硅纳米线。研究了Si–C–C ₂ F ₄和Si–C–C ₂ F ₄ -Ta混合物的燃烧波中化学转变的顺序和结构形成。燃烧波中形成的碳化硅纳米线具有高结晶度和无缺陷的TaSi ₂/ SiC接口。界面处晶格的取向错误约为6％。纳米线能够通过沿着生长方向的旋转来松弛生长期间的机械应力。碳化硅纳米纤维生长的最佳燃烧温度为C ₂ F ₄：C = 2时的最佳燃烧温度为1700K 。碳化硅纳米线生长的较低温度阈值是由于活性氟化物的产量降低而引起的，高温阈值是由于纳米纤维表面的吸附阻断机制失效和TaSi ₂ + Si共晶液滴的失稳引起的。SiC-TaSi ₂复合材料通过热压获得陶瓷基体，相对密度为98％，硬度为19GPa，抗弯强度为420MPa，断裂韧性为12.5MPm ^1/2。碳纤维-基体界面强度的增加已显示出抑制了碳纤维从基体中拉出。