导　　师： 武七德

学科专业： H13

授予学位： 硕士

作　　者： ;

机构地区： 武汉理工大学

摘　　要： 碳化硅/(SiC/)和碳化硼/(B4C/)都是典型的超硬材料,具有高熔点、高硬度、良好的导热和导电性能,可广泛应用于工具材料和高温结构材料。但是由于其共价键非常强,都是极难烧结致密的陶瓷材料。反应烧结是一种可通过渗硅反应在较低温度下获得致密烧结体的方法。本研究通过B4C与SiC的配比变化,以真空反应烧结的方法制备了B4C//SiC复相陶瓷材料。 本研究采用B4C、SiC、C为主要原料,采用原位凝固固化——破碎造粒——压制成型制备坯体。烧结工艺为真空下的渗Si反应烧结,1550℃保温2h。分别制备出以B4C和以SiC为主晶相的SiC//B4C复相陶瓷材料。 本研究通过配方设计,控制反应烧结SiC//B4C复相陶瓷材料中fSi体积含量为12-16vo1/%,推导了以素坯密度和B4C含量为基础,SiC//C配料比的计算方法。据此设计了一系列不同B4C含量的B4C//SiC复相陶瓷。研究了B4C含量对复相陶瓷的力学性能和显微组织等的影响规律。 实验结果表明：SiC//B4C复相陶瓷材料的烧结体的最终物相为α-SiC、β-SiC、B4C和Si,未发现有残留C。SiC和B4C与Si的化学相容性良好,所获得的烧结体结构致密无孔。SiC//B4C复相陶瓷断口主要呈沿晶断裂。掺量40wt/%B4C的烧结体抗弯强度最高,达475.4 MPa。烧结体的硬度随B4C掺量增加而提高,最高85wt/%B4C掺量时硬度达33.2 GPa。材料的断裂韧性在70wt/%B4C达到最高值,为5.84MPa.m1//2。 SiC、Si和B4C颗粒膨胀系数不匹配导致的残余应力场增韧以及微裂纹增韧是材料韧性提高的主要原因。 本研究表明采取低温反应烧结制备SiC//B4C复相陶瓷材料是一种低成本获得致密陶瓷材料的有效方法。 Silicon carbide /(SiC/) and carbonization boron /(B4C/) are typical superhard materials, with high melting point, high hardness, good thermal conductivity and conductivity, can be widely applied in the tool material and high temperature structural materials. But, because of its covalent bond is very strong, it is extremely difficult to sintering dense ceramic materials. Reaction sintering is a kind of method which could at relatively low temperatures by permeability silicon reaction got sintered body get density. This study through the B4C and SiC content changes, is the preparation of B4C//SiC ceramics material by vacuum of reaction sintering procedure. This study uses B4C,SiC, C as main raw materials, getting preparation green body by in situ solidification-prilling- pressure molding. Infiltration Si at the vacuum sintering process of reaction sintering, and controlling the reacting temperature at 1550℃and 2 hours heating time. SiC// B4C ceramic materials is preparation out, respectively by SiC primarily phase or B4C primarily phase. This study through the formula design, controlling the fSi volume content in reaction sintering SiC//B4C ceramic materials for 12～16vol/%. Based on density and B4C content, SiC//C proportioning calculation method is derived.A series of different B4C content of SiC//B4C ceramics material is designed。The ceramic mechanical's microstructure and mechanical property of different B4C content were discussed. The results show that the SiC//B4C composites are compact structure and mainly composed of B4C,α-SiC, /(3-SiC and Si. The chemical compatibility of SiC, B4C and Si is good, obtained by the compact structure of sintered body without hole.The main fracture of ceramic materials is intergranular fracture.With the increase of B4C content, the hardness of the composite increases gradually. the hardness of the composite with 85wt/% B4C is 33.2 GPa. Bending strength of the composite with 40wt/%B4C is 475.4 MPa. Fracture toughness of the composite with 40wt/%B4C is 5.84MPa.m1//2. By mierostructures observation and mechanical properties discussion,reinforce- ment of toughness is interpreted as residual stress and micro-crack via mismatch of thermal expansion between SiC, Si and B4C. This research shows that taking low temperature reaction sintering in phase preparation of SiC//B4C ceramic materials is a low cost obtain effective method of dense ceramic materials.

关 键 词： 复相材料 反应烧结 显微组织 力学性能

分 类 号： [TU]

领　　域： [建筑科学]