硼酸碳热还原-渗硅反应烧结制备碳化硼陶瓷复合材料

Fabrication of Boron Carbide Ceramic Composites by Boronic Acid Carbothermal Reduction and Silicon Infiltration Reaction Sintering

碳化硼性能优良,应用广泛,但制备成本较高。为了从源头解决碳化硼陶瓷材料制备成本高的问题,本工作直接以碳热还原法合成的碳化硼-C复合粉体为原料,无需进行破碎提纯,通过渗硅反应烧结制备碳化硼复合材料,所得材料性能与以市售碳化硼粉体为原料制备的材料性能相当,有效降低了其制备成本。主要研究了原料碳硼摩尔比对合成粉体以及碳化硼复合材料物相、显微组织和性能的影响,并探讨了碳化硼陶瓷复合材料的强韧化机理。结果表明:随着碳硼摩尔比增加,合成粉体中碳化硼粉体的碳硼原子比增加,且合成粉体中游离C含量增加;当碳硼摩尔比为2.01时,游离C包覆在碳化硼粉体颗粒表面。复合材料相组成均为B_(12)(C,Si,B)_(3)、SiC和Si,随着碳硼摩尔比的增加,复合材料中碳化硼和游离Si含量降低,SiC含量、大尺寸SiC区域的尺寸、大尺寸SiC区域和纳米SiC颗粒的数量均增加。大尺寸SiC区域的产生会降低材料的强度和韧性,而SiC纳米颗粒的形成有利于提高材料的强度和韧性。当碳硼摩尔比为1.35时,复合材料的抗弯强度和断裂韧性最高,分别为338 MPa和4.06 MPa·m^(1/2)。

Boron carbide possesses excellent properties and has a wide range of applications,but its production cost is relatively high.To address this issue,boron carbide-C composite powder was directly used,synthesized by carbothermal reduction method,as the raw material without any crushing and purification.Boron carbide composites were prepared through silicon infiltration reaction sintering,yielding material properties comparable to those prepared from commercially available boron carbide powder,which effectively reduced its preparation cost.This study mainly investigated the influence of the molar ratio of carbon to boron in the synthesis of powder on the phase composition,microstructure and properties of boron carbide ceramic composite materials,and explored the toughening mechanism of boron carbide ceramic composites.With the increase of the molar ratio of carbon to boron,the atomic ratio of carbon to boron in the synthesized boron carbide powder increases,as well as the content of free C,which coats the surface of the boron carbide particles at the molar ratio of 2.01.The phase composition of the boron carbide composite materials is B_(12)(C,Si,B)_3,SiC and Si.With the increase of carbon-boron molar ratio,the content of boron carbide and free Si in the composite decrease,while the content of SiC,the size of large SiC region,and the number of large SiC regions and SiC nanoparticles increase.Formation of large SiC regions decreases the strength and toughness of the material,while creation of SiC nanoparticles contributes to improvement of strength and toughness.When the carbon to boron molar ratio is 1.35,the composite exhibits the highest flexural strength and fracture toughness,reaching 338 MPa and 4.06 MPa·m^(1/2),respectively.