纳米结构超硬块材研究进展  

Nanostructured superhard materials

作　　者：田永君[1] Yongjun Tian(State Key Laborotary of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, Chin)

机构地区：[1]燕山大学亚稳材料制备技术与科学国家重点实验室,秦皇岛066004

出　　处：《科学通报》2018年第14期1320-1331,共12页Chinese Science Bulletin

基　　金：国家自然科学基金(51332005;51421091)资助

摘　　要：超硬材料作为基础性的工具材料,在工业与科学研究领域发挥着重要的作用,发展高性能超硬材料一直是科学界和产业界共同奋斗的目标.我们从共价晶体硬度的微观模型出发,系统研究了多晶共价材料的硬化机制,揭示了两种主要的硬化效应,分别为霍尔-佩奇效应和量子限域效应.随着显微组织特征尺寸的减小,多晶共价材料可持续硬化,为大幅度提高材料的硬度指明了全新的发展方向.在此基础上,提出了在金刚石和立方氮化硼两种超硬材料中形成超细纳米孪晶组织来获得超高性能的新思路.通过洋葱结构碳和氮化硼前驱体在高温高压下的马氏体相变,合成出具有超细纳米孪晶结构的金刚石和立方氮化硼块材.纳米孪晶结构同时提高了两种材料的硬度、断裂韧性和热稳定性.纳米孪晶金刚石的硬度达到200 GPa,为天然金刚石的2倍,将合成出比天然金刚石更硬材料的梦想变成了现实.纳米孪晶极硬材料的成功合成极大推动了高性能超硬材料研究,有望带来机械加工业和高压科学等领域的技术变革.Superhard materials play irreplaceable roles in the industry areas including mechanical processing,oil exploration,geological exploration,etc.,as well as in the scientific fields such as earth science and high pressure science.Developing high-performance superhard materials with extraordinary hardness,fracture toughness,and thermal stability has been a long-lasting goal for both scientific and industrial communities.Natural diamond has been thought of the hardest material in nature since it was discovered in ancient India more than 6000 years ago.Ever since the successful synthesis of diamond in the laboratory in 1955,finding artificial materials with hardness exceeding that of the natural diamond has been a pursued dream of human beings.However,this is truly a challenge to materials science,and many researchers have argued that it is impossible to fulfill this dream.In 2003,we proposed a microscopic understanding of the indentation hardness as the combined resistance of chemical bonds in a material to indentation,and established a microscopic hardness model for covalent single crystals.This model reveals several key factors,such as short and strong chemical bonds,high valence electron density or high bond density,and strongly directional bonds,which are beneficial to enhance the hardness.On the base of the hardness model for covalent single crystals,we systematically investigated the hardening mechanisms in polycrystalline covalent materials,and established a hardness model for polycrystalline covalent materials.Two main hardening effects in polycrystalline covalent materials are identified,namely the Hall-Petch effect and the quantum confinement effect,both of which contribute increasingly to hardness with decreasing microstructural characteristic size.As a result,polycrystalline covalent materials can be continually hardened with the microstructural characteristic size down to the deep nanoscale,which is significantly different from the nanostructured metals and designates a brand-new direction to greatly enha

关 键 词：超硬材料 纳米结构化 纳米孪晶 硬化机制 断裂韧性 热稳定性 

分 类 号：TQ163[化学工程—高温制品工业]