摘要
由于报道获得了超过金刚石的硬度,TiN/Si3N4纳米复合薄膜成为十多年来超硬材料和薄膜材料的重要热点。本文从实验基础方面对这类薄膜的Veprek模型和＂超高硬度＂进行了评述。在微结构方面,Veprek提出的非晶Si3N4包裹TiN纳米晶的结构模型（即nc-TiN/a-Si3N4）缺乏足够的实验依据,直接观察表明：高硬度薄膜中的TiN晶粒并非等轴晶,而是纳米直径的柱状晶。就Si3N4界面相来说也并非以1个单分子层（~0.3 nm）的非晶态存在,而是厚度约3个分子层（~0.7 nm）的晶体态,更重要的是Si3N4界面相与相邻的TiN晶体形成了共格结构。在制备技术方面,十余年来始终没有人在这类材料中重复出Veprek超过金刚石硬度的结果,Veprek不仅将其归咎于缺乏足够高的沉积温度和氮分压,甚至归咎于薄膜中存在不可避免的微量氧,但也缺乏足够的直接证据。在超高硬度的样品方面,Veprek所报道超过金刚石硬度（最高达138.9 GPa）的样品不但未经任何他人检测确认,而且现在这些样品已经不存在了。
Since hardness exceeding that of diamond was reported by Vepreke, TiN/Si3N4 nanocomposite film has at- tracted much attention from the scientific community and resulted in a ballooning number of publications over the past 15 years. This paper commented on the Veprek＇s microstructure model and ＂superhardness＂ of this kind of films from experimental fundamental aspects. In term of the microstructure, the model of nc-TiN/a-Si3N4 proposed by Veprek, in which equiaxed nanocrystalline TiN （nc-TiN） were embedded in an amorphous Si3N4（a-Si3N4） matrix, was short of sufficient experimental evidence. Direct transmission electron micrographs observations showed that the TiN nanocrystals still had a colunmar morphology instead of equiaxed morphology. Si3N4 interface tissue had a thickness of about 0.5-0.7 nm and existed in the crystalline state. Low-energy coherent interfaces are formed between Si3N4 and neighbouring elongated TiN grains. As far as the preparation technology, the hardness exceed diamond has not been repeated by others in this material up to now. Veprek attributed it not only to the lack of a sufficiently high temperature and partial pressure of nitrogen, but also to the unavoidable oxygen in preparation. However, those critical conditions were imposable to satisfy in technology. For the samples, although Veprek declared their films received the hardness exceed diamond （up to 138.9 GPa）, they have not confirmed by any others, and moreover, these samples have disappeared now.
出处
《无机材料学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第1期1-8,共8页
Journal of Inorganic Materials
基金
973计划(2012CB619601)
国家自然科学基金(51371118)~~
