Mg-B_2O_3-TiO_2系的自蔓延高温合成机理  

Self-propagating High Temperature Synthesis Mechanism of Mg-B_2O_3-TiO_2 System

作　　者：王明远[1] 李俊寿[1] 武小娟[1] 李苏[1] 赵芳[1] 

机构地区：[1]中国人民解放军军械工程学院先进材料研究所,石家庄050003

出　　处：《材料研究学报》2015年第1期32-38,共7页Chinese Journal of Materials Research

基　　金：国家自然科学基金51172281资助项目~~

摘　　要：根据对Mg-B2O3-Ti O2体系的热力学计算结果,对反应的顺序做出初步判断;然后用Cu楔块燃烧波淬息法分析SHS反应各区域产物的组成及形貌变化,研究了晶体的合成和生长机理。热力学计算结果表明:在反应过程中首先由Mg还原B2O3得到B和Mg O,其次Mg还原Ti O2得到Ti和Mg O,最后B与Ti结合生成Ti B2。对于在反应过程中的中间产物,生成Ti3O5、Ti2O3、Ti O的可能性依次降低。实验结果表明:在燃烧中心由于反应较完全,没有产生中间产物;反应次中心和边缘的温度仍然较高,有少量的Ti2O3、Ti O;在燃烧底部因温度较低反应不完全,因而有少量的Ti3O5,实验结果与热力学分析结果吻合。在反应过程中Mg O先形核长大,部分Ti B2附着在Mg O上形核,随着温度的升高形成了细小的颗粒;部分Ti B2在粗大的Mg O之间独立形核,生长成典型的六角晶型;Ti B2的生长机理属于L-S机理,B和Ti交互富集生成了典型的六角晶型。The order of reactions for Mg-B2O3-Ti O2 system was determined by thermodynamic calculation. Then the composition and morphology evolution of the product prepared by self-propagating high temperature synthesis were analyzed in terms of reaction zones of the process by Cu wedge combustion wave quenching method. The formation and growth mechanism of the Ti B2 crystal grains was investigated as well. The results of thermodynamic calculation show that in the process of SHS reaction B and Mg O were firstly obtained by reduction reaction between Mg and B2O3, then Ti and Mg O was obtained by reduction reaction between Mg and Ti O2; finally B reacts with Ti to form Ti B2.In this process, the formation possibility of the intermediate products decreases corresponding to the following order: Ti3O5、Ti2O3and Ti O. The experimental results show that no intermediate products may be detected in the combustion center, where the reaction was entirely complete; however in zones near the center or at the edge there existed a small amount of Ti2O3 and Ti O, where temperature was not high enough for completing the reaction; at the bottom zone of the combustion there existed a little Ti3O5, where temperature was too low for the reaction. Therefore, thermodynamic prediction coincides well with experimental results. It follows that during the reaction process of SHS, Mg O firstly nucleates and grows up, while Ti B2 may form through tow ways, by one way Ti B2 nucleates on Mg O crystals, and then grows into tiny particles as the rising temperature; by the other way Ti B2 independently nucleates and grows up into hexagonal crystal in between large Mg O crystals. The growth of Ti B2 follows typical L-S mechanism; B and Ti alternatively gather and grow up to form hexagonal crystal.

关 键 词：无机非金属材料 TIB2 SHS 燃烧波淬息法 合成机理 

分 类 号：TQ174.1[化学工程—陶瓷工业]