(西安建筑科技大学 材料科学与工程学院，西安 710055)
摘 要: 以TiO2、B2O3、C为原料，采用碳热还原法合成TiB2粉末。通过热力学分析，绘制Ti-C-O、B-C-O系统的优势区相图和TiO2-B2O3-C系统的优势区相图叠加图，从优势区相图的角度研究碳热还原法合成TiB2的反应机理。结果表明：在Ti-C-O系统中，随着反应温度的升高，TiO2被碳还原的先后顺序为TiO2→Ti4O7→Ti3O5→Ti2O3，其中中间产物Ti4O7和Ti3O5最容易出现，也是较稳定的。在B-C-O系统中，随着碳热还原反应的进行，B2O3被C还原生成B2O2，B2O2进一步被碳还原生成B4C。碳热还原TiO2和B2O3合成TiB2的反应机理如下：在1 200~ 1 300 ℃温度下，TiO2被C还原成中间产物Ti3O5；在1 250~1 300 ℃温度范围，B2O3被C还原生成中间气相产物B2O2；当还原反应温度达到1 300 ℃以上时，中间产物Ti3O5与B2O2一起被C还原生成TiB2。
关键字: TiB2；优势区相图；碳热还原法；反应机理
synthetic reaction mechanism of TiB2
（School of Material Science and Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China）
Abstract:Using TiO2, B2O3 and C as raw material, TiB2 powder was synthesized by carbothermal reduction. The predominance area phase diagram (PAPD) of Ti-C-O system and B-C-O system were plotted by thermodynamic analysis. In addition, the superposition of predominance area phase diagram of TiO2-B2O3-C system was achieved. The reaction mechanism of synthesizing TiB2 by carbothermal reduction was studied from the standpoint of predominance area phase diagram (PAPD). The results show that in Ti-C-O system, with reaction temperature rising, TiO2 was reduced according to following subsequence: TiO2→Ti4O7→Ti3O5→Ti2O3. In these intermediate products, Ti4O7 and Ti3O5 appear easily. In B-C-O system, along with carbothermal reduction happening, B2O3 is reduced to revert B2O2 while B2O2 is further reduced by carbon to revert B4C. The reaction mechanism of synthesizing TiB2 by carbothermal reducing TiO2 and B2O3 can be decripted by the following reactions: at reduction temperature area of 1 200−1 300 ℃ and 1 250−1 300 ℃, TiO2 and B2O3 are reduced by carbon to revert intermediate products Ti3O5 and B2O2, respectively, when the reduction temperature reaches above 1 300 ℃, the intermediate products Ti3O5 and B2O2 are together reduced by carbon to form product TiB2.
Key words: TiB2; predominance area phase diagram; carbothermal reduction; reaction mechanism
