(西安建筑科技大學 材料科學與工程學院，西安 710055)
摘 要: 以TiO2、B2O3、C為原料，采用碳熱還原法合成TiB2粉末。通過熱力學分析，繪制Ti-C-O、B-C-O系統(tǒng)的優(yōu)勢區(qū)相圖和TiO2-B2O3-C系統(tǒng)的優(yōu)勢區(qū)相圖疊加圖，從優(yōu)勢區(qū)相圖的角度研究碳熱還原法合成TiB2的反應(yīng)機理。結(jié)果表明：在Ti-C-O系統(tǒng)中，隨著反應(yīng)溫度的升高，TiO2被碳還原的先后順序為TiO2→Ti4O7→Ti3O5→Ti2O3，其中中間產(chǎn)物Ti4O7和Ti3O5最容易出現(xiàn)，也是較穩(wěn)定的。在B-C-O系統(tǒng)中，隨著碳熱還原反應(yīng)的進行，B2O3被C還原生成B2O2，B2O2進一步被碳還原生成B4C。碳熱還原TiO2和B2O3合成TiB2的反應(yīng)機理如下：在1 200~ 1 300 ℃溫度下，TiO2被C還原成中間產(chǎn)物Ti3O5；在1 250~1 300 ℃溫度范圍，B2O3被C還原生成中間氣相產(chǎn)物B2O2；當還原反應(yīng)溫度達到1 300 ℃以上時，中間產(chǎn)物Ti3O5與B2O2一起被C還原生成TiB2。
關(guān)鍵字: TiB2；優(yōu)勢區(qū)相圖；碳熱還原法；反應(yīng)機理
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
