Ti-Al-Nb2O5系原位合成Al2O3晶须的形成机理分析

本文研究了以粉埋法原位合成的Al2O3晶须的形态和反应过程以及晶须的生长机理.通过物相测试表明产物由Al2O3、TiAl3、NbAl3和少量的AlN相组成,SEM结合EDS分析表明原位合成了直径小于100nm的Al2O3晶须,晶须呈棉絮状分布于基体交界处.基于铝的过剩,TiAl3相是Ti-Al界面的唯一产物.Ti与O2以反应时间短的动力学势优先形成的TinOm中间产物是Al2O3晶须生成的控制步骤.Nb2O5与铝液的双效复合催化作用,提高了晶须的生成速率;同时Al的用量因AlN的生成而减小,导致生成晶须的催化活性点减小,而扩散到每个活性点周围的TinOm及Nb2O5浓度增加,导致晶须分布密而均匀.Al2O3晶核在催化剂的作用下以螺旋位错生长形成长径比较为理想的Al2O3晶须.

Analysis of Formation Mechanism of in situ Al2O3 Whiskers in Ti-Al-Nb2O5 System

The morphology and process of in situ Al_2O_3 whiskers synthesized by embedding method and its growth mechanism are studied in the paper.The results show that the phases of the composites are consisted of TiAl_3,Al_2O_3,NbAl_3 and a small amount of AlN.SEM coupled with EDS reveals that the average diameter of in situ Al_2O_3 whiskers is under 100nm,which presents a flocculence distribution at the interface.Due to the rest of Al fluid,there only exists TiAl_3 phases at Ti-Al interface.The formation reaction of the intermediate phase of Ti_nO_m from Ti and O_2 in a short reaction time controlled by dynamics dominance is the rate-determing step in Al_2O_3 whiskers synthesizing process.Under the effect of catalysts of Nb_2O_5 and Al liquid,the growth rate of Al_2O_3 whiskers increases.Al catalyst decreases along with the formation of AlN,which results in the catalysis active sites of the formation of Al_2O_3 whiskers decrease and the Ti_nO_m concentration diffused around the active sites increase,and the distribution of the whiskers is more thick and homogeneous.The growth process of Al_2O_3 whiskers was controlled by screw dislocation growth in the role of the catalysts and the whiskers present a good length-diameter ratio.