Hot‐Pressed Silicon Nitride with Lu2O3 Additives: Oxidation and Its Effect on Strength
Hot‐Pressed Silicon Nitride with Lu2O3 Additives: Oxidation and Its Effect on Strength
复制标题
DOI：
10.1111/j.1151-2916.2003.tb03579.x
复制
发表时间：
2003-11
影响因子：
3.9
通讯作者：
Shuqi Guo;N. Hirosaki;T. Nishimura;Yoshinobu Yamamoto;M. Mitomo
中科院分区：
文献类型：
--
作者：
Shuqi Guo;N. Hirosaki;T. Nishimura;Yoshinobu Yamamoto;M. Mitomo
研究了添加3.33和12.51wt%Lu2O3的热压Si3N4陶瓷在1400 °和1500 ° C空气中暴露200 h的氧化行为及其对室温抗弯强度的影响。观察到两种组合物的抛物线氧化行为。氧化产物由Lu_2Si_2O_7和SiO_2组成。Lu_2Si_2O_7以择优取向从表面硅酸盐中生长出来。氧化表面的形态是依赖于添加剂的量; Lu2Si2O7晶粒在3.33重量%的组合物中出现部分在针状类型，相比之下，在12.51重量%的情况下表现出更等轴型。两种组合物所显示的高抗氧化性归因于在烧结过程中形成的大量结晶耐火第二相。此外，在1400 °和1500 ° C下氧化200小时后，两种组合物显示的强度保持率分别为93%-95%和85%-87%。强度下降与氧化物层和Si3N4块体之间的界面处的新的缺陷的形成相关联。
The oxidation behavior and effect of oxidation on room-temperature flexural strength were investigated for hot-pressed Si3N4 ceramics, with 3.33 and 12.51 wt% Lu2O3 additives, exposed to air at 1400° and 1500°C for up to 200 h. Parabolic oxidation behavior was observed for both compositions. The oxidation products consisted of Lu2Si2O7 and SiO2. The Lu2Si2O7 grew out of the surface silicate in preferred orientations. The morphology of oxidized surfaces was dependent on the amount of additive; Lu2Si2O7 grains in the 3.33 wt% composition appeared partially in a needlelike type, compared with a more equiaxed type exhibited in the 12.51 wt% case. The high resistance to oxidation shown for both compositions was attributed to the extensive amounts of crystalline, refractory secondary phases formed during the sintering process. Moreover, after 200 h of oxidation at 1400° and 1500°C, the strength retention displayed by the two compositions was 93%–95% and 85%–87%, respectively. The strength decrease was associated with the formation of new defects at the interface between the oxide layer and the Si3N4 bulk.