Mechanism and Kinetics of Oxidation of ZrN Ceramics
Mechanism and Kinetics of Oxidation of ZrN Ceramics
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DOI：
10.1111/jace.13575
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发表时间：
2015-07-01
影响因子：
3.9
通讯作者：
Lee, William Edward
中科院分区：
文献类型：
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作者：
Harrison, Robert W.;Lee, William Edward
在静态条件下，973-1373K的ZrN陶瓷的氧化表现出抛物线速率行为，表明了扩散控制过程。原位高温粉末XRD发现氧化机制始于ZrN的失稳，形成ZrN1-x相，氧化峰最初在773K左右检测到。通过原位x射线衍射发现氧化锆层为单斜晶，在1023K中没有四方晶或立方晶的存在。在1173和1273K下氧化的陶瓷样品比在973和1073K下氧化的陶瓷样品的氧化速度要慢。这种氧化速率的变化及其机理是由于形成了由氮缺陷稳定的更致密的c-ZrO2多晶。这种氮掺杂的致密ZrO2层对氧的扩散起着扩散屏障的作用。然而，在1373K的氧化温度下，由于扩散增加导致晶界氧化，该层不再具有保护作用。
Oxidation of ZrN ceramics from 973-1373K under static conditions reveals parabolic rate behavior, indicative of a diffusion-controlled process. In-situ high temperature powder XRD found the oxidation mechanism begins with destabilization of ZrN through formation of a ZrN1-x phase with oxide peaks initially detected at around 773K. The zirconium oxide layer was found to be monoclinic by in-situ XRD with no evidence of tetragonal or cubic polymorphs present to 1023K. Bulk ceramic samples oxidized at 1173 and 1273K underwent slower oxidation than those oxidized at 973 and 1073K. This change in oxidation rate and hence mechanism was due to formation of a denser c-ZrO2 polymorph stabilized by nitrogen defects. This N-doped dense ZrO2 layer acts as a diffusion barrier to oxygen diffusion. However, at an oxidation temperature of 1373K this layer is no longer protective due to increased diffusion through it resulting in grain boundary oxidation.