Recovery of mechanical strength by surface crack disappearance via thermal oxidation for nano-Ni/Al2O3 hybrid materials
Recovery of mechanical strength by surface crack disappearance via thermal oxidation for nano-Ni/Al2O3 hybrid materials
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DOI：
10.1016/j.ceramint.2012.10.008
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发表时间：
2013-04-01
影响因子：
5.2
通讯作者：
Nanko, Makoto
中科院分区：
文献类型：
--
作者：
Maruoka, Daisuke;Nanko, Makoto
通过表面裂纹消失率，研究了在α -Al2O3基杂化材料中添加5 vol%分散Ni纳米粒子（nano-Ni/Al2O3）后，机械强度随热处理温度和时间的变化规律。氧化产物NiAl2O4使维氏压痕引起的表面裂纹完全消失。烧结态和破裂态试样的抗弯强度分别为490 +/- 58和180 +/- 15 MPa。在1000℃下热处理1小时，弯曲强度恢复到550 +/- 190 MPa，裂纹消失率为10%。经过高温或长时间热处理的样品的抗弯强度与烧结样品相当。当表面裂纹消失率大于55%时，弯曲强度达到并保持在604 MPa左右。在三点弯曲试验中，as - recovery样品在表面裂纹处未发生断裂。因此，机械强度的恢复是通过表面裂纹的部分消失来实现的。这种观察到的机械强度的恢复是由于沿Al2O3基体晶界被Ni2-形成的NiAl2O4覆盖的裂纹尖端应力集中的减少引起的。(C) 2012 Elsevier Ltd and Techna Group S.r.l版权所有
Recovery of mechanical strength as a function of heat-treatment temperature and time was investigated in alpha-Al2O3-based hybrid materials containing with 5 vol% dispersed Ni nanoparticles (nano-Ni/Al2O3) via fraction of surface crack disappearance. Surface cracks introduced by Vickers indentation disappeared completely because of the oxidation product NiAl2O4. Bending strengths of as-sintered and as-cracked samples were 490 +/- 58 and 180 +/- 15 MPa, respectively. Heat-treatment at 1000 degrees C for 1 h resulted in recovery of bending strength up to 550 +/- 190 MPa with 10% fraction of crack disappearance. The bending strength of samples heat-treated at higher temperatures or for longer durations was comparable with that of the as-sintered samples. Bending strength reached and remained at approximately 604 MPa when the fraction of surface crack disappearance was over 55%. As-recovered samples did not fracture at the surface cracks during the three-point bending test. Thus, recovery of mechanical strength was achieved by partial disappearance of the surface cracks.This observed recovery of mechanical strength was caused by a reduction in stress concentration at crack-tips covered with NiAl2O4 formed from Ni2- along grain boundaries of the Al2O3 matrix. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.