Reinforcing effects of SiC whiskers and carbon nanoparticles in spark plasma sintered ZrB2 matrix composites
Reinforcing effects of SiC whiskers and carbon nanoparticles in spark plasma sintered ZrB2 matrix composites
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DOI：
10.1016/j.ceramint.2018.07.258
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发表时间：
2018-11-01
影响因子：
5.2
通讯作者：
Asl, Mehdi Shahedi
中科院分区：
文献类型：
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作者：
Azizian-Kalandaragh, Yashar;Namini, Abbas Sabahi;Asl, Mehdi Shahedi
采用放电等离子烧结(SPS)工艺，在1900℃、40 Mpa、7min的真空条件下，分别制备了体积分数为25%的碳化硅晶须(SiCw)和质量分数为0、2.5、5和7.5wt%的碳纳米颗粒(C-NP)增强的ZrB_2基陶瓷。研究了C-NP含量对ZrB2-SiCw陶瓷的致密化行为、显微组织演变、硬度和断裂韧性的影响。加入C-NP后，与无碳样品相比，添加C-NP后，ZrB_2基体的晶粒长大速度略有下降(接近20%)。B4C和ZRC相的原位生成归因于它们与C-NP添加剂的化学反应消除了表面氧化物杂质。所有的复合样品都接近其理论密度。当C-NP含量为7.5wt%时，材料的硬度为14.6 Gpa，软碳添加剂的加入使材料的硬度线性下降。断裂韧性呈现出另一种趋势，从无碳的4.7 Mpa m(1/2)增加到5wt%C-NP增强复合材料的7.1 Mpa m(1/2)。新碳化物的形成和未反应C-NP的存在导致了韧性的提高。检测和讨论了各种增韧机制，如裂纹分叉、桥联和偏转。
ZrB2-based ceramics, reinforced with 25 vol% SiC whiskers (SiCw) as well as 0, 2.5, 5 and 7.5 wt% carbon nanoparticles (C-np), were prepared by spark plasma sintering (SPS) at 1900 degrees C under 40 MPa for 7 min in a vacuum environment. The influences of C-np content on densification behavior, microstructure evolution, hardness and fracture toughness of ZrB2-SiCw ceramics were investigated. Compared to the carbon-free sample, the grain growth of ZrB2 matrix was moderately decreased (similar to 20%) after the addition of C-np. The in-situ formation of B4C and ZrC phases was attributed to the elimination of surface oxide impurities through their chemical reactions with the C-np additive. All composite samples approached their theoretical densities. A hardness of 21.9 GPa was obtained for ZrB2-SiCw sample, but the hardness values linearly decreased by the addition of soft carbon additives and reached 14.6 GPa for the composite doped with 7.5 wt% C-np. The fracture toughness showed another trend and increased from 4.7 MPa m(1/2) for the carbon-free sample to 7.1 MPa m(1/2) for 5 wt% C-np-reinforced composite. The formation of new carbides and the presence of unreacted C-np resulted in toughness improvement. Various toughening mechanisms such as crack branching, bridging, and deflection were detected and discussed.