It is necessary to give self-healing function to ceramic materials because of their notch sensitivity. In the past, studies on self-healing ceramics have mainly focused on the high-temperature stage, and less research has been done below 1000°C. In this study, SiC/Al 2 O 3 /TiB 2 ceramic composites were prepared by spark plasma discharge sintering, and cracks were introduced on the surface of the polished specimens. Crack healing at 600°C–800°C was investigated, and the recovery of macroscopic bending strength and the change of microscopic crack morphology after heat treatment were used to evaluate the crack-healing effect. It was found that the surface cracks of the material were completely filled and healed by oxidation products after heat treatment at 700°C for 60 min, and the highest healing efficiency exceeded 95% for both specimens with different crack lengths, and the main mechanism of crack by Si-Al-B-Na-Ca-O type glass produced by the reaction of TiB2 and a small amount of SiC with oxygen to produce oxides and glass powder. Good healing effect and fast healing speed effectively improve the service life and reliability of ceramic materials, which has very far-reaching significance for the practical application with ceramic materials.
Jianlong Chai,Yabin Zhu,Peng Jin,Tielong Shen,Lijuan Niu,Shufen Li,Minghuan Cui,Zhiguang Wang
SiC-Al 2 O 3 -ZrO 2 ceramic composite with heterointerfaces was prepared by hot pressing and irradiated with 1.2 MeV Si ions at room temperatures. The microstructural evolution and mechanical properties were investigated. The results showed that the phase transformation of zirconia revealed by GIXRD and TEM are associated with the accumulation of oxygen vacancies clusters originated by damage and the size of displacement cascades. Complete amorphization of SiC particles were observed at 5.5 dpa, and developed into collection band at 55 dpa due to the mixture of point defect clusters and extend defects at high damage level. The nanohardness and elastic modulus irradiation decreased with increasing of damage level. The fracture behavior of materials and relative mechanism under ion irradiation were discussed.
Lijian Wang,Yanqun Zhu,Hui Yang,Yong He,Jun Xia,Yanwei Zhang,Zhihua Wang
The effect of several catalyst supports with large specific surface area (such as SiC, Al 2 O 3 , SiC–Al 2 O 3 –ball, and SiC–Al 2 O 3 ) on catalytic activity was evaluated in this study. CuO–CeO 2 supported on SiC–Al 2 O 3 exhibited high stability and activity, which was considerably close to the thermodynamic equilibrium curve at 625 °C during the stability test for 50 h. The SO 3 decomposition temperature decreased from 750 °C to 625 °C. SiC–Al 2 O 3 contained numerous micropores and mesopores and had a large specific area, indicating strong adsorption, as determined by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and nitrogen adsorption measurement. X-ray photoelectron spectroscopy (XPS) revealed that the surface of SiC–Al 2 O 3 consisted of Al 2 O 3 , SiC, and SiO 2 and that the cerium oxide surface had the largest number of defects. Temperature-programmed reduction (H 2 -TPR) results indicated that the cerium–copper oxides on the surface of powdered SiC–Al 2 O 3 had the strongest redox potential and that CuO had the lowest reduction temperature.
Yushi Qi,Jiangfan Xu,Yanhan Fei,Lanjun Du,Yan Ren,Wenbo Han,Gang Chen,Zhiming Du
This study investigated the preparation of SiC porous ceramics using an organic foam impregnation-high temperature sintering process. To address the poor wettability of SiC ceramics when used as the reinforcement phase, the surface of SiC porous ceramics was modified with Al 2 O 3 . SiC-Al 2 O 3 /2A50 co-continuous composites were then fabricated by infiltrating 2A50 aluminum alloy into the SiC-Al 2 O 3 porous ceramics under pressure. Microstructural observations, along with friction, wear performance, and thermal stability test, demonstrated that Al 2 O 3 surface modification significantly enhances the friction and wear performance as well as the thermal stability of the co-continuous composites. The prepared SiC-Al 2 O 3 /2A50 co-continuous composite exhibited excellent wear resistance, good thermal stability and stable bonding at heterogeneous interfaces. Compared to 38CrSi steel, the SiC-Al 2 O 3 /2A50 co-continuous composite not only offers the advantage of reduced weight but also shows a significantly lower wear rate of 9.3 × 10 −5 mm 3 /N·min under a 50 N load. These findings suggest that the SiC-Al 2 O 3 /2A50 co-continuous composite has the potential to replace 38CrSi steel as a wear-resistant material.
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