摘要
High-purity porous Ti3SiC2 with a porosity of 54.3%was prepared by reactive synthesis and its oxidation behavior was evaluated under air in the temperature range from 400 to 1000°C.Thermogravimetric analysis and differential scanning calorimetry(TG-DSC),scanning electron microscope(SEM),X-ray diffractometometry(XRD),energy dispersive spectrometer(EDS),Raman spectrum,BET surface area analysis,and pore-parameter testing were applied to the studies of the oxidation kinetics,phase composition,micro morphology,and porous structure parameters of porous Ti3SiC2 before and after oxidation.The results showed that the formation of TiO2 oxidized products with different modifications was the primary factor influencing the oxidation resistance and structural stability of porous Ti3SiC2.Cracks were observed in the samples oxidized in the full temperature range of 400-1000°C because of the growth stress and thermal stress.At 400-600°C,anomalous oxidation with higher kinetics and the aberrant decrement in pore size and permeability were attributed to the occurrence of severe cracking caused by the formation of anatase TiO2.At raised temperatures over 600°C,the cracking phenomena were alleviated by the formation of rutile TiO2,but the outward growth of the oxide scales detrimentally decreased the connectivity of porous Ti3SiC2.
采用反应合成方法制备孔隙度为54.3%的高纯Ti_3SiC_2多孔材料,并研究其在400~1000°C下空气中的氧化行为。采用热重-差热分析法、扫描电镜、X射线衍射技术、能谱仪、拉曼光谱、BET比表面分析法和孔结构测试等研究Ti_3SiC_2多孔材料在氧化前后的氧化动力学、物相组成、微观形貌以及孔结构参数演变。结果表明:形成不同晶型TiO_2氧化产物是影响Ti_3SiC_2多孔材料抗氧化性及孔结构稳定性的主要因素。由于氧化产物体积应力以及热应力的存在,因此,在400~1000°C试验过程中试样表面均出现开裂现象。其中,在400~600°C下形成的锐钛矿型TiO 2会导致Ti_3SiC_2晶粒出现严重开裂,并引发快速氧化以及孔径和透气度的异常减小。600°C以上在氧化过程中主要形成金红石型TiO_2,开裂现象得以缓解,但是氧化膜的外延生长大幅降低了Ti_3SiC_2多孔材料孔隙的连通性。
基金
Projects(51801183,51634006,51504296,51604305)supported by the National Natural Science Foundation of China
