Single-source-precursor synthesis of novel V8C7/SiC(O)-based ceramic nanocomposites
Single-source-precursor synthesis of novel V8C7/SiC(O)-based ceramic nanocomposites
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DOI：
10.1016/j.jeurceramsoc.2016.03.023
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发表时间：
2016-11
影响因子：
5.7
通讯作者：
Sarabjeet Kaur;G. Cherkashinin;C. Fasel;H. Kleebe;E. Ionescu;R. Riedel
中科院分区：
文献类型：
--
作者：
Sarabjeet Kaur;G. Cherkashinin;C. Fasel;H. Kleebe;E. Ionescu;R. Riedel
本文采用乙酰丙酮钒基对聚碳硅烷进行化学改性的方法，对聚合物源单前驱体进行热转化，合成了新型的V8C7/SiC(O)陶瓷纳米复合材料。前驱体在氩气环境中进行高温处理，首先得到非晶SiVOC单相陶瓷，随后经过相分离、结晶，最终转化为V8C7/SiC(O)纳米陶瓷复合材料。有趣的是，在退火过程中，V8C7/SiC(O)的高温稳定性与SiC(O)基体或大气中的氧含量密切相关。因此，较大的氧含量诱导v8c7相转化为V5Si3相。制备的纳米复合粉体的比表面积（SSA）与处理温度有关，热解温度从600℃升高到1300℃，SSA从64 ~ 4 m2/g减小。然而，当样品暴露于1700°C（6小时退火）时，由于CO的演化，它再次增加到约50 m2/g。V8C7/SiC(O)基材料的催化活性的初步结果表明，它们对氨的分解有活性。在650°C左右，最大氨转化效率为35%，高于文献报道的纯碳化钒（约13%）。
In the present work, novel V8C7/SiC(O) ceramic nanocomposites were synthesized upon thermal transformation of a polymer-derived single-source-precursor, which was obtained by the chemical modification of a polycarbosilane with vanadyl acetylacetonate. High-temperature treatment of the precursor in argon atmosphere first leads to an amorphous SiVOC single-phase ceramic which subsequently undergoes phase-separation, crystallization and finally converts into V8C7/SiC(O) ceramic nanocomposites. Interestingly, the high-temperature stability of V8C7/SiC(O) was shown to strongly depend on the oxygen content present either in the SiC(O) matrix or in the atmosphere during the annealing process. Thus, larger oxygen contents induce a conversion of the V8C7phase into V5Si3. The specific surface area (SSA) of the obtained nanocomposite powders depends on the processing temperature: The SSA decreases from 64 to 4 m2/g as the pyrolysis temperature increases from 600 to 1300 °C, respectively. Whereas it increases again to ca. 50 m2/g as the sample is exposed to 1700 °C (6 h annealing), due to the evolution of CO. Preliminary results of the catalytic activity of the V8C7/SiC(O)-based materials show that they are active for the decomposition of the ammonia. The maximum ammonia conversion efficiency was found to be 35% at around 650 °C, which is higher than that of the pure vanadium carbide reported in the literature (ca. 13%).