發(fā)布時間：2018-04-13 23:40

  本文選題：密度泛函理論 + 碳化硅納米粉體　； 參考：《高等學(xué)�；瘜W(xué)學(xué)報》2017年09期

【摘要】：以Si_(55),Si_(43)M_(12)和Si_(37)M_(18)(M=Fe,Co或Ni)團(tuán)簇為模型,采用密度泛函理論(DFT)研究了Fe,Co及Ni納米團(tuán)簇催化硅粉轉(zhuǎn)化為SiC的機(jī)理.計算結(jié)果表明,Fe,Co及Ni納米催化劑先與Si形成合金,拉長并弱化Si—Si鍵的強(qiáng)度,起到活化Si粉的作用;合金的形成有利于C原子的吸附及Si原子和C原子間的反應(yīng);Fe的催化能力強(qiáng)于Co和Ni.在此基礎(chǔ)上,以Si粉和酚醛樹脂為原料,以Fe,Co及Ni硝酸鹽為催化劑前驅(qū)體,通過微波加熱反應(yīng)制備了3C-SiC納米粉體.研究了催化劑種類、反應(yīng)溫度、催化劑用量和反應(yīng)時間等對制備3C-SiC納米粉體的影響.結(jié)果表明,催化劑Fe,Co和Ni的加入均可顯著降低3C-SiC的合成溫度.當(dāng)以2.0%(質(zhì)量分?jǐn)?shù))的Fe為催化劑時,Si粉在1100℃下反應(yīng)30 min后即可全部轉(zhuǎn)化為3C-SiC納米粉體;而在相同條件下,無催化劑時Si粉的完全轉(zhuǎn)化溫度為1250℃;Fe的催化效果優(yōu)于Co和Ni,與DFT計算結(jié)果吻合.
[Abstract]:The mechanism of the conversion of silica fume to SiC catalyzed by FeCo and Ni nanoclusters was studied by using density functional theory (DFT) based on the model of SiS5 / S / SiS / P / M _ (12) and SiS _ (37) / M _ (18) / M _ (18) / T _ (2) / T _ (2) / T _ (2) / T _ (2) / T _ (2) / T _ (T _ (T)) model.The calculated results show that FeCo and Ni nanocatalysts form alloys with Si at first, elongate and weaken the strength of Si-Si bond, and play the role of activating Si powder.The formation of the alloy is advantageous to the adsorption of C atom and the reaction between Si atom and C atom. The catalytic activity of Fe is stronger than that of Co and Ni.On this basis, 3C-SiC nanocrystalline powders were prepared by microwave heating reaction using Si powder and phenolic resin as raw materials and FeCo and Ni nitrate as catalyst precursors.The effects of catalyst type, reaction temperature, amount of catalyst and reaction time on the preparation of 3C-SiC nanoparticles were studied.The results show that the addition of FeCo and Ni can significantly decrease the synthesis temperature of 3C-SiC.When Fe (2.0%) was used as catalyst, Si powder could be converted to 3C-SiC nano-powder after 30 min reaction at 1100 鈩，

本文編號：1746770