微波加热催化反应低温制备β-SiC粉体

doi:10.15541/jim20160541

摘要/Abstract

摘要：

以硅粉和酚醛树脂为原料, 硝酸镍为催化剂前驱体, 采用微波加热催化反应法, 在流通氩气气氛中1150℃/0.5 h反应后合成了β-SiC粉体。研究了反应温度、催化剂用量和保温时间等对合成β-SiC的影响。采用XRD、SEM和TEM对产物的物相组成及显微结构进行了表征。结果表明: 微波加热条件下, 无催化剂存在时, β-SiC的完全合成温度为1250℃; 而添加1.0wt%的Ni作催化剂时, 1150℃/0.5 h反应后即可合成纯相的β-SiC。所合成的试样中都存在着颗粒状和晶须状两种SiC, 加入催化剂后会使试样中β-SiC晶须的长径比变大。密度泛函理论(DFT)计算结果表明, Ni-Si合金纳米颗粒的形成使Si原子之间的键长拉长, 弱化了Si原子之间的结合强度, 进而促进了Si粉在低温下的碳化反应。

关键词: β-SiC, 微波加热, 催化反应, 密度泛函理论

Abstract:

β-SiC powders were synthesized by a microwave heating method at 1150℃ for 30 min under Ar atomosphere using silicon powders and phenolic resin as raw materials, and nickel nitrate as catalyst precursor. The effects of temperature, catalyst content and holding time on the formation of SiC were investigated. XRD, SEM and TEM were used to characterize the phase and microstructure of the prepared samples. It indicated that β-SiC can be synthesized at 1150℃ for 0.5 h by using 1.0wt% Ni as catalysts. In contrast, for the sample prepared without Ni catalysts, corresponding preparation temperature of β-SiC was as high as 1250℃. Both β-SiC whiskers and particles were formed in the samples prepared with or without catalysts, and the length of formed β-SiC whiskers in the samples prepared with Ni catalysts were larger than those without catalyst. Density functional theory (DFT) calculation shows that the formation of Ni-Si alloy can elongate the length of Si-Si chemical bond, weaken its bond strength, and finally accelerate the carbonization reaction of Si powder at a relative low temperature.

Key words: β-SiC, microwave heating, catalytic-reaction, density functional theory

中图分类号:

TB35

王军凯, 张远卓, 李俊怡, 张海军, 李发亮, 韩磊, 宋述鹏. 微波加热催化反应低温制备β-SiC粉体[J]. 无机材料学报, 2017, 32(7): 725-730.

WANG Jun-Kai, ZHANG Yuan-Zhuo, LI Jun-Yi, ZHANG Hai-Jun, LI Fa-Liang, HAN Lei, SONG Shu-Peng. Low Temperature Catalytic Synthesis of β-SiC Powders via Microwave Heating[J]. Journal of Inorganic Materials, 2017, 32(7): 725-730.

图/表 8

图1 无催化剂时, 不同温度下反应0.5 h后试样的XRD图谱

Fig. 1 XRD patterns of samples reacted at various temperatures for 0.5 h without any catalysts(Si: JCPDS 01-077-2109; SiC: JCPDS 01-073-1708)

图2 2wt% Ni为催化剂时, 不同温度反应0.5 h后试样的XRD图谱

Fig. 2 XRD patterns of samples reacted at various temperatures for 0.5 h with 2 wt% Ni catalysts(Si: JCPDS 01-077-2109; SiC: JCPDS 01-073-1708)

图3 催化剂Ni加入量不同时, 1150℃反应0.5 h产物的XRD图谱

Fig. 3 XRD patterns of samples reacted at 1150℃ for 0.5 h with various contents of Ni catalysts(Si: JCPDS 01-077-2109; SiC: JCPDS 01-073-1708)

图4 加入1.0wt% Ni催化剂时, 1150℃反应不同时间后试样的XRD图谱

Fig. 4 XRD patterns of samples reacted at 1150℃ for various holding time with 1.0wt% Ni catalysts(Si: JCPDS 01-077-2109; SiC: JCPDS 01-073-1708)

图5 不同条件下合成β-SiC的SEM 照片

Fig. 5 SEM images of the as-prepared β-SiC(a) 1250℃/0.5 h, without catalyst; (b) 1150℃/0.5 h, with 1.0wt% Ni as catalyst

图6 所合成β-SiC晶须的TEM((a)低倍, (b)高倍)、SAED (c)和HR-TEM (d)照片

Fig. 6 TEM ((a) low-and (b) high-magnification), SAED (c) and HR-TEM (d) images of as-prepared β-SiC whiskers

表1 Si55、Si43Ni12和Si37Ni18纳米团簇的总能量和内聚能

Table1 Total energies and cohesive energies of Si55, Si43Ni12 and Si37Ni18 clusters

Clusters composition	Single Si atom	Single Ni atom	Si₅₅	Si₄₃Ni₁₂	Si₃₇Ni₁₈
Total energy/(a.u.)	-290.133	-1390.136	-15957.557	-30668.916	-38024.613
Cohesive energy/(kJ·mol^-1)	—	—	582.458	940.142	1165.307

图7 (a) Si55、(b) Si43Ni12和(c) Si37Ni18纳米团簇中(111)面上边缘位置Si原子间的键长计算结果,

Fig. 7 The DFT calculations of bond length of Si atoms at edge sites0 on (111) face of Si55 (a), Si43Ni12 (b) and Si37Ni18 (c) clusters

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