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采用单质硅粉、铝粉和二氧化硅微粉(Al+SiO2),以及硅粉和二氧化硅微粉(Si+SiO2)作为3种不同硅源,在埋碳床中于1 000～1 500℃处理多壁碳纳米管(multi-walled carbon nanotubes,MWCNTs),研究了不同含硅气相介质与MWCNTs的作用机理。结果表明:不同温度条件下以Si为硅源时,Si(g)分压最高;Si+SiO2为硅源时SiO(g)分压最高;而以Al+SiO2为硅源时,SiO(g)和Si(g)分压均最低。硅源决定了含硅气相介质与MWCNTs的作用机理:以Si为硅源时,Si(g)在MWCNTs表面反应并沉积,使得MWCNTs在1 400℃处理后表面出现2～4 nm厚的SiC涂层,在1 500℃时,大部分MWCNTs转化为实心SiC纳米线;以Si+SiO2为硅源时,SiO(g)不断沉积,1 300℃处理后MWCNTs表面出现了无定形SiO2涂层,随处理温度升高,涂层厚度增加。在上述沉积过程中,含硅气相介质在MWCNTs顶端催化剂Ni中不断发生溶解反应并形成纳米SiC晶粒。
Single elemental silicon powder, aluminum powder and silica powder (Al + SiO2), and silicon powder and silica powder (Si + SiO2) were used as three different silicon sources in a carbon burial bed at 1000 ~ 1500 ℃ Multi-walled carbon nanotubes (MWCNTs) were treated to study the mechanism of interaction between MWCNTs and different silicon-containing gas-phase media. The results show that the partial pressure of Si (g) is the highest when Si is used as the silicon source under different temperatures. The partial pressure of SiO (g) is the highest when Si + ) And Si (g) partial pressure are the lowest. The silicon source determines the mechanism of action of the silicon-containing gas-phase medium and the MWCNTs. When Si is used as the silicon source, Si (g) reacts and deposits on the surface of the MWCNTs, so that the surface of the MWCNTs is treated with 1 400 ℃, Layer, most of the MWCNTs were transformed into solid SiC nanowires at 1 500 ℃. When Si + SiO2 was used as the silicon source, SiO (g) was deposited continuously, and amorphous silica coatings appeared on the surface of MWCNTs after 1 300 ℃ treatment. Processing temperature increases, the coating thickness increases. During the above deposition process, the silicon-containing gas phase solution continuously dissolves in the Ni catalyst at the top of the MWCNTs and forms nano-SiC grains.