Study On The Controllable Preparation Of Carbon Silicon Materials By Magnesium Thermal Reduction In Carbon Dioxide Atmosphere

Carbon-silicon materials have excellent application prospects in the fields of new energy,electronics,selective separation/analysis,and catalysis.The preparation of nano-carbon-silicon materials by the magnesium thermal reduction method has the disadvantages of multiple steps,uncontrollable reaction process,and difficult control of the product morphology and composition.This paper regulates the atmosphere and temperature of the magnesium thermal reaction,the morphology and type of silicon source,and the mass ratio of reactants.A series of carbon-silicon materials with controllable morphology and selectable products have been prepared by one-step reduction.（1）The feasibility of one-step reduction to prepare carbon-silicon materials by magnesium thermal reduction in carbon dioxide atmosphere was studied:Firstly,by changing the mass ratio of Mg/SiO₂,the analysis of the magnesium thermal reaction products in carbon dioxide atmosphere confirms that there is no obvious sequence between the reaction of magnesium and carbon dioxide and the reaction of silicon dioxide and magnesium,which confirms the feasibility of preparing silicon-carbon materials in one-step reduction;secondly,through the comparative tests of montmorillonite（MMT）and kaolin（GLT）as silicon sources,It is presumed that all compounds with silicon-oxygen bonds can prepare nano silicon-carbon materials in one-step reduction through the above-mentioned reaction.（2）The product distribution of magnesium thermal reduction of SiO₂@C under carbon dioxide atmosphere was studied:First,the product analysis of the magnesium thermal reaction of SiO₂@C and magnesium powder mixtures with different mass ratios under carbon dioxide atmosphere was made,which confirms that the increase of the mass ratio of Mg/SiO₂@C can change the distribution of reaction products and the optimal ratio for preparing Si@C has been found;second,theβ-SiC@C with regular morphology was prepared with high selectivity by adjusting the reaction temperature with the temperature regulator like sodium chloride and controlling the mass ratio of Mg/SiO₂@C.（3）CNT@Si@C nanowires and silica nanotubes were prepared by magnesium thermal reduction under carbon dioxide atmosphere:First of all,carboxylated multi-walled carbon nanotubes were used as templates to prepare CNT@SiO₂@C nanowires through two assembly processes,and then CNT@Si@C materials were obtained by magnesium thermal reduction in carbon dioxide atmosphere;secondly,CNT@SiO₂@C was processed by HF or calcined in air atmosphere to obtain CNT@Void@C and silicon nanotubes respectively.