Preparation of hollow SiC spheres by combustion synthesis

Abstract

Hollow spherical β‐SiC was successfully prepared in argon by combustion synthesis using Si powder and polytetrafluoroethylene (PTFE) powder. The phase composition and morphology of spherical products can be controlled by adjusting the Si/C2F4 molar ratio (MSi/(C2F4)). When MSi/(C2F4) = 3, the phase content of β‐SiC is the highest (up to 85.54%), and hollow spherical products obtained; When MSi/(C2F4) ≥ 5, the Si/SiC microspheres are solid. The synthesis mechanism of hollow β‐SiC microspheres is as follows: Si particles react with PTFE releasing heat. Then unreacted Si absorbs heat to form liquid phase microspheres, which is equivalent to the core template to form β‐SiC microspheres by reaction with cracked C. Meanwhile, the silicon diffuses from the core to the shell to form the cavity. This method can synthesize the hollow spherical β‐SiC in a simple way without prearranged spherical template and long synthesis cycle.

Preparation of SiC coated graphite composite powders by nitriding combustion synthesis

“…3(a). In addition, the Si-C system is weakly exothermic (∆H 298 = -73 kJ•mol −1 ) [57], and thus Reaction ( 5) is difficult to occur at low temperatures. The heat released from Reaction (1) increases the temperature of the reactants, leading to the melt of unreacted Si particles and activating the chemical reaction between the Si-N 2 and Si-C systems (Reactions ( 4)-( 6)).…”

Spatially confined magnesiothermic reduction induced uniform mesoporous hollow silicon carbide nanospheres for high-performance supercapacitors

“…6 However, the high temperatures required to form strong covalent Si-C chemical bonds often lead to sintering, making it difficult to obtain well-dispersed SiC hollow nanospheres, let alone those with diameters less than 100 nm. [6][7][8][9][10][11] In addition, the inadequate contact interface between SiO 2 and carbon will reduce the yield of SiC, 8-10 while requiring excess carbon shells to maintain the spherical morphology. 6 In this respect, the magnesiothermic reduction (MR) strategy is more ideal than conventional carbothermal reduction because MR can keep mesoporous and/or hollow SiC nanostructures from collapsing 5,8,10,12,13 because the exothermic reaction at the SiO 2 /C interface is carried out at a relatively low temperature (650 1C).…”

“…[8][9][10] Nevertheless, most SiC nanospheres inevitably suffer from the problems of mutual adhesion and structural defects because of the sudden and massive exothermic reaction at the contact interface of Si or SiO 2 /C, resulting in SiC sintering without protection. [10][11][12][13][14] It remains challenging to develop a simple and effective strategy to synthesize nanoscale HS-SiC with high homogeneity and dispersion, large specific surface area (S BET ), and desirable mesoporosity.…”