Ultralight SiC foams with improved strength from sucrose and silicon powder using magnesium nitrate blowing agent

•Magnesium nitrate is used as a bowing and setting agent.•Magnesium nitrate decreases the foaming time and setting time by half and quarter, respectively.•Magnesium nitrate decreases the density, cell size and thermal conductivity of SiC foam.•Magnesium nitrate increases the compressive strength of SiC foam. The magnesium nitrate (MN) blowing agent reduced the time required for thermo-foaming and setting of silicon powder dispersions in molten sucrose by nearly half and quarter, respectively. The sucrose-silicon powder formulations were optimized at MN concentrations in the range of 2 to 6wt% to achieve stoichiometric carbon-silicon composite foams. The reaction sintering of carbon-silicon composite foams produced open cellular SiC foams with density in the range of 0.168–0.08g/cm3. A decrease in density, cell size and thermal conductivity and an increase in compressive strength of SiC foam were obtained by the use of MN blowing agent.