Abstract: Microwave sintering technique has recently attracted more and more attentions, due to its special heating such as high-efficiency, fast and energy-saving.Boron carbide (B4C) nano-powders were successfully synthesized by microwave sintering through rapid crabon-thermal reduction (RCR), with coal(C) and boric acid(H3BO3) used as raw minerals and in a 2.45 GHz microwave furnace (TE666) without any catalysts or shielding gas atmosphere.As a result, B4C crystals in different morphologies of nanosheets or particles can be obtained by microwave sintering at 1400-1800 ℃ for 5 min, when the weight ratio of coal to boric acid is 3∶1.The morphology of B4C crystals can be controlled by adjusting the relative parameters, obtaining spherical particles with diameter of 50-150 nm or boron carbide lamellar structure.Different sizes of B4C nanosheets with edge lengths form 200 to 800 nm can be obtained by changing the content of Na2CO3 additive (3wt;-9wt;), which can't be achieved by conventional resistance sintering.

Key words: Microwave sintering technique has recently attracted more and more attentions, due to its special heating such as high-efficiency, fast and energy-saving.Boron carbide (B4C) nano-powders were successfully synthesized by microwave sintering through rapid crabon-thermal reduction (RCR), with coal(C) and boric acid(H3BO3) used as raw minerals and in a 2.45 GHz microwave furnace (TE666) without any catalysts or shielding gas atmosphere.As a result, B4C crystals in different morphologies of nanosheets or particles can be obtained by microwave sintering at 1400-1800 ℃ for 5 min, when the weight ratio of coal to boric acid is 3∶1.The morphology of B4C crystals can be controlled by adjusting the relative parameters, obtaining spherical particles with diameter of 50-150 nm or boron carbide lamellar structure.Different sizes of B4C nanosheets with edge lengths form 200 to 800 nm can be obtained by changing the content of Na2CO3 additive (3wt;-9wt;), which can't be achieved by conventional resistance sintering.