反应温度和添加剂含量对微波合成碳化硼微观形貌的影响

Effect of Heat-treatment Temperature and Additive Content on Micro-morphology of Boron Carbide Synthesized by Microwave Sintering

微波烧结由于具有高效、快速、绿色等特点越来越受到人们的关注。本文以天然煤粉(C)和硼酸(H3BO3)为原料,在无气氛保护条件下,利用2.45 GHz的TE666单频微波烧结炉,快速碳热还原反应法制备出纳米碳化硼(B_4C)粉体。结果发现:当煤粉(C)和硼酸(H3BO3)质量比为3∶1,微波烧结温度为1400~1800℃,保温时间为5min,即可制备出结晶良好的碳化硼(B_4C)晶体,调整相关工艺参数可以控制B_4C晶体的形貌,如直径为50~150nm的球形颗粒或碳化硼片状结构,通过改变Na_2CO_3添加剂含量(3wt%~9wt%),可得到不同尺寸的碳化硼纳米片(边长为200~800 nm),获得传统电阻烧结条件下无法得到的碳化硼(B_4C)晶体。

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 Na2CO3additive（3wt%-9wt%）,which can ’t be achieved by conventional resistance sintering.