不同碳硅比稻壳对原位制备多孔Si_3N_4陶瓷的影响

Effect of Rice Husk with Different C/SiO_2 Ratio on In-Situ Preparation of Porous Silicion Nitride Ceramics

以不同C/Si O2的碳化稻壳为硅源、碳源和成孔剂,添加α-Si3N4和少量烧结助剂,利用碳热还原氮化法原位制备多孔氮化硅陶瓷,研究了不同C/Si O2和烧结温度对多孔陶瓷相组成、显气孔率、抗弯强度和微观结构等性能的影响。结果表明：当选用碳化稻壳C/Si O2（质量比）为0.5和0.7时,在1450-1500℃的试样中有α-Si3N4和β-Si3N4,在1550℃的试样中只有β-Si3N4。C/Si O2为0.7、1450-1550℃下制备出多孔氮化硅陶瓷,其气孔率为52.53%-38.48%,抗弯强度为44.07-83.40 MPa;1550℃制备的多孔β-Si3N4陶瓷中孔隙分布均匀,孔径约为2μm,β-Si3N4呈团簇状生长,长径比约为6-8。

The porous Si3N4 ceramics were directly fabricated by carbothermal reduction and nitridation method which carbonized rice husks with different ratios of C / Si O2（ mass ration） as silica source,carbon source and pore forming agent,with assistant of α-Si3N4 and a few of sintering additives. The influences of different rations of C / Si O2 as well as sintering temperature on the phase compositions,apparent porosity,flexural strength and microstructure of porous Si3N4 ceramics were studied. The results reveal that α-Si3N4 phase and β-Si3N4 appear in as-prepared samples when sintering temperatures are in the range of 1450-1500 ℃ with ration of C / Si O2 is 0. 5 or 0. 7. When sintering temperature is 1550 ℃,only β-Si3N4 appears in samples. When the ration of C / Si O2 is 0. 7 and sintering temperatures are in the range of 1450-1550 ℃,the pure phase of porous Si3N4 ceramics are prepared with the porosity of 52. 53%-38. 48% and flexural strength of 44. 07-83. 40 MPa. The best sintering temperature is 1550 ℃,the sample shows uniform distribution porosity with the pore diameter about 2 μm. Also,β-Si3N4 phase grow in cluster with aspect ratio of 6-8.