碳热还原氮化法制备超细AlN粉体的过程及特性

Syntheses and characteristics of ultrafine AlN powder by carbothermal reduction-nitridation

将超细Al_2O_3粉、纳米碳黑和有机粘结剂混合,通过挤压成形和排胶处理制成多孔前驱体,然后高温煅烧发生碳热还原氮化反应,最后脱除残余的碳,得到AlN粉体。对AlN粉体的形貌、结晶度、晶粒尺寸、平均粒度以及O、N、C含量进行观察与分析。结果表明,经360℃/2 h排胶后的前驱体为多孔结构,比表面积大,孔隙为球形。1 650℃以上温度下煅烧的产物中无Al_2O_3,AlN合成过程趋于完成,与热力学计算结果相吻合。脱碳温度对粉末C含量影响最大,其次是进料速率。多孔前驱体在1 700℃下煅烧12 h,然后在温度为700℃、纯氧气氛、进料速率为4 kg/h的条件下脱碳,得到的AlN粉体O,N,C含量分别为0.77%,33.42%和323×10^(-6),粉末颗粒圆整,粒径分布范围较窄,平均粒径d_(50)=1.36μm。AlN粉体特性与国外同类产品接近。

The porous precursors were fabricated by extruding the mixture of superfine Al2O3powder,nano carbon black and organic binder,and then adhesives-discharging.The precursors were calcined at high temperature to form AlN via the carbothermal reduction-nitridation reaction.Finally,the residual carbon was removed from the AlN calcined bodies and the AlN powder was obtained.Morphology,crystallinity,grain size,average particle size and the O,N and C contents of the AlN powder were investigated.The results show that the precursor has a porous structure with a high special surface area and spherical pores after adhesives-discharging at360℃for2h.After calcining at1650℃and above,the product is composed of AlN,no Al2O3residues is detected,indicating fulfillment of the AlN synthesis process.This experimental result agrees well with the thermodynamic calculation.The decarburization temperature has the greatest effect on the C content of the AlN powder and the feed rate is in the second place.The AlN powder synthesized by calcining at1700℃for12h and decarburizing at700℃under the conditions of the pure oxygen atmosphere and the feed rate of4kg/h has a composition of0.77%O,33.42%N and323×10^-6C.The powder also has a high degree of sphericility,a narrow particle size distribution and an average particle size(d50)as low as1.36μm.Such characteristics of the AlN powder are close to those of the foreign similar products