煅烧硫酸铝铵复盐低温合成α-Al_(2)O_(3):葡萄糖和预压的影响

Low-Temperature Synthesis ofα-Al_(2)O_(3) Powder via Calcining Aluminum Ammonium Sulfate Double Salt Process:Effects of Glucose and Pre-Pressing

以NH_(4)Al(SO_(4))_(2)·12H_(2)O为原料,通过加入不同质量分数的葡萄糖合成α-Al_(2)O_(3),研究了葡萄糖含量和预压处理对α-Al_(2)O_(3)粉体合成工艺和温度的影响。结果表明:葡萄糖的加入可以明显改变相变过程,降低合成温度。添加质量分数为30%的葡萄糖时,可在950℃合成单相α-Al_(2)O_(3)粉体,合成温度比不添加葡萄糖时低200℃左右;添加质量分数为75%的葡萄糖时,α-Al_(2)O_(3)的合成温度可进一步降低至900℃。添加葡萄糖可以降低α-Al_(2)O_(3)合成温度的主要原因有两个:一是葡萄糖氧化分解产生的热加速了NH_(4)Al(SO_(4))_(2)·12H_(2)O的热分解,二是葡萄糖的添加使NH_(4)Al(SO_(4))_(2)·12H_(2)O分散均匀并无定形化。实验结果还表明预压处理可使α-Al_(2)O_(3)的合成温度进一步降低25~50℃,这可能是由于团聚体的破坏和粉末分散体的进一步均质化所导致。

Aluminum is a widely used material in the industries of electronics,automobiles,and aviation due to its excellent properties.However,the synthetic temperature of commercialα-Al_(2)O_(3) powder is high,and the obtained powder has coarse particles,low activity,serious agglomeration,and it is not easy to disperse,which affects its subsequent applications.Therefore,the synthesis ofα-Al_(2)O_(3) powder at a low temperature is challenging.In this paper,α-Al_(2)O_(3) powder was synthesized by calcining NH_(4)Al(SO_(4))_(2)·12H_(2)O with different added glucose contents.The effects of glucose content and sample pre-pressing on the synthetic temperature ofα-Al_(2)O_(3) powder were investigated.The results showed that the presence of glucose changed the phase transition process and significantly decreased the synthetic temperature.With 30%(mass fraction)glucose added,α-Al_(2)O_(3) powder could be synthesized at 950℃,which was about 200℃lower than that of the glucose-free control.With 75%glucose added,the synthetic temperature ofα-Al_(2)O_(3) further decreased to 900℃.The presence of glucose is believed to accelerate the thermal decomposition of NH_(4)Al(SO_(4))_(2)·12H_(2)O,and make NH_(4)Al(SO_(4))_(2)·12H_(2)O be dispersed evenly and amorphous.The results also showed that pre-pressing further decreased the synthetic temperature ofα-Al_(2)O_(3) by 25—50℃,which might be a result of the attenuation of agglomeration and the further homogenization of powder dispersion.Moreover,single-phaseα-Al_(2)O_(3) with a uniform distribution of particle size(average particle size 110 nm)were obtained at 850°C by using 25 MPa pre-pressing and 75%(mass fraction)glucose process.