形核密度对AlON粉体合成及其透明陶瓷制备的影响

Nucleation Density on the Synthesis of AlON Powder and Preparation of Transparent Ceramics

以α-Al_2O_3为原料,采用碳热还原氮化法合成AlON粉体,利用活性炭和亚微米碳粉改变球磨后一次粉体(α-Al_2O_3和C混合粉体)的形核密度,并研究形核密度对AlON粉体相组成、形貌及其透明陶瓷透光性的影响。结果表明,形核密度不同的一次粉体在1750℃保温60 min均能合成纯相AlON粉体,但是所合成的两种AlON粉体形貌和性能差异较大。高形核密度下(添加活性炭)合成的AlON粉体形貌不规则、结构疏松且晶粒较小,并易于球磨获得细颗粒粉体(~0.93μm);而低形核密度下(添加亚微米碳粉)合成的AlON粉体整体形貌呈近球形,晶粒发育较完整,且尺寸较大,该粉体球磨后颗粒尺寸较大(~2.13μm)。因此,形核密度是影响AlON粉体形貌、结构特征和破碎性的主要因素。研究结果表明,高形核密度粉体合成的AlON粉体具有更好的烧结活性,它在1880℃保温150 min获得的透明陶瓷最大红外透过率达76.5%(3 mm厚),比低形核密度粉体制备的透明陶瓷提高48.3%。因此,以α-Al_2O_3为原料时,提高形核密度有利于制备颗粒较小的高活性AlON粉体,该粉体适合制备高透过率AlON透明陶瓷。

Aluminum oxynitride （A1ON） powders were synthesized by carbothermal reduction and nitridation pro- cess using α-Al2O3 powder as starting material. Activated charcoal powder and submicron carbon powder were mixed with α-Al2O3 respectively to vary nucleation density of A1ON. Influence of nucleation density on phase assemblages, morphology of A1ON powders and transparence of AION ceramics were studied. Single phase A1ON powders were synthesized after holding at 1750℃ for 60 rain with for both mixture powders of different nucleation density. The results show that the synthesized powders exhibit different morphology and milling property. The A1ON powder synthesized by α-Al2O3and activated charcoal mixture show irregular shape, loose structure and small particle size, due to its high nucleation density. Moreover, it is easier to mill the obtained A1ON powder into small particle （0.93 μm）. However, for the A1ON powder synthesized by mixture of α-Al2O3 and submicron carbon powder, their grain grow obviously during the synthesis of the AION powder, due to its low nucleation density with large near sphere particles close to 2.13 μm in diameter. Therefore, nucleation density plays a key role in controlling morphology, structure characteristics and milling performance of the A1ON powders. Using the A1ON powder synthesized by high nucleation density powders, high transparent A1ON ceramics was fabricated by pressureless sintering at 1880℃ for 150 min, the maximum transmittance was -76.5% （3 mm in thickness）. It is 48.3% higher than that using AION powder synthesized by low nucleation density powders. Therefore, for using α-Al2O3 as starting material to prepare A1ON powder, high nucleation density is beneficial to A1ON powder with small particle size and high sintering ability, which contributes to the high transmittance of AION ceramics.