Effect Of The Absorbance Of Al₂O₃/C Mixed Powder On The Properties Of AlON Powder And Transparent Ceramics

Spinel y-AlON is a structure-functional integrated transparent ceramic with excellent light transmittance and good mechanical properties at the same time,which makes it widely used as transparent window of advanced carrier equipment.Nowadays,the two-step method,synthesis AlON powder fisrt and then sinter AlON ceramic,is widely used in the preparation of AlON.The performance of AlON powder is the key to the preparation of subsequent transparent ceramics.In this paper,influence of the absorbance and synthesis process of mixed raw material powder on the properties of AlON powder and its transparent ceramics was studied.First of all,micrometer activated carbon and nanometer alumina are mixed as raw powder(the content of activated carbon is 5.6 wt.%).By using planetary ball mill machine,mixed powder with different absorbance are obtained by changing series of ball milling parameters.Then,mixed powder with representative absorbance are chosen to study the effect of mixed powder absorbance on the properties of AlON powder by changing sintering process.Finally,the effect of powder absorbance and powder sintering process on the properties of AlON transparent ceramic is studied by preparing AlON transparent ceramic in the same process(hold for 150 min at 1880 ?,pressureless sintering).Research on ball milling process of raw material powder shows that mixed powder with different absorbance can be obtained by changing milling-ball filling ratio,ball-to-powder weight ratio,liquid-to-solid ratio,milling speed and milling time.Four kinds of mixed powders with absorbance of 0.8,1.0,1.2 and 1.4 were selected for further study.The result shows that raw mixed powder with higher absorbance is beneficial to synthesis pure phase AlON powder with lower O/N under the condition of lower temperature and shorter heat preservation time,which also has a smaller and more uniform particle size after ball milling.On the contrary,when the absorbance of the mixed powder is low,the Al2O3 residue is easily found in the AlON powder synthesized at lower temperature or short heat preservation time with high O/N.AlON powder,synthesized from mixed powder with low absorbance,contains large size particles after ball milling.Research on the preparation of AlON transparent ceramics by pressureless sintering shows that the O/N of AlON transparent ceramics is significantly lower than the O/N of its powder,and the maximum decrease of O/N is about 8,which means AlON ceramics can be continually nitrided during pressureless sintering process.For AlON powder synthesized from mixed powder with absorbence of 0.8 or 1.0,the O/N could reach 8-10 by synthesizing at 1775 ? for 30 min or 1750 ? for 60 min.AlON ceramic sintered from AlON powder above can finally possess a O/N of about 5.4,which is closer to its theoretical value and makes the ceramic has a high transmittance.The maximum transmittance can be up to 79%.