Preparation Of Aluminum Oxynitride Powder And Study On Its Influencing Factors

The spinel-type aluminum oxynitride??-AlON,hereinafter referred to AlON?is a solid solution of Al₂O₃ and AIN and it is also called as a cubic-phase alumina that the nitrogen stabilized.As a representative of multi-component transparent ceramics,AlON has a lot of excellent performance that can be applied to many modern areas.We put forward a synthesis method in which "hydrothermal process" of Al powder was combined with high-temperature solid-state·calcining technology to synthesis AlON powder.This method is simple and has many advantages like low calcining temperature,short holding time and good powder properties.The main contents of this paper include the following two aspects:?1?Oxygen-containing precursor was synthesized by a hydrothermal method,and the obtained precursor mainly consisted of AlOOH and Al phase which was characterized by XRD and SEM.The effects of hydrothermal temperature?T?and time?t?,solution pH,and the mass?m?of initial addition of aluminum powder on the precursor formation were studied in the hydrothermal process.The AlON?JCPD 01-080-2171 and JCPD 01-048-1579 in this paper?powders can be obtained through optimizing hydrothermal processing parameters.The results of this part show that prolonging the hydrothermal time,elevating the hydrothermal temperature,and increasing the initial mass of aluminum powder would be favorable to the formation of AlOOH phase whether in acidic or alkaline conditions.?2?The hydrothermal condition can be optimized through calcining different precursors at high temperature under nitrogen atmosphere.The results can be summarized as follows:at pH?7,the optimized temperature is 180?,hydrothermal time 120h,and the ratio of Al powder mass to distilled water volume 4:55.During the calcination,the influence of graphite,activated carbon,additives such as B4C,h-BN?hexagonal phase?and c-BN?cubic phase?on AlON powder formation were also studied,where calcination temperature and the holding time were optimized.The results of TG-DTA and XRD suggested that graphite was better than that of activated carbon for promoting AlON formation.The best ratio of graphite to precursor was 1:6.Addition of additives in the calcination process significantly promoted the formation of AlON.For example,adding h-BN obviously promoted AlON phase formation,but the enhancement of B4C and c-BN as additives is weaker.Moreover,the addition of B4C and c-BN would trigger the appearance of a large amount of ?-Al2O3.The best adding amount of h-BN is 15 wt%of the total mass of graphite and processor,and the best calcination temperature and holding time under N2 atmosphere are 1580? and 4h,respectively.In summary,this method has the advantages of simple experimental conditions,low cost and low temperature of AlON formation.The pure phase AlON powder can be obtained by adjusting and optimizing the processing parameters of hydrothermal and calcination process.