无压渗透工艺制备MgO/AlN复相材料

采用无压渗透工艺，研究了在高纯氮气氛下Al-Mg-Si合金反应渗透氧化镁预形体制备MgO/AIN复合材料。借助XRD，SEM/EDS，EMPA等测试手段检测了产物的物相组成，观察了材料的微观形貌，并对复合材料微区成分进行了分析。结果表明：在氮气气氛中，用Al-Mg-Si合金渗透氮化原位复合氧化镁形成了MgO/AIN复合材料。在氮化温度范围内，Al-Mg-Si合金中的Mg元素极易蒸发，与气氛中的微量氧发生反应，起到深脱氧作用，而Si元素的存在使合金熔体容易浸渗入MgO预形体中，同时氮化反应生成AIN原位复合氧化镁形成MgO/AIN复合材料。合金熔液向预形体渗透的过程中，同时存在合金熔液的原位氮化自反应。氮化产物中除了AIN，MgO外，还生成了含氮尖晶石。氧化镁颗粒的存在，可能导致合金液在各局部区域中的温度、组成浓度、蒸气压等生长条件存在差异或变化，从而造成AIN生长形态的多样化和生长机制的复杂化。

PREPARATION OF MgO/AlN COMPOSITE MATERIALS BY MELT INFILTRATION PROCESS

MgO/AlN composite materials were prepared by pressureless infiltrating AlMgSi melted alloy into preformed MgO in high pure N_(2), and the microstructure, phase composition and chemical elements in the materials were analyzed by SEM, XRD, EMPA respectively. The results show that MgO/AlN composite material can be made successfully by in situ direct nitrizing of the AlMgSi alloy infiltrated in MgO in the N_(2)atmosphere. It is also found that Mg is vaporized easily from the alloy and reacts with the small amount of O_(2) in the nitrogen stream at a given temperature, which plays a role of removing oxygen completely. At the same time, Al in the melted alloy can easily infiltrate into the preformed MgO at the existence of Si and react with N_(2)to form AlN. The nitridation also happens in the melted alloy while it infiltrates into preformed MgO.Spinel containing nitrogen can also be found in the nitridation materials besides AlN, MgO. The existence of MgO grains leads to the difference or change in partly reaction conditions such as the temperature, concentration, vapor press etc., and may be resulted in the variety of AlN morphology and complexity of reaction mechanism ultimately.