三步流程直接氮化法制备AlN粉末及其性能研究

发布时间：2018-06-28 13:30

  本文选题：AlN + 直接氮化法　； 参考：《五邑大学》2016年硕士论文

【摘要】：氮化铝(AlN)是一种类金刚石结构的综合性能良好的新型氮化物陶瓷材料,在各产业中具有广泛的应用。一般来说,优质的Al N粉末才能制备出性能优越的Al N陶瓷。本文以低成本制备优质Al N粉末为宗旨,在传统的直接氮化法基础上添加镁粉和氯化铵为反应助剂,通过三步流程制得纯度高、粒径细小、抗水解能力强的Al N粉末。实验按照以下三步流程进行:第一步制备Al N粉末,研究不同反应参数下的铝粉氮化情况;第二步对未反应完全的氮化产物进行酸洗提纯;第三步研究Al N粉末的水解性和抗水解工艺。实验中,铝粉和两种添加剂按照一定的比例均匀混合,然后置于密封性良好的管式电阻炉中,通氮气升温,升温阶段氮气流量30sccm,升温速度5℃/min;升温到预定保温温度800℃~1000℃时氮气流量调高到60sccm;保温时间1~4h,保温结束后在20sccm的流动氮气保护气氛下冷却到室温,产物研磨后即可得到Al N粉末样品。初探实验中发现,同时添加镁粉和氯化铵做为添加剂,得到的氮化产物为疏松团聚物,易于粉碎,并且通过XRD分析发现铝粉完全氮化,无残余添加剂存在。这主要是由于镁粉活性大于铝粉,氮化过程中会先和氮反应生成氮化镁,而氮化镁稳定性差,700℃升华,800℃分解,会在熔融的铝粉中形成大量孔洞,减少结块,提高氮化率。氯化铵热稳定性差,337.8℃时会分解为NH3和HCl,两种气体从熔融的铝中逸出,形成多孔洞,加速氮在铝粉内的扩散。氮化产物的XRD分析显示无镁粉和氯化铵峰存在,说明两种添加剂均为低残留的添加剂。氮化产物的SEM分析发现产物中有纵横交错的少量晶须存在,调节不同的工艺参数可得到不同的晶须生长形貌,EDS分析显示晶须为Al N。调整反应参数的实验结果显示,Al/Mg/NH4Cl质量比为9:2:4,保温时间为3h,保温温度为1000℃时,反应物能够完全氮化,产物的N元素具有最高的含量33.4%,Al N晶须形貌均匀。对产物进行粉碎处理,手工研磨2h平均粒径可达9.5um,用球磨机球磨1h粉末粒径可达3um,说明氮化产物具有易于粉碎的特点。实验中未完全氮化的粉末(氮化温度小于1000℃)采用酸洗方法提纯,对提纯后的粉末进行XRD分析,无杂质峰出现,说明酸洗可用于提纯未完全氮化的产物。水解试验发现,用磷酸提纯的Al N样品有比硫酸和盐酸提纯的Al N样品更高的抗水解性。用磷酸对Al N粉末浸泡24h,发现水解180h溶液仍保持酸性,说明粉末具有了极高的抗水解性。可知,用磷酸不仅有提纯作用,还能用来对Al N进行抗水解处理。对Al N粉末进行氧化热退火处理,结果显示在900℃保温1h的Al N粉末具有一定的抗水解性,但是效果没有磷酸浸泡处理的好。
[Abstract]:Aluminum nitride (AlN) is a new type of nitride ceramic material with good comprehensive properties, which has been widely used in various industries. Generally speaking, Al N ceramics with superior properties can be prepared by high quality Al N powders. The aim of this paper is to prepare high quality Al N powder at low cost. Magnesium powder and ammonium chloride are added as reaction aids on the basis of traditional direct nitridation method. Al N powder with high purity, fine particle size and strong hydrolysis resistance is prepared by three steps process. The experiment was carried out in the following three steps: the first step was to prepare Al N powder to study the nitridation of aluminum powder under different reaction parameters, the second step was to purify the nitrided product without reaction completely. The third step is to study the hydrolysis and anti-hydrolysis process of Al N powder. In the experiment, the aluminum powder and the two additives are evenly mixed in a certain proportion, then placed in a well sealed tube resistance furnace, and the nitrogen gas is heated. At the heating stage, the nitrogen flow rate is 30sccm, the heating rate is 5 鈩，

本文编号：2078147