Mo/AlN/Mo功能梯度材料的制备

Preparation of Mo/AlN/Mo Functionally Graded Materials

实验选用细粉AlN和Mo粉末为原料,采用放电等离子烧结（SPS）技术进行Mo/AlN/Mo功能梯度电极材料的制备与表征,采用X射线衍射（XRD）法确定SPS烧结块体的相组成,用扫描电子显微镜（SEM）观察块体断口的显微结构,用阿基米德法和HXD-1000型显微硬度仪对块体的硬度和密度进行测试。研究发现：金属Mo与AlN混合烧结后并没有发生化学反应,只是简单的复合,Mo/AlN/Mo块体抛光截面层对称结构清晰,中间层为AlN层,最外层为金属Mo,过渡层均匀且结合良好,没有发现裂纹等缺陷,符合梯度设计要求。当Mo含量为70%时,Mo/AlN复合材料的硬度值下降缓慢,由于高韧性金属Mo的加入提高了AlN的韧性而同时缓和了其硬度,这使金属Mo层和AlN陶瓷层之间的结合稳定,这种过渡利于Mo/AlN/Mo功能梯度材料的内部结合;当Mo/AlN复合材料的Mo含量达到70%时致密度曲线有明显的上扬达到99.3%,随后致密度曲线随着Mo含量的增加而下降,这由于随着Mo含量的增加烧结后晶粒尺寸逐渐长大造成的。在Mo含量小于19%之前,介电常数有指数增长的趋势,Mo/AlN复合材料的导通阀值为Mo含量大于19%。

Mo/AlN/Mo Functionally Graded Materials were prepared by spark plasma sintering(SPS） and using AlN and Mo as raw materials. The phase composition of SPS sintered block was determined by X-ray diffraction(XRD）,and the microstructure of block fracture was observed by scanning electron microscopy(SEM）. The hardness and density of the blocks were tested using Archimedes method and HXD-1000 Microhardness Tester. The research showed that the combination of Mo and AlN did not undergo chemical reaction after sintering,but only simple compound shown by the XRD analysis. The polished cross-section layer of Mo/AlN/Mo block had a clearly symmetrical structure,with AlN in the middle layer and Mo in the outermost layer,the transition between the layers of the block was uniform and the combination was good,with no structural defects such as cracks,meeting the gradient design requirements.The hardness value of Mo/AlN composites decreased slowly when the Mo content was 70%. The firmly bonding between Mo layer and AlN ceramic layer was attributed to the addition of high toughness Mo that enhanced the toughness of AlN and also eased its hardness,and this transition facilitated the internal bonding of Mo/AlN/Mo functional gradient materials. When the Mo content of Mo/AlN composites reached 70%,the density curve was up to 99. 3%,and then the density curve decreased with the increase of Mo content,which might be due to the gradually growth of grain size after sintering. The dielectric constant increased exponentially when the content of Mo was less than 19%,and the conduction threshold of Mo/AlN composites was that the Mo content was more than 19%.