Preparation of Mo/AlN/Mo Functionally Graded Materials

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%. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.