Study On Preparation And Property Of Piezoelectric Ceramic/Metal Matrix Composites

BaTiO₃/Cu composites which made from copper and ultrafine BaTiO₃ powders was fabricated by ball milling, cold forming and hot pressed sintering process. The non-spontaneous nucleation surface deposition process was adopted to coat Cu₂O on the surface of ultrafine BaTiO₃ piezoelectric ceramic powders. And Cu₂O-coated BaTiO₃/Cu composites was prepared then. The compatibility of the composites was analyzed by DSC. The microstructures of the composites were studied with XRD, OM, SEM, EDS and XPS; The mechanical properties of the piezoelectric ceramic/metal matrix composites were studied with tensile test, compression test and Vickers-hardness measurement at room temperature. The morphological features of the fracture surface were analyzed by SEM. The temperature damping characteristics as well as the strain damping characteristics of the composites were tested by DMA and the damping mechanism was studied then.The microstructure analysis of two kinds of the composites indicated that when ceramic particles content was low, the particles were distributed uniformly in the matrix, exhibiting the good bonding in interface. In Cu₂O-coated BaTiO₃/Cu composites, the complete and pure Cu₂O coating was observed, and the size of the coated ceramic powders was about 0.3 1.5μm. With the increase of the ceramic content, the ceramic particles tended to agglomerate into a three-dimensional network structure.To the Cu₂O-coated BaTiO₃/Cu composite, when ceramic particles content was low, the tensile strength was increaed with the increase of ceramic content, but elongation was decreased; the compressive strength decreased slightly as ceramic content getting low, but the compression ratio declined significantly. The fracture surfaces of the composites were investigated by means of SEM, and the results indicated that the low ceramic content composites showed a character of partial fracture toughness.BaTiO₃/Cu composite temperature damping characteristics were: at room temperature 130℃, the internal friction almost had no value changes, over 130℃, the internal friction values dropped significantly, and when low- frequency was applied, the temperature dependence of the internal friction was more obvious; Cu₂O-coated BaTiO₃/Cu composite temperature damping characteristics were: internal friction values increased with the decrease of the temperature, over 120℃, then increased substantially; The strain damping characteristics were : with the increase of the strain, the internal friction values improved significantly.There were four damping mechanism existed in piezoelectric ceramic/metal matrix composite as dislocation damping, interface damping, the oxygen diffusion and piezoelectric-conductive dissipation mechanism, respectively. Both of the composites of high ceramic content have occurred in the internal friction values maximum which caused by the oxygen diffusion in BaTiO₃.In the Cu₂O-coated BaTiO₃/Cu composite, when under the Curie temperature of BaTiO₃, the theoretical temperature damping characteristics of piezoelectric-conductive dissipation mechanism and the real temperature damping characteristics were consistent. It proved that the piezoelectric-conductive dissipation mechanism was the main damping mechanisms in Cu₂O-coated BaTiO₃/Cu composite in the vicinity of the room temperature.