| Laminated ceramics is a novel of toughening material, which is imitative of the framework of shell and nacreous layer in the nature. The special superposition of the laminated ceramics makes it possible for researchers to design and prepare new material with comprehensive performances. It has become one focus of researches on the toughening of ceramics recently.The mullite/aluminum-titanate laminated ceramics including different matrix layers and separating layers thickness has been prepared by roll forming and hot pressed sintering. Effects of geometrical factor and hot pressing temperature on the mechanical properties of laminated ceramics were investigated by means of the test of mechanical properties, optical microscope and scanning electron microscope. The main enhancing and toughening mechanisms were analyzed.The results of flexure strength and fracture toughness of samples showed that not only the thickness of matrix layers and interfacial layers but also the ratio of layer thickness should be considered. The thickness 230330um of mullite layer ,the ratio of layer thickness 4.1 were considered the optimal geometrical parameter. Composites with better mechanical properties can be prepared under the condition of 1500℃x1hx20Mpa, The flexure strength of the composite is of 172.9MPa, and the fracture toughness is of 4.04 MPa m1/2. The fracture toughness of the composite was increased 62% with little decrease of flexure strength when compared with mullite monolithic ceramics.The result of microstructure examination indicated that mullite/aluminum-titanate laminated ceramics has uniform macrostructure, orderly layer, distinct interface and good interfacial bonding. Cracks deflect at aluminum-titanate layer. Themullite/aluminum-titanate laminated ceramics displays non-brittle fracture. The analysis indicated that the toughening mechanisms of mullite/aluminium-titanate include crack deflection, crack parallel propagation and crack bluntness.
|
PDF Full Text Request