Papers by Keyword: Laminated Ceramic

Abstract: Laminated xCNTs-HAP/yCNTs-HAP ceramic composites were consolidated using a spark plasma sintering(SPS) technique at SPS temperature 900°C, pressure 40MPa and holding time 5min. The effect of carbon nanotubes content and thickness of each layer on mechanical properties of the composites was investigated. It was demonstrated that the stratified structure improvedthe flexural strength obviously. All the flexural strength of laminar compositewashigher than that of single CNTs-HAP ceramic, up to 112.4MPa. Since the matrix of each layer wereHAP, the difference liesonly in the content of carbon nanotubes, thus avoiding the common problem of the interlayer bonding in other layered composites with different materials. In order to characterize the toughness of the layered composite, the stress-strain curve was compared showingthat the existence of the stratified structure improved the stress-strain obviously.

Abstract: The relationship between the processing technology and the dielectric property of the laminated AlN/h-BN ceramic composites has been studied. The results showed that the main polarization mechanism of laminated ceramic composites in low frequency range is space charge polarization at the interface of AlN layer and BN layer. Due to the affection of porosity, the permittivity increases and the dielectric loss decreases with increasing the hot pressing temperature. The permittivity increases and the dielectric loss decreases with increasing thickness ratio of different layer., Both permittivity and dielectric loss increase with increasing the content of AlN doping in BN layer.

Abstract: The B4C/BN laminated ceramics were prepared by tape casting/coating. The effect of structure on the mechanical behavior of the B4C/BN was studied. The results showed that the fracture toughness and bending strength are optimal when the layer thickness ratio (eB4C/eBN) is 15. The SEM photographs of B4C/BN laminated ceramic indicated that the high fracture energy mainly resulting from crack deflection and crack delamination at the BN weak interface.

Abstract: In order to obtain dense-porous laminated structure in green bodies of SiC ceramics, rapid aqueous electrophoretic deposition (EPD) was introduced. The suspension for the electrophoretic deposition was prepared using silicon carbide, silicon and carbon powders as the starting materials. During the electrophoretic deposition process, the intending dense and porous layers were deposited alternately to form the green body. After drying, the green bodies were reaction-bonded at 1550°C in vacuum atmosphere. Pore fraction of the porous layers could be adjusted by changing process preferences of EPD and suspension composition. Pore size and size distribution could be controlled by using different sized starting powders. Using this process, no additional substance is necessary to generate the pores via burnt-off, and the dense/porous laminated structure can be obtained by one-step sintering process.

Abstract: Laminated ceramics with high mechanical properties were fabricated in the Si3N4/BN system. The mechanical properties at elevated temperatures were tested, and the oxidation behavior during tested procedure was studied at the same time. The flexure strength of the Si3N4/BN laminated ceramics changed a little below 1000°C. The displacement-load curves appeared non-linear characteristic even at high temperature. During testing procedure at high temperature, oxidation behavior of silicon nitride and silicon carbide happened, and no oxidation product of boron nitride was found. The silicon nitride layers were oxidized to form a protective silicate scale, which prevented oxidation of the boron nitride interlayers. The stability of boron nitride was beneficial to the boron nitride interlayer to partition the silicon nitride matrix layers at high temperature.