Papers by Keyword: Rapid Densification

Abstract: PAN-carbon fibers were pretreated using three methods. 2D-C/C composites were fabricated by a rapid chemical liquid-vaporized infiltration (CLVI) processing. Surface morphologies of carbon fiber pretreated and fracture micrographs of 2D-C/C composites were observed by scanning electron microscopy (SEM) and high resolution transmission electron microscope (HRTEM). The interlaminar shear strength(ILSS) of C/C composites was tested. The influences of carbon fiber surface pretreatments on ILSS and fracture behaviors of C/C composites were analyzed. The experimental results indicated that the C/C composite with carbon fiber coated CVI pyrocarbon possesses both higher flexural strength and interlaminar shear strength than composites with other fiber pretreatments. The fractographes revealed the differences in the mechanical behavior depending on the interface strength of fiber/matrix.

Abstract: Capabilities of synthesizing new structural and functional materials by SPS processing were indicated by exemplifying the synthesis of nano-structured alumina with high bending strength or high transparency, Al/diamond composites with high thermal conductivity and zirconia(3Y)/ SUS410L FGM. In the synthesis of alumina, the bending strength of more than 720MPa was attained by choosing suitable SPS conditions. It was also indicated that SPS processing could easily synthesize Al/diamond composites with high thermal conductivity of more than 400W/(m･K), suggesting elaborate control of interface between Al and diamond in SPS consolidation. Further, zirconia(3Y)/SUS410L FGM could easily be fabricated by SPS. Mechanical weakness in the zirconia(3Y)-rich layers of the FGM was shown from the analysis of stress state based on Raman scattering method. It is suggested that the designing of the layer staking in FGM based on the Raman scattering analysis is effective for the improvement of the weakness in the FGM.

Abstract: The morphologies and textures of the pyrolytic carbon matrix in 2D-C/C composites after graphitization were investigated by means of polarized light microscope (PLM) and high resolution transmission electron microscope (HRTEM). The microstructure parameters of the pyrolytic carbon matrix before and after graphitization were characterized with X-ray diffraction (XRD) technology. It was found that the interplanar distance of (002) planes (d002) of pyrolytic carbon matrix decreases, and the microcrystalline stack height (LC) increases after graphitization. Graphitization treatment resulted in a coarsening of the surface texture and in the formation of circumferential cracks within the matrix. The lattice fringes of the pyrolytic carbon matrix are continuous and longer in each domain and the (002) peak spot is smaller and more intense after graphitization.

Abstract: Characteristics of heating processing based on millimeter-wave or pulsed high current are discussed from the standpoint of the interaction between electromagnetic energy and solid materials. Capabilities of the electromagnetic processing are indicated by exemplifying several successful results such as millimeter-wave sintering of AlN, millimeter-wave post-annealing of aerosol-deposited PZT films and synthesis of single-phase nano-structured anatase by SPS (or pulsed high current heating). It is shown in these examples that well-characterized properties such as high thermal conductivity and preferential orientation are created by the inherent effect due to the electromagnetic field, which is called microwave or SPS effect in millimeter-wave or SPS processing.

Abstract: Rapid densification of the SiC-10, 20, 30, 40wt% TiC powder with Al, B and C additives was carried out by spark plasma sintering (SPS). In the present SPS process, the heating rate and applied pressure were kept at 100°C/min and at 40 MPa, while the sintering temperature varied from 1600-1800°C in an argon atmosphere. The full density of SiC-TiC composites was achieved at a temperature above 1800°C by spark plasma sintering. The 3C phase of SiC in the composites was transformed to 6H and 4H by increasing the process temperature and the TiC content. By tailoring the microstructure of the spark-plasma-sintered SiC-TiC composites, their toughness could be maintained without a notable reduction in strength. The strength of 720 MPa and the fracture toughness of 6.3 MPa·m1/2 were obtained in the SiC-40wt% TiC composite prepared at 1800°C for 20 min.