The Preparation process of fused silica matrix composites reinforced with threedimensional (3-D) braid via liquid phase infiltration deposition was investigated. The results indicate that the densification is significantly enhanced by using infiltration process with suspension of silica and the addition of a non-ionic surfactant. The 3D SiO 2 f/ SiO 2 specimens have density of 1.65g/cm 3 , flexural strength of 75MPa. Flexural testing and scanning electron microscopy of fracture surface were used to determine mechanical properties and fracture mechanisms. Fractography reveals that the fiber and matrix interface debonding and fiber pulling-out absorb the majority of fracture energy, which is regarded as the principal reason for resulting in the pseudo ductility and toughening mechanisms of the composites.

Nanocomposites and heavy doping both are regarded as effective way to improve materials’ thermoelectric properties. 0.7at% Bi-doped Mg2Si nanocomposites were prepared by spark plasma sintering. Results of thermoelectric properties tests show that the doping of Bi atom effectively improves the electrical conductivity of Mg2Si，and the nanocomposite structures are helpful to reduce thermal conductivity and increase Seebeck coefficient, hence improving the thermoelectric performance. A maximum dimensionless figure of merit of 0.8 is obtained for the Bi-doped Mg2Si nanocomposite with 50 wt % nanopowder inclusions at 823K, about 63% higher than that of Bi-doped Mg2Si sample without nanopowder inclusions and 119% higher than that of microsized Mg2Si sample without Bi-doped, respectively.

Silica fiber preform reinforced fused silica composites were fabricated with the variation of silica fiber content by repeated vacuum-assisted liquid-phase infiltrations. Flexural test was conducted to investigate the effect of silica fiber content and treatment temperature on the flexural strength of the 3D-SiO 2 /SiO 2 composite. Fracture behavior of the composites was investigated to study the relationship with the flexural property data. The flexural strength improved with the increment of silica fiber content and decreased with the increment of treatment temperature. The flexural strength of the composite showed the maximum value at 50vol% silica fiber content and treatment temperature at 700 o C. Fractography revealed that the composite was damaged by microdebonding at the fiber/matrix interface and the fracture of fiber.

In the present study, α-Si3N4 is prepared by using MgO and Al2O3 as the sintering additives and spark plasma sintering (SPS) technique. The SPS sintering mechanism is discussed. The relationship between the content of sintering additives, sintering temperature and relative densities of the samples is analyzed. The results suggest that when the sintering temperature is 1300-1500°C, the content of sintering additives is 6wt.%-10wt.%, the relative density of sintered samples is 64%-96%. When the sintering temperature reaches 1400°C, the content of sintering additives is 10%, the samples can be fully dense sintered and the relative density can be up to 95%. The sintering mechanism is liquid phase sintering. The bending strength of the sintered samples is 50-403MPa and has a close correlation with the relative density.

Tape casting play a significant role in industrial area, such as multilayered ceramic (MLC) packages, functionally graded materials (FGM), low temperature co-fired ceramics (LTCC) and so on. For the complexity of the rheology for slurry during tape casing process, the control of tape thickness by experience was unstable. Although few numerical and analytical studies on predicting the tape thickness have been done, but these efforts have focused on Newtonian, Bingham, Power law, respectively. There is no unified equation to calculate the tape thickness among different rheological models. In this paper, the calculation results are characterized by wide adaptability; the blade gap, the casting speed and the slurry rheological property are incorporated into calculation; the effect of parameters in the result is studied; Parameter Pnd can be used as a guide to check which mark patterns of the flow velocity profiles in the channel. The results proposed and the experimental measurements from existing publications are in close agreement. Compared with the prediction of the existing models, the calculation results proposed has good agreement with them.