The ambient and elevated temperature mechanical properties of two kinds of hot-pressed fused silica matrix composites, SiO2+5vol.% Si3N4 and SiO2+5 vol.% Si3N4+ 10 vol.% Cf, were investigated. Si3N4 additions greatly enhanced the ambient strength and fracture toughness, while, further incorporation of chopped carbon fibers only but sharply increased the fracture toughness value from 1.22 to 2.4 MPa m1/2. The strength of the two composites synchronously exhibited anomalous gains at certain elevated temperature range especially from 1000 to 1200 ℃, and reached their maximum values at 1000℃, 168.9 and 130.6 MPa, which were 77.0 and 77.4% higher than their ambient strength, respectively. The two composites exhibited catastrophic fracture even at 1000 ℃, but manifested prominent plastic deformation at 1200 ℃ and usually no fracture occurred during the strength test. Vickers’ indentation crack propagation behavior, combined with fractographs studies, suggested that toughening from carbon fiber was attributed primarily to the fiber bridging, pull-out and crack deflection.

The in situ TiB particle reinforced titanium metal matrix composites were prepared using MA followed by park plasma sintering (SPS) with a heating rate of 50℃/min. The in situ TiB were synthesized by chemical reaction between TiB2 and Ti during the SPS process. The microstructure of the composites sintered at 800, 1000 and 1200℃ were investigated. TiB whiskers are needle-shape and uniformly dispersed in the titanium matrix. The interface between the in situ TiB needles and the titanium matrix is singular and faceted. The composite sintered at 1000℃ has a maximum value of relative density of 99.6%, and good mechanical properties with a flexural strength of 1007 MPa, Young’s modulus of 146 GPa and fracture toughness of 8.64 MPa·m1/2, respectively. The fractographs of all composites exhibit a predominantly brittle cleavage fracture mechanism. The elastic modulus of synthesized TiB was estimated.

Silicon nitride (Si3N4) ceramics incorporated various amount of titanium diboride (TiB2) were fabricated by hot pressing at 1800℃ for 1 h. The influence of TiB2 on the microstructure and mechanical properties of Si3N4 ceramic was investigated. When a small amount of TiB2 (2vol.%) was added, the mechanical properties of Si3N4 were improved significantly, whereas they began to degrade when more TiB2 (＞4vol.%) was introduced. The reaction between TiB2 and Si3N4 matrix is responsible for the variation in mechanical properties of the TiB2/Si3N4 composites.

Chitosan/magnetite nanocomposite was synthesized induced by magnetic field via in situ hybridization in ambient condition. Results of XRD patterns and TEM micrographs indicated that magnetite particles with 10–20nm were dispersed in chitosan homogeneously. An interesting result is that magnetite nanoparticles were assembled to form chain-like structures under the influence of the external magnetic field, which mimics the magnetite chains inside of magnetotatic bacteria. The saturated magnetization (Ms) of nano-magnetite in chitosan was 50.54 emu/g, which is as high as 54% of bulk magnetite. The remanence (Mr) and coercivity (Hc) were 4 emu/g and14.8 Oe, respectively, which indicated that magnetite nanoparticles were superparamagnetic. The key of route is that a preprecipitated chitosan hydrogel membrane, used as chemical reactor, which controlled the precipitation of chitosan precipitation and in situ transformation of magnetite from the precursor simultaneously in the magnetic field environment.