No abstract

Silicon carbide (SiC) reticulated porous ceramics were prepared by organic foam impregnation, using polyurethane sponges as template and deionized water or alcohol as slurry solvent. The sintering behavior, microstructures and apparent density of struct of the SiC reticulated porous ceramics fabricated using the aqueous slurry under different sintering aids and sintering process and the alcohol slurry were investigated comparatively. The experimental results showed that both the microstructures and apparent density of the samples fabricated by Y2O3+AlN as sintering aid were better than those Al2O3 as sintering aid while the aqueous slurry, and the samples fabricated by two-step process (firstly heated to 700 oC in air furnace, and then sintered at 1800 oC in Ar atmosphere) while Y2O3+AlN as sintering aid obtained the optimal properties. In particular, the samples fabricated by the alcohol slurry and reaction sintering process were provided better properties than the aqueous slurry.

The diamond honing oilstone was fabricated by hot-pressing at 550–650 °C and 25 MPa pressure for 4 min, using Cu–Sn based alloys as binder metal and uncoated or W-coated diamond grains as abrasive material. The microstructures and phase compositions of the honing oilstone were examined and analyzed by SEM and XRD. Effects of the oilstone composition, sintering temperature and volume fraction of diamond grains on the mechanical properties of diamond honing oilstone were investigated. The experimental results show that the interfaces between the diamond grains and metal matrices of all the oilstone samples are smooth and no defects are observed in the metal matrices. The bending strength and rockwell hardness of the honing stones increase with the sintering temperature increasing from 550 °C to 650 °C, and the bending strength decrease with the increase of diamond grains faction. The minimum grinding ratio is obtained as the diamond was W-coated, which can be attributed to the improved interfacial bonding derived from the W coating.

A ZrO2/Al2O3 (molar ratio of 1: 1, ZA) composite ceramic was formed by slip casting as solid electrolyte in a zirconia oxygen sensor. The bonding of the ZA ceramic green body to 95% Al2O3 ceramic green body support tube was carried out at 900 oC for 60 min by the gradient joining technique using pure Al2O3 slurry as the interlayer. Subsequently, the Pt slurry was coated on the surface of the pre-sintered composite ceramic, and then co-sintered at 1550 oC for 60 min to fabricate a Pt/ceramic composite probe. The interface microstructure and bonding mechanism were briefly investigated, and the electrical conductivity of the probe was tested. The experimental results show that the two high-quality ZA/Al2O3 and ZA/Pt interfaces were obtained. In particular, the relationship between the logarithm of conductivity (lnρ) and the reciprocal of temperature was well in accord with the Arrhenius equation. The Pt/ceramic composite probe presented the typical characteristic of high-temperature ionic conduction.

The Be/Ce/γ-Al2O3 compound catalysts were prepared by sol-gel process using γ-Al2O3, Ba (AC)2 and Ce (NO3)3·6H2O as raw materials, and the effect of calcination heating rate on microstructure and performance of the NOx storage and reduction (NSR) catalyst was investigated. The crystal structure, microstructure, absorption and reduction performances of the NSR catalyst were characterized and analyzed by X-Ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Brunauer Emmett Teller (BET) and H2 temperature program reduction (H2-TPR). The experimental results show that the Ba and Ce elements mainly exist in the forms of BaCO3 and CeO2, respectively, and partial CeO2 is amorphous. The calcination heating rate can play a key role in the grain size and distribution of BaCO3 and CeO2, so that it can affect the surface area, pore volume and pore diameter of the NSR catalyst. Moreover, the reduction temperature of the NSR catalyst decrease first and then increase with the increase of calcination heating rate, and the reduction temperature of as-received NSR catalyst is the lowest as the reduction temperature is 6 °C/min, that is its reduction performance is the optimal.