In order to synthesize cordierite ceramics with low thermal expansion coefficient and good properties, in our work, the cordierite ceramics were prepared by using talc, natural containing zirconium kyanite, common kyanite and industrial Al2O3 as raw materials, introducing the right amount of WO3 (introducing tungsten acid) as catalyst. The effects of the introduced WO3 on the phase composition, sintering characters, microstructure and thermal expansion coefficient of the cordierite ceramics were investigated. The results show that the introduction of WO3 can eliminate the intermediate phase magnesia-alumina spinel and promote the formation of cordierite; the as-prepared cordierite ceramics synthesized by using natural containing zirconium kyanite as raw materials have high densification degree and low thermal expansion coefficient (1.53×10-6/°C, Rt~1000 °C).

Cordierite thermal insulation materials were prepared via a starch consolidation casting (SCC) technique, using kyanite, MgO and SiO 2 as raw materials. Aluminosilicate ceramic fiber were used as the substrate for in situ synthesized mullite whiskers. The mullite whiskers grew in situ on the surface of the aluminosilicate ceramic fiber via AlF 3 and were interspersed among the cordierite crystalline. The as-prepared cordierite materials reinforced by the aluminosilicate ceramic fiber/ mullite whiskers hierarchical structure had a relatively high cold modulus strength and cold compression strength. Moreover, the thermal conductivity of the materials was as low as 0.329 W/(m K) (RT-1000°C). We propose a growing mechanism of mullite whiskers on the surface of the aluminosilicate ceramic fiber.

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Microwave sintering behaviors of four different compositions of YSZ electrolyte materials were investigated. The samples were sintered in 2.45GHz microwave furnace. For comparison, conventional sintering was performed at 1821K.The densities of sintered samples showed considerable enhancement in the densification process under the influence of microwave fields. The samples with lower Y2O3 content are easy to sinter. The influence of the composition and sintering methods on the final phase composition and microstructure were investigated by X-ray diffraction and scanning electron microcopy. Finer and more uniform microstructures were observed in the microwave sintered samples comparing to the conventionally sintered samples.

In order to assess the behavior of ceramic fibers that are respired and accumulate in the lung, the solubility of bio-soluble CaO-MgO-SiO2 system ceramic fibers was determined by measuring the concentrations of the main components in the Gamble solution after different solution periods. The effect of ZrO2, TiO2, B2O3, Al2O3 and the different CaO/MgO ratio of fibers on the solubility of the ceramic fibers were investigated. The results indicated that the pH value of the Gamble solutions increase with the increasing of solution time. CaO, MgO, SiO2 in the ceramic fiber have greater solubility. The existence of ZrO2 and Al2O3 in the fibers would reduce the solubility of the fibers, and the existence of TiO2, and B2O3 in fibers will benefit the solubility of the fibers.

The effects of Y2O3, La2O3 and Nd2O3 on the sintering, microstructure and mechanical properties of magnesia refractories were investigated. Addition of rare earth oxide (ReO) to magnesia refractories increases the bulk density, decreases the porosity and improves the mechanical strength of the refractories. The improved sinterability was attributable to the vacancies generation associated with the solid-solution reactions between MgO and ReO. In the samples with ReO, rare earth silicate phases form at magnesia grain boundaries, providing additional bonding between magnesia grains and between magnesia grains and matrix. Consequently, the samples with ReO showed much higher high temperature strengths than those without ReO.

Forsterite powders with controllable morphology were synthesized using oxides as raw materials in NaCl-KCl molten salt media. The effects of MgO/SiO 2 ratio, calcining temperature, and salt/oxide ratio on the phase composition and morphology of the powders are investigated. The results indicate that single-phase forsterite powders can be synthesized from a mixture of MgO and SiO 2 with a MgO/ SiO 2 molar ratio of 2:1.3 at 700°C. With the increase of calcining temperature, the powders obtained changes from an irregular to a columnar morphology. In addition, the morphology of the forsterite powders produced can also be controlled by altering the salt/oxide ratio. K E Y W O R D Smorphology, powders, silicates, synthesis

Porous silica ceramics were prepared from rice husk ash with a small amount of soft clay as workability agent by the in situ combustion pore-forming technique. Then, the effects of the forming pressures on the linear shrinkage, density, porosity, absorption of water and mechanical strength were investigated. The results showed that the pores in the samples consisted of two groups. One was original porous texture from rice husk silica, which ranged from 1-10 μm. The other was formed by burning of carbon and grain packing. Obviously, the greater the forming pressure, the denser the sample. Especially, the amounts of the pores with bigger diameter dropped significantly when the forming pressure was greater than 25KN. Porous ceramics with density 1.07g/cm3have high porosity and excellent comprehensive properties up to 10MPa.The preparation of porous ceramics utilizing high content rice husk would provide advantages of economical and ecological aspect.