Papers by Author: Sheng Long Wang

Abstract: Acicular mullite porous ceramics were synthesis by high-temperature sintering technique. In the present work, Kaolin and industrial aluminum hydroxide were selected as raw materials, AlF₃ used as catalyst. XRD and SEM were used to detect the crystal type and microstructure of prepared mullite ceramics, respectively. The influences of sintering temperature on the growth of crystal, the apparent porosity and compressive strength of the resulting porous ceramics were investigated. The results indicate when sintering temperature ranges from 1250 ~ 1400°C, much acicular mullite crystal appeared in the resulting ceramics. The apparent porosity, the compressive strength and the morphology of the mullite whisker changed obviously with the sintering temperature. When sintering temperature is 1400°C, the porous ceramics showed the maximum compressive strength of ~28 MPa and the maximum apparent porosity of ~63%.

Abstract: Lithium carbonate, zinc oxide and silica as the main raw materials, potassium oxide and sodium as flux, phosphorus pentoxide as nucleating agent, the glass in Li₂O-ZnO-SiO₂ was synthesized by conventional melt cooling method and then converted to glass-ceramics. The crystallization behavior, microstructure and thermal expansion coefficient of the resulting glass-ceramics were investigated by XRD, SEM and thermal performance test. The results show that the Tg of the matrix glass is about 508°C, initial crystallization temperature is about 620°C. When the crystallization temperature ranges from 650°C to 750°C, the main crystal phase is Li₂ZnSiO₄. Increasing crystallization temperature to 850°C, much cristobalite crystals is formed. Owing to the high TEC of the cristobalite, the glass-ceramics with TEC of 12.27×10^-6°C^-1 were obtained, which is matched with the TEC of stainless steel SAE 1010.

Abstract: Germanate oxyfluoride glass in CaF2/BaF2-AlF3-SiO2-GeO2 was prepared by melt quenching technique and subsequently converted to glass-ceramics with microstructures comprised nano-crystallites in a residual glass matrix by two-step heat treatments process. DSC, XRD, SEM and IR transmission investigations were used to determine structural characteristics and optical property of the prepared germanate oxyfluoride glass-ceramics. The influences of heat treatment conditions on crystallization behaviors and infrared transmission were discussed. The results show that crystal phase in the glass-ceramics is only Ge2Al6O13 and the crystal size is about 20nm-80nm when treated temperature ranges from 900 oC to 960oC. Good transparency is exhibited in visible light band to midinfrared band (5.0um) when treated temperature is low than 940 oC.

Abstract: Lithium aluminosilicate (LAS) glass-ceramics with 0 ~ 10 wt% phosphoric anhydride were prepared by sol-gel method and sintering at high temperature. Tetraethyl orthosilicate (TOES), aluminum nitrate, lithium carbonate were used as precursors. Differential thermal analysis (DTA), X-ray powder diffraction (XRD) and thermal expansion coefficient (TEC) were used to characterize the dried LAS gels and glass-ceramic blocks. The results suggest β-spodumene solid-solution is the only crystals phase in the P2O5 doped LAS glass-ceramics when sintering temperature is 950 oC. The thermal expansion coefficient of the P2O5 doped LAS glass-ceramics range from -0.1×10-6 oC-1 to 1.2×10-6 oC-1. Compared with the conventional melt quenching method, this process route provides a low temperature and timesaving method for preparing LAS glass-ceramics.