Fluxing action of illite and microcline in a triaxial porcelain body

Comparative studies were made on two types of triaxial porcelain bodies; one used conventional potash feldspar (ST0) and the other used illite (IT0) as the fluxing agents. Scanning electron micrographs showed that densification and mullite formation in the IT0 body had already occurred at 1000 °C suggesting that there was enough liquid to assist densification and mullite crystal growth. In the ST0 body, mullite crystals started to emerge around 1100 °C, while potash feldspar completely melted around 1200 °C. Full vitrification of the ST0 body required the firing temperature of 1300 °C, which was around 50 °C higher than the IT0 body. The IT0 body showed superior strength to the ST0 body at all studied firing temperature ranges and thus was possibly due to (i) a better densification, (ii) a higher amount of interlocking mullite crystals and (iii) the smaller amounts of residual quartz.     

Characterization and gene expression profiles of thermotolerant Saccharomyces cerevisiae isolates from Thai fruits

For industrial applications, fermentation of ethanol at high temperature offers advantages such as reduction in cooling costs, reduced risk of microbial contamination and higher efficiency of fermentation processes including saccharification and continuous ethanol stripping. Three thermotolerant Saccharomyces cerevisiae isolates (C3723, C3751 and C3867) from Thai fruits were capable of growing and producing 38 g/L ethanol up to 41°C. Based on genetic analyses, these isolates were prototrophic and homothallic, with dominant homothallic and thermotolerant phenotypes. After short-term (30 min) and long-term (12 h) exposure at 37°C, expression levels increased for the heat stress-response genes HSP26, SSA4, HSP82, and HSP104 encoding the heat shock proteins small HSP, HSP70, HSP90 and the HSP100 family, respectively. In isolates C3723 and C3867, expression was significantly higher than that in reference isolates W303 and TISTR5606 for TPS1 encoding trehalose-6-phosphate synthase, NTH1 encoding neutral trehalase and GSY1 encoding glycogen synthase. The results suggested that continuous high expression of heat stress-response genes was important for the long-term, heat stress tolerance of these thermotolerant isolates.     

Preparation and phase development of yttria-doped ceria coated TZP powder

This paper presents a simple technique for preparation of yttria-doped ceria (YDC) coated tetragonal zirconia polycrystal (3Y-TZP) powder and its phase development upon firing. The coating solution was prepared using yttrium nitrate hexahydrate and cerium nitrate hexahydrate as starting reagents. Thermochemical reactions of the coated powder were studied using TGA and FTIR while phase development upon firing was examined using XRD. Inward diffusion of the coating YDC into the TZP particles was monitored by observing the change of crystal structure and lattice parameter as a function of sintering temperature and time. At sintering temperature of 1300 °C for 1 h, crystal structure of the sample was still tetragonal (t-ZrO₂). Increasing sintering time to 5 h at 1300 °C, diffusion of YDC into TZP particles occurred drastically and the structure was changed to cubic (c-ZrO₂) as indicated by the disappearance of (002)/(200) peak splitting. Increasing sintering temperature to 1400 and 1500 °C, however, resulted in the co-existence of tetragonal and cubic phases as indicated by the appearance of triples around 72.5–74° 2θ and also the decrease of cubic lattice parameter. When the sintering temperature was further increased to 1600 °C, lattice parameter was only slightly changed, suggesting that inward diffusion of YDC reached saturation point around this temperature.