Zinc hydroxide acetate (ZHA) is a promising material for anion exchange applications because it has a layered structure with intercalating CH 3 COO − and H 2 O. ZHA can be synthesized through a direct precipitation method by adding sodium hydroxide solution to a Zn(OCOCH 3) 2 solution. In this study, ZHAs were synthesized under various conditions and tested as phosphorous removal agents. The ZHA precipitates were obtained at pH 6, 7, and 9. They were then aged at 25°C, 60°C, 90°C, and 120°C under hydrothermal conditions. At pH 6, nearly pure single-phase ZHAs were obtained regardless of the aging temperature. On the other hand, most of the ZHAs that were prepared at higher pH and aged at higher temperature were transformed to ZnO. For the phosphorous removal experiments, the single-phase ZHA precipitates removed approximately 99% of the phosphate ions in a 100 mg L −1 phosphorous solution, and the phosphorus removal efficiency decreased with increasing amounts of ZnO. Therefore, ZHAs that were prepared at lower pH and aged at lower temperatures contained little to no ZnO, thereby showing high phosphorous removal capabilities.

We applied magnesiothermic reduction for porous silica glass, which was prepared from sodium borosilicate glass. The powdered porous silica glass was reduced to silicon and magnesium silicide at temperatures higher than 600°C. The silicon was isolated by the hydrochloric acid treatment and the subsequent hydrofluoric acid treatment for the reduction products. The SEM observation revealed that the prepared silicon had a porous structure. The pore size distribution measured with a porosimeter was similar to that of the stating porous silica glass in the region less than several tens nanometers. Keywords: Porous silicon | Porous silica glass | Magnesiothermic reductionSilicon is generally produced from silicon dioxide (silica, SiO 2 ) through various reduction processes. One of the most widespread methods for the industrial process is carbothermic reduction, in which silicon dioxide is reduced with carbon at a temperature above 1700°C. 13 As an alternative method, the electrochemical reduction in molten salts at much lower temperatures was proposed by Nohira et al. 4 Recently, however, attention has been paid to the magnesiothermic reduction of silica crystallites and amorphous silica. Since the reports by Bao et al., in which diatom frustules, mineralized unicellular algae, were reduced to silicon at 650°C, 57 this method has been applied for various types of silica, having well-developed nano-or mesoporous structures, 825 such as silica sands, silica films, silica channels, silica fume, silica spheres, and silica nanofibers. The most characteristic feature of this reduction process is that the silica starting materials can be converted to silicon retaining their nanostructures because the reduction proceeds at lower temperatures, typically at 650750°C. Thus, the magnesiothermic reduction of silicon dioxides with nano-to mesoporous structures can be regarded as a topic of the trend toward the template-aided creation of nanostructures. 2629 The porous silicon with various nanostructures has been expected to be applied for sensors, photoluminescent materials, lithium ion batteries, and so on. 3032 In fact, Bao et al. demonstrated that the prepared silicon microcrystals have the nanoporous structure derived from the structure on the surface of the diatom frustules and can play the role of NO gas sensors. 6 Here, the magnesiothermic reduction was applied for porous silica glass as starting materials for the first time as the authors know. The porous silica glass was prepared from sodium borosilicate glass through phase separation and acid leaching. It has been known that glass phases of sodium borosilicate (SiO 2 -B 2 O 3 -Na 2 O) with adequate compositions within the immiscibility region are separated into silica-rich and sodium borate-rich phases by heat treatments at some temperatures higher than the glasstransition region. 33,34 When the phase separation occurs by the spinodal decomposition, the two phases have interconnected structures. The borate-rich phase is leached by acid treatments for the phase-separated...

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The present work was undertaken as part of a study to clarify the relationship between the electrical properties and the microstructure of the SnO2-glass composite. The glass composites with different particle dispersions of SnO2 were prepared under various mixing conditions of the starting powder. The densification behaviour and the electrical properties of the glass composites were discussed from quantitative analysis of the dispersion of SnO2 particles in glass matrices. As a result, the glass composite having homogeneous particle dispersion densified and showed an abrupt increase in conductivity (K) and the temperature coefficient of resistance (TCR) at a low firing temperature. But after the completion of densification, the glass composite with the inhomogeneous dispersion of SnO2 particles showed a high K and a TCR close to zero because the highly aggregated SnO2 particles connect with each other to form highly electrically conductive networks.

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