A cordierite powder was synthesized from a batch composition of talc, diatomite and alumina. Sintered samples of the synthesized cordierite were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), and Rietveld analysis. The XRD analysis showed hexagonal or a-cordierite (indialite) as a major phase along with MgAl2O4 spinel and cristobalite as secondary phases in the s...

Ab initio density functional theory and ballistic transport theory are applied to the calculation of tunneling current through ultra-thin SiO2 gate dielectrics. The Si/SiO2/Si model interface has been constructed by orienting a crystalline SiO2 (β−cristobalite) slab such that the misfit with Si (001) was minimized and no dangling bonds appear at the interface. The structure was then sandwiched ...

The transformation of SiO2 from low pressure tetrahedral phases into denser octahedral phases takes place via the collapse of the oxygen sublattice into a close-packed arrangement. The transition paths and the resulting products are known to be affected by the presence of anisotropic stresses, which are difficult to control, so interpretation of the experimental results is problematic. Based on...

Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume. In consequence, the adsorption and diffusion of oxygen in PSi are particularly important phenomena and frequently cause significant changes in its properties. In this paper, we study the thermal oxidation of p+-type free-standing PSi fabricated by anodic electrochemical etching. These free-standing...

The aim of the present study was to design and fabricate a maxillary posterior fixed partial denture (FPD) made of a type 4 gold alloy and an indirect composite. Unlike the conventional framework design of a resin veneered restoration, cut-back was extended approximately 1/4 to 1/3 width in the occlusal table of the buccal cusp. Multiple retentive beads 150-200 mum in diameter were placed on th...

In this paper, using sewage sludge carried out to manufacture high performance ceramsite. At the same time, the performance of concrete made from sewage sludge ceramsite was analyzed. The results show that the ceramist is mainly composed of cristobalite and mullet, and has dense enamel structure on surface and honeycomb closed fine porous structure in internal. Too large ceramsite size can caus...

Respirable crystalline silica dust generated during stone crushing operations has been linked to chronic lung disease and increased risk of tuberculosis. In India, most stone crushing mills operate without any dust control or containment systems. This investigation in the Khurda District of Orissa demonstrated a reduction in respirable particulate mass following the application of a fine mist o...

In this study, different glasses were investigated to improve reusable investments. Borosilicate glass (BSG) powder and soda-lime glass (SLG) powder were prepared by milling broken beakers and microscope slides, respectively, and used in experimental investments (I-BSG, I-SLG) by blending glass powder (10 wt%) with cristobalite (90 wt%). Some properties and casting fits were evaluated with comm...

The doping effects of Al2O3 on SiO2 ( -cristobalite) have been studied by first principles calculations, with emphasis on the structural, electronic and optical properties. Compared to pure SiO2 crystal, the electronic density of states (DOS) of the Al2O3 doped SiO2 show significant changes. The electron energy states corresponding to the newly emerged sharp DOS peaks are found to exhibit local...