in this study, preparation of nano-sized gamma alumina with high specific surface area and high yield by thereaction between aluminum nitrate and sodium carbonate, without using any surfactant is reported. bohemite (aluminum oxyhydroxide) was prepared as a precursor by strict control of ph and reaction temperature. the gel produced was purified by washing followed by centrifugation. the specifi...

A new rapid, very simple and one-step sol-gel strategy for the large-scale preparation of highly porous γ-Al₂O₃ is presented. The resulting mesoporous alumina materials feature high surface areas (400 m² g-1), large pore volumes (0.8 mL g-1) and the γ-Al₂O₃ phase is obtained at low temperature (500 °C). The main advantages and drawbacks of different preparations of mesoporous alumina materials ...

Monolithic ceramics have been fabricated from coated green fibers to create fibrous microstructures. The fibrous monoliths consist of high aspect ratio polycrystalline regions (cells) of a primary phase separated by thin secondphase regions (cell boundaries) designed to improve fracture resistance. The cells are the remnants of the green fiber which consists of ceramic powder and a polymer bind...

The paper reports a process for synthesis of γ-alumina from kaolin. Kaolin was transformed to meta-kaolin by calcination at 800 ̊C for 2h. γ-alumina powder was synthesized through extracting alumina from metakaolin via H2SO4 and meta-kaolin reactions and consequently precipitation in ethanol, which led to form the aluminum sulfate. The precipitated aluminum sulfate was dried and calcined at 900 ̊...

the aim of this research is to develop a silica gel and alumina column chromatography for separation of polycyclic aromatic hydrocarbons (pahs) and polychlorinated biphenyls (pcbs) into two groups. this is achieved by optimizing the cut-off volume of eluting solvent and weight ratio of silica gel and alumina. in this process mixture of pahs and pcbs divide in two groups and simultaneously other...

OBJECTIVES The objective of the present study was to analyze the superficial roughness and the interface between enamel and composite resin restorations after dental bleaching procedure. MATERIALS AND METHODS Black's class V cavities were made and restored with composite resin, and the whole set, enamel-restorative material, was treated with 35% hydrogen peroxide. Seven procedures of 30 min e...

The paper reviews progress for a program of research on alumina ceramics processing, with particular reference to diffraction results achieved using tube x-rays, neutrons and synchrotron radiation. Outcomes from three related studies are examined. l Calcination of alumina hydrates to o-alumina via intermediate aluminas, including some new results indicating the co-existence of cubic and tetrago...

Thin alumina films have found applications in electronic circuits and cutting tools and have been recently explored as protective coatings against high temperature oxidation, but these studies have been relatively rare. In this study, amorphous alumina films 3.5 pm thick were produced by reactive sputtering on Co-30Cr-6Al-0.5Y coatings, using a pure aluminum target in Ar + 0 2 atmosphere. Isoth...

The purpose of the present study was to evaluate the effect of cooling rates after firing procedures of veneering porcelain on shear bond strength between veneering porcelain and a zirconium dioxide (zirconia; ZrO₂) ceramic material. A total of 48 ZrO₂ disks were divided equally into three groups. Two veneering porcelains that are recommended for ZrO₂ material - Cerabien ZR (CZR), IPS e.max Cer...

OBJECTIVES To evaluate the in vitro blending effect (BE) of layered resin composites related to material, shade, and differences in color and translucency between compared materials. METHODS Specimens made of two composites (2CS, n=5) consisted of the outer composite with an outer diameter of 10mm, 4mm thick and an inner diameter of 4mm, 2mm thick for the inner composite. Thus, the inner comp...