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The fabrication of porous forsterite samples through starch consolidation casting (SCC), utilizing waste silica fume and calcined magnesia has been performed. Three different forsterite contents of solid loading (56.5, 52 and 48 mass-%) were prepared, calculated in a stoichiometric ratio based on utilizing highly pure calcined magnesia and waste silica fume. In addition, corn starch was used as the source of pore forming that was added to the colloidal suspensions then gelatinized in water at elevated temperature (80 °C) followed by pressing and firing at 1400, 1450 and 1500 °C/2 h). The effect of corn starch content versus the fired temperatures on the physical properties, linear shrinkage, apparent pore size distribution, phase variation, microstuctural evolution and electrical resistivity as well as the cold crushing strength on the fired ceramics was investigated. Results showed that open porosity ranged from 45.5 to 80.5 % and compressive strength ranging from 38.1 to 20.2 MPa was obtained depending on starch content in precursor suspensions and firing temperatures, to develop porous forsterite ceramics having varied thermal and electrical applications. [ABSTRACT FROM AUTHOR]

The aim of this work is to synthesize the seeds of CoxMg1-xAl2O4 nano-spinel particles for pigment fabrication using a microwave-assisted method. Also, we report on a novel, less toxic, flexible, and reproducible microwave- assisted method for starch-based synthesis of spinels. Furthermore, substantial efforts were devoted to obtaining a nanopowder while reducing total synthesis time from many hours to a few minutes. The obtained powders were characterized by XRD, FT-1R, TEM, and EDSA techniques. The results show that CoxMg1-xAl2O4 spinel is in an amorphous form after microwave treatment at 1000 W with particle sizes of less than 20 nm and that spinel first began to crystallize at a temperature of 550 °C. [ABSTRACT FROM AUTHOR]

The sinterability of gelcast Fe2O3-doped and MgO-doped alumina ceramics containing 55 vol.-% solid loading was studied at different temperatures and compared with gelcasted sintered pure alumina. Physical properties (bulk density and apparent porosity), phase composition, microstructure and mechanical properties (microhardness and toughness) of the sintered bodies were investigated. The results revealed that the sintered doped bodies exhibited dense and compact microstructure as compared with pure alumina bodies. The hardness of Fe2O3-doped bodies showed the lowest values among the others due to the lower elastic modulus of the secondary phases formed and due to the enhanced grain growth after addition of a higher amount of Fe2O3. On the contrary, the addition of a small amount of MgO reduced the grain growth which enhanced hardness. Fracture toughness results showed a great increase in Fe2O3 doped ceramics due to the presence of large grains, while in MgO-doped ceramics, the facture toughness increase was related to a residual decrease in porosity. [ABSTRACT FROM AUTHOR]