نشریه علم و مهندسی سرامیک
سال دوم شماره 3 (پیاپی 6، پاییز 1392)

In the present research work possibility of Silicon Carbide (SiC) synthesis in a SiO2-Mg-C system by use of a low power domestic microwave (850W) heating device has been studied. It has been concluded that Silicon (Si) is easily reduced by Mg and subsequently reacts with carbon to form SiC. According to the experimental results، it has been revealed that carbon content of the initial mixture has only a small effect on the carbide formation process. The amount of SiC in the final product increases considerably if the heat of reduction reaction of SiO2 by Mg is not allowed to escape from the system easily and remains for a period of time which is necessary for the progress of carbide formation reaction. This fact indicates while the reduction reaction is vigorous with a SHS nature، carbide formation is relatively slower and needs to proceed for a longer time at higher temperatures

To develop lead free piezoelectric materials Bi0. 5 (Na1-xKx) 0. 5TiO3-yBiFeO3 (abbreviated as BNKTx-BFy، x=0. 18، 0. 20 and 0. 22، y=0. 03 and 0. 07) ceramics were prepared by solid state synthetic method. The formation of a solid solution of BNKT with BF has proven to omit the impurity of bismuth ferrite and resulted in a pure perovskite phase. The room temperature ferroelectric and piezoelectric properties of these ceramics were studied. The morphotropic phase boundary (MPB) of Bi0. 5 (Na1-xKx) 0. 5TiO3 ceramics between rhombohedral and tetragonal exactly locates at x=0. 20. Polarization versus electric field (P-E) hysteresis and relative dielectric constant ɛr studies show maximum remanent polarization Pr= 33µC/cm2and ɛr =5435، respectively. The depolarization temperature Td، the maximum temperature Tm and piezoelectric coefficient d33 were obtained at x=0. 20 and y=0. 03، 80 oC، 275 oC and 120 pC/N، respectively.

Crystallization behavior of different composition of the Li2O-TiO2-P2O5 glass system that is used as a solid electrolyte was investigated. The glass composition was changed according to 45Li2O-xTiO2- (55-x) P2O5 in which x could adopted 10،15،20،25، respectively. The glasses were melted at 1350 °C and then casted into preheated graphite mold. Heat treatment of glasses was done at theirs Differential Thermal Anaalysis crystallization peak temperatures. According to X-ray diffraction and microstructural analysis، nasicon was crystallized in the glass that contained 25 mole percent TiO2. Moreover، the results indicate that surface crystallization is the dominant mechanism for crystallization and a two-step heat treatment process is required for precipitation of nasicon as a sole crystalline phase.

In this study، the synthesis of hollow nano-bio-glass fibers with Polyvinylpyrrolidone polymers were developed using electrospinning. Firstly، the ceramic sol in SiO2-CaO-P2O5-TiO2 system was prepared and stabilized. Then، the resulted sol was added to the polymeric solution. The final solutions with different viscosity were sent for the coaxial electrospinning under voltages of 10، 15، 20، and 25 kV. The morphology study of the electrospun fibers using SEM showed tolerable sizes for the samples and optimum conditions such as amount of Polyvinylpyrrolidone polymer and also the applied voltage were defined to reach hollow nano-bio-glass fibers with the high surface area. Regarding the obtained results، severals analysis such as STA، XRD، FTIR، and BET were developed on the optimized samples. Finally، The surface area results demonstrated that this nano-bio-glass fibers could be a good candidate as drug delivery system.

Nowadays use of semiconductors in particular titania in photocatalytic activities has been a lot of interest. Among many candidates for photocatalysis، TiO2 is almost the only material suitable for industrial uses. Conventional powder catalysts suffer from disadvantages in stirring during the reaction and in separation after the reaction. Preparation of the coatings make it possible to overcome these disadvantages. In this study، nano-titania coatings was prepared by sol gel-dip coating onto the high purity aluminum surface and degradation of methylene blue as a dye pollutant، was investigated in the presence of TiO2 thin films. The anodizing process is used to create nanometer pores and increase surface roughness and for these reasons، the degradation of methylene blue increase significantly In this research، The structure and composition of the coatings were characterized by means of X-ray Diffraction (XRD)، Scanning Electron Microscopy (SEM) and UV-Visible Spectrophotometery (UV-Vis).

In this study، CeO2-MgO nanopowder was synthesized via co-precipitation method using cerium (III) nitrate hexahydrate and magnesium nitrate hexahydrate as precursors، and aqueous ammonia solution as a precipitating agent. The Taguchi experimental design has been used to optimize the critical parameters to achieve a smaller particle size of CeO2-MgO nanopowder. The studied parameters were pH، temperature، and concentration of soluble elements. The prepared samples were characterized by X-ray Diffraction (XRD)، and Scanning electron microscopy (SEM). X-ray diffraction revealed that MgO and CeO2 phases were formed. The determined optimum operating conditions were a pH value of 11، temperature of 5 and concentration of 0. 1 M. Under these optimal conditions، average particle size of 30 nm has been obtained.

In this Reaserch fabrication of anAl/ (Al2O3+AlxVy) in-situ compositevia mechanical-thermal activations in an Al–V2O5 system has been investigated. For this PurposethemixedpowdersofAlandV2O5 with different weight ratios (C1: Al-22. 93wt%V2O5 and C2: Al-15. 78wt%V2O5) ball milled and then compressed. Rawsamplesat temperatures650 ºC، 850 ºC and1000 ºC were heated. XRDanalysisof thesamplessinteredat temperature 1000 ºC showed that thephasesAl21V2، Al3Vandα-Al2O3formedinbothsampleas thereinforcmentthe diffrence thatthesamplesC1، also there isphaseAl45V7. compressive strength and strain of both composite samples Proportion with pure aluminum show a significant increase that knew due Presence of ceramic and Al-V intermetallic reinforcment particles and also were sintering of sample in presence of molten aluminum.