جستجوی مقالات مرتبط با کلیدواژه « آیتریا » در نشریات گروه « مواد و متالورژی »

In the present research, nanoparticles based on the alumina-yttria system were synthesized using a sol-gel method. Then, the effect of heat treatment on the phase evolution and crystallite size in this composite system was investigated. The produced composite powder was characterized using X-ray diffraction and scanning electron microscopy. Scherrer equation was used to investigate the effect of temperature on crystallite sizes. The composite powder was cold isostatically pressed and subjected to a pressureless sintering process at different temperatures to evaluate its density changes. The X-ray diffraction results showed that the powder sample was initially amorphous. By increasing the temperature, the components of this composite system reacted and Alpha-Al2O3 and Y3Al5O12 phases are formed. The crystallite size of the Theta-alumina phase grew with increasing temperatures up to 1000 C. At higher temperatures, crystallite size decreased due to the decomposition of theta-alumina. The density of the samples increased by increasing the temperature up to 1600 C so that the samples reached a relative density of about 96%. The densification curve of the composite showed three different stages during sintering. Examining the hardness of the samples showed that the hardness increases with the increase of the sintering temperature, and in the sample sintered at 1600 C for 3 hours, the Vickers hardness reached about 14 GPa.

In this article, the effects of stabilized zirconia oxide by Y2O3 and silicon carbide on physical ‎stability of magnesite based refractories was evaluated. For this purpose, the simultaneous deposition was used to produce MgO-ZrO2 and Y2O3-MgO-ZrO2 precursor ceramic powders, and then these compounds were analyzed using various analytical methods, including QELS laser diffraction (quasi-elastic light scattering), XRD, BET and SEM.  Evaluate. Nanoscale powders with a specific surface area greater than 60 m2/g were created. Using the Vickers indentation method, which was done to determine the hardness of the porous ceramic that was composed of synthetic powders, the hardness of the ceramics is increased by the incorporation of Y2O3, and this process also helps to stabilize the entire cubic crystal phase.

In this study, the effect of yttria and benzotriazole doping on corrosion behavior and activation of self-healing mechanism in Alumina-based nanostructured coatings was investigated. Single-component Alumina, double-component Alumina-Ytteria, and triple-component Alumina-Ytteria-benzotriazole ceramic-based coatings have been ‎layer-deposited over St52 steel surface by the sol-gel process in order to improve the abrasion and corrosion behaviour of this steel. Afterwards, phase analysis, morphology, and topography of these coatings have ‎been carried ‎out respectively by Grazing Incidence X-ray Diffraction (GIXRD), Field Emission Scanning ‎‎Electron Microscopy (FE-SEM), and Atomic Force Microscopy (AFM).‎ Moreover, in order to investigate ‎elemental distribution in layer-deposited coatings, Energy ‎Dispersive Spectroscopy (EDS) ‎was performed.‎ Also, the corrosion behaviour of under-investigation coatings ‎and substrate were studied using electrochemical impedance spectroscopy and potentiodynamic ‎polarization for 1, 48, and 96 hours of immersion in 3.5wt%NaCl solution. GIXRD results revealed the ‎amorphous nature of the coatings and the absence of formation of ‎crystalline structure. AFM and FE-SEM ‎observations revealed intactness of double-component Alumina-Ytteria and Alumina-Ytteria-benzotriazole ‎coatings in comparison with single component Aluminacoating.

Stabilized zirconia has desirable properties including high hardness, high chemical stability and a thermal expansion coefficient close to metals. Therefore, in this study, zirconia-yttria-Benzotriazole hybrid based coatings were applied on the surface of AA2024 by sol-gel method. To this aim, zirconia and zirconia-yttria-Benzotriazole solutions synthesized by alkoxide precursors were applied on the surface by immersion process, and then heat treated at 150°C. Phase analysis, morphology and the chemical bond properties were investigated by GIXRD, FESEM and FTIR, respectively. Furthermore, corrosion properties were evaluated by electrochemical methods such as polarization and electrochemical impedance techniques in 3.5% NaCl solution. Results showed a homogeneous and crack free zirconia-yttria-Benzotriazole hybrid coating, which exhibited proper corrosion resistance.

In this study، the effect of different amounts of Y2O3 on the properties of mullite-zirconia composites was investigated. For this purpose، these composites were fabricated by reaction-sintering of alumina and zircon as raw materials. Besides، the slip casting method was used for forming these composites، and sintering process was carried out at 1600 °C. Then، the physical and mechanical properties، phase composition and the microstructure of these composites were investigated. The results showed that yittria addition up to 0. 5 wt. % has no effect on the properties of these composites. Besides، addition of more than 0. 5 wt. % yittria formed solid solution with zirconia grains and led to stabilization of tetragonal zirconia phase and increasing of its amount. Hence، yittria addition increases the hardness and bending strength of composite by stabilizing tetragonal zirconia phase and then، decreasing the micro-crack formation during zirconia phase transformation. As results show، addition of 0. 75 wt. % yittria leads to a considerable increase in the bending strength.

In this study، nano sized Al2O3. Y2O3 (YAlO3) powder was synthesized by sol-gel combustion method. The starting materials were Al (NO3) 3. 9H2O as a source of Al3+ ions، Y2O3 and HNO3 for production of Y (NO3) 3 as a source of Y3+ ions، and glycine as a fuel. Taguchi experimental design was used to obtain the optimum condition of gaining nano sized Al2O3. Y2O3 powder. The studied parameters were concentration، pH، and the ratio of fuel to oxidant. ANOVA varianse analysis was used to obtain the least average particle size. The prepared nano powder was characterized by XRD، FESEM، and BET analysis. The optimum conditions were found to be concentration 0. 2 mol/L، fuel to oxidizer ratio 1. 25، and pH of 4. In these cnditions، the average particle size was calculated around 45 nanometers.

In the present work، Bismuth oxide co-doped with Y2O3 and Dy2O3 with the mole percentage 12 was synthesized by solid-state reaction. The crystal structure characterization was carried out using X-ray powder diffraction. The as-sintered samples was cubic at room temperature. The sample annealed at 600˚C for various periods of time to studying the stabilization of cubic structure. According to XRD result the cubic phase transformed into other structures.