نشریه علم و مهندسی سرامیک
سال نهم شماره 4 (پیاپی 35، زمستان 1399)

In this research Cr2O3-SiO2 and Cr2O3-TiO2 green pigments have been fabricated using a mixture of Cr2O3-SiO2 and Cr2O3-TiO2 powder by ceramic method. The samples have been homogenized using planetary mill in a solvent with a ratio of 1:4 for 5 h and then printed on the ceramic using screen printing method and heated in the industrial condition. The crystal structure of samples, the shape and the size of the particles and their optical properties have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis spectroscopy and CIE L*a*b* colorimetric methods. The XRD results show two-phase structure has been created in both samples. The average of crystallite size for Cr2O3-SiO2 and Cr2O3-TiO2 were measured 40 and 34 nanometers, respectively. The SEM images show that the average size of Cr2O3-SiO2 and Cr2O3-TiO2 are 290 and 143 nanometers, respectively. The physical properties of printed ceramic were investigated by SEM and colorimetric methods. The average particle size for printed samples, Cr2O3-SiO2 and Cr2O3-TiO2, on the ceramic were measured 131 and 106 nm respectively.

In this research LiMn1.5Ni0.5O4 nano powders that are used as cathode material for lithium-ion batteries were prepared by solution combustion synthesis route. Cetyl trimethyl ammonium bromide (CTAB), mixture of “CTAB and glycine” and also mixture of “CTAB and citric acid” were used as fuel using fuel to oxidant ratio of 0.5. The effect of fuel type on microstructure and electrochemical properties of the powders was studied. Differential thermal analysis (DTA) results demonstrated that the gel combustion intensity increases in presence of glycine and citric acid fuels. XRD results of the powders synthesized by mixture of “citric acid and CTAB” and “glycine and CTAB” shows formation of single phase LiMn1.5Ni0.5O4 with a higher crystallinity. BET results show that the surface area of the powders prepared by mixture of fuels are equal to 400 m2/g and 269 m2/g for “CTAB and glycine” and” CTAB and citric acid” mixtures respectively that are higher than the surface area of the powders prepared by CTAB. SEM results show spherical fine particles (15 to 10 nm). The highest discharge capacity (125mAh/g) was obtained for the powders synthesized with the mixture of citric acid and CTAB due to its high surface area and small cell parameter (8.1671 Å).

In this project, mesoporous titanium oxide-silicon oxide doped by silver (TiO2-SiO2-Ag) was hydrothermally synthesized. Titanium isopropoxide, tetraethyl orthosilicate and silver nitrate were used as precursors for TiO2, SiO2 and Ag, respectively. Initially TiO2-SiO2 mesoporous nanocomposite was synthesized with weight ratios of silica to titania SiO2:TiO2:3:1 via hydrothermal method at 70˚C and 130˚C, then 5wt% of silver was added to each sample. The samples were characterized using XRD, SEM, EDS, Map and BET analysis and photocatalytic performance of synthetic samples under visible light and ultra-violate were investigated using UV-Vis spectroscopy The results of isotherm adsorption-desorption of nitrogen indicate the mesoporous structure of TiO2-SiO2 samples. XRD analysis confirmed the presence of anatase and rutile phases in TiO2-SiO2 samples and also the presence of silver phase along with anatase and rutile in TiO2-SiO2-Ag composition. Examination of the photocatalytic activity of the specimens by visible and ultraviolet light showed that the highest degradation percentage of pollutant (33%) under visible-light and ultra-violate was observed for the sample with silica to titania ratio of 3 via hydrothermal method at 70˚C with additions of silver during synthesis (TS3A-70).

Gadanium doped cerium oxide ceramic (GDC) is widely used as solid electrolytes in solid oxide fuel cells because of its high oxygen ion conductivity. In this study, the effect of addition of nano CuO as a sintering aid on the properties of GDC electrolyte were investigated. For this purpose, 0.2, 0.5, and 1% mole of nano Cuo was added to GDC ceramics, which was synthesized by the solid-state method and the effect in microstructure and ionic conductivity of this solid electrolyte were investigated. The results of X-ray diffraction showed that the presence of the CuO phase as an impurity phase was detected by adding 1% mole nano CuO. Based on the results of density and ionic conductivity, 0.5% mole nano CuO was introduced as the optimal value. With the addition of 0.5% mole nano CuO, the density of GDC ceramic increased to 97% theoretical density and the ion conductivity improved by 89%. The SEM results showed that adding nano CuO had a great effect on the microstructure of the GDC ceramic and the uniform microstructure was obtained. An increase in ionic conductivity and a decrease in the activation energy of GDC electrolyte in the presence of nano CuO could be due to increased density, grain growth and reduced resistance of grain boundaries.

Composite coatings containing P and ceramic particles are considered in terms of properties such as corrosion resistance, oxidation resistance and high hardness. In this study, Co-P-nanoAl2O3 composite coating was fabricated on the AISI 430 stainless steel substrate using a direct current electric deposition technique. The quality of the coating and its corrosion resistance were studied by changing the amount of alumina (3, 4, 5 and 6 g/L) in the electrolyte bath. In order to investigate the morphology of the composite coating and the analysis of the Co-P-nanoAl2O3 composite coated samples, a scanning electron microscope (SEM) and EDS analyzer were used, respectively. The results showed that by increasing the concentration of nano-alumina particles in the electrolytic solution from 3 g/L with a 1 unit increase to 5 g/L, the weight of nano-alumina particles in the coating increased. Then by increasing the concentration of nano-alumina particles in the electroplating solution the weight percentage of nano-alumina particles in the coating reduced. Also the results showed that, the composite coating formed in the bath containing 5 g/L alumina is perfectly uniform and continuous, while with increasing amount of alumina, it is not possible to form a suitable coating on the entire surface of the substrate. In order to investigate the corrosion resistance, potentiodynamic polarization experiments were applied in aqueous solution of 3.5% NaCl on coated and non-coated samples. The results of Tafel and electrochemical polarization tests were also correlated with microscopic images and showed that the coated in the bath containing 5 g/L alumina had the highest corrosion resistance.

Zinc hydroxide chloride nanostructure was successfully synthesized through a simple method at low temperature by sonochemical process. The morphology and crystalline of the products were analyzed by XRD, FESEM and TEM. The effect of independent variables including contact time, solution pH, adsorbent dosage and the concentration of dyes on response performance with response to surface methodology based on Central Composite Designs. ANOVA was applied to analyze the responses.  Investigating the isotherm and  kinetic models showed that the experimental data were correlated with Temkin adsorption isotherm model and pseudo-second order kinetic. In optimal conditions, Zinc hydroxide chloride nanostructure has the potential to remove Reactive Blue 39 dye.

Albumin is a protein macromolecule that it has been attractive since the early 20th century and has several therapeutic applications. Albumin is an aboundant serum with good biocompatibility, hematopoiesis and biodegradability in blood. The existence of multiple functional groups makes it possible to carry significant amounts of therapeutic and diagnostic factors, as well as targeting factors. This protein, on the one hand, has therapeutic uses and, on the other hand, is used in various formulations to carry pharmaceutical and diagnostic agents. There are many benefits to albumin-based nanocomposites in facilitating their clinical applications in a variety fields, including drug release, imaging, teranostic, tissue engineering, and coatings.

The aim of this study is to create TiO2 coating on the tile substrate using cell-gel and immersion method. Initially, TiO2 coating was prepared by sol gel method and then, deposition was performed in three stages with different immersion periods of 20, 40 and 60 s and finally, the samples were calcined at 450 °C. The phases and microstructural characteristics of the samples were analyzed using X-ray analysis and scanning electron microscopy. The results of phase analysis showed that in samples with immersion time of 20 and 40 seconds, the dominant phases were sublayer phases include of mulite and corundum, while in samples with immersion time of 60 seconds, the predominant phase was the anatase phase. Microstructural studies using scanning electron microscopy showed that, in the early stages of deposition, the initial nuclei of TiO2 was formed, and as the deposition time increased, a cover of TiO2 nanoparticles about 50 nm was grown on the initial nuclei. AFM results showed that, the surface porosity fraction of the samples and the surface roughness increased with increasing layer thickness of sample with immersion time of 20 s to sample with immersion time of 60 s. Stearic acid has been used to modify the surface and reduce the surface energy of TiO2 coating.  After surface modification of samples, the sample with immersion time of 20 s showed hydrophilic behavior and the samples with immersion time of 40 and 60 s showed hydrophobic behavior. The contact angles of the samples with immersion time of 20, 40 and 60 s were obtained 74.42 °, 91.23 ° and 99.01 °, respectively. At last, the abrasion resistance of the coatings was assessed using Pin on disc method and the average friction coefficient for TiO2 coating for all three samples was 0.2.