فصلنامه سرامیک ایران
سال هفدهم شماره 3 (پیاپی 67، پاییز 1400)

Nanofluid is a suspension obtained by adding nanoscale particles (100 nm) to a base fluid to improve heat transfer. In this study, the effect of temperature and concentration of nanoparticles consisting of Alumina nanoparticles and Graphene nanosheets on the thermal conductivity of a base fluid consisting of water and ethylene glycol was studied. Also, 0.2% by volume of oleic acid (OA) and 0.2% by weight of sodium dodecyl sulfonate (SDS) were added to the base fluid as a surfactant to stabilize and disperse the nanoparticles. The volume fraction of nanoparticles of 0.05, 0.1, 0.5, 1, 1.5, 2 and 2.5% by volume and the tested temperatures were selected in the temperature range of 260-305 K. The morphology and microstructure of the nanoparticles were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thermal conductivity of hybrid nanofluids was measured and compared with the base fluid. Results showed that thermal conductivity of water-ethylene glycol / nano Graphene-nano Alumina hybrid nanofluid depends on nanoparticle concentration and temperature. The thermal conductivity measurements of water-ethylene glycol / nano Graphene-nano Alumina hybrid nanofluid were compared with the thermal conductivity prediction models of nanofluids but there was no acceptable agreement. The results showed that increasing the temperature and volumetric concentration of nanoparticles increases the thermal conductivity of hybrid nanofluids. The maximum increase in thermal conductivity of hybrid nanofluid was 44.02% which was obtained in solid volume fraction of 2.5% and at temperature of 303 K.

In recent years, research into materials with high dielectric constants, including doped titanium oxide, has increased because of the potential for modern microelectronics applications and high-density energy storage. The aim of this study was to investigate the effects of zinc oxide as an acceptor additive on the dielectric properties and microstructure of titanium oxide ceramics. The amount of 0.5, 1 and 2 wt% of the additive was added to the titanium oxide and the samples were prepared by powder pressing method and then sintered at 1420 ºC for 5 hours. The properties of the samples including density, phases, dielectric constant, dielectric loss and microstructure were investigated. The results showed that zinc oxide improved the density of titanium oxide. The results of X-ray diffraction test showed that there was no secondary phase and impurities in the samples containing the additive, which could indicate the replacement of the additive in the crystalline lattice of titanium oxide and the formation of a solid solution. The addition of zinc oxide resulted in the decreasing of dielectric constant and dielectric loss of titanium oxide. Zinc oxide additive caused grain growth and increase of grain size of titanium oxide ceramic. Microstructures with very large grain sizes and the possibility of creating oxygen vacancy with using zinc oxide additives can lead to the reduction in the dielectric constant of the titanium oxide ceramic.

Cu-substituted 58S bioactive glasses (0-10%mol CuO) were synthesized by sol-gel method and the effect of copper substitution for calcium on their biodegradability, bone-like apatite formation, cell proliferation, alkaline phosphatase activity of M3T3-E1 osteoblast cells and antibacterial efficiency were investigated. The results of x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) and surface analysis using SEM confirmed the formation of a layer of bone-like apatite on the BGs after 7 days of immersion in SBF. The surface analysis with SEM indicated that the addition of copper to the structure led to a reduction of the amount of apatite formed on the surface. The evaluation of cellular response by MTT assay and alkaline phosphatase activity showed that the proliferation and differentiation of MC3T3-E1 cells in 58S BG substituted with 5 mol% CuO had the highest value compared to other samples while, the substitution of 10 mol% CuO in composition led to a reduction in cell proliferation and differentiation and induction of cell cytotoxicity. In addition, Cu-substituted glasses showed significant antibacterial effect against Escherchia coli (E.coli) and Staphylococcus aureus (S.aureus) bacteria so that the antibacterial activity coefficient against E.coli in 58S containing 5 mol% CuO has doubled compared to base glass and was more than 99% (p<0.01). Taken together, 58S glass containing 5% mol CuO has been recommended for use in repair of bone defects in tissue engineering due to its in vitro bioactivity, stimulation of MC3T3-E1 cell proliferation and differentiation and excellent antibacterial activity.

In this study, the effect of simultaneous doping of magnesium, calcium, and copper ions on the properties of zinc oxide doped with cobalt was investigated. The sol-gel method has been used for the synthesis of nanoparticles. The structural and optical properties of the synthesized nanoparticles were investigated using X-ray diffraction (XRD), infrared spectroscopy (FTIR), and DRS spectroscopy. Rietveld’s analysis of XRD patterns confirmed the hexagonal wurtzite phase structure. In infrared spectroscopy, bands related to this structure were detected at a wavenumber of about 400 cm-1. Microscopic images showed that fine zinc oxide particles with dimensions of 10 to 20 nm were agglomerated by sticking to each other. In addition, it was found that the bandgap of the doped samples was reduced relative to pure zinc oxide. Due to the addition of cobalt as a dopant, the bandgap energy reduced from 3.0 eV to 2.5 eV. Also, copper ion as a second dopant in the composition caused a further reduction in the bandgap and reaches about 2.1 eV. The examination of the samples by the VSM device showed that the magnetic properties of the particles are enhanced by the addition of cobalt dopant and reach 40 memu / g. However, as a result, the magnetic property is reduced with other co-doped samples. copper and cobalt co-doped zinc oxide have no significant changes in magnetic properties. Therefore, with a lower bandgap and the best magnetic properties, this sample can be considered the most suitable sample in the dilute magnetic semiconductors’ application.

Water purification is a vital and essential thing for human life. The presence of pollutants in water is a major threat to the environment and human health. Various materials have been proposed and used for water treatment in recent years. Recent research has shown the potential of two-dimensional materials such as graphene oxide and its composites for water purification. The goal of this project is to make a clay filter coated with graphene oxide / polydopamine composite for water treatment. To achieve this goal, Graphene oxide was synthesized by modified Hummers method and GO/PDA composite were prepared by dopamine self-polymerization in the presence of graphene oxide in weakly alkaline solution and the immersion method was used to cover the substrate. Finally, X-ray diffraction analysis (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and field emission scanning microscopy (FE-SEM) results are indicated that graphene oxide and graphene oxide / polydopamine composites are well synthesized and the extent of methylene blue contamination degradation was evaluated by visible-ultraviolet spectroscopy. The results showed that all samples have high potency in absorbing methylene blue pollutants And with the addition of graphene oxide to polydopamine, the absorption rate increased from 63% to 99% due to the increase in oxygen-containing groups. According to cross-sectional scanning electron microscopy images, the applied GO coating was removed from the substrate and by adding PDA to graphene oxide, the stability of the coating on the clay substrate was improved. Using this composite coating on an inexpensive clay substrate , the efficiency of the body increased from 20% to 82% in the first 40 minutes of organic dye absorption.

In this research, CdS/g-C3N4 /rGO ternary composite was prepared by hydrothermal method and characterized using various techniques including X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and UV-Visible spectrophotometer. The photocatalytic activity of the prepared composite was evaluated from kinetics perspective by studying the removal of ciprofloxacin antibiotic under visible light. Kinetics studies based on the Langmuir-Hinshelwood model showed that the photocatalytic removal of ciprofloxacin by CdS/g-C3N4 /rGO follows the first-order kinetics model. It was found that the removal rate decreases with increasing drug concentration. In addition, by increasing the amount of catalyst from 0.1 to 0.7 gL-1, the reaction rate increases and further increase of the catalyst leads to a decrease in rate. The effect of pH showed that the photocatalytic removal rate of ciprofloxacin at neutral medium is much higher than acidic and alkaline conditions.