مجله مواد و فناوری های پیشرفته
سال یازدهم شماره 1 (بهار 1401)

In this research, the equipment required to produce ceramic coatings based on Solution Precursor Plasma Spray (SPPS) method was first identified and manufactured by exploring the relevant sources and contained information. Then, aluminum oxide coating was applied to the substrate with MCrAlY bond coat using the set-up. Further, a solution of aluminum sulphate with the concentrations of 0.5 and 1 molar was prepared and used as a precursor injected into the plasma plume in order to evaluate the effect of the precursor concentration on the coating microstructure. The results revealed that the alumina coating obtained from the more diluted precursor had a more porous structure than its counterpart, and its microstructure contained some bubble-like fractured shells as well as small spherical particles. However, the coating obtained from the precursor with higher concentration was found to be denser mainly due to the phenomenon occurring during the deposition through the SPPS process. The XRD analysis yielded similar results for both coatings where the α-Al2O3 was the predominant phase in the coating.

The current study aims to investigate the microstructural and dielectric properties of the composite based on Polyvinyl alcohol-CaCu3Ti4O12 (CCTO-PVA) containing 0, 10, 30, and 70 wt % ceramic phase as the dielectric promoter. To this end, CCTO particles were first prepared by calcination of CuO, TiO2, and CaCO3 mixture at 1000 °C to fabricate the composite. Then, solutions with adequate amounts of PVA in water were provided, and the CCTO was added to solutions considering the composite weight percentage. Finally, the mixtures were dried at 60 °C. The X-Ray Diffraction (XRD) results of the powder indicated that upon increasing the amount of CCTO considerably, the semi-crystal peak height of the PVA would decrease. In addition, according to Scanning Electron Microscopy (SEM), the CCTO particles were dispersed preferably well in the polymeric phase. Dielectric properties were measured at 1 KHz, and the findings revealed that the dielectric constant and dissipation factors of the CCTO were measured as 1360 and 0.04, respectively. Moreover, these parameters of the PVA were obtained as 4 and 0.15, respectively. Increasing the CCTO weight percent of composites from zero to 70 % would increase the dielectric constant from 4 to 68 and reduce the dissipation factor from 0.17 to 0.04. The comparison of the dielectric constants with the results from different models indicated that the composite behavior was in good agreement with the logarithm model output.

Hydroxyapatite (HA) is one of the effective and efficient adsorbents of strontium ions in aqueous solutions. Considering this fact, the current study put its main focus on investigating the structure of hydroxyapatite after strontium adsorption to better understand the mechanism of this process. Nanostructured hydroxyapatite was prepared using a wet chemical method used for the adsorption of strontium ions with various initial concentrations after calcination. The structure of hydroxyapatite was well characterized after adsorption based on X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and Fourier Transform Infrared Spectrometer (FTIR) analyses. The micro-strain of the structure was also investigated based on fitting the XRD patterns by Voigt function and Williamson-Hall analysis. The crystallite size and degree of anisotropy in the presence of Sr were measured. Interpreting the obtained data and comparing it with different existing adsorption mechanisms suggested dissolution-precipitation as an effective mechanism for strontium adsorption by hydroxyapatite. The SEM images and EDS results also confirmed this mechanism.

Concrete is the most widely used construction material around the globe due to its high strength, durability, and relatively low cost. However, concrete cracks and their detrimental effects are inevitable even in the early life of structures, thus emphasizing the necessity of repair. Given that in most cases, concrete appears uncoated in the environment, and the environmental conditions significantly affect its longevity, application of some specific methods to increase the durability and longevity of concrete stuructures is highly recommended. According to the statistics, research findings, and objective observations, the cost of repairing a structure is sometimes higher than that of construction itself. Concrete cracks significantly reduce the life time of concrete structures. Therefore, it is more cost-effective to prevent the appearance and growth of small cracks from the very first moments rather than repairing the cracks after their formation. To this end, it is recommended to add repair materials to the concrete beforehand to improve premature cracking, a method called self-healing. For this reason, self-healing concrete has found a special place in the construction industry in the world, especially in recent years. The current study presented a review and made a comparison of some of these self-healing concrete methods to find the method with the highest capability of industrialization.

The main objective of the current study was to investigate the effects of titanium dioxide nanoparticles on some Multi-Drug Resistant (MDR) bacteria and consequently, on the liver of male Wistar rats. In this experimental study, nanoparticles in the form of spheres of 20 nm in diameter were synthesized through co-precipitation method, and their antibacterial effect on several bacterial strains was evaluated based on agar well diffusion and macrodilution methods. In addition, the activities of liver enzymes, i.e., ALT, ALP, and AST, and liver tissues in the mice were examined. The obtained data were compared using one-way ANOVA. The results confirmed the ability of these nanoparticles with the concentration of 640 (mg/L) to inhibit the growth of clinical and standard strains of Pseudomonas aeruginosa, Enterococcus faecium, and Staphylococcus aureus. In the case of the activities of liver enzymes AST and ALP, the mentioned concentration of nanoparticles caused a significant decrease in the structure of liver tissue with some disorders. The findings of this study revelaed that these nanoparticles halted the growth of some pathogenic bacteria. However, after intraperitoneal injection into the mice body, the mentioned nanoparticles reduced the activity of liver enzymes and tissue abnormalities.

The main objective of the current study was to synthesize porous nickel foam through a cost-effective method and study its novel applications. Several characteristics such as a mix of mechanical and physical properties with low density, high fluid permeability, and thermal conductivity have made synthesis methods of metal foams attractive in specific applications for researchers compared to polymers or ceramics foams. Foams are either open or closed cells that mainly affect the material properties and end usage. Wide applications of metallic foams in electrodes, heat exchangers, and filters and nickel foams in battery electrodes and catalysts for hydrogen production as clean energy sources are increasingly investigated nowadays. In this regard, the current study aimed to investigate open cell nickel foams synthesized through multi chemical processes including degreasing, roughening, sensitization, and activation methods to nickel deposition over non-conductive polyurethane. To this end, a thicker layer was coated by hard nickel electrodeposition. Then, polyurethane substrate was removed by pyrolysis in a tube furnace with pure argon gas flow. The characteristics of the nickel coatings were studied using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), metallography, and measurement of specific surface area (BET). In the Nickel foam, the compression strength of the electroless foam was calculated as 0.07 MPa and for the electrodeposited foam, this value increased up to 1.1 MPa. In addition, its hardness was measured as 145 Vickers Hardness (HV).

The current research aims to synthesize LiFePO4 nanoparticles as common cathodic materials used for lithium-ion batteries through the solution combustion synthesis method using a mixture of different types of organic fuels such as CetylTrimethylAmmonium Bromide (CTAB)-Glycine (CG), CTAB-Citric Acid (CCA), and CTAB-Urea (CU), considering the effects of fuel contents with the oxidant ratio of 5. The low rate of combustion reaction led to direct formation of LiFePO4 phase which was accompanied by some impurity phases. According to the results from the X-ray powder diffraction, single-phase LiFePO4 powders can be obtained followed by calcination at 700 °C for three h under the 95 % Ar + 5 % H2 atmosphere. The functional groups of the LiFePO4 powders were characterized based on Fourier Transform Infrared (FTIR) spectroscopy. In addition, small particles (~ 100-400 nm) with spherical morphologies as a function of fuel type were detected in Scanning Electron Microscopy (SEM) images. The electrochemical properties confirmed that the highest discharge capacity could be obtained using a mixture of CTAB and citric acid fuels (at the rate of 0.2 C, 127 mAh g-1) characterized by high crystallinity and small particle size.

Although Hydroxyapatite (HA) is one of the biocompatible and insulating ceramics, Carbon Nanotube (CNT) is superior due to its high thermal conductivity. This research aims to compare the thermal conductivity of HA/CNT composite in two fluids, i.e., water and Simulated Body Fluid (SBF), to achieve simultaneous biocompatibility and thermal conductivity for dental coatings. To this end, followed by synthesizing the hydroxyapatite, the HA nanofluid was made, and the prepared carbon nanotube was added to the HA nanofluid (volume ratio of HA:CNT was 1:1) to achieve the hybrid nanofluid with different volume fractions (0.2 to 1.0 Vol %). The thermal conductivity was then measured for the two water and SBF fluids in the temperature range of 20 to 50 °C. The results showed that 1.0 Vol % sample of the hybrid nanofluid had the maximum thermal conductivity enhancement compared to the SBF-based hybrid and water-based hybrid nanofluids with 32 % and 20 % enhancement, respectively, at 50 °C.