مجله مواد و فناوری های پیشرفته
سال دوازدهم شماره 2 (تابستان 1402)

In this research, transparent alumina ceramic was synthesized through the Spark Plasma Sintering (SPS) process. In this respect, its chemical deposition in the presence of Magnesium Nitrate and Lanthanum Nitrate, as the sintering agents, was surveyed. For this purpose, two types of alpha alumina powders (200 and 1000 nm) were used to prepare samples containing 100 ppm Magnesium Oxide and 100 ppm Lanthanum Oxide. In the chemical deposition process, the pH factors were compared, and the absence of powder calcination was investigated. In order to evaluate the phases, the samples were compared before and after SPS using X-Ray Diffraction (XRD) analysis, and deliberation of the microstructure was done using Field Emission Scanning Electron Microscopy (FESEM) analysis. Further, SPS was performed at 1500 °C at the rate of 50 °C/min under the pressure of 70 MPa for 15 min. The results of the IR transmittance test showed that the pH was adjusted and calcination was performed in 65 % of the 200-nm sample. EDS-Line analysis was then done to determine the mechanism of the sintering aids. The obtained results revealed the placement of Lanthanum oxide along the Alumina grain boundaries and the exclusion of the growth of Alumina grains during the sintering process while Magnesium oxide formed a spinel lattice to increase the density of alpha Alumina. Of note, pH adjustment and calcination reaction had significant effects on the enhanced transparency of the samples produced through the chemical deposition process.

In the present research, cellulose-conjugated graphene oxide (CCG) was prepared, and its efficiency as a targeted carrier was explored for loading curcumin, an anti-cancer drug. The structural and surface properties of CCG were examined by FESEM, BET, and FTIR techniques. Response surface method (RSM) with the central composite design was employed to optimize the effective parameters, such as pH, contact time, and initial drug concentration, on the drug adsorption on the composite. The central composite design results indicated that a second-order equation can properly fit the experimental data with a coefficient of determination of 0.9845 and p < 0.0001. The maximum adsorption (70%) was achieved at pH = 6, contact time of 60 min, and initial concentration of 20 mg L−1. The drug release from the CUR@CCG nanocarrier at pH = 5.6 was significantly higher than pH = 7.4, demonstrating the effectiveness of the system in the cancer cell environment. The MTT assay was used to assess the cytotoxicity of CUR, CCG, and CUR@CCG on two cell lines, including normal (MCF 10A) and breast cancer (MDA-MB 231). The cytotoxicity of CUR@CCG at a concentration of 96 μg mL−1 for 24 h on MDA-MB 231 was almost 45%, slightly lower than free CUR (50%). Based on these results, the CCG bio-nanocomposite can be utilized as a biocompatible nanocarrier for targeted delivery of the CUR anti-cancer agent.

In this study, dextran-based Aqueous Two-Phase Systems (ATPS) were used as the environmentally-friendly systems for extraction of metal ions. To this end, sodium citrate or sodium phosphate was used to create the two-phase region. The temperature, pH, metal ion concentration in wastewater, and amount of extractant were among the factors affecting the extraction efficiency in aqueous two-phase systems that were investigated in this study. For this purpose, the effect of pH on the extraction of lead, arsenic, and cadmium ions was investigated at the pH levels of 7-10, and the experiments were repeated at the temperatures ranging from 5 to 45 degrees Celsius. The laboratory results showed that cadmium and lead ions could be removed up to 100 % in the dextran/sodium phosphate system while the maximum separation of the lead ions was 60 % in the dextran/sodium citrate system. The maximum separation of arsenic ions was found to be 88 %. The UNIQUAC model was used to investigate the thermodynamic equilibrium in the aqueous two-phase systems. According to the obtained results, the proposed model could accurately predict the distribution coefficient of the metal ions in the ATPS. The error rate of the model was approximately 1 %. The proposed model can also be used to predict the distribution coefficient of the metal ions in the ATPS.

Use of γ-glycidoxypropyltrimethoxysilane (GPTMS) enhances the stability and strength of hydrogels and improves the bioactivity and cellular performance of the scaffolds in bone applications. Given that one of the leading factors that affects the properties of the scaffold is the percentage of the cross-linking agent, chitosan and gelatin scaffolds with different percentages of GPTMS were prepared and evaluated through freeze-drying method. The results from Scanning Electron Microscope (SEM) confirmed the achievement of porous scaffolds with open pores and upon increasing the amount of cross-linking agent, the size of the pores reached approximately 290 microns. The results of the infrared spectrum showed the interaction among the polymers and process of cross-linking with the formation of silane groups. In this study, upon increasing the amount of the transverse bonding agent, the contact angle decreased, the optimal contact angle of the sample with 75 (weight percent) GPTMS reached 60.7 ± 3.5 degrees, and the percentages of both swelling and degradation ultimately decreased. It should be noted that the mechanical properties were improved by adding GPTMS up to 1590 ± 267 kPa. According to the findings of this study, application of GPTMS led to an enhancement in the bioactivity properties and deposition of the hydroxyapatite layer, and the X-ray diffraction pattern confirmed this claim. The obtained results support the hypothesis that gelatin-chitosan scaffolds with 75 (wt %) GPTMS seem to be the best samples for use in bone tissue engineering.

In this research, PZT fibers were fabricated using PZT-5A commercial powder, polymeric additives and deionized water as solvent. The rheological behavior of different pastes with various amounts of solids and additives was investigated and the best paste was selected for syringe injection (extrusion process). Meanwhile, the paste containing 85wt% solid content and 1wt% glycerol, which was prepared using a 15wt% PVA solution, showed the best rheological behavior. The obtained fibers were dried at 100°C and the burnout process was carried out at 600°C with heating rate of 1°C/min for 2 hours. The sintering process was carried out in the temperature range of 1220-1270 ͦC for 2.5-4 hours. The phase investigations conducted by X-ray diffraction analysis showed that the fibers sintered at 1220°C have a single-phase perovskite structure and peak splitting confirms the ferroelectric nature of fiber. However, at higher sintering temperature, secondary peaks related to zirconium and titanium oxides were observed in the fiber diffraction patterns. Scanning electron microscope (SEM) images from the surface of the fibers showed that the fibers sintered at 1220°C for 2 hours were free of any cracks and had an acceptable density. In addition, based on the SEM images from the fracture surface of the fibers, the microstructure of this sample consisted of cuboid grains with average size of 1.5 μm, which is half of the average grain size of bulk PZT with spherical grains at its optimum sintering temperature.

Nickel-rich layered oxide cathode materials with the chemical formula of LiNi0.8Co0.1Mn0.1O2 (NCM) are increasingly utilized in the electric vehicle industry owing to their high energy density and high capacity. Although increasing the nickel concentration would enhance the chemical reaction between the surface layer and Li+/Ni2+ cationic mixing, the structural and thermal stability of the cathode material would be degraded. The single crystallization strategy of the particles can improve the structural stability and electrochemical performance of the cathode materials; however, their mechanism is not well understood yet. In this research, a computational model was proposed to show that by reducing the pH and controlling the amount of supersaturation, the nucleation rate of hydroxide particles and consequently the number of formed nuclei would decrease. Based on the results of this model, the numbers of hydroxide nuclei formed at the end of co-precipitation synthesis at pH 11.5, 11, and 10.5 were, respectively, 5.73, 4.3, and 2.27 times the number of nuclei formed in co-precipitation synthesis at pH 10. According to the observations, by reducing the pH during the synthesis process from 11.5 to 10, the fine particles produced in the system will be completely transformed into larger crystals, thus tending to become single crystals. As a result, the problems of the cathode/electrolyte intermediate layer will be minimized. The results of this model can justify the experimental results obtained by other researchers who synthesized single-crystal cathode materials.