Advanced Ceramics Progress
Volume:6 Issue: 4, Autumn 2020

Oxyfluoride glass-ceramics containing CaF2 nanocrystals are kind of attractive materials for the optical applications due to their low phonon energy and high transparency. Moreover, the crystallization control and consequently, the kinetic properties are important for oxyfluoride glasses. Therefore, in the present research, the crystallization kinetics of isochronal transformation of the 37.26SiO2-28.11Al2O3-7.73CaO-26.89CaF2-4.5 K2O (wt%) glass have been determined upon the basis of maximum transformation rate using Differential Thermal Analysis (DTA) technique. Hence, it is concluded that the crystallization of the mentioned glass is a process controlled by Avrami nucleation, three-dimensional diffusion-controlled growth, and anisotropic growth impingement mode. The effective activation energy Qp =181 kJ.mol-1, growth exponent n=2.272, nucleation activation energy QN= 123, and growth activation energy QG=211 have been determined.

The current study aimed to characterize the hydroxyapatite, zirconia, and graphene oxide nanocomposite coatings on titanium substrate by the use of electrophoretic deposition. In the first stage, besides the characterization of the created composite coating, the thickness and uniformity of the created coating were evaluated by the use of Scanning Electron Microscope (SEM). Also, the distribution of the Nano-powder particles was investigated by the elemental analysis. In the second stage, by the use of X-ray diffraction analysis, the position of the materials used in the coating was drawn and investigated. In the third stage, in order to evaluate the coating’s corrosion behavior due to the addition of nanoparticles to the hydroxyapatite and compare it with the non-coated sample, the electrochemical analyses in the form of chemical polarization were investigated and analyzed with drawing the related charts. Finally, in the fourth stage, the antibacterial tests on the Escherichia coli and Staphylococcus bacteria on the coating were conducted and compared to the uncoated alloy samples. The corrosion test results indicated that the use of nano-composite coating leads to the increase in corrosion resistance of the surface. The antibacterial tests results demonstareted that the use of nano-composite coating effectively decreases the bacteria growth on the surface.

Nanocrystalline Magnetic Hydroxyapatite (MHAp) was synthesized through co-precipitation method and the subsequent heat treatment. Phase analysis, particle morphology, chemical bonding, and magnetic properties were studied using XRD, FESEM, FTIR, and VSM, respectively. The XRD results showed that MHAp was formed by heat treatment at 1100 °C. The samples heat-treated at 500 and 1100 °C incorporated a plate-like morphology with a mean crystallite size of 11.7 and 59.9 nm, respectively. In addition, the VSM results indicated that the synthesized MHAp was characterized by magnetic features after heat treatment. According to the findings in this study, the coercive field (Hc), saturation magnetization (Ms), and magnetism stayed (Mr) were 0.175 kOe, 0.00147, and 0.02615 emug-1, respectively, in -10 to 10 kOe  magnetic field. The growth kinetics of the MHAp was alo studied. According to the results, the growth activation energies for low and high temperatures were 45.51 and 67.33 kJ/mol, respectively. Owing to several properties already proven, the MHAp powder was successfully synthesized.

Conversion of methane to syngas via plasma technology is a cost-effective approach to obtaining syngas. Methane conversion by means of ceramic electrodes was significantly increased. In plasma reformer, while electrical discharge is available in gas, very active species such as electrons, radicals, ions, atoms, and excited molecules are produced and they function as catalysts. Methane and carbon dioxide gases at atmospheric temperature and pressure in the non-thermal with TiO2-coated electrode plasma reactor with an inner diameter of 9 mm are converted to hydrogen and carbon monoxide (syngas) through one chemical step. The main objective of this research was to investigate the effects of changes in feed flow rate and feed ratio on methane conversion and product selectivity, as well as product distribution. Furthermore, the results were obtained when three synthesized catalysts were inserted in a section             (3 mm) of plasma length (100 mm). The obtained results demonstrated that the voltage of 15 kV was required for methane conversion and hydrogen production. Reducing voltage and/or increasing the partial pressure ratio of methane to carbon monoxide in the reactor inlet resulted in the reduction of methane conversion rate. Moreover, according to the findings, increasing the ratio of carbon dioxide to methane would increase methane conversion and consequently, decrease the conversion of carbon dioxide. The conversion of methane and carbon dioxide was higher for co-precipitated Ce-Mn oxide support than those using the two other methods.

In this study, glasses with 41.6 SiO2, 28.5 Al2O3, 15.5 CaF2, 3.7 AlPO4, 1.5 AlF3, (9.2-X) NaF, and X LiF (X= 0, 3, 6, and 9.2) compositions were prepared. Fourier Transform Infrared Spectroscopy (FTIR) showed the red shift of Si-O-Si vibration mode by Lithium substitutions. According to the results of Differential Thermal Analysis (DTA), ΔTg = 60 ºC was proved by the lithium substitution. Field Emission Scanning Electron Microscopy (FESEM), antibacterial property, glass solubility in Artificial Saliva (AS), and pH variation in AS by dissolution were measured. Following the initial substitution of lithium, the glass density was reduced from 2.62 to 2.40 g/cm3, whereas in the 6 wt. % Li concentration, the high field strength played the main role and the density increased from 2.40 to 2.58 g/cm3. In artificial saliva with basic pH, the durability of Li bearing glasses increased and the degradation rate decreased. Durability decreased in the acidic environment. By increasing the Li substitution, the antimicrobial property of the cement was enhanced.

In this research, the effect of microstructure, chemical composition, and open porosity on the oxidation resistance of ZrB2-based composites was investigated. To this end, four composites with different chemical compositions were consolidated by Spark Plasma Sintering (SPS) method in different conditions, namely different temperature, time, and pressure. The open porosity was measured using the Arashmidouse method. Image Analysis Tools (IAT) were also utilized to determine the grain size of all composites through SEM images. For oxidation test, the samples were put on the box furnace and oxidized at 1400 C at different holding times of 20, 40, 60, and 120 minutes. The oxidation resistance was evaluated by weighing the samples before and after oxidation and the 𝛥w was considered as the oxidation criterion. In addition, EDS analysis was used to identify the phases. The results showed that chemical composition was the most significant factor in terms of the oxidation resistance, least affected by open porosity. Sample 9, with a grain size of 2.5 µm and open porosity of 1.5%, had the least oxidation value of 0.0026 gr; however, Sample 4 with a grain size of 12 µm and open porosity of 0.68% had the highest oxidation value of 0.0176 gr.