فصلنامه سرامیک ایران
سال هجدهم شماره 4 (پیاپی 72، زمستان 1401)

In this study, by selecting the appropriate process conditions and using aluminum cans, the aluminum alkoxide compound was prepared and used as a precursor in aluminum oxide (Al2O3) nanoparticle synthesis processes by sol-gel method. In the production of mesoporous Al2O3 nanoparticle via sol-gel process, the aging temperature of 25, 60, 80 °C and time of 12, 24 and 48 h were selected and investigated as the main parameters in determining the solute particle size and bonding during the gel process. The results showed that the aging temperature is 80 °C and 24h time as the optimal conditions for the synthesis of Al2O3 nanoparticle with superior properties in terms of specific surface area and porosity. The calcination temperature showed that the minimum temperature required to reach the alumina phase is 500 °C. However, due to the necessity of the presence of crystalline phase with maximum ordering in the layout of the atomic plates of 900 °C and 1 hour storage time, the optimum calcination conditions were selected. Scanning and transmission electron microscopy studies of the optimum sample showed that the final product had the same appearance as the nanoparticles, and the particle size distribution was in the range of 20 to 40 nm. It was also found that the synthesized nanoparticles have very distinct crystalline plates, and as a result of the nanoparticles bonding to each other and forming larger masses, porosities in the meso-range were formed in their microstructure which made the end product to be used as a catalyst substrate.

Nanoparticles have brought significant advantages in a wide range of fields due to their unique size-dependent physical and chemical properties. In this research, the combustion solution method is used to make La0.7Sr0.3MnO3 (LSMO) nanoparticles. Then the nanoparticles are covered with polyethylene glycol polymer. Due to the presence of hydrophilic molecular chains and high flexibility, polyethylene glycol is one of the most ideal coating agents to increase the colloidal stability and biocompatibility of LSMO nanoparticles. Using X-ray diffraction (XRD), the crystal structure, nanoparticle size and nanoparticle composition of LSMO were investigated, and a hexagonal structure with a crystal size of 18.4 nm was observed. Field emission electron microscopy (FESEM) was used to investigate the shape and size distribution of nanoparticles. The images showed that most of the grains are spherical with uniform distribution and the grain size in the processed sample is between 20 and 60 nm. The behavior of nanoparticles was estimated as ferromagnetic using Vibrating Sample Magnetic Analysis (VSM) and the saturation magnetization value before and after nanoparticle coating is 24.8 (emu/g) and 23.6 (emu/g), respectively. FTIR spectroscopy showed effective bonding between LSMO nanoparticles before and after treatment with polyethylene glycol.

In this research, we investigated the protective characteristics of ionizing rays (gamma and neutron) of Nextel-312, Nextel-440, Nextel-550, Nextel-720 ceramic fibers using Geant4 Monte Carlo simulation tool. In this study, parameters related to photon attenuation such as: mass attenuation coefficient (𝜇m), half-value layer (HVL) and mean free path (MFP) in the range of 0.015 to 15 MeV and the absorption cross section of fast neutrons for different energy levels were calculated. To validate the simulation results, we compared them with the results extracted from the XMuDat database, which shows that they are in good agreement with each other. The agreement between the data extracted from the XMuDat database and the results of the simulations of this study shows that Monte Carlo modeling is a good method to investigate the properties of gamma ray shielding. Also, the obtained results of ceramic fibers show more effective attenuation parameters in addition to physical properties compared to conventional protective materials such as concrete. Due to its higher density, Nextel-720 ceramic has the most favorable condition compared to other investigated ceramics.

The effect of a mixture of barium, molybdenum and cobalt ions on the dielectric and piezoelectric properties of PZT5 ceramics was investigated. Ba, Co and Mo doped  lead zirconate titanate (PZT) were prepared via conventional wet chemical method. PZT-type samples were polling by a low-temperature method. XRD analysis of the calcined powders confirms that there is no change in the crystal structure of PZT on co-doping with Ba, Co and Mo. It was found that the addition of 2% mol Ba, 2% mol Co, and 2% mol Mo simultaneously has a positive effect on a set of dielectric and piezoelectric parameters, which are important for the practical applications of this PZT - type ceramics. The mechanical quality factor Qm was 250 for the sample mixed with 1% mol Ba and 2% mol Co and 220 for the sample mixed with 1% mol Mo and 2% mol Co. The maximum electromechanical coupling coefficient and piezoelectric charge coefficient d33 for the sample combined with 2% mol Ba and 1% mol Co was obtained, which is equal to 0.36 and pC/N185, respectively. PZT samples doped with Ba, Co, and Mo may be potential candidates for underwater sonar and high power ultrasonic transducer systems.

Stable photoluminescence is a phenomenon that is excited by irradiating high-energy light (usually ultraviolet light and sometimes beta rays) to a given substance. After the excitation stops, visible light is emitted from the excited electron states. The material will be done for a time that can be evaluated from seconds to several hours.In the present research, in the first stage, the synthesis of SrAl2O4 with stoichiometric percentages was investigated by solid-state reaction method at temperatures of 900, 1100, 1300, and 1500 ℃. Then, Dy2O3 and Y2O3 additives were added to the SrAl2O4 mixture with ratios of 1 to 4% by weight. The crystal structure and network of the SrAl2O4 host were determined by X-ray diffraction (XRD) analysis. The emission intensity of the mentioned factors was investigated by photoluminescence spectrophotometry (PL) with radiation at the wavelength of 237 nm, and the emission obtained in the wavelength range of 500-540 nm in the sample with different additives. Also, Fourier Transform Infrared Spectroscopy (FTIR) of the host composition and optimized samples with additives were also performed. The microstructure of the synthesized particles was examined using a scanning electron microscope (SEM).

The nickel oxide layer doped with cerium was applied on a glass slide using the solution obtained from two precursors, nickel hexacetate and cerium ammonium hexanitrate with the general formula Ni1-eCexO and heated at different temperatures up to 550 degrees Celsius. Structural studies showed that the coated layers were composed of nickel oxide nanocrystals with a size of 40 to 120 angstroms. The thickness of the applied layer was 600 nm and it was formed with 5 layers. Electrochemical measurements including cyclic voltammetry and electrochemical impedance showed the reversibility of the electrochromic layer in 25 cycles. The ability of lithium ions to enter the tested layer was confirmed by 0.1 M solution of lithium perchlorate in isopropyl alcohol and current measurement compared to the Ag/AgCl electrode. During the conducted studies, the molar ratio of 0.05 to 0.1% was found to be appropriate due to the minimum electrical resistance and slight change in the visible transmission spectrum. Spectroscopy of the layers showed that this coating has near infrared absorption capability of 40% without causing any color change under the glass base, and its use as an optically passive electrode is suitable.