نشریه علم و مهندسی سرامیک
سال یازدهم شماره 1 (پیاپی 40، بهار 1401)

Sirvan historical site is located in Sarāb Kalān village in northern area of Ilam province and according to experts and remains belongs to Sasanian and Early-Islamic periods. The purpose of this research, for the first time, was to investigate the chemical structure of 10 glass fragments (mainly including parts of the body of the vessel) obtained from geoarchaeological studies of this area, using XRF analytical method. The results of analysis show that these samples have been classified in the group of alkaline glass (silica - soda - lime) and according to the ratio of their alkaline elements, vegetable ash (probably local plants) has been used to prepare the glass load. The average weight percentage of silicon oxide is 60.97 with a variance of 15.100 and due to the amounts of aluminum and iron oxides, different sources of silica with low purity have been used in the production of these glasses. Observing variation in amounts of elements in glass lattice and lack of correlation between elements, strengthens the hypothesis of diversity and alteration in primary sources. Also, a comparative study between these samples with the analytical results of glass artifacts belonging to the closest historical sites to Sirvan (Goryeh and Jahangir Dome), indicates that probably the samples of Sirvan are older than these two sites, and trial and error has been played a main role in their production.

In this research, the electronic and optical properties of the (001) surface of SbNSr3 with SbSr and NSr2 terminations and surface passivation impact on electronic properties were investigated. The calculations were done within density functional theory and using pseudo-potential method. HSE hybrid functional was used for exchange correlation potential. The surface calculations were performed taking into account tetragonal supercell, periodic boundary conditions, sufficient vacuum and minimum force on atoms. Results of the electronic calculations show that despite the semiconducting nature of the SbNSr3 bulk, the electron states were observed near the Fermi level. The active surface bonding was saturated through adsorbing hydrogen atoms on the surface. Due to this, the electron states were removed and opened the band gap in both terminations. The calculated band gap of the SbSr and NSr2 terminations were calculated 0.808 and 1.029 eV, respectively. The optical properties of the SbNSr3 surface were investigated without and with the surface passivation. The results showed that in both terminations, the surface passivation which causes the elimination of surface electron states, leads to an increase in the optical gap. The calculated optical gap in both bare and passivated surfaces for the polarized incident light in the direction perpendicular to the surface was obtained greater than in the direction parallel to the surface. The optical gap of the SbSr termination was calculated to be less than that of the NSr2 termination in agreement with the results of the electronic calculations. It was also observed that the static dielectric constant at both terminations decreases with surface passivation and the static dielectric constant in the z-direction is less than in the x- direction.

Low pressure injection molding (LPIM) method in this paper is investigated as a method of forming alumina parts. This is one of the methods of making engineering ceramics with complex shapes and high dimensional accuracy. In this method, a binder system (paraffin wax + carnuba wax) was used as a plastic agent for easy formation of alumina particles. Different parameters such as feedstock temperature, injection pressure, injection time, mold temperature, etc. are effective in shaping ceramic parts by LPIM. The study of these parameters and the selection of their optimal value are discussed in this article. The optimum injection temperature was in the range of 90-90 ° C, the optimum pressure was in the range of 4-6 bar, the injection time was in the range of 10-15 seconds for a cylindrical shape with dimensions of 20×125 mm (D × H).

In this research, the aim is to achieve strong and ablation-resistant composite parts C / Cf-ZrB2-ZrC-SiC and C / Cf-ZrB2-SiC by non-pressure sintering method. C / Cf-ZrB2-SiC samples were prepared using synthesized ZrB2 and SiC powders between layers of resin-impregnated carbon fabric. After pressing with pressure 5 times at 1600 وC and heat treatment for 2 hours in a controlled atmosphere furnace under Ar atmosphere. In the next step, C / Cf-ZrB2-ZrC-SiC composite parts were prepared to investigate the effect of ZrC addition and compare it with C / Cf-ZrB2-SiC samples. This was done by synthesizing ZrB2-ZrC-SiC ceramic powder between layers of carbon fabrics using zircon (ZrSiO4), B4C, activated carbon, with or without Si, along with shredded carbon fibers. For this purpose, the prepared powders after wetting and drying along with resin were sprayed between carbon fabrics and the resulting samples were pressed 5 times by cold pressing after 20 layers. After pressing and finding the raw strength, the samples were transferred to a control atmosphere furnace under Ar atmosphere and subjected to heat treatment for 2 hours at 1600 .C. Scanning electron microscopy (SEM) and X-ray analysis (XRD) were used to investigate the microstructural and fuzzy properties of the samples, and the three-point flexural strength test and oxytocin flame were used to investigate the mechanical properties and oxidation resistance of composites. The linear erosion rates of C / Cf-ZrB2-SiC and C / Cf-ZrB2-SiC-ZrC samples in the oxytocin flame abrasion test were 2.16 and 1.74 μm / s, respectively, and the average erosion rates were 3.28. And 2.41 (4-10 g / s *) were measured. Also, the mean density values ​​for C / Cf-ZrB2-SiC and C / Cf-ZrB2-SiC-ZrC samples were 4.67 and 05.03 gr / cm3, respectively, and the flexural strength was 303 and 245 MPa, respectively. .

In this work, the photocatalytic degradation of organic dyes was studied employing zinc oxide based nanocomposites. In this purpose, ZnO based nanocomposites were synthesized using three different procedures including co-precipitation, hydrothermal and combustion methods. The samples were characterized by SEM, XRD, IR and UV-Vis spectrophotometer. Afterwards, the prepared samples were utilized for the photocatalytic degradation of Direct Red 23 (DR23). The effect of operational parameters containing photocatalyst amount, time, pH and dye concentration were investigated as effective factors on photocatalytic degradation process. The results represented that the particles synthesized by combustion method was the appropriate one for the decolorization of DR23. In this regards, the decolorization percentage of 97.5% was attained using 0.08 g photocatalyst and dye concentration of 20 mg L-1 after 120 min.

In the present study, the effect of nano Al2O3 and nano graphene ceramic additives in optimizing performance and improving thermophysical properties of aircraft anti-icing/de-icing fluids was investigated. Nanoparticles were characterized by TEM, SEM and XRD methods. The thermal conductivity, surface tension and dynamic viscosity of the hybrid nanofluids were experimentally assessed for temperatures between 253 and 303K and results were compared with some existing theoretical models. Results revealed that the thermal conductivity properties and thus the efficiency of aircraft anti-icing/de-icing fluids are improved by the addition of nanoparticles. Considering the performance of the aircraft anti-icing/de-icing fluids, increasing the surface tension of the fluid helps to improve its performance in covering the aircraft surfaces against the precipitation of super cooled raindrops and snow, resulting in better performance of aircraft anti-ice/de-ice fluid. Based on the results of measuring the dynamic viscosity of graphene-Al2O3/ aircraft anti-icing/de-icing -water hybrid nanofluid, the addition of nanoparticles in the volume fraction ranges from 0 to 0.5%, in addition to increasing the viscosity, show non-newtonian behavior Shear-thinning nanofluid the base, which is the main requirement for the performance of the aircraft anti-icing/de-icing fluid. However, at higher concentrations, the hybrid nanofluid shows a tendency to non-Newtonian shear-thickening behavior. Therefore, the addition of these two types of nanoparticles in volume fractions below 0.5% helps to enhance the performance of aircraft anti-icing/de-icing fluid.

In the present work, we report a novel design and preparation for the mechanochemical synthesis of calcium carbide-derived carbon (CaC2-CDC) at ambient temperature. Thermodynamic calculations confirmed the possibility of calcium carbide-derived carbon formation by the reaction of calcium carbide with sulfur, iron sulfide and zinc oxide at ambient temperature. The CDCs were synthesized by the ball-milling of calcium carbide and reactants with stoichiometric ratio, and explore the effect of milling time on CDC formation for 1, 3, 5, 7 and 10 hours for the reaction of calcium carbide and sulfur. Then, the as-synthesized powders were dissolved in 5% hydrochloric acid to remove by-products, and the CDCs was obtained by repeated washing with distilled water and filtration. The as-prepared CDCs and raw materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, FTIR and SEM. The XRD patterns reveals merely the reaction between calcium carbide and sulfur at 10 h. SEM images proved the formation of the numerous nanometer porosities. According to Raman results, CDCs had high graphitization degree, and also FTIR results confirmed the formation of carbon bonds. Moreover, CDCs obtained by the reaction with sulfur had the highest graphitization degree and lowest disorder.