فصلنامه سرامیک ایران
سال هفدهم شماره 2 (پیاپی 66، تابستان 1400)

In this research, geopolymer composites were prepared using metakaolin along with silica fume and potassium hydroxide as alkaline activators and alumina particles. The effect of alumina particle size to achieve castable microstructure and their mechanical properties were investigated. Different Si:Al mole ratio (1.5, 2, 2.5 and 3) and K:Si mole ratio (0.20, 0.25, 0.33) were formulated and the strength was maximized at Si:Al=2.5 and K:Si=0.33. However, its deformation and porous microstructure at high temperatures greatly reduced dimensional stability and strength. Microstructural properties and mechanical strength of samples sintered at 600, and 1000 oC after heating and at environmental conditions were studied and significant changes in the microstructure and strength of samples were observed. Sintering in the presence of the liquid phase caused the pores to collapse, creating a strong bond between the particles and increasing the density at 1000oC.

This research was conducted to develop antibacterial properties in HA composite by doping Ag-Co simultaneously. Chemical compounds Ca10-x Ag x/Co y(PO4)6 (OH)2 with values (x, y= 0, 0.5, 1) were synthesized by co-precipitation method which is an economical and simple way. XRD, FESEM and EDS analysis were used to investigate structural and microstructural characteristics. The result of XRD analysis revealed pure HA phase with no minor other phase and dopants ions displaced to Ca sites well. Spherical morphology was appeared in all samples by FESEM test however the size of particles decreased by inserting dopants. To determine antibacterial properties, zone inhabitation test have utilized. The samples were prepared against E.coli bacteria, which are the most infections agent. Finally, this antibacterial characteristic observed the most effect against bacteria in Ag- Co doped HA sample.

Zinc oxide (ZnO) is widely used in various fields such as electronic devices, converters, varistors, catalysts, photoelectric devices, and piezoelectric application due to its unique properties. In the present study, the effect of titanium oxide (TiO2) additive on the properties of ZnO ceramic was studied. 0.5, 1 and 2 wt% of TiO2 were added to ZnO and various properties of ZnO ceramic including density, phase behavior, dielectric properties and microstructure were investigated. The obtained samples had a high relative density and about 98% of the theoretical density. The results of X-ray diffraction (XRD) showed that TiO2 additive leads to the formation of a secondary phase of Zn2TiO4 in ZnO ceramic and with increasing the amount of TiO2, the amount of impurity phase increases and the peaks move to lower angles. TiO2 additive considerably reduced the dielectric constant and the dielectric loss of ZnO ceramic. With addition of 2 wt% TiO2, the dielectric constant of ZnO was decreased from 48200 to 1400 and the dielectric loss of ZnO was decreased from 20 to 5.4, measured at 100 kHz. The results of microstructure study showed that TiO2 additive will have a significant effect on the microstructure of ZnO ceramic, so that with increasing the amount of TiO2 additive, grain growth decreases. The reduction in the constant dielectric of ZnO ceramic can be attributed to the smaller grain size, the existence of the impurity phase and the defect of the cation vacancy in the presence of TiO2 additive.

In the present study, zinc oxide nanoparticles were synthesized by simultaneous doping of Zn0.98Cu0.02O with Ca2+, Mg2+, and Co2+ ions using the microemulsion method. The phase, crystallization, and particle size of samples were identified by X-ray diffraction (XRD) analysis. The formation of the desired phase was confirmed by, X-ray diffraction. Also, the infrared spectrum (Far-FTIR) was confirmed the existence of the wurtzite structure, according to the position of the bands in the range between 420 cm-1 to 250 cm-1. The vibrating sample magnetometer (VSM) was used to investigate the magnetic properties, which the presence of magnetic properties was indicated in the produced samples. Morphological and particle size was obtained by Transmission electron microscopy (TEM). The particle size of spherical zinc oxide samples was found in the nano range (15 ±3 nm). Differential reflectance spectroscopy (DRS) analysis was used to investigate the electrical properties and measure the bandgap energy. The bandgap of the Cu-ZnO sample was 2.7 eV. The bandgap energy was reduced by the substitution of dopants in zinc oxide samples. Co-doped Ca-Cu-ZnO has the lowest bandgap energy among samples, and, the bandgap of the Co-Cu-ZnO sample was around 2.5 eV, so that, this sample can be optimum concerning higher magnetic properties and haven’t any impurity in the XRD pattern.

Titanium dioxide (TiO2) is a semiconductor material that has excellent optical, electronic and photocatalytic properties in various applications. But the wide band gap of anatase (eV3.2) has reduced its optical and electronic properties under visible light. For this reason, this gap needs to be narrowed, and one of these methods is contamination by various elements. The aim of this study was to investigate the effect of various cationic, anionic and common contaminants on the band gap and optical properties of anatase. Alternative type contamination at the site of oxygen atoms (anionic contamination) has shown that the addition of carbon to the structure in addition to reducing the band gap leads to the formation of intermediate levels below the Fermi surface and the presence of these levels in improving light absorption in the visible area he does. In contrast, the addition of sulfur atoms instead of oxygen leads to the mixing of O 2p and S 3p states, and with the addition of contaminant concentrations, the band gap gradually decreases. The important point about the concentration of nitrogen pollutants, which is one of the most important anionic pollutants, is that at concentrations higher than 1.4%, it leads to the creation of intermediate levels in the forbidden gap in areas close to the Fermi surface and increases the recombination of charge carriers. Be. In cationic contaminants, the contaminant is replaced at the site of the titanium atom. Contamination of intermediate elements has created semi-solid impurity levels in the restricted area and at the same time has reduced the band gap. In addition, iron pollutants in the presence of oxygen depletion have reduced the gap to eV1.94, which is the most effective compared to other pollutants. Common contamination in anatase is considered to improve the band gap and reduce the recombination of charge carriers, and this leads to the addition of impurity levels above the capacity strip and below the conduction band, and in some applications such as photocatalytic processes can provide optimal performance.

Aventurine glaze is one of the Macrocrystalline glaze that is the result of saturation of iron oxide in the glaze. In general, the formation of crystals in crystalline glazes requires special conditions, so the purpose of this study is to investigate the effective factors on the formation of aventurine glaze of iron oxide including combination, temperature, firing conditions and surface that is used. And also effective factors that improve crystals were investigated. The question is asked: what is the effect of each factor on the formation and improvement of the features of the aventurine glaze. The current research is functional research and experimental in terms of method, and has been done in a laboratory-studio. In this section, raw materials which include silica, kaolin, borax and iron oxide in appropriate amounts were combined by a ball mill and fired in an electric kiln and then analyzed. The method of analysis has been used in both quantitative and qualitative analysis. Quantitative analysis was used to examine the quantities of basic material and qualitative analysis was used to examine the visual features that were created in the glaze. The method of data collection in this research is the library method in the theoretical section and observation in the glaze production section. The results have shown that red clay bodies are not suitable for aventurine glaze, while white bodies that fired in low temperature are suitable. The type and amount of iron oxide used is effective in creating and improving crystals in this glaze. The best effects of aventurine were achieved with two types of iron oxides that include black iron oxide and ferric oxide. And 20% and above amount of iron oxide were the best amounts for Aventurine glaze, we can see the most desirable quality of crystals in terms of size and brightness, in terms of temperature, the most desirable glazes in terms of quantity of crystals and brightness, at 1080 degrees Centigrade. The amount of glaze base materials, which include silica, kaolin, boron oxide and sodium oxide, affects the quality of the aventurine glaze, and the lower the kaolin base, the better crystals have grown.