CERAMIC SCIENCE & ENGINEERING
Year:2019 | Volume:8 | Issue:1 |Papers Count:7

Cordierite ceramics are used as refractory materials and kiln furnaces tools due to their very low coefficient of thermal expansion, high corrosion resistance and excellent thermal shock resistance. The aim of the present work was to synthesis of cordierite with raw materials including nano silica, magnesium chloride and reactive alumina. The synthesis procedure is done at solid state. Mechanism of cordierite formation was studied by simultaneous thermal analysis (STA) and x-ray diffraction (XRD). Microstructure of synthesized powder at various temperatures were observed by a scanning electron microscope (SEM). The results showed that the mechanism of cordierite formation from the mentioned materials was different from mechanisms for the formation of cordierite using other raw materials. Probable reactions on the way to form the cordierite were proposed at various temperatures. Cordierite formation temperature from raw materials including nano silica, magnesium chloride and reactive alumina determined as 1330° C. The synthesized cordierite was not pure and alumina, cristobalite, spinel and forsterite were present as impurities.

Granulation method in the mixture of oil, water, and PVA was used to synthesize HA/β TCP porous nano-powders. Results showed that the presence of oil in PVA/oil system results in crystallization of mesoporous HA/β TCP particles with the surface area of 93  cm2/g. Using Rietveld method, the amounts of HA/β TCP and amorphous phases in the oven-dried PVA substrate powders after heat-treatment were calculated as about 65, 13, and 22  wt. %, respectively. RSM modeling showed that TEOS is the optimum surfactant in this method. Bioactivity test showed that HA/ β TCP sample is bioactive in SBF medium. According to cell viability results, synthesized powder in the presence of oil/PVA, which was then modified by 25  wt. % of TEOS, did not cause toxicity. Using Alizarin Red S staining quantification assay, it was found that after modification by TEOS, bone-nodule formation was enhanced by 25%.

High conductivity and high level of electrolyte availability are the main requirements of active materials used in supercapacitors (SCs) to achieve high electrochemical efficiency. In recent years, metal-organic frameworks (MOFs) have been used as electrode materials for SCs due to their suitability of porosity and high surface area. However, using single-component MOFs in supercapacitors results in poor electrical conductivity, insufficient stability, and poor mechanical properties, and neutralize the effect of high capacity and efficient performance. In this paper, using a hydrothermal synthesis method, Cu-based MOFs were fabricated and graphene was added during synthesis to enhance the conductivity of these materials. To investigate the structure of nanocomposites were used XRD, FTIR, and FESEM analyze. To investigate the electrochemical behavior of electrodes, cyclic voltammetry, electrochemical impedance and repeatability behavior were performed. The Cu based MOFs had a capacity of 372 F. g-1, while its composite capacity with graphene is 570 F. g-1. In these composites, graphene enhances electrical conductivity, porosity accessibility, and charge storage through a non-Faradic mechanism and metal-organic frameworks increase the total capacity with high porosity, porosity adjustable, and charge storage through the Faradic Mechanism.

In this mentioned study for sea water treatment ceramic composites were made from natural alumina and adsorbent active ingredients. According to the experimental results, filters along with active agents have acceptable effects on drinking water parameters and contaminants in compare with 1053 ISIRI standard. Modular set up was made for sea water treatment tests. Water flowrate after filtration was 300 ml/hr at 3 bar condition. Totally, the best results was obtained for the composite filter with 21 1nd 2 %wt active carbon and titanium oxide content. A significant removal was achieved by filter No. 7 with potential removal of nitrate, nitrite, total dissolved solids and total hardness 90, 78, 98 and 68%, respectively. The low cost ceramic composite filter was found to be easily reusable, durable, and effective for the treatment of sea water at household level.

In this study it was tried to investigate on the effective parameters of the formation and increasing tetragonal zirconia phase in reaction sintering of alumina and zircon. In this way, alumina and zircon powders were mixed by the ratio of 85 to 15 wt. % and sintered at different conditions. Sintering temperature (1500-1650˚ C), furnace type (conventional and microwave) and the milling time of reactant (0. 25, 1 and 3 h) were studied. Tetragonal zirconia phase was calculated and compared by semi quantitative analysis method using XRD. Also, porosity, microstructure and strength of the prepared composites were compared with each other. Results showed that increasing the milling time of reactant or using microwave heating were lead to the increasing of tetragonal zirconia formation but increasing the sintering temperature did not any significant effect on it.

In this paper, zirconium oxide ceramics coating (ZrO2) were produced on Zircaloy-4 alloy using plasma electrolytic oxidation (PEO). Sodium silicate and Sodium aluminate based electrolyte was selected in PEO process and the effects of the concentration of Sodium aluminate (0, 2. 5, 5, 7. 5, and 10 g/L) on the microstructure, phase structure and the behavior of corrosion of formed coatings. In order to examine the morphology and phase structure of coatings, scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used respectively. The corrosion behavior of the coated samples was evaluated by potentiodynamic polarization in 0. 5 M LiOH solution. All oxide ceramics showed improved corrosion resistance. The results show that it's the NaAlO2 leads to inhibition of monoclinic ZrO2 phase in PEO coatings and stabilization of the t-ZrO2 phase in the electrolyte of 10g/L NaAlO2 (A10) leads to decrease corrosion current density its up to 1. 10*10-7A/Cm2. After the addition of 10 g/L Sodium aluminate (A10) in the electrolyte %20 tetragonal zirconia was formed on the surface. The improvement in corrosion properties mainly depends on the phase composition of the produced coatings, so that in the electrolyte of 10g/L NaAlO2 (A10) showed the best corrosion resistance in comparison to other coatings.

Cobalt-based blue ceramic pigments are widely used in ceramic industries due to characteristics such as temperature stability, chemical stability and high resistance to these coatings. In this research, the blue silicate-titanate cobalt ceramic pigment is synthesized by sol-gel method and the dispersed pigments were printed on the ceramic by silk screen printing method in the industrial production line. Then its color and physical properties are investigated. The reflectance spectrum and colorimetric test (CIE L*a*b*) were performed to study of color value of the printed sample. Also, X-ray diffraction experiments and electron microscopy were used to study the crystalline structure and surface microstructure on the samples. Methylene blue test for determining of photocatalytic property and chemical resistance using ISO 10545-13 European standard have been used. The results of the b * parameter and the reflection spectra indicate a dramatic increase in the blue value of the samples. Furthermore, the sample also has photocatalytic properties and good chemical resistance to the reference sample (white tile).