نشریه علم و مهندسی سرامیک
سال دهم شماره 4 (پیاپی 39، زمستان 1400)

The Nasriya complex (build up in 1478), also known as the Sultan Hassan Grand Mosque and the Mosque-Madrasa of Hassan Padshah, were destroyed due to earthquake in 1780, along with most of the historical monuments in Tabriz. Over archaeological speculations, two pieces of blue and white porcelain were discovered in this complex in 2006. As Tabriz was considered as an important commercial center in the Silk Road with respect to geographic position and plays a main role in extending relationships with Far East (East Asia), especially China, Chinese blue and white dishes were regarded as one of Chinese goods which were demanded by Iran and Tabriz. Therefore the authenticity and origin of two discovered potteries with respect to historic period and construction area were regarded as the main questions in the present study. In this regard, research on the samples carried out by using experimental methods such as thermo-luminescence dating (TLD), scanning electron microscopy (FE-SEM/EDS) and petrography as well as comparing the motifs and symbols of these potteries with Chinese ones. The results indicated that the potteries under study belong to the late Safavid government (1640-1648). Based on petrography and elemental analysis of the samples to compare the Zonous Kaolinite located in the northwest of Tabriz indicated that the soil of this area was probably used to construct these potteries. Further, the glaze of these samples was under color and alkaline and their blue pigment involved cobalt and iron, while bright blue consisted of chromium, cobalt, and iron. Due to high percentage of iron and low percentage of aluminum in these pigments, the blue ink of these samples was related to cobalt silicate which was inconsistent with Chinese potteries in which cobalt aluminate leads to blue color. The shape of the mark which was drawn on the exterior of these potteries is the type of “character marks” drawn by the potters of Safavid era on the products of their workshop. The motif related to the pottery having the mark is blue and grey plant, animal, and geometric with high delicacy, while that of other pottery is dark and bright blue human motifs (narrative) with lower delicacy. These potteries were probably constructed in Safavid era and probably created in Tabriz. Studying further samples and comparing with control ones can help conclusive results.

In this study, the effect of coating time on the microstructure and corrosion behavior of AZ31 Mg alloy coated by plasma electrolytic oxidation (PEO) method has been investigated. For this purpose, phosphate-based electrolyte containing hydroxyapatite nanoparticles was used at different times of 5, 10 and 15 minutes. The surface properties and chemical composition of the coatings were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) pattern. The corrosion properties of coatings in the simulated body fluid have been studied by potentiodynamic polarization and electrochemical impedance spectroscopy tests. The results of this study showed that with increasing the coating time to 15 minutes, the size of the pores and the thickness of the coatings increased. The coating created in 10 minutes has the lowest percentage of porosity among the samples. The results also showed that the coating created in 10 minutes had the lowest corrosion current density (2.33 × 10-8 A/cm2) among the samples.

Ti3SiC2 bulks were synthesized using Si melt infiltration into porous preforms with different chemical compositions. The initial composition of the preforms was prepared on the basis of the TiC, 2TiC/Ti, 3TiC/0.3Si, 3Ti/2C (carbon active) and 3Ti/2C (graphite) formulations and was pressed into pellet using a cold press method. The Si ingots were weighed 3 times the stoichiometric value and in order to carry out the melt infiltration process were placed on pellets. The melt infiltration process was carried out at a temperature of 1500°C for 1 hour in a vacuum of 10-4torr. Phase analysis, morphological observation and elemental analysis were performed by XRD, FE-SEM and EDS, respectively, and it was observed that the best result was for a sample with 3TiC/0.3Si preform and the samples with 3Ti/2C preform has a lot of impurities. It was also found that the size of the nano layers observed with the FE-SEM analysis is mainly in the range of 20 to 40 nm.

In this study, TiB2 particles were synthesized by sol-gel method in nanometer size. First, the sol was prepared in a four-component system of alkoxide -boron carbide -water-alcohol based on the sol-gel chemical process under acidic conditions at pH = 5. Titanium tetra-isopropoxide and boron carbide were used as raw materials. After hydrolysis and gel formation followed by heat treatment, TiB2 nanopowder product was prepared. The effect of pH and temperature parameters on the synthesis process of these nanopowders was investigated. To evaluate the mechanism of product formation in the sol-gel process DLS, Zetameter, SEM-DTA / TG-XRD-FTIR analysis methods were used. It was shown that by controlling the pH in the range of 5, precursor particles containing Ti sources was below 10 nm. The FTIR data showed that the powder prepared at 900°C had boron and titanium bonds and detected carbon bonds in the range of 1100- 1650 cm-1 . DTA analysis showed that the early nuclei of TiB2 particles formed in the range of 1380 °C. This was confirmed by X-ray diffraction studies and was completed by increasing the temperature to 1430 °C in TiB2 crystalline phase. SEM microscopy images showed that the synthesized TiB2 particles were in the range below 100 nm with a narrow and uniform distribution amplitude.

Zinc oxide is one of the most widely used and important materials in today's science and industry. In this study, ZnO nanoparticles were synthesized by hydrothermal method. Zinc acetate, citric acid and deionized water was respectively used as a source of zinc ion, solvent and chelating agent. In this study, the effect of citric acid concentration as an additive was studied on morphology and particle size of ZnO. The synthesized powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) ,infrared spectroscopy (FTIR) and specific surface analysis (BET).The results of XRD analysis showed, the final products have hexagonal structure and are Single-phase. Increasing additive concentration changes the intensity of peaks and crystallizes rate.The results of FTIR and its comparison with existing functional groups confirmed the absence of citric acid in the final product. And the functional groups are just related to pure zinc oxide. SEM images showed that the use of chelating agent affects the growth of particles and morphology. BET showed noticeable changes in the specific surface area of synthesized samples in the presence of chelating agent.

WC-10Co cemented carbides containing 1 to 4 wt% SiC nanoparticles were prepared by spark plasma sintering. The effects of SiC content on microstructure, mechanical properties and wear resistance of the sintered materials were studied. Microstructural studies showed that SiC addition resulted in WC grain coarsening. In addition, the hardness decreased with increasing SiC content. However, the fracture toughness and wear resistance significantly improved with SiC incorporation. The lowest wear rate (1 mm3/m) was attained for the nanocomposite reinforced with 2 wt% SiC. In the unreinforced cemented carbide, the extensive plastic flow of the Co binder and WC grain pullout led to a high wear rate (23 mm3/m). In the nanocomposite samples, solid solution strengthening of the Co binder by partial dissolution of SiC particles decreased the degree of plastic deformation on the worn surfaces. In addition, coarser WC particles within the nanocomposite samples exhibited a higher resistance against pullout resulting in the enhanced wear resistance.

Smart materials have been used extensively because of the need for new energy sources. One of the most important types of these materials is the CuxO / blackTiO2 heterogeneous photocatalyst semiconductor. In this study, copper foam was used as a substrate and by performing the anodizing process in a solution of one molar of sodium hydroxide under pulsed and direct currents, a CuxO layer was formed on the copper foam. Then, in order to prepare black TiO2, spin coating of TiO2 sol was used and the samples were calcined in argon atmosphere. The results showed that the use of pulsed current led to the formation of Cu2O with octahedral microstructure and the contact angle of this hydrophobic oxide was determined to be 121.85̊. While, surface pits consisting of Cu2O and CuO oxides were formed with a contact angle of 127.85 ͦ under direct current. After the copper oxides were coated by black TiO2, the photocatalysts produced had a high hydrophilicity and passed water rapidly. Under these conditions, the energy gap was determined for the sample prepared by direct current 1.95 ev and for the sample prepared by pulse current 2 ev. Obviously, according to the results, the built-in photocatalyst semiconductor will be a suitable option for use in systems for degradation of dyes using visible light.