فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 21 (تابستان 1396)

In this study, surface alloying of steel ST52 was carried out by gas tungsten arc welding using shielding gas and tungsten carbide powder. To evaluate the metallurgical structure, wear and corrosion resistance properties of the coating, optical microscopy, scanning electron microscopy (SEM), hardness and potentiostat test is used. Corrosion test of prepared samples evaluated by uniform corrosion tests. Microstructural evaluation of corrosion surfaces was performed by scanning electron microscopy (SEM). The results of worn surfaces by SEM showed in general, increasing the amount of reinforcing particles of WC increased matrix resistance against deformation and ultimately improve the wear resistance of the samples. Also, the most wear resistance of the sample is obtained with 20 percent of the WC. Corrosion test results showed that the uniform corrosion potential of samples increased by increasing reinforcement phase compared to steel potential. Also, with increasing percentages of tungsten carbide reinforcing particles corrosion resistance of samples has increased.

Recently, CoAl2O4, MgAl2O4 and ZnAl2O4 have been considered as the most widely used spinel structures in industrial applications as catalysts, basic catalysts and pigments especially at nano scale. Studies have shown that the composites including the combination of different types of spinels have more desirable properties in comparison to the absolute spinels. In this research review paper, the structures, properties, advantages and disadvantages of the neat spinels have been studied. Moreover, the effect of cations replacement, M=Zn, Mg, Mn, Ba, Sr, in CoxM1-xAl2O4 structures has been evaluated as one of the novel methods of spinel improvement. The results show that these replacements strongly improve the characteristics of the new combined spinels structures. For example; Increasing Zn cation results in reducing the toxicity and cobalt aluminate pigment production costs and leads to control the phenomenon of ion exchange between tetrahedral and octahedral position.

This study is based on making polystyrene conductive by using metallic reinforcements. After making polystyrene conductive, the resulted nanocomposites were used as Diazinon sensor by molecular imprinting method. The synthesized nanocomposites were characterized by FT-IR spectroscopy and FE-SEM. The operation of these composites as sensor was studied by cyclic voltammetry.
The results of this study confirm that the sensor had been produced positively. The imprinted nanocomposite with diazinon can be used as recognition element in electrochemical with high sensitivity and selectivity for diazinon insecticide.
Beside diazinon detection, the synthesized nanocomposite with magnetic property can be used as diazinon adsorber and separated by a magnetic field from polluted medium.

The polymer particles have been used in various fields of chemistry, biology and physics applications and subsequently there is a need for coating of various substrates by these particles to achieve a thin film in many applications. So far, several methods have been proposed for the production of micro-particles; but these methods often suffered from limitations such as low enclosure efficiency or difficulty in separating particles from the aqueous phase. In this study, attempts have been made to produce micro platelet particles and create a thin film by electro-centrifuge spinning for the first time. Electro-centrifuge spinning is the cost-effective method with high production rate. Therefore, the effect of parameters such as concentration, voltage, centrifugal force has been investigated on the shape and size of the micro-platelet particles of poly (ε-caprolactone). In this regard, concentrations of 3 and 5 wt% of poly (ε-caprolactone) in dichloromethane were used. Solutions with different concentrations were subjected to electro-centrifuge spinning system to fabricate micro platelets. In order to investigate the effect of voltage and centrifugal force on the particle diameter, poly (ε-caprolactone) particles were produced at voltages of 15, 18 and 21 kV and rotational speeds of 1740 and 3190 rpm. The results showed that by increasing the concentration of polymer solution, under the constant voltage and rotational speed, the diameter of the micro platelets decreases. Also, by keeping constant the concentration of the solution and the rotational speed, increasing the voltage leads to a decrease in the diameter of the micro platelets. In addition, under the constant the concentration and the voltage, the diameter of the micro platelets increases with increasing rotational speed. Also, by decreasing the solution concentration, satellite droplets increase, which leads to an increase in the uniformity of the diameter of the micro-plates.

The development and application of self-cleaning treatments on historical and architectural stone surfaces could be a significant improvement in conservation, protection and maintenance of Cultural Heritage. In this research, a coating based on titanium dioxide was prepared and applied on travertine stone. The prepared coating was analyzed and the result, confirmed the formation of small crystals of Anatase. The hydrophilic behavior was observed on the surface due to titanium dioxide coatings. Also self-cleaning behavior was proved by using Rodamine B.

In this study, anodized aluminum oxide nanostructures were prepared by anodization process under constant potential in an oxalic acid solution that was improved with sulfuric acid. The effects of various parameters such as voltage, electrolyte solution composition, anodizing time and type of stripping solution of oxide layer on the morphology of prepared nanostructures were optimized and scanning electron microscopy images were obtained. According to the results, voltage 45 V as optimized voltage and oxalic acid improved with sulfuric acid as the best electrolyte solution were obtained. The optimized times for first and second anodizing steps were 60 and 240 minutes, respectively, and a mixture of phosphoric acid and chromic acid was as the perfect solution to dissolve the oxide layer. Nanopores in the prepared samples under optimum conditions had the higher average distance and interpore distance and the porosity was increased. Also, array and uniformity of the pore size were increased in these samples. These nanostructures with unique properties have special applications in the field of membrane, synthesized template for various nanostructures, sensors and biosensors.

A castor oil-based fatliquoring agent was successfully synthesized using metallic organic frameworks (MOFs) via Pickering emulsion polymerization. TEM image indicated that the castor oil was surrounded by MOFs. Visual control of the synthesized fatliquoring agent showed that the presence of MOFs lead to a stable oil/water emulsion for more than 8 months. The prepared fatliquoring agent was applied to the leather and mechanical properties were evaluated, and compared to a leather sample fatliquored by a conventional agent. Elongation at break and tensile strength were 114% and 28MPa, respectively. The results show that the prepared fatliquoring agent significantly improved mechanical properties of leather. In this work, the natural chitosan material, which has good compatibility with collagen leather, was used to increase UV resistance. UV resistance of leather was 2.5 times more than leather sample fatliquored by a conventional agent.