Iranian Journal of Materials Science and Engineering

The micro layers micaceous iron oxide and nano-TiO 2 were incorporated into the epoxy resin by mechanical mixing and sonication process. Optical micrographs showed that the number and diameter size of nanoparticle agglomerates were decreased by sonication. The structure and composition of the nanocomposite was determined using transmission electron microscopy which showed the presence of dispersed nano-TiO 2 in the polymer matrix. The anticorrosive properties of the synthesized nano-composites coating were investigated using salt spray, electrochemical impedance spectroscopy and polarization measurement. The EIS results showed that coating resistance increased by addition of micaceous iron oxide micro layers and nano-TiO 2 particles to the epoxy coatings. It was observed that higher corrosion protection of nanocomposite coatings obtained by the addition of 3 %wt micaceous iron oxide and 4%wt nano-TiO 2 into epoxy resin.

In situ Al2024- Mg₂Si composite was fabricated by spark plasma sintering (SPS) of reactive powder. Reactive powder was obtained from mechanical alloying (MA) of elemental powders. Clad layers of in situ composite were fabricated on Al substrates by spark plasma sintering (SPS). Structural evolution during MA process and after SPS was investigated by X-ray diffractometery (XRD). Scanning electron microscopy (SEM) was utilized to study the microstructure of sintered samples. Hardness and tensile behavior of sintered samples were investigated. The results showed that SPS of mechanically alloyed unreacted powder can result in the in situ formation of Mg₂Si and Mg₂Al₃ within the Al matrix. SPSed clad layer showed a sound and clear interface to the Al substrate with a hardness of about 140 HV. Sintered in situ composite exhibited a tensile strength of 288 MPa.

In this study, polyaniline-graphene composites with different nano-structures are synthesized and the behaviour of the obtained composites serving as electrode materials in electrochemical capacitors is studied. The morphology, crystal structure, and thermal stability of the composites are examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Thermal gravimetric analysis (TGA). Electrochemical properties are characterized by cyclic voltammetry (CV). According to the results, the obtained composites show different crystal structures and different thermal stabilities, and consequently different electrochemical capacities, when used as electrodes in electrochemical capacitors. A nano-fibre composite is shown to have a good degree of crystallization, 5.17% water content, 637oC degradation onset temperature, and 379 Fg-1 electrochemical capacity.

A homogenous TiO₂ / multi-walled carbon nanotubes(MWCNTs) composite film were prepared by electrophoretic co-deposition from organic suspension on a stainless steel substrate.  In this study, MWCNTs was incorporated to the coating because of their long structure and their capability to be functionalized by different inorganic groups on the surface. FTIR spectroscopy showed the existence of carboxylic groups on the modified carbon nanotubes surface. The effect of applied electrical fields, deposition time and concentration of nanoparticulates on coatings morphology were investigated by scanning electron microscopy. It was found that combination of MWCNTs within TiO₂ matrix eliminating micro cracks presented on TiO₂ coating. Also, by increasing the deposition voltages, micro cracks were increased. SEM observation of the coatings revealed that TiO₂/multi-walled carbon nanotubes coatings produced from optimized electric field was uniform and had good adhesive to the substrate.

Functionally graded aluminium/zirconia metal matrix composite was fabricated using stir casting technique followed by horizontal centrifugal casting process and a hollow cylindrical functionally graded composite (150 x 150 x 16 mm) was obtained with centrifuging speed of 1200 rpm. The microstructural evaluation and hardness test was carried out on the outer and inner surface of the functionally graded composite at a distance of 1 and 13 mm from the outer periphery. In Response Surface Methodology, Central Composite Design was applied for designing the experiments and sliding wear test was conducted as per the design using a pin-on-disc tribometer for varying ranges of load, velocity and sliding distance. The model was constructed and its adequacy was checked with confirmation experiments and Analysis of Variance. The microstructural examination and hardness test revealed that the outer surface of FGM had higher hardness due to the presence of  particle rich region and the inner surface had lesser hardness since it was a particle depleted region. The wear results showed that wear rate increased upon increase of load and decreased with increase in both velocity and sliding distance. Scanning Electron Microscopy analysis was done on the worn specimens to observe the wear mechanism. It was noted that wear transitioned from mild to severe on increase of load and the outer surface of FGM was found to have greater wear resistance at all conditions.

Up to now, lots of materials such as active carbon, iron, manganese, zirconium, and metal oxides have been widely used for removal of dyes from contaminated water. Among these, ferrite nanoparticle is an interesting magnetic material due to its moderate saturation magnetization, excellent chemical stability and mechanical hardness. Graphene, a new class of 2D carbonaceous material with atom thick layer features, has attracted much attention recently due to its high specific surface area. Reduced graphene oxide (rGO) has also been of great interest because of its unique properties, which are similar to those of graphene, such as specific surface area, making it an ideal candidate for dye removal. Thus far, few works have been carried out on the preparation of CoFe₂O₄-rGO composite and its applications in removal of contaminants from water. In this paper, CoFe₂O₄ reduced graphene oxide nanocomposite was fabricated using hydrothermal process. During the hydrothermal process, the reduction of graphene oxide and growth of CoFe₂O₄ simultaneously occurred on the carbon basal planes under the conditions generated in the hydrothermal system. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy contaminant and UV-Vis spectroscopy as the analytical method. The experimental results suggest that this material has great potential for treating Congo red contaminated water.

The synthesis of micro-sized, uniformly distributed Al₂O₃-15Vol% Ni powders were studied through three step co-precipitation of hydroxides mixtures from proper solution, calcination at air atmosphere and final step of calcined powders in a carbon bed. Al and Ni hydroxide and amorphous phase were first obtained from their salt’s solutions through chemical co-precipitation method by adjusting pH. The precipitated powders were then calcined to obtain a mixture of their oxides as NiO and NiAl₂O₄ which were reduced in a carbon bed at various temperatures up to 1300. Proper temperature for calcination in air was determined through TG analysis; 900. SEM observation of powders after reduction, revealed micro-sized Ni particles, along with fin distribution of Ni and Al₂O₃ elements. XRD analysis of the calcined sample showed the presence of NiAl₂O₄ and NiO and the same analysis for the reduced sample confirmed the formation of Al₂O₃ and Ni.    

In this paper the feasibility of fabricating controlled porous skeleton of pure tungsten at low temperature by addition of submicron particles to tungsten powder (surface activated sintering) has been studied and the best parameters for subsequent infiltration of Cu were acquired. The effects of addition of submicron particles and sintering temperature on porous as well as infiltrated samples were studied. The samples were examined by scanning electron microscopy (SEM), Vickers hardness measurements and tensile test. The composites made have been investigated and revealed the making W-Cu composite with good density, penetrability, hardness and microstructure. Consequently, the sintering temperature was reduced considerably (Ts≤1650^oC) and a homogeneous porous tungsten was obtained. Also, composite prepared by this method exhibited elongation about 28% that is much more than conventional W-15%wt Cu composites. This method of production for W–Cu composites has not been reported elsewhere

The effects of applied load, sliding speed and sliding distance on the dry sliding wear behavior of aged Al-SiC_p-Gr composites were investigated. The specimen were fabricated by stir-casting technique. The pin-on-disc wear testing machine was used to investigate the wear rate by design of experiments based on L₂₇ using Taguchi technique. Sliding distance was the most important variable that influenced the wear rate followed by sliding speed and applied load. The worn out surfaces were analyzed by SEM and EDS to study the subsurface mechanism of wear. The addition of reinforcements showed improved tribological behavior of the composite than base alloy.

Material selection is a main purpose in design process and plays an important role in desired performance of the products for diverse engineering applications. In order to solve material selection problem, multi criteria decision making (MCDM) methods can be used as an applicable tool. Bumper beam is one of the most important components of bumper system in absorbing energy. Therefore, selecting the best material that has the highest degree of satisfaction is necessary. In the present study, six polymeric nanocomposite materials were injection molded and considered as material alternatives. Criteria weighting was carried out through analytical hierarchy process (AHP) and Entropy methods. Selecting the most appropriate material was applied using technique for order preference by similarity to ideal solution (TOPSIS) and the multi-objective optimization on the basis of ratio analysis (MOORA) methods respect to the considered criteria. Criteria weighting results illustrated that impact and tensile strengths are the most important criteria using AHP and Entropy methods, respectively. Results of ranking alternatives indicated that polycarbonate containing 0.5 wt% nano Al₂O₃ is the most appropriate material for automotive bumper beam due to its high impact and tensile strengths in addition to its low cost of raw material. Also, the sensitivity analysis was performed to verify the selection criteria and the results as well.