Iranian Journal of Materials Science and Engineering

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Partially Lateritised Khondalite (PLK) rocks are the waste materials generated as a result of mining of bauxite. The major discolouring elemental impurity in the PLK is iron oxides, which render it unsuitable for its use as a refractory material. The iron can be removed by suitable beneficiation methods. The main aim of this present investigation is to prepare a value added material from the mining waste by preparation of PLK rock containing less than 2% Fe2O3 which finds application in the refractory industries and then preparation of brick suitable for industrial applications. The feed sample containing 4.31 % Fe2O3 subjected to hydrocyclone for refractory of low iron content product in the underflow. The results of these studies reveal that the hydrocyclone underflow sample contains 1.9% Fe2O3 is suitable for making bricks due to presence of low iron content. However, bricks are made from a feed sample as well as from hydrocyclone underflow and overflow products. Physical, chemical and thermo-mechanical properties of these bricks are evaluated. Mineralogical properties of these bricks are also correlated with the thermomechanical properties. The developed bricks are compared with the standards for their suitability in industrial applications. Hence the bauxite mining waste can be a value added material but not a waste material which at present
creates environmental pollution at the mining site.

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Friction welding is widely used in various industries. In friction welding, heat is generated by conversion of mechanical energy into thermal energy at the interface the work pieces during pin rotation under pressure. A three-dimensional thermo mechanical simulation of friction stir welding (FSW) processes is carried out for Aluminium Alloys of 6061and 7050 where the simulation results are compared directly with the measured temperature histories during FSW after process. The objective of the present work is to study and predict the heat transient generated in alloy aluminium plate welded by FSW method. A three dimensional model was developed by LS-Dyna software and heat cycles have been proposed during the welding of aluminium alloys 6061 and 7050. In this research, the simulations were carried out with linear velocity in the range of 140 to 225 mm/min and pin rotational speeds of 390 and 500 rpm. Increase in pin rotational speed, from 390 to 500 rpm, resulted in greater temperatures which translated to rise of recorded temperature of top and bottom of the specimens. This is in turn to a wider HAZ. In addition, it was observed that raising the linear velocity had an opposite effect. Finally, results of experimental and numerical data were correlated and validated

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The aim of the present study is to assess the hardness, corrosion, and cytotoxicity of a commercially available cobalt-chromium (Co-Cr) alloy before and after simulated heat treatments at porcelain firing temperature. Five Co-Cr samples were fabricated using lost wax casting procedure. Heat treatments were carried out at 650°C, 750°C, 850°C, and 950°C. Vickers hardness was measured for as-cast and heat treated samples. The corrosion test was carried out separately in 0.1 N NaCl, 1% citric acid and artificial saliva at room temperature using potentiodynamic polarization technique. Gingival tissue biopsy of patients was taken and cultured to measure the cell viability by MTT colorimetric assay. Lowest hardness was observed at 650°C. 0.1 N NaCl and 1% citric acid corrosion medium showed a similar trend of corrosion rate. The least corrosion rate was found in artificial saliva. Firing temperature has an impact on the physical, chemical and biological properties of Co-Cr alloy in long-term clinical use.

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Abstract
In this research, Gelatine (GEL)/ Chitosan (CH) wound dressing was prepared and irradiated with gamma rays from ⁶⁰Co source for wound healing applications. GEL-CH composite characterization and functional properties were determined. The structural changes occurring after γ-irradiation at doses from 5 to 25 kGy were reported by physico-chemical techniques such as Electron Paramagnetic Resonance (EPR), Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Electrochemical Impedance Spectroscopy (EIS) studies. The antioxidant capacity was studied using DPPH (1,1-diphenyl-2-picrylhydrazyl free radical) scavenging and the antibacterial activities of Staphylococcus aureus and Escherichia coli were observed using liquid medium. Results revealed that EPR spectroscopy of un-irradiated GEL-CH showed 2 paramagnetic centers correspond to g=2.077 and g= 2.079. After irradiation, no active centre was appeared. A dose-dependent decrease in the central signal intensity was detected, then the EPR signal intensity almost disappears at 20 kGy. Gamma rays caused a slight increase in ion conductivity. FTIR suggest a slightly crosslinking phenomenon at 20 kGy. The XRD analysis does not show peak indicating crystallinity between a range of 2θ (15–30°). Moreover, γ-irradiation elevated the Scavenging DPPH radical activity (0.75 ± 0.07%). Gamma rays did not affect the antibacterial activity of GEL-CH wound dressing against pathogenic bacteria. The innovative results showed that the required γ-radiation for sterilization was ranged from 5 to 25 kGy. It permits to improve the physico-chemical and biological properties and maintain the native structural integrity of the GEL/ COL wound dressing

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Abstract
Gelatin (GEL) is most extensively used in various fields, particularly in therapeutics and pharmaceuticals. GEL was extracted from goat skin using hot temperature extraction process and compared with that of commercial GEL. The physico-chemical characterization and functional properties were investigated by using temperature denaturation (T_d), water-holding and fat-binding capacities (WHC and FBC), colour measurement and UV-light spectrum. In vitro biocompatibility was studied for the first time and was evaluated by blood coagulation index (BCI) and haemolytic tests for using as wounds dressing. The results revealed thermal stability of goat GEL at T_d 37°C. WHC and FBC capacities represented 2.5 and 1.2 g/ml, respectively. The hunter colour spaces a*, b* and L* showed a -0.27, -1.97 and 25.23 values, respectively. UV-Vis absorption spectrum of the goat GEL showed a maximum absorption peak at 280 nm. The in vitro anticoagulant activities of extracting GEL were higher than 70% after incubation for one hour. After being in contact with red blood cells for 1 h, the haemolysis ratio increased from to 0.46 to 1.4 when the concentration of goat GEL increased from 1 to 50 mg/ml suggesting the safety of the tested samples. These results suggest that thromboresistivity and hemocompatibility of this biopolymer retained the biological activity of our samples for biomaterial applications. According to this, goat GEL successfully competes with, and significantly could be useful for substitution of bovine in wound healing.

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The present study used a hydrothermal technique to synthesize undoped and Mn2+ doped CdS/Zn3(PO4)2 semiconducting nanocomposite materials. Powder X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectrometer, Fourier transform-Infrared Spectroscopy-FT-IR, and photoluminescence techniques were employed to study structural, optical, and luminescence properties of produced nanocomposites. The hexagonal structure of CdS and the monoclinic structure of Zn3(PO4)2 are both reflected in the powder X-ray diffraction spectra. When Mn2+ ions are present in the host lattice, a lattice distortion occurs, causing a phase change from the phase of γ-Zn3(PO4)2 to the β-phase of Zn3(PO4)2, without affecting the hexagonal phase of CdS. The average crystallite size of produced nanocomposites was 22-25 nm, and also calculated the lattice strain and dislocation density to better understand internal deformation of the samples. The FT-IR spectra were used to investigate the molecular vibrations and functional groups in the samples. The surface morphology of the nanocomposites is hexagonal spheres on rectangular shaped nano-flakes, and the interatomic distance between the hexagonal spheres is decreased as the doping concentration increases, forming a rod-like structure on the flakes. EDAX results confirm the presence of various relevant elements in the prepared samples. The quantum confinement of produced samples reduces as the Mn2+ doping concentration in the host lattice increases. The photoluminescence results demonstrate shallow trapped states due to the transition: d-d (4T1 → 6A1) of the tetrahedrally coordinated Mn2+ states and the impact of Mn2+ ions exhibiting several peaks in the UV-Visible region (365-634 nm) generating RGB (Red, Green, Blue) luminescence. Color coordinates and CCT values were calculated using the CIE diagram, and color correlated temperatures in the range of 2513–7307 K were discovered, which might be used in solid state lighting applications.

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This paper investigated the optimization, modelling and effect of welding parameters on the tensile shear load bearing capacity of double pulse resistance spot welded DP590 steel. Optimization of  welding parameters was performed using the Taguchi design of experiment method. A relationship between input welding paramaters i.e., second pulse welding current, second pulse welding current time and first pulse holding time and output response i.e, tensile shear peak load was established using regression and neural network. Results showed that maximum average tensile shear peak load of 26.47 was achieved at optimum welding parameters i.e., second pulse welding current of 7.5 kA, second pulse welding time of 560 ms and first pulse holding time of 400 ms. It was also found that the ANN model predicted the tensile shear load with higher accuracy than the regression model.

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In this research, after pressing in a cylindrical mold, the AA 7075 alloy swarf was melted and cast in a wet sand mold. After rolling and cutting, sheets with two different thicknesses of 6 and 20 mm were obtained. The sheets after homogenization were solutionized at 485°C for 30 and 90 minutes, respectively, due to differences in thickness and thermal gradients. The solutionized samples were quenched in 3 polymer solutions containing 10, 30, and 50% Poly Alekylene Glycol. The results showed that melting, casting, rolling, and heat treatment of AA7075 alloy swarf similar properties to this alloy is achievable. Microstructural studies by optical microscopes (OM), Field Emission Scanning Electron Microscopy (FESEM), and X-ray diffraction (XRD) showed that by increasing the quenching rate after the solutionizing process, precipitation increases during aging. The tensile test results indicated that as the quench rate and internal energy increase, the diffusion driving force would increase the precipitation of alloying elements. Hence, this leads to an increase in hardness and reduction of its strain after aging.

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Nowadays metal oxide nanoparticles and transition metal dichalcogenides play a vital role in various areas like optical sensors, solar cells, energy storage devices, gas sensors and biomedical applications. In the current research work, we synthesized ZrSe₂ nanoparticles by hydrothermal method. The ZrSe₂ nanoparticles were synthesis using precursors such as ZrOCl₂.8H₂O and Na₂SeO₃.5H₂O in the addition of surfactant cetyl trimethyl ammonia bromide CTAB and reductant hydrazine hydrate, respectively. By using synthesized ZrSe₂ nanopowder thick films were developed on a glass substrate
using the screen printing method. The structural properties of ZrSe₂ powder were studied by X-ray diffraction (XRD). The X-ray diffraction analysis revealed that the hexagonal crystal structure and crystalline size were found to be 55.75 nm. The thick films of ZrSe₂ were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDAX). The surface morphological analysis of ZrSe₂ nanostructured thick film shows hierarchical nanoparticles. The energy band gap of synthesized powder was calculated using a Tauc plot from UV-visible spectroscopy. The gas-sensing properties of ZrSe₂ thick films were studied. The developed ZrSe₂ thick films show maximum sensitivity and selectivity towards the ammonia NH₃ gas at an operating temperature of 120 °C and the gas concentration was 500 ppm. The developed thick films show fast response and recovery time.Nowadays metal oxide nanoparticles and transition metal dichalcogenides play a vital role in various areas like optical sensors, solar cells, energy storage devices, gas sensors and biomedical applications. In the current research work, we synthesized ZrSe₂ nanoparticles by hydrothermal method. The ZrSe₂ nanoparticles were synthesis using precursors such as ZrOCl₂.8H₂O and Na₂SeO₃.5H₂O in the addition of surfactant cetyl trimethyl ammonia bromide CTAB and reductant hydrazine hydrate, respectively. By using synthesized ZrSe₂ nanopowder thick films were developed on a glass substrate
using the screen printing method. The structural properties of ZrSe₂ powder were studied by X-ray diffraction (XRD). The X-ray diffraction analysis revealed that the hexagonal crystal structure and crystalline size were found to be 55.75 nm. The thick films of ZrSe₂ were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDAX). The surface morphological analysis of ZrSe₂ nanostructured thick film shows hierarchical nanoparticles. The energy band gap of synthesized powder was calculated using a Tauc plot from UV-visible spectroscopy. The gas-sensing properties of ZrSe₂ thick films were studied. The developed ZrSe₂ thick films show maximum sensitivity and selectivity towards the ammonia NH₃ gas at an operating temperature of 120 °C and the gas concentration was 500 ppm. The developed thick films show fast response and recovery time.