Iranian Journal of Materials Science and Engineering

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The goal of the present study is to prepare a room temperature cured hydrophobic and self-cleaning nano-coating for power line insulators. As a result, the installed insulators operating in power lines can be coated without being removed from the circuit and without the need to cut off power. For this purpose, hydrophobic silica nanoparticles were synthesized by sol-gel method using TEOS and HMDS. The synthesized hydrophobic silica nanoparticles were characterized by XRD, FTIR, SEM, and TEM analyses to investigate phase formation, particle size, and morphology. Then the surface of the insulator was cleaned and sprayed by Ultimeg binder solution, an air-dried insulating coating, as the base coating. Then the hydrophobic nano-silica powder was sprayed on the binder coated surface and left to be air-cured at room temperature. After drying the coating, the contact angle was measured to be 149^o. Pull-off test was used to check the adhesion strength of the hydrophobic coating to the base insulator. To evaluate the effect of environmental factors, UV resistance and fog-salt corrosion tests were conducted. The results showed that 150 hours of UV radiation, equivalent to 9 months of placing the samples in normal conditions, did not have any significant effect on reducing the hydrophobicity of the applied coatings.

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This study investigates the synthesis of Al/MoS₂ nanocomposite coating by the electro spark deposition (ESD) method for its lubricating properties. ESD method was selected because it is a very easy, rapid, and cost-saving method and the resulting coating has a strong bonding with the substrate. As a substrate, a Ti-6Al-4V alloy sheet containing 6.12 % Al, 4.06 % V, 0.19% Fe, and 0.05 % Ni was used. For coating, an aluminum-molybdenum disulfide composite electrode in the form of a cylindrical rod was employed. Three frequencies of 5, 8, and 11 kHz, three current limits of 15, 25, and 35 amps, and three duty cycles of 50, 60, and 70% were used in the coating operation. AFM analysis was used to study the topography, morphology, and calculate roughness. The samples were then subjected to hardness tests. To determine the wear resistance of the samples, pin on disk tests were performed. XRD analysis was performed to identify the phases on the surface of the coated samples. SEM was used to examine the microstructure of the coating before and after wear testing, in order to determine the wear mechanism. The results indicated that the Al/MoS2 nanocomposite coating was synthesized on the substrate surface. The hardness of the reference sample is 353 Vickers, and that of the coated samples is about 200 Vickers. For the reference sample, the roughness was measured at 15.7 nm, and for the coated sample at 268.1 nm. As spark energy increased, the coefficient of friction increased by approximately 0.09. As spark energy increased, the wear rate increased by 27%. A significant increase in the Lancaster coefficient occurred around 5 joules of energy. According to the wear rate results, the sample with the lowest thickness wears 4% less than the sample with the highest thickness. The wear rate of sample 351170 is 78% lower than that of sample 150550.

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The principal goal of this research is to produce a CrN/Cu multilayer coating and a CrN single-layer
coating and also compare their electrochemical and antibacterial behavior. In this investigation, the coatings were
applied to the stainless steel substrate by cathodic arc evaporation a sub-division of physical vapor deposition
(CAE-PVD). The present phases were characterized and the thickness of the coatings was measured using X-ray
diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. Rockwell-C tester was
used to evaluate the adhesion quality. Also, to evaluate the mechanical properties of the coatings such as modulus
of elasticity and hardness, a nanoindentation test was used and the indentation effect and coating topography were
evaluated using atomic force microscopy (AFM). Studying the electrochemical behavior of the coatings was done
using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests in Ringer's
solution. The results of EIS tests showed that the CrN coating had higher polarization resistance in comparison to
the CrN/Cu coating and an increasing trend of polarization resistance related to both coatings was identified by
rising the time of immersion. Also, using the PDP curves, the CrN and CrN/Cu coating current densities were
estimated at 1.835×10-8 and 2.088×10-8, respectively. The antibacterial activity of CrN and CrN/Cu coatings was
evaluated by the spot-inoculation method. The results of the antibacterial test indicated that compared to CrN
coating, CrN/Cu coating had a better impact on the control of the bacteria growth.

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The beneficiation of coal tailings is usually difficult by common oily collectors in the flotation process, so
it is necessary to use a suitable method for clean coal recovery from coal tailing dams. Thus, this study was aimed
to investigate the behavior of dissolved air flotation by zero prewetting time for the clean coal recovery and to
optimize the conditions of zero prewetting time for an effective flotation. In this regards, the effects of the process
parameters, i.e., pH, frother type, collector type on the rougher flotation recovery of coal tailings were assessed and
optimized. Additionally, Fourier transform infrared (FTIR) spectroscopy was used to understand the functional
groups of oily collectors on the surface of floated products. The findings indicated that the frother type and the
interactive effects between the type of frother and collector had the most effect on the performance of flotation. It
was also found that under the optimal conditions (150 g/t Methyl isobutyl carbinol, 1500 g/t gas oil, and pH 4), the
combustible recovery, yield reduction factor, and flotation efficiency index of coal reached to 67.79%, 0.056%, and
37%, respectively. Meanwhile, the FTIR analysis confirmed that the less adsorption of gas oil collector occurred in
the presence of SDS (Sodium dodecyl sulfate) as frother due to the interaction of SDS and collectors

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In this paper, an investigation was carried out to test the suitability of potential additive materials in
WOKA 3533 (WC-10Co4Cr) cermet HVOF coating subjected to slurry erosion in ash conditions. The additives
namely molybdenum carbide, yttrium oxide, and zirconium oxide were added in equal percentages (3 wt.%) in
WOKA cermet powder. High-velocity oxy-fuel (HVOF) spraying was performed to develop the additive-based
WOKA cermet coatings. The slurry erosion in ash conditions was tested using the pot tester. Microstructural and
mechanical properties of traditional and additive-based WOKA cermet coatings were also tested in the present
study; for example, microstructure, crystalline phases of as-sprayed coatings, and microhardness. Results present a
comparison of surface erosion wear of different cermet coatings. It was found that the yttrium oxide was a suitable
additive for the WOKA cermet coatings than the molybdenum carbide. However, zirconium oxide is unsuitable for
WOKA cermet coatings in erosion wear applications.

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This study was undertaken to investigate the influence of graphene nano sheets on the structural characteristics and dry sliding wear behaviour of Al-5Cu-1Mg aluminium alloy. The optimum amount of GNPs for proper grain refining was selected as 0.5 wt.%. T6 heat treatment was applied for all specimens before wear testing. Significant improvements in wear properties were obtained with the addition of GNPs combined with T6 heat treatment. Dry sliding wear performance of the alloy was examined in normal atmospheric conditions. The experimental results showed that the T6 heat treatment considerably improved the resistance of Al-5Cu-1Mg aluminium alloy to the dry sliding wear. The results showed that dry sliding wear performance of without T6 microstructure specimens was a lower value than that of with T6 specimens.
 

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The introduction of the 2D materials in recent years has resulted in an emerging type of the constructed structures called van der Waals heterostructures (vdWHs) that take advantage of the 2D materials in forming atomically thin components and devices. The vdWHs are constructed by the stacking of 2D materials by van der Waals interactions or edge covalent boning. The electron orbitals of the 2D layers in vdWHs extend to each other and influence the electronic band structures of the constituent layers. The tunable optical response over a wide range of the wavelengths (NIR to visible) can be obtained by assembling vdWHs through combining of the monolayers. By application of 2D layers in vdWHs, p-n heterojunctions without lattice mismatch can be formed. The photodiodes based on the van der Waals interactions could be considered as promising candidates for future optoelectronic devices. Furthermore, on-chip quantum optoelectronics can move to the next generation by using 2D materials in vdWHs. In this review, the vdWHs are introduced and their properties and applications in light-emitting diodes (LEDs) have been discussed. The vdWHs allow bandgap engineering, and hence, LEDs working in a range of the wavelengths can be realized. The applications of vdWHs in forming atomically thin components in optoelectronic devices and LEDs have been addressed.
 

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We report a simple and practical approach for the easy production of superhydrophobic coatings based on TiO₂-SiO₂@PDMS. In this study, we used tetraethylorthosilicate (TEOS) and titanium tetraisopropoxide (TTIP) as a precursor for the sol-gel synthesis of SiO₂ and TiO₂, respectively. Afterward, the surface of nanoparticles was modified by 1,1,1,3,3,3-hexamethyldisilazane (HMDS) before being combined with polydimethylsiloxane (PDMS). The hydrophobic property of coatings was evaluated by static contact angle measurements. The phase composition and structural evolution of the coatings were examined by X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analysis. It was shown that changing the weight ratio of the solution composition of the coating can affect the hydrophobicity of the surface. The best sample has shown a superhydrophobic property with a 153˚ contact angle which contained (75%TiO₂-25%SiO₂) and PDMS at a weight ratio of 1:1. Moreover, the results showed that the superhydrophobic coating retains its hydrophobic properties up to a temperature of 450 ˚C, and at higher temperatures, it converts to a super hydrophilic with a water contact angle close to 0 ˚. The SiO₂-TiO₂@PDMS coating degrades methylene blue by about 55% and was shown to be capable of photocatalytically decomposing organic pollutants.

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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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Elevating component performance through advanced surface coatings finds its epitome in the domain of laser cladding technology. This technique facilitates the precision deposition of metallic, ceramic, or cermet coatings, accentuating their superiority over conventional methods. The application spectrum for laser-clad metallic coatings is extensive, encompassing critical components. Central to the efficacy of laser cladding is the modulation of laser parameters—encompassing power, speed, and gas flow—which decisively influence both process efficiency and coating properties. The meticulous calibration of these parameters holds the key to producing components endowed with refined attributes while ensuring the sustainable continuation of the process. As such, this study embarks on an empirical investigation aimed at transcending existing process limitations. It delves into the characterization of laser-clad WC-17Co coatings on AISI H13 and AISI 4140 steels. The importance of WC-17Co coatings lies in their capacity to enhance wear resistance, extend component life, reduce maintenance costs, and improve the performance of various industrial components across diverse sectors. On the other hand, the substrates have pivotal roles. AISI H13 is lauded for its exceptional hot work capabilities, while AISI 4140 steel is renowned for its robust strength and endurance. Through rigorous evaluation, the resultant deposited coatings offer crucial insights into the efficacy of manufacturing parameters. Employing a comprehensive suite of analytical techniques including laser confocal microscopy, Vickers microhardness assessment, and micro-adhesive wear testing, the study thoroughly characterizes the samples. The outcomes underscore the achievement of homogenous coatings marked by elevated hardness and exceptional wear resistance, thereby signifying a substantial enhancement over the substrate materials.

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In the present work, development models of a new artificial human soft heart and artificial heart valves using nanocomposite materials and synthetics were designed, manufactured, and tested. The fabricated mechanical artificial heart valves were examined to determine the best service life for each type. The fatigue life results were implemented by using the transient repeated and continuously applied blood pressure on each produced value to simulate diastolic and systolic that occur in the natural heart at each pulse cycle. The obtained results showed that a 3D printing of a new generation soft artificial heart for a permanent replacement was implemented as an alternative to the high-cost available temporary implant mechanical hearts, which may exceed the price by tens and hundreds of thousands of dollars, with a working life of not more than five years. The obtained fatigue safety factors for the produced artificial valves using different materials and designs were decreased with the complexity of the movement of the moving parts of the valve. The highest rates were obtained when using the valves with flat, simple movement in one direction like the single-leaflet type valve, where all the used materials are suitable for the production of this type of valve. The highest obtained safety factor was reached (15). The lowest rates were recorded when using the highly flexible and strong PSN4 nanocomposite material for fabricating the mitral tri-leaflet valve (thick. = 1.0 mm) reached 1.91. This value decreases to 0.99 when using the same type and material of valve but with a thickness equal to 0.5 mm. It can be noted here that the only suitable for the manufacture of this artificial valve type is the nanocomposite polyetherimide/ silicone rubber with nano silica (PSN4), whereas the other used materials failed because the fatigue factor values are less than 1. The service life span of this material is about 9200 x 106 cycles, which is equivalent to about 290 years, followed by SIBSTAR 103 with a default age of 209.6 x 106 cycles or 9 years.
 

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The coated β-tricalcium phosphate (β-TCP) with dicalcium phosphate dihydrate (DCPD) has attracted much attention in the biomaterials field due to the increase in its osteoconductivity. Besides, the porous bioceramic scaffolds with controlled pore sizes are significant in stimulating bone-like cell activity. In this study, the effect of the setting-time process and acidic-calcium phosphate (CaP) concentrations on the fabrication and properties of porous DCPD/ β-TCP scaffolds were studied. Subsequently, the specimens were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), compression strength and Fourier transforms infrared (FTIR). The study results revealed that the porous DCPD/ β-TCP scaffolds with macro- and micropore sizes were successfully obtained after the 300-600 µm of porous β-TCP granules were exposed to an acidic-CaP solution. Furthermore, the setting-time process and acidic-CaP concentrations increased the DCPD interlocking between granules, and the mechanical strengths of scaffolds increased up to 0.5 MPa. Meanwhile, the porosity levels were changed based on the formation of DCPD crystals. This study was expected to provide novel insights to researchers in the field of bioceramics through its investigation on the creation of porous DCPD/ β-TCP scaffolds.

 

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Magnesium alloys are increasingly valued for biomedical applications due to their biocompatibility. This study investigates Mg-AZ31B alloy samples treated with quartz and alumina grits (<200 μm) at varied pressures, followed by anodization in an eco-friendly alkaline electrolyte. The results show that increased blasting pressure produces a rougher surface. Anodization time significantly affects the thickness of the anodic film, leading to a transition in surface morphology from fine to coarse structures with complete film coverage. Characterization by XRD reveals that the anodic film mainly comprises magnesium oxide and hydroxide phases. Open Circuit Potential (OCP) measurements demonstrate enhanced corrosion resistance post-anodization, particularly notable at 40 minutes on alumina-blasted samples. ANOVA confirms that both blasting pressure and anodization time significantly influence coating thickness and OCP, indicating the formation of a dense anodized layer.

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Abstract
The power line insulators are permanently exposed to various environmental pollutants such as dust and fine particles. This may lead to flashovers and therefore widespread power blackouts and heavy economic damage. One way to overcome this problem is to make the insulator surface superhydrophobic. In this research, the superhydrophobic properties of the insulators were improved by applying room-temperature cured composite coatings consisting of epoxy and hydrophobic nano-silica particles. Either octadecyl trichlorosilane (ODTS) or hexamethyldisilazane (HMDS) was used to coat the silica nanoparticles and make them hydrophobic. Then, the hydrophobic silica was added to a mixture of epoxy resin and hardener. The suspension was applied on the surfaces of a commercial porcelain insulator and cold cured at ambient temperature. The coating increased the water contact angle from 50° to 149°. Even after 244 h exposure to the UV light, the samples preserved their hydrophobic properties. The adhesion of the coating was rated as 4B according to the ASTM D3359 standard. The coating decreased the leakage current by 40% and increased the breakdown voltage by 86% compared to the uncoated sample and showed promise for making power line insulators self-cleaning.
 

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In this research, a nickel-tungsten coating as a catalyst for hydrogen evolution reaction (HER) with different current densities was synthesized and the resulting electrocatalytic properties and morphology were assessed. Linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry in 1 M NaOH were used to evaluate the electrocatalytic activity for HER. By increasing the current density of electrodeposition up to 500 mA/cm², a columnar morphology was observed. The cyclic voltammetry test (CV) revealed that when the plating current density increases, C_dl has increased from 248 to 1310 µF/cm² and the active surface area increases 5 times. The results showed that by modifying the coating morphology, the current density of the hydrogen evolution increased up to two times.
 

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Acrylic resins are one of the most important thermoplastic resins used in various industries due to their significant properties. However, they are inherently brittle and addition plasticizers to them is very common. In this study, role of both Polyethylene Glycol (PEG) and Triacetin on the mechanical properties of acrylic resin have been investigated. To do so tensile test, bending and wear tests have been performed. To achieve the optimal mixture of plasticizers, a tensile test has been carried out, and the best percentage of the mixture has been determined. Subsequently, bending and wear tests were conducted, which showed a significant increase in the bending strength of the acrylic resin after the addition of plasticizers. Furthermore, it was found that the abrasion mechanism of the resin was significantly altered compared to its pure state.