Journal of Advanced Materials in Engineering (Esteghlal)

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Despite excellent bioactivity of bioactive ceramics such as hydroxyapatite, their clinical applications have been limited due to their poor mechanical properties. Using composite coatings with improved mechanical properties could be a solution to this problem. Therefore, the strength of metal substrate and the bioactivity of the improved composite coating combined could yield suitable results. The aim of this work was fabrication and characterization of hydroxyapatite-forsterite-bioactive glass nanocomposite coating. The sol-gel technique was used to prepare hydroxyapatite-forsterite-bioactive glass nanocomposite in order to coat on 316L stainless steel (SS) by deep coating technique. The X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray analysis (EDX) techniques were used to investigate the microstructure and morphology of the prepared coating. The results obtained from XRD analysis showed that the suitable temperature for calcination is 600 °C. At this temperature, the homogenous and crack-free coating could attach to the 316L SS substrate. The crystallite size of composite coatings determined via AFM was lower than 100 nm. Overall, the results obtained from this work indicate that hydroxyapatite-forsterite-bioactive glass nanocomposite coating can be a good candidate for biomedical applications.

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Although titanium has been recognized for its excellent bio-compatibility with human tissues and good corrosion resistance in some specific environments, little attention has been paid to the surface enrichment of the components by titanium. In this paper, titanium diffusion coating was formed on the surface of Ni-based alloy B-1900 via pack cementation technique and the microstructure of the coatings obtained was studied. Diffusion titanizing was carried out via pack cementation technique at 850 and 950 C for 3 hours in a mixture of commercially pure titanium, Al2O3 and NH4Cl powder. Microstructure, phase composition and concentration profile of the coatings were examined using optical and electron metallography, X-ray diffraction, and glow discharge optical spectroscopy. The results showed that Ti2Ni and AlNi2Ti were the main constituents of the coating. The formation mechanism of the coatings was also evaluated.

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Polyethylene terephthalate (PET) based nanocomposites containing three differently modified silica particles were prepared by melt compounding. The influence of type and amount of nanosilica on various properties of nanocomposite was studied using atomic force microscope, thermal degradation, thermal-mechanical properties, scanning electron microscope, and reflectance spectra. AFM test was used to study the roughness of composites which indicated that the roughness is related to hydrophilicity degree of silica, increasing with an increase in hydrophilicity of particles. SEM images were studied on the surface, confirming that the surface roughness of nanocomposite depends on the type of nano-silica used. Results of thermal analysis showed that the interaction between nanosilica particle and polyethylene terephthalate chains is effective in thermal stability of composite. UV-vis spectra of polyester nanocomposites indicated that the refraction of hydrophilic silica nanocomposites is more than hydrophobic one, indicating agglomeration of hydrophilic particles at the surface of nanocomposite compared with hydrophobic one.

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In recent years, use of Sol-gel procedure for laboratory and industrial synthesis of Nanostructures and especially silica Nano-particles has increased. In this research, silica particles were synthesized by Sol-gel procedure and their physical properties were studied by means of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Thermal Gravimetric Analysis (TGA). Effect of structural modifiers on the morphology and diameter of Nano-particles was investigated. In addition, the reaction was carried out in the presence of ultrasonic waves in periods of 10, 30 and 60 minutes and the effect of these waves on different stages of reaction was studied by means of SEM. Finally, in this research, spherical particles of 50 to 80 nanometer sizes were synthesized and characterized. They can be very useful hosts for lanthanide complexes that can be used in drug delivery systems, radiotherapy, photoluminescence applications and manufacturing of special lasers. Also, different amounts of Lanthanum Nitrate hexahydrate were added to the mixture during the creation of Nano-particles. Then, Simulated Body Fluid (SBF) was produced for the study of ability of the Nanostructures in regulated delivery of drugs such as Lanthanides, and releasing of Lanthanides in 10 minute periods for 80 h was studied. Lanthanide concentration in SBF was also studied by means of Inductively Coupled Plasma (ICP). According to the results of ICP, loaded Lanthanide was not released from the silica network. Loaded Lanthanides in the mesopores can be used in radiation, especially in cases of liver cancer.

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In this paper, preparation and characterization of a-SiNx thin films deposited by LPCVD method from free radicals of TCS and NH3 gaseous system were investigated. These radicals are made by passing each of the precursor gases separately over Pt-Ir/Al2O3 catalyst at the temperature of 600 ᐤC. Kinetics of this process was investigated at different total pressures, NH3/TCS flow rate ratios and temperatures. Surface topography and chemical concentrations were studied by Ellipsometry, XXPS, AFM and ADP. Our analyses of the performed experiments indicated that at the temperatures between 730 ᐤC and 830 ᐤC, the growth rate of thin films follows an Arrhenius behavior with activation energy of 166.3 KJ.mol-1. The measured H2 contamination in a-SiNx thin films is 1.05 at%, which is 17 times lower than the corresponding contamination in the films produced by PECVD and 3.4 times lower than the contamination in the LPCVD thin films with SiH4 or DCS and NH3. The created surface topography of the prepared films is smooth and uniform.

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Composite and nanocomposite Ni-Co/SiC coatings were synthesized by electro-codeposition of micro and nano-sized SiC particles with average diameter of 10m and 20nm using horizontal electrodes. Surface morphology, chemical composition, phase composition, hardness and corrosion resistance of the deposited coatings were studied using SEM observations and EDX, XRD, microhardness and polarization measurements as a function of the electrodeposition current density. The results indicated that the nanocomposite coatings exhibit higher hardness and corrosion resistance compared with the composite coatings containing micro-sized SiC particles despite their lower percentage of the SiC content. The maximum hardness values of 615HV and 490HV were obtained for nanocomposite and composite coatings deposited at current density of 3A/dm2. The observed properties were discussed based on the structural details.

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Coherency elastic strain between γ and  is one of the effective factors which affect the morphology, spatial re-arrangement and coarsening kinetics of  precipitates in nickel-base superalloys. In this investigation, using X-ray diffraction (XRD) technique, the - constrained and unconstrained lattice misfits were calculated for different morphologies of the  precipitates in Inconel 738LC nickel-base superalloy. The constrained and unconstrained misfits, hence the coherency elastic strains of different morphologies of the  precipitates were calculated from the XRD patterns of the bulk sample and electrolytically extracted  precipitates, respectively. According to the results, as the sizes of the  particles increased the - coherency as well as the compressive strain of the  precipitates was reduced and consequently their morphology changed from spherical to cubic, then flower-like, and finally dendritic shapes.

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In this research, M-type Mn-Zr doped Ba-ferrites powders with a general chemical composition of BaFe10.6(ZrxMn1-x)O19 ( x= 0, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1) were synthesized and prepared by a solid state method, and were then mixed with anAraldite + hardner and processed into polymer matrix composite specimens. Phase analyses of synthesized samples wereperformed by an XRD technique and magnetic properties of the composite specimens were measured using a hysteresis graphsystem. EM absorbtion characteristics of the composite samples in the (8-12 GHz) frequency ranges were determined using aVNA system.Among the compositions investigated in the present work, the highest absorbtion of -11.25 dB accured in BaFe10.6Zr0.28Mn1.12O19 (x= 0.2) at a frequency of 8.4 GHz. Based on EM absorbtion behaviors and magnetic properties, BaFe10.6Zr0.28Mn1.12O19 is classified as a potential EM absorber material.

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In this study, magnetite (Fe3O4) nanoparticles were synthesized by chemical co-precipitation from the solution containing iron salts in alkaline medium under N2 gas and room temperature. Magnetite nanoparticles were characterized by X- ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), Brunauer-Emmet-Teller (BET), and vibrating-sample magnetometer (VSM). The rheological properties of magnetite ferrofluid were examined by rheology apparatus. The biocompatibility and cytotoxity of magnetite nanoparticles were evaluated by 3T3 and fibroblast cells. The results showed that the Fe3O4 magnetite nanoparticles coated by polyvinyl alcohol (PVA) could be an appropriate candidate for biomedical applications.

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Carbon fiber composite is one of the most important materials in aerospace engineering applications. For fabrication of this composite, optimum polymerization and carbonization cycles of phenolic resin were obtained [1]. Then, carbon/phenolic composite was fabricated by mixing different weight percentages of T700 carbon fiber with phenolic resin, and the flexural strength of specimens was examined.The samples were pyrolyzed at 1100°C to form high temperature phenolic matrix. Because of high porosity of samples, the composite was impregnated to increase the density and reduce porosity. The maximum flexural strength of samples was obtained with 40 wt. % of fiber. With addition of TiO2 and ZrO2 nanoparticles to carbon/phenolic composite, thermal and mechanical improvement was measured. The samples were examined by ablation test and microstructures of composites were analyzed by SEM.

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This study aims to characterize and evaluate the applicability of Polyhedral OligomericSilsesquioxane (POSS)/ Poly (carbonate-urea) Urethane (PCU) nanocomposite films as a temporary skin substitute by means of FTIR, MTT assay, cell proliferation assay and SEM studies. FTIR spectra showed all the characteristic peaks of POSS/PCU nanocomposite. The indirect cytotoxicity of membranes was investigated by MTT assay. In MTT test, L929 mouse fibroblasts were exposed to the extract of the films for 24 h. MTT results showed no sign of cell cytotoxicity for the extracts at the extraction times up to14 days. Menwhile, it was found that POSS nanocages have a stimulating effect on L929s. In cell proliferation assay, L929s were cultured on the films for 3, 7 and 14 days. The cells showed a high rate of proliferation in direct contact with the biomaterial after 7 and 14 days. Morphology and density of the cells on the nancomposite surface was investigated through SEM observations. SEM micrographs showed that the cells adhered well on the surface after 3 days of culture. Moreover, after 7 days, cell density increased so substantially that a cell layer was formed on the membranes.

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Short life of current total hip replacement metallic implants is generally dependent on the aseptic loosening of the implant, which occurs due to mismatch of elastic modulus between bone and metallic implant materials. Decreasing in elasticmodulus of implant could be successful. Forsterite is biocompatible and bioactive ceramic which has suitable mechanical properties. In presented research the composite materials based on Co-Cr-Mo alloy with 10, 15 and 20wt% of forsteritenanopowder as reinforcement were fabricated and mechanical behavior of the composites were evaluated. Composites were fabricated by ball milling, cold pressing and sintering. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for characterization and evaluation phase composition and microstructure of the composites. Density, microhardness, compressive strength and elastic modulus of fabricated composites were evaluated. Obtained results showed elastic modulus of composite materials based on Co-Cr-Mo alloy reinforced with 10, 15 and 20wt% of forsteritenanopowder decreased significantly. Results also showed that the compressive strength of Co-base alloy composites reinforced with 10, 15 and 20 wt% forsterite were lower than cast Co-Cr-Mo alloy. With increasing in the content of reinforcement, compressive strength of the composites were decreased. Microhardness of prepared composites were higher than cast Co-Cr-Mo alloy. With increasing in content of bioceramic reinforcement, microhardness of the composites were increased.

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In this study, mullite– irconia composite samples were prepared by reaction sintering of alumina and zircon powder via gel casting process. Gel casting is a new ceramic forming technique. This process is based on the casting of slurry, containing ceramic powder, dispersant and premix monomer solution. To achieve stabilized, high solid loading (80 wt%) and castable slurry, the rheological properties of slurry were optimized. The monomers polymerized the slurry to form gelled specimens. After gelation, the specimens were unmolded, then dried out under controlled condition. Burning out and sintering of the specimens was carried out in the range of 1400-1700°C. Apparent porosity and bulk density of the sintered samples were measured by soaking in water. Crystalline phase evolution and microstructure were determined by XRD and SEM techniques. Results showed that the reaction sintering and mullite formation was completed at 1700°C due to very slow diffusion of Al3+ ions within amorphous silica formed at the decomposition of zircon. The sintered samples at this temperature also showed the lowest apparent porosity (≈ 4%) and the highest bulk density (≈3.40 gr/cm-3).

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The effects of temperature, time and atmosphere on microstructure and magnetic properties of NiFe2O4 glassceramic were investigated utilizing differential thermal analysis, X-ray diffraction, vibrating sample magnetometer and scanning electron microscope techniques. Various compositions were studied in the Na2O-NiO-Fe2O3-B2O3-SiO2 system to obtain amorphous phase. The sample heat-treated in graphite bed at 510°C for 1 hr showed higher magnetization than the one heattreated in the air under the same condition. XRD analysis showed the presence of nickel ferrite and some non-magnetic phases such as sodium borate and silicate phases in the heat treated samples. The maximum magnetization of samples reduced by increasing the holding time from 1hr to 3 hr at 510°C. Increment of temperature to 700°C increased the amount of NiFe2O4 and maximum magnetization.

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The particles of ferrite Ni0.6-xCuxZn0.4Fe2O4, (0-0.5 in step with 0.1) were prepared by the sol-gel method. Sintering process of powders was carried out at 600, 800 and 1000 oC. The effect of the sintering temperature and chemical composition on the structural and magnetic properties of the Cu substituted NiZn ferrite was investigated. EDS analysis and X-ray diffraction patterns confirmed a well defined of single crystal phase with spinel structure. The thermal behavior process and particle size of samples were investigated by thermal analysis TG, DTA techniques and scanning electron microscope, respectively. VSM curves reveal that the sintering temperature and copper content affect saturation magnetization. M ssbauer spectra displays that the copper cations occupy the octahedral sites. With increasing of copper cations, the iron cations immigrate to tetrahedral site, consequently the saturation magnetization decrease.

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Refractory carbides are becoming a group of promising material due to their unique properties, such as high hardness, high wear and corrosion resistance, high thermal conductivity, high melting point, high strength even at high temperatures, and a high degree of chemical stability. Among these carbides, titanium carbide (TiC) is one of the most important engineering material, based on its promising properties. This paper presents a novel approach to preparing ultrafine TiC by sol–gel processing. This novel process would minimize kinetic barriers because carbon (coming from sucrose) was homogeneous dispersed in the precursor of TiO2 by sol–gel process. As a result, the increased contact area between reactants should make the reaction to complete at lower temperatures.

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In this project, we prepared biomimetic nanocomposite scaffolds from gelatin and chitosan and hydroxyapatite and subsequently the scaffolds were evaluated by common used bulk technique. For this purpose, the nanocomposite hydrogel/apatite bone tissue engineering scaffolds were fabricated using applied biomimetic method accompanied with freeze drying technique. The apatite was precipitated using double diffusion mechanism within gelatin hydrogel in similar pH and temperature to the human body. Chitosan initial percentage (20, 30 and 40%) was set as variables. Nanocomposites were soaked in glutaraldehyde solution in order to enhance mechanical properties and make them insoluble in water. Diffusion of calcium and phosphate from lateral hydrogel into the middle hydrogel caused formation of parallel white layer-formed precipitate. Analysis of precipitates formed within middle hydrogel for the samples, showed that detected materials are composed of carbonated hydroxyapatite and dicalcium phosphate dihydrate (DCPD, brushite). Also, mechanical behavior obtained for the scaffolds were comparable with spongy bone. With increasing chitosan in the composite scaffold, the water up-take was increased from 379 to 661%. Phase composition, microstructure and structural groups in the composite samples were also characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infra-red (FTIR) analyses. Eventually, the obtained results showed that the composite contains 20% chitosan had appropriate properties for fabricating bone scaffold.

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In the present work, molecular dynamics simulation method was used for determining Young's modulus, Shear modulus and Poisson’s ratio of Al-SiC nanocomposites, with different volume fractions of the reinforcements. For simulation, the open source package, LAMMPS, was used. After putting Aluminum and Silicon Carbide atoms in their initial positions, interatomic potentials between them were defined. EAM potential was used for Aluminum atoms, Morse potential was used for Al-C and Al-Si, and for C-C, Si-C, and Si-Si Tersoff potential was used. According to the elastic bounding principal, and the comparison between the simulations results and Voigt, Ruess and Halpin-Tsai micromechanical models showed that the results were close to the upper bound Voigt model.