Journal of Advanced Processes in Materials Engineering
Year:2015 | Volume:9 | Issue:3 (34)|Papers Count:22

Recently for tissue healing, tissue extractions have been used. But now tissue engineering and the scaffolds are used to repair the damaged tissue and organs, this caused to improve quality of life of patients. Regarding the restriction of biopolymers and bioceramics, metallic biomaterials are more considerable. High density, not bioactivity and high elastic modulus are the restriction of metals. These restrictions can cause to loosening of implants in hard tissue and accelerating the cell lysis and losing the function of implants. With foaming the metal, density and elastic modulus of metal reduced and alleviate these problems. Regarding to titanium has good corrosion resistance in the body, in this research foaming the titanium by space holder method, the superior structural and mechanical properties can be achieved. The effect of sintering temperature on mechanical properties, porosity and pore morphology of porous titanium is investigated. Pores with appropriate amount, size and shape make better implant fixation in hard tissue of the bone or tooth. Results indicate that with increasing sintering temperature, the strength of metallic foam will increased and the amount of micro pores will reduced.

A velocity control strategy was adopted in the limite element analysis of the surface transformation hardening ofS355 steel in order to adjust temperature at the surface of the work piece in the vicinity of edges. This strategy which is based on controlling the traveling speed of the heat source as a function of the maximum temperature at the surface, allows for gaining a more uniform microstructure as a result of a uniform thermal history at the surface. The results indicate that the applied strategy is highly effective. Besides, the results obtained from the simulations suggest a combination of a smaller beam size and a high power of the heat source in the absence of the proposed approach.

Nanostructured Zr3Co intennetallic getter compound, due to its high surface area, show enhanced pumping properties and gas sorption response in contrast to the bulk, thin film and commercial getters. Nanostructured Zr3Co intennetallic powders were produced by mechanical alloying (MA) ofthe elemental powders. In the production process, the weight ratio of balls to powder was 1:15 and the rotation speed of planetary ball mill considered as 300rpm After 16 hours of milling, amorphous powder white desired compound was obtained. The phase evolution, microstructural characteristics and formation mechanism of Zr3Co powders during mechanical alloying were studied by means of X- ray diffraction method, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The results showed that after an optimum mechanical alloying time and optimum heat treatment, nanostructured Zr3Co intennetallic powder was achieved. The crystallite grains with sizes of 10 to 20 nm, was achieved respectively. It was found that Zr3Co intennetallic compound is formed by the diffusion of Cobalt into Zirconium during mechanical alloying. In the second stage, after an optimum heat treatment, formation and growth of ZrjCo intennetallic compound are controlled by interdiffusion of Co and Zr.

Nowadays, lightweight sandwich panels with aluminum foam core have a wide range of application in industries as good energy absorbers. In this paper, aluminum foams stabilized and reinforced by SiC particles were manufactured with direct foaming route of melt using CaC03 foaming agent. The density of produced foams was calculated about 0.63 g/cm3. Uniform cell size of the structure and well distributed SiC particles in cell walls was shown using optical and scanning electron microscopy of composite foams. A dhesive bonding of foam-foam, foam-sheet and sheet-sheet connections with three different industrial glues were investigated by using single lap tensile-shear test. Modeling of this test was performed with ABAQUS 6.10.1 and results were compared with experiments. Thermal stability of glues was investigated with thermogravimetry analysis (TGA) and finally glue with the best mechanical and thermal properties was chosen.

Due to important effects of Niobium on properties of steels. the effect of Nb addition on hot deformation behavior of martensitic stainless steels was investigated in this paper. To do it, after being solution treatment the steels 403 and 403Nb were subjected to hot compression tests. The results were showed that Dynamic Recrystallization (DRX) phenomenon usually occured in all cases in 403 steel and in many cases in 403Nb steel. However, it was found that by hot deformation of 403Nb at some low temperature it is possible to retard the restoration phenomenon through precipitation and interaction of precipitations with DRX. Precipitation was studied by Stress Relaxation tests. The presence of niobium carbides was porved by scanning electron microscopy (SEM) and EDS Analysis. It was found that in 403Nb steel niobium carbide precipitations may be of significant potential in restriction of restoration.

In this paper, effect of standoff distance parameter on morphology and mechanical properties of explosively bonded AlMg5-AI-Steel is being studied. Results have shown that by changing standoff distance and loss of kinetic energy, the shape of interface is transited from Smooth-wavy to Wavy and wavy in a vortex way. With increasing of the standoff distance due to the loss of kinetic energy also local melted zone has been created in front of vortices. Chemical composition of local melting zone was mixed of parent and flyer plates due to circular movement of jet. These areas have reduced bonding strength due to stress concentratio; results also have shown that strength level of all weldment was above standard level .The sample without local melting zone and wavy interface has the highest strength.

Barrier membranes made by various natural and artificial polymers are used for guided regeneration of periodontal tissue. These membranes employ the placement between epithelial tissue and teeth to prevent early epithelial migration while osteoblasts and periodontal ligament cells can find chance to regenerate periodontal tissue. The aimof this study was to prepare and characterize polycaprolactone fumarate (PCLF) membrane by electrospinning met hod for periodontal guided tissue regeneration application. First, polycaprolactone diol (PCL diol) and PCLF was made and characterized with Nuclear Magnetic Resonance (H NMR) and Fourier Transformed Infrared Spectroscopy (FTIR). Electrospinning of PCLF could be performed successfully by adding the gelatin to PCLF. In fact, blending of PCLF with gelatin allowed it to be electrospinned. Gelatin solution in acetic acid has more electrical conductivity and viscosity in comparison to PCLF solution in acetic acid. Solution of 3Owt% PCLF in acetic acid has 146ms/cm electrical conductivity at 23°C and 55.26 m Pa.s viscosity at shear rate of 692.48 S-1. These numbers for solution of 30wt% gelatin in acetic acid are 1015 us/ern electrical conductivity at 23oC and 265.51 rnPa.s viscosity at shear rate of 692.48 S-l. The obtained results using characterization techniques such as scanning electron microscopy (SEM) and FTIR approved this claim.

With the development of microelectronics and micromachining technology, micro-heater has found plenty of applications in micro-sensor. The sensitivity and resolution of gas sensors that use a micro-hotplate are dependent on the temperature uniformity of the sensitive device .In this work, placing a thin Si-island underneath the dielectric membrane for achieving uniform temperature distribution over the active heater area is investigated. Two micro- heaters with suspended membrane structure are designed, fabricated and characterized on the silicon substrate based on MEMS fabrication process. In the one of them, l Ourn thick silicon layer is placed unearth dielectric membrane while another one is fabricated without this layer. The simulation results show that with placing silicon layer, temperature uniformity and mechanical strength are improved whereas power consumption and response time are increased. Furthermore, Experimental results are in closed agreement with the results obtained from the simulation and show that power consumption and response time in fabricated micro-heater with thin silicon island are 50mW and 4.23ms respectively to reach a temperature of 500oC, but they in micro-heater without this layer are 13mW and 2Ams respectively to reach this temperature.

In this study effect of heat treatment on hardness and wear resistance of Ni-P/Ni-B-B4C composite duable layer coating investigated. In the first, the Ni-P electroless coating deposited on the Ck45 substrate for 15 mm and then the Ni-B-B4C electroless coating with same thickness deposited. For comparing properties of Ni-P/Ni-B-B4C coating with conventional coatings the Ni-P/Ni-B double layer coating with same thickness and Ni-B single layer coating with 30 urn thickness deposited on Ck45 substrate too. Tafel polarisation analyse used for investigation role of Ni-P electroless layer. The coated samples heat treated in 400°C temperature for I hr. effect of heat treatment on morphology and microstructure investigated with scanning electron microscopy and X-ray diffractometry. The pin- on -disk test with 5 N load and 1000 m sliding distance was used to wear resistance studies of coatings in the room temperature. Result show that adding B4C particles to Ni-B layer and presence of Ni-P layer development corrosion resistance of Ni-PlNi-B-B4C double layer coating. Uniform distribution of B4C particles in the Ni-B layer and heat treatment process caused to semi arnorph structure of coatings converted to nano crystallin structure. On the other hand heat treatment process results to formation Ni3B hard phase in the coatings. Uniform distribution of hard particles, nanocrystallin structure and presence of Ni3B phase are general reasons that increase wear resistance of Ni-P/Ni-B- B4C double layer coating. It can forecast that good properties of Ni-PlNi-B-B4C double layer coating result to development Ck45 steel in the industries.

HP alloys in the casting conditions have good weld ability but the major concern is in repair- welding on the used materials, The reason to this phenomenon is when the HP alloys serve at high temperatures (1000 "C) for a long time, they start to develop big and dispersive carbide in the background and thereby causing sever embrittlement and inflexibility. In this study, the effect of solution annealing temperatures on weldability of aged cast-heat resistant alloy (HP) has been studied. Hence five samples of used material that had lost basic conditions due to long-term service (30000 hr) were selected and after annealing-heat treatment in 900, 1100, 1150 and 1200oC, all annealed samples and one aged sample, were welded with GTAW process and ER-2535 filler metal. After welding, all standard samples were tested with light and electron microscopy, hardness test and hot tension test at 950oC equivalent to operating temperature of the samples' service conditions. The results explained an increasing trend in elongation and solution of carbides, also reduction of sample hardness and tensile strength with increasing annealing temperatures. However, the mechanical test results and study of microstructure of sample annealed in 1150oC indicated the best results (due to considerably less variation in mechanical test results) of various experiments during repair-welding. Therefore, the 1150oC is suggested as the best temperature to anneal HP alloys.

in this-article, behavioral analysis of Silicon anisotropic etching in Tetramethyl Ammonium Hydroxide (TMAH) water solution is investigated. Therefore, silicon Etching process is performed with different concentration of 5, 10, 15 and 25 wt. %, and in the various temperatures of70, 80 and 90°C. Measured results show that the etching rate intensifies by increasing the solution temperature, but it decreases with increasing in TMAH concentration greater than 10 wt. %. a maximum etching rate on the p-type Si (100) surface; reaches a value of 6211m1h at a solution temperature of 90oC and TMAH concentration of 10 wt. %. SEM images show that the silicon surface lumps appear like small pyramid-shaped hillocks in which form and distribution on silicon surface is completely random The surface roughness increases with decreasing of TMAH concentration and much smoother silicon surface can be observed for higher concentration. Moreover, the maximum <100>/<111> etch rate ratio is 10.6 obtained in 10 wt. %TMAH. This concentration of TMAH has the minimum undercut.

Each year, thousands of deaths occur while the patients wait for getting new graft. Tissue engineering can help solving many of the problems and this consider with placing the cells in a particular tissue in 3D structure called scaffolds, in order to recovery of natural function of organs. In this study bioactive glass (BG) was synthesized by using tetraetyeorthosilicate (TEOS), triethyle phosphate (TEP) and calcium nitrate tetrahydrate (Ca (N03)2.4H20) via sol-gel method. Polyvinyl alcohol and cetyltrimethylamrnonium were mixed with nanofiber of BGS to facilitate electro spinning. Then scaffolds calcinated at 600oC and their bioactivity of the samples studied ill simulated body fluid (SBF) and some other different methods. The most effective parameters on electrospinn ing were studied such as voltage, solution feeding rate, needle diameter, distance between needle tip and collector. Regarding the scanning electron microscope images, fibers with a diameter of 300 nm to I J.UTI were prepared. The atomic force microscopy images shown pores about 2 nm on the surface of fibers. Immersion of the scaffolds in SBF and evaluation of them with Fourier transform infrared spectroscopy and X-ray diffraction, indicated the hydroxyapatite peek on the samples. Zeta potential of the bioactive glass was -10.1 mVthat is like bone tissue, therefore it was susceptible for bone cell culture. Concerning the MTT assay by using MG63 cell line, all of the samples did not show cytotoxicity. Thus the bioactive glass nano fibers could able to attach bone cells and form hydroxyapatite on the surface and can be used as scaffolds for tissue engineering.

Manganese steels have extensively application in industries due to good resistance to wear, high work hardening capability with high toughness and ductility. Heat treatment is the main process to obtain desired mechanical properties and microstructure in this steel. The austenitizing temperature, the austenitizing time and the rate of quenching by increasing salt content are the main factors in heat treatment. For dissolving of carbide, the austenitizing temperature and austenitizing time are very important. Quenching rate must be high for minimizing the grain boundary carbids. In this research the effects of these input parameters on the grain boundary carbide content, austenite grain size and hardness have been critically analyzed using Taguchi method. In the optimization by Taguchi approach, L9 (3)3 array, employing nine experiments, with three levels for each factor, was chosen for DOE. It has been found that the austenitizing temperature is the most important process parameter affecting the carbide content, grain size and hardness. The heat treatment produces the minimum carbide content and low grain size when the process parameters were set at their optimum values. It has been shown that heat treatment parameters set as their optimum levels can ensure significant improvement in the objectives.

The present paper investigates the microstructure and macrostructure of a newly Mn-25Ni-5Cr (%wt) (Mn70) alloy during homogenization. The structure was analyzed by optical microscopy, energy dispersive spectroscopy and differential thermal analysis. The results show that dendritic segregation exist in Mn70 alloy ingot. The inter dendritic regions are rich in Ni and Cr and depleted in Mn. Macrostructure of Mn70 as -cast alloy consist of three zone: chill, columnar and equiaxed. For elimination of segregation during solidification various heat treatments were performed. For complete elimination of dendrite microstructure of casting alloy homogenization heat treatment was done at 900oC for 10-hour our studies show that by increasing the homogenization temperature to 1000oC can decrease the holding time, but, our studies indicates that for complete elimination of macro segregation and columnar to equiaxed transition 15-hour heat treatment at 1000°C is necessary. According to the obtained results, the dendritic microstructure, inhomogenity of macrostructure and segregation of alloying elements can be reduced by heat treating at 1000oC for 15-hour remarkably.

Montmorillonite (MMT) nanostructures were selected as reinforcement agent to improve the mechanical properties of polyvinylchloride (PVC). PVC-MMT nanocomposite was prepared by mixing of MMT with a solution of PVe. Taguchi experimental design method was used to determine the optimal conditions for preparment ofnanocomposite. The effects of five factors containing MMT percentage, kind of solvent, MMT adding method, film drying temperature and stirring time were investigated in different levels. Optimal conditions were determind by using of the standard analysis method. The results indicated that, three factors ofMMT percentage, kind of solvent and film drying temperature are dominant in significance level of 95%. Fourier transform infrared ( FTIR ) spectroscopy and scanning electron microscopy ( SEM) techniques were used to characterize the composition and structure of optimal nanocomposite. In another test, thermo gravimetric analysis (TGA) showed the improvement of thermal stability of nanocomposite.

The aim for this study is characterization performance of polyacrylamide gel method at preparation CoAl204 nano particles. The effects of monomer to salt ratio (0.5, 2) and temperature on the microstructure of the nano-pigments were investigated. Cobalt nitrate and Aluminum nitrate salts were used as starting materials with a ratio of 1:2 (Co: AI). Structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The CoAlz04 phase was achieved after calcinations at temperatures between 600 -1200oC for 2 h. The average particle size was about 48 nm, The results show a varying in particles size as a result of different calcinations temperatures.

Lithium volatility at high sintering temperatures resulted in low magnetic and dielectric properties. In this project, lithium ferrite was produced by conventional method using oxide and carbonate of raw materials. Nano Si02 was used as sintering aid at different sintering temperatures. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the microstructure of prepared Li0.4Zn0.4 Ti0.2Fe2O4 compound. Result shows that the Nano silica changes the sintering mechanism from solid state sintering to liquid phase sintering due to its high surface area and promotes microstructure. In addition the magnetic properties increased due to larger grain size at lower sintering temperature. Optimum properties (Bmax=380mT, Hc=333A/m) was obtained for the 1 wt.% doped sample sintered at 1050oC.

In this research, chlorination of chalcopyrite in a high-energy mill was carried out in order to convert chalcopyrite to copper chloride. Chalcopyrite milling was performed at ambient temperature and dry chlorine gas atmosphere, in time rang 30 to 120 minutes and ball to powder weight ratio 10 and 20. X-ray diffraction analysis was used to identify the phases formed in the samples. X-ray diffraction pattern of milled chalcopyrite powders showed that in the high-energy milling, after a specified time, chalcopyrite is converted to chloride of iron, copper and sulfur. Scanning electron microscope images were obtained to evaluate the products morphology and reaction kinetics. Eventually, milling time of 100 minutes with a ball to powder ratio of 20 was obtained as the optimum conditions. Kinetic analysis also indicated that the process is controlled by chemical reaction.

In this study, the effects of friction stir welding parameters on the formation of intennetallic compounds, defects and tensile strength of AAII00 aluminum joints A441 AISI steel were studied. Thick Intermetallic compound formed at high tool rotational speed and low traverse welding speed. iChemical compositions of these components were Al6Fe2 and Al6Fe that formed in joints interfaces. Tunnel defects were main voids that formed in the stir zone. Due to improper heat generation in lower rotational speeds, this void made in low rotational tool speeds and these voids vanished with increasing the frictional heat. Frictional heat increased by tool plunge depth and stir zone void became smaller. By controlling mechanical parameters of the process strongest joint produced in 800rpm tool speed, 63 mm/min traverse speed and 0.2 mm tool plunge depth. This joint had 90% of the aluminum base metal strength.

In this study, formation of composite coating containing silicon carbide amplifiers on ASTM AI06-Gr B steel surface using the gas tungsten arc welding process is investigated. Therefore silicon carbide particles with different volume percentages on the steel surface were placed and by changing the current density, melting and mixing process was done with the base metal. The study coating microstructure by optical microscopy and scanning electron microscopy (SEM) was conducted alongside the spot analysis. The results showed that the dendritic structure of the resulting coating contains silicon carbide are capable of reinforcing that could be improved hardness and wear behavior of the coatings. Hard coatings by a micro-hardness measurement and with slab vickers and wear behavior of the coatings was evaluated by testing the wear-trip basis. Microhardness test results showed increased hardness was created (about 650 to 1150 Vickers) compared to uncoated samples (about 200 Vickers) is. Reviews wear behavior of coatings represent significant improvements in wear behavior of is added silicon carbide reinforcement. The main wear mechanism of uncoated samples delamination wear and surface oxidation and the samples were coated with a mixture of delamination wear; surface oxidation and adhesive wear were detected.

Both of chitosan (CS) and magnetite are biocompatible and biodegradable materials. In this study, natural CS/magnetite nanocomposite was prepared with in situ precipitation. Surface morphology, magnetite nanoparticles size and investigation of nanocomposite composition was done with scanning electron microscope(SEM), Transmition electron microscope(TEM) and Fourier transform infrared (FTIR). Magnetite nanopartic\es and its crystal size investigation were done with X-ray diffraction (XRD) which was 23.5 nm magnetic properties measurements were done with Vibrating sample magnetometer (VSM) which saturated magnetization was 3.04 e mug-1 and cohersive force was 128.390e. Chitosan/magnetite nanocomposite with lower contents of magnetite had lower saturated magnetization. This nanocomposite was superparamagnetic. For investigation of viability, samples cultured in the presence of stem cells and results show that this nanocomposite has biocompatibility.

The friction welding of titanium alloys with aluminum impeller due to issues such as the appropriate selection of process parameters and tool wear is associated with many problems. Appropriate control variables to obtain a healthy and free of defects in the weld metal are extremely important. The aim of this study was to evaluate the impact of rate changes on microstructure and mechanical properties of rotation speed and welding speed tool to connect the friction stir welding of titanium alloys and commercially pure aluminum is H321-5083. Therefore, the micro-structure, hardness and tensile tests on the binding were investigated. Studies show that the rotational speed of the welding speed parameter in determining the strength and microstructure of the final weld tool is the best result for the microstructure, hardness and tensile test results in 4.22 optimum ratio, and that the rotational speed 1120 and welding speed 50 achieved an optimal result in the increase or decrease of this ratio decreases the strength and rigidity comes. Weld strength obtained at the optimum ratio is equal to 20% of the strength of the base metal is aluminum.