Hamid Omidvar

Hamid Omidvar
Amirkabir University of Technology | TUS · Department of Mining and Metallurgical Engineering

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122
Publications
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Publications

Publications (122)
Article
Rechargeable aqueous zinc ion batteries (ZIBs) are one of the most promising candidates for large-scale energy storage, due to their high capacity, high hydrogen evolution potential, safe and cost-effective components while benefiting from the abundance of active materials. However, ZIBs still suffer from suitable cathode materials with high capaci...
Article
Full-text available
Formation of a decent Solid-Electrolyte Interface (SEI) is recognized as an approach to improve the performance of Lithium-ion Batteries. SEI is a passivation layer generated on the anode during the initial cycles. Characteristics of the Graphite SEI depends on the operational parameters, state of the anode, and the content of the electrolyte. Intr...
Article
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eat-affected zones (HAZs) of Inconel 939 (IN-939) superalloy are susceptible to cracking during the welding process. Preventing cracking during the repair welding of turbine components is important. In this study, the effects of heat input and pre-welding heat treatment on the microstructure, mechanical properties and crack formation in tungsten in...
Article
Full-text available
The solid–electrolyte interphase (SEI), the passivation layer formed on anode particles during the initial cycles, affects the performance of lithium-ion batteries (LIBs) in terms of capacity, power output, and cycle life. SEI features are dependent on the electrolyte content, as this complex layer originates from electrolyte decomposition products...
Article
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Laser metal deposition (LMD) is one of the manufacturing processes in the industries, which is used to enhance the properties of components besides producing and repairing important engineering components. In this study, Stellite 6 was deposited on precipitation-hardened martensitic stainless steel (17-4 PH) by using the LMD process, which employed...
Article
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The hot components of a gas turbine are susceptible to damage in the high-temperature environment of turbine engine operation. Given that these components are relatively costly to manufacture, they are often repaired than replaced when damaged. Fusion welding is an economical method for repairing the damaged components of a gas turbine. This resear...
Article
The effects of joining temperature (TJ) and time (tJ) on microstructure of the transient liquid phase (TLP) bonding of GTD-111 superalloy were investigated. The bonding process was applied using BNi-3 filler at temperatures of 1080, 1120, and 1160 °C for isothermal solidification time of 195, 135, and 90 min, respectively. Homogenization heat treat...
Article
The anode materials are one of the critical components in rechargeable lithium ion batteries (LIBs). The monoclinic tungsten trioxide (mWO3) is introduced as interesting anode electrode for LIBs due to its good structure for intercalation and de-intercalation of lithium ions, high abundance and various oxidation state of tungsten and etc. In this s...
Article
Turbine blade face with crack generation during high-temperature application. Due to its high cost of manufacturing, repair of the damaged section is usually more desirable than its replacement. transient liquid phase (TLP) bonding is a common joining procedure used for maintenance of a gas turbine damaged vein and blade. This paper describes how t...
Thesis
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In the present study, the effects of temperature and bonding time on creep behavior of nickel-based superalloy GTD-111 joints produced by transient liquid phase (TLP) process were studied. The bonding process with BNi-3 filler has been performed at temperatures of 1080-1160 °C and at different times. At each temperature, the isothermasl solidificat...
Article
Gas turbine blades working under extremely harsh operating conditions are made of superalloys. These superalloys are exposed to various damage mechanisms, which wear them out gradually. Welding is often preferred to repair the damaged components for cost minimization. This study aimed to investigate the effects of flexural load, heat input, and wel...
Article
As a new class of materials, High Entropy Alloys (HEAs), have been recently used for various usages such as high-temperature applications. High entropy alloys have such unique properties as high strength, high-temperature phase stability, good fracture resistance, and excellent softening resistance at high temperatures. Studies on the oxidation beh...
Article
In this paper, the effects of temperature and bonding time on creep behavior of nickel-based superalloy GTD-111 joints produced by transient liquid phase (TLP) process were studied. The bonding process was performed using BNi-3 filler at temperatures of 1080, 1120, and 1160 °C and isothermal solidification times of 195, 135, and 90 min, respectivel...
Article
Full-text available
Transient liquid phase (TLP) bonding as an effective and precise bonding process attracted enormous attentions. However, there are several parameters affecting the mechanical properties of the joint zone which are crucial to be studied. In this work, two pieces of Inconel 625 alloy was bonded via TLP process using a BNi-2 interlayer. TLP process wa...
Article
Nickel-based filler alloy with a liquidus temperature of 1024 °C was used for transient liquid phase (TLP) bonding of A564-630 martensitic precipitation hardening stainless steel. TLP experiments were carried out at a constant temperature of 1050 °C for different times between 30 to 90 min employing 75 μm thick filler metal to achieve the best TLP...
Article
Conventional and two-step heating transient liquid phase bonding (TLP) experiments of martensitic precipitation hardening stainless steel 17-4-PH were studied employing AMS 4777 braze filler at temperature of 1050 °C for different times (15 to 90 min) to accomplish the ideal brazing condition. The effect of TLP methods and bonding conditions on the...
Article
An ideal transient liquid phase (TLP) joint is achievable with the complete isothermal solidification and homogenization of the Diffusion Affected Zone (DAZ), in which case, a joint with a similar microstructure to the Base Metal (BM) is obtained. In this study, Inconel 738 (IN-738) was joined by TLP bonding using a BNi-2 filler alloy at 1120 °C fo...
Article
Hot-dip aluminum and Si-modified aluminum diffusion coatings were applied on the substrate of nickel-base superalloy IN-738LC to enhance its hot corrosion behavior for high-temperature applications. Aluminizing salt bath consisted of KCl, NaCl, NaF, Na3AlF6, and Al powder, while the Si-modified salt bath contained NaCl, NaF, KCl, Na2SiF6, and Na3Al...
Article
Full-text available
Nickel-based superalloys are widely used at elevated temperature applications because of their high corrosion and oxidation resistance characteristics as well as high stability. To improve the hot corrosion resistance of Nickel-based superalloys, different coatings are applied. In this study, nickel-base superalloy Inconel 738LC was coated via a no...
Article
Full-text available
In this paper, the effect of bonding temperature and time on the microstructure of transient liquid phase bonding of GTD-111 nickel-based superalloy was studied. The bonding process was performed at temperatures of 1080, 1120 and 1160 °C at different times and the microstructure of the various bonding regions was analyzed by light and scanning elec...
Article
Pure nickel and nano-composite nickel-silicon nitride (Si3N4) coatings were fabricated using pulsed current electrodeposition technique. A control sample for each coating was created and the effect of current density, duty cycle, and pulse frequency on the tribological properties of the electrodeposited coatings was investigated by altering these p...
Article
Full-text available
The aim of this survey was an evaluation of the diffusion brazing (DB) bonding properties of the Inconel 625 superalloy using a BNi-3 interlayer. During the inter-diffusion and the dissolution of the alloy elements at the bonding temperature, and also cooling-cycle process, the joining zone (JZ) divided into three sections namely isothermal solidif...
Article
Inconel 738LC (IN-738LC), a nickel-based superalloy, was joined by the transient liquid phase (TLP) bonding method using a BNi-2 filler metal. The bonding process was carried out at 1120 °C under vacuum for 45 and 120 min and was followed by the standard heat treatment (SHT) to homogenize the joints. The microstructures of the specimens were studie...
Conference Paper
Full-text available
The effect of Transient liquid phase (TLP) bonding temperature on microstructural characteristics of Hastelloy X superalloy joints with BNi-2 filler metal was investigated. TLP process at 1055, 1115 and 1175 for 45 minutes of bonding time in a vacuum furnace at a pressure of 1.33 pa by BNi2 filler metal was done. At 1055, the eutectic phases were f...
Article
Nowadays, friction stir spot welding (FSSW) is used in automotive, rail vehicle construction, the aerospace industry, and electrical industry. In the current research, a modified version of the FSSW process entitled friction stir spot vibration welding was introduced to join Al5083 specimens. The joining specimens were vibrated normal to the tool m...
Article
Full-text available
A series of xLiMn1.4Ni0.4Cr0.2O4. (1 − x) Li1.2Mn0.54Ni0.13Co0.13O2, where x = 0, 0.25, 0.5, 0.75, and 1, were synthesized by solid-state method. The cathode composites included x values of 0.25, 0.5, and 0.75 showed both spinel and layered structures. When the amount of spinel component increased in the cathode composite, specific capacity decreas...
Article
In spite of the high capacity of Co3O4 nanomaterial to employ in lithium-ion battery anodes, the reduced conductivity and significant volume change of Co3O4 during long cycling of insertion and extraction of Li ions remain a challenge. Utilization of composite materials making use of graphene-based materials together with Co3O4 nanostructures can o...
Article
Fluorine-doped anatase TiO2 (FATO) is successfully coated with thickness of 4–6 nm on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 particles to improve the electrochemical and thermal properties of the Li-rich cathode via a wet chemical method. The cathode coated by 2 wt% of FATO shows excellent electrochemical performances and high thermal stability....
Article
The effect of bonding time on microstructure and mechanical properties of a transient liquid phase (TLP) bonded Inconel 625 superalloy, using a BNi-2 interlayer, was investigated. The superalloy was kept in a vacuum furnace at a pressure of 10⁻⁵ torr and a temperature of 1025 °C for 35, 65 and 95 min until TLP process occurred. Microstructure analy...
Article
In this work, we synthesized nano plate oxalate precursor via solvothermal method to obtain Nano Sponge Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 (NS-LMNCO) cathode material. During solvothemal process, ethanol and water solvents arrange oxalate nuclei to form plate-like shape. With increasing temperature at calcination step, the oxalate precursor is conv...
Article
Traditional tools in friction stir welding (FSW) of thermoplastics fail to achieve high quality and strong welds. In this paper, a new heat-assisted stationary shoulder FSW tool design, which provides constant tool temperature during the process using a controllable hot air gun, is introduced. Effect of the process parameters, including tool temper...
Article
Despite all achievements to improve nickel-based superalloy, these classes of alloys are still prone to degradation via high-temperature oxidation and hot corrosion. Repairing damaged parts could decrease the life cycle, cost of equipment, and a transient liquid phase (TLP) bonding is a favorable method that has successfully been used for this purp...
Article
In this study, solid state joining technology of friction stir welding (FSW) was carried out for Al and Mg butt joints. To improve the microstructural characteristics of the banded structure zone, before to the FSW process, a Zn interlayer was also inserted in the butt joints. Optimal conditions for friction stir welding were obtained using a combi...
Article
Prior to friction stir welding (FSW), silicon carbide (SiC) nanopowders were placed inside the groove on the adjacent side of magnesium sheet. In order to make a good distribution of these nanoparticles, first, friction stir processing (FSP) with a pinless tool was conducted on this side. Second, using a frustum pin tool, a combination of two trave...
Article
Influences of gap size and cyclic-thermal-shock treatment on the mechanical properties of transient liquid phase (TLP) bonded IN-738LC superalloy were investigated. For this purpose, TLP bonding of IN-738LC superalloy was carried out in a vacuum furnace using powdered AMS 4777 as the filler metal. The results showed that isothermal solidified zone...
Conference Paper
To acquire highly efficient and cost-effective fuel cells, numerous research works have been carried out to the development low cost and excellent performance of electrocatalysts. In this paper, a solution-based electrophoretic deposition (EPD) technique for fabrication of Pt-based catalyst layers is studied. Nanographitic flake coatings used as ca...
Article
Diffusion joining of commercially pure titanium was successfully prepared via transient liquid phase bonding in vacuum environment. The process was carried out using AMS 4772 silver-based filler alloy at 900–1000°C for various holding time under the vacuum of 6 × 10−7 Torr. Optical and scanning electron microscopy equipped with an EDS analyzer was...
Article
Excellent strength, joining effectiveness and low cost of brazing make it one of the most favoured methods for hard metals attachments. In this study, WC-Co, as a hard metal, was furnacebrazed by BAg1 (Ag–Cu–Zn–Cd) filler alloy and Ni-electroplated BAg1, and the influence of Ni-electroplating in joint properties was thoroughly studied. The brazing...
Article
A metal matrix composite made of AZ31 containing SiC nano-particles was successfully produced by friction stir welding (FSW), and the effect of processing parameters such as rotational and transversal speeds on the microstructure (grain size) and mechanical properties (tensile and hardness tests) were investigated. Prior to friction stir welding, n...
Article
Nickel and Nickel-nanodiamond coatings have been successfully electrodeposited on copper substrates by the pulse plating method. The variables investigated within this work include the current density, pulse frequency, bath temperature, duty cycle and nanodiamond concentration of the bath. Pure nickel coatings possess a preferred orientation along...
Article
WC−Co hard metal was furnace brazed by Ag−Cu−Zn+Ni/Mn filler alloy using a tube furnace under high-purity argon at 730 °C. The influence of brazing time and gap size of joints were studied. The results revealed the maximum shear strength of (156±7) MPa for samples with 150 µm gap size at a holding time 15 min. The characterization and microstructur...
Article
In this research work, the effects of pulse electroplating parameters on the microstructure, crystallographic texture and corrosion resistance of electrodeposited nickel−nanodiamond composite coatings are studied. The nickel coatings containing diamond nanoparticles were obtained from an additive-free Watts bath. It was found that increasing duty c...
Article
The effects of applied current density (1–10 A/dm2), pulse frequency (1–100 Hz) and duty cycle (10–75 %) on the morphology and microhardness of Ni and Ni–ZnO coatings, incorporation rate of ZnO nanoparticles, current efficiency and deposition rate were investigated. Ni–ZnO composites exhibited a nodular morphology. At low current densities, smooth...
Article
Nanocrystalline nickel electrodeposits were fabricated from an additive-free Watts bath by pulse current electrodeposition technique. The coatings were obtained at different current densities, duty cycles and pulse frequencies and were characterised using Field Emission Scanning Electron Microscope and X-ray diffraction. The corrosion properties of...
Article
In this article, filling friction stir welding (FFSW) of the remaining exit holes of AA5456 alloy friction-stir-welded lap joints was studied. For this purpose, the influences of different rotating speeds, holding times, and pin materials, AA5456 and AA2024, on the metallurgical structure and joint strength were investigated. The observations showe...
Article
In this study, 6 mm thick AA6061-T6 plates were friction stir welded (FSWed) at different traveling speeds while Al2O3 nano-particles were incorporated between adjoining plates. The solution heat treatment was applied on samples for one hour at 540 ℃ and subsequently aged for 18 h at 180 ℃ to investigate the effect of post-weld heat treatment on me...
Article
The solid-state nature of the friction stir welding (FSW) process leads to several advantages over fusion welding methods as problems associated with cooling from the liquid phase are avoided. This process eliminates many of the defects associated with fusion welding techniques such as shrinkage, solidification cracking and porosity. In general, FS...
Article
Thin films of titanium oxide were obtained by dip-coating, using the sol–gel method. TiO2 powder (Degussa, P25) and polyethylene glycol (PEG) were added to enhance the photocatalytic properties of resulting films. Effects of experimental variables on the photocatalytic properties of the coatings were evaluated based on the degradation efficiency of...
Article
In this research, effect of applying second-pass welding and rotational and travel speeds for second-pass welding on defects and mechanical properties of lap joint were studied. Lap joint of 5456-H321 and 5456-O, with thicknesses of 5 and 2.5 mm, respectively, were made. Specimens were welded using two passes: in the first pass, all specimens were...
Article
Full-text available
Titanium alloys have been extensively used as promising implant materials. The anodic oxide layer on the surface of this alloy can be a compact, porous or a tubular structure, which has a direct impact on the final characteristics of the implants. In this study, nano topographic oxide arrays were synthesized on the surface of titanium substrates us...
Article
In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase (TLP) bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification tim...
Article
Titanium dioxide (TiO2) nanoparticles have been successfully deposited onto acid treated carbon nanotubes via a simple chemical route. It was demonstrated that the CNTs were coated by well-dispersed TiO2 nanoparticles. The CNTs-TiO2 nano composites were characterised by XRD, FTIR, SEM, EDAX and TEM. The photo catalytic activity of the prepared nano...
Article
The effect of particle size of ZrO2in the Nano and micrometer scale on wear behavior of the ARBed composite Al-1%wt.ZrO2, has been investigated in this research. The phase matrix in the composite was aluminum 1050 and zirconia powder has been used as the reinforcing phase. The effect of zirconia particle size, 4µm and 40nm on wear behavior of the...
Article
Welding and joining of magnesium alloys exert a profound effect on magnesium application expansion, especially in ground and air transportations where large-size, complex components are required. Due to specific physical properties of magnesium, its welding requires great control. In general, the solid-state nature of friction stir welding (FSW) pr...
Article
Transient liquid phase (TLP) bonding of Inconel-738 LC superalloy was investigated using AMS 4777 filler alloy. The bonding was performed at 40 and 80. μm gap sizes at sufficient time in order to achieve complete isothermal solidification. Solution treatment (1120. °C/2. h) was carried out in two different sequences, one before and the other after...
Article
Full-text available
Friction stir welding is suitable for joining series 5000 alloys because no fusion welding problems arise for the alloys in this process. The present study examined the effects of double-pass welding and tool rotational and travel speeds for the second-pass welding on the mechanical and microstructural properties of friction stir lap welding of AA5...
Article
Friction stir welding of AA5456 aluminium alloy with different thicknesses was investigated for single- and double-pass lap joint configurations. The influences of tool tilt angle in first and second passes, and rotational and welding speeds in second pass on metallurgical structure and joint strength were studied. The results indicated that tilt a...
Article
In this study, filling friction stir welding was used to remove the exit hole of friction stir welding lap joints made from AA5456 sheets. For this purpose, the exit holes were filled by consumable pins with various geometries and different pin applying methods. Then, the structures and mechanical properties of the resulting joints were investigate...
Article
We report a novel and simple method to prepare high rate performance CuO/graphene nanosheets (GNs) modified LiFePO4 cathode composites (CLFP/G/CuO) via co-precipitation followed by hydrothermal method. Incorporation of CuO into graphene nanosheets greatly enhances the electrical conductivity and electrochemical performance of the LFP/graphene (LFP/G...
Article
Immobilized TiO2 photocatalytic films were produced by the sol-gel method on stainless steel substrates from four different sols. Starting TiO2 solutions were prepared with and without Polyethylene Glycol (PEG) and p-25 nano powder. PEG and p-25 were added to sols to improve the photocatalytic properties and homogeneity of the titanium oxide films....
Article
Dynamic Chemical Plating “DCP” is an alternative for producing metallic deposits on nonconductive materials and can be considered as a modified electroless coating process. This article describes the formation of composite NiB-particle films by the Dynamic Chemical Plating “DCP” technique. The particles used were micrometric graphite (1-2 micron) o...
Article
The dynamic chemical plating technique is used to deposit NiBP coatings with incorporation of PTFE particles. This technique is faster and simpler to perform compared to other electroless deposition techniques. Using a double nozzle gun, metal salt solution and reducing agents are sprayed to the surface, forming a deposit. Using Scanning Electron M...
Article
In this study, friction stir welding (FSW) technique was employed for joining AZ31 magnesium plates. Since SiC particles had been injected along the joint line, AZ31/SiC nano-composite was developed in the stir zone (SZ). To find the optimum condition, FSW was conducted under the combination of three rotational and two traveling speeds. Microstruct...
Conference Paper
The purpose of this study was to investigate the effect of brazing time on mechanical properties and microstructure of tungsten carbide joints brazed with BAg22. Because of this filler dos’t have any active elements like Ti and Nb, the brazing process was carried out using a resistance furnace at a constant brazing temperature of 730ºC. The brazing...
Conference Paper
The purpose of this study was to investigate the effect of Ni electroplating on BAg1a brazing filler, on wettability and mechanical properties of tungsten carbide brazing joints. Ni electroplating has done with Watt’s bath method. Thickness of Ni layer was about 5 micron that is about 3 percent of all filler alloys. Brazing process with BAg1a or Ea...
Article
Undoped and S-doped TiO2 thin films were prepared on titanium substrate through a sol–gel method. The photoelectrochemical behavior of S-doped TiO2 thin film (as photoanode) was studied. The effect of Sulfur doping on structural, optical and morphological properties of TiO2 was studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (X...
Article
Pure Zn and Zn matrix composite coatings containing nano-sized SiC particles with an average size of 50 nm were prepared from the zinc sulphate bath. The effect of the particle concentration and current density on the amount of particles embedded was examined. Electron microscopic studies revealed that the coating morphology was modified by the pre...
Article
Applications for magnesium as the lightest structural metal are increasing; however, its low ductility at room temperature could be considered a limitation. The friction stir process (FSP) is a solid state process that can overcome this limitation by producing a fine-grained material and uniform texture. This study used overlapping passes FSP to cr...
Article
Full-text available
The conical nanostructure improves the applications of alumina membranes and provides three dimensional nanometer scale systems to study the chemical and physical properties. In this study, the nano cone structure is produced in porous anodic alumina (PAA) by two-step anodizing. This conical nanostructure will improve the application of PAA membran...
Article
Pure Zn and Zn matrix composite coatings containing nano-sized SiC particles with an average size of 50 nm were prepared from the zinc sulfate bath. The effects of the pulse frequency, maximum current density and duty cycle on the amount of particles embedded were examined. Electron microscopic studies revealed that the coating morphology was modif...
Article
Friction stir processing, as a method of changing the properties of a metal, through intense, localized plastic deformation, has been developed based on the basic principles of friction stir welding. In the current research, mechanical properties of AZ91 magnesium alloy were modified by the application of friction stir processing. Surface composite...