Sharif Digital Repository

This research aims to introduce a nanocatalyst based on open-cell nickel foam (NiFm) with 40 pore per inch(ppi) to save energy during methane steam reforming (MSR), an endothermic reaction, by increasing catalyst thermal properties with improved progressive compression strength. The nanocatalyst is synthesized with a chemical stepwise synthesis approach, thermal-chemical pretreatment, pulsed electrocodeposition of Ni-Al2O3 (γ) nanoparticles, and calcination. Herein, a polyurethane (PU) nonconductive substrate is transformed to nickel foam by using replication sponge method. The purchased PU became conductive by nickel electroless bath using sodium hypophosphite with 5-15 (µm) thickness... 

Adding solid lubricant particles such as PTFE, Graphite and MoS2, has major influence on electroless composite nickel coatings in order to make low friction surfaces. Among these lubricants, MoS2 has attracted great attention due to its highest stability under wearing condition. In this work Ni-P-MoS2 composite coatings using MoS2 nano-particles have been made and in the next step, we evaluated tribological properties of these coatings. For exploring these coatings different experiments were utilized, like Scanning Electron Microscope study (SEM), chemical composition analysis exploiting AAS and XRF method, and thickness measurements. Two kinds of surfactants, CTAB and PVP, have been applied... 

Well worn gas turbine blade made of Nickel based superalloy, IN738LC was remelted due to remove inclusion and use it in casting process of new blade after microstrucrure investigation in neutral atmosphere and vacuum. The composition of slags for removing inclusions used for this practice were 70CaF2-20CaO-10Al2O3 and 55CaO-45Al2O3. The microstructural characterization involved use both optical as well as electron microscope including application of EDS technique for denoted the type of carbides and inclusion investigation. Chemical composition was determined by despersive spectroscopy method. The changing in main elements were reported too low. Number of inclusions were decreased in the... 

In this study solid lubricants MoS2 nanoparticles with average size 50 nm and hard ZrO2 nanoparticles with average size 51 nm were used in watts bath and Ni/ZrO2-MoS2 composite coatings were prepared by pulse plating technique. Effect of current density, frequency, duty cycle, surfactant type and concentration of particles in the electrolyte on the amount of particles in the coatings were investigated and optimum conditions were determined to create composite coatings. Scanning Electron Microscopy (SEM) and x-ray diffraction (XRD) analysis were performed to study the morphology, structure, chemical composition of coatings. Corrosion testing of coatings by potentiodynamic polarization in... 

Superalloys are widely used in aerospace and power industries due to the good performance at high temperatures for examples gas turbines, steam turbines and aircraft components. In addition to the turbines cobalt-base superalloys are used in medical implants such as knee and hip joints. The main strengths of the superalloys are heat-resistant, retaining their high mechanical and chemical properties at high temperatures, high melting temperatures, high corrosion resistance, resistance to thermal fatigue, thermal shock, creep, and erosion. Because of difficult to machine properties of superalloys, grinding is one of the effective methods for machining superalloys. The surface integrity of the... 

Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation called “Grain”. As the grain size reduces to the values below 100nm, the overall material properties are remarkably changed, and thus the resulting nanocrystalline materials have provided much better engineering properties at the same chemical composition compared to the microcrystalline. The main objective of the present study is to synthesize a nanocrystalline (22nm-25nm) coating based on Nickel over the yellow-brass plates. To do this, an electroplating technique in a modified Watts bath is employed in which the current density and stirring speed varied between 3 to 9.5 Ampere per... 

Transient liquid phase (TLP) bonding of 316L/17-4PH bimetals using a thin layer of nanostructured nickel was studied. The nanostructured nickel interface was deposited through pulse current coating in a Watt bath. The TLP bonding was performed at different temperatures ranging from 1000 °C to 1300 °C using a nickel interface having different thicknesses (2-17µm) and crystallite size (14-67 nm). The microstructure of the joint bimetals and phase formation were studied using the optical and scanning electron microscopes and X-ray diffraction (XRD) method. The mechanical properties of the bimetals were evaluated by micro-hardness and shear tests. To evaluate the corrosion behavior of the... 

NiTi intermetallic is well known for its unique physical and mechanical properties, such as superelasticity, shape memory effect, good tribological properties, excellent corrosion resistance and biocompatibility. It is widely used in several areas including aerospace and medical applications and surface engineering. Several approaches, such as casting, powder metallurgy, self-propagating high-temperature synthesis, mechanical alloying and explosive shock-wave compression have been used to produce NiTi alloys. However the formation of the undesirable phases such as NiTi2 and Ni3Ti still is the biggest concern. According to Ni-Ti phase diagram, stability region of NiTi compound is at... 

The purpose of this project is to survey the created kind of inclusion in super alloyed based nickel. primarily, for this matter for the preparing of super alloyed based nickel, the vacuum induction melting furnace has been designed and built , then for surveying the kind of inclusion the effective parameters such as temperature , timing and material of crucible has been considered accordingly , the material of crucibles was considered based on mud-clay- graphitic- pure graphitic- aluminum- zirconium. From the obtained analysis samples of SEM has been distinguished which, with increasing of the temperature and the time ,the percentage of impurity will go up in super- alloyed and the... 

The current work is carried out to characterize welding of AISI 304 Austenitic Stainless Steel to Ductile Cast Iron. The welding method was SMAW and the welds were produced using a Nickel-Buttering by a pure Nickel electrode(ENi1) on Cast Iron side, then by 4 types of filler materials the joints were produced; Ni-base electrode(Ni1), E308 and E309 Austenitic stainless steel electrodes and E7018 electrode. The preheat temperature of Cast Iron has been selected to be 250○ and 500 ○C to avoid crack of weldments. The comparative evaluation was based on metallography, chemical composition, hardness and corrosion behavior on two different preheat temperatures. According to metallography, the best... 

Synthesis gas is a gaseous mixture which mainly consists of carbon monoxide and hydrogen. Different methods are used to produce synthesis gas but the most important method is auto thermal reforming. This method is based upon catalytic reactions. Steam, oxygen and natural gas are the influents to the reactor and synthesis gas will be the effluent. Ni catalysts on alpha-alumina as the support media are usually used in this process. These catalysts are highly heat resistant and insure great qualifications for reactions. This thesis tries to find best solutions of synthesis gas production suitable for feeding to a methanol production unit. There are four main reactions. Three of which are highly... 

The purpose of this investigation was to study the microstructure of the Inconel718 alloy wich was produced by VAR and suction casting method, and study the effect of cooling rate on the solidification structure of Inconel718 alloy. In the first a labratoary scale VAR furnace was made. After producing some sample's with this furnace, a suction casting sample was produced using a 3mm diameter copper mold. Metallography, SEM, EDS, and microhardness analysis was carried away. Cooling rate evaluation was done by using a equation between secondary dendrite arm spacing and solidification time. Results showed that by increasing cooling rate from 63 c/s to around 2000 c/s, columnar and equiaxed... 

Electrodeposition of composite coatings containing nano particles is very important because this technique is simple and economic. In this research, in order to produce a coating with high hardness and wear resistance, Ni-Co/WC nano composite was co-deposited. Watt’s based bath containing cobalt and tungsten carbide was used and parameters such as preparation of solution, concentration of ingredients and current density were controlled and adjusted. Surface morphology, microstructure and mechanical properties of coatings were studied by SEM and AFM microscopes. Mechanism of electrodeposition was investigated by cyclic voltametry, cronoamperometry and cronopotentiometry techniques and... 

A study of the electro-oxidation and surface reactions of C1 compounds on Ni and Cu electrodes, Ni(111) and Cu (111) has been performed by methods of cyclic voltammetry, BOC-MP and DFT. The diffusion coefficients and activation energies of the electro-oxidation of methanol and formaldehyde in alkaline solution on Ni electrode have been derived. Values around 2.27×10-6 cm2s-1, 1.98×10-5cm2s-1, 12.15 Kcal mol-1 and 11.65 Kcal mol-1 have been obtained respectively. In theoretical study , the elimination of hydrogen from CH3 and CH2 groups has been proposed as a mechanism in surface reactions of methanol and formaldehyde on Ni(111) ... 

In this project, TiO2 nanoparticles were prepared by the sol gel method. The band gap of TiO2 was modified with transition metal ions Pt, Pd, Ni. The kinetics and photocatalytic degradation of AB92 investigated. The effect of some parameters such as pH and amount of photocatalysis and calcination tempreture were examined. Also effect of transition metal increase on surface morphology and photocatalytic activity were investigated by XRD, BET, SEM, DRS and FT-IR Techniques. Dyes are an abundant class of colored organic compounds that represent and increasing environmental danger. Azo dyes are well-known carcinogenic organic substances. Advanced oxidation processes (AOPs) have been proposed as... 

In this project, nonocrystalline nickel coatings with grain sizes within the range of 9-27 nanometers were produced on yellow-brass plates by electroplating in a modified Watts bath applying current densities from 2 to 6 A/dm2 and bath stirring speeds from 0 to 400 rpm. To determine crystallite size, X-ray diffraction technique (XRD) was utilized; it was observed that grain size declined continuously with increase in current density and then in bath stirring speed. The experimental results coming from XRD tests were compared with a theoretical model in order to verify their reliability; the obtained curve indicated a good correspondence between the experimental data and the theoretical... 

In this research, for optimization of repair welding of control valve and flange that use in East Oil& Gas Company, effect of chemical composition, microstructure, hardness and stress relive on sulfide stress cracking (SSC) investigated with select of four electrodes. All welds were prepared by shielded metal arc welding (SMAW) and investigated with optical microscope, hardness test, tensile test and SSC test. The results showed that increase of nickel content in the range of 0.032–1.58 wt. % in weld metals, decrease of acicular ferrite and increase of side plate ferrite, grain boundary ferrite and M/A micro constituent in microstructure. Ni3S2 decrease SSC resistance and (FeCu).S increase... 

Syntheses of coats including nickel nano-particles by electrodeposition have been
investigated for over 10 years. A method of testing according to surface reply was chosen
to reveal the effect of each pulse parameters (including duty cycle, frequency, average
current density, off time (toff) and on time (ton)) and the effect of saccharin concentration
on electroplating cathode efficiency, nanostructure. Pulse electroplating test of nickel was
composed by 30 tests. Pulse electroplating with relatively high peak current density was
employed and saccharine was added to increase deposition and rate of nickel nucleation on
surface. According to the results of cathode... 

Joining of yttria-stabilized zirconia (YSZ) to stainless steel (SS) is considered for various applications such as solid oxide fuel cells, thermal barrier coatings, and medical implants. In the present work, a series of brazing pastes utilizing silver and nickel nanoparticles (~80 nm) mixed with carboxymethyl cellulose as the organic phase were developed to join 5YSZ to 420 SS. The effects of processing parameters such as time and temperature of brazing and the composition of the paste on the microstructure of the joint and its mechanical strength were studied. The mechanism of interface formation was elaborated by scanning electron microscopy (SEM) and electron probe micro analyzer (EPMA).... 

Stainless steels have many applications in different industries. Therefore, it was always a main concern to find an appropriate joining method for using these materials in complex structures. In the present investigation, AISI 304 stainless steel was successfully joined by transient liquid phase (TLP) bonding, using a MBF-30 interlayer. The joining process was carried out at 1150 ℃ temperature and for different bonding times. Also joints with complete isothermal solidification were homogenized at 950 ℃ for different holding times. Microstructure and compositional changes of the joints were studied using optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive...