Journal of Advanced Processes in Materials Engineering
Year:2015 | Volume:9 | Issue:1 (32)|Papers Count:20

Iron-nickel alloy nanoparticles with different Ni contents have attracted much attention because of their outstanding properties; but controlling of these nonoparticles' size and morphology is crucial in their applications. In this study, iron-nickel nonoparticles were synthesized using water/ hexanoll/ CT AB microemulsion system with different water to surfactant molar ratios. Resultant phase was attributed to g-fcc FeNi lattice according to X-ray diffraction pattern. Transmission electron microscopy images showed that nonoparticles had spherical morphology and small size distribution. It was shown that particles' size increased by increasing water to surfactant ratio.

In this project, the boxite was examined to determine its thermal behavior for production of fire-bricks. Some samples were burned at temperatures of 1100, 1200 and 1300 °C for 5 hours. The porosity and density of the samples was determined after burning. The chemical and mineralogical compositions of the raw and burned material was determined by using XRF and XRD, which the constituent minerals of the raw material was diaspore, boehmite, kaollinite and anatase. The burned boxite consisted of mullite, silica, corundum and rutile. TiO2 undergoes a phase transition when heated and expands at high temperatures which may lead to cracks in the fired material. The high porosity of boxite at 1300 °C can be the result of cracks made by expansion of TiO2 or be the result of exit of lattice water of diaspore, boehmite and kaolinite minerals. The presence of about 3% of TiO2 in refractory soil increases the total and average porosity. According to the data resulting of examinations, the best temperature to sintering this boxite is 1200 °C.

In this study, the corrosion behavior of carbon steel API 5L Gr.B and injection rate of an Imidazoline-based inhibitor was investigated in Artificial Seawater. For this purpose, after immersion of samples at open circuit potential for 30 min, Tafel polarization and Electrochemical Impedance Spectroscopy (EIS) measurements were done. Tafel polarization curves showed that the minimum values for corrosion current density achieve at 40 ppm concentration of inhibitor. EIS results expressed that maximum values for polarization resistance achieve at 40 ppm concentration of inhibitor and demonstrated an agreement with the Tafel polarization results. Also, EIS results showed that the best electrical equivalent circuit presents two time constants.

Aluminum nanocomposite powder including of silicon carbide nanoparticles synthesized by mechanical alloying. TEM micrographs showed presence of silicon carbide nanoparticles inside the aluminum nanocrystals. Central tendency of nanocomposite particles such as mode, median, and mean obtained in different milling conditions namely: milling time and milling speed, and balls to powder weight ratio. Maximum and minimum mean particle size in different milling conditions were 62 and 14 micrometer, respectively. Maximum and minimum reduction of mean particle size in different milling conditions were 70 and 8 percent, respectively. Two mathematical modeling 3- parameter Weibull and smallest extreme value were chosen for representation of particle size distribution. Finally, it was distinguished that multiplication of milling time and speed has greater effect on reduction of mean particle size than balls to powder weight ratio.

Hydroxyapatite (HA) can be used as a bioceramic due to its bioactivity and osteoconductive properties. It is clear that the morphology of HA crystal can affect on its specifications such as surface, bioactivity and so on. Because of importance of morphology, in the current research nano sized HA particles were produced using sol-gel and precipitation methods and to change the morphology poly-ethylene glycol (PEG) was used as an organic modifier. The produced samples were characterized using X-ray powder diffraction (XRD) and Scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results of XRD spectrum show that the pure HA can be produced using two methods. Microscopic evaluations prove that the presence of PEG has a significant effect on HA morphology. Indeed PEG changes the morphology of HA produced by precipitation method to irregular whereas in sol-gel method its shape leads toward fibrous with high aspect ratio. The exact reason of this variation can be attributed to the difference at mechanism of HA growth in two methods.

This research was carried out in order to investigate the effect of temperature on the morphology of types of calcareous deposits on the low carbon steel surface in natural seawater under cathodic protection. The results of Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analyzer revealed that with increase in temperature the tendency for vaterite of calcium carbonate precipitate on the surface is increased while the tendency of aragonite and calcites of calcium carbonate formation decreased. The results also showed that at low temperature aragonite is the main deposit.

In the present study, dissimilar welding between Inconel 718 nickel base superalloy and 310S austenitic stainless steel using gas tungsten arc welding process was performed in order to microstructural characterization and weldability assessment of filler metal used. For this purpose, three filler metals including Inconel 625, Inconel 82 and 310 stainless steel were used. After welding, the microstructure of different regions including base and weld metals were metallographically characterized using the optical and scanning electron microscope equipped with energy dispersive spectroscopy. Moreover, to estimate susceptibility to solidification cracking of weld metals, Varestraint tests were used. Microstructural observations showed that solidification conditions have created a dendritic structure for Inconel 625 weld metal. Moreover, microstructure of the 310 weld metal was consisted of solidification micro-cracks that distributed along the solidification sub grain boundaries. Varestraint test also determined that, at all applied strain, Inconel 82 weld metal has the lowest susceptibility to solidification cracking among the weld metals. Finally, by comparing the results obtained, Inconel 82 filler metal was diagnosed the best choice for mentioned dissimilar joint.

In this study, the corrosion behavior of Al-nano ZrO2 nano composites fabricated by Accumulative Roll bonding (ARB) process was investigated. Strips of 1050-aluminum alloy of length 250 mm, width of 40 mm, and thickness of 1 mm annealed at 623K in ambient atmosphere and analytical grade of ZrO2 powder with an average size of 40 nm were used as raw materials. The Al-nano ZrO2 composite was produced in 5 cycles. For electrochemical measurements, the square specimens of 10mm × 10mm × 1mm were cut, connected to copper wires and cold mounted. The open circuit potentials (OCP) of the specimens were measured after 24h immersion in the artificial seawater (3.5wt% NaCl), then electrochemical impedance spectroscopy (EIS) and potentiodynamic test were carried out at a scan rate of 1mV/s.The results of potentiodynamic tests indicated that when rolling cycles increase, the corrosion current densities decrease. The results of EIS were also indicative that the increase in rolling cycles increases the polarization resistant (Rp), SEM image of cycles 1, 3, and 5 represents the uniform distribution of ZrO2 particles in aluminum matrix by increasing the rolling cycles.So one can conclude that the corrosion resistant of this composite was promoted because the thickness and uniformity of the oxide layer were increased by the increase in the rolling cycles. This denser oxide layer is as a result of uniform distribution of nano ZrO2 particles in the matrix and helps to increase the corrosion resistant of the composite.

In this study, zirconia coatings have been prepared by atmospheric plasma spraying under different parameters in air on mild carbon steel substrates. The effects of spraying parameters; powder feed rate and spraying distance (SD), on Microstructure of 8wt%Y2O3-rZrO2 (YSZ) coatings were studied. Measurements were made on specimens in the as- sprayed state. The microstructures of coatings were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). Phase analyses of the YSZ powder/coatings were examined by X-ray diffractometer (Rigaku, Tokyo, Japan) operating with Cu Ka and the size and amount of their porosity were evaluated using an Image Analysis method. The results showed by varying spray distance/ powder feed rate, significant changes were detected in the microstructure of the top coat. The total porosity, pore morphology and unmelted particles are correlated with the powder feed rate and spray distance. Also, It was found that the powder feed rate has a larger effect on the coating microstructure than the spray distance in the conditions investigated.

This study is an attempt to understand the influence of natural nano crystalline hydroxyapatite in microstructure and mechanical properties of Sorel cement. To study the morphology and microstructure of cement containing nano crystalline hydroxyapatite, scanning electron microscopy (SEM) was used. Phase analysis of the samples were evaluated by XRD technique and the hydroxyapatite phase was confirmed in Sorel cement. The compressive strength test was used to measure the compressive strength of the sample. The results showed that the addition of nano crystalline hydroxyapatite in amounts of 15% by weight of cement increased compressive strength in Sorel cement.

In this study, aluminum matrix nanocomposites reinforced with 0, 0.25, 0.5, 0.75 and 1.0 weight percentages of silicon dioxide nanoparticles were fabricated using ultrasonic and stir casting techniques. In the following, fabricated nanocomposites were transformed in to the foam by direct foaming melt method using 1 wt% of titanium hydride foaming agent and then compression tests were conducted on manufactured foams at a strain rate of 3×10-3 s-1. structural studies indicated that foams reinforced with 0.5 wt% and 0.75 wt% of SiO2 nanoparticles show the best structures. Investigation of stress-strain compression curves showed that plateau stress increases with increasing relative density but for increasing energy absorption capacity, cellular structures need to be improved in addition to increasing the relative density.

Among the hard coatings, TiN and TiCN, due to their superior hardness, high wear resistance and low friction coefficients could enhance the lifetime of the tools, in some cases, more than ten times.The microstructure, hardness and tribological properties of TiN and TiCN are significantly related to method of coating. Until now, no scientific work has been done on TiN, TiCN and TiN-TiCN-TiN coatings, deposited by EB- PVD technique. In this research, after conventional heat treatment of D2 tool steel, the coating process was done on as polished substrates. Then, using SEM and AFM microspores, XRD and ball on disk exams, microstructure, hardness and theological behavior of the samples were investigated.From X-ray diffraction data using the Scherrer equation was determined that the EB-PVD coatings with 2-3 mn thickness had microstructures with the grain size in the range of 5 to 6 nm. The results of nanoindenter tests and wear experiments clarified that TiCN and TiN had the highest and lowest hardness and wear resistance, respectively. Also, Using the AFM images and roughness curves obtained that the roughness of the coatings were 12, 22 and 29 nanometer for TiN, TiCN and TiN- TiCN- TiN coatings, respectively.

Castable alumina spinel refractories have more resistance to the molten and slagear than refractory bricks. So these kind of material are gradually replacing with these bricks in the industrial application, specially in the industry of steels. In this paper, the effect of spinel-cement on properties of the castable alumina spinel has been studied at 110, 700, 800, 1000, 1400 °C and 1500°C. The castable alumina spinel was made by mixing the aggregate alumina tabular with spinel-cement, including alumina calcined and dolomite. Properties such as cold crushing strength (C.C.S), density, phase analysis (by X.R.D), microstructure (by SEM), have been investigated. Finally the resulted data of these kind of materials were compared with those of cement sekar. Results showed that the spinel cement which was sintered at 1650 °C Contained MA and CA phased futher more. By increasing the sintering temperature the amount of CA2 and MA phases has been increased while the amount of Al203 phases has been decreased on the other hand the sintering temperature leaded to rising the crystalline size of spinel and falling the lattice constant. The castable mass has a higher compressive strength with increasing temperature due to the formation of spinel. The highest density and lowest porosity at 1000 °C has been observed that the reasons can be pointed out L O I. and pointed out hydrate water. The porosity is increased with increasing higher spinel phase at 1500 °C.

Hexafluorozirconic acid (H2ZrF6) based conversion coating has been presented as a novel and environmentally friendly pretreatment to repleace phosphating. Recently, modifing hexafluorozirconic acid-based treatments with various nano particles, ions and chemical compounds have been expanded. In this study, effect of sodium dodecyl sulfate (SDS) presence on the morphology and corrosion resistance of NanoZirconia-based conversion coating on galvanized steel sheet was investigated. The results of scanning electron microscope (SEM) showed that, unlike the SDS positive influence on the quality of phosphate coatings, theis additive has a negative effect on the NanoZirconia- coated surfaces. The results of salt spray and polarization tests also confrrmed same resulst about negative influence of SDS additive on the anticorrosive properties.

In this study, in order to increase surface area of zinc oxide as a catalyst, ZnO impregnated to Alumina-Silica matrix using simultaneous reaction of zinc nitrate, tetraethyl orthosilicate, zinc oxide and aluminum nitrate by Sol-gel method. Values of 20, 30, 40, 50, 70 and 100 weight percents of zinc oxide with an equal weight ratio of SiO2-Al2O3 were mixed to achieve the desired composite. The characterizations of nano-structural composites were investigated by X-ray diffraction, FESEM/ EDS and BET studies. The results showed that crystalline ZnO in Alumina-Silica matrix has been formed and dispersed in this matrix caused to reduction in growth of ZnO, prevention of agglomeration and increasing of area surface of composites. Performance of these composites with ZnO as a photocatalyst was evaluated in degradation and adsorption of methyl orange as a textile dyes model.

In this research, thermal expansion behavior of aluminum-matrix composites reinforced by SiC particles up to 500°C was investigated. For this purpose, thermal analysis equipments were utilized. The main objective is to explain thermal expansion behavior of aluminum-matrix composites reinforced by different percentages of SiC alongside the effect of reinforcement particles on thermal behavior of these materials that are used as base materials in electronic industries. Composites with different percentages of reinforcement (containing 10, 15, 20, and 25%) and different meshes (45, 100, and 150 m) of SiC reinforcement particles and Al-4%Cu alloy matrix were prepared by powder metallurgy. Instant coefficient of thermal expansion which is a function of temperature was compared based on Turner's model and Shapry model with predictions from thennoelastic models. Thermal expansion behavior depends on various parameters such as microstructure, matrix deformation, and internal stresses. Dependence of copper-in- aluminum solution on temperature has a significant effect on thermal expansion coefficient of Al-4%Cu alloy matrix and hence thennal behavior of the composite. Results of the experiments performed on the composites reveal that with increase of percentage of silisium carbide ceramic particles, the amount of thermal expansion coefficient decreases.

Petrography, XRD and DTA- TG studies indicate that serpentine decomposition to forsterite in high temperature. Serpentine has been expanded in Iranian ophiolitic rocks. Testing Iranian ophiolitic rocks shows that forsterite has been produced from heating of serpentine in 600 °C. Therefore it facilitates the usage of serpentinic rocks as primary material in refractory industry. The test results show that, Dehydration reactions on serpentine started at approximately between 100 to 150 °C and dehydroxilation reactions started at approximately 550-700°C. As a result of thermal reaction the decomposition of serpentine will take place and then changing in to olivine (forsterite). Crystallization of olivine (forsterite) will start at 600 °C.

In this article the effect of temperature and time of addition of boron carbide on properties and microstructure of Al- B4C nano composite is investigated. 3 vol.% B4C particles with 300 nm average grain size added to melted Al-356 alloy. The compound casted at 750°C, 850 °C and 950°C temperatures and 10, 15 and 20 minutes in a metal mold. The results represent an increase in tensile strength at composite samples compared to matrix. Maximum amount of tensile strength was 178 MPa is achieved after 15 minutes mixing at 850°C that is increased 72 percent compared to metal matrix (Al). Also the effect of temperature and time of mixing on type of fracture showed that brittle fracture was occurred in all nano composite samples and the most ductile fracture surface is belong to the samples were produced in 15 minutes mixing and 850°C. These samples have maximum value of tensile strength.

Nowadays, ZnO nanorods have attracted much attention due to their various applications in different industries as solar cells, light-emitting diodes, catalysts, gas sensors, varieties of nanosensors and superhydrophobic surfaces. In this research, at first a thin film of ZnO with 50, 150, and 300 nm thicknesses was coated on sodalime glass by sol-gel method via spin coating at 4000rpm. After annealing the substrates at 300°C, ZnO nanorods were grown on the substrates by hydrothermal method in the solution composed of hexahydrate zincnitrate and ammonium for 2 hours. SEM studies were performed in order to investigate morphology (diameter and length) of nanorods. For phase analysis x-ray diffraction (XRD) was used. For studying hydrohpbicity and contact angle measurements (CA), hydrophobicity test was carried out. AFM test was performed for topography of seed layer surface. Results revealed that with increase of seed layer thickness from 50 nm to 300 nm the alignment of nanorods synthesized on the seed layers has decreased and average diameter of nanorods has increased from 55 nm to 90 nm. Also, the results obtained from contact angle instrument showed that nanorods synthesized on the seed layer with 50 nm thickness have larger contact angle (145.9°), compared to those synthesized on 300 nm-thick seed layer with the smallest contact angle (135.4°).