JOURNAL OF ADVANCED MATERIALS AND TECHNOLOGIES
Year:2015 | Volume:4 | Issue:2|Papers Count:8

Zinc-Tin alloy coatings have many applications because of their unique properties such as corrosion resistance, solder ability, and flexibility. In this study, the effect of current density and temperature on the cathodic current and structures of the coatings was investigated. Structure of the coatings obtained was evaluated via Scanning Electron Microscope (SEM) equipped with Energy Dispersive Analysis (EDS). The experimental results showed that increasing the current density to 4 mA/cm2, result in decreasing the particle size and increasing the cathodic current efficiency. Then, by incrementing the current density to 10 mA/cm2, the reduction of the cathodic current efficiency was observed also with incrementing temperature the coating morphology became coarser grains and the content of zinc decreased. The result of hardness testing revealed that increasing zinc ion to the 72 wt.% Zinc-tin alloy coating has the highest value of hardness.

Lead free piezoceramics of the (K0.44Na0.52Li0.04)(Ta0.1Sb0.06Nb0.84)O3 specimens were prepared using the conventional ceramic and aqueous colloidal coating approach. The microstructure and dielectric properties of sintered samples prepared by both techniques were investigated for comparison. The XRD patterns indicate the formation of pure perovskite phase for samples prepared by colloidal technique. An additional impurity phase with tungsten bronze structure was detected for samples synthesized by the conventional method. For both methods, the typical cube-like morphology of KNN-LST systems with the bimodal distribution was clearly observed. The relative permittivity and loss factor of samples synthesized by aqueous colloidal coating approach were higher and lower than those obtained by conventional ceramic technique, respectively.

Corrosion behavior of 1.4361 high Si-alloyed austenitic stainless steel in red fuming nitric acid (RFNA) was compared with 316 SS by using linear and cyclic potentiodynamic polarization techniques, immersion corrosion test method and SEM observations. In addition, the inhibition effect of different concentrations of hydrofluoric acid (HF) on the corrosion behavior of the alloys was studied. The results obtained from electrochemical measurements, immersion test and SEM observations are in good agreement and indicate that HF is a good inhibitor against uniform and intergranular corrosion. A high initial corrosion rate of 16.77 mpy was observed in absence of inhibitor, which was decreased to 0.24 mpy with addition of 0.6 wt% HF. Moreover, pitting potential at the same condition increases from 1.57 to 2.31 V (vs. Ag/AgCl), indicating to improve the localized corrosion resistance with addition of HF inhibitor. Also, it is indicated that the Si alloying element, on one hand, leads to increase the intergranular corrosion resistance and, on the other hand, leads to reduce the general corrosion resistance. An initial corrosion rate of 1.18 mpy was obtained for the 316 SS, lower than that of the 1.4361 Si-alloyed SS.

Principally, mineral processing and beneficiation process on some placer mines can be considered from two points of view i.e. technical and economical aspects. Although, co-extraction of some strategic elements with high added value is conceivable, utilizing of these type of mines is also possible as raw material and feed in ferrous and non-ferrous metal industry. In this research, feasibility study of placer mine beneficiation for co- extraction of strategic elements and Iron has been investigated. Firstly, mineralogy, chemical properties and physical properties of samples have been studied via different characterization methods such as: screening, XRD, XRF, OM and EPMA analysis. Furthermore an appropriate process has been designed by using the gravity separation, ball mill grinding and magnetite separation in order to achieve suitable fineness for iron, titanium and vanadium concentrates. The designed process is capable of producing the ore concentrate with approximate 57 wt% Iron,  8wt% TiO2 and 0.8 wt% V2O5. The outcome of the aforementioned process is valuable since it has been shown in the literature that the extraction of vanadium can be completed by leaching process with hot water and separation of titanium can be achieved during the melting process of iron from the slag.

The corrosion and corrosion inhibition of CK10 carbon steel in CO2-saturated 3% NaCl solution by anise extract (AE) dissolved in ethylene glycol (EG) was studied using polarization curves, electrochemical impedance spectroscopy (EIS) and surface analysis (AFM) methods. Inhibition efficiency increased with increase in AE concentration and temperature. The data suggest that AE functioned as inhibitor via a mixed-inhibitor mechanism and the inhibition process is attributed to the formation of a chemically adsorbed film of AE and EG on the surface of the metal via its polycentric adsorption sites. Thermodynamic adsorption parameters of studied inhibitor were calculated using the Langmuir adsorption Isotherm. Morphological studies of the carbon steel electrode surface were undertaken by atomic force microscopy (AFM).

TaN-(Ag/Au) nanocomposite thin film was deposited on stainless steel (type 316) substrates by cylindrical DC Cosputtering technique. Samples were annealed at 400oC for different times 3, 5 and 7 minutes. Surface topography, crystalline structure, surface morphology and contact angle measurement of the prepared films were analyzed by using atomic force microscopy (AFM), X-ray diffractometry (XRD) and scanning electron microscopy (SEM) techniques, respectively. Antibacterial activity was measured by using Staphylococcus aurous bacteria at 1, 3 and 6 hours incubation times. The average size of nanoparticles measured less than 40 nm. The average size of particles and contact angle property could be controlled by annealing time and temperature. Results showed that the TaN- (Ag/Au) thin film is hydrophobic (its contact angle is more than 90 degree), so it can decrease the bacteria adhesion to the surface of the samples.

The St37 steel has low hardness and low wear resistance. The purpose of this study is improvement of tribology properties this steel by formation of a composite layer containing alumina particles by GTAW welding method. To do this, the steel surface with 10% volume of alumina particles at three different currents of 90, 110 and 130 Amper with this method was covered. Reciprocating wear test, for wear resistance of the samples was carried out and their wear surfaces were examined by scanning electron microscopy. The results show that the coating of this process is having freeze-dendritic structure containing the alumina particles. The presence of these particles with reducing heat input cause increasing hardness and improvement wear behavior of the coatings. The range of increasing hardness the coatings made between 225 to 332 Vickers was measured and the amount hardness of the uncoated sample is about 180 Vickers. The results of the wear behavior of the coatings represent a significant improvement in their wear behavior in presence of the alumina reinforce with reducing heat input. The main mechanism of wear in the uncoated sample and the coated samples is adhesive wear.

In this research, elemental powder mixture of pure tungsten and copper powders was prepared after 1 hr of mixing, and pressed under a load of 500 MPa. Samples from the pressed mixture were liquid phase sintered in a furnace under pure hydrogen atmosphere at different temperatures (1150-1200-1300-1400oC) for 2 hrs. Structure, grain size, density, hardness and strength of produced samples after sintering were studied in different temperatures. Results showed that increasing in temperature up to 1300oC results in increasing in density, hardness and strength. However, at 1400oC due to extensive number of voids among tungsten particles, these properties were found to decrease. The microstructure was associated with wide and deep holes.