Journal of advanced materials and processing
Volume:2 Issue: 3, Summer 2014

The aim of the present work is to study the effects of the nanostructured WC-20 wt. % (Fe,Co) with different ratios of iron to cobalt on the microstructure and hardness of sintered samples. Furthermore, a sample with a cobalt binder under the same condition was produced for the comparison purposes. The nanocomposite development, after different milling times, has been monitored by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A homogenous distribution of nanostructured WC (crystallite size less than 30 nm) in the binder matrix was formed after 25 h milling. The hardness and the relative density of the WC-20wt. % (Fe,Co) composites consolidated by conventional sintering at 1350˚C were investigated. In sintered samples after 25 h milling, tungsten carbide grains have a uniform distribution with a lower grain size. Densification and hardness improved after 25 h milling and reached optimum levels for the 25 h milled powders with equal ratio of iron to cobalt.

The 70SiO2-15TiO2-15ZrO2 membrane was prepared by a sol-gel procedure. The corrosion behavior of microporous toplayers along with the membrane characterization in terms of pore size, surface area, pore volume and weight loss is described. The final ceramic membrane with a thickness of 400 nm and uniform surface was obtained. This membrane confirmed the fine microporous characteristic with mean pore size < 2 nm. After corrosion test, the corroded membrane revealed a surface with non-uniform coverage of the toplayer. The heated ceramic membrane after and before corrosion test was amorphous. Dissolution of ions was increased in acidic and basic solutions. The weight less of samples increased when pH increased at RT. Porosity of samples increased after the corrosion test. The pore size of membrane increased as compared to the pore size of the original membrane after corrosion conditions. Surface area of the membrane increased in basic solution whereas decreased in acidic solution.

The inhibition effect of N-(8-bromo-3H-phenoxazin-3-ylidene)-N,N’-dimethylaminium (DPhDMA) on the corrosion behavior of mild steel in 1.0 M HCl solution has been studied. Weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemical calculations were used in this study. Electrochemical results revealed that DPhDMA is an effective mixed type inhibitor for mild steel in 1.0 M HCl solution, and its inhibition efficiency increased with increasing its concentration and with the immersion time of the samples in the corrosive media. The adsorption of DPhDMA also led to a reduction in electric double layer capacitance and an increase in charge transfer resistance confirming its inhibitive effect on the corrosion behavior of mild steel samples. The thermodynamic parameters governing the adsorption process showed that DPhDMA was adsorbed spontaneously on mild steel surface through a combination of physical and chemical mechanisms following Langmuir adsorption isotherm. Quantum chemical calculations were used to correlate the performance of DPhDMA with its electronic structural parameters.

Using the Frobenius series method (FSM), an analytical solution is developed to obtain mechanical stresses of thick spherical pressure vessels made of functionally graded materials (FGMs). The cylinder pressure vessel is subjected to uniform internal pressure. The modulus of elasticity is graded along the radial direction according to power functions of the radial direction. It is assumed that Poisson’s ratio is constant across the cylinder thickness. Primarily, displacements and stresses is obtained as closed-form solutions. Next, the profiles are plotted for different values of inhomogeneity constant along the radial direction. Finally, the problem was solved, using the finite element method (FEM). The obtained results of finite element method were compared with those of the analytical method. The analytical solutions and the solutions carried out through the FEM show good agreement. The values used in this study are arbitrary chosen to demonstrate the effect of inhomogeneity on displacements, and stresses distributions.

Amorphous alloys has been taken into consideration because of their unique properties and are nominated as the future engineering materials. In this research, the effect of Ni and milling time on amorphization process and thermal stability of Ti50Cu50-xNix(x=10, 15, 25 at%) alloy system were investigated. The evolution of amorphization during milling, thermal stability and subsequent heat treatment were evaluated by x-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results showed that alloys reached to the highest content of amorphous phase in Ti50Cu40Ni10, Ti50Cu15Ni35 and Ti50Cu25Ni25 alloy compounds after 60, 40 and 10 hours respectively. Differential scanning calorimetry showed thermal stability of amorphous alloy, exhibiting a distinct glass transition and crystallization temperature and a wide supercooled liquid region for Ti50Cu25Ni25 powder alloy with a value about 45 k. Heating Ti50Cu25Ni25 amorphous alloy at 943 k for 10 min results in the formation of intermetallics such as CuTi and NiTi2 phases. In addition, mechanical properties of amorphous powders were studied by Vickers microhardness test. The alloy with 25 percent Ni showed The high value of hardness about 884 Hv after 40 hours milling.

The application of Fe–TiO2 photocatalysis using sol–gel method by hot–dipping technique was investigated. Then, the influences of fabrication parameters, molar ratios of Fe to TiO2, the sol temperature, poly ethylene glycol (PEG) content and the number of dipping cycles on the photocatalytic activity in visible light region were mainly studied. The experimental results revealed the sample with the molar ratios of Fe to TiO2: 0.015, the sol temperature: 70 °C, PEG content: 2 wt. % and the number of dipping cycles: 5 showed the best result. The photodegradation efficiency of this sample after 2 h visible light irradiation increased up to 80% and no crack was detected on the surface of the thin film. When the sol temperature increased from 25 to 70 ºC (the boiling point of the sol), its viscosity increased due to the existence of PEG via forming cross linkage. This phenomenon caused to change the microstructure and improve in optical properties.

Nanocrystalline magnesium hydride powder was synthesized by mechanical milling of MgH2 in a planetary ball mill for various times. The effect of MgH2 structure, i.e. crystallite size, lattice strain, particle size and specific surface area on the hydrogen desorption properties was investigated. A single peak of hydrogen desorption was observed for as-received powder, exhibiting an average particle size of 30 µm. In contrast, all milled powders with much reduced particle size exhibited desorption peak doublet in DTA. It was shown that the dehydrogenation temperature of MgH2 decreased from 421 ºC to 319 ºC after 30 h mechanical milling. Here, the average crystallite size, specific surface area and accumulated lattice strain were 18 nm, 9.3 m2/g and 0.7%, respectively. There was no significant difference on the onset temperature of dehydrogenation between powders milled in different times. However, the amount of hydrogen release was decreased, i.e. from 5.9 wt.% to 4 wt.% with increasing the milling time from 5 h to 30 h.

A considerable amount of mill scale is generated from steelmaking plants annually. Although some industries use it as raw material however, since it contains iron in the form of FeO, Fe2O3, and Fe3O4, it can be considered as a valuable metallurgical raw material for iron and steelmaking industry as well. Thus, the aim of this study was to evaluate the possibility, efficiency, and consequences of the reduction of mill scale in the electric arc furnace. Accordingly, different portions of mill scale were charged into electric arc furnace (with two different charging methods) and the results were compared with reference heats. Results revealed that charging mill scale into electric arc furnace decreases oxygen and carbon powder consumptions while negatively influences on production time, energy and coke consumptions, and slag composition. Moreover, reduction rate evaluations based on tapping weight and oxygen consumption showed that almost %13 of mill scale is reduced in electric arc furnace.