Journal of advanced materials and processing
Volume:4 Issue: 4, Autumn 2016

Having sufficient and accurate understanding about kinetics of phenomena, could be an important reason for further technological progresses. Finding a white-box mathematical model for weight vs. time curves of Electrophoretic Deposition (EPD) using large and small signal analysis has been studied thoroughly in the present investigation. Weight-Time curves of nano-Mullite suspension have been trained using Simulink modeling tool. Results of the investigation illustrate that, the frequency of particles i.e. the probability of particles for collision to another ones, is decreased due to reduction of the concentration of particles in suspension. When the solid load becomes higher close to the electrode surface, the mobility of individual particle will be restricted and a collective pressure onto the particles closer to the electrode surface is supposed to develop. The accumulated particles will be forced to flocculate and form a solid packing structure. According to results of modeling, times before flocculation is suitable for deposition of highly dense coating.

Co-precipitation procedure was applied in order to obtain different kinds of magnetic nanoadsobents for the removal of Pb(II) and Cu(II) toxic metal ions from wastewater samples. Prepared nanoadsorbents were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The average sizes of these nanoparticles were found to be about 15 to 35 nm. Adsorption studies of heavy metal ions were carried out by batch experiments. pH, temperature, contact time and adsorbent dose were studied as the factors that effecting the adsorption of heavy metal ions on the surface of magnetic nanoadsorbents. The optimized values for pH, temperature, contact time and adsorbent dose were 10, 313 K, 50 min and 0.2 g, respectively. Also the maximum amounts of removal efficiency for pb2 and Cu2 ions was 98%. Thermodynamic parameters reveal the feasibility and spontaneity nature of the adsorption process and the adsorption kinetics of pb(II) and Cu(II) ions follow a pseudo-second-order kinetic model.

TaN films with different N2 partial pressure were deposited on 304 stainless steel using the magnetron sputtering method. The effect of gas pressure on the mechanical property, morphology and phase structure of the films is investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), microhardness testing, friction coefficient measurements, and wear mechanism study. The XRD results confirmed that increasing N2 partial pressure does not affect the formation of the new phases but intensity of peaks increased. AFM images showed that surface roughness and grain size increased with increasing of N2 partial pressure. It was found that hardness decreased as N2 partial pressure increased. From the friction coefficient measurements, it could be inferred that the friction coefficient increased as N2 partial pressure increased. The images of samples after wear test showed that with increasing N2 partial pressure wear resistance decreased. The results show that the partial pressure of N2 has a great influence on the mechanical properties.

In industrial applications, most materials are exposed to wear and friction because multiple conditions are used. However, the tribological properties of these materials can be improved with different techniques. One such technique that improves the frictional property of a surface is the use of self-lubricating coatings. In this study, multicomponent coatings of nominal composition Cu-Ni3Al-MoS2 have been sputter from the target using the best sputtering condition to get a good morphology and microstructure of the coating. The morphology and micro structure of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy depressive spectroscopy (EDS). The measured microhardness of this coating was 380 HV over 25 g load. Tribological properties of Cu-Ni3Al-MoS2 coatings were investigated using ball-on-disk (BOD) tribometer at atmospheric condition of room temperature. These composite coatings showed a good morphology and adhesion of the coating to the substrate, also it had acceptable friction coefficient and higher wear resistance, because it has hard matrix containing Cu-Ni3Al and MoS2 Nano particles.

A water–soluble gelatin combined with polyethylene microspheres were developed to prepare alumina composite foam. Gelatin was used as the gelling agent and polyethylene was used as pore making template. On the other hand, kaolin was used to provide green strength and CuO was applied to decrease the required temperature as a sinter aid. Alumina bodies need elevate temperature for sintering, increasing the process cost. This process could be carried out at 1000 ºC, therefore more appropriate than that of the previous studies. The effect of CuO amounts on the open porosity, water adsorption, and density as well as on the mechanical strength of sintered foams was evaluated. The resulting samples, with relative densities between 0.97 and 1.16 g/cm3, and compressive strength between 1.4 – 5.5 MPa, comprised microstructures of semi–spherical pores. The phase component of the samples consist ~60 % alumina, 11 – 15 % CuAl2O4, and 24 – 27 % Al2SiO5. The degree of crystallinity measured in range of 66 – 83 %. These changes are related to the CuO/Al2O3 ratio. On the other hand, gelatin and polyethylene as the gelling agent and pore template were used successfully in gel–casting process.

In this paper, the influence of the constituent volume fractions by changing the values of the power-law exponent with uniform pressure on the vibration frequencies of reinforced functionally graded cylindrical shells is studied. The FGM shell with ring is developed in accordance to the volume fraction law from two constituents namely stainless steel and nickel. These constituents are graded through the thickness direction, from one surface of the shell to the other and are controlled by power-law volume fraction distribution. The reinforced FGM shell equations with ring and uniform pressure are established based on first order shear deformation theory. The governing equations of motion were employed, using energy functional and by applying Ritz method. The boundary conditions represented by end conditions of the FGM cylindrical shell are simply supported-simply supported, clamped-clamped and free-free. Effects of the different values of the power-law exponent, uniform pressure, reinforced ring and different symmetric boundary conditions on natural frequencies characteristics are studied. To check the validity of the present study, the results obtained are compared with those available in the literature.

The effect of evaporation rate on structural, morphological and optical properties of electron beam evaporated CdS thin films have been investigated. CdS thin film deposited by electron beam evaporation method in 12nm/min and 60nm/min evaporation rates on glass substrates. X-ray diffraction, scanning electron microscopy, UV-Vis-NIR spectroscopy and Atomic Force Microscopy were used to characterize thin films. The x-ray diffraction analysis confirms that films have polycrystalline hexagonal phase and exhibited preferred orientation along the (002) plane. The crystallite size were calculated and found to be increased from 23 nm to 30 nm by increasing deposition rate. Results of Atomic Force Microscopy revealed that the RMS roughness values of the CdS films decreased as deposition rate increased. The relation between deposition rates and optical properties of deposited films was investigated. It was found that stoichiometric properties and band gap values of the deposited films are correlated to deposition rates. These dependencies are associated to the Cd/S ratio variation by deposition rate. The optical band gap values of CdS films increased slightly in a range of 2.32–2.34 eV for deposition rate varied from 12nm/min and 60nm/min .

In this work, SiO2 –ZrO2 mixed oxides was prepared by the polymeric sol–gel route. The characterization of pore structure, which determines the permeation process of membrane, is of great importance. So far, most investigations have focused on such pore structure as specific surface area and pore size distribution, but the surface fractal, the important parameter reflecting the roughness of pore surface. Pore surface roughness change in SiO2-ZrO2 unsupported membranes induced by chemical composition and heating process has been investigated by the analysis of surface fractal dimension. Fractal features are analyzed from N2 adsorption–desorption measurements. It was found that a decrease in the surface fractal dimension occurs while zirconia content increases at the unsupported membranes with different molar ratio of zirconia to silica heating at 500 ºC. The surface fractal dimension of membrane with 30 mol% silica content slightly increases while heating from 200 to 500 ºC due to shrinkage and increase of mass fractal dimension of silica clusters.