Applied Mechanics and Materials Vols. 446-447

Abstract: Molecular modelling methods were used to investigate the structural and interatomic potential of bulk cubic zirconia. To widen the scope of the expected outcome, GULP and CASTEP software were used based on the concept of minimizing the energy of the crystal structure with respect to atomic coordinates. The crystal structure of cubic zirconia was modelled and optimized; the lattice parameter of 5.10 Å obtained is similar to available calculated and experimental values. The developed interatomic potential is based on Born model for ionic solids without defects. The calculated interatomic potential of 109.67eV per atom is also within acceptable range, but variation was observed depending on the relative position of individual atoms. The modelling gave a better understanding of the bulk crystal structure of cubic zirconia due to detailed parameters that were obtained. Also, the determined parameters were used to estimate the Young’s Modulus of bulk zirconia as 397GPa.

Abstract: Hot compression of AZ3l magnesium alloy was carried out at deformation temperatures of 523-723K and strain rates of 0.01-10s^-1. The effects of deformation process on the microstructure and flow stress were investigated. The flow stress curves showed the characteristic of dynamic recrystallization (DRX) with deformation process parameters. Optical microscopy and TEM observations indicated that dynamic recrystallisation and twins structure were found during hot compression. Deformation mechanism of AZ3l magnesium alloy at elevated temperature was discussed in this paper.

Abstract: At room temperature and pressures, the reaction between sodium cyanide and platinum group metals (PGMs) does not occur because of poor kinetics. However, at elevated temperatures, PGMs can be leached by sodium cyanide like the reaction of gold. However, few rate expression which describe the leaching of Palladium in cyanide solution has been developed. In this paper, the rate of Palladium dissolution was measured in pressure clear cyanide solution using a Palladium rotating disk. The data at different rotation speed, cyanide concentrations, temperature and oxygen pressure are obtained. The dissolution rates were independent of rotation speed for oxygen-saturated solutions between 100-400rpm. With increasing temperature the dissolution rate is increased. With increasing cyanide concentration and oxygen pressure, the dissolution rate first increased to a maximum value and then decreased.

Abstract: The decarbonylation of acetaldehyde assisted by Ni⁺², which was selected as a representative system of transition metal ions assisted decarbonylation of acetaldehyde, has been investigated using density functional theory (B3LYP) in conjunction with the 6-31+G** basis sets in C,H,O atoms and Lanl2dz basis sets in Ni atom The geometries and energies of the reactants, intermediates, products and transition states relevant to the reaction were located on the triplet ground potential energy surfaces of [Ni, O, C₂,H₄]⁺². Our calculations indicate the decarbonylation of acetaldehyde takes place through four steps, that is, encounter complexation, CC activation, aldehyde H-shift and nonreactive dissociation, it is that CC activation by Ni⁺² that lead to the decarbonylation of acetaldehyde.

Abstract: This paper presents a study on the influence of cutting parameters (Cutting speed and Feed rate) on drilling multi walled carbon nanotubes (MWCNTs) filled epoxy / glass fabric hybrid polymeric nanocomposite. For comparison neat epoxy / glass fabric polymeric composite was also fabricated. Drilling tests were carried out on these materials with HSS twist drill of diameter 6mm. Optimal cutting conditions were found using grey relational analysis by simultaneously considering the surface delaminations of the drilled holes at the entrance and exit sides. Surface delaminations of the drilled holes were quantified in terms of delamination factor. From the mean grey relational grades, it is observed that the multi walled carbon nanotubes (MWCNTs) has significant effect in improving the drilled hole quality. Mean grey relational grades of MWCNTs filled epoxy composite was found to be better than that of neat epoxy composite.

Abstract: Diffusive behaviors for two-dimensional (2D) monodispersed polystyrene array of droplet spreading by either methanol or ethanol suspension are observed on a rigid surface. Methanol solution can spread speedily on the glass surface because of the positive spreading coefficient. Conversely, the ethanol will not easily proliferate out. Monodisperse polystyrene particles are involved in Brownian motion in a thick layer during alcohol evaporation. A monolayer dimension of the drop has been developed at the final spreading. Lateral capillary forces are produced and caused the aggregation of particles. Evaporation at the edge of the ethanol film did not lead to the film to retract. The formation of 2D array, which preceded the spreading of the microscopic droplet across the surface, is able to indicate the dense structure to the dynamic correlation function.

Abstract: Zinc oxide nanoparticles were synthesized by the thermal-treatment method. Polyvinyl pyrrolidone was used as capping agent and Zinc nitrate was used as a precursor. The samples were calcined at 500 and 550°C for removal of the organic compounds. The structural characteristics of the calcined samples were examined by X-ray diffraction and transmission electron microscopy. The results show that the average particle size increases with increase in calcination temperature. The optical properties were characterized at room temperature using a UV–Vis spectrophotometer in the wavelength range between 200–800 nm and the band gap energy was calculated from reflectance spectra using kubalka munk function and the results indicated that the band gap energy decreased from 3.23 eV at 500 oC to 3.21 eV at 600 °C due to an increase of particle size. This simple thermal-treatment method has advantages of the pure nanoparticles formation as no additional chemicals were required, a lack of by-product effluents, and environmentally friendly process.

Abstract: This paper explains the influence of oxygen partial pressure on crystallographic structure, surface morphology and sensing properties of sputtered MoO₃ thin films. The MoO₃ thin films were deposited by DC reactive magnetron sputtering technique on glass substrate at different oxygen partial pressures in the range of 5×10^-5-4×10^-4 mbar. X-ray diffraction (XRD) results showed that all prepared films were polycrystalline of α-MoO₃ stable orthorhombic phase. Atomic force microscopy (AFM) images depicted a needle-like structure for deposited film at lowest oxygen partial pressure (5×10^-5 mbar) and a granular structure for formed samples at higher oxygen partial pressures (1×10^-4 and 2×10^-4 mbar). These results also showed that increasing of oxygen partial pressure up to 2×10^-4 mbar caused increasing of grains size and surface roughness, while an increase in oxygen partial pressure to the highest pressure (4×10^-4 mbar) had an inverse effect. The electrical response of samples was measured in vacuum and NO environments in the temperature range of 150-350 K. This study showed that the NO gas detection sensitivity of MoO₃ thin films improved with increasing of oxygen partial pressure up to 2×10^-4 mbar, and then decreased.

Abstract: Removed at authors request

Abstract: Nano-structured hydrotalcite based mixed oxides have been synthesized using coprecipitation method under variable pH and low supersaturation condition. XRD technique has been used to confirm the hydrotalcite structure and its derived different phase of mixed oxides. The metal dispersion of mixed oxides was analyzed using ICP-MS. The nanostructures of the mixed oxides have been investigated using FESEM and HRTEM. The textural properties of mixed oxides were analyzed using N₂ adsorption-desorption (BET) technique. The Characterizations have revealed that the developed mixed oxides were consisted with hexagonal/rhombohedral well dispersed nano-particles. Polycrystalline mixed oxides formed mesopore surface and narrower pore size distribution.