Analytical modeling for nanostructure quantum wells with equispaced energy levels in semiconductor ternary alloys (Ax B1-x C)

The purpose of this study is to formulate an Analytical model of equispaced energy levels quantum wells (QWs) in semiconductor ternary alloys (AxB1-xC). The procedure is by mapping the envelop function Schrodinger equation for realistic QW, with the local conduction band edge as the potential experienced by an electron in the QW into an effective mass Schrodinger equation with a linear harmonic oscillator potential by the method of coordinate transformation. The electron effective mass and potential are then obtained as the signature for the equispaced energy level for QWs in semiconductor ternary alloys.Keywords: Semiconductor nanostructures, Ternary alloys, Quantum wells, Equispaced energy levels, Effective mas

Effect of paint-bake like treatment on mechanical properties of Mg-Zn-Ca alloy

Magnesium alloys are promising materials for the fabrication of automotive components due to their lightweight which could help car manufacturers reduce the amount of emissions generated per automobile and to meet present and future regulations of owning more environmentally friendly vehicles. However, the low strength of magnesium alloys compared to aluminium and steel have limited its usage and has necessitated the search for more potent strengtheningmechanism, like precipitation strengthening, to widen the application of magnesium alloys in the automotive industries. Precipitation hardening response of a Mg-4wt%Zn-0.3 wt%Ca(ZX40) alloy in an ageing process at 180oC temperature typical of those used during paint baking cycle in automotive industries were studied using optical microscopy, Scanning electron microscopy (SEM), micro - hardness and thermoelectric power machine (TEP). Prior to the ageing process, one alloy was subjected to a 30 minutes solution heat treatment while the other sample was without solution heat treatment. Although, an initial decrease in hardness and strength of the alloy was observed due to solution treatment prior to ageing. The overall results showed that the mechanical (strength and hardness) and microstructure (fracture surface and precipitate formation) properties were enhanced in the 30 minutes solution treated sample s, which further emphasizes the need for solution treatment for better properties in an alloy. Keywords: Paint baking, Magnesium alloys, Precipitation strengthening, scanning electron microscop

Suppressed HF Behaviour in the Periodic Anderson Model

The periodic Anderson model is applied to 4 electrons on 4 sites with periodic boundary conditions. We applied magnetic field to the localized forbitals, Eσf. The number of electrons is taken to be one per site and the interactions between different sites is restricted to nearest neighbors. The many body eigenvalues are calculated exactly using exact diagonalization technique. We find that the specific heat is suppressed by the variation of the band energy of the localized f-orbitals as mediated by the application of the magnetic field, H, under various hybridization energy. A continuous suppression of the specific heat reduces the heavy fermion behavior in the system

Crevice Corrosion Behavior of Nickel-Based Alloy 718 in both Aerated and De-Aerated Chloride Environment

In this study, anodic potentiodynamic polarization techniques were used to study the crevice corrosion behaviour of Nickel alloy 718 (with and without a crevice former) in both aerated and de-aerated solution of 3.5wt% sodium chloride solution. Surface observation of the specimens after each experiment was done with the optical microscope. The results showed that crevice corrosion were initiated at potentials as low as 520mVSCE, while the surface observation on the specimen with a crevice former revealed that the crevice corrosion attack was restricted under the crevice gap and at the border areas of the crevice former but did not occur at the surfaces outside the shielded areas. Conversely, the specimen without a crevice former showed evidence of waterline corrosion. These results can be attributed to the development of differential oxygen concentration in the specimen depending on the exposure of the parts to dissolved oxygen. This study has developed a more comprehensive understanding of the crevice corrosion initiation mechanism and behaviour of Nickel-based Alloy 718 under applied crevice torques, chloride environment and exact potentials, thereby leading to better prevention and control of localized corrosion in this alloy