Defect and Diffusion Forum Vol. 423

Abstract: We study ultrafast magnetization dynamics induced by laser heating using various phenomenological temperature models. The temperature dynamics of the electrons, spins and lattice for thin foils is investigated. Numerical results for the temperature and magnetization dynamics for them are compared with those available in the literature.

Abstract: We have successfully constructed a Kerr lens mode-locked (KLM) Ti:sapphire oscillator to generate ultrashort pulses of ~18 fs. The oscillator consists of only 5 elements including a pair of double-chirped mirrors to balance negative group delay dispersion in the cavity. The bandwidth of the mode-locked laser oscillator spectrum is from 600 nm to 950 nm and pulse energy is 1.5 nJ. Both the output spectrum and the output power were stable against environmental disturbance. For the pulse characterization, a second harmonic generation frequency resolved optical gating method was used.

Abstract: We solve the site-site Ornstein-Zernike equation using the Percus-Yevick closure for binary hard-sphere mixture. We calculate an excess chemical potential for the mixture’s diameter ratios of 0.3, 0.5, 0.6 and 0.9, and at packing fraction of 0.49 using the analytical expression. Our numerical results are in good agreement with those in the literature.

Abstract: Herein, we have predicted the electronic and magnetic properties and magnetocrystalline anisotropy (MCA) of the most stabilized antiferromagnetic (AFM) ground state of bulk chalcopyrite (CuFeS$_{2}$) and films with various different thicknesses. We have shown that the easy axis of bulk structure is along the [001] direction and it agrees with the results of neutron measurements. For the CuFeS$_{2}$ film, our results have indicated that the ground state of ultra-thin film is ferromagnetic (FM) and the easy axis of ultra-thin film is in-plane. As increased the thickness of the film, its ground state becomes the AFM, and the easy axis is changed as out-plane. It may be a natural candidate material for integrating spintronics.

Abstract: In this work, some properties of the InAs/InGaAs quantum well (QW) were calculated, such as the wave functions and the charge density of the 2D free electron gas (2DEG) by solving the Poisson- Schroedinger equation. The thinner capping layer gives charge densities forming inside the QW that are higher than the thicker values. The optimal thickness of the capping layer can be 10 nm due to the most stable charge density and fully symmetrical wave functions. Our result indicates that higher charge densities can be found with higher Si-delta doping concentrations. However, the distance of the Si-delta doping also affects the charge population. The charge density linearly decreases with a higher Si-delta doping spacer; the thickness was chosen as 7nm. We performed the growth with different concentrations of Si with optimal thicknesses and compared them with the calculated values. There is good agreement between the simulations and experiments with the lower Si-doping concentrations.

Abstract: Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ (L2MO) material coated with Li_1.3Al_0.3Ti_1.7(PO₄)₃(LATP) was synthesized by sol-gel method. The coating amount was 0%, 0.5%, 1%, 1.5%, 2%. It is found that LATP coating improves the cycle stability of the material. After 200 cycles at 0.6 C rate, the cycle retention rate of the uncoated sample is 72.7%, while the retention rate of sample with 1% coating amount reaches 85%. LATP coating improves the rate performance of the material. The sample with 1% coating amount has the best rate performance, and the discharge specific capacity is 71.5 mAh/g at 10 C rate, while the discharge specific capacity of the sample without coating is 60.1 mAh/g. LATP coating alleviates the side reaction between the material surface and the electrolyte. As a solid electrolyte, it promotes the transmission of Li⁺ and reduces the charge transfer impedance of the material. The thermal stability of these materials was tested by DSC. The results show that LATP coating could improve the thermal stability of the material in charged state.

Abstract: We have presented the results of detailed studies of oxygen vacancy and niobium (Nb) substituted spinel Li4Ti5O12 (LTO) materials using first-principles method within the framework of the density functional theory (DFT). We have shown that the ground state of oxygen vacancy and Nb substituted LTO is paramagnetic (PM), and the Nb substitution is most stable on the 16d sites of both the Li and Ti ions. We have indicated that the Nb substitution in the 16d site of Li ion become the n-type metallic material. But the oxygen vacancy containing NbT i substituted LTO is changed from the p-type to the n-type, as increased a concentration of Nb ions.

Abstract: Heat and mass transfer performance of Casson nanofluid for both non-conducting (m=0), electrically conducting (m≠0) fluids with solar radiation effects in stagnation point flow is considered. In this model, entropy, irreversibility, and multi slip impacts over a shrinking, static, and stretching sheet are investigated. To minimize the energy used in the solar system, it is important to monitor the processes of heat and mass transfer in the solar radiation process. The slips boundary conditions acts as a closure of the fluid velocity, mass, and heat transfer differential equations. The equations obtained are solved numerically via Galerkin Weighted Residual Method (GWRM). In the limiting sense, the present results conform with the existing work. The Behaviors of the flow physical quantities, temperature, concentration, and velocity for distinct values of the applicable dimensionless numbers are demonstrated with tables and graphs. The results reveal that, for a theoretical account of thermal boundary layers, Prandtl number serves as a variable. Furthermore, higher values of variable thermal conductivity have a significant influence on the skin friction coefficient than the case of constant variable thermal conductivity even when the fluid viscosity is assumed to be variable. The structure of the new method can be applied to the development of oil production.

Abstract: This paper examined the three-dimensional stretched flow, heat, and mass transports analysis of Prandtl fluid with the influences of chemical reactions, over a Riga surface. This analysis is investigated in presence of Catteneo-Cristov heat and mass fluxes. The resulting nonlinear models are simplified by appropriate similarity variables. The solutions of the reduced set of coupled equations are obtained numerically via the Chebyshev spectral collocation technique. The obtained numerical results were used to address and discuss the characteristics of flow, heat transfer, mass distribution, skin friction, Nusselt, and Sherwood numbers for various pertinent parameters. In addition, the validation of the present numerical scheme is achieved by comparing it with previous results obtained through other numerical results. It is noticed that the rate of heat and mass transfer escalate for the Prandtl parameter. Also, the thermal and mass distributions scale back with a high estimation of relaxation parameters.This paper examined the three-dimensional stretched flow, heat, and mass transports analysis of Prandtl fluid with the influences of chemical reactions, over a Riga surface. This analysis is investigated in presence of Catteneo-Cristov heat and mass fluxes. The resulting nonlinear models are simplified by appropriate similarity variables. The solutions of the reduced set of coupled equations are obtained numerically via the Chebyshev spectral collocation technique. The obtained numerical results were used to address and discuss the characteristics of flow, heat transfer, mass distribution, skin friction, Nusselt, and Sherwood numbers for various pertinent parameters. In addition, the validation of the present numerical scheme is achieved by comparing it with previous results obtained through other numerical results. It is noticed that the rate of heat and mass transfer escalate for the Prandtl parameter. Also, the thermal and mass distributions scale back with a high estimation of relaxation parameters.