Synthesis, Characterization and Investigation of Optical and Electrical Properties of Polyaniline/Nickel Ferrite Composites.

Nickel ferrite nanoparticles are prepared by using a low-temperature self-propagating solution combustion method using urea as fuel. The prepared nickel ferrite nanoparticles were doped with polyaniline in the three different weight ratios of 10%, 30% and 50% by using an in situ polymerization method and by adding ammonium persulfate as an oxidizing agent. The obtained samples were characterized by using XRD, FTIR, SEM and a UV-visible spectrophotometer. XRD examined crystalline peaks of ferrites and amorphous peak of polyaniline and confirmed the formation of the composites. FTIR examined the chemical nature of samples and showed peaks due to polyaniline and the characteristic peaks that were less than 1000 cm-1 wavenumber were due to metal-oxygen bond vibrations of ferrites. AC conductivity increased with frequency in all samples and the highest AC conductivity was seen in polyaniline/nickel ferrite 50%. DC conductivity increased in all samples with the temperature showing the semiconducting nature of the samples. Activation energy was evaluated by using Arrhenius plots and there was a decrease in activation energy with the addition of ferrite content. The UV-visible absorption peaks of polyaniline showed shifting in the composites. The optical direct and indirect band gaps were evaluated by plotting Tauc plots and the values of the optical band gap decreased with addition of ferrite in polyaniline and the Urbach energy increased in the samples with 10%, 30% and 50% polyaniline/nickel ferrite composites. The optical properties of these composites with a low band gap can find applications in devices such as solar cells.

Electro-osmotic flow of biological fluid in divergent channel: drug therapy in compressed capillaries.

The multi-phase flow of non-Newtonian through a divergent channel is studied in this article. Jeffrey fluid is considered as the base liquid and tiny gold particles for the two-phase suspension. Application of external electric field parallel to complicated capillary with net surface charge density causes the bulk motion of the bi-phase fluid. In addition to, electro-osmotic flow with heat transfer, the simultaneous effects of viscous dissipation and nonlinear thermal radiation have also been incorporated. Finally, cumbersome mathematical manipulation yields a closed-form solution to the nonlinear differential equations. Parametric study reveals that more thermal energy is contributed in response to Brinkman number which significantly assists gold particles to more heat attain high temperature, as the remedy for compressed or swollen capillaries/arteries.

Entropy optimized dissipative flow of hybrid nanofluid in the presence of non-linear thermal radiation and Joule heating.

Present article reads three dimensional flow analysis of incompressible viscous hybrid nanofluid in a rotating frame. Ethylene glycol is used as a base liquid while nanoparticles are of copper and silver. Fluid is bounded between two parallel surfaces in which the lower surface stretches linearly. Fluid is conducting hence uniform magnetic field is applied. Effects of non-linear thermal radiation, Joule heating and viscous dissipation are entertained. Interesting quantities namely surface drag force and Nusselt number are discussed. Rate of entropy generation is examined. Bvp4c numerical scheme is used for the solution of transformed O.D.Es. Results regarding various flow parameters are obtained via bvp4c technique in MATLAB Software version 2019, and displayed through different plots. Our obtained results presents that velocity field decreases with respect to higher values of magnetic parameter, Reynolds number and rotation parameter. It is also observed that the temperature field boots subject to radiation parameter. Results are compared with Ishak et al. (Nonlinear Anal R World Appl 10:2909-2913, 2009) and found very good agreement with them. This agreement shows that the results are 99.99% match with each other.

Dual solution framework for mixed convection flow of Maxwell nanofluid instigated by exponentially shrinking surface with thermal radiation.

This paper presents the analysis of transfer of heat and mass characteristics in boundary layer flow of incompressible magnetohydrodynamic Maxwell nanofluid with thermal radiation effects confined by exponentially shrinking geometry. The effects of Brownian motion and thermophoresis are incorporated using Buongiorno model. The partial differential equations of the governing model are converted in non-dimensional track which are numerically inspected with proper appliances of Runge-Kutta fourth order scheme.The significant effects of heat and mass fluxes on the temperature and nanoparticles volume fractions are investigated. By the increases in Lewis number between [Formula: see text] to [Formula: see text], the decrease in nanoparticle volume fraction and temperature is noted. With the change in the Prandtl constant that varies between [Formula: see text] to [Formula: see text], the nanoparticles volume fraction and temperature are dwindled. Nanoparticles volume fraction and temperature distribution increase is noted with applications of radiation constant. With consequent variation of thermophoresis parameter between [Formula: see text] to [Formula: see text], nanoparticles volume fraction and temperature distribution increases. It is also noted that the increase in thermophoresis parameter and Brownian parameter from [Formula: see text] to [Formula: see text], nanoparticles volume fraction decreases while temperature distribution increases.