This paper addresses the issue of mechanistic aspects of sonocrystallization with approach of coupling experiments with simulations of bubble dynamics. The major experimental result of our study is that, as compared to a mechanically agitated crystallization system, the dominant crystal size (or median) of the crystal size distribution (CSD) of sonocrystallization systems is smaller, but span of CSD is larger. The CSD is influenced by nucleation rate and growth rate. The nature of convection in the medium is found to be the crucial factor. In a mechanically agitated system, uniform velocity field prevails in crystallization volume, due to which both dominant crystal size and span of CSD reduce. The convection in a sonicated system is of a different kind. This convection has two components, viz. microturbulence (or micro-convection), which is continuous oscillatory motion of liquid induced by radial motion of cavitation bubble, and shock waves, which are discrete, high pressure amplitude waves emitted by the bubble. These components have different impact on crystallization process due to their nature. Shock waves increase the nucleation rate and microtubulence governs growth of the nuclei. However, the effect of shock waves is more marked than microturbulence (or micro-convection). Nucleation rate shows an order of magnitude rise with sonication, while growth rate (and hence the dominant crystal size) reduces with sonication as compared to the mechanically agitated system.

A significant amount of work on electrochemical energy storage focuses mainly on current lithium-ion systems with the key markets being portable and transportation applications. There is a great demand for storing higher capacity (mAh/g) and energy density (Wh/kg) of the electrode material for electronic and vehicle applications. However, for stationary applications, where weight is not as critical, nickel-metal hydride (Mi-MH) technologies can be considered with tolerance to deep discharge conditions. Nickel hydroxide has gained importance as it is used as the positive electrode in nickel-metal hydride and other rechargeable batteries such as Ni-Fe and Ni-Cd systems. Nickel hydroxide is manufactured industrially by chemical methods under controlled conditions. However, the electrochemical route is relatively better than the chemical counterpart. In the electrochemical route, a well-regulated OH− is generated at the cathode forming nickel hydroxide (Ni(OH)2) through controlling and optimizing the current density. It produces nickel hydroxide of better purity with an appropriate particle size, well-oriented morphology, structure, et cetera, and this approach is found to be environmentally friendly. The structures of the nickel hydroxide and its production technologies are presented. The mechanisms of product formation in both chemical and electrochemical preparation of nickel hydroxide have been presented along with the feasibility of producing pure nickel hydroxide in this review. An advanced Ni(OH)2-polymer embedded electrode has been reported in the literature but may not be suitable for scalable electrochemical methods. To the best of our knowledge, no such insights on the Ni(OH)2 synthesis route for battery applications has been presented in the literature.

In this work, the combined effects of contamination and shear-thinning (power-law) viscosity on the free rise of a single bubble have been studied numerically. The influence of insoluble contaminants on the surface of the bubble has been incorporated in the analysis by employing the spherical stagnant cap model which has been employed successfully in Newtonian fluids. The governing differential equations have been solved numerically over a range of conditions: Reynolds number, Re = 10–200; power-law index, n = 0.6–1; and stagnant cap angle, α = 0°–180°. Finally, the effect of each of the parametersnamely, Re, n, and αon streamline patterns, surface pressure and vorticity distributions, and individual and total drag coefficients is discussed in detail. Briefly, for α > 30° and Re ≥ 50, the recirculation length increases and the separation angle moves forward with the increasing Re; however, mixed trends are observed with respect to the power-law index and the stagnant cap angle. The total drag coefficient increases as the cap angle and/or the power-law index increases and/or the Reynolds number decreases; while mixed trends are observed on the dependence of the ratio of the individual drag coefficients on these parameters.

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