There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The phase-field method has become an important and extremely versatile technique for simulating microstructure evolution at the mesoscale. Thanks to the diffuse-interface approach, it allows us to study the evolution of arbitrary complex grain morphologies without any presumption on their shape or mutual distribution. It is also straightforward to account for different thermodynamic driving forces for microstructure evolution, such as bulk and interfacial energy, elastic energy and electric or magnetic energy, and the effect of different transport processes, such as mass diffusion, heat conduction and convection. The purpose of the paper is to give an introduction to the phase-field modeling technique. The concept of diffuse interfaces, the phase-field variables, the thermodynamic driving force for microstructure evolution and the kinetic phase-field equations are introduced. Furthermore, common techniques for parameter determination and numerical solution of the equations are discussed. To show the variety in phase-field models, different model formulations are exploited, depending on which is most common or most illustrative.

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An introduction to phase-field modeling of microstructure evolution

The term superhydrophilicity is only 11–12 years old and was introduced just after the explosion of research on superhydrophobic surfaces, in response to the demand for surfaces and coatings with exceptionally strong affinity to water. The definition of superhydrophilic substrates has not been clarified yet, and unrestricted use of this term to hydrophilic surfaces has stirred controversy in the last few years in the surface chemistry community. In this review, we take a close look into major definitions of hydrophilic surfaces used in the past, before we review the physics behind the superhydrophilic phenomenon and make recommendation on defining superhydrophilic surfaces and coatings. We also review chemical and physical methods used in the fabrication of substrates on surfaces of which water spreads completely. Several applications of superhydrophilic surfaces, including examples from the authors' own research, conclude this review.

Hydrophilic and superhydrophilic surfaces and materials

This paper provides a review of superhydrophobicity and related phenomena (superoleophobicity, omniphobicity, self-cleaning) induced by surface micro- and nanostructuring. The classical approaches to superhydrophobicity using the Young, Wenzel, and Cassie–Baxter models for the contact angle (CA) are presented. After that, the issues that are beyond the Wenzel and Cassie–Baxter theories are discussed, such as multiscale effects, 1D vs. 2D interactions, the effects of contact line, size of roughness details, curvature, and CA hysteresis dependence on roughness. New potential applications of superhydrophobicity are reviewed, such as new ways of energy transition, antifouling, and environment-friendly manufacturing.

Superhydrophobic surfaces and emerging applications: Non-adhesion, energy, green engineering

Contact angle hysteresis is an important physical phenomenon. It is omnipresent in nature and also plays a crucial role in various industrial processes. Despite its relevance, there is a lack of consensus on how to incorporate a description of contact angle hysteresis into physical models. To clarify this, starting from the basic definition of contact angle hysteresis, we introduce the formalism and models for implementing contact angle hysteresis into relevant physical phenomena. Furthermore, we explain the influence of the contact angle hysteresis in physical phenomena relevant for industrial applications such as sliding drops, coffee stain phenomenon (in general evaporative self-assembly), and curtain and wire coating techniques

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Contact angle hysteresis: a review of fundamentals and applications

The classical JMAK model of recrystallization kinetics has been widely used to describe the growth of randomly distributed nuclei under constant driving force. These conditions are not satisfied in many systems. The driving force for growth generally varies with time, and the nuclei are usually not uniformly distributed. In this paper, we present a physically motivated alternative model of recrystallization kinetics, which accounts for the variation of driving force due to recovery and the effect of clustering of the nuclei. The model is based on the growth kinetics of initially circular, strain free nuclei in a deformed matrix. The effect of recovery on the recrystallization kinetics is studied in terms of the parameters governing initial stored energy and the decay rate. The model predicts cessation of recrystallization when the stored energy decreases below a certain critical limit. This cessation depends on both the initial stored energy value as well as the recovery time constant. The effect of clustering of nuclei on recrystallization kinetics is analyzed by considering representative volume elements with different nuclei distributions. It is shown that recrystallization kinetics becomes slower with increased clustering. The results of this mean field model are compared to phase field simulations.

A physically based model of the effect of recovery and clustering on recrystallization kinetics

Fiber-reinforced composite materials offer a number of distinct advantages such as higher specific strengths and stiffness over more conventional engineering materials such as aluminum or steel. When loaded in the fiber direction, these materials are the best choices in the modern world, but they do suffer severe limitations when undergoing impact loadings such as dropped tool or runway debris. To design a composite material that can offer solutions to the problems discussed above is important. Thus in this paper, our aim is to introduce a highly ductile, energy dissipating shape memory alloy (SMA) wire inside a composite material as a fiber that exhibits pseudoelastic response. To predict the behavior of the SMA composite, as SMA is a non-linear hysteretic material, we have developed an incremental SMA composite model using the Voigt method. 

Srikanth Vedantam

Papers

A physically based model of the effect of recovery and clustering on recrystallization kinetics

Incremental modelling of alloy embedded composite