Showing papers in "Journal of the Indian Institute of Science in 2016"

Characterization of the State-of-the-art and Identification of Main Trends for Ecodesign Tools and Methods: Classifying Three Decades of Research and Implementation

Abstract: Ecodesign is a proactive management approach that integrates environmental considerations in product development and related processes (such as purchasing, marketing and research & development). Ecodesign aims to improve environmental performance of products throughout their life cycle, from raw material extraction and manufacturing to use and end-of-life. Over the last three decades, an intense development of new ecodesign methods and tools could be observed, but uptake by the industry remains a challenge. The purpose of this research is to perform a review of existing ecodesign tools and methods through a systematic literature review linked to bibliometric analyses, in order to explore the state of the art of ecodesign methods and tools and identify trends and opportunities in the field for the next decade.

Applications of the Phase-Field Method for the Solidification of Microstructures in Multi-Component Systems

Abstract: The solidification of multicomponent alloys is of high technical and scientific importance. In this review, we describe the ongoing research of the phase-field method for the solidification of dendritic and eutectic structures. Therefore, the corresponding experimental and theoretical investigations are presented. First, an overview of the historical development in solidification research is given. Thereafter, the ongoing progress of the phase-field models is reviewed. Then, we address the experimental and simulative investigations of different forms of dendritic and eutectic solidification. We distinguish between thermal and solutal dendritic growth as well as thin-sample and Bridgman furnace experiments of eutectic growth. Impurity-driven Mullins-Sekerka instabilities like cell structures, eutectic colonies and spiral dendritic growth are presented. Then, validation methods for the comparison between simulations, experiments and theoretical approaches are addressed. Subsequently, related aspects to simulate solidification are introduced. Especially, further physical aspects and computational optimizations are considered. Concluding, possible future research in the context of the phase-field method for solidification is discussed.

A Review of Theories and Models of Design

Abstract: This paper intends to provide an overview of the rich legacy of models and theories that have emerged in the last fi fty years of the relatively young discipline of design research, and identifies some of the major areas of further research. It addresses the following questions: Whatare the major theories and models of design? How are design theory and model defined, and what is their purpose? What are the criteria they must satisfy to be considered a design theory or model? How should a theory or model of design be evaluated or validated? What are the major directions for further research?

Weyl Semi-Metals: A Short Review

Abstract: We begin this review with an introduction and a discussion of Weyl fermions as emergent particles in condensed matter systems, and explain how high energy phenomena like the chiral anomaly can be seen in low energy experiments. We then explain the current interest in the field due to the recent discovery of real materials which behave like Weyl semi-metals. We then describe a simple lattice model of a topological insulator, which can be turned into a Weyl semi-metal on breaking either time-reversal or inversion symmetry, and show how flat bands or Fermi arcs develop. Finally, we describe some new phenomena which occur due to the chiral nature of the Weyl nodes and end with possible future prospects in the field, both in theory and experiment.

Phase-Field Modelling of Solidification Microstructures

Abstract: Phase-field models have become the most popular method for the numerical simulation of solidification microstructures. This is due to several reasons: (i) they are based on thermodynamic principles, which facilitate their application in metallurgy, (ii) they are numerically simple, and standard mathematical methods for the solution of partial differential equations can be employed, and (iii) they can be very accurate, which has been demonstrated by number of benchmark simulations. In order to be both accurate and efficient, the dynamics of the interfaces in the model has to be precisely controlled. This is achieved by the construction of the model, and demonstrated by matched asymptotic expansion methods. Here, some fundamentals of phase-field modelling will be introduced, and several examples of their application in the modelling of solidification microstructures will be reviewed.

Studies of Design Creativity: A Review and its Prospects

Abstract: This paper provides an overview of current studies on design creativity by analyzing them with respect to two aspects. The first aspect is the foundation of Design Creativity. To analyze this, we survey fundamental studies on design and creativity, which have been developed as a means of building basic knowledge on design creativity. Additionally, key issues in the human cognition of design and creativity are examined. We also survey the methodological challenges that have enhanced creativity in design. Various methods and tools are considered as applicable technology for fostering the creative competencies of individuals or teams in relation to design. Additionally, techniques for assessing creativity that are strongly related to these methods and tools are also reviewed. For the second aspect, we discuss examples of criticism of contemporary art. In the domain of art, critics evaluate practitioners and assume responsibility for guaranteeing the quality of art. For this reason, critics are expected to be “connoisseurs” who can ‘foresee the future’ from an authoritative position. The structure in which such a role for criticism resides, can be understood as an artistic creation at a social level. Further, morality and ethics are examined from the perspective of social creativity. Finally, we suggest how design critiques will be able to enhance social innovation.

Models and Mechanisms of Oxygen Evolution Reaction on Electrocatalytic Surface

Abstract: A profound change has taken place in understanding surface electrochemistry during water-splitting reaction due to the accumulated knowledge over the past decades and supported by recent advances in spectroscopic techniques and high-performance quantum chemical simulations. The design of electrocatalysts has been improved due to better understanding of surface structures of electrocatalysts and their active sites. This review provides insights into both theoretical and experimental electrochemistry that are directed towards a better understanding of the rate-determining step of water splitting, i.e., oxygen evolution reaction (OER). The emphasis of this review is on the origin of the electrocatalytic activity of nanostructured catalysts toward the aforementioned reaction by correlating the electrode performance with their intrinsic electrochemical properties. Also, the design aspects of acidic- and alkaline-medium electrocatalysts is discussed from preliminary discussion on active site engineering to a more applied concern of achieving highly stable and active electrode fabrication. The design concerns while choosing a support for OER electrocatalyst has also been discussed. At the end, challenges in electrolyser designs and problems faced by the industry to commercialize the electrolyser in a cost-effective manner have been discussed.

Recent Developments in Environment-Friendly Corrosion Inhibitors for Mild Steel

Abstract: In 2002, our group and collaborators began initial investigations on the use of rare-earth carboxylates as non-toxic and environment-friendly corrosion inhibitors for mild steel. This was followed by a more comprehensive study, reported in 2004 by Blin et al., in which a range of such carboxylate compounds were investigated. This study identified lanthanum 4-hydroxycinnamate, La(4-OHcin)3 as a promising compound. In the review presented here our more recent investigations on mild steel corrosion inhibitors with structures closely related to La(4-OHcin)3 are presented. In another study, Lee investigated the effect on corrosion of subtle changes to the La(4-OHcin)3 structure. Seter et al. found that small structural changes could have a major effect on the inhibition performance. Nam et al. investigated cerium, lanthanum and praseodymium 4-hydroxycinnamate as corrosion inhibitors for mild steel in carbon dioxide atmospheres in sodium chloride solution. In this particular situation, Pr(4-OHcin)3 led to the largest reduction in corrosion current. A totally organic complex, imidazolinium 4-hydroxycinnamate (Imn 4-OHcin) has been investigated with the aim of developing a compound that can inhibit both corrosion and microbial growth. This compound was found to inhibit mild steel corrosion across a wide pH range and was particularly effective at a pH of 2. We have also been investigating a rare-earth compound with an alternative carboxylate structure to the cinnamate; 3-(4-methylbenzoyl)propionate(mbp). This ligand differs from 4-hydroxycinnamate by having a carbonyl group present, which may give an extra anchor point to a metal surface when forming a barrier coating. A range of rare-earth mbp complexes was investigated, with Nd(mbp)3 resulting in the largest reduction in corrosion current density at a concentration of 0.125 mM.

Electrode Disorder, Electrochemical Processes and Governing Length Scales

Abstract: Surface of a solid electrode ubiquitously possesses morphological and energetic disorders, and therefore it greatly influences their thermodynamics, kinetics and transport properties. Also, the anomalies in an electrochemical response are governed by the synergistic effect of the morphological and phenomenological lengths. For theoretical understanding of disordered systems, it becomes mandatory to characterize these length scales, and their dependence on electrochemical and morphological characteristics. In this review, we mainly focus on two aspects: (1) statistical characterization of electrode surface using FE-SEM micrographs and electrochemical microscopic area, and (2) the physical significance of various length scales arising in theoretical models and electrode surface topography. Finally, a common scale is generated to show the synergistic effects of morphological and phenomenological length scales in disordered electrochemical system.

Investigating Nucleation Using the Phase-Field Method

Abstract: The first order phase transitions, like freezing of liquids, melting of solids, phase separation in alloys, vapor condensation, etc., start with nucleation, a process in which internal fluctuations of the parent phase lead to formation of small seeds of the new phase. Owing to different size dependence of (negative) volumetric and (positive) interfacial contributions to work of formation of such seeds, there is a critical size, at which the work of formation shows a maximum. Seeds that are smaller than the critical one decay with a high probability, while the larger ones have a good chance to grow further and reach a macroscopic size. Putting it in another way, to form the bulk new phase, the system needs to pass a thermodynamic barrier via thermal fluctuations. When the fluctuations of the parent phase alone lead to transition, the process is called homogeneous nucleation. Such a homogeneous process is, however, scarcely seen and requires very specific conditions in nature or in the laboratory. Usually, the parent phase resides in a container and/or it incorporates floating heterogeneities (solid particles, droplets, etc.). The respective foreign surfaces lead to ordering of the adjacent liquid layers, which in turn may assist the formation of the seeds, a process termed heterogeneous nucleation. Herein, we review how the phase-field techniques contributed to the understanding of various aspects of crystal nucleation in undercooled melts, and its role in microstructure evolution. We recall results achieved using both conventional phase-field techniques that rely on spatially averaged (coarse grained) order parameters in capturing the phase transition, as well as molecular scale phase-field approaches that employ time averaged fields, as happens in the classical density functional theories, including the recently developed phase-field crystal models.

Visualization of Supersonic Free and Confined Jet using Planar Laser Mie Scattering Technique

Abstract: Planar Laser Mie Scattering (PLMS) imaging technique isemployed in supersonic axisymmetric free jet and supersonic rectangular confined jet to extract out the prominent flow features. Efficient seedingof the flow field is achieved using an in-house seeder unit which employsmodified Laskin Nozzle. For this imaging, flow field is seeded with particles of water or DEHS in case of free jet studies and with acetone for confined jet studies. Using high power laser and high speed camera, flow field is illuminated and captured.A series of simple image processing routines are carried out to extractthe noticeable attributes of the flow. Prominent flow features like Mach disc, shear layerinstability and shock cells are captured in the instantaneous PLMS imagesof a severely under-expanded supersonic axisymmetric free jet of designMach number (MD) 1.367. Qualitative increase in the shock cell spacing(Ls) for increasing Mach number ratio (MR) is observed for time-averagedPLMS imaging of a supersonic axisymmetric free jet (MD = 2.0 & 2.5). Alsoan effective increase in the jet width of an over-expanded jet undergoingscreech is noticed. Major flow features like large scalecoherent structures and terminal potential core instability are seen clearly in the instantaneous PLMS images of a rectangular supersonic confined jet of M PD = 2.0.Shock cell spacing and mixing layer formation are observed distinctly inthe time-averaged PLMS images. Qualitative increase in Ls for increasingstagnation pressure ratio (SPR) is highlighted along with the increase inthe wavelength of the potential core instability. More details regardingthe experimentation procedure and the underlying physics behind the observed flow features along with the variations encountered for differentoperating conditions are discussed elaborately in this paper.

Tunable Diode Laser Absorption Spectroscopy as a Flow Diagnostic Tool: A Review

Abstract: Optical diagnostic techniques are routinely being used in highspeed fl ow facilities to measure fl ow properties such as concentration,temperature and velocity, and thus, to study the fl ow physics. One suchtechnique, tunable diode laser absorption spectroscopy (TDLAS), hasproved to be particularly suitable for hostile environments such as shocktunnels and fl ight tests. The fundamentals, operating principle, applicationsand scope of the technique in high speed fl ow research is discussed inthis review, with references to some relevant examples.

Proton-Conducting Channels in Polybenzimidazole Nanocomposites

Abstract: The interfacial interactions of hybrid organic-inorganic nanocomposite membranes, when tuned appropriately, can replicate to some extent the conduction mechanism of Nafion where hydrophilic and hydrophobic regions are dispersed randomly and the proton conduction takes place via the conducting channels. A wide variety of functionalizing molecules can be used for tuning the interface. The dynamic physical interactions between the particles and the polymer chains, and the hydrogen-bonding interactions among the functionalized silica nanoparticles in polybenzimidazole (PBI) matrix manifest as self-assembled inorganic networks or domains of different sizes depending on the filler content. These domains can trap phosphoric acid via strong hydrogen bonding and can act as reservoirs of phosphoric acid thus creating an acid gradient in the matrix. This gradient morphology gives rise to directed and faster proton conduction process in the PBI matrix. Thus, these inorganic-organic hybrid materials can be tuned for controlled conductivity as well as mechanical and thermal stability of proton exchange membrane for the fuel-cell applications.

Non-Intrusive Flow Diagnostics for Aerospace Applications

Abstract: A brief account of several non-intrusive qualitative andquantitative visualization techniques used in aerospace research ispresented. The broad principles of operation are described along withapplications that are illustrative of their capabilities.

Interfaces of Solid Electrolytes: Fundamentals and Applications

Abstract: All solid-state batteries are candidates for the next-generation batteries owing to their potentially high safety, high reliability, and high energy density. In this review, first, the recent development of ASSBs is briefly summarised by showing both their advantages and shortcomings. Then, the interfaces of solid electrolytes, one of key factors of ASSBs, are discussed with some experimental results.

Elastic Stress Effects on Microstructural Instabilities

Abstract: Phase field modelling, which is ideal for the study of the formation and evolution of microstructures, has been used extensively to study the effect of elastic stresses on microstructural instabilities. In this review, we focus primarily on four elastic stress driven instabilities, namely (i) Spinodal phase separation; (ii) Particle splitting; (iii) Rafting; and, (iv) Asaro-Tiller-Grinfeld (ATG) instabilities, and, review the phase field studies of these instabilities. The review begins with a brief description of some of the important and interesting experimental observations followed by a reasonably detailed description of the theoretical developments. Both the description of experimental observations and the theoretical developments are neither comprehensive nor complete; however, they are helpful in setting the stage for discussion of (and, in giving a perspective on) phase field modelling studies on elastic stress effects on instabilities. We conclude with a summary and indication of future directions.

Spin Polarization of Majorana Zero Modes and Topological Quantum Phase Transition in Semiconductor Majorana Nanowires

Abstract: A number of recent works have discussed the issue of spinpolarization of a Majorana zero mode in condensed matter systems. Here we show that the spin polarization density of a Majorana zero mode, computed as an average of the spin operator over its wave function, isidentically zero. A single non-degenerate Majorana zero mode, therefore, does not couple to an applied magnetic field, except via hybridization with higher energy excited states (if present), which may perturb its wave function. If spin is defined by considering only the particle components of the wave function, as has been done in some recent works, Majorana zero modes do have a non-zero spatial profile of this quantity, which is measurable in scanning tunneling microscopy (STM) experiments. However, if such a quantity is measured in spin-resolved tunneling experiments (without spatial resolution), we show that it cannot be used as a unique signature of Majorana zero modes in the topologically nontrivial phase. As a by product, we show that in spatially in homogeneous systems (specifically, in systems with a soft boundary), accidental zero energy modes (which for all practical purposes behave as Majorana zero modes) can appear with increasing magnetic field even in the absence ofa topological quantum phase transition (TQPT). But only after gap closing and the associated TQPT, the modes are localized near the system edges, resulting in the maximum topological protection. In light of these considerations, demonstrating the nonlocal character of the topologically protected Majorana pair and its emergence after the systems undergoa TQPT, become critical tasks for the ongoing experimental search for Majorana bound states in condensed matter systems.

Electrochemistry of Nanostructured Materials: Implementation in Electrocatalysis for Energy Conversion Applications

Abstract: The study of electrochemical phenomena and electrocatalytic properties using chemical structures at nanoscale is a rapidly emerging area in electrochemical and material science. A notable achievement in the performance of functional materials has been the understanding of the electrochemical mechanisms and the development of advanced catalytic nanostructured materials. Consequently, efforts will continue to synthesise and explore novel nanoscale materials to meet the requirement of sustainable and renewable resources owing to climate change and the decreasing availability of fossil fuels. The present review explores in depth the current state of the nanoscale frontier in electrochemistry. It includes investigation of electrochemical processes of nanostructured materials, electroanalysis using nanostructured materials, fundamental aspects of electron transfer and mass transfer at nanoscale surface during catalysis. It will also provide an understanding of the activity and stability of electrocatalysts under critical experimental conditions. A brief discussion on the utilisation of nanostructured materials in energy domains such as fuel cells is presented at the end.

Measuring Temperature of Reflected Shock Wave Using a Standard Chemical Reaction

Abstract: The importance of temperature calibration of a single pulseshock tube for obtaining precise kinetics data is well recognized. Someof the commonly used standard reactions for chemical thermometricmeasurements and their uses in our recent studies are discussed in thisarticle. The chemical standards listed include cyclopropane-carbonitrile,1,1,1-trifluoroethane, cyclohexene, and ethyl chloride. A recent temperaturecalibration study of one of our chemical shock tubes performed using ethylchloride as external standard for the temperature range from 982–1183 Kis presented. The reflected shock temperatures calculated using machnumber, T5(Ms), and those using ethyl chloride as external standard (T5kin)were found to differ by ~1.3–4.5 % in the studied temperature range.This is an improvement compared to our previously reported calibrationdata where the corresponding difference was in the range ~8–14 %. Thedifference in the calibration factor is due to the various changes made inthe shock tube and it highlights the importance of calibration, if and whenthe shock tube is modified.

Electrical Transport in Vanadium Dioxide Nanostructures – New Physics and Potential Applications

Abstract: VO2 is an interesting correlated electron material that exhibits an above room temperature metal-insulator transition that spans more than four orders of magnitude in conductivity. This system has been studied extensively due to the fundamental questions about the mechanism behind the metal-insulator transitions and the possibility of utilizing these nanostructures in a variety of applications such as electrical switches, optical switches and bolometers. The tunability of the transition temperature, hysteresis widths, and magnitude of hysteresis using a slew of experimental techniques make this system an interesting material to study. In this review, we present an experimental overview of the electrical transport properties of vanadium oxide nanostructures and discuss its potential for applications.

Application of Fiber Bragg Grating Sensors for Dynamic Tests in Wind Tunnels

Abstract: This paper presents an introduction to Fiber Bragg Grating(FBG) sensors and a typical application for dynamic tests in wind tunnels.Bench tests were carried out to measure the dynamic response of a crossflexure pivot using FBG sensor and a conventional strain gage sensorsimultaneously. The results suggest that FBG sensors, which are mucheasy to handle as compared to strain gages, can be effectively used formeasurement of dynamic derivatives in a wind tunnel.

A Pedagogic Review on Designing Model Topological Insulators

Abstract: Following the centuries old concept of the quantization of fluxthrough a Gaussian curvature (Euler characteristic) and its successivedispersal into various condensed matter properties such as quantum Halleffect, and topological invariants, we can establish a simple and fairlyuniversal understanding of various modern topological insulators (TIs).Formation of a periodic lattice (which is a non-trivial Gaussian curvature) of‘cyclotron orbits’ with applied magnetic field, or ‘chiral orbits’ with fictitious‘momentum space magnetic field’ (Berry curvature) guarantees its fluxquantization, and thus integer quantum Hall (IQH), and quantum spin-Hall(QSH) insulators, respectively, occur. The bulk-boundary correspondence associated with all classes of TIs dictates that some sort of pumping orpolarization of a ‘quantity’ at the boundary must be associated with theflux quantization or topological invariant in the bulk. Unlike charge or spin accumulations at the edge for IQH and QSH states, the time-reversal (TR) invariant Z2 TI class pumps a mathematical quantity called ‘TR polarization’to the surface. This requires that the valence electron’s wavefunction (say,ψ ↑(k)) switches to its TR conjugate ψ↓ ( †(-k) ) odd number of times in halfof the Brillouin zone. These two universal features can be considered as‘targets’ to design and predict various TIs. For example, we demonstrate that when two adjacent atomic chains or layers are assembled with opposites pin-orbit coupling (SOC), serving as the TR partner to each other, the system naturally becomes a Z2 TI. This review delivers a holistic overview on various concepts, computational schemes, and engineering principles of TIs.

Phase-Field Modeling of Electrochemical Phenomena

Abstract: In this article, we review the progress in the field of application of phase-field models for simulating electrochemical phenomena such as etching, electro-deposition, electromigration, intercalation etc. As we will see the present models can be considered as extensions of the already existing models for diffusion coupled phase transformations. We briefly visit the essential thermodynamics of the electrochemical interfaces and the basis of phase-field formulations existing in literature for modeling electrochemical reactions and electromigration. Thereafter, we give a brief overview of the present state of literature in this field.

Time-Resolved Digital Interferometry for High Speed Flow Visualization in Hypersonic Shock Tunnel

Abstract: In this article we report on the development of time-resolved digital interferometric visualization technique integrated with short duration (1 ms) hypersonic shock tunnel. Dynamics of the Mach 6 flow field around 40° blunt cone model is visualized using a combination of cw laser, Mach-Zehnder interferometer and a very high-speed digital camera. Digital interferograms with time resolution of 139 μs were recorded during 1 ms test time of our HST4 facility. Measured time-resolved evolution of shock structure around the model is compared with Schlieren technique and CFD simulation results to validate the proposed technique. Infinite fringe interferograms are evaluated using active contour technique and Fourier transform fringe analysis to extract density data of the hypersonic flow field around the model. Estimated time-resolved density data show the variation in the density within shock layer.

Non-Enzymatic Sensing of D-Sorbitol using Polyaniline-Coated Stainless Steel Electrodes

Abstract: The Potentiodynamic deposition of polyaniline on stainless steel electrodes has been carried out using the anionic surfactant sodium tetradecyl sulphate in the presence of acetic acid. The PANI-coated SS electrode was characterized using different spectroscopic and microscopic techniques. The efficacy of the electrode was analyzed for non-enzymatic sensing of D-sorbitol. Amperometric and impedimetric studies reveal the suitability of the electrode for sensing. A detection limit of 5 μM along with a linear range spanning of 75–637 μM and sensitivity of 0.027 μA μM−1 is deduced from the amperometric analysis.