Department of Metallurgical and Materials Engineering

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

A composite of two different medium entropy alloys (MEAs, i.e., CoCrFeNi and AlCoCrFe) was synthesized using ball milling and spark plasma sintering. The composite microstructure contains a homogenous distribution of fcc and bcc phases with submicron-sized grains and exhibits excellent microstructural and phase stability even after 100 h heat treatment at 800 °C. The composite provides a combination of high compressive strength, adequate plastic strain, and multiple strain-hardening stages at room temperature. This first exploratory study on a MEA composite can be used as a template to other systems and illustrates the feasibility of combining two or more MEAs. © 2020 Acta Materialia Inc.

World University root node

Department of Applied Mechanics

Scripta Materialia

Composite of medium entropy alloys synthesized using spark plasma sintering

Nanoparticles have a wide range of applications due to their unique geometry and arrangement of atoms. For a precise structure-property correlation, information regarding atomically resolved 3D structures of nanoparticles is utmost beneficial. Though modern aberration-corrected transmission electron microscopes can resolve atoms with the sub-angstrom resolution, an atomic-scale 3D reconstruction of a nanoparticle using Scanning Transmission Electron Microscopy (STEM) based tomographic method faces hurdles due to high electron irradiation damage and “missing-wedge”. Instead, inline 3D holography based tomographic reconstructions from single projection registered at low electron doses is more suitable for defining atomic positions at nanostructures. Nanoparticles are generally supported on amorphous carbon film for Transmission Electron Microscopy (TEM) experiments. However, neglecting the influence of carbon film on the tomographic reconstruction of the nanoparticle may lead to ambiguity. To address this issue, the effect of amorphous carbon support was quantitatively studied using simulations and experiments and it was revealed that increasing thickness and/or density of carbon support increases distortion in tomograms. © 2020 Elsevier B.V.

Ultramicroscopy

Atomically resolved tomographic reconstruction of nanoparticles from single projection: Influence of amorphous carbon support

The generation of novel mesoporous materials with well-defined structure and accessible pore networks is helpful in both fundamental and energy-related research. Nanocasting mesoporous earth-abundant materials and their composite materials offer opportunities to make electrochemically active materials that allow scalable production and cost-effectiveness. Recently, due to their intrinsic open pore structure as well as high surface areas, various mesoporous cobalt-based ordered materials have been applied to electrocatalysis, rechargeable batteries, and supercapacitors. In this review, we have critically evaluated the advancements made specifically in three- and two-dimensionally (3D/2D) electrode Co-based materials (oxides, nitrides, phosphides, and sulfides). We outline foreseeable challenges and issues for the utilization of mesostructured cobalt-based electrode materials. This review also provides guidelines for further work to those who work on energy-related applications of mesoporous cobalt-based materials. [Figure not available: see fulltext.] © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Electrocatalysis

Recent Advances in Nanocasting Cobalt-Based Mesoporous Materials for Energy Storage and Conversion

The potential impacts of climate change on the water resources of the Narmada basin in central India has been investigated using the Soil and Water Assessment Tool (SWAT). The existing dams in the river basin have been incorporated in the model setups, calibration and validation. The COordinated Regional climate Downscaling EXperiment datasets for South-Asia (CORDEX-SA) at 0.5° × 0.5° resolution for four-time horizons, viz., 1970–05 (historical), 2006–40 (near-term), 2041–70 (mid-term) and 2071–99 (end-term) under Representative Concentration Pathways (RCP) scenarios, RCP4.5 and RCP8.5 has been used to investigate the changes in the future climate and simulation of future streamflow. The proposed dams have also been incorporated for modeling the future developmental scenarios. The scenario analysis based on the projected climate variables has led to the inference that the change in the precipitation pattern coupled with the warming trends, maybe contributing towards higher variability in water availability. A future scenario of lower water availability and higher water demands thus calls for optimal utilization of available water resources in the future, so that the higher water demands can be satisfied with lower anticipated future flows. Various alternatives were explored for devising adaptation strategies using the engineering/technical solutions in which the optimal water resources management approaches were explored using the simulation-only and the genetic algorithm based simulation–optimization approaches. The simulation–optimization framework based integrated reservoir operation of four reservoirs has led to better reservoir performance and the number of irrigation failures has decreased substantially from 92 to 12 during 2006–40, 86 to 22 during 2041–70 and 89 to 10 during 2071–99. The hydropower failures have also decreased considerably from 202 to 96 during 2006–40, 192 to 28 during 2041–70 and 179 to 67 during 2071–99 under the RCP8.5 scenario. There were no failures in meeting the domestic water supply and environment flow demands. This may be an important adaptation measure to address the issues of climate change impacts on the water resources in the future in the Narmada basin. © 2021 Elsevier B.V.

Department Of Civil Engineering

Journal of Hydrology

Optimal reservoir operation – A climate change adaptation strategy for Narmada basin in central India

Semiconducting metal oxides (SMOXs) are used widely for gas sensors. However, the effect of ambient humidity on the baseline and sensitivity of the chemiresistors is still a largely unsolved problem, reducing sensor accuracy and causing complications for sensor calibrations. Presented here is a general strategy to overcome water-sensitivity issues by coating SMOXs with a hydrophobic polymer separated by a metal–organic framework (MOF) layer that preserves the SMOX surface and serves a gas-selective function. Sensor devices using these nanoparticles display near-constant responses even when humidity is varied across a wide range [0–90 % relative humidity (RH)]. Furthermore, the sensor delivers notable performance below 20 % RH whereas other water-resistance strategies typically fail. Selectivity enhancement and humidity-independent sensitivity are concomitantly achieved using this approach. The reported tandem coating strategy is expected to be relevant for a wide range of SMOXs, leading to a new generation of gas sensors with excellent humidity-resistant performance. © 2020 Wiley-VCH GmbH

Angewandte Chemie - International Edition

Surface Functionalized Sensors for Humidity-Independent Gas Detection

Oxygen electroreduction (ORR)viaa two-electron pathway is a promising alternative for hydrogen peroxide (H2O2) synthesis in small-scale applications. In this work, nitrogen and sulfur co-doped carbon coated zinc sulfide nanoparticles (ZnS@C) are synthesized using facile high-temperature annealing. In an alkaline electrolyte, the presence of ZnS suppresses the reduction of H2O2during the ORR and contributes to high H2O2selectivity (∼90%) over a wide potential range (0.40-0.80 V). Continuous generation of H2O2is in turn achieved at an outstanding rate of 1.485 mol gcat.−1h−1with a faradaic efficiency of 93.7%. © The Royal Society of Chemistry 2021.

Dalton Transactions

Nitrogen, sulfur co-doped carbon coated zinc sulfide for efficient hydrogen peroxide electrosynthesis

Hypothesis: Encapsulation of core nanoparticles using reverse micelles is a widely used approach owing to its effective organization. Hence, it is of value to analyze the physicochemical mechanisms associated with the reverse micelle-based encapsulation for the choice of appropriate surfactant for the encapsulation process. The presence of ionic micelles, catalyst ions and surface charge of the core nanoparticles are expected to influence the stability of reverse micelles. Hence, it is of value to find the optimized conditions for stable reverse micelles formation through understanding the multiple double layer formation inside of ionic reverse micelles. Experiments: Reverse micelle systems stabilized by non-ionic, anionic and cationic surfactants are formulated with the presence of ammonia ions and negatively charged core nanoparticles. The structure of reverse micelles is studied by measuring its average hydrodynamic diameter and optical transmittance measurements. Shell encapsulation experiments are performed in stable and unstable reverse micellar structures. Findings: Ionic surfactants help to form stable reverse micellar structures. Multiple double layers formation is explained in ionic reverse micelles for the first time. Magnetite@silica is chosen as a model system to demonstrate the observed effects. The results obtained could remove the complexity in understanding the ionic reverse micellar systems for the functionalization of nanoparticles. © 2021 Elsevier B.V.

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Ionic amphiphile stabilized reverse micellar systems and their implications for nanoencapsulation

The main focus of the present study is to compare the effect of different alloying elements on Al–Mg alloy foams. Al–Mg15–X10 (X = Cu, Zn and Si) alloy foams were produced via powder metallurgy route by using Mg as a blowing agent. Macro- and microstructural characterisations of the foams were performed using X-ray tomography, X-ray diffraction and scanning electron microscope. Corrosion studies such as weight loss measurement, hydrogen evolution method and potentiodynamic test were conducted. Mechanical properties were evaluated by subjecting the samples to quasi-static compression and microhardness tests. All the alloy foams showed a comparable structure. The Cu-containing foams exhibited the highest strength, while the Zn-containing foams showed the highest expansion. However, the other properties such as brittleness, elastic modulus and burning nature were found to be better for the Si-containing foams. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Journal of Materials Science

Influence of Cu, Zn and Si alloying elements on Al alloy foams produced using Mg blowing agent

The electrocapillary effect is the change in interfacial tension between two immiscible liquids when subjected to an electric field across the interface. The change in interfacial tension occurs due to variations in the surface charge density of adsorbed ions or polar species at the interface. In the present work, we provide fluid mechanical insights into electrocapillarity-based dynamics of an interface between a passive air layer and a thin liquid film that has small, but finite electrical conductivity. We formulate and solve mathematical equations that model the situation in which a liquid film bounded by an air layer of controllable thickness is sandwiched between two electrode plates, and an electric field is applied across the layers. As the liquid and air have different conductivities, free charges would accumulate at the liquid-air interface to ensure that current is conserved across the layers. In our model, the interfacial tension is assumed to vary as per the classical Lippmann's equation. The present mathematical model describes spatiotemporal variation of the film height and interfacial charge density as a function of the applied potential, air layer width, and the sensitivity of interfacial tension to the electric potential. Our results show that ultrathin liquid films (<100 nm) in presence of electrocapillary Marangoni effect are destabilized and break up faster than in its absence. Furthermore, by controlling the air gap width, different morphological patterns can be generated. Finally, we illustrate that the dynamics is profoundly affected if the electrode plate bounding the liquid film possesses patterned wettability. © 2021 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

Electrocapillary effect in liquid films with an electrically charged interface

In this investigation, the hybrid of ZrO2 decorated rGO functionalised carbon foam (ZRCF) as template has been introduced for removing arsenic (V) (As(V)) contamination from the water and easily separated out from water after post decontamination without any separation techniques. An excellent arsenic (As(V)) removal efficiency of 45.4μgg−1 in 60 min has been revealed by prepared ZRCF treated at 300 °C in air. Further probing the adsorption mechanism, both linear and nonlinear kinetics and isotherm models have been employed on the experimental data. It is revealed that the fitted linear kinetics data better explains the PSO kinetics and linear adsorption isotherm describes the best fitting of equilibrium data in Langmuir isotherm based on the regression coefficient (0.98) and χ2 (7.40) value. The present investigation is evaluated the adsorption mechanism between adsorbate and adsorbent such as electrostatic attraction, HSAB reaction and bi-dentate ligand formation. © 2020 Elsevier B.V.