Papers by Abhishek Tewari
Journal of the European Ceramic Society
WIREs Computational Molecular Science
The efficient search for crystals with targeted properties is a significant challenge in material... more The efficient search for crystals with targeted properties is a significant challenge in materials discovery. The rapidly growing field of materials informatics has so far primarily focused on the application of AI/ML models to predict the properties of known crystals from their fundamental and derived properties as descriptors. In the last few years, deep learning-based approaches have spawned a slew of innovative data-driven materials research applications. Materials scientists have used these techniques for the reverse engineering of crystal structures for target applications. However, one of the challenges has been the representation of the crystal structures in the machine readable format. Proposed representations in the literature lack in generality and scalability. In this paper, we train a conditional variational autoencoder with a scalable and invertible representation along with the elemental properties of the constituents as descriptors to inverse-design new crystal struc...
Chemistry of Materials, 2006
The preparation of biphasic mixtures (HAP +-TCP) of controlled ratios with the combined substitut... more The preparation of biphasic mixtures (HAP +-TCP) of controlled ratios with the combined substitution of essential biocompatible trace elements (Na, Mg, and F) was carried out by an aqueous precipitation method. The results showed that incorporated elements have played a significant role in the thermal stability of the apatites up to 1400°C, and that increased calcium deficiency in the apatites has led to the formation of a higher proportion of-TCP in the biphasic mixtures. However, minor discrepancies in the structural parameters due to the incorporated trace elements and the matching of phases of the synthesized powders with respect to the stoichiometric HAP were apparent from the present investigation.
Computational Materials Science
Journal of the European Ceramic Society, 2011
Journal of Applied Physics, 2009
Page 1. Time constant determination for electrical equivalent of biological cells Ashutosh Kumar ... more Page 1. Time constant determination for electrical equivalent of biological cells Ashutosh Kumar Dubey, Shourya Dutta-Gupta, Ravi Kumar, Abhishek Tewari, and Bikramjit Basua) Department Materials and Metallurgical Engineering ...
Acta Materialia, 2009
In selecting and designing materials for certain engineering applications, the resistance to mate... more In selecting and designing materials for certain engineering applications, the resistance to material damage or removal of material from contacting surfaces in relative motion is an important factor. To determine these properties, laboratory tests are routinely conducted on new materials using a variety of tribometers with different contact configurations (ball-on-flat, pin-on-disc, etc.). The wear volume is typically measured as a
The dataset includes all the input files for the molecular dynamics simulation of Glauber's s... more The dataset includes all the input files for the molecular dynamics simulation of Glauber's salt phase change simulations and the effect of ionic salt additives on phase change behavior.
Computational Materials Science
Data-Centric Engineering
The search space for new thermoelectric oxides has been limited to the alloys of a few known syst... more The search space for new thermoelectric oxides has been limited to the alloys of a few known systems, such as ZnO, SrTiO3, and CaMnO3. Notwithstanding the high power factor, their high thermal conductivity is a roadblock in achieving higher efficiency. In this paper, we apply machine learning (ML) models for discovering novel transition metal oxides with low lattice thermal conductivity ( $ {k}_L $ ). A two-step process is proposed to address the problem of small datasets frequently encountered in material informatics. First, a gradient-boosted tree classifier is learnt to categorize unknown compounds into three categories of $ {k}_L $ : low, medium, and high. In the second step, we fit regression models on the targeted class (i.e., low $ {k}_L $ ) to estimate $ {k}_L $ with an $ {R}^2>0.9 $ . Gradient boosted tree model was also used to identify key material properties influencing classification of $ {k}_L $ , namely lattice energy per atom, atom density, band gap, mass density,...
Ceramics International, 2016
Wear, 2012
For a large number of non-oxide ceramic/metal as well as for non-oxide particulate reinforced com... more For a large number of non-oxide ceramic/metal as well as for non-oxide particulate reinforced composite/metal tribocouples, oxidative wear is reported to play a major role in the overall damage and material removal process. The designing of new materials with improved resistance to oxidative wear requires understanding of the combined effect of the material properties and operating parameters on the wear resistance. In this paper, an analytical model to predict the dependence of the oxidative wear volume on load and sliding velocity is presented. The model is developed using basic chemical kinetics and Hertzian contact mechanics, and is valid for the case of a stable oxide layer. Exponential dependence of wear volume on operating parameters (load, sliding velocity) is predicted in the proposed model. It has been shown to successfully explain the qualitative experimental load dependence of the wear volume for five ceramic/metal tribocouples (Al 2 O 3 /steel, WC-TiC-Co/steel, TiB 2-MoSi 2 /steel, ASP23 steel/alumina and Ti6Al4V/alumina) that exhibit oxidative wear. The activation energy of the oxidation of metallic counter bodies under fretting conditions was also calculated using the model, which turns out to be significantly lower than in the static conditions.
Journal of the American Ceramic Society
Transition element dopants (e.g., Y, La) are commonly used as sintering aids in polycrystalline a... more Transition element dopants (e.g., Y, La) are commonly used as sintering aids in polycrystalline alumina ceramics, which segregate to the grain boundaries and control the grain-boundary mobility. However, due to the extremely thin (<2 nm) layer of segregated dopants, the experimental characterization of the segregated alumina grain boundaries is a complex task. Computational studies have focused only on tilt grain boundaries, which are only a small fraction in a sintered alumina sample. In this study, a quantitative characterization of the segregation of Y and La at general high angle grain boundaries in transparent alumina is carried out using a unique combination of advanced TEM and near coincidence grain-boundary atomistic simulations. The result show that high angle grain boundaries may lead to enhanced grain growth in comparison to symmetric tilt twin grain boundaries due to the reduced configuration entropy for dopant segregation and higher order grain-boundary complexions. ...
Journal of the American Ceramic Society, 2015
ABSTRACT Transition element dopants (e.g., Y, La) are commonly used as sintering aids in polycrys... more ABSTRACT Transition element dopants (e.g., Y, La) are commonly used as sintering aids in polycrystalline alumina ceramics, which segregate to the grain boundaries and control the grain-boundary mobility. However, due to the extremely thin (&lt;2 nm) layer of segregated dopants, the experimental characterization of the segregated alumina grain boundaries is a complex task. Computational studies have focused only on tilt grain boundaries, which are only a small fraction in a sintered alumina sample. In this study, a quantitative characterization of the segregation of Y and La at general high angle grain boundaries in transparent alumina is carried out using a unique combination of advanced TEM and near coincidence grain-boundary atomistic simulations. The result show that high angle grain boundaries may lead to enhanced grain growth in comparison to symmetric tilt twin grain boundaries due to the reduced configuration entropy for dopant segregation and higher order grain-boundary complexions. On the other hand, multidoping with different dopants was shown to be more beneficial than single doping due to its contribution in increasing the configurational entropy for segregation. The advanced TEM analysis showed Y and La distributions and concentrations on a series of general grain boundaries in very good agreement with the atomistic simulations. This validation of atomistic modeling technique used in this study means, as it a generic method, can be used as a predictive tool to design ceramic microstructure and properties.
Oxygen diffusion plays an important role in grain growth and densification during the sintering o... more Oxygen diffusion plays an important role in grain growth and densification during the sintering of alumina ceramics and governs high-temperature processes such as creep. The atomistic mechanism for oxygen diffusion in alumina is, however, still debated; atomistic calculations not being able to match experimentally determined activation energies for oxygen vacancy diffusion. These calculations are, however, usually performed for perfectly pure crystals, whereas virtually every experimental alumina sample contains a significant fraction of impurity/ dopants ions. In this study, we use atomistic defect cluster and nudged elastic band (NEB) calculations to model the effect of Mg impurities/dopants on defect binding energies and migration barriers. We find that oxygen vacancies can form energetically favorable clusters with Mg, which reduces the number of mobile species and leads to an additional 1.5 eV energy barrier for the detachment of a single vacancy from Mg. The migration barriers of diffusive jumps change such that an enhanced concentration of oxygen vacancies is expected around Mg ions. Mg impurities were also found to cause destabilization of certain vacancy configurations as well as enhanced vacancyvacancy interaction.
Small amounts of anion impurities (e.g. Cl), which are incorporated during the synthesis of ceram... more Small amounts of anion impurities (e.g. Cl), which are incorporated during the synthesis of ceramic powders, can affect the properties and microstructure of the final sintered ceramic. The effect of anion impurities is a little studied and poorly understood phenomenon. In this work a combination of STEM-EDX analysis and atomistic modeling approach was used to understand the segregation of Cl in transparent alumina ceramics. A high resolution analytical electron microscopy study showed the presence of Cl at the grain boundaries and especially at triple points. Atomistic simulations were carried out to understand the origins and consequences of such segregation. Segregation energy calculations predict a strong segregation of Cl at the different surfaces and grain boundaries of alumina. A higher coordination number of Cl at surfaces was observed, which indicates strong ionic bonds making it difficult to remove at low temperature, which explains the presence of Cl at triple points.
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Papers by Abhishek Tewari