(18l) Nanoscale Materials for Energy Storage and Conversion

High efficiency energy storage and conversion are among the main challenges facing governments and industries that supply the energy needs of modern societies. Progress in the development and manufacturing of new low-dimensional and nanostructured materials, which can efficiently store and convert energy, may help us overcome these challenges â?? if we can design them correctly. In this regard, looking into the molecular structure and dynamics of new materials and characterizing their properties for such applications is an advantage of atomistic modeling.

My research goal is to adopt and utilize molecular modeling-based methods to characterize and predict the properties/behavior of novel materials/systems, and ultimately improve the efficiency of energy storage and conversion systems. I propose to create a multidisciplinary research program focusing on characterizing and predicting thermo-physical, transport and thermo-electrical properties of newly developed materials for energy applications.

Postdoctoral Project:  â??Thermal transport in Metal Organic Frameworks (MOFs)â?

Under supervision of Professor C. Wilmer and Professor A. McGaughey

Visiting Scholar:  â??Thermoelectric properties of single layer MoS₂ by using ab initio calculationsâ?

Under supervision of Professor S. Sinha

PhD Dissertation: â??Molecular-Level Modeling of Thermal Transport Mechanisms within Carbon Nanotube/Graphene-based Nanostructure-Enhanced Phase Change Materialsâ?

Under supervision of Professor J. M. Khodadadi and Professor P. Keblinski, RPI

MS Dissertation: â??Simulation of Turbulent Vortex Shedding Past a Square Cylinder near a Wallâ?

Under supervision of Professor M. Raisee

BS Dissertation: â??Analysis of Turbulent Flow through a Channel using 2nd and 3rd Grade Fluidsâ?

Under supervision of Professor G. Atefi

 

Past and Current Research:

My academic career path has been a blend of several fields of science and engineering. My formal training was in simulation, which I have learned on many different physical scales: Density Functional Theory (femto), Molecular Dynamics (nano), and Computational Fluid Dynamics (continuum).

My PhD research project was devoted to non-continuum-based modeling of the effects of adding nanoparticles to fluids/phase change materials (PCM) and the heat transport within the resulting nanoparticle suspensions/composites. I adopted the methodology within molecular dynamics simulation approach to calculate the thermal conductivity of multi-component systems. Using the established method and other advanced molecular dynamics-based methods, I studied heat transfer in nanofluids and nanostructure-enhanced PCM (NePCM). I found that among different reported mechanisms of heat transfer in nanofluids, only clustering of nanoparticles can result in high enhancement in thermal transport. For PCM (here, paraffin), introducing CNT and graphene sheets promotes aligning of the molecules in the direction parallel to the CNT axis and graphene surfaces, respectively and consequently leads to considerable enhancements in its thermal conductivity along those directions. Moreover, in collaboration with Dr. Jacksonâ??s group at Auburn University, by using molecular modeling, I found that presence of nanoparticles enhances the thin film elasto-hydrodynamic lubrication.

During my one-year stay at UIUC, by utilizing first principle and phonon calculations, I investigated the thermoelectric properties of single-layer molybdenum disulfide (SL-MoS₂) (a 2-D material) and found an anomalously large thermoelectric power factor. Moreover, I developed a new methodology in finding phonon relaxation times.

During the past two years at Pitt and CMU, I have been studying the mechanisms of heat transfer in Metal-organic frameworks (MOFs) during gas adsorption using molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations and spectral energy density (SED) calculations. All these research projects have led to important findings so far and have opened up room for new ideas to the nanoscale heat transfer community which call for more research work, some of which will be outlined in the following section.

Furthermore, over these years I have gained deep knowledge of various aspects of different modeling techniques including MD simulation, Density Functional Theory (DFT), Density Functional Perturbation Theory (DFPT), MC, SED, lattice dynamics, thermal conductivity calculations and quantum modeling that are suitable to be used in studying other interdisciplinary nanoscale research problems as well.

Future research plans

Project 1. Low-dimensional thermoelectric materials

Thermoelectric materials provide a direct way of converting waste heat and solar energy into electricity. For instance, they can be used to convert waste heat in vehicles into electricity. However, lack of a scalable source of thermoelectric materials having the required conversion efficiency has prevented commercializing these devices. One way to overcome the problem of low efficiency is to use low-dimensional materials. Recent developments in nanotechnology have made it possible to adjust the electrical and thermal properties of materials in such a way that they provide a higher amount of thermoelectric figure of merit.

I will devote one part of my research to study thermoelectric properties of 1- and 2-D materials (e.g., nanotubes, nanowires, single and few-layer materials) whose electronic structure and transport properties potentially allow designing more efficient thermoelectric systems. In this general research project, I will focus my research on three properties of materials required for evaluating their thermoelectric efficiency: (1) Seebeck coefficient, (2) electrical conductivity and (3) thermal conductivity. For evaluating the first two properties one needs information on electron relaxation times. I will use ab initio calculations to obtain the relaxation times for phonons and electrons, which are the parameters needed to evaluate the transport properties involved in characterizing the efficiency of thermoelectric materials.

Project 2. Thermal properties of metal-organic frameworks

Metal-organic frameworks (MOFs), porous materials with extremely high internal surface areas, can adsorb large amount of gases and can be used for natural gas storage (e.g. in passenger vehicles). However, one challenge with MOFs is the heat generated during gas adsorption which leads to high temperatures, and in turn, prevents gas adsorption and reduces storage capacity. In principle, designing systems that could dissipate heat more quickly can allow for faster filling times. However, designing porous materials with better thermal properties requires a detailed understanding of the atomic-scale heat transfer mechanisms, which is still lacking in the literature. I propose a research project aiming to further our understanding of heat transfer in these systems. In this project I will use the adopted state-of-the-art molecular modeling approaches including MD, GCMC and SED calculations to study these systems and predict the needed thermal properties.

Project 3. Thermal transport in nanostructure-enhanced energy storage systems

One of the most convenient ways to store thermal energy is using phase change materials (PCM). PCM offer their sizeable latent heat for storing thermal energy at a constant temperature. However, a weakness of such materials is their relatively low thermal conductivity, which strongly suppresses the energy charge/discharge rates. A challenging option is to suspend highly-conductive particles into PCM, which produces â??free-formâ? mixtures/composites5. This challenging problem is one of my research interests on which I will assign one part of my research group to work. I will use non-equilibrium MD method to characterize the required thermal properties of PCM composites. MD is an excellent candidate for handling the length and time scales that are expected in this problem.

Teaching Interests: 

For my future academic career, I am prepared to teach general undergraduate and advanced graduate level courses in chemical Engineering, mechanical engineering and materials science, such as heat transfer, fluid mechanics and thermodynamics. Moreover, I would also like to teach interdisciplinary courses such as â??statistical physicsâ? and â??transport phenomenaâ?.

I believe that with the recent growing demands for smaller scale technologies (e.g. nanotechnology), leading engineering departments need to develop courses related to these areas. During the past years dealing with projects in nanoscience, I have always been thinking of developing a course or courses that can effectively address both basic physics and techniques required in the burgeoning areas for engineering students. I think â??nanoscale transport phenomenaâ? and â??molecular modelingâ? could be two of such new proper courses within the department of mechanical engineering.

Selected Publications:

H. Babaei, A. J. H. McGaughey and C. E. Wilmer, Effect of pore size and shape on the thermal conductivity of metal-organic frameworks, Chemical Science (2016). DOI: 10.1039/c6sc03704f.

H. Babaei and C. E. Wilmer, Mechanisms of Heat Transfer in Porous Crystals Containing Adsorbed Gases: Applications to Metal-Organic Frameworks, Physical Review Letters 116, 025902 (2016). PRL Editors' Suggestion.

H. Babaei, J. M. Khodadadi, and S. Sinha, Large theoretical thermoelectric power factor of suspended single-layer MoS₂, Applied Physics Letter 105, 193901 (2014).

H. Ghaednia, H. Babaei, R. L. Jackson, M. J. Bozack, J. M. Khodadadi, The effect of nanoparticles on thin film elasto-hydrodynamic lubrication, Applied Physics Letters, 103(26), 263111 (2013). *The first two authors contributed equally to this work*.

H. Babaei, P. Keblinski, and J. M. Khodadadi, Improvement in thermal conductivity of paraffin by adding high aspect-ratio carbon-based nano-fillers, Physics Letters A, 377, 1358â??1361 (2013).

H. Babaei, P. Keblinski, and J. M. Khodadadi, A Proof for Insignificant Effect of Brownian Motion-Induced Micro-Convection on Thermal Conductivity of Nanofluids by Utilizing Molecular Dynamics Simulations, J. Appl. Phys, 113, 084302 (2013).

J. M. Khodadadi, Liwu Fan and Hasan Babaei, Thermal Conductivity Enhancement of Nanostructure-Based Colloidal Suspensions Utilized as Phase Change Materials for Thermal Energy Storage: A Review, Renewable & Sustainable Energy Reviews, 24, 418 (2013).

H. Babaei, P. Keblinski, and J. M. Khodadadi, Thermal conductivity enhancement of paraffin by increasing the alignment of molecules through adding CNT/Graphene, International Journal of Heat and Mass Transfer, 58, 209 (2013).

H. Babaei, P. Keblinski, and J. M. Khodadadi, Equilibrium Molecular Dynamics Determination of Thermal Conductivity for Multi-Component Systems, J. Appl. Phys. 112, 054310 (2012).

M. Raisee, A. Jafari, H. Babaei, H. Iacovides, Two-Dimensional Prediction of Time-Dependent, Turbulent Flow around a Square Cylinder Confined in a Channel, International Journal for Numerical Methods in Fluids, 62, 1232 (2010).

Successful Proposals: ACS Petroleum Research Fund, 2015-2018; AL-EPSCoR GRSP Fellowship 2010-2014 ($75,000)