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Materials Science Engineering (MSE) Department

>>Department Members

The Materials Science and Engineering (MSE) Department aims to advance materials science and target leading edge applications such as materials for alternative energy and nanostructured devices. The Department’s research efforts seek to establish relationships among structure, property and functions through the use of computer modelling and simulation techniques.


The MSE Department consists of five major Capability Groups:

Defects

Interfaces

Microstructure

Optics & Transport

Applied Thermodynamics

Defects

The Defects Capability Group seeks to design new materials or modify properties of materials through the computational quantum chemistry simulations on point defects, such as interstitials, substitutions, vacancies and antisites.

Research areas:

  • Native defects in semiconductors
  • Effects of defect on electrical and optical properties
  • Experimental growth conditions for achieving desired properties
  • Other issues relative to defects

Figure 1: Experimental I-V Curve of p-type ZnO.

Selected Publications

  • G. M. Gavaza, Z. G Yu , P. Wu, “A universal theoretical approach for examining the efficiency of doping processes in semiconductors” J. App. Phys. 105, 113711 (2009)
  • P. Wu, V. Ligatchev. Z. G Yu, J. Zheng, M. Sullivan, and Y. Zeng, “Defects in codoped NiO with gigantic dielectric response” Phys. Rev. B. 79, 235122 (2009)

Interfaces

The researchers in the Interfaces Capability Group are interested in studying interfaces between two materials. There is a need to understand if any two materials adhere, and what the properties of the interface are. In many cases especially for electronics applications, we need to know if the interface between a polymer and metal are compatible for the particular use.

Research areas:

  • Study of interfacial properties
  • Test new methodologies to include van der Waals interactions in density functional theory
  • Study chemical reactions on surfaces, especially metals
  • Study interesting interfacial problems, including consumer care and graphene applications

Figure 2: Polymide Composite.

Selected Publications

  • Jia Zhang, Hongmei Jin, Michael B. Sullivan, Freda Chiang Huay Lim, and Ping Wu. Study of Pd-Au bimetallic catalysts for CO oxidation reaction by DFT calculations Phys. Chem. Chem. Phys., 2009, 11, 1441-1446. DOI: 10.1039/b814647k
  • Jia Zhang, Michael B. Sullivan, Jianwei Zheng, Kian Ping Loh and Ping Wu. Theoretical Study on Polyimide-Cu(100)/Ni(100) Adhesion Chem. Mater., 2006, 18, 5312-5316. DOI: 10.1021/cm052865n

Microstructure

Most engineering materials are polycrystalline, the properties of which can depend strongly on processing conditions during fabrication. The causal link is via changes in microstructure, which includes the arrangement of grain- or interphase-boundaries, the distribution of the size of grains or additional phases, and so on.

The Microstructure Capability Group undertakes research in microstructures and materials through the following paradigms:

  • Science: Understand the relationship between microstructure, processing, and property of materials.
  • Engineering: Optimize material properties by manipulating processing conditions.
  • Application: Guide experimentalists/industrial partners to improve properties of materials and devices.

Figure 3: Research in Microstructure Capability Group.

Research Directions

  • Methodology: Use multiphysics/multiscale approach to model microstructure-processing & microstructure-property relations. Tools for simulation/modeling include
    • molecular dynamics
    • kinetic monte carlo
    • phase field
    • population balance

  • Testbed: Choose interesting systems that have potential for applications; e.g.,
    • stress effect: Ge-Sb-Te (phase change memory)
    • chain-like structure: C-H (crude oil)
    • cage-like structure: CH4-H2O (natural gas)
    • ferroic transition: Ba-Ti-O (ferroelectric)


Optics and Transport

The work in the Optics and Transport Capability Group focuses on two main areas: Thermoelectrics and linear and nonlinear optics.

Thermoelectric Properties:
Thermoelectrics provide a technology for producing electrical energy from solar and other heat sources. Thermoelectric performance requires materials with high thermopower and low thermal conductivity.

Research areas:

  • Use ab initio methods such as Full Potential Linearize Augmented Plane Wave (FP-LAPW), and Boltzmann theory to simulate electronics structure and thermoelectric properties of materials to understand and improve thermal power.
  • By using the Non-equilibrium Green Function method, we study thermal transport in nanotructures, such as graphene nano-ribbons and nanowires.
  • Study the geometric effect on thermal transport to reduce the thermal transport in thermoelectric materials efficiently.
  • Design new thermoelectric materials for real applications.


Cover Picture of Physical Review Letters, Volume 104, Issue 17 (2010). Evolution of the Fermi surface of PtCoO2 with energy. (top) The surface at the actual Fermi energy; (bottom) The 0.1 electron volts higher.


Defect Graphene used to study thermoelectric properties

Papers

  • Khuong P. Ong, Jia Zhang, John Tse, Ping Wu, Phys. Rev. B. 81, 115120 (2010)
  • Khuong P. Ong, David J. Singh, Ping Wu, Phys. Rev. Lett. 104, 176601(2010)
  • J. Lan, J.-S Wang, C. K. Gan, and S. K. Chin, Phys. Rev. B 79, 115401(2009)
  • G. Liang, W. Huang, C. S. Koong, J.–S. Wang, and J. Lan, JAP 107, 014317 (2010)
  • J.–W. Jiang, J. Lan, J.-S. Wang, and B. Li, JAP 107, 054314 (2010)

Linear and Non-linear Optics
Optical materials play an important role in our lives. They have a very wide range of applications from LCD, to sensors and energy. Understanding the optical properties of materials will help us to design better materials for applications.

Research areas:
  • Study linear/non-linear optical properties and photovoltaic effects
  • Study exciton spectra
  • Design new optical materials
  • Study laser-solid interaction: dynamical response of solids to laser radiation:


Figure 5: Dielectric constant (a), reflectivity (b), optical conductivity (c) and (αhν)2 spectrum of LaCrO3. Δ1=3.40eV is the charge transfer gap and Δ0=2.15eV is the is the lowest optical gap (4A2g - 4T2g) (predicted)

Papers

  • Khuong P. Ong, Peter Blaha, Ping Wu, Phys.Rev. B.77, 073102(2008)
  • Khuong P. Ong, Kewu Bai, Peter Blaha, Ping Wu, Chem. Mat. 19, 634(2007)

Applied Thermodynamics

The Applied Thermodynamics Capability Group does research into the design of materials composition and processing parameters by thermodynamic and kinetic modeling, including
  • Prediction of melting points, surface tension, viscosities and so on
  • Simulation of microstructure evolution
  • Design of materials processing parameters

The Capability Group also undertakes research in material property prediction by a combination of first principles calculation and empirical modeling, including study of
  • Heat capacity by phonon calculation
  • Electron-phonon coupling in materials
  • Surface phases stability of the materials
  • Heat conductivity of materials

Application of molecular dynamics and quantum mechanical/ molecular modeling (QM/MM) hybrid method to property prediction, including
  • Solvation energy, conductivity and catalytic property of ionic liquid (Program)
  • Amorphous structure


Solder microstructure and XRD Results

Calculated Results

Modeling of ionic liquids

Programmes

Consumer Care


Everybody wants shinier hair and softer skin. The Consumer Care programme aims to build up capabilities relevant to the consumer product industry so as to better engage and collaborate with the consumer product companies. We are using molecular modeling techniques to improve fundamental understanding of the chemical, structural, and binding properties of materials which could help consumer product companies design and develop better products. We will focus on the following 3 research areas.

Research areas:
  • Hair and skin surface model. We would like to develop and refine a simple but accurate atomistic model of the hair and skin surface so as to be able to study material interactions with the surfaces.
  • Deposition. We are interested to study the various ways and factors that can affect material deposition onto a surface so as to be able to achieve targeted deposition.
  • Encapsulation. We would like to study how encapsulation can be used to affect the deposition and release of materials. This is important in situations where controlled release is desirable.

Figure 7: Model of Micellization of SDS Surfactant.

Corrosion

The performance of a structural material in critical environment depends on the material composition, the stability of oxide film and the effectiveness of any protection measures. Proper selection of materials can avoid or minimize the occurrence of different forms of corrosion, and enhance the structural life. The aim of this research is to understand the surface reactivity and stability of the structure materials under different environmental parameters, for examples, the dissolved O2, salinity, temperature, pressure and other external gases.

Research areas:
  • Surface reactivity, the electronic conductivity or the ionic conductivity of materials which control the kinetics of passivity formation.
  • Interface reaction and adhesion
  • Interaction of coating system with environment

Figure 8: Theoretical modeling of steel hot dip galvanizing of zinc to protect corrosion.


Nanomaterials
One main area within the nanomaterials program is spin transfer torque in magnetic materials.
Physics of the spin transfer torque in magnetic materials
Spin valves and magnetic tunnel junctions (MTJ) are critical components of existing and near-future high performance memory devices such as magnetoresistive random access memory (MRAM). The optimal design of these devices hinges on a clear understanding of the underlying physics of various factors that control the switching mechanism of the magnetization.
Research areas:

  • Magnetization dynamics involving spin transfer torque using micromagnetic codes
  • Density-functional calculations of the properties of magnetic materials

Catalysis
There are a number of areas we’re pursuing within the catalysis program. One is in clean energy. Hydrogen is considered to be an ideal energy carrier of the future due to its ultra-cleanness and high efficiency. Catalysis plays an important role in sustainable hydrogen economy, such as renewable H2 production from bio-ethanol.

Research areas:
  • To study catalytic reaction mechanisms
  • To investigate electronic structures of catalysts
  • To design new catalyst with improved activity and selectivity

Ionic Liquids

Ionic liquids (ILs) are molten salts with melting points that are in many cases below room temperature. The constituting cations and anions can be modified independently. The resulting possible combinations allow the synthesis of a virtually infinite number of possible ILs. This enables the design of task-specific liquids with desired chemical and physical properties. Ionic liquids are used as adjustable solvents, catalysts and electrolytes, just to mention a few of their applications.

Research areas:
  • ILs as alternative solvents:
    • Establishing the relation between ions and solvation properties
  • ILs in biocatalysis:
    • Analyzing the enzyme solvation and stabilization properties of ILs
  • ILs in extraction processes:
    • Finding the relation between ions and their extraction power
  • ILs in contact with water:
    • Predicting miscibility with water and water saturation concentrations

Figure 10: Intrusion of cations from IL into active site of solvated lipase enzyme.

Selected Publications

  • M. Klahn, A. Seduraman, P. Wu, J. Phys. Chem. B, 2008, 112, 10989
  • M. Klahn, A. Seduraman, P. Wu, J. Phys. Chem. B., 2008, 112, 13849
  • A. Seduraman, M. Klahn, P. Wu, CALPHAD J., 2009, 33, 605
  • M. Klahn, C. Stuber, A. Seduraman, P. Wu, J. Phys. Chem. B, 2010, 114, 2856
  • M. Klahn, G. S. Lim, A. Seduraman, P. Wu, Phys. Chem. Chem. Phys., 2011, DOI: 10.1039/C0CP01509A

Crystal Growth
Crystal growth is part of the phase transformation process which broadly covers:

  • nucleation, the initiation of a new phase from the parent phase,
  • growth, which leads to increase in size of the post-critical nuclei, followed by
  • coarsening, the process driven by interfacial energy reduction leading to the final microstructure, and
  • agglomeration, the process of collection of crystallites by collision into a larger mass.

We address the crystal growth process using atomistic simulations (molecular dynamics/kinetic monte carlo methods), continuum methods (phase field approach), and population dynamics relevant to different length and time scales.

Our pilot projects are
  • Formation of alkane wax and gas hydrate formation in deep sea environment.
  • Factors affecting crystalline to amorphous transformation in phase change materials for electronic memory applications.
Research areas:
  • Dynamics during nucleation to extract quantities such as nucleation rate, critical size, and free energy.
  • Calculation of effective and accurate equilibrium properties such as phase diagram and interfacial energy. Influence of nucleation and kinetic factors leading to growth, coarsening, and agglomeration.

Figure 11: Evidence of precursor phase during reverse sublimation.


Figure 12: Dendrite crystal with anisotropic surface energy grown from solution.


Dr. Michael Sullivan
Department Director



This page is last updated at: 11-Mar-2012