Research

Current Students

	Shawn Coleman Ph.D. Microelectronics/Photonics: Materials Resume
	James Stewart M.S. Microelectronics/Photonics: Materials Resume
	Alex Sudibjo M.S. Mechanical Engineering Resume
	Varun Ullal M.S. Mechanical Engineering Resume

Current Research Projects

Atomistic Modeling of Vapor Deposition Processes

The research objective of this project is to elucidate the fundamental nanoscale and mesoscale mechanisms associated with microstructure development and evolution during vapor deposition, through combined use of atomistic and phase-field simulations. Historically, models for microstructure development during vapor deposition are formulated via extensive experimentation and materials characterization. These phenomenological models do not consider atomic or mesoscale material behavior and thus cannot predict microstructure development in complex heterophase material systems, such as alumina. In this work, atomistic simulations will be used to provide an understanding of the role of ion flux on phase evolution and to compute interface energies between solid metastable phases in alumina. This information will be incorporated into a phase-field model and used to study phase formation and evolution in alumina thin films during simulated physical vapor deposition conditions.

Student: Shawn Coleman
Collaborators: Matt Gordon (University of Arkansas), Dave Glocker (IsoFlux Inc.)
Funding: National Science Foundation CAREER CMMI#0954505, National Science Foundation S-STEM DUE#0728636

Nucleation and Motion of Defects in MoS₂

Recent focus on energy efficiency has motivated heavy machinery manufacturers to use nanoparticle-based lubricants that respond at different pressure and temperature widows. In this work, environmentally-friendly nanoparticles of molybdenum disulphide (MoS2) are studied as a solid lubricant. To elucidate the ability of MoS2 nanoparticles to be tunable to specific temperature regimes, it is first necessary to understand fundamentally the structure and size-dependent mechanical behavior of MoS2 nanoparticles.

Student: James Stewart
Collaborator: Ajay Malshe (University of Arkansas)
Funding: National Science Foundation S-STEM DUE#0728636

Diffusion of Atmospheric Penetrate in PDMS

This research focuses on the fundamental processes of corrosion and multi-phase diffusion in metal particle polymer composites with functionalized nano behavior. The knowledge attained by this research will enable a new type of MEMS-based corrosion sensor technology that is small-size, tailorable and smart, ultimately allowing the US to better focus financial investments earmarked for infrastructure repair. Atomistic simulation is used to study the nanoscale details of diffusion in particle polymer composites. The proposed simulations will provide a detailed understanding of the role of the inclusions on the structure of the polymer chains in the matrix and on the transport of corrosive molecules through the composite. Fundamental aspects of diffusion in the composites studied in this work potentially have broad applicability to other sensing technologies.

Students: Alex Sudibjo, Varun Ullal
Collaborator: Adam Huang (University of Arkansas)
Funding: National Science Foundation CMMI#0800718

Plastic Deformation of Nanocrystalline Metallic Alloys

In this work, molecular dynamics simulations are used to study dislocation activity in single-crystal and nanocrystalline copper with low concentrations of antimony (0.0-1.0 at.%Sb). In single crystal models, MD simulations show that the strained regions around substitutional Sb atoms act as sources for partial dislocations and that the dislocation nucleation stress decreases with increasing concentration of antimony. Substitutional Sb atoms positioned at the slip plane lower the intrinsic and unstable stacking fault energies in copper, effectively reducing the barrier for nucleation of partial dislocations. In nanocrystalline models, MD simulations show that very small concentrations of Sb positioned at the grain boundaries increase the flow stress of nanocrystalline Cu, but do not appear to shift the grain diameter associated with maximum strength.

Student: Rahul Rajgarhia (graduated Ph.D. ME, August 2009)
Collaborators: Ashok Saxena (University of Arkansas), K. Ted Hartwig (Texas A&M), Oak Ridge National Laboratory
Funding: University of Arkansas (Irma and Ray Giffels' Chair in Engineering), ORAU (Ralph E. Powe Junior Faculty Enhancement Award)

Cyberinfrastructure

Research tasks require the use of advanced cyberinfrastructure resources, including large-scale cluster computers and visualization, maintained by the Arkansas High Performance Computing Center (AHPCC).

A partnership between Arkansas (AR) and West Virginia (WV) has been established to build on common research in geosciences, virtual environments, and computational sciences while leveraging technical expertise within the two states: WV leverages expertise in the deployment and operation of shared high performance computing resources while AR leverages expertise in visualization and modeling. This consortium seeks to create a nationally competitive computation and visualization environment; to provide visualization display devices at each partnering institution; and to procure a suite of hardware and software for data capture and content creation that can enable a broad range of research and education activities across several science and engineering domains. The consortium seeks to build the needed cyberinfrastructure to advance the frontiers of knowledge in several scientific domains, and to transform information technology services for enabling discovery and innovation. Dr. Spearot serves a critical role in this project as Faculty Campus Champion for Cyberinfrastructure.

Collaborators: Amy Apon (University of Arkansas), Fred Limp (University of Arkansas), et al.
Funding: National Science Foundation EPS#0918970, State of Arkansas