Department of Mechanical Engineering

ME Seminar - Thermal Phenomena at Nanoscales: Experimental Characterization and Atomistic Exploration

 

Mechanical Engineering Seminar
Faculty Candidate
Wednesday, March 28, 2007
11:00 A.M., 3004/3006 Black Engineering Building

Thermal Phenomena at Nanoscales: Experimental Characterization and Atomistic Exploration

by
Xinwei Wang
Department of Mechanical Engineering
University of Nebraska-Lincoln  

Abstract
In the context of fast development of nanoscience and nanotechnology in the last decade, significant challenges have arisen in understanding a wide spectrum of thermal phenomena at nanoscales. Examples include heat transfer in nanoscale and nanostructured materials, thermal transport, phase change, and phase explosion in ultrafast laser-material interaction and laser-assisted near-field nanomanufacturing. The significantly confined domain/scale for thermal processes has made continuum approaches fail to study the underlying physics. Traditional experimental techniques are found incapable of characterizing the thermal transport in nanoscale materials, especially one-dimensional nanostructures. In addition, the intense heating process and complex phase explosion in ultrafast laser material processing make it extremely difficult to study the mechanisms based on equilibrium thermodynamics. 

This talk will focus on experimental characterization and atomistic exploration of thermal phenomena at nanoscales on three aspects. (1) Molecular dynamics (MD) simulation of the thermophysical properties of nanoscale and nanostructured materials. Emphasis will be placed on how the nanodomain enhances phonon scattering and reduces the thermal transport. (2) Novel technology development to characterize the thermophysical properties of, and the dynamic thermal transport in, nanoscale materials, especially single one-dimensional nanostructures. (3) Hybrid atomistic-macroscale computer modeling of the heating, melting, phase explosion, and long-time solidification/crystallization, in ultrafast laser-material interaction and surface nanostructuring. 

Additionally, introduction will be given about the existing exploratory research going on in our laboratory, including (1) nanoscale surface amorphization of Si induced by ultrafast cooling, which results from nano-/picosecond laser heating, (2) shock waves induced by the fast moving plume in laser-material interaction, and (3) mapping of the ultrafast (sub-nanosecond) thermal transport in nanowires/tubes using ultrafast optical pumping and photoconductor-gated electro-thermal sensing. Finally, discussions will be provided about the near-future research (under preliminary result development) in our laboratory for (1) laser-assisted in-vivo thermal wave bio-imaging, and (2) photo-thermal therapy based on nanoparticle-enhanced surface plasmonics. 

Biography
Dr. Wang received a B.S. from the University of Science and Technology of China, Department of Thermal Science and Energy Engineering in 1994 and a M.S. in 1996.  He attended Purdue University in the School of Mechanical Engineering, and earned a Ph.D. in 2001.  Currently, he is an Associate Professor in Department of Mechanical Engineering at the University of Nebraska at Lincoln.  His research interests include large-scale molecular dynamics simulation of thermal transport and phonon scattering in nanoscale and nanostructured materials, characterization of thermophysical properties of one-dimensional nanostructures, hybrid atomistic-macroscale modeling of the thermal transport, phase change, and structural evolution in laser-assisted material processing and near-field nanomanufacturing.
                                           

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