Faculty Profile for:

J. David Schall

Assistant Professor

(248) 370-2870

Dept. of Mechanical Engineering
Oakland University
130 DHE
Rochester, MI 48309

schall 2 @ oakland dot edu


Basic Information


Dr. Schall obtained his Ph.D. in Materials Science and Engineering from the North Carolina State University in 2004. His disseration work was on the effect of applied strains on the measurement of elastic modulus using nanoindentation. After graduation he completed a post-doctorate appointment at the United States Naval Academy where he research friction and wear in diamond-like carbon materials prior to coming to the Mechanical Engineering department at Oakland University in 2009.

General Research Interests

Course Taught

Computational Materials Science
Classical molecular dynamics
Atomic scale friction, wear, and lubrication
Advanced Materials
Carbon based materials and coatings
EGR 280: Electromechanical Systems Design
ME 322: Engineering Mechanics (Statics and Dynamics)
ME 472/572: Materials Properties and Processes
ME 443/543: Polymer Properties
ME 544: Polymer Processing

Note: Course materials are available to registered students on Moodle


Simulated atomic force microscope image of a ultrananocrystalline diamond surface.

Current and Former Group Members

Current Students

Alumni

Kiran Vummaneni - MS Student - Project: scanning probe tip wear and adhesion.

Rob Petrach - PhD Student - Project: finite element contact mechanics models for polycrystalline materials and thin films. Currently working for Molex Corporation

Claudiu Harta - Undergraduate research assistant - Project: Tribological and rheological properties of nanofluids.
Chris Powers - Undergrad research assistant - Project: thermal properties of nanofluids. Currently working for Henkel.

Kelly Daly Flynn - MS Student - Project: Tribological properties of WS2 nanoparticles. Currently working for Gates Corporation

Join our group

A position is available for a graduate student. The project has been funded by NSF (3 years of funding) and will investigate the effect of environment on friction and wear properties of diamond-like carbon. We may also look into graphene epitaxial growth. The proposed work is largely a computational study and involves porting some subroutines written in fortran into a parallel code (LAMMPS) written in C++, MPI, and openMP. The student will gain valuable experience in high performance computing, algorithm development, and computational materials science. Please contact Prof. Schall for details.


Water desalinization using carbon nanotubes. The water molecules (red and white), being small enough, pass through the nanotube pores while the sodium and chlorine (blue and yellow) ions are left behind. This project was conducted in collaboration with REU students from Prof. George Martins' group (OU-PHYSICS)

Nanoparticle Enhanced Heat Transfer Fluids

Research on nanofluids has become increasingly popular since Choi's first publication on the topic in 1995. [1.] A nanofluid is a colloidal suspension of nanoparticles in a base fluid and a nanoparticle is defined as a solid substance with at least one dimension smaller than 100's of nanometers in length. Nanomaterials have an unprecedentedly large surface area to volume ratio which makes them uniquely reactive when compared to their bulk counterparts. Increased surface reactivity combined with quantum size effects have given rise to new materials effecting virtually every branch of science. The novel mechanisms of nanofluid aggregation and heat transfer enhancement are still unknown after nearly two decades of study by other research groups. Our goal is to combine experimental data with MD simulation results to uncover the phenomenological heat-transfer properties of nanofluids.

A 2-step wet chemical approach was used to prepare the nanofluids used in this study. By this method, engineered nanoparticles are mixed with water and surfactant to achieve a stable suspension. Flocculents of nanoparticles are then broken up with ultrasound to ensure that the nanofluid is thouroghly dispersed. The Schall group has succeeded in achieving water-based nanofluids cabable of remaining stable for over one month. All nanofluids are being tested in collaboration with the US Army Tank Automotive Research and Development Center (TARDEC) and the Southwest Research Institute (SwRI). We have tested particle size distribution, zeta potential, thermal conductivity, refractive index, viscosity, and pH at varying particle concentrations for each class of nanofluids - i.e. alumina, carbon nanoplatelets, nanodiamond, etc. Most publications correlate trends between a few of these variables, but very few research groups have reported data for all of the variables mentioned.

Preliminary results have shown that increasing surfactant concentration decreases nanofluid thermal conductivity. The Schall group has however achieved stable nanofluids that show enhanced thermal conductivities above that of deionized water. The first round of nanofluids testing is complete and awaiting publication. We have also been collaborating with Michigan State University's Composite Materials and Structures Center on the production and testing of graphite-based nanofluids. The Schall group at Oakland University is rapidly expanding its experimental and simulation capabilities through continued external funding.


Simulation of bilayer graphene sheets (purple) in an alkane solvent (cyan). The green molecules are pyrene with alkane tails. Molecules such as these could potentially act as stablizers for the graphene particles.

Interesting Links

Nanoscience Documentary

The Basics of Nanofluids

Reference

[1.] Choi, U. S., 1995, “Enhancing Themxd Conductivity of Fluids with Nanoparticles, ” Developments and Applications of Non-Newtonian Flows, eds. D. A. Siginer and H. P. Wang, The American Society of Mechanical Engineers, New York, FED-VO1. 23 VM.D-VO1.66, pp. 99-105.

Potential Development

Existing models for the C-Si-H potential are all based on the original version of the REBO potential developed by Donald Brenner in 1990. Since these models do not calculate elastic modulus accurately, I have been developing a new parameterization for the inclusion of Si into the second generation REBO potential. This includes the development of a large database of ab initio calculations of molecules containing C, Si, and H. Calculations of elastic modulus from the second generation Brenner potential are in much better agreement with experimental values. Currently, this new C-Si-H parameterization is being tested and will be used to calculate elastic modulus and tribological properties of films as a function of silicon content.

Diamond-like Carbon

From 2004 to 2009 I was post-doctoral associate of Judith A. Harrison in the Department of Chemistry at the United States Naval Academy in Annapolis, Maryland. Our group is using molecular dynamics simulation to investigate low-friction, low-wear coatings for devices that operate in extreme environments, such as those experienced in outer space. Microelectromechanical systems (MEMS) have potentially important applications in space craft. To be of use they must survive launch from a terrestrial (i.e. humid) environment to the space (i.e. dry) environment and be capable of operating over a wide range of temperatures once in orbit.

Of particular interest to me are thin nanocrystalline diamond, diamond-like carbon, and amorphous carbon films. Investigations have shown that when such films are deposited on mechanical components in MEMS devices the device’s operational lifetime and operational temperature range increases. Film composition plays a critical role in the performance of these films. For instance, incorporation of silicon into hydrogenated amorphous carbon films (α-CSiH) has been shown to reduce film stress, make the friction coefficient less sensitive to moisture, and increase thermal stability while maintaining high hardness, low wear, and small friction coefficient.

Because molecular dynamics (MD) simulations explicitly include of temperature, such simulations are uniquely suited to study the effects of temperature on material properties. I have been using MD and the reactive empirical bond-order potential (REBO) to examine the temperature dependence of the material properties of hydrogenated amorphous carbon films containing silicon. The REBO potential is used because it is one of the few potential energy functions capable of modeling chemical reactions, which are likely to accompany sliding. Initial studies have shown that the inclusion of Si in the amorphous carbon films increases the amount of sp3 bonding present in the film while decreasing the graphitic sp2 content, making the films more diamond-like.

Tribofilm Formation

FE Microstructure Modeling

Recent Publications

Full list of citations (from Google Scholar)

Full CV