Nanoparticle Self-Assembly in Phase-Separating Liquid Media
Directed Self-assembly of Block Copolymers for Nanoscale Surface Patterning
Microstructure Evolution in Nuclear Materials

The mutual interactions between phase-separating liquids (such as oil-in-water or polymer blend melts) and dispersed nanoparticles are scientifically challenging to understand.  However, they are also very important, as such systems can self-assemble into technologically desirable microstructures.  Our group studies nanoparticle-polymer mixtures that evolve to form phase-separated liquid domains with nanoparticle-coated interfaces.  Such assemblies can be used to fabricate microporous materials with nanoparticle-coated internal surfaces by freezing the structure and then chemically removing one of the phase domains.   Our group is interested in computationally simulating the time evolution of these mixtures from a homogeneous state to the metastable state. 
The phase separation of block copolymers into ordered, nanoscale domains is a highly promising approach to fabricate nanoscale surface patterns in a scalable and cost-effective manner.  One distinct challenge that exists in this field concerns the fact that the self-assembly process typically results in a lack of truly long-range order due to the creation of defects such as grain boundaries and dislocations.  A second challenge concerns the fact that for many applications, a regular array of square patterns is preferable to close-packed hexagonal patterns (the latter being the stable phase of the commonly-studied diblock copolymer).  This is particularly true for the semiconductor industry. 

Our group studies strategies to direct the self-assembly of diblock and triblock copolymers into ordered nanoscale domains with hexagonal or square symmetry.  Such structures are important for future microprocessor designs as well as bit-patterned media storage exceeding 5 terabits per square inch.
Irradiation can drive non-equilibrium microstructural changes in solid-state materials including the formation of gas-filled bubbles, unexpected alloy segregation and precipitation, and prismatic dislocation loop formation.  Dr. Millett has studied irradiation effects in nuclear fuel and structural alloys with particular focus on the resultant changes in thermo-mechanical properties.  A particular emphasis has been on gas bubble nucleation, growth, and coarsening in uranium dioxide fuels, and the effects on thermal transport.
Financial support for our group has been provided by generous grants from the National Science Foundation, the Department of Energy, and the University of Arkansas.  Thank you !!

Group Members