The optical and magneto-optical properties of the ferromagnetic semiconductors, InMnAs and its alloy InMnAsP were investigated to determine the band structure and nature of the ferromagnetism in these materials. Alloys were grown by metal-organic vapor phase epitaxy. Infrared absorption of InMnAs was investigated to determine the presence and properties of...
Fundamental investigations on the origins of friction at the nanoscale were carried out using both theoretical and experimental approaches. A model was developed that analytically solves for friction by the motion of dislocations at atomically flat crystalline interfaces. It combines known concepts from dislocation drag, grain boundary theory, and contact...
Solid oxide fuel cells (SOFCs), renowned for their high electrical generation efficiency with low pollutant production, are promising for reducing global energy and environmental concerns. However, there are major barriers for SOFC commercialization. A primary challenge is reducing the capital cost of SOFC power plants to levels that can compete...
Biomorphic silicon carbide (bioSiC) is a novel porous ceramic material derived directly from wood precursors. This material is fabricated by pyrolysis of a natural wood precursor in an inert atmosphere leaving an amorphous carbon scaffold. The amorphous carbon is infiltrated with molten Si in vacuum at elevated temperature, which reacts...
The electronic transport and magnetoresistive properties of the ferromagnetic semiconductor In1-xMnxAs were investigated in order to determine the nature of the transport and ferromagnetism in the films. p-InMnAs/n-InAs and metal/oxide/InMnAs heterojunctions were fabricated and characterized to elucidate the transport and magnetoresistance mechanisms at these technologically important interfaces.
The electronic transport...
The transport properties of mayenite-based materials, Ca12Al14O33, were investigated. Systems studied included H-doped/ UV-irradiated Ca12Al14O33, Ca(12-x)MgxAl14O33 (x = 0.1, 0.3, 0.5, 0.8, 1) and Ca12Al(14-x)SixO(33+x/2) (x = 1, 2, 3, 4). The as-prepared Ca12Al14O33 exhibited a room temperature electronic conductivity on the order of 10^-10 S/cm, and a high temperature...
Graphene offers promising opportunities for applications in printed and flexible electronic devices due to its high electrical and thermal conductivity, mechanical flexibility and strength, and chemical and environmental stability. However, scalable production and processing of graphene presents a critical technological challenge preventing the application of graphene for flexible electronic interconnects,...
In today's rapidly changing world, there is constant demand for the development of new, high performance materials. Fire resistant steels can provide greater safety in the event of a building fire, creep resistant stainless steels can allow for higher power plant efficiency, and cobalt based superalloys have potential for use...
Accurate thermodynamic databases are the foundation of predictive microstructure and property models. An initial assessment of the commercially available Thermo-Calc TCAL2 database and the proprietary aluminum database of QuesTek demonstrated a large degree of deviation with respect to equilibrium precipitate phase prediction in the compositional region of interest when compared...
Metal and bimetallic nanoparticles are of interest and are widely used in various applications because of their unique optical, electronic, and catalytic properties, which differ from those of their bulk counterparts. Better understanding of the thermodynamic and kinetic properties of nanoparticles and their underlying growth mechanisms can serve as a...