Research
Thrusts
.... .Nanostructures
.... .Biomimetics
..... Bio-Nano
Fereshteh Ebrahimi - We are interested in deformation and fracture of materials and the relationships between fabrication, processing, microstructure and mechanical properties. Presently we are working on metallic nanostructures (nanocrystals, multilayers, etc.) and high temperature materials (intermetallics, single crystals, superalloys, etc.).
- Nanostructures
Nanotechnology involves the control of matter atom by atom and molecule by molecule in order to fabricate a structure that its components are at nanometer (one billionth of a meter) scale. Metallic nanostructures can be designed to have ultra-high strength, excellent corrosion resistance and superior magnetic properties. Their main areas of application are in data storage technology (disc drives, heads, etc.), magnets and coatings.
We synthesize our own nanostructures via electrodeposition. We have succeeded in fabricating bulk nanocrystals (100-20nm grain size) of nickel and nickel-copper alloys and multilayers (300-7nm bi-layer thickness) of copper/silver and nickel/copper. Our future goal is to fabricate nanocrystalline nickel-iron alloys with BCC and FCC crystal structures.
The microstructure of these nanostructures is characterized by x-ray diffraction, transmission electron microscopy, microprobe analysis, and scanning electron microscopy. Due to the high quality of our nanostructured samples, we are able to conduct tensile testing on bulk specimens. We are one of few research groups in the world that can fabricate and test metallic nanostructures.
- High Temperature Materials
The performance of jet engines can be improved by decreasing the weight and increasing the operating temperature. Presently, the turbine blades of advanced jet engines are made of nickel-based superalloy single crystals. Intermetallics have been considered for creating alternative materials with lower density and/or better high temperature properties.
We are studying a variety of high temperature materials including nickel-based superalloys, Ni3Al, NiAl and Nb-Ti-Al alloys. Our objective is to manipulate the structure in order to achieve an optimized combination of toughness, fatigue and creep properties. In the case of single-phase single crystals, the objective is to understand the effect of crystallographic orientation on phenomena such as sheer localization and ductile-to-brittle transition.