Research Projects

ATOMIC-SCALE CHARACTERIZATION OF NANOPARTICLES

Faculty Mentors: Profs. H. Heinrich and S. Seal

Materials containing nanometer sized crystallites or phases are frequently showing interesting and useful new properties in comparison to bulk properties of similar materials. Technologies for fabrication processes of nanophase materials are currently developed in various fields of biological, chemical and physical sciences. The evolution of nanomaterials towards new applications requires knowledge on effects of processing routes and on aspects of  long-term stability. Analyzing and understanding of structural and chemical changes on these extremely small scales are therefore crucial for further success.

Transmission electron microscopy offers a variety of techniques for structural and chemical analysis of materials with atomic or near-atomic resolution. For nanomaterials, these techniques are especially important, as they allow to characterize properties of individual nanoparticles.

Figure A shows an scanning transmission electron micrograph with atomic resolution of silver-rich clusters forming in an aluminum alloy. These nanometer-sized clusters are important as nucleation sites for precipitates effectively hardening light-weight aluminum alloys. For many materials, structural defects like these precipitates appearing bright in figure A are essential for optimizing mechanical properties. For other materials, structural defects are associated with a deterioration of properties. One example of thin-film solar cells with a high density of planar defects is shown in Figure B.

Nanoscale cerium oxide particles can be used to improve the oxidation resistance of many metallic materials. These ceria particles are especially effective in protecting alumina- and chromia-forming alloys. In the current project, monodispersed and non-agglogerated c eria particles with diameters of 5 nm are investigated.

The undergraduates will be involved in:

• Learning basic principles and the operation of a transmission electron microscope.
• Atomic-scale imaging and electron diffraction for an analysis of particle sizes and of the particle distribution.
• Data analysis and comparison with results from other experimental techniques.
• In addition to experiments at the microscope, students will learn aspects of fabrication of nanomaterials.