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New roles for two common materials

The goal is to improve the strength and mechanical stability of alumina while promoting the orderly distribution of pores on its surface.

Aluminum-oxide, or alumina, is hard, is resistant to corrosion and abrasion and is, for a ceramic, a good conductor of heat. It is used in spark plugs and cutting tools, hip replacements and water filters, toothpaste and prefinished wood flooring.

Researchers in Lehigh’s Institute of Metal Forming (IMF) are attempting to equip one type of alumina for a new role – the production of a more-efficient kidney dialysis filter.

Alejandro Toro, Wojciech Misiolek, Kylan McQuaig and William Van Geertruyden studied the structure of anodic alumina with an aberration-corrected transmission electron microscope (TEM) that resolves specimens to 0.1nm. They also performed diffraction analyses with conventional TEM to learn how groups of atoms form the crystal structure. They published their results in the Journal of Materials Science.

Alumina is amorphous in the samples fabricated by the IMF anodization process. Under proper heat treatment, it becomes crystalline and acquires an orderly structure. Toro and Misiolek used TEM to determine how heat treatment affects the chemical structure and crystallography of anodic alumina. They were able to improve the ceramic’s strength and mechanical stability and promote the orderly distribution of pores on its surface.

The project follows the development by Misiolek and Van Geertruyden of a ceramic dialysis filter whose nanopores correspond more closely with the nano-sized toxins in the body’s blood than do the larger pores in conventional polymeric dialysis filters. This gives it the potential to remove toxins more quickly and efficiently from the blood and shorten the length of a dialysis session.

Misiolek is IMF director and Loewy Chair of materials forming and processing. Toro, professor of materials science and engineering at the National University of Colombia in Medellin, recently concluded a Loewy professorship at Lehigh. McQuaig, the university’s first Loewy graduate fellow, earned his M.S. in 2010.

In a separate collaboration with General Motors, Misiolek and Toro used TEM to determine the structure and mechanical stability of a magnesium alloy containing zinc and cesium.

“Magnesium is even lighter than aluminum,” says Misiolek. “The hope is that it can make cars lighter, more fuel-efficient, cleaner and easier to handle. This alloy improves magnesium’s ability to deform without compromising its strength and its ability to bear loads.

“This is especially important to auto manufacturers. The parts of a car are geometrically complex and require a material that can deform to create the right shape and thickness.”