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April 7th, 2010

Will DC electric fields transform ceramics shaping, manufacturing?

Published on April 7th, 2010 | By: pwray@ceramics.org
Grain boundary and adjacent space-charge. Credit: Conrad and Yang

Grain boundary and adjacent space-charge. Credit: Conrad and Yang

According to a paper just published in Philosophy Magazine, researchers at North Carolina State University, who have been playing around with how ceramic materials behave in the presence of DC electric fields, apparently think they may have discovered an approach that could “revolutionize” ceramics manufacturing. At a minimum, they say that using a modest electric field can affect grain boundaries, and may make the process of shaping ceramics significantly more energy efficient and inexpensive compared with traditional manufacturing methods.

The researchers, lead by Hans Conrad, emeritus professor of materials science and engineering at NC State, wanted to look at how to influence the mechanical and electrical forces at grain boundaries in crystalline materials, such as ceramics.

“We found that if we apply an electric field to a material, it interacts with the charges at the grain boundaries and makes it easier for the crystals to slide against each other along these boundaries. This makes it much easier to deform the material,” says Conrad.

According to Conrad, the material becomes superplastic, allowing the ceramic to be shaped using a relatively small amount of force.

“We’ve found that you can bring the level of force needed to deform the ceramic material down to essentially zero, if a modest field is applied,” Conrad says. “We’re talking between 25 and 200 volts per centimeter, so the electricity from a conventional wall socket would be adequate for some applications.”

Diagram of dc electric field testing rig. Credit: Conrad and Yang

Diagram of DC electric field testing rig. Credit: Conrad and Yang

Conrad and his team say their findings could transform ceramic manufacturing of products from fuel cells to spark plugs to rocket nose cones. “It will make manufacturing processes more cost-effective and decrease related pollution,” Conrad says. “And these findings also hold promise for use in the development of new ceramic body armor.” Conrad says he intends to carry out more work particularly aimed at performance–cost improvements for body armor manufacturing

Conrad and Di Yang, a senior research associate at NC State, paper is titled, “Influence of an applied DC electric field on the plastic deformation kinetics of oxide ceramics.”

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2 Responses to Will DC electric fields transform ceramics shaping, manufacturing?

  1. Rishi Raj says:

    Dear Dr. Mackenzie, We are actively working on the influence of electrical fields on sintering and deformation of ceramics. I would be very interested to read your papers and would appreciate it if you can send me pdf copies, especially those of your earliest work. Rishi Raj


  2. Kenneth MacKenzie says:

    This work is extremely interesting, as it extends some of the work of my group done many years ago on the effect of dc (and ac) electric fields on the processing of clay-based and oxide-based ceramics. We found that the solid-state diffusion steps of solid-state oxide reactions were electrically enhanced, and where protons were involved (as in clay-based ceramics) their migration to the cathode improved the physical properties such as the hardness, especially in that region.
    References: J. Appl. Chem. (1970)20:80-86
    Proc. Brit. Ceram. Soc. (1971)19:202-27, J. Thermal Anal. (1973)5:5-17, 19-32, 363-77, Trans. J. Brit. Ceram. Soc. (1973)72:209-14, Thermochim Acta (1974)9:389-98, J. Thermal Anal (1975)7:619-33, 8:3-14, Thermochim Acta (1976)16:1-16, (1978) 25:161-73, 175-84, 277-88, J. Thermal Anal (1979) 16:487-98, J. Mater Sci (1979)14:333-8, 339-44, Thermochim Acta (1980) 35:227-37, J.Mat.Sci (1981)16:579-88, (1982)17:3663-71.

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