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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

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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In the revolutionary way that aerogel is starting to redefine insulation, geopolymer may be poised to redefine cement, concrete and a lot of other advanced composite materials. And, like aerogel, geopolymer hasn’t received the public attention it should.

In this video,  geopolymer expert Trudy Kriven, a professor of material science at the University of Illinois at Urbana-Champaign, explains how geopolymers are essentially inorganic polymers made from readily available aluminum- and silica-containing materials.

As Kriven explains, a motive for finding a replacement like geopolymer for traditional Portland cement is environmental: Portland cement production requires a tremendous amount of energy to heat and convert the raw materials (at 1450°C), and can generate nearly one ton of CO₂ for every ton of processed cement.

Geopolymer, on the other hand, doesn’t have to be fired. In addition, Kriven notes, geopolymer is twice as strong as cement in compression, three-times as strong in flexure and can set up in one day.

The reality is that given the need to reduce global CO₂ emissions and given the plans for large scale construction and transportation growth in countries such as China, alternatives to Portland cement are extremely important.

Besides using geopolymer to make concrete, this novel material can be used for fire and corrosion resistant coatings, water and air filtration, CO₂ sequestration materials, projectile armor, substrates for solar and fuel cells, and even a paint substitute.

Adding for clarification . . . Trudy’s comments at around the 3 minute mark can be misconstrued when she says the geopolymer “looks like a ceramic, feels like a ceramic, but wasn’t fired at high temperature.” She is referring to “traditional” ceramics that are fired in a kiln or sintered. However, geopolymer falls within the broad grouping of “ceramic materials.”

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