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Thunderstruck: AC/DC Rocks Sintering

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By applying a 60 Hertz alternating current (AC) field, researchers were able to reduce the grain size of ceramics by 63 percent - and eliminated porosity at 1,250 degrees Celsius, as opposed to the 1,500 degrees Celsius needed without the electric field.

When I say ceramics, you think of bowls and plates, right? But ceramics are also used in body armor, fuel cells, spark plugs, nuclear rods, space shuttles, superconductors and hundreds of other things you probably didn’t know about and would think are really important. New research is now showing that manufacturers can make and shape ceramics and ceramic products for less money, using less energy. And, they can do that while also making the ceramics stronger. What’s the trick? Electricity.

Let’s start with a process called sintering. Sintering is when a manufacturer (or researcher) takes some ceramic powder (such as zirconia), compresses it into a desired shape and then exposes it to incredibly high heat until the powder particles are bound together and the material is no longer porous. For zirconia (3Y-TZP), we’re talking about cooking your ceramic at around 1,500 degrees Celsius. When it’s done, you’ll have a fine-grained ceramic product, with grains measuring around 360 nanometers (nm) in diameter.

New research shows that applying a 60 Hertz AC electric field (at 13.9 volts/centimeter) can eliminate the porosity at only 1,250 degrees Celsius. And using the AC field gets you much finer grain sizes – on an order of around 134 nm in diameter. The finer grain size gives you a stronger ceramic (but that’s another blog entry). In other words, using a little bit of electricity means you can use lower heat for the sintering process. That saves energy, which saves money. And it means a stronger ceramic for the end user. That’s good news for manufacturers and consumers.

Using a DC electric field also boosts sintering efficiency, but not to the same extent as AC.

The findings come on the heels of research earlier this year, which showed that the use of electric fields could make it vastly easier to deform ceramic materials. In other words, electricity could make it easier for manufacturers to shape ceramics into whatever form is needed for their products. And high voltage isn’t necessary.

It looks like electric fields may be the future of ceramics.

PS: Here are some of the AC/DC song titles I tried unsuccessfully to incorporate into this post – High Voltage, Live Wire and Money Talks. However, I got Kicked In The Teeth and Shot Down In Flames.