Materials

Nature-inspired process takes the heat off of ceramics production

Nature-inspired process takes ...
A ceramic sample created using the cold sintering process
A ceramic sample created using the cold sintering process
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A ceramic sample created using the cold sintering process
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A ceramic sample created using the cold sintering process

Ordinarily, when ceramic items are manufactured, the raw material has to be fired in a kiln at temperatures exceeding 1,000 ºC (1,832 ºF). Needless to say, it's a very energy-intensive process. Now, however, scientists from Switzerland's ETH Zurich research center have succeeded in doing away with the kiln, replacing it with a much more energy-efficient room-temperature technique.

Known as cold sintering, the process utilizes very finely-powdered calcium carbonate which is mixed with water and placed in a mold. Pressure is then applied to the mixture via a hydraulic press, compacting it into a solid. It's similar to the way in which sedimentary rock such as limestone is made naturally, wherein sediment is compressed into rock by the pressure of overlying deposits.

While it takes millions of years to create limestone, however, the cold-sintered ceramics are ready in an hour. The finished product is claimed to be as stiff as stone or concrete, and can withstand about 10 times as much force as concrete before breaking.

Not only does the process require considerably less energy than kiln-use, but the calcium carbonate could conceivably be derived from carbon dioxide captured from industrial waste gases – thus permanently storing the CO2 in the form of ceramics. It's also possible that the calcium carbonate could be mixed with other materials such as plastic powder, to create composites.

So far, however, production has been limited to samples about the size of a one-franc coin. While small objects like ceramic bathroom tiles should also be possible using the current setup, larger items would require proportionally higher amounts of pressure.

Source: ETH Zurich

6 comments
MD
But is it strong? (compared to high temp ceramics. Sedimentary rock is generally not very strong (I know difficult term to define, UTS/UCS/ hybridised into Bending Stress etc) And larger pieces may need higher force, but likely the same pressure will suffice.
Racqia Dvorak
You can do a lot with something the size of a bathroom tile.
myale
So I guess you have to keep these away from any acid rain, coca cola or anything acidic? Or you turn into a bubbling mess ?
Douglas Bennett Rogers
You need a calcium source to sequester CO2. If you use calcium chloride, you need to do something with the chlorine. With calcium sulfate, you get sulfur dioxide or, with a lot more energy, sulfur. Most concrete is a limestone aggregate so it is essentially limestone. Marble is highly compressed limestone that has melted. These won't work for thin plates and beams. This product seems similar to asbestos cement, which works well in a 3/16 in. x 24 x 12 in. plate.
F. Tuijn
Presumably for a thicker product the pressure can be kept the same but it needs to be applied for a longer time. What about including strong fibres? And my main question: What happens to the water? How does it escape?
Ralf Biernacki
Unlike fired ceramics, this material can be reinforced, with fibers or simply with steel rebar. Being limestone, it should have the same corrosion-protective effect on iron that concrete does.