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.
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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