Cement can be transformed into metal using a new process called electron trapping. The new semi-conducting material produced exhibits qualities of both glass and metal, making this a strange hybrid substance that may have a wide variety of uses in the future.
The new metallic concrete conducts electricity and heat and is resistant to corrosion. Normal concrete is an electrical insulator, composed of calcium oxide and other minerals, including aluminum oxide and silicon dioxide.
This metallic concrete was created by heating a type of concrete powder called mayenite up to temperatures over 3600 degrees Fahrenheit through the use of lasers. This turned the powder into a liquid. Then, the sample was lifted into the air by jets of inert gas, using a device called an aerodynamic levitator. The streams of gas prevented the heated material from touching the sides of the equipment which housed it. This was done to prevent unwanted crystals from forming in the sample. As the material cooled down into a glass, a series of gases were introduced into the chamber in order to modify the material's molecular bonds.
When the material solidified, the molecules of calcium oxide had formed cages that trapped electrons with their structures. This allows for the free flow of electricity through the material, operating in much the same way as free electrons in normal metals. Such electron trapping had been observed before in ammonia, but this marks the first time such a mechanism has been observed happening in a solid insulator.
This new process was developed by Chris Benmore from the Argonne National Laboratory and Shinji Kohara, who works at the SPring-8 synchotron in Japan. The pair worked in conjunction with material scientists from the United States, Germany and Finland to create the new process.
"This phenomenon of trapping electrons and turning liquid cement into liquid metal was found recently, but not explained in detail until now," Benmore said.
Metallic glass has been manufactured before, but the raw material had, until now, always been normal metals. The glass-like properties of the metal help to prevent corrosion, while the metallic nature of the substance provides strength.
Applications for the new material may include use in computer chips, the manufacture of thin film resistors for use in LCD monitors and protective coatings.
"Now that we know the conditions needed to create trapped electrons in materials, we can develop and test other materials to find out if we can make them conduct electricity in this way," Benmore said.
