Texas A&M University (College Station, Texas) researchers have developed a technology that enables ceramics and metals to be processed together into cermets with little to no reaction between constituent materials.
Many ceramics and metals are unstable when combined at high temperatures and react with each other, leaving the final composite materials with undesirable properties like brittleness or poor resistance to high temperatures. “This severely limits the number of new composite materials that can be developed for our growing needs,” says Miladin Radovic, associate professor and head of Texas A&M’s materials science and engineering department.
To address this, Radovic, other faculty, and students developed a current-activated, pressure-assisted infiltration (CAPAI) method to combine ceramics and metals—creating stable, high-performance composites after as little as 9 s. The method uses electric current to instantly heat the metal, and applied pressure to drive the molten metal into a ceramic foam.
In their study, the researchers selected aluminum for its light weight, corrosion resistance, and popularity in automotive and aerospace industries, along with titanium aluminum carbide (Ti2AlC) ceramic foams for fracture toughness, and electrical and thermal conductivity.
“The electric current and the pressure together provided simultaneous heating and pressure that actively drove the molten metals into the ceramic preform,” Radovic says. “The fast and controllable heating rate, which was as high as 700 °C, offered an easy and efficient way to avoid reactions between ceramics and molten metal.”
Researchers found the resulting composite (Ti3AlC3/Al) was lightweight with competitive mechanical properties at ambient and elevated temperatures. It is 10 times stronger at room temperatures and 14 times stronger at 400 °C than aluminum alloys, and is less prone to severe degradation after exposure to high temperatures.
Source: College of Engineering, Texas A&M University, engineering.tamu.edu.