Room-Temperature Ceramic CoatingEd Brown | March 02, 2017
Researchers at the U.S. Energy Department's Sandia National Laboratory in New Mexico say they have achieved a process of applying ceramic coatings by “splatting” – spraying them onto a surface at high velocity.
“The ability to put down ceramics at room temperature means you can process ceramics and lower-melting-temperature materials at the same time," says project leader Pylin Sarobol.
The process makes it possible to put ceramics on copper, for example. Before, the ceramics had to be made first with the copper down on it. "You can imagine spraying functional materials onto a circuit board rather than high-temperature processing, followed by tedious manual assembly," she says.
In the process, submicron particles suspended in a gas, are accelerated by a nozzle and layered onto the surface. The small scale of the particles activates plastic deformation, which causes consolidation of subsequent deposition layers and generates the continuous surface that layers are built upon. This makes it possible to build up coatings that are tens of microns thick.
Another key is deposition in a vacuum, which enables high momentum particles to get through the thin gas boundary layer called the bow shock layer.
The team has deposited materials such as copper, nickel, aluminum oxide, titanium dioxide, barium titanate and carbide compounds. These materials can be used for capacitors, resistors, inductors, electrical contacts and wear surfaces.
A promising application for barium titanate films is to use them as the dielectric in high-voltage capacitors. These capacitors are prone to failure where the dielectric material meets the copper material and air, creating electric field stress. Spraying on the barium titanate, would solve that problem and could open up the possibility of higher power capacitors, says Sarobol.
Splatting, by depositing material in the range of several hundred nanometers to a hundred microns will bridge the microscale gap between thin films at nanometers to a few microns, and thermal spray technology starting at about 50 microns up to a few centimeters.