The advanced technology of tomorrow will require electronics capable of tolerating extreme conditions. That’s why a group of researchers led by Jason Nicholas of Michigan State University are building stronger circuits today.
Nicholas and his team developed more heat resistant silver circuits with nickel assist. The team described the work, which was funded by the US Department of Energy’s Solid Oxide Fuel Cell Program, on April 15 in the journal Materials.
The types of devices that the MSU team are striving to benefit from – next-generation fuel cells, high-temperature semiconductors, and solid-oxide electrolysis cells – could have applications in the automotive industries, energy and aerospace.
While you can’t buy these devices off the shelf now, researchers are currently building them in labs to test them in the real world, and even on other planets.
For example, NASA developed a solid oxide electrolysis cell that enabled the Mars 2020 Perseverance Rover to make oxygen from gases in the Martian atmosphere on April 22. NASA hopes this prototype will one day lead to equipment that allows astronauts to create rocket fuel and breathable air. while on Mars.
However, to help these prototypes become commercial products, they will need to maintain performance at elevated temperatures for long periods of time, said Nicholas, an associate professor at the College of Engineering.
He was drawn to this field after years of using solid oxide fuel cells, which work like solid oxide electrolysis cells in reverse. Rather than using energy to create gas or fuel, they create energy from these chemicals.
“Solid oxide fuel cells work with gases at high temperature. We are able to electrochemically react these gases to extract electricity and this process is much more efficient than fuel explosion like an internal combustion engine does. said Nicholas, who heads a laboratory in the Department of Chemical Engineering and Materials Science.
But even without an explosion, the fuel cell must withstand intense working conditions.
“These devices typically operate between 700 and 800 degrees Celsius, and they have to do that for a long time – 40,000 hours in their lifetime,” Nicholas said. For comparison, that’s about 1,300 to 1,400 degrees Fahrenheit, which is about twice the temperature of a commercial pizza oven.
“And over that lifetime, you thermally cycle it,” Nicholas said. “You cool it down and heat it up. It’s a very extreme environment. You can blow the wires in the circuit.”
So, one of the hurdles that this cutting-edge technology faces is rather rudimentary: the conductive circuits, often silver, have to stick better to the underlying ceramic components.
The researchers discovered that the secret to improving adhesion was to add an intermediate layer of porous nickel between the silver and the ceramic.
By performing experiments and computer simulations of how materials interact, the team optimized the way they deposited nickel on ceramic. And to create the thin, porous layers of nickel on the ceramic in a pattern or design of their choice, researchers turned to screen printing.
“It’s the same screen printing that is used to make T-shirts,” Nicholas said. “We just screen print electronics instead of shirts. It’s a very easy technique to make.”
Once the nickel is in place, the team puts it in contact with molten silver at a temperature of around 1,000 degrees Celsius. Nickel not only resists this heat – its melting point is 1,455 degrees Celsius – but it also distributes liquefied silver evenly over its fine features using what is called capillary action.
“It’s almost like a tree,” Nicholas said. “A tree obtains water up to its branches by capillarity. Nickel evacuates the molten silver by the same mechanism.”
Once the silver cools and solidifies, the nickel keeps it locked to the ceramic, even in the heat of 700 to 800 degrees Celsius, it would face the inside of a solid oxide fuel cell or a solid oxide electrolysis cell. And this approach also has the potential to help other technologies, where electronics can heat up.
“There are a wide variety of electronic applications that require circuit boards that can withstand high temperatures or high power,” said Jon Debling, chief technology officer at MSU Technologies, the transfer and marketing office of Michigan State Technology. “These are the existing applications in the automotive, aerospace, industrial and military markets, but also more recent applications such as solar cells and solid oxide fuel cells. . “
As CTO, Debling works to commercialize Spartan innovations and he works to help patent this process to create stronger electronic components.
“This technology is a significant improvement – in terms of cost and temperature stability – over existing pulp and vapor deposition technologies,” he said.
For his part, Nicholas remains keenly interested in cutting-edge applications on the horizon, such as solid oxide fuel cells and solid oxide electrolysis cells.
“We are working to improve their reliability here on Earth – and on Mars,” Nicholas said.