'Cold Sintering' to Revolutionize Manufacturing Industry
Researchers in Penn State's Materials Research Institute, led by Clive Randall, recently discovered a process that they say could revolutionize the manufacturing industry. Known as cold sintering, the process could be used for developing materials used every day, like bricks and glass, at a much lower energy cost than the process used today. Most sintering processes occur at high temperatures above 1,000°C. This technology could achieve dense ceramic solids at extremely low temperatures (under 300°C). The cold sintering process (CSP) uses a transient aqueous environment to effect densification by a mediated dissolution-precipitation process. These temperatures enable co-sintering of ceramic materials with other materials such as thermoplastics to develop unique composites and new functionalities in a one-step process. The researchers have reduced the technology to practice using over 50 compositions, including advanced ceramics such as BaTiO3 and ZrO2, which are used extensively in electronic devices.
Transcript
00:00:03 Penn State researchers recently discovered a way to revolutionize a way to a widely used manufacturing process known as sintering. Sintering is the process of compacting and forming a solid mass by heat or pressure. This is traditionally done at temperatures of more than 1000 degrees Celsius for many hours. In the sintering process you basically for a given material you'll take powder that can react to temperature and that temperature has to be below the melting temperature. And so this process is different from a melt forging process. It's a densification that is driven by molecules and atoms moving at the surface of these interfaces and minimizing that total amount of surface energy.
00:00:46 Even the process, one could argue, of making a snowball is the compaction of particles and then applying some pressure with them. Maybe some local melting and in the process of that it helps bring things together. People have been sintering ceramics, metals, plastics and other materials for thousands of years. Today sintering is used to create a wide variety of materials. Refractory materials, brick technologies, tiles, alumina and zirconia. Bearing type materials and pipes very small functional materials for capacitor technologies so, for example, in your iPhone you may have 700 pieces of ceramic capacitors. Three trillion of them are made per year.
00:01:30 Randall and his team have developed a new technique where dense ceramics can be achieved with temperatures below 200 degrees Celcius and in minutes instead of hours. This new technique uses liquid such as water as a transient solvent to help densify the material. What we're doing is using a liquid and a dissolution process, as it's called, which then works by an evaporation process. You're evaporating a liquid at the same time that you're dissolving it. And so you're catching this so-called dissolution and precipitation process, the crystal growth process, at the same time, in and around surfaces of this powder compact, and in doing that you pick up what is commonly known as the liquid phase sintering process.
00:02:17 Now that's been done before but usually with phases that aren't transient. And so what's really important about this process is the liquid is there and then it's gone. But in the process of it being there and gone it's capturing all the exchange and diffusional and growth processes that you need to drive the sintering. This approach was named the cold sintering process because of the drastically lower temperatures needed compared to conventional high temperature sintering. This breakthrough opens up a new age of ceramics processing. The ability to make things at the same quality that you can in a conventional process but thousands of degrees below the temperatures that you could previously do by the sintering
00:03:03 process, the ability to incorporate new materials into the process and make new types of functionality and then finally to have a system where it's basically densified in 20 minutes means that your throughput and your manufacturing yields could go up enormously. This is great for manufacturing, it is great for energy savings, it is great for the environment, and it is great for new intellectual endeavors. After making their initial discovery, the team has already cold sintered many materials. Probably within three months we had worked on over 50 systems and got them all to work. Dialectric materials that have very very good properties. We're beginning to get more functional materials to work for piezoelectrics and for sensors and for other things.
00:03:56 The real breakthrough in terms of helping the planet will be in the infrastructural use of ceramics. This is the glass, this is bricks, this is tile, this is this type of space. Through an industry-university cooperative research partnership with North Carolina State University, Randall and his collaborators are exploring ways to implement cold sintering in everyday manufacturing. The next steps is to then figure out how to scale it into industry. They, at the end of the day, have the machinery, and the industrial know-how of how to scale this up. Cold sintering has the potential to create cost-effective and energy efficient ways of
00:04:36 manufacturing materials used in everyday life while opening doors for a whole new realm of materials. The most important thing about cold sintering is it can bring new ideas into the field and this is right at the beginning, so there's plenty of room to expand those ideas.