A path to the future, ceramic paving

When you hear the word "ceramic", you can think of the mug that you made during pottery or the vases that pick up dust on your grandmother's shelf. Although these objects are made of ceramic, they represent only a small part of the whole. Ceramics are used in armor, lasers, electronics, tooth replacement, etc. They ensure the proper functioning of the motherboard of your computer. They protect space shuttles when most other materials burn in the atmosphere. In other words, ceramics are ubiquitous and essential.

They also come with a price. The treatment of many ceramics requires heating them to temperatures above 2,000 degrees Celsius for several hours. It is an important energy expense. B. Reeja Jayan is working at Carnegie Mellon University to solve this problem with its unconventional energy source.

Jayan is an assistant professor in mechanical engineering and directs the Materials Laboratory away from the equilibrium of the CMU. She is studying the use of electromagnetic fields in the manufacture of ceramics, particularly with regard to sintering and synthesis. Sintering is the process by which a porous material, such as clay, densifies under pressure or heat. She detailed the new developments in this area of ​​research in the cover article of January 2019 of the Journal of the American Ceramic Society.

The paper originated from a two-day workshop held at Carnegie Mellon in June 2017 entitled Electromagnetic Effects in Materials Synthesis. The workshop brought together scientists working in three different fields of site-assisted material synthesis. "This workshop was a good opportunity to learn from each other," says her postdoctoral researcher, Shikhar Jha. "These methods (microwave, laser and electric field) are very different from each other, but we hope to find a common theme to link them to a single mechanism."

At the workshop, scientists wondered why electromagnetic fields accelerate sintering. "We want to see if these field-based sintering and synthesis processes are all thermally directed, or if the field itself induces additional motive power," said Jayan. In other words, does the field simply provide additional heat or do they do anything else?

This question presents unique search opportunities. In addition to making the process more efficient, researchers can also process new materials with new properties. "We do not expect the behavior and properties of the materials to be the same as they were," says Jayan. "We found them different, but we do not know how and we have opportunities there."

However, there are several barriers to their full understanding of the process, including available characterization tools. "You can not use a thermocouple to measure it," says Jayan, "because the field will also interact with the thermocouple and provide you with unreliable data."

Another problem is the dynamic nature of the process. "If you only measure the properties of the material and the microstructure afterwards, you will not know what happened in the middle phase," says Jayan. As a result, studies that measure processes over time, called in situ studies, have become invaluable. The Jayan group is working with national laboratories to use a synchrotron source, a type of electron accelerator, to shed light on the intermediate stages of structural changes occurring during such processes.

The last problem is that of scale. When studying sintering, "you must be able to connect and assemble all length scales," says Jayan, "from atoms to large pieces that you can hold in your hands ". For scientists to understand the underlying mechanisms, they need to develop characterization and modeling techniques that can determine the evolution of structures over time at different scales.

Although the challenges may seem enormous, the result would be worth it. If scientists understood the role of external domains in the sintering process, they could accelerate technological development in a wide range of areas, including manufacturing, pharmaceuticals, electronics and clean energy. Already, their efforts are producing results. "The 20 hour delay" is reduced to a few seconds, "said Jayan," and the temperature has been reduced to a few hundred degrees. It is a significant energy saving. "

Jayan and his team hope that their article will constitute a call for action for a new generation of students and researchers. More than anything, it was "bridging the lack of knowledge in the community," says Jayan, "and tell them: here's an opportunity, let's work together."

Explore further:
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More information:
The effects of the external fields on the sintering of the ceramic, Journal of the American Ceramic Society, doi.org/10.1111/jace.16061