The Flash Ecosystem: Electrification of Ceramics Manufacturing

Abstract: Recent discovery of flash sintering whereby ceramics can be sintered in a few seconds at furnace temperature far below 1000 oC by injecting current directly into the workpiece spells a new paradigm in the manufacturing of ceramics. Science-wise the phenomenon is related to the generation of a solid-state plasma, which can be migrated into a free-standing workpiece (without electrodes) by superposition of magnetic fields. We call it touch free flash sintering. This “flash ecosystem” has several attributes: (i) single phase multicomponent ceramics, e.g. solid state electrolytes for Li+ batteries (LLZO) can be created from elemental powders of the constituents (lithia, lanthana and zirconia), that react and sinter in a few seconds, (ii) graphene infused copper with high conductivity is formed by reactive flash of carbon black and copper powders, (iii) refractory metals, tungsten and rhenium can be sintered at ultralow temperatures in less than one minute.

Energy-wise the discovery is transformational. It is as revolutionary as the transition from internal combustion engine to all-electric vehicles. In EVs high efficiency is achieved by applying the power directly to the wheels. Similarly in flash sintering electrical energy is injected directly into the workpiece in a table-top device, without the need for large sintering furnaces that must operate at very high temperatures for several hours. The science is also different, rather than time and temperature which drives diffusion, the injection of current generates a plasma within which chemical reactions occur at astronomical rates, generating far from equilibrium materials that may have unusual properties. This new manufacturing vision will be implemented by new companies.

Bio: After his undergraduate degree in Electrical Engineering, Raj received the Ph.D. in Engineering and Applied Physics from Harvard University in 1970. After one year at Chase Brass and Copper Company in Cleveland, and about four years as a young faculty at the University of Colorado Boulder, he moved to Cornell University where he served on the MS&E faculty until 1996. He is a vigorous scientist who collaborates with senior and young students at institutions throughout the world. He is known for leading several new fields of research where he has applied fundamental knowledge of defect physics to different problems: for example high temperature fracture, sintering, Li+ battery electro-chemo-mechanical phenomena, and most recently electro-chemo sintering as described in the abstract. He is very proud of his Ph.D. students and post-docs (more than 60), as well as many undergraduates who have interned with him.  He loves science and is always interested in its practical impact. His interdisciplinary experience and mentorship from Mike Ashby and David Turnbull (at Harvard) have served him well.