In a Flash! A New Way for Making Ceramics

The Science

Potentially saving precious processing time and significant amounts of energy in producing a variety of materials, a new method rapidly consolidates even hard-to-deform ceramic materials. The method stabilizes the processing temperature. It does so by applying an external pressure on the material. The pressure equalizes the distribution of temperature. The process almost instantaneously densifies the ceramic with only limited grain growth, confirming theoretical calculations.

The Impact

In this new process, scientists can manufacture difficult-to-deform super-hard ceramic materials into parts while preserving microstructural features. These features are important to maintain the material’s properties and vital for manufacturing ceramic components. The new process even worked on super-hard silicon carbide, SiC, a material used in bulletproof vests.

Summary

Scientists developed a new ultra-rapid consolidation process called “flash spark plasma sintering.” The process stabilizes the thermal runaway by applying an external pressure that equalizes the distribution of temperature. The process can be used to manufacture parts made from difficult-to-deform super-hard ceramic materials (for example, SiC) while maintaining the microstructural features important to their properties. Theory was advanced to understand the role of thermal runaway and used to develop the new flash spark plasma sintering (or flash hot pressing) process. The process used sacrificial dies to heat pre-compacted SiC powder specimens to a critical temperature before applying voltage to the powder volume and allowing the electrode-punches of the spark-plasma sintering apparatus to contact the specimens and pass electric current through them under elevated temperatures. Scanning electron microscopy showed that the SiC was almost instantaneously densified with limited grain growth proving out the theoretical considerations.

Funding

The support was from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

Publication

E.A. Olevsky, S.M. Rolfing, and A.L. Maximenko, “Flash (ultra-rapid) spark-plasma sintering of silicon carbide.” Scientific Reports 6, 3348 (2016). [DOI: 10.1038/srep33408]