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Spark Plasma Sintering (SPS) is a powerful process for densifying nanosize ceramics, metals, and composites. The electric power loads on the powder or compact samples and heats them by direct joule heating along with conductive heat from the graphite mold. The current may be up to several ten's of thousands of Amperes and is very effective for quickly heating samples. The whole SPS process is so fast that crystalline grains do not have time to grow--producing consistent nanosize grains and high-density results! The proficiency of the SPS processes derives from the electrical field acting on the surfaces and interfaces between the particles. In 1922, A.L. Duval d'Adrian first developed this sintering technique for Alumina when he theorized that the isolative powder becomes conductive when heated. At first, only DC power was used. Today the power sources have expanded to include AC, pulse DC, pulse duration DC and their combinations, allowing the electrical field to produce more reactive effects with the surface or interface between powder particles. For example, the electrical field may cause the spark between metal particles to remove the oxide layers from surfaces or spark plasma between particles to produce a local high temperature. |
Another key factor is the proper use of the mechanical pressure to make processing fast and to prevent the building of neck formations at the initial stage of sintering. The mechanical pressure on samples closely interfaces the crystalline grains. The interface and crystal diffusions are much slower than surface diffusions so that the grains grow slowly while removing the porosity during the densification stage. We developed a quantum sintering technique that clearly shows the effective window for the application of pressure in the nanosintering of ceramics. Our alumina results are consistently under 1300C and 80Mpa. The sizes of grains are in the range 200-1000nm. And, density is better than 98% of theoretical. SPS NanoCeramics is dedicated to the development of SPS technologies for compacting nanophase ceramics and composites. We plan to manufacture every kind of SPS equipment for laboratories and factories for both experiment and production. We currently provide sintering service and professional consulting in our Chicago facility. We welcome cooperation to further develop SPS technologies for sintering nanoceramics and composites. We also welcome investors to join the great innovation. |
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