Electric Field Assisted Sintering and Related Phenomena Far From Equilibrium Conference
Abstract
This overall objective of this conference, the first of its kind, is to discuss how electrical and electromagnetic fields can influence the generation and the movement of defects in ceramics. Mass transport in ionic ceramics is controlled by the diffusion of defects. Electrical conductivity depends on the transport of charged defects as well as holes and electrons. Recent research has shown that mass transport and electrical conductivity can change, together, and abruptly, under a critical combination of applied field and temperature. The most remarkable evidence of this non-linearity is so-called Òflash sinteringÓ where ceramics sinter from a powder compact to a dense body in just a few seconds, at furnace temperatures that are hundreds of degrees below conventional sintering. That nearly half the mass can be transported by solid-state diffusion in mere seconds is striking. The phenomenon has been shown to occur in several oxide ceramics, and more recently, in non-oxides as well. The rise in electrical conductivity, which coincides with flash sintering, leads to Joule heating, adding considerable complexity to the fundamental understanding of this phenomenon. Spark Plasma Sintering (SPS) is another process which accelerates sintering. Whereas flash sintering is a low power process which employs fields of about 100 VcmÐ1 and currents that are much less than one Ampere, SPS is a high power, low voltage process. In SPS high currents are used to rapidly heat a graphite die. They produce very high heating rates, which combined with applied pressure achieve fast sintering. SPS is often used to sinter materials which are otherwise very difficult to fabricate. A third process for field assisted processing of ceramics is microwave sintering, which has been shown to induce high rates of sintering while preserving small grain size. It has been shown to apply to several ceramics. The simplicity of the flash sintering experiments which can be carried out in conventional furnaces, heated to relatively low temperature, with the electrical field being applied directly to the specimens with a pair of electrodes, opens up the possibility of fundamental elucidation of the mechanisms by which electrical fields act to accelerate sintering. The electrical parameters can now be controlled at the millisecond time scale to resolve the underlying atomistic mechanisms. The design of these experiments makes them amenable for real time experiments in the laboratory and at X-ray synchrotrons for in-situ characterization of structural events at the atomic scale. Such experiments hold the potential of revealing a unified understanding of field assisted sintering....
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 04, 2018
- Source ID
- W911NF1610079
Entities
People
- Rishi Raj
Organizations
- Army Contracting Command
- Engineering Conferences International
- United States Army