NSF-Europe: Nanoparticle Sintering Under the Influence of External Electrical Fields

University Of California-Davis, Davis CA

Investigators

Abstract

This project is a joint study with Fraunhofer Institute Silicatforschung (ISC) in Germany on sintering nanoparticles under the influence of an external electrical field. The final goal is to understand the fundamentals and exploit the benefits of field-assisted sintering to enable the processing and manufacture of bulk nanomaterials. Field-assisted processing has emerged as a topic of current interest due to new phenomena, which occur upon field exposure such as microdischarges, with resultant surface effects and electrodiffusion. Technologically, electrical field application has distinct benefits: enhanced sintering rates, control and production of novel microstructures, and flexible manufacturing capabilities (near net shape, modulated structures). Laboratory experiments at UC Davis have succeeded in processing difficult-to-sinter materials by a field assisted sintering technique (FAST) equally applicable to ceramics and metals, to composites and nanometer size powders. ISC has developed a microwave processing (MWP) facility capable to control the MW energy and heat flow. The system also enables the application of extremely high heating rates, which are known to suppress grain growth during powder sintering. A high sensitivity thermo-optical measuring (TOM) technique at ISC is capable of monitoring neck formation, changes of the chemistry of contact points, and densification of powders. The objective of this proposed research is to study the operative mechanisms in the early stages of sintering of nanopowders and to quantify their interaction with the externally applied fields. Building the partnership with Germany will bring benefits to the scientific community by advancing the knowledge and predictive capability for processing of nanopowders. The quantification of field effects possible due to this partnership is critical to the advancement of field-activated processing and is valuable for both research and teaching. The new perspectives opened by this collaborative work will better prepare graduate students to work in an increasingly interdependent world economy and motivate undergraduate students to pursue doctoral studies. This NSF project is co-funded by the Division of Design, Manufacture, and Industrial Innovation and the International Office (Western Europe) as a Cooperative Activity in Materials Research between the NSF and Europe (NSF 02-135). This project is being carried out in collaboration with the Fraunhofer Institute Silicatforschung (ISC), Wuertzburg, Germany.