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

该项目是与德国弗劳恩霍夫硅酸盐研究所（ISC）在外部电场影响下对纳米颗粒进行烧结的联合研究。最终的目标是了解基本原理，并利用场辅助烧结的好处，使散装纳米材料的加工和制造。场辅助处理已经成为当前感兴趣的话题，由于新的现象，发生在场暴露，如微放电，与所得的表面效应和电扩散。在技术上，电场应用具有明显的好处：提高烧结速率，控制和生产新的微观结构，以及灵活的制造能力（近净形，调制结构）。加州大学戴维斯分校的实验室实验成功地通过场辅助烧结技术（FAST）处理了难以烧结的材料，该技术同样适用于陶瓷和金属，复合材料和纳米尺寸粉末。ISC开发了一种能够控制微波能量和热流的微波处理（MWP）设施。该系统还能够应用极高的加热速率，这是已知的抑制粉末烧结过程中的晶粒生长。ISC的高灵敏度热光测量（TOM）技术能够监测颈部形成、接触点化学变化和粉末致密化。这项研究的目的是研究纳米粉末烧结的早期阶段的操作机制，并量化它们与外部施加的场的相互作用。与德国建立伙伴关系将通过推进纳米粉末加工的知识和预测能力为科学界带来好处。场效应的量化可能是由于这种伙伴关系是至关重要的领域激活处理的进步，是有价值的研究和教学。这种合作工作开辟的新视角将更好地为研究生在日益相互依存的世界经济中工作做好准备，并激励本科生攻读博士学位。 该NSF项目由设计、制造和工业创新部门以及国际办公室（西欧）共同资助，作为NSF和欧洲之间材料研究的合作活动（NSF 02-135）。 该项目是与德国维尔茨堡的弗劳恩霍夫硅研究所合作进行的。

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.