the capabilities of that system were presented. These included the ability to scale up and to implement automation, the rapidity of processing, and the shape-making capability.

The presentation by Dr. Sudarshan also discussed wet processing methods, including osmotic consolidation, pressure filtration, and tape casting. Each of these methods was said to produce consolidated materials with limited thickness.

One processing factor discussed in detail was the effect of powder size distribution on the green density of tungsten powder compacts, with the green density in turn having an effect on the final consolidated density. It was shown that finer particles typically had lower green densities than coarse-grained counterparts and that multimodal distributions had higher densities than single-mode distributions. There may be advantages to considering multiphase, multigrained, multistructured materials.

Dr. Sudarshan indicated that powder chemistry was vital in determining the density during densification. He also said that oxygen content and other impurities may limit densification if one uses powder that is impure to start with. Dr. Sudarshan spoke of the need for measuring impurities, most importantly, oxygen. Finally, Dr. Sudarshan stated that the storage life of these nanopowders was an issue as they tend to agglomerate with time and create closed pores that compress and are hard remove.

Dr. Sudarshan summarized his presentation as follows:

• Powder characteristics are critical in obtaining dense nanocrystalline materials.

• Powder sizing is very important as it determines the grain boundaries.

• The effect of orientation of boundaries is not well understood.

• Several techniques for fast consolidation are available, with the choice depending on the material and the user’s processing requirements.

• Densification mechanisms must be modeled (similar to densification maps available for sintering and HIPing).

• More mechanistic evaluations are needed—grain boundary sliding versus grain growth?

• Sensors are needed to understand what is happening at the nanolevel.

The second presentation, by Merrilea Mayo of Pennsylvania State University, was “(Bulk) Processing of Nanocrystalline Ceramics.” It discussed the difficulties in taking an ultrafine ceramic material and producing a fully dense structure, without dopants or second phases, while maintaining the grain size below 100 nm. Professor Mayo outlined a series of surprises that can occur when ultrafine particulate ceramic materials are being processed.

The first of the surprises is that the phase diagram can shift unexpectedly owing to shrinking particle size. This type of phase shift is unexpected since this shift is not seen in conventional materials. The shift in the phase diagram also means that critical material properties change along with the change in crystallographic structure. This change, in turn, affects the processing parameters. Without having prior knowledge of the nanoscale

Front Matter (R1-R7)

Introduction (1-2)

Session 1: Synthesis, Assembly, and Processing (3-8)

Session 2: Fabrication and Production (9-16)

Session 3: Applications (17-22)

Session 4: Structure, Properties, and Characterization (23-24)

Session 5: Modeling and Simulation (25-28)

Workshop Wrap-up (29-32)

Appendix A: Workshop Participants and Agenda (33-38)

Appendix B: List of Attendees (39-40)