Clarkson's Center for Advanced Materials Processing (CAMP) sponsored its Fifth International Symposium on Chemical-Mechanical Polishing (CMP). This very successful meeting, held August 13-16 in Lake Placid, New York, continues to grow in stature. It involved over 100 participants from the United States and other countries such as Belgium, Japan and Germany. Details of this meeting and CAMP's continued progress in the area of CMP will be described in the December 2000 newsletter.
The much heralded word 'nanoparticles', and the proclamations about their diverse and miraculous future in materials development will only become reality if technologists can discover conditions by which they can be uniformly dispersed as primary species in various media. Towards that goal Professors Richard Partch and Don Rasmussen and their CAMP student research team Deborah Forryan and Nicholas Pavel have been investigating conditions for preparing dispersions of various nanocarbon particles in both aqueous and organic solvents. They report that so far minimum sizes of carbon particles obtained in stable dispersions are in the range of 15-50 nm, depending on the source. A sonic horn is employed to assist dispersion and the addition of surfactants does not appear to enhance particle dispensability nor dispersion stability over time. It has been observed, however, that the type and size of flask the dispersions are prepared and stored in affects stability.
In separate work Postdoctoral Associate Hongyu Wang and Professor Partch have succeeded in dispersing 80 nm silicon carbide particles in water containing an anionic surfactant and carrying out in situ synthesis of a polycarbonate coating on the surface of the particles. The fillers prepared coated particles are then readily dispersible in and can serve as for several polymer matrices.
Professor Greg Campbell,
director of CAMP's Extrusion and Mixing Consortium,
continues to develop a more descriptive analysis for screw
pumps, augers, and extruders. Over the past year much of his group's effort
has been focused on the conveying of particular solids with these devices.
In addition, his group is working to understand structure development
in concentrated two phase systems. They found that bimodal dispersions
act quite differently from single particle size systems. Also they have
an actual program focused on understanding the reactions and physical
changes that occur in an epoxy which forms liquid crystalline structures.
Advanced Factor Analysis
Professor Ian Suni has been studying the kinetics of noble metal deposition from hydrofluoric acid and dissolution into typical cleaning solutions using spectroscopic methods. He has discovered that Cu deposition from HF is rate-limited by diffusion, while Au deposition from HF is rate-limited by a surface reaction involving HF. These investigations may lead to the development of additives which can minimize the nucleation and growth of metal clusters on silicon wafers. Professors Suni and Busnaina have also developed a model for metal removal in SC-1 and SC-2 solutions which includes convection, diffusion, and surface reaction.
Professor Don Rasmussen has published extensively in the areas of nucleation and growth of new phases and on techniques to study nucleation and particle growth processes. Currently his research is focused on the study of characterizing concentrated colloidal systems, depositing thin films and modifying binder systems for high temperature ceramics. His ongoing experimental projects include: (1) measurement of the dynamic light power spectrum from concentrated colloidal systems using a fiber optic probe (This fiber optic probe is being developed to study particle breakdown, aggregation or growth in concentrated systems.), (2) determination of the particle size from the shape of the power spectrum and the particle concentration from the integrated power spectral density, (3) controlled precipitation of nanoscale alumina from bauxite liquors; (4) nucleation and growth of particles in supersaturated systems, both aerosols in vapors and particles in supersaturated liquors and (5) the characterization of the hardness and surface properties of CMP polishing pads by surface energy determination and measurement of hardness using nanoindentation resistance.