Physics of Colloids in Space (PCS): Results

Results

After
some initial difficulties, PCS was successfully activated in June 2001.
Twelve-hour experiment runs were conducted on July 8 and 10. "This
was the first experiment run where we were able to complete the full scope
of diagnostics requested by the principal investigator teams, " stated
Michael Doherty, project manager at Glenn Research Center. "Our team
is getting the hang of how to do this stuff and take advantage of the
Ku (communications) band windows." The science team reported that
PCS is providing excellent data on colloid polymer gas and liquid phases,
and the performance of polymer gel.

During
an 80-hour run the week of September 10, one of the Single Photon Counting
Modules failed. The other module is still functioning and, with some operational
changes, all of the planned experiments will be conducted. Operations
were temporarily suspended in late September while EXPRESS
Rack 2 received new software. A 96-hour run was begun on October 9.

Ground vs. space:  The two photos above are of white light shown through binary alloy samples.  The left sample was grown on the ground and the right sample (sample AB6) was grown on the ISS during Increment 2. The different colors are a result of different wavelengths of light as they reflect off the crystal nuclei, indicating the placement of particles in the suspension.  The sharply defined spectrum of the bottom sample reveals highly-ordered particle placement in the colloidal suspension.

Similar
investigations conducted by other principal investigators (P.M. Chaikin,
Control and Dynamics of Hard Sphere Colloidal Dispersions) have yielded
some unexpected and pleasantly surprising results:  solutions that
formed glasses on Earth formed crystals and dendritic growth in space;
and nucleation and growth that had been anticipated by preliminary studies,
but never observed during the crystal growth process.

Applications

Colloids
appear frequently in nature (milk is an example) and are used in industrial
processes.  Paints, aerosols, and foams are examples of manufactured
colloidal mixtures.  Understanding the properties of colloids may
allow researchers to specifically engineer them for the manufacture of
new materials and products.  The results of PCS may lead to new display
units, lasers, semiconductors, and strong lightweight structures. 
Colloids are also used as model systems for the studies of the properties
of fluids and solids, with colloids acting as analogs for atoms.

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