Binary Colloidal Alloy Test - 5: Compete (BCAT-5-Compete)
Research Area: Complex Fluids
Expedition(s): 19- 26
Principal Investigator(s): ● Barbara Frisken, PhD, Simon Fraser University, Burnaby,
British Columbia, Canada
RESEARCH OBJECTIVES
For the Binary Colloidal Alloy Test - 5: Compete
(BCAT-5-Compete) investigation, a crew member
photographs microscopic particles (colloids)
suspended in a liquid over time. This experiment
investigates the competition between crystallization
and the separation of solids from liquids. An
improved understanding of these processes leads to
improved manufacturing methods and commercial
products.
EARTH BENEFITS
These samples provide important data that are not
available on Earth, data that can guide our
understanding of crystallization, which impacts
production (eg, when making plastics). Production
processes often have defects introduced when there
is a competition between processes like phase
separation and crystallization. Studying this
competition in the absence of gravitational settling
provides insights into how to control it.
SPACE BENEFITS
Microgravity is essential for colloid crystallization
research because gravity greatly interferes with
crystal formation. The experiment looks to answer
basic physics questions that could be applied to
colloidal products used in the space program,
including food and consumable products.
RESULTS
Using samples containing 3 equilibrium phases, the BCAT-5-Compete project studied the
interplay between phase separation and crystallization in a colloid-polymer mixture along one
kinetic pathway. In analogy with atomic systems, the range of the effective attractive
interaction between colloids was sufficiently long to allow for a stable liquid phase. On the
International Space Station, direct imaging obtained in microgravity allowed the observation of
a unique “crystal gel” that occurs when gas-liquid phase separation arrests due to crystallites
within the liquid portion spanning the cell. From the initial onset of spinodal decomposition
ISS025E008239 – NASA astronaut
Shannon Walker, Expedition 25 flight
engineer, uses a digital still camera to
photograph Binary Colloidal Alloy Test-5
experiment samples in the Kibo laboratory
of the International Space Station.