A golden chance to understand diffusion

17 Jun 2002

A small gold oven sent to Russia's MIR space station may give scientists valuable insights into diffusive transport in liquids, a fundamental physical process that is so little understood that there are a half dozen conflicting theories about how the process actually works.

"One cannot measure diffusivity in liquids on Earth to any high accuracy, so it is not possible to identify the correct theory," explained Dr. Franz Rosenberger, director of the Center for Microgravity and Materials Research (CMMR) at The University of Alabama in Huntsville. "Buoyancy-driven convective mixing (cool liquids settling, warm liquids rising) almost always dramatically overpowers diffusion."

A UAH experiment that takes advantage of convection's "absence" is scheduled to be sent to MIR in early 1997. Five tiny samples of indium, each with a small disk of a radioactive indium isotope on one end, will be melted one by one inside the little gold oven. Gold was chosen because it conducts heat, but blocks radiation.

As the isotope diffuses through the sample and past detectors, escaping gamma rays will tell scientists on the ground how rapidly diffusion has occured. The accuracy of the data expected from the experiment will illuminate the molecular processes in self-diffusion.