Ames Laboratory-made materials are out of this world

ESA -- D. Ducros

AMES, Iowa – Materials produced at the U.S. Department of Energy's Ames Laboratory were launched into space on May 14 with the European Space Agency's Planck Mission. Ames Laboratory's Materials Preparation Center synthesized over 20 kilograms of a lanthanum-nickel-tin alloy for use in a metallic hydride sorption cryocooler system—built by NASA's Jet Propulsion Laboratory—that will cool instruments during the space mission.

The Planck satellite will collect precise measurements of Cosmic Microwave Background, the remnants of radiation that filled the universe immediately after the big bang. Scientists will use the data to help answer questions about how the universe began, how it evolved, and how it will continue to evolve.

The Materials Preparation Center not only cast the lanthanum-nickel-tin alloy for the Planck cryocooler systems, but it also produced the high-purity lanthanum and refined the nickel, all with the precision required to meet stringent purity and homogeneity specifications.

The project drew on a significant range of MPC skills: high-purity rare earths production, electron beam melting, arc casting, interstitial gas tests, electron-microprobe tests, metallography, rolling mill work, annealing furnaces.

Creating the materials was a big job. To ensure quality, MPC staff had to make the 20 kilograms in 50 gram batches, for a total of 400 batches.

Casting large amounts of the alloy caused inhomogeneity within ingots, and gas-atomized particles proved very homogenous but didn't provide the needed performance, in this case. So, small ingots were created in an arc melter, a type of furnace that melts metals with a 400-500 amp electronic arc through argon gas. The components of the alloy posed another challenge: their varied melting points required some special preparation of the materials.

"We rolled the nickel and formed it into a dish-like shape. Then we put the tin and lanthanum in the nickel dish and heated the nickel from the edges," says Trevor Riedemann, manager of the MPC's rare-earth materials division. "As the nickel got hotter and hotter, the other two materials melted on the dish and created an intermediate intermettalic. From there, we melted the whole thing several times in the arc melter.

"Senior research technician Arne Swanson and John Wheelock, who is now retired, led the arc melting" says Riedemann, "But it was a chance for everyone at the MPC to do some arc melting or to weigh materials while someone else ran the arc melter, so we could get to make as many ingots as possible. It was a great project because it fully engaged the MPC, and everyone had a role."

Ames Laboratory is a U.S. Department of Energy Office of Science laboratory operated for the DOE by Iowa State University. Ames Laboratory creates innovative materials, technologies and energy solutions. We use our expertise, unique capabilities and interdisciplinary collaborations to solve global challenges.