Charles C. Hays

Solar Wind Neon from Genesis: Implications for the Lunar Noble Gas Record

Lunar soils have been thought to contain two solar noble gas components with distinct isotopic composition. One has been identified as implanted solar wind, the other as higher-energy solar particles. The latter was puzzling because its relative amounts were much too large compared with present-day fluxes, suggesting periodic, very high solar activity in the past. Here we show that the depth-dependent isotopic composition of neon in a metallic glass exposed on NASAs Genesis mission agrees with the expected depth profile for solar wind neon with uniform isotopic composition. Our results strongly indicate that no extra high-energy component is required and that the solar neon isotope composition of lunar samples can be explained as implantation-fractionated solar wind.

Thin Film Platinum Alloys for Use as Catalyst Materials in Fuel Cells

Introduction: In state-of-the-art polymer electrolyte fuel cells (PEFCs) using an acid polymer electrolyte, platinum (Pt) and platinum group metal (PGM) alloy catalysts are used as the cathode materials for the reduction of oxygen. Some challenges limiting the widespread application of PEFCs, that utilize PGM catalysts are: 1) slow kinetics for oxygen reduction; 2) insufficient long-term durability manifest by metallurgical effects (e.g., Ostwald particle ripening, and surface area loss due to corrosion); and 3) the high cost of platinum. Motivated by these challenges, we report the results of a study designed to discover new Pt-based, transition metal alloy catalysts that are stable in acid and electrochemically active for the oxygen reduction reaction (ORR). Results: Using a high-throughput, co-sputtering, synthesis technique [1], an array of thin film specimens in the ternary series (Pt3Co)1-xZrx, 0 ≤ x ≤ 30 (At.%), were simultaneously prepared. The individual films were deposited onto an 18-segment current collector structure comprised of nanostructured Au thin films, with average Au grain size of 40-50 nm. The Au films were strongly oriented, with a (111) crystallographic orientation, as shown in Fig.-1. The XRD patterns for representative films from the array, with 0 < x < ~20 (At.%) [some labeled w/nominal compositions] are shown in this figure, indicating that the Pt-Co-Zr thin films are also ordered, with a (111) crystallographic orientation. The decreased intensity for Pt56Co24Zr20 is consistent with the reduced thickness of the films in this part of the array.