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Vanfleet, Richard R.

Publications and source records attributed to Vanfleet, Richard R..

3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Revisiting the revised Ag-Pt phase diagram

Because of the important applications of platinum alloys and related platinum-group-metals phases, complete phase diagrams for these systems are important for materials engineering. The currently accepted phase diagram for the Ag-Pt system is questionable because of its disagreement with earlier experiments and because of its claim for a lone ordered structure at 53%-Pt which was not characterized and which contradicts both computational predictions and analogy to the isoelectronic system Cu-Pt. A complete re-examination of the Ag-Pt system by computational and experimental means suggests a phase diagram similar to the isoelectronic system Cu-Pt. The unknown compound, claimed to be 53%-Pt, is found to be the L1 1 structure at 50%-Pt.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Sputtered carbon as a corrosion barrier for x-ray detector windows

Sputtered amorphous carbon thin films were explored as corrosion resistant coatings on aluminum thin films to be incorporated into x-ray detector windows. The requirements for this application include high corrosion resistance, low intrinsic stress, high strains at failure, and high x-ray transmission. Low temperature sputtering was used because of its compatibility with the rest of the window fabrication process. Corrosion resistance was tested by exposure of carbon coated and uncoated Al thin films to humidity. Substrate curvature and bulge testing measurements were used to determine intrinsic stress and ultimate strain at failure. The composition and bonding of the carbon films were further characterized by electron energy loss spectroscopy, Raman spectroscopy, and carbon, hydrogen, and nitrogen elemental analyses. Samples had low compressive stress (down to.08 GPa), a high strain at failure (3%), and a low fraction of sp{sup 3} carbon–carbon bonds (less than 5%). The high breaking strain and excellent x-ray transmission of these sputtered carbon films indicate that they will work well as corrosion barriers in this application.

36 MATERIALS SCIENCE↗