National Aeronautics and Space Administration Progress Report: Alloy C-103 Behavior in High Vacuum August 27, 2012 N. Jacobson, J. Horwath, D. Humphrey* NASA Glenn Research Center *ZIN Technologies/NASA GRC Group

National Aeronautics and Space Administration Alloy C-103 Behavior very sensitive to trace amounts of oxygen. Thermochemical modeling T = 1450C: No oxygen P(O 2 ) = 1 x bar

National Aeronautics and Space Administration Oxygen Active Metals at 1450C Calculate minimum P(O 2 ) to form oxide Zr, Hf –Zr + O 2 (g) = ZrO 2 (s) P(O 2 ) = 2.8 x bar –Hf + O 2 (g) = HfO 2 (s) P(O 2 ) = 3.8 x bar Nb –Nb + 3/2 O 2 (g) = Nb 2 O 5 (s) P(O 2 ) = 7.3 x bar

National Aeronautics and Space Administration Task to Support FIELDS Project Evaluate behavior of candidate alloys in high vacuum with thermogravimetric analysis –Use heat schedule provided by SSL/UCB –All vacuum has some amount of oxygen –Control this with a getter Characterize microstructure of post-exposure samples –Field emission scanning electron microscopy (FE-SEM) –X-ray diffraction (XRD)—in progress Characterize optical properties of post-exposure samples (S. Miller)

National Aeronautics and Space Administration

National Aeronautics and Space Administration Hot Zone and Placement of Getter (Zr foil) 1. No getter—just W heat shields and W element. 2. Zr foil on top of bottom elements. 3. Zr foil on thermocouple, adjacent to sample.

National Aeronautics and Space Administration C h runs according to SSL Heat Schedule Date/DesignationTemperatureLocation of GetterComments C IsothermalNoneHigh T leads to weight loss C SSL ScheduleNoneWt gain—0.73 mg C SSL ScheduleNoneNew elements/rapid weight gain inconsistent with others C SSL ScheduleBottomWt gain—0.07 mg C SSL ScheduleBottomWt gain—0.08 mg C SSL ScheduleNoneWt. gain—1.32 mg C SSL ScheduleOn ThermocoupleWt. gain—1.63 mg C SSL ScheduleNoneWt. gain—3.68 mg C SSL ScheduleOn ThermocoupleWt. gain—2.81 mg

National Aeronautics and Space Administration No Getter

National Aeronautics and Space Administration C No Getter Post Exposure to UCB SSL Heat Schedule All images taken using a Hitachi S4700, images with red at the bottom were taken off EDS computer. All Images used for EDS scans are BSE BSE Image Hf Nb

National Aeronautics and Space Administration Getter at Bottom

National Aeronautics and Space Administration C Getter at Bottom Post Exposure to UCB SSL Heat Schedule

National Aeronautics and Space Administration Alloy C Getter at Bottom Post Exposure to UCB SSL Heat Schedule BSE image; Corresponding SE image is on previous slide Nb Hf Nb

National Aeronautics and Space Administration Getter Near Sample on Thermocouple

National Aeronautics and Space Administration C Getter on Thermocouple Post Exposure to UCB SSL Heat Schedule BSE Image Hf

National Aeronautics and Space Administration Conclusions to Date C-103 consistently gains a few percent of its weight under these conditions Very sensitive to oxygen content in vacuum Appropriate placement of getter minimizers this weight gain Mechanism of weight gain appears to be related to Hf in alloy Changes in optical properties to be measured

National Aeronautics and Space Administration Supplemental Data: Higher Temperature and Outlier Run