1. National Aeronautics and Space Administration www.nasa.gov 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

2. National Aeronautics and Space Administration www.nasa.gov Alloy C-103 Behavior very sensitive to trace amounts of oxygen. Thermochemical modeling T = 1450C: ---------------------------------------------------------------------------------------------- No oxygen P(O 2 ) = 1 x 10 -6 bar

3. National Aeronautics and Space Administration www.nasa.gov 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 10 -24 bar –Hf + O 2 (g) = HfO 2 (s) P(O 2 ) = 3.8 x 10 -25 bar Nb –Nb + 3/2 O 2 (g) = Nb 2 O 5 (s) P(O 2 ) = 7.3 x 10 -15 bar

4. National Aeronautics and Space Administration www.nasa.gov 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)

5. National Aeronautics and Space Administration www.nasa.gov

6. National Aeronautics and Space Administration www.nasa.gov 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.

7. National Aeronautics and Space Administration www.nasa.gov C-103 100 h runs according to SSL Heat Schedule Date/DesignationTemperatureLocation of GetterComments 0216121600C IsothermalNoneHigh T leads to weight loss 0515121450C SSL ScheduleNoneWt gain—0.73 mg 0531121450C SSL ScheduleNoneNew elements/rapid weight gain inconsistent with others 0723121450C SSL ScheduleBottomWt gain—0.07 mg 0727121450C SSL ScheduleBottomWt gain—0.08 mg 0801121450C SSL ScheduleNoneWt. gain—1.32 mg 0808121450C SSL ScheduleOn ThermocoupleWt. gain—1.63 mg 0815121450C SSL ScheduleNoneWt. gain—3.68 mg 0822121450C SSL ScheduleOn ThermocoupleWt. gain—2.81 mg

8. National Aeronautics and Space Administration www.nasa.gov No Getter

9. National Aeronautics and Space Administration www.nasa.gov C-103 080112 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

10. National Aeronautics and Space Administration www.nasa.gov Getter at Bottom

11. National Aeronautics and Space Administration www.nasa.gov C-103 072312 Getter at Bottom Post Exposure to UCB SSL Heat Schedule

12. National Aeronautics and Space Administration www.nasa.gov Alloy C-103 072312 Getter at Bottom Post Exposure to UCB SSL Heat Schedule BSE image; Corresponding SE image is on previous slide Nb Hf Nb

13. National Aeronautics and Space Administration www.nasa.gov Getter Near Sample on Thermocouple

14. National Aeronautics and Space Administration www.nasa.gov C-103 080812 Getter on Thermocouple Post Exposure to UCB SSL Heat Schedule BSE Image Hf

15. National Aeronautics and Space Administration www.nasa.gov 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

16. National Aeronautics and Space Administration www.nasa.gov Supplemental Data: Higher Temperature and Outlier Run