Hydrogen Generation in Submerged Friction Stir Welding of Aluminum

1. Paul Fleming Vanderbilt University Hydrogen Generation in Submerged Friction Stir Welding of Aluminum

2. Overview • Background • FSW, SFSW, Aluminum and Hydrogen • Experiment • Discussions • Future Research

3. Friction Stir Welding • Recently (1991) developed solid state welding technique • Uses mechanical stirring to join metals • Yields high weld strength • Can be used to join aluminum

4. Submerged Friction Stir Welding • The case when the joining process is run underwater • Has been shown to be useful to prevent overheating • May produce lower grain sizes

5. Aluminum and Hydrogen • Aluminum in its pure form will react with air or water • In the case of water the reaction often leads to a release of hydrogen • Typically however, an oxide skin develops on the surface of aluminum which prevents the reaction from continuing through the aluminum • However, several researchers have proposed uses of this reaction for hydrogen generation

6. An example technology • Article from physics.com (May 16, 2007): • “New process generates hydrogen from aluminum alloy to run engines, fuel cells” • Jerry Woodall at Purdue uses gallium to prevent the development of the “skin” or oxide layer. • The reaction continues therefore until all aluminum is used

7. Another example • The paper, “Hydrogen gas generation in the wet cutting of aluminum and its alloys”, shows that when aluminum is cut underwater there is a fresh surface revealed which reacts with the water and hydrogen is released. • Experiments were conducted in the paper and the gas released during underwater cutting was confirmed to be hydrogen. • Also provides a probable chemical reaction: • 2Al + 3H2O → Al2O3 + 3H2

8. Our research • Demonstrate that hydrogen is released during submerged FSW, a technology which is useful in and of itself • Build an apparatus which can perform submerged FSW and collect the resulting Hydrogen • Attempt to discern the total amount of hydrogen released

9. Research Apparatus

10. Block Diagram PEMFC 1.2 W http://www.fuelcellstore.com/products/h2interpower/bz12-16.html

11. Experiment 1 • Weld reprocessed three times • Voltage on fuel cell recorded • (Play Video)

12. Experiment 1

13. Experiment 2 • Resistor (985 Ohms) added as load path between terminals of fuel cell • Voltage measured across resistor

14. Experiment 2

15. Discussion • Technology is potentially useful: • As a means of safely storing hydrogen and releasing without the use of chemicals • As a means of regenerative braking, where the friction provides the braking force and hydrogen is collected and used later as fuel • As a useful byproduct of a process which is itself useful (submerged FSW)

16. Future Research • Improve apparatus and determine the total amount of hydrogen which can be collected during normal submerged FSW

17. References • Ted Clark. An analyis of microstructure and corrosion resistance of underwater friction stir processed 304l stainless steel. Technical report, BYU, 2007. • George E. Cook, Reginald Crawford, Denis E. Clark, and Alvin M. Strauss. Robotic friction stir welding. Industrial Robot, 31(1):55–63, November 2004. • Jerome J. Cuomo and Jerry M. Woodall. Solid state renewable energy supply, November 1982. US Patent 4,358,291. • Douglas C. Hofmann and Kenneth S. Vecchio. Submerged friction stir processing (sfsp): An improved method for creating ultra fine grained bulk materials. Materials Science & Engineering, 402:234–241, 2005. • Terry Khaled. An outsider looks at friction stir welding. Technical report, Federal Aviation Administration, 2005. • Kunio Uehara, Hideo Takeshita, and Hiromi Kotaka. Hydrogen gas generation in the wet cutting of aluminum and its alloys. Journal of Materials Processing Technology, 127:174–177, 2002. • http://www.webelements.com/webelements/elements/text/Al/chem.html • http://www.physorg.com/news98556080.html