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

Overview Background  FSW, SFSW, Aluminum and Hydrogen Experiment Discussions Future Research

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

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

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

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

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 + 3H 2 O → Al 2 O 3 + 3H 2

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

Research Apparatus

Block Diagram PEMFC 1.2 W

Experiment 1 Weld reprocessed three times Voltage on fuel cell recorded  (Play Video)

Experiment 1

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

Experiment 2

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)

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

References Ted Clark. An analyis of microstructure and corrosion resistance of underwater friction stir processed 304l stainless steel. Technical report, BYU, George E. Cook, Reginald Crawford, Denis E. Clark, and Alvin M. Strauss. Robotic friction stir welding. Industrial Robot, 31(1):55–63, November Jerome J. Cuomo and Jerry M. Woodall. Solid state renewable energy supply, November 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, Terry Khaled. An outsider looks at friction stir welding. Technical report, Federal Aviation Administration, 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,