July 2005

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First safety tests of hydrogen-charged nano-scale natrium alanates indicate that, contrary to what had been expected in a tank burst, these powders don’t ignite or burn, reports the HyTecGroup at the Karlsruhe Research Center in Germany. “Initially at least, this is surprising, because we had assumed that nanoscale powder exposed to air would quickly ignite and would cause a deflagration,” said Dr. Maximilian Fichtner, head of the center’s hydrogen storage activities. In the test setup, regarded as typical in a future advanced hydrogen storage system, the natrium alanate with 7 weight % hydrogen was heated to 130 deg. C inside a sealed tube. The resulting hydrogen pressure broke a pressure burst disk at about 9 bar overpressure, and the nano-powder was ejected into the air, but no ignition of the dust cloud or deflagration. Fichtner added there are “some indications” that hydrogen released at that time prevented an extra-rapid reaction of the material with the air’s oxygen. Apparently the material was able to form a thin passive layer on the surface of the powder particles, that significantly slowed the reaction, he explained. “The conclusion drawn from this test is that an mishap in operating the vehicle does not necessarily lead to fire and deflagration,” Fichtner added. More tests are planned. The hydrogen safety center was created last fall with support from carmakers and energy companies (H&FCL Oct 04).

Contact: Research Center, Inge Arnold (media), +49/7247/82 2861; e-mail inge.arnold@oea.fzk.de; www.fzk.de