Researchers have synthesized a new class of aluminum-hydrogen compounds with a unique chemistry that could lead to the development of more powerful solid rocket fuel and may also, in time, be useful for hydrogen-powered vehicles or other energy applications.
An article about this research, led by scientists at the Johns Hopkins and Virginia Commonwealth universities, was published in the January 19, 2007, issue of the journal Science. The team also included scientists at University of Konstanz and University of Karlsruhe, both in Germany.
Through combined theoretical and experimental study, the team created this new class of aluminum/hydrogen molecules (called "hydrides") that are relatively stable and are similar in structure to boranes, which are composed of boron and hydrogen atoms. This relative stability may hold the key to the compound's possible future uses in rocket fuel, said team co-leader Kit Bowen, the E. Emmet Reid Professor in the departments of Chemistry and Materials Science at Johns Hopkins.
"It's always tough to predict how things will play out in the future, but our research finding is interesting enough for me to be willing to say that this synthesis may have the potential for some possibly very useful future applications, including the development of solid rocket fuel with more thrust," Bowen said.
Most solid rocket fuels already rely on aluminum as a co-fuel, but the compounds synthesized by the research team "might turn out to be more efficient," Bowen said.
"But that remains to be seen," he said. "These complexes are a new class of thing that, because of their various properties, can at this point only be imagined to have uses in propulsion or even in the forecasted hydrogen economy."
Today's so-called "petroleum economy" relies heavily on fossil fuels for energy. In a "hydrogen economy," however, electricity to power vehicles and for the power grid could be produced with much cleaner technologies using hydrogen, the most abundant element in the universe, as a fuel. Storing this fuel, however, presents tremendous challenges, including finding a solid that efficiently "soaks up and holds" hydrogen and then releases it on demand.
"There are many bridges to cross," Bowen said. "Perhaps it's best to think of the science we are doing with these new compounds as being like inventing new words. From those come sentences, paragraphs, chapters, whole books and even, eventually, Shakespeare. Small things can be the building blocks of larger ones down the line."
Team co-leader Puru Jena, distinguished professor of physics at Virginia Commonwealth University, said that developing new materials and compounds that meet some of the current technological problems in energy-related fields is one of the objectives of this kind of collaborative research.
"Our work has demonstrated that a synergy between experiment and theory can go a long way in meeting these challenges, particularly in developing novel nano-materials for storing and releasing hydrogen as well as for high-energetic materials applications," Jena said.
The experimental work for this project was conducted by Bowen and his graduate students, X. Li, A. Grubisic, and S.T. Stokes in the Chemistry Department at Johns Hopkins and by Gerd Ganteför and his graduate student, J. Cordes, from the Department of Physics at Konstanz University. The theoretical investigations were conducted by Jena and Boggavarapu Kiran, along with M. Willis, a graduate student in the Physics Department at Virginia Commonwealth University. In addition, Hansgeorg Schnöckel and his graduate student, R. Burgert, in the Institute of Inorganic Chemistry at the University of Karlsruhe also contributed to this research.
This research was funded by the U. S. Air Force Office of Scientific Research (which supports Bowen), the U. S. Department of Energy (which supports Jena) and by the Deutsche Forschungsgemeinschaft (which supports Ganteför and Schnöckell).
X. Li, A. Grubisic, S. T. Stokes, J. Cordes, G. F. Ganteför, K. H. Bowen, B. Kiran, M. Willis, P. Jena, R. Burgert, H. Schnöckel:
Unexpected Stability of Al4H6: A Borane Analog?.
In: Science; Vol. 315 no. 5810 pp. 356-358; 19 January 2007, DOI 10.1126/science.1133767
Source: Johns Hopkins University, USA
Last update: 18.01.2007
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