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Researchers at the Colorado School of Mines (CSM) are working to help the U.S. Department of Energy (DOE) find a way to extract ultra-pure hydrogen from the country's vast coal reserves using a palladium membrane. The gasification of coal produces a stream of hydrogen and other gases, such as carbon monoxide and carbon dioxide. Palladium membranes can extract the hydrogen from the gasified coal stream to produce hydrogen that is pure enough to be used directly by a proton exchange membrane (PEM) fuel cell.
The fundamental chemistry and physics of palladium-based production of ultra-pure hydrogen have been studied for more than 100 years. The first commercialized version of this technology was developed in the 1960s, but the high price of palladium has been a barrier to its widespread use. More recently, researchers have discovered ways to deposit thin palladium films onto ceramic supports to minimize the amount of palladium required and reduce costs. However, the bond between the thin palladium film and the ceramic support membrane has been problematic. In addition, incorporating the ceramic support elements into metal modules with gas-tight seals has been challenging-most designs have presented the possibility of leaks between the ceramic supports and the metallic tube-sheet header of the module.
The ionic plasma deposition (IPD) technology, which has the potential to solve both of these issues, is currently being evaluated at CSM.
"The IPD technology will enable the fabrication of very thin palladium membranes, which reduces the costs involved. By using the IPD technology, we might be able to increase the membrane durability with a superior metal interface that will extend its lifetime," says Paul Thoen, a research professor at CSM.
According to John Petersen, chief technology officer of Ionic Fusion Corp., Longmont, Colo., which invented and markets the proprietary IPD surface engineering nanotechnology, the IPD process enables the metal to penetrate the ceramic substrate in a uniform, highly ordered structure that creates a superior, cost-effective ceramic-to-metal interface. The process is performed in a vacuum to remove all contaminants, water vapor and oxygen. High kinetic energies at ambient temperature drive the ions of the selected target material into the selected substrate. The depositing material ions are accelerated through proprietary devices to ensure that the depositing species are the correct energy for the process and substrate material, which allows for a broad range of custom stoichiometries.
Unlike other deposition technologies, the IPD process can be carefully controlled for particle size, density and rate of dispersion. This high degree of control-coupled with the energy generated-enables the ion particles to be driven into the substrate material to a depth and uniformity of application that hasn't been possible with conventional "coating" technologies.
CSM and Ionic Fusion are considering applying for a joint grant under the recently passed $200 million federal energy bill to expand their palladium PEM research.
For more information about ionic plasma deposition, contact Ionic Fusion at 105 S. Sunset St., Suite T, Longmont, CO 80501; (303) 485-8111; fax (303) 485-8866; e-mail Tim@IonicFusion.com; or visit www.ionicfusion.com.
More information about the Colorado School of Mines can be found at www.mines.edu.