Since the early report of adsorption on single-walled carbon nanotubes in 1997, a number of controversial publications have claimed the hydrogen capacity of these materials to be between 0.1 and 10.0 wt %. However, no study has yet demonstrated a plateau of adsorption with pressure that is consistent with monolayer saturation. Others have suggested that the tube bundle structure expand under high pressure to enable higher adsorption on newly uncovered surfaces, but received no confirmation. Using a high-pressure instrument with in situ electrical probes, we found that a plateau is nearly achieved at about 300 atm in the room temperature isotherm. And that nanotube bundles do not expand or swell, shown by the in situ electrical measurements of purified single-walled nanotube (SWNT) bundles. The monolayer saturation plateau was found on bundled SWNT at room temperature corresponding to an adsorption of 0.9 wt %.
Reliable performance of SOFC stacks and Integrated Stack Modules (ISM) is determined by a robust stack design as well as an optimized operation regime. The following paper gives insight to some of the test methods Staxera has established to develop operation procedures that will allow a robust and long term stable performance of stacks and ISMs. As a result, more than 12000 h of operation and more than 50 thermal cycles could be demonstrated.
The present paper describes the investigation of a 1 kWel Integrated Stack Module (ISM) operated with reformate from a steam reforming process. It could be shown that no performance losses occur compared to a synthetic CPOX mixture even when high rates of internal reforming were employed. High thermal gradients that are expected to be present at the location of reforming were not observed to affect either the performance or the mechanical stability of the stack. The stack was operated in counter-flow and co-flow arrangements without showing differences in the performance. Use of internal reforming significantly reduces the air flow required for cooling the stack, which decreases parasitic power losses. The high potential of the ISM stands out above all in part load, where fuel utilizations of more than 80 % could be achieved.
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