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Thermo Analytic Investigation of Hydrogen Effusion Behavior - Sensor Evaluation and Calibration
(2011)
The well established carrier gas analysis (CGA) method was used to test different hydrogen detectors comprising a thermal conductivity detector (TCD) and a metal oxide semiconducting (MOx) sensor. The MOx sensor provides high hydrogen sensitivity and selectivity, whereas the TCD exhibits a much shorter response time and a linear hydrogen concentration dependency. Therefore, the TCD was used for quantitative hydrogen concentration measurements above 50?µmol/mol. The respective calibration was made using N2/H2 gas mixtures. Furthermore, the hydrogen content and degassing behaviour of titanium hydride (TiH2-x) was studied. This material turned out to be a potential candidate for a solid sample calibration. Vacuum hot extraction (VHE) coupled with a mass spectrometer (MS) was then calibrated with TiH2-x as transfer standard. The calibration was applied for the evaluation of the hydrogen content of austenitic steel samples (1.4301) and the comparison of CGA-TCD and VHE-MS.
Due to its high energy density hydrogen is a capable energy carrier to store the electrical energy surplus resulting from energy production by wind and solar energy in chemical energy. In this context, corrosion stable, pressure resistant glasses offer a promising opportunity for long term hydrogen storage e.g. at high pressure in glass capillaries.
In this context, investigations of hydrogen permeation and diffusion can provide important fundamental knowledge to evaluate the applicability. Different sample geometries as planary, bulb shaped, capillary shaped, as well as powders are compared in order to evaluate the experimental operability and the sensitivity of each approach. Limiting factors are e.g. gas thight sealing of planar samples, wall thickness of small glass bulbs, availability of glass capillaries and a defined grain of powders. High pressure experiments and the application of fast furnaces to ensure quick heating to the extraction temperature using vacuum hot extraction coupled with MS. The correctness is ensured comparing the obtained results of the mentions geometries emong each other as well as with literature data.
The H2 effusion from H2 saturated glass powders, H2 permeation through the wall of blown glass bulbs, and H2 permeation through the wall of glass capillaries were applied to evaluate the permeability of hydrogen gas in a barium-aluminoborosilicate (BABS) glass. To validate these methods, two commercial glasses (vitreous silica and borosilicate) were used as a reference. Permeation values obtained from the different experiments agreed within a factor of 3 or less. The H2 permeability of BABS glass at temperatures close to ambient was found to be at least 3 orders of magnitude below that of borosilicate and silica glasses. The powder method, which requires minimal sample preparation efforts, turned out to provide easy access to the measurement of H2 permeability of glasses down to P = 3.9 × 10- 21 mol s- 1 Pa- 1 m- 1.