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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.
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.