Fiber optic hydrogen detectors containing Mg-based metal hydrides

We report on the implementation of Pd-capped chemo-chromic metal hydrides as a sensing layer in fiber optic hydrogen detectors. Due to the change in optical properties of Mg-based alloys on hydrogen absorption, a drop in reflectance by a factor of 10 is demonstrated at hydrogen levels down to 15% of the lower explosion limit. The switching takes place in only a few seconds. Comparing Mg-Ni and Mg-Ti based alloys, we find that the latter has superior optical and switching properties. Using a 50 nm thick Mg70Ti30 film capped with a 30 nm Pd catalytic layer as the sensing layer, we report on the sensitivity of the fiber optic detector for hydrogen both in argon and oxygen, the temperature behavior and the reversibility. (c) 2006 Elsevier B.V. All rights reserved.