Research on Long-term Reliability of Pd/Ag Fiber Bragg Grating Hydrogen Sensor

Abstract:
Owing to the advantages of small size, strong anti-electromagnetic interference ability and good gas selectivity, fiber Bragg grating (FBG) hydrogen sensor coated with palladium/silver (Pd/Ag) alloy film is used for on-line detection of dissolved hydrogen in transformer oil. However, the key factors restricting the long-term reliability of FBG hydrogen sensor are still unclear, and there is little relevant research to prove whether the sensor can work reliably in transformer oil for a long time. In this paper, the long-term reliability of Pd/Ag alloy film-coated FBG hydrogen sensor is investigated. Pd/Ag alloy films are prepared through magnetron sputtering process. The thickness of Pd/Ag alloy film is around 400 nm, and the mass percentage of Pd: Ag is about 3:1. The basic performance of the hydrogen sensors were calibrated before the experiment, the gas-phase sensitivities of Sensor 1 and Sensor 2 were 10.06 pm/% H2 and 9.55 pm/% H2 respectively. Under the condition that the oil temperature is 120 °C and the dissolved hydrogen concentration in the oil was 2000 ppm, 50 cycles of hydrogen absorption and desorption aging experiment are carried out for a total of 100 hours. The results show a good reliability for long-term usage.