Abstract
In this paper, in order to improve the durability of optical fiber grating hydrogen sensors, an optical fiber grating hydrogen sensor with high precision, stability, and durability is prepared. Based on the simplified two-dimensional model and finite element analysis, the effects of film thickness, coating speed, and coating times on the residual Mises equivalent stress between the sensor film and substrate were studied, and the optimum coating parameters were determined. The finite element analysis results show that the residual equivalent stress between the film and the substrate increases with the increase in the film thickness between 50 and 150 nm. The range of 200–250 nm is relatively stable, and the value is small. The coating speed has almost no effect on the residual equivalent stress. When the thickness of the film is 200 nm, the residual equivalent stress decreases with the increase in coating times, and the equivalent force is the lowest when the film is coated three times. The best coating parameters are the thickness of 200 nm, the speed of 62.5 μm/s, and the times of coating three times. The results of finite element analysis are verified by the hydrogen sensitivity test and durability test.
Highlights
Taking the left end of the substrate–palladium film interface as the origin and the node reflected in the distance from the origin, the effect of the coating process on the residual stress between the palladium film and substrate of the hydrogen sensor was investigated
The function of the turntable is to ensure the uniform rotation of the fiber grating during the coating process, make the Pd particles uniformly adhere to the gate area, and reduce the residual stress between the palladium film and the gate and improve the durability of the sensor
According to the finite element analysis results, the residual equivalent stress in the film and the substrate system is proportional to the film thickness between 50 and 150 nm; between 200 and 250 nm, the value of residual equivalent stress decreases and is relatively stable
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Most of the market mature hydrogen sensors are mostly based on electrochemical principles, which makes it easy to reduce the sensor’s sensitivity by the influence of the external environment, resulting in measurement errors This sensor generates electric sparks [6] during use, and the liquid hydrogen fuel used for aerospace creates a very high risk. Most of the research on fiber grating hydrogen sensors pays attention to the influence of film thickness and coating material on the sensor’s performance. We can use the optimal coating process to make fiber grating hydrogen sensors with high precision, short response time, and stability These sensors can make timely and accurate monitoring of the dangerous phenomenon of hydrogen leakage
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