Physicists create safe fiber-optic hydrogen sensors

Physicists from the Institute of Telecommunications. Fraunhofer modified optical fiber to create

hydrogen sensor.Engineers use a laser to form a Bragg grating at the core of an optical fiber. This structure provides selective reflection of light with a certain wavelength. Then a coating is applied around the sensitive part of the fiber, which can interact with hydrogen.

“We work with catalytic layers, for example,palladium or palladium alloys,” says Günther Flachenecker, a researcher at the Institute for Telecommunications. Fraunhofer. Palladium has the ability to absorb hydrogen like a sponge. As soon as the two substances meet, the hydrogen breaks down into atoms that penetrate the palladium crystal framework.”

Inclusion of hydrogen atoms in the palladium structureleads to an elongation of the optical fiber, the researchers note. This can be instantly measured by the change in reflected light signals using a fiber Bragg grating. As the concentration of hydrogen in the air around the sensor drops, the gas atoms are released from the palladium and the optical fiber contracts. In this case, the coating is not damaged, which means that the sensor can be used repeatedly.

Scientists emphasize that the absorption of hydrogenonly possible because of the tiny size of atoms. Other substances will not be able to integrate into the palladium structure, which means that a false alarm of the sensor is excluded.

Hydrogen is considered as a promisingand environmentally friendly fuel, but its use is associated with certain risks. In addition to the ignition hazard inherent in all fuels, hydrogen leaks in tanks or pipelines can lead to a massive explosion. If the concentration of hydrogen in the air exceeds a threshold of 4%, which can be quickly reached with sufficient pressure in the hydrogen tank, a single spark is enough to cause an explosion, the researchers note.

“There are commercial devices on sale,designed to measure the level of hydrogen, as a rule, these are catalytic thermochemical or galvanic sensors. Both types of sensors are powered by electricity. Therefore, a malfunction of the device or wires can trigger the explosion that they were supposed to prevent,” says Flachenecker.

Electronics for recording measurement datafiber optic sensors, such as a spectrometer for evaluating sensor readings, can be installed in a safe place at any distance. No direct contact with electricity minimizes the chance of an explosion.

The developers believe that the sensors they have createdcan become an integral part of hydrogen-powered vehicles, gas stations, car repair shops. In addition, the technology allows the creation of a large network of sensors that simultaneously monitors the hydrogen infrastructure at many points.

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