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Humidity sensing under aggressive conditions using nafion conductors


A sensor capable of detecting moisture in a chlorine-air environment has been assembled from Nafion and platinum. Nafion acts as the solid electrolyte while platinum chemically deposited on the Nafion is the electrode material. Thermogravimetric analysis suggests that Nafion is stable up to 473 K. A Frequency Response Analyser (FRA) was used to calibrate the sensor in terms of impedance as a function of relative humidity. The frequency range was 10−2 to 107 Hz and an amplitude of 100 mV was applied. Impedance measurements show that only a bulk process occurs and when relative humidity is high, diffusion of moisture into and out of the platinum/Nafion composite becomes significant. This is reflected in the form of a spike at about 45° to the real axis. The sensor detects chlorine in air without loosing its chemical and physical stability. Conductivity increases as a function of temperature and reaches its peak at 433 K. The response time of the sensor is governed by temperature, thickness of the Nafion film and the amount of platinum on the surface. In practice the sensor can be operated with a frequency controller.

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Tailoka, F., Fray, D. & Kumar, R. Humidity sensing under aggressive conditions using nafion conductors. Ionics 6, 383–388 (2000).

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  • Physical Chemistry
  • Analytical Chemistry
  • Platinum
  • Relative Humidity
  • Response Time