Novel 3D Lightweight Carbon Foam for Ultrasensitive Humidity Sensor Operated at Different Frequencies

Abstract

In recent times, lightweight porous carbon materials have attracted significant attention from the scientific community in gas and humidity sensing performance due to their excellent properties including low density, high surface area, high electrical conductivity, and good mechanical strength. The lightweight carbon foam was synthesized from the phenolic resin using the polyurethane (PU) foam impregnation method followed by carbonization at 1000 °C. The prepared carbon foam was confirmed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and Thermogravimetric analysis. The bulk density, porosity, compressive strength, electrical conductivity, and BET surface area of carbon foam are also investigated. The electrical conductivity of the carbon foam is 32 S cm−1, and it has a very low density of 0.28 g cm−3. Electrical humidity sensors are utilized with carbon foam as sensing element that has been manufactured for operating in various frequency regions. The electrical humidity sensing parameters were measured at various frequencies and the average sensitivity was determined to be 8.260 M/%RH at 40 Hz. Less recovery and response times were measured from the sensing curve and computed as 6 s and 49 s, respectively. The repeatability and aging curve shows the carbon foam-based humidity sensor is 94% reproducible and quite stable.