QCM-based sensor for volatile organic compounds characterization

Abstract

Thermogravimetry (TG) or Thermogravimetric Analysis (TGA) is a widely used technique to obtain information about thermal stability and composition and to monitor different thermal processes of materials. The TGA analysis is frequently used to monitor the deposition/sublimation and absorption/desorption processes of volatiles compounds in different environments: outgassing rates from degassing in space [1], dehydration and organics decomposition in minerals [2] and the fate of various materials in atmospheric environments [3]. In particular, it is possible to obtain a characterization of organic compounds by using Quartz Crystal Microbalance (QCM)-based sensors, equipped with an integrated heater in order to study the deposition and desorption processes. In this work, an organic compound (used as contaminant source) was characterized by using the breadboard of a QCM-based sensor, i.e. CAM (Contamination Assessment Microbalance), which shows several improvements compared to the previous Quartz Crystal Microbalance sensors used by European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) [1,4]. CAM instrument aims to monitor contaminants and outgassing materials which are released by spacecrafts during in-orbit space missions characterizing the contaminant source by means of Thermogravimetric technique. The organic compound desorption rates and the enthalpy of sublimation (ΔHsub) were retrieved by using the Langmuir relation while the sensor regeneration was obtained by means of thermal cycles by using the integrated heaters on crystal surface. The CAM breadboard validation, the experimental procedure and results are presented, and compared previous works.