Piezoelectric crystal microbalance measurements of enthalpy of sublimation of C<sub>2</sub>–C<sub>9</sub> dicarboxylic acids

Abstract

Abstract. We present here a novel experimental set-up that is able to measure the enthalpy of sublimation of a given compound by means of piezoelectric crystal microbalances (PCMs). The PCM sensors have already been used for space measurements, such as for the detection of organic and nonorganic volatile species and refractory materials in planetary environments. In Earth atmospherics applications, PCMs can be also used to obtain some physical-chemical processes concerning the volatile organic compounds (VOCs) present in atmospheric environments. The experimental set-up has been developed and tested on dicarboxylic acids. In this work, a temperature-controlled effusion cell was used to sublimate VOC, creating a molecular flux that was collimated onto a cold PCM. The VOC recondensed onto the PCM quartz crystal, allowing the determination of the deposition rate. From the measurements of deposition rates, it has been possible to infer the enthalpy of sublimation of adipic acid, i.e. H sub : 141.6 ± 0.8 kJ mol −1 , succinic acid, i.e. 113.3 ± 1.3 kJ mol −1 , oxalic acid, i.e. 62.5 ± 3.1 kJ mol −1 , and azelaic acid, i.e. 124.2 ± 1.2 kJ mol −1 . The results obtained show an accuracy of 1 % for succinic, adipic, and azelaic acid and within 5 % for oxalic acid and are in very good agreement with previous works (within 6 % for adipic, succinic, and oxalic acid and within 11 % or larger for azelaic acid).

A review of quartz crystal microbalances for space applications

“…QCM readings had been confirmed by independent measurements with SEM analysis (Effiong and Morris 2011). QCMs are used in industrial and pharmaceutical fields, to monitor chemical/physical processes (Freedman et al 2008), the vapour pressure and enthalpy of sublimation of (solid or liquid) substances or compounds (Dirri et al 2016) or to monitor the bacterial attachment and growth on the crystal gold coated surface (QS 405-05-1, http://www.biolinscientific.com/publications/q-sense/). The mechanical improvements and scientific objectives that QCM devices will reach during the next years will make it suitable instrument for contamination and degradation monitoring of spacecraft surfaces and sensitive payloads of future ESA and NASA space missions.…”

“…By controlling the QCM temperature (TQCM is the temperature controlled device), the mass deposition as a function of surface temperature can be determined and by associating the condensation temperatures of the different contaminants, in principle an analysis of the composition can be performed. Recently, QCM capability to identify the characteristics of pure organic compounds in relevant environment has been demonstrated by Dirri et al (2016) while the effectiveness in characterizing mixtures in space conditions is still under investigation. Due to the different and multiple sources of contamination, monitoring is frequently mandatory to validate onground test and to warrant confidence on the performances of the thermal control surfaces and the measurement of many scientific (optical in particular) instruments in space conditions.…”

“…Looking to the previous advantages, it can be understood why QCM technology is expected to be widely used in the next planned Space missions for contamination monitoring (and degradation of telescope mirrors, solar panel, detectors and other sensitive surfaces. As an instance, for ESA and NASA Solar Orbiter and Athena Missions, the contamination requirements would like to identify 300 ng cm -2 year -1 , 50 ppm (particulate) and characterization) obtained during the recent years ), it will be also possible to characterize and distinguish volatiles and refractories contaminants, or pure compound in-situ by using TGA technique that can provide physical and thermochemical characterization of the analysed materials (Dirri et al 2016). Finally, the QCM technology is also currently used in non-space fields.…”

Effects of Oscillation Amplitude Variations on QCM Response to Microspheres of Different Sizes

“…Equation (4) shows that when F I ≤ F A , a particle adheres to the QCM surface, resulting in D p ≤ D crit , and it can be detected. On the other hand, it cannot be detected when F I > F A because a particle tends to dislodge from the surface (D p > D crit ).…”

Characterization of Thermal Gradient Effects on a Quartz Crystal Microbalance

“…The possibility of the active thermal control of the crystal enables performing thermogravimetric analyses (TGA), a common technique for in-ground applications that would be very interesting for planetary exploration [ 8 ]. Given these perspectives, in 2014, under an ESA contract, our group developed the Contamination Assessment Microbalance (CAM) instrument, a QCM with potential usage for the contamination assessment of space hardware, both during ground activities and during flight [ 9 , 10 , 11 , 12 ].…”