Application of a GaPO₄Crystal Microbalance for the Detection of Coke Formation in High-Temperature Reactors and Solid Oxide Fuel Cells

Abstract

Piezoelectric crystal microbalance devices based on gallium orthophosphate (GaPO 4 ) have recently become commercially available. This material allows for operation at over 900 °C and therefore has potential as an analytical technique for the study of surface reactions at high temperatures. This paper describes preliminary work to assess the suitability of this technology for such applications. Change in oscillation frequency associated with temperature and gaseous environment is studied, and the ability to detect coke formation on a Ni-modified crystal is demonstrated. These results suggest that the technology can be developed as a low cost, high sensitivity gravimetric sensor for monitoring surface processes in high temperature chemical reactors such as reformers and solid oxide fuel cells (SOFCs)

Effect of humidity on the interaction of CO2 with alkaline anion exchange membranes probed using the quartz crystal microbalance

“…The processed frequency shift for each microbalance response is reported in f/f0 (ppm) to normalise the specific resonant frequency and thus allow direct comparison between each investigation which has taken place on a different baseline due to each system being exposed to a different RH prior to introducing air (CO2) [35]. Figure 3(a) shows that at 0% RH, when there is no water in the system, there is no change in the composite resonator's resonant frequency.…”

Rare-Earth Calcium Oxyborate Piezoelectric Crystals ReCa4O(BO3)3: Growth and Piezoelectric Characterizations

“…However, the maximum operating temperature of LN-based piezoelectric devices, restricted by their low electrical resistivity (a requirement of >10 6 Ohm· cm was proposed for comparison, where the materials with low resistivity yet can be used for high frequency applications [1]) at elevated temperature is limited to <600 °C, though the Curie temperature is above 1150 °C [5]. Other important trigonal piezoelectric crystals include the langasite family with the general formula of A 3 BC 3 D 2 O 14 [6][7][8][9][10][11][12] and gallium orthophosphate GaPO 4 , in the point group of 32 [13][14][15][16][17][18][19], these crystals were reported to show modest piezoelectric coefficients (5-7 pC/N) and high melting points (1300-1500 °C for langasite family crystals and ~1670 °C for GaPO 4 ), prior to which, there are no phase transitions observed for langasite family crystals (the phase transition for GaPO 4 is about 970 °C). However, the costly component Ga 2 O 3 restricted their further implements.…”

“…and fresnoite crystals (point group 4mm, such as Ba 2 TiSi 2 O 8 ) were investigated for piezoelectric applications. These crystals show the merits of high melting points (1400-1700 °C) and high effective piezoelectric coefficients d eff (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) pC/N) [20][21][22][23][24][25][26]; the evaluations of the temperature dependence of dielectric, piezoelectric and electromechanical properties, however, are limited. Of particular significance is that the monoclinic rare-earth calcium oxyborate crystals (ReCa 4 O(BO 3 ) 3 , ReCOB, Re: rare earth), which have been extensively investigated for nonlinear optical applications in the last two decades [27][28][29][30][31][32][33], were reported to exhibit good piezoelectric properties and high electrical resistivity at an elevated temperature of 1000 °C, with no phase transition prior to their melting points (~1400-1520 °C) [1][2][3][34][35][36][37][38].…”

“…44 and s 66 can be determined by using Equations (8), (9), (12) (10) and (14), while for the compliance s 23 , s 12 and s 25 evaluations, crystal cuts (m-o) were designed, combining Equations (10) and (15)- (17). Particularly, the elastic compliance s 46 was obtained using Equations (13) and (18) …”

Development of an impedance-based sensor for detection of catalyst coking in fuel reforming systems

“…al. [8] used a crystal micro balance with an attached catalyst surface to measure the mass change due to carbon formation on the catalyst surface.…”