A Fiber Optic Interferometric Sensor Platform for Determining Gas Diffusivity in Zeolite Films

Abstract

Fiber optic interferometer (FOI) sensors have been fabricated by directly growing pure-silica MFI-type zeolite (i.e., silicalite) films on straight-cut endfaces of single-mode communication optical fibers. The FOI sensor has been demonstrated for determining molecular diffusivity in the zeolite by monitoring the temporal response of light interference from the zeolite film during the dynamic process of gas adsorption. The optical thickness of the zeolite film depends on the amount of gas adsorption that causes the light interference to shift upon loading molecules into the zeolitic channels. Thus, the time-dependence of the optical signal reflected from the coated zeolite film can represent the adsorption uptake curve, which allows computation of the diffusivity using models derived from the Fick’s Law equations. In this study, the diffusivity of isobutane in silicalite has been determined by the new FOI sensing method, and the results are in good agreement with literature values obtained by various conventional macroscopic techniques. The FOI sensor platform, because of its robustness and small size, could be useful for studying molecular diffusion in zeolitic materials under conditions that are inaccessible to the existing techniques.

Characterizing the Gas adsorption-dependent Dielectric Constant for Silicalite Nanoparticles at Microwave Frequencies by a Coaxial Cable Fabry-Pérot Interferometric Sensing Method

“…The XRD and EDS test results verified that the zeolite particles were of pure MFI-type crystal phase and the zeolite was of pure silica in the structure. In our recent study, the isotherms of isobutane adsorption in silicalite were experimentally measured in a temperature range from room temperature to 120°C, as shown in Figure 3 [12]. The isobutane isotherms were found to be wellcorrelated by the following Langmuir equation of state,…”

“…Thus, for convenience of operation, isobutane was carried in helium at a total flow rate of 10 cm 3 (STP)/minfor studying the effect of its adsorption on the silicalite dielectric constant. For more strict measurement of the gas-adsorption dependence of zeolite dielectric contestant, a large tank of sample gas with pre-set pressure may be used to supply the environmental gas without using the carrier gas [12]. The interferogram under each equilibrium (given by volume fraction of the gas flow at ambient pressure) was recorded after the reflection spectrum was fully stabilized.…”

“…The MFI-type zeolite has been specifically selected for this study because it is a very versatile group of materials that has so far attracted the most extensive research efforts in exploration of new applications as catalysts, low-k electronic components, ion conductors, and photonic and microwave substrates, etc. The measurement of the silicalite r e under gas adsorption state by the MCCC-FPI method is demonstrated using isobutane (i-C 4 H 10 ) as the sample gas in this work because of the availability of its extensive thermo physical properties and specified Langmuir adsorption equation of state [11,12].…”

SILVER SULFATE (Ag2SO4): MOLECULAR ANALYSIS AND ION TRANSPORT

“…Hukum Fick (96)(97)(98)(99)(100)(101) Persamaan ini tertata ulang menjadi hasil yang sangat penting, yang dikenal sebagai hubungan Einstein, antara oefisien difusi dengan mobilitas ion (88)(89)(90)(91) .…”

“…elektron (56)(57)(58)(59)(60)(61)(62)(63)(64) yang digunakan untuk membentuk ikatan kovalen polar (65)(66)(67)(68)(69)(70)(71)(72)(73) lebih kuat tertarik pada salah satu atom. Parameter transfer ion (74)(75)(76)(77)(78) disini yaitu kecepatan hanyut (79)(80)(81)(82) , bilangan transport (83)(84)(85)(86)(87) , mobilitas ion (88)(89)(90)(91) , difusi (92)(93)(94)(95) , dan hukum I Fick (96)(97)(98)(99)(100)(101) dari senyawa perak sulfat (Ag2SO4).…”