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

Area of Science:

• Materials Science
• Chemical Engineering
• Sensor Technology

Background:

• Zeolites, particularly MFI-type silicalite, are crucial microporous materials for gas separation and storage.
• Accurate measurement of molecular diffusion within zeolites is essential for optimizing their industrial applications.
• Existing techniques for measuring molecular diffusivity can be complex and limited in scope.

Purpose of the Study:

• To develop and demonstrate a novel fiber optic interferometer (FOI) sensor for determining molecular diffusivity in pure-silica MFI-type zeolite (silicalite) films.
• To investigate the adsorption dynamics of isobutane in silicalite using the developed FOI sensor.
• To validate the FOI sensor's performance against established macroscopic techniques.

Main Methods:

• Fabrication of FOI sensors by growing silicalite films on optical fiber endfaces.
• Monitoring temporal changes in light interference patterns during gas adsorption.
• Analyzing optical signal shifts to determine zeolite film optical thickness changes.
• Applying Fick's Law models to compute molecular diffusivity from adsorption uptake curves.

Main Results:

• The FOI sensor successfully monitored the dynamic gas adsorption process in silicalite films.
• The optical thickness variations directly correlated with gas adsorption, providing adsorption uptake curves.
• The diffusivity of isobutane in silicalite was accurately determined using the FOI sensor.
• Results showed good agreement with literature values obtained from conventional methods.

Conclusions:

• The developed FOI sensor provides a robust and compact platform for in-situ measurement of molecular diffusion in zeolites.
• This technique offers a sensitive method for studying adsorption kinetics and determining diffusion coefficients.
• The FOI sensor's capabilities extend to conditions not accessible by existing measurement techniques, opening new avenues for materials characterization.