We have prepared zeolites from gels with different aging times. The cristallinity is evaluated from the relationship between the intensity of 550 cm -1 band (ZSM-5) and the intensity of the silica band (1075 cm -1). A coherent curve was obtained for the aging x crystallinity. Is this reliable? Are there other ways to accompanish the evolution of the zeolite phase in solution?
I think it would be possible to use X-ray diffraction of the sample at different time intervals and check the X ray intensity which may correlate to the crystalline phase of the sample. In FITR, I think a higher intensity can not be related to intensity but may possible to confer a reaction resulted in higher concentration of certain bonds, which in this case are bonds indicative of Zeolite.
I am not familiar with zeolite gels but in polymers there are "crystallinity specific IR bands", sometimes even crystal typa specific bands which can be used to estimate the cystallinity. One shoudl check whether such bands exist is zeolites. it if is well separated and detectable, it can be sued for that purpose. it is true, however that XRD is a more direct method. In polymers DSC is also widely used. Depending on the melting point of the crystals to be detected you may use DTA as well. It may happen, however, that during heating you will see a combinaton of crystallization in the pre-melting range and melting afterwards. It also gives you valuable information on the state of yur system.
The key words in the comments (see above) are "evaluated" and "estimated"(for FTIR). In case of application of thermal analysis methods -
as prof. Banhegyi mentioned - the contribution of the pre-melting should be
taken into consideration. A precisely reproducible technique of measurements should be used in order to obtain quantitative results to be compared.
The XRD of zeolite gels with aging time up to 15 days showed amorphous diffraction patterns. According to Cullity (famous author of the book on XRD theory), crystalline nanostructures smaller than 100 angstrom have no detectable peaks. DTA / DTG and DSC analyzes of the dry gel show a single outflow peak of the organic template that does not differentiate crystallites and solution. This is why I'm looking for reliable analysis. Thank you colleagues for your valuable discussion. Let's continue!
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