Hello everyone,

I am performing SAXS (small-angle X-ray scattering) of mesoporous
materials, like MCM-41.

I have two queries.

1. Which is the correct/better way of quantifying percentage of
crystallinity of mesoporous powders like MCM-41, from their small angle
X-ray diffraction peaks - by the peak height, width or area? I mean a more
intense (higher peak) or a sharper (less width) peak both mean better
crystallinity/order of pores in the mesoporous sample. To compare a set of
samples, which is the better way to quantitatively compare their
crytallinity?

2. We use a line source of X-ray, which therefore requires desmearing of
the resulting diffraction profile, to get the ideal profile corresponding
to a point source of X-ray. Now in comparing the intensity of the spectra
of several samples, one needs to first normalize all the profiles with
respect to the primary (undeviated) X-ray beam energy, because it can vary
during the run, from sample to sample.

We use the 3-D view software (provided by MBraun-Graz) to do normalizing
and de-smearing. Now, which is a better way of processing the raw
scattering data of intensity versus diffraction angle.

i) First normalize all the samples together (with respect to the
primary beam energy of one of the samples) and then de-smear?

or, ii) First de-smear each sample and then do the normalization of all
the de-smeared samples together.

For a set of samples, the two procedures gave qualitatively broadly
similar but quantitatively quite different peak height and width.

Thanks for reading. Any suggestion is welcome.
Regards,
Rajdip

-----------------------------------------------------------------------------
Rajdip Bandyopadhyaya     *BREATHE ON THE RUN, 'coz TIME is SHORT and SWEET*

Dept. of Chemical Engg.       | E-mail: [log in to unmask]
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