This is the XRD plot of natural fiber. Usually in almost all the papers, 2 peaks appear for natural fiber. One broader amorphous peak at lower diffraction angle and lower intensity and another sharper crystalline peak at higher diffraction angle and higher intensity. Percentage crystallinity equation is PC = Intensity of crystalline peak/(intensity of crystalline + amorphous peaks). In my graphs I am getting multiple sharp peaks. Why is this ? Should I add up all the peak intensities to get total intensity of crystalline phase ?
Dear Muralishwara Kakunje ,
all 'crystalline' peaks*) belonging to the natural fiber have to be integrated and the result has to be divided by the integral of the whole XRD pattern; (not, just the sum of peak intensites; the peak widths are essential too)
*) there may be some peaks arising from the sample support or impurities in the fiber sample
Best regards
G.M.
Crystallinity of the polymer can be calculated using XRD deconvolution method, where the amorphous and crystalline contributions to the diffraction spectrum were separated. Crystallinity can be calculated from the ratio of the integrated area of all crystalline peaks to the total integrated area under the XRD peaks.
Akeel M. Kadim Is it possible that multiple crystalline peaks exist in natural fiber ? Most of the papers only two peaks are observed- broader one for amorphous and sharper one for crystalline.
Gerhard Martens So, the second peak from left since it is broader and not well defined for a particular angle, should I consider it as amorphous peak ?
Dear Muralishwara Kakunje ,
I would assign that broad peak at around 23° to the amorphous phase fraction.
Best regards
G.M.
Gerhard Martens when exactly will you really call a peak crystalline ? What is the minimum width of the band that is needed to qualify as amorphous ? or is it subjective and must be complemented with other tests ?
Dear Muralishwara Kakunje ,
I admit, that that decision is a more subjective one.
Compared to well known amorphous material, such as for example water, your 'amorphous' peak is quite narrow; but still significantly broader than your 'crystalline' ones.
Small crystallite sizes will also cause peak broadening... A rough estimation of a hypothetical crystallite size in the case of your 23° peak reveals a size of about 3nm, which is about 15 atomic distances; and that is quite small. But there is a significant difference: crystallite size broadening would affect all peaks but not a single one only...
Let us wait for some comments from the RG audience with respect to the question about a minimum peak width for being an 'amorphous' peak.
Best regards
G.M.
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