While calculating percentage of crystalline, I am having trouble in intensity data. Means upon treatment with some chemicals, we assume that crystallinity index should be increased. But can it is always possible that the value of highest intensity peak (Icr) should be more and Iam value should be less for increase in crystallinity of cellulose fiber ?
Dear Chinmayee,
you are right: for increasing crystallinity the peak height (better peak integral *)) should increase and the peak height of the amorphous peak should decrease. But hower you deal with fibers. So your XRD pattern most propably suffer from preferred orientation artifacts.
So you should start on focussing on the amorphous part only . But from intensity comparison of diffraction pattern of different samples you may not get reliable results because the intensity is affected by
a) the total amount of material in the x-ray interaction volume of your set up,
b) its chemical composition and thus intrisic x-ray attenuation,
c) the mean density ( think on pores or voids)
and d) on (height) adjustment of your sample.
Thus it is advised to do a relative comparision within an XRD pattern. So for overcomming the orientation artifacts you should mill or crush your sample prior to the XRD measurement.
The following link, especially the equations therein, may help you.
Article Determination of cellulose crystallinity by X-ray diffraction methods
*) among others peak widths and thus peaks heights depend on crystallite size and stress/strain. So it is advised to use the peak integrals in oder to be independent on these parameters.
But I am having another doubt. Upon treatment sometimes it is observed that the intensity value of amorphous peak is increasing and the crystalline peak is decreasing but giving higher value of crystallinity. And some of cases, with increase in crystallinity value, crystallite size value is decreasing. So how can someone deal with such kind of results ? For me it is really confusing. Please help me out.
Thank you
It is confusing indeed.
But instead looking on the peak height (of crystalline peak above background) you should focus on the peak integral.
Peak height is governed
a) by the amount of crystalline material (direct proportional)
and thus proportional to crystallinity,
and
b) by the crystallite size (also proportional) via peak broadening (invers proportional to crystallite size)
So there is no contradiction: you may have higher crystallinity but on the other hand you may have got smaller mean crystallite size.
Please look at the peak integral; that helps.
Additional remark:
due to a bug in the RG editing system multiple answers having the same content may show up.
The relation between crystallinity and reactivity of cellulose is discussed in the below mentioned articles. Happy new year.
https://www.researchgate.net/publication/312695203_On_fine_structure_of_cellulose_fibers?_sg=gMfP5CcIeMtf8Ui1o2D3FcfifSd-jir1GBvosgkmxo4A8We9XFQwCIfRFn1pzs1by7vyJTa0sbnrQ1xzC4F_-rJPLyqkQUE04RNdPfWO.p5kh-DbWyXujNy9tZupEqqlEFISvwAfpAQS7gxv5QQb6LoNuY77hWx1CJaLD2_Puf4MN-E19g5ZJ51ZcP27ceg
https://www.researchgate.net/publication/250425822_Fine_structure_and_reactivity_of_cellulose?_sg=5fWap_Bo_4zdD_fvqH_ik_rICR79B2MqsJkQJ-GpEk0-kWUql-OagXiQ1htoCGtqy5kKGHOkgcXg6Iwn4D16loYczMtz8vJCHsSulhkH.IexQikLYtmzkEXZKF7V0Hp1o92stM2-UVAXYD-fAlxbH24tcvwxDuP_sMPad0e1_V30QOrezdoD_Gdr1Cdoxsw
https://www.researchgate.net/publication/298681455_Reactivity_of_biological_cellulose_and_properties_of_some_of_its_derivatives?_sg=5fWap_Bo_4zdD_fvqH_ik_rICR79B2MqsJkQJ-GpEk0-kWUql-OagXiQ1htoCGtqy5kKGHOkgcXg6Iwn4D16loYczMtz8vJCHsSulhkH.IexQikLYtmzkEXZKF7V0Hp1o92stM2-UVAXYD-fAlxbH24tcvwxDuP_sMPad0e1_V30QOrezdoD_Gdr1Cdoxsw
https://www.researchgate.net/publication/294690836_On_the_properties_of_never-dried_and_nature-dried_cotton?_sg=5fWap_Bo_4zdD_fvqH_ik_rICR79B2MqsJkQJ-GpEk0-kWUql-OagXiQ1htoCGtqy5kKGHOkgcXg6Iwn4D16loYczMtz8vJCHsSulhkH.IexQikLYtmzkEXZKF7V0Hp1o92stM2-UVAXYD-fAlxbH24tcvwxDuP_sMPad0e1_V30QOrezdoD_Gdr1Cdoxsw
https://www.researchgate.net/publication/312702652_On_the_activation_of_cellulose_through_xanthation_II_Viscose_and_rayon_from_activated_cellulose?_sg=5fWap_Bo_4zdD_fvqH_ik_rICR79B2MqsJkQJ-GpEk0-kWUql-OagXiQ1htoCGtqy5kKGHOkgcXg6Iwn4D16loYczMtz8vJCHsSulhkH.IexQikLYtmzkEXZKF7V0Hp1o92stM2-UVAXYD-fAlxbH24tcvwxDuP_sMPad0e1_V30QOrezdoD_Gdr1Cdoxsw
Chinmayee Dash
Crystallinity index is the ratio of the crystalline peaks to the crystalline+amorphous peaks. Amorphous peaks are the noise in XRD data, while, from crystalline+amorphous, we mean the whole XRD profile. In the following 17 min video, I have explained in detail the crystallinity index and how to calculate it from XRD data. In the first 2.5 min, I have first explained 'what is meant by the crystallinity index'. In the rest of the video, I have taught 'how to calculate the crystallinity index from XRD data in origin for crystalline as well as amorphous materials. If you need anything further to ask, let me know. I'll appreciate your feedback on the video tutorial. I have attached the discussed files (Origin file and Excel template) here, as well as, they can be accessed from the description in the video. Thanks
How to calculate crystallinity index from XRD data using origin
https://youtu.be/D65k1yHPKaM
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