One carbon's surface has been modified with potassium hydroxide while the other is plain. Can anyone suggest what is the inference from these graphs. What do the peaks at 2theta = 20 and 25 indicate? Thanks
Dear Abinaya Arunachalam
Have a nice time and good day.
You don’t mentioned to your sample type; thin or thick film, powder, bulk,?
If your sample is thin or thick film, the obtained XRD is totally for the substrate and your film so firstly you should subtract the XRD of the substrate from the obtained XRD for your modified and unmodified samples then the obtained XRD can be carefully identified. If your two samples are powder or bulk you don’t need to the aforementioned procedure. In this case - powder or bulk – the hump from 2 theta 10: 30 is a well-known hump which characterizes the amorphous materials. So you two samples are amorphous or as amorphous in nature may contain particles within nano scale (may quantum dots, TEM can be used to check this assumption). The XRD of the modified sample shows another hump at 2 theta range (40-50) deg., this means that the modified sample is highly disordered than the unmodified one. Also you can use Scherrer's equation to estimate the size of the crystallite after subtracting the instrumental broadening factor from the experimental line profile. After correction the obtained “pure”line profile can be used to calculate the crystallite size. You can compare the size of the calculated crystallite size by Scherrer's equation and TEM. The modified sample’s hump is shifted to higher values of 2 theta. This means the presence of strained samples; you can calculate it using the procedure described through the attached file, see the attached figure. If you are experience in radial distribution function, RDF you can use the XRD of your two samples to study the short range, SRO order or medium range order, MRO.
I wish this is useful and help you.
Yours
A. EL-Denglawey
Dear Arunachalam,
Peak at around 26 deg. is due to (002) lattice plane of graphite structure of carbon-black. when you treat the sample, it goes lattice expansion or contraction depending upon the treat condition and due to that peak shift happened to left side or right side form original position respectively. If your naming of the data is correct then in your sample goes lattice contraction after KOH treatment. (i think your sample naming is not correct, check it)
Best Regards,
Bapi
Dear Arunachalam ,
Additional for the above answer, It can be seen a weak peak at 2theta around 45 which indicate the presence of amorphous carbon
Best Regards
Abdul Salam
Article X-ray diffraction patterns of graphite and turbostratic carbon
Abinaya,
The hump between 20 and 25 degree indicates the material starts gaining short range order, in other words, becomes a little bit more crystalline. But the order has not expanded to long term to form periodically repeated crystal structure yet. The hump at 40 for the blue pattern seems to be a bit more intensive, too, indicating the same difference.
So, the red trace is amorphous, whereas the blue trace becomes a bit more crystalline.
I am not sure which trace is which sample. I would imagine the red pattern is after-treatment, and the blue is before. The surface treatment of KOH disrupts the lattices within the carbon, which becomes more amorphous.
Aaron Gao
Dear Abinaya Arunachalam
Have a nice time and good day.
You don’t mentioned to your sample type; thin or thick film, powder, bulk,?
If your sample is thin or thick film, the obtained XRD is totally for the substrate and your film so firstly you should subtract the XRD of the substrate from the obtained XRD for your modified and unmodified samples then the obtained XRD can be carefully identified. If your two samples are powder or bulk you don’t need to the aforementioned procedure. In this case - powder or bulk – the hump from 2 theta 10: 30 is a well-known hump which characterizes the amorphous materials. So you two samples are amorphous or as amorphous in nature may contain particles within nano scale (may quantum dots, TEM can be used to check this assumption). The XRD of the modified sample shows another hump at 2 theta range (40-50) deg., this means that the modified sample is highly disordered than the unmodified one. Also you can use Scherrer's equation to estimate the size of the crystallite after subtracting the instrumental broadening factor from the experimental line profile. After correction the obtained “pure”line profile can be used to calculate the crystallite size. You can compare the size of the calculated crystallite size by Scherrer's equation and TEM. The modified sample’s hump is shifted to higher values of 2 theta. This means the presence of strained samples; you can calculate it using the procedure described through the attached file, see the attached figure. If you are experience in radial distribution function, RDF you can use the XRD of your two samples to study the short range, SRO order or medium range order, MRO.
I wish this is useful and help you.
Yours
A. EL-Denglawey
From XRD patterns it is seen that there are two hump at around 20-25 deg and 40-45 deg. The characteristic peaks positioned at 2θ = 20-25 24° and 40-45 deg correspond to the reflections of the (002) and (100) planes, respectively. These hump nature of the XRD pattern confirm that your samples is an amorphous state [Ref: RSC Adv., 2015, 5, 75728-75734]
2theta = 20 and 25 indicate the amorphous and graphitic nature of the materials, respectively. The amorphous turned to graphitic nature due to the surface modification so the 2 theta shifted to higher region.
A. El-Denglawey What do you mean by "modified"? I obtinaed a XRD spectrum of Carbon Black. The peaks are systematically shifted down by ~5 degrees.
Carson Chu In my comment "modified" means XRD of thin film and the substrate if you subtract XRD data from XRD of film and substrate you will get only XRD of your film "unmodified".
A. El-Denglawey Thanks. I tried a single crystal XRD. The sample was gelled on a tip. Would it also introduce a background?
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