Yes, you can do it if you have cif file for that sample.

Rietveld refinement can be applied to XRD data of carbon nanotubes (CNTs), but it requires careful consideration of factors such as peak broadening, preferred orientation, and the complex structural features of CNTs. While it can provide valuable structural insights, the accuracy of the refinement depends on both the characteristics of the sample and the refinement approach.

If your pattern shows some peaks you can apply the structural refinement. It could be difficult because you can have an amorphous component and you could see only a limited number of peaks, so your refinement could be less reliable

Thank you to you all for your valuable answers. They are very helpful.