The attached files are related to a ceramic-MWCNT composite layer. However, I am not sure that the G nd D peaks in the Raman spectra are the characteristic of MWCNT or carbon fibers? Also as the ceramic materials deposited on carbon materials and increased their diameteres (see SEM image), I can not speaks very strongly that these fibers are MWCNT or carbon fiber.
it is very hard to say something very concretely as the Raman signal of ceramic and MWCNT composite show numerous bands. This may certainly be due to lack of molecular symmetry and contribution arising from amorphous phases. Signature band of MWCNT is found be around 1582(G) and 2700(G') and 1350(D), which is also true for SWCNT, graphene and graphite.
I would suggest you to characterize ceramic and MWCNT separately to confirm contribution of individual component. Kindly, go through the attached application note to clarify your doubt about carbon materials or check this link
https://tools.thermofisher.com/content/sfs/brochures/D19504~.pdf
good luck
In general one could assume a higher degree of disorder associated with Carbon Nano-Fibers (CNFs) than that in Carbon Nanotubes (CNTs). Imaging techniques such as TEM could help determine the differences. In Raman scattering one of the modes that could be revel the differences between CNFs and CNTs is the Radial Breathing Mode (RBM) associated with the tube like shape of CNTs. The frequency of this RBM is closely associated with the tube diameter, and actually could be used to estimate the CNTs diameter, which are normally smaller than CNFs, even when CNFs have a shape that might resemble that of CNTs. You may see example of such relationship between RBM frequency and CNT diameter at: http://www.shimadzu.com/an/industry/electronicselectronic/cnt_0101005.htm and read about it in related publications such as: http://www.physik.fu-berlin.de/einrichtungen/ag/ag-reich/docs/Maultzsch2005.pdf or http://www.ou.edu/engineering/nanotube/pubs/2005-3.pdf. Please note that 1st and 2nd order Raman peaks will move with factors such as number of layers and other structural properties.
Dear Prof. Roughani,
I really thank you for your valuable help. Using the RBM frequency (that is 145 cm-1 in the attached Raman spectra) and by assuming C1 = 223 cm-1 and C2 = 12 cm-1, the diameter of the CNTs is calculated 1.67 nm. As I undrestood (but I am not sure), this value is an estimation for the internal diameter of the MWCNTs (assumed as a SWCNT), incorporated in the ceramic layer.
Sorry, but RBM occurs only in single or double-walled CNTs. In the case of MWCNTs RBM cannot arise and your peaks at low cm-1 correspond to probably ceramics or metal impurities. About the question: You cannot determine and prove by Raman is it CNF or CNT because both these materials can be either defective or not. Only TEM studies may help you.
As pointed out by other researchers, TEM that too HRTEM can only tell you conclusively about the differences. but actual problem will be to separate the nanomaterials from composite without generating additional defects. So, it is better to take samples before generating composites.
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