Raman spectroscopy of CNT composites

This Chapter provides an overview of micro-Raman spectroscopy of CNTs and its application in studying CNT reinforced polymer composites. By choosing and presenting various important and characteristic paradigms, we intend to elucidate the usefulness of Raman scattering as a valuable tool to characterize different types of composite materials and probe the interactions between CNTs and polymer molecules. More detailed information is available in topical reviews. ... 

In this research, Yttria Stabilized Zirconia (3YTZP) - CNT composites are manufactured by direct in-situ growth of CNTs on the Zirconia particles followed by densification via Spark Plasma Sintering (SPS) technique. Detailed electron microscopy analysis of the 3YTZP-CNT powders shows uniform distribution of CNTs in the matrix without the formation of agglomerates frequently seen with traditional ex-situ mixing of CNTs in ceramic compositions. The samples were sintered to nearly 100% theoretical density and showed a finer grain size microstructure. Raman Spectroscopy confirms CNT retention in the sintered nanocomposite. 

The self-organization of both thermotropic and lyotropic liquid crystals make these ordered fluids remarkable media for the dispersion and organization (alignment) of CNTs. This subject has been the focus of a recent excellent review by Scalia [231], theoretical work on anchoring at the liquid crystal/CNT interface by Popa-Nita and Kralj [458], and a number of earlier experimental reports on liquid crystal/CNT composites demonstrating that liquid crystal orientational order can be transferred to dispersed CNTs, which is commonly illustrated using polarized Raman spectroscopy [459 -62]. 

Benoit et al. (41) obtained electrically conductive nanocomposites by dispersing SWCNT and PMMA in toluene, followed by drop casting the mixture on substrates. Thin films of SWCNT-PMMA composites for different CNT concentration were produced by spin casting by Chapelle et al. (54) and Stephan et al. (55). They characterized these nanocomposites by Raman spectroscopy to study interactions between nanotubes and PMMA and found that PMMA tends to intercalate between the CNTs thereby increasing the distance between the nanotubes in the film. 

In situ Raman spectroscopy during heating in a controlled environment allows for a time-resolved investigation of the oxidation kinetics of carbon nanomaterials and can identify changes in material structure and composition during oxidation. In this chapter, we describe the application of in situ Raman spectroscopy to determine conditions for selective oxidation and purification of carbon nanotubes (CNT) and nanodiamond (ND). 

Electrochemical polymerization of pyrrole on an SWNT electrode using an aqueous HCl 0.5 M solution as electrolyte, resulted in deposition of a PPy film onto the SWNT layer leading to a composite with a bilayer structure, as demonstrated by Raman spectroscopy [112]. Anew method was developed by S.Cosner eta/, in 2008 [111] SWNTs were functionalized by electropolymerizable pyrrole groups following covalent and noncova-lent strategies. The covalent pyrrole grafting was carried out by ester formation between pyrrole alcohol and chemically oxidized SWNTs. The strong Ti-interactions between pyrene and SWNTs were exploited for the noncovalent adsorption of a new pyrene-pyrrole derivative on the pristine CNT surface. The pyrrole-ester-SWNTs were solubilized in THE and electropolymerized by controlled potential electrolysis at 0.95 V. The PPy/SWNT... 

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