Effect of the Multi-Walled Carbon Nanotubes on Dilatometric and Optical Properties of the Micro/Nano-Sized Cellulose

The concentration set of the composites, where the micro/nano crystalline cellulose (M/NC) was used as a matrix, while multi-walled carbon nanotubes (MWCNT) were used as fillers, were prepared and studied. The dilatometric properties (relative linear thermal expansion, coefficient of the thermal expansion (CTE)), diffuse reflection spectra, photoluminescence spectra and luminescence intensity have been measured and analyzed. The band gap Eg was evaluated, so it was found that Eg value decreases (3.6 →3.4 eV) when the MWCNT content increases. The temperature behaviors of the relative expansion and CTE revealed two temperature ranges with different values of CTE. Noted ranges correspond to parts of the cellulose matrix with various amorphous phase structures. Nanocomposite materials under study are characterized by photoluminescence (PL), whose spectra range from soft ultraviolet to red light. The PL spectra of “pure” M/NC are formed by a complex band lying in the range 350 - 650 nm with peak position near 425 nm. When MWCNTs are incorporated into the cellulose matrix the PL intensity decreses and the spectral profile is deformed. Thus, the UV band (peak position near 330 nm) becomes the most intensive in the spectra. An appearance of the and increasing its relative intensity is considered as features of the micro/nanosized carbon fragments/clusters/dots luminescence in the cellulose matrix. Concentration dependences of the intensity and of luminescence spectra confirmed the conclusion about the selective interaction of the carbon filler with different phase components of the cellulose matrix.