Structural and mechanical properties of free-standing multiwalled carbon nanotube paper prepared by an aqueous mediated process

Free-standing carbon nanotube film (bucky paper) is a very important material for various applications, but its commercial production is still limited due to size, cost and properties. In the present work, different methods are used to prepare five different types of bucky papers, namely normal, pure refluxed, oxidized, oxidized refluxed and functionalized by using as-produced multiwalled carbon nanotubes (MWCNTs), refluxed MWCNTs, air-oxidized MWCNTs, oxidized refluxed MWCNTs and HNO3 functionalized MWCNTs, respectively. Morphological, physical and structural changes appeared due to different methods are analysed by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction spectroscopy and Raman spectroscopy. Changes in the relative characteristic peak ratio (i.e. I G /I D, I G′ /I D and I G′ /I G) as a function of MWCNTs quality are determined. It is observed that oxidized refluxed MWCNTs have an average value of I G /I D, I G′ /I D and I G′ /I G ratio as 4.12, 7.15 and 1.71, respectively, which is higher as compared to other samples. The mechanical properties of different bucky papers are studied by performing tensile tests. The result showed that tensile strength, Young’s modulus and toughness of oxidized refluxed MWCNTs bucky paper are 3.9 MPa, 440 MPa and 780 Jm−3, respectively, which are higher as compared to as-produced MWCNTs bucky paper. The air oxidation and back-to-back refluxing generates nanoscale irregularities within the hexagonal C-structure of a nanotube wall. This helps in improving intermolecular bonding and packing which resulted into significant improvement in the mechanical properties. These bucky papers prepared by economical ways of air oxidation and refluxing in an alkali-soluble emulsifier assisted aqueous medium are potential candidates for field emission devices, energy storage devices and structural materials.