Studies Of The Liquid Adsorption Behavior And Surface Properties Of Carbon Materials

The terrific electrical and physical properties of carbon materials have brought great attention of researchers and scientists studying their characteristics related to the chemical, physical and environmental conditions mainly for the purpose of aerospace, marine and electronic industries. The aim of this project is to study the liquid adsorption behavior and determine the surface free energy of carbon materials by capillary rise method. The methods used to characterize CB were BET, XRD and FTIR. BET test revealed the mesoporous structure of CB with greater specific surface area of the oven dried CB than the as received one. The XRD test exposed the difference in spacing between the hexagonal layered planes of the two samples. From FTIR spectra test of CB the existence of the following functional groups was deduced:O-H (hydroxyl or carboxyl), C-H (aliphatic), C=C (olefin), C-O (hydroxyl, ester, or ether), and O-H (residual hydroxyl groups), sulfide (C-S) and bromide(C-Br). The capillary rise method was used to study the surface free energy and liquid adsorption behavior of four different carbon materials:carbon black, carbon nanotubes, carbon fibers and graphene. The four probe liquids used for the experiment were hexane and diiodomethane (non polar liquids) and water and formamide (polar liquids). Four of the carbon materials were found to adsorb diiodomethane greatly which indicates the major role of Lifshitz-van der Waals interaction component in the adsorption process. The total surface free energies of all four carbon materials are contributed greatly by the Lifshitz-van der Waals interaction component. The surface free energy of CB was greater for as-received sample than for oven-dried sample due to the difference in Lewis acid base component of the two samples. Surface free energy of SWCNTs was found to be greater than MWCNTs and MWCNTs were found to be greatly in Lewis acid, ys+, where as SWCNTs greatly in Lewis base, γs-. The liquid adsorption behavior of CNTs seems to be influenced by the wall structure or the surface properties because the SWCNT adsorbed polar liquid greatly and the MWCNT adsorbed non-polar liquid greatly. Furthermore, the capillary rise method has approved the acidic nature of carbon fibers. The uncertainty exhibited in the surface energy of graphene could be attributed to either the few number of literature reported data (actually one) or the purity of graphene. Carbon materials are found to be hydrophobic with greater Lifshitz-van der Waals component than the Lewis acid base component of their surface free energy.