Date of Award
Doctor of Philosophy (PhD)
Multi-functional polymer composite materials are of great interest in the field of fabrication of composites owing to their high volume of applications. Different nano and micron sized filler materials are embedded into the matrix to achieve desirable functionalities. Graphene, a sheet of a single atom thick, sp2 bonded carbon atoms arranged in honeycomb structures is one of the most extensively used filler because of its several exceptional features such as high electrical and thermal conductivities, mechanical and gas barrier properties. Few layer and multilayer graphene sheets are also very promising alternatives of single layer graphene sheet. The biggest challenge in working with graphene is to keep them well dispersed as they always tend to agglomerated due to strong van der Waals force. In this thesis, graphene based polymer composite materials are fabricated and their various engineering properties have been studied. The primary goal of the thesis is to find out different strategies to disperse graphene sheets uniformly in the matrix. A non-conductive, second filler is added to the matrix as a dispersion aid to prevent restacking of graphene sheets. The electrical conductivity of the composites is studied. Several orders of magnitude increase in the electrical conductivity is observed with the addition of non-conductive filler. Different multi-functional polymer composite materials using appropriate fillers are fabricated. Incorporating some fillers can deteriorate the mechanical properties of the system. Suitably selected fillers can act as dispersion aid as well as can enhance the toughness of the composites. Quasi-static compression test and three-point flexural test are performed on these materials. X-ray diffraction and scanning electron microscope are used to study the dispersion of graphene sheets in the matrix. Also Instron Universal testing machine and two-point probe technique are used to examine the electrical and mechanical properties of the composites. The effect of the size of the second filler on the electrical conductivity of the composites is also studied using silica nanoparticles (200 nm) and alumino-silicate ceramic microspheres (12 microns). Smaller particles are found to be more effective in improving the dispersion of graphene compared to the bigger particles.
Chakraborty, Indrani, "Fabrication of Multifunctional Graphenebased Polymer Composite Materials Using Different Fillers" (2015). Open Access Dissertations. Paper 335.