Supervisor: Prof N. Manyala Production of nanofibers by electrospinning of polymer-graphene solutions By Isaac Manabile PhD Student DST Chair in carbon materials and technology, IAM, University of Pretoria, Lynnwood road, Pretoria , 0002 Supervisor: Prof N. Manyala

Outline Introduction Aims and objectives Experimental Results Conclusions

Introduction Electrospinning or ‘‘electrostatic spinning’’ is a process in which nanofibers are generated by the application of electrostatic forces to a jetting polymer solution Graphene is a two dimentional sheet of SP2-hybridised carbon Polymer is a large molecule composed of repeating subunits called monomers Properties of polymer nanofiber have been improved and enhanced using various nanofillers Graphene is a multifunctional nanofiller that can enhance polymer fiber properties at a very small loading (Das, S et al., 2012)

Introduction cont Schematic illustration of basic electrospinning setup (Li, D and Xia, Y. 2004)

Objectives Mass produce graphene with good properties To investigate the influence of graphene on properties of polymer fibers To produce graphene/polymer fibers that could used in various application including solar cells and supercapacitors

Experimental Materials: Expandable graphite, synthetic graphite and exfoliating and dispersing solvents/polymers Two method have been employed to produce graphene through microwave irradiation 1. Commercial synthetic graphite suspension was irradiated with microwave to yield graphene. 2. Commercial expandable graphite was irradiated with microwave and dispersed The resultant products were successfully incorporated in polymer fibers

Results SEM of raw expandable graphite (left) and irradiated expandable graphite (right)

Results cont Raman spectra of raw expandable graphite and irradiated expandable graphite Malard, et. al., (2009), Physics Reports (473) 5187

SEM of PVA fibers incorporated with graphene Results cont SEM of PVA fibers incorporated with graphene

Results cont SEM of synthetic graphite and synthetic graphite derived graphene powders

Results cont SEM of synthetic graphite derived graphene and some nanoparticles

Results cont Raman spectra of synthetic graphite and synthetic graphite derived graphene

SEM of PVA fibers incorporated with graphene Results cont SEM of PVA fibers incorporated with graphene

Conclusions Graphene could be mass produced using established method and a relatively new method all involving microwave irradiation Graphene produced by both method could be incorporated in to the polymer matrix during electro-spinning

Acknowledgements The South African Research Chairs Initiative of the Department of Science and Technology The National Research Foundation. University of Pretoria My supervisor and colleagues

Reference 1]. Kuilla, T., Bhadra S., Yao, D., Kim, N.H., Bose, S. Recent advances in graphene based polymer composites Progress in Polymer Science 35 (2010) 1350–1375 [2]. Malard L.M., Pimenta, M.A., Dresselhaus, G., Dresselhaus, M.S. Raman spectroscopy in graphene, Physics Reports 473 (2009) 5187 [3]. Chung D. D. L. Review Exfoliation of graphite, Journal of materials science 22 (1987) 4190 4198 [4]. Das, S., Wajid, A.S., Bhattacharia, S.K., Wilting, M D., Rivero, I V. and Green, M.J. (2012). Electrospinning of Polymer Nanofibers Loaded with Noncovalently Functionalized Graphene Journal of applied polymer science

Thanks