Morpholpgy Dependence of Hybrid Nanofibers Incoorporated with Nanoparticles of Electrospinning and Post-treatment Conditions

Abstract

Hybrid nanofibers incorporated with nanoparticles (HNIN) are very useful in several application domains. Electrospinning and electrospraying are very effective processes to fabricate nanofibers and nanoparticles, respectively. Integration of these two production processes into a single one to produce controlled-structure HNIN is a challenging task for material scientists and engineers. The principal difficulty is bead-fiber transition during processing, which is easy to be triggered by tuning rheological properties of solution, as well as processing conditions. The second difficulty is morphology control of nanofibers and nanoparticles, which highly depends on the evaporation, sorption and swelling during post-treatment. In the present work, the bead-fiber transition conditions are initially investigated in the parameter space of concentration, molecular weight, applied voltage, conductivity, surface tension and viscosity. The bead-fiber transition is explained by Deborah number. Then the formation and evolution of the skin of nanofibers\nanoparticle during evaporation is analyzed from a physicochemical point of view, and the morphology dependence on volatility of solvent is given by the second characteristic number: skinning number. Finally the morphology of nanofibers is tailored by sorption and swelling of vapor, and beads are successfully introduced to nanofibers. The bead growth is related to the third characteristic number: beading number. By tuning the three characteristic numbers, HNIN of well-controlled morphologies are obtained.