A Study On The Structure And Propetries Of Nano/Micro-materials Produced By Electrospun

Electrospray ionization and electrospinning are two simple and effective technicsfor producing micro/nanomaterials based on the high voltage. Because of thesimpleness of the setup and the relatively high productivity comparing most of othermethods for producing micro/nanomaterials, electrospray ionization andelectrospinning attract more and more scientest's interest. Electrospray ionization andelectrospinning have been used to prepare a series of micro/nanomaterials withdifferent structures and functions combined with heat treatment, metal doping,hydrothermal reaction, pore-forming and other methods.In general, the network structures produced by electrospray ionization andelectrospinning have three main characteristics: super high porosity, high specificsurface area and rough suface structure. In this thesis, according to the threecharacteristics, we developed or studied three properties or applications of themicro/nanomaterials produced by electrospray ionization and electrospinning.Detailed research results are shown as follows:1. In view of the k of air, it is widely accepted that the introduction of pores inmaterials is a promising method to produce ultra-low-k materials. Considering thehigh porosity of nanofiber membranes, we prepared a few kinds of polymerselectrospun membranes with ultra low dielectric constant. The results of dielectric constant measurements reveal that k-values of polymers can be reduced dramaticallyby electrospun technique, which suggest that electrospinning technique is an effectivemethod for the preparation of low dielectric constant materials. The ultra-lowdielectric constants are mainly ascribed to the porous structure formed by a stack offibrous layers and interstices between the fibers. The effects of polymer types, thedensity of membranes, and diameters of fibers on the reducing of k-values have beeninvestigated respectively. What's more, the Ag/PAN nanofiber membrane and thePVDF fibers containing BaTiO3nanoparticles were prepared. The dielectric constantof the complex nanofiber membranes increases with increasing the Ag or BaTiO3nanoparticles or decreasing the porosity of the membranes. And the complexnanofiber membrane has a higher dielectric constant at a relatively lower frequncy.The dielectric constant of the complex nanofiber membranes was controlled from2-1000by tuning the doping composite and the membrane properties.2. Carbon, metal oxide and conductive polymer are three main types of materialsfor supercapacitors. However, all of them have obvious defects when they use alone.For preparing the supercapacitor materials with excellent comprehensive properties,including high specific capacity, good conductivity, low cost and so on, we made twokinds of carbon/metal oxide complex fibers (the carbon nanofibers with nickel oxidenanoparticles and the nickel oxide nanofibers with CNT). SEM, TEM, XRD and EDXwere used to characterize the morphology and stuctrures of the obtained samples. CVand chronopotentiogram test were used to study the capacity properties:1, the cyclicvoltammograms for the as-prepared CNT/nickel oxide nanofibers in6mol/L KOHsolution has a pair of redox peaks and the discharge curves have flat parts, whichindicates the pseudocapacitance characteristics. The estimated capacitance of thecomplex electrode is about171F/g.2, The carbon nanofibers with nickel oxidenanoparticles were obtained by heating the as-spun PAN/Ni(C5H7O2)2nanofibers. Thespecific capacitance increases when increasing the content of Ni. The estimatedcapacitance reached138F/g when the initial weight percent of Ni(C5H7O2)2is40wt%.3. The micro/nano materials have a rough surface structure which has a direct effecton the surface wettability. In this thesis, we employed a simple one-step technique,based on electrospinning beads on to textured surfaces, to develop re-entranthierarchically structured superomniphobic surfaces. The low surface energy andsignificantly reduced solid-liquid contact area allows our surfaces to exhibit ultra-low contact angle hysteresis even for extremely low surface tension liquids like heptane.This ultra-low contact angle hysteresis allows droplets of essentially all contactingliquids to easily roll-off and bounce on our surfaces. To our knowledge, this is thefirst-ever report of a superomniphobic surface with ultra-low contact angle hysteresisthat allows even extremely low surface tension liquids like heptane to bounce.