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Preparation of Composite Nanofibers Via Elecrtrospinng

Author: ChenRui
Tutor: LiChaoRong
School: Zhejiang University of Technology
Course: Applied Chemistry
Keywords: electrospinning natural cellulose composite nanofibers UV absorption photocatalystic
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 57
Quote: 1
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Abstract

Composite nanofibers as a new kind of functional materials have attracted much attention in recent years, with the development of the technology. It consists of two or more structure parts with different properties by several techniques. In the matrix of the composites, there is usually a continuous phase, known as matrix; the other part is dispersed phase, known as the reinforcing material. In this paper, we are mainly discussing two parts of composite nanofibers: first one is inorganic nanoparticle/polymer composites, the other one is composite nanofibers of oxide. The main results achieved in this paper were listed as below:1: Preparation of cotton lines cellulose ultra-fine fibers and silver/cellulose composite nanofibers with electrospinning techniqueFirstly, ultra-fibers of natural cotton lines cellulose （CC）, with a degree of polymerization above 10000, were prepared by electrospinning. The effects of cellulose solution property, electrospinning parameters, environment condition together with the morphologies of the fibers were systematically investigated. High quality cellulose nanofibers were obtained under the optimized electrospining conditions as following: 1.15wt% of CC, 0.04ml/min of flow rates, 1.2KV/cm of electric field strength. Secondly, two effective improvements on the electrospinning apparatus were carried out, which make sure it is more suitable to the electrospinning. Moreover, oriented cotton nanofibers were acquired by elevating the rotation speed of the drum collector. Compared with the random CC fibers, the mechanical property of this oriented fiber became much stronger. Furthermore, the wettability of the nonwoven was greatly improved compared with the original activated cellulose. The obtained nonwoven or nanofibers of the natural cotton cellulose could be potentially applied in tissue scaffolds, protective clothing and high efficient water absorbing materials etc.Afterwards, considering its multi-hydroxy structure, through immersing the electrospun CC nonwoven into silver nitrate aqueous solution, we could make sure there were enough silver ions adsorpted by the CC molecule. Combining the UV reduction technology, we might change silver ions adsorbed on the surface of fiber into silver nano-particles. The result showed that we had achieved doping functional Ag nanopaiticles into the matrix of cellulose nanofibers, and obtained the cellulose /Ag composite nanofibers. The optical properties of electrospun cellulose fibers and cellulose/Ag composite nanofibers were characterized using UV-absorption spectroscopy, the results showed that this composite shows strong absorption property in the UV range, which is expected to have a potential as shielding material in future.2: cellulose acetate （CA）-based composite nanofibersFirstly, we made some foundation experiments: electrospinning of CA nanofibers, investigating the transition process from the original CA fibers into regenerative cellulose fibers by alkali treatment. Next, we had successfully acquired cellulose/CeO₂ composite nanofibers via the physic doping technique. The composite nanofibers were characterized by means of TGA、SEM、XRD and TEM. The results demonstrated that CeO₂ nanoparticles were successfully doped into CA polymer. What is interesting is that the nanoparticles were not only well stabilized on the surface, but also exist in the fibers overall. The optical properties testing showed that this composite shows strong UV absorption property in the UV and visible light range, which is expected to have a potential as UV shielding material in future.3: Semiconductor composite nanofibers----CeO₂-ZnO composite nanofibers and ZnO-CuO composite nanofibersThe results suggested that the inorganic composite nanofibers could be obtained via the calcinations of the as-spun fibers at 500℃, and the fibers change from the smooth to the rough surface, the diameter changed from 227nm to 46nm. Moreover, this fiber was consisted of two kinds of nanoparticles, one was cubic fluorite structure of CeO₂, and another was hexagonal wurtzite structure of ZnO.The PVP / Zn（CH3CO O）2 Cu（NO3）2 as-spun nanofibers were prepared via the electrospinning technique using zinc acetate and cerium nitrate as the precursors, poly（vinylpyrrolidone） as the fiber template, and 2:1（v/v） ethanol/water mixtures as the co-solvent. Then, ZnO/CuO composite nanofibers were obtained by high temperature calcinations of above compo site nanofibers. The morphologies and structures of the samples were characterized by TGA、SEM、EDS、FTIR、XRD、FE-SEM etc. Photocatalytic activity experiments showed that the CeO₂-ZnO nanfibers revealed hogher catalytic ability than the pure CeO₂ or ZnO nanofibers. Rhodamine B was almost completely decomposed when it was catalyzed by CeO₂-ZnO nanfibers within 3h. Lastly, the ZnO-CuO compositie nanofibers were prepared with the same method, and the morphorlogy and property were characterized by XRD, FESEM, UV-vis spectra and so on.

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