Electrospinning Of Micro, Nano-transition Metal Oxides And Their Properties

Metal oxide with one-dimensional nano-structure is a kind of important materialthat has been widely used in fields of optical, electrical and mechanical devices,catalyst, gas sensor, sunscreen and cosmetics. Researches on metal oxide havebecome an indispensable part of nano science and technology. The methods forpreparation one dimensional nano-metal oxides are diverse, such as solid phasemethod, liquid phase method, gas phase method and so on. Among these methods,electrospinning is selected as the most suitable for the preparation of nanofiber due toits advantage of simple and convenient. However, the current studies for preparingmetal oxide nanomaterials through electrospinning still exist some limitations, such as:the morphology is too single, the applicability is not good, the cost is high and so on.Thus, it is necessary to develop new methods to improve the preparation of materialwith nanofiber mophology. As a result, we put forward the methods such aselectrospinning respectively combined with sol-gel, material modification, physicaladsorption, liquid-solid reaction to solve the problem. In addition, in the current study,although the polymer parameters in the process of electrospinning have been reportedto have effect on the morphology and properties of product, the causes of thedifferences on morphology of metal oxide is still a mystery. Therefore, in order toexplore the specific influence of polymer template on the morphology of metal oxide,different polymer templates are also needed.Polylactic acid (PLA), poly-(L-lactide-co-ε-caprolactone-diOH)(PCLA) andcarboxylic-functionalized poly(arylene ether ketone)(PCA-PAEK) are three kinds of synthetic polymer materials with high performances. For an example, the productioncost of PLA is low and in the process of combustion it does not release harmfulsubstances; PCLA has a special structure and thermal decomposition behavior; PCA-PAEK has a good thermal stability and adsorption properties, etc. Take advantages oftheir characteristics, we can produce the product with various structures. Thus, it isvery helpful to improve the application of the product. In order to achieve this goal, inthis article, we use the three polymers as templates to synthesize nanoscale metaloxides in different morphologies and discuss their formation mechanism. We alsoanalyze the role of the polymer in the process of fiber formation.First of all, we use polylactic acid (PLA) as template and through three ways torealize the preparation of metal oxides nanofibers. One is using electrospinningcombined with sol-gel method and calcination technology to prepare TiO2nanofiberswith stripes on the surface. After its degradation on methyl orange dye, it is found thatthe prepared TiO2nanofibers has the same degradation efficiency as business nano-TiO2, and even has a higher rate of degradation. Second is using electrospinningmethod combined with material modification and calcination technology to prepareZnO nanofibers. This method has solved the problem of the formation of film afterdirect calcination of fiber. After the study of the fiber morphology formationmechanism, it is found that NaOH can react with PLA and zinc acetate respectively atthe same time to generate multiple-COOH and Zn(OH)2, respectively. They canfurther reacted with each other to generate PLA-COOZn1/2, thus, the melt of PLA andzinc acetate can be avoided. Furthermore, photocatalytic performance of the ZnOsamples was investigated. Comparing with ZnO film, ZnO nanofibers exhibited muchhigher activity. Third is using electrospinning combined with physical adsorption andcalcination technology to prepare nano NiO products with multi-layer structures. Thestructures of NiO products from surface to center are nanogrooves inlaid film, hollowpores and honeycomb-like nanofibers with nanogrooves, successively. After the studyof the morphology formation mechanism, it is found that the morphology is related tothe thermal properties of polymer and inorganic salt. The sensitivity of the NiOproducts to formaldehyde was investigated. As a result, the multilayer NiO exhibited much higher sensing signal than NiO powders. This indicated that the preparedmultilayer NiO could be used as a candidate to fabricate formaldehyde sensors. Thismethod realizes the preparation of nano-NiO with multilayer structure in one time.The specific surface area can be greatly increased and expand its application range.Secondly, we use a low toxicity, convenient chain extension method tosynthesize PCLAblock copolymer with (ABA)ntype. And then, it is taken as spinningraw materials to prepare pure PCLA micro/nano fibers through electrospinning. Inorder to explore the influence of electrospinning process parameters on fibermorphology and diameter, orthogonal experiments are designed. As a result, theoptimum condition for electrospinning is obtained and the influence is quantified.Then, using PCLA as template, electrospinning, sol-gel and calcination technology asmethod, nano-Mn2O3and Mn3O4with special morphology are prepared. We alsodiscuss their catalytic properties using methylene blue solution. Through productmorphology formation mechanism research, it found that the formation of themorphology is related to the decomposition temperature of each block in PCLA. Thisshows that the morphology of metal oxide nanofibers is determined by the choice ofthe template. In addition, we also use PCLAas template, using solvent in combinationwith UV irradiation to in situ reduce Ag+to prepare PCLA fiber loaded with Agnanoparticles for the first time. It found that the distribution and the size of theprepared Ag nanoparticles is uniform. This is because that the PCLAcan promote Ag+reduction, and at the same time prevent reunion of Ag nanoparticles. This indicatesthat the choice of the template can improve the reunion of inorganic nanoparticle.Finally, taking PCA-PAEK as the main line, we prepare pure PCA-PAEKsuperfine fibers for the first time. And research to obtain the optimal spinningparameters and study the influence of these parameters on the fiber diameter. Theresults show that when the polymer concentration is20wt.%, the ratio of solvent is5/5, the voltage is17kV and the collect distance is15cm, we can get uniform andfine fiber. In the experiments, it also can be found that the influence degree of the fourparameters is polymer concentration, solvent ratio, collect distance and spinningvoltage, successively. The results have a vital role for regulating fiber morphology. Then, we use PCA-PAEK fiber as a template, combine liquid-solid reaction withcalcination technology to obtain rope-like CuO, perforated CdO and hollowed-outCuO/CdO composite fibers. After the discussion of the mechanism, it is found that themain point of preparation uniform metal oxide fiber is the coordination between metalions and the-COOH on polymer. After the investigation of chemical and physicalproperties of the product, it is found that compared with Cu(CH3COO)2, PCA-PAEKare more likely to interact with Cd(CH3COO)2. When PCA-PAEK react withCu(CH3COO)2and Cd(CH3COO)2at the same time, Cu(CH3COO)2can inhibits thereaction between Cd(CH3COO)2and polymer. All in all, we have used the PCA-PAEK as template to prepare the CuO, CdO and CuO/CdO composite fibers withspecial morphology through a simple chemical reaction. This result againdemonstrates that the choice of the polymer is closely related to the morphology ofmetal oxide fiber.