几种金属氧化物纤维的制备及其性能研究

发布时间：2018-04-25 00:00

本文选题：静电纺丝 + 离心甩丝　；参考：《山东大学》2017年博士论文

【摘要】：一维纳米材料相对于其他纳米材料有明显的优势,如大长径比、各向异性、比表面积大、电子定向传输等,在催化剂、电极、超级电容器、超强超硬复合材料、传感器等领域都有很广的应用。因此对一维纳米材料的制备、形貌、结构、成分以及性质进行深入的研究是一项非常重要的研究工作。金属氧化物纤维,也就是由金属元素和氧元素结合构成的化合物纤维。金属种类繁多,除了几种不活泼的贵金属外,其他金属均可以形成相应的氧化物,如氧化镍(NiO)、二氧化钛(Ti02)、二氧化锆(Zr02)、四氧化三钴(Co304)等。金属氧化物因具有良好的电、光、热、力、磁、声学等性质,受到了广泛研究。每一种氧化物结构不尽相同,导致各自具有独特的性质,应用往往也有很大差别。制备一维纤维材料的方法通常有水热法、模板法、溶剂热法、静电纺丝法、离心甩丝法等。其中静电纺丝法是近些年来新兴的制备纤维材料的方法,该方法通过调整不同的溶胶性质、工艺参数和环境条件,可以得到多种形貌和直径的纳米纤维。离心甩丝法工艺简单,产率高,极易实现批量化制备纤维。材料的性质不仅与其结构有关,还与组成物质的成分、结晶状态等因素有关。Ti02是一种常用的光催化材料,其光催化活性受到本身禁带宽度大和光生载流子复合率高的限制而往往偏低;Zr02作为一种极重要的超高温隔热材料,要求具备高的强度和低的热导率,这与本身的晶型、结晶度、晶粒大小等有很大关联;NiO和Co304纤维的研究偏少,更鲜有批量制备两种纤维的报道。基于此,本论文首先通过用静电纺丝或离心甩丝法制备几种氧化物纤维,再分别对各个纤维存在的问题进行了进一步优化。这对于氧化物纤维的研制具有重要的理论意义和应用价值。本论文主要研究内容如下:1.Ti02复合纤维的制备及其光催化性能研究通过静电纺丝获得直径均匀的T丨02纳米纤维,纤维直径大约在500 nm左右,用Turkevich方法得到直径为16 nm的金纳米球,再采取配体交换的方式将纳米金负载在T丨02纤维上。SEM和TEM检测结果表明,所得Au/Ti02复合纤维中金纳米粒子在纤维表面均匀分布,含量可控,应用此方法还可以制备多种尺寸纳米金(6 nm和30 nm)负载的复合纤维。在紫外或可见光条件下进行光降解甲基橙实验,发现Au1/Ti02复合纤维的光催化活性要明显高于P25和纯Ti02纤维,在40 min时降解率可达90%。对不同金含量Au/Ti02复合纤维的光催化活性进行了对比,表明随着纳米金含量的增加,光催化活性逐渐变高,直到含量超过1%后,光催化活性减弱。在紫外光和可见光条件下,纳米金含量为1%时复合纤维光催化效果均最好。通过对不同金含量Au/Ti02复合纤维的紫外可见漫反射光谱,荧光光谱和光电流谱图测试,研究了光催化机理。结果表明,在紫外光条件下,光生电子从Ti02的导带转移到纳米金的能带上,从而被有效分离。在可见光照射下,基于表面等离子共振效应,纳米金可以吸收可见光,激发所得的热电子转移到Ti02导带参与光催化反应,从而有效利用了可见光。纳米金含量较大时,可能会作为复合中心,也会覆盖Ti02的部分表面,复合纤维的光催化效率反而变低。此外,还制备了类石墨相氮化碳(g-C3N4)纳米片,通过SEM,TEM,FT-IR和XRD等测试证明了其片层结构和成分。采用沉积方法得到了 g-C3N4/Ti02复合纤维,并且对复合纤维做了光降解甲基橙测试,表明了复合纤维在可见光下有较好的光催化效果。同时也对光催化机理作了讨论,g-C3N4在可见光下被激发产生的光生电子可以转移到TiO2的导带,光生电子被有效分离,更高效地参与光催化反应。2.Zr02纤维的制备、高压水蒸汽处理及高温结构研究采用溶胶凝胶结合静电纺丝方法得到了 Zr02前驱体纤维,然后将纤维进行了高压水蒸汽处理。纤维经高压水蒸汽处理后,内部的有机物几乎可以全部去除,且可以在较低温度下结晶,形成小晶粒组成的多晶纤维。直接将前驱体纤维高压水蒸汽处理效果不佳,原因前驱体中溶剂含量过多,而将前驱体纤维先在300 ℃预处理2 h后再高压水蒸汽处理效果最佳。对高压水蒸汽处理不同条件进行了对比实验,研究了温度、水量和保温时间对纤维处理的影响。温度较低时,效果不明显,当温度为300 ℃或400 ℃时有机物去除更充分。保温时间的不同(2 h、5 h和10 h)对高压水蒸汽处理效果影响不显著,结果无太大差异。水对高压水蒸汽处理起重要作用,能够在封闭系统内提供蒸气压,有利于促进前驱体结晶。最终优选条件是400 ℃,保温2 h,水量为30%。此外,还研究了纤维在高温热处理后的特性。高压水蒸汽处理过的纤维在1000 ℃热处理后比未处理的样品晶粒明显减小。晶粒随着处理温度升高而长大,1400 ℃以上时晶粒出现异常长大现象。3.NiO和Co304纤维的制备及性能研究采用溶胶凝胶法结合离心甩丝制备了 NiO和Co304微米纤维,纤维直径均在10 μm左右。用柠檬酸作为配体制备相应的前驱体溶胶,研究发现镍盐或钴盐与柠檬酸的比例对前驱体溶胶的可纺性有重要的影响,在比例为1.5时所得前驱体溶胶可纺性最好。利用TG-DSC、FT-IR、XRD分析了前驱体纤维在不同热处理温度下的演变过程,发现前驱体纤维先后经历了吸附水的脱除,有机物分解和氧化物结晶几个阶段。TEM和拉曼分析证实了纤维的成分。根据SEM结果进一步确认了纤维的微观形貌,结果显示NiO纤维为实心结构,而Co304纤维是空心结构。测定了两种纤维的磁滞回线,证明了 NiO和Co304纤维具有弱的铁磁性,和块体材料的反铁磁性不同。随着热处理温度增大,磁饱和强度和矫顽力都变小。NiO纤维还表现出对于刚果红良好的光催化活性。此外,还用类似的方法制备出了多孔NiO/Co304复合纤维,证明其也具有了一定的铁磁性。综上所述,本论文中采用静电纺丝法制备T丨02和ZrO2纤维,用离心甩丝法制备NiO和Co304纤维,在此基础上,分别对纤维的性能做了进一步的优化调整。将纳米金均匀负载在Ti02纤维的表面,增强了复合纤维的光催化性能,并且讨论了纳米金负载量对复合纤维光催化活性的影响。制备了 g-C3N4/TiO2复合纤维,并研究了其在可见光下的光催化性能。将静电纺丝得到的ZrO2前驱体纤维进行高压水蒸汽处理,有效去除有机物并在较低温度实现结晶。将柠檬酸作配体制备前驱体,用离心甩丝法获得了 NiO和Co304纤维,研究了其磁学和光催化性质。
[Abstract]:One dimensional nanomaterials have obvious advantages relative to other nanomaterials, such as large length to diameter ratio, anisotropy, large specific surface area, electronic directional transmission and so on. It has a wide application in the fields of catalyst, electrode, supercapacitor, super hard composite material, sensor and so on. The preparation, morphology, structure, composition and properties of one-dimensional nanomaterials are made. Qualitative research is a very important research work. Metal oxide fiber, a compound made of metal elements and oxygen elements, is a great variety. In addition to several kinds of inert precious metals, other metals can form corresponding oxides, such as nickel oxide (NiO), titanium dioxide (Ti02), and two oxidation. Zirconium (Zr02), four oxidation three cobalt (Co304), etc. metal oxide has been widely studied because of its good electrical, light, thermal, force, magnetic, acoustic and other properties. Every oxide structure is not the same, which leads to the unique properties and the application is often very different. The methods of preparing one dimensional fiber are usually hydrothermal method, template method, solvent. The electrostatic spinning method is a new method for preparing fiber materials in recent years. By adjusting the properties of the sols, the process parameters and the environmental conditions, this method can get a variety of nanofibers with different morphology and diameter. The process of centrifugal spinning is simple, high yield, and easy to achieve mass production. The properties of the materials are not only related to their structure, but also related to the composition of the components and the state of crystallization..Ti02 is a commonly used photocatalytic material. The photocatalytic activity is limited by the limitation of the band gap and the high recombination rate of the photogenerate carrier. As an extremely important ultra high temperature insulation material, Zr02 is a very important material. In order to obtain high strength and low thermal conductivity, there is a great relationship between the crystalline form, crystallinity and grain size of its own. The study of NiO and Co304 fibers is less, and there are few reports on the preparation of two kinds of fibers. Based on this, the paper first prepared several oxide fibers by electrostatic spinning or centrifugal spinning, and then separately deposited the fibers. The main research content in this paper is as follows: the preparation and photocatalytic properties of 1.Ti02 composite fiber and its photocatalytic performance study by electrospinning to obtain T 02 nanofibers with uniform diameter, the diameter of fiber is about 500 nm, and Tur Kevich method obtained gold nanospheres with a diameter of 16 nm. Then the gold nanoparticles were loaded on the T 02 fiber by ligand exchange. The results showed that the gold nanoparticles in the Au/Ti02 composite fiber were evenly distributed on the surface of the fiber and the content was controllable. The load of various sizes (6 nm and 30 nm) could be prepared by this method. The photocatalytic activity of Au1/Ti02 composite fibers was significantly higher than that of P25 and pure Ti02 fibers. The photocatalytic activity of the composite fibers at 40 min was compared to 90%., and the photocatalytic activity of Au/Ti02 composite fibers with different gold content was compared at 40 min. The catalytic activity gradually becomes higher, and the photocatalytic activity is weakened until the content exceeds 1%. Under the conditions of ultraviolet and visible light, the photocatalytic effect of the composite fiber is best when the gold content is 1%. The UV visible diffuse reflectance spectrum, the fluorescence spectrum and the photoelectricity spectrum of the Au/Ti02 composite fibers with different gold content are tested, and the photocatalytic machine is studied. The results show that under ultraviolet light, the photoelectrons transfer from the guide band of Ti02 to the energy band of nanoscale gold, which can be effectively separated. Under the visible light, the nano gold can absorb visible light based on the surface plasmon resonance effect, and the thermal electrons can be transferred to the Ti02 guide band to participate in the photocatalytic reaction, thus effectively utilizing the visible light. When the content of nanoscale gold is larger, it may be used as a compound center, which will also cover the part of the surface of Ti02, and the photocatalytic efficiency of the composite fiber becomes lower. In addition, the graphite like carbon nitride (g-C3N4) nanoscale is prepared, and the layer structure and composition are proved by the tests of SEM, TEM, FT-IR and XRD. The deposition method is used to obtain the g-C3N4/Ti02. The composite fiber has been tested by photodegradation of methyl orange, which shows that the composite fiber has better photocatalytic effect under visible light. Meanwhile, the photocatalytic mechanism is discussed. The photoinduced electrons produced by g-C3N4 in visible light can be transferred to the guide band of TiO2, and the photoelectrons are effectively separated and more efficiently participated in the light. The preparation of catalytic reaction.2.Zr02 fiber, high pressure water vapor treatment and high temperature structure study by using sol-gel combined electrostatic spinning method to obtain the Zr02 precursor fiber, and then the fiber is treated with high pressure water vapor. After the fiber is treated with high pressure water vapor, the internal organic matter can be completely removed and can be at a lower temperature. Crystallization, forming a polycrystalline fiber composed of small grain. The effect of high pressure water vapor in the precursor fiber is not good. The solvent content in the precursor is too much, and the precursor fiber is pretreated at 300 C for 2 h and then the high pressure water steam treatment is the best. The effect of water and heat preservation time on fiber treatment is not obvious when the temperature is low. When the temperature is 300 or 400, the organic matter is more fully removed. The difference of heat preservation time (2 h, 5 h and 10 h) has no significant effect on the effect of high pressure water vapor treatment. The vapor pressure in the system is helpful to promote the crystallization of the precursor. The optimum condition is 400, 2 h and 30%., and the properties of the fiber after heat treatment at high temperature are also studied. The grain of the high pressure steam treated fiber is less than that of the untreated sample after heat treatment at 1000. The preparation and properties of.3.NiO and Co304 fibers were prepared by sol-gel method and centrifugation by sol-gel method and centrifugation. The diameter of the fiber was about 10 mu m. The precursor sol was prepared with citric acid as the ligand, and the ratio of nickel salt or cobalt salt to citric acid was found in the study. The ratio of.3.NiO and Co304 fiber was prepared by sol-gel method and centrifugation The spinnability of precursor sol has an important influence. The spinnability of precursor sol is the best when the ratio is 1.5. TG-DSC, FT-IR and XRD have been used to analyze the evolution process of precursor fibers at different heat treatment temperatures. It is found that the precursor fibers have experienced the removal of adsorbed water, organic matter decomposition and oxide crystallization in several stages of.TEM. The fiber composition was confirmed by the Raman analysis. The micromorphology of the fibers was further confirmed according to the SEM results. The results showed that the NiO fibers were solid structures and the Co304 fibers were hollow structures. The hysteresis loops of the two fibers were measured. It is proved that the NiO and Co304 fibers have weak ferromagnetism, and the antiferromagnetism of the bulk materials is different from that of the bulk materials. As the temperature increases, the magnetic saturation strength and coercive force are smaller,.NiO fibers also exhibit good photocatalytic activity for Congo red. In addition, a porous NiO/Co304 composite fiber has been prepared by similar methods, proving that it has a certain ferromagnetism. In this paper, T 02 and ZrO2 fibers are prepared by the electrospinning method in this paper. NiO and Co304 fibers were prepared by centrifugal shredding method. On this basis, the properties of the fibers were further optimized. The photocatalytic properties of the composite fibers were enhanced by loading the nano gold evenly on the surface of Ti02 fiber, and the influence of the nano gold load on the photocatalytic activity of the composite fibers was discussed. The g-C3N4/TiO2 composite was prepared. The photocatalytic properties of the fibers under visible light were studied. The ZrO2 precursor fibers obtained by electrostatic spinning were treated with high pressure water vapor to effectively remove organic compounds and crystallize at a lower temperature. NiO and Co304 fibers were obtained by using citric acid as ligands to prepare the precursors. The magnetic and photocatalytic properties of the fibers were studied by centrifugation.

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ343.5

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