【作者】 王密；

【导师】 房鼎业； 郭旭虹； 高彦峰；

【作者基本信息】 华东理工大学 ， 化学工艺， 2014， 博士

【摘要】 能源的可利用性在很大程度上决定了人们的生活质量。然而,随着全球经济的飞速发展,能源短缺、环境污染和气候变化已经成为制约人类社会可持续发展的重要问题。太阳能取之不尽、用之不竭、节能环保,是最具发展潜力的可再生能源,其研究吸引了众多科学研究工作者。太阳能开发和利用的主要手段是将其转化为其它形式的能量,如电能和化学能等。近几年来,对太阳能的应用已经涉及到太阳能电池、光催化、光存储、光电开关和建筑节能等各个领域。本文主要研究了具有特殊光电性能的纳米半导体氧化物和聚合物微凝胶的可控制备及其在节能环保领域的应用。纳米半导体氧化物,二氧化锡(SnO2)和二氧化钒(VO2),由于其特殊的能带结构,可以用于光催化降解有机染料、太阳能电池的透明电极,也可以被用作热致变色材料,通过元素掺杂等工艺改进可以有效调控其光电性能。而具有最低临界溶解温度(LCST)的聚N-异丙基丙烯酰胺(PNIPAm)微凝胶,随温度变化会发生可逆的相变行为,并伴随着光学性能的变化,是制备热致变色型智能窗的理想材料。本文研究了纳米SnO2和PNIPAm微凝胶的可控制备,探索了它们在光催化、透明导电和智能窗领域的应用。为了进一步提高PNIPAm型热致变色智能窗的节能效果,本文还通过原位聚合反应将纳米VO2和PNIPAm复合,制备出无机-有机复合微凝胶,研究了复合微凝胶的复合机理和相变行为,并探索了其在智能窗领域的应用。具体工作如下：1.分别以聚乙烯吡咯烷酮(PVP)、十二烷基磺酸钠(SDS)、十六烷基三甲基溴化铵(CTAB)和四丙基溴化铵(TPAB)作为表面活性剂,利用180℃水热反应实现了不同形貌Sn02纳米粉体的可控制备。产物Sn02均为四方晶系,通过改变有机表面活性剂的种类和浓度,成功合成出纳米立方体、纳米棒、纳米片、纳米带和纳米颗粒等。水热反应过程中,表面活性剂可以通过静电作用和范德华力改变Sn02纳米晶的生长取向,使其长成不同的形貌。其作用效果取决于溶剂类型是水系还是醇系。一方面,相同溶剂条件下,加入适量的阴离子表面活性剂(SDS)或阳离子表面活性剂(CTAB和TPAB),均可以从很大程度上改变SnO2纳米晶的形貌,但二者的作用效果明显不同；另一方面,不同溶剂条件下,同一表面活性剂对产物形貌的影响亦不相同。非离子表面活性剂(PVP)对产物形貌的影响与SDS类似,但其作用效果弱很多。2.利用不含表面活性剂和模板的水热反应合成出具有不同三维微观结构(如花状和球状)的金红石相SnO2纳米粒子。研究了醇含量对SnO2纳米粒子形貌的影响及花状和球状微观结构的形成机理,并探索了不同微观形貌对纳米SnO2光催化性能的影响。结果显示,产物SnO2纳米粉体的吸附性能和光催化活性主要取决于其比表面积的大小并在一定程度上受其光学带隙的影响,而这两者均随SnO2微观结构的改变发生变化。改变醇添加剂的含量可以调控SnO2纳米晶的生长取向和尺寸大小,形成不同的生长模式。与花状结构相比,纳米SnO2微球对酸性品红的吸附性能和光催化活性均较高。当溶剂的醇水比为3：1时,产物形貌是破损的空心微球,比表面积为58.2m2/g。它对酸性品红的光催化降解速率约为0.073min-1,35min内其脱除效率即超过80%,且循环使用性能良好,可用作高效净水材料。3.以无机盐为原料,聚乙烯醇为成膜促进剂制备出稳定的前驱体溶液,通过旋涂技术在石英玻璃基板上涂覆了不同厚度(60-600±10nm)的透明导电钨(W)掺杂Sn02薄膜。研究了W掺杂浓度、旋涂速率和退火温度对薄膜形貌、电学性能和光学性能的影响。结果显示,所有膜层均由粒径十几个纳米的颗粒组成,分布均一,表面光滑无裂纹,且薄膜能级带隙较宽(3.93-4.31eV),透光性良好。W掺杂可以从很大程度上改变Sn02基薄膜的微观结构和电导率。当前驱体溶液中W含量为Sn原子的3at%时,经3000rpm旋涂,800℃空气退火后,薄膜的电阻率低至2.8×10-3Ω·cm,经八次涂覆后,膜层的厚度可达606nm,面电阻仅有60Ω,可见光(400-760m)透过率仍然超过80%,适用于太阳能电池的透明电极。4.利用简单的乳液聚合法实现了对热敏性PNIPAm微凝胶的可控制备,探索了各因素对PNIPAm微凝胶形貌的影响,计算了产物的太阳光调控能力,并组装了实验室规模的模型房间以评估PNIPAm型智能窗的节能效果。结果显示,单体浓度、交联剂种类和用量、表面活性剂类型可以从很大程度上改变PNIPAm微凝胶的尺寸大小、网络致密度和太阳光调控能力(最高可达80%),但对其LCST几乎没有影响。而通过添加共溶剂,可以制备出相变温度可调(20.4-32.2℃)、冰点可调(-32～-18.1℃)的PNIPAm微凝胶,其太阳光调控能力仍然高于60%、光学响应时间较短(50～150s)、循环使用性能良好、粘度适中、挥发性低。通过模拟房间测试发现,在150W光照条件下,相对于普通玻璃,PNIPAm微凝胶可以带来超过20℃的温降,是理想的热致变色型智能窗功能材料。5.通过水热法合成了VO2(M)纳米粒子,并采用原位乳液聚合法首次制备出纳米粒子填充型和核壳型VO2-PNIPAm复合微凝胶。研究了无机纳米粒子对PNIPAm型微凝胶网络结构和光学性能的影响,并探索了无机纳米粒子与聚合物微凝胶的复合机理。无机-有机复合微凝胶体系光学性能的改变主要归因于无机纳米粒子对聚合物微凝胶网络结构的影响。当V02含量适当时,将太阳光调控能力为13%的V02纳米粉体和太阳光调控能力为35%的PNIPAm微凝胶体系复合后,所制备VO2-PNIPAm复合微凝胶的太阳光调控能力可以达到88%。更多还原

【Abstract】 The quality of human life depends to a large degree on the availability of energy. However, with the rapid development of the global economy, energy crisis, environmental pollution and climate change have become the most serious problems, which will restrict the sustainable development of human society. As a kind of energy saving and environment friendly energy, solar energy is really inexhaustible and natural renewable, which makes it one of the most attractive research fields. The utilization of solar energy is mainly concentrated on transforming into other forms of energy, such as electrical energy and chemical energy. In the last few years, research fields in solar energy have been developed, such as solar cells, photocatalysis, optical storage, photoelectric switch, and building energy conservation.The controllable synthesis of semiconductive metal-oxides and thermosensitive polymer microgels with special photoelectric properties, and their applications in energy conservation and environmental protection, were studied in this thesis. Because of their special band structures, semiconductive metal-oxides can be applied as photocatalysts for the degradation of organic dyes and transparent electrodes for solar cells. Their photoelectric properties can be effectively regulated by element doping and process improvement. Poly(N-isopropylamide) microgels, which possess the lower critical solution temperature (LCST), undergo a reversible swelling-deswelling process upon heating and cooling. The great change of their optical properties during the phase transition makes them potential materials for thermochromic smart windows. Due to the synergistic effect, inorganic-organic composite materials usually exhibit better performance than that of a single material. Thus, at the last charpter of this thesis, inorganic-organic composite microgels were synthesized from thermochromic materials. Their phase transition behavior, composite mechanism and the application in smart windows were also investigated. Details of this thesis are outlined as follows:1. Nanosized SnO2with different morphologies were synthesized via a simple hydrothermal process at180℃, using polyvinylpyrrolidone (PVP), sodium dodecyl sulfonate (SDS), cetyl trimethyl ammonium bromide (CTAB) or tetrapropyl ammonium bromide (TPAB) as surfactant. All the prepared SnO2are of a tetragonal crystal structure, and nanocubes, nanorods, nanosheets, nanobelts and nanoparticles were prepared when changing the type and dosage of organic surfactants. The effect of surfactants on the morphology of SnO2is probably attributed to the electrostatic interactions and Van der Waals’forces, which can change the growth oriention of SnO2nanocrystals during the hydrothermal process. So the effect of surfactant on the morphology of SnO2is significantly dependent on the solvent type:water or alcohol. With the same solvent, the addition of anionic surfactant (SDS) and cationic surfactant (CTAB or TPAB) can both largely affect the morphology of SnO2nanocrystals, but showing really different results. While, with the same kind of surfactant, resulting morphologies of SnO2were also different under different solvents. The non-ionic surfactant (PVP) can also change the morphology of SnO2like SDS, but showing less obvious impact.2. Pure rutile-phase SnO2nanoparticles with different3D microstructures (e.g., flower-like architectures and microspheres) were prepared via a feasible surfactant-free hydrothermal process. These microstructures were composed of nanosheets, nanocubes or nanopyramids. By changing the amount of ethanol additives, the growth orientation and size of the SnO2nanocrystals were changed, which resulted in the formation of different growth patterns. The effect of ethanol content on the morphological evolution of the SnO2nanoparticles, and the formation mechanism of the flower-like architectures and microspheres were explored. Furthermore, the microstructure morphology of SnO2showed great effect on its surface area. Both the adsorption and photocatalytic properties are mainly dependent on the surface area of SnO2and slightly influenced by the band gap energy. Compared to the flower-like architectures, the SnO2microspheres exhibited higher adsorption capacity and photocatalytic activity toward the degradation of acid fuchsine. When the ratio of ethanol/water in the solvent was3:1, the products were broken SnO2microspheres with a surface area of58.2m/g and a photocatalytic activity of0.073min-1. They showed a removal efficiency of acid fuchsine over80%in35min. With excellent recycling performance, these microspheres can be used as efficient water treatment materials.3. Transparent and conductive tungsten-doped tin oxide (SnO2:W) thin films with different thickness (from60to600±10nm) were fabricated on quartz glass substrates by a spin-coating method. A stable precursor solution was prepared from tin chloride and ammonium tungstate, together with polyvinyl alcohol as a film-forming promoter. It was found that all the synthesized films showed homogeneous composition, smooth surface with no cracks and high transparency with an optical band gap ranging from3.93to4.31eV. The effect of tungsten concentration, spin rate and annealing temperature on the morphological, electrical and optical properties of the films were investigated. W doping had a strong impact on the microstructure and the conductivity of SnO2thin films. The lowest resistivity of2.8×10-3Ω·cm was obtained for a SnO2:3at%W film, which was prepared at3000rpm and annealed at800℃in air. An eight-layer film with a sheet resistance of60Ω and a thickness of606nm was fabricated by multiple coating operation, which exhibited an optical transmittance over80%in the visible region from400to760nm, suitable for transparent electrodes of solar cells.4. Thermosensitive poly(N-isopropylacrylamide)(PNIPAm) microgel colloids were prepared by a simple emulsion polymerization method, and a model house was made to test their energy-saving performance for smart windows. The solar modulation ability of PNIPAm microgels can be largely influenced by the monomer concentration, the crosslinker type and dose, and emulsifiers, which showed no obvious effect on the LCST. While, the addition of cosolvent could effectively change the LCST of PNIPAm microgels. By using glycerol as cosolvent, PNIPAm microgel colloids with a LCST between20.4and32.2℃, a freezing point between-18.1and-32℃, were obtained. And they displayed an excellent solar modulation ability (more than60%), resulting in a temperature reduction of20℃compared to float glass, under irradiation. More importantly, the prepared PNIPAm microgel colloids also exhibited high response rate (less than150s), suitable viscosity, restrained evaporation rate, which make them ideal candidates for smart windows.5. Thermochromic VO2(M) nanopowders were prepared via a hydrothermal route, and nanoparticles filled or core-shell VO2-NIPAm composite microgels were synthesized for the first time by in-situ emulsion polymerization. The influences of inorganic nanoparticles on the polymer network structure and the optical properties of PNIPAm-based microgels were studied, and the composite mechanism was investigated. The solar modulation ability of VO2-PNIPAm composite microgels was dependent on the control of PNIPAm network structure by VO2nanoparticles. With appropriate amount of VO2, VO2-PNIPAm composite microgels with a solar modulation ability of88%can be obtained by the combination of VO2nanoparticles with a solar modulation abilty of13%and PNIPAm microgels with a solar modulation of35%.更多还原