【作者】 黄学光；

【导师】 周济；

【作者基本信息】 清华大学 ， 材料科学与工程， 2009， 博士

【摘要】 本论文以复杂胶体晶体为主要研究对象,基于逐层生长、共沉积和结晶化胶体阵列等三种制备方法,系统研究了其形成机制、微观结构及光子带隙性质。发展了基于逐层生长方式的模板辅助电场诱导沉积方法,研究发现模板层中微球与水的介电失配是二元胶体晶体形成的驱动力,模板层内间隙位置的空间限制是影响二元胶体晶体结构的动力学因素。系统讨论了微球粒径比、乳液体积分数、电场加载条件等因素对二元胶体晶体结构的影响。该方法突破了现有逐层生长方法在微球粒径比方面的限制,并首次制备了三元胶体晶体。采用加速蒸发沉积方法制备二元胶体晶体,讨论了微球粒径比和数量相对比例对所得二元胶体晶体结构的影响。从空间填充的角度论证了毛细作用力诱导共沉积制备二元胶体晶体的临界粒径比为0.33。实验证明,当微球粒径比高于该值时,大球将无法形成具有密排有序结构的基本点阵,所得二元胶体晶体的有序度很低。这与现有文献报道一致。以二元胶体晶体为模板,通过溶胶-凝胶方法制备了二氧化硅复杂有序多孔膜。这种膜继承了胶体晶体模板的结构,微孔尺寸比模板中微球有一定收缩。通过离子交换方法制备了结晶化胶体阵列,研究表明其光子带隙波长与微球体积分数的关系满足Bragg公式。实验考察了不同溶剂类型对结晶化胶体阵列光子带隙的影响,证实了其光子带隙对染料发光的抑制作用。通过紫外光引发聚合制备了聚合结晶化胶体阵列,实验证明:在一定载荷范围内,聚合结晶化胶体阵列的光子带隙与外加压力呈可逆线性关系。首次制备了二元结晶化胶体阵列,并研究了其中微球排列结构及光子带隙与微球有效粒径差异的关系。发现当有效粒径相差较小时,二元阵列的光子带隙及微球有序点阵的有效晶格常数与微球百分数呈线性关系;当差异较大时,乳液中微球堆积呈无序-有序混合结构,光子带隙性质也有所劣化。对比发现二元结晶化胶体阵列与固溶体在微观结构、相变行为等方面存在很高的相似性,提出其可作为凝聚态物理、金属物理学等领域的研究模型,并在光子晶体等诸多等领域具有潜在的应用价值。更多还原

【Abstract】 This dissertation focuses on complex colloidal crystals. The formation mechanism, microstructure and photonic bandgap properties of complex colloidal crystals were investigated systematically based on three different preparation ways, i.e. layer-by-layer method, co-assembly method, and crystalline colloidal arrays.Template-assisted electric field-induced assembly (TAEFIA) on the basis of layer-by-layer method was developed. It was revealed that the mismatch of relative permittivity between the colloidal particles and water in template layer was the driving force in the formation of binary colloidal crystals, and the steric constraint of the interstitial sites in template layer was the dynamic factor responsible for the structure of binary colloidal crystals. The influence of particle size ratio, volume fraction and electric field parameters on the structure of binary colloidal crystals was systematically studied. By TAEFIA, we were able to overcome the limit on size ratio in current layer-by-layer methods, and fabricated ternary colloidal crystal for the first time.Binary colloidal crystals were prepared by accelerated evaporation deposition, and the influence of particle size ratio and relative content on crystal structure was discussed. It was revealed that the critical size ratio of binary colloidal crystals fabricated in capillary force-induced co-assembly method is 0.33 from the viewpoint of space-filling. It was found that with a size ratio higher than the critical value the particles with larger diameter cannot form ordered close-packed basic lattice, and as a result the corresponding binary colloidal crystal had a low degree of order, which was in accordance with previous literatures. Moreover, with binary colloidal crystals as templates, complex ordered porous silica films were fabricated by sol-gel technology. The as-prepared films replicated the structure of colloidal crystal templates, and its pore size shrunk compared with those of the particles in templates.Crystalline colloidal arrays (CCAs) were prepared via ion-exchange technology. It was found that the relation between the photonic bandgap wavelength of CCA and its volume fraction conformed to Bragg equation. The effect of different solvent on the photonic bandgap of CCA was investigated, and the suppression on dye fluorescence by photonic bandgap in CCA was confirmed. Moreover, polymerized crystalline colloidal arrays (PCCAs) were fabricated by ultraviolet-initiated polymerization. It was revealed that the photonic bandgap wavelength of PCCA film was reversibly proportional to extrinsic pressure in certain load range.Binary CCA was prepared for the first time, and the influence of effective particle size difference on its particle arrangement and photonic bandgap properties was studied. It was found that the photonic bandgap wavelength of binary CCA and the effective lattice parameter of particle lattice were proportional to the particle number percentage in binary CCA with a small size difference. But the particle arrangement exhibited a mixed structure of order and disorder with a large size difference, whereas degradation of photonic bandgap properties was also resulted. The resemblance between binary CCA and solid solution on microstructure and phase transition was revealed via comparison. We suggested that binary CCA can be used as a research model in condense matter physics and metal physics, and may find potential applications in many fields, such as photonic crystals.更多还原