Hypersonic Phononic Colloidal Crystals on the Basis of Submicroscopic Silica, Polymer and Hybrid Beads

基于亚显微二氧化硅、聚合物和混合珠的高超声速声子胶体晶体

• 批准号: 61437418
• 负责人: Privatdozent Dr. Goetz P. Hellmann
• 金额: --
• 依托单位: Bereich Kunststoffe
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/61437418?language=en
• 关键词: Hypersonic; Phononic; Colloidal; Crystals; Basis

3D structures with a periodically modulated dielectric constant, coined photonic crystals, can display bandgaps around Bragg resonances associated with the lattice constants where the propagation of the light is forbidden. Theoretically, similar phononic bandgaps have been predicted in structures with periodic variations of the density or sound velocity. Such a bandgap at hypersonic frequencies was indeed recently detected by some of us. This project aims at the intensive study of these bandgaps in appropriately designed hypersonic crystals with submicron periodicities. Suited objects are synthetic opals with an fcc lattice. They will be prepared by various techniques from colloidal polymer, silica or core-shell hybrid beads differing in size and core-shell ratio. A manifold of opals varying in the lattice dimensions, the local structure and the elastic modulus contrast can be designed so the phononic bandgaps can be tuned. The phonon dispersion relation ω(k) of the opals will be studied by Brillouin light scattering (BLS) at different wave vectors and interpreted using theoretical computations based on the multiple phonon scattering formalism. The relevant characteristics of the beads will be deduced from their vibration eigenmodes measured also by BLS. The goal is a quantitative theoretical description of the experimental dispersion ω(k) essentially without adjustable parameters. Eventually, a computer- aided design of hypersonic phononic crystals based on core-shell colloids is aimed at.

具有周期性调制介电常数的 3D 结构（创造的光子晶体）可以显示布拉格共振周围的带隙，该带隙与禁止光传播的晶格常数相关。理论上，在密度或声速周期性变化的结构中已经预测出类似的声子带隙。我们中的一些人最近确实检测到了高超音速频率的这种带隙。该项目旨在深入研究适当设计的具有亚微米周期性的高超声速晶体中的带隙。合适的物体是具有面心立方晶格的合成蛋白石。它们将通过各种技术由尺寸和核壳比不同的胶体聚合物、二氧化硅或核壳混合珠制备。可以设计晶格尺寸、局部结构和弹性模量对比不同的蛋白石流形，从而可以调节声子带隙。将通过不同波矢量下的布里渊光散射 (BLS) 研究蛋白石的声子色散关系 ω(k)，并使用基于多重声子散射形式的理论计算进行解释。珠子的相关特性将从 BLS 测量的珠子振动本征模式中推断出来。目标是对实验色散 ω(k) 进行定量理论描述，基本上无需调整参数。最终，目标是基于核壳胶体的高超声速声子晶体的计算机辅助设计。