尝试采用自蔓延高温合成 (SHS)、具有近球形特征且表面粗糙的新型 Si C颗粒 ,以替代传统的角状磨料级 Si C颗粒 ,作为光学 /仪表级的高体分 Si Cp/Al复合材料的增强体。研究结果表明 :与传统角状 Si C颗粒相比 ,SHS- Si C颗粒的无棱角...尝试采用自蔓延高温合成 (SHS)、具有近球形特征且表面粗糙的新型 Si C颗粒 ,以替代传统的角状磨料级 Si C颗粒 ,作为光学 /仪表级的高体分 Si Cp/Al复合材料的增强体。研究结果表明 :与传统角状 Si C颗粒相比 ,SHS- Si C颗粒的无棱角、近球形几何特征 ,使其附近铝基体中的应力集中程度显著降低 ,进而使材料的强度包括表征尺寸稳定性的微屈服强度明显提高 ;SHS- Si C颗粒所特有的粗糙表面形貌 ,使 Si C- Al之间的界面结合通过机械镶嵌机制得到了进一步的增强 ,跨越界面的载荷传递效率进一步提高 。展开更多
Nanocomposite thin films formed by noble metal nanoparticles embedded in a dielectric matrix show attractive optical properties at the surface plasmon resonance (SPR) wavelength due to dielectric and quantum confineme...Nanocomposite thin films formed by noble metal nanoparticles embedded in a dielectric matrix show attractive optical properties at the surface plasmon resonance (SPR) wavelength due to dielectric and quantum confinements effects. When such a metal-dielectric nanocomposite is excited by light, photons are coupled to the metal-dielectric interface, causing an induced charged density oscillation and showing a strong absorption maximum at a particular wavelength, called the SPR wavelength. Such pronounced resonance lines shown by noble-metal nanoparticles caused by collective excitations of conduction electrons are also known as particle plasmons (PPR) or Mie plasmons [1]. Many applications of these metal nanoparticle composite materials have been proposed taking advantage of the optical response at the SPR/PPR, including their use in surface enhanced Raman spectroscopy, surface enhanced second harmonic generation, and for the developement of color filters, sensors and all-optical switching devices. Polymer-metal nanocomposites are promising candidates for such optical functional applications. In these systems, very small particle sizes enhance the optical properties while the polymer matrix materials will act to stabilize the particle size and growth besides providing the required transparent medium. Of great significance is the ability to tune and extend the plasmon resonance wavelength, which is highly desirable in various applications of metallic nanoparticles. Since the plasmon resonance depends on the particle size, shape, filling factor (i.e. volume fraction of the metallic nanoparticles), dielectric properties of the metallic nanoparticles itself, as well as the surrounding dielectric medium, there are several approaches towards the ability to tune plasmon resonance wavelengths by varying these parameters. In this regard, a multicomponent optical system equipped with several plasmon resonance wavelengths and equally tunable response over a spectral range would be of interest for potential multifunctional operations at many wavelengths. However, no optical system exists with tunable multiple PPR wavelengths without affecting the geometry of the nanoparticles or the materials system. We demonstrate a simple method of vapor phase co-deposition at elevated target temperature [2] coupled with a novel selective masking technique [3] to produce a multicomponent optical material with as many as seven different ultraviolet-visible optical active planes. Such system consists of different nanocomposites of Teflon AF/Ag, Teflon AF/Au and Teflon AF/Cu with sharp interfaces. The fabricated system has regions of single nanocomposite plane together with multilayer structures facilitating tunable multiple particle plasmon resonance wavelength response from a single system. Distinct double and triple plasmon wavelength resonance absorptions could be obtained from such interfaces forming multilayers of either two or three nanocomposite structures. Production of ultra-thin (50 - 100 nm) polymer-metal color filters are also shown.展开更多
文摘尝试采用自蔓延高温合成 (SHS)、具有近球形特征且表面粗糙的新型 Si C颗粒 ,以替代传统的角状磨料级 Si C颗粒 ,作为光学 /仪表级的高体分 Si Cp/Al复合材料的增强体。研究结果表明 :与传统角状 Si C颗粒相比 ,SHS- Si C颗粒的无棱角、近球形几何特征 ,使其附近铝基体中的应力集中程度显著降低 ,进而使材料的强度包括表征尺寸稳定性的微屈服强度明显提高 ;SHS- Si C颗粒所特有的粗糙表面形貌 ,使 Si C- Al之间的界面结合通过机械镶嵌机制得到了进一步的增强 ,跨越界面的载荷传递效率进一步提高 。
文摘Nanocomposite thin films formed by noble metal nanoparticles embedded in a dielectric matrix show attractive optical properties at the surface plasmon resonance (SPR) wavelength due to dielectric and quantum confinements effects. When such a metal-dielectric nanocomposite is excited by light, photons are coupled to the metal-dielectric interface, causing an induced charged density oscillation and showing a strong absorption maximum at a particular wavelength, called the SPR wavelength. Such pronounced resonance lines shown by noble-metal nanoparticles caused by collective excitations of conduction electrons are also known as particle plasmons (PPR) or Mie plasmons [1]. Many applications of these metal nanoparticle composite materials have been proposed taking advantage of the optical response at the SPR/PPR, including their use in surface enhanced Raman spectroscopy, surface enhanced second harmonic generation, and for the developement of color filters, sensors and all-optical switching devices. Polymer-metal nanocomposites are promising candidates for such optical functional applications. In these systems, very small particle sizes enhance the optical properties while the polymer matrix materials will act to stabilize the particle size and growth besides providing the required transparent medium. Of great significance is the ability to tune and extend the plasmon resonance wavelength, which is highly desirable in various applications of metallic nanoparticles. Since the plasmon resonance depends on the particle size, shape, filling factor (i.e. volume fraction of the metallic nanoparticles), dielectric properties of the metallic nanoparticles itself, as well as the surrounding dielectric medium, there are several approaches towards the ability to tune plasmon resonance wavelengths by varying these parameters. In this regard, a multicomponent optical system equipped with several plasmon resonance wavelengths and equally tunable response over a spectral range would be of interest for potential multifunctional operations at many wavelengths. However, no optical system exists with tunable multiple PPR wavelengths without affecting the geometry of the nanoparticles or the materials system. We demonstrate a simple method of vapor phase co-deposition at elevated target temperature [2] coupled with a novel selective masking technique [3] to produce a multicomponent optical material with as many as seven different ultraviolet-visible optical active planes. Such system consists of different nanocomposites of Teflon AF/Ag, Teflon AF/Au and Teflon AF/Cu with sharp interfaces. The fabricated system has regions of single nanocomposite plane together with multilayer structures facilitating tunable multiple particle plasmon resonance wavelength response from a single system. Distinct double and triple plasmon wavelength resonance absorptions could be obtained from such interfaces forming multilayers of either two or three nanocomposite structures. Production of ultra-thin (50 - 100 nm) polymer-metal color filters are also shown.
