Surface contacts strongly influence the elasticity and thermal conductivity of silica nanoparticle fibers

Abstract

Granular materials are often encountered in science and engineering disciplines, in which controlling the particle contacts is one of the critical issues for the design, engineering, and utilization of their desired properties.

Influence of Surfactant-Mediated Interparticle Contacts on the Mechanical Stability of Supraparticles

“…The low-frequency mode is assigned to a longitudinal phonon in a cluster of particles. It corresponds to the (1,1) translational mode, which is of zero frequency in independent particles, that is, no particle–particle interaction. ,,, The strength and number of contacts of individual particles in a cluster influence their vibration eigenmodes. Thus, if primary particles in the supraparticles strongly adhere to their neighbors, their individual vibration modes cannot be experimentally resolved.…”

“…Using energy and momentum conservation laws, a doublet with frequency, ω = ± cq , relative to the central Rayleigh line (ω = 0) appears in the spectrum of the scattered light analyzed by a six-pass tandem-Fabry–Perot interferometer. 66 , 83 Here, c denotes the sound velocity (longitudinal or transverse) in the medium, and the momentum magnitude q depends on the scattering geometry. In the so-called transmission geometry, q trans = (4π/λ)sin α, where α = θ/2, with θ being the scattering angle between k i and k s and λ (=532 nm) is the laser wavelength in vacuum.…”

“…For isotropic transparent material, a single acoustic phonon at frequency ω (=2π f ) is probed at a given wave vector, ± q = k i – k s selected by the scattering geometry, where ± q is for Stokes and anti-Stokes components, k i and k s are wavevectors of the incident and scattered light. Using energy and momentum conservation laws, a doublet with frequency, ω = ± cq , relative to the central Rayleigh line (ω = 0) appears in the spectrum of the scattered light analyzed by a six-pass tandem-Fabry–Perot interferometer. , Here, c denotes the sound velocity (longitudinal or transverse) in the medium, and the momentum magnitude q depends on the scattering geometry. In the so-called transmission geometry, q trans = (4π/λ)sin α, where α = θ/2, with θ being the scattering angle between k i and k s and λ (=532 nm) is the laser wavelength in vacuum.…”

“…From bulk studies of colloidal assemblies, it has been established that surprisingly attractive mechanical properties can result from a strengthening of the interparticle bonds, for example, by the addition of binders, sintering, or chemically interconnecting organic ligands on the surface of the materials. − Recently, we focused on the mechanical properties of supraparticles in the absence of such binders. Intuitively, it would be anticipated that such a material easily breaks upon compression due to the relatively weak interparticle contacts .…”

Optomechanic Coupling in Ag Polymer Nanocomposite Films

“… 4 This spectral modification has been already utilized in granular nanomaterials. 5 − 8 However, the application horizon is restricted in colloid-based materials in air as their infiltration by either liquid or solid medium renders the strong resonances (in air) weakly localized and hence hardly resolved.…”