Heat conduction tuning using the wave nature of phonons

The world communicates to our senses of vision, hearing and touch in the language of waves, as the light, sound, and even heat essentially consist of microscopic vibrations of different media. The wave nature of light and sound has been extensively investigated over the past century and is now widely used in modern technology. But the wave nature of heat has been the subject of mostly theoretical studies, as its experimental demonstration, let alone practical use, remains challenging due to the extremely short wavelengths of these waves. Here we show a possibility to use the wave nature of heat for thermal conductivity tuning via spatial short-range order in phononic crystal nanostructures. Our experimental and theoretical results suggest that interference of thermal phonons occurs in strictly periodic nanostructures and slows the propagation of heat. This finding broadens the methodology of heat transfer engineering by expanding its territory to the wave nature of heat

Review of coherent phonon and heat transport control in one-dimensional phononic crystals at nanoscale

Phononic crystals are the acoustic analogs of photonic crystals and aim at manipulating phonon transport using phonon interference in periodic structures. While such periodic structures are typically two-dimensional, many applications require one-dimensional (1D) wire-like or bulk structures instead. In this Research Update, we summarize the past decade of theoretical and experimental studies of coherent control of phonon and heat transport in one-dimensional phononic crystals. At the hypersonic frequencies, phononic crystals successfully found applications in optomechanical devices at the microscale. However, at higher terahertz frequencies, experimentalists struggle to demonstrate that coherent thermal transport at room temperature is possible at length scales of hundreds of nanometers. Although many theoretical works predict a reduction in the thermal conductivity in 1D phononic crystals due to coherent effects, most observations conclude about the incoherent nature of heat conduction at least at room temperature. Nevertheless, experiments on superlattices and carbon nanotubes have demonstrated evidence of coherent heat conduction even at room temperature in structures with the periodicity of a few nanometers. Thus, further miniaturization and improving fabrication quality are currently the main challenges faced by 1D phononic nanostructures

The integrated effect on properties and composition of high-paraffin oil sludge

The study is devoted to the integrated effect of acoustic treatment and addition of an inhibitor on viscosity-temperature properties and n-alkane composition in high-paraffin oil sludge. Ultrasonic treatment for 1 minute and addition of the inhibitor at the concentration of 0.05% wt. decrease viscosity by 10 times and pour point by 8°С

Materials Today Physics

Thermal transport at the nanoscale level is attracting attention not only because of its physically interesting features such as the peculiar behavior of phonons due to their pronounced ballistic and wave-like properties but also because of its potential applications in alleviating heat dissipation problems in electronic and optical devices and thermoelectric energy harvesting. In the last quarter-century, researchers have elucidated the thermal transport properties of various nanostructured materials, including phononic crystals (PnCs): artificial periodic structures for phonons. PnCs are excellent platforms for investigating thermal transport owing to their well-defined structural parameters. In addition, it is interesting to control thermal transport by interference, as demonstrated in the low-frequency regime with elastic waves and sounds. In this article, we focus on high-frequency phonons and review the thermal transport in semiconductor PnCs. This comprehensive review provides an understanding of recent studies and trends, organized as theoretical and experimental, in terms of the quasiparticle and wave aspects

Propriétés optiques des InAs/InP hétérostructures de nanofils

This thesis is focused upon the experimental investigation of optical properties of InAs/InP NW heterostructures by means of photoluminescence (PL) spectroscopy. First, it was demonstrated that the host-substrate may have significant impacts on the optical properties of pure InP NWs, as due to the strain, created by the difference in the LTECs of the NWs and the host-substrate, as due to some other surface effects. Next, the optical properties of such nanowire heterostructures as quantum rod (QRod) and radial quantum well (QWell) NWs were investigated. The features of obtained spectra were explained using theoretical simulation of similar NW heterostructures. The polarization properties of single InP NWs, InAs/InP QWell-NWs, InAs/InP QRod-NWs and ensemble of the InAs well ordered NWs were studied at different temperatures. Further, we report on the evidences of the strain-induced piezoelectric field in WZ InAs/InP QRod-NWs. Finally, PL QE of NW heterostructures and their planar analogues are measured by means of a PL setup coupled to an integrating sphere. In general, the obtained knowledge of the optical and mechanical properties of pure InP NWs and InAs/InP NW heterostructures will improve understanding of the electrical and mechanical processes taking place in semiconductor NW heterostructures and will serve for the fabrication of future nanodevice applications.Ce travail de thèse porte sur l’étude des propriétés optiques de nanofils InP et d’hétérostructures nanofils InAs/InP épitaxiés sur substrat silicium. Ce travail de thèse a été réalisé principalement dans le cadre du projet ANR «INSCOOP»

Phonon and heat transport control using pillar-based phononic crystals

Phononic crystals have been studied for the past decades as a tool to control the propagation of acoustic and mechanical waves. Recently, researchers proposed that nanosized phononic crystals can also control heat conduction and improve the thermoelectric efficiency of silicon by phonon dispersion engineering. In this review, we focus on recent theoretical and experimental advances in phonon and thermal transport engineering using pillar-based phononic crystals. First, we explain the principles of the phonon dispersion engineering and summarize early proof-of-concept experiments. Next, we review recent simulations of thermal transport in pillar-based phononic crystals and seek to uncover the origin of the observed reduction in the thermal conductivity. Finally, we discuss first experimental attempts to observe the predicted thermal conductivity reduction and suggest the directions for future research

Coherent Thermal Conduction in Silicon Nanowires with Periodic Wings

Artificial periodic nanostructures, known as phononic crystals, promise to control the thermal properties of nanostructures in the coherent regime, which can be achieved in semiconductors at low temperatures. Here, we study coherent thermal conduction in silicon nanowires with added periodic wings at sub-Kelvin temperature. Our simulations show that the added periodic wings flatten the phonon dispersion and thus reduce the thermal conductance. We investigate the dependence of this reduction on the size of the wings and conclude that the reduction is mainly caused by the periodicity of the wings, rather than by local resonances in them. These findings help to better understand the mechanisms controlling coherent heat conduction in periodic resonant nanostructures