Nanowire Thermoelectrics: An Approach for Enhancing ZT. Nanostructured silicon thermoelectrics 2019-01-09

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Silicide Nanowires and Nanoparticles for Thermoelectrics

Nanowire Thermoelectrics: An Approach for Enhancing ZT

An emerging topic is flexible devices, where the use of bulk inorganic materials is precluded by their inherent rigidity. The catalyst retained its high activity after four photoreaction cycles. It is found that metallic bismuth nanoparticles are well covered by porous silica Bi SiO2 to form hybrids. The fabrication and measurement methodologies are also explained in this chapter. We are also developing unconventional synthetic pathways to bulk quantity nanostructured silicide and silicon materials to enable the practical applications of these nanomaterials in high performance thermoelectrics. Although the bulk allotropy of elemental solids is fairly well understood, it remains challenging to reliably produce an allotrope at the nanoscale that has a different crystal structure and accompanies a change in physical properties for specific applications. Here, atom probe tomography is used in conjunction with a first-principles simulation to investigate the 3D structure and chemistry of InGaAs nanowires, and reveals i the nanowires form a spontaneous core-shell structure with a Ga-enriched core and an In-enriched shell, due to different growth mechanisms in the axial and lateral directions; ii the shape of the core evolves from hexagon into Reuleaux triangle and grows larger, which results from In outward and Ga inward interdiffusion occurring at the core-shell interface; and iii the irregular hexagonal shell manifests an anisotropic growth rate on {112}A and {112}B facets.

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Enhanced Thermoelectric Properties in Bulk Nanowire Heterostructure

Nanowire Thermoelectrics: An Approach for Enhancing ZT

Several promising thermoelectric materials with intrinsically low thermal conductivities are introduced. Both ρ330 and ρ110 are closely proportional to T2 between 8 and 20°K. From the direct thermal conductivity measurement via suspended microstructure platform, the coherent scattering mechanism effectively reduces the thermal conductivity of silicon by a factor of two from the nanowire value. Accordingly, a model in terms of the core-shell shape and chemistry evolution is proposed, which provides fresh insights into the growth of these nanowires. The temperature dependence of the coherence length derived from the weak antilocalization effect using the Hikami—Larkin—Nagaoka model is consistent with that from the universal conductance fluctuations theory. In support of this mechanism, the electron and hole mobilities at 4.

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(PDF) Nanowire Thermoelectrics: An Approach for Enhancing ZT

Nanowire Thermoelectrics: An Approach for Enhancing ZT

In the last part of the thesis Chapter 4 , the phononic nanomesh approach is extended to a nanomesh superlattice structure. Here we report on the vapor-transport growth and thermoelectric study of high-quality single-crystalline PbTe and PbSnTe nanowires. Moreover, Bi Fe3O4 could be separated and collected easily using an external magnetic field. The results of the experiments indicated that the diameters of the nanospheres were controlled within approximately 100—300 nm. In this context, a particular emphasis has been made on electronic confinement effects in bismuth nanostructures or nanobismuth. The electrical resistivities of four bismuth nanowires with diameter of 356 nm, 376 nm, 622 nm, and 633 nm were measured in the temperature range from 4.

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Thermoelectrics

Nanowire Thermoelectrics: An Approach for Enhancing ZT

Most of these methods have demonstrated single-crystal nanowire growth of a quality unmatched in bulk Bi. Among these alloys, PbSnTe hosts unique topological surface states that may have improved thermoelectric properties. Publications 1 Szczech, J; Schmitt, A. We have investigated various kinds of nanowires Si, Bi2Te3, SiGe in order to evaluate the influence of the nanostructuration on their thermal conductivity. In essence, the phononic metamaterial approach essentially creates a new class of silicon-based material with distinct phonon properties, in other words, the theoretical lower limit of thermal conductivity of silicon based on bulk dispersions no longer applies to the phononic nanomeshes.

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Thermoelectric materials: Energy conversion between heat and electricity

Nanowire Thermoelectrics: An Approach for Enhancing ZT

The carrier density, constant with temperature, is 2. Some anisotropy in thermal properties due to particle shape and the direction of compression was also observed. Her main research interests focus on the fabrication and properties of thermoelectric materials. These results suggest that the metallic surface states in Bi nanoribbons should be topologically protected which can provide key information in understanding the surface properties of Bi in nanometer scale. By extending this approach to other nanostructured systems, it represents a key step toward low-cost solution-processable nanomaterials without heavy doping level for high-performance thermoelectric energy harvesting. Five reversibly thermochromic bismuth-based inorganic-organic hybrid materials were synthesized via facile one-step condensation reactions between triphenylbismuth and four arenedithiols and a diselenol. However, it is difficult to determine the temperature dependence of the resistivity in the low-temperature region, in which a much higher temperature coefficient is indicated, especially at temperatures lower than 50 K.

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Nanostructured silicon thermoelectrics

Nanowire Thermoelectrics: An Approach for Enhancing ZT

This presentation will review recent measurement results of thermoelectric properties of individual bismuth telluride nanoplates, semiconductor nanowires, and silicide nanocomposites. At the end, a discussion of future possible strategies is proposed, aiming at further thermoelectric performance enhancements. The general silicide nanowire synthesis we have developed enabled us to make the first nanowire of any Nowotny chimney ladder phase, a higher manganese silicide MnSi 1. Free standing bismuth nanowires of two different diameters, 250 nm and 20 nm, were synthesized through a vapor deposition process and compressed into pellets. All eight magnetoresistance coefficients have an approximate T-2 dependence, while the large Hall term ρ23,1 decreases approximately 7% as the temperature increases from 6 to 16°K. This work explores the effects of anisotropy and particle size and shape on the thermal transport behavior in compressed materials formed from bismuth nanowires. For carriers of differing charge or of sufficient anisotropy, this mechanism contributes to the resistivity.

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Enhanced Thermoelectric Properties in Bulk Nanowire Heterostructure

Nanowire Thermoelectrics: An Approach for Enhancing ZT

The as-synthesized samples were characterized by the powder X-ray diffraction, scanning electron microscope, transmission electron microscope, the Brunauer-Emmett-Teller surface areas and X-ray photoelectron spectroscopy. The phase coherence length was obtained from the fluctuation pattern of the magnetoresistance below 40 K using universal conductance fluctuation theory. The microparticle pellets showed a higher degree of anisotropy as well as higher thermal conductivity. This review summaries the thermoelectric phenomena, applications and parameter relationships. She started her doctoral research as a member of Li-Dong Zhao's group in 2014. His research interests include the thermoelectric materials, superconductors and thermal barrier coatings.

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Bottom

Nanowire Thermoelectrics: An Approach for Enhancing ZT

Moreover, by controllable exposing the ribbons to ambient environment 1 atm and room temperature , the metallic surface states were found to be robust to the oxidation although the carrier density in the surface states are modified after the exposures. B 2006, 110, 18142-18146 4 Schmitt, A. In Chapter 3, the phonon transport mechanism of the silicon nanomesh, a new class of phononic metamaterial, is investigated. Given the excellent stability and catalytic activity of the Bi Fe3O4 nanocomposite, it displays high potential for a broad range of applications. This is the first report of the anisotropy investigating all the thermoelectric-transport properties of single-crystalline Bi nanowires. Here, we report the angular-dependent magnetoresistance measurements in single-crystal Bi nanoribbons, and found that both the low-field weak antilocalization behavior and the high-field angle-dependent SdH oscillations follow exactly the 2D character, indicative of the 2D metallic surface states which dominate the transport properties of thin Bi nanoribbons.

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