Nanophononic metamaterials

Patent metadata

Field	Value
Publication number	US-9417465-B2
Application number	US-201414247228-A
Country	US
Kind code	B2
Filing date	Apr 7, 2014
Priority date	Apr 7, 2013
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

Nanophononic metamaterials and methods for reducing thermal conductivity in at least partially crystalline base material are provided, such as for thermoelectric energy conversion. In one implementation, a method for reducing thermal conductivity through an at least partially crystalline base material is provided. In another implementation, a nanophononic metamaterial structure is provided. The nanophononic metamaterial structure in this implementation includes: an at least partially crystalline base material configured to allow a plurality of phonons to move to provide thermal conduction through the base material; and at least one nanoscale locally resonant oscillator coupled to the at least partially crystalline base material. The at least one nanoscale locally resonant oscillator is configured to generate at least one vibration mode to interact with the plurality of phonons moving within the base material and slowing group velocities of at least a portion of the interacting phonons and reduce thermal conductivity through the base material.

First claim

What is claimed is:

1. A method for reducing thermal conductivity through an at least partially crystalline base material, the method comprising:
generating a plurality of local vibration modes within the at least partially crystalline base material by the oscillation of at least one nanoscale locally resonant oscillator coupled to the base material;
interacting at least one of the local vibration modes created by the at least one nanoscale locally resonant oscillator with a plurality of phonons moving within the base material slowing group velocities of at least a portion of the interacting phonons.

2. The method of claim 1 wherein the plurality of local vibration modes interact with an underlying lattice dispersion of the at least partially crystalline base material and the interaction of the at least one vibration mode and the plurality of phonons reduce the group velocities of the at least a portion of the interacting phonons at and near a coupling in a frequency between the vibration modes and the plurality of phonons.

3. The method of claim 1 wherein the at least partially crystalline base material comprises at least one of the group comprising: a semiconductor material, a silicon semiconductor material, a germanium semiconductor material, a gallium arsenide semiconductor material, a superlattice material, a nanocomposite material, a nanostructured nanocomposite material, a thermoelectric material, a nanostructured thermoelectric material, a nanostructured thermoelectric material including one or more holes or inclusions in a periodic or random spatial distribution within a body of the nanostructured thermoelectric material, a nanophononic crystal.

4. The method of claim 1 wherein the at least one nanoscale locally resonant oscillator comprises at least one nanoscale pillar extending from at least one surface of the base material.

5. The method of claim 4 wherein the extension of the at least one nanoscale locally resonant oscillator from at least one surface of the base material improves the thermoelectric energy conversion figure of merit, ZT, by freeing the at least partially crystalline base material from local resonators acting as internal scatterers that hinder motion of electrons and cause a reduction in electrical conductivity of the base material.

6. The method of claim 1 wherein the at least one nanoscale locally resonant oscillator comprises at least one oscillator disposed within the at least partially crystalline base material.

7. The method of claim 1 wherein the at least partially crystalline base material comprises a plurality of repeated unit cells, each repeated unit cell having at least one nanoscale pillar locally resonant oscillator extending from at least one surface of the repeated unit cell of the base material.

8. The method of claim 7 wherein each repeated cell unit comprises a plurality of nanoscale pillar locally resonant oscillators extending from a surface of the repeated unit cell, the plurality of nanoscale pillar locally resonant oscillators varying in at least one of the group comprising: height, cross-sectional area, shape, orientation, material, material composition, material distribution and surface roughness.

9. The method of claim 4 wherein a plurality of nanoscale pillar locally resonant oscillators are disposed randomly across a surface of the base material.

10. The method of claim 1 wherein the at least partially crystalline base material comprises a plurality of repeated unit cells, each repeated unit cell having at least one nanoscale locally resonant oscillator disposed within the repeated unit cell of the base material.

11. The method of claim 10 wherein each repeated cell unit comprises a plurality of nanoscale locally resonant oscillators disposed within the repeated unit cell, the plurality of nanoscale locally resonant oscillators varying in at least one of the group comprising: shape, size, orientation, surface roughness and material.

12. The method of claim 6 wherein a plurality of nanoscale locally resonant oscillators are disposed randomly within the base material.

13. The method of claim 1 wherein the at least one nanoscale locally resonant oscillator comprises an oscillator material the same as the at least partially crystalline base material.

14. The method of claim 1 wherein the at least one nanoscale locally resonant oscillator comprises at least one oscillator material different than the at least partially crystalline base material.

15. The method of claim 1 wherein multiple nanoscale locally resonant oscillators comprise at least one oscillator material within at least one locally resonant oscillator different than the at least partially crystalline base material.

16. The method of claim 1 wherein the at least partially crystalline base material comprises at least one of the group comprising: a nanoscale single dimension material, a nanoscale wire-shaped base material, a nanoscale rod-shaped base material, a nanoscale two dimensional base material, a nanoscale thin-film base material, a nanoscale membrane base material, a surface with material extending into its depth, a three dimensional base material and a bulk material.

17. The method of claim 1 wherein at least one feature size in the base material including one or more of the group comprising a thickness of a thin film, a thickness of a membrane, a cross-sectional size of a wire, a cross-sectional size of a rod, a size of the locally resonant oscillators and a spacing distance between the locally resonant oscillators is on the order of 1 nm to 500 nm.

18. The method of claim 1 wherein at least one feature size in the base material including one or more of the group comprising a thickness of a thin film, a thickness of a membrane, a cross-sectional size of a wire, a cross-sectional size of a rod, a size of the locally resonant oscillators and a spacing distance between the locally resonant oscillators is less than a mean free path in the base material.

19. The method of claim 1 wherein the type, geometrical and material features of the at least one nanoscale locally resonant oscillator and the type, geometrical and material features of the at least partially crystalline base material are selected in a manner that allows the interacting local resonances to have the following characteristics: be numerous and be well spread out across a phonon spectrum of the base material starting within a frequency range corresponding to as low as that of acoustic branches of the base material.

20. A nanophononic metamaterial structure comprising:
an at least partially crystalline base material configured to allow a plurality of phonons to move to provide thermal conduction through the base material;
at least one nanoscale locally resonant oscillator coupled to the at least partially crystalline base material,
wherein the at least one nanoscale locally resonant oscillator is configured to generate at least one vibration mode to interact with the plurality of phonons moving within the base material and slowing group velocities of at least a portion of the interacting phonons and reduce thermal conductivity through the base material.

21. The nanophononic metamaterial structure of claim 20 wherein the plurality of local vibration modes interact with an underlying lattice dispersion of the at least partially crystalline base material and the interaction of the at least one vibration mode and the plurality of phonons reduce the group velocities of the at least a portion of the interacting phonons

Assignees

• Univ Colorado Regents

Inventors

• Hussein Mahmoud I
• Davis Bruce L

Classifications

• G02F1/015

  based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction (G02F1/03 takes precedence) · CPC title

• B82Y30/00

  Nanotechnology for materials or surface science, e.g. nanocomposites · CPC title

• G02F1/0072

  Mechanical, acoustic, electro-elastic, magneto-elastic properties · CPC title

• Y10S977/833

  Thermal property of nanomaterial, e.g. thermally conducting/insulating or exhibiting peltier or seebeck effect · CPC title

• H03H2009/155

  using MEMS techniques · CPC title