thermal transport
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THERMAL
PROPERTIES
FISICA de
NANOMATERIALESAitor Lopeandia
Associated ProfessorDespatx: C5-250Department of Physics
Universitat Autnoma de Barcelona
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OUTLINE
Thermoelectricity: Seebeck and Peltier effect. Figure of merit. Infuenceof dimensionality. Applications. Experimental.
Thermal transport: Macroscopic theory. Fouriers LawMicroscopic Theory: Kinetic approach
Phonons: Macroscopic theory. Fouriers LawMicroscopic Theory: Kinetic approach
Specific heat: Lattice and electronic contributions. Examples
Phase transitions of low-dimensional materials: Melting behaviourof nanoparticles. Curie transition. Glass transition. Experimental: Calorimetry
Thermal conductivity: Influence of dimensionality. Experimental
THERMAL PROPERTIES OF NANOMATERIALS
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BIBLIOGRAPHY / GENERAL REFERENCES
Nanoscale Energy Transport and Conversion, Gang Chen.
NanoMicroscale Heat Transfer, Zhang.
Solid State Physics, Ashcroft and Mermin.
Introduction to Solid State Physics. Charles Kittel.
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READING TASK: EFFECTS ON HEAT CAPACITY DUE TO FINITE SIZE DIMENSION
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1 SESIN
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Shall we talk
about enegy
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Perspectiva energtica?
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+ 50% demanda en el 2030
Consumo energtico mundial petrleocarbngas
nuclear
hidro28%
36%
23%
6% 5%
88% fuentes fsiles
Consumo energtico global
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Poblacin
7000 millones
2 kWh por
persona/dia!!!
15 TW
En 2008, la potencia energtica promedio consumida a nivel
mundial fue 15 TW = 1,5x1013 W ; en energa 474 exajulios474x1018julios
Consumo energtico global
m= 70 Kg
v= 20 km/h
100-200 Wdurante 1h
20-10 horas
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Flujo de ENERGTICO
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Calentamiento Global I
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Evolucin emisiones CO2
SOURCE: http://climate.nasa.gov/evidence
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Cmo vamos de reservas?
2004 Petrleo(x 1000 M barriles)
Gas(x1000 Millones de m3)
Carbn(M tons)
Reservas 1210 182.000 900.000Consumo 30 2950 6.4Aos 40 62 132
0
400
800
1200
1600
1860 1900 1940 1980 2020 2060
Exajou
les
otras
Fsil
NuclearHidroelctrica
Renovables
DesconocidasEUROPEANCOMMISSION
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3.000.000 AC 3.000 BC
Opcin A
Opcin B
Consumocombustibles
fsiles
Toca elegir camino !!
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AHORRO/EFICIENCIA ALMACENAMIENTOGENERACIN/CONVERSIN
Fotovoltaica
Pilas de combustible
Trmica solar
Termoelctricosetc
Aislamiento trmico
Solid State Lighting
Termoelctricos
Cables superconductores energy harvesting
etc.
Almacenamiento H2Bateras de ltioUltracondensadores
etc
ENERGA EFICIENTE
CIENCIA DE MATERIALES
NANOTECNOLOGA
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Qu papel puede jugar laTERMOELECTRICIDAD ?
FUENTE CALOR ELECTRICIDAD
GENERACIN
REFRIGERACIN
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Thomas Seebeck1770-1831
Jean Charles Peltier1785-1845
Trmica Elctrica Elctrica Trmica
Efecto Seebeck
--1821
Efecto Peltier
-- 1834
Calor corriente elctrica Corriente refrigeracin
Termoelectricidad
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Efecto Seebeck
ntipoyptipoTT
V
00;
12
Generacin
S C ff
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Seebeck Coefficient
S b k C ffi i f l
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Seebeck Coefficient for metals
S b k C ffi i t f t l
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Seebeck Coefficient for metals
Ef t P lti f
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Efecto Peltier
Cuando circula una corriente por una barrase crea una T entre los extremos de la barra
IQ /
Coeficiente Peltier
Energa
MetalMetal
Semicond.
Refrigeracin
iEf t P lti
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imageEfecto Peltier
Ef t P lti
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Efecto Peltier
P lti fi i t
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Peltier coeficient
f f d
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Eficiencia y figura de merito ZT
hch
ch
TTZT
ZT
T
TT
/1
11h
Eficiencia termoelctrica
Eficiencia de una mquina trmica
conductividad trmica conductividad elctrica
S Coeficiente Seebeck
h
ch
entrada
salida
T
TT
E
E
E
)(W
dasuministra
neto h
TS
ZT
2
Figura de mrito Powerfactor
fi i i fi d i
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From D.J. Paul
Eficiencia y figura de merito ZT
Figure of merit ZT
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Figure of merit ZT
region of interest
ZT= K
S2
T
P i i
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Pero vs mquinas trmicas.
Simple Escalable Portable
P i i
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Pero vs mquinas trmicas.
Aplicaciones actuales de la termoelectricidad
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HeatGenerator
Calor til
Calor de desecho
PowerRecovery
Device
Electricidad
Calor
Generador
Potencia
RecuperacinDispositivo
Aplicaciones actuales de la termoelectricidad
SIMPLICIDAD PORTABILIDAD o DESLOCALIZACIN
Aplicaciones actuales de la termoelectricidad
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Generador Termoelctrico de Radioistopos
Aplicaciones actuales de la termoelectricidad
Desintegracin radioactivadel 238Pu en partculas alfa.
Aplicaciones actuales de la termoelectricidad
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12V refrigerador/calefactor de tazas/latas Sistema de control deTemperatura
en vehculos
Sistemas de visin nocturna
por infrarrojosRefrigeracin de lseres
Reloj termoelctrico
Aplicaciones actuales de la termoelectricidad
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Evidentemente este NO es elFIN DE LA HISTORIA !!!
EMPEZAMOS LA BSQUEDADEL GRIAL!!
ZT>2
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2 SESIN
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Evidentemente este NO es elFIN DE LA HISTORIA !!!
EMPEZAMOS LA BSQUEDADEL GRIAL!!
ZT>2
CINCIA DE MATERIALES
Ci i d M t i l
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4000 3000 2000 1000 19601 1000 1900 1990 2010
Edat de pedra
(~35000 anys)
AC DC
Edat de bronze
(~ 1800 anys)
Edat de ferro
(~ 3300 anys)
Formig i acer
(~ 60 anys)
Edat del polmer
Edat del silici
Edat de la informaci
NANO?
CINCIA DE MATERIALESCiencia de Materiales
Dimensionalidad y ZT
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Dimensionalidad y ZTEarly90s Dresselhauss
Hicks, L. D. & Dresselhaus, M. S. Thermoelectric figure of merit of a one-dimensional
conductor. Phys. Rev. B 47, 1663116634 (1993).
S 2Dimensionalidad y ZT
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TS
ZTphe
Dimensionalidad y ZTLow dimensionality provides:
1.- Quantum size effects: Enhancement of the electron density ofstates increase of the Seebeck coefficient.
D E dS
E kS E
( )( )
( )
4
13
Dimensionalidad y ZT S2
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Hicks, L. D. & Dresselhaus, M. S. Thermoelectric figure of merit of a one-dimensional
conductor. Phys. Rev. B 47, 16631
16634 (1993).
Low dimensionality provides:
2.- Increase the boundary scattering of phonons at the barrier-wellinterfaces, without as large increase in electron scattering at theinterface. If the width of the semiconductor is smaller than the mean
free path of phonons and larger than that of electrons or holes
Dimensionalidad y ZT TSZTphe
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Evolucin de la ZT
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Evolucin de la ZT
Evolucin de la ZT
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Evolucin de la ZT
Vineis et al.Advanced materials, 22, 2010
The transistor
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John Bardeen, William Shockley and WalterBrattain at Bell Labs, 1948.
A stylized replica of the firsttransistor invented at Bell Labs onDecember 23, 1947.
The transistor
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Energy disipation and transport in nanoscaled devices
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gy p p
Eric Pop,
EXAMPLE
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Venkatasubramanian et al. Nature, (2001) 597-.
Localized and high-speed heating/cooling
with thin film devices
EXAMPLE
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Example: Phonon-blocking/electron transmitting interfaces in Si/Ge and other superlattices
Use of the acoustic mismatch between the superlattice components to reduce ph.
Bi2Te3/Sb2Te3 superlattices show significantly reduced ph.
Venkatasubramanian et al. Nature, (2001) 597-.
If the mean free path of phonons spans multiple interfaces in a superlattice
Phonon band gaps may appear
Phonon dispersion relation is modified.
Localized and high-speed heating/coolingwith thin film devices
Aplicaciones --- Nanorefrigerador
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p g
Si substrate
SL
Metal contact
Insulating
layer
Si substrateSi substrate
SL
Metal contact
Insulating
layer
Zona caliente~700 W/cm2
microrefrigerador con ZT~0.5enfriamiento 1000 W/cm2 en 15oC
Integracin de SiGe en circuitos integrados base Silicio
Thermoelectric efficiency in Silicon (Hochbaum et al. Nature 451 (2008)
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Microgenerator using Si nanowires
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g g
Davila et al. NANO ENERGY 1, 812-819 (2012)
Microgenerator using Si thin films
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g g
Gnams work. NANO ENERGY (2014)