Novel magnetocaloric materials formagnetic cooling applications

M. Katter Vacuumschmelze GmbH & Co. KG

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outline

• introduction

• thermodynamic basics of magnetic cooling

• LaFeSi-based alloys produced by powder metallurgy

• prototypes and applications

• conclusions

page 3

magnetocaloric effect: discovered by Wartburg 1881magnetic cooling: Debye and Giauque 1926

page 4

magnetic refrigeration at room temperature

Features

no compressorno green house gaseshigh efficiencynew magnetocaloric materialspermanent magnets

Applications

industrial coolingair conditioningfood refrigeration

O. Tegus, E. Brück, K.H.J. Buschow, F.R. de Boer, Nature, vol. 415 (2002) 150.

„compression“

„expansion“

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motivation for magnetic cooling

- > 180 Mio. new cooling devices every year, needing ten-thousand tonsof environmentally harmful coolants (HFCs), 28-45% of CO2 equivalent in 2050 (Velders 2009)R134a banned in newly developed cars since 2011 in Europe

magnetic cooling uses solid, environmentally friendly coolants

- alternative CO2-compressors need pressures > 100 barmagnetic cooling devices need only 1-2 bar

- gas compression cycles reach ca. 40 % of Carnot-efficencymagnetic coolers reached ca. 60% in laboratory

- compressors are noisymagnetic cooling devices are silent

magnetic cooling cycle for a single magnetocaloric material

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COP = 90

ΔS = 15 J/kgK

magnetic cooling cycle for a set of 10 magnetocaloric materials

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COP = 10

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„Giant“ magnetocaloric effect

K. Gscneidner (2007)

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new magnetocaloric materials

K. Gscneidner (2007)

accessable withNd-Fe-B magnets

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Designs for active magnetic regenerators

J.A. Barclay and S. Sarangi 1984 in A.M. Tishin and Y.I. Spichkin 2003

large pressure drops in powder beds?

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- casting- anneal, e.g. 1080°C/140 h- optionally load with hydrogen

⇒ long annealing times, ⇒ with hydrogen only powder

- melt spinning- short anneal, e.g. 1000°C/2 h

⇒ only flakes or powder, no shaped parts for heat exchangers

conventional preparation of La(Fe,Si)13

S. Fujieda et al. 2005F.X. Hu et al. 2005 (with Co)

O. Gutfleisch et al. 2005S. Hirosawa et al. 2006

K. Niitsu 2012

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Powder Metallurgical (PM) Processing of La-Fe-Si

P

Vacuum Induction Alloying and Casting

Crushing

Milling

Blending

Pressing:CIP - die

isostatic pressing

die-pressing

elemental powders

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Powder Metallurgical (PM) Processing of La-Fe-SiP

Pressing:CIP - die

die-pressing

Isostaticpressing

Reactive Sintering

Machining and Surface Finishing

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set of La-Fe-Co-Si parts for a magnetic regenerator

0

1

2

3

4

5

6

7

8

9

10

-20 -10 0 10 20 30 40 50 60 70 80temperatur (°C)

entr

opy

chan

ge -Δ

Sm

(J/k

gK)

ΔH = 16 kOe

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MFP-1056, TC = -14°C

-0,50

-0,40

-0,30

-0,20

-0,10

0,00

0,10

0,20

-100 -50 0 50 100 150 200

temperature [°C]

stra

in [%

]

magnetocaloric passive statea-Fe = 71 %

magnetocaloric active statea-Fe = < 2%

reversible conversion

good machinability

good magnetocaloric properties

0,0

2,0

4,0

6,0

8,0

10,0

230 240 250 260 270 280

temperature T (K)

- ∆S

m (J

/kgK

)

4,0

8,0

12,0

16,0

Hmax (kOe)

Thermally induced Decomposition and Recombination (TDR) process

difficult to machine

tensile stress=> cracks

Katter et al. 2009

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La-Fe-Co-Si blocks and platelets with thicknesses of 0.25 – 1.0 mm

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monolithic La-Fe-Co-Si regenerators with 0.2 mm slots

Linearly graded LaFeCoSi parts

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P

1. Compaction of powderswith different Co content

2. Sintering and diffusion treatmentto generate linearly varying TC

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sintered La-Fe-Mn-Si-Hx powders

particle sizeca. 400 µm

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prototype for wine cooler, HEIG, Yverdons le Bains, CH, M. Balli (2010)

regenerator with Gd

regenerator with LaFeCoSi

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prototype of Astronautics, USA

with La-Fe-Si-Hx powder from VAC400 W cooling power at 14°C temperature span

best performance up to now!

S. Russek(2010)

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magnetocaloric cooling systemmaterials

magnet assemblies

thermo-hydraulicsmechanics

Cooltech Applications (2008)

ca. 0,3 kg La-Fe-Si +ca. 1,5 kg Nd-Fe-Bper kW cooling power

Astronautics (2001)

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room temperautre magnetic refrigeration prototypes

K. Gscneidner (2007)

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conclusion

- magnetocaloric effect is the temperature change of a material in dependence on a magnetic field change

- La(Fe,Co,Si)13 and La(Fe,Si)13Hx with tunable Curie temperaturecan be produced by powder metallurgy

- prototypes for application at room temperature under construction

- there is a huge market for magnetic cooling, also due to upcomingenvironmental legislation for HFCs