Temperature Dependence of the Specific Absorption Rate of a Frozen Ferrofluid

Presented by:Nathaniel MosherKettering UniversityFlint, Michigan

Other contributors:R.J. Tackett, R.E. Kumon, C. Rablau, E. Perkins-Harbin,L. Wang, J.S. Thakur, and P.P. Vaishnava

Motivation

Sp

ecif

ic

Ab

sorp

tio

n R

ate

Temperature

?

Brownian Relaxation

Néel Relaxation

Specific Absorption Rate (SAR) of Ferrofluid

S𝐴𝑅 =𝑀𝑠𝑎𝑚𝑝𝑙𝑒

𝑚𝑁𝑃𝐶𝑖𝑐𝑒

∆𝑇

∆𝑡

𝑆𝐴𝑅 =𝑃

𝑚𝑁𝑃=𝜇0𝜋𝜒

′′𝑓𝐻02

𝑚𝑁𝑃

First Law of Thermodynamics in the Adiabatic Limit

Cice(T) per Yen, et. al. CRREL-81-10 (1981).

Turning off Brownian Relaxation by Freezing

VS

Fluid Dependent

Magnetic AnisotropyDependent

Brownian Relaxation Néel Relaxation

Synthesis of Fe3O4 via coprecipitation

Iron oxidenanoparticles

+NaOH

Add Dextran (15-20 kDa)

Dextran coated Fe3O4

Sonicate for 24 h

FeCl2.4H2O+

HCl(aq)

Add NH4OH

until pH 10

Iron oxide nanoparticles

FeCl3.6H2O+

HCl(aq)

Fe3O4

Nanoparticle

Dextran

Molecule

O2

protection

Sample is Fe3O4 with a 13.4 ±4.7 nm diameter

1.5 2.0 2.5 3.0

(44

2)

(53

1)

(44

0)

(33

3)

(42

2)

(33

1)

(40

0)

(22

2)

(31

1)

I (a

rb. unit

s)

d (Å)

(22

0)

Space Group: Fm3m

a = 8.36 Å

20 nm

0 5 10 15 20 25 30 350

5

10

15

20

25

Nu

mb

er o

f P

arti

cles

Nanoparticle diameter (nm)

𝐷 = 13.4 nm ± 4.7 nm

Experimental Setup for Hyperthermia

Copper coil

Amplification Circuit

TransformerC1 C2

Induction Heating System

Sample vial

Frozen ferrofluid

Thermometer

Fiber optic sensor

Computer

Thermal insulation

Temperature curves were recorded with/without alternate magnetic fields and then fitted

𝑆𝐴𝑅magnetic 𝑇 =𝑀sample

𝑚np𝐶ice 𝑇

∆𝑇magnetic

∆𝑡𝑆𝐴𝑅ambient 𝑇 =

𝑀sample

𝑚np𝐶ice 𝑇

∆𝑇ambient

∆𝑡

0 30 60 90 120 150 180 210 240 270-110

-100

-90

-80

-70

-60

-50

-40

Ambient

T (

°C)

t (s)

0 10 20 30 40 50 60 70 80-110

-100

-90

-80

-70

-60

-50

-40

150kHz

232kHz

T (

°C)

t (s)

Magnetic Field On Magnetic Field Off

SAR has significant ambient component that was subtracted

𝑆𝐴𝑅corrected 𝑇 = 𝑆𝐴𝑅magnetic 𝑇 − 𝑆𝐴𝑅ambient 𝑇

-110 -100 -90 -80 -70 -60 -50 -40

45

50

55

60

65

70

75

80

Uncorrected

Corrected

SA

R (

W/g

)

T (°C)

150 kHz

-110 -100 -90 -80 -70 -60 -50 -40

85

90

95

100

105

110

115

Uncorrected

Corrected

SA

R (

W/g

)

T (°C)

232 kHz

SAR shows a temperature dependence

-110 -100 -90 -80 -70 -60 -50 -4082

84

86

88

90

92

SA

R (

W/g

)T (°C)

232 kHz

~10 % decrease in SAR

over the temperature interval

-110 -100 -90 -80 -70 -60 -50 -40

44

46

48

50

52

54

56

SA

R (

W/g

)

T (°C)

150 kHz

~20 % decrease in SAR

over the temperature interval

0 10 20 30 40 50 60 70 80-110

-100

-90

-80

-70

-60

-50

-40

150kHz

232kHz

T (

°C)

t (s)

-110 -100 -90 -80 -70 -60 -50 -40

45

50

55

60

65

70

75

80

Uncorrected

Corrected

SA

R (

W/g

)

T (°C)

150 kHz

-110 -100 -90 -80 -70 -60 -50 -40

44

46

48

50

52

54

56

SA

R (

W/g

)

T (°C)

150 kHz

~20 % decrease in SAR

over the temperature interval

Summary

Conclusions

-110 -100 -90 -80 -70 -60 -50 -40

44

46

48

50

52

54

56

SA

R (

W/g

)

T (°C)

150 kHz

~20 % decrease in SAR

over the temperature interval• SAR shows

temperature

dependence

in Néel regime

• Ambient needs

correcting for

accurate results

Future Work

• Extending results to liquid samples

• Quantify Brownian contribution

Acknowledgements

We thank Research Council and the Provost of Kettering university Dr. James Zhang for the award of the Academic Research Fellowship and the travel grant.

Also, we thank the Society of Physics Students for providing a research grant as well as a travel grant

Questions?