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
Specific Absorption Rate (SAR) of Ferrofluid
S๐ด๐ =๐๐ ๐๐๐๐๐
๐๐๐๐ถ๐๐๐
โ๐
โ๐ก
๐๐ด๐ =๐
๐๐๐=๐0๐๐
โฒโฒ๐๐ป02
๐๐๐
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 Nรฉel 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 ยฑ4.7 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 (ร )
(22
0)
Space Group: Fm3m
a = 8.36 ร
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)
๐ท = 13.4 nm ยฑ 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
๐๐ด๐ magnetic ๐ =๐sample
๐np๐ถice ๐
โ๐magnetic
โ๐ก๐๐ด๐ ambient ๐ =
๐sample
๐np๐ถice ๐
โ๐ambient
โ๐ก
0 30 60 90 120 150 180 210 240 270-110
-100
-90
-80
-70
-60
-50
-40
Ambient
T (
ยฐC)
t (s)
0 10 20 30 40 50 60 70 80-110
-100
-90
-80
-70
-60
-50
-40
150kHz
232kHz
T (
ยฐC)
t (s)
Magnetic Field On Magnetic Field Off
SAR has significant ambient component that was subtracted
๐๐ด๐ corrected ๐ = ๐๐ด๐ magnetic ๐ โ ๐๐ด๐ ambient ๐
-110 -100 -90 -80 -70 -60 -50 -40
45
50
55
60
65
70
75
80
Uncorrected
Corrected
SA
R (
W/g
)
T (ยฐC)
150 kHz
-110 -100 -90 -80 -70 -60 -50 -40
85
90
95
100
105
110
115
Uncorrected
Corrected
SA
R (
W/g
)
T (ยฐC)
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 (ยฐC)
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 (ยฐC)
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 (
ยฐC)
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 (ยฐC)
150 kHz
-110 -100 -90 -80 -70 -60 -50 -40
44
46
48
50
52
54
56
SA
R (
W/g
)
T (ยฐC)
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 (ยฐC)
150 kHz
~20 % decrease in SAR
over the temperature intervalโข SAR shows
temperature
dependence
in Nรฉel regime
โข Ambient needs
correcting for
accurate results
Future Work
โข Extending results to liquid samples
โข Quantify Brownian contribution