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CIMTEC 2008
Ferrofluids
andMagnetorheological Fluids
Ladislau Vks
Laboratory of Magnetic Fluids
Center for Fundamental and Advanced Technical ResearchRomanian Academy-Timisoara Branch, Timisoara, Romania
and
National Center for Engineering of Systems with Complex Fluids
University Politehnica of Timisoara, Timisoara, Romania
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OUTLINE
Short history of the field
Magnetically controllable fluids
Magnetic nanoparticles and ferrofluids, application orientated synthesis
Colloidal stability and structural processes
Magnetic and flow properties
Magnetorheological fluids, main types and composition
Structural processes and magnetorheological behavior
New type of composite materials
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FLUIDITY + MAGNETIC PROPERTIES = ??
New kind of materials, new phenomena
The beginning
Magnetorheological fluid National Bureau of Standards Technical News Bulletin 1948;32(4):54-60.
J. Rabinow Proceedings of the AIEE Trans., 1948. 67. p. 1308-1315.
Ferrofluid/Magnetic fluid T.L. OConnor, Belgian Patent 613,716 (1962)
S. Papell (NASA), US Patent 3,215,572 (1965)
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Magnetically controllable fluids
Ferrofluids, magnetic (nano)fluids
Ultrastable colloidal suspensions of magnetic nanoparticles (MNPs) in acarrier liquid (CL)- no sedimentation Quasihomogeneous magnetizable liquids
Approximatively Langevin type magnetic behavior and Newtonian flowproperties, small magnetoviscous effect
Magnetorheological fluids Suspensions of micron-sized ferromagnetic particles in a carrier liquid-
significant sedimentation rate
Non-Newtonian behavior, strongly magnetic field dependent yield stress andeffective viscosity (about 100-1000 times increase)
Magnetizable gels&elastomers Nano- or micro-meter range magnetic particles dispersed in a polymer matrix
Field dependent size and mechanical properties, tunable elastic properties
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Synthesis procedures
I. Synthesis of magnetic nanoparticles
Chemical co-precipitation
Thermal decomposition of organo-metallic compounds
II. Stabilization/dispersion in non-polar or polar carrierliquids
Electrostatic stabilization (water)
Steric or electro-steric stabilization (organic carriers and water)
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Composition & mechanism of sterical stabilization
Composition: MNP - magnetite, maghemite, cobalt-ferrite, iron, cobalt; CL- non-polar and polarorganic solvents, water; S - carboxylic or sulphonic acids, polymers
Sterical stabilization: MNPs dispersed in a CL are coated with mono- or double-layer of organic
surfactant (S) molecules in order to prevent their agglomeration due to magnetic dipole-dipole andvan der Waals interactions
Entropic repulsion betweensurfacted MNPs
- distance between particles
Nuclear and magnetic particle structures in FFs2R1- surfacted particle size, incl. surfactant layer s2R particle size; 2 Rm- magnetic size
Nuclear structure Sterical stabilization
Solvent (CL)
Surfactant layer
Magnetic structure
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Colloidal stability
S. Odenbach, Ferrofluids, 2006M. Klokkenburg et al., JoPhys CM, 2008
Stabilization procedures prevent gravitational settling of MNPs,agglomerate formation by magnetic and van der Waals interactions
Non-dimensional dipolar
interaction energy
Tk
dM
b
md
=72
32
0int
int > 1
Unstable FF, agglomerate formation
dTEM = 9.0 nm
int = 0.5
Cryo-TEM: FF/Decalin (OA)
200 nm
int < 1
Stable FF, no agglomerates
dTEM = 18.6 nmint = 4.4
Cryo-TEM: FF/Decalin (OA)500 nm
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Synthesis procedures (1)Organic non-polar carrier liquids - monolayer surfactant coated MNPsAqueous
solutionsCoprecipitation
NH4OH
(solution 25%)
Fe3+, Fe2+
Subdomain Fe3O4
nanoparticles
Surfactant (pure
oleic acid 96%)Sterical stabilisation
(chemisorption)
353 K
Phase separation
Magnetic
decantation
Aqueous solution of
residual salts
Monolayer coveredmagnetic particles
Distilled water
t = 70 - 80oCRepeated washing
Magnetic decantation Aqueous solutionresidual salts
Surfactants: oleic acid (OA), stearic acid (SA), palmitic acid (PA), myristic acid (MA), lauric acid (LA)Carriers : hydrocarbons (H), deuterated hydrocarbons(D-H), halogenated compounds(Hal)
80-82 C
Lab. Magnetic Fluids Timisoara
MF/H/OA: D. Bica, R.Minea, Patent RO 97556(1989); D. Bica, Rom. Rep. Phys. 47(1995)MF/H/LA; MA : L. Vekas et al. Rom. Rep. Phys. 58(2006); M.V. Avdeev, D. Bica et al. JMMM, 311 (2007)
Monolayer covered magneticnanoparticles + free oleic acid
Acetone Extraction
Magnetic decantation Acetone, water,
free oleic acid
Stabilised magneticnanoparticles
HydrocarbonDispersion
Primary monolayer stabilisedmagnetic fluid on light
hydrocarbon carrier
Magnetic decantation /filtration
Repeated flocculation /redispersion of surfacted
nanoparticles
Free oleic acid
NONPOLAR PURIFIED MAGNETIC FLUID
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Synthesis procedures (2)Organic polar carrier liquids - double layer surfactant coated MNPs
D. Bica et al. Patents RO 93107 (1987), 93162 (1987), 97224 (1989),97599(1989), 105048 (1992),
115533 (2000); D. Bica, Rom. Rep. Phys. 47(1995)
D. Bica, L. Vekas, M. Rasa, J.Magn.Magn.Mater. 252 (2002)
DBS-dodecyl-benzen-sulphonic acid
PIBSA-poly-izobutylen-succin-anhydrideLab. Magnetic Fluids Timisoara
Acetone Flocculation
Magnetic decantation Acetone +
hydrocarbon
Monolayer stabilisedmagnetic nanoparticles
DBS or PIBSA
(C8)
- Secondary stabilisation
(physical adsorbtion)
- Dispersion
Alcohols C3-C10/HVO/
Diesters(DOA/DOS)
MF/HIGH
VACUUM OIL
MF/ALCOHOLS
(Polialcohols)
MF/DIESTERS
(DOA, DOS)
VEGETAL
OILS
- Coprecipitation Fe2+, Fe3+, NH4OH sol. 25%- Sterical stabilisation, (chemisorbtion, oleic
acid 96%)- Phase separation- Repeated washing- Dispersion
Primary magnetic fluid onlight hydrocarbon carrier
- Magnetic decantation- Filtration- Repeated flocculation /
redispersion of surfactednanoparticles
Free oleic acid
Nonpolar purified magnetic
fluid
FF/organic polar carrierOA+DBS,OA + PIBSA,OA + PIBSIdouble layer
sterical stabilization
MNP
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Magnetic decantation
Fe3O4 nanoparticles
Repeated washing
Fe3O4 nanoparticles
Chemisorbtion
Phase separation
Coprecipitation, pH=11Fe3+, Fe2 solution NaOH6N solution
or NH4OH80C
Distilled water
70-80C
Lauric acid (LA)(or MA/PA/OA)
Residual salt solution
Residual salt solutionMagnetic decantation
80C
Magnetic decantation
Dispersion
Primary magnetic fluid
Magnetic decantation
Magnetic organosol, pH= 8. 5 9.0
Residual salt solution
NaOH
Water
MF/Water (LA+LA /MA+MA/PA+PA/
OA+OA)
Uncoated magnetite
nanoparticles, agglomerates
Synthesis procedure (3)
Biocompatible FFs
FF/waterLA+LA, MA+MA,
OA+OA, LA+DBS,MA+DBS, OA+DBS
double layersterical stabilization
D.Bica, Patent RO 90078 (1985); Rom. Rep. Phys.,47(1995)
D. Bica. L. Vks, M. Rasa, J. Magn. Magn. Mater.,252(2002)
D.Bica, L. Vekas, M.V.Avdeev, O. Marinica, V. Socoliuc,
M. Balasoiu, V.M.Garamus, J.Magn. Magn. Mater. 311(2007)
MNP
Water (highly polar) carrier- double layersurfactant coated MNPs
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Generalized synthesis procedure of monodisperse Fe nanoparticlesSize-selective process: varying the molar ratio Fe- carbonyl /OA andthe steric bulkiness of surfactants used
Thermal decomposition of iron pentacarbonyl in the presence of oleic acid at 100 C
The iron oleate complex was prepared by reacting Fe(CO)5 and oleic acid at 100 C Iron nanoparticles were then generated by aging the iron complex at 300 C
TEM images of iron nanoparticles:(a) three-dimensional array of 7nm
Fe nanoparticles and
(b) 11 nm Fe nanoparticles
Liquid phase synthesis of iron NPs by thermaldecomposition
T. Hyeon, Chem.Comm., 2003
20 nm
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- Synthesis procedure for monodisperse -Fe2O3 nanoparticles -
Maghemite nanoparticles with sizes of 7 and 11 nm synthesized by using reaction mixtures with
[Fe-(CO)5]:[oleic acid] molar ratios of 1:2 and 1:3, respectively.
Dominating size controlling factor: the molar ratio of iron pentacarbonyl /oleic acid.
Liquid phase synthesis of iron oxide NPsby thermal decomposition
Monodisperse iron nanoparticles monodisperse -Fe2O3 nanocrystals
Controlled oxidation using trimethylamine N-oxide ((CH3)3NO)- mild oxidant
T. Hyeon, Chem.Comm. 2003
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S. Behrens et al Z. Phys. Chem. 2006S. Behrens et al., J Phys: Condens. Matter, 2006
a. TEM image displaying several Co nanoparticles
b. HRTEM image of a single Co nanoparticleshowing the polycrystalline structure.
High magnetization FFs with Co nanoparticles
Liquid phase synthesis of Co NPs by thermal decomposition of Co2(CO)8
Co2(CO)
8+ Al-R
3
toluen (80-900C)
heating (1100C;18 h) under stirring
cooling to room temperature
smooth oxidation (synthetic air)
black precipitate Co(O) with oxidized protecting shell
stabilization of Co NPs (Korantin SH or oleic acid+Oleyl
amine) in hydrocarbon carrier
high magnetization FF (1000-1700 G)
2 nm
Axial magnetohydrostatic bearing
a) Stator b) Section enlargement of the stator withthe ferrofluid c) General view of the bearing
10 nm
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Experimental setupfor the laser pyrolysis of
iron/iron oxide nanoparticles+system for powder collection in
the toluene bubbler
Focused CW CO2 laser radiation (l = 10.6 mm,output power 35 W) orthogonal to the reactant gas stream
Reactive mixture: Fe(CO)5 vapors + C2H4 gas carrier. Synthesis parameters: 3000 Pa for the reactor pressure and100 sccm for the ethylene flow (bubbling through the
liquid carbonyl reservoir at temperature of 25 0C)
E. Popovici et al., Appl.Surf.Sci. 2007
Gas phase synthesis of iron/iron oxid NPs bylaser pyrolisis
TEM/HRTEM:iron/iron oxide coreshell MNPsenhanced magnification TEM : encapsulated featureof the nano-Fe powder - higher inset; HRTEM: single
nanoparticle - lower inset
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a) XRD diagram: well defined Fepeaks mixed with Fe2O3 and Fe3O4
b) TEM image: hydrocarbon-based FFrevealing almost single particles orassemblies of a few nanoparticles
E. Popovici et al., Appl. Surf. Sci. 2007
Laser pyrolisis synthesized iron/iron oxide MNPsdispersed in hydrocarbon carrier
a)
b)
Iron/iron oxide core-shell MNPs
Sterical stabilization - oleic acid (OA) (heating up to 353 K;pH 8.5; continuous stirring; chemisorption of OA
Monolayer coated MNPs
Elimination of free OA - magnetic decantation
Stabilized MNPs
Addition of carrier - hydrocarbon, e.g. petroleum
Heating up to 110120 8C - elimination of water + acetone
Primary hydrocarbon-based ferrofluid
Magnetic decantation; repeated flocculation/re-dispersion of MNPs(elimination of free oleic acid)
Sterically stabilized, highly purified FF with surface protected MNPs
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Application orientated evaluation of ferrofluidsManifold characterization
Size distribution of magnetic nanoparticles: TEM, HRTEM
Composition and magnetic field dependent structural processes, sterical stabilization and
long-term colloidal stability: SANS, SANSPOL (B = 0-2.5 T)
Mechanism of stabilization and chemical size selection of dispersed magnetic particles
Dilution stability and phase transition phenomena: magneto-optical investigations, DLS
Magnetic properties vs. concentration: VSM measurements
Flow properties under the influence of applied magnetic field: MR investigations
Evaluation and selection of FFs for various applications
FFs for rotating seals, bearings high magnetization
organic carrier liquids
excellent stability in intens and stronglynon-uniform magnetic fields
FFs for biomedical applications
biocompatibile components
usually water carrier
stability in physiological conditions
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Sterical stabilization: efficiency of differentchain length surfactants
R. Tadmor, R. E. Rosensweig, J. Frey, J. Klein,
Resolving the Puzzle of Ferrofluid Dispersants, Langmuir16 (2000)
Unsaturated mono-carboxylic acid
palmitic acid (PA)
C16H32O2stearic acid (SA)
C18H36O2
oleic acid (OA)C18H34O2
Excellent stabilizerdue to high solvation!
Non-efficient
stabilizers
because of
worse solvation?short chain?
myristic acid (MA)
C14H32O2
lauric acid (LA)
C12H32O2
Non-efficient stabilizer
because of worse solvation
doublebond kink
Saturated mono-carboxylic acids
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Schematic view of SANS experiment on system of magnetic
nanoparticles. In case of unmagnetized system scattering
pattern is isotropic over radial angle on detector plane
Schematic view of SANSPOL experiment on system of
magnetic nanoparticles. Anisotropy in the scattering pattern
over radial angle is caused by magnetization of the system
Small Angle Neutron Scattering investigationsStructural processes in ferrofluids
FFs in zero field (B=0) conditions FFs under the influence of applied
magnetic field (B>0)
1-100 nm range
GKSS Geesthacht BNC KFKI Budapest JINR Dubna
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Small Angle Neutron Scattering investigationsSANS Interparticle interaction
magnetite/oleic acid/H-benzene
Type of structure-factor: long-range attraction withshort-range (contact) repulsion
JINR Dubna, BNC Budapestline: model of polydisperse
core-shell particles
)()(~ 2 qSqF NN
0,1 1
0,01
0,1
1
10
100
m = 0.15m = 0.075m = 0.038m = 0.019m = 0.01
I(q),cm-1
q, nm-1
Cluster fractal dimension D ~ 1,5 2.5Mean radius of cluster units R ~ 10 nm
magnetite/water: OA+DBS, DBS+DBS, OA+OA
Highly stable ferrofluids Weakly stable ferrofluids
M.V. Avdeev, V.L Aksenov, M. Balasoiu et al. J. Coll. Interface Sci, 2006L. Vekas, M.V. Avdeev, D. Bica, Magnetic fluids: Synthesis and Structure (Springer V, to appear)
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Small Angle Polarized Neutron Scattering investigationsSANSPOL High magnetic field stability test
Highly stable magnetic nanofluid, maximal m~10 %.
Investigation at B= 2.5 T d-cyclohexane + Fe3O4 + MA , m= 2.8 %
0.1 1
0.1
1
10
I(q),cm
-1
q, nm-1
I
I+
0.1 1
1E-3
0.01
0.1
1
10
F2
N
F2
M
Rg=3.7 nm
Rg=4 nm
I(q),cm-1
q, nm-1
Averaged (over radial angle ) intensities of the scattering
for two spin orientations of polarized neutrons
Blue solid line fit of the core-shell model.Final parameters are
R0=2.3 nm; S=0.28; =1.35 nm.
Dashed lines are Guinier approximations.SANSPOL tests-GKSS Geesthacht-V. Garamus, M.V. Avdeev
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SANS and VSM analyses
Samples stabilized with different chain length carboxylic acids
Magnetization curves (points) for ferrofluids/ DHN, m = 1.5 %.Lines are the results of the polydisperse Langevin approximation.
SANS curves (points) FFs in DHN normalized to m= 1.5 %.Lines are the results of approximation by the model of polydisperse
independent spheres
Inset : particle sizedistributions of magnetite
(atomic size)
Inset : particle sizedistributions of magnetite(magnetic size)
SANS
0.1 11E-4
1E-3
0.01
0.1
1
10
100
SA, PA, MA, LA
q, nm-1
I(q),cm-1
OA
0 1 2 3 4 5 6 7 8
DN
(R)
R, nm
OA
SA, PA, MA, LA
VSM
0 500 10000.0
0.2
0.4
0.6
0.8
1.0
SA, PA, MA, LA
OA
LA, MA, PA,
SA
OA
M/M
s
H, kA/m
0 1 2 3 4 5 6 7 8
DN
(R)
R, nm
Lab. Magnetic Fluids Timisoara GKSS Geesthacht BNC Budapest
M.V. Avdeev, D. Bica, L. Vekas,V.L. Aksenov, A.V. Feoktystov,
L. Rosta, V.M. Garamus,
R. Willumeit JMMM 2008
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SANS curves and resulting size distributions
Mixed surfactants monolayer (MA + OA) with 1:0, 1:1 and 0:1 mixing ratios
FFs with chemically tailored magnetic nanoparticlesSize selective synthesis-stabilization of magnetic nanoparticles
with mono-layer of mixed surfactants
Non-polar carrier (D-benzen), =1.1 %
Increased MA content, more reduced diameter and standard deviation M.V. Avdeev, D. Bica et al. (MISM, 2008)
Resulting log-normal size-distribution functions
0 1 2 3 4 5 6 7 8
OA/MA 1/1
DN(R)
R, nm
MA (Dm=5.15 nm; = 1.26)
(Dm=6.24 nm; = 1.79)
OA (Dm=7.34 nm; = 2.98)
Nuclear scattering contribution. Solid lines are fits of
the core-shell model
0.1 1
I(q),cm
-1
q, nm-1
OAOA/MA 1/1
MA
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Flow properties under the infuence of appliedmagnetic fieldNon-polar carrier, mono-layer sterical stabilization with MA (C14) and OA (C18)
Concentrated (Ms= 61 kA/m)
OA stabilized MF/Utr sampleMR effect ~20-30%
Concentrated (Ms= 62 kA/m)
MA stabilized FF/Utr sampleMR effect 10%
Coil
Magnetic Field
Highly Permeable Material
Parallel Plate
non-magnetic
Magnetic Fluid
MR cell MCR 300
Well stabilized FFs have veryreduced MR effect
L.Vekas, D. Bica et al. Rom. Rep. Phys. 2006
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Colloidal stability of water based ferrofluidsDynamical Light Scattering investigations-NanoZSDouble layer sterical stabilization using different chain length surfactants
Biocompatible ferrofluids
-4.5
-3
-1.5
0
1.5
3
4.5
2 3 4 5 6 7 8 9 10pH
Electrophoreticmobility(
cmV
-1s-1)
Cationic particles
Anionic particles
OA+OA
LA+LA
MA+MA
Magnetite
Double la yer coated magne tite0
10 0
20 0
30 0
40 0
50 0
60 0
70 0
80 0
2 3 4 5 6 7 8 9 10pH
Magnetite 0.001 MLA +LA 0.001 MLA +LA 0.01 MMA+MA 0.01 MMA+MA 0.1 MOA+OA 0.001 MOA+OA 0.01 M
Aggregation
Dilute ma gnetic fluids
Averagehydrodyn
amicsize(nm)
Aggregation of magnetite particles in 0.001,
0.01 and 0.1 M NaCl solutions at 25+0.10C.
E. Tombcz, D. Bica et al, JoPhys CM 2008
Effect of anionic surfactant double layer coating
on the pH-dependent charge state
OA+OA and MA+MA stabilized FF/water samples keep theircolloidal stability in the physiological range of pH (6-8)
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Restoring force Frinduced by
magnetic field H
in shearing flow
No field: H=0Fe particles diffusing
randomly; blades
moving freely
Increasing field: H > 0Fe particles start forming
chains; resistance between
blades increases
Saturating field: H HsatStrong field forms continuous
chains-quasi-solid state;blades movement restricted
Composition & intense structuring mechanismMagnetic particles: magnetically soft multi-domain Fe, Fe alloys of 1-10 mCarrier liquids: petroleum based oils, silicon oils, mineral oils, synthetic oils, waterSuspension agents: thixotropic and surface active agents (e.g., carboxylic acids,
stearats, polymers, organoclays)
Field dependent magnetic moment of particles m= 40fa3H
0; =(p -f)/(p+2f)
Field dependent magnetic coupling parameterint
MR = 0fa3H
02/(2kT)
int
MR = 1 for H0=127 A/m; 2a=1m
intMR ~ 108 1 for usual H values
Strongly non - Newtonian behaviorYield stress: 50-100 kPaLarge MR effect: 102 103 timesincrease of effective viscosity
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Main characteristics MR effect ~ 102 - 103
Yield stress 50-100 kPa
Max. applied field 150-250 kA/m
Density 3-4 g/cm3
Response time < 1 ms
Off-state viscosity 0.10 - 1.0 Pa.s (at 25 0C)
Operational temp - 400C to + 1500C
Magnetic particles Fe (~ 3m), magnetically soft
No hysterezis
Main problems to be solved Gravitational settling
Difficult redispersing of sediment
Further increasing the yield stress / MR effect
Possible solutions Non-magnetic nanofillers
Non-spherical shaped magnetic particles
Extremely bidisperse MR suspensions
Magnetorheological fluids
G. Bossis, O. Volkova, S. Lacis, A. Meunier, in:S. Odenbach (Ed) Ferrofluids.Magnetically controllable fluids and their applications(Springer-Verlag 2002)
J. D. Carlson, M. R. Jolly, Mechatronics(2000)
F. D. Goncalves, J.-H. Koo, M. Ahmadian,The Shock and Vibration Digest(2006)
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MRFs with magnetic fibers Lopez-Lopez, Vertelov, Bossis, Kuzhir, Duran, J. Mater. Chem., 2007
Dynamic yield stress, as a function ofthe external magnetic field strength
Cobalt suspensions in silicone oil (solid
concentration 5 vol%). Cobalt spheres, 1.3 m
Cobalt wires
Co wires
Co spheres
Extremely bidisperse MRFs Viota, Gonzalez-Caballero, Duran, Delgado, J. Coll.Int. Sci., 2007
Three-times increase of yield stress
Role of magnetic particle shape & size
Photographs of bidisperse MR suspensions after 24 h sedimentation. the arrows indicate the sediment height.
in all cases, micron size particle concentration m= 10%;
nanoparticle concentrations nare, from left to right (in %),0, 1, 2, 3, 5, 7.
Nano-micro MRFComposition
Spherical particles
Decrease ofsedimentation rate
Halo structure formation
Cloud of magnetic nanoparticlesaround micron sizedparticles, large size aggregates
Micro-Magnetite 1450 nm Nano-Magnetite 8 nm Carrier: water
SEM image of Co wiresLength 30-60m; Width 4-5 m
10m
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1
00 1
*
1 tanh tanh
1
n
m
= + +
+
& & & &
& & &&
&
Shear stress vs. shear rate curves forB = 0,..., 502 mT MRF-140CG; micro 0.40
Commercial sample Lord Co(~mFe)
Shear stress vs. shear rate curves forB = 0,..., 502 mT D1; total 0.40
micro 0.2; nano 0.2
Nano-micro MRF lab sample
1
0 0 11 tanh tanh
n
= + +
& & &&
& & &
Fit: Herschel-Bulkley (H-B) type behavior for B>0 Fit: Cross+ H-B formula for B>0
Fit: Carreau-YasudaFormula for B=0
MR effect
Nano-micro MRF
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)()0(/)]0()([ BfB =
Effect of nanosized magnetic particles on MR effectmicro 0.2; nano 0.2
D. Resiga, D. Bica, L. Vks, ERMR 2008, Dresden
MRF-140CG comercial sample
D1 lab sample
MR effect
Nano-micro MRF
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Composite with field induced uniaxial ordered structure
New generation of magnetic elastomers - new type of magnetic compositesNano- and/or micron-sized magnetic particles dispersed in a high elastic polymeric matrix-Poly(dimethyl siloxane (PDMS)
Schematic picture ofthe bending of themagnetic PVA gels
under compression.
Anisotropic mechanical (a)and swelling [(b) and (c)]behaviour as seen by the naked eye.
The arrow indicates the direction of themagnetic field during the preparation.
Preparation of uniaxially ordered composite deformation ratio
Smart composites with controlled anisotropy, POLYMER, 2006, Zs. Varga, G. Filipcsei, M. Zrnyi*HAS-BUTE Laboratory of Soft Matters, Dept Physical Chemistry, Budapest
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Intelligent polymeric nanocomposite membrane
Schematic representation of channels made of MPS-PNIPA latex built in the PVA gel matrix:
(a) off state below the collapse transition temperature;
(b) on state above the collapse transition temperature.
Response to external stimuli-regulation of drug permeation and release- biomedical applications
Ordered nanochannels can act as on-offswitches or permeability valves
Poly(Nisopropyacrylamide)gel ---- PNIPA gel Magnetic polystyrenelatex --- MPS
Macromolecules 2006, 39, 1939-1942 I.Csetneki, G.Filipcsei, M. Zrnyi* HAS-BUTE Laboratory of Soft Matters, Budapest
Arrows indicate the
diffusive mass transferin the channels of PVAmembrane
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CONCLUSIONS
Properties of magnetically controllable fluids are tailored
mainly by varying the size range of magnetic particles 100104 nm
Saturation magnetization is determined by the volume fraction
and magnetic properties of the solid component 10 7x103 G
Non-dimensional particle interaction energy int covers a wide range 0.5 ... 108
Magnetorheological effect / 10-1 103
OUTLOOK
Increasing trend of applicationsof
magnetically controllable fluidsin
biology and medicine
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Acknowledgements
Dr. Doina BICA Laboratory of Magnetic Fluids-CFATR TimisoaraRomanian Academy-Timisoara Division
Dr. Mikhail AVDEEV- JINR-Dubna, Russia
Prof. Mikls ZRINYI - Dept.Physical Chemistry, Budapest Technical University, Hungary
Dr. Ion MORJAN - INFLPR Bucuresti, Romania
Prof. Etelka TOMBCZ - Dept. Colloid Chemistry-Univ. Szeged, Hungary
Ass.Prof. Dr. Daniela Susan-Resiga- West University Timisoara, Romania
Dr. Rodica TURCU - INCDTIM Cluj-Napoca, Romania
Dr. Adelina HAN - CNISFC- Univ. Politehnica Timisoara, Romania
National Authority for Scientific Research (Romania):CEEX Research projects FeMANANOF, NanoMagneFluidSeal
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Thank you for attention!
Lab. Vant Hoff of Colloids - 100 years anniversary
Exhibition at Univ. Utrecht 2004 - A.P. Philipse (Utrecht), Doina Bica (Timisoara)
Dynamicalsurface
instabilities