1
|
Philip J. Magnetic nanofluids (Ferrofluids): Recent advances, applications, challenges, and future directions. Adv Colloid Interface Sci 2023; 311:102810. [PMID: 36417827 DOI: 10.1016/j.cis.2022.102810] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/28/2022] [Accepted: 11/05/2022] [Indexed: 11/16/2022]
Abstract
Impelled by the need to find solutions to new challenges of modern technologies new materials with unique properties are being explored. Among various new materials that emerged over the decades, magnetic fluids exhibiting interesting physiochemical properties (optical, thermal, magnetic, rheological, apparent density, etc.) under a magnetic stimulus have been at the forefront of research. In the initial phase, there has been a fervent scientific curiosity to understand the field-induced intriguing properties of such fluids but later a plethora of technological applications emerged. Magnetic nanofluid, popularly known as ferrofluid, is a colloidal suspension of fine magnetic nanoparticles, has been at the forefront of research because of its magnetically tunable physicochemical properties and applications. Due to their stimuli-responsive behaviour, they have been finding more applications in biology and other engineering disciplines in recent years. Therefore, a critical review of this topic highlighting the necessary background, the potential of this material for emerging technologies, and the latest developments is warranted. This review also provides a summary of various applications, along with the key challenges and future research directions. The first part of the review addresses the different types of magnetic fluids, the genesis of magnetic fluids, their synthesis methodologies, properties, and stabilization techniques are discussed in detail. The second part of the review highlights the applications of magnetic nanofluids and nanoemulsions (as model systems) in probing order-disorder transitions, scattering, diffraction, magnetically reconfigurable internal structures, molecular interaction, and weak forces between colloidal particles, conformational changes of macromolecules at interfaces and polymer-surfactant complexation at the oil-water interface. The last part of the review summarizes the interesting applications of magnetic fluids such as heat transfer, sensors (temperature, pH, urea detection, cations, defect detection sensors), tunable optical filters, removal of dyes, dynamic seals, magnetic hyperthermia-based cancer therapy and other biomedical applications. The applications of magnetic nanofluids in diverse disciplines are growing day by day, yet there are challenges in their practical adaptation as field-worthy or packaged products. This review provides a pedagogical description of magnetic fluids, with the necessary background, key concepts, physics, experimental protocols, design of experiments, challenges and future directions.
Collapse
Affiliation(s)
- John Philip
- Smart Materials Section, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, India.
| |
Collapse
|
2
|
Mohapatra DK, Laskar JM, Philip J. Temporal evolution of equilibrium and non-equilibrium magnetic field driven microstructures in a magnetic fluid. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.112737] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
|
3
|
Yang J, Yan H, Niu F, Zhang H. Probing of the magnetic responsive behavior of magnetorheological organogel under step field perturbation. Colloid Polym Sci 2017. [DOI: 10.1007/s00396-017-4249-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
4
|
Brunel F, Pochard I, Gauffinet S, Turesson M, Labbez C. Structure and Yielding of Colloidal Silica Gels Varying the Range of Interparticle Interactions. J Phys Chem B 2016; 120:5777-85. [PMID: 27284941 DOI: 10.1021/acs.jpcb.6b04047] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The relationship between interaction range, structure, fluid-gel transition, and viscoelastic properties of silica dispersions at intermediate volume fraction, Φv ≈ 0.1 and in alkaline conditions, pH = 9 was investigated. For this purpose, rheological, physicochemical, and structural (synchrotron-SAXS) analyses were combined. The range of interaction and the aggregation state of the dispersions were tuned by adding either divalent counterions (Ca(2+)) or polycounterions (PDDA). With increasing calcium chloride concentration, a progressive aggregation was observed which precludes a fluid-gel transition at above 75 mM of calcium chloride. In this case, the aggregation mechanism is driven by short-range ion-ion correlations. Upon addition of PDDA, a fluid-gel transition, at a much lower concentration, followed by a reentrant gel-fluid transition was observed. The gel formation with PDDA was induced by charge neutralization and longer range polymer bridging interactions. The refluidification at high PDDA concentrations was explained by the overcompensation of the charge of the silica particles and by the steric repulsions induced by the polycation chains. Rheological measurements on the so-obtained gels reveal broad yielding transition with two steps when the size of the silica particle clusters exceeds ≈0.5 μm.
Collapse
Affiliation(s)
- Fabrice Brunel
- C2P2, UMR 5265, CNRS - CPE , BP 82077 - 69616 Villeurbanne, France
| | - Isabelle Pochard
- UTINAM, UMR 6213 CNRS, Université de Bourgogne-Franche-Comté , 25000 Besançon, France
| | | | | | | |
Collapse
|
5
|
Felicia LJ, Philip J. Effect of hydrophilic silica nanoparticles on the magnetorheological properties of ferrofluids: a study using opto-magnetorheometer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:3343-3353. [PMID: 25734232 DOI: 10.1021/acs.langmuir.5b00103] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
For many technological applications of ferrofluids, the magnetorheological properties require being precisely controlled. We study the effect of hydrophilic silica on the magnetorheology of an oil-based ferrofluid containing Fe3O4 nanoparticles of size ∼10 nm. We observe that the presence of silica nanoparticles lowers the yield stresses, viscoelastic moduli, and shear thinning behavior of the ferrofluid because of the weakening of dipolar interactions, which was evident from the observed lower yield stresses exponent (<2). The ferrofluid containing silica exhibits a dominant elastic behavior, a reduced hysteresis during the forward and reverse magnetic field sweeps, and a longer linear viscoelastic regime under nonlinear deformation. The Mason number plots at low shear rates and magnetic fields show deviations from the master curve in the presence of silica. The magnetic field induced microstructures, visualized using opto-magnetorheometer, showed columnar aggregate structures along the field directions, which are reoriented along the shear flow direction at high shear rates. The image analysis shows that the average thickness of the columnar aggregates in pure ferrofluid is much larger than that of the mixed system, which suggests that the intervening silica matrix hampers the zippering transition of columns at higher magnetic field and shear rates. Our results suggest that optimization of rheological properties of ferrofluids is possible by carefully adding suitable silica nanoparticles, which may find practical applications such as dynamic seals, heat transfer, sensors, and opto-fluidic devices, etc.
Collapse
Affiliation(s)
- Leona J Felicia
- SMARTS, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
| | - John Philip
- SMARTS, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
| |
Collapse
|
6
|
Felicia LJ, Philip J. Probing of field-induced structures and their dynamics in ferrofluids using oscillatory rheology. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:12171-12179. [PMID: 25268053 DOI: 10.1021/la502878v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We probe field-induced structures and their dynamics in ferrofluids using oscillatory rheology. The magnetic field dependence of the relaxation time and crossover modulus showed two distinct regions, indicating the different microstructures in those regions. The observed relaxation at various magnetic field strengths indicates that side chains are attached to the pinned single-sphere-width chains between the rheometer plates. Our results suggest that the ferrofluid under a magnetic field exhibits a soft solidlike behavior whose relaxation is governed by the imposed strain rate and the magnetic field. Using the scaling factors obtained from the frequency and modulus at the crossover point in the oscillatory rheological measurements, the constant strain-rate frequency sweep data is superimposed onto a single master curve. The frequency scaling factor increases with the strain rate as a power law with an exponent close to unity, whereas the amplitude scaling factor is almost strain-rate-independent at high magnetic field strengths. These findings are useful for a better understanding of field-induced ordering of nanoparticles in fluids and their optimization for practical applications.
Collapse
Affiliation(s)
- Leona J Felicia
- SMARTS, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research , Kalpakkam-603 102, India
| | | |
Collapse
|
7
|
Felicia LJ, Philip J. Magnetorheological properties of a magnetic nanofluid with dispersed carbon nanotubes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:022310. [PMID: 25353475 DOI: 10.1103/physreve.89.022310] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Indexed: 06/04/2023]
Abstract
We investigate the effect of multiwalled carbon nanotubes (MWCNTs) on the magnetorheological properties of an oil based magnetic nanofluid (ferrofluid). The shear resistant plateau observed in a pure ferrofluid disappears when 0.5 wt% of MWCNT is incorporated. The yield stress values of the composite system are slightly smaller than that of the pure system. This shows that the presence of carbon nanotubes (CNTs) weakens the magnetic field induced microstructure of the ferrofluid due to their interaction that affects the hydrodynamic and magnetic interactions between the dispersed nanoparticles. Interestingly, the Mason number plots for both the pure and composite system show scaling of the viscosity curves onto a single master curve for magnetic fields of 80 mT and above while deviations are observed for lower magnetic fields. The weakening of the ferrofluid microstructure in the presence of CNTs is further evident in the amplitude sweep measurements where the linear viscoelastic region develops only at a higher magnetic field strength compared to lower magnetic fields in pure ferrofluids. These results are useful for tailoring ferrofluids with a faster response for various applications.
Collapse
Affiliation(s)
- Leona J Felicia
- SMARTS, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, India
| | - John Philip
- SMARTS, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, India
| |
Collapse
|
8
|
Anwar Bég O, Zueco J, Norouzi M, Davoodi M, Joneidi AA, Elsayed AF. Network and Nakamura tridiagonal computational simulation of electrically-conducting biopolymer micro-morphic transport phenomena. Comput Biol Med 2013; 44:44-56. [PMID: 24377688 DOI: 10.1016/j.compbiomed.2013.10.026] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 10/24/2013] [Accepted: 10/26/2013] [Indexed: 11/30/2022]
Abstract
Magnetic fields have been shown to achieve excellent fabrication control and manipulation of conductive bio-polymer characteristics. To simulate magnetohydrodynamic effects on non-Newtonian electro-conductive bio-polymers (ECBPs) we present herein a theoretical and numerical simulation of free convection magneto-micropolar biopolymer flow over a horizontal circular cylinder (an "enrobing" problem). Eringen's robust micropolar model (a special case of the more general micro-morphic or "microfluid" model) is implemented. The transformed partial differential conservation equations are solved numerically with a powerful and new code based on NSM (Network Simulation Method) i.e. PSPICE. An extensive range of Hartmann numbers, Grashof numbers, micropolar parameters and Prandtl numbers are considered. Excellent validation is also achieved with earlier non-magnetic studies. Furthermore the present PSPICE code is also benchmarked with an implicit tridiagonal solver based on Nakamura's method (BIONAK) again achieving close correlation. The study highlights the excellent potential of both numerical methods described in simulating nonlinear biopolymer micro-structural flows.
Collapse
Affiliation(s)
- O Anwar Bég
- Gort Engovation (Propulsion and Biophysics), Southmere Avenue, Bradford, BD7 3NU, UK.
| | - J Zueco
- Departamento de Ingeniería Térmica y Fluidos, Universidad Politécnica de Cartagena, Murcia, Spain
| | - M Norouzi
- Mechanical Engineering Department, Shahrood University of Technology, Shahrood, Iran
| | - M Davoodi
- Mechanical Engineering Department, Shahrood University of Technology, Shahrood, Iran
| | - A A Joneidi
- Mechanical-Polymer Technology Group, Eindhoven University of Technology, Eindhoven, Netherlands
| | - Assma F Elsayed
- Mathematics Department, Faculty of Education, Ain shams, University, Heliopolis, Cairo, Egypt
| |
Collapse
|
9
|
Richardi J, Weis JJ. Influence of short range potential on field induced chain aggregation in low density dipolar particles. J Chem Phys 2013; 138:244704. [DOI: 10.1063/1.4811290] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
|
10
|
Felicia LJ, Philip J. Probing of field-induced structures and tunable rheological properties of surfactant capped magnetically polarizable nanofluids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:110-120. [PMID: 23210900 DOI: 10.1021/la304118b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Oil-based nanofluid containing surfactant-capped magnetite nanoparticles are synthesized by a simple coprecipitation approach, and their magnetorheological properties are studied for different magnetic field strengths and volume fractions. We observe a distinct "plateau-like region" in the shear thinning viscosity curve, under an external magnetic field, possibly due to a peculiar alignment of the chains with respect to the field direction where the structure is stable against fragmentation. The observed plateau regime is reminiscent to that of kinetically arrested gel networks. Interestingly, such a plateau regime has been observed only above certain critical magnetic field when the dipolar interaction strength is much greater than the thermal energy where the aggregation becomes a nonequilibrium transport-limited process. The good collapse of specific viscosity data against Mason number for different magnetic field strengths onto a single curve suggests the dominance of hydrodynamic and magnetic forces on thermal force above a certain magnetic field strength. The observed increase in both static and dynamic yield stresses under the magnetic field confirms the formation of columnar structures that hinder the flow behavior. The hysteresis observed in the magnetic sweep experiments shows the inability of the chains to relax within the measurement time. The dynamic measurements confirm that the field-induced structures impart elastic behavior to the dispersion, which is found to increase with magnetic field and saturates at higher field strengths.
Collapse
Affiliation(s)
- Leona J Felicia
- SMARTS, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
| | | |
Collapse
|
11
|
Rich JP, McKinley GH, Doyle PS. Arrested chain growth during magnetic directed particle assembly in yield stress matrix fluids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:3683-3689. [PMID: 22335399 DOI: 10.1021/la204240f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The process of assembling particles into organized functional structures is influenced by the rheological properties of the matrix fluid in which the assembly takes place. Therefore, tuning these properties represents a viable and as yet unexplored approach for controlling particle assembly. In this Letter, we examine the effect of the matrix fluid yield stress on the directed assembly of polarizable particles into linear chains under a uniform external magnetic field. Using particle-level simulations with a simple yield stress model, we find that chain growth follows the same trajectory as in Newtonian matrix fluids up to a critical time that depends on the balance between the yield stress and the strength of magnetic interactions between particles; subsequently, the system undergoes structural arrest. Appropriate dimensionless groups for characterizing the arresting behavior are determined and relationships between these groups and the resulting structural properties are presented. Since field-induced structures can be indefinitely stabilized by the matrix fluid yield stress and "frozen" into place as desired, this approach may facilitate the assembly of more complex and sophisticated structures.
Collapse
Affiliation(s)
- Jason P Rich
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | | |
Collapse
|
12
|
Richardi J, Weis JJ. Low density mesostructures of confined dipolar particles in an external field. J Chem Phys 2011; 135:124502. [DOI: 10.1063/1.3638048] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
13
|
Park JS, Saintillan D. Electric-field-induced ordering and pattern formation in colloidal suspensions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:041409. [PMID: 21599160 DOI: 10.1103/physreve.83.041409] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 03/06/2011] [Indexed: 05/30/2023]
Abstract
The long-time dynamics and pattern formation in semidilute suspensions of colloidal spheres in a viscous electrolyte under a uniform electric field are investigated using numerical simulations. The rapid chain formation that occurs in the field direction as a result of dipolar interactions is found to be followed by a slow coarsening process by which chains coalesce into hexagonal sheets and eventually rearrange to form mesoscale cellular structures, in qualitative agreement with recent experiments. The morphology and characteristic wavelength of the patterns that emerge at steady state are shown to depend on the suspension's volume fraction, electrode spacing, and field strength, suggesting additional ways of controlling effective suspension properties in practical applications.
Collapse
Affiliation(s)
- Jae Sung Park
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | | |
Collapse
|
14
|
Laskar JM, Philip J, Raj B. Experimental investigation of magnetic-field-induced aggregation kinetics in nonaqueous ferrofluids. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:021402. [PMID: 20866804 DOI: 10.1103/physreve.82.021402] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 06/22/2010] [Indexed: 05/15/2023]
Abstract
We investigate the influence of field ramp rate on the kinetics of magnetic dipole-dipole induced chainlike structure formation in a nonaqueous nanoparticle dispersion using light scattering studies. With increase in magnetic field, at a constant ramp rate, the transmitted light intensity diminishes and the transmitted light spot is transformed to a diffused ring due to scattering from the self-assembled linear aggregates. The decay rate of transmitted intensity increases up to an optimum ramp rate, above which the trend becomes reverse. At an optimum ramp rate, the minimum time for initial aggregation coincides with the exposure time where the intensity decay is fastest. The variation of transmitted intensity at different ramp rate is explained on the basis of initial aggregation time that depends on Brownian motion, dipolar magnetic attraction and multibody hydrodynamic interactions. The slope of the transmitted light intensity after the removal of magnetic field depends on the time required for dissociation of ordered linear structures. Disappearance of the ring pattern and the reappearance of original light spot, upon removal of the magnetic field, confirm the perfect reversibility of the linear aggregates. The observed concentration dependant decay rates are in good agreement with aggregation theory.
Collapse
Affiliation(s)
- Junaid M Laskar
- SMARTS, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu, India
| | | | | |
Collapse
|
15
|
Laskar JM, Philip J, Raj B. Experimental evidence for reversible zippering of chains in magnetic nanofluids under external magnetic fields. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:041401. [PMID: 19905308 DOI: 10.1103/physreve.80.041401] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 08/24/2009] [Indexed: 05/28/2023]
Abstract
We study the time-dependent transmitted intensity and the scattered pattern from magnetic nanofluids at constant ramping of uniform external magnetic field. The nanofluid used is the dispersion of magnetite particles with an average diameter of 6.5 nm with a protective surfactant coating. We observe several critical fields at which the transmitted light intensity decreases drastically followed by the formation of a ringlike pattern on a screen placed perpendicular to the field direction. Interestingly, the critical fields occur at a regular interval of 20 G. The observed critical fields are attributed to zippering transitions of the chains due to attractive energy well when the chains are of different lengths or shifted with respect to one another. Interaction energy calculations show a decrease in the energy of the system due to dipolar interactions at different critical fields confirming the lowering of the system energy through lateral coalescence. The observed zippering phenomenon is perfectly reversible.
Collapse
Affiliation(s)
- Junaid M Laskar
- Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu, India
| | | | | |
Collapse
|
16
|
Yang W, Nelissen K, Kong M, Zeng Z, Peeters FM. Structure of binary colloidal systems confined in a quasi-one-dimensional channel. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:041406. [PMID: 19518232 DOI: 10.1103/physreve.79.041406] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Indexed: 05/27/2023]
Abstract
The structural properties of a binary colloidal quasi-one-dimensional system confined in a narrow channel are investigated through modified Monte Carlo simulations. Two species of particles with different magnetic moment interact through a repulsive dipole-dipole force are confined in a quasi-one-dimensional channel. The impact of three decisive parameters (the density of particles, the magnetic-moment ratio, and the fraction between the two species) on the transition from disordered phase to crystal-like phases and the transitions among the different mixed phases are summarized in a phase diagram.
Collapse
Affiliation(s)
- Wen Yang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P.O. Box 1129, Hefei 230031, China
| | | | | | | | | |
Collapse
|
17
|
Laskar JM, Philip J, Raj B. Light scattering in a magnetically polarizable nanoparticle suspension. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:031404. [PMID: 18851035 DOI: 10.1103/physreve.78.031404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Revised: 08/13/2008] [Indexed: 05/26/2023]
Abstract
We investigate magnetic-field-induced changes on transmitted light intensity in a magnetic disordered phase of iron oxide nanoparticle suspension. We observe a dramatic decrease in the transmitted light intensity at a critical magnetic field. The critical magnetic field follows power-law dependence with the volume fraction of the nanoparticles suggesting a disorder-order structural transition. The light intensity recovers fully when the magnetic field is switched off. We discuss the possible reasons for the reduction in the light intensity under the influence of magnetic field. Among the various mechanisms such as Kerker's condition for zero forward scattering, Faraday effect, Christiansen effect, photoinduced refractive index mismatch between the two components of the dispersion, etc., the resonances within the magnetic scatterers appear to be the plausible cause for the extinction of light. The circular pattern observed on a screen placed perpendicular to the incident beam confirms the formation of rodlike structures along the direction of propagation of the light.
Collapse
Affiliation(s)
- Junaid M Laskar
- SMARTS, NDED, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu, India
| | | | | |
Collapse
|
18
|
Philip J, Shima PD, Raj B. Evidence for enhanced thermal conduction through percolating structures in nanofluids. NANOTECHNOLOGY 2008; 19:305706. [PMID: 21828773 DOI: 10.1088/0957-4484/19/30/305706] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The unusually large enhancement of thermal conductivity (k/k(f)∼4.0, where k and k(f) are the thermal conductivities of the nanofluid and the base fluid, respectively) observed in a nanofluid containing linear chain-like aggregates provides direct evidence for efficient transport of heat through percolating paths. The nanofluid used was a stable colloidal suspension of magnetite (Fe(3)O(4)) nanoparticles of average diameter 6.7 nm, coated with oleic acid and dispersed in kerosene. The maximum enhancement under magnetic field was about 48φ (where φ is the volume fraction). The maximum enhancement is observed when chain-like aggregates are uniformly dispersed without clumping. These results also suggest that nanofluids containing well-dispersed nanoparticles (without aggregates) do not exhibit significant enhancement of thermal conductivity. Our findings offer promising applications for developing a new generation of nanofluids with tunable thermal conductivity.
Collapse
|