ABSTRACT
Ferrofluid is a liquid that is magnetically attracted to magnetic items, but the Ferrofluid isn’t magnetic itself. Ferrofluid is a colloidal liquid made of nanoscale Ferromagnetic, or ferrimagnetic, particles suspended in a carrier fluid (usually an organic solvent or water). Each magnetic particle is thoroughly coated with a surfactant to inhibit clumping. Large Ferromagnetic particles can be ripped out of the homogeneous colloidal mixture, forming a separate cluster of magnetic dust when exposed to strong magnetic fields. The magnetic attraction of tiny nanoparticles is weak enough that the surfactant’s Van der Waals force is sufficient to prevent magnetic clumping or agglomeration. Ferrofluids usually do not retain magnetization in the absence of an externally applied field and thus are often classified as “superparamagnets” rather than Ferromagnets.
Down below, from the scientific article: INVESTIGATION OF WATER-BASED AND OIL-BASED FERROFLUIDS WITH A NEW MAGNETORHEOLOGICAL CELL: EFFECT OF THE MICROSTRUCTURE
A new magnetorheological cell is implemented into the Ferrofluid, to perform measurements of temperature-controlled flows and determine viscoelastic properties in magnetic complex fluids under applied continuous magnetic fields. The flow properties of water-based and oil-based Ferrofluids with volume fractions up to 10% are investigated here in various situations of interparticle interaction, also leading to various microstructures already known from previous works. Shear flow behaviors under magnetic fields resulting in a competition between magnetic and hydrodynamic forces are directly related to the microscopic structure of the probed magnetic fluids.
Stephen S. Papell invented the Ferrofluid for NASA in 1963.
In the 1960s, Steve Papell, an engineer at Lewis Research Center, (Glenn Research Center), came up with the idea of magnetizing rocket fuel as a way to draw it from a storage tank into an engine in the absence of gravity. He discovered a way to stably disperse magnetic nanoparticles throughout a carrier fluid, making the first Ferrofluid. A few years later, a company called Avco Space Systems – won a NASA contract to further characterize and develop Ferrofluid and managed to create a variety of liquids that ranged up to 10 times the magnetic strength of the initial Lewis invention.
In February 1982: NASA’s Inventions and Contributions Board presented Stephen Papell with a $15,000 check (its highest monetary award at the time) for inventing magnetic fluids or ferrofluids in the early 1960s. While this technology was originally intended for rocket fuels, Papell’s invention has gone on to impact applications in electronics, chemical energy processing, medical advances, and many other industries.
After serving as an Army Air Corps navigator in World War II, Papell pursued a mechanical engineering degree at the Case Institute of Technology. He joined the NACA Lewis Flight Research Laboratory (today Glenn Research Center) shortly after graduating in 1955.
Initially, Papell worked on the film cooling of turbine blades for aircraft engines. He and a colleague developed the Hatch-Papell Correlation to predict the wall equilibrium temperature needed to determine coolant heat transfer requirements. The equation was later used to design rocket nozzle cooling systems.
With the onset of the space program in the early 1960s, Papell’s focus turned to the behavior of fluids in microgravity. Advanced space missions would require spacecraft to restart their engines. It was not yet understood how liquid propellants would react to the absence of gravity. Rocket designers had to make sure that the fuel—which might settle or disperse inside the tank—could be pumped to the combustion chamber.
Papell suggested the use of the magnetic fluid to solve the problem. He suspended finely-ground iron oxide particles in standard rocket fuel. The activation of an electromagnet near the turbopump would draw the liquid to the intake so the engine could be restarted. The low-density mixture did not breakdown over time and was easily pumped. Papell received three patents and a $500 NASA award for his invention.
During the same period, however, colleagues discovered that the low gravity of space caused liquids to collect at the center of the tank. Therefore, simpler methods such as baffles could be used to guide the fuel to the pump. NASA decided to contract with the AVCO Corporation to pursue magnetic fluids and redirected Papell’s work to heat transfer in cryogenic fluids.
Former AVCO researchers who formed the Ferrofluidics Corporation used ferrofluids to create a magnetic seal for semiconductor manufacturing. Soon other companies were exploring additional uses.
By the mid-1970s, ferrofluids were widely used to cool loudspeaker components and seal rotating shafts. Applications have since expanded to include the improvement of car suspension systems, high-speed printing, petroleum refining, and cancer diagnostics. More recently, a growing number of artists have begun using ferroluids as their medium.
Papell returned to turbine blade cooling in the 1970s and developed a unique blade perforation that facilitated the injection of cooling air. He retired in 1983 after 33 years of government service.
Stephen Solomon Papell passed away at the age of 97 in 2015: https://www.dignitymemorial.com/obituaries/cleveland-heights-oh/solomon-papell-6510706
The basic trick to creating a ferrofluid is to make the magnetic nanoparticles so tiny they naturally spread throughout the carrier fluid, rather than settling out of it, and to coat them with a surfactant that prevents them from clumping together.
Technology Transfer
Two Avco engineers licensed the technology from NASA to found Ferrofluidics Corporation, now Ferrotec. The material has come to be used in a variety of applications, from loudspeakers to petroleum refining and chemical processing facilities, to semiconductor chip manufacturing (Spinoff 1980, 1981, 1993, 2015).
Since around 2000, a small but growing number of artists around the world, including Ilic, have begun using ferrofluids to create striking visual displays. They have faced some technical hurdles, though, such as the problem of staining.
On that front, Ilic took what he calls “the Edison approach: try 10,000 things, and one of them works, and you build on it.” He finally came up with a suspension solution that wouldn’t mix with the educational-grade ferrofluid he buys from Ferrotec. He guards his recipe closely but hasn’t patented it because he’s wary of patenting and the effects it may have on ingenuity, he says. “If someone else figures it out, they can go for it.”
In 2011, he started the online, Hamburg, New Jersey-based business Concept Zero. The site sells glass displays of various shapes and sizes, each filled with his clear suspension fluid and a small amount of black ferrofluid. When a magnet is placed close to a display, the dark fluid leaps into a hemisphere of spikes that follows the magnet around the glass.
Benefits
-“People absolutely love it,” Ilic says of the Concept Zero product line. -“A lot of people use it as a fidget—it’s sort of like a high-tech stress ball people play with while they think about other things.”
He says sales are healthy. -“I can barely handle what comes in on my end, but I do it.”
Ilic has also developed glass chambers for a number of other ferrofluid artists.
-“People doing this in the United States, most of them came here as a starting point,” he says.
For example, he provided the chambers for artist Matt Robinson’s automated, lava lamp-like Ferroflow displays. He also provides suspension fluid to artist Linden Gledhill, who uses ferrofluid to create intricate abstract images. He helped promote (and Gledhill helped photograph) Mike Pecci’s horror film 12 Kilometers, in which the black, animated fluid plays the villain—a malignant entity released by Russian miners.
He also provided flat-panel chambers to designer Zelf Koelman, who used them with ferrofluid and an array of electromagnets to create a digital clock. Ilic has been working on his own flat panel display, with the electromagnet arrangement to be programmed by the user. He notes that designer Martin Frey used a similar setup to recreate an early video game with ferrofluid pixels. Ilic says he’s also experimenting with dried ferrofluid to create fixed sculptures.
Overall, though, the number of artists working with ferrofluid remains smaller than Ilic would like, he says.
-“The more talented people that get involved, the higher the quality of art.” On his website, he promotes designers new to the medium, as well as some of the original vanguard.
–“If anyone comes up with something I think is interesting, I put it on my website,” he says. -“If it’s cool, it’s going up there, even if it’s a competitor.”
But Ilic says the scarcity of people repurposing this space-age substance for art is also part of its allure.
–“It draws people who want to pioneer something because the field isn’t saturated,” he says. -“It’s like finding a new continent. You don’t know what’s around the corner.”
In contrast to ferrofluids,
magnetorheological fluids (MR fluids) are magnetic fluids with larger particles. That is, a ferrofluid contains primarily nanoparticles, while an MR fluid contains primarily micrometre-scale particles. The particles in a ferrofluid are
suspended by Brownian motion and generally will not settle under normal conditions, while particles in an MR fluid are too heavy to be suspended by Brownian motion. Particles in an MR fluid will therefore settle over time because of the inherent density difference between the particles and their carrier fluid. As a result, ferrofluids and MR fluids have very different applications.
A process for making a ferrofluid was invented in 1963 by NASA’s Steve Papell to create liquid rocket fuel that could be drawn toward a fuel pump in a weightless environment by applying a magnetic field.[2] The name ferrofluid was introduced, the process improved, more highly magnetic liquids synthesized, additional carrier liquids discovered, and the physical chemistry elucidated by R. E. Rosensweig and colleagues. In addition Rosensweig evolved a new branch of fluid mechanics termed ferrohydrodynamics which sparked further theoretical research on intriguing physical phenomena in ferrofluids.
In 2019, researchers at the University of Massachusetts and Beijing University of Chemical Technology succeeded in creating a permanently magnetic ferrofluid which retains its magnetism when the external magnetic field is removed. The researchers also found that the droplet’s magnetic properties were preserved even if the shape was physically changed or it was divided.
DESCRIPTION l
R. E. Rosensweig with ferrofluid in his lab (1965)
Ferrofluids are composed of very small nanoscale particles (diameter usually 10 nanometers or less) of magnetite,
hematite or some other compound containing
iron, and a liquid (usually oil). This is small enough for thermal agitation to disperse them evenly within a carrier fluid, and for them to contribute to the overall magnetic response of the fluid. This is similar to the way that the ions in an aqueous paramagnetic salt solution (such as an aqueous solution of copper(II) sulfate or manganese(II) chloride) make the solution paramagnetic. The composition of a typical ferrofluid is about 5% magnetic solids, 10% surfactant and 85% carrier, by volume.
Particles in ferrofluids are dispersed in a liquid, often using a surfactant, and thus ferrofluids are colloidal suspensions
– materials with properties of more than one state of matter. In this case, the two states of matter are the solid metal and liquid it is in.
This ability to change phases with the application of a magnetic field allows them to be used as seals, lubricants, and may open up further applications in future
nanoelectromechanical systems.
True ferrofluids are stable. This means that the solid particles do not agglomerate or phase separate even in extremely strong magnetic fields. However, the surfactant tends to break down over time (a few years), and eventually the nano-particles will agglomerate, and they will separate out and no longer contribute to the fluid’s magnetic response.
The term;
magnetorheological fluid (MRF) refers to liquids similar to ferrofluids (FF) that solidify in the presence of a magnetic field. Magnetorheological fluids have micrometre
scale magnetic particles that are one to three orders of magnitude larger than those of ferrofluids.
However, ferrofluids lose their magnetic properties at sufficiently high temperatures, known as the Curie temperature.
NORMAL-FIELD INSTABILITY
Ferrofluid is the oily substance collecting at the poles of the magnet which is underneath the white dish.
When a paramagnetic fluid is subjected to a strong vertical magnetic field, the surface forms a regular pattern of peaks and valleys. This effect is known as the Rosensweig or normal-field instability. The instability is driven by the magnetic field; it can be explained by considering which shape of the fluid minimizes the total energy of the system.
From the point of view of magnetic energy, peaks and valleys are energetically favorable.
In the corrugated configuration, the magnetic field is concentrated in the peaks; since the fluid is more easily magnetized than the air, this lowers the magnetic energy. In consequence the spikes of the fluid ride the field lines out into space until there is a balance of the forces involved.
At the same time the formation of peaks and valleys is resisted by gravity and surface tension. It requires energy both to move fluid out of the valleys and up into the spikes, and to increase the surface area of the fluid. In summary, the formation of the corrugations increases the surface free energy and the
gravitational energy of the liquid, but reduces the magnetic energy. The corrugations will only form above a critical magnetic field strength, when the reduction in magnetic energy outweighs the increase in surface and gravitation energy terms.
Ferrofluid simulations for different parameters of surface tension and magnetic field strengths.
Ferrofluids have an exceptionally high magnetic susceptibility and the critical magnetic field for the onset of the corrugations can be realised by a small bar magnet.
Macrophotograph of Ferrofluid influenced by a magnet.
COMMON FERROFLUID SURFACTANTS
The soapy surfactants
used to coat the nanoparticles include, but are not limited to:
• Oleic Acid
• Tetramethylammonium Hydroxide
• Citric Acid
• Soy Lecithin
These surfactants prevent the nanoparticles from clumping together, so the particles can’t fall out of suspension nor clump into a cluster of magnetic dust on near the magnet. The magnetic particles in an ideal ferrofluid never settle out, even when exposed to a strong magnetic field. A surfactant has a polar head and non-polar tail (or vice versa), one of which adsorbs to a nanoparticle, while the non-polar tail (or polar head) sticks out into the carrier medium, forming an inverse or regular
micelle, respectively, around the particle. Electrostatic repulsion then prevents agglomeration of the particles.
While surfactants are useful in prolonging the settling rate in ferrofluids, they also hinder the fluid’s magnetic properties (specifically, the fluid’s
magnetic saturation).
The addition of surfactants (or any other foreign particles) decreases the packing density of the ferroparticles while in its activated state, thus decreasing the fluid’s on-state viscosity, resulting in a “softer” activated fluid. While the on-state viscosity (the “hardness” of the activated fluid) is less of a concern for some ferrofluid applications, it is a primary fluid property for the majority of their commercial and industrial applications and therefore a compromise must be met when considering on-state viscosity versus the settling rate of a ferrofluid.
[image]:
A ferrofluid in a magnetic field showing normal-field instability caused by a neodymium magnet beneath the dish
APPLICATIONS
ACTUAL
ELECTRONIC DEVICES
(Main article: Ferrofluidic Seal)
Ferrofluids are used to form liquid seals around the spinning drive shafts in computer hard disks. The rotating shaft is surrounded by magnets. A small amount of ferrofluid, placed in the gap between the magnet and the shaft, will be held in place by its attraction to the magnet. The fluid of magnetic particles forms a barrier which prevents debris from entering the interior of the hard drive. According to engineers at Ferrotec, ferrofluid seals on rotating shafts typically withstand 3 to 4 psi; additional seals can be stacked to form assemblies capable of withstanding higher pressures.
MECHANICAL ENGINEERING
Ferrofluids have
friction-reducing capabilities. If applied to the surface of a strong enough magnet, such as one made of neodymium, it can cause the magnet to glide across smooth surfaces with minimal resistance.
Ferrofluids can also be used in semi-active dampers in mechanical and aerospace applications. While passive dampers are generally bulkier and designed for a particular vibration source in mind, active dampers consume more power. Ferrofluid based dampers solve both of these issues and are becoming popular in the helicopter community, which has to deal with large inertial and aerodynamic vibrations.
MATERIALS SCIENCE RESEARCH
Ferrofluids can be used to image magnetic domain structures on the surface of ferromagnetic materials using a technique developed by Francis Bitter.
LOUDSPEAKERS
Starting in 1973, ferrofluids have been used in loudspeakers to remove heat from the voice coil, and to passively damp the movement of the cone. They reside in what would normally be the air gap around the voice coil, held in place by the speaker’s magnet. Since ferrofluids are paramagnetic, they obey Curie’s law and thus become less magnetic at higher temperatures. A strong magnet placed near the voice coil (which produces heat) will attract cold ferrofluid more than hot ferrofluid thus pulling the heated ferrofluid away from the electric voice coil and toward a heat sink. This is a relatively efficient cooling method which requires no additional energy input.
Bob Berkowitz, of Acoustic Research
began studying ferrofluid in 1972, using it to damp resonance of a tweeter. Dana Hathaway of Epicure in Massachusetts was using ferrofluid for tweeter damping in 1974, and he noticed the cooling mechanism. Fred Becker and Lou Melillo of Becker Electronics were also early adopters in 1976, with Melillo joining Ferrotec and publishing a paper in 1980.
In concert sound,
Showco began using ferrofluid in 1979 for cooling woofers.
Panasonic was the first Asian manufacturer to put ferrofluid in commercial loudspeakers, in 1979. The field grew rapidly in the early 1980s. Today, some 300 million sound-generating transducers per year are produced with ferrofluid inside, including speakers installed in laptops, cell phones, headphones and earbuds.
CELL SEPARATIONS
Ferrofluids conjugated with antibodies or common capture agents such as Streptavidin (SA) or rat anti-mouse Ig (RAM) are used in Immunomagnetic separation, a subset of Cell sorting. These conjugated ferrofluids are used to bind to target cells, and then magnetically separate them from a cell mixture using a low-gradient magnetic separator. These ferrofluids have applications such as Cell Therapy, Gene therapy, Cellular manufacturing, among others.
FORMER
MEDICAL APPLICATIONS
Several ferrofluids were marketed for use as contrast agents in magnetic resonance imaging, which depend on the difference in magnetic relaxation times of different tissues to provide contrast. Several agents were introduced and then withdrawn from the market, including Feridex I.V. (also known as Endorem and ferumoxides), discontinued in 2008; resovist (also known as Cliavist), 2001 to 2009; Sinerem (also known as Combidex), withdrawn in 2007; Lumirem (also known as Gastromark), 1996 to 2012; Clariscan (also known as PEG-fero, Feruglose, and NC100150), development of which was discontinued due to safety concerns.
FUTURE
SPACECRAFT PROPULSIÓN
(Further information: Spacecraft propulsion)
Ferrofluids can be made to self-assemble nanometer-scale needle-like sharp tips under the influence of a magnetic field. When they reach a critical thinness, the needles begin emitting jets that might be used in the future as a thruster mechanism to propel small satellites such as CubeSats.
ANALYTICAL INSTRUMENTATION
Ferrofluids have numerous optical applications because of their refractive properties; that is, each grain, a micromagnet, reflects light. These applications include measuring
specific viscosity of a liquid placed between a polarizer and an
analyzer, illuminated by a helium–neon laser.
MEDICAL APPLICATIONS
Ferrofluids have been proposed for magnetic drug targeting. In this process the drugs would be attached to or enclosed within a ferrofluid and could be targeted and selectively released using magnetic fields.
It has also been proposed for targeted magnetic hyperthermia to convert electromagnetic energy into heat.
It has also been proposed in a form of nanosurgery to separate one tissue from another—for example a tumor from the tissue in which it has grown.
HEAT TRANSFER
An external magnetic field imposed on a ferrofluid with varying susceptibility (e.g., because of a temperature gradient) results in a nonuniform magnetic body force, which leads to a form of heat transfer
called thermomagnetic convection. This form of heat transfer can be useful when conventional convection heat transfer is inadequate; e.g., in miniature microscale devices or under reduced gravity conditions.
Ferrofluids of suitable composition can exhibit extremely large enhancement in thermal conductivity (k; ~300% of the base fluid thermal conductivity). The large enhancement in k is due to the efficient transport of heat through percolating nanoparticle paths. Special magnetic nanofluids with tunable thermal conductivity to viscosity ratio can be used as multifunctional ‘smart materials’ that can remove heat and also arrest vibrations (damper). Such fluids may find applications in microfluidic devices and microelectromechanical systems (MEMS).
OPTICS
Research is under way to create an adaptive optics shape-shifting magnetic mirror from ferrofluid for Earth-based astronomical telescopes.
Optical filters are used to select different wavelengths of light. The replacement of filters is cumbersome, especially when the wavelength is changed continuously with tunable-type lasers. Optical filters tunable for different wavelengths by varying the magnetic field can be built using ferrofluid emulsion.
ENERGY HARVESTING
Ferrofluids enable an interesting opportunity to harvest vibration energy from the environment. Existing methods of harvesting low frequency (<100 Hz) vibrations require the use of solid resonant structures. With ferrofluids, energy harvester designs no longer need solid structure. One simple example of ferrofluid based energy harvesting
is to place the ferrofluid inside a container to use external mechanical vibrations to generate electricity inside a coil wrapped around the container surrounded by a permanent magnet.
First a ferrofluid is placed inside a container that is wrapped with a coil of wire. The ferrofluid is then externally magnetized using a permanent magnet. When external vibrations cause the ferrofluid to slosh around in the container, there is a change in magnetic flux fields with respect to the coil of wire. Through Faraday’s law of electromagnetic induction, voltage is induced in the coil of wire due to change in magnetic flux.
SEE ALSO:
• Smart Fluid – Fluid whose properties can be changed by applying an electric or magnetic field
• Magnetic Field viewing film
• Magnetorheological fluid
• Electrorheological fluid
• Magnetohydrodynamics – Study of the magnetic properties of electrically conducting fluids
• Magnetic ionic liquid
• Plasma physics
• Fluid mechanics – Branch of physics concerned with the mechanics of fluids (liquids, gases, and plasmas)
• Continuum mechanics – Branch of physics which studies the behavior of materials modeled as continuous masses
REFERENCES:
^ Voit, W.; Kim, D. K.; Zapka, W.; Muhammed, M.; Rao, K. V. (21 March 2011). “Magnetic behavior of coated superparamagnetic iron oxide nanoparticles in ferrofluids”. MRS Proceedings. 676. doi:10.1557/PROC-676-Y7.8.
^ US Patent # 3215572 filed Oct 9, 1963 https://www.google.com/patents/US3215572
^ Rosensweig, R.E. (1997), Ferrohydrodynamics, Dover Books on Physics, Courier Corporation, ISBN 9780486678344
^ Shliomis, Mark I. (2001), “Ferrohydrodynamics: Testing a third magnetization equation”, Physical Review, 64 (6): 060501, arXiv:cond-mat/0106415, Bibcode:2001PhRvE..64f0501S, doi:10.1103/PhysRevE.64.060501, PMID 11736163, S2CID 37161240
^ Gollwitzer, Christian; Krekhova, Marina; Lattermann, Günter; Rehberg, Ingo; Richter, Reinhard (2009), “Surface instabilities and magnetic soft matter”, Soft Matter, 5 (10): 2093, arXiv:0811.1526, Bibcode:2009SMat….5.2093G, doi:10.1039/b820090d, S2CID 17537054
^ Singh, Chamkor; Das, Arup K.; Das, Prasanta K. (2016), “Flow restrictive and shear reducing effect of magnetization relaxation in ferrofluid cavity flow”, Physics of Fluids, 28 (8): 087103, Bibcode:2016PhFl…28h7103S, doi:10.1063/1.4960085
^ Lawrence Berkeley National Laboratory (July 18, 2019). “New laws of attraction: Scientists print magnetic liquid droplets”. phys.org. Retrieved 2019-07-19.
^ Helmenstine, Anne Marie. “How to Make Liquid Magnets”. ThoughtCo. Retrieved 2018-07-09.
^ “Vocabulary List”. education.jlab.org. Retrieved 2018-07-09.
^ Andelman & Rosensweig 2009, pp. 20–21.
^ Andelman & Rosensweig 2009, pp. 21, 23, Fig. 11.
^ Andelman & Rosensweig 2009, pp. 21.
^ Mee, C D (1950-08-01). “The Mechanism of Colloid Agglomeration in the Formation of Bitter Patterns”. Proceedings of the Physical Society, Section A. 63 (8): 922. Bibcode:1950PPSA…63..922M. doi:10.1088/0370-1298/63/8/122. ISSN 0370-1298.
^ Rlums, Elmars (1995). “New Applications of Heat and Mass Transfer Processes in Temperature Sensitive Magnetic Fluids” (PDF). Brazilian Journal of Physics. 25(2).
^ Melillo, L. and Raj, K. (1980). “Ferrofluids as a Means of Controlling Woofer Design Parameters,” Journal of the Audio Engineering Society, Volume 29, No. 3, March 1981, pp. 132-139.
^ Free, John (June 1979). “Magnetic Fluids”. Popular Science. p. 61.
^ “Brief History of Ferrofluid”.
^https://biomagneticsolutions.com/pages/ferrofluid
^ a b Scherer, C.; Figueiredo Neto, A. M. (2005). “Ferrofluids: Properties and Applications”(PDF). Brazilian Journal of Physics. 35 (3A): 718–727. Bibcode:2005BrJPh..35..718S. doi:10.1590/S0103-97332005000400018.
^ Wang, YX (December 2011). “Superparamagnetic iron oxide based MRI contrast agents: Current status of clinical application”. Quantitative Imaging in Medicine and Surgery. 1 (1): 35–40. doi:10.3978/j.issn.2223-4292.2011.08.03. PMC 3496483. PMID 23256052.
^ “Feridex – Products – AMAG Pharmaceuticals”. Amagpharma.com. Archived from the original on 2012-06-15. Retrieved 2012-06-20.
^ Softways. “Magnetic Resonance TIP – MRI Database : Resovist”. Mr-tip.com. Retrieved 2012-06-20.
^ “AMAG Pharmaceuticals, Inc. Announces Update on Sinerem(TM) in Europe. – Free Online Library”. Thefreelibrary.com. 2007-12-13. Retrieved 2012-06-20.
^ “Newly Approved Drug Therapies (105) GastroMARK, Advanced Magnetics”. CenterWatch. Retrieved 2012-06-20.
^ “AMAG Form 10-K For the Fiscal Year Ended December 31, 2013”. SEC Edgar.
^ “NDA 020410 for GastroMark”. FDA. Retrieved 12 February 2017.
^ Wang, Yi-Xiang J. (2011). “Superparamagnetic iron oxide based MRI contrast agents: Current status of clinical application”. Quantitative Imaging in Medicine and Surgery. 1 (1): 35–40. doi:10.3978/j.issn.2223-4292.2011.08.03. PMC 3496483. PMID 23256052.
^ Raval, Siddharth (2013-10-17). “Novel Thrusters Being Developed for Nanosats”. Space Safety Magazine. Retrieved 2018-07-09.
^ Pai, Chintamani; Shalini, M; Radha, S (2014). “Transient Optical Phenomenon in Ferrofluids”. Procedia Engineering. 76: 74–79. doi:10.1016/j.proeng.2013.09.250.
^ Kumar, CS; Mohammad, F (14 August 2011). “Magnetic nanomaterials for hyperthermia-based therapy and controlled drug delivery”. Advanced Drug Delivery Reviews. 63 (9): 789–808. doi:10.1016/j.addr.2011.03.008. PMC 3138885. PMID 21447363.
^ Kafrouni, L; Savadogo, O (December 2016). “Recent progress on magnetic nanoparticles for magnetic hyperthermia”. Progress in Biomaterials. 5 (3–4): 147–160. doi:10.1007/s40204-016-0054-6. PMC 5304434. PMID 27995583.
^ Shima, P. D.; Philip, John (2011). “Tuning of Thermal Conductivity and Rheology of Nanofluids Using an External Stimulus”. The Journal of Physical Chemistry C. 115 (41): 20097. doi:10.1021/jp204827q.
^ Hecht, Jeff (7 November 2008). “Morphing mirror could clear the skies for astronomers”. New Scientist.
^ Philip, John; Jaykumar, T; Kalyanasundaram, P; Raj, Baldev (2003). “A tunable optical filter”. Measurement Science and Technology. 14 (8): 1289. Bibcode:2003MeScT..14.1289P. doi:10.1088/0957-0233/14/8/314.
^ a b Bibo, A.; Masana, R.; King, A.; Li, G.; Daqaq, M.F. (June 2012). “Electromagnetic ferrofluid-based energy harvester”. Physics Letters A. 376 (32): 2163–2166. Bibcode:2012PhLA..376.2163B. doi:10.1016/j.physleta.2012.05.033.
BIBLIOGRAPHY
Andelman, David; Rosensweig, Ronald E. (2009). “The Phenomenology of Modulated Phases: From Magnetic Solids and Fluids to Organic Films and Polymers”. In Tsori, Yoav; Steiner, Ullrich (eds.). Polymers, liquids and colloids in electric fields: interfacial instabilities, orientation and phase transitions. Polymers. pp. 1–56. Bibcode:2009plce.book…..T. doi:10.1142/7266. ISBN 978-981-4271-68-4.
Berger, Patricia; Nicholas B. Adelman; Katie J. Beckman; Dean J. Campbell; Ellis, Arthur B.; Lisensky, George C. (1999). “Preparation and properties of an aqueous ferrofluid”. Journal of Chemical Education. 76 (7): 943–948. Bibcode:1999JChEd..76..943B. doi:10.1021/ed076p943. ISSN 0021-9584.
EXTERNAL LINKS:
Wikimedia Commons has media related to Ferrofluids.
How ferrofluid works video on YouTube
A comparison of ferrofluid and MR fluid (at the bottom of the page)
Chemistry comes alive: Ferrofluid (subscription required)
Sachiko Kodama art projects: Ferrofluid Sculptures (Google Video), Ferrofluid Sculptures
Daniel Rutter has some fun with Ferrofluid
Marketing material at INVENTUS Engineering GmbH website: High pressure valve
Liquid seal for Stirling piston (video) on YouTube
FerroFluid Synthesis
Teaching materials: Interdisciplinary education group: Ferrofluids (contains videos and a lab for synthesis of ferrofluid)
“Synthesis of an Aqueous Ferrofluid”. voh.chem.ucla.edu. Retrieved 2018-07-09.
SOURCE: https://en.m.wikipedia.org/wiki/Ferrofluid
RELATED VIDEO:
https://www.bitchute.com/video/ZK8I47otRriK/
FERROFLUID, GRAPHENE IRON OXIDE NANOPARTICLES:
https://www.bitchute.com/video/ZK8I47otRriK/
EXPOSING MEDICAL TYRANNY