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Preparation and Properties of an Aqueous Ferrofluid Research Paper

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Updated: Apr 27th, 2022

Introduction

A ferrofluid is a liquid that contains very small pieces of a magnetic substance and hence acquires its magnetic properties when placed in a magnetic field. Ferrofluids were initially discovered in the 1960s at the NASA Research Center, where scientists were investigating different probable methods of controlling liquids in space (Jech & Odenbach, 5). The material comprise of very tiny pieces of iron alloys, usually with a maximum diameter of 10nm. Nevertheless, ferrofluids are demagnetized at high temperatures. Their fluids can also undergo resistance change following this formula:

ρ = Ve-B2 + p

Where:

  • ρ is the resistance in MΩ
  • V is the Vollema value, unique to each ferrofluid
  • B is the strength of the magnetic field
  • p is the Pietrow constant

The term ‘ferrofluid’ can be used interchangeably with a magnetorheological fluid (MR fluid), although the latter contains slightly larger particles. A ferrofluid primarily consists of small particles which are suspended in a fluid consisting of a solvent and surfactant. While ferrofluid particles will not settle under ordinary conditions, MR fluid particles will settle over time due to the large size of the particles. Today, ferrofluids are used in many different fields even as research continues into how their inherent and unique characteristics can further be made use of.

How ferrofluids are prepared

Ferrofluids are normally prepared by reacting minute fragments of iron with other solvents (normally kerosene) together with a surfactant, usually oleic acid, which stops the particles from sticking together in the suspension. Water can be used in place of solvents. Surfactants are used because when iron particles are in close proximity to each other, the van der Waals forces of attraction between them increases (Jech & Odenbach, 5). The natural magnetic forces between the particles can make them stick together. Surfactants prevent the particles from sticking together by generating either steric or electrostatic repulsions between the magnetic particles which counters the van der Waal and magnetic forces.

A typical ferrofluid is made up of roughly 5% magnetic particles, 10% surfactant, while the rest of the volume is taken up by the carrier fluid. Magnetite is the most commonly used iron ore. Ferrofluids that contains magnetite can be prepared by combining the required amounts of an Fe(II) salt and an Fe(III) salt in basic solution (Berger, Adelman, and Beckman, 12), this reaction gives an oxide, Fe3O4, which precipitates from solution, i.e.

2 FeCl3 + FeCl2 + 8 NH3 + 4H2O —-> Fe3O4 + 8 NH4Cl

During the reaction, safety procedures must be put in place because the reactants are flammable while the products include heat and lethal fumes. It is recommended that safety glasses should be used, and the reaction must be carried out in a well-aired area.

Applications

The most common commercial application of ferrofluids is in electronic products, mainly speakers and hard drives. The fluid prevents debris from entering the inner delicate parts of the hard drives and this is achieved by placing a small amount of ferrofluid between the magnets and shaft. Ferrofluids enhance the performance of loudspeakers by dissipating heat from the coils, helping to dampen the cone movement. Electric energy produced in a speaker is usually transmitted via a coil found at the center of the large permanent magnet. As a result, a magnetic field is formed momentarily and this causes the coil to vibrate, producing sound. Immersing the coil in a ferrofluid causes damping of the undesired resonance and also offers a channel for dissipating heat energy produced during coil movement (Pitt, 77). These two processes improve the performance the speaker resulting in quality sound and durability.

In the late 1980s, ferrofluids were found out to repel radar waves and as a result have been used in military planes up to date. When ferrofluids are added to paint and used on any surface, it creates a surface that is able to absorb radar waves (Jech & Odenbach, 5). Fighter and intelligence-gathering planes covered with this kind of paint are able to absorb radar waves and remain invisible to radar when they pass overhead. Fighter jets made using this technology are referred to as stealth bombers due to their ability to partake in mission without being recognized by the enemy.

Ferrofluids are used widely in healthcare. For instance, they are used to discover and treat ulcers and fistulas in patients. In this process, a ferrofluid is inserted in the fistulous tract and a permanent magnet placed on the outer opening thus shutting the fistula while not affecting the healing progress. Ferrofluids are also used in the treatment of cancer. Under this process, the magnetic particles in the fluids reach cancer cells and puncture their membranes, killing them. Ferrofluids can preserve eye functioning among persons with retinal defects. When a person suffers from trauma or certain sicknesses, the retina becomes laminated and this weakens vision. This can lead to total blindness. Magnetized ferrofluids can help to return the retina back to its position and hence sustain normal eye functioning (Odenbach, 24).

Still focusing on healthcare, a hyperthermia undertake using a ferrofluid can treat a malignant brain tumor (Johannsen, Jordan, Scholz, Koch, and Lein, 496). Under this process, the ferrofluid is inserted into the tumor tissue while the patient is sedated. Iron particles from the fluid are up taken by the cancerous cells which are then acted upon by the outside magnetic field, causing the iron nanoparticles to grow hotter, up to 45°C, destroying the tumor. Research is still ongoing on the application of this process on humans as previous experiments on animals have been successful.

The unique properties of ferrofluids make it a viable technology for use in sensor and switch applications. Experiments and research have proven that this material can be used in transformers to provide several benefits, for instance, they can enhance cooling processes within the coils thereby reducing the consumption rate of transformer oil (Ferrotec). It can also be used to enhance the transformer ability to counter lightning shocks, whereas also lessening the impact of moisture on normal insulation fluids. The inherent advantages of ferrofluid can help in designing smaller transformers with improved performance, or to make the current ones more durable or increasing their loading ability (Ferrotec). Lastly, the use of a ferrofluid in a solenoid significantly lessens the noise produced by certain equipment. Consequently, this cancels, or reduces the need to insulate such machines from noise thus making it possible to have a smaller and more affordable design with improved portability.

The future of ferrofluids

Ferrofluid have a potential for use in many fields, some of which are currently ongoing. These include the military, manufacture of electronic devices, mechanical engineering, analytical instrumentation, optics, art, thermal physics, and so on. Many uses of these fluids are being researched, for instance, in making liquid armor and for tracing chemicals in biological systems using magnetic resonance imaging (MRI). It is probably going to find a lot more uses in the future because of its smart and unique capabilities (Odenbach, 52). Its use in healthcare could save a lot of lives and even help treat some diseases and disorders. Its probable use as a tracer and in transporting medicine to the appropriate organs would also potentially save lives, making the material even more useful.

Conclusion

A ferrofluid is a liquid that contains small, suspended pieces of a magnetic substance and hence gets its magnetic properties when placed in a magnetic field. Similar to all other magnetic materials, they become demagnetized at high temperatures. They are prepared by reacting iron oxides with organic solvents, then adding a surfactant to prevent the minute particles from sticking together and ensuring they remain suspended. Ferrofluids have found application in many fields. These include their use to design planes that are invisible to radar waves, dissipating heat from loudspeaker coils and damping undesired resonance, treating ulcers and fistulas among patients and treating malignant brain tumor, preserving vision, improving the performance of transformers, reducing the noise produced by certain machines and equipment, among many other functions. Research is still ongoing on the application of this technology in a number of fields. The success of these research and experiments could potentially save many lives and improve the health of many others. In addition, inventions made using this technology cloud make everyday processes become simpler through the design of efficient machines, equipment, and apparatus.

Works Cited

Berger, Patricia, Nicholas B. Adelman, and Katie J. Beckman. “Preparation and properties of an aqueous ferrofluid”. Journal of Chemical Education, 76.7 (1999): 943–948. Print.

Ferrotec. Other Forrofluid Applications. 2012. Web. Web.

Jech, Thomas, and Stefan Odenbach. Ferrofluids: Magnetically Controllable Fluids and Their Applications. New York: Springer New, 2003. Print.

Johannsen, Manfred, Andreas Jordan, Regina Scholz, Martin Koch, and Michael Lein. “Evaluation of Magnetic Fluid Hyperthermia in a Standard Rat Model of Prostate Cancer”. Journal of Endourology, 18.5 (2004): 495-500. Print

Odenbach, Stefan. Magnetoviscous effects in ferrofluids. New York: Springer, 2002. Print.

Pitt, Annie. Magnetic Fluids and Planetary Influence. Montana: Kessinger Publishing, 2011. Print.

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