Ferrofluid is a liquid that is attracted to the poles of a magnet. It 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 clump 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.[1]
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.[3][4][5][6] 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.[7]
Description
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.[8]
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.[9] 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. Howevehe 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.
दोस्तों अभी आप जिस liquid को देख रहे हों वह एक Magnetic Fluid यानि एक तरल चुंबक है, जिसे Ferrofluid कहा जाता हैं। इस Ferrofluid को सबसे पहले 1960 के दशक की शुरुआत में NASA के Engineer, Steve Papell द्वारा किसी खास मकसद के लिए आविष्कार किया गया था। लेकिन वोह mission failled हो गया था, अगर आप नासा के उस खास मकसद के पीछे की रहस्य को जानना चाहते हों तो कमेंट में बताइए।
Friends, the liquid you are seeing now is a magnetic fluid i.e. a liquid magnet, which is called Ferrofluid. This ferrofluid was first invented for a specific purpose in the early 1960s by NASA engineer, Steve Papell. But that mission failed, if you want to know the secret behind that special objective of NASA, then tell in the comment.
@AyE_sciEncE
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