Superparamagnetism Superparamagnetism is a property found mainly in small, single-domain magnetic particles without magnetic memory. It is more related to ferromagnetism than paramagnetism. For example, when a ferromagnetic multi-domain Fe3O4 sample is reduced to less than about 40 nm, a single-domain magnetic particle will eventually form. When placed in an external magnetic field, this molecule develops strong internal magnetization as a result of the interchangeable coupling of electrons in the domain, and thus becomes superparamagnetic. Since only one domain is involved, the susceptibility of a superparamagnetic substance is not as great as that of a ferromagnetic substance. Additionally, since each domain is in a separate particle, there must be no interactions or the order of the domains in the sample. Thus, unlike ferromagnetic materials, superparamagnetic substances do not retain net magnetization when the external field is removed. In other words, they don't have magnetic memory.

Ferrofluid Developed by NASA scientists in the 1960s, ferrofluids have the properties of a liquid and the magnetic properties of a solid. They actually contain fine particles (10-20 nm) of a magnetic solid suspended in a liquid medium. The benefits of magnetic fluids became immediately obvious: the position of the fluid can be precisely controlled by applying a magnetic field, and by varying the field strength, the fluid can be forced to flow. Scientists prepared ferrofluids containing fine particles of ferromagnetic metals such as cobalt and iron, and magnetic compounds such as manganese-zinc ferrite. However, so far most of the work has been carried out on ferrofluids containing Fe3O4 magnetite nanoparticles. The fluid medium of choice is kerosene for educational research or simple experiments, and synthetic oils for professional use. While the characteristic spike pattern on the ferrofluid surface is spectacular, this property is not particularly useful. However, ferrofluids have found a wide range of applications, including, for example, in rotary shaft seals. Ferrofluid can behave like a liquid O-ring as the rotating shaft enters the low or high pressure chamber. The ferrofluid is held in place by permanent magnets and creates a tight seal, eliminating most of the friction produced in a traditional mechanical seal. These rotary shaft seals can be found in rotary anode X-ray generators and in vacuum chambers used in the semiconductor industry. Ferrofluid seals are also used in high-speed computer disks to eliminate harmful dust particles or other contaminants that can cause data reading heads to collide with the disks. Another use of ferrofluids is to improve speaker performance. In a loudspeaker, electricity is transmitted through a coil placed in the center of the circular permanent magnet. The magnetic field induced by electricity causes the coil to vibrate and thus produces sound and heat. The bath of the electric coil in the ferrule, which is held in place by circular permanent magnets, suppresses unwanted resonances and also provides a mechanism for dissipating heat from excess energy supplied to the coil. Both of these factors lead to an overall improvement in sound quality. Finally, there is great hope for future biomedical applications of ferrofluids. For example, scientists are trying to design ferrofluids that can transport drugs to specific places in the body using applied magnetic fields. Another ongoing work concerns the use of ferrofluids as contrast agents for magnetic resonance imaging (MRI).

FAQs Archive - Wion Technology

Superparamagnetism

By admin|2023-03-14T15:04:58+00:00March 14th, 2023|

Superparamagnetism Superparamagnetism is a property found mainly in small, single-domain magnetic particles without magnetic memory. It is more related to ferromagnetism than paramagnetism. For example, when a ferromagnetic multi-domain Fe3O4 sample is reduced to less than about 40 nm, a single-domain magnetic particle will eventually form. When placed in an external magnetic field, this [...]

Ferrofluid

By admin|2023-03-14T15:04:03+00:00March 14th, 2023|

Ferrofluid Developed by NASA scientists in the 1960s, ferrofluids have the properties of a liquid and the magnetic properties of a solid. They actually contain fine particles (10-20 nm) of a magnetic solid suspended in a liquid medium. The benefits of magnetic fluids became immediately obvious: the position of the fluid can be precisely [...]

Iron (II,III) oxide nanoparticles

By admin|2023-03-14T15:02:43+00:00March 14th, 2023|

Iron (II,III) oxide nanoparticles One of the basic elements of our daily life is iron. This element responsible for the core of technological development is prone to form many compounds with other elements, in particular with oxygen. Therefore, iron oxides have become common and widely used, and due to their low price, they play [...]

Pigment Volume Content (PVC)

By admin|2023-03-14T14:56:53+00:00March 14th, 2023|

PVC coefficient Decorative and industrial paints consist of: binders / binder, pigments, solvent, rheological additives (wetting, defoaming, thixotropic agent) The addition of pigments is to give the appropriate color to the coating or to act as a filler to obtain the correct consistency of the paint. Most often, pigments [...]