Magnetic fluid is a unique man-made miracle, the brainchild of technological progress and scientific thought of the twentieth century. Unlike the vast majority of inventions of human genius, such liquid substances, with pronounced magnetic properties, have no analogues in nature. With the rapid development of technology, characteristic of our time, there are more and more applications for substances with such unusual properties.
Magnetic fluid is a highly dispersed suspension, in other words, a colloidal solution of a ferromagnetic material in an ordinary liquid medium, which can be plain water, hydrocarbons, and organosilicon or fluorine substances. Such unusual substances have appeared for a long time. Back in the mid-sixties, they were synthesized in the United States and the Soviet Union almost simultaneously.
At that time, magnetic fluids were used in various space programs thatintensively pursued by the two superpowers. These unusual substances have become available to a wider scientific community relatively recently. Now magnetic fluid is being actively studied by most developed countries with high scientific potential: Japan, France, Germany, Great Britain and others.
These amazing substances are unique in their unsurpassed combination of high fluidity with exceptional magnetic properties, which are tens of thousands of orders of magnitude higher than any known liquid. The secret of such a phenomenal magnetization lies in the dispersion of ferromagnets to sizes not exceeding ten nanometers, with their subsequent introduction into an ordinary liquid medium.
Thus, a substance with initially excellent fluidity is saturated with an unimaginable number of powerful miniature permanent magnets of spherical shape. Each such nanoparticle is covered with a protective-repellent film that prevents them from sticking together. Thermal motion distributes small magnets throughout the volume of the substance, thereby avoiding the settling of particles to the bottom. As a result, the magnetic fluid is able to maintain its unique qualities and performance characteristics for many years.
Each such microscopic magnet randomly circulates in a liquid under the influence of thermal energy. The magnetic moments of microparticles are oriented in a certain way by an external magnetic field, which causes a change in the optical, rheological and magneticproperties of the colloidal solution. Therefore, a high level of suspension sensitivity to an external magnetic field source makes it possible to control their behavior. Thus, the magnetic fluid itself acquires controllability, the use of which becomes possible for solving a wide range of applied problems.
Ferromagnetic slurries are already being used in the manufacture of hard drives, where they are applied to a rotating axle to prevent foreign particles from entering. Such suspensions are also used in the manufacture of high-frequency speakers, in the aerospace and military industries, in optics and medicine, in electronics and instrumentation industries.
