Magnetic fluid is a uniquely 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 technologies characteristic of our time, substances with such unusual properties are finding more and more applications.
A magnetic fluid is a highly dispersed suspension, in other words, a colloidal solution of a ferromagnetic material in an ordinary liquid medium, which can serve as simple water, and hydrocarbons, and organosilicon or fluorine. Such unusual substances appeared a long time ago. 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, which were intensively conducted by two superpowers. To a wider scientific community, these unusual substances have become available relatively recently. Now magnetic fluid is actively studied by most developed countries with high scientific potential: Japan, France, Germany, Great Britain and others.
These amazing substances are unique in their unrivaled combination of high fluidity with exceptional magnetic properties, which are tens of thousands of orders of magnitude higher than any of the known liquids. The secret of such a phenomenal magnetization is the dispersion of ferromagnets to sizes not exceeding ten nanometers, followed by their introduction into a normal 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 coated with a protective and repulsive film, preventing their adhesion. Thermal motion distributes small magnets over the entire volume of the substance, which helps to avoid settling of particles to the bottom. As a result, magnetic fluid is able to maintain its unique qualities and performance over many years.
Each such microscopic magnet circulates randomly in a liquid under the influence of thermal energy. The magnetic moments of the microparticles are oriented in a certain way by the external magnetic field , which causes a change in the optical, rheological, and magnetic properties of the colloidal solution. Therefore, the high level of sensitivity of the suspension to an external source of magnetic field makes it possible to regulate their behavior. Thus, the magnetic fluid itself also acquires controllability, the use of which becomes possible to solve a wide range of applied problems.
Ferromagnetic suspensions are already used in the manufacture of hard drives, where they are applied to a rotating axis to prevent foreign particles from entering from outside. Such suspensions are also used in the manufacture of tweeters, in the aerospace and military industries, in optics and medicine, in electronics and instrument-making industries.