Ferrofluid

Ferrofluid is a very interesting material orginally developed by NASA it has now found itself been used for a whole range of devices indluding dumpers for controlling and stablizing large buliding that more around in the wind. What also amazing is that they have such lovely visual qualities when magnetized.
Basiclly, ferrofluids appear as a black fluid. They are prepared by dissolving nanoscale ferromagnetic particles in a solvent such as water or oil and remain strongly magnetic even in a fluid condition. Therefore, they are more flexibly transformable as compared to iron sand. It is well known that ferrofluids from spikes along magnetic field.
Lines when the magnetic surfaces force exceeds the stablizing effects of the fluid weight and surface tension.

Ferrofluids are made from a suspension of tiny magnetic particles in a liquid such as water or oil. Such a mixture creates a liquid that can be attracted by a magnetic field.
NASA discovered ferrrofluid at one ot their research centers in th 1960's while were looking for different methods of controlling liquids in space.

The magnetic materials used are often made from iron or cobalt particles, but compounds such as manganese zinc ferrite are also used. The most common form of ferrofluid is made using particles of a type of iron oxide known as magnetite (Fe3O4).

Making a stable ferrofluid is not quite as simple as mixing tiny particles into a liquid. First of all the particles must be very small. The average size is around 10 nm ( 0.00000001 meters ). These particles can not be made by crashing or grinding a material, but are preciptated out of a solution during a chemical reaction.

Ferrofluids are made from a suspension of tiny magnetic particles in a liquid such as water or oil.
Such a mixture creates a liquid that can be attracted by magnetic field.

During the precipitation the particles would naturally amalgamate (come together) due to magnetic and Van der Walls forces. To prevent this the mixture is heated so that thermal motion of the magnetite particles prevents them from sticking together. In order to prevent the particles from amalgamating after the reaction they must be kept apart from each other.
This can be achieved by coating each particles with another materials known as a surfacant (surface active agent) to produce electrostatic or steric repulsive forces between the particles.

In an oil based ferrofluid, cis-oleic acid can be used as a surfacant. This is a long-chain hydrocarbon with a polar head that sticks to the surface of the magnetite particles. The long molecules stick out in all directions around each magnetite particle preventing them from getting close enought to stick together.

Water based (aqueous) ferrofluids often use ionic sufficants such as tetramethlammonium hydroxide. The negative hydroxide ions stick to the surfaceof the magnetite, and the tetramethylammonium cations form a positively charged layers around the outside. This means that the magnetite particles are held apart by the electrostatic repulsive force of the surrounding molecules.
The spikes form in a manner as if they are following the field lines. In a stronger magnetic field there are more filed lines hance more spikes in the ferrofluid.

Ferrofluid have several uses due to their magnetic properties. They can be used inside a magnetized bearing like an o-ring seal so that rotating shafts can pass from high to low pressure zones and vise versa. This is a much more efficient method than using solid seals as there is significantly less friction.
This makes them ideal for use in submarines, rotating anode x-ray machines, disk drivers, and vacuum chambers with external manipulators.

Liquid magnets do not exist, since all magnetic substances lose their ferromagnetic properties above a certain temperature, the curie temperature, which is always lower then the melting temperature.
However, magnetic liquid do exist in the form of so-called ferrofluids.

Magnetic fiels are generated by electric current. The motion of electrons around the nuclei of atoms thus causes the presence of magnetic field on the atomic level. Many atoms have a non-zero magnetic moment of the order of 10^-23 Am^2. However, fot most substances, the net magntic moment is zero due to random orientation of all atomic moments within the assembly. A non-zero magntic moment can be induced by application of a magnetic field. Science the atomic rotate in a Brownian way the degree of alignment depends on the temperature and field strength and the susceptibility of the material.