TOP > Rotary Feedthrough > What is a magnetic fluid?The characteristic of magnetic fluid

What is a magnetic fluid?
The characteristic of magnetic fluid

What is a magnetic fluid?

magnetic fluid is a fluid that is attracted to a magnet, just like iron. In the 1960s, NASA developed magnetic fluid as part of the space program. magnetic fluid has three main constituents: ferromagnetic particles such as magnetite and composite ferrite, a surfactant, and a base liquid such as water or oil. The surfactant coats the ferromagnetic particles, each of which has a diameter of about 10 nm (ten millionths of a millimeter). This prevents coagulation and keeps the particles evenly dispersed throughout the base liquid. Its dispersibility remains stable in strong magnetic fields.

magnetic fluid dispersion model


Spiking phenomenon

This photo shows a phenomenon that occurs when magnetic fluid is placed in a container and a magnet is placed under the container. The magnetic force acting on the surface of the magnetic fluid produces 'spikes', which look like large nails sticking out of the surface. Therefore, this phenomenon is called 'spiking'.


Representations of magnetic force (shapes formed by magnetic fluid)
Works presented by a graphic designer, Ms. Minako Takeno
Partner companies Sigma Hi-Chemical Inc.
Denshijiki Industry Co., Ltd.


Characteristics of Rigaku's magnetic fluid(magnetic fluid)?

  New magnetic fluid
Amount of out gas 180°C 10 min.
1 wtppm or less
Vapor pressure [Pa]
at 20°C
6.0x10-12

The magnetic fluid used in Rigaku's rotary feedthrough units can be one of two basic types, one for applications featuring vacuums and high-speed rotation, and the other for active gases. The type for use with active gases is available in three grades to suit your service temperature requirements. Rigaku will recommend a magnetic fluid that best suits your service requirements.
The "vapor pressure - temperature characteristics" graph, above, shows how the vapor pressure varies with the temperature in a magnetic fluid. This is called a "vapor pressure curve". The graph indicates that the fluid evaporates less when the vapor pressure is lower, even at high temperatures or high vacuums, and the amount of generated out gas, which can cause contamination, is also less.

Precaution :Above mentioned "Vapor pressure curve" does not guarantee the activity and the service time of the magnetic seal. Recommended operating pressure in the circumstance of actual processing in the equipment should be more than one hundred times of the pressure in the "vapor pressure curve".

Notes on Use

  • If a seal has not been used for some time, run it in before applying a vacuum.
  • When removing contamination from a surface, use caution to prevent the solvent being used (acetone, thinner, alcohol, freon, water, etc.) from entering the rotary feedthrough unit.
  • To conduct a leak test, use a He leak detector.
  • When mounting a seal, orient it correctly, paying careful attention to the vacuum and atmosphere sides.
  • Do not apply lubricant to ball bearings.
  • If you wish to have a seal overhauled or repaired, return it to Rigaku. Do not attempt to disassemble it.

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