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GUIDE TO magnetic liquid TECHNOLOGY

What is a magnetic liquid?

magnetic liquid consist of a carrier liquid and small magnetic particles held in suspension by a surface active layer, a surfactant. Carrier liquids are selected to meet the needs of particular applications with frequently used liquids just as hydrocarbon oils. The most common source of magnetic particles is iron oxide, ferrite, because it oxidises less readily than other metal oxides. These magnetic particles are stabilised within the carrier fluid so that they are maintained in suspension under all conditions.

What can it do?

Put simply, a magnetic liquid can be held in place against forces, such as gravity, by a magnetic field often produced by a permanent magnet. If the magnetic field is moved, the magnetic liquid will move with it.

A demonstration of magnetic liquid in an external magnetic field

Magnetic liquid

Type

Base

Magnetization 

@ 1.2 MAT/m(mT)

Viscosity

@27¡æ(cp)

Specific Gravity

@20¡æ(g/cm3)

Vapor Pressure

@ 20¡æ(Pa) 

Applications

W-XXX Water

10-30 

  

1.35
 		 Sink & Float Separation
C-XXX Thermal conductivity oil

15-50

200~1200

1.2~1.5

   loudspeaks
H-XXX Hydrocarbon

25-50

  

 

    
D-XXX Diester

35-70

550~1500

1.2~1.7

<3¡Á10-5

 Magneto-optic devices

Magnetic liquid characters

1. Magnetic liquid shows super-paramagnetism,  with zero  intrinsic coercivity and no residual magnetism.

2. Magnetic liquid will be magnetized by an external magnetic field and will  satisfy the amended Bernoulli's equation. Compare with the ordinary Bernoulli's equation, another magnetic property is added to vest liquids with the magnetic, which other liquids have none and is related with magnetism, such as magnetic liquid' named density will be increased by the increasing of external magnetic field intensity.

3. When light goes through a magnetic liquid thin film or a diluted magnetic liquid, the magneto-optical effects such as dichroism and birefringence will happen. When the magnetic liquid is putted into an external magnetic field, the absorbing electric vector of polarized light that in parallel to the external magnetic field is stronger than that in vertical, and has more highly refractive index.

4. When the ultrasonic wave propagated in magnetic liquid, it velocity and attenuation is related with outside magnetic field and shows anisotropy.

5. There are phenomena such as permeability frequency dispersion, magneto-viscosity etc. in the alternating magnetic field.¡¡

Where is it used?
Rotating shaft seal:
Damper:
Loudspeaker:
Sensor:
Sink & float separation:
Magneto-optic devices: 		Vacuum, gas, dust and mist seals
Use of viscosity increases in magnetic field
Use of damping effect and heat transfer
Combination of transformability and magnetic properties
Use of fluid's buoyancy changes in magnetic field
Fluids' birefringence  in magnetic field

Even though there has been many applications of magnetic liquid, the use of the unique properties of magnetic liquid in devices has not yet been fully exploited.

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