A ferrofluid is a stable colloidal suspension of sub-domain magnetic
particles in a liquid carrier. The particles, which have an average
size of about 100Å (10 nm), are coated with a stabilizing
dispersing agent (surfactant) which prevents particle agglomeration
even when a strong magnetic field gradient is applied to the ferrofluid.
In the absence of a magnetic field, the magnetic moments of the
particles are randomly distributed and the fluid has no net magnetization.
When a magnetic field is applied to a ferrofluid,
the magnetic moments of the particles orient along the field
lines almost instantly. The magnetization of the ferrofluid
responds immediately to the changes in the applied magnetic
field and when the applied field is removed, the moments randomize
In a gradient field the whole fluid responds
as a homogeneous magnetic liquid which moves to the region
of highest flux. This means that ferro-fluids can be precisely
positioned and controlled by an external magnetic field. The
forces holding the magnetic fluid in place are proportional
to the gradient of the external field and the magnetization
value of the fluid. This means that the retention force of
a ferrofluid in a gap can be adjusted by changing either the
magnetization of the fluid or the magnetic field in the gap.
Audio ferrofluids are based on two classes
of carrier liquid: synthetic hydrocarbons and esters. Both
oils possess very low volatility and high thermal stability.
The choice of fluid is dictated by the environmental considerations
of the application (e.g. humidity, adhesives, contact with
water, solvent vapors and reactive gases) combined with the
best balance of magnetization and viscosity values to optimize
the acoustical performance.
By varying the quantity of magnetic material in
a ferrofluid, and by using different carrier liquids, it can be
tailored to meet a variety of needs. The saturation magnetization
(the maximum value of the magnetic moment per unit volume when all
the domains are aligned) is determined by the nature of the suspended
magnetic material and by the volumetric loading of the material.
The physical and chemical properties such as density and viscosity
correspond closely to those of the carrier liquid.
refined manufacturing process, combined with a long term quality
assurance program is the key to its repeatable, reproducible
Ferrofluid | Vacuum
Feedthroughs | Thermoelectric Modules
Contract Manufacturing | Literature
Rack | Specialty Seals
Inertia Dampers | Electron