Magnetic foams
Magnetic foams can be fabricated in solid and liquid forms. Their magnetic properties are
determined by magnetic nanoparticles incorporated into the cavity walls. The main
problem in the foams fabrication is that the commercially available magnetic powders
contain the particles with dimensions of about micrometer. At the same time the foam
cavity wall thickness is about several hundred nanometers. That means that such powder
will destroy the foam. To preserve the foam it is necessary to use the magnetic particles
of nanometer range sizes. Advanced Magnetic technologies and Consulting company
conducts development of the methods allowing to form and introduce the magnetic
nanoparticles into the foam cavities walls during the process of the foam production.
With application of appropriate chemical technological scheme it is possible to prepare
foams containing magnetic nanoparticles with soft or hard magnetic properties - metallic
nanoparticles (Fe, Co, Ni, etc.), including the particles with complex composition,
nanoparticles of various oxides (such as various magnetic ferrites, etc.) and nanoparticles
on the basis of other magnetic compounds. The process of magnetic foams fabrication is
in general features analogous to that which is used for preparation of magnetic liquids.
Among possible application of the magnetic foams it is necessary to distinguish two main
applications:
1. solid foam for absorption and shielding of electromagnetic radiofrequency radiation,
including very high frequency (VHF) and ultrahigh frequency (UHF) radiation, which is
used for TV broadcasting;
2. solid and liquid magnetic foam for collection of oil or other hydrophobic pollution
from water or solid surface.
Solid magnetic foam for absorption of radio waves can be prepared on the basis of soft
magnetic ferrites, which possess good absorption properties for radiofrequency radiation.
Presence of cavities of various diameters in the foam (and consequently absorption units
consisting of magnetic nanoparticles) makes it possible to provide the absorption
properties in wide range of frequencies. The magnetic and absorption properties of the
foam can be regulated in wide range by choosing of the particles material and
dimensions. It is also possible to create multilayered covering using solid magnetic foams
with different magnetic properties in order to provide change of magnetic and dielectric
permeability on the cover thickness necessary to obtain maximum absorption effect. The
magnetic solid foam can be easy, fast and cheaply deposited on the surfaces even with
complex form by well-known and developed methods.
Liquid foam with residual magnetization can be used as highly effective material for
collection hydrophobic pollutions (oil and other spills, etc.) from the surface of water or
solid body because it is attracted by magnets. Such foam should contain magnetic
nanoparticles with hard magnetic properties. Liquid foams themselves have good ability
to absorb oil or other hydrophobic products. Besides, liquid foams can be easily
destructed in order to extract absorbed products. The problem is in collection of the foam
containing absorbed pollution. There are many different methods of hydrophobic
pollution collection from water or solid body surface. Among them mechanical,
biological, physical and chemical methods can be mentioned. The general drawback of
the listed methods – their low productivity. In particular, mechanical methods do not
allow collecting thin films on the water surface and are useful only for collection of big
oil spills. Such method as burning is rather dangerous and produces products of burning
harmful for nature. Biological methods require much time and elevated temperatures.
Using of the magnetic liquid foam can essentially increase effectiveness of hydrophobic
pollution collection from water or solid body surface. Besides application of the magnetic
foam is effective for collection of thin oil films from water surface. Liquid magnetic
foam is hydrophobic and can be stable on water surface for tenths of minutes. At the
same time the process of pollution absorption takes several minutes. Rapid absorption of
the pollution by the foam allows to begin the process of the foam collection practically
immediately with the help of magnetic pick-up devices. High speed of the foam
generation makes it possible to cover the removing spill repeatedly. Such repeated
treatment of the oil pollution can essentially increase the effectiveness of the its
removing. The foam can be produced in large quantities on the place of pollution (i.e. on
the ships or seaports), which is especially important because in accordance with
international agreements seaports should have special equipment for removing the oil
pollutions. Solid foam sorbents with magnetic properties also increases the cleaning
process effectiveness because they essentially simplifie the collection stage. The
mentioned potential advantages of the magnetic foams using for oil pollution removing
make development of the method of its production very actual task.
The Advanced Magnetic Technologies and Consulting Company proposes joint research
and development activity in the field of liquid and solid magnetic foams containing
magnetic nano- and submicron particles. The company can demonstrate the samples of a
solid magnetic foam.