Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
FERRITE/POLYMER COMPOSITION AND PROCESS OF PRODUCTION THEREOF
Document Type and Number:
WIPO Patent Application WO/2005/071698
Kind Code:
A1
Abstract:
The invention relates to a composition with high electrical capacitance and low electrical inductance. The composition comprises a ferrite and polymers product further comprising at least one substance selected from, Fe, Mg, Ni, Cu, Zn, Mn, Li, polymers, mixed together forming a mixture, wherein said substance is arranged in a predetermined way during formation.

Inventors:
JONSSON STURLA (IS)
SNORRASON BRYNJOLFUR (IS)
JONSSON THORGEIR (IS)
Application Number:
PCT/IS2005/000003
Publication Date:
August 04, 2005
Filing Date:
January 24, 2005
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
JONSSON STURLA (IS)
SNORRASON BRYNJOLFUR (IS)
JONSSON THORGEIR (IS)
International Classes:
H01F1/00; H01F1/26; H01F1/37; H01F41/02; H01Q17/00; H05K9/00; H01F27/255; H01F38/10; H05K1/02; (IPC1-7): H01F1/00; H01F41/02; H01Q17/00; H05K9/00
Foreign References:
EP0884739A11998-12-16
US6063511A2000-05-16
US3987334A1976-10-19
EP1286371A22003-02-26
Other References:
PATENT ABSTRACTS OF JAPAN vol. 018, no. 501 (C - 1251) 20 September 1994 (1994-09-20)
Attorney, Agent or Firm:
A & P ARNASON (IS-103 Reykjavik, IS)
Download PDF:
Claims:
Claims
1. A composition with high electrical capacitance and low electrical inductance, said composition comprising: a ferrite and polymers product further comprising: at least one substance selected from, Fe, Mg, Ni, Cu, Zn, Mn, Li, polymers, mixed together forming a mixture, wherein said substance is arranged during formation.
2. A composition according to claim 1, wherein each granule of said substances is coated with diamagnetic material to form capsulated grains.
3. A composition according to claim 1, wherein each granule of said substances is not coated to form noncapsulated grains.
4. A composition according to any of the preceding claims, wherein the combination of said substances and the content of said polymers are in fixed proportions.
5. A composition according to any of the preceding claims, wherein the content of the polymers is a fixed proportion of the volume of the ferrite composition.
6. A composition according to any of the preceding claims, wherein said mixture forms spherical ferrite grains stacked in the mixture with polymers filling the void between the grains.
7. A composition according to any of the preceding claims, wherein said mixture forms cubic ferrite grains stacked in the mixture with polymers filling the void between the ferrites.
8. A composition according to any of the preceding claims, wherein said mixture forms irregularly shaped ferrite grains stacked in the mixture with polymers filling the void between the ferrites.
9. A composition according any of the preceding claims, wherein said composition is composed of uniform grain size.
10. A composition according to any of the preceding claims, wherein said composition is composed of nonuniform grain sizes.
11. A composition according to any of the preceding claims, wherein said composition is ferromagnetic.
12. A composition according to any of the preceding claims, wherein said composition is paramagnetic.
13. A composition according to any of the preceding claims, wherein the composition is aligned in a parallel position in the mixture between the polymers.
14. A composition according to any of the preceding claims, wherein said mixture forms capsulated ferrite grains, stacked in alignment to a magnetic field.
15. A composition according to any of the preceding claims, wherein said mixture forms capsulated ferrite grains, stacked in alignment to a reversed magnetic field.
16. A composition according to any of the preceding claims, wherein said mixture forms capsulated ferrite grains, stacked in a geometric fashion.
17. A composition according to any of the preceding claims, wherein said mixture forms capsulated ferrite grains, periodically stacked in a geometric fashion and periodically stacked in an alignment to a magnetic fields.
18. A composition according to any of the preceding claims, wherein said mixture forms capsulated ferrite grains, stacked in an angled alignment to a magnetic field.
19. A composition according to any of the preceding claims, wherein the polymers have a high thermal conductivity.
20. Use of a composition according to any of the proceeding claims for the manufacture of a shielding material for reducing radio frequency emission from electrical, and electronic devices.
21. A method of producing a ferrite and a polymer composition, said method comprising: selecting substances from at least one of Fe, Mg, Ni, Cu, Zn, Mn, and Li, and a polymer, mixing together in fixed proportions the substances and the polymer, arranging the substance in the mixture, wherein said substance, Fe, Mg, Ni, Cu, Zn, Mn and Li forms capsulated grains which are further arranged in the mixture.
22. A method according to claim 21, wherein the combination of said substances and the content of said polymers are in fixed proportions.
23. A method according to claim 21 or 22, wherein the content of the polymers is a fixed proportion of the volume of the ferrite composition.
24. A method according to claim 2123, wherein said mixture forms spherical ferrite grains stacked in the mixture with'polymers filling the void between the grains.
25. A method according to claim 2124, wherein said mixture forms cubic ferrite grains stacked in the mixture with polymers filling the void between the ferrites.
26. A method according to claim 2125, wherein said mixture forms irregularly shaped ferrite grains stacked in the mixture with polymers filling the void between the ferrites.
27. A method according to claim 2126, wherein the composition is aligned in a parallel position in the mixture between the polymers.
28. A method according to claim 2127, wherein said mixture forms capsulated ferrite grains, stacked in alignment to a magnetic field.
29. A method according to claim 2128, wherein said mixture forms capsulated ferrite grains, stacked in alignment to a reversed magnetic field.
30. A method according to claim 2129, wherein said mixture forms capsulated ferrite grains, periodically stacked in a geometric fashion and periodically stacked in an alignment to a magnetic field.
31. A method according to claim 2130, wherein said mixture forms capsulated ferrite grains, stacked in an angled alignment to a magnetic field.
Description:
FERRITE/POLYMER COMPOSITION AND PROCESS OF PRODUCTION THEREOF Field of the Invention The present invention relates to a nano to macro scale ferrite and a polymer composition and the process of production. The composition produces material qualities not present in Prior Art. The qualities are useful in electronic components where magnetism is utilized.

Background of the invention It is known that magnetism lies in the orbital and spin motions of electrons and the manner of how electrons interact with one another. Different types of magnetism have been described, where the difference is based on how materials respond to magnetic fields. The main distinction is that in some materials there is no collective interaction of atomic magnetic moments, whereas in other materials there is a very strong interaction between atomic moments. This known distinction is used in the present invention to develop material qualities not present in prior art. Diamagnetism is a fundamental property of all matter. It is due to the behaviour of orbiting electrons when exposed to an applied magnetic field.

Diamagnetic substances are composed of atoms, which have no net magnetic moments, all the orbital shells are filled and there are no unpaired electrons.

However, when exposed to a field, a negative magnetization is produced and thus the susceptibility is negative. This susceptibility is temperature independent.

Paramagnetism is when some of the atoms or ions in the material have a net magnetic moment due to unpaired electrons in partially filled orbitals. One of the materials with unpaired electrons is iron. However, the individual magnetic moments do not interact magnetically, and like diamagnetism, the magnetization is zero when the field is removed. In the presence of a field, there is now a partial alignment of the atomic magnetic moments in the direction of the field, resulting in a net positive magnetization and positive susceptibility. In addition, the efficiency of the field in aligning the moments is opposed by the randomising effects of temperature. <BR> <BR> <P>M =CT<BR> T Where M is the magnetization, B is the magnetic field, T is the temperature, and C is a constant. This results in a temperature dependent susceptibility is known as the Curie Law. At normal temperatures and in moderate fields, the paramagnetic susceptibility is small

Many iron-bearing minerals are paramagnetic at room temperature.

Ferromagnetism is when the atomic moments in materials exhibit very strong interactions. These interactions are produced by electronic exchange forces and result in a parallel or anti-parallel alignment of atomic moments. Exchange forces are very large, equivalent to a field on the order of 1000 Tesla, or approximately a 100 million times the strength of the earth's field. The exchange force is a quantum mechanical phenomenon due to the relative orientation of the spin of two electrons. Ferromagnetic materials exhibit parallel alignment of moments resulting in large net magnetization even in the absence of a magnetic field.

The elements Fe, Ni, and Co and many of their alloys are typical ferromagnetic materials. The spontaneous magnetization is the net magnetization that exists inside a uniformly magnetized microscopic volume in the absence of a field. The magnitude of this magnetization, at 0 K, is dependent on the spin magnetic moments of electrons.

The saturation magnetization can be measured in a laboratory. The saturation magnetization is the maximum induced magnetic moment that can be obtained in a magnetic field (Hsat); beyond this field no further increase in magnetization occurs. The difference between spontaneous magnetization and the saturation magnetization has to do with magnetic domains. Saturation magnetization is an intrinsic property, independent of particle size but dependent on temperature.

There is a big difference between paramagnetic and ferromagnetic susceptibility.

As compared to paramagnetic materials, the magnetization in ferromagnetic materials is saturated in moderate magnetic fields and at high temperatures.

Even though electronic exchange forces in Ferro magnets are very large, thermal energy eventually overcomes the exchange and produces a randomising effect.

This occurs at a particular temperature called the Curie temperature (TC). Below the Curie temperature, the Ferro magnet is ordered and above it, disordered. The saturation magnetization goes to zero at the Curie temperature. In addition to the Curie temperature and saturation magnetization, Ferro magnets can retain a memory of an applied field once it is removed. This behaviour is called hysteresis and a plot of the variation of magnetization with magnetic field is called a hysteresis loop. Another hysteresis property is the coercivity of remanence (Hr).

This is the reverse field which, when applied and then removed, reduces the saturation remanence to zero. It is always larger than the coercive force. The initial susceptibility (c0) is the magnetization observed in low fields, on the order of the earth's field (50-100 mT).

In ionic compounds, such as oxides, more complex forms of magnetic ordering can occur as a result of the crystal structure. One type of magnetic ordering is called Ferrimagnetism. The magnetic structure is composed of two magnetic sub- lattices (called A and B) separated by oxygen. The exchange interactions are mediated by the oxygen anions. When this happens, the interactions are called

indirect or super-exchange interactions. The strongest super-exchange interactions result in an anti-parallel alignment of spins between the A and B sub- lattice. In ferrimagnets, the magnetic moments of the A and B sub-lattices are not equal and result in a net magnetic moment. Ferrimagnetism is therefore similar to ferromagnetism. It exhibits all the hallmarks of ferromagnetic behaviour-spontaneous magnetization, Curie temperatures, hysteresis, and remanence. However, ferro-and ferrimagnets have very different magnetic ordering It is known that atoms behave as magnets for two reasons: i), the electrons are magnets, with magnetic dipole moments of magnitude one Bohr magneton: ii), the atoms are moving around the nucleus, and this motion is often equivalent to circulation of charge, which means the electron is like a current loop.

Hence, there is the possibility of an orbital dipole moment. These orbital dipole moments have magnitudes on the order of few Bohr magnetons. Different materials respond to applied magnetic fields in different ways because of the various ways the atomic dipole moments respond to the applied field and to the fields of neighbouring atoms. In the nano scale where it is possible to construct structures of thermally conductive diamagnetic material enclosing a Ferrite molecular composition structure, similar effects can be produced but without the presence of oxygen. Ferrite compositions are widely used in various types of electronic applications. As a core material, it has been the industrial trend to manufacture cores with high permeability and good ability to produce and maintain high magnetic flux. In high frequency power applications the prior art cores are often unable to maintain stability due to thermal development and magnetic capacity. This problem is presently solved by making a gap in the core thus lowering the permeability while maintaining the magnetic flux useful for balancing the current and the voltage Faraday's law is a fundamental relationship which comes from Maxwell's equations. It serves as a succinct summary of the ways a voltage (or emf) may be generated by a changing magnetic environment. The induced emf in a coil is equal to the negative of the rate of change of magnetic flux times the number of turns in the coil. It involves the interaction of charge with magnetic field.

VXE =_@B at When an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it. The induced magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant.

cjM=-L<BR> dt Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be"induced"in the coil.

Material. used to make cores commonly used in electrical equipments today can be roughly divided into four categories according to the temperature and frequency of the application. F, P, and R material is for relatively low frequency applications and working temperature at 20 °C-40 °C, 70 °C-80 °C, and 100 °C - 110 °C respectively. Material called K is used for higher frequency and working temperature of 40 °C-60 °C. In the current state of the art, the characteristics of the material depends the proportions of different ferrites and polymers mixed together. Thus common cores are characterized by : narrow frequency band, high inductance, they create humming sound, and have low efficiency due to energy loss through heat transfer.

Summary of the invention It is an object of the present invention to provide a stable composition with high mechanical strength and superior electro magnetic characteristics. More specifically a ferrite polymer composition is provided comprising high mechanical strength and superior electro magnetic characteristics even when used in high voltage and or high frequency applications. The composition of the present invention may be used as the magnetic core for an inductor, transformer, coil, etc. used for radios, televisions, communication devices, office automation equipment, switching power sources, and other electronic components utilizing electro-magnetism.

The present invention therefore provides composition and process of production thereof by isolating and limiting the physical movements, extensions and vibrations that occur in magnetic materials when they are exposed to alternating magnetic fields. Furthermore the use of thermally conductive diamagnetic material to isolate the paramagnetic material, the thermal development will be more moderated. This arrangement of materials is self-similar from nano scale to large core structures.

The various hysteresis parameters are not solely intrinsic properties but are dependent on grain size, domain state, stresses, and temperature. Because hysteresis parameters are dependent on grain size, they are useful for magnetic grain sizing of natural samples. The presented invention uses this parameter to obtain the composite quality of the composition.

In addition to controlling the proportions, the claimed invention controls the granularity and shape of the material as well as controlling the orientation of the grains in the core. Therefore, cores can easily be optimized according to the application domain. Thus the new cores are characterised by wide frequency band (0-900KHz), low inductance, operates quietly, are very efficient, and cover wider power range Description of the present invention According to the first aspect, the present invention relates to a composition with high electrical capacitance and low electrical inductance, said composition comprising: - a ferrite and polymers product further comprising: - at least one substance selected from, Fe, Mg, Ni, Cu, Zn, Mn, Li, - polymers, wherein the substances and the polymers are mixed together forming a mixture and wherein said substance is arranged during formation.

The ferrite and polymer composition according to the present invention is characterized by including at least one of Fe, Mg, Ni, Cu, Zn, Mn, and Li in pre capsulated grains, mixed with polymers in a fixed proportion by volume to address temperature issues as well as problems in connection with resonance frequency. As known in the Prior Art it is the Curie temperature (TC) that marks the maximal upper limit for all magnetic materials. If the material temperature rises above that mark there will be no magnetization, rendering all components useless that are dependent of magnetization. Preventing the composed material from heating is therefore important if a better performance is desired. A ferrite/polymer composition including at least one of Fe, Mg, Ni, Cu, Zn, Mn, and Li, and having a fixed proportion in relation to the total volume. The ferrite composition preferably includes, in addition to Mg, at least one of Cu, Zn, Mn, Ni, and Li. A typical example of this ferrite composition is Mn-Ni and or Zn ferrite. In such a ferrite composition, the grain size can be at minimum the volume of the above-mentioned molecules, capsulated in a closed polymer structure, preventing direct contact between the ferrite grains.

Preferably substantially non-conductive resin-based polymers, e. g. epoxy or acetal resin-based polymer, however many conventional plastic polymers may as well be used, e. g. termoplastic compositions comprising one or more of polypropylene, polyethylene, nylon, polyurethane, acetal, polyphenylene sulfide, polycarbonate, polyesters, plyvinylchloride and others.

In the present context the term"inductance"relates to a property of an electric circuit by which an electromotive force is induced in it by a variation of current or an electrical device that introduces inductance into a circuit. Furthermore an

inductor is a passive electrical device that stores energy in a magnetic field, typically by combining the effects of many loops of electric current.

In the present context the term"capacitance"relates to an electrical phenomenon whereby an electric charge is stored or an electrical device characterized by its capacity to store an electric charge. Furthermore a capacitor according to the present invention relates to a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electric charges have been placed.

The following embodiments relate to the composition of the invention as well as the method and the use of the present invention.

In an embodiment of the present invention each granule of said substances is coated with diamagnetic material to form capsulated grains and in a further embodiment each granule of said substances is however not coated to form non- capsulated grains. The combination of said substances, according to the present invention, and the content of said polymers are in fixed proportions and the content of the polymers may further be a fixed proportion of the volume of the ferrite composition.

The composition mixture of the present invention may form a spherical ferrite grains stacked in the mixture with polymers filling the void between the grains or a cubic ferrite grains stacked in the mixture with polymers filling the void between the ferrites. Furthermore, the composition mixture of the present invention may form irregularly shaped ferrite grains stacked in the mixture with polymers filling the void between the ferrites.

The compositions of the present invention may be composed of uniform grain size or of non-uniform grain sizes. Furthermore, the composition of the present invention may be ferromagnetic, but can also be paramagnetic.

The compositions of the present invention may be aligned in a parallel position in the mixture between the polymers. In one embodiment the mixture forms capsulated ferrite grains, stacked in alignment to a magnetic field, whereas in another embodiment the mixture forms capsulated ferrite grains, stacked in alignment to a reversed magnetic field. In yet another embodiment the mixture forms capsulated ferrite grains, stacked in a geometric fashion.

Other possibilities of stacking the grains according to the present invention is where the mixture forms capsulated ferrite grains, periodically stacked in a geometric fashion and periodically stacked in an alignment to a magnetic fields or where the mixture forms capsulated ferrite grains, stacked in an angled alignment to a magnetic field.

The polymers of the composition of the present invention have a high thermal conductivity.

In a second aspect of the present invention a method is provided for producing a ferrite and a polymer composition, said method comprising: - selecting substances from at least one of Fe, Mg, Ni, Cu, Zn, Mn, and Li, and - a polymer, - mixing together in fixed proportions the substances and the polymer, - arranging the substance in the mixture, wherein said substance, Fe, Mg, Ni, Cu, Zn, Mn and Li forms capsulated grains which are further arranged in the mixture.

After mixing together the desired composition, the grains are aligned by applying magnetic field of predetermined strength and direction during the coagulation process.

In a third aspect of the present invention a use of a ferrite and a polymer composition is provided for the manufacture of a shielding material for reducing radio frequency emission from electrical, and electronic devices. The ferrite and polymer composition comprises at least one substance selected from, Fe, Mg, Ni, Cu, Zn, Mn, Li, and a polymer (s), wherein the substances and the polymer (s) are mixed together forming a mixture and wherein said substance is arranged during formation.

There is a myriad of applications for the shielding material of the present invention, and the following list is not intended to be exhaustive or limiting in any way. To name few ideas, the shielding material may be used for producing shield for reducing RF emission from cell phones. Furthermore, Housing for electronic oscillators and circuits in RF emitting legacy circuits can be built to reduce RF emission. The shielding material can be further used in the making of printed circuit boards. However, the material is equally well adapted to shield instruments and circuit boards from RF emitted from other sources.

Brief description of the drawings Fig 1. Shows the alignment of magnetic force (3) in relation to the general direction of an imaginary applied magnetic field (5). The 12 variations represent the initial paramagnetic positions before the magnetic filed is applied.

Fig 2. Shows how the grains of a one possible geometric layout align according to the applied magnetic field.

Fig 3. Shows a torus, one possible application of a finished product.

Fig 4. Shows the cross section of said torus.

Fig 5. Shows oscilloscope screen capture of an input wave analysis for electronic magnetic ballasts, to drive plasma device, manufactured using a core from the prescribed composition.

Fig 6. Shows oscilloscope screen capture of an input wave analysis for electronic magnetic ballasts, to drive plasma device, provided by the device manufacturer.

Detailed description of the invention As seen in FIG 1, a ferrite and a polymer composition, including at least one of Fe, Mg, Ni, Cu, Zn, Mn, and Li mixed in a content of polymers in a fixed proportion, where the said components, Fe, Mg, Ni, Cu, Zn, Mn and Li are forming capsulated (2) grains (4). wherein the ferrite composition is arranged in the mixture, between the polymer material (1), preventing the grains from being in a direct contact with each other.

The capsulated (2) grains (4) are made by synthesis the ferrite material into the shapes of cubic or spherical grains. The grain size can be from the diameter of one sintered molecule to few millimetres in diameter. After the grains are made they are covered with polymer material (2) to form the capsulated grains (4). The cover will prevent a direct contact between individual ferrite grains in the mixture and conduct the heat away from the grain. The heat developed inside the grain is due to alternating alignment of the angular momentum of the nucleus that develops heat and sound in prior art. The isolation of the individual grains limits the angular momentum and reduces the thermal development and eliminates the humming sound that is always present in prior art. After capsulation of the ferrites, the grains are put into polymers in a liquid form and mixed evenly in the mould by vibration. The mould will gain enough pressure to eliminate all air inside the mixture. After the air has been removed from the mold it is placed in a magnetic force field while the mixture changes state from liquid/solid to solid/solid. The magnetic particles in the grains will align the grains to the applied magnetic field lines and form a parallel position accordingly. When solid state has been reached the magnetic force is removed. The position of the grains in the solid mixture simulates the position they would have if the material was a solid permanent magnet, but without being ferromagnetic.

In Fig. 2, a section of finished material (6) is shown In one of many possible geometric layouts. All the grains (4) are coated with polimer layer (2) forming capsulated grains. Each capsulated grain is magnetically ligned um using magnetic force during the coagulation process.

What looks like a conventional torus is shown in Fig. 3, with insulated wire (8) wrapped around the core (9), shown in Fig. 4. Fig. 4, moreover reveals that the wire is completely surrounded by a shielding material made from one of the

possible ferrite compositions described earlier. In between layers, and outside the torus is covered with insulating material (11).

Examples.

Magnetic ballast for electrical devices.

This invention introduces a new generation of electronic magnetic ballasts for High Intensity Discharge lamps, X-ray devices, Gas-Laser, Spark-gaps and general plasma devices. An electronic magnetic ballasts was manufactured using a core from the prescribed composition to drive plasma device.

The performance using the core made according to the claims of the invention is shown in Fig. 5. Due to the low inductance of the core the phase lag of the input current is only 1°, and the losses are only 5%. Transient in the input is negligible 1% while the transient in the output is only 4%, an improvement of two magnitudes. Moreover, the ballast generates no radio frequency interference, and the energy of the I't harmonic in the output current is reduced by 50dB. This is a significant improvement compared to the ballast provided by the manufacturer of the plasma device.

The performance of the electronic magnetic ballasts as provided by the plasma device manufacturer is shown in Fig. 6. Due to the high inductance the phase lag of the input current is 18°, and the ballast exhibits losses of 12%. Transient in the input is 10% while it is 400% in the output. Moreover, the ballast generates radio frequency interference at 4. 8MHz, and the energy of the Ist harmonic in the output current is very high.