CA2219503C - Magnetofluid with high saturation magnetisation - Google Patents
Magnetofluid with high saturation magnetisation Download PDFInfo
- Publication number
- CA2219503C CA2219503C CA002219503A CA2219503A CA2219503C CA 2219503 C CA2219503 C CA 2219503C CA 002219503 A CA002219503 A CA 002219503A CA 2219503 A CA2219503 A CA 2219503A CA 2219503 C CA2219503 C CA 2219503C
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- CA
- Canada
- Prior art keywords
- magnetofluid
- particles
- modified
- volume
- concentration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
- H01F1/442—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids the magnetic component being a metal or alloy, e.g. Fe
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/90—Details not provided for in groups A61M60/40, A61M60/50 or A61M60/80
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/02—Details of the magnetic circuit characterised by the magnetic material
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K33/00—Motors with reciprocating, oscillating or vibrating magnet, armature or coil system
- H02K33/02—Motors with reciprocating, oscillating or vibrating magnet, armature or coil system with armatures moved one way by energisation of a single coil system and returned by mechanical force, e.g. by springs
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- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Heart & Thoracic Surgery (AREA)
- Power Engineering (AREA)
- Hematology (AREA)
- General Health & Medical Sciences (AREA)
- Anesthesiology (AREA)
- Biomedical Technology (AREA)
- Cardiology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- Mechanical Engineering (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Soft Magnetic Materials (AREA)
- Lubricants (AREA)
- Hard Magnetic Materials (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
It has been the task of the invention to form a magnetofluid with a hig h saturation magnetisation which has a saturation concentration that lies above 100 mT in order to be able to transmit higher forces. According to the invention, this is attained by stably dispersing cobalt a nd nanometer particles modified with mono-molecular adsorption layers in carrier liquids, whereby the volume concentration of the ferromagnetic component comes to 5 to 35 per cent, preferably to 15 to 30 %, and the volume concentration of the modified particles (naked particles with adsorption shell) comes up to 50 per cent by volume.
Description
Magnetofluid with a high saturation magnetisation Magnetofluids are so-called "smart" materials that are locally fixed in in-teraction with strong external magnetic fields or magnetic field gradients as well as brought in positions that are previously determined - even against the force of gravity. Thereby, their colloidal stability is maintained, and they behave like a continuous liquid phase.
The term of a magnetofluid has usually been introduced for them.
A decisive factor for their quality is the value of the saturation polarization because this value proportionally becomes part of the specific interaction force of the magnetofluid with the external magnetic field.
The magnetofluids are used in blood pumps, for the manufacture of mag-netofluid sensors with a high sensitivity or for the production of magneto-fluid gaskets with a higher sealing power.
In general, such magnetofluids are stable dispersions with super-paramagnetic properties. They are composed of ferri- or ferromagnetic nanometer particles, surface-active agents and a carrier liquid. The sur-face-active materials effect a dispersing and colloidal stabilisation of the particles in the carrier liquids.
Very different carrier liquids, such as water, hydrocarbons, perfluorocar-bon ether, diester, and silicone oils are used. Magnetite which is modified with special surface-active materials, such as medium-chained organic acids, is used as a magnetic component.
Magnetofluids with saturation magnetisations of 10 to 40 mT (Ferrofluidics Corporation) and up to 90 mT are commercially offered The manufacture of magnetic liquids which contain metallic nanometer particles instead of magnetite particles is also known. Typical ferromag-netic metals are iron, cobalt and nickel. Their particles are made by ther-molysis of their carbonyls or by aerosol formation.
Polymers, such as polybutadiene derivatives with a molecular weight of at least 1,000 or polybutenyl succinpolyamine and surface-active agents, such as oil-soluble alkyl sulfonates or sarcosyl-0 and duomeen-TDO, are described as stabilising agents. However, the value of the saturation magnetisation lies far below 30 mT, mostly only at 5 mT. In this way, low forces can also be transmitted regularly.
Accordingly, the surface-active agent concentrations in solvents are so low that the critical micelle concentration for the inverse micelles is not reached.
Therefore the invention is based on the task to create a magnetofluid having a saturation concentration that lies above 100 mT in order to be able to transmit higher forces.
The term of a magnetofluid has usually been introduced for them.
A decisive factor for their quality is the value of the saturation polarization because this value proportionally becomes part of the specific interaction force of the magnetofluid with the external magnetic field.
The magnetofluids are used in blood pumps, for the manufacture of mag-netofluid sensors with a high sensitivity or for the production of magneto-fluid gaskets with a higher sealing power.
In general, such magnetofluids are stable dispersions with super-paramagnetic properties. They are composed of ferri- or ferromagnetic nanometer particles, surface-active agents and a carrier liquid. The sur-face-active materials effect a dispersing and colloidal stabilisation of the particles in the carrier liquids.
Very different carrier liquids, such as water, hydrocarbons, perfluorocar-bon ether, diester, and silicone oils are used. Magnetite which is modified with special surface-active materials, such as medium-chained organic acids, is used as a magnetic component.
Magnetofluids with saturation magnetisations of 10 to 40 mT (Ferrofluidics Corporation) and up to 90 mT are commercially offered The manufacture of magnetic liquids which contain metallic nanometer particles instead of magnetite particles is also known. Typical ferromag-netic metals are iron, cobalt and nickel. Their particles are made by ther-molysis of their carbonyls or by aerosol formation.
Polymers, such as polybutadiene derivatives with a molecular weight of at least 1,000 or polybutenyl succinpolyamine and surface-active agents, such as oil-soluble alkyl sulfonates or sarcosyl-0 and duomeen-TDO, are described as stabilising agents. However, the value of the saturation magnetisation lies far below 30 mT, mostly only at 5 mT. In this way, low forces can also be transmitted regularly.
Accordingly, the surface-active agent concentrations in solvents are so low that the critical micelle concentration for the inverse micelles is not reached.
Therefore the invention is based on the task to create a magnetofluid having a saturation concentration that lies above 100 mT in order to be able to transmit higher forces.
According to the invention, this is done by stably dispersing modified co-balt and nanometer particles in carrier liquids with mono-molecular ad-sorbed layers, whereby the volume concentration of the ferromagnetic component comes to 5 to 35 per cent, mainly to 15 to 30 %, and the vol-ume concentration of the modified particles (naked particles with adsorp-tion shell) up to 50 per cent by volume.
Due to the high volume concentration of the ferromagnetic component and the value which is by the factor 3 to 4 times higher than magnetite for the saturation polarization of the naked particles which have a size of 5 to 20 nm, the value resulting for the saturation polarization lies between 100 and 400 mT, however, preferably between 150 and 300 mT.
The modified particles are manufactured on the basis of the known chemical procedure through nucleation/crystalline growth processes, namely the thermolysis of their carbonyls directly conducted in an organic solvent in the presence of polymers and surface-active agents. According to the invention, polymers or surface-active agents with reactive nitrogen compounds are clearly used above the critical inverse micelle concentra-tion in order to produce iron-nanometer particles. In the same way, poly-mers or surface-active agents with reactive sulfo- or nitrogen compounds are also used above their micelle concentration for the stabilisation of the cobalt particles.
The reactive groups are adsorbed at the surface of the metallic particles while forming mono-molecular layers.
The strong adsorptive capacity and the firm bonding of the surface-active agents result in the fact that these agents have an oxidation inhibiting ef-feet on the ferromagnetic particles.
Due to the high volume concentration of the ferromagnetic component and the value which is by the factor 3 to 4 times higher than magnetite for the saturation polarization of the naked particles which have a size of 5 to 20 nm, the value resulting for the saturation polarization lies between 100 and 400 mT, however, preferably between 150 and 300 mT.
The modified particles are manufactured on the basis of the known chemical procedure through nucleation/crystalline growth processes, namely the thermolysis of their carbonyls directly conducted in an organic solvent in the presence of polymers and surface-active agents. According to the invention, polymers or surface-active agents with reactive nitrogen compounds are clearly used above the critical inverse micelle concentra-tion in order to produce iron-nanometer particles. In the same way, poly-mers or surface-active agents with reactive sulfo- or nitrogen compounds are also used above their micelle concentration for the stabilisation of the cobalt particles.
The reactive groups are adsorbed at the surface of the metallic particles while forming mono-molecular layers.
The strong adsorptive capacity and the firm bonding of the surface-active agents result in the fact that these agents have an oxidation inhibiting ef-feet on the ferromagnetic particles.
The following prerequisites must be met in order to produce a magneto-fluid with a high saturation polarization by means of ferromagnetic par-ticles: use of ferromagnetic particles, such as iron and cobalt which have a 3 to 4-fold higher saturation polarization than magnetite particles: use of iron and cobalt particles in particle sizes of up to 20 nm under consid-eration of ensuring a sufficient, colloidal particle stability; use of polymers and/or surface-active agents which adsorb mono-molecularly with layer thicknesses of 1.2 to 2 nm under consideration of ensuring a sufficient colloidal particle stability.
Surprisingly, it has been found out that ferromagnetic iron or cobalt parti-cles which have mono-molecular adsorption layers as a shell can still be dispersed stably in colloidal respect in carrier liquids if the proportion of the radii of the modified to the naked particles lies between 1.10 and 1.30, preferably between 1.15 and 1.20. In this way, a solids content of the fer-romagnetic component from 5 to 35 per cent by volume is attained. This increases the saturation magnetisation again up to 400 mT.
Even at a high particle concentration, the magnetofluid shall remain in such a state that it is still flowable. This is attained by the viscosity of the carrier liquid at room temperature lying between 0.7 and 10 mPas, mainly between 1 and 5 mPas on the one hand, and by dissolving only the re-quired amount of polymers and/or surface-active agents in the carrier liq-uid on the other.
The cobalt and iron nanometer particles are manufactured by modification of the chemical methods described according to the state of the art by thermolysis of their carbonyls in organic carrier liquids. One-molecular metal carbonyl solutions are used for the manufacture of highly concen-trated particles. Thereby, the thermolysis causes that a much higher num-ber of metallic nuclei is created by thermolysis - compared with known methods.
Surprisingly, it has been found out that ferromagnetic iron or cobalt parti-cles which have mono-molecular adsorption layers as a shell can still be dispersed stably in colloidal respect in carrier liquids if the proportion of the radii of the modified to the naked particles lies between 1.10 and 1.30, preferably between 1.15 and 1.20. In this way, a solids content of the fer-romagnetic component from 5 to 35 per cent by volume is attained. This increases the saturation magnetisation again up to 400 mT.
Even at a high particle concentration, the magnetofluid shall remain in such a state that it is still flowable. This is attained by the viscosity of the carrier liquid at room temperature lying between 0.7 and 10 mPas, mainly between 1 and 5 mPas on the one hand, and by dissolving only the re-quired amount of polymers and/or surface-active agents in the carrier liq-uid on the other.
The cobalt and iron nanometer particles are manufactured by modification of the chemical methods described according to the state of the art by thermolysis of their carbonyls in organic carrier liquids. One-molecular metal carbonyl solutions are used for the manufacture of highly concen-trated particles. Thereby, the thermolysis causes that a much higher num-ber of metallic nuclei is created by thermolysis - compared with known methods.
From the very beginning, the concentration of the surface-active agents/polymers in the solution has been clearly kept above its micelle concentration in order to ensure the stability and mono-dispersity of the particles. Therefore, it can be based on the idea that the nucleation of the metallic particles takes place within the interstice of the inverse micelle and thus in the direct nearness of the reactive groups of the surface-active agents/polymers enabled for the naked particle surface. It stands to reason that this reaction runs fully under the exclusion of air and water.
The particle size of the naked metal core can be changed in a controllable way by the reaction control (temperature), by the chemical composition and concentration of the reaction partners, in particular the chemical composition of the solvent.
Cobalt and particularly iron particles tend to oxidation to non-magnetic particles in contact with air if the surface is not protected (retarded). A
protection can also be reached by the chemical adsorption of surface-active agentslpolymers, in particular of surface-active agents with internal loads, such as the betaine structure. The reaction half-time of the oxida-tion can be decreased in orders of magnitudes by the use of such bi-functional surface-active agents which effect the colloidal as well as the chemical stabilisation of the ferro-magnetic particles.
In the following, the invention is described in detail by means of embodi-ments.
Embodiment 1:
40 g dicobalt octacarbonyl are mixed with 100 ml anhydrous 1,3,5 triiso-propylbenzene (boiling point 235°) in which 8 g dehydrated sodium bis (ethyl, hexyl) sulfosuccinate had been dissolved.
The mixture is fed into a three-neck bottle with stirrer, cooler and gas inlet pipe and heated at 120°C under superpure argon until the carbon mon-oxide formation is completed. The formed Co-magnetofluid has an Ms-value of 30 mT. Its magnetisation curve has no hysteresis; the viscosity comes to 4 mPas only. The half-life period of the oxidation comes to sev-eral months. The Ms-value has been increased up to 250 mT by evapora-tion of the solvent.
Embodiment 2 In the same way as in Embodiment 1, 50 g iron pentacarbonyl, together with a mixture consisting of 10 g oleylsarcoside and 10 g polyisobutylene succinimide in 100 ml anhydrous decane are dropped into a surface-active solution at a temperature of 180 °C. Afterwards, the solution is kept at this temperature until the formation of carbon monoxide has been com-pleted.
The Ms-value of the formed iron-magnetofluid of 150 mT has been in-creased by partially evaporating the decane to 250 mT. The product has no hysteresis in the magnetisation curve and its viscosity lies at 2 Pas.
The half-life period of the oxidation in contact with air comes to several weeks.
The particle size of the naked metal core can be changed in a controllable way by the reaction control (temperature), by the chemical composition and concentration of the reaction partners, in particular the chemical composition of the solvent.
Cobalt and particularly iron particles tend to oxidation to non-magnetic particles in contact with air if the surface is not protected (retarded). A
protection can also be reached by the chemical adsorption of surface-active agentslpolymers, in particular of surface-active agents with internal loads, such as the betaine structure. The reaction half-time of the oxida-tion can be decreased in orders of magnitudes by the use of such bi-functional surface-active agents which effect the colloidal as well as the chemical stabilisation of the ferro-magnetic particles.
In the following, the invention is described in detail by means of embodi-ments.
Embodiment 1:
40 g dicobalt octacarbonyl are mixed with 100 ml anhydrous 1,3,5 triiso-propylbenzene (boiling point 235°) in which 8 g dehydrated sodium bis (ethyl, hexyl) sulfosuccinate had been dissolved.
The mixture is fed into a three-neck bottle with stirrer, cooler and gas inlet pipe and heated at 120°C under superpure argon until the carbon mon-oxide formation is completed. The formed Co-magnetofluid has an Ms-value of 30 mT. Its magnetisation curve has no hysteresis; the viscosity comes to 4 mPas only. The half-life period of the oxidation comes to sev-eral months. The Ms-value has been increased up to 250 mT by evapora-tion of the solvent.
Embodiment 2 In the same way as in Embodiment 1, 50 g iron pentacarbonyl, together with a mixture consisting of 10 g oleylsarcoside and 10 g polyisobutylene succinimide in 100 ml anhydrous decane are dropped into a surface-active solution at a temperature of 180 °C. Afterwards, the solution is kept at this temperature until the formation of carbon monoxide has been com-pleted.
The Ms-value of the formed iron-magnetofluid of 150 mT has been in-creased by partially evaporating the decane to 250 mT. The product has no hysteresis in the magnetisation curve and its viscosity lies at 2 Pas.
The half-life period of the oxidation in contact with air comes to several weeks.
Claims (9)
1. A magnetofluid with an extremely high saturation polarization, the magnetofluid having a ferromagnetic component, a surface-active agent, and a carrier liquid, in which the particle size of the ferromagnetic component is between 5 and 20 nm, the ferromagnetic component containing finely dispersed particles selected from the following group:
cobalt and iron - nanometer particles, the particles being modified with mono-molecular adsorption layers in carrier liquids having a low viscosity between 0.7 and 10 mPas, whereby the volume concentration of the ferromagnetic component is between 5 and 35 per cent by volume, the volume concentration of the modified particles is up to 50 per cent by volume, and the concentration of the surface-active agent is maintained above its micelle concentration to ensure stability and mono-dispersity of the modified particles in the carrier liquid.
cobalt and iron - nanometer particles, the particles being modified with mono-molecular adsorption layers in carrier liquids having a low viscosity between 0.7 and 10 mPas, whereby the volume concentration of the ferromagnetic component is between 5 and 35 per cent by volume, the volume concentration of the modified particles is up to 50 per cent by volume, and the concentration of the surface-active agent is maintained above its micelle concentration to ensure stability and mono-dispersity of the modified particles in the carrier liquid.
2. A magnetofluid as defined in Claim 1 in which the modified particles are manufactured by thermolysis of one-molecular metal carbonyl solutions in organic carrier liquids.
3. A magnetofluid as defined in any one of claims l and 2 in which the volume concentration of the ferromagnetic component is between 20 and 30 per cent by volume.
4. A magnetofluid as defined in any one of claims 1 to 3 in which the viscosity of the carrier liquid at room temperature is between 0.8 and 2 mPas.
5. A magnetofluid as defined in any one of claims 1 to 4 in which the surface-active agents have corrosion-inhibiting characteristics.
6. A magnetofluid as defined in any one of claims 1 to 5 in which unmodified nanometer particles have a particle size between 5 and 20 nm.
7. A magnetofluid as defined in any one of claims 1 to 6 in which said mono-molecular adsorption layers have a thickness of between 1.2 and 2 nm.
8. A magnetofluid as defined in any one of claim 1 to 7 in which the ratio of the modified particle radius to the unmodified particle radius is between 1.10 and 1.30.
9. A magnetofluid as defined in claim 8 in which the ratio of the modified particle radius to the unmodified particle radius is between 1.15 and 1.20.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19609281.7 | 1996-02-27 | ||
| DE19609281A DE19609281C1 (en) | 1996-02-27 | 1996-02-27 | Magneto-fluid-supported electromagnetic drive for blood pump |
| DE19654864A DE19654864A1 (en) | 1996-02-27 | 1996-02-27 | Magnetofluid with a saturation magnetization of 150 to 450 mT |
| DE19654864.0 | 1996-02-27 | ||
| PCT/DE1997/000443 WO1997032321A1 (en) | 1996-02-27 | 1997-02-27 | Magnetic fluid with high saturation magnetisation |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2219503A1 CA2219503A1 (en) | 1997-09-04 |
| CA2219503C true CA2219503C (en) | 2001-04-24 |
Family
ID=26023644
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002219503A Expired - Fee Related CA2219503C (en) | 1996-02-27 | 1997-02-27 | Magnetofluid with high saturation magnetisation |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0823123A1 (en) |
| CA (1) | CA2219503C (en) |
| WO (1) | WO1997032321A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20230081426A (en) * | 2021-11-30 | 2023-06-07 | 현대자동차주식회사 | Cooling Structure for End Coil of Induction Motor |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3284358A (en) * | 1963-06-10 | 1966-11-08 | Chevron Res | Process for improving the magnetic properties of colloidal dispersion of magnetic particles |
| JPS6043803A (en) * | 1983-08-19 | 1985-03-08 | Pioneer Electronic Corp | Magnetic fluid |
| JPS6293911A (en) * | 1985-10-21 | 1987-04-30 | Natl Res Inst For Metals | Manufacturing device for magnetic fluid |
| JPS6293910A (en) * | 1985-10-21 | 1987-04-30 | Natl Res Inst For Metals | Manufacture of magnetic fluid |
| JP2623500B2 (en) * | 1988-04-02 | 1997-06-25 | コスモ石油株式会社 | Manufacturing method of magnetic fluid |
-
1997
- 1997-02-27 EP EP97918008A patent/EP0823123A1/en not_active Withdrawn
- 1997-02-27 CA CA002219503A patent/CA2219503C/en not_active Expired - Fee Related
- 1997-02-27 WO PCT/DE1997/000443 patent/WO1997032321A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0823123A1 (en) | 1998-02-11 |
| CA2219503A1 (en) | 1997-09-04 |
| WO1997032321A1 (en) | 1997-09-04 |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |