WO2008121069A1 - Magnetic nanoparticle cellulose material - Google Patents
Magnetic nanoparticle cellulose material Download PDFInfo
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- WO2008121069A1 WO2008121069A1 PCT/SE2008/050366 SE2008050366W WO2008121069A1 WO 2008121069 A1 WO2008121069 A1 WO 2008121069A1 SE 2008050366 W SE2008050366 W SE 2008050366W WO 2008121069 A1 WO2008121069 A1 WO 2008121069A1
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- 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
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/34—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials non-metallic substances, e.g. ferrites
- H01F1/36—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials non-metallic substances, e.g. ferrites in the form of particles
- H01F1/37—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials non-metallic substances, e.g. ferrites in the form of particles in a bonding agent
- H01F1/375—Flexible bodies
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/12—Powdering or granulating
- C08J3/14—Powdering or granulating by precipitation from solutions
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/20—Compounding polymers with additives, e.g. colouring
- C08J3/205—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase
- C08J3/21—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase the polymer being premixed with a liquid phase
- C08J3/215—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase the polymer being premixed with a liquid phase at least one additive being also premixed with a liquid phase
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/005—Reinforced macromolecular compounds with nanosized materials, e.g. nanoparticles, nanofibres, nanotubes, nanowires, nanorods or nanolayered materials
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/02—Cellulose; Modified cellulose
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- 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
- H01F1/0036—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties showing low dimensional magnetism, i.e. spin rearrangements due to a restriction of dimensions, e.g. showing giant magnetoresistivity
- H01F1/0045—Zero dimensional, e.g. nanoparticles, soft nanoparticles for medical/biological use
- H01F1/0063—Zero dimensional, e.g. nanoparticles, soft nanoparticles for medical/biological use in a non-magnetic matrix, e.g. granular solids
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12014—All metal or with adjacent metals having metal particles
- Y10T428/12028—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, etc.]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12014—All metal or with adjacent metals having metal particles
- Y10T428/12028—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, etc.]
- Y10T428/12035—Fiber, asbestos, or cellulose in or next to particulate component
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
- Y10T428/249962—Void-containing component has a continuous matrix of fibers only [e.g., porous paper, etc.]
- Y10T428/249964—Fibers of defined composition
- Y10T428/249965—Cellulosic
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
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- Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
- Y10T442/20—Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
- Y10T442/2762—Coated or impregnated natural fiber fabric [e.g., cotton, wool, silk, linen, etc.]
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- Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
- Y10T442/20—Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
- Y10T442/2762—Coated or impregnated natural fiber fabric [e.g., cotton, wool, silk, linen, etc.]
- Y10T442/277—Coated or impregnated cellulosic fiber fabric
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y10T442/20—Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
- Y10T442/2861—Coated or impregnated synthetic organic fiber fabric
- Y10T442/2869—Coated or impregnated regenerated cellulose fiber fabric
Definitions
- Magnetic nanoparticles with large surface to bulk ratio is a growing area of interest.
- their relatively poor representation in comparison to micron-sized filler materials in polymers is an effect of the difficulties related to the processing of high-surface area nanoparticles.
- the explanation mainly lies in the fact that large surface areas also brings problems in achieving evenly distributed nanoparticle systems due to the favoured particle-particle interaction in comparison to particle-polymer/liquid interactions.
- the result is often severe agglomeration and aggregates of nanoparticles.
- the agglomerates in turn affect many macroscopic properties, such as mechanical, optical and magnetic etc. since these properties on a macroscopic scale are affected by the degree of close interaction at the nano scale level.
- the control over dispersion is therefore an unavoidable prerequisite.
- agglomerates clusters of nanoparticles
- 10 nm maghemite could be overcome to great extent by creating a non-polar spacer of sufficient number of carbon atoms between the nanoparticles, which reduced the interactions to great extent in a nonpolar solvent.
- particle sizes are increased and dipolar forces become dominant, it has been shown that abrupt transitions from separate particles to randomly oriented linear agglomerates/aggregates appears.
- the dispersion of magnetic nanoparticles is not simply solved by surface modifying the nanoparticles with one coating due to the fact that the surface coating with optimal solubility for a specific liquid polymer system is not the same for different system with different chemical character.
- the coating procedure of the magnetic nanoparticles can potentially make dispersion even more difficult due to the potential risk of obtaining coated agglomerates rather than single particles.
- Agglomerates are quickly formed when producing a magnetic material by precipitating transition metal salts already in the precipitation phase due to the magnetic forces between the particles. Considerably stronger agglomerates are formed when the particles are dried, i.e. it is extremely difficult to distribute these particles in polymers.
- the unique features relating to the particles being in the nano-scale range (1-200 rim) and that they consist of individual crystals can not be taken advantage of since functional material properties related to the nano-scopic dimension are negated.
- Agglomeration is a major problem since the magnetic properties of a hybrid material on a macroscopic scale depend on the degree of agglomeration and is related to the degree of exchange coupling and dipolar forces between particles in the hybrid material. Coating the nanoparticles has also been investigated. But there are several problems with this technique such as not only one coating works in all situations for different polymers and no solution has been suggested how to optimize the coating in respect of the polymer matrix to have an optimal solubility.
- US20050245658 discloses a wettable polymer having ion-exchangeable groups to form metal oxides trapped within the polymer structure. Further, a technique for the synthesis of magnetic nanocomposites is disclosed where the polymers have ion exchangeable groups attached.
- Yano et al. Optically transparent composites reinforced with networks of bacterial nanofibres, Adv. Mater. 17, 153-155, 2005
- resins such as epoxy, acrylic, and phenol- formaldehyde under vacuum.
- the new material increased in weight and got new physical properties.
- the resin used by Yano et al. resulted in a mechanically stable and flexible transparent material.
- a new magnetic nanoparticle containing material can be made.
- the new magnetic nanoparticle cellulose material with a network of cellulose nanofibres as scaffold can be used for the production of new functional nano-materials. Further, it can be used for in-situ precipitation of inorganic nanoparticles within the cellulose network, to produce evenly distributed nanoparticles inside an organic matrix and to prepare nano-functional lightweight "foam-like" materials with very low apparent density based on bacterial cellulose and provide possibilities to prepare magnetic hydrogels based on cellulose.
- the new method provides possibilities to prepare high mechani- cal performance nanoparticle functional hybrid films.
- cast three-dimensional magnetic polymer composites are provided. Such composites are obtained by impregnation of the scaffold by a polymer, prepolymer or monomer liquid, followed by solidification
- the magnetic nanoparticle cellulose material can be used within a broad range of applications. To illustrate the broad application area a number of different applications are suggested below without being limited in any way.
- the magnetic nanoparticle cellulose material can be used within the acoustical industry (loud-speaker membrane), magnetic filtration systems, chemical analysis methods, separation methods, etc.
- advantages of the invention is to provide products such as; superfine magnetic filters/sieves, magnetic filtration set-ups activated by external field, catalytic support structures high-sensitivity magnetic membranes, magnetic films with uni- formly/evenly distributed nanoparticles, microwave absorbers, magnetic foams based on nanoparticles, support structure for ferro-fluid based dampeners and template structures for fabrication of nanocomposites characterized by evenly distributed nanoparticles, i.e. sensitive electromagnetic switches, generators, magnetic actuators, magnetic storage media, etc.
- the method makes it possible to produce highly reproducible magnetic nanoparticle cellulose material.
- the use of the polymer magnetic nanoparticle cellulose material provides a new type of "nanocomposite" where all constituents are dimensioned in the nano-scale range and the inorganic nanoparticle phase is distributed inside the material (cellulose nanofibre network). Since the bacterial cellulose hy- drogel is a readily available material with high mechanical integrity due to the nanometrically scaled fibrils, the invented material with its possibilities to be modi- fied for specific applications becomes particularly interesting. Additional modifications on top of what has been described above can also be made due to the facile direct impregnation of the freeze-dried bacterial cellulose.
- Various monomers can be used for in-situ polymerization/cross-linking after impregnation of the freeze-dried aerogel.
- Reactive monomers can effectively be soaked in to the material and cross- linked inside the material in order to create a rigid matrix material. Such modifications can potentially improve the functionalized material.
- bacterial cellulose is intended to encompass any type of cellulose produced via fermentation or synthesised of a bacteria of the genus Acetobacter xy such as linum, Alcaligenes, Pseudomonas, Acetobacter, Rhizobium, Argobacterium, Scarcina, Enterobacter and includes materials referred popularly as microfibrillated cellulose, reticulated bacterial cellulose, microbial cellulose and the like.
- prokaryotic organisms such as the prokaryotic cyanophycean alga Nostoc are encompassed.
- bacterial cellulose refers to a product essentially free of residual bacteria cells made under agitated culture conditions by a bacterium of the genus Acetobacter. Bacterial celluloses are normally available in a gel produced by the bacteria.
- magnetic cellulose is intended to encompass a material, referred to as a material consisting of both an inorganic particles fraction/phase with magnetic properties and an organic carbon-based phase/fraction.
- millioxidation agent is intended to encompass any type of oxidating media which is capable of oxidizing ferrous ions to ferric ions to a sufficient extent that magnetic particles can be obtained (ferrites).
- transition metal ions is intended to encompass metal ions such as all elements in the periodic table that can be used to obtain ironoxide based magnetic nanoparticles.
- coordination compounds and d-block elements is intended to encompass metal compounds / elements such as Manganese/Iron/Cobalt, Zinc etc.
- d-block elements are also referred to as transition metals, the d-block elements in period 4 are Sc 5 Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn.
- alkaline solution is intended to encompass NaOH, KOH, LiOH, NH 3 , and the like.
- metal hydroxide/oxide complex is intended to encompass coordination complexes that are created upon dissolving metal salts in a liquid phase.
- freeze drying is intended to encompass a method to sublime solid water (ice) to gas phase.
- metal salt solution is intended to encompass metal ions such as Co 2+ , Fe 2+ , Fe 3+ , Mn 2+ and the like, generated form the corresponding salts.
- magnetic nanoparticle cellulose material is intended to encompass a material comprising a fibre network, interconnected.
- magnetic nanoparticles physically attached on the cellulose material is intended to encompass magnetic nanoparticles in the size region 1-200 nm.
- evenly distributed is intended to encompass that the nanoparticles are mostly separated, i.e. no agglomerate formation.
- agglomerate is defined herein as a collection of nanoparticles adhering together or laying very close together, i.e. ⁇ 5nm particle to particle inter-distance and the collection of nanoparticles is composed of 20 or more nanoparticles.
- An agglomerate material (non-uniform) would have more than 30% of the nanoparticles lying in above entities of 20 or more nanoparticles.
- the bacterial cellulose utilized herein may be of any type associated with the fermentation product of Acetobacter genus microorganisms, and was previously available from CPKelco U.S. under the tradename CELLULON®.
- Figure 1 shows the outline of the method for making the magnetic nanoparticle cellulose material ( ⁇ ferromagnetic aerogel).
- the letter means A) the cellulose material in a solution, B) freeze drying, C) submers the cellulose material in a solution of metal ion, D) precipitate the metal ions on the cellulose material, E) convert the precipitated metal hydroxid/oxid to magnetic nanoparticles, and F) re- move the solvent.
- Figure 2 shows x-ray diffractogram confirming that the magnetic crystalline particle phase consists of spinel ferrite nanoparticles.
- the peaks were index matched with the Miller indices corresponding to the reflections Of CoFe 2 O 4 (JCPDS Card No. 22- 1086).
- the x-ray data refers to samples obtained using procedure exemplified in example 1 and 3, which generated 40 and 95 nm average particle sizes, respectively.
- the upper curve represents the results from Ex. 1 and the lower results from Ex. 3.
- Figure 3 shows high-resolution FE-SEM micrograph showing that particles are not arranged as large agglomerates.
- Figure 4 shows high-resolution FE-SEM micrograph displaying the grafting (attaching) nature of the nanoparticles to the bacterial cellulose fibres.
- Figure 5 shows low-resolution FE-SEM micrograph displaying the uniformity of the evenly distribute particles through out the material. It is further seen that the particles are physically attached to the fibres. The micrograph is taken on the material obtained using experiment procedure outlined in example 2.
- a magnetic nanoparticle cellulose material wherein the magnetic nanoparticles are evenly distributed onto the material and are free from agglomerate.
- the magnetic nanoparticle cellulose material can be characterised as the collection of nanoparticles adhering together or laying very close together, i.e. ⁇ 5nm particle to particle inter-distance and an entity is composed of less than 20 nanoparticles.
- the magnetic nanoparticle cellulose material can further be characterised in that the density range is between 5-100 kg/m 3 and the nanofibre diameter is in the range of 1-100 nm, typical in the range of 4-20 nm, 20-50 nm, 50-70 nm, and 70-90 nm.
- the density ranges relates to the specific application of the magnetic nanoparticle cellulose material thus other ranges could be 5-10 kg/m 3 , 5-50 kg/m 3 , 50-100 kg/m 3 , 50- 500 kg/m 3 and 500-1000 kg/m 3 .
- Magnetic nanoparticle cellulose material which is a hydrogel or an aerogel.
- a method for forming magnetic nanoparticle cellulose material comprising the steps of: a) providing cellulose material in a solution, b) adding the cellulose material from step (a) to a solution of metal ions, c) precipitating the metal hydroxide/oxide complexes formed in the solution from step spreading/distributing the precipitated complexes on the cellulose material (b), d) adding the precipitated metal hydroxide/oxide complexes to an alkaline solution converting the hydroxide/oxide complexes to magnetic nanoparticles, and e) freeze-drying or solvent exchanging the material from step (d) to preserve the agglomerate free and evenly distributed magnetic nanoparticles physically attached on the cellulose material.
- step (a) is providing cellulose material in a liquid suspension.
- step (b) is replaced with step (b') b') freeze-drying the cellulose solution from step (a), in order to remove the H 2 O in the cellulose material, then adding the freeze-dried solution to a solution of metal ions.
- step (d) is chosen from NaOH, NH 3 and the like, providing a pH above 7,0.
- the method wherein the metal ions in the solution is selected from the coordination compounds including divalent or trivalent atoms from the d-block elements in the periodic table such as Co , Fe , Mn , Fe or metal ion hydroxide complexes or metal ion oxide complexes.
- the concentration range could be between 0,005 molar - saturated solution.
- step (b) is performed until the cellulose material is saturated.
- the alkaline solution in step (d) comprises NaOH and a mild oxidation agent and in a specific embodiment the alkaline solution in step (d) comprises NaOH and KNO 3 . Further, the alkaline solution in step (d) has an initial pH of above 7,0.
- step (d) comprises a dissolved mild oxidation agent that oxidise the metal ions to their preferred state in the spinel ferrite nanoparticles.
- step (c) The method wherein the solution in step (c) is heated to above 5O 0 C, at latm. If ammonium is used ambient temperature could be used.
- the method wherein the precipitated magnetic nanoparticles can be referred to as magnetic particles, super-paramagnetic, paramagnetic, ferri-magnetic or ferromagnetic and thus showing such properties.
- step (e) proceeds until the diffusion of the alkaline oxidising solution has equilibrated/saturated the network and converted the metal hydroxide/oxide complexes to magnetic nanoparticles, i.e: the agglomerate free and evenly distributed magnetic nanoparticles are physically attached on the cellulose material.
- cellulose material is chosen from a plant, a tree, pulp or cotton.
- the method wherein the magnetic nanoparticle cellulose material is a hydrogel or an aerogel.
- the aerogel could also be described as a porous fibril network of low density.
- the cellulose material is bacterial cellulose material it could be treated with a solution of NaOH in bath of boiling water to allow the total removal of the bacteria. Thereafter the hydrogel is washed with de-ionized water and stored at room temperature before use.
- the dried aerogel or the hydrogel is immersed in a metal ion solution where metal hydroxide/oxide complexes will be formed and grown by precipitation uniformly over the cellulose network.
- metal hydroxide/oxide complexes will be converted to magnetic nanoparticles i.e. the created magnetic nanoparticles are evenly distributed/separated uniformly over the cellulose network as shown in Figure 4.
- the magnetic nanoparticle cellulose material wherein the magnetic nanoparticle cellulose material fibre network is impregnated with a liquid of a monomer, a prepolymer or a polymer. Further embodiments is when the magnetic nanoparticle cellulose material and wherein the impregnated magnetic nanoparticle cellulose material is solidified.
- the great benefit of the new method and new magnetic nanoparticle cellulose material according to the invention is to produce agglomerate free magnetic nanoparticle cellulose material, magnetic nanocompo- sites.
- Nanocomposites based on ferromagnetic nanoparticles are considered to be among the most difficult to produce due to the addition of magnetoelastic interactions such as exchange (isotropic and anisotropic), super exchange, dipole-dipole interactions in addition to the chemical interactions such as van der Waals attractions. Eliminating these forces, interactions in agglomerates, results in composites behaving significantly different from ferromagnetic composites based on agglomerated nanoparticles.
- a composite based on non-agglomerated nanoparticles have properties such as reflecting the individual magnetic nanoparticles with single domain character.
- the method comprises the steps of using freeze-dried bacterial cellulose as scaffold for in-situ precipitation of magnetic nanoparticles onto the nanofibres inside the matrix, i.e. the particles are bonded to the bacterial cellulosic fibres.
- the precipitation is generated by thermally forced hydrolysis of metal salt solution in order to create complexes (hydroxides/oxides), which have been allowed to precipitate in the confined space between the fibres before their conversion to their final magnetic phase.
- the freeze-drying technique of the bacterial cellulose results in an aerogel.
- the aerogel enables the inventors to overcome the difficulty to obtain a homogeneous and evenly distribution of metal salt complexes in the space between the fibres, since the metal salt solution easily saturates the hydrogel scaffold of nanofibres when it is soaked in the metal salt solution.
- the freeze-drying step fur- ther provides an undisturbed mechanically stable network of nanofibres with high surface area available for interaction with precipitation reagents.
- the cage-like spaces that exist between the fibres constitute a sort of nano-reactors, i.e. dimensions are in sub micron range.
- the method produces extremely evenly distributed and physically attached nanoparticles in a lightweight cellulosic nanofibres based network.
- the material is characterized by high interactive surface area both from the viewpoint of the nanoparticles and the cellulosic nanofibres.
- Pre- vious attempts to prepare nanoparticles in the confined space between the nanofibres inside the fibre matrix have failed due to a number of unknown reasons.
- the inventors have concluded that it is essential to have complete control over the experimental conditions and methods. It can be concluded from the available literature that the methodology is unique in terms of using the cellulose such as bacterial eel- lulose. Important aspects of the discovery were the combination of the freeze drying technique and the establishment of the reaction conditions. Further, the aerogel from cellulose nanofibrils differs from other ceramic or polymer aerogels in the unique mechanical stability.
- the preferred cellulose material is bacterial celluloses normally available in a gel produced by bacteria.
- the gel needs to be cleaned from bacteria.
- the gel is about 1 % cellulose by weight as produced by the bacteria, and the rest is water.
- Cellulose has very high Youngs modulus, 130 GPa and strength, as a consequence, the gel is mechanically very stable despite the small cellulose content.
- Microfibrils from cellu- lose can also be disintegrated by chemical treatment of cellulose containing substance, normally plant tissue such as wood pulp or cotton.
- This cellulose is often called microfibrillated cellulose (MFC) and is often delivered as a suspension in water of about 2%, it also is gel-like in character, a gel is a solid material by definition due to its mechanical properties and lack of liquid flow, even if it contains 98% wa- ter.
- Cellulose can also be obtained from tunicates, and is then called TC, these are sea animals sitting on rocks, and they are filter feeders, they use a cellulose tunica as protection.
- TC also forms a gel in water.
- Microcrystalline cellulose is produced by acid hydrolysis of cellulose rich materials. The aspect ratio is low, typically 10-20, and therefore its gelforming capability is less than for MFC.
- the gel has not the same mechanical stability as for MFC or BC.
- the gel character of cellulose in water comes from nanofibre interaction with each other, they bond to each other and form a physical network, and this is facilitated by large aspect ratio.
- Cellulose in the form of nanofibres called MFC, BC, TC, MCC form a gel in water already at low cone. The phenomenon will show also in other liquids. By removing the liquid "carefully" it is possible to preserve the physical network as a porous material in the form of an aerogel (low density) or xerogel (higher density). The volume fraction in the aerogel is low, typically in the range of 0.5-10%.
- the gel In a commercially available freeze dryer, the gel is quickly frozen, and then the wa- ter is sublimated by exposure to low pressure but still at low temperature. An aerogel remains. If the freezing is quick, the network structure in water is preserved and the quality by specific surface area can easily be measured. If the freezing is slow, the nanofibres agglomerate and the specific surface area becomes lower which could affect the network to be less useful in certain specific application.
- a cellulose material such as an aerogel can also be made by solvent exchange.
- the gel is moved to a series of solvents. It is possible to start from a very polar liquid, water. Then the liquids of decreasing polarity are exchanged. For a given liquid, such as acetone, the start concentration is low and then the concentration is in- creased in steps by moving from vessel to vessel.
- a non-polar liquid has little interaction with cellulose, and then the aerogel can be made by just evaporating the solvent, with out collapse. Drying at room temperature will result in that the whole network collapses due to capillary forces.
- the fibre network in the form of an aerogel can be made from BC (best quality aerogel), MFC, TC, MCC (worst quality aerogel). Freeze drying is mostly discussed in the application but solvent-exchange (liquid-exchange) could also be applied.
- the aerogel piece is soaked in a solution of metal salt.
- the solutions with the immersed pieces of aerogel is heated in order to thermally force the precipitation of the metal salt solution to the related hydroxide/oxide structures of the metal ions inside the matrix network of aerogel.
- This matrix is then transferred into an alkaline solution.
- the piece is kept in this alkaline solution during a given time. During this process the metal ion will be oxidized and the magnetic inorganic oxide nanoparti- cles will be formed inside the cellulose network matrix.
- the new method comprises in one embodiment the steps of using a preformed network of cellulosic nanofibres, with its confined space volumes working as nano- metric reactors, for the precipitation of magnetic inorganic oxide nanoparticles.
- the spherical nanoparticles could be single-phase cobalt ferrite nanoparticles with sizes varying between approximately 1 and 500 nm.
- XRD X-ray diffraction
- TEM transmission electron micrograph
- Figure 4 shows a micrograph that depicts the material with its evenly/finely distributed cobalt ferrite nanoparticles arranged inside the material. It can be seen that the magnetic nanoparticles are uniformly distributed on the fibres. The particles are not agglomerated even though the magnetic interactions between these particles are large due to the high coercivity values typically characteristic of the single domain cobalt ferrite nanoparticles.
- Figure 3 shows that the particles are not arranged as agglomerates.
- Figure 4 shows the grafting (attaching) nature of the nanoparticles to the bacterial cellulose fibres.
- the solutions with the immersed pieces of cellulose is heated to 90 0 C and kept at 90 0 C for 3 h in order to thermally force the precipitation of the iron/cobalt salt solution to the related hydroxide/oxide structures of the cobalt/iron ions inside the matrix network of the bacterial cellulose.
- the piece is kept in this alkaline solution, which is maintained at 9O 0 C for 6 h.
- the piece is transferred into room temperature distilled water in order to neutralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled water for 6 h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 40-70 nm, as determined FE-SEM.
- the note (*) under step 4 refers to the concentration of iron in the solution used for swelling the bacterial cellulose, i.e. prior to the transfer of the cellulose into the alkaline solution.
- a piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10vol% NaOH solution (3h) and sub sequentially washed with running dis- tilled water (6h) before immersion in liquid nitrogen followed by freeze- drying during a period of 12 hours.
- the piece is kept in this alkaline solution, which is maintained at 9O 0 C for 6 h.
- the piece is transferred into room temperature distilled water in order to neutralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled wa- ter for 6 h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 60-90 nm, as determined FE-SEM.
- the note (*) under step 4 refers to the concentration of iron in the solution used for swelling the bacterial cellulose, i.e. prior to the transfer of the cellulose into the alkaline solution.
- a piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10vol% NaOH solution (3h) and sub sequentially washed with running distilled water (6h) before immersion in liquid nitrogen followed by freeze- drying during a period of 12 hours .
- the solutions with the immersed pieces of cellulose is heated to 90 0 C and kept at 90 0 C for 3 h in order to thermally force the precipitation of the iron/cobalt salt solution to the related hydroxide/oxide structures of the cobalt/iron ions inside the matrix network of the bacterial cellulose.
- the piece is kept in the alkaline solution at 90 0 C for 6 h.
- the piece is transferred into room temperature distilled water in order to neutralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled water for 6 h. 7.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 80-150 nm, as determined FE-SEM.
- the note (*) under step 4 refers to the concentration of iron in the solution used for swelling the bacterial cellulose, i.e. prior to the transfer of the cellulose into the alkaline solution.
- a piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10 vol% NaOH solution (3h) and sub sequentially washed with running distilled water (6h) before immersion in liquid nitrogen followed by freeze-drying during a period of 12 hours.
- the dry cellulose piece is swollen in freshly prepared MilliQ-water solution of metal salt consisting of MnCl 2 x4H 2 O (0.055 M) and FeSO 4 x7H 2 O (0.11 M), i.e. stoichiometric proportions of Mn:Fe (1:2).
- the solutions with the immersed pieces of cellulose is heated to 90 0 C and kept at 9O 0 C for 3 h in order to thermally force the precipitation of the iron/cobalt salt solution to the related hydroxide/oxide structures of the cobalt/iron ions inside the matrix network of the bacterial cellulose.
- the piece is transferred into room temperature distilled water in order to neutralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled wa- ter for 6 h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size similar to as in Example 2.
- the methodology is described in general terms and the skilled person could make modifications that will fall within the scope of protection, i.e. several parameters can be varied to obtain similar results. This is further discussed below.
- the bacterial cellulose does not necessarily need to be freeze-dried in step 1.
- the cellulose can actually be used as wet after cleaning.
- the loading of the metal salt solution is then relying on the osmosis of metal species into the cellulose network, however with this methodology it will take more time to fill the cellulose network with the metal salt solution and it will be more difficult to be ensure that the network is uniformly filled with metal species.
- the freeze-drying procedure can in all steps be exchanged to a similar procedure generating the same result, i.e. an unperturbed porous open network available for the grafting of the nanoparticles to the walls of the cellulose.
- the chemical parameters can also be varied.
- the starting material is selected form metal salts containing ions with oxidation state that is the same as the oxidation state as in the final particles, then there is no need for KNO 3 as a mild oxidation agent.
- the temperature is preferred to be as high as possible, such as above 65 0 C, 75 0 C, 85 0 C, 9O 0 C, etc., since at lower temperatures around 50 0 C the process could generate a different phase, i.e. not the pure spinel phase synonymous with the ferrite material.
- the temperature is not limited to the specific mentioned above and precipitation at room temperature also falls within the scope of protection.
- Example 5 CMnFe 2 O ⁇ : 1. A piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10vol% NaOH solution (3h) and sub sequentially washed with running distilled water (6h) before immersion in liquid nitrogen followed by freeze- drying during a period of 12 hours. 2. The dry cellulose piece is swollen in freshly prepared MilliQ-water solution of metal salt consisting of MnCl 2 x4H 2 O (0.055 M) and FeSO 4 x7H 2 O (0.11 M), i.e. stoichiometric proportions of Mn:Fe (1 :2).
- the solution with the immersed piece of cellulose is heated to 90 0 C and kept at 9O 0 C for 3 h in order to thermally force the precipitation of the iron/manganese salt solution to the related hydroxide/oxide structures of the manganese/iron ions inside the matrix network of the bacterial cellulose.
- the particle-modified cellulose network is washed with running distilled water for 6 h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 60-150 nm, as determined from FE-SEM microscopy. (*) noted under step 4. Refers to the concentration of iron in the solution used for swelling the bacterial cellulose, i.e. prior to the transfer of the cellulose into the alkaline solution.
- a piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10vol% NaOH solution (3h) and sub sequentially washed with running dis- tilled water (6h) before immersion in liquid nitrogen followed by freeze- drying during a period of 12 hours.
- the dry cellulose piece is swollen in freshly prepared MilliQ-water solution of metal salt consisting of FeSO 4 x7H 2 O (0.055 M) and FeCl 3 x6H 2 O (0.11 M) 5 i.e. stoichiometric proportions of Fe :Fe (1:2).
- the solution with the immersed piece of cellulose is heated to 90 0 C and kept at 90 0 C for 3 h in order to thermally force the precipitation of the iron salt solution to the related hydroxide/oxide structures of the iron ions inside the matrix network of the bacterial cellulose.
- the piece is transferred into a water solution of ammonia (12.5%) at r.t.
- the piece is kept in the alkaline solution at 23° C for 6 h.
- the piece is transferred into room temperature distilled water in order to neutralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled wa- ter for ⁇ h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 30-50 nm, as determined from FE-SEM microscopy. A significant amount of the particles were smaller than 30 nm.
- a piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10vol% NaOH solution (3h) and sub sequentially washed with running distilled water (6h) before immersion in liquid nitrogen followed by freeze- drying during a period of 12 hours.
- the dry cellulose piece is swollen in freshly prepared MilliQ-water solution of metal salt consisting of FeSO 4 x7H 2 O (0.165 M). 3.
- the solution with the immersed piece of cellulose is heated to 90 0 C and kept at 90 0 C for 3 h in order to thermally force the precipitation of the iron salt solution to the related hydroxide/oxide structures of the iron ions inside the matrix network of the bacterial cellulose.
- the piece is transferred into a 9O 0 C water solution of NaOH (1.32 M) with
- the piece is transferred into room temperature distilled water in order to neutralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled wa- ter for ⁇ h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 80-150 nm, as determined from FE-SEM microscopy.
- a piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10vol% NaOH solution (3h) and sub sequentially washed with running dis- tilled water (6h) before immersion in liquid nitrogen followed by freeze- drying during a period of 12 hours.
- the dry cellulose piece is swollen in freshly prepared MilliQ-water solution of metal salt consisting of FeSO 4 x7H 2 O (0.055 M) and FeCl 3 XoH 2 O (0.11 M), i.e. stoichiometric proportions of Fe 2+ :Fe 3+ (1:2).
- the solution with the immersed piece of cellulose is heated to 90 0 C and kept at 90 0 C for 3 h in order to thermally force the precipitation of the iron salt solution to the related hydroxide/oxide structures of the iron ions inside the matrix network of the bacterial cellulose.
- the piece is transferred into a water solution of NaOH (1.32 M) at 90 0 C.
- the piece is kept in the alkaline solution at 90° C for 6 h. 5.
- the piece is transferred into room temperature distilled water in order to neutralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled water for 6 h. 7.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 70-90 nin, as determined from FE-SEM microscopy.
- a piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10vol% NaOH solution (3h) and sub sequentially washed with running distilled water (6h) before immersion in liquid nitrogen followed by freeze- drying during a period of 12 hours.
- the solution with the immersed piece of cellulose is heated to 90 0 C and kept at 9O 0 C for 3 h in order to thermally force the precipitation of the iron salt so- lution to the related hydroxide/oxide structures of the iron ions inside the matrix network of the bacterial cellulose.
- the piece is transferred into a water solution of ammonia (12.5%) at r.t. with KNO 3 (0.25 M). The piece is kept in the alkaline solution for 6 h.
- the piece is transferred into room temperature distilled water in order to neu- tralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled water for 6 h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 120-130 nm, as determined from FE-SEM microscopy.
- Example 10 (NiFe 2 OA L A piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with
- the solution with the immersed piece of cellulose is heated to 90 0 C and kept at 9O 0 C for 3 h in order to thermally force the precipitation of the nickel/cobalt salt solution to the related hydroxide/oxide structures of the nickel/iron ions inside the matrix network of the bacterial cellulose.
- the piece is transferred into a water solution of ammonia (12.5%) at r.t. with KNO 3 (0.25 M). The piece is kept in the alkaline solution for 6 h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 400-600 nm (as determined from FE-SEM microscopy) and separated by a distance of approx. 5 ⁇ m.
- Example 11 fCoFe-OA 1.
- a piece of gel-like bacterial cellulose (0.5x0.5x1.5 cm) is boiled with 10vol% NaOH solution (3h) and sub sequentially washed with running distilled water (6h) before immersion in liquid nitrogen followed by freeze- drying during a period of 12 hours. 2.
- the dry cellulose piece is swollen in freshly prepared MilliQ-water solution of metal salt consisting of CoCl 2 x6H 2 O (0.055 M) and FeCl 3 XOH 2 O (0.11 M) 5 i.e. stoichiometric proportions of Co 2+ :Fe 3+ (1 :2).
- the solution with the immersed piece of cellulose is heated to 90 0 C and kept at 90 0 C for 3 h in order to thermally force the precipitation of the cobalt/iron salt solution to the related hydroxide/oxide structures of the cobalt/iron ions inside the matrix network of the bacterial cellulose.
- the piece is transferred into a water solution of NaOH (1.32 M) at 90 0 C.
- the piece is kept in the alkaline solution at 90° C for 6 h.
- the piece is transferred into room temperature distilled water in order to neu- tralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled water for 6 h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the "platelet-like" particles attached to the fibres were determined to have an average size of approx. 100-150 nm in width and 30-40 nm in thickness, as determined from FE-SEM microscopy.
- the piece is transferred into a water solution of ammonia (12.5%) at r.t. with KNO 3 (0.25 M). The piece is kept in the alkaline solution for 6 h. 5. The piece is transferred into room temperature distilled water in order to neutralize the alkaline solution inside the cellulose network matrix.
- the particle-modified cellulose network is washed with running distilled water for 6 h.
- the particle-modified cellulose is immersed in liquid nitrogen, followed by freeze-drying until all water has been removed from the network.
- the particles attached to the fibres were determined to have an average size of approx. 100-150 nm in diameter, as determined from FE-SEM microscopy.
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CN101647077A (en) | 2010-02-10 |
US20100203313A1 (en) | 2010-08-12 |
JP2010526158A (en) | 2010-07-29 |
EP2140463A1 (en) | 2010-01-06 |
EP2140463B1 (en) | 2017-05-31 |
CN101647077B (en) | 2013-10-30 |
EP2140463A4 (en) | 2011-06-29 |
DK2140463T3 (en) | 2017-07-10 |
ES2635724T3 (en) | 2017-10-04 |
JP5382545B2 (en) | 2014-01-08 |
US8785623B2 (en) | 2014-07-22 |
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