METHOD, A SYSTEM AND A PACKAGE FOR PRODUCING A MAGNETIC COMPOSITE

Abstract

Provided are methods for producing magnetic composites. In some embodiments, the methods include providing a material in a non-continuous solid form; providing optically resonant particles dispersed within at least a region of said material; and exposing the optically resonant particles to electromagnetic radiation to be absorbed thereby to optically resonate to generate heat to fuse together portions of the material in thermal contact therewith. In some embodiments, the optically resonant particles have magnetic properties and/or are adapted to have magnetic properties induced by a stimulus, and the material is a non-magnetic material. Also provided are systems, computer program products, and packages adapted to implement the presently disclosed methods.

Claims

1. A method for producing a magnetic composite, wherein the method comprises: providing a material in a non-continuous solid form; providing optically resonant particles dispersed within at least a region of said material; and exposing at least said optically resonant particles to electromagnetic radiation to be absorbed thereby to optically resonate to generate heat to at least partially fuse together portions of said material in thermal contact therewith; wherein said optically resonant particles have magnetic properties and/or are adapted to have magnetic properties induced by a stimulus, and said material is a non-magnetic material.

2. The method according to claim 1, wherein said optically resonant particles are: ferromagnetic, ferrimagnetic, paramagnetic or superparamagnetic particles; and/or are non-magnetic but adapted to become permanently or temporarily ferromagnetic, ferrimagnetic, paramagnetic or superparamagnetic during and after being exposed to said stimulus.

3. The method according to claim 1, wherein said stimulus is an external magnetic field stimulus and/or a temperature stimulus associated to a temperature which is different than room temperature.

4. The method according to claim 1, further comprising exposing the optically resonant particles to said stimulus before, during and/or after they are provided dispersed within at least said region of the material and/or before, during and/or after they are exposed to said electromagnetic radiation and/or before, during and/or after the at least partially fused material is cooled down to solidify.

5. The method according to claim 1, wherein the optically resonant particles have magnetic properties that are permanently alterable when submitted to said stimulus.

6. The method according to claim 1, wherein the optically resonant particles have magnetic properties that are temporarily alterable when submitted to said stimulus.

7. The method according to claim 1, wherein said non-magnetic material is adapted not to have magnetic properties when exposed to any type of stimulus.

8. The method according to claim 1, wherein the optically resonant particles and electromagnetic radiation to be absorbed thereby are adapted and arranged so that heat generated by the optically resonant particles, when optically resonating, is at a temperature that is below the melting, sintering and glass transition temperatures of the optically resonant particles but equal or higher than at least one of the melting temperature, sintering temperature, and glass transition temperature of the non-magnetic material.

9. The method according to claim 1, wherein the non-magnetic material is made not to absorb or to absorb at least 50% less efficiently the electromagnetic radiation compared to the optically resonant particles, so that heat at a temperature which is equal or larger than at least one of the sintering temperature, melting temperature, and glass transition temperature of the non-magnetic material is not generated thereby.

10. The method according to claim 1, comprising providing said non-magnetic material and said optically resonant particles according to a spatially graded stoichiometry for producing a magnetic composite with spatially graded magnetic properties.

11. The method according to claim 10, further comprising providing a non-magnetic electromagnetic radiation absorber dispersed within the non-magnetic material to generate heat to at least partially fuse together portions of the non-magnetic material in thermal contact therewith, wherein said non-magnetic electromagnetic radiation absorber is distributed within the non-magnetic material so that heat generated thereby added to heat generated by the optically resonant particles result in a uniformly distributed global heat.

12. The method according to claim 1, wherein said optically resonant particles are made of at least one of the following materials: Co, Fe, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, FeOFe.sub.2O.sub.3, NiOFe.sub.2O.sub.3, CuOFe.sub.2O.sub.3, MgOFe.sub.2O.sub.3, MnBi, Ni, MnSb, MnOFe.sub.2O.sub.3, Y.sub.3Fe.sub.5O.sub.12, CrO.sub.2, MnAs, Gd, Tb, Dy, EuO, NdFeB, SmCo, SrFe.sub.12O.sub.19, or a combination thereof.

13. The method according to claim 1, wherein said optically resonant particles have a core and a shell including at least one layer, wherein one of said core and said at least one layer of said shell is made of at least one first material that has said magnetic properties and/or is adapted to have magnetic properties induced by said stimulus, and the other one of said core and said at least one layer of said shell is made of at least one second material that is a non-magnetic material.

14. The method according to claim 1, further comprising providing said optically resonant particles dispersed within at least said region of said material, configured and arranged to prevent at least one of: agglomeration and self-sintering of the optically resonant particles with each other.

15. A system for producing a magnetic composite, comprising: at least one supplier device for providing: a material in a non-continuous solid form; and optically resonant particles dispersed within at least a region of said material; and a controllable electromagnetic radiation source configured and arranged for exposing said optically resonant particles to electromagnetic radiation that causes the optically resonant particles to optically resonate to heat up and transfer heat to at least partially fuse together portions of said material in thermal contact therewith; at least one controller adapted to control said at least one supplier device to provide the material in a non-continuous solid form and the optically resonant particles, and said controllable electromagnetic radiation source to emit said electromagnetic radiation to expose the optically resonant particles thereto; wherein the system further comprises: a supply of said optically resonant particles, to feed said at least one supplier, wherein said optically resonant particles of said supply have magnetic properties or are adapted to have magnetic properties induced by a stimulus, and a supply of said material in a non-continuous solid form, to feed said at least one supplier, wherein said material in a non-continuous solid form of said supply is a non-magnetic material.

16. A package for producing a magnetic composite, wherein the package comprises, enclosed therein, a supply of optical resonant particles having magnetic properties or being adapted to have magnetic properties induced by a stimulus, and in that the package is configured and arranged to cooperate with at least one supplier device of a system, for providing said supply of optical resonant particles by extracting the same from the package, wherein said system comprises: said at least one supplier device for providing: a material in a non-continuous solid form; and said supply of optically resonant particles dispersed within at least a region of said material; and a controllable electromagnetic radiation source configured and arranged for exposing said optically resonant particles to electromagnetic radiation that causes the optically resonant particles to optically resonate to heat up and transfer heat to at least partially fuse together portions of said material in thermal contact therewith; and at least one controller adapted to control said at least one supplier device to provide the material in a non-continuous solid form and the optically resonant particles, and said controllable electromagnetic radiation source to emit said electromagnetic radiation to expose the optically resonant particles thereto; wherein the system further comprises a supply of said material in a non-continuous solid form, to feed said at least one supplier, wherein said material in a non-continuous solid form of said supply is a non-magnetic material.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0113] In the following some preferred embodiments of the invention will be described with reference to the enclosed FIGURE. They are provided only for illustration purposes without however limiting the scope of the invention.

[0114] FIG. 1 is a schematic representation of the method and system of the present invention, for an embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0115] The method and system of the present invention is schematically depicted in FIG. 1, for an embodiment, wherein the method comprises printing 2D or 3D magnetic objects made of a composite material consisting of at least two mixed component materials, namely a polymer organic non-magnetic component material in a powder form G and a second inorganic magnetic component material in the form of particles P.

[0116] The terms magnetic component material refers to both a material already having magnetic properties and to a component material that acquires magnetic properties induced by a stimulus, as already explained in a previous section.

[0117] According to the method of the first aspect of the invention, for the illustrated embodiment:

[0118] (a) The non-magnetic material particles G are mixed with the magnetic material particles P, thus forming a composite layer Y (not yet sintered). They are provided with at least one supplier S of the system of the second aspect of the invention under the control of controller C.

[0119] (b) The composite layer Y or part of it, or part of a layer formed by repositioning a composite layer, is illuminated on its surface at once and/or in parts successively, by means of controllable electromagnetic radiation source R under the control of controller C of the system of the second aspect of the invention, with electromagnetic radiation which wholly or partly is optically resonant to the resonance of the magnetic component material particles P, for any of the resonance types explained in a previous section.

[0120] (c) At the composite layer Y being irradiated with said electromagnetic radiation, the electromagnetic radiation is absorbed by the magnetic component material particles P which are thus heated due to the photothermal effect at a temperature which is smaller than the melting temperature of the magnetic material but equal or greater than the melting temperature and/or sintering temperature or/and glass transition temperature of the non-magnetic component material of particles G which is thus also heated towards being sintered while remaining mixed with the magnetic component material P, and becoming a solid continuous sintered magnetic composite layer L.

[0121] (d) The temperature of the sintered magnetic composite layer L is reduced to a temperature which is smaller than the melting temperature and/or sintering temperature or/and glass transition temperature of the non-magnetic component material of particles G, so that the sintered magnetic composite layer L solidifies.

[0122] The magnetic component material of particles P is ferromagnetic, ferrimagnetic, or superparamagnetic, or non-magnetic but that can become permanently or temporarilymeaning for time periods greater than 1 hourferromagnetic or ferrimagnetic or superparamagnetic during and after being exposed to an external magnetic field and/or when exposed to a temperature which is different than room temperature.

[0123] The non-magnetic component material of particles G is not ferromagnetic or ferromagnetic, and generally is a thermoplastic having melting temperature and decomposition temperature smaller than the melting temperature of the magnetic component material of particles P.

[0124] The electromagnetic radiation is not absorbed by the non-magnetic component material of particles G or is absorbed weakly, meaning that the portion of it being absorbed by the non-magnetic component material of particles G does not suffice for heating the latter at a temperature which is equal or larger than its sintering temperature or/and melting temperature.

[0125] Any of the steps (a)-(d) and the entire process can be repeated by one or more times for the purpose of increasing the concentration of the magnetic component material P in the composite layer Y and/or any of its part or for the purpose for increasing the degree to which the surface in thermal contact therewith is sintered.

[0126] After the composite layer Y wholly or partially is sintered an additional layer may be deposited above and in contact with it for the purpose of repeating steps-(a)-(d) for increasing the total thickness and overall dimensions of the sintered magnetic composite layer L towards forming a sintered magnetic object as is generally known in the art related to 3D printing, and such processes can be repeated several times.

[0127] Before and/or during and/or after any of the steps (a)-(d) the magnetic material component individually or in the composite may be positioned within a magnetic field of constant or varying intensity and direction for the purpose of altering permanently or temporarily its magnetic properties, such as for magnetizing it or for inducing a change in the individual and collective strength and orientation of the magnetic dipole of the particles P of the magnetic material component within the composite and/or within the final sintered layer and/or within the final sintered 3D object.

[0128] The shape and dimensions of the package layer being sintered are chosen as to be the ones of the intended sintered magnetic composite for 2D printing or as the ones of the particular layer of the sintered magnetic object for 3D printing, as is generally known in the art. In either case, the shape and dimensions are defined by the shape and dimensions of the package layer and its sintered part and these are further controlled by the shape and dimensions of the areas containing mixed magnetic and non-magnetic components and/or by the parts of such areas being irradiated with said electromagnetic radiation.

[0129] The size of the powder particles G of the non-magnetic component material is 0.001-1000 m and preferably 0.01-200 m and most preferably 1-100 m.

[0130] The size of the particles P of the magnetic component material is 0.001-1000 m and preferably 0.001-10 m and most preferably 0.001-0.01 m.

[0131] The weight ratio in the composite between the non-magnetic component material and the magnetic component material is 100000:1-1:10 and preferably 1000:1-10:1 and most preferably 1000:1-100:5.

[0132] Before, during and after steps (a) to (d) the non-magnetic component material and/or magnetic component material and/or the composite layer Y or L can be heated, by any means such as via thermal convection, to a temperature, which is higher than room temperature but lower than the sintering and melting temperatures of the non-magnetic component material.

[0133] The non-magnetic component material of particles G can be a mixture of any materials that individually can be identified as a said non-magnetic component material.

[0134] The magnetic component material of particles P can be a mixture of any materials that individually can be identified as a said magnetic component material.

[0135] The magnetic component material and/or the non-magnetic component material and/or the composite layer Y can contain or be mixed with other materials that are neither magnetic nor thermoplastic and are used for adding other various functionalities, such as preventing sintering or physical attachment of the magnetic particles P or colouring the sintered composite.

[0136] The magnetic component material before being mixed with the non-magnetic component material may be in the form of dry powder or may be dissolved or suspended within a liquid and be deposited and mixed with the-non-magnetic material by being drop casted onto the non-magnetic material. In such case the solvent or solvents of the liquid are chosen as to have a boiling or evaporation temperature which is smaller than sintering temperature of the non-magnetic component material and are also chosen as not being able to dissolve or induce swelling of the particles G of the non-magnetic component material, meaning that the volume of the powder particles G of the latter does not change by more than 50% when is in contact with the solvent for more than 10 hours. The solvent is also chosen as to allow sufficient wetting of the non-magnetic powder G by the amount of liquids being drop casted on its surface.

[0137] When the magnetic component material is deposited and mixed with the non-magnetic component material via drop casting, this can be done via any known methods in the art, a non-limiting list of such methods are the inkjet method and the spray method.

[0138] The magnetic component material can also be mixed with the non-magnetic component material via other known in the art methods, a non-limiting list of such methods are: mechanical mixing of powders, extrusion method and variations of it, mixing within a liquid possibly under mechanical stirring and/or or ultra-sonication and then allowing the liquid to be evaporated.

[0139] For an embodiment, the magnetic and non-magnetic materials are pre-mixed in the form of a package which is transferred to an SLS 3D printer which is equipped with a laser/light source of wavelength suitable for being absorbed by the magnetic component material. Within this printer, part of the said package is transferred for forming the composite layer Y.

[0140] For another embodiment, the composite layer Y is formed by first forming a layer made of particles G of the non-magnetic composite material and then depositing on it, or parts of it, the magnetic component material via the use of inkjet heads dispersing liquids containing the magnetic component material particles P. The positioning of the inkjet head as well as the droplet volume and number of droplets and frequency at which the droplets are released are controlled as to control the spatial and gravimetric density of the magnetic component material on the composite layer Y receiving it.

[0141] For a slight variation of the just above described embodiment, the composite layer Y is illuminated by light coming from a laser or an array of LEDs or from a broadband light source such as a halogen lamp or a short-wave IR lamp or mid-wave IR lamp or a combination of such light sources.

[0142] For another similar embodiment, before, during or after printing/manufacturing the printed/manufactured object a magnetic field, created by a permanent magnet or an electromagnet which may be part thereof and that is enclosed within a 3D printer, is applied to whole or part of the composite layer Y being printed for altering its magnetic properties.

[0143] For another similar embodiment, the whole or part of the finally printed/manufactured object is subject to a magnetic field generated by a permanent magnet or electromagnet which is attached to the 3D printer.

EXAMPLES

[0144] In the following, some specific examples of experiments carried out by the present inventors for implementing the method of the first aspect of the invention, are described in detail:

Example 1

[0145] A colloidal ink of Fe.sub.3O.sub.4 nanoparticles with an intended size of 20 nm, which is an example of particles P of a magnetic (superparamagnetic) component material in the present invention, were synthesized according to a method described in ACS Nano, 2012, 6 (4), pp 3080-3091. The synthesized nanoparticle ink was evidently paramagnetic as indicated by its attraction to a strong magnet which was positioned aside of a glass vial containing the ink, and had a broadband optical absorption spectrum in which a plasmon peak centred at 850 nm and electronic-transition related absorption onsets were measured via optical absorption measurements. The ink was then mixed with particles G of powder of PA12, which is an example of the non-magnetic component material of the present invention. The solvent of the ink (toluene) was allowed to evaporate, and the composite material was used to form a layer Y of thickness 10-500 m. This layer was positioned atop a hotplate the temperature of which was set to 160 C. and was further illuminated with mid-IR light for heating the layer Y to final temperature of 160 C. Subsequently, part of the surface of the composite layer Y was illuminated with a laser beam of wavelength of 808 nm, which is an example of the electromagnetic radiation used in the present invention, and the beam was scanned over the surface across a gear-like geometrical pattern. Each point of the pattern on the layer surface being illuminated with surface was sintered due to the photothermal effect induced by the absorption of the laser light by the iron oxide nanoparticles P in the composite, and as an end-result solid continuous gear-like shaped and arrow-shaped objects were formed. These objects had the shame thickness as the thickness of the original layer Y and could be removed by hand from the surrounding composite part of the layer which was not sintered/lasered. The objects were mechanically robust, maintaining their integrity under bending and unbending it. The objects were then placed atop a magnetic stirring plate. When the plate was switched on, thus generating a rotating magnetic field on its surface, the objects were also rotating due to the presence of a rotating force being applied by the plate's rotating magnetic field to the magnetic component of the composite objects. This example thus demonstrates that the present invention can be useful for making magnetic objects that can mechanically respond to external alternating magnetic fields.

Example 2

[0146] In a second example 1 kg of PA12 was mixed with 1 g of commercially available Fe.sub.2O.sub.3 magnetic nanoparticles P (of diameter <100 nm) purchased by a major chemical company. The nanoparticles P were originally in a powder form and for mixing them with particles G of PA12, they were first dispersed in ethanol, the dispersion was sonicated for 10 minutes at a sonicating power of 100 W, and the dispersion was then mixed mechanically with the PA12 powder and was left overnight in open air for allowing the ethanol to dry. The dry mixture was then loaded on a commercial SLS 3D printer to which an 808 nm laser was added and the system was used to print a ballerina-shaped 3D object of total length of around 5 cm. The formed object was mechanically robust and this example demonstrates the applicability of the present method for making complex shaped magnetic composite 3D objects.

[0147] A person skilled in the art could introduce changes and modifications in the embodiments described without departing from the scope of the invention as it is defined in the attached claims.