IL265815A - Particulate matter comprising a coated microparticle and uses of same in printing objects - Google Patents

Description

PARTICULATE MATTER COMPRISING A COATED MICROPARTICLE AND USES OF SAME IN PRINTING OBJECTS TECHNOLOGICAL FIELD The present disclosure concerns coated microparticles and uses of same in printing technologies.

BACKGROUND ART References considered to be relevant as background to the presently disclosed subject matter are listed below: - US Patent No. 8,900,704 - US Patent No. 9,263,166 - US Patent No. 9,127,515 - US Patent No. 9,833,836 Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

BACKGROUND US 8,900,704 describes a thermal interface material, comprising a plurality of metal-diamond composite nanoparticles, each composite nanoparticle comprising a diamond core surrounded by a continuous metal shell in contact with the diamond core, the metal shell comprising a plurality of metal nanoparticles, the metal nanoparticles having a fusion temperature of less than about 220 ºC.

US 9,263,166 describes a sintered structure and method for forming it. The method includes obtaining core-shell particles having a core material and a shell material, forming the particles into a powder compact, and annealing the powder compact at an annealing temperature. The shell material is a metal that diffuses faster than the core material at the annealing temperature and diffuses to the contacts between the core-shell particles during annealing to form sintered interfaces between the core-shell particles.

The sintered structure can have discontinuous regions of shell material between the sintered interfaces. The core material can be a metal, semiconductor or ceramic. As an example, the core material can be copper and the shell material can be silver.

US 9,127,515 describes a nanomatrix carbon composite that includes a plurality of dispersed particles comprising a particle core material that comprises an allotrope of carbon dispersed in the nanomatrix and a bond layer extending throughout the nanomatrix between the dispersed particles. Specifically, these composites are made from metal coated carbon nanoparticle powders that include various carbon nanoparticle cores, such as various graphene, fullerene or nanodiamond nanoparticles, or combinations thereof, with the nanomatrix formed from various nanoscale metallic coating layers.

US 9,833,836 describes a composition including a plurality of multi-metallic nanoparticles each consisting essentially of a core comprising at least one first metal (Me1) and a continuous shell comprising atoms of at least one second metal (Me2).

GENERAL DESCRIPTION The present invention is based on the understanding that it is possible to utilize microparticles with a unique physical property, e.g. thermal conductivity, coated with a second material, acting as a binder, in 3D printing so as to form 3D objects or patches exhibiting the physical property of the microparticles.

Thus, the present disclosure provides, in accordance with a first of its aspects, particulate matter comprising a microparticle of a first material having a first physical property, the microparticles being coated with a layer of second material, wherein the melting point of said first material is higher than the melting point of said second material.

Such particulate matter is for use in printing, preferably, 3D printing.

The present disclosure also provides, in accordance with a second aspect thereof, a powder comprising a plurality of particulate matter, the particulate matter comprising a microparticle of a first material having a first physical property, and being coated with a layer of second material, wherein the first material melting point being higher than the second material melting point.

In accordance with a third of its aspects, the present disclosure provides a method of printing, the method comprises sintering a powder comprising particulate matter, the particulate matter comprising a plurality of microparticles of a first material having a first physical property, the microparticles being coated with a layer of second material, wherein the first material has a melting point that is higher than the second material melting point, to form a printed model.

In accordance with a fourth of its aspects, the present disclosure provides an article of manufacture comprising two or more stacked layers of microparticles of a first material being interconnected by a second material; wherein the first material has a first physical property; wherein the first material has a first material melting point that is higher than the second material melting point to form a printed model.

DETAILED DESCRIPTION OF EMBODIMENTS The present disclosure is based on a development of a method for imparting a new physical property to a material, optionally in a well-defined patch-wise structure (herein referred to at times as objects).

The innovative development addresses inter alia a long-felt need to mount high power devices that generate massive amounts of heat with material that is thermally conductive and can facilitate the heat dissipation from the device.

One non-limiting example of a material which is highly thermally conductive is diamond. Yet, diamond cannot be directly deposited on a carrier substance (be it an electric device, circuit, chip etc) and therefore it has been envisaged to coat the diamond microparticles with a thin layer of a binder such that the diamond microparticle will essentially maintain its physical properties and yet upon sintering of the coated diamond, a highly conductive diamond object or patch is formed.

A similar solution is significant for other purposes such as magnetism, electric insulation, explosive and combustible, as will be further discussed below.

Based on the above realization coated microparticles have been developed, these coated microparticles, referred to herein as particulate matter comprise the core microparticle of a first material that is characterized by a first physical property, the core microparticle is coated with a thin layer of second material. To form a patch-like structure that maintains the physical properties of the first material, it has been realized that the microparticle should have a diameter in the lower micrometer scale; and that the melting point of the first material should be higher than the melting point of said second material.

Thus, for the purpose used herein, the term "particular matter" denotes a single microparticle made of a first material which is coated with a thin layer of a second material, wherein the first material is characterized by at least the following: - it has a physical property that can be of benefit when incorporated into devices and circuits for improving the properties of the device; as will be further explained below; - the microparticle has a diameter that is in the lower range of the micrometer scale, preferably ranging of between about 1µm and about 100µm; - it has a melting point that is above the melting point of the thin layer, such that upon heating, the thin layer fluidizes, without affecting the physical state of the first material.

In some examples, the first material forming the microparticle is an inorganic material, i.e. an inorganic microparticle.

In some examples, the second material forming the coating is an inorganic material or at least comprises inorganic material.

It is noted in the context of the present disclosure that the microparticles or the particulate matter is not an organic particle, and at most the coating may contain some organic component such as a polymer linked to an inorganic material.

For the purpose disclosed herein, the term "physical property" encompasses a variety of physical properties known to be associated with inorganic material, including, without being limited thereto, capacitance, electric conductivity, electric impedance, electric insulation, dielectric, thermal conductivity, thermal resistance, magnetism, wave impedance, explosiveness and combustibility, each property representing an independent embodiment of the present disclosure.

The microparticle may vary depending on the desired physical property.

In some embodiments, the microparticle is a diamond microparticle. Such diamond microparticle can be utilized, in accordance with some embodiments, due to its high thermal conductivity.

In some other embodiments, the microparticle is a samarium oxide microparticle.

Such samarium oxide microparticle can be utilized, in accordance with some embodiments, due to its high magnetism.

In some other embodiments, the microparticle is an iron microparticle, at times an iron oxide microparticle. Such microparticles can be used, for example, in magnetic applications.

In yet some other embodiments, the microparticle is an explosive.

In yet some other embodiments, the microparticle is a combustible material.

The microparticles may be of any shape, ranging from finely rounded particles to discrete amorphous structures. Independent of their physical shape, it is preferable that the particles are in a size at the lower micrometer range.

The microparticles may be characterized by their size (dimension), form and/or shape. Further, the microparticles may be defined by a length in one dimension (e.g. major axis length, medium axis length, minor axis length), width, length to width ratio, elongation ratio, aspect ratio, flatness ratio, level of sphericity and/or roundness.

In some embodiments, the particles have a major axis length in the range of 1 µm and 100 µm, at times between 5 µm and 100 µm, at times between 20 µm and 80 µm, at times between 30 µm and 70 µm, at times between 40 µm and 60µm, at times between 1 µm and 50µm, at times between 10 µm and 50µm, at times between 50 µm and 100µm, at times between 10µm to 80µm, and at times between 20 µm and 100µm, each of the above ranges constitute a separate embodiment of the present disclosure.

In some embodiments, the microparticles are essentially round and have a diameter in the range of 1 µm and 100 µm, at times between 5 µm and 100 µm, at times between 20 µm and 80 µm, at times between 30 µm and 70 µm, at times between 40 µm and 60µm, at times between 1 µm and 50µm, at times between 10 µm and 50µm, at times between 50 µm and 100µm, at times between 10 µm to 80µm, and at times between 20 µm and 100µm, each of the above ranges constitute a separate embodiment of the present disclosure.

In some embodiments, the microparticle has a diameter of between 10 µm and 50 µm.

In some other embodiments, the microparticle has a diameter of between 5µm and 100 µm.

The microparticle is coated with a thin layer of a second material.

For the purpose disclosed herein, the second material is one that may act as a binder for the particles such that upon fluidization of the second material it forms a medium interconnecting the microparticles, typically, although not exclusively, forming a layer over the microparticles. It is noted that such a layer can be continuous or non- continuous in terms of coverage of the surface of the first material. To this end, it is essential that the particles, namely, the first material (from which the microparticles are formed) are greater than the thin layer formed over the microparticles.

In some embodiments, the melting point of the first material is higher by at least about 100ºC from that of the second material, at times, by at least about 200 ºC, at times by at least about 300ºC, at times by at least about 400 ºC, at times by at least about 500 ºC, at times by at least about 600 ºC, at times by at least about 700 ºC, at times by at least about 800ºC, at times by at least about 900 ºC, at times by at least about 1,000ºC.

In some preferred embodiments, the melting point of the second material is lower than that of the first material. As such, when consolidated, the first material is engulfed by the second material, forming a body or article with desired properties.

In some embodiments, the melting point of the first material is higher by at least 200ºC from the melting point of the second material.

In some embodiments, the melting point of the second material is between about 50ºC and about 1,000ºC. In the context of the present disclosure, any value or range between about 50 ºC and about 1,000ºC also constitutes an embodiment of the present disclosure. Thus, the melting point of the second material may be at times between about 100ºC and about 1,000ºC, at times between about 200ºC and about 1,000ºC, at times between about 300ºC and about 900ºC, at times between 400ºC and about 800ºC.

The coating of the microparticle may be a complete coating, i.e. that the entire outer surface of the particle of the first material is coated, or it may be incomplete such that some portions of the particle's outer surface are exposed and some are coated. Yet, the coating is not made of discrete particles, e.g. nanoparticles.

The coating is a thin layer, and by the term "thin layer" it is to be understood that the amount of the second material forming the coating has a total volume that is less than %v/v of the total volume of the microparticle, at times, less than 10%v/v or even less than 8%v/v or even less than 5%v/v of the volume of the microparticle.

In some embodiments, the second material is a sinterable material, namely, a material that can be converted into a thin, optionally or preferably continuous, layer of the microparticles without necessarily turning into a melt.

In some embodiments, the second material is or comprises a metal. Without being limited thereto, when the second material is a metal, it can be selected from titanium, nickel, gold, platinum, silver, rhodium, aluminum, each metal defining a separate embodiment of the present disclosure.

In some embodiments, the second material is a metal alloy. Without being limited thereto, when the second material is a metal alloy it can be selected from any aluminum alloy (such as Al-Ti), copper alloy, nickel alloy, plutonium alloy, silver alloy, gold alloy (for example Au-Pt), and zinc alloy (for example Zn-Cu), each metal alloy defining a separate embodiment of the present disclosure.

In some embodiments, the second material is a metal polymer which is known as hybrid structures (for example ionic polymer metal composites).

In some embodiments, the second material is a metal matrix composite (MMC).

In some embodiments, the particulate matter disclosed herein is a diamond microparticle coated with a thin layer of a metal. In one specific example, the particulate matter disclosed herein is a diamond microparticle coated with a thin layer of titanium.

In some embodiments, the particulate matter disclosed herein is a samarium oxide microparticle coated with a thin layer.

Coating the particulate matter as disclosed herein can be achieved by method for the deposition of a powdered coating onto microparticles. Specifically, coating may be obtain via any one of plasma spray coating and thermal spray, also known as metal spraying methods.

In some embodiments, the plasma spray is selected from atmospheric plasma and vacuum plasma.

A plurality of the particulate matter disclosed herein forms a powder, which also constitutes part of the present disclosure. The powder is defined as a population of particulate matter that are essentially the same. In this context, when referring to a population of particulate matter that are essentially the same it is to be understood that the particulate matter in the powder may still differ from each other in or more measurable parameter, such as in the volume of second material coating the microparticle, the coating thickness and/or the dimensions of the microparticles; yet, the overall deviation in such measurable parameter among the members of the population will amount to no more than %.

Thus, for example, when referring to powder comprising particulate matter having a major axis length or a diameter of between about 10 µm and 100µm, the size distribution of the particulate matter in the powder is defined as such that no more than 10%, at times, less than 5% of the population have a diameter that is smaller than 10 µm or higher than 100µm.

The particulate matter comprising microparticles coated with a thin film layer of a material (such as metal) may be used in a 3-dimensional (2D) or 3-dimensional (3D) printing techniques. Thus, for example, upon heating, the thin layer of the second material sinters and causes binding of the microparticles together. This may be, without being bound by theory, due to consolidating coating layers. When used in printing techniques, the powder may be formulated with other printing material to form an ink formulation.

For example, the powder can be mixed with an ink that will facilitate printing and then evaporates during the sintering.

The particulate matter or powder disclosed herein can be utilized for the production of objects, such as patches or patch-like structures, high thermal conductivity substrates, and/or chips. The objects may be of any form or structure, and will be characterized by the physical property of the first material.

In some examples, the powder disclosed herein is used for the formation of a thermally conductive patch. To this end, the particulate matter is one comprising diamond microparticles, coated with a metal layer, e.g. titanium. The resulting patch comprise a continuous layer, typically of 5-50microns, depending of the particular application of diamond particles of essentially the same dimensions, interconnected by metallic medium, acting as a binder. The patch, being practically made of diamond particles, exhibits essentially the same thermal conductivity as that of diamond (with only a slight change from the high thermal conductivity of pure diamond).

Of particular interest, for instance, are patches having diamond-like thermal conductivity, for use in mounting high power electronic devices, e.g. LED lighting.

In some examples, a thermally conductive patch comprising diamond microparticles can be incorporated into light-emitting diode (LED) lamp to improve the thermal conductivity of the LED.

Similarly, a magnetic patch can be formed by using magnetic iron oxides, or samarium oxide microparticles coated with a non-magnetic binder, for example Ti, Ni or Rh. This will allow 2D or 3D printing of magnetic patches with a defined and controlled ceramic thickness, without the need to employ very high temperatures that may be needed for sintering ceramic material.

In some examples, a magnetic patch comprising samarium oxide microparticles can be incorporated into an hybrid circuit and serve as the inductor coil.

The present disclosure also provides a method of utilizing the particulate matter or powder disclosed herein in a printing a material, the method comprises at least sintering the powder as disclosed herein onto a defined model.

Any printing technique known in the art that involves a sintering stage may employ the powder disclosed herein. This includes 2D, 3D or even 4D printing methods the model may be a physical or digital model.

The term sintering as used herein is to be understood to have the meaning as known in the art, namely, to the application of heat (e.g. by laser) or pressure for any one of compactization, solidification, pyrolysis and annealing at least part of the particulate matter without causing complete melting.

In some embodiment, the sintering is performed by thermal heating.

In some other embodiments, the sintering is by the use of a laser source, e.g. for selective laser sintering (SLS).

The present disclosure also provides an article of manufacture comprising a plurality of stacked layers of a microparticles of the first material defined herein being interconnected by the second material defined herein. The article of manufacture can be obtained by 2D or 3D printing making use of the particulate matter or powder disclosed herein as or within an ink formulation.

As used herein the term "about" defines approximations which are varied (+) or (-) by up to 10%, at times by up to 5% of from the stated values. It is to be understood, even if not always explicitly stated, all numerical designations are preceded by the term "about".

NON LIMITING EXAMPLES Preparation of coated diamond microparticles Diamond microparticles are coated by a plasma spray process, specifically a thermal spray technique, in which a metal coating, in a powder form, is inserted into a plasma jet to generate a metal mist (molten or semi-molten form). This metal mist is sprayed at a high speed onto the diamond microparticles and then is rapidly consolidate to thereby continuously coat the microparticles.

Preparation of a diamond patch Diamond patches are prepared by selective laser sintering (SLS) which uses a CO 2 laser beam to fabricate models in a layered manner. A bin of powder is placed onto the powder feed of an SLS machine. The laser bean scans the diamond microparticles, heats them and fuses them to form a solid layer. Next the laser beam scans X and Y and optionally Z axes to obtain the structure based on a Computer Aided Design (CAD) data.

Upon the fusion of the first layer a new layer is deposited and sintered and so on according to the number of layers.

Claims (18)

- 11 - CLAIMS:

1. Particulate matter comprising microparticles of a first material having a first physical property, the particles being coated with a layer of second material, wherein said first material is an inorganic material with a melting point that is higher than a melting point of said second material; and wherein the particulate matter is for printing objects characterized by at least said first physical property.

2. The particulate matter of claim 1, wherein the melting point of the second material is below 1,000ºC, preferably between 50ºC and 1,000ºC.

3. The particulate matter of claim 1 or 2, wherein said microparticle is selected from the group consisting of diamond particle, samarium oxide particle, powdered combustible material, and particles of an explosive.

4. The particulate matter of any one of claims 1 to 3, wherein the microparticle of a first material being coated with a continuous layer of second material.

5. The particulate matter of any one of claims 1 to 3, wherein the microparticle is at least partially coated with a layer of said second material.

6. The particulate matter of any one of claims 1 to 5, wherein said layer of said second material has a volume that is less than 15% the volume of the microparticle.

7. The particulate matter of any one of claims 1 to 6, wherein said microparticle has a diameter or a dimension along its longitudinal axis of between 1µm and 100µm.

8. The particulate matter of any one of claims 1 to 7, wherein the first physical property is selected from the group consisting of thermal conduction, magnetism, electric insulation, explosive and combustible.

9. The particulate matter of any one of claims 1 to 8, wherein said microparticle is a diamond microparticle.

10. The particulate matter of any one of claims 1 to 9, wherein said second material comprises a metal.

11. The particulate matter of any one of claim 1 to 10, wherein said second material is a metal, metal polymer or metal alloy. - 12 -

12. The particulate matter of any one of claims 1 to 11, wherein said second material comprises a metal selected from the group consisting of titanium, nickel, gold, platinum, silver, rhodium, aluminum.

13. The particulate matter of any one of claims 1 to 12, comprising a diamond particle coated with a titanium layer.

14. A powder for use in printing, the powder comprising a plurality of particulate matter according to any one of claims 1 to 13.

15. The powder of claim 14, where said plurality of particulate matter has a particle size distribution with less than 10% of the population having a diameter or dimension along the particulate matter's longitudinal axis that is smaller than 10µm or higher than 50µm.

16. An ink formulation comprising a plurality of particulate matter according to any one of claims 1 to 13.

17. A method of printing a material, the method comprises sintering a powder according to claim 14 or 15 or an ink formulation according to claim 16 onto a defined model.

18. An article of manufacture comprising one or more stacked layers of microparticles of a first inorganic material being interconnected by a second material; the first material has a melting point being higher than a melting point of said second material, and wherein said first material has a physical property.