WO2012027194A2

WO2012027194A2 - Boron nitride with attached mettalic particles, methods of making, and uses thereof

Info

Publication number: WO2012027194A2
Application number: PCT/US2011/048241
Authority: WO
Inventors: Suresh Annavarapu; Eugene A. Pruss
Original assignee: Saint-Gobain Ceramics And Plastics, Inc.
Priority date: 2010-08-25
Filing date: 2011-08-18
Publication date: 2012-03-01
Also published as: WO2012027194A3; TW201208979A

Abstract

The present invention relates to a powder including hexagonal boron nitride particles and metallic particles. The metallic particles are attached to at least a portion of a surface of the hexagonal boron nitride particles. The present invention further relates to cosmetic compositions, polymer blends, thermal management compositions, and catalyst compositions including the powder and methods of making the powder.

Description

BORON NITRIDE WITH ATTACHED METALLIC PARTICLES, METHODS OF MAKING, AND USES THEREOF

[0001] This application claims the benefit of U.S. Provisional Patent

Application Serial No. 61/376,874, filed August 25, 2010, which is hereby

incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to a powder including hexagonal boron nitride (hBN) particles and metallic particles attached to at least a portion of a surface of the hBN particles. The present invention also relates to cosmetic compositions, polymer blends, thermal management compositions, and catalyst compositions including the powder and methods of making the powder.

BACKGROUND OF THE INVENTION [0003] Products for use in cosmetic and body care preparations have to meet stringent requirements. They have to be highly compatible with formulations used for cosmetic purposes. In particular, they are expected to be compatible with many other components, such as bases, salts, and surfactants. Further, the composition should be easy to apply and should leave the skin with a pleasant feeling. In addition, they should be universally useable in aqueous, emulsoidal, alcoholic and oil-containing bases, readily processable, and should be amenable to easy and even distribution or removal under clean and simple conditions. The compositions are also expected to show stable and unchanging physical and chemical quality even in the event of long- term storage and changes in pH and temperature.

[0004] There still exists an unfulfilled need for a cosmetic composition meeting all of the requirements of feel, color, and sheen. The present invention is directed to overcoming this and other deficiencies in the art. SUMMARY OF THE INVENTION

[0005] The present invention relates to a powder including hBN particles and metallic particles. The metallic particles are attached to at least a portion of a surface of the hBN particles.

[0006] Another aspect of the present invention relates to a cosmetic composition including the powder of the present invention and a cosmetic agent.

[0007] Yet another aspect of the present invention relates to a polymer blend including the powder of the present invention and a polymer matrix.

[0008] The present invention also relates to a system including a heat source, a heat sink, and a thermally conductive material connecting the heat source to the heat sink. The thermally conductive material comprises a powder phase including hBN particles and metallic particles attached to at least a portion of a surface of the hBN particles.

[0009] The present invention also relates to a catalyst composition including the powder of the present invention and, optionally, a catalyst.

[0010] The present invention further relates to a method for making a powder including hBN particles and attached metallic particles. The method involves providing hBN particles and treating the hBN particles under conditions effective to attach metallic particles to at least a portion of a surface of the hBN particles.

[0011] The powders and compositions of the present invention provide variable color formulations while maintaining a soft and lubricious feel to human touch. The powders are compatible with cosmetic formulations, as they are easy to distribute on the skin and in hair. These compositions are capable of enhancing the sheen or gloss associated with cosmetic products by improving the reflective capabilities of the product. In addition, these compositions can provide antibacterial properties useful, in particular, in cosmetic formulations. Moreover, the powders and compositions of the present invention can provide UV absorbing properties, useful, for example, in products and cosmetics for protecting against sun damage. These benefits are achieved without the need for further components or processing steps, thereby reducing cost and simplifying manufacture. The powders can also be used as a filler for the thermal management applications, e.g., in composites, polymers, and fluids.

BRIEF DESCRIPTION OF THE DRAWINGS [0012] Figure 1 is a graphic showing the structure of hexagonal boron nitride.

[0013] Figure 2 is a photocopy of a scanning electron micrograph (SEM) showing metallic particles attached to hBN platelets.

[0014] Figure 3 is a photocopy of an SEM of a spherical agglomerate of hBN platelets with copper particles attached to its surface.

[0015] Figure 4 is an optical stereomicroscopic image of spherical

agglomerates of hBN platelets with copper particles attached to their surfaces.

[0016] Figure 5 an SEM of spherical agglomerates of hBN with copper particles attached to their surfaces.

[0017] Figures 6 A and 6B show copper particles of different sizes attached to the outer surface of boron nitride platelets.

[0018] Figure 7 is a photograph of hBN powder having four shades of beige shown in grey scale.

[0019] Figure 8 shows silver particles attached to hBN platelets.

[0020] Figure 9 shows gold particles attached to hBN platelets.

[0021] Figure 10 shows copper particles on hBN platelets (not seen) with hairlike surface features characteristic of thermally formed copper oxide.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention relates to a powder including hBN particles and metallic particles. The metallic particles are attached to at least a portion of a surface of the hBN particles.

[0023] Hexagonal boron nitride is an inert, lubricious ceramic material having a hexagonal crystalline structure arranged like stacked plates (similar to that of graphite). The well-known anisotropic nature of hBN can be easily explained by referring to Figure 1, which shows hexagons within an hBN particle. Many of these units make up a BN platelet. The diameter of the hBN particle platelet is the dimension shown as D in Figure 1 , and is referred to as the a-direction. BN is covalently bonded in the plane of the a-direction. The particle thickness is the dimension shown as Lc, which is perpendicular to diameter and is referred to as the c- direction. Stacked BN hexagons (i.e., in the c-direction) are held together only by Van der Waals forces, which are relatively weak. When a shearing force greater than the weak Van der Waals force is imparted across of the planes of BN hexagons, the weak Van der Waals force is overcome and the planes slide relative to each other. The relative ease with which these planes of BN slide against each other may be one of the reasons for the high lubricity of hBN.

[0024] In one embodiment, the hBN particles are hBN platelets. In another embodiment, the hBN platelets have an average platelet size of from about 0.5 microns to about 100 microns. In yet another embodiment, a majority of the hBN platelets have an average platelet size of from about 6 microns to about 30 microns. As used herein, "platelet size" of the hBN platelet is the dimension shown as D in Figure 1. This is typically measured by scanning electron microscopy and laser scattering techniques (using, e.g., a laser scattering type particle size measuring device, such as a Leeds and Northrup Microtrac XI 00 (Clearwater, FL)).

[0025] In one embodiment, the particles have a thickness of no more than about 5000 nm, more preferably, between about 10 and 2000 nm, and, most preferably, between about 100 and 1000 nm. The particle thickness is the dimension shown as Lc in Figure 1. This is typically measured by scanning electron microscopy (SEM), calculated indirectly from SEM diameter and surface area data and, if the platelets are not multi-crystalline, sometimes by x-ray diffraction line broadening technique ( Hagio et al, J. Am. Cer. Soc. 72:1482-84 (1989), which is hereby incorporated by reference in its entirety) using, e.g., a SIEMENS Model D500 diffractometer.

[0026] The hBN platelets of the present invention may be in the form of a hBN powder having a highly ordered hexagonal structure. Such powders have a crystallization index (Hubacek, J. Cer. Soc. of Japan, 104:695-98 (1996), which is hereby incorporated by reference in its entirety) of at least 0.12 (quantification of highly hexagonal hBN) and, preferably, greater than 0.15. In one embodiment, the hBN powder has a crystallinity of about 0.20 to about 0.55, most preferably, from about 0.30 to about 0.55.

[0027] Typically, this starting powder is produced by a "high fire" treatment of a raw, essentially turbostratic (amorphous) boron nitride powder (see Hagio et al, J. Mat. Sci. Lett. 16:795-798 (1997), which is hereby incorporated by reference in its entirety) to produce what is conventionally referred to as "high purity hexagonal boron nitride." In a preferred embodiment, a fine turbostratic BN powder having a crystallization index of less than 0.12 is heat treated in nitrogen at about 1400 to 2300°C for about 0.5-12 hours. This heat treatment typically acts to produce a more coarse hBN powder, as the fine, <1 μιη crystallites, of turbostratic powder particles become more ordered (crystallized) and larger (>1 micron) during the heat treatment.

[0028] It may be desirable to adjust the amount of B₂0₃ in the hBN starting powder based on the potential use of the resulting powder. In particular, for cosmetic applications, the hBN particles of the present invention may have a low weight percentage of B₂0₃ to increase the hydrophobic nature of the resulting powder (to reduce drying of the skin). For cosmetic applications, in one embodiment, the hBN powder of the present invention has no more than 500 ppm B₂0₃, more preferably, from about 0 ppm to about 200 ppm B₂0₃. Low B₂0₃ content can be achieved by careful washing (such as solvent washing with, e.g., dry alcohol, cold water, etc) and drying (by, e.g., freeze drying).

[0029] In one embodiment, the particles have a surface area of at least about

2 2

0.5 m /g, preferably, at least about 1 m /g, and, more preferably, at least about 1.5 m /g. The specific surface area of the hBN particle is typically measured by BET adsorption technique, e.g., using a surface area analyzer, such as a Micromeritics, Flowsorb II 2300 (Norcross, GA).

[0030] In another embodiment, the hBN particles are agglomerates of hBN.

As used herein, an agglomerate is a collection of boron nitride platelets bonded together. In one embodiment, the agglomerates have an average agglomerate size of from about 1 micron to about 750 microns. In another embodiment, the majority of hexagonal boron nitride agglomerates have an average agglomerate size of from about 1 micron to about 50 microns. In another embodiment, the majority of hexagonal boron nitride agglomerates have an average agglomerate size of from about 5 microns to about 25 microns. In another embodiment, the majority of hexagonal boron nitride agglomerates have an average agglomerate size of from about 5 microns to about 10 microns. The term "agglomerate size" means the maximum dimension which it is possible to measure between two points of the particle. Such sizes can be measured directly by microscopic techniques, such as scanning electron microscopy and atomic force microscopy, or by indirect techniques, such as dynamic light scattering.

[0031] In a one embodiment, the agglomerates of hBN have an agglomerate size distribution of from about 1 to 750 microns, or 1 to 75 microns, or 1 to 50 microns, or 1 to 25 microns, or even 1 to 10 microns. As used herein, agglomerate size distribution is the range of agglomerates from the smallest agglomerate present to the largest agglomerate present, as defined by characteristic diameter of the agglomerates, where the agglomerates span the range. This is typically measured by laser scattering techniques. Preferably, at least about 90-95%, most preferably, at least about 98% of agglomerates fall within the agglomerate size distribution.

[0032] The boron nitride agglomerates can be classified under conditions effective to obtain a desired agglomerate size distribution. Suitable methods for classification include screening, air classifying, and elutriation, (see Chem. Eng. Handbook, Perry & Chilton, 5^th Ed., McGraw-Hill (1973), which is hereby

incorporated by reference in its entirety). Such techniques are described, for example, in U.S. Patent Nos. 6,764,975, 7,189,774, 6,645,435, and 6,645,612, which are hereby incorporated by reference in their entirety.

[0033] The agglomerates incorporated in the powders as disclosed herein can have various shapes. They can, for example, assume the shape of spheres, flakes, fibers, tubes, or polyhedra. They can also have an entirely random shape.

[0034] In one embodiment, the agglomerates are spherical in shape. In accordance with the present invention, spherical means having a shape approximating that of a sphere which would include, for example, a 22-sided polyhedron (e.g., substantially spherical). In accordance with this embodiment, the spherical agglomerates may have an average agglomerate diameter of from about 1 micron to about 50 microns. More preferably, the majority of spherical agglomerates have an average diameter of from about 5 microns to about 25 microns. More preferably, the majority of spherical agglomerates have an average diameter of from about 5 microns to about 10 microns.

[0035] Spherical agglomerates may be produced as described, for example, in

U.S. Patent No. 6,645,612, which is hereby incorporated by reference in its entirety.

[0036] In yet another embodiment, the hBN particles are crushed boron nitride briquettes.

[0037] Different size ranges of hBN particles can be used to produce varied colored powders, with larger particles producing deeper or darker colors.

[0038] In accordance with the present invention, metallic particles are attached to at least a portion of a surface of the hBN particles. In one embodiment, the metallic particles are specular metallic particles. As used herein, specular particles refers to particles exhibiting specular reflection, i.e., mirror- like reflection of at least a portion of incident light (or of other kinds of wave) from a surface, in which light from a single incoming direction is reflected into a single outgoing direction

[0039] In another embodiment, the metallic particles are oxidized, sulfidized, and/or nitrided. In this embodiment, the metallic particles can form metal oxides or metal sulfides or metal nitrides. The metallic particles can be used to impart varied colors to the powders. For example, iron oxides can be used to impart green or brown colors, manganese oxides can be used to impart color such as deep amber or amethyst, cobalt oxides can be used to impart deep blue, and copper oxides can be used to give, for example, a red color. In addition, the oxidized, sulfidized, and/or nitrided metallic particles can be used to enhance UV absorption of the powders. For example, zinc oxide and titanium oxide can be used to enhance UV absorption of the powder.

[0040] In one embodiment, the attached metallic particles have a size of from about 0.01 micron to about 25 microns. In another embodiment, the size of the majority of the metallic particles is from about 0.1 micron to about 10 microns. The term "size" when used in relation to the metallic particles means the maximum dimension which it is possible to measure between two points of the metallic particle. Such sizes can be measured directly by microscopic techniques, such as scanning electron microscopy and atomic force microscopy, or by indirect techniques, such as dynamic light scattering.

[0041] Different size ranges of metallic particles can be used to produce different colored powders. For example, at a low concentration and small size (about 3 to 5 microns), copper particles attached to a surface of hBN particles yield a pink- colored hBN. At a higher concentration and larger size (about 10 microns), copper particles attached to a surface of hBN particles yield a beige-colored hBN.

[0042] Suitable metals for the metallic particles include all metals. In one embodiment, the metallic particles include, but are not limited to, copper, silver, aluminum, tin, nickel, gallium, germanium, indium, lead, silicon, chromium, platinum, palladium, gold, iron, zinc, titanium, or combinations thereof. In one particular embodiment, the metallic particles are copper particles. The metallic particles can also comprise a mixture of two or more of these metals and/or alloys thereof. Thus, as used herein, the term "metal" also includes all the alloys of these elements, and the mixtures of these metals and alloys.

[0043] The metallic particles in the powders and compositions as disclosed herein can have various shapes. They can, for example, assume the shape of spheres, flakes, fibers, tubes, or polyhedra. They can also have an entirely random shape. In one embodiment, the metallic particles are spherical.

[0044] In accordance with the present invention, the metallic particles are attached to at least a portion of a surface of the hBN particles. The metallic particles can be attached through a mechanical attachment, for example, wetting of the hBN particle surface. Alternatively, the metallic particles can be attached to the hBN particle surface by chemical bond or static bond. In particular, the hBN particles may be reacted with a surface agent to create a surface linker suitable for attachment of the metallic particles, e.g. , treatment with a surface agent suitable to change the charge on the surface of the hBN particles to attach metallic particles having the opposite charge. Suitable surface linkers include, but are not limited to, amines, silanes, and glycols, for example, polyethylene-imine, triethyl-amine, aminopropyltriethoxysilane, or amino-polyethyleneglycol. [0045] In one embodiment, the hBN particles and/or the metallic particles are coated at least in part by a surface coating layer. In certain cases, the surface coating layer can encapsulate the metallic particles and the hBN particles. The surface coating layer can be made from glass (an amorphous solid material which is typically transparent or translucent) or a polymer, for example, silanes, silicones, amorphous silica, tetraorthosilicate, methicone, dimethicone, borate glass, and/or borosilicate glass. This surface coating can prevent degradation of the metallic particles by oxidizing or reducing agents such as air, moisture, sweat, oils, weak acids, or weak bases.

[0046] In one embodiment, at least about 0.5% to about 50% of the surface of the hBN particles includes attached metallic particles. More preferably, from about 0.5% to about 20% of the surface of the hBN particles includes attached metallic particles. This can be measured, for example, using the specific surface area of the boron nitride powder and the size of the attached metallic particles.

[0047] In one embodiment, the powder of the present invention has a coefficient of friction of from about 0.1 to about 0.2.

[0048] Specular metallic particles in the powders of the present invention enhance gloss by direct reflection. In addition, spherical specular metallic particles can enhance haze or soft focus effect by diffuse reflectance due to spherical morphology. Moreover, metallic particles with antibacterial properties, such as copper, silver, platinum, or gold, can be used to enhance the antibacterial properties of the powders.

[0049] Another embodiment of the present invention relates to a cosmetic composition including the powder of the present invention and a cosmetic agent. The term "cosmetic agent," as used herein, means any active compound having a cosmetic or dermatological activity or alternatively any compound capable of modifying the appearance, the feel, and/or the physicochemical properties of surfaces, such as the skin and hair. Cosmetic compositions in accordance with the present invention can be, for example, water-based, polymer-based, or dry formulations.

[0050] Suitable cosmetic agents include, but are not limited to, creams, moisturizers, lotions, oils, powder phases, filling phases, proteoglycans, cosmetic constituents of mineral or animal origin, saccharides, oligosaccharides and polysaccharides which may optionally be hydrolyzed and/or modified, amino acids, oligopeptides, peptides, proteins, which may optionally be hydrolyzed and/or modified, poly(amino acid)s and enzymes, branched and unbranched fatty acids and alcohols, animal, vegetable and mineral waxes, ceramides and pseudoceramides, hydroxylated organic acids, UV screening agents, antioxidants and agents for combating free radicals, chelating agents, antidandruff agents, seborrhoea-regulating agents, soothing agents, cationic surfactants, cationic and amphoteric polymers, organomodified and non-organomodified silicones, mineral, vegetable and animal oils, polyisobutenes and poly(a-olefm)s, esters, soluble and dispersed anionic polymers, soluble and dispersed non-ionic polymers, reducing agents, coloring agents and coloring materials, such as hair dyes, foaming agents, film-forming agents, abrasive particles, and mixtures thereof.

[0051] Hexagonal boron nitride is a component of certain cosmetic compositions and is used to improve tactile sensation of the formulations. Hexagonal boron nitride powders are white and, therefore, in color compositions, they are blended with pigments to obtain the desired color. The addition of pigments requires additional processing steps and the use of additional components in the cosmetic composition in order to produce compositions exhibiting the desired properties, as described above.

[0052] The cosmetic composition may further include, however, a pigment to obtain a desired color. Suitable pigments include, but are not limited to, Remazole Black B, Reactive Blue 2, Reactive Blue-Sepharose CL6B, Reactive Blue 4, Reactive Blue 5, Reactive Blue 15, Reactive Blue 72-agarose, Reactive Blue 114, Reactive Brown 10, Reactive Brown 10-agarose, Reactive Green 5, Reactive Green 5-agarose, Reactive Green 19, Reactive Green 19-agarose, Reactive Orange 14, Reactive Red 2, Reactive Red 4, Reactive Red 120, Reactive Violet 5, Reactive Yellow 2, Reactive Yellow 3, Reactive Yellow 13, Reactive Yellow 81, Reactive Yellow 66, and mixtures thereof.

[0053] Dispersion of fine metal particles is known to offer both antibacterial and antifungal effects. In addition, metal particles are known to provide gloss or sheen in certain compositions. Thus, metal particles are used in some cosmetic compositions. European Patent Publication EP 1,082,952, which is hereby incorporated by reference in its entirety, discloses compositions, such as for the nails, including glass particles covered with a metal layer which make it possible to obtain a make-up exhibiting a sparkling and wear-resistant metallic appearance. In addition, PCT Publication No. WO 02/03913, which is hereby incorporated by reference in its entirety, discloses nail varnish compositions including particles in the form of aluminum platelets in proportions by weight of 0.4% to 0.75% and film-forming agents having high molecular weights for producing a make-up of mirror type, that is to say, in this instance, a make-up having not only the color of the aluminum but also a sheen and an ability to reflect the separate components of an object. European Patent Publication EP 1,064,918, which is hereby incorporated by reference in its entirety, discloses that metal particles have also been incorporated in compositions used for application to hair to improve sheen.

[0054] The cosmetic compositions of the present invention are useful, for example, for enhancement of appearance, enhancing UV absorption, enhancing photoluminescence, and enhancing antibacterial properties, as compared to traditional cosmetic compositions.

[0055] Another embodiment of the present invention relates to a polymer blend including the powder of the present invention and a polymeric matrix. The polymer blend may be useful, for example, in thermal interface management. The term "thermal interface management," as used herein, means any compound having a thermal conductivity of > 1 W/m/K when produced in the form of a composite or fluid for use in applications such as microelectronics. Suitable polymers for the polymer matrix in accordance with the present invention include, for example, silicone polymers (e.g., silicone rubbers), epoxy formulations, melt-processable polymers, polyesters, polyimides, polyamides, urethane resins, phenolics, acrylics, waxes, thermoplastic polymers (e.g., polyolefins and fluoro-polymers), low molecular weight fluids, epoxy molding compounds, and combinations thereof. In one embodiment, the powder is distributed homogeneously within the polymer matrix. [0056] In one embodiment, the polymer blend comprises from about 30 wt.% to about 80 wt.% powder. However, the loading of the powder of the present invention into the polymer blend is determined by numerous factors, including the desired flexibility of the resulting polymer blend, the flowability of the polymer blend, and the thermal conductivity desired. For example, lower loading of the hBN powder, such as 30 wt.% to 50 wt.%, may be desirable for high flexibility

applications, but may result in lower thermal conductivity. Thus loading at from about 50 wt.% to about 80 wt.% may be desirable in high thermal conductivity/low flexibility applications.

[0057] The thermal conductivity of the resulting polymer blend is determined by loading, dispersion, and other factors. In one embodiment, the polymer blend has a thermal conductivity of from about 1 W/mK to about 15 W/mK.

[0058] Another aspect of the present invention relates to a system including a heat source, a heat sink, and a thermally conductive material connecting the heat source to the heat sink, wherein the thermally conductive material includes a powder phase including hBN particles and metallic particles attached to at least a portion of a surface of the hBN particles.

[0059] As used herein, a heat sink is a body of matter, gaseous, liquid, or solid, that receives a heat transfer from its surrounding environment.

[0060] Suitable heat sources for the present invention include integrated circuit chips, power modules, transformers, and other electronic devices.

[0061] Suitable heat sinks in accordance with the present invention include, for example, finned aluminum, copper, beryllium, and diamond.

[0062] As used herein, a thermally conductive material may be a composite, polymer, or fluid. In one embodiment, the thermally conductive material is a polymer, such as a melt-processable polymer, a polyester, a phenolic, a silicone polymer (e.g., silicone rubbers), an acrylic, a wax, a thermoplastic polymer, a low molecular weight fluid, or an epoxy molding compound.

[0063] The thermally conductive material preferably includes from about 30 wt.% to about 80 wt.% hBN powder in accordance with the present invention and has a thermal conductivity of from about 1 W/mK to about 15 W/mK. [0064] Another embodiment of the present invention relates to a catalyst composition including the powder of the present invention, wherein the attached metallic particles may function as a catalyst. The term "catalyst" as used herein, means any compound or composition having the ability to enable a chemical reaction to proceed at a usually faster rate or under different conditions than otherwise possible (e.g., to accelerate decomposition of gaseous species such as N0₂, CO, C0₂, S0₂ etc). The catalyst composition can also include a separate catalyst, such as γ-alumina. Catalyst compositions in accordance with the present invention can include a catalyst support, such as γ-alumina, or use hBN as the support.

[0065] Another aspect of the present invention relates to a method for making a powder including hBN particles and attached metallic particles. The method involves providing hBN particles and treating the hBN particles under conditions effective to attach metallic particles to at least a portion of a surface of the hBN particles.

[0066] In one embodiment, the treating step includes combining the hBN particles with an evaporative phase including the metallic particles under conditions effective to attach the metallic particles to the hBN particles. In accordance with this embodiment, an evaporative phase including the metallic particles can be produced by heating a metallic source, leading to melting of the metal and then formation of an evaporative phase including metallic particles. The metallic particles in the evaporative phase, which are combined with the hBN particles, attach to hBN particles (e.g., condense onto the hBN). Alternatively, an evaporative phase including the metallic particles can be produced by mixing the hexagonal boron nitride particles with the metallic particles to form a powder mixture and heating the powder mixture to form the evaporative phase including the metallic particles. The hBN particles and evaporative phase can be combined in a container, such as a closed crucible, such that the metallic particles can come into contact with and attach to the hBN particles.

[0067] In one embodiment, heating of the metallic source is performed in an inert or reducing atmosphere. The inert or reducing atmosphere can be obtained by using, for example, a noble gas or a mixture thereof. [0068] In another embodiment, heating of the metallic source is at a temperature of from about 25°C to about 1000°C above the metal's melting point at atmospheric pressure, preferably from about 500°C to about 1000°C above the metal's melting point at atmospheric pressure.

[0069] In yet another embodiment, the treating step involves mixing particles of hBN with metallic particles, such that the metallic particles mechanically adhere to the hBN particles. Mixing can be carried out dry or wet in a mixer, such as a V- blender or a Cowles dissolver.

[0070] In a further embodiment, the treating step involves using atomic layer deposition ("ALD") to adhere metallic particles to the surface of the hBN particles. Techniques for ALD are described, for example, in Atomic Layer Deposition for Nanotechnology by Arthur Sherman, Ivoryton Press (2008), which is hereby incorporated by reference in its entirety.

[0071] In yet a further embodiment, the treating step involves reacting the surface of the hBN particles or metallic particles to form a surface linker and attaching the metallic particles through the surface linker. Suitable surface linkers include, but are not limited to, amines, silanes, and glycols, such as

polyethyleneimine, triethylamine, and aminopropyltriethoxysilane. Such compounds can be adsorbed onto the hBN particles by adding excess surfactant (up to 10 wt %) to a suspension of hBN in either deionized water or alcohol (1-10 vol% of hBN), and repeatedly rinsing to remove unadsorbed surfactant. The surface treatment of BN or the metal particle and particle attachment to hBN can be done together or separately.

[0072] In a further embodiment, the treating step involves using thermal spray or plasma spray deposition to adhere metallic particles to the surface of the hBN particles. Techniques for thermal spray and plasma spray deposition are described, for example, in the Handbook of Thermal Spray Technology by Joseph R. Davis, ASM International Press (2004), which is hereby incorporated by reference in its entirety.

[0073] In one embodiment, the method further includes oxidizing, sulfidizing, and/or nitriding the attached metallic particles, for example, to form oxides or sulfides or nitrides. [0074] In one embodiment, the method further includes coating at least a part of the hBN particles and/or the metallic particles with a surface coating layer. The surface coating layer can be made from glass or a polymer, for example, silanes, silicones, amorphous silica, tetraorthosilicate, methicone, and/or dimethicone. In one embodiment, the entire surface of the hBN particles and the metallic particles are encapsulated with the surface coating layer.

[0075] The boron nitride powders and compositions of the present invention may exhibit a lubricious feel and soft touch due to the lubricious nature of boron nitride. This helps in providing for and improving the texture and quality of a cosmetic product by helping the product to spread evenly on a surface such as skin, scalp, or hair, while also providing a color formulation. This is a significant advantage over the use of oil, waxes, or other lubricant materials with pigments traditionally used in cosmetics. Oil or fat based products are sometimes linked to harmful side effects, for example, allergic responses, skin inflammations or outbursts, bacterial infections, and skin pore blockage. The powders and compositions of the present invention overcome these limitations without sacrificing the soft and lubricious feel which is preferred in cosmetic products.

[0076] The powders of the present invention provide for enhancement of appearance when used in cosmetic products. The use of specular metal particles may lead to enhancement of sheen or gloss in the cosmetic products. The attached specular metal particles may enhance gloss due to direct reflection. Further, spherical metallic particles may add a soft-focus haze to the composition. In addition, the use of metal particles which are known for their antibacterial properties, such as copper, silver, platinum, and gold, can help in preventing or treating bacterial skin infections.

Oxidation of some metal particles such as titanium or zinc or tin to form Ti0₂ or ZnO or Sn0₂, respectively, can add ultra-violet ray absorbing properties. Oxidation of other particles such as copper or iron to form CuO or Fe₂0₃, respectively, can add other colors mimicking inorganic pigments. Formation of sulfide layers of zinc can yield ZnS and provide a photo-luminescence to hBN.

[0077] Further, the powders of the present invention may reduce cost and improve efficiency in manufacture, as color is provided with the attached metallic particles or their oxides, sulfides, or nitrides. Accordingly, additional steps and agents are not required in the powders to add pigment for color requirements. Moreover, the use of organic pigments, which have been found to cause an allergic response, is not required in the powders of the present invention.

EXAMPLES

Example 1 - Boron Nitride (BN) Powder Used as a Starting Material

[0078] Table 1 below lists the hBN platelet powders used in the Examples below and method of powder manufacture.

Table 1.

[0079] To produce the hBN powders in Table 1 boric acid or boric oxide was reacted with nitrogen or ammonia at 1000-1800°C for 0.5-12 hours to yield raw or turbostratic (amorphous) boron nitride powder or briquettes (see Hagio et al,

"Microstructural Development with Crystallization of Hexagonal Boron Nitride," J. Mat. Sci. Lett., 16:795-798 (1997), which is hereby incorporated by reference in its entirety). The resulting powder or briquettes were then high- fired in nitrogen at 1400- 2300°C for 0.5-12 hours and milled to break up any briquettes or agglomerates. [0080] Table 2 below lists the agglomerated hBN powders used in the

Examples below and method of powder manufacture.

Table 2.

[0081] The agglomerated hBN powders in Table 2 above were prepared using a 50 wt % solid loaded BN slurry, as set forth in Table 3, below: Table 3.

Solids - 50 wt.% Liquids - 50 wt.%

XP1011 BN¹ 1400 g 95% DI water (pH 9) 1900g

HPP 325 BN² 600g 2.5% PEG-8000³ (binder) 50g

2.5% 111M⁴ (surfactant) 50g

¹ Saint-Gobain Ceramics & Plastics, Amherst, NY

Saint-Gobain Ceramics & Plastics, Amherst, NY

Union Carbide Chemicals and Plastics Company, Inc.

⁴ Rhodoline 111M, Rhodia, Inc., Cranbury, NJ

The correct amounts of powders and liquids set forth in Table 3 were measured out. The deionized (DI) water was pH adjusted to 9-9.5. Surfactant was added to the water and agitated using an impeller for 5-10 minutes. Powder was slowly added to the surfactant- water solution and stirred for 15-30 minutes to allow complete dispersion. Then the binder (PEG8000) was added and the slurry was mixed for another 15-30 minutes. The BN slurry was spray dried using a Pentronix atomizer - the inlet temperature was set to 235 °C which gave an outlet temperature of 85 °C. The flow rate of the slurry was 60 ml/minute and the atomizer (Pentronix, Detroit, MI) was set at 12,500 rpm. Larger particle sizes can be obtained using lower atomizer speeds in larger spray drying chambers. The desired particle size range was obtained by screening using the appropriate sieves in a Rotap unit.

Example 2 - Preparation of Specular Copper Particles Attached to hBN

Particles

[0082] Samples of boron nitride powder produced as described above in

Example 1 including hexagonal boron nitride platelets (0.2 to 0.5 g) having size ranges of 0.1 μιη to 125 μιη and spherical agglomerates of hBN (0.5g) having size ranges of 1 μιη to 75 μιη and Ι μιη to 750μιη (0.5g) were placed in boron nitride crucibles containing melted copper (7g). The crucibles were closed and then heated to 2000°C for 0.5 to four hours under argon or nitrogen. The copper evaporated from the molten copper and condensed onto the surface of the hBN platelets or the hBN agglomerates. The condensed phase was composed of spherical copper particles (3-10 μιη in diameter) that were preferentially attached to the hBN surface at the edges of the platelets or at step edges on the planar faces of the platelets i.e. to (011) , (010), etc family of crystal planes. The spherical copper particles attached to the surface of the crucible as well as the boron nitride particles within the crucible.

[0083] The hBN particles were then analyzed for the presence of metal particles using a scanning electron microscope. Results are shown in Figures 2-5. As shown in Figure 2, copper particles attached to the outer and step edges of the boron nitride platelets. In particular, the hBN platelets (grey) have copper particles (white) attached to the outer and step-edges. The hBN platelets and copper particles were heated in a crucible to 2000°C for four hours under Argon. In addition, Figures 3, 4, and 5 show copper particles attached to the outer surface of spherical boron nitride agglomerates of varying sizes. In Figures 3 and 5, the hBN agglomerates and copper particles were heated in a crucible to 2000°C for 0.5 hours under Argon. Example 3 - Comparison of Varying Metal Particle Size [0084] Samples of boron nitride powder produced as described above in

Example 1 including hexagonal boron nitride platelets (2g) having size ranges of 0.1 μιη to 125 μιη were mixed with copper powders (2g) (5-10 μιη in diameter) and placed in boron nitride crucibles. The crucibles were closed and then heated to 1500- 2000°C for 0.5 to four hours under argon or nitrogen. After heating to 1500°C, the copper powder melted and attached to hBN platelets at preferential sites. The size of the copper droplets was the same as the starting material i.e. 5-10 μιη in diameter. After heating to 2000°C, a part of the copper droplets evaporated from the molten copper droplets and condensed onto the surface of the BN powder. The condensed phase was composed of spherical copper particles (0.5-2 μιη and 3-10 μιη in diameter) that were preferentially attached to the hBN surface at the edges of the platelets or at step edges on the planar faces of the platelets.

[0085] The hBN particles were then analyzed for the presence of metal particles using a scanning electron microscope. Results are shown in Figures 6A-B with copper particles of different sizes (white) attached to the outer surface of boron nitride platelets (grey). Figure 6 A shows attached copper particles after heating to 2000°C (0.5-2 μιη and 3-10 μιη in diameter). Figure 6B shows attached copper particles after heating to 1500°C (5-10 μιη in diameter). Example 4 - Comparison of Varying Metal Particle Concentration

[0086] Samples of boron nitride powder produced as described above in

Example 1 including hexagonal boron nitride platelets (2g) having size ranges of 0.1 μιη to 125 μιη were mixed with different proportions of copper powders (5-10 μιη in diameter) ranging from 10 wt% to 50 wt% and placed in boron nitride crucibles. The crucibles were closed and then heated to 1500-2000°C for 0.5 to four hours under argon or nitrogen. After heating to 1500°C, the copper melted and attached to hBN platelets at preferential sites with minimal weight loss so that the final content of attached copper particles was very close to the starting concentration. After heating to 2000°C, a part of the copper droplets evaporated from the molten copper droplets so that the final content of attached copper particles was 20-50% lower than the starting concentration.

[0087] The hBN particles were then analyzed to assess the effect of different concentrations of attached copper. Figure 7 is an exemplary photograph of hBN powders having four shades of beige obtained by varying the concentration of copper microspheres attached to the hBN platelets (shown in grey scale). As shown in Figure 7, hBN powder including 10-25 wt% copper particles exhibit a light beige appearance and hBN powder including 33-50wt% copper particles exhibit a dark beige appearance.

Example 5 - Preparation of Silver Particles Attached to hBN Particles.

[0088] Samples of boron nitride powder produced as described above in

Example 1 including hexagonal boron nitride platelets (2g) having size ranges of 0.1 to 125 μιη were mixed with different proportions of silver powder (0.5-1 μιη and 5-10 μιη in diameter) ranging from 10 wt% to 50 wt% and placed in boron nitride crucibles. The crucibles were heated to 1500-2000°C for 0.5 to four hours under argon. After heating to 2000°C, the silver evaporated from the molten silver droplets and condensed onto the surface of the BN powder. The condensed phase was composed of spherical silver particles (1-10 μιη in diameter) that were attached to the hBN surface at the preferred sites. The spherical silver particles attached to the surface of the crucible as well as the boron nitride particles within the crucible. After heating to 1500°C, the silver powders melted and attached to hBN platelets at preferential sites. The size of the silver droplets was the same as the starting material i.e. 0.5-1 μιη or 5-10 μιη in diameter.

[0089] The hBN particles were then analyzed for the presence of metal particles using a scanning electron microscope. Results are shown in Figure 8 (silver particles appear white and hBN platelets appear grey). The hBN platelets and silver particles were heated in a crucible to 2000°C for 0.5 hours under Argon. As shown in Figure 8, silver particles attached to the boron nitride platelets. Example 6 - Preparation of Gold Particles Attached to hBN Particles.

[0090] Samples of boron nitride powder produced as described above in

Example 1 including hexagonal boron nitride platelets (lg) having size ranges of 0.1 to 125 μιη were dispersed into 20 ml deionized water and reacted with a red-colored aqueous gold colloid (10 ml) containing gold particles of about 100 nm at room temperature allowing gold particles to preferentially attach to terminal amine bonds at the edges of the hBN platelets. The color of the hBN powder changed to a light pink color. As a comparison, hBN treated with aminopropyltriethoxysilane to increase the concentration of terminal amine bonds was mixed with the same aqueous gold colloid at room temperature. A higher concentration of gold particles attached to the hBN surface producing a blue-violet powder.

[0091] The hexagonal boron nitride particles were then analyzed for the presence of metal particles using a scanning electron microscope. Results are shown in Figure 9. As shown in Figure 9, gold particles (which appear white in the figure) are attached to the boron nitride platelets (grey background).

Example 7 - Preparation of Oxidized Copper Particles Attached to hBN

Particles.

[0092] A 0. lg sample of boron nitride powder, produced as described above in Example 4 including hexagonal boron nitride platelets having size ranges of 0.1 to 125 μιη with 50 wt% copper particles (5-10 μιη in diameter), was heated in air to 400°C for 1 hour. The color of the hBN powder changed to dark grey indicative of the formation of black copper oxide.

[0093] The hexagonal boron nitride particles were then analyzed for the presence of oxide coating on the metal particles using a scanning electron microscope. Results are shown in Figure 10. As shown in Figure 10, the surface of the copper particles attached to the boron nitride platelets, show a hair-like surface characteristic of thermally formed copper oxide. The copper oxide was formed by thermal oxidation at 400°C for 1 hour in air. Example 8 - Preparation of Copper Particles Attached to hBN Particles with an encapsulating protective film.

[0094] A 0.5g sample of boron nitride powder, produced as described above in Example 4 including hexagonal boron nitride platelets having size ranges of 0.1 to 125 μιη with 50 wt% copper particles (5-10 μιη in diameter), was mixed with 50 ml Isopropanol (IP A) into which 0.5 ml 3-aminopropyltriethoxysilane (APTES) and 0.25 ml deionized water had been dissolved. The suspension was stirred 48-72 hours at room temperature, then filtered, rinsed, dried, and cured at 100-200°C for 30 minutes to form an encapsulating protective film.

[0095] Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the claims which follow.

Claims

WHAT IS CLAIMED:

1. A powder comprising hexagonal boron nitride particles and metallic particles attached to at least a portion of a surface of the hexagonal boron nitride particles.

2. The powder according to claim 1, wherein the hexagonal boron nitride particles are hexagonal boron nitride platelets.

3. The powder according to claim 2, wherein the platelets have an average platelet size of from about 0.5 microns to about 100 microns.

4. The powder according to claim 3, wherein a majority of the platelets have an average platelet size of from about 6 microns to about 30 microns.

5. The powder according to claim 1, wherein the hexagonal boron nitride particles are hexagonal boron nitride agglomerates.

6. The powder according to claim 5, wherein the agglomerates have an average agglomerate size of from about 1 micron to about 750 microns.

7. The powder according to claim 5, wherein the agglomerates are spherical in shape.

8. The powder according to claim 1, wherein the hexagonal boron nitride particles further comprise a surface linker for attachment of the metallic particles.

9. The powder according to claim 8, wherein the surface linker is selected from the group consisting of amines, silanes, and glycols.

10. The powder according to claim 9, wherein the surface linker is polyethyleneimine, triethylamine, aminopropyltriethoxysilane, or amino-polyethylene glycol.

11. The powder according to claim 1 , wherein the metallic particles are from about 0.01 microns to about 25 microns.

12. The powder according to claim 11 , wherein a majority of the metallic particles are from about 0.1 microns to about 10 microns.

13. The powder according to claim 1, wherein the metallic particles are copper, silver, aluminum, tin, nickel, gallium, germanium, indium, lead, silicon, chromium, platinum, palladium, gold, iron, zinc, titanium, or combinations thereof.

14. The powder according to claim 13, wherein the metallic particles are copper, silver, or gold.

15. The powder according to claim 1, wherein the metallic particles are spherical in shape.

16. The powder according to claim 1, wherein the metallic particles are specular metallic particles.

17. The powder according to claim 1, wherein the metallic particles are oxidized, sulfidized, or nitrided.

18. The powder according to claim 1 , wherein the metallic particles are attached to from about 0.5% to about 50% of the surface of the hexagonal boron nitride particles.

19. The powder according to claim 18, wherein the metallic particles are attached to from about 0.5% to about 20% of the surface of the hexagonal boron nitride particles.

20. The powder according to claim 1, wherein the powder has a coefficient of friction of from about 0.1 to about 0.2

21. The powder according to claim 1 , wherein at least a portion of the hexagonal boron nitride particles or the metallic particles comprise a surface coating layer.

22. The powder according to claim 21, wherein the surface coating layer comprises glass or a polymer.

23. The powder according to claim 22, wherein the surface coating layer comprises silanes, silicones, amorphous silica, tetraorthosilicate, methicone, dimethicone, borate glass, borosilicate glass, or combinations thereof.

24. The powder according to claim 21, wherein the surface coating layer encapsulates the hexagonal boron nitride particles and metallic particles.

25. A cosmetic composition comprising:

the powder according to claim 1 , and

a cosmetic agent.

26. The cosmetic composition according to claim 25, wherein the cosmetic agent is selected from the group consisting of creams, moisturizers, lotions, oils, powder phases, filling phases, proteoglycans, cosmetic constituents of mineral or animal origin, saccharides, oligosaccharides, polysaccharides, amino acids, oligopeptides, peptides, proteins, poly(amino acid)s, enzymes, branched and unbranched fatty acids and alcohols, animal, vegetable or mineral waxes, ceramides, pseudoceramides, hydroxylated organic acids, UV screening agents, antioxidants, agents for combating free radicals, chelating agents, antidandruff agents, seborrhoea- regulating agents, soothing agents, cationic surfactants, cationic and amphoteric polymers, organomodified and non-organomodified silicones, mineral oil, vegetable oil, animal oil, polyisobutenes, poly(a-olefm)s, esters, soluble and dispersed anionic polymers, soluble and dispersed non-ionic polymers, reducing agents, coloring agents, coloring materials, foaming agents, film-forming agents, abrasive particles, and mixtures thereof.

27. The composition according to claim 25 further comprising:

a pigment.

28. The composition according to claim 27, wherein the pigment is selected from the group consisting of Remazole Black B, Reactive Blue 2, Reactive Blue-Sepharose CL6B, Reactive Blue 4, Reactive Blue 5, Reactive Blue 15, Reactive Blue 72-agarose, Reactive Blue 114, Reactive Brown 10, Reactive Brown 10-agarose, Reactive Green 5, Reactive Green 5-agarose, Reactive Green 19, Reactive Green 19- agarose, Reactive Orange 14, Reactive Red 2, Reactive Red 4, Reactive Red 120, Reactive Violet 5, Reactive Yellow 2, Reactive Yellow 3, Reactive Yellow 13, Reactive Yellow 81 , Reactive Yellow 66, and mixtures thereof.

29. A polymer blend comprising:

the powder according to claim 1 , and

a polymer matrix.

30. The polymer blend according to claim 29, wherein the polymer matrix is selected from the group consisting of silicone polymers, epoxy formulations, melt- processable polymers, polyesters, polyimides, polyamides, urethane resins, phenolics, acrylics, waxes, thermoplastic polymers, low molecular weight fluids, epoxy molding compounds, and combinations thereof.

31. A catalyst composition comprising the powder according to claim 1.

32. The catalyst composition according to claim 31 further comprising: a catalyst.

33. The catalyst composition according to claim 32, wherein the catalyst is γ-alumina.

34. A system comprising a heat source, a heat sink, and a thermally conductive material connecting the heat source to the heat sink, wherein the thermally conductive material comprises a powder phase including hexagonal boron nitride particles and metallic particles attached to at least a portion of a surface of the hexagonal boron nitride particles.

35. The system according to claim 34, wherein the heat source is an integrated circuit chip, power module, transformer, or an electronic device.

36. The system according to claim 34, wherein the heat sink is finned aluminum, copper, beryllium, or diamond.

37. The system according to claim 34, wherein the thermally conductive material is a composite, polymer, or fluid.

38. The system according to claim 37, wherein the thermally conductive material is a polymer selected from the group consisting of a melt-processable polymer, a polyester, a phenolic, a silicone polymer, an acrylic, a wax, a

thermoplastic polymer, a low molecular weight fluid, an epoxy molding compound and combinations thereof.

39. A method for making a powder comprising hexagonal boron nitride particles and attached metallic particles, said method comprising: providing hexagonal boron nitride particles, and

treating the hexagonal boron nitride particles under conditions effective to attach metallic particles to at least a portion of a surface of the hexagonal boron nitride particles.

40. The method according to claim 39, wherein treating comprises:

combining the hexagonal boron nitride particles with an evaporative phase including the metallic particles under conditions effective to attach the metallic particles to the hexagonal boron nitride particles.

41. The method according to claim 40, wherein combining comprises: mixing the hexagonal boron nitride particles with the metallic particles to form a powder mixture and heating the powder mixture to form the evaporative phase including the metallic particles.

42. The method according to claim 39, wherein treating comprises:

mixing particles of hexagonal boron nitride with metallic particles, such that the metallic particles mechanically adhere to the hexagonal boron nitride particles.

43. The method according to claim 39, wherein treating comprises:

applying the metallic particles to the surface of the hexagonal boron nitride particles using atomic layer deposition.

44. The method according to claim 39, wherein treating comprises:

reacting the surface of the hexagonal boron nitride particles to form a surface linker and attaching the metallic particles through the surface linker.

45. The method according to claim 44, wherein the surface linker is selected from the group consisting of amines, silanes, and glycols.

46. The method according to claim 45, wherein the surface linker is polyethyleneimine, triethylamine, aminopropyltriethoxysilane, or amino-polyethylene glycol.

47. The method according to claim 39 further comprising:

oxidizing, sulfidizing, or nitriding the metallic particles.

48. The method according to claim 39 further comprising:

coating at least a portion of the hexagonal boron nitride particles or the metallic particles with a surface coating layer.

49. The method according to claim 48, wherein the surface coating layer comprises glass or a polymer.

50. The method according to claim 49, wherein the surface coating layer comprises silanes, silicones, amorphous silica, tetraorthosilicate, methicone, dimethicone, borate glass, borosilicate glass, or combinations thereof.

51. The method according to claim 48, wherein the surface coating layer encapsulates the hexagonal boron nitride particles and metallic particles.