WO2013114029A1

WO2013114029A1 - Method for preparing hexagonal boron nitride particles with metal nanoparticles attached thereto by stable bonds

Info

Publication number: WO2013114029A1
Application number: PCT/FR2013/050166
Authority: WO
Inventors: Philippe Miele; Ouardia AKDIM; Philippe Guarilloff
Original assignee: Universite Claude Bernard Lyon I; Centre National De La Recherche Scientifique
Priority date: 2012-01-31
Filing date: 2013-01-28
Publication date: 2013-08-08
Also published as: FR2986166B1; FR2986166A1

Abstract

The present invention relates to a method for preparing so-called modified hexagonal boron nitride particles with metal nanoparticles attached thereto by stable bonds, comprising the following steps: a) providing a reaction mixture comprising either the metal nanoparticles directly, or a water soluble precursor salt of the metal nanoparticles, urea, hexagonal BN particles, water, and an acid, so as to reduce the pH of the reaction mixture, b) then, stirring and heating the reaction mixture, in such a way as to attach the metal nanoparticles or nanoparticles containing the metal element used in order to obtain the desired metal nanoparticles after treatment, to the BN particles, c) washing the modified boron nitride particles closed in this way, and the modified BN particles which can be obtained according to such a method.

Description

!

The present invention relates to the technical field of inorganic materials, specifically, the invention relates to a process for the preparation of hexagonal ore nitride particles, and preferably cristaJHr., On which are fixed in stable bonds, metal nanoparticles 0 (the metal nanoparticles having a degree of oxidation II) or metal oxide, generically called metal nanoparticles, and the modified boron nitride particles that can be obtained by such a process,

Boron nitride is a ceramic consisting of an equivalent number of boron and nitrogen atoms whose crude formula is BN. Its structure is close to that of carbon and can therefore be in several polymorphic forms; hexagonal (tvBN), cubic (c-BN),

(r-BN), wurzfttique (w-BN) [Thermochim / ca Acia

(1993 The hexagonal shape is the most common because it is easier to obtain,

The hexagonal shape of the BN is in the form of sheets {mulocouches} Each sheet consists ^of boron atoms ^and alternating nitrogen and connected to input them by covalent bonds, forming a network hexagons 8 ₃ M In contrast to graphite, aromatic character is weak because the electrons of the p orbitals of nitrogen are little delocalised. The boron and nitrogen atoms are also alternated along the axis c (Le, the axis which is perpendicular to each of the axes a and b of the elementary mesh of the hexagonal lattice, the axes a and b forming an angle between them. of 120 ^e ). The sheets are interconnected by Van Der Waals type links. This lamellar structure, therefore anosotropic, gives the BN many properties depending on the eristallograpfic direction, including high lubricity, high electrical insulation and high thermal conduction [Journal of the European Ceramic Society ¥ 28, (2008), . 1105-1109], The hexagonal BN is characterized in the crystal sense! strict ographl by a arrangement of alternating boron and nitrogen atoms in yaws and perpendicular to the plane (3D structural organization). It is common practice for those skilled in the art to consider that the hexagonal arrangement B ₃ f% is sufficient to define "hexagonal" BN whose crystal rate! inity is variable.

The organization of the sheets of hexagons with each other and in the axis perpendicular to these sheets increases with the temperature of treatment and it is therefore convenient for the skilled man to define major subpolytypes, resulting in h- Crystallized MS, obtained in ranges of treatment temperatures in the range 0 ~ 2Û € G * CI exist three main sub-types of the BN hexagonal farm (grades) which are characterized by different degrees of finite crystallinity fTherrnochimica Âcta Y282 _; (19%), p359-367; Journal of American Chemical Society V84, (1963), p4619-4622)]. It should nevertheless be noted that the structure is organized continuously when increasing the heat treatment temperature. The degree of crystallization obtained at a given temperature can nevertheless also vary depending on the production process and the starting material, so there are no precise temperatures for obtaining these varieties but temperature corresponding to a degree of orgarusatiori therefore to a grade.

In the context of the invention, we will call "hexagonal 8N" or h-BN, any BN being in a form of sheets characterized by: a hexagonal arrangement f¾r¾ boron and nitrogen atoms alternated in the plane according to a structural organization 2D _f the organization in the perpendicular axis which can be more or less important and depends on the degree of crystallinity. Whatever its degree of crystallinity and therefore its sub-polytype, the - H will be characterized by X-ray diffraction (XRD) by the presence of a peak in the range of values of 2Θ ranging from 20 ° to 30 ° corresponding u (002), and the presence of at least one peak in the range of 2Θ values from 40 ° to 46 ° which corresponds to the plane (10) when only one peak is present or to the (100) and ( 191) when two peaks present. The three sub-olies of h ~ BM can be defined as

- Turbostratigic grease; it is described as a hexagonal arrangement of the alternating boron and nitrogen atoms in the plane (2D structural organization) but a weak organization in the axis perpendicular to the hexagonal planes (semi-crystalline structure). In contrast to the graphitic farm, ifs are disordered according to the generalized formula (rotations and random translations with respect to normal exaggerations). In view of the disorganization, this grade is characterized by XRD by the presence of two peaks associated with the planes (002) and (10), generally in the form of two broad peaks situated respectively between the values 30 ° <28 <30 ° and 40 ° <28 <46 ° These peaks are associated with the (002) and (10) pians.This grade is present for synthesis or post-synthesis treatment temperatures, such as 30D ° C <Ts <i200 ° C. The average distance between two planes <is generally such that 3.36 "fco2 <33" The width of the crystals (width of a single-crystal area measured in the direction of the hexagonal planes) is generally between And about 20 nm.

Mesographitic scale: The degree of relative crystallization increases with the crystallization time to at least 1500 ° C., but the crystallization is not complete, however, and rather reflects a "mesographitic" aspect of an incomplete three-dimensional cryptographic structure. Is layers have a partial structural organization in 3D. This grade is characterized by XRD by the presence of at least magpies associated with the (002), (100), (101) and (004) planes between 25 ° <28 <27% 41 ° <28 <43 °, 43 ° <<28 ° and <55 ° <2 ° <56 ° respectively This grade is present during the synthesis or post synthesis synthesis temperatures Ts such that 140 ° ° <Ts <16 ° C ° The distance between the ota hex planes is generally between 3.35 <doo2 <3, -36 nm. The width of the crisallites (width of a single-crystal zone measured in the direction of the hexagonal planes) is generally between about 20 and 60 nr.

Graphitic grading: the most organized polytype of the hexagonal BN. The layers B ₃ M ₃ have an organized structure in 3D, are parallel to each other and stack according to i¾xe c "This grade is characterized in DR by the presence of the associated peaks u planes (0Û2) _f (iOG), ( 101), (102), (004) and (103) between 26 ° <2 ^β <27 °, 41 ° <29 <42 °, 43 ° <28 <4 °, 49 ⁶ <2Θ <51 °, 55 ° <2Θ <56 ° and 59 ° <20 <60 ^th respectively. This grade is present for synthesis temperatures Ts or post-synthesis processing such that 1600 ^e C <Ts <2GQ0 * The distance between the planes of hexagons z, close to the theoretical value, is such that 3,33 <€ ₂ <3.35 nrm The width of the crystals L _¾ (width of a monocrystaline zone measured in the direction of the planes of hexagons) is generally greater than 60 nm.

Thus, the oristallini of the hexagonal variety of B increases with the temperature of synthesis or post-synthesis treatment to pass from an amorphous phase, to a turbistratic potytype, and then a mesograptil polytype, this one being a transit transit stage between the turbostratiqy and graphitic grades, and grown in the graphitic phase. This is where held over ^'in 1600 has the highest degree of hau crfstaiiinlté if traduisan by a peak (002) fine and intense. It is therefore the most stable form and the most resistant to oxidation. It has the lowest coefficient of friction (Le, the highest lubricity).

In the context of the event, X-ray diffraction (XRD) analysis may be recorded in a range of 26 = 100 ° -80 ° using CuK radiation (λ = 1.5406 °). The pure powder is ground and placed a support in such a way that the surface of the powder is in the plane of the analysis.

In addition to the diffraction peaks, the most important information that can be achieved by this technique is; Interplanar distance ά _® & S is the average stacking height of the hexagonal planes f¾M ₃ corresponding to the Miller indices (002) L _c (OQ¾, the mean length of the crystallites L _a αο _, and the relative degree of crystallization * f The dimension ¾¾ _? Is calculated at from S Bragg's law using the diffraction angle of the spleen (002).

Because of its many properties, the 8N has many applications in: electronic foundry, automotive:,., Cosmetics ... [Journal of t e European This mic. Society V28, (2008), Î5-Î1Ù

In O smetic, highly crystalline (graphitic) h-BN is highly prized for its unique sensory, softening and lubricating properties. Its high chemical resistance gives it great safety. It can be added in free form to powdered cosmetics to provide softness, stability, adhesiveness and durability (Japanese Patent Applications 61-28596 and 82-9247). It is especially used in foundation, compact and free powders, lipsticks, nail polish, shampoïngs, deodorants, creams and lotions, .Proœss engineering 84 (2QQ7) number 121,

The color of the crystallized h ~ BM, crystal pol is white. 8N is the opacifying and reflects light by producing an effect which irfdescent ^s' increases with its degree of cristallnl é,

Obtaining a colored 8N that retains its physical and optical properties is now difficult to achieve. St Gooain for example, offers a colorful range of BM obtained by mechanical mixing with pigments, and: marketed under the reference TrèsBN®. However, the addition of pigment by mechanical action influences the lubricity of the final product obtained.

It has also been proposed in the literature different methods of deposition of nanoparticles on M. The most widespread in the literature is that of dry impregnation (Applied catalyzed A: ge rat ¥ 219 (2001) 117-124], This method requires BU! has sufficient porosity to achieve the impregnation. In addition, the volume of solvent in which the metal precursor is dissolved corresponds to the pore volume of the material to be impregnated. The metal is then deposited on the H by absorption. capillary of the imitating solvent. Also, in the case of 8M with zero or very low porosity, this process is difficult to apply. Moreover, when the specific surface area of the BM is low (<10 m ² / g), the dispersion of deposited nanoparticles decreases sharply [Jôumsf The latter phenomenon reflects a low stability of the particles on the surface of the BU,

Another method is to use one with a lower crustallity than graphitic BN, to obtain a larger surface area. (Appiied œtafysis A: Genoa ¥ 219 (2001) p 117-12 _* In this case the BM loses its lubricity and its long-term stability diminishes [Journal of the Euœpean Ceramic Society VI? {1997} 1415-1422],

As part of In ention the inventors propose to provide a new method of deposition of metal nanoparticuies on the surface of the BN.

The method according to the invention must also allow the deposition of metal nanoparticles on 8M with a low specific surface area

(<10 'n ^GI) and a PMT wan porosity, vo re zero.

One of the objectives of the invention is also to provide a competitive process, in terms of cost and implementation and to obtain a satisfactory and homogeneous dispersion of nanoparticuies on the BM.

Another objective of the invention is to provide a method of deposition of metal nanoparticles on the surface of the BN, of which: the deposition efficiency of metal nanoparticles is high.

Another object of ^the invention is to provide a metal nanoparticuies deposition process on the surface of 8M which does not lead to aggregation of the particles and H leads to particles of hexagonai boron nitride (h-BN) known modified metal nanoparticles, said modified particles being particularly stable.

In this context, the invention relates to a process for the preparation of so-called modified hexagonal boron nitride particles on which ? fixed, according to stable connections, metal iianopartlets comprising the following steps:

a) providing a mixture comprising rêacttonnel either directly your nanopartscufes metal or a precursor salt of the soluble metal nanoparticles in! water _f of urea, water, hexagonal BU of the particles and an acid, so to lower the pH of the reaction mixture,

b) stirring and heating the reaction mixture, so as to obtain the binding, on the BM particles, of the metal nanoparticles or nanoparticles containing the metallic element which make it possible, after treatment, to obtain the desired metal nanofillers, c) to wash the modified boron nitride particles thus formed.

One of the advantages of the process according to the invention is that it makes it possible to obtain a cotoreed range of BN without noticeable modifications of the chemical and physical properties of the BN of ase. This method also makes it possible to deposit metal nanoparticles (in colloidal form) previously formed in solution and having the desired characteristics (color, shape).

The process according to ^the invention makes it possible to present, in the majority of cases, 95% ± 5% of the starting nanoparticyles on the surface of the BN. Far Furthermore, this method allows to maintain high dispersion of nanoparticyles deposited on the surface of the particles _t BH as is especially illustrated by photographs NET examples of implementation of the invention by the detailed syiSe.

The present invention also relates to modified hexagonal BM particles that can be obtained by such a method. More precisely, particles of hexagonal boron nitride (h-MS) on which metal or metal oxide nanoparticles are bonded in stable bonds form other aspects of the invention. The bonds between the nanoparticles 0 of metal or metal oxide and BU particles are called stable, in particular because the heating for 2 months to 5D ^e C particles in water at a concentration of 2g / L leads to a loss of less mass of metal 0 or metal oxide nanoparticles Initially: present. The nanoparticles are strongly adsorbed on the surface of the BN particles, by electrostatic bonds. It appears that the interactions between the support and the nanoparticles are complex (Book: Preparation of solid catalysts, G. Ertl, H. nözler, X Ellkamp, VWey-VCH, 1999). What we can say is that there are nuoleatlon sites for your precursors nanopartlcules. During the progressive decomposition of urea, the gradual growth of nanoparticles from these sites of nuations can take place. The deposited nanoparticles are thus strongly adsorbed on the surface of the

In function, selected metal G or metal oxide nanoparticles, the modified BN particles obtained can be stained and have a color different from the usual BN color.

The following description provides a better understanding of the invention.

Initially, the particles of hexagonal BN before: modification may have an ovoid, stick shape or be essentially speicles. In the context of the invention, the size of a particle of hexagonal BN (which corresponds within the scope of the invention to its largest size) which may, in particular, be determined by transmission electron microscope or scanning, is for example, in the range of 10 nm to 300 μm, preferably in the range of 100 nm to 200 μm, the hexagonal boron nitride may be in hexagonal form or geographically or graphitically. In particular, the hexagonal BN will be in its graphitic form, the process according to the invention being perfectly adapted to this highly crystalline form.

The porosity of the BU may range from zero porosity to a mesoporosity. Mesoporous BN means a BN having, within its structure, pores with a mean diameter of between 2 and 50 m,

The surface area of the BN under linventlon may range from 1 m¾ to 1000 m ² / g, in particular 10 i m ^a / g. By specific surface is meant the specific surface determined by adsorption _Λ

Nitrogen in accordance with ASTH D 3683-78 established from the method BRUNAUER-EMMETT-TELLER (8. EX) described in Periodical The Journal of the American Chemical Society, 60.30 (1938) ", The The above characteristics concern both the BH used in step (a) and the method according to the invention, but also that finally obtained after fixing the metal nanoparticles.

The process according to ^the invention allows to fix on hexagonal BH particles of metal oxide nanoparticuies, metal nanoparticuies 0s, of a metal alloy nanoparticuies 0 / metal oxide or a mixture of such nanoparticuies "All these are nanoparticuies named in the context of the invention "metallic nanoparticles".

The metal or metal oxide nanoparticles which are fixed on the hexagonal 8N particles have a nanoscale size. Nanoscale means, in the context of the invention, that the largest size of nanoparticles is in the range from 0 nm to 1 micron, preferably in the range from 0.5 to 500 m, and preferably in the range of 1 to 200 nm. This case can, for example, be determined by transmission electron microscopy. These particles may be ovoid, stick-shaped or essentially spherical, so that their larger size corresponds to their diameter.

The size of the metal or metal oxide nanoparticles is much smaller than the size of the hexagonal B particles on which they will be fixed, for example 20 to 1000 times less.

It is possible to use nanoparticles of metal 0 or metal oxide already closed or to prepare them in situ, either before the placing in contact with the particles of hexagonal BU, or after. Thus, the process according to the invention provides for the preparation of a reaction mixture comprising, either directly the metal nanoparticles, or a precursor salt of water-soluble metal nanoparticles, mixed with urea and water. The term "precursor salts" means a salt which leads to the formation of metal nanoparticles which are formed in one or more stages, the case of metal nanoparticles 0, 11 is in particular possible to form intermediately nanoparticles of metal oxide and / or metal hydroxide of the corresponding mixture It is also possible for the reaction mixture to comprise a dispersing agent for nanoparticles, such as polyvinylpyrrolidone, cetyltrimethyltrimetribromide bromide, ethylene-demine tetracetic acid, or sodium citrate,

B hexagonal particles and an acid are also introduced into the reaction mixture in any order. For example, the hexagonal BU particles may be introduced before the acid. Most often, but are not mandatory fool acid and the particles B are introduced into a mixture containing water, the ^f urea and the metal nanoparticles or a precursor salt of the metal soluble in water nanepardcules . Examples of acids that may be used include acids such as nitric acid or acetic acid. The acid is. used to lower the pH of the reaction medium to an acidic pH, for example below 2. The amount of acid is determined according to the desired pH. The amount of edge, for its part, is, for example, in the range of 10 to 40 g / t, preferably in the range of 30 to 2.50 g / l, the relative amount of urea relative to The BN is, for example, in the range of from 0 to 5, preferably in the range of 0.5 to 3. Among other things, urea facilitates pH adjustment.

The amount of B introduced into the reaction mixture is, for example, in the range from 20 g / l to 200 g / l, preferably in the range of 30 g / l to 150 g / l,

Then the mixture reacts! is stirred and heated, for example at a temperature in the range of 40 to 20 ° C, preferably ranging from 80 to 16CPC, so as to fix, on the nanoparticles of O hexagonal, metal nanoparticles or nanoparticles containing metal element which allow to obtain after treatment the desired metal nanoparticles, in some cases where a precursor salt is used. The agitation can be carried out mechanically at a speed, for example between 50 and 1400 rpm! n <The heating had; for example, to be maintained for 1 to 15 hours,

The amount of nanoparticles or precursor metal salts is adapted to the amount of nanoparticles that are required to be fixed on BN nanoparticles. With the method according to the invention, the yield of metal nanoparticles deposited on the SN surface is high. The ratio of the amount (by mass) of metal particles present on the surface of the B i and the amount of metal particles introduced or defined by yield is defined as; prepared in the initial preparation. This yield is obtained from chemical analyzes (measurements made with Yn Spectrornetra of Emission Ορ Coupled with a Plasma Induetlf The ICP-OES of English "Inductrvely coupled plasma optfca emission spectroscopy").

After reaction, the particles obtained are washed with water so as to eliminate the salts and excess reagents used. It is then possible to keep the modified BN particles in solution or to recover them, for example, by an isltration operation, and to dry and grind them to obtain the desired granulometry. The examples carried out have shown that the particle size of the BM particles is not modified by the addition of metal nanoparticles. In fact, nanoparticles have been deposited on BN particles of different particle sizes. Laser granulometry can be used to measure the particle size before and after deposition of metallic nanoparticles and does not show significant variations,

Advantageously, the metal nanoparticles are metal or metal oxide parts, in particular making it possible to provide coloring to the modified boron nterure particles obtained. According to a first implementation variant, the metal nanoparticles are nanoparticles of metal O, for example chosen from nanoparticles of Ag, u, Pt, Pd, Ru, Rh or an alloy or a mixture of these metals. and are preferably gold nanoparticles. In the case of this first variant, the step a) may be to have a reaction mixture comprising a metal precursor salt nanoparticyies 0 soiuble in water, and in particular in the case of HAuC¾ nanoparticyies Au _f of urea, an acid, particles of hexagonal BN and water and a reduction step is then carried out after step a), so as to obtain metal nanoparticles which are in the form of metal nanoparticyies 0. The formation of Nanoparticles of oxide or metal hydroxide from a precursor salt and their reduction in metal nanoparticles 0 is carried out according to well known methods. In particular, one can refer to the book ffenoparticles from theory to application (edited by Gunter Schmid, Wiïey VCH, 2004). The reduction step could, for example, be carried out with a solution of hydride in a basic medium, for example a solution of aBH ₄ in sodium hydroxide.

In this case (named variant 1 gloss in example 1), the method according to the invention consists in the following steps:

a) having a reaction mixture comprising a precursor salt of the water-soluble metal nanoparticles, urea and water, hexagonal, and acidic particles, so as to lower the pH of the reaction mixture,

b) then stirring the reaction mixture so as to obtain the fixation of nanoparticles of hydroxide or metal oxide on the BN particles,

^* b) reducing nanoparticuies ^of hydroxide or metal oxide metal nanoparticuies 0,

c) washing the modified particles of boron nitride, thus formed,

In the case still of the first variant, step a) may always consist in having a reaction mixture comprising a precursor salt of metallic nanoparticles which is soluble in water, and in particular HAu (¾ in the case of nanoparticles of A, particles of BN , urea, acid, hexagonal BN particles and water, but the modified boron nitride particles obtained carrying nanoparticles of metal oxide or metal hydroxide can be recovered and dried and subjected to a reduction by heat treatment, for example under infrared, so as to obtain metal nanoparticles in the form of metal nanoparticles 0.

In this case (named variant 18), the method according to the invention consists in the following steps:

a) having a reaction mixture comprising a precursor salt of water-soluble metal nanoparticles, urea and water, exogenous BN particles, and an acid, so as to lower the pH of the reaction mixture,

b) stir, stir and heat the reaction mixture, so as to obtain the fixation of nanoparticles of metal hydroxide or metal oxide on the 8N particles,

c) washing the boron nitride particles carrying nanoparticles of the hydroxide or metal oxide, thus formed, recovering them and drying them,

d) reducing the nanoparticles of hydroxide or metal oxide to metal nanoparticles 0,

e) washing the modified particles of boron nitride, thus formed.

Still, in the case of the first variant, retyped a) may comprise providing a reaction mixture comprising metal stabilized nanopartlcules 0, the yrée, acid, BU hexagonal particles and e u _*

In this case (named variant iC the method according to the invention consists in the following steps;

a) having a reaction mixture comprising melamine nanoparticles, urea and water, hexagonal B particles, and an acid, so as to lower the pH of the reaction mixture,

b) then shaking and heating the reaction mixture, so as to obtain the fixation of metal nanoparticles δ on the BN particles,

c) washing the modified boron nitride particles thus formed.

According to a second implementation variant, the metal nanoparticles are metal oxide nanoparticles, for example chosen 4 among nanoparticles of zinc oxide, titanium, iron, rare earth, chromium, cobalt, nickel, aluminum, silicon or a mixed oxide of these metals or a mixture of oxides of these metals.

In the case of this second variant, rec (a) may consist in having a reaction mixture comprising urea, an acid, hexagonal BN particles, water and a precursor of the metal oxide narsoparticles. soluble in water, for example selected from chlorides such as Ζη <¾, CoCb, NiCfe, FeCfe and f¾C "In this case, the formation of the metal oxide nanoparticles is in sfcîors step b).

In this case (named variant 2A illustrated in example 3), the method according to .Invention consists in the following steps:

a) having a reaction mixture comprising a precursor salt of water-solubilized metal nanoparticles, urea and water, hexagonal SIM particles, and an acid, so as to lower the H of the reaction mixture.

b) then stir and heat the reaction mixture so as to obtain the binding of metal oxide nanoparticles to the particles of BM; c) washing the modified particles of boron nitride thus formed.

Still, in the case of the second variant, step a) may consist in having a reaction mixture comprising urea, water, an acid, hexagonal BN particles and metal oxide nanoparticles. .

In this case (named variant 2B% the method according to the invention consists in the following steps:

a) having a reaction mixture comprising nanoparticles of metal oxide, urea and water, hexagonal particles and an acid, so as to lower the pH of the reaction mixture,

b) then stir and heat the reaction mixture, so as to obtain the binding of the metal oxide nanoparticles on the particles of 8M _;

c) washing the modified particles of boron nitride, thus formed, Irrespective of the variant of the process used, it is possible to obtain hexagonal BN particles having a particularly stable metal (metal or metal oxide) ranoparticles, as defined above.

The invention also relates to particles of hexagonal BN on which are fixed, in stable bonds metal nanoparticutes, including nanoparticutes of metal 0 or metal oxide, and in particular hexagonal BM particles bearing metal ranoparticutes susceptible In particular, according to particular embodiments, such modified hexagonal particles are characterized by the following characteristics taken alone or in combination:

the modified h-BN particles are colored e! do not have the usual color of B. in particular, the fixed metal nanoparticles are metal oxide nanoparticles chosen from nanoparticles of zinc oxide, of titanium, of 1, of rare earth, of chromium, of cobalt, of nickel, of aluminum, or silicon or a mixed oxide of these metals: or a mixture of oxides of these metals; or nanoparticles of metal 0 selected from nanoparticles of Ag, Au, Pt _: Pd, Ru, f¾h or an alloy or a mixture of these metals and are preferably d nanr nanoparticles; or nanoparticles of a metal alloy 0 / metal oxide as previously mentioned or a mixture of such nanoparticles.

the h-BN is graphitic,

h-8 has a specific surface area of 1 to 10%; h-BN has a low porosity which can range from zero porosity to a mesoporosity,

the metallic nanoparticles are dispersed homogeneously on the particles of t-BIM

the deposited metal nanoparticles are of essentially spherical shape, the equivalent diameter of the surface of these nanoparticles is in the range of 0 nm to I micron, preferably in the range of 0.5 to 500 nm and préférentietement _f in the range of i to 200 nm; The measurement of the equivalent diameter of a nanoparticle is carried out by measuring the surface of each nanoparticle on a click by the electronic transmission electron microscope. Each nanoparticle is assimilated to a perfect sphere and the equivalent diameter is calculated from the observed analysis surface (S) (cross section) from the formula S-flR ² with R which corresponds to the radius of the perfect sphere. , and therefore of the iransverse section, to which is assimilated the nanoparticle,

the size of the particles present on the surface of the particles of B is homogeneous, so that at least 70%, preferably at least 75%, have an equivalent diameter which belongs to a gamma centered on a value x and which corresponds to at x ± 20% of x,

the density of metal nanoparticles fixed on the surface of the particles of BM is, on average, greater than 58 nanoparticles per ym of SN particles, preferably greater than 150 nanoparticles per μm ² of BN particles; the color of the modified BU obtained can be modulated according to the nature of the metal nanoparticles, the mass% of nanoparticles adsorbed and the size of these nanoparticles. Such a density makes it possible, in particular, to make the color given by these different choices appear clearly,

at least 80%, preferably 90%, of the nanoparticles bound to the particles of BM are in an individualized form, that is to say that they are not agglomerated with another (see several) nanoparticles.

the metal nanoparticles are adsorbed by electrostatic bonds at the surface of the h-BN particles. Such particles of ~ 8 modified because of their modular color, depending in particular on the concentration and the number of surface-immobilized metal nano articules, find many applications as coloring agent in particular

The examples which follow, with reference to the appended figures, illustrate the invention but are not limiting in nature.

FIG. 1 and FIG. 2 are respectively the DX and UV-visiBee curves of the modified B particles obtained in FIG. 3, show a NET photograph of the modified BN particles obtained in Example L

FIGS. 4 and 5 are respectively the UV-visible analysis curve and H-photograph of the modified BU particles obtained in Example 2,

FIG. 6 and FIG. 7 are respectively the curves by X-ray analysis and UV-visMe of the modified BN particles obtained in Example 3.

FIG. 8 and FIG. 9 are respectively the curves by XRD and UV-visible analysis of the modified particles obtained in Example 4.

Figure 10 and Figure 11 are TEM photographs of the modified BH particles obtained in Example L

FIG. 12 is a TEM photograph of the modified particles obtained in example 2,

Figures 13 to 18 are TEM photographs of the modified BN particles of Example 8 according to the invention, Comparative Examples 1 and 3, Example 10 e of Comparative Examples 5 and 7.

Figure 1 shows the distribution of the equivalent diameter of gold nanoparticles deposited on the BN obtained by implementing Comparative Example 3. _

18

Figure 2Q shows the equivalent diameter distribution of gold nanopartile deposited on B obtained by using Comparative Example 1.

FIGS. 21 and 22 show: the equivalent diameter distribution of the gold nanoparticles deposited on the 8N obtained by using Example 7,

FIG. 23 shows the curve by OV-vlsl analysis of the modified BH particles obtained in Example 8,

Figura 2 shows a modified 8N HEP photograph obtained in Example 8.

I lefteffel and met c € i cs quotes caracılations:

1- CPP-OiS (English "nductfv y coupled plasma opticai emission spectroscopy ^* )

Material:

ACTIVA brand Horiba 1Q IH WON

Attack on a beaker aqua regia + HF evaporatlon maxi then recovery H2SO Principle

The principle of the measurement is based on the neollsatlon then the ionization of the liquid sample in m. argon plasma (6000-8000 ° C), the atoms of the sample are excised at a higher energy level. The return to steady state is accompanied by the emission of a series of electromagnetic waves in the range of the visible spectrum / UV characteristic of each element. The different wavelengths are separated by a spectrometer. The intensity of the radiation is proportional to the concentration of the element

2- U¾8:

Material: MINOLTA CM 3610d SpectroColorometer with integumentary sphere.

- Illuminant D65

- Observer 10 * P inci e;

Any color is represented by 3 coordinates denoted L *> a *, b *.

L * = Q the color of the object is black

t * ~ 5u the color of the object is close to gray

L * ^~ IOU color of the object is white

A positive value of a * denotes a localized red color

A negative value of a * denotes a localized color to green

line positive value of b * denotes localized color to yellow

A negative value of b * denotes a localized color to blue

3- Measurements yV ~ ¥ isi e

atériel;

Perksn spectrometer - El mer model Lambda 35

MétiHKle:

Useful operating range; 190 - 1100 nm (52 0ΌΟ-9100 cm ^-1 )

Principle allows the determination of the sorne of a compound when subjected to a given wavelength in the ultraviolet and visible, 4- DRX; X-ray diffraction

Material; Philips Panarelytical, Bruker D50Ô5 powder diffractometer, Method

CuKa radiation (>, ~ L54û)

Operating temperature iO ° <28 <9Û ^c '

Principle s Allows the determination of the micro and polycrystalline mineral phases of materials.

A monoframe and parallel X-ray beam striking a crystal is diffracted in a given direction by each of the families of the retypyflex planes each time the Bragg condition or law is realized: 5 - 1 * 1 AND (Microsomepie E! Ee toiri spe in Transnfiissl H

Hardware JEOL 1200EX

I ltliïHt

- Resolution: 0.40 nm in bit mode and 0.2 nm in line mode - Grid range from 50 to 50Ω in transmission electron microscope (H ET)

- Possible acceleration tensions from 40 to 1200 ¥

Principle; it is a technique of ml rosoople where m electron beam is transmitted through a very thin sample. The effects of interaction between the electrons and ed anbllon give birth to an Image,

6 - Study of size distritHittan

The equivalent diameter of the particles was measured using a software program called ImageJ Q-3ava). This is the software of treatment and analysis diages written by the National Institute of Health (NIH). The latter makes it possible, among other things, to count particles, to measure surfaces and distances.

This software was used to determine the equivalent diameter of the nanoparticles at the surface of the BN $ ₍ from electron microscopy to transmission (TEM) micrographs. Measurements were made by measuring the area of each nanoparticle on Then, each nanoparticle has been assimilated to a perfect sphere and the equivalent diameter has been calculated from the surface (S) of the transverse section, from the formula S = 1 ^{2 2} with which corresponds to the radius of the Nanopariicyle is a perfect sphere with a similar distribution of diameters obtained by counting the number of nanoparticles associated with a given diameter range.The number of nanoparticles present on the surface of the BU has been determined manually by counting on nanoparticles. MET. snapshots,

In the examples below the following products were used:

HAuCk.4H ₂ 0 :: marketed by the company ST EM CHEMICALS, 2

EH UHP I1.0 C: boron nitride having a specific surface area of 3 m ² / g and a particle size of 12. mierons, marketed by SAINT GOBAI.

Urea: ACS reagent §9-100.5% marketed by the company ALDRICH.

Distilled water by a Hllpore mitiRi ater apparatus with a resistance> 18 HCh: 68% marketed by the company PROLBQ. i ^sr ml ml of synhesis: Â / BH

Step i Deposition of Itsdroxide gold on the surface of the 8N from a gold salt

Order of introduction of the reagents;

1} Addition ¾G + HAuCi4.4H _Σ C

2} Urea addition

3) HNO3 Addition

4) BN Addition (Grylllometer D50 "4-7 Prn Starck LubHf rrn BN 10

lot number 95294)

Heating at 120 ° C for 7 hours

At the end of heating, the solution is cooled to room temperature.

Step 2: Reduction of metal gold hydroxide

Irv-situ reduction at room temperature

mMaBH4 ^~ 3Q0mg

VNaOH (i) = 20mL We dissolved aBrt? in NaOH, then the solution obtained is injected into the réadtonnel mixture.

Step 3 i Washing

The solution is washed with water and filtered to remove chlorides and unreacted products.

Drying at 120 ° C (it would also be possible to

Characteristics i prodly it ¾¾er¾y

a) Me Ι Ρ ϋ ϋ ΐ

% Au = 920 ppm

The particle deposition efficiency is 92%

II) naifses D U

In Figure I are reported the D X analysis results of the sample. The crystalline properties of the BN are not modified by addition of gold nanoparticles. The deposited gold particles are in a cubic phase,

(c) AB measures for speciocoradioreiratry

Table 1 below shows the LAB measurements of the BN before (referenced BNO) and after deposition of nanopartlcyles d¾r. These measurements show a notable difference between the 2 BN, the color of the BM with 0.1% of gold is: vioiet clear,

In Figure 2 are reported measures your UV ^"Visib! E made on the BU before (8N0) and after depositing gold nanoparticles, the BN§ has two peaks of Sorpt a & m 210 and 264 GTR in the field ultraviolet Following the deposition of nanoparticles d¾r, the peaks at 210 and 264 nm are still present and a broad peak at 560 nrn apparat. The latter corresponds to a visible absorption and reflects a visible coloration of the BH after deposition: nanoparticles.

Figure 3 is a photomapping of HH particles obtained, the photo shows that the ranoparticates are well dispersed and have a spherical shape. This spherical form is made when

colloid preparation. sow

0mg reagents

Urea 6S

H ₂ 0 55mL

H ⁽ ¾ti, 36%) 5mL

Sodium citrate 211 m

i ¹ %) PVP ~ polyvinylpyrrolidone 0.4ml of a gold colloid and deposit of gold nanopatters on the surface of the BM

1) Addition H ₂ 0 + HÂuC¾, 4r½0

2} Heating until ebuition

3} Sodium citrate is dissolved in SmL H ₂ 0 and added to the previous mixture The mixture changes color and changes from yellow to red in 15 seconds

4) We go to room temperature 24

5) Addition of 0.4ml of PVP, PVP is used to stabilize the nanoparticles of gold by avoiding their agglomeration when they are in solution in the water

8) Addition of HN0 ₃

7) Urea addition

8) Addition EH (granulometry 4-7pm BU tubriform Bi IO batch number 95294)

Heating at 120 ° C for 5 hours

Step 2: Washing

The solution is washed with water and filtered to remove chlorides and unreacted products,

Step 3: Drying at 120 ° C. (It would also be possible to dissolve)

Eta e 4; Grinding.

C ercacta hori c y y red ities y y

a) Hesure ICP-OES:

% Au - 0.87%

The yield of particles deposited is 87%.

(b) by the distance of the spacecraft

In Table 2 below are reported LAB measurements of the front BU (referenced BNO) and after deposition of gold nanoparticles. These measurements show a notable difference between the 2 BNs. The color of the S 1% of ^gold is purple

c) Nesures UW ~ WisIr the

In the figure are reported the UV-visibie measurements made on the BN before (S O) and after deposit of gold nartoparticyles. L B O has two absorption peaks at 210 and 264 nm in the ultraviolet range. Following the deposition of the gold nanoparticles, the peaks at 210 and 264 nm are still present and a broad peak at 532 nm appears. This corresponds to an absorption in visible Se and reflects a visible color of the BM after deposition of the nanoparticles, d) Pt otef raplie 1EI

The Fiftire S is a MET photograph of BM particles on which 0.87% gold is deposited. The paper shows that nanoparticles are well dispersed and have a special shape. This special form is: carried out during the preparation phase of the colloid,

3 ^sme "errtpl® of §f ntf esis: 5.36% Fe / SN

Order of Introduction of Reagents:

1} Addition H ₂ 0 + Fet¾

2) Addition HN0 ₃

3) Urea addition

4) Addition BN (granulometry) 4-7pm BN read SN1Q batch number

95294)

Heating at 120 ° C for 8hQ0 Eta e 2 Ï Washing

The solution is washed with water and filtered to remove chlorides and products which have not reacted.

Step 3; Drying at 120 ° C (it would also be possible to dissolve)

Step 4; Grinding,

Carae erisat oi û prscitiifc oiitenu Ξ

®) M & a s ICP-ÛES

% Fe - 540%

The yield of particles deposited is 954%

Sm the ¾yre 6 are reported the DR analysis results of the BN after deposition of iron nanoparticles,

They show that the crystalline form (highly crystalline h-8N) of BN is not impaired by the deposition of iron nanoparticles and that the iron is in the crystalline form of Fe.

(c) Measures for the period under review

In Table 3, below, the LAB measurements are shown before

(BN4) and after deposition of iron nanoparticles, These measurements show a noticeable difference between 2BNs. The BN after filing nanopartlcuies

Iron has a dark orange color »

Figura 7 shows the measurements U ¥ ~ v1sib! E of BK a ¥ ant (BO) and after deposition of the iron nanoparticles. A broad absorption peak which ELEND ^f s of 200 and 600 rtm appears and obscures the absorption pcs 8¾ when Iron nartoparticules are deposited on the surface of the BN. The BU thus obtained absorbs in your areas of communication and isible. SSMS

Step I; Preparation of a soil for fuffects

Mixture of 226 mg of NaBH * with 20 ml of an aqueous solution of NaOH Step 2: Preparation cTtin® aqueous solution KAuCi *

Dissolution of 1.23 g of Hau {¾ »4H ₂ 0 in 500 ml H ₂ 0. Then addition of 10 ml of PVP solution. It is e 3 _*

Addition of 15 μl of the NaBH 3 solution (prepared in step i) into the solution; water from HÀuCk

1} H C¾

Heating and agitation during 8rt00 to 12Q ° C Step S: Wash

The solution was washed with water and filtered to remove chlorides and products ^which do not react

Step - drying at 120 ° C (it would also be possible to dissolve)

For example, it was calculated at a rate of 0.87%.

The yield of nanoparticles deposited is about 89%.

b) My res D K

In Figure S are reported the results of DRX analysis of BN after deposition of gold nanoparticles.

They show that the crystalline form of 8 is not affected by the deposition of gold nanoparticles. The gold particles are in cubic crystalline form,

(c) Measurements by specimen

On the Tatsieats 4, below, are reported the LAB measurements of the BM before (BNG) and after deposit of the nanoparticyles d¾r. The results show a notable difference between the two BMs. The color of 8N tends to purple

Mesums i ¥ ~ ¥ i $ iMe

FIG. 4 shows the UV-vfsibfe analyzes of the B front (BNO) and after the deposition of the nanoparticles of gold. After the deposition of the gold nanoparticles, the absorption spectrum of the BM has a broad absorption band between " _N

350 and 650 nm with a peak centered on 538 rm. This absorption spectrum is different from that of Example l _f œ which results in a different coloring Riu 8 of Example 1,

S ⁶⁸ * example of synthesis: 2% Au / BN oti enu by chayffega lit

Step 1 ; Deposition of the gold hydroxide on the surface of the BM from a salt d¾r

Introduction of reagents ::

1} Addition H ₂ 0 + HauC W

2} Urea addition

3) HNC¾ Addition

4) Addition BN

Heating at 120 ° C for 6-hours

At the end of heating the solution is cooled to room temperature *

Step 2s wash

Step 3 t Drying at 120 ° C (it would also be possible to dissolve)

Step 4 Ï Heating under IR radiation

Voltage - 8 V is T ~ 600 ° C Duration i min

Step ί Preparation of HaBtt *

Dissolution of MaBf¾ in a solution of 5 ml H ₂ O (1M NaOH)

Order of translational reagents:

1) Addition H ₂ 0 (50mL) + HAuCk

2} PV addition

3) Addition of the NaBH * solution prepared during Step 1 Eti

The following reagents are added to the solution prepared in step 2

1} Addition Fe € ¾

2) Urea addition

3) Hfs Addition

m B!

Heating at 120 ° C for 6 hours

Etapa 4 * Wash

Step S 5 Drying at 120 ° C. (it would also be possible to dissolve)

Step 6: Grinding

No characterization for this sample

Flute HET f Micro Transmission to Transmission It¾ € ¾rei¾i * p¾)

Figures 10 and: There are photographs by NET for different magnification of BM particles on which are deposited 2% gold according to the procedure of Example 1, the photos show there is good dispersion of the fianoparticles on the surface of the BN. Nanoparticles have no particular shape.

Figure 12 is a TEM photograph of particles of B on which gold is deposited according to the procedure of Example 2. The photo shows that the nanoparticles are well dispersed and have a spherical shape. This spherical shape is achieved during the colloid preparation phase.

Several samples at 8 with a deposition Ð¾ nanoparticles> r 1 and 5% by mass were prepared, on the one hand with the method according llnvention, in accordance with Example l _f and secondly according to the prior art method described in the article Journal of Catalysis 210, 39-45 (2010). In this article, the product after deposition of salt is either reduced or calcined, both methods have been implemented.

Two types of BM have been selected for the deposit A BN of the supplier St Gobain with a specific surface of 1.89 m ² / § and a SN of the supplier Starck with a specific surface of 9.84 m¾.

The nomenclature of the prepared links, as well as their units, are reported in Table S below. TABLE S Mature of B Au deposited Method utfeée

theoretical (in%

mass)

Reduction under ¾ at 300 ° C

Example ST GOBAIS 1% Journal of Celsius 210.39- Comparative 3 45

Cateinatfon under O _; at 30CPC

Example STARCK 1% Journal of cataiys 210,39- om ra f 4 45

Cakànafe under O to 30SPC

Example ST GQSAÏI 5% turn of stsi sis 21039- com aratif S 45

Reductton under ¾ to 3G ^Q ° C

Exempt STARCK 5%: Journal of cataiysis 21039- com aratif 6 45

Reduction under ¾ to 3CHPC

Exempt ST GOBAI 5% Jourrai of carias 210,39- comparative? 4S

_: Cairfnaite under C½ at 300 ° C

Exempt STARCK s% Journal of cataiysis 2ÏG.39- com aratif S 45

CatelnaitoR under ^¾ ¾ at 30Q ° €

E em le? ST.AK.CK: 1% Process of the invention

Free 8 ST Q38AIN ï% Pmnpïfe ^"of fevention

Example 9 STARCK 5% Process of iovenSon xem SI GOBAI M 5% Process of the invention

The dosage of for was performed after an attack of the modified particles obtained in a beaker in water with fluorochloric acid, then sulfuric acid * The ICP-OES analyzes are presented in TaWeay 6 below. .

Tabiea 6

measures analysis HERE ⁵ Diaque made to sample. The results are presented in Tafeteata 7 and S below. Taipei 7 ι 1% Au / E¾

The chemical analyzes clearly show that the yield of gold deposited is higher than that of the process according to the invention is implemented with which it is possible to obtain up to 99% of deposit.

The LAS analyzes for each of the samples are presented in the table below.

TAB & U §

EchintHlon 1 L | A E 1

! Ex. Com arât !? 74, 58; 1.86 1.3? i

Ex, Comparative 2! 73.72 1 1.45 -0.92 I

1 Ex, compared ^" 3: 79 67 3.45 2.80 i

EXAMPLE 4 i 7, 39 I 2, δϊ -0 6 I

i Ex. com ara if 5 1 73,41 s 3 ^

Comparative example i 74.76 1 3.56 1.48

Ex, comparison 7 76.49

Ex, ratify S 1 77 _; 75 4 _f 17 1 us

|; Ex,? of the invention 1 72,74 1 2,03 j -5,01

Ex, 8 of! LrweitSon β¾32

... 1

These results, as well as the simple observation of the samples, show a very distinct color difference between the samples prepared according to the process of the invention and this x prepared according to the prior art process and this whatever the percentage of gold deposited,

Transmission electron microscopy (TEM) photographs of Example 8 according to the invention, Comparative Examples 1 and 3, Example 10 and Comparative Examples 5 and 7 are respectively shown in Figures 13 to 18.

show several notable differences between

- The nanopartlcuîes obtained by the process of ^the invention are smaller and uniform and this irrespective of the percentage of gold deposited. The gold particles prepared by the other method aggregate: and lead to the formation of large parts, regardless of the percentage of gold deposited. This aggregation shows poor stability of ^gold nanoparticles on the surface of the BN.

The dispersion of the nanoparticles on the surface of the BN is better with the process of the invention and this regardless of the percentage of gold deposited. In the case of the other process, some BN particles do not contain gold nanoparticles.

The shape of the nanoparticles obtained according to the process of the invention is more homogeneous. We observe different geometrical shapes with the other process: triangle, rhombus, stick

The size distribution of the gold nanoparticles deposited on the BU particles was also studied. FIG. 19 shows the distribution of the equivalent diameter of the gold nanoparticles deposited on the BM obtained by the implementation of the comparative example. 3. FIG. 20 shows the distribution of the equivalent diameter of the OT nanoparticles deposited on the BN obtained by implementing Comparative Example L

Figures 2 and 22 show the distribution of the equivalent diameter of gold nanoparticles deposited on the BN obtained by implementation of Example 7.

Table I below gives the number of gold nanoparticles deposited per square micrometer of

It thus appears that the products prepared according to the prior art have a size distribution of the gold nanoparticles on the surface of the UB urimodate (Figures 19 and 20) .In the case of products calcined under air, the nanoparticles d¾r have an equivalent diameter. between 70 and 470 nm (Figtire 19), those which have been reduced under r½ have yn equivalent diameter between 130 and 410 nm: (Figure 20), the number of gold nanoparticules deposited according to the prior art can range from 0 to 0.6 nanoparticles / pm ^a of BN.

In the case of the products prepared according to the invention, the size distribution of the nanoparticles is unimodal, as can be seen in FIGS. 21 and 22 in the case of Example 7.

In Figure 21 is shown the distribution of gold nanoparticles on the surface of 8N. On this graph, a point represents a nanoparticle. On the abscissa, the equivalent diameter of the nanoparticles in nanometer. This shaping of the results clearly shows that the majority of the nsnoparticles have an equivalent diameter of between 10 and 15 nrn.

Based on the results of Figure 21, Ftgyre 22 was performed as a histogram distribution of the equivalent diameter of the nanoparticles. In this case, it is observed that 77% of the nanoparticuies have an equivalent diameter of between 10 and 15 nm.

The number of nanoparticles deposited on the S according to the invention can range from 195 to 267 rare particles / μm ² of BN,

^; th e synthesis: 0.0059% Au / B¾

Step i: Deposition of the gold hydroxide on the surface of the BN from a gold salt

Order of Introduction of Reagents:

5) Addition H ₂ 0 - HA CI ₄ -4H ₂ 0

5} Urea addition

7) HN Addltion <¾

8) BN Assay (particle size Ο50 ^™ 4 ~ 7μΓ? Ι Starck Lubnform BN 10 lot number 95294)

Heating at 10o C for ^S 2hQÔ

At the end of heating the solution is cooled to room temperature,

Step 2: Reduction of the metal gold hydroxide

Irv-stu reduction at room temperature m aBH ₄ = 102mg

VNaOH {1} = 100ml

NaBB * is dissolved in sOH, and the solution obtained is injected into the nef reaction mixture.

Step 3; LAVAG

Step 4: Drying at 10 ° C (it would also be possible to proceed to dissolve it)

Itape 5: Grinding.

% Au = 59 ppm

The yield of particles deposited is 99.9% (n). LAB nesures per specfemolorimetrle

On the Taisles below are reported your measurements BN of the BN before (referenced BNO) and after deposit of nanopartlc gold. These measurements show a notable difference between the 2 8M. The color of the BN with 0.0059% gold is orange-pink.

e) Measures y ¥ - ı

FIG. 23 shows the UV-visible measurements taken on the B: before (BNO) and after deposition of the nanoparticles d¾r. The 8NO has two absorption peaks at 210 and 264 nm in the ultraviolet range. nanoparticles of gold _f the peaks at 210 and 264 nm are The latter corresponds to an absorption in the visible and reflects a visible coloration of the BU after deposition of the nanoparticuies, f) Pli tograplie MET

FIG. 24 is a photoprotection of BN particles with 0.0059% gold deposited therein. The photo shows that the nanoparticles are well dispersed and have a spherical shape. This spherical shape is achieved during the preparation phase of the coiloide

Claims

1 - Process for the preparation of modified hexagonal boron nitride particles on which are fixed in stable bonds, metal nanoparticles comprising the following steps:

a) having a reaction mixture comprising, either directly the metal nanoparticles, or a precursor salt of the water-soluble metal nanoparticles, urea and water, particles of hexagonal BM and an acid; in order to lower the pH of the reaction mixture

b) then shake and heat the reaction mixture, so as to obtain the fixing, on the particles of 8N, nanoparticles metal or nanoparticutes containing the metal element that allow to obtain after treatment the desired metal nanoparticyles, c) wash the modified particles of boron nitride, thus closed,

2 - Process according to claim I characterized in that the modified boron nitride particles are recovered, dried and crushed in order to obtain the desired particle size,

3 ^" Process according to claim 1 or 2 characterized in that in step a), the pH of the reaction mixture obtained is acidic.

4 - Process according to one of claims 1 to 3 characterized in that step b) heating is carried out at a temperature in the range of 40 to 200 preferably from 80 to i60 ° C

5 - Process according to one of the preceding claims characterized in that the metal nanoparticyles are: o nanoparticuies 0 metal or metal oxide, allowing dontammer to provide a color to the modified boron nitride particles obtained.

6 - Method scion to one of Claims i to 5, characterized in that metal ies nanoparticyles are metal ranopartlcules O selected from Ag nanoparticyles, Au, Pt _f Pd, Ru, Rh or an alloy or a " mixtures of these metals and are preferably gold nanoparticles.

7 - Process according to claim 6 characterized in that step a) consists in having a mixture réactlonnel comprising a precursor salt solopar metal fuels in water, and in particular HAuC¾ in the case of Au nanoparticles, urea, an acid, hexagonal KM particles and water and in that a reduction step is carried out after step a), so as to obtain metallopene

In the form of metal nanoparticles 0,

S - Process according to claim 7, characterized in that the reduction step is carried out with a solution of ydride in a basic medium, for example a solution of Ma8H ₄ in sodium hydroxide.

S - Process according to claim 6 characterized in this step a) consists in having a reaction mixture comprising a precursor salt nanopartic soloble metal in water, and in particular HUCUC in the case of Au nanoparticles _; urea, acid, hexagonal BN particles and water and that the modified boron nitride particles obtained carrying nanoparticles of metal oxide and metal hydroxide are recovered and dried and subjected to a reduction by heat treatment, for example under infrared, so as to obtain metal nanoparticles in the form of nanopellyl metal Ô.

10 - Process according to claim 6 characterized in that step a) 0 is to have a reaction mixture! comprising 0 metal-stabilized nanoparticles, urea, an acid, hexagonal SIM particles and: water,

11 - Method according to one of claims 1 to 5 characterized in that the metal nanopartlcyles are nanoparticuies of metal oxide 5 selected from nanopartlcyles of zinc oxide, tiane, iron, rare earth, chromium, cobalt, nickel, aluminum, or silicon or a mixed oxide of these metals or a mixture of oxides of these metals,

12 ~ Process selo claim 11 characterized in that step a) consists of having a reaction mixture! comprising urea, from 0 water, an acid, MS hexagonal particles and a precursor salt of the metal nanopartlcyles soiuble in water, for example selected from cfitofiires such as ZnCl, CoC½ N1G _¾ FeCfe and Fe €> 13 - Process according to claim 1i characterized in that step a) consists in having a mixture réacQonnei comprising urea, one acid, hexagonal BU particles, water and metal oxide nanoparticles .

14 ^»method selo warp of the preceding claims characterized in that the relative amount of urea relative to B is in the range from 0.1 to S, preferably in the range from 0.5 to 3

15 - Method according to one of the preceding claims characterized in that the acid used in step a) is nitric acid or acetic acid,

16 - Particles of hexagonal boron nitride (h-BN) on which are fixed, according to stable bonds of metal nanopartlcyles, and in particular nanopartlcyles metal 0 or metal oxide.

17 ~ particles of h-BN according to claim 16 may be obtained according to the method according to one of claims i to 15,

iS - Particles of h-8M according to claim 16 or 17 characterized in that the heating for 2 months at 5 ° C of the particles in water at a concentration of 2g L results in a loss of less than 0.1% by weight metal nanopartlcyles 0 or ^metal oxide originally present, U - particles of h-BN according to one of claims 16-18 characterized in ue the h-BN particles are colored and do not exhibit the usual color of the BN.

28 - particles of b ~ BH according to one of claims 16 to l9 characterized in that the h-BN is tur ostratkpe, mesographitic or graphitic,

21 - Particles of h-BN according to one of claims 16 to 20 characterized in that the h-BN has "n specific surface d 1 to 10 m ² / g.

22 - Particles of h-BN according to one of claims 16 to 21 characterized in that the h-BN has a low porosity which can range from zero porosity to a mesoporost. 23 - Particles of hB according to one of claims 16 to 22 characterized m œ that the metal nanopartlcyles are dispersed homogeneously on the particles of h ~ BM

2 - particles of h ~ BH according to one of claims 16 to 23 S characterized in that the deposited metal nanopartlcyles are substantially spherical shape,

Particles of h-BN according to one of Claims 16 to 24, characterized in that the equivalent diameter of the nanoparticles present at the surface is in the range from 0.1 nm to 1 micron, preferably in the range from 0.5 to 500 nm ,. and preferably in the range of from 1 to 200 m.

26 - particles of h-BN according to one of claims 16 to 25 characterized in that the size of the nanoparticles present on the surface of the particles of h-8N is homogeneous, so that at least 70%, preferably at least 75% of the surface-fixed nanoparticles of the h-BN particles have an equivalent diameter which belongs to a range centered on a value x and which corresponds to x ± 20% of this value x.

21 ~ Particles h ~ BN according to one of claims 16 to 26 characterized in that the density of metal nanoparticles attached to the surface of BN particles is, on average, greater than SO nanoparticles per pro ² particles of BN, Preferably, greater than 150 nanoparticles per ² μm BN particles.

28. Particles of h-BN according to one of Claims 16 to 27, in which at least 80%, preferably 90%, of the nanoparticles bound to the BN particles are in an individualized form, that is to say that they are not agglomerated with another (or more) nanoparticle,

29- Particles of h-BN according to one of claims 16 to 28 characterized in that the metal nanoparticles are adsorbed by electrostatic bonds at the surface of the BN particles.