FR3004441A1 - PREPARATION OF HOLLOW NANO- OR MICROPARTICLES - Google Patents

Abstract

The invention relates to a process for the preparation of hollow nanoparticles or microparticles using the treatment of inorganic nanoparticles or nanoparticles by means of at least one sulfur compound, to the exclusion of compounds comprising at least one sulphoxide group and from minus an oxygen accepting compound. The nano- or micro-hollow parts according to the invention can be used in the field of tribology as a lubricant, an anti-wear material or as a shock-absorbing material.

Description

PREPARATION OF HOLLOW NANO- OR MICROPARTICLES The invention relates to a process for the preparation of hollow nanoparticles or microparticles using the treatment of inorganic nanoparticles or nanoparticles by means of at least one sulfur compound, to the exclusion of compounds comprising at least one sulfur compound. a sulfoxide group and at least one oxygen acceptor compound. The hollow nanoparticles or nanoparticles according to the invention can be used in the field of tribology as a lubricant, an anti-wear material or as a shock-absorbing material. The lubrication of mechanical parts, in particular engine parts, makes it possible to reduce energy losses due to friction movements and also to increase the service life of these mechanical parts. Lubricating oils currently used include lubricating additives that are environmentally toxic and that, once filled, are in the form of difficult-to-dispose waste. Recently, an alternative to the use of these additives in lubricating oils has been found. It uses the use of nanoparticles or microparticles whose anti-wear and anti-friction properties are improved with respect to the properties of the present lubricating additives and which, moreover, withstand extreme pressures. These nanoparticles or microparticles also called inorganic fullerenes (IF) or fullerenes-like are hollow, that is to say that the cavity forming the heart is a closed and empty space. Their structure comes from the superposition or entanglement of solid layers generally consisting of transition metal sulfides such as molybdenum sulphide (MoS2). Processes for the preparation of hollow nanoparticles are known, in particular physical methods of preparation, for example discharge by means of an electric arc.

There are also known chemical methods of preparation, for example by MOCVD (metalorganic chemical vapor deposition) also called EPVOM (vapor phase epitaxy in organometallic). WO 2006/106517 discloses a process for the preparation of fullerenic nanoparticles of transition metals and chalcogens, especially nanoparticles of MoS2. This method involves the vapor phase interaction of compounds comprising a transition metal and chalcogen vapor.

These methods known in the state of the art are complex to implement both on an experimental scale and on an industrial scale, expensive, highly energy-consuming and inefficient in terms of production efficiency. Therefore, the use of such nanoparticles in the field of lubrication is limited because of the various problems associated with the implementation of known methods of the state of the art. A method is also known (Afanasiev et al., Top Catal., 2012, 55, 940-949) for obtaining hollow nanoparticles or microparticles coated with layers composed solely of transition metal nitride, especially nanoparticles consisting of layers of MoN2. This preparation process involves the treatment of inorganic nano- or microparticles by means of carbon tetrachloride and ammonia in a gaseous form. These hollow nano- or microparticles are only used as catalysts. Tribological assays were performed on nanoparticles of inorganic fullerenes (IFs) of MoS2 formula (Lahouij et al., Wear, 2012, 296, 558-567). An experiment for calculating the coefficient of friction was performed for inorganic fullerene particles having perfectly layered MoS2 layers in concentric layers and for inorganic fullerene particles having entangled MoS2 layers. The results obtained show that whatever the structure of inorganic fullerene nanoparticles of formula MoS2, the addition of 1% by weight of these nanoparticles in a synthetic polyalphaolefin oil (PAO6) significantly reduces the coefficient of friction with respect to coefficient of pure PAO6 oil. Indeed, the average value of the coefficient of friction obtained is 0.18 for pure PAO6 oil, unlike the coefficients of friction which are 0.4 and 0.3 respectively for these nanoparticles having superposed layers and layers entangled in PAO6 oil. There is therefore an important need for a process for preparing nano- or microparticles of transition metal sulphide which makes it possible to provide solutions to all or part of the problems of the methods of the state of the art. In particular, there is an important need for a preparation process which implements the processing of nano- or microparticles of transition metals in large quantities in devices that are not very complex, thus making it possible to reduce the installation costs of the devices, a reduction in energy consumption but also production in high quantities.

The invention provides solutions to all or part of the problems of the processes of the state of the art, in particular a process for the preparation of nanoparticles or microparticles. The invention provides a process for preparing hollow nanoparticles or microparticles of a compound of formula MS2. The hollow nano- or microparticles according to the invention make it possible to improve the exfoliation into regular and parallel lamellae, MS2 layers. The hollow nanoparticles or nanoparticles according to the invention thus make it possible to reduce mechanical friction and to improve over time the lubrication effect and the anti-wear effect. The hollow nanoparticles or microparticles according to the invention are also stable over time. The invention provides a process for the preparation of hollow nanoparticles or microparticles of a compound of formula (I): MS2 (I) wherein M represents a transition metal comprising: - the preparation of nanoparticles or microparticles of at least a compound of formula (II): AxByMzOt (II) in which: A and B, different, represent an alkali metal, an alkaline earth metal, an aluminum atom, a nickel atom, a zinc atom or a cobalt atom; M represents a transition metal or a lean metal; o x represents 1, 2, 3, 4 or 5; o is 0, 1, 2, 3, 4 or 5; z is 1, 2, 3 or 4; o is 3, 4, 5, 6, 7, 8, 9 or 10; o x + y + z is less than or equal to t; treating the nanoparticles or microparticles of the compound of formula (II) by means of: at least one sulfur compound, excluding compounds comprising at least one sulphoxide group, and at least one acceptor compound of oxygen chosen from carbon oxides and halogenated compounds comprising at least one chlorine atom or one bromine atom; the elimination of the salt of formula (III): formed AxRi, (III) or the elimination of the mixture of salts of formulas (III) and (IV) formed: AxRi, ByR, (III) (IV) in which: R is independently a chlorine atom, a bromine atom or a carbonate group; o x represents 1, 2, 3, 4 or 5; o is 1, 2, 3, 4 or 5; where u represents 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10; where v is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

The process according to the invention is carried out for the preparation of hollow nano- or microparticles of formula (I) in which M represents a transition metal or a lean metal. Preferably, the transition metal M is chosen from molybdenum, tungsten, tantalum, titanium, or niobium, more preferably from molybdenum or tungsten. Also preferably, the poor metal M is selected from aluminum, gallium, indium, tin, thallium, lead, antimony, bismuth, more preferably tin. The hollow nanoparticles or microparticles of compound of formula (I) obtained according to the method of the invention comprise at least one layer MS2. Preferably, the hollow nanoparticles or microparticles of compound of formula (I) comprise a number of layers MS2 ranging from 2 to 500, more preferably from 5 to 300. The layers MS2 of the hollow nano- or microparticles according to the invention are superimposed on each other or entangled in each other. Preferably, the layers MS2 are superimposed continuously. Also preferably, the MS2 layers are intermittently entangled. The hollow nano- or microparticles obtained according to the process of the invention advantageously have a homogeneous size and are weakly agglomerated.

The homogeneous size and low agglomeration of nano- or microparticles can be measured by microscopy or dynamic light scattering. The hollow nanoparticles or microparticles of compound of formula (I) obtained according to the process of the invention can be obtained in many forms, in particular fullerenes-like, hollow ovaloid, closed tubular forms or in the form of hollow crystals or crystals. hollow needles. Advantageously, the nano- or microparticles of compound of formula (II) are nano- or microparticles of compound of formula AxByM, Ot in which A and B, different, represent a lithium atom, a sodium atom, an atom potassium, magnesium, calcium, strontium, barium, cobalt, nickel, zinc, or aluminum. Advantageously, the nano-or microparticles of compound of formula (II) are nano- or microparticles of compound of formula AxByMzOt in which M represents a transition metal of group 4, 5, 6 or 7 or a poor metal of the group 14. Particularly advantageously, the nano-or microparticles of compound of formula (II) are nano- or microparticles of compound of formula AxByMzOt in which M represents a titanium atom, a tantalum atom, a nobium atom, a a chromium atom, a molybdenum atom, a tin atom, a tungsten atom, a zirconium atom or a rhenium atom, and more particularly a molybdenum atom or a tungsten atom. Also advantageously, the nanoparticles or microparticles of compound of formula (II) are nano- or microparticles of a compound chosen from Li2MoO4, BaMoO4, SrMoO4, CaMoO4, BaWO4, SrWO4, CaWO4, BaTaO3, SrTaO3, LiNbO3, LiTaO3, NaTaO3. , KTaO3, BaTa2O6, SrTa2O6, Li2Ta2O6, Na2Ta2O6, Na2NiMoO4, NaAl (MoO4) 2, K2Ta2O6, Li2SnO3, K4SnO4, CaSnO3 or BaSnO3. Particularly advantageously, the nano- or microparticles of compound of formula (II) are nano- or microparticles of a compound selected from Li2MoO4, BaMoO4, SrMoO4, CaMoO4, BaWO4, SrWO4 or CaWO4. The nanoparticles or microparticles of compound of formula (II) have a size ranging from 10 nm to 1000 nm, preferably ranging from 10 nm to 600 nm and more preferably ranging from 20 nm to 100 nm.

Preferably, the nano- or microparticles of compound of formula (II) comprise A and M in an A / M molar ratio ranging from 0.1 to 10, or comprise A, B and M in a molar ratio (A + B). ) / M ranging from 0.1 to 10. Particularly preferably, the nano- or microparticles of compound of formula (II) comprise A and M in an A / M molar ratio ranging from 0.2 to 4 or A, B and M in a molar ratio (A + B) / M ranging from 0.2 to 4. The process according to the invention advantageously makes it possible to be able to control the size of the nano- or microparticles of compound of formula (II) by means of the control the molar ratio A / M or the molar ratio (A + B) / M. Control of the size of the nano- or microparticles of compound of formula (II) then makes it possible to control the size of the nanoparticles hollow nanoparticles of formula (I).

Preferably, the preparation of the nano- or microparticles of compound of formula (II) comprises: the preparation in at least one solvent of a solution comprising at least one transition metal salt or a poor metal salt M and at least one salt of compound of formula A or a mixture of at least one salt of compound of formula A and at least one salt of compound of formula B; o separating the nano- or microparticles of compound of formula (II) from the residual solution. Preferably, for the salts of compounds of formula A or of formula B, A and B different, represent an alkali metal, an alkaline earth metal, an aluminum atom, a nickel atom, a zinc atom or a cobalt atom. In a particularly preferred manner, A and B, which are different, represent a lithium atom, a sodium atom, a potassium atom, a magnesium atom, a calcium atom, a strontium atom, a barium atom, an atom of cobalt, a nickel atom, a zinc atom or an aluminum atom.

Preferably, for the transition metal salt M, M represents a transition metal of group 4, 5, 6 or 7, more preferably M represents a titanium atom, a tantalum atom, a nobium atom, an atom chromium, a molybdenum atom, a tungsten atom, a zirconium atom or a rhenium atom, and more particularly a molybdenum atom or a tungsten atom.

Also preferably, for the poor metal salt M, M represents a lean metal of group 14, more preferably M represents an indium atom, tin, thallium, lead, antimony, bismuth, and more particularly an atom of tin. Advantageously, the preparation of the solution is carried out in a non-aqueous polar solvent. In a particularly advantageous manner, the nonaqueous polar solvent is chosen from ethylene glycol, glycerol, formamide, N-methylformamide and propylene carbonate. Preferably the nonaqueous polar solvent is ethylene glycol.

Also advantageously, the preparation of the solution is carried out at a temperature ranging from -20 ° C to 200 ° C. The preferred temperature is room temperature. Advantageously, the solution comprising at least one transition metal salt or a poor metal salt M and at least one salt of compound of formula A or a mixture of at least one salt of compound of formula A and of less a compound of formula B salt further comprises at least one surfactant. Preferably, the surfactant is chosen from sodium oleate, cetyltrimethylammonium bromide, sodium dodecyl sulphate and polyethylene glycol. The preferred surfactant is sodium oleate. Preferably, the surfactant has a content ranging from 0.1% to 50% by weight relative to the total weight of the salts of compounds of formula A or of formula B and transition metal salts or salts of poor metal. advantageously, the separation of the nano- or microparticles of compound of formula (II) is carried out by filtration, by centrifugation or by decantation. The preparation of the nano- or microparticles of compound of formula (II) may also comprise the addition of at least one alcohol in the solution comprising at least one salt of M and at least one salt of A or a mixture of at least a salt of A and at least one salt of B in at least one solvent. The alcohol added is chosen from alcohols comprising an alkyl chain of between 1 and 10 carbon atoms, or between 1 and 5 carbon atoms. The preferred alcohol is ethanol. The process according to the invention comprises the treatment of nano- or microparticles of the compound of formula (II).

Preferably, the treatment of the nanoparticles or microparticles of the compound of formula (II) is carried out by means of: o at least one sulfur compound, excluding compounds comprising at least one sulphoxide group, and o from minus an oxygen acceptor compound selected from carbon oxides and halogenated compounds comprising at least one chlorine atom or one bromine atom. Preferably, the sulfur compound is chosen from hydrogen sulphide, dimethyl sulphide, carbon sulphide, sulfur chloride, sulfur dichloride and elemental sulfur. More preferably, the sulfur compound is hydrogen sulfide.

Preferably, the sulfur compound is in gaseous form under normal conditions of temperature and pressure. Preferably, the oxygen scavenging compound is a carbon oxide chosen from carbon monoxide and carbon dioxide. More preferably, the oxygen scavenging compound is carbon dioxide. Also preferably, the oxygen acceptor compound is a halogenated compound selected from carbon tetrachloride, dichloromethane, chloroform, carbon tetrabromide, dibromoethane, oxalyl chloride, thionyl chloride. In a particularly preferred manner, the halogenated compound is chosen from carbon tetrachloride, dichloromethane and chloroform. More preferably, the oxygen scavenging compound is carbon tetrachloride. When carrying out the process of the invention, the treatment of the nanoparticles or microparticles of the compound of formula (II) is carried out in a temperature range of from 200 to 1500 ° C., preferably from 400 to 800 ° C. C and especially from 450 to 600 ° C. Also preferably, the treatment of the nanoparticles or microparticles of the compound of formula (II) is carried out for a period ranging from 1 to 10 hours or from 4 to 6 hours.

The process according to the invention comprises the elimination of the salt of formula (III) formed or of the mixture of salts of formulas (III) and (IV) formed. Preferably, the salt or salts formed and removed are of formulas AxRi, (III) and ByRy (IV) in which: R represents independently a chlorine atom or a carbonate group; o x represents 1, 2 or 3; o represents 1, 2 or 3; where u represents 1, 2, 3, 4, 5 or 6; where v is 1, 2, 3, 4, 5 or 6.

In carrying out the process of the invention, the salt of formula (III) formed or of a mixture of salts of formulas (III) and (IV) formed is removed using an aqueous solvent preferably by means of distilled water.

Figure 1 shows an image of nanoparticles of SrMoO4. Figure 2 shows a close-up image of hollow nanoparticles of MoS2.

Figure 3 shows a high resolution image of hollow nanoparticles of MoS2. Figure 4 shows an image of nanoparticles of BaWO4. Figure 5 shows a close-up image of WS2 hollow nanoparticles. Figure 6 shows a high resolution image of WS2 hollow nanoparticles.

The various aspects of the invention are illustrated by the following examples. These examples do not constitute a limitation of the scope of the invention. Example 1 A solution is prepared by adding 1.05 g of Sr (NO3) 2 and 1.21 g of Na2MoO4. 2H20 in 30 mL of ethylene glycol. The resulting solution is stirred for 20 h under normal conditions of pressure and temperature and filtered. The nanoparticles obtained SrMoO4 are washed successively with 200 ml of distilled water and then dried at 100 ° C. for 12 hours.

The SrMoO4 nanoparticles are obtained quantitatively (1.24 g) (Fig. 1). The nanoparticles of SrMoO4 have a size ranging from 20 to 80 nm. The average size of the SrMoO4 nanoparticles is 35 nm. 1 g of SrMoO4 nanoparticles obtained previously are treated at 500 ° C. for 4 hours under a stream of gases composed of 1.5 L / h of hydrogen sulphide and 0.6 L / h of nitrogen, saturated with CCI4 vapors at 25 ° C. The black powder obtained after this treatment is washed with 200 ml of distilled water under normal conditions of temperature and pressure. The filtrate obtained is filtered and then dried at 100 ° C. for 12 hours. The hollow nanoparticles of MoS2 are obtained with a yield of 95% (FIG 2 and FIG 3). The nanoparticles of MoS2 have a size ranging from 30 to 110 nm. The average size of the MoS2 nanoparticles is 40 nm. The nanoparticles of MoS2 have a number of layers ranging from 12 to 27. The average number of layers of the nanoparticles of MoS2 is 18. The nanoparticles of MoS2 have a hollow having a size ranging from 11 to 62 nm. The average size of the hollow nanoparticles of MoS2 is 19 nm.

Example 2 A solution is prepared by adding 1.3 g of Ba (NO3) 2, 1.65 g of Na2WO4.2H20 and 0.05 g of sodium oleate in 30 mL of ethylene glycol. The resulting solution is stirred for 20 h under normal conditions of pressure and temperature and filtered.

The nanoparticles obtained BaWO4 are washed successively with 200 ml of distilled water and then dried at 100 ° C. for 12 hours. The nanoparticles of BaWO4 in the form of fibers are obtained quantitatively (1.9 g) (FIG 4). BaWO4 nanoparticles have a length ranging from 0.5 to 6 μm. The average length of nanoparticles of BaWO4 is 3.2. Nanoparticles of BaWO4 have a thickness ranging from 50 to 300 nm. The average thickness of the BaWO4 nanoparticles is 140 nm. 1 g of BaWO4 nanoparticles obtained previously are treated at 600 ° C. for 4 hours under a stream of gases composed of 1.5 L / h of hydrogen sulphide and 0.6 L / h of nitrogen, saturated with CCI4 vapors at 25 ° C. The black powder obtained after this treatment is washed with 200 ml of distilled water under normal conditions of temperature and pressure. The filtrate obtained is filtered and then dried at 100 ° C. for 12 hours. The hollow nanoparticles of WS2 are obtained with a yield of 97% (FIGS 5 and 6). The nanoparticles of WS2 have a length ranging from 0.5 to 6 μm. The average length of the nanoparticles of WS2 is 3.2 μm. The nanoparticles of WS2 have a thickness ranging from 60 to 350 nm. The average thickness of the nanoparticles of WS2 is 160 nm. The nanoparticles of WS2 have a number of layers ranging from 14 to 35. The average number of layers of the nanoparticles of WS2 is 22. The nanoparticles of WS2 have a hollow having a length of 3.2 μm and a thickness ranging from 32 to 270 nm. . The average size of the hollow of the nanoparticles of MoS2 has a length of 3.2 μm and a thickness of 110 nm.

Claims (13)

REVENDICATIONS1. Process for the preparation of hollow nanoparticles or microparticles of a compound of formula (I): MS2 (I) in which M represents a transition metal comprising: - the preparation of nano- or microparticles of at least one compound of formula ( II): AxByMzOt (II) wherein: A and B, different, represent an alkali metal, an alkaline earth metal, an aluminum atom, a nickel atom, a zinc atom or a cobalt atom; M represents a transition metal or a lean metal; o x represents 1, 2, 3, 4 or 5; o is 0, 1, 2, 3, 4 or 5; z represents 1, 2, 3 or 4 or represents 3, 4, 5, 6, 7, 8, 9 or 10; ox + y + z is less than or equal to t; the treatment of the nanoparticles or microparticles of the compound of formula (II) by means of: at least one sulfur compound, with the exclusion of compounds comprising at least one sulphoxide group, and at least one acceptor compound of oxygen selected from carbon oxides and halogenated compounds comprising at least one chlorine atom or one bromine atom; the elimination of the salt of formula (III) formed: AxRu (III) or the elimination of a mixture of salts of formulas (III) and (IV) formed: AxRu ByRy (III) (IV) in which: R is independently a chlorine atom, a bromine atom or a carbonate group; o x represents 1, 2, 3, 4 or 5; o is 1, 2, 3, 4 or 5; where u is 1, 2, where v is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10; 3, 4, 5, 6, 7, 8, 9 or 10. 10 2. Method according to claim 1, wherein the hollow nanoparticles or microparticles of compound of formula (I) comprise at least one layer MS2. 3. Method according to claim 1 or 2, wherein the nano- or microparticles of compound of formula (II) have a size ranging from 10 nm to 1000 nm. 4. A process according to any one of the preceding claims, wherein the nano- or microparticles of compound of formula (II) comprise A and M in an A / M molar ratio of from 0.1 to 10, or include A, B and M in a molar ratio (A + B) / M ranging from 0.1 to 10. 5. Process according to any one of the preceding claims, in which: A and B, which are different, represent a lithium atom, a sodium atom, a potassium atom, a magnesium atom, a calcium atom, a a strontium atom, a barium atom, a cobalt atom, a nickel atom, a zinc atom or an aluminum atom; M represents a Group 4, 5, 6 or 7 transition metal or a Group 14 lean metal. 6. A process according to claim 5 wherein M is a titanium atom, a tantalum atom, a nobium atom, a tin atom, a chromium atom, a molybdenum atom, a tungsten atom, a a zirconium atom or a rhenium atom. 7. A process according to any one of the preceding claims, wherein the preparation of the nano- or microparticles of compound of formula (II) comprises: the preparation in at least one solvent of a solution comprising at least one salt; transition metal or a poor salt metal salt M and at least one salt of compound of formula A or a mixture of at least one salt of compound of formula A and at least one salt of compound of formula B; o separating the nano- or microparticles of compound of formula (II) from the residual solution. 8. Process according to claim 7, in which the preparation of the solution is carried out: in a non-aqueous polar solvent; or o at a temperature of -20 ° C to 200 ° C. 9. The method of claim 7 or 8, wherein the solution further comprises at least one surfactant selected from sodium oleate, cetyltrimetylammonium bromide, sodium dodecyl sulfate, polyethylene glycol. The process according to any of the preceding claims, wherein the sulfur compound is in gaseous form under normal conditions of temperature and pressure. 11. A process according to any one of the preceding claims, wherein the sulfur compound is hydrogen sulfide. The process according to any of the preceding claims, wherein the oxygen acceptor compound is a halogenated compound selected from carbon tetrachloride, dichloromethane and chloroform. 13. Process according to any one of the preceding claims, for which the treatment of the nano- or microparticles of compound of formula (II) is carried out: at a temperature ranging from 200 to 1500 ° C .; or o for a period of 1 to 10 hours.