FI117971B - Process and plant for the production of nanoparticles - Google Patents

Description

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117971 i. s

Method and apparatus for producing nanoparticles

The invention relates to a process for producing nanoparticles, wherein the nanoparticle starting materials are mixed at least as liquid droplets and possibly also gases and / or vapors in at least one of the combustion gases in a premix chamber, separating liquid droplets a flame in which the reactants 10 react and any solvents evaporate and, through nucleation and / or sintering and / or agglomeration, produce particles having a diameter of from 1 to 1000 nanometers.

The invention further relates to a nanoparticle production apparatus, wherein the device 15 comprises means for atomizing the liquid and introducing the atomized liquid into the premixing chamber, means for removing droplets larger than size d from the mixture, means for leading the mixture into the combustion head

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Nanoparticles, i.e., particles in the size range of 1-1000 nanometers, have been found to have a number of important applications such as catalytic surfaces, ♦ ♦ · * self-cleaning and antibacterial products, glass tinting, sunscreen, ♦ ♦ ·: manufacture of optical components such as optical fiber , etc. The economic production of nanoparticles • # ♦ »: ***: 25 is an essential factor for the economic use of these applications. Nanoparticles require relatively narrow size distribution: (monodispersity), avoid agglomeration and homogeneity.

The production of nanoparticles should preferably be easily scaled: from laboratory to industrial production.

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Nanoparticles can be produced by both wet chemical methods and gas phase methods, of which gas phase methods are generally simpler and more scalable than wet methods. Gas phase methods, also called aerosol reactor methods, are 5 mm. flame reactors, furnace reactors, plasma reactors, gas condensation methods, laser ablation and spray pyrolysis. The state of the art relevant to the present invention is a flame reactor and a spray pyrolysis process. The present state of the art is presented e.g. L.Mädler, Liquid-fed Aerosol Reactors for One-Step Synthesis of Nano-Structured 10 Particles, KONA (No. 22, 2004, pp. 107-120), and is briefly reviewed below for presenting prior art.

Spray processes for producing nanoparticles differ mainly in the way in which the thermal energy required for pyrolysis is introduced into the process.

15 Imports of thermal energy affect eg. maximum temperature, temperature profile and residence time. The four main methods of spray processes for producing nanoparticles are spray pyrolysis in tubular reactor (SP), vapor flame reactor spray pyrolysis (VFSP), emulsion combustion method and emulsion combustion method (emulsion combustion). (flame spray pyrolysis, PSP). Of these * 1 2 1 methods, SP uses a hot-wall reactor as a thermal reactor and thus:: 2: is not relevant to the present invention and ECM and FSP use • · 1 ·: 3: fuel oil and exothermic liquid, respectively, and hence, are relevant to the invention of "1".

The steam / flame reactor uses the term formed by combustion gases: the reactor as a heat source. The advantage of the flame compared to the furnace reactor is 7 · · · 'Λ with a significantly higher temperature and a shorter residence time. VFSP Reactor ·! : the raw material is evaporated in a bubbler or in a vaporizer.

• · 30 evaporator) and the steam is conducted to the one formed by the combustion gases. a flame. The vapors can be mixed with the combustion gas either before the burner head (pre-2 * 3 • 3 117971 mixed burner) or outside the burner head. The raw materials react in flame to form particles. The disadvantage of the process is the scarcity of the raw materials, with only a few elements having compounds with a vapor pressure high enough for the process.

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The process is further modified by atomizing the liquid raw materials and feeding them into a flame. Such modifications are disclosed with reference to US Patent 3,883,336 and Finnish Patent FI98832.

10 U.S. Patent 3,883,336 discloses an apparatus wherein a flame is injected into a syringe by means of oxygen acting as a carrier gas as a mist. Further, it is disclosed in that publication that an aerosol is sprayed onto the flame of a flame spray gun to produce glass. The apparatus in question is of poor efficiency and the supply of silicon tetrachloride by means of the carrier gas 15 to the device is slow because, if the silicon tetrachloride is too much in relation to the carrier gas, it is nucleated into larger droplets and thus not small particles can be injected.

Finnish patent F1 98832 discloses a method and apparatus in which: * 20 the substance to be injected is introduced in a liquid form into a flame and droplet »» »· with gas substantially in the vicinity of the flame such that the droplet and the flame • j '; the formation takes place on the same device. Further, this publication discloses that the apparatus includes means for introducing a liquid substance into a flame and * * *:: * · means for conducting a gas into the liquid to be injected so that the gas essentially drips the liquid to be injected into droplets in the vicinity of the flame, · · · whereby the droplet occurs in the same apparatus as the flame formation.

: The sprinkling and combustion gases used in this process; the speeds may differ significantly, causing possible ···. ·! : backflows in the flame to be generated and fouling and even clogging of • · · • 30 burner heads due to backflows. A variety of liquids ♦ · *. simultaneous sprinkling is difficult in this method.

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The scalability of the method and apparatus is difficult because each burner head requires individually controlling the mass flow of the gases in order to achieve a well controlled atomization and flame formation.

U.S. Pat. No. 5,879,783 discloses a process for preparing nanoparticles, wherein the gaseous source materials and the combustion gases are mixed with one another prior to the flame, where nanoparticles are formed as a result of thermal decomposition of the source materials. In addition, the use of nanoparticles for coating is known from this publication.

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US 5,958,361 and US 2002/0031658 disclose a method. / nanopowder, in which the starting materials are mixed with the same solution, which is further sprayed onto the flame. Said methods may further be applied to the preparation of multi-component nanoparticles 15.

The main object of the present invention is to provide a method and apparatus for the rapid and economical production of nanometer (1-1000 nm) particles. In particular: It is an object of the invention to provide a process for producing multicomponent nanoparticles.

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The process according to the invention is characterized in that the process utilizes liquid raw materials, which are most often in the form of metal salts. Solutions, the liquid is atomized into small droplets in the premix chamber, · · · mixed in the premix chamber with at least the combustion gases, mixture; ; *; is passed to the classifier which distinguishes the mixture from the aerodynamic • · ·: ***; liquid droplets larger than d in diameter, a mixture containing a diameter d «· ·, ·! . smaller droplets are conducted to the burner head, the flame is formed and the materials are · · 30 converted into flame nanoparticles, which may have a different composition from the -¾ • · • raw materials.

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Further, the process according to the invention is characterized in that droplets of several different raw materials can be separately fed to the premixing chamber and / or other nanoparticle raw materials can be fed therein in gaseous or vaporous form to produce a multi-component nanoparticle raw material mixture.

Further, the device according to the invention is characterized in that the device has means for atomizing the liquid into droplets, means for introducing droplets into the premix chamber, means for introducing combustion and other gases into the premix chamber, means for mixing gases and liquid droplets means for forming a flame.

Further, the device according to the invention is characterized in that the surfaces of the device can be heated. In this case, the liquid droplets flowing to the surfaces of the device evaporate according to the gas flow, but the salt contained in the liquid crystallizes on the surfaces of the apparatus and does not drift according to the gas flow. In this way, the liquid accumulated on the surfaces can be prevented from being released in large droplets by the gas flow: .1. 20 according to.

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# · ♦ # · ♦ • ♦ ·:. ·. The essential idea of the invention is that multi-component, nanoscale • · · ·. · 2. particles can be produced industrially and scalably.

• · · - • · • · · * · 1 * 2 · ·: ***; The following more detailed description of the invention, by way of example, will further illustrate the advantages of the invention to one skilled in the art:; 1; embodiments, as well as the 1: 2 ·: advantages achieved by the present invention.

The invention will now be described in more detail with reference to the accompanying drawings, in which: ··· 1 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · : 6, · · '. FIG. 1 illustrates a substantially prior art embodiment of the invention FIG. with semiconductor 10, Figure 5 illustrates an application of the invention in which the method of the invention produces nanoparticles for the manufacture of an optical fiber reform. Figure 6 illustrates an application of the invention wherein the device surface is heated to prevent large droplets from passing

Figure 1 shows a known state of the art in the production of nanoscale particles, for example, as disclosed in Finnish patent FI98832.

The liquid flame gun 1 produces a flame 8 of the substance to be injected:. 20 for spraying. The flame gun 1 delivers the required gases through the gas channels 2, 3 and r: · · *. ···, 4. Flame forming combustion gases are introduced through the gas channels 2, 3 and 4,. sputtering gas of liquid to be injected and possible reaction control * · »• · · · ···. the gas produced. The substance to be injected is fed in a liquid form · ·:. *. the flame spray 1 along the liquid passage 5. The liquid to be injected is transferred. 25 fluid channels 5 by pumping it with a syringe pump 6. At the end of the flame gun * * * is a nozzle 7 in which the combustion gases are ignited to produce a flame and in which. the liquid to be injected is sprayed with the spray gas. Liquid droplets are conducted * * ·. ***. by means of gas flow to flame 8, where the liquid evaporates and can be injected * * * /. the metal compounds in the substance form particles.

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The problem with producing nanoscale particles by the process of Figure 1 is that the large liquid droplets that may be produced in the process are not completely evaporated, resulting in so-called residual particles larger than the desired nanoparticle size. A further problem with this process 5 is the difficulty of producing particles of liquid components which do not mix or react undesirably, for example, to form a gel.

Figure 2 shows a preferred embodiment of the present invention 10. Liquid droplets 12 are atomized into premix mixing chamber 10 using a gas-dispersed atomizer 3, whereby liquid gas supply 5 is atomized by small burner gas 16 into other droplets 12. 28 using an oscillating disk such as an ultrasonic disk atomizer 22 to atomize the liquid source 30 into small droplets 28. The premixing chamber 10 is supplied with combustion gas from channel 32. The combustion gas may be, for example, hydrogen, methane, propane or butane, or a combination thereof. 20 other gas combinations. Similarly, oxygen * · · ··· is supplied to the premixing chamber 10. the oxygen-carrying gas may be, for example, air, oxygen, or ozone. From the gas passage 36 to the premixing chamber 10, an inert gas such as nitrogen or carbon dioxide is supplied. From the Gas Duct • · • · ·:. ·. a pre-mixing chamber 10 is supplied with some gas containing the · · · • * * * produced. 25 at least one raw material of nanoparticles. From channel 38 to steam * * * 10, steam containing at least one of the nanoparticles to be produced is fed. the raw material. Steam is supplied by supplying liquid 42 from the conduit 40 to the fluid 42 • · · '·. · * ·. through a pulverizer bottle 44, whereby the evaporated liquid (vapor) passes through the channel • «·. *. 38 along the premix chamber 10. Liquid droplets, gases and vapors mix * · · * * * * *. 30 effectively in the premix chamber 10 to form a homogeneous mixture 46.

·. The mixture is further passed to droplet separator 48, which separates from the mixture droplets larger than particle size d 50. The liquid contained in the droplets is further passed through collecting passage 52 to collecting vessel 54. The droplet separator 48 may be based, for example, on impaction, air classification. air classifier), electronic classification, cyclone or the like. The mixture 56 from which the large droplets of liquid have been removed is led to the burner head 58. At the burner end, the mixture is ignited to produce a flame 60. The flame 60 is preferably turbulent or otherwise such that effective mixing of the mixture is ensured. In flame 60, the liquid components evaporate and the raw materials react to form particles 62.

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Figure 3 shows a preferred embodiment of the present invention when used for flat glass staining. At the same time, the figure and its description serve as an example of the use of the invention in an application. S

Liquid droplets 12 and 14 are atomized into pre-mixing chamber 10 using two pressure-dispensed atomizers 18 and 20 to atomize liquid inlets 24 and 26 into small droplets. Liquid 64 is aspirated by high pressure pump 66 and is further supplied to pressure atomizer 18. Liquid 64 consists of methanol and cobalt (II) nitrate Co (NO3) 26H2O dissolved therein at a solubility of 100 ml methanol and 20 g of cobalt (II) nitrate. The supply to the high pressure pump 66 is limited by a throttle valve 68 or equivalent to 50 ml / min. Liquid 70 • · · is aspirated by a high pressure pump 72 and is further supplied to a pressure relief • · ·.

: for atomizer 20. Liquid 70 is made up of methanol and dissolved in it. calcium nitrate Ca (NO 3) 2 · 4H 2 O, with a dissolution ratio of 100 ml methanol and 18 * ·

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: g of calcium nitrate. The supply of high pressure pump 72 is limited by a throttle valve

Il * ·. ···. 74 or equivalent to 50 ml / min. The pre-mixing chamber 10 is supplied with hydrogen gas at a flow rate of 500 l / min from conduit 32.

. air is supplied to the premixing chamber 10 at a flow rate of 1250 l / min J

· ·. * ··. from channel 34. Liquid droplets and gases are efficiently mixed in the pre-mixing chamber 10 to form a homogeneous mixture 46. The mixture is further introduced into a droplet separator 48 which separates the mixture from the diameter. droplets larger than 5 micrometers in aerodynamic diameter 50. The liquid contained in the droplets is further conducted through collecting channel 52 to collecting vessel 54. The mixture 56 from which large liquid droplets have been removed is directed to burner head 58. Burner head 58 is a slot nozzle having a width of 1000 mm and slot width 20 mm. At the burner end, the mixture is ignited to produce a flame 60. In flame 605, the liquid components evaporate and the raw materials react to form particles 62. These particles are further directed to a surface of flat glass 76 having a temperature greater than 600 ° C, to which particles 78 adhere. Particles 78 diffuse and further dissolve in glass 76, causing the surface of the glass to turn blue.

Figure 4 illustrates a preferred embodiment of the present invention when used to produce a photocatalytic surface on a ceramic tile. At the same time, the figure and its description serve as an example of the use of the invention in an application. Liquid droplets 12 and 14 are atomized into the premixing chamber 10 using two gas dispersed atomizers 18 and 20, 15 to atomize the liquid feeds 24 and 26 into small droplets. Liquid 64 is supplied by a hose pump 80 to a gas-atomized atomizer 19. Liquid 64 consists of methanol and tetraethyl orthotitanate, Ti (OC 2 H 5) 4 (TEOT) dissolved therein in a 1: 1 mixing ratio. The volume flow rate of the liquid is adjusted by the hose pump 80 to 10 ml / min. Liquid 70 is supplied by hose pump 82 and gas - dispersed •. 20 for atomizer 21. Liquid 70 consists of methanol and silver nitrate dissolved therein, AgN03, with a mixing ratio of 100 ml methanol and 10 g • · · silver nitrate The volume flow rate of the liquid is adjusted by a hose pump 82 to 5 · · ·] ··· [ ml / min. Hydrogen gas is supplied to the pre-mixing chamber 10 at a volume flow rate of 40 * · l / min from channel 84, which further coalesces with the gas-dispersed atomizer 19 • · ·. ···. 25 into the gas passage before being introduced into the premix chamber 10. Also, · the premix chamber 10 is supplied with oxygen at a flow rate of 20 l / min. . ·. from channel 86, which further joins the gas-atomized atomizer 21. to the gas passage before being introduced into the mixing chamber 10. Liquid droplets and gases • ♦. ·, are effectively mixed in the premixing chamber 10 to form a homogeneous «·« ** *; 30 mixture 46. The mixture 46 is further conducted to a droplet separator 48 which separates the mixture from an aerodynamic diameter of 10 micrometres in diameter.

The liquid 56 contained in the droplets 50 is further passed through collecting passage 52 to a collecting vessel 54. The mixture 56 from which large liquid droplets have been removed is fed to burner head 58. Burner head 58 is a slot nozzle having a width of 300 mm and a slot width of 5 mm. At the burner head 58, the mixture is ignited to produce a flame 60.

5 In flame 60, the liquid components evaporate and the raw materials react to form particles 62. These particles 62 are further directed to the surface of the ceramic tile 88, to which the particles adhere to form a photocatalytic coating on the tile surface.

Figure 5 illustrates a preferred embodiment of the present invention when used in the preparation of porous fiber preforms for the manufacture of active optical fibers. At the same time, the figure and its description serve as an example of the use of the invention in an application.

Liquid droplets 12 and 14 are atomized into the premixing chamber 10 using two gas-dispersed atomizers 12 and 14 to atomize the liquid feeds 24 and 26 into small droplets. Compressed air is used as the atomization gas 90 and is supplied to the gas channels 92 and 94 of the atomization nozzles through the flow regulators 96 and 98.

Liquid 64 is supplied by a hose pump 80 to a gas-dispersed atomizer 19.

Liquid 64 consists of methanol and aluminum nitrate dissolved therein. . 20 Al (NO 3) 3 9H 2 O, with a mixing ratio of 20 g aluminum nitrate per 100 milliliters • · · • · «*! *. * Methanol. The volume flow rate of liquid 64 is adjusted by a hose pump 80 to 12 · m / ml. Liquid 70 is fed by a hose pump 82 to a gas atomizer • · · 21. Liquid 70 consists of methanol and erbium nitrate dissolved therein,

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Εγ (Ν03) 3 At a 5Η20 mixing ratio of 100 ml methanol and 2 g erbium nitrate • · »25 Adjust the volume flow rate of the liquid by means of a hose pump 82 to 12 ml / min.

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Oxygen acting as carrier gas 40 is fed through pulverizer 100 to pulverizer 44. Silicon tetrachloride, SiCl 4 in pulverizer 44 is vaporized into the carrier gas and transported with the carrier gas through a pre-mixing chamber 10. Carrier gas 40 has a flow rate of 500 ml / min and pulverizer 44

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* · * · 30 temperature 30 ° C. Hydrogen gas is supplied to the premix chamber 10 at a flow rate of 30 l / min from duct 36. Also, the premix chamber 10m · · ····· · · ...

117971 11 is supplied with oxygen at a flow rate of 15 L / min from channel 34. Liquid droplets, vapor and gases are effectively mixed in premixing chamber 10 to form a homogeneous mixture 46. Mixture 46 is further passed to droplet separator 48 which separates from 50 micrometre to 50 micrometres aerodynamic diameter the mixture 56 from which the large droplets of liquid have been removed is directed to the burner head 58. The burner head 58 is a circular nozzle having a diameter of 2 mm. At the burner head 58, the mixture is ignited to produce a flame 60.

In flame 60, the liquid components evaporate and the raw materials react 10 to form particles 62. The composition of the particles is SiO 2 -Al 2 O 3 -Er 3 O 3 in a ratio of 100 to 10-1. These particles are further directed to the surface of mandrel 102, to which the particles adhere to form a porous glass layer. After culturing, the mandrel 102 is removed, resulting in a porous glass blank.

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Figure 6 shows a preferred embodiment of the present invention when used to produce nanoparticles for coating at a downwardly directed burner head. At the same time, the figure and its description serve as an example of the use of the invention in an application.

:. ·. Liquid droplets 12 and 14 are atomized into the premix chamber 10 using two gas-atomized atomizers 19 and 21 to atomize the fluid feeds 24 and 26; •: in small drops. Liquid 64 is supplied by a hose pump 80 to a gas dispenser. ** ·. for atomizer 19. Liquid 64 consists of methanol and * * * :. ·. of copper nitrate, Cu (NO 3) 23H 2 O, with a mixing ratio of 30 g of copper nitrate • · · · 25 in 100 ml of methanol. The volume flow rate of liquid 64 is adjusted by a hose pump * · * 80 to 8 ml / min. Liquid 70 is fed to the hose pump 82 and to the gas dispenser. for atomizer 21. Liquid 70 is tetraethyl orthosilicate, TEOS. The volume flow * * * of the liquid is adjusted by the hose pump 82 to 20 ml / min.

/. Hydrogen gas is supplied to the pre-mixing chamber 10 at a volume flow rate of 30 L / min • * * 30 from channel 104, which at the same time acts as a decomposition gas channel of the gas-dispersed atomizer. Likewise, air is supplied to pre-mixing chamber 10 at a flow rate of 75 liters / minute from duct 34. Liquid droplets and gases are effectively mixed in pre-mixing chamber 10 to form a homogeneous mixture 46. The mixture is further directed to burner head 58. Burner head 58 is a slot nozzle 200 mm and a gap diameter of 1 mm. The surfaces 106 of the burner head 58 and 5 are heated by an electric heater 114 to a temperature of 120 ° C. The liquid particles 108 flowing to the surfaces 106 and the inner surface of the burner head 58 then evaporate the methanol 110 and the salts 112 contained in the liquid adhere to the surfaces. This prevents the liquid adhering to the surface from flowing / draining in large droplets out of the burner head 58. At the burner head 58 10, the mixture is ignited to produce a flame 60. In flame 60, the liquid components evaporate and the raw materials react to form particles 62. The particles are further guided to the surface 116 of the flat glass, to which the particles 62 adhere. The particles diffuse, dissolve and mix with the surface of the flat glass, making it turquoise.

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It will, of course, be apparent to one skilled in the art that various combinations of the methods, procedures, and apparatus structures described above in connection with the various embodiments of the invention may provide various embodiments of the invention that are within the spirit of the invention. Therefore, the above:. The examples presented in Fig. 20 are not to be construed as limiting the invention but embodiments of the invention may be varied within the scope of the inventive features set forth in claims * 1 · below.

• · 1 * 1 1 1 • · ♦ • · ·:. ·. It will, of course, be obvious to one skilled in the art that the accompanying drawings are * · · ·. ···. 25 are intended to illustrate the invention, and thus the structures and components shown therein are not drawn in their proper mutual dimensions.

• · · »» ♦ * 1 ·. ·· 1. Of course, it will also be obvious to one skilled in the art that the geometries shown are • · · .1. is intended to illustrate the invention and thus, for example, the shape of the mixing chamber may be arbitrary and the shape of the burner head may be very free provided that. care is taken that the geometries used, for example, do not collect ····· - '• ·' 13 117971 liquid particles. An example of such a harmful shape is, for example, a perforated burner head where the surfaces between the holes may act as particle impact collectors.

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Claims (13)

14 1 1 7971 A process for producing nanoparticles, wherein the liquid particles are introduced into a flame, said nanoparticles being led to a flame, wherein the nanoparticles are formed of liquid particles, characterized in that the atomised liquid particles and the flame forming combustion and oxidizing gases form the flame. Method according to Claim 1, characterized in that the median aerodynamic diameter of the liquid particles introduced into the flame is between 1 and 20 micrometers. Method according to Claim 1, characterized in that the aerosol particles having an aerodynamic diameter greater than 5 to 20 micrometres are removed from the gas stream before the flame. Method according to Claim 1, characterized in that the walls of the device according to the method are heated so that the liquid component of the liquid droplets applied to the wall is completely or partially evaporated and the salt contained in the liquid * * · · remains on the heated surface. »* · • * * • · · ·· * · A process according to claim 1, characterized in that at least one gas or vapor involved in the formation of the nanoparticles is mixed with the aerosol particles and the flame-forming combustion and oxidizing gases. * · · S ·· » • · ♦ · '<··· ·' **; An apparatus for forming nanoparticles comprising means (18, 20,, -¾ • * *, · [: 22) for atomizing liquid raw materials and means (32, 34, 36, 38; 84, • · 3086) ) for supplying gases and / or vapors, means (10) for mixing atomized liquids, • for mixing gases and / or vapors, means for conducting the mixture (46). 117971 burner head (58) and means for forming a flame (60), characterized in that the atomized liquid particles and the gases / vapors are mixed with each other before the flame (60) is formed. Apparatus according to claim 6, characterized in that the liquid particles are atomized by a pressure-atomized atomizer (18, 20), a gas-atomized atomizer (19, 21) or by a vibrating plate (22). Device according to Claim 6, characterized in that the device comprises means 10 for removing droplets of liquid from an aerodynamic diameter of more than 5 to 20 micrometers from the gas stream before the flame. ; Device according to Claim 6, characterized in that the device comprises means for heating the surfaces in contact with the mixture flow. r 15 Method or device according to one of Claims 1 to 9, characterized in that the method or device is used to produce nanoparticles in the staining of the flat glass surface. : 20 The method or device according to any one of claims 1 to 9, characterized in that the method or device is used to produce nanoparticles. in the manufacture of a photocatalytic surface. • · · * · · · · · »»:. ·. A method or device according to any one of claims 1 to 9, characterized by a · · · ·. ** ·. 25 that the method or apparatus is used to produce nanoparticles in the manufacture of optical fiber preforms. ··· • φ · * · · Method according to one of Claims 1 to 9, characterized in that * · · /. The method or apparatus is used to produce nanoparticles in a coating of a ceramic, glass or metal body. ····· '- • · φ • · 16 1 1 7971