FI117790B - Method and apparatus for coating materials - Google Patents

Description

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Method and apparatus for coating material

The present invention relates to a method for coating a material comprising forming particles from the raw materials, directing the particles with a gas stream, separating particles having an aerodynamic diameter greater than d micrometres from the particle stream, and directing particles smaller than d micrometres by thermophoresis. The aerodynamic diameter d is typically 0.1 to 10 micrometers.

The invention further relates to a coating apparatus comprising means for generating particles, collecting particles greater than d micrometers and guiding particles smaller than d 'micrometers to the surface to be coated.

The aerodynamic diameter d is typically 0.1 to 10 micrometers. '* 15 It is known to spray solid matter with flame spraying equipment. In this method, the substance to be injected is introduced into the flame spray as solid particles which are injected into the desired object by a flame spray device. However, as the particle size decreases, flame spraying equipment easily becomes clogged and clogged. Thus, for example, the spraying of particles smaller than 20 micrometers with flame spraying equipment is. 20 cumbersome and flame spraying equipment clogs easily and is expensive in construction.

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A further problem is that the solid to be sprayed is flame spray • · · *; . ·. in several phases, being partly vapor, partly molten, and partly molten, and • il ·· * ·. ···. when the substance cools, the result is uneven.

U.S. Patent 3,883,336 discloses an apparatus for introducing silicon tetrachloride into a flame spray by means of oxygen acting as a carrier gas. Further, that publication states:. that the aerosol is sprayed on the outside of the flame gun to produce the glass.

• · ®. ***. The apparatus in question is of poor efficiency and the supply of silicon tetrachloride as steam t * *. carrier gas to the device is slow because if too much silica tetrachloride * * * 30 is carried, it will nucleate into larger droplets and therefore not small enough

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. get the particles sprayed. i * ··· * · • * ·· * ·· - • · 2 117790

Finnish patent FI 98832 discloses a method and apparatus in which the substance to be injected is introduced into a flame in liquid form and gas-dropping substantially in the vicinity of the flame so that the droplet and flame-forming take place in the same apparatus. Further, that publication discloses that the device has means for introducing a liquid substance into a flame and means for introducing a gas into the liquid to be injected such that the gas sprays into droplets substantially in the vicinity of the flame, whereby the drop occurs in the same apparatus.

The apparatus is poor in coating efficiency and may have particles of 10 different sizes in the coating because, if the liquid droplet is too large, it produces so-called residual particles with an aerodynamic diameter of several hundred nanometers or even several micrometers or tens of micrometers. Such residual particles are often detrimental to the coating process. .

US Patent 5,622,750 discloses one way of forming glass layers using a Flame Hydrolysis Deposition (FHD) method. Em. In the process described in the patent, the starting materials required for the manufacture of glass are mixed together to form an aerosol droplet, which aerosol droplets are carried with the carrier gas to the burner and then to the flame. In a thermal reactor flame, aerosol droplets form * aerosol particles. Which aerosol particles still under the influence of thermophoresis • ...

• * * · • guide to the substrate to be coated to form a glass material coating.

• · * · · ** · To achieve a uniform and strong coating layer, the substrate is moved • · * •; *; in a plane transverse to the flame during recoating.

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The FHD process disclosed in U.S. Patent No. 5,662,750, as well as other known methods employing a flame, plasma or other term

M1: '*** reactor to produce nanosized aerosol particles of feedstock,

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, *! : The guiding coating aerosol particles to the target to be coated • · · • · 30 are substantially affected by thermophoresis. Ts. due to the temperature gradient between the reactor, etc., and the * * '' f • # significantly cooler substrate, the aerosol particles formed in the thermal 117790 reactor drift as a result of their heat movement and the resulting collisions with the substrate. Due to the small size and low mass of the aerosol particles, their flame impartation to the substrate (mass x velocity) has little relevance to the transport of aerosol particles to the surface of the substrate compared to thermophoresis.

Finnish patent FI 111 939 describes a liquid flame spraying method in which using a thermal reactor, such as a flame, to form aerosol particles necessary for providing glass coating, instead of moving the aerosol particles 10 onto the substrate to be coated, the flow of gases from said reactor towards the substrate. In this case, the aerosol particles traveling with the gas flow due to the pressure difference have a significant amount of motion exceeding the thermophoretic forces, whereby by this momentum the aerosol particles collide and adhere to the substrate, i.e. their glass surfaces are formed on the substrate. based on impact. However, the process described in the patent cannot be coated with very small particles having an aerodynamic diameter of only a few nanometers or a few tens of nanometers, but these particles follow the gas flow and do not influence .1 ··. 20 to the substrate to be coated.

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: Particles of a few nanometers or a few tens of nanometers have '• · Φ · .2 ·. very high specific surface area and are therefore important especially for coatings that require high surface energy. As an example of such a coating, · · · · 25 and / or surface modification can be mentioned the coloring of a glass body based on the fact that • the glass surface is used to control glass coloring metal compounds in the form of very small particles.

; Due to its small particle size, said metal compounds diffuse and dissolve; · into the glass matrix while staining the glass.

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The main object of the present invention is to provide a method and apparatus which can be used to simply and inexpensively coat material with nanoparticles (1 to 500 nm).

The method of forming a coating according to the invention, wherein the aerosol particles are generated, said particles being conducted along with the gas stream to the surface of the substrate, characterized in that the aerosol particles are first conducted to , whereby the thermophoretic force due to the temperature difference ΔΤ between the heated surface and the substrate collects particles smaller than the diameter d on the substrate. The aerodynamic diameter d is typically 0.1 to 10 micrometers. After the impact collector, the gas flow is allowed to expand, thereby decreasing its speed and improving the efficiency of the thermophoretic collection.

The process of the invention can be used to color a glass so that the nanoparticulate particles collected on the surface to be coated contain a glass coloring compound and that the glass particles diffuse and dissolve in the surface layer of the glass to be coated. The method of the invention can also be used to produce a photocatalytic surface or a functional surface on a substrate surface.

A device for forming a coating according to the invention, the device having means for generating aerosol particles and means for conveying aerosol particles; the gas flow is characterized by the fact that the device is equipped with a process: •: 1; and means for collecting unwanted aerosol particles on the substrate by thermophoresis.

: #i: The essential idea of the invention is that nanoparticles can be generated • 1 ·:: in a process without a large uniform size, i.e., monodispersity requirement, separates: harmful particles from the stream of particles and efficiently collects nanoparticles, • · on the surface of the material to be coated.

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· 1 1 · 5 117790

In a preferred embodiment of the invention, the aerosol particles generated in the thermal reactor or otherwise are guided along the gas flow through the nozzle portion towards the impact surface. The velocity of the gas stream is such that particles larger than a given size f are exposed to the impact surface, i. particles smaller in size f 5 follow the gas flow. The gas flow is then directed to pass between the heated surface and the surface to be coated so that the {thermophoretic force due to the temperature difference between the surfaces directs the particles to the surface to be coated.

An advantage of the invention is that the thermophoretic force does not depend on the mode of production of the particles nor on the production temperature, but only on the temperature difference between the surface to be coated and the heated surface. In a preferred embodiment of the invention, the object to be coated is a product manufactured in a continuous process, such as a float glass, ceramic tile or metal plate passing through a coating unit in a production line, whereby the material to be coated is not significantly heated by the heated surface.

An advantage of the invention is that the coating formed from nanoparticles can be produced quickly, advantageously and in a single step. Thus, the present invention achieves a much better state of the art in nanoparticles than the prior art methods. 20 coating control. This will continue to allow higher quality, for example. making colored glass surfaces. ; Φ · · · • [[[* * * * *;; The following detailed description of the invention, by way of example, will further illustrate to the person skilled in the art the preferred embodiments of the invention as well as the advantages of the prior art.

···: The invention will be described in more detail below with reference to the accompanying drawings, in which: ·· *: ***: Figure 1 illustrates the principle of prior art * ·· X; Figure 2 illustrates the mechanisms of formation of particles produced by the prior art. Figure 3 illustrates in principle a preferred embodiment of the invention ····· • · 6; Y 117790

Figure 1 shows a known state of the art in coating a material as described, for example, in Finnish patent FI98832. Flame spray 101 is used to generate flame 108 for spraying the material to be injected. The flame spray 101 is supplied with the required gases 5 through gas channels 102,103 and 104. The flue-forming combustion gases, the sputtering fluid of the liquid to be injected and any gas produced for controlling the reaction are introduced through the gas channels 102,103 and 104. The substance to be injected is supplied in liquid form to the flame spray 101 along the liquid passage 105. The liquid to be injected is conveyed along the fluid passage 105 by pumping it through a syringe pump 106. At the end of the flamethrower 10 there is a nozzle 107 in which the combustion gases are ignited to produce a flame and in which the liquid to be injected is sprayed. Liquid droplets are conducted through a gas stream to flame 108 where the liquid evaporates and the metal compounds in the injectable material form particles as further illustrated in Figure 2. The resulting particles are further directed to the gas-coated surface 109. Since 15 very small, typically less than 100 nm gas flow, they easily drift away from the surface without adhering to the surface (radial jet effect) M1, which typically has a poor collection efficiency. On the other hand, any undesired large particles (aerodynamic diameter typically greater than 1 micrometer) 112 generated in the process, on the other hand, are impacted on the surface to be coated 109, whereby? · 1 · 1 · 20 large particles 112 that are harmful to the coating build up on the surface to be coated .J. 109 better efficiency than the small particles desired for coating «· · · no.

• · · · 1 ·· * ·· • · • ♦ «·· •; 1; Figure 2 illustrates the mechanisms of the prior art particle generation of · ·· 1 · ““ · 25. The liquid is dripped, for example, with the apparatus of Figure 1. If the size of the droplet 201 is small enough and receives sufficient heat energy from the flame 108,: 1j the liquid component in droplet 201 is completely evaporated and liek · metal compounds 202 are released into the flame. These compounds may directly nucleate 203 or react first ··· · X; for example, with oxygen to form metal oxide particles which immediately • · · * · 30 nucleate 204. The nucleated particles grow through agglomeration and sintering to> • 1 • e to form particles of 10-100 nm in diameter 110. This pathway is desirable Φ · · 7117790 If the liquid does not completely evaporate from the droplet droplet 201, for example because the droplet is too large or too little energy is available for evaporation, the droplet produces a so-called residual particle 112, which is considerably larger in size than the small particles 110. Such particles are often undesirable for the coating process, but in the prior art methods are very difficult or impossible to prevent.

Figure 3 illustrates a preferred embodiment of the present invention.

Flame spray 101 is used to generate flame 108 for spraying the material to be injected.

10 The flame spray 101 is supplied with the necessary gases through the gas channels 102,103 and 104.

The flue-forming combustion gases, the spray gas for the liquid to be injected and any gas produced for reaction control are introduced through the gas channels 102,103 and 104. The substance to be injected is supplied in liquid form to the flame spray 101 along the liquid passage 105. The liquid to be injected is conveyed along the liquid passage 105 by pumping it by means of a syringe pump 106. At the end of the flamethrower is a nozzle 107 in which the combustion gases are ignited to produce a flame 108 and wherein the injectable liquid is dripped by the spray gas. Liquid droplets are conducted through a gas stream.

to flame 108, where the liquid evaporates and the metal compounds j in the material to be sprayed form particles, as further illustrated in Figure 2. Generate · * ϊ *. The particles are guided towards the impact surface 301, such as a rotating tube of quartz glass or ahamine oxide, which avoids bending of the impact surface 301 by the heat of the flame 108. The impact surface 301 collects from the particle stream 302 the large ·· * · · * “· residual particles 112, while the small particles 110 are guided by the gas flow 111 * ··: with thermophoresis one to 303. The thermophoresis unit consists of heated: ***: 25 surfaces 304. The gas flow 111 spreads beyond the impact surface 301 to a wider area, thereby substantially reducing the gas flow rate.

The temperature difference between the heated surface 304 and the coated surface 109 provides <: · a thermophoretic force that causes the fine particles 110 to migrate to: the coated surface 109. The size, distance * * · • · 30 of the coated surface 109 and the heated surface 304 109 *. the temperature difference can be changed over a relatively wide range, so that the thermophoretic ♦ · ***** ♦ · 117790

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the collection efficiency is high and thus the efficiency of the entire coating process is good.

The impact surface 301 can be heated, for example, by a burner 305, whereby the residual particles 112 accumulating on the impact surface 301 can be sintered onto the impact surface 301 and thus cannot be detached and transported to the surface 59 to be coated.

As an example of the preferred embodiment of Figure 3, the blue coloration of the flat glass is considered. Flame spray 101 generates flame 108. Oxygen gas is introduced at 15 l / min through gas passage 102, nitrogen gas at 15 l / min is introduced through gas passage 103 and hydrogen gas at 30 l / min is supplied through gas passage 104. The substance to be injected is methanol dissolved in copper nitrate 11 g / 100 ml and cobalt nitrate 18 g / 100 ml. The substance to be injected is fed in liquid form to the flamethrower 101 along the liquid passage 105 at a flow rate of 5 ml / min. The liquid to be injected is passed along the fluid passage 105; 15 by pumping it with a syringe pump 106. At the end of the flamethrower is a nozzle 107 in which the combustion gases are ignited to produce a flame 108 and wherein the liquid to be injected is dripped with hydrogen gas. Liquid droplets are conducted through a gas stream to a flame 108 where the liquid evaporates and metal compounds in the material to be injected form CoxOy-Cu7Ow particles by reacting with oxygen, nucleation, sintering and; * · *; 20 agglomeration. The resulting particles are directed towards the impact surface 301, which is served by a ··· rotating quartz glass tube. The impact surface 301 collects from the particle stream 302 the large residual particles 112, typically larger than 1 micrometer, while the small particles 110, smaller than 1 micrometer, are directed by the gas stream 111 * · · •: *; included with thermophoresis unit 303. The thermophoresis unit consists of heated f ·· * »·“ *: 25 surfaces 304 with a temperature of 1000 ° C and flat glass 109. below the heated surfaces 304. The flat glass can pass either in the on-line manufacturing process or outside device (off-line). After the impact surface 301, the gas flow 111 spreads over a wider area, whereby the gas flow rate: substantially decreases. A temperature difference of 300 ° C to 700 ° C between the heated surface 304 and • · * * · 30 the coated surface 109 produces a tennophoretic force which is · · *. under the influence of the fine particles 110 migrate to the surface to be coated 109 ..

• * • · j 9 117790

The impact surface 301 is heated by a burner 305, whereupon the residual particles 112 accumulating on the impact surface 301 can be sintered onto the impact surface 301 and thus cannot be detached and transported to the surface to be coated 109. The small particles adhering to the glass surface

As another example of a preferred embodiment of Figure 3, the coating of a ceramic plate with photocatalytic titanium dioxide is contemplated. Flame spray 101 produces a flame 108. Oxygen gas f 10 is introduced through the gas passage 102 at a flow rate of 15 1 / min, nitrogen gas is introduced at a flow rate of 15 l / min and hydrogen gas at a flow rate of 30 l / min. The substance to be injected is tetraethyl orthotitanate [Ti (OC2H5) 4], TEOT. The substance to be injected is fed in liquid form to the flamethrower 101 along the liquid passage 105 at a flow rate of 7 ml / min. The liquid to be injected 15 is conveyed along the fluid passage 105 by pumping it with a syringe pump 106.

At the end of the flamethrower is a nozzle 107 in which the combustion gases are ignited to produce a flame 108 and in which the liquid to be injected is sprayed with hydrogen gas.

Liquid droplets are conducted through a gas stream to flame 108 where the starting material forms

TiO2 particles reacting with oxygen, nucleation, sintering and · '· *: agglomerating. The resulting particles are guided toward the impact surface 301, which is operated by a ··· rotating ceramic alumina tube. The impact surface 301 collects from the particle stream 302: ··· # •: * · the large residual particles 112, while the small particles 110 are guided by the gas flow 111 f M t to the thermophoresis unit 303. The thermophoresis unit consists of heated * · ·; from surfaces 304 having a temperature of 1000 ° C and below heated surfaces 304 10 · Ceramic tiles 109. Ceramic tiles can pass either on-line or off-line in the ceramic tile process. The gas flow 111 spreads beyond the impact surface 301 to a wider area, thereby substantially reducing the gas flow rate. 300-700 ° C temperature difference; between the heated surface 304 and the coated surface 109 provides a thermophoretic force that causes the fine particles 110 to pass. the impact surface 301 is heated by the burner 305, whereby the residual particles 112 accumulating on the impact surface 301 on the 771 impact surface 301 are sintered onto the impact surface 301, and thus cannot be detached and transported to the surface to be coated 109. form a photocatalytic, mesoporous surface on the slab surface.

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It will, of course, be apparent to one skilled in the art that the methods, procedures, and apparatus structures described above in connection with various embodiments of the invention are

the combination can provide various embodiments of the invention which are in accordance with the spirit of the invention. Therefore, the foregoing examples are not to be construed as limiting the invention, but embodiments of the invention may vary freely within the scope of the inventive features set forth in the claims below.

It will, of course, also be apparent to one skilled in the art that the accompanying drawings are intended to illustrate the invention, and thus the structures and components shown therein are not drawn in their correct mutual dimensions.

It will, of course, also be apparent to one skilled in the art that the geometries shown are intended to illustrate the invention, and thus, for example, the shape of the object to be coated may be arbitrary and the surfaces to be heated and the surface to be coated? The geometries may substantially differ from the planar surfaces described in the examples.

It is, of course, also apparent to one skilled in the art that the term 'surface to be coated' t ·· · refers to a surface at some particular stage of the process and to a later stage of the process ··· •: *; this surface can be removed, leaving only the coating, the surface can be pasted «·· · 25 to another piece or otherwise treated. For example, in the manufacture of ··· optical fiber reform, the surface to be coated may be a so-called "starter": on top of which a porous glass blank is grown, after which the mandrel can be removed! ***: removed.

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Claims (8)

117790 Ί1 A process for forming a coating, wherein the aerosol particles are formed which are conducted with a gas stream to the surface of the substrate, characterized in that the aerosol particles are first conducted to impact on the impact collector, whereby the thermophoretic force due to the temperature difference ΔΤ between the heated surface and the substrate collects particles smaller than diameter d on the substrate. Method according to Claim 1, characterized in that the aerodynamic diameter d is between 0.1 and 10 micrometers. Method according to Claim 1, characterized in that after the impact collector the gas flow expands substantially, thereby substantially decreasing the gas flow rate. Method according to one of Claims 1 to 3, characterized in that the aerosol particles contain at least one glass coloring compound, the substrate is glass and the ··· aerosol particles diffuse and / or dissolve in the glass to color it. ···· • «* · · ♦ · · · · 1 · The process according to any one of claims 1 to 3, characterized in that the aerosol particles contain at least one compound of the photocatalytic material and the aerosol particles form a photocatalytic surface on the substrate. A method according to any one of claims 1 to 3, characterized in that ··· ** »4. 1 The aerosol particles contain a functional surface forming component, the substrate is glass, ceramic or metal and the coating forms a functional surface substrate. surface. • · · • · • • • · · ♦ ♦ ♦ ·· · fZ., I ': a \ 117790 Apparatus for forming a coating comprising means for generating aerosol particles and means for conveying aerosol particles with a gas stream, characterized in that the device has means for collecting unwanted aerosol particles by a process and means for undesired; for collecting aerosol particles on the substrate by thermophoresis. 4 ^ Process according to Claim 1, characterized in that the aerosol particles are produced by a CVD, PVD, laser ablation, spray pyrolysis, flame spray or liquid spray method. * »» · · · 1 • '· ···········••••••••••••••••••••••••••••••••••• ·· • · * · • 1 · • · · {• 1 · * · · · · »· •« 1! · 1 · • »§ * ·· • 1 · j • · 1 • · * · * · 1. * · ♦ · • »· Φ · • · · · · · 117790 '13