KR20130099065A - Methods for in situ deposition of coatings and articles produced using same - Google Patents

Abstract

According to the present invention a method for depositing a coating on a metal surface comprises heating the metal surface to a temperature below the melting point of the metal; Applying a vacuum while heating the metal surface; And releasing said vacuum and refilling with a first purge gas while heating said metal surface, wherein said first purge gas may react with said heated metal surface, thereby providing at least one on said surface. The coating layer is deposited. The method of the present invention can be used to deposit a coating in situ in the manufacture of a solar absorber, the solar absorber comprising an annular body defined by a metal tube as the inner surface and a material at least partially transparent to solar radiation as the outer surface. Have

Description

METHODS FOR IN SITU DEPOSITION OF COATINGS AND ARTICLES PRODUCED USING SAME}

The present invention relates generally to coatings, more particularly to methods of making the coatings.

Cross reference of related application

This application claims the benefit of 35 U.S.C. In accordance with §119, claims priority based on U.S. Provisional Patent Application 61 / 385,899, filed September 23, 2010, the contents of which are incorporated herein by reference in their entirety.

Statement on research and development under federal sponsorship

Not applicable

Coatings are commonly used in a variety of applications to protect the material under the coating from exposure to the surrounding environment, and / or to alter other physical properties of the material under the coating. Physical properties that can be altered by the coating include, but are not limited to, optical, thermal, and mechanical properties. More specifically, the thermal and electromagnetic absorptivity and release of the article can be greatly affected by the presence of a layer so thin that it is deposited on its surface.

Several different techniques have been developed for depositing thin layer coatings. Such techniques may include, for example, sputtering, evaporative deposition, pulsed laser desorption, electroplating, electroless plating, chemical vapor deposition, and the like. In the manufacture of articles, most of these coating techniques must be performed separately from other manufacturing steps used to make articles. In addition, many of these deposition techniques may require special equipment, thus increasing the time and cost required to fabricate articles with a coating.

In view of this situation, simple and low cost techniques for the manufacture of coatings, in particular for the manufacture of coatings in the manufacture of articles, will be of substantial benefit to the art. It is an object of the present invention to meet these needs and to provide advantages associated with them.

In some embodiments, described herein are methods of depositing a coating on a metal surface. The method includes heating a metal surface to a temperature below the melting point of the metal; Applying a vacuum while heating the metal surface; And releasing the vacuum and backfilling with a first purge gas while heating the metal surface. The first purge gas may react with the heated metal surface, thereby depositing one or more coating layers on the surface.

In some embodiments, described herein are methods of depositing a coating on a solar receiver. The method includes applying a vacuum to an annulus having an outer surface defined by a material that is at least partially transparent to solar radiation and an inner surface defined by a metal tube; Heating the metal tube to a temperature equal to or lower than the melting point while a vacuum is applied to the metal tube; And releasing the vacuum and refilling with the first purge gas while heating the metal tube, wherein the first purge gas can react with the heated metal tube, thereby depositing one or more coating layers on the surface thereof. .

In some embodiments, the solar heat absorber comprises: applying a vacuum to an annulus having an outer surface defined by a material that is at least partially transparent to solar radiation and an inner surface defined by a metal tube; Heating the metal tube to a temperature below the melting point of the metal tube while the vacuum is applied to the metal tube; And releasing the vacuum and refilling with the first purge gas while heating the metal tube, wherein the first purge gas can react with the heated metal tube, so that at least one coating layer is deposited on the surface thereof. It can be manufactured by the method.

As described above, the features of the present invention have been described in a general way so that the following detailed description can be better understood. In the following, further features and advantages of the invention will be described which form the subject of the claims.

According to the present invention, there is provided a method in which a coating can be deposited in a simple process and at low cost in the manufacture of an article.

For a more complete understanding of the invention and its advantages, reference may be made to the following description in conjunction with the accompanying drawings which illustrate certain embodiments of the invention.
1 is a schematic diagram of a solar heat absorber.

The invention relates in part to a method of depositing a coating on a metal surface. The invention also relates, in part, to the metal surface on which the coating is deposited, in particular the solar absorber.

Coatings are often used with a great deal of utility in a wide variety of applications, but the deposition techniques of the coatings place considerable burdens on the time and cost required to produce the article with the coating. The method described herein solves this drawback in the art by providing a simple technique for making a coating on a metal surface. More specifically, in certain cases, the coating methods described herein can be used to deposit a coating on a metal surface in situ. That is, during the manufacture of the article, the coating can be advantageously applied to the article using a method of simply changing at least some of the tasks conventionally used for the manufacture of the article. For example, when vacuum bakeout (eg, hydrogen bakeout) is used in the manufacture of the article, a coating may be applied to the article in accordance with the present invention.

One example of an article with a metal surface on which a coating may be deposited in situ in the manufacture of the article is a solar absorber. 1 shows an overview of an exemplary solar absorber 100. The solar absorber 100 can be used as a thermal energy collector in a parabolic trough solar absorber array, where the solar absorber 100 can absorb thermal energy from focused solar radiation while As much heat as possible. The illustrated solar absorber 100 has an inner metal tube 110, which is a heat transfer fluid (e.g., a high boiling point such as oil) that flows through the inner space to transport the collected heat from the solar absorber 100 to the outside. Viscous fluid). In order to maximize the amount of heat collected and to reduce heat dissipation, the inner metal tube 110 is typically surrounded by a vacuum. To this end, the solar heat absorber 100 has an outer surface 120 (eg glass) that is at least partially transparent to solar radiation, the outer surface defining the annular body 115 with the inner metal tube 110 and vacuuming. Accept. Vacuum may be applied to the annular body 115 through a port 130. Most often, the inner metal tube 110 is deformed by a coating that increases the absorptivity.

In the fabrication of typical solar absorbers, a vacuum is applied to the annulus 115 to achieve outgassing and desorption of species that can lower the applied vacuum and potentially change the heat absorption rate. Meanwhile, the inner metal tube 110 is heated using a heater (not shown). However, according to the embodiment described in the present invention, instead of sealing the annular body 115 to maintain the vacuum therein, the annular body 115 is refilled with purge gas while releasing the vacuum and heating the inner metal tube 110. It has been found that vacuum can be applied to the inner metal tube 110 in situ. The fabrication of the solar absorber 100 can then be completed by simply applying the vacuum back to the annulus 115 and then sealing to maintain the vacuum. Thus, the method of the present invention provides an opportunity to simply deform the surface of the inner metal tube 110 by coating by simply modifying existing work for the fabrication of solar absorbers.

As used herein, the term "vacuum" means any pressure below atmospheric pressure. Unless otherwise specified, the term vacuum should not be interpreted to be a vacuum of any particular size. In some embodiments, a suitable vacuum may be about 1 × 10 ⁻⁵ torr or less. In other embodiments, a suitable vacuum may be about 1 × 10 ⁻⁶ torr or less.

The term "coating" as used herein refers to a material on a metal surface having a thickness that is one or more monolayers. Examples of coatings that can be applied to metal surfaces according to the methods described herein include, but are not limited to, metal oxide coatings, metal nitride coatings, metal carbide coatings, and metal fluoride coatings. Unless otherwise specified, the term coating is not to be interpreted as being any particular type of coating or any particular number of layers in the coating.

In some embodiments described herein, a method of depositing a coating on a metal surface includes heating the metal surface to a temperature below the melting point of the metal; Applying a vacuum while heating the metal surface; And while heating the metal surface, releasing the vacuum and depositing one or more coating layers on the metal surface by refilling with a first purge gas that can react with the heated metal surface.

In general, any type of metal surface can also be modified with a coating according to the embodiments described herein. In this connection, both pure metals and metal alloys can be used. In various embodiments, suitable metals may include, without limitation, titanium, copper, iron, aluminum, tungsten, and any combination thereof. One skilled in the art can also consider using other suitable metals. In some embodiments, the metal surface may be polished to remove oxides present on the surface to facilitate deposition of the coating. In some embodiments, the metal surface may be a metal tube, such as in a solar absorber. In particular, in the case of metal tubes used in solar heat absorbers, steel such as stainless steel, carbon steel or a combination thereof may be used.

Although certain embodiments of the present invention have been described in connection with solar absorbers, it should be understood that any type of article with a metal surface may be modified with a coating according to the embodiments described herein. In other words, the description herein of solar absorbers is illustrative in nature and should be construed as non-limiting. More specifically, any type of article having a metal surface can be heated directly to the metal surface (eg, through openings in the annulus, cavity, etc. of the article) or indirectly (eg, vacuum). Can be transformed into a coating according to the embodiments described herein by applying a vacuum) by placing the article or part of the article in a heating device such as a vacuum furnace, which can be placed in a state and then refilled with purge gas. You have to understand.

In various embodiments, a method of depositing a coating on a metal surface of a solar absorber comprises vacuuming an annulus having an outer surface defined by a material that is at least partially transparent to solar radiation and an inner surface defined by a metal tube. Applying; Heating the metal tube to a temperature equal to or lower than the melting point while a vacuum is applied to the metal tube; And while heating the metal tube, releasing the vacuum, refilling with a first purge gas capable of reacting with the heated metal tube to deposit one or more coating layers on the surface.

In the case of solar absorbers, various materials can be used to form the outer surface of the annulus. In general, the material forming the outer surface of the annulus should be at least partially transparent to solar radiation such that solar radiation can be clamped to the inner surface defined by the metal tube. In addition, the material forming the outer surface of the annulus should typically be at least somewhat resistant to deformation upon heating, since significant heat can be generated if solar energy is focused on the solar absorber. to be. In some embodiments, it may be glass that is suitable as a material that is at least partially transparent to solar radiation. In some embodiments, the glass may further comprise an anti-reflection coating adapted to minimize reflection from the glass to maximize the amount of solar radiation transmitted to the metal tube.

After depositing a coating on the metal tube surface of the solar absorber according to the methods described herein, fabrication of the solar absorber can be completed simply by continuing with the standard fabrication process. To this end, in some embodiments, after heating the metal tube after depositing the coating, the method may further comprise applying a vacuum back to the annulus. In some embodiments, the method may further include sealing the annulus to maintain a vacuum therein and completing the fabrication of the solar absorber. In another embodiment, one or more additional coatings of metal tube surfaces may be deposited by repeating the methods described herein.

In some embodiments, one or more additional coating layers can be deposited by repeating the processes of the methods described herein. In some embodiments of the method of the present invention, after depositing the coating, the vacuum may be reapplied while heating the metal surface. In some embodiments of the method of the present invention, one or more additional coating layers may be deposited by releasing the vacuum and refilling with the second purge gas.

In some embodiments, the first purge gas and the second purge gas can be the same. That is, in some embodiments, the coating may contain all of the layers of the same multilayer. In other embodiments, the first purge gas and the second purge gas can be different. That is, in some embodiments, the coating may contain a plurality of layers that differ in at least some layers. By repeating the process of the method of the present invention, any number of layers, for example 1 to about 100, 1 to about 20, 1 to about 10, 1 to about 5, or 1 Coatings with two, two, two, four, five, six, seven, eight, nine, or ten layers can be deposited. In embodiments where multiple layers are present, various coating layers may impart different properties to the metal surface. For example, the first layer can enhance the electromagnetic absorption of the metal surface and the second layer of different material can reduce the heat release of the metal surface.

Various types of coatings may be formed on the metal surface according to the embodiments described herein. In some embodiments, the coating can include one or more of, for example, an oxide coating, a nitride coating, a carbide coating, or a fluoride coating. The type of coating formed on the metal surface can be selected depending on the intended use and will be apparent to those skilled in the art. For example, an oxide coating can be formed by reacting a metal surface with an oxygen-containing purge gas under heating conditions. A nitride coating can be formed by reacting a metal surface with a nitrogen-containing purge gas, in particular molecular nitrogen, under heating conditions. Carbide coatings may be formed by reacting metal surfaces with, but not limited to, carbon-containing purge gases comprising organic compounds. The fluoride coating may be formed by reacting a metal surface with a fluorine-containing purge gas, in particular hydrogen fluoride, under heating conditions. Those skilled in the art can easily envision other types of coatings.

Various purge gases and combinations thereof can be used in the embodiments described herein. It should be noted that a purge gas suitable for use in embodiments of the present invention may be a material that is a gas at room temperature and pressure, or a liquid or solid that easily evaporates with a high vapor pressure to form a gaseous phase. Examples of purge gases suitable for use in embodiments of the present invention include air, water vapor, oxygen, carbon dioxide, carbon monoxide, nitrogen, fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, boron trifluoride , Boron trichloride, boron tribromide, silicon tetrafluoride, sulfur hexafluoride, sulfur tetrafluoride, phosphorus trifluoride, phosphorus fluoride, nitrogen trifluoride, nitrous oxide, nitrogen oxide, nitrogen dioxide, dinitrogen tetroxide, diimide, Hydrogen, gaseous organic compounds, and any combination thereof.

In some embodiments, the purge gas may further include a diluent gas that is not reactive with the metal surface. In some embodiments, the diluent gas can be an inert gas such as helium, argon, krypton or xenon. When present, the diluent gas may be present in an amount ranging from about 0.1% to about 99.9% of the gas mixture, including all subranges of this amount. In some embodiments, the diluent gas may be present in an amount in the range of about 1% to about 90%, or about 5% to about 50%, or about 10% to about 70% of the gas mixture. While not wishing to be bound by theory or mechanism, it is believed that the thickness of the coating on the metal surface can be controlled by controlling the amount of purge gas present to react with the metal surface and increasing or decreasing the amount of diluent gas.

The thickness of the coating on the metal surface can vary over a significant range. In some embodiments, the thickness of each coating layer on the metal surface may range from about 1 nm to about 1 μm, and includes all subranges of this thickness. In some embodiments, the thickness of each coating layer on the metal surface is from about 1 nm to about 250 nm, or from about 1 nm to about 100 nm, or from about 5 nm to about 50 nm, or from about 5 nm to about 100 nm, or from about 10 nm to about 50 nm. It can be a range. That is, the coating may have a nanostructure in at least some embodiments.

Temperatures suitable for practicing embodiments of the invention can also vary over a wide range. As will be appreciated by those skilled in the art, the ultimate temperature range within which embodiments of the invention may be practiced will depend primarily on the melting point of the selected metal surface. Except for low melting metals (eg, metals having melting points below about 800 ° C., such as aluminum), temperatures suitable for practicing embodiments of the invention include subranges, ranging from about 200 ° C. to about 1000 ° C. It can vary over a range. In some embodiments, a suitable temperature may range from about 400 ° C to about 800 ° C. In other embodiments, a suitable temperature may range from about 300 ° C to about 600 ° C. In some embodiments, a suitable temperature may be at least about 400 ° C. In other embodiments, suitable temperatures may be at least about 500 ° C, or at least about 600 ° C, or at least about 700 ° C, or at least about 800 ° C, or at least about 900 ° C, or at least about 1000 ° C. It should also be appreciated that factors other than the melting point of the metal surface can also influence the selection temperature at which embodiments of the invention may be practiced. For example, certain purge gases may be flammable or explosive or unstable if the temperature is too high. Therefore, the temperature at which a particular coating is made in accordance with an embodiment of the present invention will be a matter of routine experimental design that falls within the capabilities of those skilled in the art.

In some embodiments, the purge gas may be subjected to a preheating process before being refilled in a vacuum around the metal surface. Reasons for preheating the purge gas may include, but are not limited to, a reason to prevent the purge gas from cooling due to adiabatic expansion that occurs upon refilling the vacuum space. Cooling of the purge gas can potentially affect the reaction of the purge gas with the heated metal surface.

Although the present invention has been described with reference to the disclosed embodiments, those skilled in the art will readily understand that such embodiments are merely illustrative of the present invention. It should be understood that various modifications may be made without departing from the spirit of the invention. The specific embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent ways that will be apparent to those skilled in the art. Also, no limitations are intended to the details of construction or design herein except as set forth in the claims below. Accordingly, the particular illustrative embodiments disclosed above may be altered, combined or modified, and all such variations are considered to be included within the scope and spirit of the invention. Although compositions and methods are described in terms of "comprising" or "containing" various components or steps, the compositions and methods may be "consisting essentially of" or "consisting of" the various components and processes. . All numbers and ranges disclosed above may vary to some extent. In any case where a numerical range with a lower limit and an upper limit is disclosed, all numbers and subranges falling within the broader range are specifically disclosed. In addition, the terms described in the claims have the plain and ordinary meaning of such terms, unless expressly defined otherwise by the patentee. In the event of a conflict between the use of a word or term in this specification and one or more patents or other documents that may be incorporated herein by reference, a definition consistent with this specification should be adopted.

Claims (25)

Heating the metal surface to a temperature below the melting point of the metal;
Applying a vacuum while heating the metal surface; And
While heating the metal surface, releasing the vacuum and backfilling with a first purge gas
Including;
The first purge gas may react with the heated metal surface, such that one or more coating layers are deposited on the surface.
Method of Deposition of Coatings on Metal Surfaces. The method of claim 1,
After depositing said coating, further comprising reapplying a vacuum while heating said metal surface. The method of claim 2,
While heating the metal surface, further comprising depositing one or more additional coating layers by releasing the vacuum and refilling with a second purge gas. The method of claim 3,
And the first purge gas and the second purge gas are the same. The method of claim 3,
And the first purge gas and the second purge gas are different. The method of claim 1,
And the heating temperature is about 400 ° C. or greater. The method of claim 1,
The first purge gas is air, water vapor, oxygen, carbon dioxide, carbon monoxide, nitrogen, fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, boron trifluoride, boron trichloride, boron tribromide, tetra Silicon fluoride, sulfur hexafluoride, sulfur tetrafluoride, phosphorus trifluoride, phosphorus pentafluoride, nitrogen trifluoride, nitrous oxide, nitrogen oxide, nitrogen dioxide, dinitrogen tetroxide, diimide, hydrogen, gaseous organic compounds and any of these Selected from the group consisting of The method of claim 1,
And the coating comprises at least one of an oxide coating, a nitride coating, a carbide coating or a fluoride coating. The method of claim 1,
And a diluent gas in which said first purge gas does not react with said metal surface. Applying a vacuum to an annulus having an outer surface defined by a material that is at least partially transparent to solar radiation and an inner surface defined by a metal tube;
Heating the metal tube to a temperature equal to or lower than the melting point while a vacuum is applied to the metal tube; And
While heating the metal tube, releasing the vacuum and recharging with a first purge gas
Including;
The first purge gas may react with the heated metal tube, such that at least one coating layer is deposited on the surface thereof.
A method of depositing a coating on a solar receiver. The method of claim 10,
After depositing the coating, further comprising reapplying a vacuum to the annulus while heating the metal tube. 12. The method of claim 11,
Sealing the annulus such that a vacuum therein is maintained. 12. The method of claim 11,
While heating the metal tube, further comprising depositing one or more additional coating layers by releasing the vacuum and refilling with a second purge gas. The method of claim 13,
And the first purge gas and the second purge gas are the same. The method of claim 13,
And the first purge gas and the second purge gas are different. The method of claim 10,
And the material comprises glass that is at least partially transparent to solar radiation. The method of claim 10,
And the heating temperature is about 400 ° C. or higher. The method of claim 10,
The first purge gas is air, water vapor, oxygen, carbon dioxide, carbon monoxide, nitrogen, fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, boron trifluoride, boron trichloride, boron tribromide, tetra Consisting of silicon fluoride, sulfur hexafluoride, sulfur tetrafluoride, phosphorus trifluoride, phosphorus pentafluoride, nitrogen trifluoride, nitrous oxide, nitrogen oxide, nitrogen dioxide, dinitrogen tetraoxide, diimide, hydrogen, a gaseous organic compound and any combination thereof Selected from the group. The method of claim 10,
Wherein the coating comprises at least one of an oxide coating, a nitride coating, a carbide coating or a fluoride coating. The method of claim 10,
And the diluent gas does not react with the metal purge. The method of claim 10,
And said metal tube is selected from the group consisting of carbon steel, stainless steel, and any combination thereof. A solar heat absorber produced by the method of claim 10. The method of claim 22,
And a heat transfer fluid located within the interior space of the metal tube. The method of claim 22,
Wherein said coating comprises at least one of an oxide coating, a nitride coating, a carbide coating or a fluoride coating. The method of claim 22,
A solar absorber, wherein said coating comprises a nanostructured coating.

Images