US2798037A - Aluminum oxide films - Google Patents
Aluminum oxide films Download PDFInfo
- Publication number
- US2798037A US2798037A US354873A US35487353A US2798037A US 2798037 A US2798037 A US 2798037A US 354873 A US354873 A US 354873A US 35487353 A US35487353 A US 35487353A US 2798037 A US2798037 A US 2798037A
- Authority
- US
- United States
- Prior art keywords
- aluminum
- oxide
- oxide films
- aluminum oxide
- films
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/02—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of inorganic substances
- H01B3/10—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of inorganic substances metallic oxides
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C24/00—Coating starting from inorganic powder
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/04—Anodisation of aluminium or alloys based thereon
- C25D11/18—After-treatment, e.g. pore-sealing
- C25D11/20—Electrolytic after-treatment
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/42—Electroplating: Baths therefor from solutions of light metals
- C25D3/44—Aluminium
Definitions
- the present invention relates to a new and improved type of thick, relatively non-porous aluminum oxide film.
- aluminum oxide films have been used for a Variety of purposes in the electronics arts; Perhaps the most important of these uses has been as an insulator between the electrodes of an electrolytic capacitor. Here such films have been extremely advantageous because of their dense character and their high dielectric constant.
- the object of the present invention is to produce a new and improved variety of aluminum oxide film which is characterized by being thicker than, but similar to, the prior art aluminum oxide dielectric films. Further objects of the invention, as well as the advantages of it, will be apparent from the balance of this specification, as well as the appended claims.
- the above aims are achieved by first oxidizing the surface of aluminum electrode in an ionogen, such as oxalic acid, sulfuric acid, phosphoric acid, or the like so as to produce a comparatively porous columnar inert film, then depositing aluminum metal within the pores of the so-produced film, and finally oxidizing the sodeposited metal in an ionogen, such as boric acid, which is capable of forming an extremely dense adherent oxide layer which effectively fills the pores of the first produced oxide.
- an ionogen such as oxalic acid, sulfuric acid, phosphoric acid, or the like
- the extreme simplicity of the present invention makes it extremely difficult to describe in the usual detailed manner.
- the first oxidation treatment is carried out by utilizing usual anodic oxidation procedures and electrolytes, such as oxalic, sulfuric, phosphoric, or the like, which are known to produce comparatively porous oxide films of columnar structure.
- electrolytes such as oxalic, sulfuric, phosphoric, or the like, which are known to produce comparatively porous oxide films of columnar structure.
- voltages up to about 400 volts and current densities of from 5 to about 40 amps. per square centimeter can satisfactorily be employed during this step.
- the temperature of the electrolyte is a comparatively immaterial factor, although it is in general preferred to use temperatures of from about 20 C. up to about the boiling point of the electrolyte.
- the oxide layer is preferably immersed within a plating bath, at approximately room temperature, such as are commonly employed in the deposition of aluminum, and is connected as a cathode in such a bath.
- a suitable electrolytic composition comprises the dispersion of toluene in a toluene solution of a fusion product of ethyl pyridiniumbromide and aluminum chloride with or without additional agents such as methyl-t-butyl ether. More specifically, this plating bath has a composition of 32% by weight of the fusion product of one mol of ethyl pyrldlniumbromide and two mols of aluminum chloride,
- plating baths are well-known to the art and are preferably baths wherein the electrolyte is dissolved in an organic solvent such as pyridine in which electrical deposition can take place at room temperatures.
- organic solvent such as pyridine
- the precise voltages and currents used throughout such deposition are well-known to the art.
- the deposition of the aluminum should be carried out just until the point at which this metal is visible on the surface of the oxide film being treated, when viewed through a comparatively low power microscope, for example, a common microscope of 200 power.
- an aqueous solution of boric acid in which an extremeely dense non-porous oxide film can be obtained in a manner known to the art for the same periods used presently in the formation of oxide films.
- voltages up to about 600 Volts are satisfactory, utilizing an initial current density of 40 amps. per square centimeter, when the electrolyte consists of a saturated solution of boric acid held at its boiling point.
- valve metals such as, for example, tantalum, zirconium, and the like
- adherent dielectric films to be produced on them by the expedient of first depositing a comparatively porous oxide film, then filling the pores of this initial film with a metal, such as the base metal, and then oxidizing the final deposited metal so as to produce an extremely dense adherent film.
- a metal such as the base metal
- the process of forming an insulating layer of oxide upon aluminum comprising the steps of anodically forming a porous layer of oxide upon the aluminum, electrodepositing a coating of aluminum within the pores of the oxide layer, and converting said deposit into the oxide.
Description
United States Patent Office it 2, ,037 Patented July 2, 1957 ALUMINUM OXIDE FILMS Preston Robinson, Williamstown, Mass., assignor to Sprague Electric Company, North Adams, Mass, a corporation of Massachusetts No Drawing. Application May 13, 1953, Serial No. 354,873
3 Claims. (Cl. 204-42) The present invention relates to a new and improved type of thick, relatively non-porous aluminum oxide film. For years, aluminum oxide films have been used for a Variety of purposes in the electronics arts; Perhaps the most important of these uses has been as an insulator between the electrodes of an electrolytic capacitor. Here such films have been extremely advantageous because of their dense character and their high dielectric constant. However, even in this use, it has been desired to obtain films possessing the basic characteristics of aluminum oxide, but which are thicker than the presently used oxide films which do not exceed 1 mil in thickness. With such thicker films, higher voltage applications are made possible.
The object of the present invention is to produce a new and improved variety of aluminum oxide film which is characterized by being thicker than, but similar to, the prior art aluminum oxide dielectric films. Further objects of the invention, as well as the advantages of it, will be apparent from the balance of this specification, as well as the appended claims.
Briefly, the above aims are achieved by first oxidizing the surface of aluminum electrode in an ionogen, such as oxalic acid, sulfuric acid, phosphoric acid, or the like so as to produce a comparatively porous columnar inert film, then depositing aluminum metal within the pores of the so-produced film, and finally oxidizing the sodeposited metal in an ionogen, such as boric acid, which is capable of forming an extremely dense adherent oxide layer which effectively fills the pores of the first produced oxide.
The extreme simplicity of the present invention makes it extremely difficult to describe in the usual detailed manner. The first oxidation treatment is carried out by utilizing usual anodic oxidation procedures and electrolytes, such as oxalic, sulfuric, phosphoric, or the like, which are known to produce comparatively porous oxide films of columnar structure. In general, voltages up to about 400 volts and current densities of from 5 to about 40 amps. per square centimeter can satisfactorily be employed during this step. The temperature of the electrolyte is a comparatively immaterial factor, although it is in general preferred to use temperatures of from about 20 C. up to about the boiling point of the electrolyte.
The deposition of aluminum within the pores of the oxide film produced as set forth in the preceding paragraph is slightly more difficult than the formation of the initial oxide layer. To accomplish the deposition, the oxide layer is preferably immersed within a plating bath, at approximately room temperature, such as are commonly employed in the deposition of aluminum, and is connected as a cathode in such a bath. A suitable electrolytic composition comprises the dispersion of toluene in a toluene solution of a fusion product of ethyl pyridiniumbromide and aluminum chloride with or without additional agents such as methyl-t-butyl ether. More specifically, this plating bath has a composition of 32% by weight of the fusion product of one mol of ethyl pyrldlniumbromide and two mols of aluminum chloride,
67% of toluene and 1% of methyl-t-butyl ether. Other plating baths are well-known to the art and are preferably baths wherein the electrolyte is dissolved in an organic solvent such as pyridine in which electrical deposition can take place at room temperatures. The precise voltages and currents used throughout such deposition are well-known to the art. In general, the deposition of the aluminum should be carried out just until the point at which this metal is visible on the surface of the oxide film being treated, when viewed through a comparatively low power microscope, for example, a common microscope of 200 power. Further deposition of the aluminum is apt to destroy the advantageous results obtained by, in effect, creating a second layer of aluminum on top of the initial base oxide layer; the second layer of aluminum then being converted to an oxide film of normal thickness. For certain applications, a floating electrode structure of this type may be desirable, but such ramifications are outside the broad scope of the present invention.
Following the aluminum deposition procedure specified in the preceding paragraph, a final oxide film is produced by immersing the coated aluminum body in an electrolyte,
such as an aqueous solution of boric acid, in which anextremely dense non-porous oxide film can be obtained in a manner known to the art for the same periods used presently in the formation of oxide films. In general, in the formation of this second oxide film, voltages up to about 600 Volts are satisfactory, utilizing an initial current density of 40 amps. per square centimeter, when the electrolyte consists of a saturated solution of boric acid held at its boiling point.
It is contemplated that the broad teachings of the present inventive concept will be extended to other valve metals, such as, for example, tantalum, zirconium, and the like, and to extremely thick adherent dielectric films to be produced on them by the expedient of first depositing a comparatively porous oxide film, then filling the pores of this initial film with a metal, such as the base metal, and then oxidizing the final deposited metal so as to produce an extremely dense adherent film. It is to be understood that within the confines of this invention, it is substantially immaterial whether the second metal used to fill the pores of the first oxide layer is the same or another valve metal as the initial base material.
It is further contemplated that the broad teachings of the invention as developed by further experimentation will show that extremely advantageous aluminum oxide and other valve metal oxide films can be obtained by first oxidizing these metals to produce a porous oxide layer, then orienting the initial oxide films, as by the use of electric field of reasonably high intensity, and then finally forming an extremely dense oxide layer as described above within the pores of the so-oriented initial porous oxide layer without the use of a second metal to fill the pores of the first layer.
As many apparently widely different embodiments of my invention may be made without departing from the spirit and scope hereof, it is to be understood that my invention is not limited to the specific embodiments hereof except as defined in the appended claims.
What is claimed is:
l. The process of forming an insulating layer of oxide upon aluminum comprising the steps of anodically forming a porous layer of oxide upon the aluminum, electrodepositing a coating of aluminum within the pores of the oxide layer, and converting said deposit into the oxide.
2. The process of forming a heavy insulating layer of oxides upon an aluminum comprising the steps of anodically oxidizing the aluminum at a voltage of up to about 400 volts and a current density of from about 5 to about 40 amperes per square centimeter, plating a coating of References Cited in the file of this patent UNITED STATES PATENTS Work July 10, 1934 Fischer Apr. 7, 1936 Lilienfeld Apr. 13, 1937 Rankin et a1. June 6, 1939 Cohn Dec. 11, 1951
Claims (1)
1. THE PROCESS OF FORMING AN INSULATING LAYER OF OXIDE UPON ALUMINUM COMPRISING THE STEPS OF ANODICALLY FORMING A POROUS LAYER OF OXIDE UPON THE ALUMINUM, ELECTRODEPOSITING A COATING OF ALUMINUM WITHIN THE PORES OF THE OXIDE LAYER, AND CONVERTING SAID DEPOSIT INTO THE OXIDE.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US354873A US2798037A (en) | 1953-05-13 | 1953-05-13 | Aluminum oxide films |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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US354873A US2798037A (en) | 1953-05-13 | 1953-05-13 | Aluminum oxide films |
Publications (1)
Publication Number | Publication Date |
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US2798037A true US2798037A (en) | 1957-07-02 |
Family
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Family Applications (1)
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US354873A Expired - Lifetime US2798037A (en) | 1953-05-13 | 1953-05-13 | Aluminum oxide films |
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Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3287862A (en) * | 1964-11-30 | 1966-11-29 | William J Abernathy | Abrasive articles and method of making abrasive articles |
US3287861A (en) * | 1964-03-06 | 1966-11-29 | Thiokol Chemical Corp | Abrasive articles and method of making abrasive articles |
US3388050A (en) * | 1965-09-07 | 1968-06-11 | Horizons Inc | Anodized aluminum alloy product |
US3793106A (en) * | 1969-12-31 | 1974-02-19 | Macdermid Inc | Process for forming plastic parts having surfaces receptive to adherent coatings |
US3929594A (en) * | 1973-05-18 | 1975-12-30 | Fromson H A | Electroplated anodized aluminum articles |
US4021592A (en) * | 1974-03-07 | 1977-05-03 | Fromson H A | Process of making electroplated anodized aluminum articles and electroless plating |
US4110147A (en) * | 1976-03-24 | 1978-08-29 | Macdermid Incorporated | Process of preparing thermoset resin substrates to improve adherence of electrolessly plated metal deposits |
US4914081A (en) * | 1988-01-15 | 1990-04-03 | American Telephone And Telegraph Company, At&T Bell Laboratories | Process for making metallized structure and article comprising structure |
US20160002805A1 (en) * | 2013-02-19 | 2016-01-07 | Alumiplate, Inc. | Hard aluminum films formed using high current density plating |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1965683A (en) * | 1932-01-26 | 1934-07-10 | Aluminum Colors Inc | Coating aluminum |
US2036962A (en) * | 1930-11-07 | 1936-04-07 | Siemens Ag | Method for production of firmly adhering galvanic coatings on aluminum and aluminum alloys |
US2076904A (en) * | 1931-08-29 | 1937-04-13 | Magnavox Co | Filming metal coatings and method of forming the same |
US2161636A (en) * | 1936-10-21 | 1939-06-06 | Gen Electric | Method of protectively coating aluminum or aluminum alloys |
US2578400A (en) * | 1947-03-29 | 1951-12-11 | Charles C Cohn | Method for providing oxide coating on aluminum and its alloys |
-
1953
- 1953-05-13 US US354873A patent/US2798037A/en not_active Expired - Lifetime
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2036962A (en) * | 1930-11-07 | 1936-04-07 | Siemens Ag | Method for production of firmly adhering galvanic coatings on aluminum and aluminum alloys |
US2076904A (en) * | 1931-08-29 | 1937-04-13 | Magnavox Co | Filming metal coatings and method of forming the same |
US1965683A (en) * | 1932-01-26 | 1934-07-10 | Aluminum Colors Inc | Coating aluminum |
US2161636A (en) * | 1936-10-21 | 1939-06-06 | Gen Electric | Method of protectively coating aluminum or aluminum alloys |
US2578400A (en) * | 1947-03-29 | 1951-12-11 | Charles C Cohn | Method for providing oxide coating on aluminum and its alloys |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3287861A (en) * | 1964-03-06 | 1966-11-29 | Thiokol Chemical Corp | Abrasive articles and method of making abrasive articles |
US3287862A (en) * | 1964-11-30 | 1966-11-29 | William J Abernathy | Abrasive articles and method of making abrasive articles |
US3388050A (en) * | 1965-09-07 | 1968-06-11 | Horizons Inc | Anodized aluminum alloy product |
US3793106A (en) * | 1969-12-31 | 1974-02-19 | Macdermid Inc | Process for forming plastic parts having surfaces receptive to adherent coatings |
US3929594A (en) * | 1973-05-18 | 1975-12-30 | Fromson H A | Electroplated anodized aluminum articles |
US4021592A (en) * | 1974-03-07 | 1977-05-03 | Fromson H A | Process of making electroplated anodized aluminum articles and electroless plating |
US4110147A (en) * | 1976-03-24 | 1978-08-29 | Macdermid Incorporated | Process of preparing thermoset resin substrates to improve adherence of electrolessly plated metal deposits |
US4914081A (en) * | 1988-01-15 | 1990-04-03 | American Telephone And Telegraph Company, At&T Bell Laboratories | Process for making metallized structure and article comprising structure |
US20160002805A1 (en) * | 2013-02-19 | 2016-01-07 | Alumiplate, Inc. | Hard aluminum films formed using high current density plating |
US10000859B2 (en) * | 2013-02-19 | 2018-06-19 | Alumiplate, Inc. | Hard aluminum films formed using high current density plating |
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