Coating processes – Coating by vapor – gas – or smoke – Mixture of vapors or gases utilized
Reexamination Certificate
1993-06-24
2001-06-05
Beck, Shrive (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Mixture of vapors or gases utilized
C427S255394, C427S255110, C427S166000
Reexamination Certificate
active
06242045
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the preparation of metal nitrides, and more particularly, to the deposition of metal nitride films onto substrates such as glass.
BACKGROUND OF THE INVENTION
Organic and metallic precursors have been used in recent years to prepare advanced coating materials such as titanium nitride, vanadium nitride, boron nitride, tungsten dinitride, etc. These advanced coating materials have advantageously been deposited onto transparent glazings, e.g., glass, by well-known coating processes such as, for example, atmospheric pressure chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), spray pyrolysis, plasma enhanced chemical vapor deposition (PECVD), laser-induced chemical vapor deposition (LCVD), etc. The ultimately produced coated glazings may be used in automotive or architectural applications which require reduced solar and infrared radiation transmittances.
Titanium nitride is a particularly useful advanced material having several desirable properties such as, for example, high hardness (8-9 on the Moh scale), excellent solar and infrared reflectances, and nonreactivity with a variety of corrosive atmosphere.
Titanium nitride films may be deposited onto glass by continuously coating a hot glass ribbon as it is being produced by the well-known float process. Conventional titanium nitride filming methods involve the high temperature reaction of a source of titanium such as, for example, titanium tetrachloride, with ammonia. Such a method is disclosed in U.S. Pat. No. 4,535,000 to Gordon.
Fix, R. M. et al., “Titanium Nitride Thin Films: Properties and APCVD Synthesis Using Organometallic Precursors,” Mat. Res. Soc. Symp. Proc., vol. 158 (1990) pp. 357-362 discloses a method for depositing thin titanium nitride films onto glass, by reacting together tetrakis(dialkylamido)titanium compounds and excess ammonia at about 100° C. to about 400° C. near the surface of the glass.
U.S. Pat. No. 3,784,402 to Reedy, Jr. discloses a method for producing metal carbonitrides. A gaseous stream containing hydrogen, a metal halide such as titanium tetrachloride, and an amine such as ethylene diamine, trimethylamine, or pyridine is reacted near the surface of a titanium metal or titanium nitride substrate. The amine decomposes during the reaction to yield nitrogen and carbon, which thereafter are used in the formation of the carbonitride. The patent also discloses the well-known reaction wherein titanium nitride is formed by the reaction between titanium tetrachloride, nitrogen, and hydrogen.
Finally, U.S. Pat. No. 4,162,338 to Schintlmeister discloses that a titanium carbonitride film may be formed by reacting together a titanium halide, a hydrocarbon gas, and an aliphatic or aromatic amine at a temperature from about 700° C. to about 1,200° C. The patent also discloses that titanium nitride may be formed by reacting together a titanium halide and nitrogen.
The prior art referred to herinabove has been collected and examined only in light of the present invention as a guide. It is not to be inferred that such diverse art would otherwise be assembled absent the motivation provided by the present invention, nor that the cited prior art when considered in combination suggests the present invention absent the teachings herein.
SUMMARY OF THE INVENTION
Accordant with the present invention, a process for preparing metal nitrides has surprisingly been discovered. The process comprises contacting a metal halide with an amine at a temperature sufficient to form a metal nitride.
Also contemplated by the present invention is a process for depositing a metal nitride film onto glass. Preferred metal nitrides according to the present invention are titanium nitride and vanadium nitride.
The processes of the present invention are particularly well suited for preparing solar control automotive and architectural coated glazings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is directed to the preparation of a metal nitride, by reacting together a metal halide and an amine.
The first reactant for use in preparing metal nitrides according to the present invention is a metal halide. Metal halides are compounds well-known to those ordinarily skilled in the chemical arts, and include, without limitation, titanium tetrachloride, titanium tetrabromide, vanadium tetrachloride, boron trichloride, tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride, and the like. Useful metal halides also include compounds containing transition metals from groups 4, 5, and 6, or elements from groups 13, 14, and 15, and halogens, i.e., chlorine, fluoring, bromine, and iodine. Preferred metal halides include titanium tetrachloride and vanadium tetrachloride, useful for depositing films of titanium nitride and vanadium nitride, respectively. Titanium tetrachloride may be prepared by heating a quantity of titanium dioxide or titanium-containing ore along with carbon while passing a stream of chlorine gas thereover. Vanadium tetrachloride may be prepared by chlorinating vanadium metal or ferrovanadium at about 300° C. Further details concerning the manufacture and properties of titanium halides and vanadium halides are more fully set forth in the Kirk-Othmer Concise Encyclopedia of Chemical Technology, John Wiley & Sons, New York (1985) pp. 1185-1186 and 1218-1219.
The second reactant for use in preparing metal nitrides according to the present invention is an amine. Suitable reactants may be primary, secondary, or tertiary amines. Examples of contemplated equivalent amines having the same operability and utility include, without limitation, t-butylamine, isoproplyamine, diethylamine, triethylamine, isobutylamine, ethylenediamine, methylamine, dimethylamine, trimethylamine, ethylamine, n-butylamine, isobutylamine, cyclchexylamine, benzylamine, phenylethylamine, tetramethylenediamine, hexamethylenediamine, aniline, triphenylamine, and the like, as well as mixtures thereof. Useful amines include, but are not limited to, straight or branched alkyl amines containing 1 to about 8 carbon atoms. Preferred amines include t-butylamine and isopropylamine, as well as mixtures thereof.
In a preferred embodiment of the process of the present invention, the metal halide and amine each, individually may be vaporized, and the vapors combined adjacent the surface of a hot glass ribbon to prepare glass having a film of a metal nitride thereon. It is preferred that the amine be present in the reaction zone at a concentration equal to at least about one stoichiometric equivalent of the metal halide. A greater excess of the amine, in the range of at least about ten stoichiometric equivalents, is particularly preferred for producing high quality metal halide films.
It is observed, as has been reported in the prior art referred to hereinabove, that hydrogen, a metal halide, and an amine react together to form a metal carbonitride on a titanium metal or titanium nitride substrate. It has now surprisingly been discovered that a metal halide may be reacted with an amine to produce a substantially carbon-free metal nitride on virtually any substrate. This is unexpected, since amines contain an equal amount or more of carbon in relation to the amount of nitrogen.
While not wishing to be bound by any particular theory regarding the mechanism by which amines react with a metal halide to form a nitride rather than a carbonitride, it is believed that, in the absence of hydrogen in the reaction mixture, the amine displaces a halide atom from the metal halide. For example, titanium tetrachloride loses a chlorine atom, which is transported away as HCl if a primary or secondary amine is used, or as an alkyl chloride if a tertiary amine is used. The resulting amido-titanium compound then eliminates additional halides or alkyl halides to produce, for example, ClTiN. Finally, this compound eliminates the halide atom to produce the metal nitride.
The inventive reaction may be carried out at the surface of a hot glass ribbon, to prepare a film of a substantially c
Proscia James William
Reck Gene P.
Williams Keith Brian
Beck Shrive
Chen Bret
McCoy-Pfau Rhonda L.
Visteon Global Technologies Inc.
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