Electricity: electrical systems and devices – Electrolytic systems or devices – Liquid electrolytic capacitor
Reexamination Certificate
2001-11-06
2003-10-28
Bell, Bruce F. (Department: 1746)
Electricity: electrical systems and devices
Electrolytic systems or devices
Liquid electrolytic capacitor
C361S528000, C419S010000, C419S019000, C419S030000, C419S035000, C419S038000, C419S039000, C419S065000, C419S066000, C075S228000, C075S229000, C075S232000, C075S245000, C428S472000, C428S702000, C423S592100, C423S594170, C029S025030
Reexamination Certificate
active
06639787
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to valve metal oxides and more particularly relates to modified oxygen reduced valve metal oxides and methods to prepare the same.
Powders, such as those used as capacitor powders, can typically have poor agglomeration properties which creates problems when the powder needs to be pressed into an anode, for instance.
Other times, powders can have poor flow properties or can have high surface hardness such that the pressing equipment used to press the powders is significantly worn by the surface of the powders. Thus, additives are used with the powders in order to modify the particle surface and thus improve the agglomeration of the particles, increase the flowability of the powders, minimize the wear on the processing equipment, enhance or not degrade post-pressing compact strength, and/or permit the easy removal of the compacted powder. With tantalum metal powders, certain additives may be used to primarily minimize wear since the industry has developed ways to produce agglomerated powders that have acceptable flow and crush strength. With valve metal oxides, such as oxygen reduced niobium oxides, (e.g. NbO), this material is a ceramic-type material with a high surface hardness compared to metals. The ceramic chemistry does not typically allow the rapid sintering to produce agglomerates used in metal processing and the diffusion behavior of ceramics is quite different than metals. Thus, the oxygen reduced valve metal oxides such as oxygen reduced niobium oxides need to be modified in order to provide the proper properties needed to form more commercially acceptable capacitor anodes.
SUMMARY OF THE PRESENT INVENTION
A feature of the present invention is to provide oxygen reduced valve metal oxides that overcome one or more of the above-described difficulties.
A further feature of the present invention is to provide oxygen reduced valve metal oxides that form into capacitor anodes with more beneficial properties.
Additional features and advantages of the present invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims.
To achieve these and other advantages, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to modified oxygen reduced valve metal oxides. The modified oxygen reduced valve metal oxides are preferably coated with at least one additive in order to promote or enhance the processing of the oxygen reduced valve metal oxide in the formation of a capacitor anode.
Preferably, the oxygen reduced valve metal oxide is an oxygen reduced niobium oxide and more preferably contains at least NbO. The additive that is coated onto at least a portion of the surfaces of the oxygen reduced valve metal oxides is preferably a binder or lubricant and more preferably is a binder or lubricant capable of promoting one or more beneficial properties in the formation of a capacitor anode such as good pressability, good flowability, minimizing the wear on pressing equipment, enhance agglomeration of the oxygen reduced valve metal oxides, and the like.
The present invention further relates to a method of forming the modified oxygen reduced valve metal oxides and includes the step of coating at least a portion of the surfaces of the oxygen reduced valve metal oxides with an additive that promotes or enhances the formation of capacitor anodes from the oxygen reduced valve metal oxides. A preferred additive is at least one binder. The coating of the oxygen reduced valve metal oxides can be done a number of ways including spray drying, fluid bed processing, coating by a precipitation or chemical reaction process, or physical mixing of the valve metal oxides with the appropriate additives.
The present invention further relates to capacitor anodes formed from the above-identified modified valve metal oxides.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to oxygen reduced valve metal oxides and further relates to methods of making the same and also relates to capacitor anodes containing the modified oxygen reduced valve metal oxides. In general, the modified oxygen reduced valve metal oxides are oxygen reduced valve metal oxides that are in the presence of at least one additive. Preferably, at least a portion of the surfaces of the oxygen reduced valve metal oxides are coated with at least one additive. More preferably, substantially the entire surface of the oxygen reduced valve metal oxides are coated with at least one additive. As an example, preferably at least 10% of the surface area of the oxygen reduced valve metal oxides are coated with at least one additive and more preferably at least 25% of the surface area, and even more preferably at least 50% of the surface area. Most preferably, at least 75%, or at least 85%, or least 95%, or even 99% or 100%, of the surface area of the oxygen reduced valve metal oxides is coated with at least one additive as described herein.
With respect to the oxygen reduced valve metal oxides, the details of the oxygen reduced valve metal oxides are set forth in the following patents, patent applications, and publications, all of which are incorporated in their entirety by reference herein and form a part of the present application: Ser. No. 09/154,452 filed Sep. 16, 1998; Ser. No. 09/347,990 filed Jul. 6, 1999; Ser. No. 09/533,430 filed Mar. 23, 2000; No. 60/229,668 filed Sep. 1, 2000; Ser. No. 09/758,705 filed Jan. 11, 2001; No. 60/246,042 filed Nov. 6, 2000; Ser. No. 09/816,689 filed Mar. 23, 2001; and PCT Published Application No. WO 00/15556.
Preferably, the oxygen reduced valve metal oxide is a oxygen reduced niobium oxide. Other oxygen reduced valve metal oxides include, but are not limited to, oxygen reduced aluminum oxide, tantalum oxide, titanium oxide, zirconium oxide, vanadium oxide, or combinations thereof.
The shape or size of the oxygen reduced valve metal oxide can be any shape or size. Preferably, the oxygen reduced valve metal oxide is in the form of a powder with a plurality of different size particles. Examples of the type of powders that can be used include, but are not limited to, flaked, angular, nodular, and mixtures or variations thereof. The details of the groups of particles and sizes as mentioned in the above-identified patent and publications can be used in the present application.
The oxygen reduced valve metal oxides can also contain levels of nitrogen, e.g., from about 100 ppm to about 80,000 ppm N
2
or to about 130,000 ppm N
2
. Suitable ranges includes from about 31,000 ppm N
2
to about 130,000 ppm N
2
and from about 50,000 ppm N
2
to about 80,000 N
2
. Other dopants can also be used.
Preferably, the oxygen reduced valve metal oxide is any valve metal oxide which has a lower oxygen content in the metal oxide compared to the starting valve metal oxide. Typical oxygen reduced niobium oxides comprise NbO, NbO
0.7
, NbO
11
, NbO
2
, and any combination thereof with or without other oxides present. Generally, the reduced niobium oxide of the present invention has an atomic ratio of niobium to oxygen of about 1:less than 2.5, and preferably 1:2 and more preferably 1:1.1, 1:1, or 1:0.7. Put another way, the reduced niobium oxide preferably has the formula Nb
x
O
y
, wherein Nb is niobium, x is 2 or less, and y is less than 2.5x. More preferably x is 1 and y is less than 2, such as 1.1, 1.0, 0.7, and the like. This would also preferably apply to other oxygen reduced valve metal oxides.
The oxygen reduced valve metal oxides of the present
Kimmel Jonathon L.
Redd Randall V.
Bell Bruce F.
Cabot Corporation
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