Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-06-02
2004-01-27
Le, H. Thi (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S548000, C428S570000
Reexamination Certificate
active
06682817
ABSTRACT:
CLAIM OF FOREIGN PRIORITY PURSUANT TO 35 U.S.C. §119
This application claims foreign priority under 35 U.S.C. §119 from both Italian Patent Application Serial Number MI99A 001241 filed Jun. 6, 1999, and Italian Patent Application Serial Number MI2000A 000475 filed Mar. 9, 2000, both of which are incorporated herein by reference for all purposes.
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to composite materials capable of selectively sorbing hydrogen without requiring an activation treatment, and to composite materials capable of sorbing hydrogen as well as other gases. The present invention also refers to methods for the production of such materials.
2. Background
In many technologically advanced applications gas sorption is achieved with non-evaporable getter (NEG) materials. NEG materials are most frequently found in two types of applications in particular. In the first type of application a NEG material is used to purify a gas stream by sorbing unwanted species. For example, in the semiconductor industry bothersome species such as hydrogen, oxygen, nitrogen, water, oxides of carbon, and oxides of nitrogen are removed from noble gas streams. Similarly, gases used in the manufacture of certain gas-filled devices such as light bulbs are similarly purified to provide advantages such as improve filament lifetimes.
In the second type of application a NEG material is used to maintain a high degree of vacuum within a sealed enclosure. Processing chambers are common examples of such enclosures in the semiconductor industry. Beyond the semiconductor industry such enclosures can be found in thermal insulation devices such as thermal bottles, dewars, and insulated pipes for oil extraction and for oil transport in arctic and undersea regions. Sealed enclosures for these applications typically consist of an inner wall and an outer wall with an evacuated volume maintained between the two walls. For oil extraction and transport it is frequently necessary to use insulated pipes in order to prevent excessive cooling of the fluid. Such cooling can cause the heavier components of the oil to solidify with a resulting increase in the total viscosity thereof, potentially creating a blockage.
NEG materials include metals such as zirconium and titanium and alloys based on these metals. Such alloys can include one or more other elements selected from amongst the transition metals and aluminum. NEG materials have been the subject of several patents. U.S. Pat. No. 3,203,901 describes Zr—Al alloys, and particularly an alloy whose weight percent composition is Zr 84%—Al 16%, produced and sold by SAES Getters S.p.A., Lainate, Italy, under the name St 101®. U.S. Pat. No. 4,071,335 describes Zr—Ni alloys, and particularly an alloy whose weight composition is Zr 75.7%—Ni 24.3%, produced and sold by SAES Getters S.p.A., Lainate, Italy, under the name St 199™. U.S. Pat. No. 4,306,887 describes Zr—Fe alloys, and particularly an alloy whose weight composition is Zr 76.6%—Fe 23.4%, produced and sold by SAES Getters S.p.A., Lainate, Italy, under the name St 198™. U.S. Pat. No. 4,312,669 describes Zr—V—Fe alloys, and particularly an alloy whose weight percent composition is Zr 70%-V 24.6%—Fe 5.4%, produced and sold under the name St 707®. U.S. Pat. No. 4,668,424 describes Zr—Ni—A—M alloys, where A represents one or more rare earth elements, and M represents one or more elements selected from amongst cobalt, copper, iron, aluminum, tin, titanium, silicon. Patent application EP-A-869,195 describes Zr—Co—A alloys, where A is an element selected from amongst yttrium, lanthanum, the rare earth elements, and mixtures thereof. This patent application particularly discloses an alloy whose weight percent composition is Zr 80.8%—Co 14.2%-A 5%, produced and sold by SAES Getters S.p.A., Lainate, Italy, under the name St 787™. Finally, U.S. Pat. No. 4,457,891 describes Ti—Ni and Ti—V—Mn alloys.
Patent EP-B-291,123 describes the use in lamps of getter materials having Zr—Pd—O compositions, where the palladium is present in molar concentrations between 0.4% and 15% and the molar ratio between oxygen and zirconium is within the range 0.02-1.
The sorption of gases by NEG materials occurs in two steps. The first step is the superficial chemisorption of the gaseous species onto the surface of the NEG material, generally accompanied by the dissociation of the species into its constituent atoms. In the second step the constituent atoms diffuse into the bulk of the NEG material. In the case of hydrogen sorption, as hydrogen atoms spread inside the material they first form solid solutions, even at low temperatures. As the hydrogen concentration increases, hydrides such as ZrH
2
are formed. Therefore, the sorption capacity for hydrogen is high even at low temperatures.
This second step is different for elements such as oxygen, carbon and nitrogen. At relatively low temperatures (generally lower than about 300-500° C. according to the type of the NEG material) only superficial chemisorption occurs and surface layers of oxide, carbide or nitride compounds are formed. These layers effectively block bulk diffusion from occurring. At higher temperatures the oxygen, nitrogen and carbon atoms are able to diffuse into the NEG material, thus regenerating a clean surface for further gas sorption. Therefore, surface cleaning can be achieved continuously by constantly maintaining a NEG material at a sufficiently high temperature. Alternately, the surface of a NEG material maintained at a low temperature can be cleaned by periodically bringing it to a sufficiently high temperature. This latter process is commonly known as an activation treatment, and may be carried out at regular intervals or when a loss of sorption capacity is observed.
However, there are many applications for NEG materials in which the working temperature is at or below room and activation treatments are practically impossible. Such applications include maintaining high vacuum levels in sealed enclosures like those found in thermal bottles, fluorescent lamps, and the insulated pipes used in oil extraction and transport. Another important application of this kind is in batteries, both of the rechargeable kind such as Ni-metal hydride batteries, and of the non rechargeable kind, such as conventional alkaline batteries. As is well known in the art, batteries include an anode, a cathode, and an electrolyte disposed between them, all contained within a casing. Both alkaline and rechargeable batteries, under certain operating conditions, may release hydrogen causing the casing to swell and creating a risk of explosion.
In these low-temperature applications the sorption of relatively small quantities of oxygen, nitrogen or carbon produces a passivating layer on the surface of the NEG material, as previously described, which prevents further gas sorption and reduces the material's sorption capacity to a fraction of its theoretical value. Further, the passivating layer blocks hydrogen sorption which, as already explained, would otherwise occur to a high extent even at room temperature.
In some applications that employ NEG materials the presence of hydrogen can be especially harmful. In the case of thermal insulation applications, this is because hydrogen is the best thermal conductor amongst the various gases. Therefore, hydrogen in an evacuated volume, even in small quantities, notably worsens the thermal insulating property thereof. The presence of hydrogen in the gaseous filling mixture of lamps modifies the discharge conditions, and thus both prevents the lamp from functioning optimally and generally shortens its life. The presence of hydrogen is even more troublesome in the pipes used for oil extraction. In this application, acid solutions containing, for instance, hydrochloric acid, nitric acid, hydrofluoric acid, or mixtures thereof, are passed through the pipe in order to promote the disintegration of rocks wherefrom oil is extracted. However, these acids can cause corrosion of the pipes, forming microperforations and while generat
Boffito Claudio
della Porta Paolo
Toia Luca
Dort David Bogart
Hickman Paul L.
Perkins Coie LLP
SAES Getters S.p.A.
LandOfFree
Composite materials capable of hydrogen sorption comprising... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composite materials capable of hydrogen sorption comprising..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composite materials capable of hydrogen sorption comprising... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3260463