Abstract:
A method for producing a superconductor by partial inter diffusion of layers of metal under a diffusion heat treatment to provide a ductile beta phase alloy, along with undiffused metal layers to permit ease of extrusion and drawing to fine layer thickness. At some point in the reduction the layers are further diffused to give an alloy superconducting product which is optimal for the high field (5-9 T) of interest in contact with a non-superconducting layer. This optimal diffusion is preferably accomplished after a sufficient reduction such that the individual metal layers are 2.5-15 microns thick.
Abstract:
Porous metal compacts suitable for use as electrodes are formed through the reduction of a metal billet consisting of multiple filaments of an appropriate valve metal, preferably tantalum, contained within, and spaced apart by, a ductile metal, preferably copper. The filaments are elongated and substantially parallel within the billet. The array of valve metal filaments within the billet is surrounded by a continuous layer of valve metal. This metal is preferably, but not necessarily, the same as that which forms the filaments. The valve metal layer preferably completely surrounds the filament array circumferentially and runs the full length of the filaments. The layer is separated from the array by the same ductile metal that serves to separate the filaments from each other. This same ductile metal forms the surface of the billet, preventing exposure of the valve metal layer. The billet is reduced by conventional means, such as extrusion and wire drawing, the composite product is cut into short lengths, and the ductile metal separating the valve metal components of the composite is removed, preferably by leaching in mineral acids. The filaments are constrained within the valve metal tube, making handling during subsequent capacitor manufacture much less difficult than if the filaments were allowed to move freely.
Abstract:
A method for producing a superconductor includes the steps of combining a plurality of metal bodies to form a composite structure, metal bodies being selected from transition metals such as niobium, tantalum, titanium, zirconium, hafnium and vanadium, alternate bodies being formed of different transition metals to form triplets. The transition metals are reacted to form a ductile superconducting ternary alloy at the interfaces of these triplets of metals. The extent of the reaction is limited so as to maintain areas of pure or nearly pure transition metal along with the superconducting ternary alloy in at least one of each triplet of transition metals.
Abstract:
A high field superconductor is formed of an A-15 superconductor in the form of a layer thinner than 1000.ANG.. This layer is carried by a support layer formed of a normal metal, the support layer having a thickness less than 1000.ANG..
Abstract:
A superconductor which is superconducting of a predetermined high field and low temperature is formed by combining a plurality of metal bodies to form a composite structure. The metal bodies are selected from transition metals such as niobium, tantalum, zirconium, hafnium and vanadium, and alloys of such metals, alternate bodies being formed of ductile alloys of the metals which are not superconducting at the predetermined high field. The alternate bodies of transition metals are reacted to form a ductile superconducting ternary alloy zone at the interfaces of these bodies. The extent of the reaction is limited so as to maintain areas of transition metal and transition metal alloys which are not superconducting at the high field. The composite structure is reduced sufficiently that each non superconducting zone is less than 1000A.degree. thick and serves as an artificial pinning site for each adjacent superconducting zone.
Abstract:
In a preferred form of the invention, a superconductor is produced by the steps of combining a plurality of layers of metal sheets to form a composite structure. The sheets are pure transition metals--niobium, titanium, zirconium, or vanadium, alternate sheets being formed of different transition metals. The resulting composite structure is mechanically reduced sufficiently so that each transition metal sheet is less than 1000 .ANG. thick. In the course of reduction, the composite is subjected to sufficient temperatures for sufficient times such that the transition metal layers are partially reacted to form a ductile superconducting material between the transition metal layers. Approximately one half by volume of the transition metal layers remain unreacted. These unreacted layers afford efficient flux pinning within the composite when the layers are reduced to the
Abstract:
Artifical pinning centers are provided in normal metal layers adjacent to a type II superconductor layer produced by reacting two normal metal layers. The transverse thicknesses of the final superconductor and normal metal layers are less than about 1000 A.degree.. Planar layers of metal which are to provide a multilayer wire whose layers are parallel. A plurality of the multilayer wires are combined to produce a multifilament superconductor, the layers in all the individual wires being parallel to each other.
Abstract:
In the present invention, a superconductor is produced by the steps of wrapping a plurality of layers of metal sheets around a support to form a composite structure. The sheets are pure transition metals-13 niobium, titanium, zirconium, or vanadium, for example--alternate sheets being formed of different transition metals. The support may be composed of any ductile metal. The resulting composite structure is mechanically reduced sufficiently so that each transition metal sheet is less than 1000 .ANG. thick. In the course of reduction, the composite is subjected to sufficient temperatures for sufficient times such that the transition metal layers are partially reacted to form a ductile superconducting material between the transition metal layers. Approximately one half by volume of the transition metal layers remain unreacted. These unreacted layers afford efficient flux pinning within the composite when the layers are reduced to the
Abstract:
A method for making superconducting material useful for forming electrolytic devices comprising the steps of establishing multiple valve metal rods in a primary billet of a ductile material; working the primary billet to a series of reduction steps to form said valve metal rods into a plurality of elongated elements surrounded at least in part by the ductile material; cutting the elongated elements from step (b) and bundling the cut elements to form a secondary billet; working the secondary billet through a series of reduction steps followed by rolling to final thickness; removing the ductile material, whereby to leave valve metal elongated fibers; and sintering the elongated fibers from step (e) under vacuum.
Abstract:
Compositions and methods for protecting a plant from an insect pest are provided. In particular, nucleic acid sequences encoding insect protoxins modified to comprise at least one proteolytic activation site that is sensitive to a plant protease or an insect gut protease are provided. Cleavage of the modified protoxin at the proteolytic activation site by a protease produces an active insect toxin. Methods of using the modified insect protoxin nucleic acid sequences and the polypeptides they encode to protect a plant from an insect pest are provided. Particular embodiments of the invention further provide modified insect protoxin compositions and formulations, expression cassettes, and transformed plants, plant cells, and seeds.