DE10215396A1 - Process for applying layers to a molded body comprises positioning the molded body in a pressure chamber, aligning the body to form a gap, filling the gap with a material and isostatically or uniaxially pressing the starting material - Google Patents

Abstract

Process for applying one or more layers to a molded body comprises: (a) positioning the molded body (1) in a pressure chamber (2) for isostatic or uniaxial pressing; (b) aligning the molded body in the pressure chamber so that a gap is formed between the inner wall of the pressure chamber and the surface of the molded body; (c) filling the gap with a starting material for a layer; and (d) isostatically or uniaxially pressing the starting material and the molded body by pressing the starting material for the layer on the surface of the molded body. An Independent claim is also included for a molded body obtained by the above process. Preferably the molded body is made from superconducting or superconducting oxidic material. Isostatic pressing is carried out using a dry die process. An adjusting aid is provided on the molded body.

Description

The present invention relates to a method for applying a layer the surface of a shaped body made of a superconductive or superconducting material by means of a pressing process and blanks, which according to the method according to the invention can be obtained and high-temperature superconducting components can be processed further, for example Power supplies, high temperature superconducting tapes and wires after the powder-in Pipe method (Oxide Powder In Tube Method, OPIT).

According to the well-known OPIT method for the production of elongated superconducting components such as wires and strips are made by pressing one powdery mixture of a base material, which is composed so that there is a later appropriate thermal treatment high temperature superconducting material forms blanks, which are usually rod-shaped exhibit.

Such methods for pressing bars for the OPIT method are basically known. Examples of such methods include that isostatic presses, for example by means of the so-called Dry matrix process or wet matrix process as described in WO 98156048 or uniaxial pressing, for example using a hydraulic press, as is also mentioned in the aforementioned WO 98/56049 is described.

For the dry matrix process as well as for the wet matrix process the starting material is in the form of a free-flowing powder or granulate given a pressure chamber. The pressure chamber is then by means of a suitable pressure transmission medium such as a liquid, wherein the pressure acts on the formed body from all sides.

The compacted bars thus obtained can then be used if necessary mechanically reworked, for example by turning on a lathe for example to smooth the surface and adjust the dimensions.

The machined rods are then encased in a metal tube, preferably silver pipes containing alloy components are added to wires stripped and rolled.

The OPIT process is used in particular for the production of superconducting Components based on BiSrCaCuO (BSCCO) are used, with cladding tubes made of Silver can be used.

When manufacturing high temperature superconducting wires according to the OPIT However, there may be method during the necessary intermediate tempering too a diffusion of copper from the superconductor material into the silver layer of the Wire come. The destabilization of the superconducting material as a result Copper depletion then leads to a reduction or even total Loss of superconducting properties as well as reduced mechanical Strength of the metal shell and consequently poorer processability. specially In the case of silver sheaths, copper can diffuse in the sheath form a copper-silver alloy through which superconductor melt emerges can, which is formed during the required heat treatments.

To minimize copper loss as well as improve Oxygen diffusion has been suggested, ceramic oxide layers between two Silver shells forming a BSCCO / Ag / ceramic Provide oxide layer / Ag composite material (P. Kovac et al. In "Electrical and Mechanical Properties of Bi-2223 / Ag / barrier / Ag-composite tapes ", Superconductors Science and Technology, edition 13 (2000), pages 378 to 384).

Another method described is to change the chemical Composition of the superconductor towards higher molar proportions of copper all the more Compensate for copper depletion occurring during production.

However, if there is another layer on top of the superconducting or already Superconducting molded body to be provided, the following problems must be encountered be taken into account. So make sure that the material that the layer trains, is applied evenly. In addition, the connection between the superconducting core and the layer be firm and durable.

The layer on the finished superconducting component must also be a have homogeneous material distribution. In addition, a controllable Phase adjustment of the superconducting material during the final one Tempering can be guaranteed. In addition, the molar Do not change the composition of the superconducting material. The above Problems mainly concern superconducting moldings caused by Presses were manufactured. However, there are also procedures in which the Melted starting material for the production of the superconducting molded body and processed directly into solid components. These melting techniques will be usually for the production of solid components with rod, tube or Ring geometries used. Such solid components can after a appropriate temperature treatment, for example directly as power supplies be used. But also the production of more complex structures like For example, coils can be made from these solid components. For the practical use of these superconducting solid components, however, must best possible contact between the superconducting body itself and the metallic conductor that is attached to the superconducting body connected. There was therefore a need as small as possible To achieve contact resistances for the use of superconducting solid components.

EP 0 467 360 describes a method for attaching metallic contacts a superconducting molded body described, the starting material for the molded body is introduced into a mold in such a way that at least one part a silver powder or a gold powder according to the shape of the contact is deposited at the desired location, being around in the area of contact to keep the material for the contact in the desired place, in the form a porous body made of silver, gold or copper is built into its Pores contains part of the silver or gold powder.

It was an object of the present invention to provide a method place with one or more layers on a molded body can be applied in particular for superconducting applications, the solves the above problems. In particular, it was the object of the present invention to provide such a method with which layers are obtained can be uniform in shape, especially in thickness are a homogeneous distribution of the layer components and an improved Have adherence to the surface of the molded body.

According to the present invention, this object is achieved by a Method for applying one or more layers to a shaped body, the in particular from a superconducting or superconducting oxidic Material is made by means of an isostatic or uniaxial pressing process, whereby the molded body in a pressure chamber for isostatic or uniaxial pressing is placed, the volume of the molding being less than the volume of the pressure chamber, the position of the shaped body in the pressure chamber is such is aligned between the inner wall of the bale chamber and the Surface of the molded body on which the layer is to be provided Gap is formed, the gap with a starting material for the layer is filled, and the starting material for the layer and the shaped body undergo an isostatic or uniaxial pressing process, the Starting material for the layer on the surface of the molded body Layer.

The method according to the invention can advantageously be the same Device are carried out as for isostatic or uniaxial pressing of molded blanks is used for superconducting applications, such as for example for the OPIT method as described above. Examples are pressure chambers for the dry die or Wet die process or a hydraulic press.

For the purposes of these inventions, the term shaped body is a body understood, which is shaped and by compression or by one Melting process as described above can be obtained.

Basically, the method according to the invention is for molded articles Any materials applicable, are suitable, for example, moldings, which in the Pressing the method according to the invention are plastically deformable and / or be coated with layer materials that are capable of restoring forces Occurrence of an elastic deformation of the core material and so to prevent the occurrence of cracks in the layer.

The molded body can optionally further process steps such as Example subjected to annealing. The molded body can essentially consist of a mixture of starting materials, so is composed that a later suitable thermal treatment superconducting material is formed, or from an annealed high temperature superconducting material. The term molded body therefore refers to a molded body in the various stages of the manufacturing process.

For the purposes of this invention, the term “blank” is used to mean a shaped body understood, which essentially consists of a mixture of a starting material exists, the starting material is preferably composed such that a superconducting material for later suitable thermal treatment is formed, and under the term "compacted blank" a blank that by means of a pressing process has been obtained. Should the blank be used to manufacture elongated shaped bodies are used, such as wires or Bands according to the OPIT procedure, this expression refers to a Shaped body that is not yet in the metallic shell (for example made of silver) has been introduced.

According to the invention, the powdery starting mixture or superconducting material used for the production of the molded body should be, a composition that is such that later suitable thermal treatment forms a high-temperature superconducting material. The formation of this annealed high-temperature superconducting material can preferably by one or more tempering steps at the end of the Component manufacture of solid components or by one or more Tempering steps in connection with, for example, rolling the one or more metallic pipes filled molded body preferred at the end of the Wire production using the OPIT method. The starting powder and the superconducting materials, as well as the processes for producing superconducting or superconducting moldings and their further processing into components for high-temperature superconducting applications are generally known.

The superconductor material or the annealed high-temperature superconducting material contains at least one of the superconducting phases with a composition essentially based on Bi-Ea-Cu-O, (Bi, Pb) -Ea-Cu-O, (Y, SE) -Ea-Cu -O or (Tl, Pb) - (Ea, Y) -Cu-O, where Ea is an alkaline earth element and can in particular be Ba, Ca and / or Sr. In this case, the phases that occur in particular have a composition of approximately
Bi ₂ (Sr, Ca) ₂ Cu ₁ O _x (Bi, Pb) ₂ (Sr, Ca) ₂ Cu ₁ O _x , (Bi, Pb) ₂ (Sr, Ca) ₃ Cu ₂ O _x , (Bi, Pb ) ₂ (Sr, Ca) ₄ Cu ₃ O _x , (Y, SE) ₁ Ba ₂ Cu ₃ O _y , (Y; SE) ₂ Ba ₁ Cu ₁ O _y , (Tl, Pb) ₂ (Ba, Ca) ₂ Cu ₁ O _{z '} , (Tl, Pb) ₂ (Ca, Ba) ₃ Cu ₂ O _z' , (Tl, Pb) ₂ (Ca, Ba) ₄ Cu ₃ O _{z '''} , (Tl, Pb) ₁ (Ca, Ba) ₃ Cu ₂ O _{z ''} , (Tl, Pb) ₁ (Ca, Ba) ₄ Cu ₃ O _{z ''''} .

In the above formulas, x, y and z each denote that suitable superconductor material suitable oxygen content.

If necessary, other suitable elements can be present. In some cases, it is advisable, for example, to add an additive from a sulfate or from sulfates to the powdered starting mixture, the superconducting material or the annealed high-temperature superconducting material, so that in addition to the superconducting phase or phases, an alkaline earth sulfate content, in particular BaSO ₄ , SrSO ₄ and / or (Ba, Sr) SO ₄ occurs.

Accordingly, the starting material for the production of the shaped body, as used according to the invention, preferably a starting material for the manufacture of the aforementioned superconducting or high-temperature superconducting materials, especially a powder oxidic starting material.

For the method according to the invention, the method is arbitrary Process obtained molded body placed in a pressure chamber that a Gap between the surface of the molded body and the inner wall of the Pressure chamber forms. This gap becomes powdery Backing material for the layer backfilled.

Due to the location and shape of the gap, the location and shape of the the layer to be trained.

For the formation of the gap it is necessary that the volume of the Shaped body is chosen less than that of the pressure chamber. For example, if Shaped a ring-shaped rod, the diameter of the rod should be smaller be chosen as the diameter of the pressure chamber.

The molded body that is to be coated should be in the pressure chamber carefully aligned to obtain a layer that is suitable for the practical use is suitable. For example, if you want to make a layer, which uniformly surrounds the circumference of the shaped body is the shaped body center as precisely as possible in the pressure chamber.

The shaped body can facilitate the exact alignment in the Pressure chamber with an adjustment aid. As an adjustment aid, a Screw, pin, mandrel or similar means that is suitable for the molded body to position in the pressure chamber in the desired position become. The adjustment aid can be in any way and on any suitable position can be connected to the molded body. For example the adjustment aid can be glued to the molded body.

If the moldings are produced by compression, the adjustment aid can be used already in the powdery starting material and in the course of the Compression can be pressed into the resulting compacted body. In this case the necessary adjustment of the moldings in the pressure chamber results automatically as a result of centering the adjustment aid.

The adjustment aid can also be used to attach a calibration aid for a possible post-processing of the one shift provided molded body, as can be done with a lathe.

The starting material for the layer can be used as needed with regard to the desired effects that are to be achieved with the layer and on the can be selected for the respective purpose. So an oxidic Ceramic material can be used, for example for compacted blanks for the OPIT Method, or a metallic material, to make solid components with contacts Mistake.

The starting material for the layer is used in a form as for such pressing method is generally used, preferably as free-flowing powder or granules.

A suitable grain size (expressed as a d ₅₀ value) is preferably chosen for a smaller 2 micrometer and the d ₉₅ value preferably for a smaller 10 micrometer.

To improve the pourability and to ensure that it is as complete as possible Suitable additives can be used to ensure filling of the mold be added and / or the powdered starting material method be subjected to, which produce or improve the flowability. An example this is the granulation.

A suitable pressure for pressing on the layer / layers lies in one Range from 20 to 600 MPa.

However, the pressure applied can vary as needed. So it depends pressure to be applied, inter alia, of the material for the layer and the machine technical possibilities of the press used.

In principle, can be used for applying a layer to a molded body isostatic or uniaxial pressure the same process parameters for the Press conditions are used as they are for the production of a Shaped body can be used by means of these techniques. These parameters are adapt to the respective application if necessary.

With the method according to the invention, two or more layers can be applied a molded body can be applied, the composition of the Layers can be the same or different. The number of layers is depending solely on the size of the pressure chamber and the respective desired layer thickness.

If necessary, the coated molded body obtained can be coated with a suitable one Processes are reworked, such as by turning. Through the Post-processing can - if necessary - the dimensions and / or Adjust the surface properties of the layer, e.g. thickness and smoothness.

For example, the surface of the compacted molded body should be before the Layer is applied, as smooth as possible to the formation of Avoid inhomogeneities in the layer.

The blank obtained according to the invention, the one or more layers can be provided, is preferably composed of a material which a high temperature superconducting material, as explained above, a composition is particularly preferred which high-temperature superconducting phases results, in particular a high-temperature superconducting BSCCO type material.

In the following, the invention is described in more detail based on preferred Embodiments explained with reference to the attached figures. This Explanation does not mean a limitation of the invention, but is only intended serve as an illustration.

Fig. 1 is a diagram showing a tool block of a dry bag isostatic press according to the template and with eingefülltem material to be pressed;

FIG. 2 shows a longitudinal section and a cross section through an elongate molded body according to the invention with a multiplicity of layers; and

Fig. 3 shows a longitudinal section and a cross section through a molded body according to the invention, which is provided at both ends with a metallic contact, which are separated from one another by an insulating material.

To carry out the method according to the invention, an isostatic pressing technique is preferably used, which can be carried out using the dry matrix method. Fig. 1 shows an example of a suitable press for the dry bag, as described in detail in WO 98/56048, which is for this purpose incorporated by reference in the present application.

Fig. 1 shows an example of a diagram of a tool block 1 , an isostatic press according to the dry die method with die 2 as a pressure chamber and inserted press material 3 and closing punches 6 , 6 a. The compression mold 4 is generally significantly thicker in the dry die process than in the wet die process and has a higher hardness, for example Shore A in the range from 80 to 90. For example, an approximately 30 mm thick polyurethane die can be used, which is characterized by high dimensional stability in a depressurized state, good elasticity when pressurized, good resilience properties when depressurized and good shape stability in long-term operation.

The die 2 is inserted in a tool block 1 and is only acted upon radially with hydrostatic pressure via an elastic separating membrane 4 by means of a pressure transmission medium 5 , for example based on water.

If hollow bodies are pressed, a metal core, for example, can preferably be used be arranged centrally in the die cavity. To the core Pressed molded body can with a suitable composition due to the Elongation of the oxidic material and / or easy with conical cores be removed from the mold.

According to the invention for the coating of a shaped body according to a preferred embodiment, first the molded body by means of isostatic Presses are generated according to the dry die process. Preferably is a screw or the like as an adjustment aid in the Base of the molded body pressed in.

In FIG. 2, an example is shown of a shaped body having an elongated shape with an annular diameter, and which is obtainable by means of a pressing technique. According to the embodiment shown in FIG. 2, a core 7 , which consists of a high-temperature superconducting material or a material that can be converted into a high-temperature superconducting material after suitable treatment, is provided with a multiplicity of layers 8 , with more or fewer layers than the four layers shown may be present.

According to the invention, the layer is applied to the shaped body preferably the same press used as for the production of the shaped body. In this case, the molded article obtained may be after a Surface finishing reset in the press for coating.

For example, surface finishing may be required to adjust the dimension of the shaped body in order to promote the formation of a gap between the surface of the shaped body and the inner wall of the die 2 when the shaped body is put back into the press.

This gap or gap is filled with a starting material with a desired composition for the layer filled on the surface of the Molded body is pressed, so as to form the desired layer.

For example, moldings in the form of rods can be used for the OPIT method getting produced. Preferably the surface of the rods thus obtained post-processed to a uniform one To achieve surface texture. This post-processing can be done, for example, by turning respectively. The provision of a smooth surface before coating is advantageous to, for example, the formation of inhomogeneities in the to avoid the layer structure to be trained.

For the application of a layer 8 or a plurality of layers 8 of a desired material on these rods, as shown in FIG. 2, the rods are put back into the pressing chamber and centered. The centering is preferably carried out by means of a screw, such as was pressed into the base of a molded body, in order to attach a twisting aid. Since the screw or the like, which is provided for fastening the twisting aid, can simultaneously serve as an adjustment aid for positioning or centering the shaped body in the pressing chamber, the method according to the invention can be simplified even further.

The shaped body is in the form of a rod, as it is after the post-processing has been received, placed back in the bale chamber, forms between the Surface of the rod and the inner wall of the bale chamber an annular Gap due to the calibration process. This gap is with the desired starting material for the layer is filled and the pressing process carried out.

If necessary, the surface of the layer obtained can also be reworked surface properties such as thickness, smoothness etc. adjust.

The finishing can be done on a lathe. For example, let thicknesses are obtained with an accuracy of ± 0.1 mm.

As stated above, there is no general limitation on that Composition of the starting material for the layer.

For example, to compensate for the Cu loss in BSCCO materials during the required annealing treatment in the manufacture of a high temperature superconducting material from a thin porous layer Cu powder are pressed onto the molded body. With such a Cu layer not only can the Cu loss be compensated, but at the same time due to the porosity of the necessary oxygen incorporation in the material of the. Shaped body by means of diffusion, which is necessary to the to achieve the desired high-temperature superconducting properties.

Alternatively, the copper loss can be counteracted by adding a layer is applied, the starting material for the layer being such Composition has that it is a high temperature superconducting material increased copper content. Because of this layer with increased Copper content can be in the transition area between the superconducting or superconducting material and the metal (silver) shell compensated for the copper loss become, whereas in the core area of the molded body the ideal chemical molar composition for the formation of a material with the desired superconducting properties is maintained.

FIG. 3 shows an embodiment for a solid component that is provided with metallic contacts 9 , 11 at both ends of the body, the metallic contacts 9 and 11 being separated from one another by an insulating material 10 . In this embodiment, the layer is formed at both ends of the solid component from a metallic material for forming the contacts 9 and 11 , and the middle region of the layer consists of an insulating material 10 . In the example shown in FIG. 3, the solid component has an annular structure with a core made of a high-temperature superconducting material 1 (or a material which can be converted into a high-temperature superconducting material by means of suitable annealing), which is surrounded by a layer which is like is composed as described above.

In the case of the production of a layer on a solid component, which is by means of a melting process is obtained, the adjustment aid can be attached to a suitable one Place on the molded body, for example the base, by gluing or the like.

Again, the surface of the molded body can be mechanical as required processed, for example by roughening the molded body surface, Calibrate to desired dimensions and so on.

The possibly reworked molded body is placed in a pressure chamber and that Starting material for the layer inserted into the gap that is between the Shaped body and the inner wall of the press chamber.

As shown in FIG. 3, the starting materials for the layer can be filled into the gap in the following sequence for the formation of contacts at both ends of a shaped body: 1) metallic powder followed by a 2) ceramic powder as insulating material and 3) again metallic powder.

As described above, with the method according to the invention simple method for applying uniform layers to moldings Can be made available from any material as required can exist and which have excellent adhesion to the surface of the Have molded body.

If the shaped bodies are compacted shaped bodies, this can Procedures can be simplified even further by pressing on the layer the same pressing device is used as for the compression of the Molding.

Below are some examples of applications.

So with the inventive method for applying a layer Blanks formed by means of an isostatic or uniaxial pressing process be obtained for high temperature superconducting applications, the one or have several layers with different molar compositions, to compensate for copper losses, for example.

The molded body can be completely or partially with an electrically conductive shell be provided, which are made of a metallic powder or granules has been used, for example, to obtain soldering and current-carrying contacts.

Protective layers and insulating layers can be provided, which can be obtained, for example, from powdery starting materials, which can consist of Al ₂ O ₃ , AlN, Si ₃ N ₄ or SiO ₂ .

It is also possible to use layers of plastic powder respectively Plastic granules as protective or insulating layers or for To provide generation of a dielectric.

The layers can also be made from metal salt compounds such as NaCl, CuSO ₄ , AlCl ₃ and similar materials or from ferromagnetic compounds.

The above examples are only intended to illustrate the broad Field of application of the present method, and it is understood that the any variations or modifications of the present invention Layer arrangements or the layer composition and in relation to the Shaped body itself and the material from which the shaped body consists includes.

The moldings according to the invention, in particular the blanks as they The present invention also relates to the invention have been coated, in particular for the production of high-temperature superconducting wires, strips, rods, tubes, hollow or solid bodies, especially for the production of power cables, transformers, Windings, magnets, magnetic bearings or power supplies are used become.

Claims (13)

1. A method for applying one or more layers to a shaped body by means of an isostatic or uniaxial pressing method, comprising the following steps: - positioning of the shaped body ( 1 ) in a pressure chamber ( 2 ) for an isostatic or uniaxial pressing process, the volume of the shaped body ( 1 ) being less than the volume of the pressure chamber ( 2 ), - Alignment of the shaped body ( 1 ) in the pressure chamber ( 2 ) so that a gap is formed between the inner wall of the pressure chamber ( 2 ) and the surface of the shaped body, which is to be provided with a layer, - Filling the gap with a starting material for the layer, and - Isostatic or uniaxial pressing of the starting material and the shaped body ( 1 ) while pressing the starting material for the layer onto the surface of the shaped body ( 1 ) to form a layer. 2. The method according to claim 1, characterized, that the molded body from a superconducting or superconducting oxide material is composed. 3. The method according to claim 1 or 2, characterized, that the method isostatic pressing using the Dry matrix process includes. 4. The method according to any one of claims 1 to 3, characterized in that an adjustment aid is provided on the shaped body ( 1 ) in order to facilitate the positioning of the shaped body ( 1 ) in the pressure chamber ( 2 ). 5. The method according to any one of claims 1 to 4, characterized in that the method steps according to claim 1 are carried out repeatedly to apply two or more layers on the molded body ( 1 ). 6. The method according to any one of claims 1 to 5, characterized in that regions of the layer which is provided on the molded body ( 1 ) is composed of different materials. 7. The method according to any one of the preceding claims, characterized, that the layer consists entirely or partially of a metal. 8. The method according to any one of the preceding claims, characterized in that the molded body ( 1 ) is obtained by a compression process. 9. Moldings obtainable by a process according to one of claims 1 till 8, characterized, that the molded body contains one or more layers pressed on. 10. Shaped body with one or more layers, which is obtainable by a process according to one of claims 1 to 8, wherein the shaped body ( 1 ) consists essentially of a mixture of an oxidic starting powder which is composed such that it is suitable for subsequent thermal Treatment forms a high-temperature superconducting material, wherein the surface of the molded body ( 1 ) contains at least one layer pressed on. 11. Shaped body according to claim 9 or 10, characterized in that the shaped body ( 1 ) is selected from a shaped body which has been obtained by means of a compression process and a shaped body which has been obtained by means of a melting process. 12. Shaped body according to one of claims 9 to 11, characterized in that the layer on the shaped body ( 1 ) contains areas ( 9 , 11 ) which consist of a metal, and the areas ( 9 , 11 ) from each other by an insulating material ( 10 ) are separated. 13. Shaped body according to one of claims 9 to 12, characterized in that the shaped body ( 1 ) has a substantially cylindrical shape, prism shape or tubular shape.