Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/02—Coating starting from inorganic powder by application of pressure only
  • C23C24/04—Impact or kinetic deposition of particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F5/006—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of flat products, e.g. sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F2003/1042—Sintering only with support for articles to be sintered
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

• the present invention relates to a method for producing a metal foil using the aerosol deposition method (ADM) and a metal foil, the metal foil comprising a relatively brittle metal or consisting of a relatively brittle metal.
• ADM aerosol deposition method
• Metal foils are used for a variety of applications. These range from household aluminum foils to photovoltaic solar modules, lithium-ion batteries, special batteries, heat exchangers, surface refinements, fuses, capacitors, transformers, electronics, medical technology, flexible circuit boards and special cables.
• metal foils usually consist of ductile metals such as nickel, copper, silver, gold, steel, lead, tin, titanium or alloys containing these metals. It is usually manufactured by repeated rolling until the desired thickness is reached. Films with a thickness of at least 5 ⁇ m can be produced in this way. Thermal post-treatment (annealing) is often necessary between individual rolling steps.
• the object of the present invention was to provide a method with which metal foils can be produced from brittle metals, in particular metals with an atomic number >30, which in the pure state have a modulus of elasticity of at least 200 GPa.
• At least one object of the invention is solved by the subject matter of the independent claims.
• the subjects of the subclaims relate to preferred embodiments.
• foils can be produced from brittle metals which have a thickness in the range of 200 ⁇ m or less, in particular in the range of 10 ⁇ m-200 ⁇ m.
• a film in the context of the invention can be understood as a homogeneous sheet made of very thin material, e.g. metal or plastic.
• a film usually extends much further in two spatial directions than in the third spatial direction.
• the present invention relates to methods for producing metal foils and the metal foils obtainable therefrom.
• the metal foil may comprise ribbons, strips and expanses, e.g., rectangular in shape.
• the metal foil can be structured.
• the film can be structured after step c), e.g. by lithographic methods, selective chemical or physical etching, embossing, folding or laser cutting, and combinations of these methods.
• the metal foil contains or consists of a metal.
• Metals are to be understood as meaning those materials which have a metallic bonding character. This typically manifests itself in high electrical conductivity, which decreases with increasing temperature, and in high thermal conductivity. Depending on the surface condition, a metal optionally has a metallic luster. Within the scope of the invention, metals are to be understood as meaning elemental metals, alloys and intermetallic phases.
• An elementary metal is a pure substance and has no other components apart from unavoidable impurities, e.g. from the manufacturing process.
• an elemental metal does not contain any intentionally added components. Alloys can be understood to mean mixtures of substances that contain one or more metals and have metallic properties.
• an alloy may contain components that are not metals in elemental form, such as carbon, nitrogen, and oxygen.
• alloys can also include amorphous alloys which have solidified in the manner of glass and have no crystallinity. Exceptions to this are optionally present nanocrystalline phases that cannot be measured with XRD.
• intermetallic phases are FeCr, TiAl, Ti3Al, TiAl3, NiAl, CuAl and FeAl.
• the intermetallic phases can optionally be present in different phases, such as alpha phases, beta phases, gamma phases, theta phases or sigma phases.
• the metal foil preferably contains or consists of a metal.
• the metal preferably has an atomic number >20, in particular >30 in the periodic table.
• the metal preferably has a modulus of elasticity of at least 150 GPa, in particular at least 200 GPa.
• the modulus of elasticity can be determined by means of a tensile test in accordance with DIN EN ISO 6892-1:2020-06.
• the metal is a brittle metal.
• a brittle metal can be understood to mean, for example, a metal at the end of which the fracture occurs essentially without plastic deformation. Therefore, hardly any plastic deformation occurs before fracture and necking does not occur.
• the metal optionally has a melting temperature of at least 1800°C.
• the metal contained in the metal foil is also preferably selected from the group consisting of Ir, Rh, Os, Ru, Pt, Pd, W, Mo, Cr, Zr, Hf, Ti, Re, Zn and Si and combinations of the aforementioned elements.
• Silicon (Si) is not a metal in the narrower sense, but a semimetal and is preferably also included in the invention. However, it can be contained in particular in alloys with the other elements of the group.
• step a) a metal layer is applied to a substrate by aerosol deposition of a powder.
• the aerosol deposition process is a coating process.
• a coating system is used for application with aerosol deposition.
• This coating system contains an aerosol generator in which the powder used is converted into an aerosol as described in step b).
• the ADM coating system contains a coating chamber in which the coating process takes place.
• a vacuum in the preferred range of 60 mbar to 1066 mbar prevails in the aerosol generator, particularly during the process.
• a pressure in the preferred range of 0.2 mbar - 20 mbar prevails in the coating chamber, particularly during the process.
• the pressure in the coating chamber is lower than the pressure in the aerosol generator.
• the pressure difference between the aerosol generator and the coating chamber is in the range of 200 mbar - 500 mbar.
• the powder is transported from the aerosol generator through a nozzle into the coating chamber via a process gas.
• the particles are accelerated due to the resulting pressure difference between the aerosol generator and the coating chamber, in particular to a speed in the range of 100 m/s - 600 m/s, and are deposited on the surface of the metal body.
• the particles deform plastically or break up as a result of the impact into fragments, particularly in the nm range, and form a dense and well-adhering layer.
• the process gas used can be selected from inert gases, oxygen, air or combinations thereof.
• the inert gas can preferably be at least one gas selected from the group consisting of helium (He), argon (Ar) and nitrogen (N 2 ) or combinations thereof.
• the substrate is preferably moved with an XY table.
• a nozzle it is possible for a nozzle to be moved over the substrate to be coated.
• ADM is a cold coating process, ie the deposition preferably takes place at a maximum temperature of 50°C.
• the application is carried out with the help of a carrier gas at several 100°C, with which 50 - 90 ⁇ m particles of ductile materials are thrown onto the surface.
• a carrier gas at several 100°C, with which 50 - 90 ⁇ m particles of ductile materials are thrown onto the surface.
• the particles do not break apart, but the particle morphology is essentially preserved. So with 50 ⁇ m particles no mean layer thicknesses >>50 ⁇ m are possible.
• An advantage of the aerosol deposition process is that small foils can be produced without significant loss of material.
• the powder used for the aerosol deposition preferably has a particle size distribution with a dso value in the range of 0.1 ⁇ m-150 ⁇ m. Furthermore, the particle size distribution can have a d 90 value of 125 ⁇ m or less.
• the particle size distribution within the scope of the invention can be determined, for example, by means of laser diffraction in accordance with ISO 13320:2009.
• the powder can have a monomodal or a multimodal particle size distribution.
• the substrate to which the metal layer is applied can have or consist of a material that is selected from the group consisting of metals, semimetals, ceramics, glasses and polymers.
• substrates are steel plates, steel foils, silicon wafers, alumina ceramics, mica substrates, silicate glass plates and polyimide substrates
• the surface of the substrate to which the metal layer is applied is preferably flat.
• the surface of the substrate on which the metal layer is applied preferably has a roughness R z with a value in the range of at most 10 ⁇ m, in particular if the surface is planar.
• the roughness can be measured using the profile method according to DIN EN ISO 4287:2010-07. A roughness that is as small as possible can be advantageous since the substrate can then be removed more easily from the metal layer.
• the substrate has a three-dimensional structure, in particular in the form of elevations and depressions.
• the elevations and depressions preferably have an extent of at least 100 ⁇ m in at least one spatial direction.
• the substrate on which the metal layer is applied has a separating layer.
• the separating layer can serve to reduce the adhesion between the substrate and the metal layer.
• the separating layer can be, for example, a film with a thickness of at most 1 ⁇ m.
• the release layer may comprise a material selected from the group consisting of oxides (oxides (e.g. quartz, glass) polymers, fats and graphite.
• the metal layer applied to the substrate preferably has an average thickness of at least 5 ⁇ m, in particular at least 10 ⁇ m and very particularly preferably at least 20 ⁇ m.
• the metal layer applied to the substrate preferably has an average thickness of at most 300 ⁇ m, in particular, in particular at most 200 ⁇ m and very particularly preferably at most 100 ⁇ m.
• the metal layer preferably has a relative density of at least 70%, in particular at least 80% and particularly preferably at least 95%.
• the relative density of the metal layer can be at least 99%.
• the purity of the metal layer preferably corresponds to the purity of the powder that was applied by means of aerosol deposition.
• the purity of the metal layer can be at least 99.5%, in particular at least 99.95% and very particularly preferably at least 99.995%.
• the purity ranges from 99.9% to 99.999%.
• the substrate and the metal layer together form a layered composite.
• a separating layer can optionally be arranged in the layer composite between the substrate and the metal layer.
• step b) the substrate is removed to obtain a metal foil.
• the removal of the substrate can be partial or complete. When the substrate is partially removed, at least a portion of the metal foil cannot be in contact with the substrate.
• the removal can take place, for example, by detaching or dissolving the substrate.
• the substrate can preferably be detached from the metal layer by heating the layered composite of substrate and metal layer. Due to the different linear thermal expansion coefficients of the substrate and the metal layer, the substrate can flake off the metal layer and subsequently be removed. This thermal detachment can be achieved in particular when the coefficient of linear thermal expansion alpha (x 10 -6 K -1 ) of the metal layer and the substrate differ from one another.
• the linear thermal expansion coefficient can be determined according to DIN 51045-1:2005-08.
• the difference in the linear thermal expansion coefficients is preferably at least 20%, in particular at least 50% and particularly preferably at least 100%.
• the difference in the linear thermal expansion coefficients is at least 2 ⁇ 10 -6 K -1 , in particular at least 5 ⁇ 10 -6 K -1 and very particularly preferably at least 20 ⁇ 10 -6 K -1 .
• the substrate can be an alumina substrate with a linear thermal expansion coefficient of 8.1 ⁇ 10 -6 K -1 and the metal layer can be tungsten and have a linear thermal expansion coefficient of about 4.4 ⁇ 10 -6 K -1 .
• the substrate can be removed by grinding and polishing.
• the substrate can be ground off completely.
• the substrate can be removed by etching, particularly wet chemical etching, or physical etching, e.g., plasma etching.
• this separating layer in which a separating layer is arranged on the substrate during the aerosol deposition, this separating layer can also be partially or completely removed by removing the substrate.
• a metal foil is obtained by removing the substrate.
• the metal foil is preferably a free-standing metal foil. This means that the metal foil is not placed on any type of support. In other words, both side faces of the metal foil can be freely accessible.
• the metal foil has a thickness in the range of at least 10 ⁇ m, in particular at least 20 ⁇ m and of at most 300 ⁇ m, in particular at most 200 ⁇ m.
• the thickness of the foil preferably essentially corresponds to the thickness of the metal layer from step a).
• the thickness of the foil can be thinner than the metal layer when the foil is post-processed.
• the metal foil preferably has a relative density of 70% or more, in particular at least 90% or even at least 99%.
• the metal foil preferably has no gas inclusions.
• the metal foil can optionally be post-treated.
• Possible post-treatment processes include temperature treatments, rolling, grinding, polishing, pressing, in particular uniaxial pressing, cold isostatic pressing, or hot isostatic pressing.
• components of this separating layer can optionally remain on the metal foil when the substrate is removed. These components of the separating layer are preferably removed from the metal foil.
• the invention relates to a metal foil, in particular producible by a method as described herein, the metal contained in the metal foil having an atomic number >30 in the periodic table and a modulus of elasticity of at least 200 GPa, characterized in that the Film has a thickness in the range of 10 - 300 microns.
• the foil can be a precious metal foil.
• the metal foil can particularly preferably be an iridium foil, a rhodium foil, a tungsten foil, an osmium foil, a ruthenium foil, a platinum foil, a palladium foil, a molybdenum foil, a chromium foil, a zirconium foil, a hafnium foil, a titanium foil, a rhenium foil, a zinc foil or a silicon foil.
• the purity of the metal foil is preferably in the range of the purity of the particles used and can be, for example, in the range from 99.5 to 99.9995%.
• the use of the metal foil according to the invention is not further restricted.
• the metal foil can be used for electromagnetic shielding, as a catalyst support or as a lining for apparatus in chemical equipment construction.
• the invention relates to a sensor or a radiation protection device containing a metal foil according to the invention.
• the metal foil can be a rhodium foil used for mammography.
• the metal foil can be a tungsten foil for medical technology or nuclear medicine.
• the radiation protection for gamma radiation provided by a tungsten foil can be about 50% higher compared to lead. This can result in particular advantages for imaging.
• tungsten powder purity 99.9%
• a tungsten layer with a layer thickness of 23 ⁇ m was produced.
• the composite of tungsten layer and aluminum substrate was then placed in hydrochloric acid (36%) for 10 minutes. After the aluminum substrate had dissolved, a self-supporting tungsten foil could be removed from the solution.

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• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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Citations (6)

• 2021
  • 2021-11-03 EP EP21206111.3A patent/EP4177377A1/fr active Pending
• 2022
  • 2022-10-10 WO PCT/EP2022/078011 patent/WO2023078641A1/fr active Application Filing

Patent Citations (6)

Non-Patent Citations (1)

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