Classifications

• • 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
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
• • 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
  • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
• • 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 invention relates to a process for manufacturing thin metal / ceramic composite films, in which the ceramic reinforcements are distributed homogeneously in the metal matrix.
• the invention finds applications in all fields using substrates or films in metal / ceramic composite and, in particular, in the field of manufacturing electronic components intended, for example, in the automobile field or
• metallic films are produced by a rolling process.
• this rolling process does not make it possible to obtain a homogeneous distribution of the ceramic reinforcements in the metal matrix; it is therefore not suitable for the production of metal / ceramic composite films.
• the residual stresses caused by rolling cause the film to crack.
• Other processes used for the production of metal / ceramic composite films are the pressing, injection and extrusion processes.
• none of these methods makes it possible to obtain films with an excellent surface condition.
• these methods become expensive, since the film thickness must be less than a millimeter.
• strip casting methods which make it possible to produce thin films. Such methods are described in the following articles: ALCOCK J., DESCRIBE S., Tape casting, a flexible approach to surface engineering, Materials orld, 13-14, February (2000); B ⁇ HNLEIN-MAU ⁇ J., SIGMUND W., EGNER G., MEYER. H., HE ⁇ EL F., SEITZ K, ROOSEN A., The function in the tape casting of alumina, Advanced Materials, vol. 4, No. 2, 73-81 (1992); MORENO R., The role of slip additives in tape casting technology: part I-Solvents and dispersants, American Ceramic Society Bulletin, vol. 71, no.
• the object of the invention is precisely to remedy the methods of manufacturing thin films described above. To this end, it proposes a process for manufacturing thin films of metal / ceramic composite using a strip casting method.
• the invention relates to a process for manufacturing thin films of metal / ceramic composite comprising: a) preparing a suspension (S) in an organic solvent from a substantially homogeneous mixture of ceramic reinforcements, particles metallic, a binder, a plasticizer, and a dispersant, the metallic particles constituting at least 5%, by mass, of the suspension; b) strip casting the suspension to form a thin film, then debinding this thin film; c) carrying out the densification of the unbinding thin film, in an oven.
• the strip casting technique makes it possible to orient and control the distribution of ceramic reinforcements.
• the method described according to the invention makes it possible to manufacture composite metal / ceramic films with an orientation of the ceramic particles in the plane of the film, in particular for very anisotropic particles, such as fibers and platelets. This improves some properties of the composite in the film plane, such as reducing the thermal coefficient of expansion and increasing the thermal conductivity.
• the suspension has a viscosity of between 0.5 and 3 Pa. s.
• the suspension is produced by mixing:
• At least one metallic powder and at least one ceramic reinforcement constituting approximately 30 to 60% of the total volume of the suspension
• an organic solvent constituting approximately 15 to 45% of the volume of the suspension; a binder and a plasticizer constituting approximately 30 to 70% of the volume of the suspension; - a dispersant representing approximately 0.1 to
• the dispersant is a phosphoric ester, a polyacrylate, a sulfonate, a perfluorate or even a carbon chain acid of 2 to 30 carbon atoms.
• the metal powder can be a powder of copper, aluminum, silver, gold, nickel, titanium, chromium, zinc or an alloy of two or more of these materials .
• the ceramic reinforcement can be a powder and / or a short fiber (that is to say a fiber whose length varies between 1 and 500 ⁇ m) of graphite, carbides, nitrides or oxides.
• the densification of the film consists of sintering the film in an oven.
• the densification of the film consists of hot rolling and annealing of the film.
• the preparation of the suspension consists of:
• the invention further relates to a process for the preparation of composite parts with a laminated structure in which several thin films are formed.
• the stacked thin films have different compositions.
• FIG. 1 schematically shows the step of preparing the suspension from metal particles and ceramic reinforcements
• FIG. 2 schematically represents the step of casting the suspension in a strip to form a thin film
• - Figures 3A and 3B show two embodiments of the film densification step in an oven.
• the invention relates to a method for manufacturing thin films of metal / ceramic composite. This process consists in preparing a suspension, also called "slip", comprising a substantially homogeneous mixture of ceramic reinforcements and metallic particles.
• These metallic particles and ceramic reinforcements are chosen, respectively, in the form of one or more metallic powder (s) and one or more ceramic reinforcement (s). These powders and short fibers are mixed with an organic solvent, a dispersant, a binder and a plasticizer. The proportion of these different elements is as follows:
• the metal powders and the ceramic reinforcements represent 30 to 60% of the total volume of dry matter of the suspension (that is to say of the whole volume occupied by the binder, the plasticizer, the dispersant and the metal powders and ceramic);
• the solvent represents 15 to 45% of the total volume of dry matter;
• the binder and the plasticizer represent 30 to 70% of the volume of dry matter;
• the dispersant represents between 0.01 and 2% of the mass of metallic powders and ceramic reinforcements;
• additives such as release agents and / or wetting agents, which represent between 0.01 and 2% of the mass of metallic and ceramic powders.
• This step of preparing the suspension S consists, first of all, of grinding in a jar, or by attrition, the metallic and ceramic powders with the solvent and the dispersant.
• This grinding step is carried out by means of an attritor mill (represented by the reference 1 in FIG. 1) or by a jar mill.
• the assembly thus obtained is then mixed with binders and plasticizers, using a mixer, referenced 2.
• the metal powder (s), intended to form the metallic matrix of the suspension can be, for example, a powder of copper, aluminum, silver, gold, nickel, titanium, chromium, zinc or an alloy of two or more of these metals.
• the ceramic reinforcement (s) intended to form the ceramic reinforcements of this suspension can be, for example, a short graphite powder or fiber or else a powder or a short fiber based on carbides, such as silicon carbide, nitrides, such as aluminum nitride, or oxides, such as silica or zirconium tungstate.
• the ceramic reinforcements may be in the form of fibers or else platelets or else substantially spherical grains, with a diameter of between approximately 0.1 ⁇ m and 100 ⁇ m.
• the fibers are generally short fibers with a diameter of 10 nm to 10 ⁇ m, and with a length of 100 nm to 10 mm.
• These ceramic reinforcements can be coated with a layer of metallic material, such as cobalt, nickel, silver or gold.
• the thickness of the metal coating is at least 0.01 ⁇ m.
• This coating can be carried out by immersion of the ceramic reinforcements in an electrolytic bath. This coating has the advantage of improving the densification of the material during the film densification step, and, in particular, when this densification consists of sintering, because it makes it possible to increase the metal / ceramic interface.
• the suspension used according to the invention is a suspension or organic system.
• the solvent used to make this suspension S is an organic solvent, generally chosen from ketones, alcohols and their mixtures.
• the role of the dispersant used to produce this suspension is to ensure the homogeneity and stability of the suspension by developing repulsion between ceramic reinforcements and metallic particles.
• the dispersant ensures good stability and good dispersion of the particles between them.
• the dispersant makes it possible to obtain, after drying, a homogeneous and compact strip.
• This dispersant is chosen from surfactants, macromolecules, such as fish oil, phosphoric esters, polyacrylates, sulfonates, perfluorates and carbon chain acids having from 2 to 30 carbon atoms, such as for example the oxalic acid and stearic acid.
• This binder used to produce this suspension is to ensure the cohesion of the strip (or film), after evaporation of the solvent.
• This binder is generally a compound which is not soluble in water chosen from polyalcohols, vinyl compounds, such as polyvinyl butyral and acrylic compounds and their mixtures.
• This plasticizer used in this suspension is to provide great flexibility, great fluidity, to the strip; this flexibility is necessary when casting the suspension in strips and subsequently when handling the strip.
• This plasticizer can be, for example, a polyethylene glycol or else dibutylphthalate.
• the suspension also contains a plasticizer which makes it possible to obtain a strip, or thin film, in flexible raw and sufficiently solid to be manipulated.
• the report binder / plasticizer makes it possible to adjust the mechanical cohesion of the strip and its flexibility. These strips can therefore be stacked and thermocompressed so as to produce stacks of strips of different compositions. This solution cannot be envisaged with the methods of the prior art.
• FIG. 2 schematically represents the second step of the method of the invention, that is to say the step of pouring the suspension into strips.
• the suspension S produced during the first step is cast on a casting bench 3 so as to form a strip B, also called a thin film.
• Casting in strips consists in casting the suspension S on a support which can be, for example, a steel strip 8 or a polymer wire, referenced 5 in FIG. 2. To allow easy casting of the suspension, the latter must have a viscosity of the order of 0.5 to 3 Pa. s.
• the suspension is poured by the relative movement between a shoe 6 of the casting bench and the support 5.
• the shoe 6 has knives 7, the height of which is adjustable.
• the thickness of the film can be modified by changing the height between these knives 7 and the support 5. It is thus possible, thanks to this strip casting, to a very regular film thickness.
• thermal debinding consists in slowly heating the strip of material under a controlled atmosphere, in an oven or dryer 4 in order to remove the organic compounds contained therein, mainly the binder and the plasticizer.
• the heating rate in the dryer is of the order of 0.2 to 2 ° C / minute between 100 ° C and 500 ° C.
• FIGS. 3A and 3B represent two different embodiments of the third step of the method of the invention, that is to say the step of densification of the film.
• This densification step consists of evaporating the solvent and drying the thin film obtained after debinding.
• This film densification step has the role of evaporating the solvent. It can be produced, for example, in two different ways: the film can be densified by sintering in a pass-through oven or in a batch oven, or by hot rolling, using a rolling mill and an annealing furnace.
• the first variant shows that the film B, obtained after debinding, is cut into plates PI to Pn. These plates are introduced into an oven, referenced 9, under a controlled atmosphere.
• This oven can be a pass-through oven or a batch oven. Densification by sintering is carried out under a controlled atmosphere, or under a reducing atmosphere, such as for example hydrogen, hydrogenated nitrogen, argon or even hydrogenated argon, so as to avoid oxidation of the material.
• the sintering temperature depends on the particle size and the nature of the metal powders and ceramic reinforcements. For example, for a metallic copper powder, the temperature is between 700 ° C and 1080 ° C; for aluminum, the temperature is between 450 ° C and 650 ° C.
• the second variant of the densification step is shown in FIG. 3B.
• the film B is introduced into a rolling mill 10, placed within an annealing furnace 11.
• the film B is then hot rolled, in the furnace 11, under a controlled atmosphere.
• the cutting of the film B into plates PI, P2, ... is carried out at the outlet of the annealing furnace 11.
• This densification method by hot rolling and annealing of the film makes it possible to improve the densification of the material under the action of pressure and temperature.
• This variant is therefore particularly well suited to metal / ceramic composites which are poorly densified by natural sintering and to composites consisting of ductile metals, such as copper, aluminum or gold.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Powder Metallurgy (AREA)
• Laminated Bodies (AREA)
• Physical Vapour Deposition (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)

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• 2000
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