EP1301434A2 - Poudre nanometrique de corindon, corps frittes produits a partir de cette poudre et son procede de production - Google Patents

Poudre nanometrique de corindon, corps frittes produits a partir de cette poudre et son procede de production

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Publication number
EP1301434A2
EP1301434A2 EP01960526A EP01960526A EP1301434A2 EP 1301434 A2 EP1301434 A2 EP 1301434A2 EP 01960526 A EP01960526 A EP 01960526A EP 01960526 A EP01960526 A EP 01960526A EP 1301434 A2 EP1301434 A2 EP 1301434A2
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EP
European Patent Office
Prior art keywords
corundum
precursor
aluminum
temperatures
powders
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01960526A
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German (de)
English (en)
Inventor
Robert Drumm
Christian Goebbert
Kai Gossmann
Ralph Nonninger
Helmut Schmidt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Leibniz-Institut fur Neue Materialien Gemeinnuet
Original Assignee
Leibniz Institut fuer Neue Materialien Gemeinnuetzige GmbH
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Application filed by Leibniz Institut fuer Neue Materialien Gemeinnuetzige GmbH filed Critical Leibniz Institut fuer Neue Materialien Gemeinnuetzige GmbH
Publication of EP1301434A2 publication Critical patent/EP1301434A2/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/34—Preparation of aluminium hydroxide by precipitation from solutions containing aluminium salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
    • C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
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    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
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    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/62605—Treating the starting powders individually or as mixtures
    • C04B35/62645—Thermal treatment of powders or mixtures thereof other than sintering
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    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
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    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
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    • C04B41/5025—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials with ceramic materials
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    • C04B2235/44—Metal salt constituents or additives chosen for the nature of the anions, e.g. hydrides or acetylacetonate
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    • C04B2235/44—Metal salt constituents or additives chosen for the nature of the anions, e.g. hydrides or acetylacetonate
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    • C04B2235/77—Density

Definitions

  • NANOSKAL1GE COROD POWDER SINTER BODIES MADE THEREOF AND METHOD FOR THE PRODUCTION THEREOF
  • the invention relates to nanoscale corundum powder, a process for their production and their processing into sintered bodies.
  • Powdered corundum ( ⁇ - Al 2 O 3 ) is an important raw material for the production of aluminum oxide ceramics, which can basically be done in two ways.
  • One way starts with shaped bodies that are made directly from corundum powder ( ⁇ -AI 2 0 3 powder), the other from shaped bodies that consist of an -AI 2 0 3 precursor (for example, the ⁇ or ⁇ phase) , which is then converted in situ into the ⁇ -AI 0 3 phase.
  • the sintering temperature of the corundum is between 1300 and 1600 ° C, depending on the size of the starting particles used.
  • the most important obstacle to this is the high activation energy of the homogeneous nucleation, which is kinetically strongly delayed, so that the other Al 2 0 3 phases (e.g.
  • US-A-4657754 describes nanoscale corundum having an average particle size of 20 and 50 nm (jr nanocorundum "), which is produced by seeding, so that the synthesis temperature may be reduced so that at 1000 ° C ⁇ -AI 2 0 3 -Powder with a density of 3.78 g / cm 3 (corresponds to 95% of the theoretical density) is present.
  • Weng et al. describe another method from salt solutions in CN-A-085187, which likewise gives nanocorundus with a diameter of 10 to 15 nm at synthesis temperatures of 1100 to 1300 ° C.
  • a synthesis temperature of 1000 ° C is too high for many purposes, in particular for cofiring processes in microelectronics with foils or the sealing sintering of pastes.
  • the synthesis temperature can be reduced to values below 1000 ° C. by means of a special process technology, an only weakly agglomerated nanoscale corundum powder being obtained which can be sintered at lower sintering temperatures.
  • This seemingly minor improvement is of eminent technical importance, since it enables a much broader field of application to be worked on.
  • new multi-layer systems can be processed in a single cofiring step (which previously required several sintering steps at higher temperatures), since all the multilayer elements contained can now be compressed at the lower sintering temperature.
  • the invention relates to a process for the preparation of nanoscale corundum powders, in which one first produces an Al 2 0 3 precursor by adding an aqueous solution of an aluminum compound with seed crystals and adding a base and the Al 2 O 3 precursor then by calcining at elevated temperatures The temperature is converted to corundum, which is characterized in that the salts present in addition to the Al 2 O 3 precursor are separated off before the calcination, the product obtained is calcined at temperatures from 700 to 975 ° C. and any fines present ( ⁇ 40 nm) are removed ,
  • Aluminum compounds suitable for producing the Al 2 O 3 precursor are preferably water-soluble aluminum salts such as aluminum (IH) nitrate, aluminum (III) chloride, aluminum (III) acetate or aluminum (III) ethylate. These aluminum compounds are dissolved, for example, in deionized water and seed crystals are added, which preferably have a particle size ⁇ 100 nm. Examples of suitable germs are corundum or diasporic germs.
  • the desired Al 2 O 3 precursor which is required for conversion to corundum at temperatures below 1000 ° C., is formed during a ripening period.
  • bases which can be used are inorganic or organic bases, such as sodium, potassium, calcium or magnesium hydroxide, ammonia, urea, aliphatic and aromatic amines, thermally separable bases such as ammonia being particularly preferred.
  • the precipitation or ripening usually takes place at temperatures of 50 to 100 ° C., preferably 70 to 90 ° C. and particularly preferably 80 to 90 ° C., over a period of 20 to 145 hours, preferably 60 to 90 hours and particularly preferably 70 to 80 hours.
  • the n-corundum is preferably produced using the following two alternative methods.
  • the aqueous solvent is preferably removed by freeze-drying and the salts contained as impurities are thermally decomposed at temperatures of 150 to 500 ° C., for example 400 ° C.
  • the product obtained is mechanically comminuted and converted into ⁇ -Al 2 O 3 by calcining at temperatures from 700 to 975 ° C., preferably 750 to 950 ° C. and in particular 800 to 900 ° C.
  • Caicination is usually carried out over a period of 1 to 3 hours.
  • the corundum powder obtained by method 1 is characterized by a high
  • Corundum content but as a secondary phase still contains a small fine fraction ( ⁇ 40 nm), which mainly consists of non- ⁇ -Al 2 0 3 phases. It is essential to the invention to at least largely remove this fine fraction by a later one To enable compaction of the nanoscale corundum powder at sintering temperatures ⁇ 1200 ° C.
  • the fine fraction is preferably removed by centrifugation.
  • the corundum powder produced is dispersed in aqueous solution with the aid of a dispersant (surface modifier) and then centrifuged one or more times.
  • Suitable dispersants are, for example, inorganic acids (preferably HNO 3 ), aromatic or aliphatic mono-, di- or polycarboxylic acids, aromatic or aliphatic oxacarboxylic acids, such as trioxadecanoic acids (TODS), ⁇ -dicarbonyl compounds and amino acids.
  • the dispersant concentration is adapted to the specific surface of the synthesized corundum powder, so that, for example, 4-5 ⁇ mol of dispersant are available per m 2 Al 2 O 3 surface.
  • the existing salt load is reduced or removed by dialysis.
  • the solution containing the AI 2 0 3 precursor is filled into dialysis tubes and stored in deionized water.
  • the dialyzed solution is then frozen and freeze-dried.
  • the powder obtained can, if necessary, be calcined at 150 to 500.degree. C. (for example 400.degree. C.) to completely remove the salt content still present.
  • the powder is converted into ⁇ -Al 2 O 3 by calcining at temperatures from 700 to 975 ° C., preferably 750 to 950 ° C. and in particular 800 to 900 ° C.
  • ⁇ -Al 2 0 3 powder obtained after surface modification with suitable surface modifiers such as inorganic acids (preferably HN0 3 ), .aromatic or aliphatic mono-, di- or polycarboxylic acids, aromatic or aliphatic oxacarboxylic acids, for example trioxadecanoic acids (TODS), ⁇ -dicarbonyl compounds or amino acids, can be compressed directly at sintering temperatures ⁇ 1200 ° C.
  • suitable surface modifiers such as inorganic acids (preferably HN0 3 ), .aromatic or aliphatic mono-, di- or polycarboxylic acids, aromatic or aliphatic oxacarboxylic acids, for example trioxadecanoic acids (TODS), ⁇ -dicarbonyl compounds or amino acids
  • the amount of surface modifier is the specific surface of the synthesized corundum powder adapted so that, for example, 4-5 ⁇ mol of dispersant are available per m 2 Al 2 O 3 surface.
  • the surface can be modified, for example, using a ball mill (3-4 h, aluminum oxide grinding balls ⁇ 1 mm), mortar mills, three-roller mill or kneading unit, adapted to the subsequent shaping technique.
  • the average primary particle size is usually 30 to 150 nm, preferably 40 to 100 nm and particularly preferably 50 to 70 nm.
  • the corundum powder is only slightly agglomerated in the redispersed state. It has a phase purity (content of ⁇ -Al 2 0 3 ) of> 80, preferably> 90 and in particular> 95% by weight and a density of> 3.90 g / cm 3 , preferably 3 3.93 g / cm 3 , particularly preferably> 3.95 g / cm 3 .
  • the corundum powder produced according to the invention is used for further shaping with conventional processing aids, e.g. organic solvents, binders, plasticizers, mixed.
  • suitable solvents are e.g. Ethylene glycol, diethylene glycol monobutyl ether and diethylene glycol monoethyl ether, individually or as mixtures.
  • binders which can be used are cellulose derivatives such as hydroxypropyl cellulose, polyvinylpyrrolidone, acrylate polymers and oligomers,
  • Methacrylates such as tetraethylene glycol dimethacrylate and polyethylene glycoidimethacrylate. The following are used e.g. 15% by weight of binder, based on the weighed solid.
  • binder e.g. 15% by weight of binder, based on the weighed solid.
  • polyethylene glycol dimethacrylates, polyethylene glycols e.g. PEG 600, PEG 800, PEG 1000, PEG 2000, PEG 6000
  • plasticizers e.g. PEG 600, PEG 800, PEG 1000, PEG 2000, PEG 6000
  • 25% by weight based on the weighed-in binder.
  • the nanoscale corundum powders according to the invention are suitable for producing dense Al 2 O 3 sintered bodies in the form of components or constituents of multilayer structures.
  • Special application areas of these components and Multi-layer systems are (micro) electronics, sensors (gas, pressure, piezo sensors), microsystem technology (eg microreactors), ceramic filter elements and catalyst carriers.
  • the solution obtained is frozen (for example at -30 ° C.) and then dried (freeze-drying).
  • the powder is then heated to 400 ° C. (air atmosphere) at a heating rate of 2 K / min and kept at this temperature for 1 h.
  • the powder is ground dry in a mortar mill for 1 hour.
  • the powder is then brought to 800 ° C. at a heating rate of 10 K / min and immediately heated to 900 ° C. at a heating rate of 2 K / min and kept at this temperature for 1 hour.
  • the powder produced in this way has a specific surface area of approximately 20-60 m 2 / g and a density of 3.6-3.9 g / cm 3 , depending on the germs used.
  • the powder After cooling, the powder is dispersed for 3-4 hours in a ball mill with aluminum oxide grinding balls ( ⁇ 1 mm) and an organic acid (TODS) as a dispersant / surface modifier.
  • the dispersant content is adapted to the specific surface of the synthesized aluminum oxide powder, so that 4-5 ⁇ mol TODS per m 2 Al 2 O 3 surface are contained.
  • the fine fraction of the aluminum oxide powder obtained is separated off by repeated centrifugation.
  • the separation limit for centrifugation is arithmetically a particle size of approximately 40 nm.
  • the fine fraction consists predominantly (> 90%) of non- ⁇ -Al 2 0 3 particles.
  • the centrifugate is freeze-dried to remove the solvent.
  • the resulting solution is purified by dialysis in portions containing approximately 400 g ammonium nitrate to remove the dissolved ammonium nitrate ions.
  • the solution is poured into a dialysis tube (pore size 2.5 - 3 nmj and approx.
  • a hold period of 1 is inserted at 900 ° C.
  • the powder thus produced has a specific surface area of approx. 18-22 m 2 / g and a density of 3.95-3.98 g / cm 3 .
  • the primary particle size is between 40-70 nm, the powder is weakly agglomerated in the redispersed state.
  • Example 1 10.5 g of the ⁇ -Al 2 0 3 prepared in Example 1 are homogeneously mixed together with 2.8 g of a 1: 1 solvent mixture of ethylene glycol and diethylene glycol monobutyl ether and 0.5 g of polyvinylpyrrolidone as a binder. Mortars, kneaders or mortar mills can be used as mixing units. The paste obtained is applied several times to a three-roll mill for the final homogenization.
  • the aluminum oxide paste is applied using a thick-film process (screen printing) to already sintered corundum substrates or green (unsintered) substrates made of yttrium-stabilized (3 mol% Y 2 0 3 ) zirconium dioxide in dry layer thicknesses of up to 30 ⁇ m and dried without cracks in a circulating air drying cabinet at 80 ° C.
  • the printed layers on the corundum substrates are thermally compacted at 1200 ° C (heating rate 5K / min) with a holding time of 1 hour.
  • the compression of the ⁇ -Al 2 0 3 layers printed on green (unsintered) substrates made of yttrium-stabilized zirconium dioxide takes place in two stages.
  • the organic matter contained in the composite is removed in a protective gas atmosphere (nitrogen) at temperatures up to 450 ° C by thermal decomposition.
  • the heating up time is 10 hours, holding time 3 hours.
  • the thermal compression up to the dense material composite takes place in an atmosphere furnace at temperatures of
  • Example 2 5 2 g of the -Al 2 0 3 powder produced in Example 1 are homogeneously mixed with 1 g of a solvent mixture of ethylene glycol / diethylene glycol monobutyl ether (1: 1) and 0.15 g of a cellulose binder and dried at 100 ° C. 200 mg of the mixture are compressed in a uniaxial pressing tool with an inner diameter of 5 mm at a pressure of 200 MPa. Then ⁇ Q is post-compressed in a cold isostatic press at 400 MPa. The compact is thermally compressed at 1200 ° C (1h) in an air atmosphere. After sintering, the shaped body has a density of 3.85 g / cm 3 (96.5% of theory).

Abstract

Pour obtenir des poudres nanométriques de corindon, on produit d'abord un précurseur Al2O3 en mélangeant une solution aqueuse d'un composé d'aluminium à des germes cristallins ; on ajoute une base puis on transforme le précurseur Al2O3 en corindon par calcination à haute température. Avant la calcination, on sépare les sels présents en plus du précurseur Al2<O>3<. Le produit obtenu à des températures de 700 à 975 DEG C est calciné et les fines éventuellement présentes sont éliminées. Les poudres de corindon obtenues peuvent être frittées à des températures ≤ 1200 DEG C en corps moulés ou constituants de systèmes multicouche.
EP01960526A 2000-07-21 2001-07-20 Poudre nanometrique de corindon, corps frittes produits a partir de cette poudre et son procede de production Withdrawn EP1301434A2 (fr)

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DE10035679A DE10035679A1 (de) 2000-07-21 2000-07-21 Nanoskalige Korundpulver, daraus gefertigte Sinterkörper und Verfahren zu deren Herstellung
DE10035679 2000-07-21
PCT/EP2001/008422 WO2002008124A2 (fr) 2000-07-21 2001-07-20 Poudre nanometrique de corindon, corps frittes produits a partir de cette poudre et son procede de production

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