DE4119499C1 - Ceramic powder sinters for fuel cells - intensively mixes starting materials esp. nitrate(s) in water and citric acid and concentrates soln. until unstirrable before azeotropic distn. - Google Patents

Ceramic powder sinters for fuel cells - intensively mixes starting materials esp. nitrate(s) in water and citric acid and concentrates soln. until unstirrable before azeotropic distn.

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Publication number
DE4119499C1
DE4119499C1 DE19914119499 DE4119499A DE4119499C1 DE 4119499 C1 DE4119499 C1 DE 4119499C1 DE 19914119499 DE19914119499 DE 19914119499 DE 4119499 A DE4119499 A DE 4119499A DE 4119499 C1 DE4119499 C1 DE 4119499C1
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Germany
Prior art keywords
soln
water
citric acid
ceramic powder
fuel cells
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Expired - Fee Related
Application number
DE19914119499
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German (de)
Inventor
Heinz Dr. 6906 Leimen De Stadelmann
Endre 6900 Heidelberg De Reich
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ABB Patent GmbH
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ABB Patent GmbH
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Publication date
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Priority to DE19914119499 priority Critical patent/DE4119499C1/en
Application granted granted Critical
Publication of DE4119499C1 publication Critical patent/DE4119499C1/en
Anticipated expiration legal-status Critical
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/14—Methods for preparing oxides or hydroxides in general
    • C01B13/18—Methods for preparing oxides or hydroxides in general by thermal decomposition of compounds, e.g. of salts or hydroxides
    • C01B13/185—Preparing mixtures of oxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G37/00—Compounds of chromium
    • C01G37/006—Compounds containing, besides chromium, two or more other elements, with the exception of oxygen or hydrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G45/00—Compounds of manganese
    • C01G45/12—Manganates manganites or permanganates
    • C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
    • C01G45/125—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type[MnO3]n-, e.g. Li2MnO3, Li2[MxMn1-xO3], (La,Sr)MnO3
    • C01G45/1264—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type[MnO3]n-, e.g. Li2MnO3, Li2[MxMn1-xO3], (La,Sr)MnO3 containing rare earth, e.g. La1-xCaxMnO3, LaMnO3
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/66—Nickelates containing alkaline earth metals, e.g. SrNiO3, SrNiO2
    • C01G53/68—Nickelates containing alkaline earth metals, e.g. SrNiO3, SrNiO2 containing rare earth, e.g. La1.62 Sr0.38NiO4
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer

Abstract

Ceramic powder used in mfr, of sintered parts for fuel cells is web-chemically manufactured from an aqueous citrate soln., which is prepared by dissolution and intensive mixing of starting cpds., partic. nitrates in water and citric acid. The soln. is concentrated until it becomes unstirrable and is then subjected to azeotropic distillation by repeated mixing the soln. at boiling heat with toluol, so that it foams up. The foamed material is calcined below 500 deg.C. ADVANTAGE - Homogeneous, high sintering activity.

Description

Die Erfindung bezieht sich auf ein Verfahren zur naßche­ mischen Herstellung keramischer Pulver.The invention relates to a method for wet mix manufacture ceramic powder.

Zur Herstellung von Hochtemperaturbrennstoffzellen wer­ den keramische Pulver benötigt, die z. B. zum Aufbringen von Elektrodenschichten auf einen keramischen Elektroly­ ten oder einen keramischen Träger verwendet werden kön­ nen. Solche Pulver können nach klassischen Methoden durch Mischen von Oxiden mit organischen Zusätzen, Cal­ cinieren bei mehr als 1000°C und anschließendes Mahlen hergestellt werden. So hergestellte Pulver enthalten je­ doch harte Agglomerate, die beim Mahlen nur zum Teil aufbrechbar sind. Die somit im fertiggestellten Pulver noch enthaltenen Agglomerate führen bei der Weiterverar­ beitung zu gesinterten keramischen Schichten zu uner­ wünschten Eigenschaften der Schichten, wie z. B. zu ge­ ringe Sinterdichten oder zu hohe Porosität, wodurch die Leistungsfähigkeit der damit hergestellten Brennstoffzellen beeinträchtigt werden kann. Das Sinterverhalten der Pulver kann zwar durch Zusatz von Sinterhilfen verbessert werden, jedoch können bei diesem Vorgehen durch unvollständiges Mi­ schen Inhomogenitäten in der chemischen Zusammensetzung auftreten, wodurch die elektrischen Eigenschaften der her­ gestellten Schichten stark beeinträchtigt werden können. Außerdem wird durch unerwünschte Diffusion dieser Zusätze in andere Funktionseinheiten die Langzeitstabilität negativ beeinflußt.For the production of high temperature fuel cells who the ceramic powder needed, the z. B. for application from electrode layers to a ceramic electrolyte ten or a ceramic support can be used nen. Such powders can be made using classic methods by mixing oxides with organic additives, Cal cine at more than 1000 ° C and then grinding getting produced. Powders produced in this way each contain but hard agglomerates, which are only partially in the grinding are breakable. So in the finished powder agglomerates still present lead to further processing processing to sintered ceramic layers too un desired properties of the layers, such as. B. ge rings sintered densities or too high porosity, which causes the  Performance of the fuel cells produced with it can be affected. The sintering behavior of the powder can be improved by adding sintering aids, however, incomplete Mi. chemical inhomogeneities occur, causing the electrical properties of the forth provided layers can be severely impaired. In addition, by undesirable diffusion of these additives long-term stability negative in other functional units influenced.

Der Erfindung liegt daher die Aufgabe zugrunde, ein verbes­ sertes Verfahren zur naßchemischen Herstellung von kerami­ schen Pulvern anzugeben.The invention is therefore based on the object, a verbes sertes process for the wet chemical production of kerami powders.

Diese Aufgabe wird durch ein Verfahren gelöst zur naßchemi­ schen Herstellung keramischer Pulver in nachstehenden Schritten:This problem is solved by a wet chemical method The production of ceramic powder in the following Steps:

  • a) Herstellen einer wäßrigen Zitratlösung durch Lösung und intensive Mischung von wasserlöslichen Ausgangs­ verbindungen, insbesondere Nitraten in Wasser und Zi­ tronensäure,a) Preparation of an aqueous citrate solution by solution and intense blend of water-soluble starting compounds, especially nitrates in water and ci tronic acid,
  • b) Einengen der Zitratlösung bis zur aufhörenden Rührfä­ higkeit,b) Concentrate the citrate solution until it stops stirring ability,
  • c) azeotrope Destillation durch mehrfaches Versetzen der eingeengten Zitratlösung in der Siedehitze mit To­ luol, wobei ein Aufschäumen eintritt,c) azeotropic distillation by repeating the concentrated citrate solution at the boiling point with To luol, foaming occurs
  • d) Calcinieren des aufgeschäumten Materials bei Tempera­ turen unterhalb von 500°C.d) calcining the foamed material at tempera doors below 500 ° C.

Das Verfahren kann vorteilhaft verwendet werden zur Her­ stellung von keramischen Pulvern des Typs Lax(Mg, Ca, Sr)1-xMM′O3, mit M = Mn, Cr, Ni und M′ = Cr, Ni, Bi. Vorteilhafte Eigenschaften der nach dem erfindungsge­ mäßen Verfahren hergestellten Pulver sind große Homo­ genität und hohe Sinteraktivität. Dadurch kann ohne Sin­ terhilfen gesintert werden. Die Pulver sind als kerani­ sche Kleber verwendbar.The method can be used advantageously for the production of ceramic powders of the type La x (Mg, Ca, Sr) 1-x MM'O 3 , with M = Mn, Cr, Ni and M '= Cr, Ni, Bi. Advantageous Properties of the powder produced by the process according to the invention are high homogeneity and high sintering activity. This allows sintering without sintering. The powders can be used as kerani adhesive.

Das erfindungsgemäße Verfahren wird nachstehend anhand des in der Zeichnung dargestellten Fließschemas näher erläutert.The method according to the invention is described below of the flow diagram shown in the drawing explained.

Es werden wasserlösliche Ausgangsverbindungen, z. B. Ni­ trate, unter Zusatz von Zitronensäure in Wasser gelöst und intensiv gemischt, z. B. im Becherglas mit einem La­ bor-Dispenser. Dadurch läßt sich eine Homogenität auf atomarer Ebene erzielen. Die beim Zusatz von Zitronen­ säure und anschließendem Einengen entstehenden Kristal­ lite liegen im Nanometer-Bereich und zeigen daher selbst ohne Zugabe von Sinterhilfen eine hohe Sinteraktivität. Da beim Einengen und anschließenden Calcinieren der ge­ bildeten Zitrate in Gegenwart von Restwasser die Gefahr einer erneuten Agglomeratbildung besteht, wird abwei­ chend von einem als Pecchini-Methode bekannten Verfahren die wäßrige Zitratlösung bis zur aufhörenden Rührfähig­ keit eingeengt und dann in der Siedehitze mehrfach mit Toluol versetzt. Dieses Toluol ist in der Lage, noch vorhandene Wasserspuren azeatrop zu entfernen. Eine Bil­ dung harter Agglomerate durch vorhandenes Restwasser beim Calcinieren wird dadurch unterdrückt. Weiterhin sind die Zitrate in Toluol unlöslich, was zu einer Haut­ bildung auf der Oberfläche des Ansatzes führt. Da diese Haut das Abdampfen des Lösungsmittels behindert, bilden sich unter der Haut Dampfblasen, die zu einem starken Aufschäumen führen. Da dieser "Schaum" eine extrem hohe innere Oberfläche besitzt, erhält man schon bei Tempera­ turen unter 500°C eine vollständige Zersetzung der Zi­ trate in die gewünschten Oxide. Da bei diesen Temperatu­ ren weder Agglomeraten gebildet werden, noch eine teil­ weise Entmischung möglich ist, sind diese Pulver sowohl sinteraktiv als auch chemisch homogen.There are water-soluble starting compounds, for. B. Ni trate, dissolved in water with the addition of citric acid and mixed intensively, e.g. B. in a beaker with a La boron dispenser. This allows homogeneity at the atomic level. The addition of lemons acid and subsequent concentration of the resulting crystal lite are in the nanometer range and therefore show themselves high sintering activity without the addition of sintering aids. Since when the concentration and subsequent calcination of the ge Citrates were a danger in the presence of residual water renewed agglomerate formation is rejected from a process known as the Pecchini method the aqueous citrate solution until it stops stirring concentrated and then several times in the boiling heat Toluene added. This toluene is still able remove existing traces of water azeatropically. A bil Formation of hard agglomerates through existing residual water this suppresses during calcining. Farther citrates are insoluble in toluene, causing skin education on the surface of the approach leads. This one Skin prevents the solvent from evaporating vapors under the skin, causing a strong Lather up. Because this "foam" is extremely high  has an inner surface, you get it from Tempera tures below 500 ° C a complete decomposition of the Zi occurred in the desired oxides. Because at these temperatu neither agglomerates are formed, nor a part wise segregation is possible, these powders are both sinter active as well as chemically homogeneous.

Die oxidischen Pulver können im Walzenstand mit geringem Energieeintrag verkleinert und anschließend gesiebt wer­ den, um Pulver mit der gewünschten Korngröße bereit zu stellen. Die Korngröße liegt im µm-Bereich, da schwach gebundene Agglomerate (Sekundärkorn) gebildet werden. Das Pulver kann zur Herstellung von Schichten oder Form­ körpern durch Pressen, Siebdruck oder ein anderes Form­ gebungsverfahren weiter verarbeitet werden, wobei eine hohe Gründichte und Homogenität feststellbar ist. Durch anschließendes Sintern lassen sich Formkörper oder Schichten herstellen, die sich durch hohe Dichte und Ho­ mogenität, sowie hohe elektrische Leitfähigkeit aus­ zeichnen.The oxide powders can be low in the roller stand Reduced energy input and then sieved to prepare powder with the desired grain size put. The grain size is in the µm range because it is weak bound agglomerates (secondary grain) are formed. The powder can be used to make layers or mold embody by pressing, screen printing or some other form processing procedures, where a high green density and homogeneity can be determined. By subsequent sintering can be molded or Produce layers that are characterized by high density and Ho homogeneity and high electrical conductivity to draw.

Claims (2)

1. Verfahren zur naßchemischen Herstellung kerami­ scher Pulver in nachstehenden Schritten:
  • a) Herstellen einer wäßrigen Zitratlösung durch Lösung und intensive Mischung von wasserlöslichen Ausgangs­ verbindungen, insbesondere Nitraten in Wasser und Zi­ tronensäure,
  • b) Einengen der Zitratlösung bis zur aufhörenden Rührfä­ higkeit,
  • c) azeotrope Destillation durch mehrfaches Versetzen der eingeengten Zitratlösung in der Siedehitze mit To­ luol, wobei ein Aufschäumen eintritt,
  • d) Calcinieren des aufgeschäumten Materials bei Tempera­ turen unterhalb von 500°C.
1. Process for the wet chemical production of ceramic powders in the following steps:
  • a) preparing an aqueous citrate solution by dissolving and intensively mixing water-soluble starting compounds, in particular nitrates in water and citric acid,
  • b) concentration of the citrate solution until it stops stirring,
  • c) azeotropic distillation by repeatedly adding the concentrated citrate solution at the boiling point with toluene, which causes foaming,
  • d) calcining the foamed material at temperatures below 500 ° C.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß keramische Pulver des Typs Lax(Mg, Ca, Sr)1-xMM′O3, mit M = Mn, Cr, Ni und M′ = Cr, Ni, Bi hergestellt werden.2. The method according to claim 1, characterized in that ceramic powder of the type La x (Mg, Ca, Sr) 1-x MM'O 3 , with M = Mn, Cr, Ni and M '= Cr, Ni, Bi produced will.
DE19914119499 1991-06-13 1991-06-13 Ceramic powder sinters for fuel cells - intensively mixes starting materials esp. nitrate(s) in water and citric acid and concentrates soln. until unstirrable before azeotropic distn. Expired - Fee Related DE4119499C1 (en)

Priority Applications (1)

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DE19914119499 DE4119499C1 (en) 1991-06-13 1991-06-13 Ceramic powder sinters for fuel cells - intensively mixes starting materials esp. nitrate(s) in water and citric acid and concentrates soln. until unstirrable before azeotropic distn.

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DE19914119499 DE4119499C1 (en) 1991-06-13 1991-06-13 Ceramic powder sinters for fuel cells - intensively mixes starting materials esp. nitrate(s) in water and citric acid and concentrates soln. until unstirrable before azeotropic distn.

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0873969A1 (en) * 1997-04-24 1998-10-28 Siemens Aktiengesellschaft Process for the preparation of a ceramic powder for powder coating and use of the process for preparing a component of a high temperature fuel cell

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4810680A (en) * 1986-06-26 1989-03-07 Corning Glass Works Preparation of high purity, homogeneous zirconia mixtures

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4810680A (en) * 1986-06-26 1989-03-07 Corning Glass Works Preparation of high purity, homogeneous zirconia mixtures

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Derwent Kurzreferat 90-152294/20 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0873969A1 (en) * 1997-04-24 1998-10-28 Siemens Aktiengesellschaft Process for the preparation of a ceramic powder for powder coating and use of the process for preparing a component of a high temperature fuel cell

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