US5219829A
Expired / Lapsed
US
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Process and apparatus for the preparation of pulverulent metal oxides for ceramic compositions
Assignee: Merck Patent GmbH
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Filing: 1991-11-04
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Granted: 1993-06-15
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Expires: 2011-11-04
Abstract
Abstract The invention relates to a process and an apparatus for converting metal nitrate or mixed metal nitrate solutions into the corresponding metal oxides in a microwave field. The invention consists in heating, while the feed stream is being metered in, in such a manner that the solvent always evaporates within seconds and the decomposition product is obtained as a porous, sponge-like, purely oxidic material, which can be ground easily to give a powder having particle sizes of 0.5 to about 10 μm. The controlled metering in of the nitrate solution simultaneously makes it possible to control the reaction temperature below the sintering temperature of the powder. The reaction of the nitrate starting solution can take place continuously/batchwise in a reaction flask or continuously in a rotating reaction pipe, which is preferably charged with grinding balls, which possibly exert a reaction-activating effect similar to that exerted very particularly by the metal oxide sponge formed during the reaction.
Inventors
- 👤 Gerd Bauer
- 👤 Matthias Kuntz
- 👤 Ingrid Grobelsek
- 👤 Dirk Reyermann
- 👤 Gunter Nimtz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 05:46
CPC Classifications
C; C01; C01B; C01B13/00; C01B13/14; C01B13/18; C01B13/185; C01G; C01G25/00; C01G25/02; C01G3/00; C01G3/006; C01P; C01P2002/00; C01P2002/80; C01P2002/88; C01P2004/00; C01P2004/60; C01P2004/61; C01P2004/62; C01P2006/00; C01P2006/80; C01P2006/82; Y; Y10; Y10S; Y10S505/00; Y10S505/725; Y10S505/737
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
125 words
In a process for the preparation of pulverulent metal oxides for ceramic compositions, from the corresponding metal nitrates dissolved in water or in dilute nitric acid, comprising evaporation of the solvent and thermal decomposition of the metal nitrate by means of microwaves, the improvement wherein a quantity of metal nitrate solution is initially introduced into a reaction vessel such that when the solvent is evaporated by means of microwave irradiation until nitrous gases are formed, a porous sponge containing metal oxides is formed, and, while microwave irradiation is continued, further metal nitrate solution is added continuously onto the porous metal oxide containing sponge in a manner such that the solvent rapidly evaporates and the newly added metal nitrate is immediately converted to the metal oxide.
Claim 2
Dependent Claim
125 words
In a process for the preparation of pulverulent metal oxides for ceramic compositions, from the corresponding metal nitrates dissolved in water or in dilute nitric acid, comprising evaporation of the solvent and thermal decomposition of the metal nitrate by means of microwaves, the improvement wherein a quantity of metal nitrate solution is initially introduced into a reaction vessel such that when the solvent is evaporated by means of microwave irradiation until nitrous gases are formed, a porous sponge containing metal oxides is formed, and, while microwave irradiation is continued, further metal nitrate solution is added continuously onto the porous metal oxide containing sponge in a manner such that the solvent rapidly evaporates and the newly added metal nitrate is immediately converted to the metal oxide.
Claim 3
Dependent Claim
25 words
A process according to claim 1, wherein the reaction temperature is controlled by adjusting the amount of metal nitrate solution added per unit of time.
Claim 4
Dependent Claim
18 words
A process according to claim 1, wherein the nitrate solution contains a crystalline organic acid in a solvent.
Claim 5
Dependent Claim
14 words
A process according to claim 3, wherein the crystalline organic acid is tartaric acid.
Claim 6
Dependent Claim
17 words
A process according to claim 1, wherein the reaction is carried out in a rotating reaction pipe.
Claim 7
Dependent Claim
15 words
A process according to claim 5, wherein grinding bodies are present in the rotating pipe.
Claim 8
Dependent Claim
21 words
A process according to claim 6, wherein the grinding bodies comprise a material which absorbs microwaves and is thereby directly heated.
Claim 9
Dependent Claim
28 words
A process according to claim 6, wherein the grinding bodies comprise a material which does not absorb a significant amount of microwaves, and is not thereby directly heated.
Claim 10
Dependent Claim
48 words
A process according to claim 6, comprising using a mixture of grinding bodies of which some absorb and some do not absorb microwaves, whereby some are heated and some are not heated by the microwaves, in the form of a reaction bed having a predeterminable reaction temperature level.
Claim 11
Dependent Claim
31 words
A process according to claim 7, wherein silicon carbide is the material of the grinding bodies absorbing the microwaves and alumina is the material of the grinding bodies not absorbing microwaves.
References Cited (Backward Citations)
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| 3.5 Years (Year 4) | 1996-06-14 | 1996-12-14 | 1997-06-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-06-14 | 2000-12-14 | 2001-06-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-06-14 | 2004-12-14 | 2005-06-15 | $7700.00 | Window Closed / Lapsed |