WO2000051948A1 - A method for producing nano-engineered precursors - Google Patents
A method for producing nano-engineered precursors Download PDFInfo
- Publication number
- WO2000051948A1 WO2000051948A1 PCT/SE2000/000429 SE0000429W WO0051948A1 WO 2000051948 A1 WO2000051948 A1 WO 2000051948A1 SE 0000429 W SE0000429 W SE 0000429W WO 0051948 A1 WO0051948 A1 WO 0051948A1
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- WO
- WIPO (PCT)
- Prior art keywords
- reactor
- solid
- solutions
- solution
- feed solutions
- Prior art date
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Classifications
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- 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
-
- 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
- C01G21/00—Compounds of lead
- C01G21/006—Compounds containing, besides lead, 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
- C01G29/00—Compounds of bismuth
- C01G29/006—Compounds containing, besides bismuth, two or more other elements, with the exception of oxygen or hydrogen
-
- 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
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
Definitions
- the present invention relates to a method for producing nano-engineered precursors, and more particularly precursors of superconductors.
- HTSC High Temperature Superconductors
- Co-precipitation in solution is a technique for preparation of precursors, so that they are very well mixed.
- the different components such as metal salts
- the dissolved components are precipitated from the solution by the addition of precipi- taring agents, such as carbonates, formates, hydroxides and oxalates.
- precipi- taring agents such as carbonates, formates, hydroxides and oxalates.
- the resultant precipitate is filtered and thereafter calcined to remove or decompose the anion to obtain a mixture of the respective cation oxide.
- Further heating at high temperature, above 900 °C result in transformation of the cation oxides to a high temperature super conducting material (HTSC).
- the co-precipitation technique of HTSC precursors is generally based on the solid formation reactions between desired metals ions (M 3+ and M 2+ ) and a specified precipitant ligand (L n- ) as follows,
- M + Y + , Bi 3+ , etc
- M 2+ Ba 2+ , Sr 2+ , Ca 2+ , Cu 2+ , Pb 2+ , etc.
- n 1 or 2
- L- OH
- I C0 3 2 ", C 2 0 4 2 -, etc.
- the conventional co-precipitation based method generally comprises the following steps:
- the solution mixing can also be obtained by adding the solution(s) of metal ions into the precipitant solution or vice versa. In order to enhance the precipitation, ad- dition of the precipitant solution in excess is always required.
- the pH of the mixed solution is adjusted, for instance by adding an alkaline solution, to the optimal level for co-precipitation during, or after, the third step. Subsequently, the co-precipitated solid is then filtered, washed, dried and calcined to obtain the desired super conducting oxide.
- a co-precipitation method described as above can provide improved precursors.
- a more uniform and smaller particle size ( ⁇ 1 urn) such a co-precipitated powder is not only better in mixing the different metal components, but also more reactive to form the superconductive oxide.
- the conventional solu- tion addition/mixing process could hardly accomplish a simultaneous co-precipitation of all the desired metal components but "precipitation-in-sequence" of the individual components.
- the precipitation sequence of the metal ions is Y> Ba »Cu, if the solution of metal ions is added into the precipitant solution. If the precipitant solution is added into the solution of metal ions, the precipitation sequence is Y>Cu» Ba. In either way, the precipitate could hardly be a uniform mixture of various oxalates formed in the respective particles of individual components. Large scale production implies more serious drawbacks, which could even overcome the advantages of the co-precipitation technique.
- an object of the present invention is to provide a new co-precipitation based method that will overcome the drawbacks of the conventional methods, while enhancing their advantages as mentioned above.
- the object of the invention is to provide a method that can easily control the quality in overall chemical composition of the co-precipitated solid, as well as the uniformity in compositional distribution among the individual particles, while reducing the particles size down to the nanometer scale ⁇ 100 nm, for producing nano-particle size precursors.
- An inventive method is primarily characterised in that the metal components, i. e. the metal compounds, are dissolved to form separate solutions before being mixed together, or a solution of known concentrations before being mixed together
- Another object of the invention is to improve the quality of powder products to obtain high reactivity, particularly for meta-stable co-precipitated powders for HTSC precursors.
- the process claimed in this invention can be used to produce high quality precur- sors of rare earth oxide and/or alkaline earth oxide and/or copper oxide based ceramics in general, and oxide superconductors in particular.
- the method involves the knowledge that the dissolution of the metal compounds to form a feed solution of all the desired metal components at a fixed ratio of known concentrations, or two separate feed solutions: one containing a metal component(s) that can only be soluble at relatively high acidity, and another containing the other metal components at a fixed ratio of known concentrations, result in a co-precipitate solid having a high and consistent purity and a narrow variation in particle size.
- a method for producing nano- particle size precursors comprises the steps of:
- the feed solutions are added to a buffer solution under controlled conditions, e. g. pH.
- the buffer solution is preferably added to the reactor and re-circulated by means of a buffer tank and a corresponding pump.
- the HTSC components are those which form high temperature superconductors.
- Such compounds are described for instance in WO- A 1-94/00385.
- the metal compounds are preferably selected from those which form high temperature superconductors, including for example compounds of Y, Bi, Ba, Sr, Ca, Cu, Pb. Compounds of other metals having similar or suitable properties are also included in the scope of the invention.
- the separated solid is heated after the filtration to remove water and carbon contents and form a precursor of oxides, preferably being superconducting.
- the precipitating agent is selected from a carboxylic acid, or its salt, an oxalic acid, an oxalate salt, or a carbonate salt.
- the pH-adjusting agents are a solution of nitric acid to decrease the pH, and a solution of an alkali hydroxide, such as sodium hydroxide to increase the pH.
- Fig. 1 is a schematic process scheme of the method according to the invention.
- Fig. 2 is a more detailed process scheme of the method according to a preferred embodiment of the invention.
- Fig. 1 shows a general process scheme.
- the overall operation can be generalised as follows:
- the precipitating agent and pH-adjusting agents are separately dissolved in water in stirred tanks forming separate solutions 10, 20, 30, while the metal compounds are dissolved in water or acid in other tanks, forming solutions 40, 50.
- the prepared solutions 60 referred to as "feed solutions” are sampled for analysis of the accurate concentrations of the respective chemicals.
- the feed solutions 60 of metal components can also be combined in one tank (not illustrated). Then, a defined molar ratio of the metal ions should be fixed if the feed solution contains more than one metal ion. Moreover, some metal compounds may have to be dissolved in an acid solution, instead of water.
- the feed solutions 60 of the reactants i. e. the precipitating agent 20 and metal ion 40, 50 solutions, are pumped at a defined flow rate into a buffer solution 85 in a batch reactor 70 under stirring.
- a recycled flow from a buffer tank 80 is also simul- taneously pumped into the reactor 70.
- the pH of the buffer solution in the reactor 70 is conveniently monitored via a combined glass electrode or the like to assure it is within a defined range.
- the pH of the buffer solution is adjusted by adding a certain amount of the base 30 (or acid 20) solution into the reactor 70.
- the overflow of the buffer solution in the reactor 70 is conducted to the buffer tank 80 and recycled. After defined quantities of the reactants have been added into the reactor 70, the feeding pumps 90 are stopped.
- the precipitated solid is sampled for analysis in a given time interval until its composition does not change.
- the stirring, as well as the pumping is then stopped to allow the suspension to sedimentate. After a certain period, the suspension is thickened at the bottom of the reactor 70, and the clear solution is drained off through a conduit to the buffer tank 80.
- the stirring is restarted and the bottom valve 100 is turned on to let the suspension flow to a thickener 110.
- the suspension from the reactor 70 is mixed with the filtrate solution in the thickener 110 under stirring for a certain period of time.
- the stirring and pumping are then stopped to allow the suspension to sedimentate.
- the suspension is thickened at the bottom of the thickener 110 and the clear upper solution is drained off to the buffer tank 80 via a valve.
- the stirring is restarted and the bottom valve 111 is turned on to let the suspension flow to a filter 120.
- the solid product 130 is separated from its mother liquor, washed with water and then dried.
- the filtrate solutions comprising the mother liquor and wash- ing water are returned to the thickener 110.
- the controlled operating conditions for mixing and co-precipitation include the overall addition ratios between the feed solutions, the respective flow rates of the feed solutions, the stirring rates and the pH ranges of the reaction mixture, and its residence period in both the reactor and thickener.
- the overall addition ratios between the feed solutions are predetermined according to the chemical equilibrium calculation for said co-precipitation.
- the actual overall addition ratios between the metal components and precipitating agent are continuously monitored and kept constant within 0.1% derivation by controlling the respective flow rates of the feed so- lutions during operation.
- the operational conditions of the respective flow rates of the feed solutions are designed according to the predetermination of the overall addition ratios, as well as the optimal residence period in the reactor.
- the operational condition of the stirring rates of the reaction mixture in the reactor is designed according to the predetermination for its influence on the solution mixing and particle growth/dispersion.
- the actual stirring rate is con- tinuously monitored and kept constant within 5% variation during operation.
- the metastable product (powder) as obtained is specified by its well-defined composition, high uniformity in compositional distribution among the individual grains on nanometer scale, its low crystalinity or amorphous phase, and its high uniformity in phase distribution.
- the metastable product is specified by its ultrafine particle size, or nanometer grain size, and its high uniformity in size distribution.
- the product i. e. the nano-engineered precursor is specified by its nano-sized grains with high reactivity for further processing toward high performance oxide superconductors.
- a stable high-Tc (1 10 K) phase like Bil.6Pb0.4Sr2Ca2Cu3O10+8 is mostly preferred.
- BiPbSrCaCuO is only referred to as Bil.6Pb0.4Sr2Ca2Cu3O10 in the following.
- the precipitating agent solution 10 is prepared by dissolving oxalic acid or sodium oxalate in water at a concentration of 0.1-0.5 M. The accurate concentration should be analysed.
- the acid solution 20 is approximately 1 M nitric acid in water.
- the basic solution 30 is 1-5 M sodium hydroxide in water.
- the solutions of metal components of Bi,Pb,Sr,Ca and Cu are prepared, either by dissolving the respective oxides, hydroxides or carbonates in 4 M nitric acid, or by dissolving the respective nitrates in water or acid. Excess nitric acid of 1-3 M is required in the solution of 0.1-1 M Bi to avoid the precipitation. The concentrations of other metal components in the respective solutions are 0.5-2 M.
- the accurate concentration should be analysed;
- the reactor 70 is half-filled with a recycled solution 85 pumped from a buffer tank
- the pH of the solution 85 should be between 4-5;
- the feed solutions 60 of 20, 30, 10, 40 and 50, are simultaneously and continuously pumped at the respective flow rates into the reactor 70 under constant stirring.
- the pH of the solution mixture 75 is continuously momtored and controlled controlled within a range of 3-5 by adjusting the flow rate of 30.
- the stirring of the suspension should continue until the bulk composition of the precipitated oxalate precursor is independent on time.
- the residence time of the suspension in the thickener 110 is about one hour.
- the operational condition to filtration are mostly dependent upon the filter 120 to be used.
- the washing operation should lower the impurity to ⁇ 0.1% in the oxalate product.
- the nano-engineered precursors are synthesised via a controlled co-precipitation procedure that produces the metastable solids of multiple metal components of well- defined composition, such as low crystalinity, ultrafine particle size, and high uniformity in their distributions within the nanometer scale ( ⁇ 100 n ).
- the actual residence period is controlled by adjusting the flow rate of the recycled solution from the buffer tank during operation.
- the operational criteria of the average residence period of the reaction mixture in the reactor can be designed according to the predetermination for completion of more than 99% of co-precipitation equilibrium.
- the actual residence period is regularly verified by on-line analysis of the soluble metal component that is known to have the slowest precipitation rate, and adjusted accordingly during operation.
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Nanotechnology (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Physics & Mathematics (AREA)
- Composite Materials (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Materials Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU36881/00A AU3688100A (en) | 1999-03-02 | 2000-03-02 | A method for producing nano-engineered precursors |
EP00915656A EP1089951A1 (en) | 1999-03-02 | 2000-03-02 | A method for producing nano-engineered precursors |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE9900759A SE9900759D0 (en) | 1999-03-02 | 1999-03-02 | A method for producing nano-engineered precursors |
SE9900759-3 | 1999-03-02 |
Publications (1)
Publication Number | Publication Date |
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WO2000051948A1 true WO2000051948A1 (en) | 2000-09-08 |
Family
ID=20414703
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE2000/000429 WO2000051948A1 (en) | 1999-03-02 | 2000-03-02 | A method for producing nano-engineered precursors |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1089951A1 (en) |
AU (1) | AU3688100A (en) |
SE (1) | SE9900759D0 (en) |
WO (1) | WO2000051948A1 (en) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4804649A (en) * | 1987-10-16 | 1989-02-14 | Akzo America Inc. | Alkaline oxalate precipitation process for forming metal oxide ceramic superconductors |
US5206215A (en) * | 1991-03-18 | 1993-04-27 | Alcatel Alsthom Compagnie Generale D'electricite | Process for obtaining precursors for high critical temperature superconductor ceramics comprising a first and second precipitation |
WO1994000385A1 (en) * | 1992-06-23 | 1994-01-06 | The University Of Queensland | SUPERCONDUCTING OXIDES BY COPRECIPITATION AT CONSTANT pH |
US5484766A (en) * | 1994-02-14 | 1996-01-16 | Electric Power Research Institute, Inc. | Preparation of Bi-Pb-Sr-Ca-Cu-O (2223) superconductors |
-
1999
- 1999-03-02 SE SE9900759A patent/SE9900759D0/en unknown
-
2000
- 2000-03-02 WO PCT/SE2000/000429 patent/WO2000051948A1/en not_active Application Discontinuation
- 2000-03-02 AU AU36881/00A patent/AU3688100A/en not_active Abandoned
- 2000-03-02 EP EP00915656A patent/EP1089951A1/en not_active Withdrawn
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4804649A (en) * | 1987-10-16 | 1989-02-14 | Akzo America Inc. | Alkaline oxalate precipitation process for forming metal oxide ceramic superconductors |
US5206215A (en) * | 1991-03-18 | 1993-04-27 | Alcatel Alsthom Compagnie Generale D'electricite | Process for obtaining precursors for high critical temperature superconductor ceramics comprising a first and second precipitation |
WO1994000385A1 (en) * | 1992-06-23 | 1994-01-06 | The University Of Queensland | SUPERCONDUCTING OXIDES BY COPRECIPITATION AT CONSTANT pH |
US5484766A (en) * | 1994-02-14 | 1996-01-16 | Electric Power Research Institute, Inc. | Preparation of Bi-Pb-Sr-Ca-Cu-O (2223) superconductors |
Also Published As
Publication number | Publication date |
---|---|
SE9900759D0 (en) | 1999-03-02 |
EP1089951A1 (en) | 2001-04-11 |
AU3688100A (en) | 2000-09-21 |
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