CA2221963C - Cobalt metal agglomerates, a method of producing them and their use - Google Patents
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- 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
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
- B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G51/00—Compounds of cobalt
- C01G51/04—Oxides; Hydroxides
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/50—Agglomerated particles
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- 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
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- 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
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The present invention relates to cobalt metal agglomerates consisting of peanut-shaped primary particles with the primary particles having average particle sizes in the range from 0.1 to 0.7 µm, process for the production thereof via CoO(OH) and uses thereof are also provided.
Description
Cobalt metal agglomerates, a method of producing them and their use The present invention relates to cobalt metal agglomerates consisting of peanut-shaped primary particles, to a process for the production thereof and to the use thereof.
Finely divided cobalt metal is mainly used as a binder in the production of hard metal and cutting tools based on various hard materials, such as for example WC, diamond, SiC and CBN. The cobalt metals used, for example, in the production of diamond tools must fulfil specific requirements. These include, in the first instance, that impurities such as Al, Ca, Mg, S and Si should be avoided as these elements readily form stabile oxides with the residual oxygen of the cobalt metal powder, so causing unwanted porosity in the segments.
It is also necessary, especially when producing segments with synthetic diamonds, to use only cobalt metal powders with very active sintering properties, as minimum densities of 8.5 g/cm3 are required in this case. These densities should be achieved at a sintering temperature range of as low as < 900 C because the diamond may be converted into graphite at higher temperatures. If the sintering activity of the cobalt metal is inadequate, sufficient hardness is not achieved.
Under the extreme stresses to which annular drilling bits or cutting tools are exposed, the abrasive action of stone dust leads to deep erosion and unwanted detachment of the diamonds or other hard materials and consequently a loss of cutting performance.
According to the prior art, cobalt metals are used, on the one hand, in the form of mixtures of atomised cobalt metal powders with hydrogen-reduced powders, as are disclosed in DE-A 4 343 594, on the other hand as ultra-fine and extra-fine grade cobalt metal powders.
Ultra-fine powders are differentiated by their FSSS value of < 1.0 gm from extra-fine powders which have FSSS values of between 1.2 and 1.4 gm.
The small particle size and the resultant large surface areas of the described cobalt metal powders promote the absorption of atmospheric oxygen and moisture, which frequently leads to degradation of the flowability of the powders.
Finely divided cobalt metal is mainly used as a binder in the production of hard metal and cutting tools based on various hard materials, such as for example WC, diamond, SiC and CBN. The cobalt metals used, for example, in the production of diamond tools must fulfil specific requirements. These include, in the first instance, that impurities such as Al, Ca, Mg, S and Si should be avoided as these elements readily form stabile oxides with the residual oxygen of the cobalt metal powder, so causing unwanted porosity in the segments.
It is also necessary, especially when producing segments with synthetic diamonds, to use only cobalt metal powders with very active sintering properties, as minimum densities of 8.5 g/cm3 are required in this case. These densities should be achieved at a sintering temperature range of as low as < 900 C because the diamond may be converted into graphite at higher temperatures. If the sintering activity of the cobalt metal is inadequate, sufficient hardness is not achieved.
Under the extreme stresses to which annular drilling bits or cutting tools are exposed, the abrasive action of stone dust leads to deep erosion and unwanted detachment of the diamonds or other hard materials and consequently a loss of cutting performance.
According to the prior art, cobalt metals are used, on the one hand, in the form of mixtures of atomised cobalt metal powders with hydrogen-reduced powders, as are disclosed in DE-A 4 343 594, on the other hand as ultra-fine and extra-fine grade cobalt metal powders.
Ultra-fine powders are differentiated by their FSSS value of < 1.0 gm from extra-fine powders which have FSSS values of between 1.2 and 1.4 gm.
The small particle size and the resultant large surface areas of the described cobalt metal powders promote the absorption of atmospheric oxygen and moisture, which frequently leads to degradation of the flowability of the powders.
The present invention provides a sintering active cobalt metal which does not exhibit or at least mitigates the stated disadvantages, but does allow the production of segments with elevated density and hardness.
It has now proved possible to provide a cobalt metal powder which exhibits these required properties.
These are cobalt metal agglomerates consisting of peanut-shaped primary particles, characterised in that the primary particles have average particle sizes in the range from 0.1 to 0.7 m. These cobalt agglomerates are the subject matter of this invention. They preferably have a spherical secondary structure with average agglomerate diameters of 3 to 50 m, preferably of 5 to 20 m. By virtue of their spherical secondary structure they are distinguished by good flow properties.
The irregularly elongated primary particles preferably have an average particle length of 0.5 to 1 m and, generally, a diameter of < 0.5 m.
Figure 1 shows the hardness values of a sintered article produced from the cobalt metal powder agglomerate of the invention in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures.
Figure 2 shows the densities of a sintered article produced from the cobalt metal powder agglomerate of the invention produced according to example 3 in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures.
2a Figures 3a and 3b show 5000 and 15000 times magnification scanning electron micrographs of the cobalt metal powder agglomerates of the invention produced according to example 3.
Figures 4a and 4b show 500 and 5000 times magnification scanning electron micrographs of cobalt metal powders according to the invention.
The specific surface areas of the cobalt metal.
agglomerates according to the invention (determined using the nitrogen single point method to DIN 66 131) are preferably 2 to 6 m2/g. These surface areas and the small particle sizes of the primary particles are responsible for the elevated sintering activity of the cobalt metal agglomerates according to the invention, from which sintered articles having densities of 8.5 g/cm3 may be produced at temperatures of as low at 700 C.
Figure 2 and Table 2 show the densities of a sintered article produced from the cobalt metal powder agglomerate of the invention produced according to example 3 in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures.
Hardness values of 110 HRB may be achieved with segments hot pressed at temperatures of only up to 620 C.
These hardness values are among the highest hitherto achieved. With prior art cobalt metal powders, sintering temperatures of approximately 780 C are required for HRRB values of 110. Figure 1 an d Table 1 show the hardness values of a sintered article produced from the cobalt metal powder agglomerate of the invention in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures. It may clearly be seen -that elevated hardness values are obtained with the cobalt metal powder- according to the invention at temperatures of as low as 620 C, the hardness values moreover remaining constant over the entire temperature range up to 900 C. This affords the manufacturer of sintered composite hard materiai and drilling tools great production latitude without any need to fear any quality fluctuations caused by differing hardness values of the cobalt binder.
The present invention also provides a process for the production of the cobalt metal agglomerates according to the invention.
The process is characterised in that in a first stage an aqueous cobalt(II) salt solution of the general formula CoX,, wherein X' = Cl', N03 and/or '/z S042"
is reacted, preferably in a continuously operated tubular flow reactor with vigorous stirring, with an aqueous solution of alkali metal and/or ammonium, carbonates and/or hydrogen carbonates. The temperature range for the reaction is here between 40 and 100 C, preferably between 60 and 90 C. In this process, in contrast with the conventional precipitation process, a rod-shaped crystallised cobalt carbonate is not formed, but instead a spherical basic cobalt carbonate. This is filtered and washed until free of neutral salt. The resultant basic cobalt carbonate is converted in a further processing stage into spherical cobalt(II) hydroxide by adding alkali liquors, so achieving the secondary morphology, and is then oxidised with suitable oxidising agents to yield cobalt(III) oxidehydroxide, heterogenite, CoO(OH). Suitable oxidising agents are, inter alia, hypochlorites, peroxydisulphates, peroxides.
It has surprisingly now been found that oxidation of the cobalt(II) hydroxide to yield heterogenite is accompanied by a reduction in primary particle size, while completely achieving the secondary morphology. This fine particle size of 0.3 to 1.0 m is retained when the heterogenite is subsequently reduced to cobalt metal over a wide range of temperatures from 300 to 800 C. Gaseous reducing agents, such as hydrogen, methane, dinitrogen oxide and/or carbon monoxide, are preferably used at furnace temperatures of 350 to 650 C.
STA 110-Foreign Countries Unlike conventional known extra-fine and ultra-fine cobalt powders, the cobalt metal agglomerates according to the invention have very good flow properties by virtue of their spherical secondary structure.
By virtue of the described properties, the cobalt metal powders according to the invention are particularly suitable as binders in the production of hard metal and/or diamond tools. It should be noted that the cobalt metal powder agglomer-ates may here advantageously be used both alone and combined with other binder metals.
The present invention accordingly provides the use of the cobalt metal agglomerates according to the invention for the production of sintered cobalt articles and for the production of composite sintered articles based on cobalt metal and hard materials from the group comprising diamond, CBN, WC, SiC and Al, 03.
By virtue of the good flow properties and the fine primary structure of the cobalt metal powder agglomerates according to the invention, they are also particularly suitable for incorporation into the positive electrode composition containing nickel hydroxide in rechargeable batteries based on nickel/cadmium or nickel/metal hydride technologies.
During the so-called forming cycles, the cobalt metal is initially oxidised in accordance with its potential to cobalt(II). In the alkaline electrolyte (30%
KOH
solution), this forms soluble cobaltates(II) and is thus uniformly distributed within the electrode composition. On further charging, it is ultimately deposited as an electrically conductive CoO(OH) layer on the nickel hydroxide particles, so allowing the desired full utilisation to be made of the nickel hydroxide in the storage battery. The described anodic dissolution of the cobalt metal powder naturally proceeds all the faster and more effectively, the finer is the primary structure or the greater is the surface area of the metal powder.
The present invention thus also provides the use of the cobalt metal agglomerates according to the invention as a component in the production of positive electrodes in alkaline secondary batteries based on nickel/cadmium or nickel/metal hydride technologies.
STA 110-Forei gn Countries The invention is illustrated in the following examples below, without this constituting any limitation.
STA 110-Foreign Countries Examples Example 1 20 1 of water were introduced into a stirred flow reactor and heated to 80 C.
5 1/h of a 1.7 molar CoC12 solution and 19 1/h of a 0.9 molar NaHCO3 solution were continuously metered into the reactor with vigorous stirring. Once the steady state had been reached, the resultant product was discharged from the reactor overflow, filtered and washed with water until free of neutral salt. The product was then dried to constant weight at T = 80 C.
Chemical analysis of the basic cobalt carbonate 6btained in this manner revealed a Co content of 54.3% and carbonate content was determined at 32.3%.
Example 2 500 g of basic cobalt carbonate, produced according to example 1, were suspended in 2 1 of water. This suspension was combined with 200 g of NaOH dissolved in 1.5 1 of water, heated to 60 C and stirred for 1 hour. The product was filtered and washed with 3 1 of hot water. While still moist, the filter cake was resuspended in 2 1 of water and oxidised within 1.5 hours with 700 ml of H702 (30%) at a temperature of 45 C. On completion of addition, stirring was continued for a further 0.5 hour, the product was then filtered, rewashed with 2 1 of hot water and dried to constant weight at 80 C. 420 g of spherically agglomerated heterogenite with ~an agglomerate D50 value of 10.5 gm were obtained. Cobalt content was analysed at 63.9%.
Example 3 200 g of spherically agglomerated heterogenite produced according to example 2, were weighed into a quartz boat and reduced in a stream of hydrogen for 3 hours at T = 450 C. 131 g of spherically agglomerated cobalt metal were obtained.
Figure 3 shows 5000 and 15000 times magnification scanning electron micrographs of this agglomerate. The D50 value of the cobalt metal powder was 10.5 m. The FSSS value was 0.62 gm.
It has now proved possible to provide a cobalt metal powder which exhibits these required properties.
These are cobalt metal agglomerates consisting of peanut-shaped primary particles, characterised in that the primary particles have average particle sizes in the range from 0.1 to 0.7 m. These cobalt agglomerates are the subject matter of this invention. They preferably have a spherical secondary structure with average agglomerate diameters of 3 to 50 m, preferably of 5 to 20 m. By virtue of their spherical secondary structure they are distinguished by good flow properties.
The irregularly elongated primary particles preferably have an average particle length of 0.5 to 1 m and, generally, a diameter of < 0.5 m.
Figure 1 shows the hardness values of a sintered article produced from the cobalt metal powder agglomerate of the invention in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures.
Figure 2 shows the densities of a sintered article produced from the cobalt metal powder agglomerate of the invention produced according to example 3 in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures.
2a Figures 3a and 3b show 5000 and 15000 times magnification scanning electron micrographs of the cobalt metal powder agglomerates of the invention produced according to example 3.
Figures 4a and 4b show 500 and 5000 times magnification scanning electron micrographs of cobalt metal powders according to the invention.
The specific surface areas of the cobalt metal.
agglomerates according to the invention (determined using the nitrogen single point method to DIN 66 131) are preferably 2 to 6 m2/g. These surface areas and the small particle sizes of the primary particles are responsible for the elevated sintering activity of the cobalt metal agglomerates according to the invention, from which sintered articles having densities of 8.5 g/cm3 may be produced at temperatures of as low at 700 C.
Figure 2 and Table 2 show the densities of a sintered article produced from the cobalt metal powder agglomerate of the invention produced according to example 3 in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures.
Hardness values of 110 HRB may be achieved with segments hot pressed at temperatures of only up to 620 C.
These hardness values are among the highest hitherto achieved. With prior art cobalt metal powders, sintering temperatures of approximately 780 C are required for HRRB values of 110. Figure 1 an d Table 1 show the hardness values of a sintered article produced from the cobalt metal powder agglomerate of the invention in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures. It may clearly be seen -that elevated hardness values are obtained with the cobalt metal powder- according to the invention at temperatures of as low as 620 C, the hardness values moreover remaining constant over the entire temperature range up to 900 C. This affords the manufacturer of sintered composite hard materiai and drilling tools great production latitude without any need to fear any quality fluctuations caused by differing hardness values of the cobalt binder.
The present invention also provides a process for the production of the cobalt metal agglomerates according to the invention.
The process is characterised in that in a first stage an aqueous cobalt(II) salt solution of the general formula CoX,, wherein X' = Cl', N03 and/or '/z S042"
is reacted, preferably in a continuously operated tubular flow reactor with vigorous stirring, with an aqueous solution of alkali metal and/or ammonium, carbonates and/or hydrogen carbonates. The temperature range for the reaction is here between 40 and 100 C, preferably between 60 and 90 C. In this process, in contrast with the conventional precipitation process, a rod-shaped crystallised cobalt carbonate is not formed, but instead a spherical basic cobalt carbonate. This is filtered and washed until free of neutral salt. The resultant basic cobalt carbonate is converted in a further processing stage into spherical cobalt(II) hydroxide by adding alkali liquors, so achieving the secondary morphology, and is then oxidised with suitable oxidising agents to yield cobalt(III) oxidehydroxide, heterogenite, CoO(OH). Suitable oxidising agents are, inter alia, hypochlorites, peroxydisulphates, peroxides.
It has surprisingly now been found that oxidation of the cobalt(II) hydroxide to yield heterogenite is accompanied by a reduction in primary particle size, while completely achieving the secondary morphology. This fine particle size of 0.3 to 1.0 m is retained when the heterogenite is subsequently reduced to cobalt metal over a wide range of temperatures from 300 to 800 C. Gaseous reducing agents, such as hydrogen, methane, dinitrogen oxide and/or carbon monoxide, are preferably used at furnace temperatures of 350 to 650 C.
STA 110-Foreign Countries Unlike conventional known extra-fine and ultra-fine cobalt powders, the cobalt metal agglomerates according to the invention have very good flow properties by virtue of their spherical secondary structure.
By virtue of the described properties, the cobalt metal powders according to the invention are particularly suitable as binders in the production of hard metal and/or diamond tools. It should be noted that the cobalt metal powder agglomer-ates may here advantageously be used both alone and combined with other binder metals.
The present invention accordingly provides the use of the cobalt metal agglomerates according to the invention for the production of sintered cobalt articles and for the production of composite sintered articles based on cobalt metal and hard materials from the group comprising diamond, CBN, WC, SiC and Al, 03.
By virtue of the good flow properties and the fine primary structure of the cobalt metal powder agglomerates according to the invention, they are also particularly suitable for incorporation into the positive electrode composition containing nickel hydroxide in rechargeable batteries based on nickel/cadmium or nickel/metal hydride technologies.
During the so-called forming cycles, the cobalt metal is initially oxidised in accordance with its potential to cobalt(II). In the alkaline electrolyte (30%
KOH
solution), this forms soluble cobaltates(II) and is thus uniformly distributed within the electrode composition. On further charging, it is ultimately deposited as an electrically conductive CoO(OH) layer on the nickel hydroxide particles, so allowing the desired full utilisation to be made of the nickel hydroxide in the storage battery. The described anodic dissolution of the cobalt metal powder naturally proceeds all the faster and more effectively, the finer is the primary structure or the greater is the surface area of the metal powder.
The present invention thus also provides the use of the cobalt metal agglomerates according to the invention as a component in the production of positive electrodes in alkaline secondary batteries based on nickel/cadmium or nickel/metal hydride technologies.
STA 110-Forei gn Countries The invention is illustrated in the following examples below, without this constituting any limitation.
STA 110-Foreign Countries Examples Example 1 20 1 of water were introduced into a stirred flow reactor and heated to 80 C.
5 1/h of a 1.7 molar CoC12 solution and 19 1/h of a 0.9 molar NaHCO3 solution were continuously metered into the reactor with vigorous stirring. Once the steady state had been reached, the resultant product was discharged from the reactor overflow, filtered and washed with water until free of neutral salt. The product was then dried to constant weight at T = 80 C.
Chemical analysis of the basic cobalt carbonate 6btained in this manner revealed a Co content of 54.3% and carbonate content was determined at 32.3%.
Example 2 500 g of basic cobalt carbonate, produced according to example 1, were suspended in 2 1 of water. This suspension was combined with 200 g of NaOH dissolved in 1.5 1 of water, heated to 60 C and stirred for 1 hour. The product was filtered and washed with 3 1 of hot water. While still moist, the filter cake was resuspended in 2 1 of water and oxidised within 1.5 hours with 700 ml of H702 (30%) at a temperature of 45 C. On completion of addition, stirring was continued for a further 0.5 hour, the product was then filtered, rewashed with 2 1 of hot water and dried to constant weight at 80 C. 420 g of spherically agglomerated heterogenite with ~an agglomerate D50 value of 10.5 gm were obtained. Cobalt content was analysed at 63.9%.
Example 3 200 g of spherically agglomerated heterogenite produced according to example 2, were weighed into a quartz boat and reduced in a stream of hydrogen for 3 hours at T = 450 C. 131 g of spherically agglomerated cobalt metal were obtained.
Figure 3 shows 5000 and 15000 times magnification scanning electron micrographs of this agglomerate. The D50 value of the cobalt metal powder was 10.5 m. The FSSS value was 0.62 gm.
Examnle 4 Sintering test The cobalt metal agglomerates obtained according to example 3 were subjected to hot pressing tests under the following conditions:
Apparatus used: DSP 25-ATV (from Dr. Fritsch GmbH) Heating time to final temperature: 3 min Holding time: 3 min Final pressure: 350 N/mm'`
Final temperature: see tables I and 2 Dimensions: 40 x 4 x 10 mm Table I and Figure 1 show the hardness values of a sintered article produced from the cobalt metal powder agglomerate of the invention from example 3 in comparison with sintered articles produced from commercially available ultra-and extra-fine cobalt metal powders as a function of sintering temperatures. It may clearly be seen that elevated hardness values are obtained with the cobalt metal powder according to the invention at temperatures of as low as 620 C, the hardness values moreover remaining constant over the entire temperature range up to 980 C.
Apparatus used: DSP 25-ATV (from Dr. Fritsch GmbH) Heating time to final temperature: 3 min Holding time: 3 min Final pressure: 350 N/mm'`
Final temperature: see tables I and 2 Dimensions: 40 x 4 x 10 mm Table I and Figure 1 show the hardness values of a sintered article produced from the cobalt metal powder agglomerate of the invention from example 3 in comparison with sintered articles produced from commercially available ultra-and extra-fine cobalt metal powders as a function of sintering temperatures. It may clearly be seen that elevated hardness values are obtained with the cobalt metal powder according to the invention at temperatures of as low as 620 C, the hardness values moreover remaining constant over the entire temperature range up to 980 C.
Table 1: (Hardness values) Rockwell hardness values (HRB) Co uFl) 91.5 109.8 109.7 107 Co eF2) 102.5 105.0 104.6 97.2 Cobalt metal powder 110.6 110.9 110.1 110.5 agglomerate from example 3 1) Ultra-fine cobalt metal powder supplied by Eurotungstene Grenoble, France '-) Extra-fine cobalt metal powder supplied by Hoboken Overpelt, Belgium IO Table 2 and Figure 2 show the densities of a sintered article produced from the cobalt metal powder agglomerate of the invention from example 3 in comparison with sintered articles produced from commercially available ultra- and extra-fine cobalt metal powders as a function of sintering temperatures.
Table 2: (Densities) Densities [g/cm3]
Co,uF') 7.72 8.58 8.60 8.59 Co eF') 8.42 8.62 8.67 8.61 Cobalt metal powder 8.47 8.49 8.53 8.50 agglomerate from example 3 Table 3 compares the particle sizes and BET specific surface areas of the cobalt metal agglomerates (determined using the nitrogen single point method to DIN
66 13 1) from example 3 with those of commercially available ultra- and extra-fine cobalt powders.
STA 110-Foreign Countries Table 3: (Particle size and specific surface areas) FSSS [ m] BET [cm2/g]
Co uFl) < 1 1.4 Co eF2) 1.2-1.4 0.8-1.0 Cobalt metal agglomerate < 0.7 2.8-4.0 from example 3
Table 2: (Densities) Densities [g/cm3]
Co,uF') 7.72 8.58 8.60 8.59 Co eF') 8.42 8.62 8.67 8.61 Cobalt metal powder 8.47 8.49 8.53 8.50 agglomerate from example 3 Table 3 compares the particle sizes and BET specific surface areas of the cobalt metal agglomerates (determined using the nitrogen single point method to DIN
66 13 1) from example 3 with those of commercially available ultra- and extra-fine cobalt powders.
STA 110-Foreign Countries Table 3: (Particle size and specific surface areas) FSSS [ m] BET [cm2/g]
Co uFl) < 1 1.4 Co eF2) 1.2-1.4 0.8-1.0 Cobalt metal agglomerate < 0.7 2.8-4.0 from example 3
Claims (12)
1. Cobalt metal agglomerates consisting of peanut-shaped primary particles, wherein the primary particles have average particle sizes in the range from 0.1 to 0.7 µm.
2. The cobalt metal agglomerates according to claim 1, having a spherical secondary structure with average agglomerate diameters of 3 to 50 µm.
3. The cobalt metal agglomerates according to claim 2, having agglomerate diameters of 5 to 20 µm.
4. The cobalt metal agglomerates according to any one of claims 1 to 3, having a specific surface area in the range from 2 to 6 m2/g.
5. A process for the production of the cobalt metal agglomerates according to any one of claims 1 to 4, wherein a cobalt salt of the general formula: CoX2, wherein X-represents Cl-, NO3, 1/2 SO4 2- or a combination thereof, is continuously reacted with an aqueous solution or suspension of an alkali metal carbonate, ammonium carbonate, hydrogen carbonate or a mixture thereof at a temperature of between 40 and 100°C, to form a basic cobalt carbonate, which is separated and washed until free of any neutral salt and then reacted with an alkali liquor, an ammonium liquor or a mixture thereof, oxidised with an oxidising agent to yield trivalent heterogenite, CoO(OH), which is reduced with a reducing agent to yield the cobalt metal agglomerates.
6. The process according to claim 5, wherein the temperature is between 60 and 90°C.
7. The process according to claim 5 or 6, wherein the oxidising agent is H2O2.
8. The process according to any one of claims 5 to 7, wherein reaction with a gaseous reducing agent is performed at a temperature of between 300 and 800°C.
9. The process according to claim 8, wherein the temperature is between 350 to 650°C.
10. Use of the cobalt metal agglomerates according to any one of claims 1 to 4, for the production of a sintered cobalt article.
11. Use of the cobalt metal agglomerates according to any one of claims 1 to 4, for the production of a composite sintered article based on cobalt metal and a hard material selected from the group consisting of diamond, CBN, WC, SiC
and Al2O3.
and Al2O3.
12. Use of the cobalt metal agglomerates according to any one of claims 1 to 4, as a component for the production of a positive electrode in an alkaline secondary battery based on nickel/cadmium or nickel/metal hydride technologies.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19519331.8 | 1995-05-26 | ||
| DE19519331A DE19519331C1 (en) | 1995-05-26 | 1995-05-26 | Cobalt metal agglomerates, process for their preparation and their use |
| PCT/EP1996/002049 WO1996037324A1 (en) | 1995-05-26 | 1996-05-14 | Cobalt metal agglomerates, a method of producing them and their use |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2221963A1 CA2221963A1 (en) | 1996-11-28 |
| CA2221963C true CA2221963C (en) | 2007-02-06 |
Family
ID=37734895
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002221963A Expired - Fee Related CA2221963C (en) | 1995-05-26 | 1996-05-14 | Cobalt metal agglomerates, a method of producing them and their use |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2221963C (en) |
-
1996
- 1996-05-14 CA CA002221963A patent/CA2221963C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2221963A1 (en) | 1996-11-28 |
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