CA2018584A1 - Process for the preparation of sintered microcrystalline a1 o bodies and their use - Google Patents
Process for the preparation of sintered microcrystalline a1 o bodies and their useInfo
- Publication number
- CA2018584A1 CA2018584A1 CA002018584A CA2018584A CA2018584A1 CA 2018584 A1 CA2018584 A1 CA 2018584A1 CA 002018584 A CA002018584 A CA 002018584A CA 2018584 A CA2018584 A CA 2018584A CA 2018584 A1 CA2018584 A1 CA 2018584A1
- Authority
- CA
- Canada
- Prior art keywords
- al2o3
- alpha
- product
- containing suspension
- process according
- 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.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B7/00—Electrophoretic production of compounds or non-metals
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K3/00—Materials not provided for elsewhere
- C09K3/14—Anti-slip materials; Abrasives
- C09K3/1409—Abrasive particles per se
- C09K3/1418—Abrasive particles per se obtained by division of a mass agglomerated by sintering
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D13/00—Electrophoretic coating characterised by the process
- C25D13/02—Electrophoretic coating characterised by the process with inorganic material
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D13/00—Electrophoretic coating characterised by the process
- C25D13/12—Electrophoretic coating characterised by the process characterised by the article coated
Abstract
Process for the preparation of sintered microcrystalline .alpha.-Al2O3 bodies and their use ABSTRACT OF THE DISCLOSURE
Sintered microcrystalline bodies based alpha-alumina (.alpha.-Al2O3) are produced by electropheretically depositing .alpha.-Al2O3 from a suspension thereof on an electrode sub-strate, removing the deposit and drying, comminuting and sintering it.
Sintered microcrystalline bodies based alpha-alumina (.alpha.-Al2O3) are produced by electropheretically depositing .alpha.-Al2O3 from a suspension thereof on an electrode sub-strate, removing the deposit and drying, comminuting and sintering it.
Description
Title: Process for the preparation of sin~ered micro-crystalline a-A1203 bodies and their use _ BACKGROUND OF THE INVENTION
The present invention relates to a process for the pre-paration of sintered microcrystalline bodies based on ~-A1203 and ~heir use.
A preferred use of o~-A120 sintered bodies is their use as abrasives.
In addition ~o fused corundum abrasivés, those of sin~e-red material have already been known for about 50 years.
Sin~ered abrasives based on ~-Al203, the microcrystal-line structure of which has provided par~icular abrasiveadvantages, have recently become known.
US Patent 4,314,827 describes a microcrystalline abra-sive material which is prepared via the sol-gel tech-nique at sintering tempera~ures of about 1400C. A
modifying component, such as HfO2, ZrO2, MgO, ZnO, CoO, Nio and the like, is added as a sintering aid.
~5 201~84 An abrasive material which is likewise prepared by sintering an aluminum oxide hydrate gel is disclosed in European Patent 0,152,768. To establish the transi-tion temperature of ~-A12O3 into ~-Al2O3, very fine ~-Al2O3 particles are added here as seeding agents. Other additions of crystal growth inhibitors, such as MgO, 10 SiO2, Cr2O3, Fe2O3 or ZrO2, can be used similarly.
Similar processes and substances are to be found in European Patent 0,024,099, ~. German Patent Application 3,219,607; US Patents 4,518,397, 4,574,003 and 15 US 4,623,364 and European patent Applications 0,168,606, 0,200,487; 0,228,856; 0,209,084 and 0,263,810.
All the abovementioned processes have the common feature that they are carried out via a sol-gel process with one or more very finely dispersed aluminium oxide monohy-drate of the bohemite type. The relatively expensive raw materials, which are obtained, for example, via hydro-lysis of organoaluminium compounds, and the expensive process technology increase the costs of the sol-gel corundum to several times that of conventional corun-dums.
W, German Patent Application 3,604,848 describes a process for grinding a dispersion of raw materials containing alumina, compounds containing silicic acid and fur~her additives (compounds of the metals, Co, Ni, Cr, Zr, Zn, Si, Ti or Ni) to a slip which can be s;ntered, from which an abrasive can be prepared by ~5 2 ~ 8 4 stepwise drying and sintering at temperatures of up ~o 1700C, the corundum crystals of the abrasive having a diameter of less than 5 microns. Although it is possible ~o bypass the expensive raw material in this manner, very expensive grinding processes and high sintering temperatures are still required in order to obtain the desired microcrystalline abrasive.
The product thus obtained also contains about 2 % sili-cates which are of no value in terms of abrasive capa-city, and with a crystallite size of less than 5 microns still does not have the fine structure of a substance which has been prepared via the sol-gel method (crystal-lite size less than 0.4 microns).
A reason for the particular abrasive advantages of these new abrasives is seen, however, in the submicron struc-ture.
European Patent Application 0,404,721 describes a pro-cess for achieving, via hydrothermal treatment of raw materials containing Al(OH)3, a microcrystalline bohe-mite which is suitable for use in the sol-gel process.
Although it was possible here to replace ~ome of the starting material by an inexpensive raw material, very finley disperse bohemite is still required, depending on the intended use of the desired product, as a seed material in amounts of between 7.5 % and 60 %, based on the Al203 end product. The very expensive starting ~5 STA 15 - ? -201~4 substance obtained via Al alkoxides is again used as the very finley dispersed bohemite.
Another disadvantaRe of the abovementioned sol-gel pro-cess is that considerable amounts of nitric acid are used, which is then bonded in the gel and liberated again as nitric oxide during drying and calcining. This is accompanied by major corrosion and environmental problems. To avoid damage here, corresponding protective measures must be resorted to, which additionally make the processes expensive.
DE-A 3,334,098 describes a process in which aluminium oxide monohydrate is deposited electrophoretically from an aqueous dispersion. The producL is dried, calcined and sintered by a method analogous to the well-known sol-gel technique and it can be used, among other things, as an abrasive. The energy saving permitted by this method is named as the main advantage of the method over the sol-gel technique. A disadvantage of the method is the fact that it is again necessary to use the relatively expensive finely dispersed aluminium oxide monohydrate as the starting material. The dispersion described contains aluminium oxide monohydrate up to a maximum level of 40 %. This small solids content, to-gether with the large volumes of liquid associated with 3~ it, calls for very laborious and energy-intensive pro-cess technology.
~: ~5 The electrophoresis in the aqueous medium has the addi-tional disadvantage ~hat electrolytic decomposition of the water frequently occurs at the electrodes. This causes difficultly controllable porosity in the depo-sited sol;d, with the result that the hardness and grinding performance of the abrasive prepared therefrom may be impaired.
The principal obJect of this invention is thus to pro-vide a process for ~he preparation of a microcrystalline a-A1203 sintered body which does not have the disadvan-tages described for the prior art.
SUMMARY OF THE INVENTION
2~It has now been found that these requirements are met by a process which is based on electrophoretic removal of -A1203 from a corresponding organic ~-A1203 sus-pension.
The invention thus relates to a process for the prepa-ration of sintered microcrystalline bodies based on K-A1203, in which A1203 is deposited on an electrode from an organic ~-A1203-containing suspension, removed from the electrode, dried, sintered and comminuted. By appropria~e choice of the particle size of the starting ~5 2018~84 substance, the crystallite size of the end product can be influenced here in a simple manner, Particularly good successes are achieved if a-Al2O3 particles having a submicron crystallite size of are employed as the star-ting material for the K-Al2O3-containing suspension.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
From economic considerations, is is advantageous to keep the ~-Al2O3 content high. In a particularly pre-ferred embodiment of the process according to the in-vention, the a-Al2O3-containing suspension has an Al2O3 content of under 50 wt.%. In order to obtain a parti-cularly stable a-Al2O3-containing suspension, it is necessary to add suitable organic suspending agents to this. Solvents such as methyl isobutyl ketone, acetone, ethers or alcohols are preferably used as the organic suspending agents.
Particularlyl suitable dispersing aids are polyelectro-lytes such as 3,6,9-trioxaundecanedioic acid, polyglycol dioic acid, polyvinyl pyrrolidone, nahp~halenesulphonir acid condensate, maleic acid copolymers, polymethacry-~5 . .
2~18~8~
lic, polyacrylic, acid, partially esterified polyacrylic arid, ni~rocellulose, polyvinylbutyral, or also wax and resins or organic bases such as triethylamine, tetra-butylammonium hydroxide or carboxylic acids such as acetic acid or p-hydroxybenzoic acid.
Particularly good successes are achieved here by addi-tion of polyacrylic acid. In a preferred embodiment of the process according to the invention, the ~-Al2O3-containing suspension thus contains 0,5 ~o 3.0 wt.%, polyacrylic acid, based on the Al203 content.
The preferred voltage in the electrophoretic process according to the invention is between 10 and 300 volt.
Under these condiLions, it is possible to deposit Al203 sheets several mm thick.
In cases where complete removal can be achieved only with problems, these can be avoided by applying a graphite film to the electrodes. Graphite as a film material provides ~he advantage here that it burns wi~hout residue during the sintering operatior~. A pre-ferred embodiment of the process according to the in-vention thus comprises coating the electrodes with a graphite film. The graphite film servoes ~he purpose of facilitating the removal of the layer from ~he elec-trode.
2 ~ 8 4 These green substances thus obtained are advantageously first dried. This is preferably effected at temperatures abvoe 50~C. A sintering operation then follows, at tem-peratures between 1300 and 1700C, preferably at 1550 to 1650~. This sintering operation has in general ended after 15 minutes. The sintering temperature and the pro-duct quality can be influenced by addition of sinteringaids to the ~-Al203-containing su6pension. Preferably 0,2 to 10 % by weight of sintering aids, most preferred 0.5 to 2 % by weight, are used.
The comminution is in general carried out after the sin-tering, because edges which have a particular cutting capacity are in this case formed. However, in addition to the advantages of saving energy, comminution before sintering can also produce good results. Porferably the communication is carried out with the aid of roller ; mills.
Another advantageous variant of the process according to the invenLion thus lies in adding one or more sin-tering aids to the ~-Al203-containing suspension, which are then deposited together with the Al203. It is in this way possible, in particular, to lower the sinLering tempersture. This preferred embodiment of the procass according to the invention is characterized in that sintering aids from 2 ~ 8 ~
~he group comprising CoO, NiO, MgO, ZnO, Cr203, Fe203, Si2' Ti2~ Y203~ Nb25~ HfO2 and ZrO2 are added to the ~-Al203-containing suspension.
The preparation of sintered microcrystallir,e bodies having a density of over 98 % theoretical and a hardness lG of 20 GPa, the crystallite size being betweer, 0,1 and 10 microns, preferably below 0,4 microns, is made possible by the process according to the invention.
On the basis of these properties, these sintered bodies are outstandingly suitable as abrasives and in related products.
This invention thus also relates to the use of the sin-tered microcrystalline bodies prepared according to the invention as abrasives and for the produc~ion of grin-ding cutting tools.
Since the abrasive properties largely depend on the crystallite structure of the particular abrasive grain, it is possible to provide abrasive grains having a crystallite structure, which is optimum for the prati-cular use for widley varying intended purposes, by the process according to the invention.
2 01 ~3;~
Exam~le 1:
1.5 % of polyacrylic acid (based on the quantity of Al20 3 employed) i5 dissolved in ethanol with stirring, 60 %
by weight of Al203 powder (based on the total starting quantity) having an average particle size of 0,6 microns are added to this solution. The suspension is homogeni-sed by ultrasonic treatment with simultaneous stirring.
The stable suspension is centrifuged at 5000 r.p.m.
until the average particle size of the Al203 particles in the suspension is 0.2 microns.
The suspension is filled into the electrophoretic cell and a green body of a thickness of about 3 mm is deposited at al voltage of 50 volts over a period of 15 minutes at 28 mA.
The green body is dried first i air an then in a drying cabinet at 50C. It is then sintered at 1600C.
A compact Al203 body with a crystallite size of ~ 1 micron is obtained.
The (Vickers) hardness of the abrasive grain thus ob-tained ist 21 GPa.
~Q~ ~84 Grindina tests Grinding material Abrasive powder in %
Fibre wheel Grinding bel~
Normal corundum 10D 100 (Electromelted corundum) Zirconium corundum 260 340 EZ 347 ex ~orton Sol-gel corundum 350 440 Example 1 290 ~60 The material ground was C-45 steel.
ExamDle 2:
Preparation of the suspension as in Example 1).
Prior to the ultrasonic treatment 5 % of MgO are added to the suspension which is then treated for 24 hours in a ball mill.
Then ultrasonic treatment is carried out. The suspension i 5 ~hen centrifuged until the average particle size is 0,2 microns.
2~18~84 Elec~rophoresis, drying and sintering are carried ou~
as in Example 1).
A compact Al203 body with a spinel content of about 2 % and a crystallite size of ~ 0,5 microns is ob-tained.
The hardness of the material is 10 GPa.
Grindina test 15 Grinding material Abrasive powder in %
Fibre wheel Grinding bel~
Normal corundum 100 100 Example 2) 330 410 Exam~le 3 The same procedure is used as in Example 2) 3 % of Mg spinel are added instead of MgO.
An abrasive grain bases on Al203 is obtained with a hardness of 20 GPa, a density of 97 % of theory and a crystallite size of below 0,7 microns.
Grindinq ~est Grinding material Abrasive powder in %
Fibre wheel Grinding belt 10 Normal ~orundum 100 100 Example 3) 310 350
The present invention relates to a process for the pre-paration of sintered microcrystalline bodies based on ~-A1203 and ~heir use.
A preferred use of o~-A120 sintered bodies is their use as abrasives.
In addition ~o fused corundum abrasivés, those of sin~e-red material have already been known for about 50 years.
Sin~ered abrasives based on ~-Al203, the microcrystal-line structure of which has provided par~icular abrasiveadvantages, have recently become known.
US Patent 4,314,827 describes a microcrystalline abra-sive material which is prepared via the sol-gel tech-nique at sintering tempera~ures of about 1400C. A
modifying component, such as HfO2, ZrO2, MgO, ZnO, CoO, Nio and the like, is added as a sintering aid.
~5 201~84 An abrasive material which is likewise prepared by sintering an aluminum oxide hydrate gel is disclosed in European Patent 0,152,768. To establish the transi-tion temperature of ~-A12O3 into ~-Al2O3, very fine ~-Al2O3 particles are added here as seeding agents. Other additions of crystal growth inhibitors, such as MgO, 10 SiO2, Cr2O3, Fe2O3 or ZrO2, can be used similarly.
Similar processes and substances are to be found in European Patent 0,024,099, ~. German Patent Application 3,219,607; US Patents 4,518,397, 4,574,003 and 15 US 4,623,364 and European patent Applications 0,168,606, 0,200,487; 0,228,856; 0,209,084 and 0,263,810.
All the abovementioned processes have the common feature that they are carried out via a sol-gel process with one or more very finely dispersed aluminium oxide monohy-drate of the bohemite type. The relatively expensive raw materials, which are obtained, for example, via hydro-lysis of organoaluminium compounds, and the expensive process technology increase the costs of the sol-gel corundum to several times that of conventional corun-dums.
W, German Patent Application 3,604,848 describes a process for grinding a dispersion of raw materials containing alumina, compounds containing silicic acid and fur~her additives (compounds of the metals, Co, Ni, Cr, Zr, Zn, Si, Ti or Ni) to a slip which can be s;ntered, from which an abrasive can be prepared by ~5 2 ~ 8 4 stepwise drying and sintering at temperatures of up ~o 1700C, the corundum crystals of the abrasive having a diameter of less than 5 microns. Although it is possible ~o bypass the expensive raw material in this manner, very expensive grinding processes and high sintering temperatures are still required in order to obtain the desired microcrystalline abrasive.
The product thus obtained also contains about 2 % sili-cates which are of no value in terms of abrasive capa-city, and with a crystallite size of less than 5 microns still does not have the fine structure of a substance which has been prepared via the sol-gel method (crystal-lite size less than 0.4 microns).
A reason for the particular abrasive advantages of these new abrasives is seen, however, in the submicron struc-ture.
European Patent Application 0,404,721 describes a pro-cess for achieving, via hydrothermal treatment of raw materials containing Al(OH)3, a microcrystalline bohe-mite which is suitable for use in the sol-gel process.
Although it was possible here to replace ~ome of the starting material by an inexpensive raw material, very finley disperse bohemite is still required, depending on the intended use of the desired product, as a seed material in amounts of between 7.5 % and 60 %, based on the Al203 end product. The very expensive starting ~5 STA 15 - ? -201~4 substance obtained via Al alkoxides is again used as the very finley dispersed bohemite.
Another disadvantaRe of the abovementioned sol-gel pro-cess is that considerable amounts of nitric acid are used, which is then bonded in the gel and liberated again as nitric oxide during drying and calcining. This is accompanied by major corrosion and environmental problems. To avoid damage here, corresponding protective measures must be resorted to, which additionally make the processes expensive.
DE-A 3,334,098 describes a process in which aluminium oxide monohydrate is deposited electrophoretically from an aqueous dispersion. The producL is dried, calcined and sintered by a method analogous to the well-known sol-gel technique and it can be used, among other things, as an abrasive. The energy saving permitted by this method is named as the main advantage of the method over the sol-gel technique. A disadvantage of the method is the fact that it is again necessary to use the relatively expensive finely dispersed aluminium oxide monohydrate as the starting material. The dispersion described contains aluminium oxide monohydrate up to a maximum level of 40 %. This small solids content, to-gether with the large volumes of liquid associated with 3~ it, calls for very laborious and energy-intensive pro-cess technology.
~: ~5 The electrophoresis in the aqueous medium has the addi-tional disadvantage ~hat electrolytic decomposition of the water frequently occurs at the electrodes. This causes difficultly controllable porosity in the depo-sited sol;d, with the result that the hardness and grinding performance of the abrasive prepared therefrom may be impaired.
The principal obJect of this invention is thus to pro-vide a process for ~he preparation of a microcrystalline a-A1203 sintered body which does not have the disadvan-tages described for the prior art.
SUMMARY OF THE INVENTION
2~It has now been found that these requirements are met by a process which is based on electrophoretic removal of -A1203 from a corresponding organic ~-A1203 sus-pension.
The invention thus relates to a process for the prepa-ration of sintered microcrystalline bodies based on K-A1203, in which A1203 is deposited on an electrode from an organic ~-A1203-containing suspension, removed from the electrode, dried, sintered and comminuted. By appropria~e choice of the particle size of the starting ~5 2018~84 substance, the crystallite size of the end product can be influenced here in a simple manner, Particularly good successes are achieved if a-Al2O3 particles having a submicron crystallite size of are employed as the star-ting material for the K-Al2O3-containing suspension.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
From economic considerations, is is advantageous to keep the ~-Al2O3 content high. In a particularly pre-ferred embodiment of the process according to the in-vention, the a-Al2O3-containing suspension has an Al2O3 content of under 50 wt.%. In order to obtain a parti-cularly stable a-Al2O3-containing suspension, it is necessary to add suitable organic suspending agents to this. Solvents such as methyl isobutyl ketone, acetone, ethers or alcohols are preferably used as the organic suspending agents.
Particularlyl suitable dispersing aids are polyelectro-lytes such as 3,6,9-trioxaundecanedioic acid, polyglycol dioic acid, polyvinyl pyrrolidone, nahp~halenesulphonir acid condensate, maleic acid copolymers, polymethacry-~5 . .
2~18~8~
lic, polyacrylic, acid, partially esterified polyacrylic arid, ni~rocellulose, polyvinylbutyral, or also wax and resins or organic bases such as triethylamine, tetra-butylammonium hydroxide or carboxylic acids such as acetic acid or p-hydroxybenzoic acid.
Particularly good successes are achieved here by addi-tion of polyacrylic acid. In a preferred embodiment of the process according to the invention, the ~-Al2O3-containing suspension thus contains 0,5 ~o 3.0 wt.%, polyacrylic acid, based on the Al203 content.
The preferred voltage in the electrophoretic process according to the invention is between 10 and 300 volt.
Under these condiLions, it is possible to deposit Al203 sheets several mm thick.
In cases where complete removal can be achieved only with problems, these can be avoided by applying a graphite film to the electrodes. Graphite as a film material provides ~he advantage here that it burns wi~hout residue during the sintering operatior~. A pre-ferred embodiment of the process according to the in-vention thus comprises coating the electrodes with a graphite film. The graphite film servoes ~he purpose of facilitating the removal of the layer from ~he elec-trode.
2 ~ 8 4 These green substances thus obtained are advantageously first dried. This is preferably effected at temperatures abvoe 50~C. A sintering operation then follows, at tem-peratures between 1300 and 1700C, preferably at 1550 to 1650~. This sintering operation has in general ended after 15 minutes. The sintering temperature and the pro-duct quality can be influenced by addition of sinteringaids to the ~-Al203-containing su6pension. Preferably 0,2 to 10 % by weight of sintering aids, most preferred 0.5 to 2 % by weight, are used.
The comminution is in general carried out after the sin-tering, because edges which have a particular cutting capacity are in this case formed. However, in addition to the advantages of saving energy, comminution before sintering can also produce good results. Porferably the communication is carried out with the aid of roller ; mills.
Another advantageous variant of the process according to the invenLion thus lies in adding one or more sin-tering aids to the ~-Al203-containing suspension, which are then deposited together with the Al203. It is in this way possible, in particular, to lower the sinLering tempersture. This preferred embodiment of the procass according to the invention is characterized in that sintering aids from 2 ~ 8 ~
~he group comprising CoO, NiO, MgO, ZnO, Cr203, Fe203, Si2' Ti2~ Y203~ Nb25~ HfO2 and ZrO2 are added to the ~-Al203-containing suspension.
The preparation of sintered microcrystallir,e bodies having a density of over 98 % theoretical and a hardness lG of 20 GPa, the crystallite size being betweer, 0,1 and 10 microns, preferably below 0,4 microns, is made possible by the process according to the invention.
On the basis of these properties, these sintered bodies are outstandingly suitable as abrasives and in related products.
This invention thus also relates to the use of the sin-tered microcrystalline bodies prepared according to the invention as abrasives and for the produc~ion of grin-ding cutting tools.
Since the abrasive properties largely depend on the crystallite structure of the particular abrasive grain, it is possible to provide abrasive grains having a crystallite structure, which is optimum for the prati-cular use for widley varying intended purposes, by the process according to the invention.
2 01 ~3;~
Exam~le 1:
1.5 % of polyacrylic acid (based on the quantity of Al20 3 employed) i5 dissolved in ethanol with stirring, 60 %
by weight of Al203 powder (based on the total starting quantity) having an average particle size of 0,6 microns are added to this solution. The suspension is homogeni-sed by ultrasonic treatment with simultaneous stirring.
The stable suspension is centrifuged at 5000 r.p.m.
until the average particle size of the Al203 particles in the suspension is 0.2 microns.
The suspension is filled into the electrophoretic cell and a green body of a thickness of about 3 mm is deposited at al voltage of 50 volts over a period of 15 minutes at 28 mA.
The green body is dried first i air an then in a drying cabinet at 50C. It is then sintered at 1600C.
A compact Al203 body with a crystallite size of ~ 1 micron is obtained.
The (Vickers) hardness of the abrasive grain thus ob-tained ist 21 GPa.
~Q~ ~84 Grindina tests Grinding material Abrasive powder in %
Fibre wheel Grinding bel~
Normal corundum 10D 100 (Electromelted corundum) Zirconium corundum 260 340 EZ 347 ex ~orton Sol-gel corundum 350 440 Example 1 290 ~60 The material ground was C-45 steel.
ExamDle 2:
Preparation of the suspension as in Example 1).
Prior to the ultrasonic treatment 5 % of MgO are added to the suspension which is then treated for 24 hours in a ball mill.
Then ultrasonic treatment is carried out. The suspension i 5 ~hen centrifuged until the average particle size is 0,2 microns.
2~18~84 Elec~rophoresis, drying and sintering are carried ou~
as in Example 1).
A compact Al203 body with a spinel content of about 2 % and a crystallite size of ~ 0,5 microns is ob-tained.
The hardness of the material is 10 GPa.
Grindina test 15 Grinding material Abrasive powder in %
Fibre wheel Grinding bel~
Normal corundum 100 100 Example 2) 330 410 Exam~le 3 The same procedure is used as in Example 2) 3 % of Mg spinel are added instead of MgO.
An abrasive grain bases on Al203 is obtained with a hardness of 20 GPa, a density of 97 % of theory and a crystallite size of below 0,7 microns.
Grindinq ~est Grinding material Abrasive powder in %
Fibre wheel Grinding belt 10 Normal ~orundum 100 100 Example 3) 310 350
Claims (8)
1. Process for the preparation of sintered micro-crystalline bodies based on .alpha.-Al2O3, characterized in that Al2O3 is deposited electrophoretically from an organic .alpha.-Al2O3-containing suspension onto an electrode, removed from the electrode, dried, sinterd and comminuted.
2. Process according to claim 1, wherein .alpha.-Al2O3 particles having a crystallite size of less than one micron are employed as the starting material for the .alpha.-Al2O3-containing suspension.
3. Process according to either of claims 1 or 2, wherein the .alpha.-Al2O3-containing suspension has an Al2O3 content of over 50 wt.%.
4. Process according to either of claims 1 or 2, wherein the .alpha.-Al2O3-containing suspension contains 0.5 to 3.0 wt.% polyacrylic acid, based on the Al2O3 content.
5. Process according to either of claims 1 or 2, wherein one or more that sintering aids from the class consisting of CoO, NiO, MgO, ZnO, Cr2O3, Fe2O3, SiO2, TiO2, Y2O3, Nb2O5, HfO2 and ZrO2 are added to the .alpha.-Al2O3-containing suspension.
6. Product as made in the process of either of claim 2 or 5.
7. Method of use of the product of claim 6 by incor-porating said product into an abrasive device.
8. Method of use of the product of claim 6 by in-corporatins said product into cutting/grinding tools.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3919044.7 | 1989-06-10 | ||
| DE3919044 | 1989-06-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2018584A1 true CA2018584A1 (en) | 1990-12-10 |
Family
ID=6382524
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002018584A Abandoned CA2018584A1 (en) | 1989-06-10 | 1990-06-08 | Process for the preparation of sintered microcrystalline a1 o bodies and their use |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0402686B1 (en) |
| JP (1) | JPH0328120A (en) |
| AT (1) | ATE92543T1 (en) |
| CA (1) | CA2018584A1 (en) |
| DE (1) | DE59002167D1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5593467A (en) * | 1993-11-12 | 1997-01-14 | Minnesota Mining And Manufacturing Company | Abrasive grain |
| US5645618A (en) * | 1993-11-12 | 1997-07-08 | Minnesota Mining And Manufacturing Company | Method for making an abrasive article |
| US7678723B2 (en) | 2004-09-14 | 2010-03-16 | Carbo Ceramics, Inc. | Sintered spherical pellets |
| US11667574B2 (en) | 2017-12-27 | 2023-06-06 | Showa Denko K.K. | Precursor of alumina sintered body, method for producing alumina sintered body, method for producing abrasive grains, and alumina sintered body |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9124816D0 (en) * | 1991-11-22 | 1992-01-15 | Rolls Royce Plc | Method of manufacturing a composite material |
| GB9124822D0 (en) * | 1991-11-22 | 1992-01-15 | Rolls Royce Plc | Method of manufacturing a composite material |
| DE19503854C2 (en) * | 1995-02-06 | 1997-02-20 | Starck H C Gmbh Co Kg | Process for the production of sintered alpha-Al¶2¶O¶3¶ bodies and their use |
| DE19629690C2 (en) * | 1996-07-23 | 1999-08-05 | Korund Laufenburg Gmbh | Process for the production of sintered alpha-AL¶2¶0¶3¶ bodies and their use |
| DE19919818C1 (en) * | 1999-04-30 | 2000-05-04 | Bosch Gmbh Robert | Nanocrystalline metal oxide electrophoretic deposition bath, for producing green ceramic bodies, is prepared by kneading and then diluting a metal oxide concentrate |
| GB0123234D0 (en) | 2001-09-26 | 2001-11-21 | Bae Systems Plc | A method of potting a component |
| JP6550374B2 (en) * | 2013-04-05 | 2019-07-24 | スリーエム イノベイティブ プロパティズ カンパニー | Sintered abrasive particles, method of making the same, and abrasive articles comprising the same |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2401119A1 (en) * | 1977-08-26 | 1979-03-23 | Comp Generale Electricite | PROCESS OF PREPARATION OF CERAMIC PARTS BY ELECTROPHORESIS |
| ZA836559B (en) * | 1982-09-23 | 1985-02-27 | Kennecott Corp | Formation of alumina products from a liquid dispersion through the use of electrophoretic deposition |
| DE3801326A1 (en) * | 1988-01-19 | 1989-07-27 | Asea Brown Boveri | METHOD FOR PRODUCING A CERAMIC SUSPENSION |
-
1990
- 1990-05-26 DE DE9090110024T patent/DE59002167D1/en not_active Expired - Fee Related
- 1990-05-26 EP EP90110024A patent/EP0402686B1/en not_active Expired - Lifetime
- 1990-05-26 AT AT90110024T patent/ATE92543T1/en not_active IP Right Cessation
- 1990-06-07 JP JP2147511A patent/JPH0328120A/en active Pending
- 1990-06-08 CA CA002018584A patent/CA2018584A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5593467A (en) * | 1993-11-12 | 1997-01-14 | Minnesota Mining And Manufacturing Company | Abrasive grain |
| US5645618A (en) * | 1993-11-12 | 1997-07-08 | Minnesota Mining And Manufacturing Company | Method for making an abrasive article |
| US5651801A (en) * | 1993-11-12 | 1997-07-29 | Minnesota Mining And Manufacturing Company | Method for making an abrasive article |
| US7678723B2 (en) | 2004-09-14 | 2010-03-16 | Carbo Ceramics, Inc. | Sintered spherical pellets |
| US11667574B2 (en) | 2017-12-27 | 2023-06-06 | Showa Denko K.K. | Precursor of alumina sintered body, method for producing alumina sintered body, method for producing abrasive grains, and alumina sintered body |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0402686B1 (en) | 1993-08-04 |
| EP0402686A1 (en) | 1990-12-19 |
| DE59002167D1 (en) | 1993-09-09 |
| ATE92543T1 (en) | 1993-08-15 |
| JPH0328120A (en) | 1991-02-06 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |