CA2050705A1 - Process for the production of beta-silicon carbide powder - Google Patents
Process for the production of beta-silicon carbide powderInfo
- Publication number
- CA2050705A1 CA2050705A1 CA002050705A CA2050705A CA2050705A1 CA 2050705 A1 CA2050705 A1 CA 2050705A1 CA 002050705 A CA002050705 A CA 002050705A CA 2050705 A CA2050705 A CA 2050705A CA 2050705 A1 CA2050705 A1 CA 2050705A1
- Authority
- CA
- Canada
- Prior art keywords
- process according
- silicon dioxide
- silicon carbide
- beta
- carbon
- 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
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
- C01B33/186—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof from or via fluosilicic acid or salts thereof by a wet process
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/90—Carbides
- C01B32/914—Carbides of single elements
- C01B32/956—Silicon carbide
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/90—Carbides
- C01B32/914—Carbides of single elements
- C01B32/956—Silicon carbide
- C01B32/963—Preparation from compounds containing silicon
- C01B32/97—Preparation from SiO or SiO2
-
- 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
-
- 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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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Carbon And Carbon Compounds (AREA)
- Silicon Compounds (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A fine-particle, pure beta-silicon carbide powder is produced by the reaction of carbon black with silicon dioxide powder, obtainable as a by-product of aluminum fluoride production, and subsequent removal of the excess carbon.
A fine-particle, pure beta-silicon carbide powder is produced by the reaction of carbon black with silicon dioxide powder, obtainable as a by-product of aluminum fluoride production, and subsequent removal of the excess carbon.
Description
~s0~
This invention relates to a process for the production of beta-silicon carbide from silicic acid and carbon.
Silicon carbide has been recovered for many decades in basically the same manner, according to the Achason process. The Acheson process involves the reaction of silicon dioxide, in the form of quartz sand, and carbon, in the form of oil coke, in an electrical resistance furnace at temperatures above 2000C. A drawback of this method is that the product thus obtained is lumpy and, depending on the intended use, has to be finely crushed to varying degrees. Where an extremely fine product is necessary, the crushing operation requires much energy and considerable equipment. Such is the case, ~or instance, where the resultant product is intended as a sinter powder for the production of silicon carbide ceramics, an ever increasingly important use. Other drawbacks of the Acheson process are that the furnace used has to be very large to make economical operation possible and that the yield per furnace run is only in the order of magnitude of 20 ~ercent, so that a large part of the mat~rial used has to be recycled. Moreover, the Acheson process yields the hexagonal high-temperature modification of silicon carbide, which generally is designated as the alpha-modification, while the cubic low-temperature modification, pre~erred for certain uses, and usually designated as the beta-modification, is not accessible according to this prior process.
Processes for the production of beta-silicon carbide are also known which start from silicon dioxide and carbon. ~or this purpose, the reactants have to be in fine particulate ~orm and intimately mixed. The reaction temperatures are generally below 1800C. The reaction rate can be increased and the particle size of the product reduced by the addition of fine-particle beta-SiC, as a nucleating agent, and/or metals or metal oxides.
7~
Previously, both finely ground quartz and precipitated silicic acids or pyrogenic silicic acid was used as the source of silicon dioxide, while, for example, oil coke or carbon black was used as carbon. However, the fine grinding of quartz is very energy-intensive, and particle sizes below 1 micron, which are desirable for the production of SiC, can be achieved only at high costs.
Moreover, where pr~cipitated silicic acids, such as those described in, for example, U.S. Patent No. 4,377,563, or pyrogenic silicic acid are used, the specific properties of these products make technical performance difficult since, by virtue of their pronounced thickening action, they can only be poorly processed in aqueous suspension. Yet the formation of suspensions with high solid content and low viscosity is desirable or necessary for mixing, deagglomerating or spray drying.
Another drawback of the pyroganic silicic acids is their relatively high price.
The main object of the invention is to provide a process for the production of beta-silicon carbide, which starts from an inexpensive silicon dioxide having favoura~le particle size and good processing properties.
Accordingly, the present invention provides a process for the production of beta-silicon carbide powder from silicon dioxide and carbon black by heating both starting materials to a temperature of from 1200 to 2000~C
in the presence of beta-silicon carbide nuclei and then removing excess carbon. Amorphous silicon dioxide, resulting from the reaction of hexafluorosilicic acid with aluminium hydroxide, is used as the silicon dioxide.
It was found in the production of aluminum fluoride from hexafluorosilicic acid and aluminum hydroxide, according to the reaction equation:
H2SiF6 + 2Al(OH)3 > 2AlF3 + SiOz + 4H2O
; ~
' . . :,: :
t~
that the resultant amorphous silicon dioxide not only has a favourable particle size, which makes possible a rapid reaction with carbon, but also forms aqueous suspensions with solid contents of up to over 40 percent by weight at low viscosity.
Silicon dioxide is a by-product in the industrial production of aluminum fluoride and, therefore, is very inexpensive and available in large quantities. The recovery on a laboratory scale is described, for example, in U.S. Patent No. ~,693,878 (Example 1).
For the production of beta-silicon carbon, the silicon dioxide is suitably washed with acid to reduce the aluminum content to harmless values. A harmless value is a level of aluminum content which, when achieved, obviates the need for a similar acid treatment of the silicon carbide product. Hexafluorosilicic acid, necessary in aluminum fluoride production, can be used as the washing liquid, but other acids, such as, for example, hydrochloric acid can also be used. Special measures for the reduction of the fluorine content are not necessary, since the fluorine escapes at the operating temperatures for silicon carbide production. However, it can be advantageous to remove the fluorine before production of silicon carbide begins, in the manner described in U.S. Patent No.
4,693,878.
In the process of the present invention gas black or furnace black is the preferred carbon source, however, any carbon blac~ may be suitably used. Where furnace black is used as the carbon source, preferably, it is washed to remove metal traces and thereby avoid the introduction of impurities into the end product.
In a preferred embodiment of the present invention, the washed silicon dioxide is first ground or deagglomerated in a stirred ball mill or attrition mill.
Water is preferably used as the grinding liquid. The preferred grinding elements are those made from silicon . - , - . ,, . ~:
:
;~
, ~1~15 L3~
dioxide, for example, balls rnade from quartz glass or rounded quartz sand. A quartz sand, known by the name "Ottawa sand", with a particle size of about 1 mm has proved to be especially advantageous.
In order to avoid the introduction of impurities by metal abrasion, a stirred ball mill or an attrition mill with an elastomer lining is preferably used. The elastomer lining may, for example, be made from polyurethane. In this grinding or deagglomeration process, it is preferable that the beta-silicon carbide powder, necessary for nucleating, be present. To make the grinding or deagglomerating process easier, the usual auxiliary agents, especially liquefiers and defoaming agents, can be added.
Moreover, it is also possible to introduce additives, such as sintering auxiliary agents, desirable for the later use of the silicon carbide produced according to the present invention.
The carbon, preferably in the form of gas black or furnace black, is also introduced lnto the stirred ball mill or attrition mill to achieve an optimal mixing. Then the suspension is dehydrated according to ona of the known methods and put into a form suitable for the production of silicon carbide. Preferably, the dehydration is performed by spray drying, which can optionally be followed by a granulation st~p, if even coarser agglomerates are desired.
The reaction can be performad in any furnace which allows for the necessary temperature and retention times.
On a laboratory scale, the furnace can be a crucible ` furnace or a muffle furnace, while, on an industrial scale, ; 30 suitable examples are shaft furnaces, rotary kilns or fluidized-bed furnaces. Rotary kilns are especially advantageous since they make possible an adecluate heat transfer without the need for an auxiliary medium. The reaction temperatures and retention times are known generally those customary in the prior ark process. The reaction can be performed, for example, at a temperature of , i ~ ` . ' ` - :
:
~:~5~5 from 1500 to 1800C with a retention time in the order of 1 hour.
After completion of the reaction it i5 often necessary to remove the excess carbon. There are several methods known in the art for th:is purpose. For example, it is possible to either burn the carbon in the presence of oxygen or to react it with hydrogen, under pressure at 600 to 1400C, to form methane. Preferably, the carbon is removed by treatment with a~lmonia at 800 to 1400C, especially at 1000 to 1200C (F.K. van Dilen, J.
Pluijmakers, J. Eur. Ceram. Soc., 5, 385 (1989), and literature cited therein). ~hen, in the process of the ~ present invention treatment with ammonia is performed, the 1 use of a fluidized-bed furnace is preferred so as to ensure an optimal interaction between the gas and solid and an efficient transfer of heat.
After removal of excess carbon, the product can be used as such or subjected to another grinding and deagglomerating process. For this purpose, again a stirred ball mill or an attrition mill is preferably used. Silicon carbide balls are preferably used as the grinding elements ù so as not to introduce any foreign substances through abrasion. For the same reason, the attrition mill is preferably lined with plastic or (SiC) ceramic. Either water or an organic liquid, such as isopropanol or heptane, can be used as the grinding liquid. In this further grinding or deagglomerating step, additiYes such as sinter additives can be introduced where appropriate to the later use of the silicon carbide powder.
The following Examples illustrate the performance of the process according to the invention.
Purification of the starting material (a) Silicon dioxide: Crude silicon dioxide powder from the procluction of aluminum fluoride was first stirred at 95C for 4 hours with a diluted (0.6 percent by weight~
:. ~ . ' ~ , ~, .
~I~S [)~5 hexafluorosilicic acid (6 1 to 1 kg o~ silicon dioxide) and then filtered off. The filter cake was washed with desalted water (10 1 to 1 kg of silicon dioxide) and dried.
The aluminum content was reduced by this treatment from 1.5 percent by weight to 130 ppm and the fluorine content from 4.5 percent by weight to 3.3 percent by weight. The specific surface of the powcler was 3 m2/g, and the agglomerate size was smaller than O.1 mm.
(b) Furnace black: Commercial furnace black (Elftex~ 470) was stirred at 90C for 60 minutes with a diluted (0.6 percent by weight) aqueous hexafluorosilicic acid (6 1 to 1 kg of furnace black) and then filtered off.
The filter cake was washed with desalted water (5 1 to 1 kg of furnace black) and dried. The metal content was reduced by this treatment from 2000 ppm to 100 ppm.
EX~NPLB 2 Production of be~a-5iC
10.5 kg of washed silicon dioxide from Example 1 was ground with 0.5 kg of beta-SiC powder (as nucleating agent), 0.5 kg of Triton~ X-100 (liquefier), 0.1 kg of silicone defoaming agent and 0.4 kg of poly~inyl alcohol (binding agent) in 25 1 of desalted water in a stirred ball mill lined with polyurethane and with Ottawa sand (0.8 -1.1 mm) for 20 minutes (effective grinding period). Then 6.9 kg of gas black (Printex~ U) was added and ground for another 15 minutes. After separation of the sand by a filter cartridge, the suspension was spray dried so that a granular material with 0.4 mm average diameter and 2 percent residual moisture was obtained. The granular material was poured into graphite crucibles with a diameter of 50 mm and heated to 1700C for 60 minutes in an argon atmosphere. After cooling, the silicon carbide powder was heated to 1100C in a fluidized-bed furnace with ammonia for 5 hours to remove the residual carbon. The silicon carbide powder thus obtained exhibited the following properties:
`
5~
phase composition (x-ray diffraction) 100% beta specific surface (BET) 5 m2/g carbon content (total) 29.8 % by weight nitrogen content 0.2% by weight oxygen content 0.3% by weight metals 220 ppm A suspension of 10.5 ]cg of washed silicon dioxide and the additives described in Example 2 were ground in 15 l of desalted water for 20 minutes in a stirred ball mill as described in Example 2. Then 6.6 kg of furnace black (Elftex 470), washed according to Example 1, and lO l of desalted water was added. The other steps took place as described in Example 2. The silicon carbide powder thus obtained exhibited the following properties:
phase composition (x-ray diffraction) 100% beta specific surface (BET) 5 m2/g carbon content (total) 29~8% by weight nitrogen content 0.2% by weight oxygen content 0.3% by weight .l metals 300 ppm : `
, , :
This invention relates to a process for the production of beta-silicon carbide from silicic acid and carbon.
Silicon carbide has been recovered for many decades in basically the same manner, according to the Achason process. The Acheson process involves the reaction of silicon dioxide, in the form of quartz sand, and carbon, in the form of oil coke, in an electrical resistance furnace at temperatures above 2000C. A drawback of this method is that the product thus obtained is lumpy and, depending on the intended use, has to be finely crushed to varying degrees. Where an extremely fine product is necessary, the crushing operation requires much energy and considerable equipment. Such is the case, ~or instance, where the resultant product is intended as a sinter powder for the production of silicon carbide ceramics, an ever increasingly important use. Other drawbacks of the Acheson process are that the furnace used has to be very large to make economical operation possible and that the yield per furnace run is only in the order of magnitude of 20 ~ercent, so that a large part of the mat~rial used has to be recycled. Moreover, the Acheson process yields the hexagonal high-temperature modification of silicon carbide, which generally is designated as the alpha-modification, while the cubic low-temperature modification, pre~erred for certain uses, and usually designated as the beta-modification, is not accessible according to this prior process.
Processes for the production of beta-silicon carbide are also known which start from silicon dioxide and carbon. ~or this purpose, the reactants have to be in fine particulate ~orm and intimately mixed. The reaction temperatures are generally below 1800C. The reaction rate can be increased and the particle size of the product reduced by the addition of fine-particle beta-SiC, as a nucleating agent, and/or metals or metal oxides.
7~
Previously, both finely ground quartz and precipitated silicic acids or pyrogenic silicic acid was used as the source of silicon dioxide, while, for example, oil coke or carbon black was used as carbon. However, the fine grinding of quartz is very energy-intensive, and particle sizes below 1 micron, which are desirable for the production of SiC, can be achieved only at high costs.
Moreover, where pr~cipitated silicic acids, such as those described in, for example, U.S. Patent No. 4,377,563, or pyrogenic silicic acid are used, the specific properties of these products make technical performance difficult since, by virtue of their pronounced thickening action, they can only be poorly processed in aqueous suspension. Yet the formation of suspensions with high solid content and low viscosity is desirable or necessary for mixing, deagglomerating or spray drying.
Another drawback of the pyroganic silicic acids is their relatively high price.
The main object of the invention is to provide a process for the production of beta-silicon carbide, which starts from an inexpensive silicon dioxide having favoura~le particle size and good processing properties.
Accordingly, the present invention provides a process for the production of beta-silicon carbide powder from silicon dioxide and carbon black by heating both starting materials to a temperature of from 1200 to 2000~C
in the presence of beta-silicon carbide nuclei and then removing excess carbon. Amorphous silicon dioxide, resulting from the reaction of hexafluorosilicic acid with aluminium hydroxide, is used as the silicon dioxide.
It was found in the production of aluminum fluoride from hexafluorosilicic acid and aluminum hydroxide, according to the reaction equation:
H2SiF6 + 2Al(OH)3 > 2AlF3 + SiOz + 4H2O
; ~
' . . :,: :
t~
that the resultant amorphous silicon dioxide not only has a favourable particle size, which makes possible a rapid reaction with carbon, but also forms aqueous suspensions with solid contents of up to over 40 percent by weight at low viscosity.
Silicon dioxide is a by-product in the industrial production of aluminum fluoride and, therefore, is very inexpensive and available in large quantities. The recovery on a laboratory scale is described, for example, in U.S. Patent No. ~,693,878 (Example 1).
For the production of beta-silicon carbon, the silicon dioxide is suitably washed with acid to reduce the aluminum content to harmless values. A harmless value is a level of aluminum content which, when achieved, obviates the need for a similar acid treatment of the silicon carbide product. Hexafluorosilicic acid, necessary in aluminum fluoride production, can be used as the washing liquid, but other acids, such as, for example, hydrochloric acid can also be used. Special measures for the reduction of the fluorine content are not necessary, since the fluorine escapes at the operating temperatures for silicon carbide production. However, it can be advantageous to remove the fluorine before production of silicon carbide begins, in the manner described in U.S. Patent No.
4,693,878.
In the process of the present invention gas black or furnace black is the preferred carbon source, however, any carbon blac~ may be suitably used. Where furnace black is used as the carbon source, preferably, it is washed to remove metal traces and thereby avoid the introduction of impurities into the end product.
In a preferred embodiment of the present invention, the washed silicon dioxide is first ground or deagglomerated in a stirred ball mill or attrition mill.
Water is preferably used as the grinding liquid. The preferred grinding elements are those made from silicon . - , - . ,, . ~:
:
;~
, ~1~15 L3~
dioxide, for example, balls rnade from quartz glass or rounded quartz sand. A quartz sand, known by the name "Ottawa sand", with a particle size of about 1 mm has proved to be especially advantageous.
In order to avoid the introduction of impurities by metal abrasion, a stirred ball mill or an attrition mill with an elastomer lining is preferably used. The elastomer lining may, for example, be made from polyurethane. In this grinding or deagglomeration process, it is preferable that the beta-silicon carbide powder, necessary for nucleating, be present. To make the grinding or deagglomerating process easier, the usual auxiliary agents, especially liquefiers and defoaming agents, can be added.
Moreover, it is also possible to introduce additives, such as sintering auxiliary agents, desirable for the later use of the silicon carbide produced according to the present invention.
The carbon, preferably in the form of gas black or furnace black, is also introduced lnto the stirred ball mill or attrition mill to achieve an optimal mixing. Then the suspension is dehydrated according to ona of the known methods and put into a form suitable for the production of silicon carbide. Preferably, the dehydration is performed by spray drying, which can optionally be followed by a granulation st~p, if even coarser agglomerates are desired.
The reaction can be performad in any furnace which allows for the necessary temperature and retention times.
On a laboratory scale, the furnace can be a crucible ` furnace or a muffle furnace, while, on an industrial scale, ; 30 suitable examples are shaft furnaces, rotary kilns or fluidized-bed furnaces. Rotary kilns are especially advantageous since they make possible an adecluate heat transfer without the need for an auxiliary medium. The reaction temperatures and retention times are known generally those customary in the prior ark process. The reaction can be performed, for example, at a temperature of , i ~ ` . ' ` - :
:
~:~5~5 from 1500 to 1800C with a retention time in the order of 1 hour.
After completion of the reaction it i5 often necessary to remove the excess carbon. There are several methods known in the art for th:is purpose. For example, it is possible to either burn the carbon in the presence of oxygen or to react it with hydrogen, under pressure at 600 to 1400C, to form methane. Preferably, the carbon is removed by treatment with a~lmonia at 800 to 1400C, especially at 1000 to 1200C (F.K. van Dilen, J.
Pluijmakers, J. Eur. Ceram. Soc., 5, 385 (1989), and literature cited therein). ~hen, in the process of the ~ present invention treatment with ammonia is performed, the 1 use of a fluidized-bed furnace is preferred so as to ensure an optimal interaction between the gas and solid and an efficient transfer of heat.
After removal of excess carbon, the product can be used as such or subjected to another grinding and deagglomerating process. For this purpose, again a stirred ball mill or an attrition mill is preferably used. Silicon carbide balls are preferably used as the grinding elements ù so as not to introduce any foreign substances through abrasion. For the same reason, the attrition mill is preferably lined with plastic or (SiC) ceramic. Either water or an organic liquid, such as isopropanol or heptane, can be used as the grinding liquid. In this further grinding or deagglomerating step, additiYes such as sinter additives can be introduced where appropriate to the later use of the silicon carbide powder.
The following Examples illustrate the performance of the process according to the invention.
Purification of the starting material (a) Silicon dioxide: Crude silicon dioxide powder from the procluction of aluminum fluoride was first stirred at 95C for 4 hours with a diluted (0.6 percent by weight~
:. ~ . ' ~ , ~, .
~I~S [)~5 hexafluorosilicic acid (6 1 to 1 kg o~ silicon dioxide) and then filtered off. The filter cake was washed with desalted water (10 1 to 1 kg of silicon dioxide) and dried.
The aluminum content was reduced by this treatment from 1.5 percent by weight to 130 ppm and the fluorine content from 4.5 percent by weight to 3.3 percent by weight. The specific surface of the powcler was 3 m2/g, and the agglomerate size was smaller than O.1 mm.
(b) Furnace black: Commercial furnace black (Elftex~ 470) was stirred at 90C for 60 minutes with a diluted (0.6 percent by weight) aqueous hexafluorosilicic acid (6 1 to 1 kg of furnace black) and then filtered off.
The filter cake was washed with desalted water (5 1 to 1 kg of furnace black) and dried. The metal content was reduced by this treatment from 2000 ppm to 100 ppm.
EX~NPLB 2 Production of be~a-5iC
10.5 kg of washed silicon dioxide from Example 1 was ground with 0.5 kg of beta-SiC powder (as nucleating agent), 0.5 kg of Triton~ X-100 (liquefier), 0.1 kg of silicone defoaming agent and 0.4 kg of poly~inyl alcohol (binding agent) in 25 1 of desalted water in a stirred ball mill lined with polyurethane and with Ottawa sand (0.8 -1.1 mm) for 20 minutes (effective grinding period). Then 6.9 kg of gas black (Printex~ U) was added and ground for another 15 minutes. After separation of the sand by a filter cartridge, the suspension was spray dried so that a granular material with 0.4 mm average diameter and 2 percent residual moisture was obtained. The granular material was poured into graphite crucibles with a diameter of 50 mm and heated to 1700C for 60 minutes in an argon atmosphere. After cooling, the silicon carbide powder was heated to 1100C in a fluidized-bed furnace with ammonia for 5 hours to remove the residual carbon. The silicon carbide powder thus obtained exhibited the following properties:
`
5~
phase composition (x-ray diffraction) 100% beta specific surface (BET) 5 m2/g carbon content (total) 29.8 % by weight nitrogen content 0.2% by weight oxygen content 0.3% by weight metals 220 ppm A suspension of 10.5 ]cg of washed silicon dioxide and the additives described in Example 2 were ground in 15 l of desalted water for 20 minutes in a stirred ball mill as described in Example 2. Then 6.6 kg of furnace black (Elftex 470), washed according to Example 1, and lO l of desalted water was added. The other steps took place as described in Example 2. The silicon carbide powder thus obtained exhibited the following properties:
phase composition (x-ray diffraction) 100% beta specific surface (BET) 5 m2/g carbon content (total) 29~8% by weight nitrogen content 0.2% by weight oxygen content 0.3% by weight .l metals 300 ppm : `
, , :
Claims (12)
1. A process for the production of beta-silicon carbide powder from silicon dioxide and carbon black, which comprises heating amorphous silicon dioxide, resulting from the reaction of hexafluorosilicic acid with aluminum hydroxide, and carbon black to a temperature of from 1200°
to 2000°C in the presence of beta-silicon carbide nuclei, and then removing excess carbon.
to 2000°C in the presence of beta-silicon carbide nuclei, and then removing excess carbon.
2. A process according to claim 1, wherein the silicon dioxide is washed with acid to remove metal compounds therefrom.
3. A process according to claim 2, wherein the acid is dilute hexafluorosilicic acid.
4. A process according to claim 3, wherein the carbon black is gas black or washed furnace black.
5. A process according to claim 1, wherein the removal of excess carbon is effected by treatment with ammonia at a temperature of from 1000° to 1200°C.
6. A process according to claim 5, wherein the treatment with ammonia is performed in a fluidized bed.
7. A process according to claim 1, wherein the silicon dioxide is ground and/or deagglomerated in a stirred ball mill or an attrition mill.
8. A process according to claim 7, wherein rounded quartz sand is used as the grinding element in the stirred ball mill or the attrition mill.
9. A process according to claim 1, wherein the reaction mixture of silicon dioxide and carbon black is dried by spray drying and granulation.
10. A process according to claim 9, wherein an aqueous suspension is spray dried.
11. A process according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein the reaction of the silicon dioxide with the carbon black is performed in a rotary kiln.
12. A process according to claim 1, wherein additives relevant to the later use of the silicon carbide product are introduced during the grinding or deagglomerating process.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH2919/90 | 1990-09-07 | ||
| CH291990 | 1990-09-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2050705A1 true CA2050705A1 (en) | 1992-03-08 |
Family
ID=4244567
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002050705A Abandoned CA2050705A1 (en) | 1990-09-07 | 1991-09-05 | Process for the production of beta-silicon carbide powder |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0476422B1 (en) |
| JP (1) | JPH04270106A (en) |
| CA (1) | CA2050705A1 (en) |
| DE (1) | DE59102334D1 (en) |
| ES (1) | ES2059003T3 (en) |
| NO (1) | NO179442C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140363675A1 (en) * | 2012-01-20 | 2014-12-11 | Lg Innotek Co., Ltd. | Silicon carbide powder and method for manufacturing the same |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0717395A3 (en) | 1994-12-12 | 1997-03-05 | Diafoil Hoechst Co Ltd | High-density magnetic recording medium |
| KR101940351B1 (en) * | 2011-08-24 | 2019-01-18 | 다이헤이요 세멘토 가부시키가이샤 | Silicon carbride powder and method for producing same |
| DE102022102320A1 (en) | 2022-02-01 | 2023-08-03 | The Yellow SiC Holding GmbH | Device and method for the production of silicon carbide |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4693878A (en) * | 1986-06-11 | 1987-09-15 | Swiss Aluminium Ltd. | Process for the production of soluble alkali silicates |
| NL8802117A (en) * | 1988-08-27 | 1990-03-16 | Stamicarbon | Method for preparing silicon-containing powders with a high level of purity |
| NL8802116A (en) * | 1988-08-27 | 1990-03-16 | Stamicarbon | Method for removing free carbon and/or metal oxide from ceramic material |
-
1991
- 1991-09-03 EP EP91114866A patent/EP0476422B1/en not_active Expired - Lifetime
- 1991-09-03 ES ES91114866T patent/ES2059003T3/en not_active Expired - Lifetime
- 1991-09-03 DE DE59102334T patent/DE59102334D1/en not_active Expired - Fee Related
- 1991-09-04 JP JP3223929A patent/JPH04270106A/en active Pending
- 1991-09-05 CA CA002050705A patent/CA2050705A1/en not_active Abandoned
- 1991-09-06 NO NO913515A patent/NO179442C/en unknown
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140363675A1 (en) * | 2012-01-20 | 2014-12-11 | Lg Innotek Co., Ltd. | Silicon carbide powder and method for manufacturing the same |
| US9534316B2 (en) * | 2012-01-20 | 2017-01-03 | Lg Innotek Co., Ltd. | Silicon carbide powder and method for manufacturing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| NO179442B (en) | 1996-07-01 |
| JPH04270106A (en) | 1992-09-25 |
| DE59102334D1 (en) | 1994-09-01 |
| ES2059003T3 (en) | 1994-11-01 |
| NO913515D0 (en) | 1991-09-06 |
| EP0476422A1 (en) | 1992-03-25 |
| NO913515L (en) | 1992-03-09 |
| NO179442C (en) | 1996-10-09 |
| EP0476422B1 (en) | 1994-07-27 |
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