CN112250452A - Alumina water-based coating material, preparation method thereof and crucible coating method - Google Patents
Alumina water-based coating material, preparation method thereof and crucible coating method Download PDFInfo
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Abstract
The invention relates to an alumina water-based coating material, a preparation method thereof and a method for coating a crucible. A preparation method of an alumina water-based coating material comprises the following steps: (1) preparing aluminum hydroxide powder by alkoxide hydrolysis; (2) calcining the aluminum hydroxide powder at ultrahigh temperature to obtain alumina powder; (3) carrying out jet milling on the alumina powder to obtain alumina fine powder; (4) adding high-purity water into the fine alumina powder, and uniformly mixing to obtain the water-based alumina coating material. The invention also discloses a method for coating the crucible. The alumina water-based coating material with high purity and strong interface bonding property can be prepared by alkoxide hydrolysis, ultrahigh temperature calcination and gas milling processes, and can be used for cold coating and hot coating processes.
Description
Technical Field
The invention belongs to the technical field of chemical processes, and particularly relates to an alumina water-based coating material, a preparation method thereof and a method for coating a crucible.
Background
In the high-purity aluminum or aluminum alloy smelting industry, a layer of alumina powder is generally required to be coated in a crucible before feeding, and the alumina coating can isolate crucible materials and molten aluminum liquid, so that the crucible is not damaged by the molten aluminum liquid, and impurity components in the crucible cannot directly enter the molten aluminum liquid.
At present, the smelting of high-purity aluminum with grade more than 5N and aluminum alloy with special component requirements puts higher requirements on the purity of an aluminum oxide coating. In addition, in order to reduce the waiting time between two times of smelting, the hot coating alumina process is often required to be carried out on the crucible while the cold coating alumina process is satisfied in the production. When the common aluminum oxide coating is coated on a crucible, obvious cracks or peeling phenomena can occur due to poor interface bonding, and the coating is peeled off in serious cases. The common solution is to add organic solvents or binders to enhance the bonding strength of the coating to the interface, but this result increases the risk of impurity introduction, which is particularly problematic in the fusion casting of ultra-high purity aluminum.
The prior art provides a coating for smelting and casting high-purity aluminum, a preparation method and application thereof. The coating comprises 20-30% of alumina, 1-3% of polyvinyl alcohol and the balance of water by mass percent. However, the purity of the alumina in the technical scheme is more than 99.999 percent by mass, and the purity of the used polyvinyl alcohol is not indicated. The addition of polyvinyl alcohol has the following risk points: (1) increasing the risk of introducing impurities, wherein the impurities comprise non-polyvinyl alcohol parts contained in polyvinyl alcohol and polyvinyl alcohol which is not dried completely; (2) the price of the polyvinyl alcohol is higher, and the cost expenditure of raw materials is increased; (3) the transportation and storage of the polyvinyl alcohol have flammable and explosive risks; (4) the cost of the process for preparing the polyvinyl alcohol is increased.
In view of the above, the present invention provides a novel alumina water-based coating material and a method for preparing the same, which can balance the contradiction between purity and interfacial bonding force in the aluminum smelting industry.
Disclosure of Invention
The invention aims to provide a preparation method of an alumina water-based coating material, which can prepare the alumina water-based coating material with high purity, good thermal stability and strong interface bonding property by alkoxide hydrolysis, high-temperature calcination and gas milling processes.
In order to realize the purpose, the adopted technical scheme is as follows:
a preparation method of an alumina water-based coating material comprises the following steps:
(1) preparing aluminum hydroxide powder by alkoxide hydrolysis;
(2) calcining the aluminum hydroxide powder at ultrahigh temperature to obtain alumina powder;
(3) carrying out jet milling on the alumina powder to obtain alumina fine powder;
(4) adding high-purity water into the fine alumina powder, and uniformly mixing to obtain the water-based alumina coating material.
Further, in the step (1), high-purity aluminum hydroxide is prepared by adopting high-purity aluminum, anhydrous isopropanol and high-purity water; wherein, the purity of the high-purity aluminum is 99.9 to 99.999 percent, and the purity of the anhydrous isopropanol is 99.9 to 99.995 percent;
in the step (2), the calcining temperature is 1500-;
in the step (4), the mass ratio of the alumina fine powder to the high-purity water is 1: 1-10.
Still further, in the step (2), the calcination temperature is 2040-.
Still further, in the step (4), the mass ratio of the fine alumina powder to the high purity water is 1: 4-8.
Furthermore, the purity of the aluminum hydroxide powder is not less than 99.999%, and the grain size is not more than 100 nm.
Another object of the invention is to provide a method for coating crucibles which is simple and does not allow the coating to fall off after the coating has dried.
In order to realize the purpose, the adopted technical scheme is as follows:
a method of coating a crucible, the method comprising: the alumina water-based coating material is sprayed or painted and coated on a crucible and then dried.
Furthermore, the crucible is made of cast iron, ceramic or graphite.
Further, the method for coating the crucible is cold coating or hot coating.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention can obtain high-purity aluminum hydroxide by an alkoxide hydrolysis method, ensures that the purity of the initial aluminum hydroxide is not less than 99.999 percent, and obtains small-size aluminum hydroxide. And can prepare the aluminum hydroxide with corresponding purity according to the requirement of smelting purity, and has wide application range and strong practicability.
2. The method for the aluminum hydroxide calcination process and the alumina jet mill processing process is simple, has low equipment requirement, and can realize large-scale production.
3. The calcination temperature in the calcination process is 1500-2300 ℃, and the alumina powder with good dispersibility is prepared by combining the airflow milling process, so that the alumina powder can be effectively combined with the ceramic and graphite interface and cannot fall off in the whole fusion casting process, and thus, no additive is required to be added into the alumina water-based coating material, and new impurities are prevented from being introduced. And the combination of alkoxide hydrolysis, ultrahigh temperature calcination and jet milling process can ensure the purity of the product while processing the alumina into powder.
4. The purity of the alumina water-based coating material is not less than 99.998 percent, and the alumina water-based coating material can completely meet the requirements of the aluminum smelting industry with special requirements on elements. After hot coating, after moisture in the alumina water-based coating material is instantly vaporized, the coating does not fall off in the whole casting process, the bonding property between the coating and an interface is still strong, the process requirement of hot coating of the crucible can be met, and the coating is suitable for isolating the crucible and aluminum liquid in the smelting process of high-purity aluminum, so that the crucible is protected and the impurity pollution is reduced.
Detailed Description
In order to further illustrate an alumina water-based coating material, a method for preparing the same, and a method for coating a crucible according to the present invention to achieve the intended objects, the following detailed description of the alumina water-based coating material, the method for preparing the same, and the method for coating a crucible according to the present invention will be given with reference to the preferred embodiments. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
The alumina water-based coating material, the preparation method thereof and the method for coating a crucible of the present invention will be further described in detail with reference to the following specific examples:
the technical scheme of the invention is as follows:
a preparation method of an alumina water-based coating material comprises the following steps:
(1) preparing aluminum hydroxide powder by alkoxide hydrolysis;
(2) calcining the aluminum hydroxide powder at ultrahigh temperature to obtain alumina powder;
(3) carrying out jet milling on the alumina powder to obtain alumina fine powder;
(4) adding high-purity water into the fine alumina powder, and uniformly mixing to obtain the water-based alumina coating material.
Preferably, in the step (1), high-purity aluminum hydroxide is prepared by using high-purity aluminum, anhydrous isopropanol and high-purity water; wherein, the purity of the high-purity aluminum is 99.9-99.999%, and the purity of the anhydrous isopropanol is 99.9-99.995%. The purity and size of the initial aluminum hydroxide are ensured by adopting an alkoxide hydrolysis method with purification capacity and preparing an aluminum hydroxide product from high-purity raw materials.
In the step (2), the calcination temperature is 1500-. The high-temperature calcination process of 1500-2300 ℃ can obtain the nearly pure-phase alumina. Under the technical parameters, the conversion rate of the alpha phase of the alumina is not less than 98 percent, thereby obtaining the alumina with the alpha phase as the main component.
In the step (4), the mass ratio of the alumina fine powder to the high-purity water is 1: 1-10. High purity water with impurities less than 10ppm is introduced to ensure the purity of the final product.
Further preferably, in the step (2), the calcination temperature is 2040-. In the ultrahigh-temperature calcination process, with the rise of temperature, the intercrystalline pores of the alumina powder are continuously reduced, and the structural defects are continuously reduced, so that the interface bonding property of the powder and the substrate is continuously enhanced, and the density of a sample is continuously increased. When the calcination temperature is: when T is more than or equal to 1500 and less than 2040 ℃, the loose-bulk ratio of the alumina powder reaches 0.7-0.9g/cm3The alumina powder has better bonding property with a substrate, and when the calcination temperature is 2040-3And the bonding property with the substrate is better.
Further preferably, in the step (4), the mass ratio of the fine alumina powder to the high purity water is 1: 4-8. The mass ratio of the alumina fine powder to the high-purity water is 1:4-8 from the consideration of economy and labor saving.
Preferably, the purity of the aluminum hydroxide powder is not less than 99.999%, and the crystal grain is not more than 100 nm. The aluminum hydroxide with high purity and small size can be obtained by an alkoxide hydrolysis method, which is beneficial to the later airflow milling process and ensures that the aluminum oxide powder with good dispersibility is obtained. The purity of alumina in the alumina water-based coating material is not less than 99.998 percent, and the alumina water-based coating material can completely meet the requirements of the aluminum smelting industry with special requirements on elements
A method of coating a crucible, the method comprising: the alumina water-based coating material is sprayed or painted and coated on a crucible and then dried.
Preferably, the crucible is made of cast iron, ceramic or graphite.
Preferably, the method of coating the crucible is cold coating or hot coating. The cold coating process refers to coating at 20-200 ℃. The hot coating process refers to: and (3) coating is directly carried out without waiting (namely, cooling process) between two times of smelting, namely, after one time of smelting is finished, the coating is directly coated without cooling, and then the next smelting is carried out.
Example 1.
The specific operation steps are as follows:
(1) 99.99 percent of high-purity aluminum scraps and 99.9 percent of isopropanol are used as raw materials, an alkoxide hydrolysis method is adopted, 1 purification process is adopted to prepare the aluminum hydroxide, and the purity of the aluminum hydroxide is 99.9991 percent (the purity is obtained by removing the content of other impurities after the aluminum hydroxide is detected by GDMS).
(2) And calcining the aluminum hydroxide powder for 4 hours at 2100 ℃ by adopting a corresponding high-temperature furnace to obtain the alumina powder.
(3) Then the fine powder of the alumina with the purity of 99.9983 percent and the D50 of 2.307 microns is obtained by milling through an airflow mill.
(4) Adding the alumina fine powder into high-purity water, and adding the alumina fine powder into the high-purity water according to a mass ratio of 1: and 5, uniformly stirring by using a non-metal rod body, wherein no precipitate is generated at the bottom of the liquid, and thus obtaining the alumina water-based coating material.
The alumina water-based coating material is painted to a painted cast iron crucible in a mode of combining spraying and painting, and an infrared measuring instrument measures the temperature of the crucible to be 108 ℃. The dried alumina powder has uniform coating and no crack and peeling phenomenon. And no shedding phenomenon is caused in the casting process.
Example 2.
The specific operation steps are as follows:
(1) 99.999 percent of high-purity aluminum scraps and 99.99 percent of isopropanol are used as raw materials, an alkoxide hydrolysis method is adopted, 1 purification process is adopted to prepare the aluminum hydroxide, and the purity of the aluminum hydroxide is 99.9995 percent (the purity is the purity obtained by removing the content of other impurities after the aluminum hydroxide is detected by GDMS).
(2) And calcining the aluminum hydroxide powder for 3 hours at 2200 ℃ by adopting a corresponding high-temperature furnace to obtain the alumina powder.
(3) Then the fine powder of the alumina is obtained by milling through an air flow mill, the purity is 99.9989 percent, and the D50 is 2.631 microns.
(4) Adding the alumina fine powder into high-purity water, and adding the alumina fine powder into the high-purity water according to a mass ratio of 1: and 7, uniformly stirring by using a non-metal rod body, wherein no precipitate is generated at the bottom of the liquid, and thus obtaining the alumina water-based coating material.
The alumina water-based coating material is painted to a graphite crucible in a mode of combining spraying and painting, and an infrared measuring instrument measures the temperature of the crucible to be 139 ℃. The dried alumina powder has uniform coating and no crack and peeling phenomenon. And no shedding phenomenon is caused in the casting process.
Example 3.
The specific operation steps are as follows:
(1) 99.99 percent of high-purity aluminum scraps and 99.9 percent of isopropanol are used as raw materials, an alkoxide hydrolysis method is adopted, 3 times of purification processes are adopted to prepare the aluminum hydroxide, and the purity of the aluminum hydroxide is 99.9994 percent (the purity is obtained by removing the content of other impurities after the aluminum hydroxide is detected by GDMS).
(2) And calcining the aluminum hydroxide powder for 10 hours at 1500 ℃ by adopting a corresponding high-temperature furnace to obtain the alumina powder.
(3) Then the fine powder of the alumina is obtained by milling through an air flow mill, the purity is 99.9986 percent, and the D50 is 2.301 microns.
(4) Adding the alumina fine powder into high-purity water, and adding the alumina fine powder into the high-purity water according to a mass ratio of 1: and 4, uniformly stirring by using a non-metal rod body, wherein no precipitate is generated at the bottom of the liquid, and thus obtaining the alumina water-based coating material.
And brushing the alumina water-based coating material to a brushed cast iron crucible in a mode of combining spraying and brushing. The coating mode is hot coating, and the coating is uniform after the alumina powder is dried, and has no crack and peeling phenomenon. And no shedding phenomenon is caused in the casting process.
Example 4.
The specific operation steps are as follows:
(1) 99.991% of high-purity aluminum scraps and 99.9% of isopropanol are used as raw materials, an alkoxide hydrolysis method is adopted, 2 times of purification processes are adopted to prepare the aluminum hydroxide, and the purity of the aluminum hydroxide is 99.9992% (the purity is the purity obtained by removing the content of other impurities after the aluminum hydroxide is detected by GDMS).
(2) And (3) calcining the aluminum hydroxide powder for 2h at 2300 ℃ by adopting a corresponding high-temperature furnace to obtain the alumina powder.
(3) Then the fine powder of the alumina with the purity of 99.9984 percent and the D50 of 2.412 microns is obtained by milling through an airflow mill.
(4) Adding the alumina fine powder into high-purity water, and adding the alumina fine powder into the high-purity water according to a mass ratio of 1: and 10, uniformly stirring by using a non-metal rod body, wherein no precipitate is generated at the bottom of liquid, and thus obtaining the alumina water-based coating material.
The alumina water-based coating material is painted to a painted cast iron crucible in a mode of combining spraying and painting, and an infrared measuring instrument measures the temperature of the crucible to be 148 ℃. The dried alumina powder has uniform coating and no crack and peeling phenomenon. And no shedding phenomenon is caused in the casting process.
Example 5.
The specific operation steps are as follows:
(1) 99.99 percent of high-purity aluminum scraps and 99.9 percent of isopropanol are used as raw materials, an alkoxide hydrolysis method is adopted, 1 purification process is adopted to prepare the aluminum hydroxide, and the purity of the aluminum hydroxide is 99.9991 percent (the purity is obtained by removing the content of other impurities after the aluminum hydroxide is detected by GDMS).
(2) And calcining the aluminum hydroxide powder for 5 hours at 2000 ℃ by adopting a corresponding high-temperature furnace to obtain the alumina powder.
(3) Then the fine powder of the alumina is obtained by milling through an air flow mill, the purity is 99.9984 percent, and the D50 is 2.389 microns.
(4) Adding the alumina fine powder into high-purity water, and adding the alumina fine powder into the high-purity water according to a mass ratio of 1: and 8, uniformly stirring by using a non-metal rod body, wherein no precipitate is generated at the bottom of the liquid, and thus obtaining the alumina water-based coating material.
The alumina water-based coating material is painted to a painted cast iron crucible in a mode of combining spraying and painting, and an infrared measuring instrument measures the temperature of the crucible to be 142 ℃. The dried alumina powder has uniform coating and no crack and peeling phenomenon. And no shedding phenomenon is caused in the casting process.
Comparative example 1.
The procedure was the same as in example 3 except that the calcination temperature in the calcination process was 1300 ℃.
The alumina water-based coating prepared in comparative example 1 was applied to a cast iron crucible. When the coating mode is cold coating, the coating is uniform after the alumina powder is dried, and the phenomena of cracks and peeling are avoided.
When the coating mode is hot coating, the coating is uniform after the alumina powder is dried, but cracks and peeling phenomena exist.
Aiming at the problem that the high-purity heat-stable alumina water-based coating material for aluminum smelting usually needs to be added with additives to solve the problems of cracks and peeling after coating. The invention provides an alumina coating which mainly comprises alumina and water, can solve the problems and is applied to smelting of high-purity aluminum, and has small influence on purity.
The method for preparing the aluminum hydroxide product by the alkoxide hydrolysis method with purification capability ensures that the initial aluminum hydroxide purity is not lower than 99.999 percent, adopts the 1500-plus-2300 ℃ high-temperature calcination process to calcine nearly pure-phase alumina, then prepares the alumina powder with good dispersibility by the jet milling process, introduces high-purity water with impurities less than 10ppm, and finally uniformly mixes the high-purity water according to a certain proportion. The components of the obtained water-based paint are alumina powder and high-purity water, and the components are simple; after hot coating, after moisture in the alumina water-based coating material is instantly vaporized, the coating does not fall off in the whole casting process, the bonding property of the coating and an interface is still strong, and the coating is suitable for isolating a crucible and aluminum liquid in the high-purity aluminum smelting process, thereby achieving the effects of protecting the crucible and reducing impurity pollution.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.
Claims (9)
1. A preparation method of an alumina water-based coating material is characterized by comprising the following steps:
(1) preparing aluminum hydroxide powder by alkoxide hydrolysis;
(2) calcining the aluminum hydroxide powder at ultrahigh temperature to obtain alumina powder;
(3) carrying out jet milling on the alumina powder to obtain alumina fine powder;
(4) adding high-purity water into the fine alumina powder, and uniformly mixing to obtain the water-based alumina coating material.
2. The production method according to claim 1,
in the step (1), high-purity aluminum hydroxide is prepared from high-purity aluminum, anhydrous isopropanol and high-purity water; wherein, the purity of the high-purity aluminum is 99.9 to 99.999 percent, and the purity of the anhydrous isopropanol is 99.9 to 99.995 percent;
in the step (2), the calcining temperature is 1500-;
in the step (4), the mass ratio of the alumina fine powder to the high-purity water is 1: 1-10.
3. The production method according to claim 2,
in the step (2), the calcination temperature is 2040-.
4. The production method according to claim 2,
in the step (4), the mass ratio of the alumina fine powder to the high-purity water is 1: 4-8.
5. The production method according to claim 2,
the purity of the aluminum hydroxide powder is not less than 99.999%, and the grain size is not more than 100 nm.
6. An alumina water-based coating material, characterized in that it is prepared by the preparation method of claims 1-5.
7. A method of coating a crucible, the method comprising: the alumina water-based coating of claim 5 is spray or brush applied to a crucible and then dried.
8. The method of claim 7,
the crucible is made of cast iron, ceramic or graphite.
9. The method of claim 7,
the method for coating the crucible is cold coating or hot coating.
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| CN114455964A (en) * | 2021-12-30 | 2022-05-10 | 西安超码科技有限公司 | C/SiC composite material crucible containing alumina coating |
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| CN101575110A (en) * | 2008-05-09 | 2009-11-11 | 大连路明纳米材料有限公司 | Preparation method of alumina powder |
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| CN110294631A (en) * | 2019-06-10 | 2019-10-01 | 青海万加环保新材料有限公司 | A kind of coating preparation method of alumina powder |
| CN111470524A (en) * | 2020-05-01 | 2020-07-31 | 苏州贝尔德新材料科技有限公司 | Preparation process of large-grain high-purity alumina |
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| CN101575110A (en) * | 2008-05-09 | 2009-11-11 | 大连路明纳米材料有限公司 | Preparation method of alumina powder |
| CN102826579A (en) * | 2012-09-05 | 2012-12-19 | 大连海蓝光电材料有限公司 | Preparation method of ultrahigh-purity and superfine aluminium oxide powder |
| CN103774209A (en) * | 2012-10-26 | 2014-05-07 | 阿特斯(中国)投资有限公司 | Crucible for silicon ingoting and preparation method of crucible coating |
| CN105948090A (en) * | 2016-06-14 | 2016-09-21 | 袁伟昊 | Ultra-pure nano-alumina green synthesis method and industrialization device |
| CN110294631A (en) * | 2019-06-10 | 2019-10-01 | 青海万加环保新材料有限公司 | A kind of coating preparation method of alumina powder |
| CN111470524A (en) * | 2020-05-01 | 2020-07-31 | 苏州贝尔德新材料科技有限公司 | Preparation process of large-grain high-purity alumina |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114455964A (en) * | 2021-12-30 | 2022-05-10 | 西安超码科技有限公司 | C/SiC composite material crucible containing alumina coating |
| CN114455964B (en) * | 2021-12-30 | 2023-09-05 | 西安超码科技有限公司 | C/SiC composite material crucible containing alumina coating |
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| CN112250452B (en) | 2021-12-07 |
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