CN114835473B - Alumina ceramic and preparation method thereof - Google Patents
Alumina ceramic and preparation method thereof Download PDFInfo
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- CN114835473B CN114835473B CN202210642731.0A CN202210642731A CN114835473B CN 114835473 B CN114835473 B CN 114835473B CN 202210642731 A CN202210642731 A CN 202210642731A CN 114835473 B CN114835473 B CN 114835473B
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims abstract description 78
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 238000005245 sintering Methods 0.000 claims abstract description 205
- 238000007731 hot pressing Methods 0.000 claims abstract description 92
- 238000002156 mixing Methods 0.000 claims abstract description 51
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical class OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 48
- 239000000919 ceramic Substances 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 9
- 239000011812 mixed powder Substances 0.000 claims description 37
- 238000000498 ball milling Methods 0.000 claims description 34
- 239000011268 mixed slurry Substances 0.000 claims description 20
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 8
- 229910018626 Al(OH) Inorganic materials 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000013078 crystal Substances 0.000 abstract description 12
- 238000004321 preservation Methods 0.000 abstract description 12
- 238000005452 bending Methods 0.000 abstract description 10
- 230000006911 nucleation Effects 0.000 abstract description 8
- 238000010899 nucleation Methods 0.000 abstract description 8
- 235000006408 oxalic acid Nutrition 0.000 abstract description 8
- IBSDADOZMZEYKD-UHFFFAOYSA-H oxalate;yttrium(3+) Chemical compound [Y+3].[Y+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O IBSDADOZMZEYKD-UHFFFAOYSA-H 0.000 abstract description 6
- 230000008020 evaporation Effects 0.000 abstract description 5
- 238000001704 evaporation Methods 0.000 abstract description 5
- 230000008569 process Effects 0.000 abstract description 5
- 230000005496 eutectics Effects 0.000 abstract description 4
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 4
- 230000001737 promoting effect Effects 0.000 abstract description 3
- 239000002245 particle Substances 0.000 description 20
- 239000000843 powder Substances 0.000 description 15
- 238000001816 cooling Methods 0.000 description 12
- 239000000463 material Substances 0.000 description 11
- 238000005520 cutting process Methods 0.000 description 7
- 238000005498 polishing Methods 0.000 description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- 229910003460 diamond Inorganic materials 0.000 description 6
- 239000010432 diamond Substances 0.000 description 6
- 238000007873 sieving Methods 0.000 description 6
- 238000001291 vacuum drying Methods 0.000 description 6
- 238000000227 grinding Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000005034 decoration Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000011534 incubation Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
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Abstract
The invention provides an alumina ceramic and a preparation method thereof, belonging to the technical field of alumina ceramics. The invention adds Y 2 O 3 Can form eutectic with alumina to lower sintering temperature; adding Al (OH) 3 The sintering temperature can be further reduced; then mixing with saturated oxalic acid solution, Y 2 O 3 Slightly soluble in oxalic acid solution, and in the cold sintering process, oxalic acid crystal and Y are separated out along with the evaporation of water 2 O 3 Reacting to generate yttrium oxalate, playing a role in nucleation and promoting the nucleation of aluminum oxide, thereby reducing the sintering temperature; and then low-temperature heat preservation and hot-pressing sintering are carried out, so that the compactness can be improved, and the mechanical property is improved. Experimental results show that the sintering temperature can be reduced to 1350-1400 ℃ when the alumina ceramic is prepared, the microhardness of the prepared alumina ceramic is 1870-2040 HV, and the fracture toughness is 6.2-6.5 MPa.m 1/2 The bending strength is 510-535 MPa.
Description
Technical Field
The invention belongs to the technical field of alumina ceramics, and particularly relates to alumina ceramics and a preparation method thereof.
Background
The alumina ceramic has excellent comprehensive properties of high mechanical strength, high hardness, low high-frequency dielectric loss, high-temperature insulation resistance, good chemical corrosion resistance and the like, and has the advantages of wide raw material source, relatively low price, mature processing and manufacturing technology and the like, so that the alumina ceramic is widely applied to the industries of electronics, electrical appliances, machinery, chemical engineering, textile, automobiles, metallurgy, aerospace and the like, and becomes one of the most-used advanced ceramic materials in the world at present.
The ionic bond of the alumina is extremely strong, the melting point reaches 2050 ℃, and high sintering temperature is needed, so that a large amount of energy and high-heat-value fuel need to be consumed in the production process of the alumina ceramic, and a large amount of high-temperature sintered high-grade refractory materials (kiln furniture, furnace materials and the like) and high-temperature heating elements need to be consumed, so that the development and application of the alumina ceramic are limited; and the excessive high sintering temperature leads to larger crystal grains of the main crystal phase of the ceramic and the aggregation and growth of residual pores, thus leading to the reduction of the mechanical property of the material. Therefore, how to reduce the sintering temperature of alumina ceramics is always an important issue that enterprises are concerned about and urgently need to solve. At present, the addition of sintering aids (TiO) is mainly adopted 2 、Cr 2 O 3 、MnO 2 Etc.), the sintering temperature of the alumina ceramic can only be reduced to 1600-1650 ℃, and the mechanical property of the prepared alumina ceramic is lower, which still limits the development and application of the alumina ceramic. Therefore, how to further reduce the sintering temperature of the alumina ceramic, thereby improving the mechanical properties of the alumina ceramic, is a difficult problem to be solved in the field.
Disclosure of Invention
The invention aims to provide alumina ceramic and a preparation method thereof. The preparation method provided by the invention has the advantages that the sintering temperature is 1350-1400 ℃ when the alumina ceramic is prepared, and the prepared alumina ceramic has high mechanical property.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of alumina ceramic, which comprises the following steps:
(1) Mixing Al 2 O 3 、Al(OH) 3 And Y 2 O 3 Mixing to obtain mixed powder;
(2) Mixing the mixed powder obtained in the step (1) with a saturated oxalic acid solution to obtain a mixed slurry;
(3) Performing cold sintering on the mixed slurry obtained in the step (2) to obtain a first sintered body; the sintering pressure of the cold sintering is 300-420 MPa; the cold sintering is first cold sintering at 100-120 deg.c and then second cold sintering at 200-250 deg.c;
(4) Preserving the temperature of the first sintered body obtained in the step (3) at 100-150 ℃ for 3-4 h to obtain a second sintered body;
(5) Carrying out hot-pressing sintering on the second sintered body obtained in the step (4) to obtain alumina ceramic; the pressure of the hot-pressing sintering is 25-30 MPa; the hot-pressing sintering is that first hot-pressing sintering is carried out at 250-400 ℃, second hot-pressing sintering is carried out at 700-900 ℃, third hot-pressing sintering is carried out at 1200-1300 ℃, and finally fourth hot-pressing sintering is carried out at 1350-1400 ℃.
Preferably, al (OH) in the step (1) 3 The mass of (b) is 5 to 15% of the mass of the mixed powder.
Preferably, Y in said step (1) 2 O 3 The mass of (b) is 1 to 2% of the mass of the mixed powder.
Preferably, the mixing in step (1) is ball milling mixing.
Preferably, the rotation speed of the ball milling mixing is 200-250 r/min, and the time of the ball milling mixing is 6-10 h.
Preferably, the ratio of the mass of the mixed powder to the volume of the saturated oxalic acid solution in the step (2) is 10g: (1-1.5) mL.
Preferably, the holding time of the first cold sintering and the second cold sintering in the step (3) is independently 0.3-1 h.
Preferably, the temperature of the second hot-pressing sintering in the step (5) is 800-900 ℃.
Preferably, the heat preservation time of the first hot-pressing sintering, the second hot-pressing sintering, the third hot-pressing sintering and the fourth hot-pressing sintering in the step (5) is independently 0.5-1 h.
The invention also provides the alumina ceramic prepared by the preparation method in the technical scheme.
The invention provides a preparation method of alumina ceramic, which comprises the following steps: mixing Al 2 O 3 、Al(OH) 3 And Y 2 O 3 Mixing to obtain mixed powder; will be provided withMixing the mixed powder obtained in the step (1) with a saturated oxalic acid solution to obtain mixed slurry; performing cold sintering on the mixed slurry obtained in the step (2) to obtain a first sintered body; the sintering pressure of the cold sintering is 300-420 MPa; the cold sintering is first cold sintering at 100-120 ℃ and then second cold sintering at 200-250 ℃; preserving the heat of the first sintered body obtained in the step (3) at 100-150 ℃ for 3-4 h to obtain a second sintered body; carrying out hot-pressing sintering on the second sintered body obtained in the step (4) to obtain alumina ceramic; the pressure of the hot-pressing sintering is 25-30 MPa; the hot-pressing sintering is that first hot-pressing sintering is carried out at 250-400 ℃, second hot-pressing sintering is carried out at 700-900 ℃, third hot-pressing sintering is carried out at 1200-1300 ℃, and finally fourth hot-pressing sintering is carried out at 1350-1400 ℃. Y is added in the invention 2 O 3 Can form eutectic with alumina to lower sintering temperature; adding Al (OH) 3 The sintering temperature can be further reduced; then mixing with saturated oxalic acid solution, Y 2 O 3 Slightly soluble in oxalic acid solution, and in the cold sintering process, oxalic acid crystal is separated out along with the evaporation of water, and is mixed with Y 2 O 3 Reacting to generate yttrium oxalate, playing a role in nucleation and promoting the nucleation of aluminum oxide, thereby reducing the sintering temperature; and then low-temperature heat preservation and hot-pressing sintering are carried out, so that the compactness of the alumina ceramic can be improved, and the mechanical property of the alumina ceramic is improved. Experimental results show that the preparation method provided by the invention can reduce the sintering temperature to 1350-1400 ℃ when preparing the alumina ceramic, the microhardness of the prepared alumina ceramic is 1870-2040 HV, and the fracture toughness is 6.2-6.5 MPa.m 1/2 The bending strength is 510-535 MPa.
Drawings
FIG. 1 is a fracture morphology diagram of an alumina ceramic prepared in example 1 by a scanning electron microscope;
FIG. 2 is a scanning electron microscope fracture morphology diagram of the alumina ceramic prepared in comparative example 1;
FIG. 3 is a scanning electron microscope fracture morphology of the alumina ceramic prepared in example 3.
Detailed Description
The invention provides a preparation method of alumina ceramic, which comprises the following steps:
(1) Mixing Al 2 O 3 、Al(OH) 3 And Y 2 O 3 Mixing to obtain mixed powder;
(2) Mixing the mixed powder obtained in the step (1) with a saturated oxalic acid solution to obtain mixed slurry;
(3) Performing cold sintering on the mixed slurry obtained in the step (2) to obtain a first sintered body; the sintering pressure of the cold sintering is 300-420 MPa; the cold sintering is first cold sintering at 100-120 deg.c and then second cold sintering at 200-250 deg.c;
(4) Preserving the temperature of the first sintered body obtained in the step (3) at 100-150 ℃ for 3-4 h to obtain a second sintered body;
(5) Carrying out hot-pressing sintering on the second sintered body obtained in the step (4) to obtain alumina ceramic; the pressure of the hot-pressing sintering is 25-30 MPa; the hot-pressing sintering is that first hot-pressing sintering is carried out at 250-400 ℃, second hot-pressing sintering is carried out at 700-900 ℃, third hot-pressing sintering is carried out at 1200-1300 ℃, and finally fourth hot-pressing sintering is carried out at 1350-1400 ℃.
In the invention, al is mixed with 2 O 3 、Al(OH) 3 And Y 2 O 3 Mixing to obtain mixed powder. The invention adds Y 2 O 3 Can form eutectic with alumina to lower sintering temperature; adding Al (OH) 3 The sintering temperature can be further reduced.
In the present invention, the Al 2 O 3 The purity of (b) is preferably more than or equal to 99.99%; the Al is 2 O 3 Preferably alpha-Al 2 O 3 (ii) a The Al is 2 O 3 The average particle diameter of (2) is preferably 400 to 700nm. In the invention, the Al is 2 O 3 The source of (A) is not particularly limited, and commercially available products known to those skilled in the art may be used.
In the present invention, the Al (OH) 3 The purity of (b) is preferably more than or equal to 99.99%; the Al (OH) 3 The average particle diameter of (2) is preferably 400 to 700nm. The inventionFor the Al (OH) 3 The source of (A) is not particularly limited, and commercially available products known to those skilled in the art can be used.
In the present invention, said Y is 2 O 3 The purity of (A) is preferably more than or equal to 99.99%; said Y is 2 O 3 Preferably 50 to 200nm. The invention is directed to said Y 2 O 3 The source of (A) is not particularly limited, and commercially available products known to those skilled in the art may be used.
In the present invention, the Al (OH) 3 The mass of (b) is preferably 5 to 15%, more preferably 10 to 15% of the mass of the mixed powder; said Y 2 O 3 The mass of (b) is preferably 1 to 2%, more preferably 1.5 to 2% of the mass of the mixed powder. The invention controls Al (OH) 3 And Y 2 O 3 Can further reduce the sintering temperature.
In the present invention, the Al is 2 O 3 、Al(OH) 3 And Y 2 O 3 The mixing of (a) is preferably ball milling mixing; the rotation speed of the ball milling mixing is preferably 200-250 r/min; the time for ball milling and mixing is preferably 6 to 10 hours, and more preferably 8 to 9 hours; the mass ratio of the ball materials during ball milling and mixing is preferably (5-15): 1; the ball milling medium of the ball milling mixture is preferably absolute ethanol. The invention is prepared by mixing Al 2 O 3 、Al(OH) 3 And Y 2 O 3 The ball milling and mixing can improve the mixing degree of the raw materials.
In the present invention, the ball milling mixing is preferably carried out in a planetary ball mill. The source of the planetary ball mill is not particularly limited in the present invention, and the equipment well known to those skilled in the art can be used.
Al 2 O 3 、Al(OH) 3 And Y 2 O 3 After the mixing is completed, the present invention preferably sequentially dries and screens the mixed product to obtain a mixed powder.
In the present invention, the drying is preferably vacuum drying; the temperature of the drying is preferably 60 ℃. The drying time is not specially limited, and the drying is carried out until the weight is constant.
In the present invention, the sieving is preferably a 120 mesh sieve.
After the mixed powder is obtained, the mixed powder is mixed with a saturated oxalic acid solution to obtain mixed slurry.
In the present invention, the ratio of the mass of the mixed powder to the volume of the saturated oxalic acid solution is preferably 10g: (1 to 1.5) mL, more preferably 10g: (1-1.2) mL. The source of the saturated oxalic acid solution is not particularly limited in the invention, and the saturated oxalic acid solution can be prepared by a preparation method well known to a person skilled in the art. In the invention, the saturated oxalic acid solution can dissolve yttrium oxide in a trace amount, and in the subsequent cold sintering process, oxalic acid crystals are separated out along with the evaporation of water to generate a trace amount of yttrium oxalate, so that the nucleation effect is achieved, the nucleation of aluminum oxide is promoted, and the sintering temperature is reduced; the sintering temperature can be further reduced by controlling the ratio of the mass of the mixed powder to the volume of the saturated oxalic acid solution.
The operation of mixing the mixed powder and the saturated oxalic acid solution is not particularly limited in the invention, and the technical scheme for preparing the mixed material, which is well known by the technical personnel in the field, can be adopted.
After the mixed slurry is obtained, the mixed slurry is subjected to cold sintering to obtain a first sintered body.
In the invention, the sintering pressure of the cold sintering is 300-420 MPa, preferably 350-400 MPa; the cold sintering is first cold sintering at 100-120 ℃, then second cold sintering at 200-250 ℃, preferably first cold sintering at 100-110 ℃ and then second cold sintering at 220-250 ℃; the holding time of the first cold sintering and the second cold sintering is independently 0.3 to 1 hour, and more preferably 0.5 to 1 hour. The invention has no special limit on the rate of heating to the first cold sintering temperature and the second cold sintering temperature, and can adjust the rate according to the actual requirement. The invention can realize the evaporation of the solvent in the mixed slurry by adopting cold sintering, and the oxalic acid crystal is separated out and reacts with Y 2 O 3 Reacting to generate yttrium oxalate, and effectively reducing the surface free energy distribution by introducing the yttrium oxalate so as to obviously reduce the sintering temperature; by controlled cold sinteringThe process parameters enable further reduction of the sintering temperature.
In the present invention, it is preferable that the temperature is raised to the second cold sintering temperature without cooling after the completion of the heat retention of the first cold sintering.
After the first sintered body is obtained, the first sintered body is kept at the temperature of 100-150 ℃ for 3-4 h to obtain a second sintered body. The alumina block can be obtained by low-temperature heat preservation, and the compactness is improved, so that the mechanical property of the material is improved.
In the present invention, the first sintered body is preferably directly kept at 100 to 150 ℃ for 3 to 4 hours without cooling to obtain a second sintered body.
In the present invention, the incubation is preferably performed in an incubator. The source of the incubator is not particularly limited in the present invention, and instruments and equipment well known to those skilled in the art can be used.
After obtaining the second sintered body, the second sintered body is subjected to hot-pressing sintering to obtain the alumina ceramic. The invention adopts hot-pressing sintering to further improve the compactness, thereby improving the mechanical property of the material.
In the present invention, the second sintered body is preferably directly subjected to hot-press sintering without cooling to obtain an alumina ceramic.
In the invention, the pressure of the hot-pressing sintering is 25-30 MPa, preferably 28-30 MPa; the hot-pressing sintering is to perform first hot-pressing sintering at 250-400 ℃, perform second hot-pressing sintering at 700-900 ℃, perform third hot-pressing sintering at 1200-1300 ℃, perform fourth hot-pressing sintering at 1350-1400 ℃, preferably perform first hot-pressing sintering at 300-350 ℃, perform second hot-pressing sintering at 800-900 ℃, perform third hot-pressing sintering at 1250-1300 ℃, and perform fourth hot-pressing sintering at 1350-1400 ℃. According to the invention, by controlling the technological parameters of hot-pressing sintering, the growth of crystal grains of the alumina ceramic at the later stage of sintering can be effectively inhibited, so that the compactness of the alumina ceramic is improved, and the mechanical property is further improved.
In the present invention, the heat-preserving time of the first hot-press sintering, the second hot-press sintering, the third hot-press sintering and the fourth hot-press sintering is independently preferably 0.5 to 1 hour, and more preferably 0.6 to 0.8 hour. The rate of heating to the first hot-pressing sintering temperature, the second hot-pressing sintering temperature, the third hot-pressing sintering temperature and the fourth hot-pressing sintering temperature is not specially limited, and can be adjusted according to actual needs.
In the invention, after the heat preservation of the first hot-pressing sintering is finished, the temperature is preferably directly raised to the second hot-pressing sintering temperature without cooling; after the heat preservation of the second hot-pressing sintering is finished, preferably, the temperature is directly raised to a third hot-pressing sintering temperature without cooling; and after the heat preservation of the third hot-pressing sintering is finished, preferably, the temperature is directly raised to a fourth hot-pressing sintering temperature without cooling.
After the hot-pressing sintering is finished, the invention preferably sequentially cools, cuts and polishes the product obtained by the hot-pressing sintering to obtain the alumina ceramic.
In the present invention, the cooling is preferably furnace-cooled to room temperature.
The cutting operation is not particularly limited, and the cutting operation can be selected according to the actual size requirement.
In the present invention, the polishing is preferably performed using a diamond paste. The invention has no special limitation on other operations of the polishing, and can be adjusted according to actual needs.
Y is added in the invention 2 O 3 Can form eutectic with alumina, and reduce sintering temperature; adding Al (OH) 3 The sintering temperature can be further reduced; then mixing with saturated oxalic acid solution, Y 2 O 3 Slightly soluble in oxalic acid solution, and separating out oxalic acid crystal and Y with water evaporation in the cold sintering process 2 O 3 Reacting to generate yttrium oxalate, playing a role in nucleation and promoting the nucleation of aluminum oxide, thereby reducing the sintering temperature; and then low-temperature heat preservation and hot-pressing sintering are carried out, so that the compactness of the alumina ceramic can be improved, and the mechanical property of the alumina ceramic is improved.
The invention selects alpha-Al with average grain diameter of 400-700 nm and purity of more than or equal to 99.99 percent 2 O 3 Raw material, using heatThe alumina ceramic is prepared by a pressure sintering furnace at the sintering temperature of 1350-1400 ℃, and the obtained alumina ceramic is polished, wherein the temperature range of the preparation method can effectively inhibit the growth of crystal grains of the alumina ceramic at the later sintering stage, so that the microhardness of the alumina ceramic reaches 1870-2040 HV, and the fracture toughness reaches 6.2-6.5 MPa.m 1/2 The bending strength reaches 510-535 MPa.
The invention adopts the sintering temperature of 1350-1400 ℃ to prepare the alumina ceramic, and compared with the traditional sintering temperature of 1600-1650 ℃, the invention can reduce the energy consumption, save the energy, reduce the cost and sinter the Al at low temperature 2 O 3 Ceramics are of great significance.
The invention also provides the alumina ceramic prepared by the preparation method in the technical scheme.
The alumina ceramic provided by the invention has excellent mechanical properties.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
A preparation method of alumina ceramics comprises the following steps:
(1) 88g of an average particle diameter D 50 400nm alpha-Al with purity not less than 99.99 percent 2 O 3 Powder, 10g average particle diameter D 50 Is 700nm Al (OH) with purity more than or equal to 99.99 percent 3 Powder and 2g of average particle diameter D 50 Y of 50nm and purity more than or equal to 99.99 percent 2 O 3 Ball-milling and mixing the powder in a planetary ball mill, then carrying out vacuum drying at 60 ℃, and sieving by a 120-mesh sieve to obtain mixed powder; wherein the rotation speed of ball milling mixing is 200r/min; the ball milling and mixing time is 9 hours; the ball material mass ratio is 10:1; the ball milling medium is absolute ethyl alcohol;
(2) Adding the mixed powder obtained in the step (1) into a saturated oxalic acid solution for mixing to obtain mixed slurry; wherein the ratio of the mass of the mixed powder to the volume of the saturated oxalic acid solution is 10g:1.5mL;
(3) Pouring the mixed slurry obtained in the step (2) into a mould for cold sintering to obtain a circular first sintered body with the diameter of 25mm and the height of 10 mm; wherein the sintering pressure of cold sintering is 400MPa; the cold sintering is to heat up to 120 ℃ for first cold sintering for 1h, and then directly heat up to 220 ℃ for second cold sintering for 1h;
(4) Putting the first sintered body obtained in the step (3) into a heat preservation box, and preserving heat for 4 hours at 100 ℃ to obtain a second sintered body;
(5) Carrying out hot-pressing sintering on the second sintered body obtained in the step (4), then cooling to room temperature along with a furnace, cutting, and polishing by using diamond grinding paste to obtain alumina ceramic; wherein the pressure of hot-pressing sintering is 30MPa; the hot-pressing sintering is to heat to 400 ℃ for first hot-pressing sintering for 1h, then directly heat to 800 ℃ for second hot-pressing sintering for 0.5h, then directly heat to 1300 ℃ for third hot-pressing sintering for 0.5h, and finally directly heat to 1350 ℃ for fourth hot-pressing sintering for 1h.
The alumina ceramic prepared in the example 1 is subjected to a performance test, wherein the micro Vickers hardness is in accordance with the international standard ISO6507/1-82; the bending strength adopts the GB/T6569-2006 standard, the fracture toughness is calculated according to the Niihara formula, and the result is as follows: microhardness of 1870HV and fracture toughness of 6.2 MPa-m 1/2 The bending strength is 520MPa.
Comparative example 1
A preparation method of alumina ceramics comprises the following steps:
(1) 88g of an average particle diameter D 50 alpha-Al with the purity of more than or equal to 99.99 percent and the particle size of 400nm 2 O 3 Powder, 10g average particle diameter D 50 Is 700nm Al (OH) with the purity of more than or equal to 99.99 percent 3 Powder and 2g of average particle diameter D 50 Y of 50nm and purity more than or equal to 99.99 percent 2 O 3 Ball-milling and mixing the powder in a planetary ball mill, then carrying out vacuum drying at 60 ℃, and sieving by a 120-mesh sieve to obtain mixed powder; wherein the rotation speed of ball milling mixing is 200r/min; while ball milling and mixingThe time is 9h; the ball material mass ratio is 10:1; the ball milling medium is absolute ethyl alcohol;
(2) Carrying out hot-pressing sintering on the mixed powder obtained in the step (1), then cooling to room temperature along with a furnace, cutting, and polishing by using diamond grinding paste to obtain alumina ceramic; wherein the pressure of hot-pressing sintering is 30MPa; the hot-pressing sintering is to heat up 800 ℃ and preserve heat for 0.5h, then directly heat up to 1300 ℃ and preserve heat for 0.5h, then directly heat up to 1350 ℃ and preserve heat for 1h.
The tensile fracture of the alumina ceramics prepared in example 1 and comparative example 1 is observed by a scanning electron microscope, and the obtained fracture morphology diagrams are respectively shown in fig. 1 and fig. 2. As can be seen from fig. 1 and 2, the alumina ceramic prepared in example 1 had well developed crystal grains, no pores, good denseness, no abnormal growth of crystal grains, and a crystal grain size of about 1 μm, as compared with comparative example 1.
Example 2
A preparation method of alumina ceramics comprises the following steps:
(1) 83g of an average particle diameter D 50 alpha-Al with the purity of more than or equal to 99.99 percent and the particle size of 400nm 2 O 3 Powder, 15g average particle diameter D 50 Is 700nm Al (OH) with the purity of more than or equal to 99.99 percent 3 Powder and 2g of average particle diameter D 50 Y of 50nm and purity more than or equal to 99.99% 2 O 3 Ball-milling and mixing the powder in a planet ball mill, then carrying out vacuum drying at 60 ℃, and sieving by a 120-mesh sieve to obtain mixed powder; wherein the rotation speed of ball milling mixing is 200r/min; the ball milling and mixing time is 10 hours; the ball material mass ratio is 10:1; the ball milling medium is absolute ethyl alcohol;
(2) Adding the mixed powder obtained in the step (1) into a saturated oxalic acid solution for mixing to obtain mixed slurry; wherein the ratio of the mass of the mixed powder to the volume of the saturated oxalic acid solution is 10g:1.5mL;
(3) Pouring the mixed slurry obtained in the step (2) into a mould for cold sintering to obtain a first sintered body with the diameter of 25mm and the height of 10 mm; wherein the sintering pressure of cold sintering is 350MPa; the cold sintering is to heat to 120 ℃ to carry out first cold sintering for 1h, and then directly heat to 250 ℃ to carry out second cold sintering for 1h;
(4) Putting the first sintered body obtained in the step (3) into a heat preservation box, and preserving heat for 4 hours at 100 ℃ to obtain a second sintered body;
(5) Carrying out hot-pressing sintering on the second sintered body obtained in the step (4), then cooling to room temperature along with a furnace, cutting, and polishing by using diamond grinding paste to obtain alumina ceramic; wherein the pressure of hot-pressing sintering is 30MPa; the hot-pressing sintering is that the temperature is firstly raised to 400 ℃ for the first hot-pressing sintering for 1h, then the temperature is directly raised to 800 ℃ for the second hot-pressing sintering for 0.5h, then the temperature is directly raised to 1300 ℃ for the third hot-pressing sintering for 0.5h, and finally the temperature is directly raised to 1350 ℃ for the fourth hot-pressing sintering for 1h.
The alumina ceramic prepared in the example 2 is subjected to a performance test, wherein the micro Vickers hardness is in accordance with the international standard ISO6507/1-82; the bending strength adopts the GB/T6569-2006 standard, the fracture toughness is calculated according to the Niihara formula, and the result is as follows: the microhardness is 2040HV, and the fracture toughness is 6.3 MPa.m 1/2 The bending strength is 525MPa.
Example 3
A preparation method of alumina ceramics comprises the following steps:
(1) 88g of the average particle diameter D 50 400nm alpha-Al with purity not less than 99.99 percent 2 O 3 Powder, 10g average particle diameter D 50 Is 700nm Al (OH) with the purity of more than or equal to 99.99 percent 3 Powder and 2g of average particle diameter D 50 Y of 50nm and purity more than or equal to 99.99% 2 O 3 Ball-milling and mixing the powder in a planetary ball mill, then carrying out vacuum drying at 60 ℃, and sieving by a 120-mesh sieve to obtain mixed powder; wherein the rotation speed of ball milling mixing is 200r/min; the ball milling and mixing time is 10 hours; the ball material mass ratio is 10:1; the ball milling medium is absolute ethyl alcohol;
(2) Adding the mixed powder obtained in the step (1) into a saturated oxalic acid solution for mixing to obtain mixed slurry; wherein the ratio of the mass of the mixed powder to the volume of the saturated oxalic acid solution is 10g:1mL;
(3) Pouring the mixed slurry obtained in the step (2) into a mould for cold sintering to obtain a circular first sintered body with the diameter of 25mm and the height of 10 mm; wherein the sintering pressure of cold sintering is 400MPa; the cold sintering is to heat to 100 ℃ for first cold sintering for 1h, and then directly heat to 200 ℃ for second cold sintering for 1h;
(4) Placing the first sintered body obtained in the step (3) in a heat preservation box, and preserving heat for 4 hours at 100 ℃ to obtain a second sintered body;
(5) Carrying out hot-pressing sintering on the second sintered body obtained in the step (4), then cooling to room temperature along with a furnace, cutting, and polishing by using diamond grinding paste to obtain alumina ceramic; wherein the pressure of hot-pressing sintering is 30MPa; the hot-pressing sintering is to heat to 400 ℃ for first hot-pressing sintering for 0.5h, then directly heat to 800 ℃ for second hot-pressing sintering for 0.5h, then directly heat to 1300 ℃ for third hot-pressing sintering for 0.5h, and finally directly heat to 1400 ℃ for fourth hot-pressing sintering for 1h.
The alumina ceramic prepared in example 3 was subjected to a performance test in which the micro vickers hardness was in accordance with international standard ISO6507/1-82; the bending strength adopts the GB/T6569-2006 standard, the fracture toughness is calculated according to the Niihara formula, and the result is as follows: microhardness of 1806HV and fracture toughness of 6.4 MPa-m 1/2 The flexural strength was 522MPa.
The tensile fracture of the alumina ceramic prepared in example 3 was observed by a scanning electron microscope, and the fracture morphology is shown in fig. 3.
As can be seen from FIG. 3, the alumina ceramic prepared in example 3 is pore-free and dense, but has a larger grain size than that of example 1.
Example 4
A preparation method of alumina ceramics comprises the following steps:
(1) 83g of an average particle diameter D 50 alpha-Al with the purity of more than or equal to 99.99 percent and the particle size of 400nm 2 O 3 Powder, 15g average particle diameter D 50 Is 700nm Al (OH) with purity more than or equal to 99.99 percent 3 Powder and 2g of average particle diameter D 50 Y of 50nm and purity more than or equal to 99.99% 2 O 3 Ball-milling and mixing the powder in a planet ball mill, then carrying out vacuum drying at 60 ℃, and sieving by a 120-mesh sieve to obtain mixed powder; wherein, the first and the second end of the pipe are connected with each other,the rotating speed of ball milling and mixing is 210r/min; the ball milling and mixing time is 10 hours; the ball material mass ratio is 10:1; the ball milling medium is absolute ethyl alcohol;
(2) Adding the mixed powder obtained in the step (1) into a saturated oxalic acid solution for mixing to obtain mixed slurry; wherein the ratio of the mass of the mixed powder to the volume of the saturated oxalic acid solution is 10g:1.5mL;
(3) Pouring the mixed slurry obtained in the step (2) into a mould for cold sintering to obtain a first sintered body with the diameter of 25mm and the height of 10 mm; wherein the sintering pressure of cold sintering is 350MPa; the cold sintering is to firstly heat up to 100 ℃ for first cold sintering for 1h, and then directly heat up to 250 ℃ for second cold sintering for 1h;
(4) Putting the first sintered body obtained in the step (3) into a heat preservation box, and preserving heat for 4 hours at 100 ℃ to obtain a second sintered body;
(5) Carrying out hot-pressing sintering on the second sintered body obtained in the step (4), then cooling to room temperature along with a furnace, cutting, and polishing by using diamond grinding paste to obtain alumina ceramic; wherein the pressure of hot-pressing sintering is 30MPa; the hot-pressing sintering is that the temperature is firstly raised to 400 ℃ for first hot-pressing sintering for 0.5h, then the temperature is directly raised to 800 ℃ for second hot-pressing sintering for 0.5h, then the temperature is directly raised to 1300 ℃ for third hot-pressing sintering for 0.5h, and finally the temperature is directly raised to 1400 ℃ for fourth hot-pressing sintering for 1h.
The alumina ceramic prepared in example 4 was subjected to a performance test in which the micro vickers hardness was in accordance with international standard ISO6507/1-82; the bending strength adopts the GB/T6569-2006 standard, the fracture toughness is calculated according to the Niihara formula, and the result is as follows: the microhardness is 1844HV, and the fracture toughness is 6.5 MPa.m 1/2 The bending strength was 535MPa.
From the above examples, it can be seen that the sintering temperature of the preparation method provided by the invention is 1350-1400 ℃ when preparing the alumina ceramic, and the prepared alumina ceramic has high mechanical properties.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A preparation method of alumina ceramics comprises the following steps:
(1) Mixing Al 2 O 3 、Al(OH) 3 And Y 2 O 3 Mixing to obtain mixed powder;
(2) Mixing the mixed powder obtained in the step (1) with a saturated oxalic acid solution to obtain mixed slurry;
(3) Performing cold sintering on the mixed slurry obtained in the step (2) to obtain a first sintered body; the sintering pressure of the cold sintering is 300-420 MPa; the cold sintering is first cold sintering at 100-120 ℃ and then second cold sintering at 200-250 ℃;
(4) Preserving the temperature of the first sintered body obtained in the step (3) at 100-150 ℃ for 3-4 h to obtain a second sintered body;
(5) Carrying out hot-pressing sintering on the second sintered body obtained in the step (4) to obtain alumina ceramic; the pressure of the hot-pressing sintering is 25-30 MPa; the hot-pressing sintering is to perform first hot-pressing sintering at 250-400 ℃, perform second hot-pressing sintering at 700-900 ℃, perform third hot-pressing sintering at 1200-1300 ℃, and finally perform fourth hot-pressing sintering at 1350-1400 ℃;
al (OH) in the step (1) 3 The mass of (b) is 5 to 15% of the mass of the mixed powder.
2. The method according to claim 1, wherein Y in the step (1) 2 O 3 The mass of (b) is 1 to 2% of the mass of the mixed powder.
3. The method of claim 1, wherein the mixing in step (1) is ball milling.
4. The preparation method of claim 3, wherein the rotation speed of the ball milling and mixing is 200-250 r/min, and the time of the ball milling and mixing is 6-10 h.
5. The production method according to claim 1, wherein the ratio of the mass of the mixed powder to the volume of the saturated oxalic acid solution in the step (2) is 10g: (1-1.5) mL.
6. The method according to claim 1, wherein the holding time for the first cold sintering and the second cold sintering in the step (3) is independently 0.3 to 1 hour.
7. The production method according to claim 1, wherein the temperature of the second hot press sintering in the step (5) is 800 to 900 ℃.
8. The method according to claim 1, wherein the holding time for the first hot press sintering, the second hot press sintering, the third hot press sintering and the fourth hot press sintering in step (5) is independently 0.5 to 1 hour.
9. An alumina ceramic produced by the production method according to any one of claims 1 to 8.
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