CN112500157A - Method for reducing shrinkage rate of nano zirconia ceramic dry-pressed product - Google Patents
Method for reducing shrinkage rate of nano zirconia ceramic dry-pressed product Download PDFInfo
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- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 title claims abstract description 208
- 238000000034 method Methods 0.000 title claims abstract description 30
- 239000000919 ceramic Substances 0.000 title claims abstract description 18
- 239000000843 powder Substances 0.000 claims abstract description 86
- 238000005245 sintering Methods 0.000 claims abstract description 32
- 238000005469 granulation Methods 0.000 claims abstract description 31
- 230000003179 granulation Effects 0.000 claims abstract description 31
- 239000007921 spray Substances 0.000 claims abstract description 22
- 238000003825 pressing Methods 0.000 claims abstract description 21
- 238000009694 cold isostatic pressing Methods 0.000 claims abstract description 10
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000001354 calcination Methods 0.000 claims abstract description 6
- 238000013329 compounding Methods 0.000 claims abstract description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 26
- 238000000227 grinding Methods 0.000 claims description 13
- 239000002002 slurry Substances 0.000 claims description 13
- 238000000498 ball milling Methods 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- 229910001928 zirconium oxide Inorganic materials 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 4
- 239000011230 binding agent Substances 0.000 claims 1
- 239000000203 mixture Substances 0.000 claims 1
- BPJYAXCTOHRFDQ-UHFFFAOYSA-L tetracopper;2,4,6-trioxido-1,3,5,2,4,6-trioxatriarsinane;diacetate Chemical compound [Cu+2].[Cu+2].[Cu+2].[Cu+2].CC([O-])=O.CC([O-])=O.[O-][As]1O[As]([O-])O[As]([O-])O1.[O-][As]1O[As]([O-])O[As]([O-])O1 BPJYAXCTOHRFDQ-UHFFFAOYSA-L 0.000 claims 1
- 239000004005 microsphere Substances 0.000 description 11
- 238000005452 bending Methods 0.000 description 9
- 239000002245 particle Substances 0.000 description 9
- 239000011858 nanopowder Substances 0.000 description 7
- 239000002270 dispersing agent Substances 0.000 description 6
- 238000001878 scanning electron micrograph Methods 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000011049 filling Methods 0.000 description 3
- 238000004321 preservation Methods 0.000 description 3
- 239000011812 mixed powder Substances 0.000 description 2
- 239000002114 nanocomposite Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000012669 compression test Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000009740 moulding (composite fabrication) Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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Abstract
The invention provides a method for reducing the shrinkage rate of a nano zirconia ceramic dry-pressed molded product, which comprises the following steps of S1, selecting nano zirconia powder, preparing a zirconia solution with a certain concentration, and performing spray granulation to prepare micron zirconia granulated powder; s2, calcining the micron zirconia granulated powder under proper conditions; s3, compounding the sintered micron zirconia granulation powder with zirconia nano powder to prepare zirconia micro-nano grading powder; s4, dry pressing and forming, and continuously carrying out cold isostatic pressing on the dry pressed zirconia green body; and S5, sintering and forming the cold isostatic pressed sample strip under certain conditions.
Description
Technical Field
The invention relates to the technical field of dry pressing of ceramics, in particular to a method for reducing the shrinkage rate of a nano zirconia ceramic dry pressing molded product.
Background
The pressure head pressure transmission is poor in the dry pressing process of the nano zirconia ceramic, the friction force between the nano powder and the mold wall is large, the pressure gradient is large, the pressed compact density is low, and the shrinkage rate of a sample after sintering is large.
Disclosure of Invention
The invention aims to provide a method for reducing the shrinkage rate of a nano zirconia ceramic dry-pressing molded product, and aims to solve the problems of poor pressure head pressure transmission, large friction force between nano powder and a mold wall, large pressure gradient, low green density and large shrinkage rate of a sample after sintering in the dry-pressing process of the nano zirconia ceramic. The technical scheme of the invention is realized as follows:
the invention provides a method which comprises the following steps of S1, selecting nano zirconia powder, preparing zirconia solution with certain concentration, and preparing micron zirconia granulation powder by spray granulation; s2, calcining the micron zirconia granulated powder under proper conditions; s3, compounding the sintered micron zirconia granulation powder with zirconia nano powder to prepare zirconia micro-nano grading powder; s4, dry pressing and forming, and continuously carrying out cold isostatic pressing on the dry pressed zirconia green body; and S5, sintering and forming the cold isostatic pressed sample strip under certain conditions. .
Further, in the step S1, the nano zirconia has a particle size of 500 nm.
Further, the concentration of the zirconia solution is 35-80%.
Further, the process conditions of spray granulation are that the rotating speed of a rotary disc of a spray dryer is 10-30Hz, the frequency of a feeding pump is 10-30Hz, and the outlet temperature is 60-120 ℃.
Further, the median particle size D50 of the prepared micron zirconia granulated powder is 10-150 microns.
Further, in the step S2, the suitable conditions are that the sintering temperature is 600-1600 ℃, and the sintering time is 1-6 h.
Further, in the step S3, the preparation of the zirconia micro-nano graded powder specifically comprises adding 200g of zirconia powder and a PVP grinding aid into 150mL of ethanol, performing ball milling at 300r/min for 48 hours; adding the ground micron calcined powder into the slurry according to 5-2000% of the mass of zirconia in the slurry to prepare micro-nano mixed zirconia slurry, stirring at a low speed for 6 hours, drying ethanol at 60 ℃, and grinding to prepare micro-nano graded powder.
Further, in step S4, the pressure applied to the micro-nano graded powder in the dry press forming is 100 MPa.
Further, the cold isostatic pressing condition is 200MPa, and the pressure is maintained for 60 s.
Further, in the step S5, the certain conditions are that the sintering temperature is 1300-1700 ℃, and the sintering time is 1-6 hours.
The invention provides a method for reducing the shrinkage rate of a nano zirconia ceramic dry-pressed molded product, which selects nano zirconia to prepare zirconia ceramic slurry, and prepares compact micron zirconia granulation powder by spray granulation. Compounding the calcined micron zirconia granulation powder and the nano zirconia powder to prepare micro-nano graded powder, and then performing press forming, cold isostatic pressing and sintering. The micron zirconia particles can be shrunk and densified in advance after being calcined at high temperature, and the shrinkage rate of the product can be reduced in the later pressing process. Meanwhile, the calcined micron zirconia granulated powder in the micro-nano graded mixed powder has certain strength, can bear the pressure of at least 100MPa, is not cracked in the dry pressing and even cold isostatic pressing process of the micro-nano graded powder, can be used as a stress concentration part in the pressing process, effectively concentrates the stress of the surrounding nano powder, forms a strong chain in the pressure direction, effectively transmits the pressing pressure, reduces the bridging phenomenon of the nano powder and the transverse transmission effect of the weak chain, effectively reduces the friction force of the wall surface of the die, improves the density of a pressed blank, and further achieves the purpose of reducing the shrinkage rate of a nano zirconia ceramic dry-pressed molded product.
Drawings
FIG. 1 is an SEM image of a micron zirconia granulated powder prepared in example 1 of the present invention.
FIG. 2 is an SEM image of the calcined micro zirconia granulated powder prepared in example 1 of the present invention.
FIG. 3 is an SEM image of calcined micron zirconia granulated powder prepared in example 1 of the present invention under 100MPa pressure compaction.
FIG. 4 is an SEM image of the cross-sectional morphology of a sintered sample strip of micro-nano graded powder prepared in example 1 of the present invention.
Fig. 5 is an SEM image of the micro zirconia granulated powder prepared in example 2 of the present invention.
Fig. 6 shows the density of the micro-nano graded powder sintered sample strips prepared under different sintering conditions in example 2 of the present invention.
FIG. 7 shows that the micro-nano graded powder sintered sample strips prepared in example 2 of the present invention have bending strength under different sintering conditions.
FIG. 8 is an SEM image of the micron zirconia granulated powder prepared in example 3 of the invention.
Fig. 9 shows the density of the micro-nano graded powder sintered sample strips prepared in example 3 of the present invention under different sintering conditions.
FIG. 10 shows the bending strength of the sintered sample strips of micro-nano graded powder under different sintering conditions, which is prepared in the embodiment 3 of the invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying tables, drawings and specific examples.
The invention provides a method comprising the following steps: s1, preparing a zirconium oxide solution with a certain concentration, and performing spray granulation; s2, sintering the zirconia microspheres under certain sintering conditions; s3, compounding the sintered zirconia microspheres and zirconia nano powder to prepare micro-nano composite powder, and then carrying out dry pressing on the micro-nano composite powder to form; and S4, continuously carrying out cold isostatic pressing on the dry-pressed zirconium oxide green body. And S5, sintering and forming the cold isostatic pressed batten under certain conditions. .
In previous experiments, technicians often improve the flowability of powder and increase the mold filling density of the powder by a method of preparing the nano zirconia powder into the granulation powder with large particle size. However, in the actual pressing process, after the granulated powder is crushed, the uniformly distributed nano powder can also cause the force chain dispersion in the pressure direction, so that the pressure distribution on the die wall in the direction perpendicular to the pressure is improved, the friction force is improved, and the larger pressure gradient distribution can still be caused. The zirconium oxide microspheres obtained by sintering the granulated powder by the specific sintering process are shrunk, can bear 100MPa of pressure, even cannot be broken in the cold isostatic pressing process, can effectively transfer stress in the pressure direction in the whole pressing process, reduce pressure gradient distribution and improve mold filling density, and the sintered granulated powder microspheres can form graded mixed powder with a certain proportion of nano powder, so that the filling density can be effectively improved, and the shrinkage rate of a sintered product is reduced.
The chemicals used in the following examples are all commercially available. Wherein the zirconia powder is 3YSZ in Oriental zirconium industry.
Example 1
The method for reducing the shrinkage rate of the nano zirconia ceramic dry-pressed molded product in the embodiment comprises the following steps:
s1, preparing zirconia slurry with the solid content of 45% by using a Dow dispersant D3018, adding a dispersant B1022, preparing spray granulation slurry, carrying out spray granulation, setting the frequency of a rotary table of a spray dryer to be 30Hz, the frequency of a feed pump to be 20Hz and the outlet temperature to be 120 ℃, and carrying out spray granulation to obtain zirconia microspheres;
s2, preserving heat for 1h at 1300 ℃, calcining micron zirconia granulation powder, and grinding;
s3, adding 180g of nano zirconia powder and PVP grinding aid into 150mL of ethanol, and performing ball milling at 300r/min for 48 hours; adding 20g of calcined zirconia granulation powder into the nano zirconia ethanol solution, stirring at a low speed for 6h, drying ethanol at 60 ℃, grinding to prepare micro-nano zirconia graded powder,
s4, carrying out dry pressing forming on the micro-nano graded powder under 100 MPa;
s6, keeping the temperature of the sample after dry pressing for 1h at 1600 ℃, and sintering and forming.
Performing SEM morphology analysis and 100MPa compression test on the micron zirconia granulated powder and the calcined zirconia granulated powder, as shown in figures 1, 2 and 3, wherein the zirconia granulated microspheres have rough and loose surfaces, the maximum particle size is about 60 microns, after the micron zirconia granulated powder is calcined, the maximum particle size is below 40 microns, obvious shrinkage occurs, but the surfaces of the micron powder are still rough and loose, and the density is not high; most of the calcined micron granulated powder can keep spherical after being pressed under the pressure of 100MPa, and only individual particles have cracks. The micro-nano grading powder is insulated for 1h at 1600 ℃, and the shrinkage rate of the sintered sample strip is 18.07 percent and is less than the shrinkage rate of the nano zirconia sample strip of 21.16 percent under the same condition. However, the bending strength of the micro-nano graded powder sintered sample is low, SEM analysis is carried out on the section of the sample strip, as shown in figure 4, part of calcined micron zirconia granulated powder is not sintered with the nano zirconia into a whole, but no obvious limit exists between the calcined granulated powder and the zirconia matrix, and the improved sintering process can promote the good sintering of the zirconia microspheres and the nano powder.
Example 2
The method for reducing the shrinkage rate of the nano zirconia ceramic dry-pressed molded product in the embodiment comprises the following steps:
s1, preparing zirconia slurry with the solid content of 55% by using a Dow dispersant D3018, adding a dispersant B1022, preparing spray granulation slurry, carrying out spray granulation, setting the frequency of a rotary table of a spray dryer to be 30Hz, the frequency of a feed pump to be 20Hz and the outlet temperature to be 120 ℃, and carrying out spray granulation to obtain zirconia microspheres;
s2, preserving heat for 1h at 1300 ℃, calcining micron zirconia granulation powder, and grinding;
s3, adding 180g of nano zirconia powder and PVP grinding aid into 150mL of ethanol, and performing ball milling at 300r/min for 48 hours; adding 20g of calcined zirconia granulation powder into the nano zirconia ethanol solution, stirring at a low speed for 6h, drying ethanol at 60 ℃, grinding to prepare micro-nano zirconia graded powder,
s4, carrying out dry pressing forming on the micro-nano graded powder under 100 MPa;
and S5, carrying out cold isostatic pressing on the dry-pressed zirconia green body under 200MPa, and keeping the pressure for 60S.
And S6, sintering and forming the cold isostatic pressed pressing bar at the temperature of 1550-1700 ℃.
SEM appearance analysis is carried out on the micron zirconia granulated powder, as shown in figure 5, the zirconia granulated microsphere has smooth and compact surface, the particle size is below 40 microns, but the sphericity is poor. The density and the bending strength of the sample strip after the micro-nano graded powder is sintered at different temperatures are shown in figures 6 and 7, the density of the sintered micro-nano graded powder sample strip is firstly increased along with the increase of the sintering temperature and the extension of the heat preservation time, and then is reduced, wherein the density of the sample strip after the micro-nano graded powder sample strip is sintered at 1600 ℃, the heat preservation time is 1 hour, the sample strip density is highest, and the sample strip density reaches 5.998 g/cm3. The bending strength gradually rises along with the rise of the sintering temperature, the sample is sintered at 1650 ℃, the temperature is preserved for 3 hours, the bending strength is the highest and reaches 690MPa, and the density of the sample is 5.991 g/cm at the moment3. The shrinkage rate of all sample strips is 17.5-18.3%, and is less than the shrinkage rate of the nano zirconia sample strips of 21.16%.
Example 3
The method for reducing the shrinkage rate of the nano zirconia ceramic dry-pressed molded product in the embodiment comprises the following steps:
s1, preparing zirconia slurry with the solid content of 65% by using a Dow dispersant D3018, adding a dispersant B1022, preparing spray granulation slurry, carrying out spray granulation, setting the frequency of a rotary table of a spray dryer to be 30Hz, the frequency of a feed pump to be 20Hz and the outlet temperature to be 120 ℃, and carrying out spray granulation to obtain zirconia microspheres;
s2, preserving heat for 1h at 1300 ℃, calcining micron zirconia granulation powder, and grinding;
s3, adding 180g of nano zirconia powder and PVP grinding aid into 150mL of ethanol, and performing ball milling at 300r/min for 48 hours; adding 20g of calcined zirconia granulation powder into the nano zirconia ethanol solution, stirring at a low speed for 6h, drying ethanol at 60 ℃, grinding to prepare micro-nano zirconia graded powder,
s4, carrying out dry pressing forming on the micro-nano graded powder under 100 MPa;
and S5, carrying out cold isostatic pressing on the dry-pressed zirconia green body under 200MPa, and keeping the pressure for 60S.
And S6, sintering and forming the cold isostatic pressed pressing bar at the temperature of 1550-1700 ℃.
SEM appearance analysis is carried out on the spray granulation powder, as shown in figure 8, the zirconia granulation microsphere has smooth and compact surface, the particle size is below 40 microns, and the sphericity is better. The density and the bending strength of the micro-nano graded powder after being sintered at different temperatures are shown in figures 9 and 10, the density of the micro-nano graded sample strip obtained after sintering is increased along with the increase of the sintering temperature and the extension of the sintering time, the density is increased and then is reduced, the micro-nano graded sample strip is sintered at 1600 ℃, and the maximum value is 6.045 g/cm under the condition of heat preservation for 2 hours3The tensile strength is gradually increased along with the increase of the sintering temperature and the extension of the sintering time, the sample is sintered at 1650 ℃, the bending strength of the sample is kept for 3 hours, the bending strength is highest and reaches 723MPa, and the density of the sample is 6.039 g/cm at the moment3. The shrinkage rate of the sample strip under all sintering conditions is 17.3-18.0%, and is less than the shrinkage rate of the nano zirconia sample strip of 21.16%.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention, and all such changes or substitutions are included in the scope of the present invention. Moreover, the technical solutions in the embodiments of the present invention may be combined with each other, but it is necessary to be able to be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent, and is not within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (6)
1. A method for reducing the shrinkage rate of a nano zirconia ceramic dry-pressed molded product is characterized by comprising the following steps: the method comprises the following steps:
s1, preparing a zirconium oxide solution with a certain concentration, and performing spray granulation to prepare micron zirconium oxide granulated powder;
s2, calcining the micron zirconia granulated powder under proper conditions;
s3, compounding the sintered micron zirconia granulation powder with zirconia nano powder to prepare zirconia micro-nano grading powder;
s4, dry pressing and forming, and continuously carrying out cold isostatic pressing on the dry pressed zirconia green body;
and S5, sintering and forming the cold isostatic pressed sample strip under certain conditions.
2. The method for reducing the shrinkage rate of the nano zirconia ceramic dry-pressed molded product according to claim 1, wherein in step S1, nano zirconia powder is selected, a zirconia solution with a solid content of 35-80% is prepared, and ball milling is carried out for 48 hours; adding a binder, and continuing ball milling for 24 hours; controlling the frequency of a rotary disc of the spray dryer to be 10-30Hz, the frequency of a feeding pump to be 10-30Hz and the outlet temperature to be 60-120 ℃, and carrying out spray granulation to prepare micron zirconia granulated powder.
3. The method of claim 1, wherein in step S2, the micron zirconia sintered powder is sintered at 600-1600 ℃ for 1-6 h to obtain a micron calcined powder, and the micron calcined powder is ground for 10 min.
4. The method for reducing the shrinkage rate of the nano zirconia ceramic dry-pressed molded product according to claim 1, wherein in the step S3, nano zirconia powder and PVP grinding aid are added into ethanol, and the mixture is subjected to ball milling for 48 hours at 300 r/min; adding the ground micron calcined powder into the slurry according to 5-2000% of the mass of zirconia in the slurry to prepare micro-nano mixed zirconia slurry, stirring at a low speed for 6 hours, drying ethanol at 60 ℃, and grinding to prepare micro-nano graded powder.
5. The method of claim 1, wherein in step S4, the micro-nano graded powder is dry-pressed at 100MPa, and then cold isostatic pressed at 200MPa, and the pressure is maintained for 60S to prepare the zirconia micro-nano graded powder green compact.
6. The method for reducing the shrinkage of the nano zirconia ceramic dry-pressed molded product according to claim 1, wherein in step S5, the zirconia micro-nano graded powder compact is sintered at 1300-1700 ℃ for 1-6 h to prepare the zirconia sample strip.
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| CN113754430A (en) * | 2021-08-05 | 2021-12-07 | 西安交通大学 | Graded zirconia paste for 3D printing and preparation method and application thereof |
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