CN115466107A - Alumina ceramic with coarse crystal-fine crystal composite microstructure characteristics and application thereof - Google Patents
Alumina ceramic with coarse crystal-fine crystal composite microstructure characteristics and application thereof Download PDFInfo
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- CN115466107A CN115466107A CN202211417494.4A CN202211417494A CN115466107A CN 115466107 A CN115466107 A CN 115466107A CN 202211417494 A CN202211417494 A CN 202211417494A CN 115466107 A CN115466107 A CN 115466107A
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- alumina
- boehmite
- alumina ceramic
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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 202
- 239000013078 crystal Substances 0.000 title claims abstract description 57
- 239000002131 composite material Substances 0.000 title claims abstract description 43
- 239000002245 particle Substances 0.000 claims abstract description 71
- 239000002994 raw material Substances 0.000 claims abstract description 41
- 238000005245 sintering Methods 0.000 claims abstract description 36
- VXAUWWUXCIMFIM-UHFFFAOYSA-M aluminum;oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Al+3] VXAUWWUXCIMFIM-UHFFFAOYSA-M 0.000 claims abstract description 25
- 239000007921 spray Substances 0.000 claims abstract description 12
- 238000005469 granulation Methods 0.000 claims abstract description 9
- 230000003179 granulation Effects 0.000 claims abstract description 9
- 238000000465 moulding Methods 0.000 claims abstract description 3
- 229910001593 boehmite Inorganic materials 0.000 claims description 53
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 53
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 25
- 238000001035 drying Methods 0.000 claims description 24
- 238000003756 stirring Methods 0.000 claims description 24
- 238000001354 calcination Methods 0.000 claims description 23
- 238000002360 preparation method Methods 0.000 claims description 21
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 19
- 238000009826 distribution Methods 0.000 claims description 17
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 16
- 239000008367 deionised water Substances 0.000 claims description 15
- 229910021641 deionized water Inorganic materials 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 235000015895 biscuits Nutrition 0.000 claims description 14
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 13
- 229910017604 nitric acid Inorganic materials 0.000 claims description 13
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 13
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 13
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 13
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 11
- VNKFYQUCHJJXQZ-UHFFFAOYSA-L calcium diacetate tetrahydrate Chemical compound O.O.O.O.[Ca++].CC([O-])=O.CC([O-])=O VNKFYQUCHJJXQZ-UHFFFAOYSA-L 0.000 claims description 11
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims description 11
- 239000000292 calcium oxide Substances 0.000 claims description 11
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 11
- 238000000498 ball milling Methods 0.000 claims description 10
- GALOTNBSUVEISR-UHFFFAOYSA-N molybdenum;silicon Chemical compound [Mo]#[Si] GALOTNBSUVEISR-UHFFFAOYSA-N 0.000 claims description 9
- 239000011521 glass Substances 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000000462 isostatic pressing Methods 0.000 claims description 7
- 239000007863 gel particle Substances 0.000 claims description 5
- 239000000377 silicon dioxide Substances 0.000 claims description 5
- 235000012239 silicon dioxide Nutrition 0.000 claims description 4
- 238000001694 spray drying Methods 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 3
- 238000001125 extrusion Methods 0.000 claims description 2
- 238000007569 slipcasting Methods 0.000 claims description 2
- 238000012216 screening Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 3
- 229910010272 inorganic material Inorganic materials 0.000 abstract description 2
- 239000011147 inorganic material Substances 0.000 abstract description 2
- 238000000034 method Methods 0.000 description 14
- 238000005303 weighing Methods 0.000 description 14
- 239000000919 ceramic Substances 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 10
- 229910001928 zirconium oxide Inorganic materials 0.000 description 8
- 238000004321 preservation Methods 0.000 description 7
- 239000007791 liquid phase Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- 238000007873 sieving Methods 0.000 description 6
- 229910052814 silicon oxide Inorganic materials 0.000 description 6
- 239000002002 slurry Substances 0.000 description 4
- 238000003980 solgel method Methods 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011268 mixed slurry Substances 0.000 description 2
- 239000002159 nanocrystal Substances 0.000 description 2
- 239000011858 nanopowder Substances 0.000 description 2
- 229910052574 oxide ceramic Inorganic materials 0.000 description 2
- 239000011224 oxide ceramic Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 229920000663 Hydroxyethyl cellulose Polymers 0.000 description 1
- 239000004354 Hydroxyethyl cellulose Substances 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 230000002902 bimodal effect Effects 0.000 description 1
- 239000000679 carrageenan Substances 0.000 description 1
- 235000010418 carrageenan Nutrition 0.000 description 1
- 229920001525 carrageenan Polymers 0.000 description 1
- 229940113118 carrageenan Drugs 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 235000019447 hydroxyethyl cellulose Nutrition 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000013001 point bending Methods 0.000 description 1
- 235000015112 vegetable and seed oil Nutrition 0.000 description 1
- 239000008158 vegetable oil Substances 0.000 description 1
- UHVMMEOXYDMDKI-JKYCWFKZSA-L zinc;1-(5-cyanopyridin-2-yl)-3-[(1s,2s)-2-(6-fluoro-2-hydroxy-3-propanoylphenyl)cyclopropyl]urea;diacetate Chemical compound [Zn+2].CC([O-])=O.CC([O-])=O.CCC(=O)C1=CC=C(F)C([C@H]2[C@H](C2)NC(=O)NC=2N=CC(=CC=2)C#N)=C1O UHVMMEOXYDMDKI-JKYCWFKZSA-L 0.000 description 1
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Abstract
The invention discloses an alumina ceramic with coarse crystal-fine crystal composite microstructure characteristics and application thereof, belonging to the technical field of inorganic materials. The alumina content of the alumina ceramic is more than or equal to 97 percent; the crystal form is alpha-alumina and comprises two crystal grains with different sizes, wherein one crystal grain is a large-size non-isometric alumina crystal grain, the thickness is 5um-40um, and the length is 30um-150um; the other is fine equiaxed alumina grains with the size of 0.1um-1um. The alumina ceramic with coarse crystal-fine crystal composite microstructure characteristics sintered at a lower temperature is provided, low-cost industrial-grade pseudo-boehmite is used as a raw material, raw material particles with high sintering activity are obtained through sol-gel and spray granulation, a blank body is obtained through molding, and the compact alumina ceramic can be obtained through sintering at a lower temperature.
Description
Technical Field
The invention belongs to the technical field of inorganic materials, and particularly relates to an alumina ceramic with a coarse crystal-fine crystal composite microstructure characteristic and application thereof.
Background
Alumina ceramics are widely applied to friction pair materials because of high wear resistance and bearing capacity. The relationship between the grain size and grain distribution of the alumina ceramic and the wear resistance of the alumina ceramic is close. The fine-grain alumina ceramic is generally considered to have lower friction coefficient, low wear rate and high wear transformation load, and the friction performance is excellent. For example, chinese patent application No. CN201810317105.8 discloses a high-purity fine-grained wear-resistant alumina lining board and a preparation method thereof, wherein a bimodal distribution of grain sizes is obtained in a microstructure of the lining board, and the lining board has a small amount of non-equiaxed grains and has high hardness and wear resistance. However, the crystal grains dropped off during the rubbing process of the fine-crystal alumina ceramic are difficult to remain on the friction interface, a smooth friction layer cannot be formed on the friction surface, the wear volume of the fine-crystal alumina ceramic shows the characteristic of slowly increasing and then rapidly increasing along with the sliding time, and the service life of the alumina ceramic friction pair is seriously influenced. Compared with fine-crystal alumina ceramics, coarse-crystal alumina ceramics have lower mechanical property and friction property, but can form a smooth friction layer on a friction interface, so that the wear rate of the alumina ceramics can be effectively reduced, and the wear volume of the alumina ceramics is characterized by increasing rapidly and then slowly along with the sliding time.
Aiming at the defects of the prior art, the invention provides the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic and the application thereof, the size of alumina crystal grains is distributed between two intervals of dozens of micrometers and dozens of nanometers, and the alumina ceramic has excellent mechanical property and friction property, and can form a smooth friction layer on a friction interface in the friction process, thereby obviously prolonging the service life of the alumina ceramic friction pair. The invention also provides a preparation method thereof, which has simple and convenient process, easy control of process parameters and stable batch production.
Disclosure of Invention
The invention aims to solve the technical problem of providing alumina ceramic with coarse crystal-fine crystal composite microstructure characteristics and application thereof. In addition, the grain size and growth rate of alumina are controlled by adding alpha-alumina (30 nm) as a seed to lower the phase transition temperature of gamma-alumina → alpha-alumina and induce the gamma-alumina to transform into equiaxed alpha-alumina during sintering. The influence of the process parameters of the sol-gel method on the grain size is also significant. Furthermore, the generation amount and the composition of the liquid phase in the sintering process are controlled by adding sintering aids and adopting different sintering schedules. Because the content of the sintering aid is low and the zirconium dioxide is introduced in the form of nano powder, the distribution and the composition uniformity of the liquid phase are poor, in the sintering process, the uneven distribution of the liquid phase causes part of aluminum oxide grains to generate anisotropic growth and abnormal growth, the grains are relatively coarse, the growth speed of the other part of the grains is inhibited, the grains are relatively fine, and finally the aluminum oxide ceramic is promoted to present the characteristics of a coarse grain-fine grain composite microstructure and has excellent mechanical property and friction property.
Technical scheme
In order to solve the problems, the invention adopts the following technical scheme:
an alumina ceramic with coarse crystal-fine crystal composite microstructure characteristics, wherein the alumina content of the alumina ceramic is more than or equal to 97 percent; comprises two kinds of crystal grains with different sizes, wherein one kind of crystal grain is large-sized non-isometric alumina crystal grain, the thickness is 5um-40um, and the length is 30um-150um; the other is fine equiaxed alumina crystal grains with the size of 0.1um-1um.
The alumina ceramic is a wear-resistant alumina lining plate obtained by molding and sintering spherical raw material particles containing gamma-alumina;
the preparation method of the gamma-alumina-containing spherical raw material particles comprises the following steps:
uniformly mixing pseudo-boehmite, deionized water, polyvinylpyrrolidone, dilute nitric acid, tetraethyl orthosilicate, calcium acetate tetrahydrate, alpha-alumina and zirconium dioxide to obtain boehmite sol, spraying, granulating and drying to obtain boehmite xerogel particles, calcining, and passing through a 180-mesh screen to obtain gamma-alumina-containing spherical raw material particles.
The alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic,
wherein the particle size of the alpha-alumina is 30nm;
wherein the particle size of the zirconium dioxide is 30nm;
the mass fraction of the pseudo-boehmite is 28-36%;
the mass fraction of the deionized water is 64-72%;
the addition amount of the polyvinylpyrrolidone is 0.2 to 1 percent of the mass fraction of the pseudo-boehmite;
the addition amount of the dilute nitric acid is 14-22% of the mass fraction of the pseudo-boehmite, and the molar concentration of the dilute nitric acid is 4mol/L;
the addition amount of the tetraethyl orthosilicate is 0.1 to 1.5 percent of the mass fraction of the pseudo-boehmite;
the addition amount of the calcium acetate tetrahydrate is 0.1 to 1.5 percent of the mass fraction of the pseudo-boehmite;
the adding amount of the zirconium dioxide is 0.1 to 0.6 percent of the mass fraction of the pseudo-boehmite;
the addition amount of the alpha-alumina is 1 to 5 percent of the mass fraction of the pseudo-boehmite.
The alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic,
in the preparation method of the spherical raw material particles containing the gamma-alumina, the processing equipment for spray granulation is a spray drying tower;
the drying processing equipment in the preparation method of the spherical raw material particles containing the gamma-alumina is an oven;
the temperature in the spray drying tower is 110-300 ℃;
the temperature in the oven is 50-100 ℃;
the boehmite xerogel particles have a size distribution of 50um to 150um.
The alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic,
the calcining temperature in the preparation method of the spherical raw material particles containing the gamma-alumina is 600-1000 ℃;
the calcining time in the preparation method of the spherical raw material particles containing the gamma-alumina is 1-5 h;
the grain size distribution of the gamma-alumina-containing spherical raw material particles is 10nm-100nm.
The alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic,
the forming mode of the gamma-alumina-containing spherical raw material particles is any one of isostatic pressing, slip casting and extrusion.
The alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic,
in the alumina ceramic, the mass fraction of alpha-alumina is more than or equal to 97 percent, the mass fraction of silicon dioxide is 0.1 to 1 percent, the mass fraction of calcium oxide is 0.1 to 1 percent, and the mass fraction of zirconium dioxide is 0.1 to 1 percent.
The alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic,
the preparation method of the alumina ceramic comprises the following steps:
(1) Mixing pseudo-boehmite, alpha-alumina, zirconium dioxide, polyvinylpyrrolidone and deionized water, and ball-milling by a ball mill to obtain a premixed solution, wherein the ball-milling time is 2-10 h;
(2) Pouring the premixed solution obtained in the step (1) into a double-layer glass reaction kettle, continuously stirring and heating to 50-90 ℃, and then gradually adding dilute nitric acid into the premixed solution and continuously stirring to obtain boehmite sol;
(3) Adding tetraethyl orthosilicate and calcium acetate tetrahydrate into the boehmite sol obtained in the step (2) and continuously stirring;
(4) Spraying, granulating and drying the boehmite sol obtained in the step (3) to obtain boehmite xerogel particles;
(5) Calcining the boehmite xerogel particles obtained in the step (4) in a muffle furnace, and sieving the calcined boehmite xerogel particles through a 180-mesh sieve to obtain spherical raw material particles containing gamma-alumina;
(6) Forming the gamma-alumina-containing spherical raw material particles obtained in the step (5) to obtain an alumina ceramic biscuit;
(7) And (4) sintering the alumina biscuit obtained in the step (6) in a silicon-molybdenum rod furnace at the sintering temperature of 1300-1500 ℃ to obtain the alumina ceramic with coarse crystal-fine crystal composite microstructure characteristics.
The application of the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic in the friction pair material is disclosed.
Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention provides an alumina ceramic with coarse-grain-fine-grain composite microstructure characteristics sintered at a lower temperature, which adopts low-cost industrial-grade pseudoboehmite as a raw material, obtains gamma-alumina-containing spherical raw material particles with high sintering activity by a sol-gel process, and can obtain compact alumina ceramic by sintering at a lower temperature. In addition, the grain size and growth rate of alumina are controlled by adding alpha-alumina (30 nm) as a seed to lower the phase transition temperature of gamma-alumina → alpha-alumina and induce the gamma-alumina to transform into equiaxed alpha-alumina during sintering. The influence of the process parameters of the sol-gel method on the grain size is also significant. Furthermore, the generation amount and the composition of the liquid phase in the sintering process are controlled by adding sintering aids and adopting different sintering schedules. Because the content of the sintering aid is low and the zirconium dioxide is introduced in the form of nano powder, the distribution and the composition uniformity of a liquid phase are poor, in the sintering process, the uneven distribution of the liquid phase causes anisotropic growth and abnormal growth of part of aluminum oxide grains, the grains are relatively coarse, the growth speed of the other part of the grains is inhibited, the grains are relatively fine, and finally the aluminum oxide ceramic is promoted to present the coarse-fine grain composite microstructure characteristic and has excellent mechanical property and friction property.
(2) The alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristics provided by the invention has the advantages that the existence of the nano crystal grains enables the alumina ceramic to have a lower friction coefficient, a low wear rate, excellent mechanical properties and high wear transformation load, and in the friction process, the existence of the coarse crystal grains enables the alumina ceramic to form a smooth friction layer on a friction interface, so that the friction coefficient is further reduced. In addition, the existence of the nano crystal grains strengthens the interface strength of the coarse crystal grains, so that the coarse crystal grains are difficult to pull out in the friction process, mainly generate micro-convex body abrasion and crystal penetration fracture, and obviously improve the friction performance of the alumina ceramic; and the existence of coarse-crystal alumina can play a pinning role on crystal grains to inhibit the expansion of cracks, thereby further improving the mechanical property of the alumina ceramic. Therefore, the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic provided by the invention has excellent mechanical property and friction property, and can obviously prolong the service life of the alumina ceramic pair.
Drawings
FIG. 1 is a microscopic structural view of example 1 of the present invention;
FIG. 2 is a view showing a structure of a microscope of example 2 of the present invention.
Detailed Description
The present invention will be described in detail with reference to the following embodiments and the accompanying drawings to help those skilled in the art to better understand the inventive concept of the present invention, but the scope of the claims of the present invention is not limited to the following embodiments, and all other embodiments obtained without inventive efforts by those skilled in the art will fall within the scope of the present invention without departing from the inventive concept of the present invention.
Example 1
The preparation method of the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristics comprises the following steps:
(1) Weighing 996g of pseudo-boehmite, 25g of alpha-alumina (30 nm), 2.7g of zirconium dioxide (30 nm), 2300g of deionized water and 5g of polyvinylpyrrolidone, mixing, and ball-milling for 2 hours by using a ball mill to obtain a premixed solution;
(2) Pouring the premixed solution obtained in the step (1) into a double-layer glass reaction kettle, continuously stirring and heating to 80 ℃, then weighing 180g of dilute nitric acid (4 mol/L) and gradually adding into the premixed solution, and continuously stirring for 30 minutes to obtain boehmite sol;
(3) 3g of tetraethyl orthosilicate and 11.1g of calcium acetate tetrahydrate are weighed and added into the boehmite sol obtained in the step (2) and continuously stirred for 10 minutes;
(4) Spray granulating and drying the boehmite sol obtained in the step (3) to obtain boehmite xerogel particles, wherein the temperature of a drying tower is 230 ℃, the temperature of an oven is 60 ℃, and the size distribution of the boehmite xerogel particles is 50-150 mu m;
(5) Calcining the boehmite xerogel particles obtained in the step (4) in a muffle furnace, and sieving the calcined boehmite xerogel particles through a 180-mesh sieve to obtain spherical raw material particles containing gamma-alumina, wherein the calcining temperature is 600 ℃, the calcining time is 3 hours, and the grain size of the spherical raw material particles containing gamma-alumina is 20-50nm;
(6) Carrying out isostatic pressing on the gamma-alumina-containing spherical raw material particles obtained in the step (5) to obtain an alumina ceramic biscuit, wherein the forming pressure is 200MPa, and the pressure maintaining time is 5 minutes;
(7) And (4) sintering the alumina biscuit obtained in the step (6) in a silicon-molybdenum rod furnace to obtain the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic, wherein the sintering temperature is 1450 ℃, and the heat preservation time is 3 hours.
The alumina ceramic prepared by the embodiment has the characteristic of coarse crystal-fine crystal composite microstructure, the microstructure is shown in figure 1, and the alumina ceramic comprises 99.10% of alumina, 0.12% of silicon oxide, 0.39% of calcium oxide and 0.39% of zirconium oxide.
Example 2
The preparation method of the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic comprises the following steps:
(1) Weighing 996g of pseudo-boehmite, 25g of alpha-alumina (30 nm), 2.4g of zirconium dioxide (30 nm), 2300g of deionized water and 5g of polyvinylpyrrolidone, mixing, and ball-milling for 2 hours by using a ball mill to obtain a premixed solution;
(2) Pouring the premixed solution obtained in the step (1) into a double-layer glass reaction kettle, continuously stirring and heating to 80 ℃, then weighing 180g of dilute nitric acid (4 mol/L), gradually adding into the premixed solution, and continuously stirring for 30 minutes to obtain boehmite sol;
(3) 4.2g of tetraethyl orthosilicate and 9.9g of calcium acetate tetrahydrate are weighed and added into the boehmite sol obtained in the step (2) and stirring is continued for 10 minutes;
(4) Spray granulating and drying the boehmite sol obtained in the step (3) to obtain boehmite xerogel particles, wherein the temperature of a drying tower is 230 ℃, the temperature of an oven is 60 ℃, and the size distribution of the boehmite xerogel particles is 50-150 mu m;
(5) Calcining the boehmite xerogel particles obtained in the step (4) in a muffle furnace, and sieving the calcined boehmite xerogel particles through a 180-mesh sieve to obtain spherical raw material particles containing gamma-alumina, wherein the calcining temperature is 600 ℃, the calcining time is 3 hours, and the grain size of the spherical raw material particles containing gamma-alumina is 20-50nm;
(6) Carrying out isostatic pressing on the gamma-alumina-containing spherical raw material particles obtained in the step (5) to obtain an alumina ceramic biscuit, wherein the forming pressure is 200MPa, and the pressure maintaining time is 5 minutes;
(7) And (4) sintering the alumina biscuit obtained in the step (6) in a silicon-molybdenum rod furnace to obtain the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic, wherein the sintering temperature is 1450 ℃, and the heat preservation time is 3 hours.
The alumina ceramic prepared by the embodiment has the characteristic of coarse crystal-fine crystal composite microstructure, the microstructure is shown as figure 2, compared with the alumina ceramic prepared by the embodiment 1, the alumina ceramic prepared by the embodiment 2 has obviously more fine crystal grains, and the coarse crystal grains are in long column shapes; the alumina ceramic prepared by the embodiment comprises 99.15 percent of alumina, 0.17 percent of silicon oxide, 0.34 percent of calcium oxide and 0.34 percent of zirconium oxide.
It is noted that the phenomenon of alumina coarse grain extraction is not observed in both fig. 1 and fig. 2, and the fracture mode is transgranular fracture, which is beneficial to improving the friction performance and mechanical performance of alumina ceramics.
Example 3
The preparation method of the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristics comprises the following steps:
(1) Weighing 996g of pseudo-boehmite, 25g of alpha-alumina (30 nm), 2.3g of zirconium dioxide (30 nm), 2300g of deionized water and 5g of polyvinylpyrrolidone, mixing, and ball-milling for 2 hours by using a ball mill to obtain a premixed solution;
(2) Pouring the premixed solution obtained in the step (1) into a double-layer glass reaction kettle, continuously stirring and heating to 80 ℃, then weighing 180g of dilute nitric acid (4 mol/L), gradually adding into the premixed solution, and continuously stirring for 30 minutes to obtain boehmite sol;
(3) 5.3g of tetraethyl orthosilicate and 9.3g of calcium acetate tetrahydrate are weighed and added into the boehmite sol obtained in the step (2) and stirring is continued for 10 minutes;
(4) Spray granulating and drying the boehmite sol obtained in the step (3) to obtain boehmite xerogel particles, wherein the temperature of a drying tower is 230 ℃, the temperature of an oven is 60 ℃, and the size distribution of the boehmite xerogel particles is 50-150 mu m;
(5) Calcining the boehmite xerogel particles obtained in the step (4) in a muffle furnace, and sieving the calcined boehmite xerogel particles through a 180-mesh sieve to obtain spherical raw material particles containing gamma-alumina, wherein the calcining temperature is 600 ℃, the calcining time is 3 hours, and the grain size of the spherical raw material particles containing gamma-alumina is 20-50nm;
(6) Carrying out isostatic pressing on the gamma-alumina-containing spherical raw material particles obtained in the step (5) to obtain an alumina ceramic biscuit, wherein the forming pressure is 200MPa, and the pressure maintaining time is 5 minutes;
(7) And (4) sintering the alumina biscuit obtained in the step (6) in a silicon-molybdenum rod furnace to obtain the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic, wherein the sintering temperature is 1450 ℃, and the heat preservation time is 3 hours.
The alumina ceramic prepared by the embodiment comprises 99.15 percent of alumina, 0.21 percent of silicon oxide, 0.32 percent of calcium oxide and 0.32 percent of zirconium oxide.
Example 4
The preparation method of the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristics comprises the following steps:
(1) Weighing 996g of pseudo-boehmite, 25g of alpha-alumina (30 nm), 2.3g of zirconium dioxide (30 nm), 2300g of deionized water and 5g of polyvinylpyrrolidone, mixing, and ball-milling for 2 hours by using a ball mill to obtain a premixed solution;
(2) Pouring the premixed solution obtained in the step (1) into a double-layer glass reaction kettle, continuously stirring and heating to 80 ℃, then weighing 180g of dilute nitric acid (4 mol/L) and gradually adding into the premixed solution, and continuously stirring for 30 minutes to obtain boehmite sol;
(3) 5.3g of tetraethyl orthosilicate and 9.3g of calcium acetate tetrahydrate are weighed and added into the boehmite sol obtained in the step (2) and stirring is continued for 10 minutes;
(4) Spray granulating and drying the boehmite sol obtained in the step (3) to obtain boehmite dry gel particles, wherein the temperature of a drying tower is 230 ℃, the temperature of an oven is 60 ℃, and the particle size distribution of the boehmite dry gel particles is 50-150 mu m;
(5) Calcining the boehmite xerogel particles obtained in the step (4) in a muffle furnace, and sieving the calcined boehmite xerogel particles through a 180-mesh sieve to obtain gamma-alumina-containing spherical raw material particles, wherein the calcining temperature is 600 ℃, the calcining time is 3 hours, and the grain size of the gamma-alumina-containing spherical raw material particles is 20-50nm;
(6) Weighing 600g of the gamma-alumina-containing spherical raw material particles obtained in the step (5) and 400g of deionized water, placing the mixture in a double-layer glass reaction kettle, stirring, heating to 75 ℃, uniformly stirring, adding 9g of carrageenan, and continuously stirring for 15 minutes to obtain mixed slurry;
(7) Pouring the mixed slurry obtained in the step (6) into a mould after vacuum foaming to be solidified to obtain an alumina wet blank;
(8) Firstly, sequentially placing the blank obtained in the step (7) in an oven at 40 ℃ and 60 ℃ for 12 hours for primary drying, and then placing the blank in an oven at 80 ℃ for drying until the weight is not changed any more, so as to obtain an aluminum oxide dry blank;
(9) And (5) sintering the alumina dry blank obtained in the step (8) in a silicon-molybdenum rod furnace to obtain the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic, wherein the sintering temperature is 1480 ℃, and the heat preservation time is 3 hours.
The alumina ceramic prepared by the embodiment comprises 99.15 percent of alumina, 0.21 percent of silicon oxide, 0.32 percent of calcium oxide and 0.32 percent of zirconium oxide.
Example 5
The preparation method of the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic comprises the following steps:
(1) Weighing 996g of pseudo-boehmite, 25g of alpha-alumina (30 nm), 2.3g of zirconium dioxide (30 nm), 2300g of deionized water and 5g of polyvinylpyrrolidone, mixing, and ball-milling for 2 hours by using a ball mill to obtain a premixed solution;
(2) Pouring the premixed solution obtained in the step (1) into a double-layer glass reaction kettle, continuously stirring and heating to 80 ℃, then weighing 180g of dilute nitric acid (4 mol/L) and gradually adding into the premixed solution, and continuously stirring for 30 minutes to obtain boehmite sol;
(3) 5.3g of tetraethyl orthosilicate and 9.3g of calcium acetate tetrahydrate are weighed and added into the boehmite sol obtained in the step (2) and stirring is continued for 10 minutes;
(4) Spray granulating and drying the boehmite sol obtained in the step (3) to obtain boehmite xerogel particles, wherein the temperature of a drying tower is 230 ℃, the temperature of an oven is 60 ℃, and the size distribution of the boehmite xerogel particles is 50-150 mu m;
(5) Calcining the boehmite xerogel particles obtained in the step (4) in a muffle furnace, and sieving the calcined boehmite xerogel particles through a 180-mesh sieve to obtain spherical raw material particles containing gamma-alumina, wherein the calcining temperature is 600 ℃, the calcining time is 3 hours, and the grain size of the spherical raw material particles containing gamma-alumina is 20-50nm;
(6) Weighing 600g of the gamma-alumina-containing spherical raw material particles obtained in the step (5), 180g of deionized water, 3g of vegetable oil and 18g of hydroxyethyl cellulose, placing the mixture in a kneader, and stirring for 1 hour to obtain a plastic pug;
(7) Extruding the plastic pug obtained in the step (6) by using vacuum pugging equipment to obtain an alumina wet blank;
(8) Firstly, sequentially placing the blank obtained in the step (7) in an oven at 40 ℃ and 60 ℃ for 12 hours for primary drying, and then placing the blank in an oven at 80 ℃ for drying until the weight is not changed any more, so as to obtain an aluminum oxide dry blank;
(9) And (4) sintering the dried alumina blank obtained in the step (8) in a silicon-molybdenum rod furnace to obtain the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic, wherein the sintering temperature is 1480 ℃, and the heat preservation time is 3 hours.
The alumina ceramic prepared by the embodiment comprises 99.15 percent of alumina, 0.21 percent of silicon oxide, 0.32 percent of calcium oxide and 0.32 percent of zirconium oxide.
Comparative example 1
The preparation method of the alumina ceramic comprises the following steps:
(1) Weighing 991.5g of commercially available alpha-alumina (D50 =400 nm), 2.1g of silicon dioxide (30 nm), 3.2g of calcium oxide (30 nm), 3.2g of zirconium oxide (30 nm), 0.6g of polyvinylpyrrolidone and 600g of deionized water, mixing, and performing ball milling for 12 hours by using a ball mill to obtain slurry;
(2) Carrying out spray granulation and drying on the slurry obtained in the step (1) to obtain granulated powder, wherein the temperature of a drying tower is 200 ℃, the temperature of an oven is 60 ℃, and the particle size distribution of the granulated powder is 50-150 mu m;
(3) Carrying out isostatic pressing on the alpha-alumina granulation powder obtained in the step (2) to obtain an alumina ceramic biscuit, wherein the forming pressure is 200MPa, and the pressure maintaining time is 5 minutes;
(4) And (4) sintering the alumina biscuit obtained in the step (3) in a silicon-molybdenum rod furnace to obtain compact alumina ceramic, wherein the sintering temperature is 1600 ℃, and the heat preservation time is 3 hours.
The alumina ceramic prepared by the comparative example comprises 99.15% of alumina, 0.21% of silicon oxide, 0.32% of calcium oxide and 0.32% of zirconium oxide.
Comparative example 2
The preparation method of the alumina ceramic comprises the following steps:
(1) Weighing 991.5g of commercially available alpha-alumina (D50 =200 nm), 2.1g of silicon dioxide (30 nm), 3.2g of calcium oxide (30 nm), 3.2g of zirconium oxide (30 nm), 0.8g of polyvinylpyrrolidone and 600g of deionized water, mixing, and performing ball milling for 12 hours by using a ball mill to obtain slurry;
(2) Carrying out spray granulation and drying on the slurry obtained in the step (1) to obtain granulated powder, wherein the temperature of a drying tower is 200 ℃, the temperature of an oven is 60 ℃, and the particle size distribution of the granulated powder is 50-150 microns;
(3) Carrying out isostatic pressing on the alpha-alumina granulation powder obtained in the step (2) to obtain an alumina ceramic biscuit, wherein the forming pressure is 200MPa, and the pressure maintaining time is 5 minutes;
(4) And (4) sintering the alumina biscuit obtained in the step (3) in a silicon-molybdenum rod furnace to obtain compact alumina ceramic, wherein the sintering temperature is 1600 ℃, and the heat preservation time is 3 hours.
The alumina ceramic prepared by the comparative example has the components of alumina 99.15%, silica 0.21%, calcium oxide 0.32% and zirconia 0.32%.
The density of the alumina ceramics of examples 1-5 and comparative examples 1-2 was tested by Archimedes drainage method; the bending strength of the alumina ceramics of examples 1 to 5 and comparative examples 1 to 2 was tested by a three-point bending method; the alumina ceramics of examples 1 to 5 and comparative examples 1 to 2 were tested for vickers hardness using a vickers hardness tester; the friction coefficient of the alumina ceramics of examples 1 to 5 and comparative examples 1 to 2 was measured by a friction tester; the alumina ceramics of examples 1 to 5 and comparative examples 1 to 2 were shown in Table 1 in terms of the degree of densification, flexural strength, vickers hardness, and coefficient of friction.
TABLE 1
As can be seen from Table 1, the alumina ceramics of examples 2 to 4 are superior to the alumina ceramics of comparative examples 1 and 2 in terms of compactness of at least 99%, flexural strength of at least 433MPa, vickers hardness of at least 16.5GPa, and friction coefficient of at most 0.45. Therefore, the alumina ceramic with the coarse-grain and fine-grain composite microstructure characteristics provided by the invention has higher density, better bending strength, hardness and wear resistance, and can be used for preparing alumina ceramic friction pairs with excellent performance.
While the invention has been described in further detail with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. An alumina ceramic having a coarse grain-fine grain composite microstructure characteristic, characterized by:
the alumina content of the alumina ceramic is more than or equal to 97 percent; comprises two kinds of crystal grains with different sizes, wherein one kind of crystal grain is large-sized non-isometric alumina crystal grain, the thickness is 5um-40um, and the length is 30um-150um; the other is fine equiaxed alumina crystal grains with the size of 0.1um-1um;
the alumina ceramic is a wear-resistant alumina lining plate obtained by molding and sintering spherical raw material particles containing gamma-alumina;
the preparation method of the spherical raw material particles containing gamma-alumina comprises the following steps:
uniformly mixing pseudo-boehmite, deionized water, polyvinylpyrrolidone, dilute nitric acid, tetraethyl orthosilicate, calcium acetate tetrahydrate, alpha-alumina and zirconium dioxide to obtain boehmite sol, performing spray granulation and drying to obtain boehmite xerogel particles, calcining and passing through a 180-mesh screen to obtain the gamma-alumina-containing spherical raw material particles.
2. The alumina ceramic having a coarse grain-fine grain composite microstructure feature of claim 1 wherein:
wherein the particle size of the alpha-alumina is 30nm;
wherein the particle size of the zirconium dioxide is 30nm;
the mass fraction of the pseudo-boehmite is 28-36%;
the mass fraction of the deionized water is 64% -72%;
the addition amount of the polyvinylpyrrolidone is 0.2 to 1 percent of the mass fraction of the pseudo-boehmite;
the addition amount of the dilute nitric acid is 14-22% of the mass fraction of the pseudo-boehmite, and the molar concentration of the dilute nitric acid is 4mol/L;
the addition amount of the tetraethyl orthosilicate is 0.1 to 1.5 percent of the mass fraction of the pseudo-boehmite;
the addition amount of the calcium acetate tetrahydrate is 0.1 to 1.5 percent of the mass fraction of the pseudo-boehmite;
the addition amount of the zirconium dioxide is 0.1 to 0.6 percent of the mass fraction of the pseudo-boehmite;
the addition amount of the alpha-alumina is 1 to 5 percent of the mass fraction of the pseudo-boehmite.
3. The alumina ceramic having a coarse grain-fine grain composite microstructure feature of claim 2 wherein:
in the preparation method of the spherical raw material particles containing the gamma-alumina, the processing equipment for spray granulation is a spray drying tower;
the drying processing equipment in the preparation method of the spherical raw material particles containing the gamma-alumina is an oven;
the temperature in the spray drying tower is 110-300 ℃;
the temperature in the oven is 50-100 ℃;
the boehmite xerogel particles have a size distribution of 50um to 150um.
4. The alumina ceramic having a macrocrystalline-fine crystalline composite microstructure characteristic of claim 3, wherein:
the calcining temperature in the preparation method of the spherical raw material particles containing the gamma-alumina is 600-1000 ℃;
the calcining time in the preparation method of the spherical raw material particles containing the gamma-alumina is 1h-5h;
the grain size distribution of the gamma-alumina-containing spherical raw material particles is 10nm-100nm.
5. The alumina ceramic having a coarse grain-fine grain composite microstructure feature of claim 4 wherein:
the forming mode of the gamma-alumina-containing spherical raw material particles is any one of isostatic pressing, slip casting and extrusion.
6. The alumina ceramic having a coarse grain-fine grain composite microstructure feature of claim 5 wherein:
in the alumina ceramic, the mass fraction of alpha-alumina is more than or equal to 97 percent, the mass fraction of silicon dioxide is 0.1 to 1 percent, the mass fraction of calcium oxide is 0.1 to 1 percent, and the mass fraction of zirconium dioxide is 0.1 to 1 percent.
7. The alumina ceramic having a macrocrystalline-fine crystalline composite microstructure characteristic of claim 6, wherein:
the preparation method of the alumina ceramic comprises the following steps:
(1) Mixing pseudo-boehmite, alpha-alumina, zirconium dioxide, polyvinylpyrrolidone and deionized water, and ball-milling by a ball mill for 2-10 h to obtain a premixed solution;
(2) Pouring the premixed solution obtained in the step (1) into a double-layer glass reaction kettle, continuously stirring and heating to 50-90 ℃, and then gradually adding dilute nitric acid into the premixed solution and continuously stirring to obtain boehmite sol;
(3) Adding tetraethyl orthosilicate and calcium acetate tetrahydrate into the boehmite sol obtained in the step (2) and continuously stirring;
(4) Spray granulation and drying are carried out on the boehmite sol obtained in the step (3) to obtain boehmite dry gel particles;
(5) Calcining the boehmite dry gel particles obtained in the step (4) in a muffle furnace, and screening the calcined boehmite dry gel particles through a 180-mesh screen to obtain spherical raw material particles containing gamma-alumina;
(6) Forming the gamma-alumina-containing spherical raw material particles obtained in the step (5) to obtain an alumina ceramic biscuit;
(7) And (5) sintering the alumina biscuit obtained in the step (6) in a silicon-molybdenum rod furnace at the sintering temperature of 1300-1500 ℃ to obtain the alumina ceramic with the coarse crystal-fine crystal composite microstructure characteristic.
8. Use of an alumina ceramic having a coarse grain-fine grain composite microstructure characteristic of claim 1 in a friction pair material.
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| CN108298964A (en) * | 2018-04-10 | 2018-07-20 | 淄博启明星新材料股份有限公司 | High-purity fine grain wear-resisting alumina liner plate and preparation method thereof |
| CN113666721A (en) * | 2021-08-26 | 2021-11-19 | 苏州炻原新材料科技有限公司 | Alumina ceramic tube shell with composite structure and preparation method thereof |
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| WO2024151690A3 (en) * | 2023-01-13 | 2024-08-22 | Shell Usa, Inc. | Preparation method for hydropyrolysis catalyst with higher density; biomass hydropyrolysis process using obtained catalyst |
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