CN113024257A - Liquid phase sintering slip casting SiC ceramic valve material and preparation method thereof - Google Patents
Liquid phase sintering slip casting SiC ceramic valve material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a liquid phase sintering slip casting SiC ceramic valve material and a preparation method thereof. The technical principle of the invention is as follows: carrying out particle grading on coarse, medium and fine silicon carbide micro powder with three different particle sizes so as to improve the bulk density of a slip casting green body; adding silicon powder and carbon powder in the formula at the same time, preserving heat at 1400-1600 ℃ to ensure that the added silicon powder, the added carbon powder and the carbon generated by cracking react in situ to generate silicon carbide, promoting the densification of the SiC ceramic composite material toughened by the whisker or fiber, then continuing to heat up, preserving heat at 1750-1900 ℃ to ensure that Al2O3And Y2O3Reacting to form YAG liquid phase to further promote densification and exert YAG andsynergistic toughening effect of whisker or fiber. The problems that a valve material with a relatively complex shape cannot be prepared by hot-pressing sintering, the performance is anisotropic, a compact whisker or fiber toughened SiC ceramic composite material cannot be prepared easily by normal-pressure sintering, more carbon cannot be added easily by liquid-phase sintering, and more residual silicon is contained in reaction sintering are solved.
Description
Technical Field
The invention relates to the technical field of SiC ceramic valve materials, in particular to a liquid phase sintering grouting forming SiC ceramic valve material and a preparation method thereof.
Background
With the progress of modern science and technology, the requirements on valve materials are higher and higher, such as corrosion resistance, high temperature resistance, oxidation resistance, wear resistance and the like, and the application requirements of traditional metal and high polymer materials cannot be completely met. The ceramic material has excellent high temperature resistance, corrosion resistance, oxidation resistance, wear resistance and other performances, and becomes an ideal material for preparing high-performance valve parts. Among the ceramic materials, silicon carbide (SiC), silicon nitride (Si)3N4) Zirconium oxide (ZrO)2) Alumina (Al)2O3) And the like have been used for the preparation of ceramic valve members and have exhibited excellent properties.
The SiC ceramic has the advantages of high temperature resistance, corrosion resistance, abrasion resistance, good thermal shock resistance, good chemical stability and the like, is widely applied to the preparation of high-performance valve elements, and is also accepted by the market. However, the SiC ceramic has poor toughness and is easy to break, so that the application of the SiC ceramic is limited.
The grouting forming can be used for preparing products with complex shapes, has the advantages of good uniformity, simple process and the like, and is a common process in production. At present, two types of processes of reaction sintering slip casting (such as Chinese patent CN201810304703.1) and pressureless sintering slip casting (Lihuanhuan 'research on forming and sintering process of high-performance silicon carbide') are commonly used, but if other reinforcing and toughening components are not added, the problems of low strength and toughness of the silicon carbide ceramic can not be solved. Although the reaction sintering process is a common process for preparing dense SiC ceramic, and can be used for preparing dense SiC ceramic composite materials containing whiskers or fibers, reaction-sintered silicon carbide ceramic generally contains more than 6% of free silicon, which can lead to the deterioration of the properties of the SiC ceramic composite materials such as high temperature resistance, corrosion resistance, wear resistance and the like. Therefore, how to reduce the residual silicon in the reaction sintering slip casting silicon carbide ceramic is a problem which needs to be solved.
The liquid phase sintering can obviously improve the strength and the toughness of the SiC ceramic material, in particular to alumina (Al) with a molar ratio of 5:32O3) And yttrium oxide (Y)2O3) When Yttrium Aluminum Garnet (YAG) is formed, the high-strength and high-toughness Yttrium Aluminum Garnet (YAG) has excellent reinforcing and toughening effects, has better high temperature resistance, corrosion resistance and higher hardness and chemical stability, and is an ideal choice for SiC-based ceramic valve materials. Therefore, combining slip casting with liquid phase sintering can improve the strength and toughness of SiC ceramic materials. However, the reactive sintering slip casting process requires the addition of more carbon. The applicant has found that when YAG is used as a liquid phase sintering aid, the green body cannot contain too high a carbon content, since a high carbon content leads to a decrease in the density of the sample, and the decrease in density is more pronounced with a higher carbon content, probably because carbon reacts with Al at high temperatures2O3And Y2O3The reaction is not favorable for forming a YAG liquid phase and is not favorable for densification.
In order to further improve the strength and toughness of SiC ceramic materials, whiskers and fibers, such as SiC whiskers and carbon fibers, are generally added to the SiC ceramic matrix. However, when the content of whiskers or fibers in the SiC ceramic matrix is high, densification of the composite material is not facilitated, and the performance of the material is reduced, and generally, the high densification can be obtained by means of processes such as hot-pressing sintering, air pressure sintering, spark plasma sintering and the like, but such processes are complex and are not suitable for preparing valve elements with complex shapes. Furthermore, the hot-pressing sintering and spark plasma sintering processes can align the whiskers or fibers perpendicular to the pressure direction, resulting in anisotropy of material properties.
The normal pressure sintering is a common production process in industrial production, and has the advantages of simple process, low comprehensive cost, no need of applying pressure, capability of preparing products with complex shapes and the like. But the normal pressure sintering is not easy to prepare the compact whisker or fiber containing toughened SiC ceramic composite material.
Aiming at the problems, the invention provides a preparation method which integrates the common advantages of 'reaction sintering-liquid phase sintering-normal pressure sintering-slip casting', and prepares the compact whisker or fiber-containing toughened SiC ceramic composite material.
Disclosure of Invention
The invention aims to provide a liquid phase sintering slip casting SiC ceramic valve material and a preparation method thereof, which solve the problems that the valve material with relatively complex shape can not be prepared by hot pressing sintering, the performance is different, the dense whisker or fiber-containing toughened SiC ceramic composite material can not be prepared by normal pressure sintering, more carbon can not be added by liquid phase sintering, and more residual silicon is contained by reaction sintering.
In order to achieve the purpose, the invention provides the following technical scheme: a liquid phase sintering slip casting SiC ceramic valve material comprises the following raw material components: the silicon carbide powder comprises 100 parts of coarse, medium and fine silicon carbide micro powder with different particle sizes, 3-15 parts of mixed powder of aluminum oxide and yttrium oxide with the molar ratio of 5:3, 1-30 parts of silicon carbide whiskers, 5-20 parts of carbon powder, 10-40 parts of silicon powder, 0.5-3.5 parts of dispersing agent, 0.3-2.3 parts of water reducing agent, 0.2-0.8 part of tributyl phosphate, 0.3-3.0 parts of tetramethylammonium hydroxide and 25-55 parts of deionized water.
Preferably, the material comprises 100 parts of coarse, medium and fine silicon carbide micro powder with different particle sizes, 5-12 parts of mixed powder of aluminum oxide and yttrium oxide with the molar ratio of 5:3, 1-30 parts of silicon carbide whiskers, 5-15 parts of carbon powder, 10-30 parts of silicon powder, 0.5-3 parts of dispersing agent, 0.5-2 parts of water reducing agent, 0.3-0.8 part of tributyl phosphate, 0.3-2.5 parts of tetramethylammonium hydroxide and 30-50 parts of deionized water.
Preferably, the dispersant is polyvinylpyrrolidone or cellulose.
Preferably, the water reducing agent is sodium hexametaphosphate or sodium tripolyphosphate.
Preferably, the mass parts of the coarse, medium and fine silicon carbide micro powders with different particle sizes are respectively 30-70 parts, 10-50 parts and 5-30 parts, the sum of the mass parts of the three silicon carbide micro powders with different particle sizes is 100 parts, the average particle sizes of the three silicon carbide micro powders with different particle sizes are respectively 40 micrometers, 6.5 micrometers and 0.5 micrometer, and the purity of the three silicon carbide micro powders with different particle sizes is not less than 98.5%.
Preferably, the average particle size of the silicon powder is 1.0 μm, the purity is not less than 98.5%, and it should be noted that the addition amount of silicon is calculated according to the theoretical carbon content, and is slightly less than the theoretical calculation amount, so as to avoid the residual silicon from reducing the performance of the SiC ceramic composite material.
Preferably, the average grain diameter of the alumina micro powder is 1.0 μm, and the purity is not less than 98.5%, and the average grain diameter of the yttrium oxide micro powder is 1.0 μm, and the purity is not less than 98.5%.
Preferably, the carbon powder is nano carbon black, the average particle size is less than 200nm, and the purity is not less than 98.5%.
A preparation method of SiC ceramic valve material by liquid phase sintering and slip casting comprises the following steps:
firstly, preparing ceramic slurry;
weighing silicon carbide micro powder, mixed powder of aluminum oxide and yttrium oxide, silicon carbide whiskers, carbon powder, silicon powder, a dispersing agent, a water reducing agent, tributyl phosphate and tetramethylammonium hydroxide according to a ratio, adding deionized water, and performing ball milling and mixing uniformly to prepare slurry;
then adding the slurry into a vacuum container with a stirrer, stirring and vacuumizing to-0.08 MPa, keeping for 1-4 hours, and removing bubbles in the slurry;
stopping stirring, closing the vacuum pump, and aging at 20-35 deg.C for 24-72 hr to further homogenize the slurry;
secondly, slip casting;
quickly and continuously injecting the slurry prepared in the first step into an assembled gypsum mold, and determining whether slurry is required to be supplemented again or for multiple times according to the size of a product and the level of the slurry;
sucking the slurry for a certain time according to the thickness of the required product, and discharging the redundant slurry;
placing the gypsum mould after slurry suction for a certain time, and removing the gypsum mould after the green body is separated from the gypsum mould;
standing at room temperature for 1-5 hours, and after the green body has certain strength, primarily repairing the green body and removing irregular corners; the standing time is adjusted according to the size, the water content and the temperature of the sample;
thirdly, drying the blank;
placing the silicon carbide blank prepared in the second step on a smooth gypsum flat plate with the surface scattered with boron nitride powder, wherein the boron nitride powder is scattered to promote the movement of drying shrinkage of the blank, the boron nitride powder can be recycled, firstly, microwave drying is utilized for quick drying and shaping, and then, the blank is placed in a drying oven or a drying chamber at the temperature of 40-80 ℃ for full drying, so as to obtain a grouting forming blank; the drying time is adjusted according to the size and the temperature of the sample, and the dried blank can be refined according to the requirement;
fourthly, low-temperature cracking;
placing the grouting blank prepared in the third step on a smooth graphite support plate with the surface scattered with boron nitride powder, and placing the grouting blank in a sintering furnace, wherein the purpose of scattering the boron nitride powder is to promote the movement of blank heating shrinkage; placing the blank body in an environment of vacuumizing or flowing argon, and preserving the heat for 0.5-10 hours at the temperature of 400-800 ℃ according to the size of a sample to ensure that the organic matters in the blank body are completely cracked into carbon;
fifthly, reaction sintering;
on the basis of the fourth step, continuously heating to 1400-1550 ℃ and preserving heat for 0.5-6 hours to enable the added silicon powder to react with carbon generated by cracking in situ to generate silicon carbide, combining the original silicon carbide powder, silicon carbide fiber and other components in the blank, and promoting substance transport by using a liquid phase to promote densification;
sixthly, liquid phase sintering;
on the basis of the fifth step, the temperature is continuously increased to 1750-2O3And Y2O3The reaction forms a YAG liquid phase, further promotes densification, and plays a role in synergistic toughening of YAG and silicon carbide whiskers.
Preferably, in the first step, the ball milling device is a roller ball mill or an attritor ball mill or a planetary ball mill.
The silicon carbide micro powder, the silicon carbide whisker, the alumina micro powder, the yttrium oxide micro powder, the carbon powder, the silicon powder, the polyvinylpyrrolidone, the cellulose, the sodium hexametaphosphate, the sodium tripolyphosphate, the tetramethylammonium hydroxide and the tributyl phosphate which are used in the invention are all commercially available raw materials.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention adopts the slip casting process, the prepared green body has high density, good uniformity and simple process, the silicon carbide fiber can be randomly and uniformly distributed in the green body, and the uniformity and the reliability of the material performance are ensured;
2. alumina and yttrium oxide with a molar ratio of 5:3 are added into the formula, so that an yttrium aluminum garnet liquid phase can be formed, the sintering temperature is reduced, the compactness is improved, and meanwhile, the fracture toughness and the bending strength of the material are improved;
3. adding a proper amount of silicon powder, and reacting with the cracked carbon of the organic matters in the green body and the added carbon in situ to generate silicon carbide, so that the silicon carbide whisker can be combined, the densification can be promoted, and meanwhile, the reaction of carbon in a reaction grouting formula with aluminum oxide and yttrium oxide is avoided, the yttrium aluminum garnet liquid phase is not generated, and the liquid phase sintering effect cannot be realized;
4. the invention adopts microwave pre-drying to rapidly shape the green body, thus reducing the deformation, warpage and cracking of the green body with complex shape;
5. the SiC ceramic composite material has the excellent performances of high strength, good toughness, high hardness, wear resistance, corrosion resistance and the like, and is an ideal material for manufacturing ceramic valves.
Drawings
FIG. 1 is a flow chart of a preparation method of a SiC ceramic valve material by liquid phase sintering and slip casting according to the invention;
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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 SiC ceramic valve material by liquid phase sintering and slip casting comprises the following steps:
(1) preparation of ceramic slurry
Respectively weighing 10 parts, 30 parts and 60 parts of silicon carbide micro powder with the particle sizes of 0.5 mu m, 6.5 mu m and 40 mu m, 100 parts of silicon carbide micro powder in total, 5 parts of mixed powder of aluminum oxide and yttrium oxide with the molar ratio of 5:3, 3 parts of silicon carbide whiskers, 10 parts of carbon powder, 20 parts of silicon powder, 1.5 parts of polyvinylpyrrolidone, 0.6 part of sodium hexametaphosphate, 1 part of tetramethylammonium hydroxide, 0.5 part of tributyl phosphate and 38 parts of deionized water according to the parts by mass, ball-milling for 10 hours by using a roller ball mill, and uniformly mixing to prepare slurry;
then adding the slurry into a vacuum container with a stirrer, stirring and vacuumizing to-0.08 MPa, keeping for 1.5 hours, and removing bubbles in the slurry;
stopping stirring, closing the vacuum pump, and aging at 25 deg.C for 50 hr to further homogenize the slurry.
(2) Slip casting
Quickly and continuously injecting the slurry prepared in the step (1) into an assembled gypsum mould to prepare a hollow cylindrical product, and discharging redundant slurry after slurry supplement for two times and 10 minutes after slurry supplement for the second time;
placing the gypsum mould after slurry suction for 30 minutes, and taking off the gypsum mould;
standing at room temperature for 2.5 hours, primarily repairing the green body, removing irregular corners and lower bottom surfaces to obtain hollow cylinders with the inner and outer diameters of 70mm and 84mm and the height of 140 mm;
(3) drying the blank
Placing the silicon carbide blank prepared in the step (2) on a smooth gypsum flat plate with the surface scattered with boron nitride powder, drying the blank in a microwave environment at 40-50 ℃ for 10 minutes, and pre-shaping;
and then placing the green body in a drying oven at 60 ℃ for heat preservation for 15 hours to obtain a dry grouting forming green body.
(4) Low temperature cracking
And (4) placing the blank prepared in the step (3) on a smooth graphite support plate with the surface scattered with boron nitride powder, placing the blank in a vacuum carbon tube furnace, and preserving the heat for 2 hours at 600 ℃ in an argon flowing environment to completely crack the organic matters in the blank into carbon.
(5) Reaction sintering
And (4) continuously heating to 1470 ℃ and preserving the temperature for 2 hours on the basis of the step (4), so that the added silicon powder, the added carbon powder and the carbon generated by cracking react in situ to generate silicon carbide.
(6) Liquid phase sintering
On the basis of the step (5), continuously heating to 1880 ℃ and preserving the heat for 1.5 hours to ensure that the added Al2O3And Y2O3Reacting to form a YAG liquid phase, and further promoting densification to obtain the silicon carbide ceramic composite material;
through detection, the relative density of the obtained silicon carbide ceramic material is 98.5 percent, the Vickers microhardness is 24.4Gpa, the three-point bending strength is 640.5MPa, and the fracture toughness is 6.7 MPa.m1/2。
Example 2: a preparation method of SiC ceramic valve material by liquid phase sintering and slip casting comprises the following steps:
(1) preparation of ceramic slurry
Respectively weighing 15 parts, 30 parts and 55 parts of silicon carbide micro powder with the particle sizes of 0.5 mu m, 6.5 mu m and 40 mu m, 100 parts of silicon carbide micro powder in total, 8 parts of mixed powder of aluminum oxide and yttrium oxide with the molar ratio of 5:3, 7 parts of silicon carbide whisker, 12 parts of carbon powder, 24 parts of silicon powder, 2.0 parts of cellulose, 0.8 part of sodium tripolyphosphate, 1.1 part of tetramethylammonium hydroxide, 0.6 part of tributyl phosphate and 39 parts of deionized water according to the parts by mass, ball-milling for 10 hours by using a roller ball mill, and uniformly mixing to prepare slurry;
then adding the slurry into a vacuum container with a stirrer, stirring and vacuumizing to-0.08 MPa, keeping for 2 hours, and removing bubbles in the slurry.
Stopping stirring, closing the vacuum pump, and aging at 30 deg.C for 45 hr to further homogenize the slurry.
(2) Slip casting
Quickly and continuously injecting the slurry prepared in the step (1) into an assembled gypsum mold to prepare a cuboid product, adding sufficient slurry at one time, sucking the slurry for 20 minutes, and discharging redundant slurry;
placing the gypsum mould after slurry suction for 30 minutes, and taking off the gypsum mould;
standing at room temperature for 2.5 hr, primarily trimming the blank, removing irregular corners, and trimming the plane to obtain rectangular bodies with length, width and height of 160mm, 120mm and 12 mm.
(3) Drying the blank
And (3) placing the silicon carbide blank prepared in the step (2) on a smooth gypsum flat plate with the surface scattered with boron nitride powder, drying the blank in a microwave environment at 40-50 ℃ for 10 minutes, and pre-shaping.
And then placing the green body in a drying oven at 60 ℃ for heat preservation for 20 hours to obtain a dry grouting forming green body.
(4) Low temperature cracking
And (4) placing the blank prepared in the step (3) on a smooth graphite support plate with the surface scattered with boron nitride powder, placing the blank in a vacuum carbon tube furnace, and preserving the heat for 2.5 hours at 600 ℃ in an argon flowing environment to ensure that the organic matters in the blank are completely cracked into carbon.
(5) Reaction sintering
And (4) continuously heating to 1500 ℃ on the basis of the step (4), and preserving heat for 2 hours to enable the added silicon powder, the added carbon powder and the carbon generated by cracking to react in situ to generate silicon carbide.
(6) Liquid phase sintering
On the basis of the step (5), continuously heating to 1860 ℃ and preserving heat for 1.5 hours to ensure that the added Al2O3And Y2O3The reaction forms YAG liquid phase to further promote densification and obtain the silicon carbide ceramic composite material.
Through detection, the relative density of the obtained silicon carbide ceramic material is 98.7 percent, the Vickers microhardness is 24.6Gpa, the three-point bending strength is 660.8Mpa, and the fracture toughness is 7.1 MPa.m1/2。
Example 3: a preparation method of SiC ceramic valve material by liquid phase sintering and slip casting comprises the following steps:
(1) preparation of ceramic slurry
Respectively weighing 15 parts, 25 parts and 60 parts of silicon carbide micro powder with the particle sizes of 0.5 mu m, 6.5 mu m and 40 mu m, 100 parts of silicon carbide micro powder in total, 12 parts of mixed powder of aluminum oxide and yttrium oxide with the molar ratio of 5:3, 15 parts of silicon carbide whisker, 12 parts of carbon powder, 24 parts of silicon powder, 2.0 parts of polyvinylpyrrolidone, 0.8 part of sodium hexametaphosphate, 1.2 parts of tetramethylammonium hydroxide, 0.7 part of tributyl phosphate and 41 parts of deionized water, ball-milling for 10 hours by using a roller ball mill, and uniformly mixing to prepare slurry;
then adding the slurry into a vacuum container with a stirrer, stirring and vacuumizing to-0.08 MPa, keeping for 2 hours, and removing bubbles in the slurry.
Stopping stirring, closing the vacuum pump, and aging at 30 deg.C for 45 hr to further homogenize the slurry.
(2) Slip casting
Quickly and continuously injecting the slurry prepared in the step (1) into an assembled gypsum mold to prepare a cylindrical product, adding sufficient slurry at one time, sucking the slurry for 25 minutes, and discharging the redundant slurry;
placing the gypsum mould after slurry suction for 30 minutes, and taking off the gypsum mould;
standing at room temperature for 2.5 hours, performing primary trimming on the green body, removing irregular corners, and trimming a plane to obtain a cuboid with the diameter of 160mm and the height of 15 mm.
(3) Drying the blank
Placing the silicon carbide blank prepared in the step (2) on a smooth gypsum flat plate with the surface scattered with boron nitride powder, drying the silicon carbide blank in a microwave environment at the temperature of 40-50 ℃ for 10 minutes, and pre-shaping;
and then placing the green body in a drying oven at 60 ℃ for heat preservation for 24 hours to obtain a dry grouting forming green body.
(4) Low temperature cracking
And (4) placing the blank prepared in the step (3) on a smooth graphite support plate with the surface scattered with boron nitride powder, placing the blank in a vacuum carbon tube furnace, and preserving the heat for 2.5 hours at 650 ℃ in an argon flowing environment to ensure that the organic matters in the blank are completely cracked into carbon.
(5) Reaction sintering
And (4) continuously heating to 1500 ℃ on the basis of the step (4), and preserving heat for 2.5 hours to enable the added silicon powder, the added carbon powder and the carbon generated by cracking to react in situ to generate silicon carbide.
(6) Liquid phase sintering
On the basis of the step (5), continuously heating to 1840 ℃ and preserving the heat for 2.0 hours to ensure that the added Al2O3And Y2O3The reaction forms YAG liquid phase to further promote densification and obtain the silicon carbide ceramic composite material.
Through detection, the relative density of the obtained silicon carbide ceramic material is 98.6 percent, the Vickers microhardness is 24.1Gpa, the three-point bending strength is 720.6MPa, and the fracture toughness is 7.8 MPa.m1/2。
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. The SiC ceramic valve material formed by liquid phase sintering and grouting is characterized by comprising the following raw material components: the material comprises 100 parts of coarse, medium and fine silicon carbide micro powder with different particle sizes, 3-15 parts of mixed powder of aluminum oxide and yttrium oxide with the molar ratio of 5:3, 1-30 parts of silicon carbide whiskers, 5-20 parts of carbon powder, 10-40 parts of silicon powder, 0.5-3.5 parts of dispersing agent, 0.3-2.3 parts of water reducing agent, 0.2-0.8 part of tributyl phosphate, 0.3-3.0 parts of tetramethylammonium hydroxide and 25-55 parts of deionized water.
2. The liquid phase sintering slip casting SiC ceramic valve material as claimed in claim 1, wherein: the material comprises 100 parts of coarse, medium and fine silicon carbide micro powder with different particle sizes, 5-12 parts of mixed powder of aluminum oxide and yttrium oxide with the molar ratio of 5:3, 1-30 parts of silicon carbide whiskers, 5-15 parts of carbon powder, 10-30 parts of silicon powder, 0.5-3 parts of dispersing agent, 0.5-2 parts of water reducing agent, 0.3-0.8 part of tributyl phosphate, 0.3-2.5 parts of tetramethylammonium hydroxide and 30-50 parts of deionized water.
3. The liquid phase sintering slip casting SiC ceramic valve material as claimed in claim 1, wherein: the dispersing agent is polyvinylpyrrolidone or cellulose.
4. The liquid phase sintering slip casting SiC ceramic valve material as claimed in claim 1, wherein: the water reducing agent is sodium hexametaphosphate or sodium tripolyphosphate.
5. The liquid phase sintering slip casting SiC ceramic valve material as claimed in claim 1, wherein: the silicon carbide micro powder with the three different particle sizes, namely the coarse, the medium and the fine, is 30-70 parts, 10-50 parts and 5-30 parts by mass respectively, the sum of the three different particle sizes of the silicon carbide micro powder is 100 parts, the average particle sizes of the three different particle sizes of the silicon carbide micro powder are 40 micrometers, 6.5 micrometers and 0.5 micrometer respectively, and the purity of the three different particle sizes of the silicon carbide micro powder is not less than 98.5 percent.
6. The liquid phase sintering slip casting SiC ceramic valve material as claimed in claim 1, wherein: the average grain diameter of the silicon powder is 1.0 mu m, and the purity is not less than 98.5%.
7. The liquid phase sintering slip casting SiC ceramic valve material as claimed in claim 1, wherein: the average grain size of the alumina micro powder is 1.0 mu m, the purity is not less than 99.0%, and the average grain size of the yttrium oxide micro powder is 1.0 mu m, and the purity is not less than 98.5%.
8. The liquid phase sintering slip casting SiC ceramic valve material as claimed in claim 1, wherein: the carbon powder is nano carbon black, the average particle size is less than 200nm, and the purity is not less than 98.5%.
9. A preparation method of a SiC ceramic valve material formed by liquid phase sintering and grouting is characterized by comprising the following steps:
firstly, preparing ceramic slurry;
weighing silicon carbide micro powder, mixed powder of aluminum oxide and yttrium oxide, silicon carbide whiskers, carbon powder, silicon powder, a dispersing agent, a water reducing agent, tributyl phosphate and tetramethylammonium hydroxide according to a ratio, adding deionized water, and performing ball milling and mixing uniformly to prepare slurry;
then adding the slurry into a vacuum container with a stirrer, stirring and vacuumizing to-0.08 MPa, keeping for 1-4 hours, and removing bubbles in the slurry;
stopping stirring, closing the vacuum pump, and aging at 20-35 deg.C for 24-72 hr to further homogenize the slurry;
secondly, slip casting;
quickly and continuously injecting the slurry prepared in the first step into an assembled gypsum mold, and determining whether slurry is required to be supplemented again or for multiple times according to the size of a product and the level of the slurry;
sucking the slurry for a certain time according to the thickness of the required product, and discharging the redundant slurry;
placing the gypsum mould after slurry suction for a certain time, and removing the gypsum mould after the green body is separated from the gypsum mould;
standing at room temperature for 1-5 hours, and after the green body has certain strength, primarily repairing the green body and removing irregular corners; the standing time is adjusted according to the size, the water content and the temperature of the sample;
thirdly, drying the blank;
placing the silicon carbide blank prepared in the second step on a smooth gypsum flat plate with the surface scattered with boron nitride powder, wherein the boron nitride powder is scattered to promote the movement of drying shrinkage of the blank, the boron nitride powder can be recycled, firstly, microwave drying is utilized for quick drying and shaping, and then, the blank is placed in a drying oven or a drying chamber at the temperature of 40-80 ℃ for full drying, so as to obtain a grouting forming blank; the drying time is adjusted according to the size and the temperature of the sample, and the dried blank can be refined according to the requirement;
fourthly, low-temperature cracking;
placing the grouting blank prepared in the third step on a smooth graphite support plate with the surface scattered with boron nitride powder, and placing the grouting blank in a sintering furnace, wherein the purpose of scattering the boron nitride powder is to promote the movement of blank heating shrinkage; placing the blank body in an environment of vacuumizing or flowing argon, and preserving the heat for 0.5-10 hours at the temperature of 400-800 ℃ according to the size of a sample to ensure that the organic matters in the blank body are completely cracked into carbon;
fifthly, reaction sintering;
on the basis of the fourth step, continuously heating to 1400-1550 ℃ and preserving heat for 0.5-6 hours to enable the added silicon powder to react with carbon generated by cracking in situ to generate silicon carbide, combining the original silicon carbide powder, silicon carbide fiber and other components in the blank, and promoting substance transport by using a liquid phase to promote densification;
sixthly, liquid phase sintering;
on the basis of the fifth step, the temperature is continuously increased to 1750-2O3And Y2O3The reaction forms a YAG liquid phase, further promotes densification, and plays a role in synergistic toughening of YAG and silicon carbide whiskers.
10. The preparation method of the SiC ceramic valve material formed by liquid phase sintering and grouting according to claim 1, which is characterized by comprising the following steps: in the first step, the ball milling equipment is roller ball milling or vertical rapid ball milling or planetary ball milling equipment.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113248274A (en) * | 2021-07-09 | 2021-08-13 | 南通高欣耐磨科技股份有限公司 | Nano silicon carbide whisker enhanced temperature-resistant and wear-resistant nozzle and manufacturing method thereof |
| CN114380610A (en) * | 2022-02-14 | 2022-04-22 | 河南雅利安新材料有限公司 | Method for manufacturing pressureless liquid phase sintered silicon carbide ceramic grinding disc |
| CN114409407A (en) * | 2022-02-15 | 2022-04-29 | 陕西固勤材料技术有限公司 | Method for purifying and improving silicon carbide content of semiconductor cantilever paddle product |
| CN114516756A (en) * | 2022-03-14 | 2022-05-20 | 台州学院 | Silicon carbide composite ceramic material and preparation method and application thereof |
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- 2021-03-31 CN CN202110345295.6A patent/CN113024257A/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113248274A (en) * | 2021-07-09 | 2021-08-13 | 南通高欣耐磨科技股份有限公司 | Nano silicon carbide whisker enhanced temperature-resistant and wear-resistant nozzle and manufacturing method thereof |
| CN114380610A (en) * | 2022-02-14 | 2022-04-22 | 河南雅利安新材料有限公司 | Method for manufacturing pressureless liquid phase sintered silicon carbide ceramic grinding disc |
| CN114409407A (en) * | 2022-02-15 | 2022-04-29 | 陕西固勤材料技术有限公司 | Method for purifying and improving silicon carbide content of semiconductor cantilever paddle product |
| CN114516756A (en) * | 2022-03-14 | 2022-05-20 | 台州学院 | Silicon carbide composite ceramic material and preparation method and application thereof |
| CN114516756B (en) * | 2022-03-14 | 2022-10-18 | 台州学院 | Silicon carbide composite ceramic material and preparation method and application thereof |
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