A method for preparing an alumina-type ceramic splitter

Abstract

The present invention relates to the technical field of alumina ceramics, and discloses a preparation method of an alumina-based ceramic splitting tool. In the present invention, water, 100 parts by weight of alumina, 0.8 - 3 parts by weight of nano-zirconia, and 3 - 6 parts by weight of terminal isocyanate polysiloxane are added to a planetary ball mill for ball milling. The ball-milled slurry is poured into a mold, dried and then pressed into a green body, sintered, polished, and an alumina-based ceramic splitting tool is obtained. The terminal isocyanate groups of the polysiloxane react with the hydroxyl groups on the surfaces of alumina and nano-zirconia respectively, realizing the bridging and bonding effects between alumina particles and zirconia nanoparticles, improving the densification and relative density of the alumina ceramics, and being beneficial to improving the mechanical strength. At the same time, the closely connected alumina and zirconia form a stable corrosion-resistant eutectic melt, significantly improving the acid and alkali resistance and anti-corrosion performance of the alumina ceramics and their splitting tool products.

Description

Technical Field

[0001] The present invention relates to the technical field of alumina ceramics, and specifically to a preparation method of an alumina-type ceramic cleaver. Background Art

[0002] Alumina ceramics have the advantages of light weight, high hardness, good wear resistance, strong high-temperature resistance, etc., and are widely used in ceramic cutting tools, electronic packaging, mechanical manufacturing, catalyst carriers, etc. In order to improve the mechanical strength, acid and alkali corrosion resistance and other properties of alumina ceramics, binders, dispersants, reinforcing agents, etc. need to be added. Common binders for alumina ceramics include polyvinyl alcohol, phenolic resin, carboxymethyl cellulose, etc. Reinforcing agents include zirconia, silicon carbide, boron nitride, carbon nanotubes, etc. Chinese Patent CN112939582B discloses a zirconia-doped alumina ceramic and its preparation method. Using alumina, zirconia, aluminum borate whiskers, polyvinyl alcohol binder, etc. as raw materials, the prepared alumina ceramic has good fracture toughness, flexural strength and hardness. However, this patent does not improve the corrosion resistance of alumina ceramics, which is not conducive to the practical application of alumina ceramics in cleavers, cutting tools and other aspects. Summary of the Invention

[0003] The present invention solves the problems of poor mechanical strength, corrosion resistance and other properties of the alumina ceramic material for cleavers.

[0004] The technical solution provided by the present invention: A preparation method of an alumina-type ceramic cleaver:

[0005] (1) Add a solvent, bis(2-hydroxypropyl)polysiloxane, and hexamethylene diisocyanate to a reaction vessel, stir and react at 70-85 °C for 2-3 h in a nitrogen atmosphere, distill off low-boiling substances under reduced pressure, and dry to obtain an isocyanate-terminated polysiloxane. The reaction formula is:

[0006] .

[0007] (2) Add water, 100 parts by weight of alumina, 0.8-3 parts by weight of nano-zirconia, and 3-6 parts by weight of isocyanate-terminated polysiloxane to a planetary ball mill for ball milling. Pour the ball-milled slurry into a mold, dry and press it into a green body, control the pressure to be 20-30 MPa, and the pressing time to be 3-6 min; then in a sintering furnace, first in an air atmosphere, at a heating rate of 2-3 °C / , heat up to 1000-1200 °C, and keep it sintered for 2-3 h; then introduce argon, and control the pressure in the sintering furnace to be 15-20 MPa, heat up to 1400-1500 °C, and keep it sintered for 1-2 h; after cooling, polish to obtain an alumina-type ceramic cleaver.

[0008] Preferably, the solvent in (1) is toluene or tetrahydrofuran.

[0009] Preferably, in (1), the mass of hexamethylene diisocyanate is 14-17% of the mass of the double-ended hydroxypropyl polysiloxane.

[0010] Preferably, in (2), the rotation speed of ball milling is 300-600 r / min, and the ball milling time is 4-7 h.

[0011] Preferably, the preparation method of nano-zirconia is as follows: Add water and zirconium oxychloride into a hydrothermal reaction kettle, stir and then dropwise add ammonia water to adjust the pH to 8-9, then heat to 180-210 °C, react for 4-7 h, cool, filter, wash with water, and dry to obtain nano-zirconia.

[0012] The beneficial technical effects of the present invention: The present invention reacts double-ended hydroxypropyl polysiloxane with excessive hexamethylene diisocyanate to obtain terminal isocyanate polysiloxane. Using it as a binder and zirconia as a reinforcing phase, it is ball-milled and blended with alumina, pressed into a blank, and sintered at high temperature to obtain alumina ceramics and their wedge materials.

[0013] During ball milling and blank forming, the terminal isocyanate groups of the polysiloxane react with the hydroxyl groups on the surfaces of alumina and nano-zirconia respectively, thereby realizing the bridging and bonding effects between alumina particles and zirconia nanoparticles, improving the interfacial bonding force between zirconia and alumina, increasing the densification and relative density of alumina ceramics, and being beneficial to improving the mechanical strength.

[0014] During the high-temperature sintering process of the terminal isocyanate polysiloxane of the present invention, high-temperature pyrolysis and oxidation generate stable silica particles and silicon carbide, which fill the micropores inside the ceramic, can improve the densification, play a strengthening role, and further improve the flexural strength and mechanical properties of alumina-based ceramics. And during the high-temperature sintering process, closely connected alumina and zirconia form a stable corrosion-resistant eutectic melt, significantly improving the acid and alkali resistance and anti-corrosion performance of alumina ceramics and their wedge products. Specific Embodiments

[0015] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention.

[0016] The following average particle size of alumina is 5 μm. Double-ended hydroxypropyl polysiloxane, with an average molecular weight of 3000, and the structural formula is , purchased from Hubei Langbowan Biomedical Co., Ltd.

[0017] Example 1

[0018] (1) Add 240 mL of water and 40 g of zirconium oxychloride into a hydrothermal reaction kettle, stir and then dropwise add ammonia water to adjust the pH to 8, then heat to 200 °C, react for 5 h, cool, filter, wash with water, and dry to obtain nano-zirconia.

[0019] (2) Add 150 mL of toluene, 30 g of bis - hydroxypropyl polysiloxane, and 4.2 g of hexamethylene diisocyanate into the reaction vessel. Stir and react at 75 °C for 3 h in a nitrogen atmosphere, then carry out vacuum distillation and drying to obtain isocyanate - terminated polysiloxane.

[0020] (3) Add 3 L of water, 1 kg of alumina, 8 g of nano - zirconia, and 30 g of isocyanate - terminated polysiloxane into the planetary ball mill. Ball - mill for 4 h, controlling the rotation speed at 500 r / min; Pour the slurry into the mold, dry it and then press it into a green body, controlling the pressure at 20 MPa and the pressing time at 6 min; Then in the sintering furnace, first in an air atmosphere, heat it at a heating rate of 2 °C / min to 1100 °C, hold for sintering for 3 h; Then introduce argon, control the pressure in the sintering furnace at 15 MPa, heat it to 1400 °C, hold for sintering for 2 h; After cooling, polish it to obtain an alumina - type ceramic cleaver.

[0021] Example 2

[0022] (1) Add 240 mL of water and 40 g of zirconium oxychloride into the hydrothermal reaction kettle. After stirring, add ammonia water to adjust the pH to 9, then heat it to 180 °C, react for 7 h, cool, filter, wash with water, and dry to obtain nano - zirconia.

[0023] (2) Add 200 mL of tetrahydrofuran, 30 g of bis - hydroxypropyl polysiloxane, and 5.1 g of hexamethylene diisocyanate into the reaction vessel. Stir and react at 85 °C for 2 h in a nitrogen atmosphere, then carry out vacuum distillation and drying to obtain isocyanate - terminated polysiloxane.

[0024] (3) Add 3 L of water, 1 kg of alumina, 14 g of nano - zirconia, and 38 g of isocyanate - terminated polysiloxane into the planetary ball mill. Ball - mill for 4 h, controlling the rotation speed at 600 r / min; Pour the slurry into the mold, dry it and then press it into a green body, controlling the pressure at 30 MPa and the pressing time at 3 min; Then in the sintering furnace, first in an air atmosphere, heat it at a heating rate of 2 °C / min to 1000 °C, hold for sintering for 3 h; Then introduce argon, control the pressure in the sintering furnace at 20 MPa, heat it to 1450 °C, hold for sintering for 2 h; After cooling, polish it to obtain an alumina - type ceramic cleaver.

[0025] Example 3

[0026] (1) Add 280 mL of water and 40 g of zirconium oxychloride into the hydrothermal reaction kettle. After stirring, add ammonia water to adjust the pH to 8, then heat it to 210 °C, react for 4 h, cool, filter, wash with water, and dry to obtain nano - zirconia.

[0027] (2) Add 200 mL of toluene, 30 g of bis - hydroxypropyl polysiloxane, and 4.7 g of hexamethylene diisocyanate to the reaction vessel. Stir and react for 3 h at 70 °C under a nitrogen atmosphere. Then, perform vacuum distillation and drying to obtain isocyanate - terminated polysiloxane.

[0028] (3) Add 3.5 L of water, 1 kg of alumina, 20 g of nano - zirconia, and 45 g of isocyanate - terminated polysiloxane to a planetary ball mill. Ball - mill for 7 h, controlling the rotation speed at 300 r / min. Pour the slurry into a mold, dry it, and then press it into a green body, controlling the pressure at 20 MPa and the pressing time at 6 min. Then, in a sintering furnace, first, in an air atmosphere, heat it to 1200 °C at a heating rate of 3 °C / min, and hold for 2 h for sintering. Then, introduce argon and control the pressure in the sintering furnace at 15 MPa, heat it to 1400 °C, and hold for 2 h for sintering. After cooling, grind and polish to obtain an alumina - type ceramic cleaver.

[0029] Example 4

[0030] (1) Add 4 L of water, 1 kg of alumina, 25 g of nano - zirconia (prepared in the same way as in Example 1), and 53 g of isocyanate - terminated polysiloxane (prepared in the same way as in Example 1) to a planetary ball mill. Ball - mill for 5 h, controlling the rotation speed at 600 r / min. Pour the slurry into a mold, dry it, and then press it into a green body, controlling the pressure at 20 MPa and the pressing time at 5 min. Then, in a sintering furnace, first, in an air atmosphere, heat it to 1100 °C at a heating rate of 2 °C / min, and hold for 2 h for sintering. Then, introduce argon and control the pressure in the sintering furnace at 20 MPa, heat it to 1500 °C, and hold for 1 h for sintering. After cooling, grind and polish to obtain an alumina - type ceramic cleaver.

[0031] Example 5

[0032] (1) Add 4 L of water, 1 kg of alumina, 30 g of nano - zirconia (prepared in the same way as in Example 1), and 60 g of isocyanate - terminated polysiloxane (prepared in the same way as in Example 1) to a planetary ball mill. Ball - mill for 5 h, controlling the rotation speed at 600 r / min. Pour the slurry into a mold, dry it, and then press it into a green body, controlling the pressure at 25 MPa and the pressing time at 5 min. Then, in a sintering furnace, first, in an air atmosphere, heat it to 1000 °C at a heating rate of 2 °C / min, and hold for 3 h for sintering. Then, introduce argon and control the pressure in the sintering furnace at 15 MPa, heat it to 1500 °C, and hold for 1 h for sintering. After cooling, grind and polish to obtain an alumina - type ceramic cleaver.

[0033] Comparative Example 1:

[0034] (1) Add 3 L of water, 1 kg of alumina, and 30 g of terminal isocyanate polysiloxane into a planetary ball mill, and ball mill for 4 h while controlling the rotation speed at 500 r / min; pour the slurry into a mold, dry it, and then press it into a green body, controlling the pressure at 20 MPa and the pressing time at 6 min; then, in a sintering furnace, first in an air atmosphere, heat it up to 1100 °C at a heating rate of 2 °C / min, and hold for sintering for 3 h; then introduce argon, control the pressure in the sintering furnace at 15 MPa, heat it up to 1400 °C, and hold for sintering for 2 h; after cooling, grind and polish it to obtain an alumina-type ceramic cleaver.

[0035] Comparative Example 2:

[0036] (1) Add 3 L of water, 1 kg of alumina, and 8 g of nano-zirconia into a planetary ball mill, and ball mill for 4 h while controlling the rotation speed at 500 r / min; pour the slurry into a mold, dry it, and then press it into a green body, controlling the pressure at 20 MPa and the pressing time at 6 min; then, in a sintering furnace, first in an air atmosphere, heat it up to 1100 °C at a heating rate of 2 °C / min, and hold for sintering for 3 h; then introduce argon, control the pressure in the sintering furnace at 15 MPa, heat it up to 1400 °C, and hold for sintering for 2 h; after cooling, grind and polish it to obtain an alumina-type ceramic cleaver.

[0037] Comparative Example 3:

[0038] (1) Add 3 L of water, 1 kg of alumina, 8 g of nano-zirconia, and 30 g of bis(2-hydroxypropyl) polysiloxane into a planetary ball mill, and ball mill for 4 h while controlling the rotation speed at 500 r / min; pour the slurry into a mold, dry it, and then press it into a green body, controlling the pressure at 20 MPa and the pressing time at 6 min; then, in a sintering furnace, first in an air atmosphere, heat it up to 1100 °C at a heating rate of 2 °C / min, and hold for sintering for 3 h; then introduce argon, control the pressure in the sintering furnace at 15 MPa, heat it up to 1400 °C, and hold for sintering for 2 h; after cooling, grind and polish it to obtain an alumina-type ceramic cleaver.

[0039] Performance test:

[0040] Prepare alumina-type ceramic samples according to the raw materials and processes of each example and comparative example. Specifically, adjust "after cooling, grind and polish" in each example and comparative example to "after cooling", and other conditions remain unchanged.

[0041] Specifically: Taking Example 1 as an example: Add 3 L of water, 1 kg of alumina, 8 g of nano-zirconia, and 30 g of terminal isocyanate polysiloxane into a planetary ball mill, ball mill for 4 h, and control the rotation speed at 500 r / min; Pour the slurry into a mold, dry it and then press it into a green body, control the pressure at 20 MPa, and the pressing time at 6 min; Then in a sintering furnace, first in an air atmosphere, with a heating rate of 2 °C / min, heat up to 1100 °C, and keep the temperature for sintering for 3 h; Then introduce argon, and control the pressure in the sintering furnace at 15 MPa, heat up to 1400 °C, and keep the temperature for sintering for 2 h; Cool down to obtain an alumina-type ceramic sample.

[0042] Test the relative density of the alumina ceramic sample according to the Archimedes method. Each specimen is tested 5 times and the average value is taken.

[0043] Test the flexural strength of the alumina ceramic sample by the three-point bending method. The specimen size is 35 mm × 4 mm × 3 mm, and the loading rate is 0.5 mm / min.

[0044] Test the acid and alkali corrosion resistance of the alumina ceramic according to the method of GB / T 1970-1996. The medium for the acid corrosion test is a sulfuric acid solution with a mass fraction of 20%. The medium for the alkali corrosion test is a sodium hydroxide solution with a mass fraction of 1%. The boiling time is 1 h. By the mass loss method, calculate the percentage of the mass reduction compared to the mass before corrosion, that is, the corrosion mass loss rate. The smaller the corrosion mass loss rate, the better the acid and alkali resistance and anti-corrosion performance.

[0045] Table 1 Performance test of alumina-type ceramics

[0046]

[0047] After testing, in Examples 1-5, using terminal isocyanate polysiloxane as the binder and zirconia as the reinforcing phase, during the ball milling and green body forming processes, the terminal isocyanate groups of polysiloxane react with the hydroxyl groups on the surfaces of alumina and nano-zirconia respectively, thus realizing the bridging and bonding effects between alumina particles and zirconia nanoparticles, improving the interfacial bonding force between zirconia and alumina, increasing the densification and relative density of the alumina ceramic, being beneficial to improving the mechanical strength. At the same time, during the high-temperature sintering process, polysiloxane undergoes high-temperature pyrolysis and oxidation to generate stable silica particles and silicon carbide, which fill the micropores inside the ceramic, can improve the densification and play a strengthening role, further improving the flexural strength and mechanical properties of the alumina-type ceramic. And during the high-temperature sintering process, the closely connected alumina and zirconia form a stable corrosion-resistant eutectic melt, significantly improving the acid and alkali resistance and anti-corrosion performance of alumina.

[0048] Compared with Example 1, in Comparative Example 1, nano-zirconia was not added, and the acid resistance and anti-corrosion performance of the alumina ceramic were poor. In Comparative Example 2, the terminal isocyanate polysiloxane binder was not added, and the interfacial bonding force between zirconia and alumina was weak, the compactness and relative density of the alumina ceramic were low, and the flexural strength was poor. In Comparative Example 3, the bis-hydroxypropyl polysiloxane did not contain isocyanate groups and could not react with the hydroxyl groups on the surfaces of alumina and nano-zirconia, and thus could not achieve the bridging and bonding effects between alumina particles and zirconia nanoparticles, and did not improve the interfacial bonding force between zirconia and alumina, resulting in low compactness and relative density of the alumina ceramic and poor flexural strength.

[0049] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, as long as they are within the scope claimed in the present application, they are protected by the patent law.

Claims

1. A method for preparing an alumina ceramic splitting knife, characterized in that: The alumina ceramic splitting tool is composed of terminal isocyanate polysiloxane, water, alumina and nano zirconium oxide, and the preparation method is as follows: (1) adding a solvent, a double-terminated hydroxypropyl polysiloxane and hexamethylene diisocyanate into a reaction container, reacting in a nitrogen atmosphere, performing reduced pressure distillation, and drying to obtain an isocyanate-terminated polysiloxane; (2) adding water, 100 parts by weight of alumina, 0.8-3 parts by weight of nano zirconium oxide, and 3-6 parts by weight of isocyanate-terminated polysiloxane into a planetary ball mill, and performing ball milling. The ball-milled slurry is poured into a mold, pressed into a green body after drying, and then sintered in a sintering furnace. After cooling, the green body is ground and polished to obtain an alumina-type ceramic splitter. The average molecular weight of double-terminal hydroxypropyl polysiloxane is 3000; The sintering in (2) is first carried out in an air atmosphere at a heating rate of 2-3°C / min to a temperature of 1000-1200°C and kept at that temperature for 2-3 hours; then argon is introduced and the pressure in the sintering furnace is controlled to be 15-20MPa, and the temperature is raised to 1400-1500°C and kept at that temperature for 1-2 hours; The preparation method of the nano zirconium oxide is as follows: adding water and zirconium oxychloride into a hydrothermal reaction kettle, stirring and then dropping ammonia water to adjust the pH to 8-9, then heating to 180-210° C., reacting for 4-7 hours, cooling, filtering, washing with water, and drying to obtain the nano zirconium oxide.

2. The method for preparing an alumina ceramic splitting knife according to claim 1, characterized in that: The solvent in (1) is toluene or tetrahydrofuran.

3. The method for preparing an alumina ceramic splitting knife according to claim 1, characterized in that: The mass of the hexamethylene diisocyanate in (1) is 14-17% of the mass of the double-terminal hydroxypropyl polysiloxane.

4. The method for preparing an alumina ceramic splitting knife according to claim 1, characterized in that: The reaction temperature in (1) is 70-85°C and the reaction time is 2-3h.

5. The method for preparing an alumina ceramic splitting knife according to claim 1, characterized in that: The rotation speed of the ball mill in (2) is 300-600 r / min, and the ball milling time is 4-7 h.

6. The method for preparing an alumina ceramic splitting knife according to claim 1, characterized in that: The pressure during pressing of the green body in (2) is 20-30 MPa and the time is 3-6 min.

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