Preparation method of composite ceramic constant-temperature water mixing valve

Abstract

The invention discloses a preparation method of a composite ceramic constant-temperature water mixing valve. The preparation method specifically comprises the following steps: preparing analytically pure AlCl3. 6H2O into a solution, adding PEG4000 and NH3. H2O, and stirring to form sol A; zrOCl2. 8H2O is prepared into a solution, cerous nitrate, magnesium nitrate, dysprosium nitrate, samarium nitrate and NH3.H2O are added, and stirring is performed to form sol B; adding analytically pure absolute ethyl alcohol into the two kinds of sol, stirring, washing, and freeze-drying to obtain a composite ceramic gel mixture; putting into a high-pressure reaction kettle and drying to obtain original crystal powder; adding fumed silica, BaSi2N2O2 and BaTiO3, grinding and mixing to obtain composite ceramic powder slurry; carrying out spray drying, and modifying the surface of the powder to obtain composite ceramic powder; putting into an internal mixer, and adding an organic binder to prepare a ceramic feed; putting into an injection machine and using a mold to complete green body forming; and putting into a medium-temperature debinding furnace to remove the organic binder, sintering at high temperature, and then processing and polishing. The invention has the advantages of high strength, high toughness, long service life, corrosion resistance, smudginess resistance and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic materials, in particular to a preparation method of a composite ceramic thermostatic mixing valve. BACKGROUND

[0002] The thermostatic mixing valve is a supporting product of the heating system, and is widely used in electric water heaters, solar water heaters and central hot water supply systems. It can also be used in electric water heaters and solar water heaters. Users can adjust the cold and hot water mixing temperature according to their needs. The required temperature can be quickly reached and stabilized, ensuring constant water temperature and being unaffected by water temperature, flow rate and water pressure changes. It solves the problem of fluctuating water temperature in the bathing center. When the cold water is interrupted, the mixing valve can automatically shut off the hot water within a few seconds, providing safety protection.

[0003] Most of the thermostatic mixing valves currently used are made of metal materials. Low-end products are made of brass, which is easy to process, and high-end products are made of 316 stainless steel. Since the hardness of brass and stainless steel is low, when there are particulate impurities such as sand and iron filings in the water, they will enter the gap between the valve core and the valve sleeve. Since the valve core and the valve sleeve need to move back and forth to ensure the stability of the water temperature when adjusting the water temperature, the hard foreign matter will cause a lot of wear and tear on the valve core and the valve sleeve during the back and forth movement. Therefore, the service life is not ideal. At the same time, the corrosion resistance of metal materials is poor, and the surface is easy to deposit scale, impurities, etc., which will cause the mixing valve temperature control to be inaccurate, and in severe cases, it will directly jam and fail. In addition, brass and stainless steel materials are not environmentally friendly, contain heavy metals, and stainless steel materials are difficult to process, time-consuming and costly. SUMMARY

[0004] The present application is to overcome the above-mentioned deficiencies in the prior art, and provides a preparation method of a composite ceramic thermostatic mixing valve with long service life and dirt resistance.

[0005] In order to achieve the above-mentioned purpose, the following technical solutions are adopted in the present application: A preparation method of a composite ceramic thermostatic mixing valve, specifically comprising the following steps: (1) Prepare an analytical pure AlCl3.6H2O solution and add PEG4000 as a dispersing agent. After stirring uniformly, add NH3.H2O at a set rate and continuously stir until the solution PH value reaches 9-10 to form sol A; (2) Prepare a ZrOCl2.8H2O solution, then add cerous nitrate, magnesium nitrate, dysprosium nitrate and samarium nitrate and stir uniformly. Add NH3.H2O at a set rate and continuously stir until the solution PH value reaches 9-10 to form sol B; (3) mixing sol A and sol B, stirring well, then washing with deionized water for several times to remove CI-, adding analytical pure anhydrous ethanol after filtration, stirring at high speed, washing for several times, then freeze-drying to obtain the composite ceramic gel mixture; (4) placing the freeze-dried composite ceramic gel mixture into a high-pressure reaction kettle, treating with high-temperature and high-pressure steam, drying the obtained primary crystal, and calcining to remove combined water; (5) adding fumed silica, BaSi2N2O2 and BaTiO3 to the prepared primary crystal powder, grinding and mixing in a sand mill to obtain a composite ceramic powder slurry for preparing a thermostatic mixing valve; (6) spray drying the prepared composite ceramic powder slurry, modifying the surface of the powder, and obtaining a composite ceramic powder; (7) putting the modified powder into a banbury mixer, adding an organic binder to prepare a ceramic feedstock; (8) putting the prepared ceramic feedstock into a ceramic special injection machine, using a mixing valve mold, and completing green body forming; (9) putting the formed ceramic mixing valve green body into a medium-temperature debinding furnace to remove the organic binder; (10) putting the green body after removing the binder into a high-temperature sintering furnace for sintering, and using the method of first increasing temperature, then decreasing temperature and finally keeping temperature for sintering; (11) precisely processing the sintered green body to reach the dimensional accuracy, then polishing the mating surface to achieve sealing effect.

[0006] In step (2), cerium nitrate and magnesium nitrate are precipitated with OH- to form hydroxide sol, and then crystallized to form cerium oxide and magnesium oxide, which partially stabilize the zirconia. Dysprosium nitrate and samarium nitrate are precipitated with OH- to form hydroxide sol, and then crystallized to form dysprosium oxide and samarium oxide, which toughen the zirconia and alumina ceramic matrix by inhibiting grain growth and enhancing grain boundary strength. In step (3), ethanol can effectively reduce the hydrogen bond binding force in the gel after drying, thereby avoiding the formation of hard agglomerates and preventing the generation of hard agglomerates during subsequent gel crystallization, which affects the performance of the product. In step (5), the role of fumed silica is to increase the density of the ceramic body and reduce the sintering temperature. The addition of BaSi2N2O2 can change the morphology of the ceramic grains, making the grains smooth and reducing the number of angular grains. Microscopically, this helps to reduce the possibility of surface deposition of dirt when the ceramic water valve is in use, but the addition of BaSi2N2O2 can reduce the strength of the ceramic body. BaTiO3 is a ferroelectric material, and a certain amount of BaTiO3 can absorb external stress energy through ferroelectric effect, disperse stress into the ceramic body, and inhibit crack propagation, thereby increasing the strength of the ceramic. In step (6), the surface of the powder is modified to facilitate the mixing process with the organic binder. In step (10), instead of the traditional sintering method of heating to the highest temperature, holding for a certain period of time, and then naturally cooling, the sintering process is as follows: first, heat to the highest temperature, open the sintering window, then cool to a certain temperature, and hold for a long time. This process not only densifies the body, but also prevents the grains from growing too large, allowing for the production of fine-grained ceramic bodies. The alumina-zirconia composite ceramic thermostatic water mixing valve prepared by the above method has the advantages of high strength, high toughness, long service life, corrosion resistance, and dirt resistance.

[0007] As preferred, in step (1), the specific operation method is as follows: 1.5 mol of analytical pure AlCl3.6H2O is configured into an aqueous solution with a concentration of 0.5 mol / L, and a certain amount of PEG4000 is added as a dispersant, wherein the amount of PEG4000 added is 0.1-0.5% of the mass of AlCl3.6H2O. After stirring uniformly, NH3.H2O is added at a rate of 2 ml / min, and stirring is continued until the pH value of the solution reaches 9-10, forming sol A.

[0008] As preferred, in step (2), the specific operation method is as follows: 0.15 mol of ZrOCl2.8H2O is configured into an aqueous solution with a concentration of 0.5 mol / L, and then cerium nitrate, magnesium nitrate, dysprosium nitrate, and samarium nitrate are added and stirred uniformly, wherein the addition amount of cerium nitrate is 0.5-1 mol% of ZrOCl2.8H2O, the addition amount of magnesium nitrate is 0.5-1 mol% of ZrOCl2.8H2O, the addition amount of dysprosium nitrate is 0.2-0.8 mol% of ZrOCl2.8H2O, and the addition amount of samarium nitrate is 0.3-0.5 mol% of ZrOCl2.8H2O, and then NH3.H2O is added dropwise at a rate of 2 ml / min, and stirring is continuously performed until the PH value of the solution reaches 9-10, and a sol B is formed.

[0009] As preferred, in step (4), the specific operation method is as follows: the freeze-dried composite ceramic gel mixture is placed in a high-pressure reaction kettle, and high-temperature and high-pressure steam treatment is performed for 10-30 hours, the temperature is controlled at 120-200°C, and the hydrothermal pressure is controlled at 1-3 Mpa, the obtained primary crystal is dried, and then placed in a medium-temperature furnace for calcination at 500-800°C to remove the combined water. The amorphous metal hydroxide gel is crystallized to form a polycrystalline composite zirconia toughened alumina ceramic primary crystal under the action of hydrothermal treatment, and by controlling the steam temperature, pressure, and hydrothermal time of the hydrothermal treatment, the morphology and particle size of the primary crystal can be controlled.

[0010] As preferred, in step (5), the specific operation method is as follows: the prepared primary crystal powder is added with fumed silica, BaSi2N2O2, and BaTiO3, wherein the addition amount of fumed silica is 0.2-1% of the mass of the primary crystal powder, the addition amount of BaSi2N2O2 is 0.05-0.2% of the mass of the primary crystal powder, and the addition amount of BaTiO3 is 1-5% of the mass of the primary crystal powder, and grinding and mixing in a sand mill obtains a composite ceramic powder slurry for preparing a thermostatic mixing valve.

[0011] As preferred, in step (6), the specific operation method is as follows: the prepared composite ceramic powder slurry is spray dried, and at the time of spray drying, oil acid is mixed into the hot air, wherein the use amount of the oil acid is 0.1-1% of the mass of the primary crystal powder, so that the dried powder particles are wrapped with a thin film of oil acid during the descending process, the surface of the powder is modified, and a composite ceramic powder is obtained.

[0012] Preferably, in step (7), the components of the organic binder are composed of the following by mass percentage: paraffin wax 40-50 wt%, palm wax 5-10 wt%, methacrylic resin 10-20 wt%, low molecular weight polyoxymethylene 10-20 wt%, syndiotactic polypropylene 10-20 wt%, behenic acid 1-5 wt%, and S-80 1-5 wt%. Among them, paraffin wax has low viscosity and acts as a flow carrier; palm wax has many surface active groups, which can enhance the bonding ability between paraffin wax and resin; methacrylic resin and low molecular weight polyoxymethylene act as a skeletal support; syndiotactic polypropylene improves the flexibility of the organic binder, enhances the fracture strength of the preform, and prevents demolding damage during molding; behenic acid and S-80 act as surfactants, which link the powder particles and the organic binder and prevent powder-adhesive separation.

[0013] As a preferred option, in step (9), the specific operation method is as follows: the formed ceramic mixing valve green body is placed in a medium-temperature degreasing furnace to remove the organic binder. The heating curve is room temperature - 100℃, 2-5℃ / min, 100-250℃, 0.5-2℃ / min, 250-450℃, 1-2℃ / min, 450-750℃, 3-5℃ / min.

[0014] As a preferred option, in step (10), the specific operation method is as follows: the blank after removing the binder is placed in a high-temperature sintering furnace, and the heating curve is room temperature - 1000℃, 5-20℃ / min, 1000-1500℃, 3-5℃ / min, 1500-1380℃, 20-50℃ / min, 1380℃, and the temperature is maintained for 10-15 hours, and then the temperature is naturally cooled.

[0015] The beneficial effects of this invention are: inhibiting grain growth and enhancing grain boundary strength; increasing the density of the ceramic body, lowering the sintering temperature, making the grains easier to become rounded, reducing the number of angular grains, increasing the strength of the ceramic, and achieving both densification of the green body during sintering and preventing excessive grain growth. The resulting alumina-zirconia composite ceramic thermostatic mixing valve has advantages such as high strength, high toughness, long life, corrosion resistance, and dirt resistance. Implementation

[0016] The present invention will be further described below with reference to specific embodiments.

[0017] A method for preparing a composite ceramic thermostatic mixing valve specifically includes the following steps: (1) Prepare analytical grade AlCl3·6H2O into a solution, add PEG4000 as a dispersant, stir evenly, add NH3·H2O dropwise at a set rate, and stir continuously until the pH value of the solution reaches 9-10 to form sol A; the specific operation method is as follows: prepare 1.5 mol of analytical grade AlCl3·6H2O into an aqueous solution with a concentration of 0.5 mol / L, and add a certain amount of PEG4000 as a dispersant, wherein the amount of PEG4000 added is 0.1-0.5% of the mass of AlCl3·6H2O, stir evenly, add NH3·H2O dropwise at a rate of 2 ml / min, and stir continuously until the pH value of the solution reaches 9-10 to form sol A.

[0018] (2) Prepare a solution of ZrOCl2·8H2O, then add cerium nitrate, magnesium nitrate, dysprosium nitrate, and samarium nitrate and stir until homogeneous. Then add NH3·H2O dropwise at a set rate while stirring continuously until the pH of the solution reaches 9-10, forming sol B. The specific operation method is as follows: Prepare a 0.15mol ZrOCl2·8H2O solution with a concentration of 0.5mol / L, then add cerium nitrate, magnesium nitrate, dysprosium nitrate, and samarium nitrate and stir until homogeneous. The addition of cerium nitrate... The amounts of cerium nitrate and magnesium nitrate are 0.5-1 mol% of ZrOCl2·8H2O, 0.2-0.8 mol% of dysprosium nitrate, and 0.3-0.5 mol% of samarium nitrate. Then, NH3·H2O is added dropwise at a rate of 2 ml / min with continuous stirring until the solution pH reaches 9-10, forming sol B. Cerium nitrate and magnesium nitrate precipitate with OH- to form a hydroxide sol, which, upon subsequent crystallization, forms cerium oxide and magnesium oxide, partially stabilizing zirconium oxide. Dysprosium nitrate and samarium nitrate precipitate with OH- to form a hydroxide sol, which, upon subsequent crystallization, forms dysprosium oxide and samarium oxide, toughening the zirconium oxide and alumina ceramic matrix by inhibiting grain growth and enhancing grain boundary strength.

[0019] (3) Mix sol A and sol B, stir thoroughly, and then wash with deionized water multiple times to remove cl-. After filtration, add analytical grade anhydrous ethanol, stir at high speed, rinse multiple times, and then freeze dry to obtain a composite ceramic gel mixture. Ethanol, compared with pure water, can effectively reduce the hydrogen bonding force in the gel after drying, minimize the generation of hard agglomerates, and prevent the formation of powder hard agglomerates during subsequent gel crystallization, which would affect the performance of subsequent products.

[0020] (4) The freeze-dried composite ceramic gel mixture is placed in a high-pressure reactor and treated with high-temperature and high-pressure steam. After drying the obtained primary crystals, they are calcined to remove bound water. The specific operation method is as follows: The freeze-dried composite ceramic gel mixture is placed in a high-pressure reactor and treated with high-temperature and high-pressure steam for 10-30 hours. The temperature is controlled at 120-200℃ and the hydrothermal pressure is controlled at 1-3 MPa. After drying the obtained primary crystals, they are placed in a medium-temperature furnace at 500-800℃ to remove bound water. The amorphous metal hydroxide gel crystallizes under hydrothermal action to form polycrystalline composite zirconia-toughened alumina ceramic primary crystals. By controlling the steam temperature, pressure, and hydrothermal time of the hydrothermal treatment, the morphology and particle size of the primary crystals can be controlled.

[0021] (5) The obtained original crystal powder is mixed with fumed silica, BaSi2N2O2 and BaTiO3 in a sand mill to obtain a composite ceramic powder slurry for preparing a constant temperature mixing valve. The specific operation method is as follows: The obtained original crystal powder is mixed with fumed silica, BaSi2N2O2 and BaTiO3, wherein the amount of fumed silica added is 0.2-1% of the mass of the original crystal powder, the amount of BaSi2N2O2 added is 0.05-0.2% of the mass of the original crystal powder, and the amount of BaTiO3 added is 1-5% of the mass of the original crystal powder. The mixture is then mixed in a sand mill to obtain a composite ceramic powder slurry for preparing a constant temperature mixing valve. Among them, the role of fumed silica is to increase the density of the ceramic body and lower the sintering temperature; the addition of BaSi2N2O2 can change the morphology of ceramic grains, making the grains easier to become rounded during sintering and reducing the number of angular grains. Microscopically, this helps to reduce the possibility of surface dirt deposition when using ceramic mixing valves, but its addition will lead to a decrease in the strength of the ceramic body; BaTiO3 is a ferroelectric material, and a certain amount of its introduction can absorb external stress energy through the ferroelectric effect, disperse the stress entering the ceramic body, prevent the propagation of cracks, and increase the strength of the ceramic.

[0022] (6) Spray dry the prepared composite ceramic powder slurry to modify the powder surface and obtain composite ceramic powder. The specific operation method is as follows: Spray dry the prepared composite ceramic powder slurry. During spray drying, oleic acid is mixed into the hot air. The amount of oleic acid used is 0.1-1% of the mass of the original crystal powder. This allows the dried powder particles to be coated with a thin film of oleic acid during the descent process, thus modifying the powder surface and obtaining composite ceramic powder. The surface modification of the powder facilitates the mixing process with the organic binder.

[0023] (7) The modified powder is put into a mixer and an organic binder is added to make ceramic feed; the components of the organic binder are composed of the following by mass percentage: paraffin wax 40-50wt%, palm wax 5-10wt%, methacrylic acid resin 10-20wt%, low molecular weight polyoxymethylene 10-20wt%, syndiotactic polypropylene 10-20wt%, behenic acid 1-5wt%, and S-80 1-5wt%.

[0024]

[0025] Among them, paraffin wax has low viscosity and acts as a flow carrier; palm wax has many surface active groups, which can enhance the bonding ability between paraffin wax and resin; methacrylic acid resin and low molecular weight polyoxymethylene provide skeletal support; syndiotactic polypropylene improves the flexibility of organic binder, enhances the fracture strength of the preform, and prevents demolding damage during molding; behenic acid and S-80, as surfactants, play a role in linking powder particles and organic binder, preventing powder-binder separation.

[0026] (8) Place the prepared ceramic feed into a ceramic injection molding machine and use a mixing valve mold to complete the green body forming.

[0027] (9) Place the formed ceramic mixing valve green body into a medium-temperature degreasing furnace to remove the organic binder; the specific operation method is as follows: place the formed ceramic mixing valve green body into a medium-temperature degreasing furnace to remove the organic binder, and the heating curve is room temperature - 100℃, 2-5℃ / min, 100-250℃, 0.5-2℃ / min, 250-450℃, 1-2℃ / min, 450-750℃, 3-5℃ / min.

[0028] (10) The binder-free green body is placed in a high-temperature sintering furnace for sintering. The sintering method is to first heat up, then cool down, and then hold the temperature. The specific operation method is as follows: The binder-free green body is placed in a high-temperature sintering furnace. The heating curve is: room temperature - 1000℃, 5-20℃ / min, 1000-1500℃, 3-5℃ / min, 1500-1380℃, 20-50℃ / min, 1380℃. Hold the temperature for 10-15 hours, and then cool down naturally. During the sintering process, the traditional sintering method is abandoned, that is, after heating to the highest temperature, holding the temperature for a certain time to complete the sintering, and then cooling naturally. Instead, the temperature is first raised to the highest temperature, the sintering window is opened, and then the temperature is lowered to a certain temperature and held for a long time. In this way, the densification of the green body occurs without causing excessive grain growth, and fine-grained ceramic bodies can be obtained.

[0029] (11) The sintered blank is precision machined to achieve dimensional accuracy, and then the mating surfaces are polished to achieve a sealing effect. Example

[0030] 1. Prepare an aqueous solution with a concentration of 0.5 mol / L by dissolving 1.5 mol of analytical grade AlCl3·6H2O, and add a certain amount of PEG4000 as a dispersant (0.2% of the mass of AlCl3·6H2O). After stirring evenly, add NH3·H2O dropwise at a rate of 2 ml / min while stirring continuously until the pH of the solution reaches 9, forming sol A.

[0031] 2. Prepare a 0.5 mol / L aqueous solution of 0.15 mol ZrOCl2·8H2O. Then add cerium nitrate (1 mol% of ZrOCl2·8H2O), magnesium nitrate (0.5 mol% of ZrOCl2·8H2O), dysprosium nitrate (0.8 mol% of ZrOCl2·8H2O), and samarium nitrate (0.3 mol% of ZrOCl2·8H2O). Stir well and then add NH3·H2O dropwise at a rate of 2 ml / min while stirring continuously until the pH of the solution reaches 9, forming sol B.

[0032] 3. Mix sol A and sol B thoroughly and evenly, then wash with deionized water multiple times to remove cl-, filter, add analytical grade anhydrous ethanol, stir at high speed, rinse multiple times, and then freeze dry to obtain a composite ceramic gel mixture.

[0033] 4. The freeze-dried gel is placed in a high-pressure reactor and treated with high-temperature and high-pressure steam for 10 hours. The temperature is controlled at 120℃ and the hydrothermal pressure is controlled at 1MPa to obtain ceramic powder primary crystals with a grain size of 0.15 micrometers and a flocculent porous morphology. The primary crystals are then calcined at 500℃ and ready for use.

[0034] 5. The obtained primary crystal powder is mixed with fumed silica (0.2% of powder mass), BaSi2N2O2 (0.05% of powder mass), and BaTiO3 (5% of powder mass) in a sand mill to obtain a composite ceramic powder slurry for preparing a constant temperature mixing valve.

[0035] 6. Spray dry the prepared composite ceramic slurry to obtain composite ceramic powder. During spray drying, 0.1% oleic acid by weight of the powder is mixed into the hot air, so that the dried powder particles are coated with a thin film of oleic acid during the descent, which modifies the surface of the powder and facilitates the mixing process with the organic binder.

[0036] 7. Put the modified powder into a mixer, add the components of the organic binder according to the formula, and make ceramic feed.

[0037]

[0038] 8. Place the prepared ceramic feed into a ceramic injection molding machine and use a mixing valve mold to complete the green body forming.

[0039] 9. Place the formed ceramic mixing valve green body into a medium-temperature degreasing furnace to remove the organic binder. The heating curve is as follows: room temperature - 100℃, 2℃ / min; 100-250℃, 0.5℃ / min; 250-450℃, 1℃ / min; 450-750℃, 3℃ / min.

[0040] 10. Place the blank after removing the binder into a high-temperature sintering furnace. The heating curve is as follows: room temperature - 1000℃, 5℃ / min; 1000-1500℃, 5℃ / min; 1500-1380℃, 20℃ / min; 1380℃, hold for 10 hours, and then let it cool naturally.

[0041] 11. The sintered blank is precision machined to achieve dimensional accuracy, and then the mating surfaces are polished to achieve a sealing effect. Example

[0042] 1. Prepare an aqueous solution with a concentration of 0.5 mol / L by dissolving 1.5 mol of analytical grade AlCl3·6H2O, and add a certain amount of PEG4000 as a dispersant (0.5% of the mass of AlCl3·6H2O). After stirring evenly, add NH3·H2O dropwise at a rate of 2 ml / min while stirring continuously until the pH of the solution reaches 10, forming sol A.

[0043] 2. Prepare a 0.15 mol ZrOCl2·8H2O aqueous solution with a concentration of 0.5 mol / L. Then add cerium nitrate (0.5 mol% of ZrOCl2·8H2O), magnesium nitrate (0.5 mol% of ZrOCl2·8H2O), dysprosium nitrate (0.5 mol% of ZrOCl2·8H2O), and samarium nitrate (0.5 mol% of ZrOCl2·8H2O). Stir well and then add NH3·H2O dropwise at a rate of 2 ml / min while stirring continuously until the pH of the solution reaches 10, forming sol B.

[0044] 3. Mix sol A and sol B thoroughly and evenly, then wash with deionized water multiple times to remove cl-, filter, add analytical grade anhydrous ethanol, stir at high speed, rinse multiple times, and then freeze dry to obtain a composite ceramic gel mixture.

[0045] 4. The freeze-dried gel is placed in a high-pressure reactor and treated with high-temperature and high-pressure steam for 30 hours. The temperature is controlled at 200℃ and the hydrothermal pressure is controlled at 3MPa to obtain ceramic powder primary crystals with a grain size of 0.8 micrometers and a morphology of near-spherical porous particles. The primary crystals are then calcined at 800℃ and ready for use.

[0046] 5. The obtained primary crystal powder is mixed with fumed silica (1% of powder mass), BaSi2N2O2 (0.2% of powder mass), and BaTiO3 (3% of powder mass) in a sand mill to obtain a composite ceramic powder slurry for preparing a constant temperature mixing valve.

[0047] 6. Spray dry the prepared composite ceramic slurry to obtain composite ceramic powder. During spray drying, 1% oleic acid by weight of the powder is mixed into the hot air, so that the dried powder particles are coated with a thin film of oleic acid during the descent, which modifies the surface of the powder and facilitates the mixing process with the organic binder.

[0048] 7. Put the modified powder into a mixer, add the components of the organic binder according to the formula, and make ceramic feed.

[0049]

[0050] 8. Place the prepared ceramic feed into a ceramic injection molding machine and use a mixing valve mold to complete the green body forming.

[0051] 9. Place the formed ceramic mixing valve green body into a medium-temperature degreasing furnace to remove the organic binder. The heating curve is as follows: room temperature - 100℃, 5℃ / min; 100-250℃, 2℃ / min; 250-450℃, 2℃ / min; 450-750℃, 5℃ / min.

[0052] 10. Place the blank after removing the binder into a high-temperature sintering furnace. The heating curve is as follows: room temperature - 1000℃, 20℃ / min; 1000-1500℃, 3℃ / min; 1500-1380℃, 50℃ / min; 1380℃, hold for 15 hours, and then let it cool naturally.

[0053] 11. The sintered blank is precision machined to achieve dimensional accuracy, and then the mating surfaces are polished to achieve a sealing effect. Example

[0054] 1. Prepare an aqueous solution with a concentration of 0.5 mol / L by dissolving 1.5 mol of analytical grade AlCl3·6H2O, and add a certain amount of PEG4000 as a dispersant (0.3% of the mass of AlCl3·6H2O). After stirring evenly, add NH3·H2O dropwise at a rate of 2 ml / min while stirring continuously until the pH of the solution reaches 9.5, forming sol A.

[0055] 2. Prepare a 0.15 mol ZrOCl2·8H2O aqueous solution with a concentration of 0.5 mol / L. Then add cerium nitrate (0.5 mol% of ZrOCl2·8H2O), magnesium nitrate (0.5 mol% of ZrOCl2·8H2O), dysprosium nitrate (0.5 mol% of ZrOCl2·8H2O), and samarium nitrate (0.5 mol% of ZrOCl2·8H2O). Stir well and then add NH3·H2O dropwise at a rate of 2 ml / min while stirring continuously until the pH of the solution reaches 9.5, forming sol B.

[0056] 3. Mix sol A and sol B thoroughly and evenly, then wash with deionized water multiple times to remove cl-, filter, add analytical grade anhydrous ethanol, stir at high speed, rinse multiple times, and then freeze dry to obtain a composite ceramic gel mixture.

[0057] 4. The freeze-dried gel is placed in a high-pressure reactor and treated with high-temperature and high-pressure steam for 24 hours. The temperature is controlled at 160℃ and the hydrothermal pressure is controlled at 2.4MPa to obtain ceramic powder precursor crystals with a grain size of 0.4 micrometers and a polygonal porous morphology. The precursor crystals are then calcined at 600℃ and ready for use.

[0058] 5. The obtained primary crystal powder is mixed with fumed silica (0.5% of powder mass), BaSi2N2O2 (0.1% of powder mass), and BaTiO3 (3.5% of powder mass) in a sand mill to obtain a composite ceramic powder slurry for preparing a constant temperature mixing valve.

[0059] 6. Spray dry the prepared composite ceramic slurry to obtain composite ceramic powder. During spray drying, 0.8% oleic acid by weight of the powder is mixed into the hot air, so that the dried powder particles are coated with a thin film of oleic acid during the descent, which modifies the surface of the powder and facilitates the mixing process with the organic binder.

[0060] 7. Put the modified powder into a mixer, add the components of the organic binder according to the formula, and make ceramic feed.

[0061]

[0062] 8. Place the prepared ceramic feed into a ceramic injection molding machine and use a mixing valve mold to complete the green body forming.

[0063] 9. Place the formed ceramic mixing valve green body into a medium-temperature degreasing furnace to remove the organic binder. The heating curve is as follows: room temperature - 100℃, 3℃ / min; 100-250℃, 1℃ / min; 250-450℃, 1.5℃ / min; 450-750℃, 3.5℃ / min.

[0064] 10. Place the blank after removing the binder into a high-temperature sintering furnace. The heating curve is as follows: room temperature - 1000℃, 10℃ / min, 1000-1500℃, 3.5℃ / min, 1500-1380℃, 40℃ / min, 1380℃. Hold at this temperature for 12 hours, then allow it to cool naturally.

[0065] 11. The sintered blank is precision machined to achieve dimensional accuracy, and then the mating surfaces are polished to achieve a sealing effect.

[0066] The composite ceramic thermostatic mixing valves prepared through the above three embodiments and thermostatic mixing valves made of stainless steel and brass are used as comparative examples. Their performance is compared as shown in the table below.

[0067]

Claims

1. A method for preparing a composite ceramic thermostatic mixing valve, characterized in that, Specifically comprising the following steps: (1) the analytical pure AlCl3.6H2O is configured into a solution, and PEG4000 is added as a dispersant, after stirring uniformly, NH3.H2O is added at a set rate, and stirring is continuously carried out until the PH value of the solution reaches 9-10, forming sol A; (2) ZrOCl2.8H2O is configured into a solution, then cerous nitrate, magnesium nitrate, dysprosium nitrate, and samarium nitrate are added, stirring is uniformly carried out, NH3.H2O is added at a set rate, and stirring is continuously carried out until the PH value of the solution reaches 9-10, forming sol B; (3) sol A and sol B are mixed, fully stirred uniformly, then cl- is removed through multiple deionized water washing, after filtration, analytical pure anhydrous ethanol is added, high-speed stirring is carried out, multiple washing is carried out, then freeze-drying is carried out, and a composite ceramic gel mixture is obtained; (4) the freeze-dried composite ceramic gel mixture is placed into a high-pressure reaction kettle, high-temperature high-pressure steam treatment is carried out, the obtained primary crystal is dried, and calcination is carried out to remove combined water; (5) the prepared primary crystal powder is added with fumed silica, BaSi2N2O2, and BaTiO3, grinding and mixing are carried out in a sand mill to obtain a composite ceramic powder slurry for preparing a thermostatic mixing valve; (6) the prepared composite ceramic powder slurry is spray dried, the surface of the powder is modified, and a composite ceramic powder is obtained; (7) the modified powder is put into a banbury mixer, and an organic binder is added to prepare a ceramic feedstock; (8) the prepared ceramic feedstock is placed into a ceramic special injection machine, a mixing valve mold is used, and green body forming is completed; (9) the formed ceramic mixing valve green body is placed into a medium-temperature debinding furnace to remove the organic binder; (10) the green body after removing the binder is placed into a high-temperature sintering furnace for sintering, and the sintering mode adopts the mode of first rising temperature, then falling temperature, and then holding temperature; (11) the sintered green body is precisely machined to reach the dimensional accuracy, then the mating surface is polished to achieve a sealing effect.

2. The method for preparing a composite ceramic thermostatic mixing valve according to claim 1, characterized in that, in In step (1), the specific operation method is as follows: 1.5 mol of analytical pure AlCl3.6H2O is configured into an aqueous solution with a concentration of 0.5 mol / L, and a certain amount of PEG4000 is added as a dispersant, wherein the addition amount of PEG4000 is 0.1-0.5% of the mass of AlCl3.6H2O, stirring is uniformly carried out, NH3.H2O is added at a rate of 2 ml / min, and stirring is continuously carried out until the PH value of the solution reaches 9-10, forming sol A.

3. The method for preparing a composite ceramic thermostatic mixing valve according to claim 1, characterized in that, In step (2), the specific operation method is as follows: 0.15 mol ZrOCl2.8H2O is configured into an aqueous solution with a concentration of 0.5 mol / L, and then cerium nitrate, magnesium nitrate, dysprosium nitrate, and samarium nitrate are added and stirred uniformly, wherein the addition amount of cerium nitrate is 0.5-1 mol% of ZrOCl2.8H2O, the addition amount of magnesium nitrate is 0.5-1 mol% of ZrOCl2.8H2O, the addition amount of dysprosium nitrate is 0.2-0.8 mol% of ZrOCl2.8H2O, and the addition amount of samarium nitrate is 0.3-0.5 mol% of ZrOCl2.8H2O, and then NH3.H2O is added dropwise at a rate of 2 ml / min, and stirring is continuously performed until the PH value of the solution reaches 9-10, and a sol B is formed.

4. The preparation method of a composite ceramic thermostatic mixing valve according to claim 1, characterized in that, in In step (4), the specific operation method is as follows: the freeze-dried composite ceramic gel mixture is placed in a high-pressure reaction kettle, and is treated by high-temperature and high-pressure steam for 10-30 hours, the temperature is controlled at 120-200℃, and the hydrothermal pressure is controlled at 1-3 Mpa, the obtained primary crystal is dried, and then is calcined in a medium-temperature furnace at 500-800℃ to remove the combined water.

5. The method for preparing a composite ceramic thermostatic mixing valve according to claim 1, characterized in that, In step (5), the specific operation method is as follows: the prepared primary crystal powder is added with fumed silica, BaSi2N2O2, and BaTiO3, wherein the addition amount of fumed silica is 0.2-1% of the mass of the primary crystal powder, the addition amount of BaSi2N2O2 is 0.05-0.2% of the mass of the primary crystal powder, and the addition amount of BaTiO3 is 1-5% of the mass of the primary crystal powder, and the mixture is ground in a sand mill to obtain a composite ceramic powder slurry for preparing a thermostatic mixing valve.

6. The method for preparing a composite ceramic thermostatic mixing valve according to claim 1, characterized in that, In step (6), the specific operation method is as follows: the prepared composite ceramic powder slurry is spray dried, and oil acid is mixed into the hot air during the spray drying, wherein the use amount of the oil acid is 0.1-1% of the mass of the primary crystal powder, so that the dried powder particles are wrapped with a thin film of oil acid during the falling process, the surface of the powder is modified, and a composite ceramic powder is obtained.

7. The method for preparing a composite ceramic thermostatic mixing valve according to claim 1, characterized in that, In step (7), the components of the organic binder are composed of the following components in percentage by mass: paraffin wax 40-50 wt%, palm wax 5-10 wt%, methyl methacrylate resin 10-20 wt%, low molecular weight polyformaldehyde 10-20 wt%, syndiotactic polypropylene 10-20 wt%, behenic acid 1-5 wt%, and S-80 1-5 wt%.

8. The method for preparing a composite ceramic thermostatic mixing valve according to claim 1, characterized in that, in In step (9), the specific operation method is as follows: the formed ceramic mixing valve green body is placed in a medium-temperature debinding furnace to remove the organic binder, and the temperature rising curve is room temperature-100℃, 2-5℃ / min, 100-250℃, 0.5-2℃ / min, 250-450℃, 1-2℃ / min, and 450-750℃, 3-5℃ / min.

9. The method for preparing a composite ceramic thermostatic mixing valve according to claim 1, characterized in that, In step (10), the specific operation method is as follows: the green body after removal of the binder is placed in a high-temperature sintering furnace, and the temperature rising curve is room temperature-1000℃, 5-20℃ / min, 1000-1500℃, 3-5℃ / min, 1500-1380℃, 20-50℃ / min, 1380℃, and the temperature is kept for 10-15 hours, and then the temperature is naturally lowered.

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