Method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system

Abstract

The present invention discloses a method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system. The steps include ball-milling ceramic powder, a dispersant, and an organic solvent to obtain a first slurry; adding an EBECRYL acrylic cross-linking agent to the first slurry, continuing ball-milling and defoaming to obtain a second slurry; mixing polyethylene glycol and water to obtain an aqueous polyethylene glycol solution, pouring oil into it to obtain a curing medium with an upper oil layer and a lower aqueous polyethylene glycol solution layer, where the oil is insoluble in polyethylene glycol and has a density less than that of polyethylene glycol and water; under ultraviolet light irradiation, dropping the second slurry into the curing medium to form spherical green bodies, taking them out after the size of the spherical green bodies no longer changes, drying, and sintering to obtain the ceramic microspheres. The method of the present invention is not only energy-saving and environmentally friendly, but the obtained ceramic microspheres also have the advantages of concentrated size distribution, high relative density, and good sphericity.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic microsphere preparation, and particularly relates to a method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system. Background Art

[0002] Oxide and non-oxide ceramic grinding media balls have gained wide favor in the industry due to many outstanding advantages such as high strength, high hardness, excellent wear resistance and corrosion resistance. In order to adapt to the rapid development of the ultrafine grinding industry, more and more researchers have focused on the research of how to prepare monodisperse sub-millimeter-sized, or even ceramic grinding media balls with a particle size less than 300 μm, which have excellent performance and strong adaptability. At present, the main preparation processes of ceramic balls include plastic extrusion molding method, external gel molding method, rolling molding method, isostatic pressing molding method, etc. However, although these technologies are relatively mature and can prepare ceramic media balls for grinding, these ceramic media balls all have certain defects and cannot simultaneously possess the characteristics of relatively large bulk density, high strength and hardness, and excellent stability.

[0003] Gelcasting is a wet forming method and has received wide attention due to its advantages such as simple operation, low cost, microscopically uniform gel structure, few defects, and net size forming. Yang Jinlong et al. from Tsinghua University mixed organic monomers, crosslinking agents and water, added different ceramic powders, then defoamed the slurry, and then added initiators during stirring. The obtained slurry was dropped into an oily medium, and the slurry was formed into spheres by using the interfacial tension difference of different media, and the spherical slurry was quickly cured into a gel by adding a catalyst in the oily medium, and finally high-density and wear-resistant ceramic small balls were obtained. However, in this method, the monomers are neurotoxic and carcinogenic, which are harmful to the human body and the environment in the long term. At the same time, there are many parameters to be controlled, the process is complex, and it is difficult to achieve stable preparation. Therefore, it is of great significance to stably prepare a kind of ceramic small balls with environmental friendliness, good sphericity and high relative density. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, which is simple to operate, energy-saving and environmentally friendly, and the ceramic microspheres have concentrated sizes, high sphericity and high relative density, aiming at the deficiencies of the prior art.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, comprising the following steps:

[0007] (1) Mix ceramic powder, a dispersant and ethyl acetate, and ball mill to obtain a first slurry;

[0008] (2) Add an acrylic crosslinking agent to the first slurry. The acrylic crosslinking agent is EBECRYL acrylic crosslinking agent, and continue ball milling and defoaming to obtain a second slurry;

[0009] (3) Mix polyethylene glycol and water to obtain an aqueous polyethylene glycol solution, pour in oil to obtain a solidification medium with an oil layer on the upper layer and an aqueous polyethylene glycol solution layer on the lower layer. The oil is insoluble in polyethylene glycol and has a density less than that of polyethylene glycol and water;

[0010] (4) Under ultraviolet light irradiation, drop the second slurry into the solidification medium to form a spherical blank, and take it out after the size of the spherical blank no longer changes to obtain a spherical wet blank;

[0011] (5) Dry and sinter the spherical wet blank to obtain ceramic microspheres.

[0012] In the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (1), by mass fraction, the ceramic powder is 60% - 85%, ethyl acetate is 10% - 35%, and the dispersant is 0.1% - 5%;

[0013] In the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (2), the addition amount of the EBECRYL acrylic crosslinking agent is 5% - 15% of the mass of the ceramic powder.

[0014] In the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (3), the mass percentage content of polyethylene glycol in the aqueous polyethylene glycol solution is 90% - 98%; the oil is vegetable oil, the thickness of the oil layer is 1 cm - 3 cm, and the thickness of the aqueous polyethylene glycol solution layer is 15 cm - 30 cm.

[0015] In the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (1), the ceramic powder is any one of alumina, zirconia, silicon carbide, silicon nitride, titanium carbide, and titanium nitride; the dispersant is any one or several of the BYK series dispersants.

[0016] In the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, the ceramic powder is zirconia toughened alumina ceramic.

[0017] For the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (1), the ceramic powder further includes a sintering aid, and the sintering aid is one or more of silicon oxide, calcium oxide, magnesium oxide, lanthanum oxide, yttrium oxide, ytterbium oxide, and boron carbide; the ball milling medium is one of alumina balls, zirconia balls, and silicon nitride balls; the mass ratio of the material to the balls is 1:1 to 3; the ball milling time is 12 h to 48 h, and the ball milling speed is 200 rad / min to 400 rad / min.

[0018] For the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (2), the EBECRYL acrylic crosslinking agent is EBECRYL-4765 acrylic crosslinking agent; the time for continuous ball milling is 5 min to 20 min; the defoaming is vacuum defoaming, the defoaming time is 15 min to 30 min, and the defoaming vacuum degree is 100 Pa to 1000 Pa.

[0019] For the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (3), the vegetable oil is one or more of castor oil, peanut oil, and palm oil, and the polyethylene glycol is any one or more between polyethylene glycol 200 and 600; the volume ratio of the oil to the polyethylene glycol aqueous solution is 1:10 to 30.

[0020] For the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (4), the outlet size when the second slurry is dropped into the curing medium is 0.2 mm to 0.5 mm; the dropping speed when the second slurry is dropped into the curing medium is 5 drops / second to 20 drops / second.

[0021] For the above method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (5), the drying regime is to dry at 60 °C for 6 h to 24 h, then dry at 90 °C for 6 h to 24 h, and then dry at 120 °C for 6 h to 24 h; the sintering method is pressureless sintering or gas pressure sintering, the sintering temperature is 1500 °C to 2300 °C, the holding time is 2 h to 5 h, the sintering atmosphere is one of air atmosphere, nitrogen atmosphere, and argon atmosphere, the heating rate between 0 °C and 600 °C is 0.2 °C / min to 1 °C / min, and the heating rate between 600 °C and the sintering temperature is 1 °C / min to 5 °C / min.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] (1) The method for preparing ceramic microspheres based on environmentally friendly non-aqueous gel casting of the present invention uses EBECRYL acrylic crosslinker as a curing agent, which has the characteristics of light / wet dual curing, and promotes the green body to be formed by synergistic action with ultraviolet irradiation and oil-polyethylene glycol aqueous solution, wherein the coordination of ultraviolet light with oil and polyethylene glycol aqueous solution is crucial and indispensable. This curing method is not only energy-saving and environmentally friendly, but also can play a complementary and reinforcing role, so that the ceramic microsphere green body can maintain good sphericity, and the prepared ceramic microspheres have concentrated size distribution, high relative density, good sphericity, simple process operation, and easy batch preparation. Compared with the traditional acrylamide gel casting system, the acrylic crosslinker used in the environmentally friendly non-aqueous gel casting of the present invention has the advantages of low toxicity and environmental protection, and does not pollute the human body and the environment.

[0024] (2) The method for preparing ceramic microbeads based on environmentally friendly non-aqueous gel injection molding of the present invention uses ethyl acetate as a solvent, which has good wettability on ceramic powders and can prepare ceramic slurries with high solid content. At the same time, ethyl acetate has a small surface tension, and the capillary force caused during the drying process is small, which can effectively avoid the drying cracking of spherical green bodies. Combined with the molding and liquid phase drying process of the oil-polyethylene glycol aqueous solution, it is easy to achieve safe and efficient molding and drying of spherical ceramic green bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart of a method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to Example 1 of the present invention.

[0026] Figure 2 This is a schematic diagram of the principle of the method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system according to Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available, among which alumina powder is purchased from Alteo Company, product model PL172LSB; zirconium oxide powder is purchased from Oriental Zirconium Industry, product model OZ-3Y; dispersant is purchased from BYK Additives (Shanghai) Co., Ltd., product model BYK-170; EBECRYL acrylic crosslinker is purchased from Allnex Company, product model EBECRYL-4765.

[0028] Example 1

[0029] A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system of the present invention, such as Figure 1 As shown, the following steps are included:

[0030] (1) Weigh 2000 g of alumina powder, 20 g of dispersant, 450 g of ethyl acetate and 4000 g of alumina balls and place them in a ball mill tank. Ball mill for 24 h at a rotation speed of 200 r / min to obtain a first slurry;

[0031] (2) Add 150 g of EBECRYL acrylic crosslinking agent to the first slurry, continue ball milling for 10 min, then pour it into a vacuum degassing device, and degas for 20 min under the condition of a vacuum degree of 1000 Pa to obtain a second slurry;

[0032] (3) Mix polyethylene glycol and water to obtain an aqueous polyethylene glycol solution, pour in the oil, and obtain a solidification medium with an oil layer on the upper layer and an aqueous polyethylene glycol solution layer on the lower layer. The oil is insoluble in polyethylene glycol and has a density less than that of polyethylene glycol and water;

[0033] Among them, the oil is vegetable oil, specifically castor oil. The polyethylene glycol is polyethylene glycol 400, and the mass percentage content of polyethylene glycol in the aqueous polyethylene glycol solution is 95%; the thickness of the oil layer is 2 cm, the thickness of the aqueous polyethylene glycol solution layer is 25 cm, and the volume ratio of the oil to the aqueous polyethylene glycol solution is 1∶12.5;

[0034] (4) As Figure 2 shown, transfer the second slurry to a storage tank, then extract it through a delivery pump, enter it into a dropping tube through a peristaltic pump. A vibrating dropping head is provided at the output end of the dropping tube. The second slurry forms droplets at the discharge port of the vibrating dropping head. The size of the discharge port is 0.2 mm. Under ultraviolet light irradiation, drop it into the solidification medium at a speed of 6 drops per second to form a spherical blank. After the size of the spherical blank no longer changes, take it out to obtain a solidified spherical wet blank;

[0035] (5) Transfer the spherical wet blank to an oven for drying. The drying regime is 60 °C * 8 h + 90 °C * 8 h + 120 °C * 8 h; use a high-temperature sintering furnace to sinter the dried blank to obtain alumina ceramic microspheres; the sintering method is pressureless sintering, the sintering atmosphere is air atmosphere, the sintering temperature is 1600 °C, the holding time is 3 h, and the heating rate between 0 °C and 600 °C is 0.4 °C / min, and the heating rate from 600 °C to the sintering temperature is 2 °C / min.

[0036] Example 2

[0037] A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system of the present invention, as Figure 1 shown, includes the following steps:

[0038] (1) Weigh 2000 g of alumina powder, 20 g of dispersant, 400 g of ethyl acetate and 4000 g of alumina balls and place them in a ball mill tank. Ball mill for 24 h at a rotation speed of 200 r / min to obtain a first slurry;

[0039] (2) Add 200 g of EBECRYL acrylic crosslinker to the first slurry, continue ball milling for 10 min, then pour it into a vacuum degassing device and degas for 20 min under a vacuum of 1000 Pa to obtain the second slurry;

[0040] (3) Mix polyethylene glycol and water to obtain an aqueous polyethylene glycol solution, pour in the oil, to obtain a solidification medium with an oil layer on the upper layer and an aqueous polyethylene glycol solution layer on the lower layer. The oil is insoluble in polyethylene glycol and has a density less than that of polyethylene glycol and water;

[0041] Among them, the oil is vegetable oil, specifically palm oil; the polyethylene glycol is polyethylene glycol 400, and the mass percentage of polyethylene glycol in the aqueous polyethylene glycol solution is 95%; the thickness of the oil layer is 2 cm, and the thickness of the aqueous polyethylene glycol solution layer is 20 cm; the volume ratio of the oil to the aqueous polyethylene glycol solution is 1:10;

[0042] (4) As Figure 2 shown, transfer the second slurry to a storage tank, then extract it through a delivery pump and pump it into a drip tube through a peristaltic pump. A vibrating drip head is provided at the output end of the drip tube. The second slurry forms droplets at the discharge port of the vibrating drip head. The size of the discharge port is 0.2 mm. Under ultraviolet light irradiation, the droplets are dropped into the solidification medium at a speed of 6 drops per second to form spherical blanks. After the size of the spherical blanks no longer changes, take them out to obtain the solidified spherical green blanks;

[0043] (5) Transfer the spherical green blanks to an oven for drying. The drying regime is 60 °C * 8 h + 90 °C * 8 h + 120 °C * 8 h; use a high-temperature sintering furnace to sinter the dried blanks to obtain alumina ceramic microspheres. The sintering method is pressureless sintering, the sintering atmosphere is air atmosphere, the sintering temperature is 1600 °C, the holding time is 3 h, the heating rate between 0 °C and 600 °C is 0.4 °C / min, and the heating rate from 600 °C to the sintering temperature is 2 °C / min.

[0044] Example 3

[0045] A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system of the present invention, as Figure 1 shown, includes the following steps:

[0046] (1) Weigh 3000 g of zirconia powder, 30 g of dispersant, 600 g of ethyl acetate and 6000 g of zirconia balls and place them in a ball mill jar for ball milling. Ball mill at a speed of 250 r / min for 36 h to obtain the first slurry;

[0047] (2) Add 300 g of EBECRYL acrylic crosslinker to the first slurry, continue ball milling for 10 min, then pour it into a vacuum degassing device and degas for 20 min under a vacuum of 1000 Pa to obtain the second slurry;

[0048] (3) Mix polyethylene glycol and water to obtain an aqueous polyethylene glycol solution, and pour in the oil to obtain a solidification medium with an upper oil layer and a lower aqueous polyethylene glycol solution layer. The oil is insoluble in polyethylene glycol and has a density lower than that of polyethylene glycol and water;

[0049] Among them, the oil is vegetable oil, specifically castor oil; the polyethylene glycol is polyethylene glycol 400, and the mass percentage content of polyethylene glycol in the aqueous polyethylene glycol solution is 95%; the thickness of the oil layer is 2 cm, and the thickness of the aqueous polyethylene glycol solution layer is 20 cm; the volume ratio of the oil to the aqueous polyethylene glycol solution is 1:10;

[0050] (4) As Figure 2 shown, transfer the second slurry to a storage tank, then extract it through a delivery pump and pump it into a dropping tube through a peristaltic pump. A vibrating dropping head is provided at the output end of the dropping tube. The second slurry forms droplets at the discharge port of the vibrating dropping head. The size of the discharge port is 0.2 mm. Under ultraviolet light irradiation, the second slurry is dropped into the solidification medium at a speed of 6 drops per second to form a spherical blank. After the size of the spherical blank no longer changes, take it out to obtain a solidified spherical wet blank;

[0051] (5) Transfer the spherical wet blank to an oven for drying. The drying regime is 60°C * 8 h + 90°C * 8 h + 120°C * 8 h; use a high-temperature sintering furnace to sinter the dried blank to obtain alumina ceramic microspheres; the sintering method is pressureless sintering, the sintering atmosphere is air atmosphere, the sintering temperature is 1550°C, the holding time is 3 h, and the heating rate between 0°C and 600°C is 0.4°C / min, and the heating rate from 600°C to the sintering temperature is 2°C / min.

[0052] Comparative Example 1

[0053] A method for preparing ceramic microspheres is basically the same as that of Example 1, except that: in step (3), the solidification medium is only castor oil.

[0054] Comparative Example 2

[0055] A method for preparing ceramic microspheres is basically the same as that of Example 1, except that: in step (3), the solidification medium is only the aqueous polyethylene glycol solution.

[0056] Comparative Example 3

[0057] A method for preparing ceramic microspheres is basically the same as that of Example 1, except that: in step (4), ultraviolet light irradiation is not used.

[0058] Table 1 Performance test table of Examples 1-3 and Comparative Examples 1-3

[0059]

[0060] As can be seen from Table 1, the relative densities of the ceramic microspheres provided in Examples 1 to 3 and Comparative Examples 1 to 3 are all greater than 99%, indicating that the method for preparing ceramic microspheres based on environmentally friendly non-aqueous gel casting provided by the present invention can prepare dense ceramic microspheres with high mechanical strength. In addition, it can be seen that the sizes of the ceramic microspheres provided in Examples 1 to 3 are relatively concentrated, and the sphericity is relatively high, all greater than 0.95. In contrast, the maximum sphericity of the ceramic microspheres provided in Comparative Examples 1 to 3 is 0.92, and the size distribution of the microspheres is relatively wide. The alumina ceramics provided in Examples 1 to 2 have higher sphericity and more concentrated size distribution compared with the alumina ceramics provided in Comparative Examples 1 to 3 respectively. Therefore, the method for preparing ceramic microspheres based on environmentally friendly non-aqueous gel casting provided by the present invention can achieve the preparation of high-performance ceramic microspheres.

[0061] Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, characterized in that, It includes the following steps: (1) Mix ceramic powder, dispersant and ethyl acetate, and ball mill to obtain a first slurry; (2) Add an acrylic crosslinking agent to the first slurry, where the acrylic crosslinking agent is EBECRYL acrylic crosslinking agent, continue ball milling, and remove bubbles to obtain a second slurry; (3) Mix polyethylene glycol and water to obtain an aqueous polyethylene glycol solution, pour in oil, to obtain a curing medium with an oil layer on the upper layer and an aqueous polyethylene glycol solution layer on the lower layer, where the oil is insoluble in polyethylene glycol and has a density less than that of polyethylene glycol and water; (4) Under ultraviolet light irradiation, drop the second slurry into the curing medium to form a spherical green body, take it out after the size of the spherical green body no longer changes to obtain a spherical wet green body; (5) Dry and sinter the spherical wet green body to obtain ceramic microspheres; In step (1), by mass fraction, the ceramic powder is 60% - 85%, the ethyl acetate is 10% - 35%, and the dispersant is 0.1% - 5%; In step (2), the addition amount of the EBECRYL acrylic crosslinking agent is 5% - 15% of the mass of the ceramic powder; In step (3), the mass percentage content of polyethylene glycol in the aqueous polyethylene glycol solution is 90% - 98%; the oil is vegetable oil.

2. The method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system according to claim 1, characterized in that, The thickness of the oil layer is 1 cm - 3 cm, and the thickness of the aqueous polyethylene glycol solution layer is 15 cm - 30 cm.

3. The method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system according to claim 1 or 2, characterized in that, In step (1), the ceramic powder is any one of alumina, zirconia, silicon carbide, silicon nitride, titanium carbide and titanium nitride; the dispersant is any one or several of BYK series dispersants.

4. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to claim 1 or 2, characterized in that, In step (1), the ceramic powder further includes a sintering aid, and the sintering aid is one or several of silica, calcium oxide, magnesium oxide, lanthanum oxide, yttrium oxide, ytterbium oxide and boron carbide; the ball milling medium is any one of alumina balls, zirconia balls and silicon nitride balls; the mass ratio of material to balls is 1:1 - 3; the ball milling time is 12 h - 48 h, and the ball milling speed is 200 rad / min - 400 rad / min.

5. The method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system according to claim 1 or 2, characterized in that, In step (2), the EBECRYL acrylic crosslinking agent is EBECRYL - 4765 acrylic crosslinking agent; the time for continued ball milling is 5 min - 20 min; the defoaming is vacuum defoaming, the defoaming time is 15 min - 30 min, and the defoaming vacuum degree is 100 Pa - 1000 Pa.

6. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to claim 1, wherein, In step (3), the vegetable oil is one or several of castor oil, peanut oil and palm oil, and the polyethylene glycol is any one or several between polyethylene glycol 200 and 600; the volume ratio of the oil to the aqueous polyethylene glycol solution is 1:10 - 30.

7. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to any one of claims 1 to 2 or 6, characterized in that, In step (4), the size of the discharge port when the second slurry is dropped into the curing medium is 0.2 mm - 0.5 mm; the dropping speed of the second slurry when dropped into the curing medium is 5 drops / second - 20 drops / second.

8. The method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system according to any one of claims 1 to 2 or 6, characterized in that, In step (5), the drying regime is to dry at 60°C for 6 h to 24 h, then dry at 90°C for 6 h to 24 h, and then dry at 120°C for 6 h to 24 h; the sintering method is pressureless sintering or gas-pressure sintering, the sintering temperature is 1500°C to 2300°C, the holding time is 2 h to 5 h, the sintering atmosphere is one of air atmosphere, nitrogen atmosphere and argon atmosphere, the heating rate between 0°C and 600°C is 0.2°C / min to 1°C / min, and the heating rate from 600°C to the sintering temperature is 1°C / min to 5°C / min.

Images