Dynamic rapid high-purity alpha alumina ceramic ball preparation method

Abstract

The invention belongs to the technical field of preparation of inorganic non-metallic materials, and relates to a method for dynamically and rapidly preparing high-purity alpha alumina ceramic balls. The preparation method comprises the following steps: adding high-purity nano aluminum oxide powder into water, uniformly mixing, adding a dispersing agent to obtain a dispersion liquid, and adding a gel casting monomer to obtain the titrating solution. Blending an initiator with a non-polar solvent to obtain a mother solution; dropwise adding the titrating solution into the mother solution to obtain a mixed solution containing gel particles; and filtering and calcining to obtain the high-purity spherical alpha alumina particles. According to the process provided by the invention, on the basis of titration forming, an emulsion method and a gel casting method are combined, and the prepared ceramic balls are high in purity, sphericity and strength, good in toughness and good in wear resistance. Aluminum sol or other sintering aids are not required to be added, so that the sintering temperature is reduced on the premise of ensuring high purity, and the energy consumption is effectively reduced. And the mother liquor can be recycled, thereby reducing the use of organic solvents and being energy-saving and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic non-metallic material preparation, and relates to a dynamic and rapid method for preparing high-purity alpha alumina ceramic balls. Background Art

[0002] Alumina ceramic balls are the most widely used grinding and crushing carriers in the fields of ceramics, coatings and inks, and minerals. Different fields have different requirements for their size, grinding rate, and wear. The most common alumina balls 92 alumina balls and 96 alumina balls are often added with sintering aids and toughening phases such as silicon oxide, zirconium oxide, magnesium oxide, and calcium oxide to improve their wear resistance, hardness, and toughness. However, with the development of industry, some special fields such as new energy, electronic ceramics, semiconductors, and aerospace have strict requirements on the possible presence of substances with conductive and wave-absorbing properties, and there are also strict restrictions on the content of elements such as Na, K, Ca, Zr, Fe, Si, and Mg, which makes it difficult for current conventional alumina ceramic balls to meet these requirements.

[0003] At present, the common methods for preparing ceramic balls include ball rolling, cold isostatic pressing, extrusion molding, and titration molding. Among them, the ball rolling method is highly efficient and has a large output. It is currently a common molding method used by ceramic ball manufacturers, but it has technical problems such as uneven inside and outside of the spheres, shelling, and poor sphericity. In addition, the ball rolling process places extremely high demands on the cleanliness of the ball rolling machine and the cleanliness of the ball rolling chamber, which can easily introduce impurities. The cold isostatic pressing method has relatively good sphericity, but the production of larger spheres requires very high viscosity of the powder, and the production process is prone to cracking during sintering due to internal and external unevenness. This method is very inefficient in producing small balls, especially balls below 5 mm, which cannot be produced. Since the balls are prone to stress after isostatic pressing, the wear performance of the balls is poor. The extrusion molding method is generally used for catalyst carrier ceramic balls. The alumina balls prepared by it are mostly porous structures and are not suitable for grinding. Titration molding is a new molding method that has emerged in recent years. However, conventional titration molding has extremely high requirements for slurry solid content, dispersion, and solidification molding. It is very easy to break the emulsion, resulting in cracking and breakage of the spheres. Therefore, the current process for preparing alumina ceramic balls has not yet been reported to produce high-purity alpha alumina ceramic balls in large quantities. Summary of the Invention

[0004] Aiming at the problems existing in the production of traditional high-purity alpha alumina ceramic balls, the present invention proposes a novel dynamic and rapid method for preparing high-purity alpha alumina ceramic balls.

[0005] In order to achieve the above object, the present invention is implemented by adopting the following technical solutions: A dynamic and rapid method for preparing high-purity alpha alumina ceramic balls, the steps are as follows: (1) Add high-purity nano-alumina powder to water and mix evenly to obtain dispersion A, add dispersant and mix evenly to obtain dispersion B.

[0006] (2) Add the injection molding monomer to the dispersion B to obtain a titrant.

[0007] (3) The initiator is mixed with a non-polar solvent to obtain a mother liquor.

[0008] (4) Add the titrant dropwise into the mother liquor to obtain a mixed solution containing gel particles.

[0009] (5) The mixed liquid is filtered to obtain a spherical solid. The filtrate can be used as the recovered mother liquor to replace step (3) and directly used in step (4) for repeated use, which is energy-saving and environmentally friendly.

[0010] (6) After the spherical solid is dried, it is calcined at a high temperature of 1200-1400°C in an air atmosphere to obtain high-purity spherical alpha alumina particles.

[0011] The dispersant in step (1) is any one of polyacrylic acid, ammonium polyacrylate, and 0505K (NOF).

[0012] The injection molding monomer in step (2) is any one or more of acrylic amine, N-hydroxymethyl acrylamide, polyvinyl pyrrolidone / N-vinyl pyrrolidone, methyl methacrylate, and isobutylene maleic anhydride copolymer.

[0013] In step (3), the initiator is any one of ammonium persulfate, tetramethylethylenediamine, and hydrogen peroxide, and the non-polar solvent is any one of carbon tetrachloride, liquid paraffin, fatty oil, cyclohexane, and xylene.

[0014] Note that the injection molding monomer and initiator need to be used together. You can choose any of the following three combinations: When the injection molding monomer is acrylic amine or N-hydroxymethyl acrylamide, ammonium persulfate needs to be used as the initiator.

[0015] When the injection molding monomers are polyvinyl pyrrolidone / N-vinyl pyrrolidone and methyl methacrylate, tetramethylethylenediamine needs to be used as the initiator.

[0016] When the injection molding monomer is isobutylene maleic anhydride copolymer, hydrogen peroxide needs to be used as the initiator.

[0017] Preferably, the solid content of aluminum oxide in the dispersion A in step (1) is 30-90 wt %, and the pH is 3-6; the mass of the dispersant added accounts for 1-3% of the mass of the aluminum oxide powder.

[0018] Preferably, the mass of the injection molding monomer added in step (2) accounts for 1-10 wt% of the mass of the alumina powder.

[0019] Preferably, in step (3), the mass of the initiator accounts for 0-1 wt% of the mass of the non-polar solvent, and is not 0.

[0020] Preferably, the drying temperature in step (6) is 60-120°C.

[0021] When the aqueous alumina dispersion is dripped into a non-polar solvent, it is wrapped and formed into a sphere. At the same time, the monomer in the dispersion reacts with the initiator in the non-polar solvent to form a gel, and spherical alumina gel particles are gradually formed. The wrapping of the non-polar solvent ensures that the alumina forms a sphere, and the gel formed by the rapid reaction of the monomer and the initiator allows the alumina dispersion to solidify evenly in the dynamic process of contact and sinking in the non-polar solvent, so that the formed alumina sphere is not easy to crack. The size of the spherical alumina gel particles can be controlled by controlling the size of the titration device needle, the distance between the titrated liquid and the solvent liquid surface, the gel particle formation time and sedimentation time, etc. The present invention combines the emulsion method and injection molding on the basis of the titration spheroidization process. During the preparation process, the alumina dispersion is dripped into the non-polar solvent and is wrapped to form spherical droplets. At the same time, the monomer in the dispersion reacts chemically with the initiator in the non-polar solvent to form a three-dimensional network structure of the gel, so that the powder is solidified and not easy to loosen or crack. The gel curing process is dynamic and rapid, ensuring that the spheres are fully solidified before contact with other spheres, preventing adhesion and irregular shaped spheres. The product particle size can be adjusted within a range of 10-2000μm, with a regular spherical shape and uniform size distribution. The purity can reach over 99.99%, the sphericity is above 95%, and the density is over 99%. Its wear resistance is far superior to that of traditional ball rolling or isostatic pressing methods.

[0022] Compared with the prior art, the advantages and positive effects of the present invention are: 1. The process proposed in the present invention is based on titration molding, combined with emulsion method and injection molding, to produce ceramic balls with high purity, high sphericity, high strength, good toughness and good wear resistance.

[0023] 2. The entire process can control the ball size by controlling the needle size, titration speed, time of entry into the non-polar solvent, and solidification time, meeting the needs of producing ceramic balls of different diameters. Furthermore, because the solidification of the ball is a fully uniform chemical reaction, there is no internal or external unevenness or stress. The ceramic balls produced are easier to sinter and have better wear resistance.

[0024] 3. Using high-purity nano-alumina high-concentration dispersion, there is no need to add aluminum sol or other sintering aids, which reduces the sintering temperature while ensuring high purity and effectively reduces energy consumption.

[0025] 4. The mother liquor can be recycled, reducing the use of organic solvents and saving energy and protecting the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM image of the spherical product prepared in Example 1.

[0027] Figure 2 This is a photo of the spherical product prepared in Example 2.

[0028] Figure 3 This is the XRD characterization result of the spherical product prepared in Example 2. DETAILED DESCRIPTION

[0029] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below in conjunction with specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] The manufacturers and specifications of some raw materials in the following examples are as follows. The remaining raw materials not otherwise specified are conventional commercially available reagents used in the production process of alumina ceramic balls.

[0032] High-purity nano-alumina powder: purity 4N, particle size 200nm, provided by Guozhuang New Materials Technology (Jiangsu) Co., Ltd.

[0033] 0505K: NOC.

[0034] Alumina coarse powder: Chinalco, 10 microns.

[0035] Aluminum sol: Guozhuang New Material Technology (Jiangsu) Co., Ltd., solid content 20%, viscosity 10cp.

[0036] Example 1 Add 60g of high-purity nano-alumina powder to 40g of deionized water and stir at 200rpm for 30 minutes until uniformly mixed (pH around 4). Add 0.6g of dispersant 0505K (NOF) and stir at 300rpm for 30 minutes until thoroughly mixed and set aside. Add 0.9g of ammonium acrylate, a monomer for gel-injection molding, and continue stirring at 300rpm for 1 hour to obtain a titrant. Mix ammonium persulfate and cyclohexane at a mass ratio of 1:100, and take 1kg of the mother liquor for later use. Add the titrant to a titration apparatus equipped with a needle. In this example, a needle with an outlet diameter of 50μm and a length of 5cm is used. The diameter of the titrant in the syringe is 50μm. The titration rate is controlled at 3 drops / second. The distance between the needle and the mother liquor surface is 10cm, and the total mother liquor level is 30cm. During the dropwise addition process, the aqueous alumina dispersion is wrapped by cyclohexane to form a spherical shape. At the same time, the monomer acrylic amine in the dispersion reacts with the initiator ammonium persulfate in the cyclohexane to form a macromolecular network structure gel. As the gel gradually forms, the wrapped spherical alumina dispersion solidifies to form gel particles. After the dropwise addition is completed, the solid particles are screened and filtered using a sieve to remove excess mother liquor to obtain wet gel particles. The wet gel particles are placed in an oven, first blown at room temperature for 6 hours to remove the surface solvent (air, flow rate 100L / min), and then dried at 80°C for 6 hours to obtain dry gel particles. The dried gel particles are placed in a high-temperature atmosphere furnace, air is introduced at a flow rate of 10L / min, the temperature is increased to 1300°C at a rate of 20°C / min, calcined for 1 hour, and then naturally cooled to room temperature to obtain high-purity spherical alpha alumina particles. After testing, the true density of the spherical particles reached 3.92g / cm 3 The particle size is concentrated in the range of 60-100 μm, with uniform distribution, purity of more than 99.99%, and sphericity of more than 95%. 50g of the balls are added to a sand mill, the linear speed is controlled at 10m / s, 50g of alumina sand with a particle size of 10 microns is added, and the grinding is carried out for 2h. The loss is 200ppm / h. The SEM image of the granular product prepared in this embodiment is shown in the attached figure. Figure 1 shown.

[0037] Example 2 The process of Example 1 is consistent with that of Example 1 where no special instructions are given in this embodiment. 400g of high-purity alumina particles are added to 100g of deionized water and stirred at 200rpm for 30min. 4g of NOF 0505K dispersant is added and stirred at 200rpm for 1h to mix thoroughly. At this time, the slurry viscosity is slightly large. 12g of acrylic amine is added and stirred at 200rpm for 1h to obtain a titrant. Ammonium persulfate and cyclohexane are mixed in a mass ratio of 1:100 and 5kg is taken as a mother liquor for standby use. The titrant is added to a titration apparatus with a needle. In this embodiment, a needle with an outlet diameter of 500 microns and a needle length of 5cm is used. The diameter of the titrant in the syringe is 500μm. The titration rate is controlled to 2 drops / second. The distance between the needle and the mother liquor liquid level is 50cm, and the total liquid level of the mother liquor is 100cm. After the addition is complete, the solid particles are sieved and filtered using a screen to remove excess mother liquor to obtain wet gel particles. The wet gel particles were placed in an oven, first blown at room temperature for 6 hours to remove the surface solvent, and then dried at 80°C for 6 hours to obtain dry gel particles. The dried gel particles were placed in a high-temperature atmosphere furnace, air was introduced at a flow rate of 100L / min, and the temperature was increased to 1350°C at a rate of 20°C / min. They were calcined for 1.5 hours to obtain high-purity spherical alpha alumina particles, which were naturally cooled to room temperature to obtain the product. After testing, the true density of the spherical particles reached 3.90g / cm 3 The particle size is 1.5 mm, the distribution is uniform, the purity is above 99.99%, and the sphericity is higher than 95%. 50 g of the balls are added to a sand mill, the linear speed is controlled at 10 m / s, and 50 g of alumina sand is added to grind, and the loss is 1000 ppm / h. The particles prepared in this embodiment are shown in the attached photo. Figure 2 As shown, the XRD test results of the spherical product are as follows Figure 3 As shown, from Figure 3 It can be seen that the ball has been completely sintered into the alpha phase.

[0038] The spherical product prepared in this example was further tested for purity, and the results are shown in Table 1 below.

[0039] Table 1 Purity test report of high purity alpha alumina ceramic balls From the test results in Table 1 above, it can be seen that the purity of the alpha alumina ceramic balls obtained in this embodiment reaches 99.99%.

[0040] Example 3 The present embodiment is not specifically described, and the process is consistent with that of Example 1. 400g of high-purity alumina particles are added to 100g of deionized water, stirred at 200rpm for 30min, 4g of NOF 0505K dispersant is added, and stirring is continued at 200rpm for 1h. Mix thoroughly until the slurry viscosity is slightly higher. 12g of methyl methacrylate is added, and stirring is continued at 200rpm for 1h to obtain a titrant. Tetramethylethylenediamine and liquid paraffin are mixed in a mass ratio of 1:100, and 5kg is taken as a mother liquor for standby use. The titrant is added to a titration apparatus with a needle. In this embodiment, a needle with an outlet diameter of 500 microns and a needle length of 5cm is used. The diameter of the titrant in the syringe is 500 microns. The titration rate is controlled to 2 drops / second, and the distance between the needle and the mother liquor liquid level is 50cm. The total liquid level of the mother liquor is 100cm. After the addition is completed, the solid particles are screened and filtered using a sieve to remove excess mother liquor to obtain wet gel particles. The wet gel particles are placed in an oven, first blown at room temperature for 6 hours to remove the surface solvent, and then dried at 80°C for 6 hours to obtain dry gel particles. The dry gel particles are placed in a high-temperature atmosphere furnace, air is introduced at a flow rate of 100L / min, and the temperature is increased to 1350°C at a rate of 20°C / min, and calcined for 1.5 hours to obtain high-purity spherical alpha alumina particles. After testing, the true density of the spherical particles reached 3.90g / cm 3 The particle size is 1.2mm, evenly distributed, with a purity of more than 99.99% and a sphericity higher than 95%. 50g of the ball is added to the sand mill at a linear speed of 10m / s and ground with 50g of 10-micron alumina sand. The loss is 800ppm / h.

[0041] Example 4 The present embodiment is consistent with the process of Example 1 where no special instructions are given. 400g of high-purity alumina particles are added to 100g of deionized water and stirred at 200rpm for 30min. 4g of polyacrylic acid dispersant is added and stirred at 200rpm for 1h to mix thoroughly. At this time, the slurry viscosity is slightly larger. 12g of acrylic amine is added and stirred at 200rpm for 1h to obtain a titrant. Ammonium persulfate and carbon tetrachloride are mixed in a mass ratio of 1:100 and 5kg is taken as a mother liquor for standby use. The titrant is added to a titration apparatus with a needle. In this embodiment, a needle with an outlet diameter of 500 microns is used. The diameter of the titrant in the needle tube with a length of 5cm is 500 microns. The titration rate is controlled to 2 drops / second. The distance between the needle and the mother liquor liquid level is 50cm, and the total liquid level of the mother liquor is 100cm. After the addition is complete, the solid particles are sieved and filtered using a screen to remove excess mother liquor to obtain wet gel particles. The wet gel particles were placed in an oven and first blown at room temperature for 6 hours to remove the surface solvent, and then dried at 80°C for 6 hours to obtain dry gel particles. The dried gel particles were placed in a high-temperature atmosphere furnace, air was introduced at a flow rate of 10L / min, and the temperature was increased to 1350°C at a rate of 20°C / min. They were calcined for 1.5 hours to obtain high-purity spherical alpha alumina particles. After testing, the true density of the spherical particles reached 3.90g / cm 3 The particle size is 1.5mm, evenly distributed, with a purity of more than 99.99% and a sphericity higher than 95%. 50g of the ball is added to a sand mill at a linear speed of 10m / s and ground with 10-micron alumina sand. The loss is 1200ppm / h.

[0042] Example 5 In this example, the mother liquor filtered from Example 1 was reused and supplemented to 1 kg with fresh mother liquor having a mass ratio of ammonium persulfate to cyclohexane of 1:100. The remaining preparation process remained the same as in Example 1. Testing showed that no significant change in product performance was observed after the mother liquor was recycled and reused five times.

[0043] Comparative Example 1 This comparative example differs from Example 1 in that acrylated amine is omitted from the mother liquor and replaced entirely with an equal volume of cyclohexane. All other conditions remain unchanged. Testing has shown that when the titrant from this comparative example is added to cyclohexane, the aqueous alumina dispersion can be encapsulated into spheres, but complete solidification is not achieved. After forced air drying and oven drying at 80°C, the gel spheres exhibit adhesion and cracking.

[0044] Comparative Example 2 The difference between this comparative example and Example 1 is that, during the titration process, ammonium acrylate is not added to the dispersion, but 0.9g of aluminum sol is added instead, and ammonium persulfate is replaced with the same mass of tetramethylammonium hydroxide in the mother liquor. After testing, the aqueous alumina dispersion can be wrapped by cyclohexane to form a spherical shape after being added dropwise, but the aluminum sol in the alumina encounters tetramethylammonium hydroxide, and the gradual gelation process is slow. It takes at least 12 hours to gradually form gel particles after the titration is completed. After filtering, the gel particles are dried with forced air and dried, and the obtained dry gel balls show adhesion and cracking.

[0045] Comparative Example 3 The difference between this comparative example and Example 1 is that 70 g of pure water is added to 30 g of alumina powder. At this time, the concentration of the alumina dispersion is lower. Other factors remain unchanged. The true density of the prepared spherical particles is only 3.90 g / cm 3 The particle size is 40-60 μm, with a high shrinkage rate, a purity of over 99.99%, and a sphericity of over 95%. When 50 g of these balls are added to a sand mill at a linear speed of 10 m / s, grinding with 10-micron sand alumina material, the loss is 1000 ppm / h. This indicates that when the solid content of the alumina dispersion is reduced, the ideal process effect cannot be achieved.

[0046] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A dynamic and rapid method for preparing high-purity alpha alumina ceramic balls, characterized in that: Here are the steps: (1) High-purity nano-alumina powder is added to water and mixed uniformly to obtain dispersion A, and a dispersant is added and mixed uniformly to obtain dispersion B; (2) Adding the injection molding monomer to the dispersion B to obtain a titrant; (3) mixing the initiator with a non-polar solvent to obtain a mother liquor; (4) Add the titrant dropwise to the mother liquor to obtain a mixed solution containing gel particles; (5) Filter the mixed solution to obtain a spherical solid; (6) After drying the spherical solid, calcining it at 1200-1400°C to obtain high-purity spherical alpha alumina particles; The dispersant in step (1) is any one of polyacrylic acid, ammonium polyacrylate, and 0505K; The injection molding monomer in step (2) is any one or more of acrylic amine, N-hydroxymethyl acrylamide, polyvinyl pyrrolidone / N-vinyl pyrrolidone, methyl methacrylate, and isobutylene maleic anhydride copolymer; In step (3), the initiator is any one of ammonium persulfate, tetramethylethylenediamine, and hydrogen peroxide, and the non-polar solvent is any one of carbon tetrachloride, liquid paraffin, fatty oil, cyclohexane, and xylene.

2. The method for preparing dynamic and rapid high-purity alpha alumina ceramic balls according to claim 1, characterized in that: In step (1), the solid content of aluminum oxide in the dispersion A is 30-90 wt % and the pH is 3-6; the mass of the added dispersant accounts for 1-3% of the mass of the aluminum oxide powder.

3. The method for preparing dynamic and rapid high-purity alpha alumina ceramic balls according to claim 1, characterized in that: The mass of the injection molding monomer added in step (2) accounts for 1-10wt% of the mass of the alumina powder.

4. The method for preparing dynamic and rapid high-purity alpha alumina ceramic balls according to claim 1, characterized in that: In step (3), the mass of the initiator accounts for 0-1 wt% of the mass of the non-polar solvent and is not 0.

5. The method for preparing dynamic and rapid high-purity alpha alumina ceramic balls according to claim 1, characterized in that: The drying temperature in step (6) is 60-120°C.

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