Method for preparing large-size ceramic part through 3D printing

Abstract

The invention discloses a method for preparing a large-size ceramic part by utilizing 3D printing, which comprises the following steps: weighing ceramic powder, a dispersing agent, an isobutylene-maleic anhydride copolymer, acrylamide and N, N-dimethylformamide; the preparation method comprises the following steps: mixing and ball-milling N, N, N ', N'-tetramethylethylenediamine and ammonium persulfate into ceramic slurry to obtain ceramic slurry, adding N, N, N ', N'-tetramethylethylenediamine and ammonium persulfate into the ceramic slurry, continuously ball-milling, defoaming the obtained slurry, pouring the slurry into a charging barrel, sealing and baking to obtain printing feed, performing screw extrusion printing by adopting direct-writing 3D printing equipment to obtain a wet blank, and performing secondary gelling and drying on the wet blank to obtain the 3D printing material. And sintering the green body to obtain a ceramic blank, and carrying out precision machining and polishing to obtain the large-size ceramic part. According to the method, the printing working stroke is large, the printing feeding binder content is low, the solid content is high, cracking is not prone to occurring in the drying and sintering process, and rapid and safe preparation of large-size ceramic parts can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic parts preparation, and in particular to a method for preparing large-size ceramic parts by using 3D printing. Background Art

[0002] With the rapid development of modern science and technology, new requirements have been put forward for materials in the field of cutting-edge manufacturing. Ceramics not only have excellent thermodynamic properties and stable physical and chemical properties, but also have unique properties in the fields of light, electricity, biology, etc., and have been widely used in aerospace, new energy, biomedicine and other fields. However, ceramics are difficult to process due to their hard and brittle characteristics. Traditional manufacturing technology is difficult to prepare ceramic products with complex and special-shaped structures, and the cost is high and the preparation cycle is long, which cannot meet the needs of modern industry for product diversification and rapid market response.

[0003] Ceramic 3D printing technology has essentially changed the traditional manufacturing technology of turning, planing, milling, grinding and other processing techniques. 3D printing technology is based on a three-dimensional digital information model. Through a layer-by-layer processing method, the 3D printing raw materials are first shaped and then sintered. It has obvious advantages in lightweight simulation design and integrated preparation and molding of complex structural ceramic parts. In addition, this technology has the advantages of simple preparation process, short cycle and low cost, which reduces the time and economic cost of product development.

[0004] However, in the 3D printing of large-sized ceramic parts, the drastic temperature changes in the printing process of laser energy-based technologies such as SLS and SLM often lead to the formation of cracks and residual stress. FDM, DLP and DIW technologies often require the addition of a large amount of organic binders and other ingredients, which will also cause cracks and other defects in the subsequent drying and debinding process, and the density after sintering is low, which greatly hinders the application of 3D printing technology on large-sized ceramic parts. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing large-sized ceramic parts using 3D printing, which has a large working stroke, low feed binder content, high solid content, is not easy to crack during drying and sintering, and can realize rapid and safe preparation of large-sized ceramic parts.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] A method for preparing large-size ceramic parts by 3D printing comprises the following steps:

[0008] (1) Weighing ceramic powder, dispersant, isobutylene-maleic anhydride copolymer, acrylamide, N,N'-methylenebisacrylamide and water, mixing and ball-milling to obtain a ceramic slurry, wherein, by mass fraction, the ceramic powder is 70% to 90%, the dispersant is 0 to 1%, the isobutylene-maleic anhydride copolymer is 0.1% to 0.4%, the acrylamide is 0.5% to 2%, the N,N'-methylenebisacrylamide is 0.05% to 0.2%, and the water is 9% to 29%;

[0009] (2) adding N,N,N',N'-tetramethylethylenediamine and ammonium persulfate to the ceramic slurry, continuing ball milling, defoaming the obtained slurry, and then pouring it into a barrel, sealing the barrel and baking it to solidify the slurry gel to obtain a printing feed;

[0010] (3) connecting the above-mentioned barrel containing the printing feed to the direct writing 3D printing device, importing the printing model, and using a screw extrusion printing method to prepare a wet blank, wherein at least one dimension of the model is ≥50 cm;

[0011] (4) The obtained wet blank is subjected to secondary gelation, and the wet blank after the secondary gelation is dried until the weight no longer changes to obtain a green blank, and the green blank is sintered to obtain a ceramic blank, which is then precisely processed and polished to obtain a large-sized ceramic part.

[0012] In the above-mentioned method for preparing large-size ceramic parts by 3D printing, preferably, in step (1), the ball milling medium is one of alumina balls, zirconia balls and silicon nitride balls, the material ball mass ratio is 1:2-3, and the ball milling time is 3h-24h; in step (2), the ball milling time is 5min-10min.

[0013] In the above-mentioned method for preparing large-size ceramic parts by 3D printing, preferably, in step (1), the isobutylene-maleic anhydride copolymer includes one or more of Isobam-104, Isobam-104-WS and Isobam-600-AF, the dispersant includes one of ammonium citrate, ammonium polyacrylate and tetramethylammonium hydroxide, and the ceramic powder includes one or more of aluminum oxide powder, silicon nitride powder, magnesium oxide powder and yttrium oxide powder.

[0014] In the above-mentioned method for preparing large-size ceramic parts by 3D printing, preferably, in step (2), the mass of the N,N,N',N'-tetramethylethylenediamine is 0.01% to 0.1% of the mass of the ceramic slurry, and the mass of the ammonium persulfate is 0.01% to 0.1% of the mass of the ceramic slurry.

[0015] In the above method for preparing large-sized ceramic parts by 3D printing, preferably, in step (2), the baking temperature is 40° C. to 70° C., and the baking time is 0.5 h to 2 h.

[0016] In the above-mentioned method for preparing large-sized ceramic parts by 3D printing, preferably, in step (3), the speed of the screw extrusion printing is 10 mm / s to 30 mm / s.

[0017] In the above-mentioned method for preparing large-size ceramic parts by 3D printing, preferably, in step (4), the secondary gelation is carried out in a low-temperature and humid environment, the temperature of the low-temperature and humid environment is 20°C to 40°C, the humidity of the low-temperature and humid environment is 30% to 80%, and the drying temperature system is first dried at 20°C to 40°C for 12h to 48h, then dried at 50°C to 70°C for 12h to 48h, and then dried at 80°C to 100°C for 12h to 48h.

[0018] In the above-mentioned method for preparing large-size ceramic parts by 3D printing, preferably, in step (4), the sintering temperature is 1400°C to 2000°C, the sintering method is one of gas pressure sintering, normal pressure sintering and hot pressing sintering, the atmosphere of the gas pressure sintering is nitrogen or argon, the atmosphere of the hot pressing sintering is nitrogen or argon, and the atmosphere of the normal pressure sintering is air.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] The present invention provides a method for preparing large-sized ceramic parts by 3D printing. The method has a large working stroke and can meet the needs of fast printing of large-sized ceramic parts. In the prior art, acrylamide system and ISOBAM have not been applied to DIW3D printing. The applicant found that when a large-sized green body is prepared by simply using the acrylamide system, if more acrylamide is added, the strength after curing is high and the viscosity is large, which is not suitable for DIW3D printing process. If less acrylamide is added, the viscosity is appropriate and suitable for DIW3D printing, but the wet green body has low strength and is very easy to crack during the drying process. If the ISOBAM system is used alone, the organic additive content is small and it is easy to dry, which can be used to prepare large-sized ceramic parts, but the gel time of ISOBAM is slow, the gel network is broken after extrusion, the viscosity decreases, and it is difficult to achieve fast gelation, which is not suitable for DIW3D printing. Therefore, the present invention uses the ISOBAM gel system and the acrylamide gel system in a coordinated manner, utilizes the acrylamide system to achieve rapid gelation, obtains a printing feed with a suitable viscosity, and can effectively prevent powder sedimentation during the ISOBAM gel process, thereby realizing DIW3D printing of large-sized blanks. After printing, the ISOBAM secondary gel provides strength for the wet blank, and can achieve safe drying of large-sized ceramic parts, and finally obtain large-sized ceramic parts after sintering. DETAILED DESCRIPTION

[0021] 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.

[0022] Example 1

[0023] A method for preparing large-sized ceramic parts by 3D printing of the present invention comprises the following steps:

[0024] (1) Weigh 5000 g of alumina powder, 15 g of ammonium citrate, 15 g of Isobam-104, 60 g of acrylamide, 6 g of N,N'-methylenebisacrylamide, and 1120 g of deionized water, place them in a ball mill and mix and ball mill them to obtain a ceramic slurry. The ball milling medium is alumina balls, wherein the mass ratio of material to ball is 1:2, and the ball milling time is 10 h.

[0025] (2) Add 0.7 g of N,N,N',N'-tetramethylethylenediamine and 1.8 g of ammonium persulfate to the ceramic slurry and continue ball milling for 5 min. Pour out the ball-milled slurry and place it in a vacuum degassing machine for degassing. After degassing, pour it into a barrel, seal the barrel and place it in an oven for baking at 60°C for 1 h to solidify the slurry gel (acrylamide cross-linking) to obtain printing feed.

[0026] (3) The barrel containing the printing feed is connected to the direct writing 3D (DIW3D) printing equipment through a pipeline, and the printing model is introduced. The wet blank is prepared by screw extrusion printing. The printing speed is 15 mm / s. The printing model is a cylindrical structure (i.e., a cylindrical structure for semiconductor equipment) with a diameter of 60 cm, a height of 30 cm, and a wall thickness of 2.2 cm.

[0027] (4) The wet blank is placed in a low temperature and humid environment for secondary gelation (mainly Isobam gelation process), the temperature of the low temperature and humid environment is 25°C, the humidity is 40%, and the time is 48 hours. The wet blank after secondary gelation is transferred to an oven for drying until the weight no longer changes, and a green blank is obtained. The baking system is 30°C×24h+60°C×24h+90°C×12h. The dried green blank is placed in a sintering furnace for sintering. The sintering method adopts normal pressure sintering, the atmosphere is air atmosphere, and the sintering temperature is 1600°C to obtain a ceramic blank. After precision machining and polishing of the ceramic blank using a CNC machine tool, a large-sized alumina ceramic part is obtained.

[0028] Example 2

[0029] A method for preparing large-sized ceramic parts by 3D printing of the present invention comprises the following steps:

[0030] (1) Weigh 5000 g of alumina powder, 15 g of ammonium citrate, 10 g of ISOBAM-104, 5 g of Isobam-600-AF, 45 g of acrylamide, 4.5 g of N,N'-methylenebisacrylamide, and 1050 g of deionized water, place them in a ball mill and mix and ball mill them to obtain a ceramic slurry, wherein the ball milling medium is alumina balls, the material: ball mass ratio is 1:2, and the ball milling time is 10 h.

[0031] (2) Add 0.7 g of N,N,N',N'-tetramethylethylenediamine and 1.8 g of ammonium persulfate to the ceramic slurry and continue ball milling for 5 min. Pour out the ball-milled slurry and place it in a vacuum degassing machine for degassing. After degassing, pour it into a barrel, seal the barrel and place it in an oven for baking at 60°C for 1 h to solidify the slurry gel (acrylamide cross-linking) to obtain printing feed.

[0032] (3) The barrel containing the printing feed is connected to the direct writing 3D printing device through a pipeline, the printing model is introduced, and the wet blank is prepared by screw extrusion. The printing speed is 12 mm / s. The printing model is the same as the model in Example 1.

[0033] (4) Place the wet blank in a low temperature and humid environment for secondary gelation. The temperature of the low temperature and humid environment is 25°C, the humidity is 40%, and the time is 60 hours. Transfer the wet blank after secondary gelation to an oven for drying until the weight no longer changes to obtain a green blank. The baking system is 30°C×24h+60°C×24h+90°C×12h. Place the dried green blank in a sintering furnace for sintering. The sintering method is normal pressure sintering. The atmosphere is an air atmosphere and the temperature is 1600°C to obtain a ceramic blank. Use a CNC machine tool to perform precision processing and polishing on the ceramic blank to obtain a large-sized alumina ceramic part.

[0034] Example 3

[0035] A method for preparing large-sized ceramic parts by 3D printing of the present invention comprises the following steps:

[0036] (1) 5000 g of alumina powder, 25 g of tetramethylammonium hydroxide, 10 g of ISOBAM-104 (isobutylene-maleic anhydride copolymer), 5 g of Isobam-600-AF, 50 g of acrylamide, 5 g of N,N'-methylenebisacrylamide, and 1080 g of deionized water were weighed and placed in a ball mill to obtain a ceramic slurry. The ball milling medium was alumina balls, the material: ball mass ratio was 1:3, and the ball milling time was 10 h.

[0037] (2) Add 1g N,N,N',N'-tetramethylethylenediamine and 2g ammonium persulfate to the ceramic slurry and continue ball milling for 5 minutes. Pour out the ball-milled slurry and place it in a vacuum degassing machine for degassing. After degassing, pour it into a barrel. After sealing the barrel, place it in an oven for baking at 60°C for 1 hour to solidify the slurry gel (acrylamide cross-linking) to obtain printing feed.

[0038] (3) The barrel containing the printing feed is connected to the direct writing 3D printing device through a pipeline, the printing model is introduced, and the wet blank is prepared by screw extrusion. The printing speed is 15 mm / s, and the printing model is the same as the model in Example 1.

[0039] (4) Place the wet blank in a low temperature and humid environment for secondary gelation. The temperature of the low temperature and humid environment is 25°C, the humidity is 40%, and the time is 40 hours. Transfer the wet blank after secondary gelation to an oven for drying until the weight no longer changes to obtain a green blank. The baking system is 30°C×24h+60°C×24h+90°C×12h. Place the dried green blank in a sintering furnace for sintering. The sintering method is normal pressure sintering. The atmosphere is air atmosphere and the sintering temperature is 1600°C to obtain a ceramic blank. After precision machining and polishing the ceramic blank using a CNC machine tool, a large-sized alumina ceramic part is obtained.

[0040] Example 4

[0041] A method for preparing large-sized ceramic parts by 3D printing of the present invention comprises the following steps:

[0042] (1) Weigh 5100 g of silicon nitride powder, 250 g of magnesium oxide powder, 250 g of yttrium oxide powder, 35 g of tetramethylammonium hydroxide, 10 g of Isobam-104, 5 g of Isobam-600-AF, 130 g of acrylamide, 13 g of N,N'-methylenebisacrylamide, and 2200 g of deionized water in a ball mill to obtain a ceramic slurry. The ball milling medium is silicon nitride balls, the material: ball mass ratio is 1:3, and the ball milling time is 15 h.

[0043] (2) Add 1g N,N,N',N'-tetramethylethylenediamine and 3g ammonium persulfate to the ceramic slurry and continue ball milling for 5 minutes. Pour out the ball-milled slurry and place it in a vacuum degassing machine for degassing. After degassing, pour it into a barrel, seal the barrel and place it in an oven for baking at 60°C for 1 hour to solidify the slurry gel (acrylamide cross-linking) to obtain printing feed.

[0044] (3) The barrel containing the printing feed is connected to the direct writing 3D printing device through a pipeline, the printing model is introduced, and the wet blank is prepared by screw extrusion. The printing speed is 15 mm / s, and the printing model is the same as the model in Example 1.

[0045] (4) The wet blank is placed in a low temperature and humid environment for secondary gelation. The temperature of the low temperature and humid environment is 25°C, the humidity is 40%, and the time is 60 hours. The wet blank after secondary gelation is transferred to an oven for drying until the weight no longer changes to obtain a green blank. The baking system is 30°C×48h+60°C×24h+90°C×12h. The dried green blank is placed in a sintering furnace for sintering. The sintering method is gas pressure sintering. The atmosphere is a nitrogen atmosphere. The sintering temperature is 1850°C and the air pressure is 2.5MPa to obtain a ceramic blank. The ceramic blank is precision machined and polished using a CNC machine tool to obtain large-sized silicon nitride ceramic parts.

[0046] Comparative Example 1

[0047] A method for preparing large-sized ceramic parts is basically the same as Example 1, except that 150 g of hydroxyethyl cellulose is used instead of acrylamide and Isobam-104. As a result, the ceramic parts are dried and cracked, and no ceramic parts can be prepared.

[0048] Comparative Example 2

[0049] A method for preparing large-sized ceramic parts is substantially the same as that of Example 1, except that 400 g of hydroxyethyl cellulose is used instead of acrylamide and Isobam-104.

[0050] Comparative Example 3

[0051] A method for preparing large-sized ceramic parts is substantially the same as that of Example 4, except that 500 g of hydroxyethyl cellulose is used instead of acrylamide, Isobam-104 and Isobam-600-AF.

[0052] Comparative Example 4

[0053] A method for preparing large-sized ceramic parts is basically the same as Example 1, except that acrylamide is replaced by Isobam-104, which cannot be molded due to its low viscosity.

[0054] Comparative Example 5

[0055] A method for preparing large-sized ceramic parts is basically the same as Example 1, except that Isobam-104 is replaced with acrylamide, which will cause drying and cracking.

[0056] Table 1 Ceramic parts performance test table of Examples 1-4 and Comparative Examples 2-3

[0057] Relative density (%) Vickers hardness(GPa) Flexural strength(MPa) Is it dry and cracked? Example 1 99.3 16.4 395 no Example 2 99.4 16.6 416 no Example 3 99.4 16.7 423 no Example 4 99 14.3 871 no Comparative Example 2 95.7 13.6 192 no Comparative Example 3 94.3 11.7 377 no

[0058] As can be seen from Table 1, the large-sized alumina ceramics of Examples 1-3 have a density of at least 99.3%, a bending strength of at least 395 MPa, and a Vickers hardness of at least 16.4 GPa. The large-sized silicon nitride ceramics of Example 4 have a density of 99%, a hardness of 14.3 GPa, and a bending strength of 871 MPa, and none of them cracks due to drying. Compared with Example 1, Comparative Example 1 has a higher binder content, but it cracks directly during the drying process and cannot be subjected to the subsequent sintering step; the large-sized alumina ceramics provided by Examples 1-3 have significantly improved mechanical properties compared to the alumina ceramics provided by Comparative Example 2, mainly because more binders are added in Comparative Example 2 to prevent drying and cracking, resulting in insufficient sintering density and poor mechanical properties. For the same reason, the large-sized silicon nitride ceramics provided by Example 4 also have significantly improved mechanical properties and density compared to the silicon nitride ceramics provided by Comparative Example 3. Therefore, the method for preparing large-sized ceramic parts by 3D printing provided by the present invention can prepare ceramic parts with excellent mechanical properties and complex shapes. Compared with traditional DIW printing technology, the method provided by the present invention effectively avoids the generation of drying defects, reduces the binder content, improves the density and mechanical properties of ceramic parts, and can achieve the safe preparation of large-sized heterogeneous ceramic parts. Compared with ceramic parts prepared by traditional methods, the method provided by the present invention has a simple process, is suitable for industrial production and can save a lot of processing costs.

[0059] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with 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 without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of 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 large-size ceramic parts using 3D printing, characterized in that: The following steps are involved: (1) Weighing ceramic powder, dispersant, isobutylene-maleic anhydride copolymer, acrylamide, N,N'-methylenebisacrylamide and water, mixing and ball-milling to obtain a ceramic slurry, wherein, by mass fraction, the ceramic powder is 70% to 90%, the dispersant is 0 to 1%, the isobutylene-maleic anhydride copolymer is 0.1% to 0.4%, the acrylamide is 0.5% to 2%, the N,N'-methylenebisacrylamide is 0.05% to 0.2%, and the water is 9% to 29%; (2) adding N,N,N',N'-tetramethylethylenediamine and ammonium persulfate to the ceramic slurry, continuing ball milling, degassing the obtained slurry, and then pouring it into a barrel, sealing the barrel and baking it to solidify the slurry gel to obtain a printing feed; (3) connecting the above-mentioned barrel containing the printing feed to the direct writing 3D printing device, importing the printing model, and using a screw extrusion printing method to prepare a wet blank, wherein at least one dimension of the model is ≥50 cm; (4) The obtained wet blank is subjected to secondary gelation, and the wet blank after the secondary gelation is dried until the weight no longer changes to obtain a green blank, and the green blank is sintered to obtain a ceramic blank, which is then precisely processed and polished to obtain a large-sized ceramic part.

2. The method for preparing large-size ceramic parts by 3D printing according to claim 1, characterized in that: In step (1), the ball milling medium is one of alumina balls, zirconium oxide balls and silicon nitride balls, the material-ball mass ratio is 1:2-3, and the ball milling time is 3h-24h; in step (2), the ball milling time is 5min-10min.

3. The method for preparing large-size ceramic parts by 3D printing according to claim 1, characterized in that: In step (1), the isobutylene-maleic anhydride copolymer includes one or more of Isobam-104, Isobam-104-WS and Isobam-600-AF, the dispersant includes one of ammonium citrate, ammonium polyacrylate and tetramethylammonium hydroxide, and the ceramic powder includes one or more of aluminum oxide powder, silicon nitride powder, magnesium oxide powder and yttrium oxide powder.

4. The method for preparing large-size ceramic parts by 3D printing according to claim 1, characterized in that: In step (2), the mass of the N,N,N',N'-tetramethylethylenediamine is 0.01% to 0.1% of the mass of the ceramic slurry, and the mass of the ammonium persulfate is 0.01% to 0.1% of the mass of the ceramic slurry.

5. The method for preparing large-size ceramic parts by 3D printing according to any one of claims 1 to 4, characterized in that: In step (2), the baking temperature is 40° C. to 70° C., and the baking time is 0.5 h to 2 h.

6. The method for preparing large-size ceramic parts by 3D printing according to any one of claims 1 to 4, characterized in that: In step (3), the speed of the screw extrusion printing is 10 mm / s to 30 mm / s.

7. The method for preparing large-size ceramic parts by 3D printing according to any one of claims 1 to 4, characterized in that: In step (4), the secondary gelation is carried out in a low-temperature and humid environment, the temperature of the low-temperature and humid environment is 20°C to 40°C, the humidity of the low-temperature and humid environment is 30% to 80%, and the drying temperature system is first drying at 20°C to 40°C for 12h to 48h, then drying at 50°C to 70°C for 12h to 48h, and then drying at 80°C to 100°C for 12h to 48h.

8. The method for preparing large-size ceramic parts by 3D printing according to any one of claims 1 to 4, characterized in that: In step (4), the sintering temperature is 1400°C to 2000°C, and the sintering method is one of gas pressure sintering, normal pressure sintering and hot pressing sintering. The atmosphere of the gas pressure sintering is nitrogen or argon, the atmosphere of the hot pressing sintering is nitrogen or argon, and the atmosphere of the normal pressure sintering is air.