CN113105244A

CN113105244A - Extrusion molding 3D printing silicon carbide ceramic and preparation method thereof

Info

Publication number: CN113105244A
Application number: CN202110326698.6A
Authority: CN
Inventors: 黄政仁; 陈健; 陈忠明; 朱云洲; 姚秀敏; 刘雷敏
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2021-03-26
Filing date: 2021-03-26
Publication date: 2021-07-13

Abstract

The invention discloses an extrusion molding 3D printing silicon carbide ceramic and a preparation method thereof. The preparation method comprises the following steps: (1) granulating; (2) mixing: adding a first adhesive into the silicon carbide particles and uniformly mixing to obtain a pug with good plasticity; the first binder is cured at room temperature and melted at a temperature of 60 ℃ or higher to bond the silicon carbide particles to each other; (3) printing and forming; (4) degreasing: degreasing the printed biscuit to obtain a prefabricated body; (5) densification: and sintering the prefabricated body at normal pressure or carrying out vacuum siliconizing treatment to obtain the silicon carbide ceramic. The preparation method can realize the preparation of large-size SiC parts and simultaneously avoid the cracking of the parts caused by the existence of stress in the forming process.

Description

Extrusion molding 3D printing silicon carbide ceramic and preparation method thereof

Technical Field

The invention relates to the technical field of 3D printing, in particular to the field of 3D printing and forming of SiC (silicon carbide) ceramic materials, and particularly relates to an extrusion-formed 3D printed SiC ceramic and a preparation method thereof.

Background

Silicon carbide (SiC) has the characteristics of small atomic radius, long bond, strong covalent property and the like, thereby having excellent mechanical, chemical, thermal and electrical properties, simultaneously having the characteristics of radiation resistance, radioactive resistance, wave absorption and the like, being an important nuclear reactor neutron irradiation resistant material and wave absorption stealth material, and thus being widely concerned by people. Among ceramic materials, SiC has the most excellent chemical stability and high-temperature phase stability, and is the only ceramic material that can resist corrosion by hydrofluoric acid. Meanwhile, the electrical property of SiC can be adjusted by doping from an insulating material, a semiconductor material to a conductor, so that the SiC ceramic can be used as an electronic component under a severe operating environment condition. Due to its excellent physicochemical properties, SiC ceramics outperform other commercial ceramics or metal alloys, including many ultra-high temperature alloy materials, in corrosive environments, extreme wear conditions, or at temperatures in excess of 1400 ℃. At present, SiC ceramics are applied in various industries such as aviation, aerospace, nuclear industry and the like, and comprise the following components: mirrors for optical applications, heat exchangers, microchannel reactors, semiconductor hardware (chuck/rail/platform), high power devices, and the like.

Because the conventional SiC ceramic has higher hardness, the conventional SiC ceramic needs to be processed by diamond, and the processing and forming are more difficult. Meanwhile, the poor conductivity of the SiC ceramic is difficult to meet the requirements of electric spark machining, and the difficulty in realizing the rapid and precise machining of the SiC ceramic is one of the main bottlenecks which restrict the application of the SiC ceramic.

Based on the above disadvantages, SiC ceramic preparation combined with 3D printing technology becomes the main development direction of current research and application. The 3D printing technology is an additive manufacturing technology which is completely opposite to the traditional material processing method, and is characterized in that materials such as ceramic powder, resin, metal powder and the like are subjected to layered processing, stacking and bonding through a software layered dispersion and numerical control forming system on the basis of the design of a three-dimensional digital model, and finally, a three-dimensional entity is manufactured through superposition forming. Compared with the traditional manufacturing method, the 3D printing technology saves raw materials, is beneficial to rapid manufacturing of complex structures, shortens the research and development period, is more suitable for production of personalized products, and is widely applied to the fields of biomedicine, tissue engineering, automobile parts, aerospace, micro-nano devices and the like.

At present, there are various methods for 3D printing SiC ceramics, mainly including Fused deposition modeling-FDM (Fused deposition modeling-FDM), stereolithography-SL (stereolithography-SL), 3D printing-3DP (3D printing-3DP), layered Object Manufacturing-LOM (plated Object Manufacturing-LOM), Selective laser sintering-SLs (Selective laser sintering-SLs), Selective laser melting-SLM (Selective laser melting-SLM), and Direct-write free-form (DIW). However, most of 3D printing technologies have high requirements for devices (e.g., laser printing devices), and are relatively high in cost, which is not favorable for application and popularization, and for methods for preparing ceramic slurry for direct printing of DIW, etc., due to the existence of a large amount of solvents (e.g., water), ceramic blanks are easy to crack during drying, and large-sized SiC ceramic materials are not easy to prepare.

Disclosure of Invention

In most of the existing forming processes for preparing SiC ceramic by 3D printing, ceramic particles are loosely connected, green bodies are low in density and are easy to crack in the forming, debonding and sintering processes, so that the density and mechanical properties of SiC green bodies obtained by 3D printing need to be enhanced by means of reactive siliconizing. The presence of a certain amount of silicon in the ceramic results in relatively poor material uniformity and corrosion resistance. Aiming at the problems, the invention provides the extrusion molding 3D printing SiC ceramic and the preparation method thereof, which can realize the preparation of large-size SiC parts and simultaneously avoid part cracking caused by stress in the molding process, and the preparation method can give consideration to normal pressure sintering and siliconizing treatment to prepare the SiC ceramic, has relatively low requirements on equipment, is beneficial to large-scale low-cost preparation of the SiC ceramic, and thus obviously improves the practical application potential of the 3D printing SiC ceramic.

In a first aspect, the invention provides a preparation method of an extrusion molding 3D printing SiC ceramic, which comprises the following steps: (1) and (3) granulation: preparing SiC powder into SiC particles with the particle size of 20-100 mu m;

(2) mixing: adding a first adhesive into the SiC particles and uniformly mixing to obtain a pug with good plasticity; the first binder is solidified at room temperature and melted at a temperature of 60 ℃ or higher to bond the SiC particles to each other;

(3) printing and forming: putting the pug into printing equipment, adjusting equipment parameters, printing under the control of computer software, bonding a newly processed layer and a previous layer into a whole, and repeating the printing process until a biscuit is formed;

(4) degreasing: degreasing the printed biscuit to obtain a prefabricated body;

(5) densification: and sintering the prefabricated body at normal pressure or carrying out vacuum siliconizing treatment to obtain the SiC ceramic.

Different from slurry printing, the invention adopts a mud printing method, the first adhesive is melted along with the rise of printing temperature in the printing process, the function of bonding SiC powder is achieved, and meanwhile, the stress in the printing process can be eliminated by keeping smaller temperature difference in the printing process.

Preferably, the first binder is a mixture of one or more of wax-based binder, methylcellulose and polyethylene glycol. Preferably, the wax-based binder is paraffin wax and/or polyethylene wax.

Preferably, the first binder accounts for 5-40wt% of the SiC particles, so that it is possible to avoid the use amount of the first binder being too low to be advantageous for extrusion molding, and it is possible to avoid too much first binder causing failure to obtain dense ceramics.

Preferably, the first adhesive further comprises a mixture of one or more of polypropylene (PP), Stearic Acid (SA), High Density Polyethylene (HDPE), Ethylene Vinyl Acetate (EVA).

The first binder plays a significant role in the printing process of the present invention. The first binder serves both as a carrier for providing fluidity during printing and as a means for maintaining the shape of the compact during the degreasing phase. Preferably, the first binder is composed of a low molecular mass, low melting point first component and a high molecular mass, high melting point second component. In some embodiments, paraffin wax is used as the first component of the first binder, and a different type of polymer is used as the second component of the first binder. For example, PP acts as a backbone, SA acts as a surfactant, and HDPE and EVA act as modifiers to enhance the adhesion of the binder.

Preferably, the temperature of a nozzle of the printing equipment is controlled to be 100-300 ℃, the temperature of an objective table is controlled to be 20-150 ℃, the temperature of the atmosphere of a cavity is controlled to be 20-100 ℃, the printing speed is 10-100mm/s, the printing interval is 0.05-0.1mm, and the thickness of a single layer is 0.05-0.3 mm.

Preferably, the normal pressure sintering temperature is 1900-2200 ℃, the atmosphere is argon, and the sintering time is 1-2 h; the vacuum siliconizing treatment temperature is 1450-1850 ℃, and the vacuum siliconizing treatment time is 0.5-4 h. Since porous SiC can be obtained by the production method of the present invention, reaction bonded SiC ceramics can be obtained by vacuum siliconizing. Meanwhile, the normal pressure sintered SiC ceramic can be obtained by normal pressure sintering with the help of a sintering aid.

Preferably, the SiC powder, the sintering aid and the solvent are subjected to ball milling and mixing to obtain mixed slurry; drying or spraying and granulating the obtained mixed slurry to obtain SiC particles with the particle size of 20-100 mu m; preferably, the sintering aid is a B-C system sintering aid, the mass of the sintering aid is not less than 5wt% of the total mass of the SiC powder and the sintering aid, wherein the content of B is not more than 1wt% of the total mass of the SiC powder and the sintering aid, and the content of C is not less than 2wt% of the total mass of the SiC powder and the sintering aid; more preferably, the sintering aid is Al₂O₃And a mixture of rare earth oxides, said rare earth oxide being Y₂O₃、CeO₂、Er₂O₃At least one of (1).

Preferably, the mixed slurry also comprises a second binder for binding SiC powder for granulation; preferably, the second adhesive is at least one of phenolic resin, polyvinyl alcohol PVA, polyvinyl butyral PVB and polymethyl methacrylate PMMA; the mass of the second adhesive is not less than 5wt% of the total mass of the SiC powder and the sintering aid.

Preferably, the solids content of the mixed slurry is 40 to 50 wt%, preferably 40 to 45 wt%.

Preferably, the solvent of the mixed slurry is water or absolute ethyl alcohol.

Preferably, the degreasing temperature is 600-1200 ℃, and the degreasing time is 2-24 h.

Preferably, the pug can be uniformly mixed by stirring. Preferably, the stirring time is 12 to 24 hours.

In a second aspect, the present invention provides an extrusion-molded 3D-printed SiC ceramic obtained by the production method described in any one of the above. The density of the SiC ceramic is 2.60-3.20 g-cm^-3The bending strength is 250-500 MPa.

Drawings

Fig. 1 is a pictorial view of a 3D printed SiC ceramic greenbody.

Fig. 2 is a pictorial view of a degreased 3D printed SiC ceramic preform.

Fig. 3 is a physical diagram of a 3D printed SiC ceramic product after atmospheric pressure solid phase sintering.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative of, and not restrictive on, the present invention. Unless otherwise specified, each percentage means a mass percentage.

The following illustrates a method for preparing an extrusion-molded 3D-printed SiC ceramic according to the present invention.

SiC particles (may also be referred to as "SiC mixed powder") were prepared.

For example, a SiC powder, a sintering aid, a binder (may also be referred to as a "second binder"), and a solvent are ball-milled and mixed to obtain a mixed slurry. The mixtureThe solids content of the composite slurry is 40 to 50 wt.%, preferably 40 to 45 wt.%. The sintering aid is a B-C system sintering aid, wherein the content of B is not higher than 1wt% of the total mass of the SiC powder and the sintering aid, and the content of C is not lower than 2wt% of the total mass of the SiC powder and the sintering aid. Preferably, the sintering aid is Al₂O₃And a mixture of rare earth oxides, wherein the rare earth oxide is Y₂O₃、CeO₂、Er₂O₃At least one of (1). The mass of the sintering aid is not less than 5wt% of the total mass of the SiC powder and the sintering aid.

In the mixed slurry, the binder is at least one of phenolic resin, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and polymethyl methacrylate (PMMA). The binder in this process functions to obtain uniformly mixed SiC powder, and the composition of the binder is not particularly limited as long as it has cohesiveness after being dissolved in a solvent. The mass of the adhesive is not less than 5wt% of the total mass of the SiC powder and the sintering aid.

In the mixed slurry, the solvent is water or absolute ethyl alcohol.

And drying or spraying and granulating the obtained mixed slurry to obtain SiC mixed powder with the particle size of 20-100 mu m.

And (3) mixing the powder.

For example, the SiC mixed powder prepared above is mixed with a mixture of one or more of a wax-based binder, methylcellulose, and polyethylene glycol as a binder (may also be referred to as "first binder") during kneading, and stirred for 12 to 24 hours to obtain a highly plastic paste which is uniformly mixed. The wax-based binder or methyl cellulose or polyethylene glycol is melted at high temperature and can be solidified at normal temperature. By introducing the adhesive in the mud, the compact connection between SiC particles can be promoted by virtue of the bonding effect of the adhesive in the high-temperature printing process, and pores generated by a few cracks can be filled to eliminate printing stress, so that the preparation of large-size SiC ceramic parts is facilitated. The mass of the first adhesive is 5-40wt% of the SiC mixed powder.

And (5) printing and molding the pug. For example, the sludge is put into a printing apparatus; preheating the printing equipment; when the temperature of the printing equipment is stable, starting a printing nozzle, and selectively printing the pug layer by layer under the control of computer software according to parameters of each layer of section of the workpiece; the printed materials are bonded together due to the adhesive action of the adhesive; after the first layer is processed, the nozzle prints the new layer under the control of computer software, the new processed layer is bonded with the previous layer into a whole, and the above processes are repeated until the whole part is processed.

In the process, the temperature of the spray head is controlled to be 100-300 ℃, the temperature of the objective table is controlled to be 20-150 ℃, the temperature of the atmosphere of the equipment cavity is controlled to be 20-100 ℃, the printing speed is 10-100mm/s, the printing interval is 0.05-0.1mm, and the single-layer thickness is 0.05-0.3 mm. The equipment chamber atmosphere may be air.

And (6) degreasing. And degreasing the printed biscuit in a vacuum sintering furnace to remove organic matters. Preferably, the degreasing temperature is 600-.

Sintering under normal pressure or siliconizing by vacuum reaction.

And putting the degreased preform into a vacuum sintering furnace for normal pressure sintering or siliconizing treatment. The high-temperature sintering temperature is 1900-2200 ℃, the atmosphere is Ar atmosphere, and the heat preservation time is 1-4 h. The vacuum siliconizing treatment is carried out at 1450-1850 ℃ and the heat preservation time is 0.5-4 h.

The density of the SiC ceramic was measured by the archimedes drainage method, and the bending strength of the SiC ceramic was measured by the three-point bending method.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

965g of SiC powder and B as a sintering aid₄5g of C (0.5 wt%), 30g of carbon black (3 wt%) and 1000g of powder, adding 100g of phenolic resin, mixing to prepare slurry with the solid content of 45 wt% (the solvent is alcohol), mixing for 24 hours by taking 2000g of SiC balls as a ball milling medium, and performing spray granulation to obtain uniformly mixed SiC powder; mixing 20 wt% of wax-based adhesive into the powder subjected to spray granulation, mixing for 12 hours, then loading the obtained pug into printing equipment, simultaneously obtaining SiC ceramic structures with different shapes according to computer aided design, controlling the temperature of a printing nozzle to be 200 ℃, controlling an object stage to be 100 ℃, controlling the atmosphere temperature of a cavity of the equipment to be 60 ℃, controlling the printing speed to be 10mm/s, controlling the printing interval to be 0.05mm and controlling the single-layer thickness to be 0.1 mm. The obtained SiC ceramic biscuit is shown in figure 1; degreasing the printed biscuit in a vacuum sintering furnace, removing the organic binder, and keeping the temperature at 1100 ℃ for 12h to obtain a preform as shown in figure 2; sintering the obtained biscuit at high temperature and normal pressure, wherein the sintering temperature is 2200 ℃, the atmosphere is Ar atmosphere, and the heat preservation time is 2 hours, and the obtained ceramic product is shown in figure 3; the obtained normal pressure sintered SiC ceramic has a density of 3.00 + -0.05 g-cm^-3。

Example 2

Mixing SiC powder 900g and Al₂O₃And Y₂O₃(10 wt%) 10g of powder, 1000g of PVA, 50g of PVA are added and mixed to prepare slurry with solid content of 45 wt% (the solvent is water), 2000g of SiC balls are used as a ball milling medium and are mixed for 24h, and the SiC powder which is uniformly mixed is obtained through spray granulation; mixing 10 wt% of methylcellulose into the powder subjected to spray granulation, mixing for 24 hours, then loading the obtained pug into printing equipment, simultaneously obtaining SiC ceramic structures with different shapes according to computer aided design, controlling the temperature of a printing nozzle to be 180 ℃, controlling an object stage to be 100 ℃, controlling the atmosphere temperature of a cavity of the equipment to be 60 ℃, controlling the printing speed to be 50mm/s, controlling the printing interval to be 0.1mm and controlling the single-layer thickness to be 0.2 mm. Obtaining a SiC ceramic biscuit; degreasing the printed biscuit in a vacuum sintering furnace, removing the organic binder, and keeping the temperature at 1100 ℃ for 24 hours to obtain a prefabricated body; the obtained biscuit is sintered under high temperature and normal pressure by powder embedding, the sintering temperature is 1950 ℃, the atmosphere is Ar atmosphere,keeping the temperature for 1h to obtain a ceramic product; the obtained normal pressure sintered SiC ceramic has a density of 3.15 + -0.05 g-cm^-3。

Example 3

850g of SiC powder, 150g of carbon black (15 wt%) and 1000g of powder are mixed, 100g of phenolic resin and PMMA10g are added and mixed to prepare slurry with the solid content of 45 wt% (the solvent is alcohol), 2000g of SiC balls are used as a ball milling medium and are mixed for 24 hours, and the SiC powder which is uniformly mixed is obtained through spray granulation; mixing the powder subjected to spray granulation with 40wt% of wax-based binder, mixing for 12 hours, then loading the obtained pug into printing equipment, simultaneously obtaining SiC ceramic structures with different shapes according to computer aided design, controlling the temperature of a printing nozzle to be 200 ℃, controlling an object stage to be 100 ℃, controlling the atmosphere temperature of a cavity of the equipment to be 60 ℃, controlling the printing speed to be 100mm/s, controlling the printing interval to be 0.1mm and controlling the single-layer thickness to be 0.3 mm. The obtained SiC ceramic biscuit is shown in figure 1; degreasing the printed biscuit in a vacuum sintering furnace, removing organic matters, and keeping the temperature at 1100 ℃ for 12h to obtain a prefabricated body as shown in figure 2; and (3) putting the degreased preform into a vacuum sintering furnace for siliconizing treatment, wherein the treatment temperature is 1550 ℃, and the heat preservation time is 0.5 h. The density of the obtained reaction sintered SiC was 3.05. + -. 0.02 g-cm^-3。

As can be seen from fig. 1 to 3, the production method of the present invention enables a large-sized SiC ceramic part to be obtained, and no significant cracks are observed in the part.

Claims

1. The preparation method of the extrusion molding 3D printing silicon carbide ceramic is characterized by comprising the following steps:

(1) and (3) granulation: preparing silicon carbide powder into silicon carbide particles with the particle size of 20-100 mu m;

(2) mixing: adding a first adhesive into the silicon carbide particles and uniformly mixing to obtain a pug with good plasticity; the first binder is cured at room temperature and melted at a temperature of 60 ℃ or higher to bond the silicon carbide particles to each other;

(4) degreasing: degreasing the printed biscuit to obtain a prefabricated body;

(5) densification: and sintering the prefabricated body at normal pressure or carrying out vacuum siliconizing treatment to obtain the silicon carbide ceramic.

2. The preparation method according to claim 1, wherein the first binder is a mixture of one or more of wax-based binder, methylcellulose and polyethylene glycol; the first binder comprises 5-40wt% of the silicon carbide particles; preferably, the wax-based binder is paraffin wax and/or polyethylene wax.

3. The method of claim 2, wherein the first adhesive further comprises a mixture of one or more of polypropylene, stearic acid, high density polyethylene, and ethylene-vinyl acetate copolymer.

4. The method as claimed in any one of claims 1 to 3, wherein the temperature of the nozzle of the printing apparatus is controlled to be 100-300 ℃, the temperature of the stage is controlled to be 20-150 ℃, the temperature of the atmosphere in the chamber is controlled to be 20-100 ℃, the printing speed is 10-100mm/s, the printing pitch is 0.05-0.1mm, and the monolayer thickness is 0.05-0.3 mm.

5. The method according to claim 4, wherein the chamber atmosphere is air.

6. The method according to any one of claims 1 to 5, wherein the normal pressure sintering temperature is 1900-2200 ℃, the atmosphere is argon, and the sintering time is 1-2 h; the vacuum siliconizing treatment temperature is 1450-1850 ℃, and the vacuum siliconizing treatment time is 0.5-4 h.

7. The preparation method according to any one of claims 1 to 6, wherein the silicon carbide powder, the sintering aid and the solvent are mixed by ball milling to obtain the silicon carbide powderMixing the slurry; drying or spraying and granulating the obtained mixed slurry to obtain silicon carbide particles with the particle size of 20-100 mu m; preferably, the sintering aid is a B-C system sintering aid, the mass of the sintering aid is not less than 5wt% of the total mass of the silicon carbide powder and the sintering aid, wherein the content of B is not more than 1wt% of the total mass of the SiC powder and the sintering aid, and the content of C is not less than 2wt% of the total mass of the SiC powder and the sintering aid; more preferably, the sintering aid is Al₂O₃And a mixture of rare earth oxides, said rare earth oxide being Y₂O₃、CeO₂、Er₂O₃At least one of (1).

8. The method according to claim 7, wherein the mixed slurry further contains a second binder for binding the silicon carbide powder to be granulated; preferably, the second binder is at least one of phenolic resin, polyvinyl alcohol, polyvinyl butyral and polymethyl methacrylate; the mass of the second binder is not less than 5wt% of the total mass of the silicon carbide powder and the sintering aid.

9. The method as claimed in any one of claims 1 to 8, wherein the degreasing temperature is 600-1200 ℃ and the degreasing time is 2-24 h.

10. The extrusion-molded 3D-printed silicon carbide ceramic obtained by the production method according to any one of claims 1 to 9, characterized in that the density of the silicon carbide ceramic is 2.60 to 3.20 g-cm^-3The bending strength is 250-500 MPa.