Rapid sintering and heat treatment method for ceramic 3D printing green body

Abstract

The invention discloses a rapid sintering and heat treatment method for a ceramic 3D printing green body. The rapid sintering and heat treatment method comprises the following steps: preparing ceramic slurry; carrying out 3D printing on the ceramic slurry to obtain a ceramic 3D printing green body; and the ceramic 3D printing green body is placed in a degreasing sintering furnace to be subjected to degreasing, sintering and heat treatment. Degreasing is conducted under the inert atmosphere, and cracking of a degreased product can be improved; after degreasing is completed, rapid vacuum sintering is carried out, the consistency of product grains is improved, and internal air holes can be removed; by adding the sintering aid into the ceramic powder, the ceramic slurry can react at a high temperature to form a liquid phase, intermolecular migration is promoted, the sintering reaction is promoted, the product compactness is further improved, the interlayer defect existing in ceramic 3D printing is improved, and the product performance is improved; and heat treatment and heat preservation are carried out after sintering is completed, product grains can grow to a certain degree, oxygen vacancies generated in the vacuum sintering process of the product are improved, and the performance of the product is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic preparation, and in particular relates to a method for rapid sintering and heat treatment of ceramic 3D printed green bodies. Background Art

[0002] Ceramic 3D printing, tape casting, and injection molding are all common ceramic molding methods. The ceramic green body after molding usually contains a large amount of organic resin, which needs to be removed in the subsequent degreasing and sintering. The ceramic green body can only form a dense three-dimensional crystal structure after degreasing and sintering. When ceramic 3D printing is degreased, interlayer cracking is prone to occur due to interlayer bonding.

[0003] The traditional degreasing and sintering method is mainly air thermal degreasing. During degreasing in an air atmosphere, the resin decomposes under the action of oxygen and reacts quickly. Generally, a lower degreasing rate is used. After degreasing, ceramics are formed by air sintering. However, due to the slow degreasing rate, ceramic products are prone to cracking, and the performance consistency of the sintered products is poor. Summary of the invention

[0004] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a method for rapid sintering and heat treatment of ceramic 3D printed green bodies.

[0005] In order to achieve the above purpose and the above technical effect, the technical solution adopted by the present invention is:

[0006] A method for rapid sintering and heat treatment of a ceramic 3D printed green body comprises the following steps:

[0007] 1) preparing ceramic slurry;

[0008] 2) 3D printing ceramic slurry to obtain ceramic 3D printed green body;

[0009] 3) The ceramic 3D printed green body is placed in a degreasing and sintering furnace for degreasing, sintering and heat treatment.

[0010] Furthermore, in step 1), the ceramic slurry is prepared by ceramic powder, sintering aid, photocurable resin monomer, dispersant, plasticizer and photoinitiator, the ceramic powder accounts for 75%-85% of the mass of the ceramic slurry, the sintering aid accounts for 0.05%-0.5% of the mass of the ceramic powder, the photocurable resin monomer accounts for 5%-15% of the mass of the ceramic slurry, the dispersant accounts for 1%-3% of the mass of the ceramic powder, the plasticizer accounts for 30%-60% of the mass of the photocurable resin monomer, and the photoinitiator accounts for 1%-5% of the mass of the photocurable resin monomer.

[0011] Furthermore, the ceramic powder is one or a combination of ZrO2, Al2O3, ZTA, ATZ, and the sintering aid is MgO, Y2O3, TiO2 compounded in a mass ratio of (20-40): (20-40): (20-40).

[0012] Furthermore, the photocurable resin is compounded by PPTTA and one or more combinations of HDDA, IDA, TMPTA, and PPTTA; the dispersant is one or more combinations of BYK110, BYK218, BYK111, and KOS110; the plasticizer is one or more combinations of PEG200, PEG400, PPG400, DBP, and DOP; and the photoinitiator is one or more combinations of photoinitiator 819, photoinitiator 184, and photoinitiator TPO.

[0013] Furthermore, the preparation steps of the ceramic slurry include:

[0014] Add the photocurable resin, dispersant, plasticizer and photoinitiator into a vacuum stirring degassing machine, mix at a speed of 500-2000 rpm for 2-10 minutes, then add the sintering aid, mix at a speed of 500-2000 rpm for 2-10 minutes to form a premixed solution;

[0015] Subsequently, the ceramic powder and the premixed liquid are added into a planetary ball mill and ball-milled at a speed of 200-300 rpm for 6-10 hours to obtain a mixture;

[0016] Finally, the mixture is added into a vacuum drying oven for vacuum degassing for 10-30 minutes to obtain the desired ceramic slurry.

[0017] Further, in step 3), the process conditions for degreasing are:

[0018] Degreasing is carried out under an inert atmosphere, the degreasing temperature is 60-600°C, and the degreasing heating rate is 0.1-2°C / min.

[0019] Furthermore, the inert atmosphere is nitrogen, argon or a combination of both.

[0020] Further, in step 3), the sintering process conditions are:

[0021] Vacuum sintering, sintering heating rate is 20-100℃ / min, the maximum sintering temperature is 1400-1700℃, and the holding time is 1-3h.

[0022] Further, in step 3), the process conditions of the heat treatment are:

[0023] The heat treatment temperature is 1100-1400°C, the holding time is 1-4h, and the cooling rate is 2-20°C / min.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention discloses a method for rapid sintering and heat treatment of a ceramic 3D printed green body. The ceramic 3D printed green body is first degreased in an inert atmosphere, and the resin cracking speed is slow, which is conducive to improving the cracking of the degreased product; after the degreasing is completed, rapid vacuum sintering is performed, and the rapid sintering heating rate is conducive to improving the consistency of the product grains and avoiding the abnormal growth of the grains. In a vacuum environment, due to the pressure difference, the internal pores are conducive to being eliminated; by adding a sintering aid to the ceramic powder, it is conducive to the ceramic slurry to react at a high temperature to form a liquid phase, promote the migration between molecules, and the sintering aid can To replace the elements of the sintered body, oxygen vacancies or lattice distortion are formed, the sintering reaction is promoted, the reaction density is improved, the product density is further improved, the interlayer defects existing in ceramic 3D printing are improved, and the product performance is improved; after the vacuum sintering is completed, heat treatment and insulation are carried out at 100-300°C below the sintering temperature, which can make the product grains grow to a certain extent, which is beneficial to improve the oxygen vacancies generated during the vacuum sintering process of the product and improve the performance of the product; the present invention can obtain ceramic products with high hardness, large 3PB, high fracture toughness, and small and consistent grain size. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an electron microscope image of the product of Example 3 of the present invention. DETAILED DESCRIPTION

[0027] The present invention is described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0028] A brief summary of one or more aspects is given below to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceived aspects, and is neither intended to identify the key or critical elements of all aspects nor to define the scope of any or all aspects. Its only purpose is to give some concepts of one or more aspects in a simplified form as a prelude to a more detailed description that will be given later.

[0029] The present invention discloses a method for rapid sintering and heat treatment of a ceramic 3D printed green body, comprising the following steps:

[0030] 1) preparing ceramic slurry;

[0031] 2) 3D printing ceramic slurry to obtain ceramic 3D printed green body;

[0032] 3) The ceramic 3D printed green body is placed in a degreasing and sintering furnace for degreasing, sintering, and heat treatment, followed by product performance testing.

[0033] In step 1), a ceramic slurry is prepared by means of ceramic powder, a sintering aid, a photocurable resin monomer, a dispersant, a plasticizer and a photoinitiator, wherein the ceramic powder accounts for 75%-85% of the mass of the ceramic slurry, the sintering aid accounts for 0.05%-0.5% of the mass of the ceramic powder, the photocurable resin monomer accounts for 5%-15% of the mass of the ceramic slurry, the dispersant accounts for 1%-3% of the mass of the ceramic powder, the plasticizer accounts for 30%-60% of the mass of the photocurable resin monomer, and the photoinitiator accounts for 1%-5% of the mass of the photocurable resin monomer.

[0034] The steps for preparing the ceramic slurry include:

[0035] Add the photocurable resin, dispersant, plasticizer and photoinitiator into a vacuum stirring degassing machine, mix at a speed of 500-2000 rpm for 2-10 minutes, then add the sintering aid, mix at a speed of 500-2000 rpm for 2-10 minutes to form a premixed solution;

[0036] Subsequently, the ceramic powder and the premixed liquid are added into a planetary ball mill and ball-milled at a speed of 200-300 rpm for 6-10 hours to obtain a mixture;

[0037] Finally, the mixture is added into a vacuum drying oven for vacuum degassing for 10-30 minutes to obtain the desired ceramic slurry.

[0038] The ceramic powder is one or a combination of ZrO2, Al2O3, ZTA and ATZ.

[0039] The sintering aid is a compound of MgO, Y2O3 and TiO2 in a mass ratio of (20-40): (20-40): (20-40). The addition of the sintering aid is conducive to the formation of a liquid phase of the ceramic slurry at a high temperature, reduces the sintering temperature, and promotes the sintering process.

[0040] The photocurable resin is compounded by mixing PPTTA with one or more of HDDA, IDA, TMPTA and PPTTA.

[0041] The dispersant is one of BYK110, BYK218, BYK111, and KOS110, or a combination of several thereof.

[0042] The plasticizer is one or a combination of PEG200, PEG400, PPG400, DBP and DOP.

[0043] The photoinitiator is one of photoinitiator 819, photoinitiator 184, and photoinitiator TPO, or a combination of several of them.

[0044] In step 2), the prepared ceramic slurry is placed in the SLA ceramic 3D printer and the printing parameters are set:

[0045] Printing speed 1000-3000mm / s;

[0046] Printing power 0.3-0.6W;

[0047] Scanning and printing spacing 0.03-0.05mm;

[0048] The thickness of each printed layer is 0.02-0.04mm;

[0049] After the product is printed, it is cleaned and placed in a vacuum degreasing sintering furnace.

[0050] In step 3), the process conditions for degreasing are:

[0051] Degreasing is performed under an inert atmosphere, the degreasing temperature is 60-600° C., and the degreasing heating rate is 0.1-2° C. / min, wherein the inert atmosphere is one of nitrogen and argon or a combination of the two.

[0052] In step 3), the sintering process conditions are:

[0053] Rapid vacuum sintering, sintering heating rate is 20-100℃ / min, the highest sintering temperature is 1400-1700℃, and the holding time is 1-3h. Sintering under vacuum is beneficial to the removal of product pores during the sintering process, which is beneficial to improving the consistency of grains and the mechanical properties of products.

[0054] In step 3), the process conditions of heat treatment are:

[0055] The heat treatment temperature is 1100-1400℃, the holding time is 1-4h, and the cooling rate is 2-20℃ / min. It is beneficial to improve defects such as vacancies during the sintering process and improve product performance.

[0056] In step 3), product performance testing includes:

[0057] The three-point bending strength of the product is tested by a universal mechanical testing machine;

[0058] Test the hardness of the product by slicing, grinding and polishing the product;

[0059] Through the indentation method, the crack length of the product is tested to calculate the fracture toughness of the product;

[0060] Grain test: the size of the product grains is tested after grinding, polishing and thermal etching.

[0061] The formulations of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] The process parameters of Examples 1-3 and Comparative Examples 1-3 are shown in Table 2.

[0066] Table 2

[0067]

[0068] In Example 3, the grain size of the product obtained after heat treatment is 0.74 μm. Figure 1 .

[0069] The performance test results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 3.

[0070] Table 3

[0071] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Hardness(Hv) 1625 2145 1970 1423 2079 1620 3PB(MPa) 1245 652 948 857 470 845 Grain(μm) 0.66 0.85 0.74 0.9 0.87 0.68 Fracture toughness 8.5 5.6 6.7 7.2 4.3 5.2

[0072] From Table 1-3 we can see that:

[0073] Comparing Example 1 with Comparative Example 1, Example 1 uses nitrogen atmosphere degreasing and rapid vacuum sintering, so the product grains have no time to grow and are retained as small grains to high temperature. After adding the ternary sintering aid, TiO2 in the ternary sintering aid will introduce lattice vacancies at high temperature to reduce the sintering activation energy, and the rare earth oxide Y2O3 can improve the toughness of the sintered product. MgO sintering will form a liquid phase to promote the sintering process. At the same time, the vacuum sintering environment will accelerate the flow of the liquid phase and promote the densification of sintering, so that the product retains smaller grains and higher hardness, 3PB and fracture toughness. Comparative Example 1 uses air atmosphere degreasing, slow temperature rise sintering and no sintering aid, so that the product grains are larger, and the hardness, 3PB and fracture toughness are all lower than those of Example 1.

[0074] Comparing Example 2 with Comparative Example 2, Comparative Example 2 uses degreasing in an air atmosphere, and the degreasing reaction speed is fast, and there may be small defects, which causes the performance of the product of Comparative Example 2 to be reduced. The hardness, 3PB and fracture toughness of the product obtained in Comparative Example 2 are all lower than those of Example 2, and the grain size is larger than that of Example 2;

[0075] Comparing Example 3 with Comparative Example 3, Comparative Example 3 was not subjected to heat treatment and heat preservation, so that the product of Comparative Example 3 turned black after sintering, and there were certain oxygen vacancies, which would serve as micro-defect outbreak points during the mechanical property test of the product, causing the 3PB, hardness and fracture toughness of the product to decrease. The hardness, 3PB and fracture toughness of Comparative Example 3 were all lower than those of Example 3, and the grain size was larger than that of Example 3;

[0076] This shows that only by adopting inert atmosphere degreasing, rapid vacuum sintering and heat treatment and heat preservation after sintering according to the present invention can ceramic products with high hardness, high 3PB, high fracture toughness and small grain size be obtained. When degreasing under inert atmosphere, the polymer decomposition form is molecular cracking, the reaction rate is slow, and the product is not easy to crack. By adopting vacuum rapid sintering, the product has a fast heating rate, small grains, and no time to grow abnormally, so that the grain consistency is good, which is conducive to improving the strength and hardness of the product; at high temperature, TiO2 in the ternary sintering aid will introduce lattice vacancies and reduce the sintering activation energy, and the rare earth oxide Y2O3 can improve the toughness of the sintered product, and adding MgO sintering will form a liquid phase to promote the sintering process, which has better coordinated interaction with vacuum rapid sintering, so that the product retains smaller grains and higher hardness, 3PB and fracture toughness. By heat treatment and heat preservation after sintering, defects such as vacancies in the sintering process can be improved, and the performance of the product can be further improved.

[0077] Parts or structures not specifically described in the present invention may adopt existing technologies or existing products and will not be described in detail here.

[0078] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for rapid sintering and heat treatment of ceramic 3D printed green bodies, characterized in that: The following steps are involved: 1) preparing ceramic slurry; 2) 3D printing ceramic slurry to obtain ceramic 3D printed green body; 3) The ceramic 3D printed green body is placed in a degreasing and sintering furnace for degreasing, sintering and heat treatment.

2. A rapid sintering and heat treatment method for ceramic 3D printing green body according to claim 1, characterized in that: In step 1), the ceramic slurry is prepared by ceramic powder, sintering aid, photocurable resin monomer, dispersant, plasticizer and photoinitiator, the ceramic powder accounts for 75%-85% of the mass of the ceramic slurry, the sintering aid accounts for 0.05%-0.5% of the mass of the ceramic powder, the photocurable resin monomer accounts for 5%-15% of the mass of the ceramic slurry, the dispersant accounts for 1%-3% of the mass of the ceramic powder, the plasticizer accounts for 30%-60% of the mass of the photocurable resin monomer, and the photoinitiator accounts for 1%-5% of the mass of the photocurable resin monomer.

3. A method for rapid sintering and heat treatment of ceramic 3D printed green bodies according to claim 2, characterized in that: The ceramic powder is one or a combination of ZrO2, Al2O3, ZTA, and ATZ, and the sintering aid is MgO, Y2O3, and TiO2 compounded in a mass ratio of (20-40): (20-40): (20-40).

4. A method for rapid sintering and heat treatment of ceramic 3D printed green bodies according to claim 2, characterized in that: The photocurable resin is compounded by PPTTA and one or more combinations of HDDA, IDA, TMPTA, and PPTTA; the dispersant is one or more combinations of BYK110, BYK218, BYK111, and KOS110; the plasticizer is one or more combinations of PEG200, PEG400, PPG400, DBP, and DOP; and the photoinitiator is one or more combinations of photoinitiator 819, photoinitiator 184, and photoinitiator TPO.

5. The rapid sintering and heat treatment method for ceramic 3D printing green body according to claim 2, characterized in that: The preparation steps of the ceramic slurry include: Add the photocurable resin, dispersant, plasticizer and photoinitiator into a vacuum stirring degassing machine, mix at a speed of 500-2000 rpm for 2-10 minutes, then add the sintering aid, mix at a speed of 500-2000 rpm for 2-10 minutes to form a premixed solution; Subsequently, the ceramic powder and the premixed liquid are added into a planetary ball mill and ball-milled at a speed of 200-300 rpm for 6-10 hours to obtain a mixture; Finally, the mixture is added into a vacuum drying oven for vacuum degassing for 10-30 minutes to obtain the desired ceramic slurry.

6. The rapid sintering and heat treatment method for ceramic 3D printing green body according to claim 1, characterized in that: In step 3), the process conditions for degreasing are: Degreasing is carried out under an inert atmosphere, the degreasing temperature is 60-600°C, and the degreasing heating rate is 0.1-2°C / min.

7. A method for rapid sintering and heat treatment of ceramic 3D printed green bodies according to claim 6, characterized in that: The inert atmosphere is nitrogen, argon or a combination of the two.

8. The rapid sintering and heat treatment method for ceramic 3D printing green body according to claim 1, characterized in that: In step 3), the sintering process conditions are: Vacuum sintering, sintering heating rate is 20-100℃ / min, the maximum sintering temperature is 1400-1700℃, and the holding time is 1-3h.

9. The rapid sintering and heat treatment method for ceramic 3D printing green body according to claim 1, characterized in that: In step 3), the process conditions of the heat treatment are: The heat treatment temperature is 1100-1400°C, the holding time is 1-4h, and the cooling rate is 2-20°C / min.

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