Aluminum oxide ceramic compositely molded by injection coagulation and injection processes and preparation method of aluminum oxide ceramic

Abstract

The invention discloses an aluminum oxide ceramic compositely molded by injection and coagulation processes and a preparation method thereof, and belongs to the technical field of preparation of aluminum oxide ceramic, Al2O3 ceramic in a complex shape is prepared by composite molding of the injection and coagulation processes or the injection processes, agarose is used as a gel agent, and after full mixing, heating, stirring and other operations are carried out, the aluminum oxide ceramic is prepared. The preparation method comprises the following steps: preparing Al2O3 ceramic slurry with the solid content of 80wt.%, injecting the slurry into a mold at high pressure through an injection machine, generating a three-dimensional network structure in the mold, fixing ceramic in situ, cooling to obtain a biscuit, and discharging glue and sintering to prepare an Al2O3 ceramic sample; the technology combines the characteristics of high-temperature melting and low-temperature solidification of agarose, realizes composite molding of a gel injection process and an injection process of the ceramic, and has the remarkable advantages of no pollution, complete molded body, no fracture, no residue after sintering and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of alumina ceramics, and in particular relates to an alumina ceramic compositely formed by a condensation and injection process and a preparation method thereof. Background Art

[0002] Ceramic injection molding is a new near-net-size ceramic molding technology. Its technical features are similar to those of metal powder injection molding, enabling the production of a variety of complex, dimensionally demanding ceramic parts. The ceramic powder used in injection molding is typically Al2O3 powder, which offers advantages such as versatility, excellent fluidity, and high filling properties. Its excellent chemical properties are well-suited to the requirements of ceramic injection molding. In the current market environment, slurries used for injection molding are mostly formulated with organic binders such as paraffin wax and polyethylene.

[0003] Patent document CN108218441B develops a new binder for ceramic injection molding, aiming to improve binder removal efficiency and reduce defects such as blistering, deformation, and cracking in ceramic green bodies during sintering. The binder mentioned in the patent is paraffin wax and microcrystalline wax, which optimizes fluidity and mold release properties.

[0004] Patent document CN113213896B discloses a feed material for alumina ceramic injection molding and a feed material injection molding method. The feed material for alumina ceramic injection molding is made of alumina powder and organic matter; the proportion of alumina powder is 70wt.%-85wt.%, and the proportion of organic matter is 15wt.%-30wt.%.

[0005] Ceramic gelcasting is an advanced net-size molding technology. It involves uniformly dispersing ceramic powder in a water-based or organic solvent with a dispersant, creating a fluid slurry. Subsequently, the organic monomers in the slurry polymerize in situ under the action of a crosslinker, initiator, and catalyst, forming a three-dimensional polymer network that encapsulates the suspended ceramic particles and solidifies in situ into a uniform, dense, and high-strength green body. Agarose, a natural macromolecule, is commonly used in ceramic gelcasting, primarily as a gelling agent.

[0006] Patent document CN105835209B discloses a ceramic gel molding method based on agarose, which comprises preparing an agarose solution with a mass fraction of 3 to 4.5 wt.%, injecting the agarose solution into a vacuum-degassing and preheated ceramic slurry in proportion, and then injecting the mixture into a preheated mold and cooling it to obtain a green body; the green body is left to stand, dried in multiple steps, and then sintered.

[0007] As can be seen from this, traditional binder systems in ceramic injection molding rely heavily on high-molecular-weight organic compounds such as paraffin and polyethylene. While these materials can be effectively removed through solvent and thermal degreasing, the removal process is complex and environmentally polluting. Agarose, a natural polysaccharide derivative, is commonly used in ceramic gelcasting. Its curing process produces zero emissions, and its degradation products are environmentally friendly. Al2O3 ceramic bodies made with agarose gel can be directly sintered after freeze-drying, eliminating the need for a complex degreasing process. However, the use of agarose gel in ceramic gelcasting faces a key bottleneck: the gel curing time is as long as 2–4 hours, far exceeding the 5–10 minute curing speed of paraffin-based binder systems used in injection molding, severely restricting continuous production.

[0008] Therefore, the research and development of a formula for preparing Al2O3 ceramic slurry using agarose for composite molding is urgent. In the process of preparing Al2O3 ceramic slurry with agarose as a gelling agent, it is necessary to take advantage of the high green body strength, net size, and fast molding of injection molding, while effectively avoiding the environmental pollution problems caused by the volatilization of traditional organic binders such as paraffin. Therefore, it is particularly important to develop an Al2O3 ceramic slurry suitable for ceramic composite molding process and using agarose as a gelling agent for the preparation of Al2O3 ceramics. Through this innovative slurry formula, Al2O3 ceramics with high strength, complete molding body and high fracture resistance are prepared.

[0009] After in-depth research, it was found that there are not many literature or patents on the use of agarose as a gelling agent system in injection molding. Existing research is more focused on the study of agarose gel blocks. Patent document CN110935403A discloses a method for efficiently making agarose gel. This patent research mainly focuses on the mechanical properties, stability and other aspects of the gel block; there is also Hao Junliang's research on the gel injection device, patent number: CN113910529B agarose gel injection molding device, which focuses on optimizing the structure of the injection device to improve the efficiency and accuracy of the injection process. These patents basically focus on the study of agarose as a gelling agent and the exploration of the characteristics of agarose itself, but lack the overall research and development of the Al2O3 ceramic slurry formula with agarose as a gelling agent, which also provides a new direction and entry point for subsequent research. Summary of the Invention

[0010] Technical issues solved:

[0011] This application addresses the shortcomings of the existing technology, such as the complex elimination process, environmental pollution, and a gel time of 2 to 4 hours, which is much higher than the 5 to 10 minute curing speed of the paraffin-based binder system, and seriously restricts continuous production. The application provides an alumina ceramic compositely formed by injection molding and injection process and a preparation method thereof.

[0012] Technical solution:

[0013] To achieve the above objectives, this application is implemented through the following technical solutions:

[0014] A method for preparing alumina ceramics by composite molding using a condensation and injection process, comprising the following steps:

[0015] Step 1: Prepare a powder binder material by mixing 85-90 parts of agarose, 3-5 parts of oleic acid, and 5-12 parts of stearic acid according to the mass ratio;

[0016] Step 2: Place the powdered binder material in a beaker and heat until completely dissolved to obtain an agarose gel;

[0017] Step 3: Weigh four times the mass of Al2O3 powder of the agarose gel, and add the powder to the agarose gel in three batches according to the mass ratio of 5-6:2-2.5:2-2.5 to obtain Al2O3 ceramic slurry, that is, add 50-60wt.% of Al2O3 powder in the first batch, add 20-25wt.% of Al2O3 powder in the second batch, and add 20-25wt.% of Al2O3 powder in the third batch;

[0018] Step 4: Place the Al2O3 ceramic slurry on a magnetic stirrer and heat and stir to prepare a ceramic slurry;

[0019] Step 5: placing the ceramic slurry in a vacuum pressure degassing machine for degassing to obtain alumina ceramic slurry that can be used for composite molding;

[0020] Step 6: Alumina ceramic slurry is used as the raw material of composite molding process equipment, and the composite molding process equipment is an injection molding machine. Al2O3 ceramic green body is made through injection molding process; the Al2O3 ceramic green body is subjected to binder removal, vacuum sintering and polishing to obtain a ceramic finished product.

[0021] Furthermore, in the second step, the heating temperature of the powder binder material is 80-90°C.

[0022] Furthermore, in the third step, the time interval after each batch of Al2O3 powder is 1.8 to 2.3 hours before the next batch of Al2O3 powder is added.

[0023] Furthermore, in the fourth step, the heating temperature of the magnetic stirrer is 95-105° C., the magnetic stirring speed is 480-550 r / min, and the stirring time is 7-9 h.

[0024] Furthermore, the vacuum pressure degassing time in the fifth step is 70 to 90 seconds.

[0025] Furthermore, in the sixth step, the injection molding process is performed for 2 to 2.5 seconds, the injection pressure is 15 to 30 MPa, and the temperature is 95 to 105° C., and an Al 2 O 3 ceramic blank is obtained by injection.

[0026] Furthermore, the debinding process in the sixth step is as follows: the temperature rise rate from room temperature to 120°C is 1.8-2.3°C / min, the temperature rise rate from 120-160°C is 10-12°C / h, the temperature rise rate from 160-360°C is 20-22°C / h, the temperature is kept at 360°C for 1 hour, the temperature rise rate from 360-600°C is 30-32°C / h, the temperature is kept at 600°C for 2 hours, and then cooled to room temperature at 5-8°C / min.

[0027] Furthermore, the vacuum sintering process in the sixth step is to heat the material from room temperature to 1700° C. at a rate of 8 to 10° C. / min, keep the temperature at 1700° C. for 3 hours, and then cool the material to room temperature with the furnace.

[0028] The present application also discloses an alumina ceramic produced by composite molding using the condensation casting and injection processes and obtained by any of the above-mentioned preparation methods.

[0029] Principle explanation: Complex-shaped Al2O3 ceramics are prepared by "casting + injection" composite molding. The casting process uses agarose as a binder. After mixing, heating, stirring and other operations, an Al2O3 ceramic slurry with a solid content of 80wt.% is prepared after sufficient mixing. Most slurries prepared by the casting process are poured by the pouring method. This patent changes the pouring to injection, and the injection machine is injected into the mold under high pressure to generate a three-dimensional network structure in the mold, so that the ceramic is fixed in situ. After cooling, a blank is obtained. The blank produced by injection molding is sintered by debinding to prepare Al2O3 ceramic samples; this technology combines the characteristics of high-temperature melting and low-temperature solidification of agarose, so that the "casting + injection" composite molding of ceramics has significant advantages such as no pollution, complete molding body, no breakage, and no residue after sintering.

[0030] Beneficial effects:

[0031] The present application provides an alumina ceramic compositely formed by gelcasting and injection molding and a preparation method thereof, which has the following advantages compared with the prior art:

[0032] 1. The present invention provides a method for composite molding of alumina ceramics using gelcasting and injection molding processes. By innovatively integrating gelcasting and injection molding processes, the limitations of single molding technology are overcome.

[0033] 2. Compared with traditional gelcasting, this method achieves efficient encapsulation of ceramic particles during the injection molding process through the in-situ solidification of the agarose three-dimensional network structure, effectively preventing particle agglomeration and ensuring that the green body has both high integrity and the ability to form complex shapes.

[0034] 3. The flexural strength of the ceramic green body obtained by the present invention is improved compared with that of single injection molding, while breaking through the technical bottleneck of traditional injection molding, which is that it is highly dependent on molds and difficult to prepare highly complex Al2O3 ceramic components;

[0035] 4. Use naturally degradable agarose to completely replace the traditional paraffin binder system, eliminating VOCs pollution caused by the volatilization of organic solvents in paraffin-based processes;

[0036] 5. The biocompatibility and environmental friendliness of agarose enable the production process to comply with the requirements of the ISO 14000 environmental management system, shortening the waste degradation cycle by 80%, achieving green manufacturing throughout the entire process from raw materials to finished products, and providing a sustainable development solution for the precision ceramics industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a physical picture of the high-strength Al2O3 ceramic blank after injection molding in Example 1 of the present application, where the left picture is a top view and the right picture is a three-dimensional view. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and should not be used to limit the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing alumina ceramics by composite molding using a condensation and injection process, comprising the following steps:

[0041] Step 1: Prepare a powder binder material by mixing 89.5 parts of agarose, 4.5 parts of oleic acid, and 6 parts of stearic acid according to the mass ratio, weighing 17.9g of agarose, 0.9g of oleic acid, and 1.2g of stearic acid, for a total of 20g;

[0042] Step 2: Place the powdered binder material in a beaker and heat it at 88°C until it is completely dissolved to obtain an agarose gel;

[0043] Step 3: Weigh 80g of Al2O3 powder, divide the Al2O3 powder into three portions and add them one by one into agarose gel to obtain Al2O3 ceramic slurry; add the next batch of Al2O3 powder after each batch of Al2O3 powder is added at an interval of 1.8 to 2.3 hours, that is, after the initial addition of 40g (50wt.%) Al2O3 powder, add 20g (25wt.%) Al2O3 powder after an interval of 2 hours, and then add 20g (25wt.%) Al2O3 powder after an interval of 2 hours;

[0044] Step 4: Place the Al2O3 ceramic slurry on a magnetic stirrer and heat and stir it at a temperature of 100°C, a magnetic stirring speed of 550 r / min, and a heating and stirring time of 7 hours to prepare a ceramic slurry;

[0045] Step 5: Place the ceramic slurry in a vacuum pressure degassing machine for 80 seconds to obtain an alumina ceramic slurry that can be used for composite molding;

[0046] Step 6: Alumina ceramic slurry is used as the raw material of the composite molding process equipment, and the composite molding process equipment is an injection machine. Al2O3 ceramics are made by injection molding process. The injection molding process has an injection time of 2.2s, an injection pressure of 20Mpa, and an injection temperature of 100℃. The green billet is obtained by injection; the green billet is subjected to debinding, vacuum sintering, and polishing to obtain an Al2O3 ceramic gear with an outer diameter of about 30mm; the debinding process is to start from room temperature and heat up to 120℃ at a heating rate of 2℃ / min, then to 160℃ at a heating rate of 12℃ / h, then to 360℃ at a heating rate of 22℃ / h, and keep warm for 1h, then to 600℃ at a heating rate of 32℃ / h, and keep warm for 2h, and finally to cool to room temperature at a cooling rate of 4.8℃ / min; the vacuum sintering process is from room temperature to 1700℃ at a heating rate of 8℃ / min, keep warm at 1700℃ for 3h, and then cool to room temperature with the furnace.

[0047] Example 2

[0048] A method for preparing alumina ceramics by composite molding using a condensation and injection process, comprising the following steps:

[0049] Step 1: Prepare a powder binder material by mixing 90 parts of agarose, 5 parts of oleic acid, and 5 parts of stearic acid according to the mass ratio, weighing 9g of agarose, 0.5g of oleic acid, and 0.5g of stearic acid, for a total of 10g;

[0050] Step 2: Place the powdered binder material in a beaker and heat at 90°C until completely dissolved to obtain an agarose gel;

[0051] Step 3: Weigh 40g of Al2O3 powder, divide the Al2O3 powder into three parts according to the mass ratio of 6:2:2, and add them one by one into agarose gel to obtain Al2O3 ceramic slurry; after each batch of Al2O3 powder is added, the time interval is 1.8 to 2.3 hours before the next batch of Al2O3 powder is added, that is, after the initial addition of 24g (60wt.%) Al2O3 powder, 8g (20wt.%) Al2O3 powder is added after an interval of 2 hours, and 8g (20wt.%) Al2O3 powder is added after an interval of 2 hours;

[0052] Step 4: Place the Al2O3 ceramic slurry on a magnetic stirrer and heat and stir it at a temperature of 95°C, a magnetic stirring speed of 500 r / min, and a heating and stirring time of 9 hours to prepare a ceramic slurry;

[0053] Step 5: Place the ceramic slurry in a vacuum pressure degassing machine for 70 seconds to obtain an alumina ceramic slurry that can be used for composite molding;

[0054] Step 6: Alumina ceramic slurry is used as the raw material of the composite molding process equipment. The composite molding process equipment is an injection molding machine. Al2O3 ceramics are made by injection molding process. The injection time of the injection molding process is 2s, the injection pressure is 15Mpa, and the injection temperature is 95℃. The green billet is obtained by injection; the green billet is subjected to debinding, vacuum sintering, and polishing to obtain an Al2O3 ceramic gear with an outer diameter of about 30mm; the debinding process is to start from room temperature and heat up to 120℃ at a heating rate of 1.8℃ / min, then heat up to 160℃ at a rate of 10℃ / h, then heat up to 360℃ at a rate of 20℃ / h, and keep warm for 1h, then heat up to 600℃ at a rate of 30℃ / h, and keep warm for 2h, and finally cool to room temperature at a rate of 5℃ / min; the vacuum sintering process is room temperature to 1700℃

[0055] The heating rate was 8°C / min, and the sample was kept at 1700°C for 3 h, and then cooled to room temperature along with the furnace.

[0056] Example 3

[0057] A method for preparing alumina ceramics by composite molding using a condensation and injection process, comprising the following steps:

[0058] Step 1: Prepare a powder binder material by mixing 85 parts of agarose, 3 parts of oleic acid, and 12 parts of stearic acid according to the mass ratio, weighing 25.5g of agarose, 0.9g of oleic acid, and 3.6g of stearic acid, for a total of 30g;

[0059] Step 2: Place the powdered binder material in a beaker and heat at 95°C until completely dissolved to obtain an agarose gel;

[0060] Step 3: Weigh 120g of Al2O3 powder, divide the Al2O3 powder into three parts according to the mass ratio of 5.5:2.25:2.25, and add them one by one into agarose gel to obtain Al2O3 ceramic slurry; after each batch of Al2O3 powder is added, the time interval is 2h before adding the next batch of Al2O3 powder, that is, after the initial addition of 66g (55wt.%) Al2O3 powder, 27g (22.5wt.%) Al2O3 powder is added after an interval of 2h, and 27g (22.5wt.%) Al2O3 powder is added after an interval of 2h;

[0061] Step 4: Place the Al2O3 ceramic slurry on a magnetic stirrer and heat and stir it at a temperature of 105°C, a magnetic stirring speed of 480 r / min, and a heating and stirring time of 8 hours to prepare a ceramic slurry;

[0062] Step 5: Place the ceramic slurry in a vacuum pressure degassing machine for 90 seconds to obtain an alumina ceramic slurry that can be used for composite molding;

[0063] Step 6: Alumina ceramic slurry is used as the raw material of the composite molding process equipment, and the composite molding process equipment is an injection machine. Al2O3 ceramics are made by injection molding process. The injection molding process has an injection time of 2s, an injection pressure of 30Mpa, and an injection temperature of 105℃. The green billet is obtained by injection; the green billet is subjected to debinding, vacuum sintering, and polishing to obtain an Al2O3 ceramic gear with an outer diameter of about 30mm; the debinding process is to start from room temperature and heat up to 120℃ at a heating rate of 1.8℃ / min, then to 160℃ at a heating rate of 10℃ / h, then to 360℃ at a heating rate of 20℃ / h, and keep warm for 1h, then to 600℃ at a heating rate of 30℃ / h, and keep warm for 2h, and finally to cool to room temperature at a cooling rate of 5℃ / min; the vacuum sintering process is room temperature to 1700℃ at a heating rate of 8℃ / min, keep warm at 1700℃ for 3h, and then cool to room temperature with the furnace.

[0064] The examples selected in the above materials are intended to facilitate understanding and are not intended to limit the process. Those skilled in the art may readily modify the process or transfer it to other cases without inventive change. If such modifications fall within the same scope of claims or similar technologies as the present invention, the invention is intended to encompass such modifications.

Claims

1. A method for preparing alumina ceramics by composite molding using a condensation and injection process, characterized in that: The specific steps are: Step 1: Prepare a powder binder material by mixing 85-90 parts of agarose, 3-5 parts of oleic acid, and 5-12 parts of stearic acid according to the mass ratio; Step 2: Place the powdered binder material in a beaker and heat until completely dissolved to obtain an agarose gel; Step 3: Weigh four times the mass of Al2O3 powder of the agarose gel, and add the powder to the agarose gel in three batches according to the mass ratio of 5-6:2-2.5:2-2.5 to obtain Al2O3 ceramic slurry, that is, add 50-60wt.% of Al2O3 powder in the first batch, add 20-25wt.% of Al2O3 powder in the second batch, and add 20-25wt.% of Al2O3 powder in the third batch; Step 4: Place the Al2O3 ceramic slurry on a magnetic stirrer and heat and stir to prepare a ceramic slurry; Step 5: placing the ceramic slurry in a vacuum pressure degassing machine for degassing to obtain alumina ceramic slurry that can be used for composite molding; Step 6: Alumina ceramic slurry is used as the raw material of composite molding process equipment, and the composite molding process equipment is an injection molding machine. Al2O3 ceramic green body is made through injection molding process; the Al2O3 ceramic green body is subjected to binder removal, vacuum sintering and polishing to obtain a ceramic finished product.

2. The method for preparing alumina ceramics by composite molding using a gelcasting and injection process according to claim 1, characterized in that: In the second step, the heating temperature of the powder binder material is 80-90°C.

3. The method for preparing alumina ceramics by composite molding using a gelcasting and injection process according to claim 1, characterized in that: The time interval between each batch of Al2O3 powder in the third step is Add the next batch of Al2O3 powder after 1.8 to 2.3 hours.

4. The method for preparing alumina ceramics by composite molding of gelcasting and injection molding according to claim 1, characterized in that: In the fourth step, the heating temperature of the magnetic stirrer is 95-105° C., the magnetic stirring speed is 480-550 r / min, and the stirring time is 7-9 h.

5. The method for preparing alumina ceramics by composite molding of gelcasting and injection molding according to claim 1, characterized in that: The vacuum pressure defoaming time in the fifth step is 70 to 90 seconds.

6. The method for preparing alumina ceramics by composite molding of gelcasting and injection molding according to claim 1, characterized in that: The injection molding process time in the sixth step is 2 to 2.5 seconds, and the injection pressure is 15~30Mpa, temperature 95~105℃, Al2O3 ceramic green body is obtained by injection.

7. The method for preparing alumina ceramics by composite molding of gelcasting and injection molding according to claim 1, characterized in that: The debinding process in the sixth step is as follows: the temperature rises from room temperature to 120°C at a rate of 1.8 to 2.3°C / min, the temperature rises from 120 to 160°C at a rate of 10 to 12°C / h, the temperature rises from 160 to 360°C at a rate of 20 to 22°C / h, the temperature is kept at 360°C for 1 hour, the temperature rises from 360 to 600°C at a rate of 30 to 32°C / h, the temperature is kept at 600°C for 2 hours, and then the temperature is cooled to room temperature at a rate of 5 to 8°C / min.

8. The method for preparing alumina ceramics by composite molding of gelcasting and injection molding according to claim 1, characterized in that: The vacuum sintering process in the sixth step is room temperature to 1700°C and the heating rate is 8~10℃ / min, keep warm at 1700℃ for 3h, and then cool to room temperature with the furnace.

9. Alumina ceramics produced by composite molding using the gelcasting and injection processes according to any one of the preparation methods of claims 1-8.

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