Silicon nitride four-hole sleeve and manufacturing method thereof

Abstract

This invention provides a silicon nitride four-cavity sleeve and its manufacturing method, relating to the field of special ceramic product manufacturing technology. The method includes sequentially subjecting the silicon nitride slurry to vacuum degassing, vibration degassing, and sieve degassing, then injecting it into a paraffin mold with four-cavity sleeve cavities for integral sealing and gel molding. After demolding by water bath heating, the slurry undergoes staged drying (first sealed, then opened) and is then trimmed to obtain a silicon nitride four-cavity sleeve green body. This silicon nitride four-cavity sleeve and its manufacturing method, through ball milling and dispersion of silicon nitride powder, spray drying and granulation pretreatment, and mixing the granulated powder with an organic system for gel injection molding, combined with vacuum degassing, vibration degassing, and sieve degassing treatments, achieves improved slurry dispersion uniformity and powder sphericity, thereby increasing the solid content, density, and structural uniformity of the green body, reducing internal voids and molding defects, and facilitating the integral molding of the complex structure of the four-cavity sleeve.

Description

Technical Field

[0001] This invention relates to the field of special ceramic product manufacturing technology, specifically to a silicon nitride four-cavity sleeve and its manufacturing method. Background Technology

[0002] Silicon nitride ceramics possess characteristics such as low coefficient of thermal expansion, good thermal shock resistance, high thermal conductivity, and good dimensional stability at high temperatures. They have been used in the manufacture of special ceramic components, such as sleeves, where high temperature resistance, dimensional accuracy, and operational stability are required. In existing technologies, these components are typically produced by mixing ceramic powder with additives, followed by ball milling dispersion, granulation, slurry forming, green body demolding and drying, and high-temperature sintering. For more complex porous sleeve-like products, injection molding, debinding and sintering, and subsequent finishing processes are usually required to meet the structural forming and dimensional accuracy requirements of the product.

[0003] However, existing manufacturing processes for silicon nitride sleeve-type special ceramic products still have shortcomings: insufficient powder dispersion and mixing uniformity can easily lead to poor slurry stability and affect sintering density; inadequate degassing of the slurry, improper control of green body demolding and drying can easily result in porosity, cracking, or deformation; and unreasonable debinding and sintering processes can also lead to incomplete binder removal and insufficient densification. Especially for complex silicon nitride ceramic components such as four-cavity sleeves, these problems are more likely to affect their dimensional stability, structural integrity, and yield, thus existing technologies still cannot reliably meet the manufacturing requirements of this type of special ceramic product. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a silicon nitride four-cavity sleeve and its manufacturing method. The technical problem this invention aims to solve is: how to address the problems of uneven powder dispersion, insufficient defoaming of slurry, easy cracking and deformation of green body, incomplete glue removal, and insufficient sintering density in the manufacturing process of four-cavity sleeve-type silicon nitride ceramic products by means of silicon nitride powder pretreatment, gel casting molding, staged drying, and staged pressurized sintering.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a silicon nitride four-cavity sleeve, comprising:

[0006] The sleeve body is a special ceramic sintered body made of silicon nitride as the main material; the sleeve body is provided with model holes, the number of which is 4, the model holes are cylindrical through holes that penetrate the two opposite end faces of the sleeve body, and the model holes are distributed in two rows and two columns at equal intervals.

[0007] The sleeve body is provided with a feed port, and there are two feed ports. Each feed port is a cylindrical through hole that passes through the two opposite side ends of the sleeve body. The feed ports are arranged side by side at equal intervals and are located between two model holes in a corresponding row.

[0008] The sleeve body is provided with a fixing groove, and the number of fixing grooves is 4. The fixing grooves are opened on the outer peripheral wall of the sleeve body and are respectively located on the upper side, lower side, left side and right side of the sleeve body.

[0009] The sleeve body is provided with a positioning hole, and the number of positioning holes is one. The positioning hole is located in the central area surrounded by four model holes, and the positioning hole is a cylindrical through hole that penetrates the two opposite end faces of the sleeve body.

[0010] Preferably, the alumina sintering aid content in the sleeve body is 2 wt.%, the axes of the model holes are parallel to each other, the axis of the positioning hole is parallel to the axis of the model hole, and the axes of the two feed ports are parallel to each other and both are perpendicular to the axis of the model hole.

[0011] Preferably, the fixing grooves are respectively disposed at the middle position of the four sides of the outer peripheral wall of the sleeve body, wherein the two fixing grooves located on the upper and lower sides are arranged opposite each other, and the two fixing grooves located on the left and right sides are arranged opposite each other.

[0012] A method for manufacturing a silicon nitride four-cavity sleeve includes:

[0013] S1. Mix silicon nitride powder with alumina sintering aid, add dispersant and pure water, and ball mill to disperse the mixture to obtain a mixed slurry. Then, spray dry and granulate the mixed slurry to obtain silicon nitride granulated powder.

[0014] S2. The silicon nitride granulated powder is mixed with an organic system containing monomers, crosslinking agents, dispersants, catalysts and initiators to prepare silicon nitride slurry;

[0015] S3. After the silicon nitride slurry is subjected to vacuum degassing, vibration degassing and sieve degassing in sequence, it is injected into a paraffin mold with a four-cavity sleeve for overall sealing and gel molding. After demolding by water bath heating, it is dried in stages by sealing and then opening, and then trimmed to obtain a silicon nitride four-cavity sleeve green blank.

[0016] S4. The silicon nitride four-cavity sleeve green blank is subjected to negative pressure degreasing, micro-positive pressure sintering, and segmented pressurized gas pressure sintering under nitrogen atmosphere in sequence. The furnace pressure of the micro-positive pressure sintering is 35 mbar. During the segmented pressurized gas pressure sintering process, the furnace pressure is adjusted to 8±0.1 bar, 10±0.1 bar and 55±0.1 bar in sequence as the temperature rises. After heat preservation sintering, cooling and depressurization, it is finely ground to obtain the silicon nitride four-cavity sleeve.

[0017] Preferably, the amount of alumina sintering aid added is 2 wt.% of the mass of the silicon nitride powder, the dispersant includes ammonium polyacrylate and tetramethylammonium hydroxide, the amount of ammonium polyacrylate added is 1 wt.% of the mass of the silicon nitride powder, and the amount of tetramethylammonium hydroxide added is 3 wt.% of the mass of the silicon nitride powder.

[0018] Preferably, the ball milling dispersion uses silicon nitride grinding stones, the mass ratio of silicon nitride powder to silicon nitride grinding stones is 1:2, the solid content of the mixed slurry is 55%, the ball milling time is 6 hours, the inlet air temperature of the spray drying granulation is 220°C, the outlet air temperature is 120°C, and the peristaltic pump speed is 30 r / min.

[0019] Preferably, the monomer in the organic system is acrylic acid, the crosslinking agent is N,N-methyleneacrylamide, the dispersant in the organic system is tetramethylammonium hydroxide and ammonium polyacrylate, the catalyst is tetramethylethylenediamine, the initiator is sodium persulfate, and the mass ratio of the monomer, crosslinking agent, dispersant and catalyst is 16:2:1:1.

[0020] Preferably, the vacuum defoaming, vibration defoaming, and sieving defoaming are performed sequentially. The vacuum defoaming is used to remove air bubbles from the slurry, the vibration defoaming is used to further remove residual air bubbles from the slurry, and the sieving defoaming is used to remove agglomerated particles from the slurry.

[0021] Preferably, the integral sealing gel molding involves injecting the silicon nitride slurry into the paraffin mold and then sealing it entirely for 18 hours; the staged drying involves demolding the mold after water bath heating, first sealing it in a sealing bag and drying it at 50°C for 12 hours, then opening it and drying it at 90°C for 12 hours.

[0022] Preferably, the negative pressure degreasing involves raising the temperature from room temperature to 320°C within 90 minutes, then raising it to 370°C within 30 minutes, and then raising it to 450°C within 60 minutes and holding it at that temperature for 30 minutes; the micro-positive pressure sintering involves raising the temperature from 450°C to 1000°C within 82 minutes after the negative pressure degreasing, and adjusting the gas pressure inside the furnace to 35 mbar; the segmented pressurized gas pressure sintering involves raising the temperature from 1000°C to 1450°C at a rate of 3°C / min after the micro-positive pressure sintering, and adjusting the nitrogen gas pressure inside the furnace during the heating process. The pressure was increased to 8±0.1 bar and held for 50 min; then the temperature was increased from 1450℃ to 1600℃ over 60 min, and the furnace pressure was adjusted to 10±0.1 bar and held for 30 min; then the temperature was increased from 1600℃ to 1880℃ over 100 min, and the furnace pressure was adjusted to 55±0.1 bar and held for 60 min; then the temperature was decreased from 1880℃ to 1400℃ at a rate of 3℃ / min under a pressure of 40±0.1 bar and held for 100 min, and then cooled with the furnace and the pressure was released to room temperature and atmospheric pressure.

[0023] This invention provides a silicon nitride four-cavity sleeve and its manufacturing method. It has the following beneficial effects:

[0024] The silicon nitride four-cavity sleeve and its manufacturing method involve ball milling and dispersing silicon nitride powder, spray drying and granulation pretreatment, mixing the granulated powder with an organic system and then performing gel casting molding. Simultaneously, vacuum degassing, vibration degassing and sieving degassing treatments are used to improve the uniformity of slurry dispersion and the sphericity of powder, thereby increasing the solid content, density and structural uniformity of the green body, reducing internal voids and molding defects, and facilitating the integrated molding of the complex structure of the four-cavity sleeve.

[0025] The process employs a combination of integral sealing molding with paraffin molds, staged drying after demolding, and sintering processes including negative pressure degreasing, micro-positive pressure sintering, and segmented pressurized gas pressure sintering. This process helps to prevent cracking of the green blank, promotes sufficient glue removal, and improves sintering density. As a result, the obtained silicon nitride four-cavity sleeve has better dimensional stability, thermal shock resistance, and yield, making it more suitable for stable use in mobile phone lens molds under high-temperature conditions. Attached Figure Description

[0026] Figure 1 A three-dimensional structural diagram of a silicon nitride four-cavity sleeve;

[0027] Figure 2 A partial cross-sectional view of a silicon nitride four-cavity sleeve;

[0028] Figure 3 This is a flowchart of the preparation method of the present invention;

[0029] Figure 4This is a schematic diagram of the segmented pressurized gas pressure sintering of the present invention.

[0030] The components include: 1. feed inlet; 2. fixing groove; 3. positioning hole; 4. model hole; and 5. sleeve body. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] like Figure 1-4 As shown, an embodiment of the present invention provides a silicon nitride four-cavity sleeve, comprising: The sleeve body 5 is a special ceramic sintered body made primarily of silicon nitride. The sleeve body 5 has four model holes 4, each a cylindrical through-hole penetrating two opposite end faces of the sleeve body 5, arranged in two rows and two columns at even intervals. The alumina sintering aid content in the sleeve body 5 is 2 wt.%. The axes of the model holes 4 are parallel to each other, the axis of the positioning hole 3 is parallel to the axis of the model holes 4, and the axes of the two feed inlets 1 are parallel to each other and perpendicular to the axis of the model holes 4.

[0035] The sleeve body 5 is provided with a feed port 1. There are two feed ports 1. The feed ports 1 are cylindrical through holes that penetrate the two opposite side end faces of the sleeve body 5. The feed ports 1 are arranged side by side at equal intervals and are located between two model holes 4 in a corresponding row.

[0036] The sleeve body 5 is provided with four fixing grooves 2. The fixing grooves 2 are formed on the outer peripheral wall of the sleeve body 5 and are located on the upper, lower, left, and right sides of the sleeve body 5, respectively. The fixing grooves 2 are respectively located at the middle of the four sides of the outer peripheral wall of the sleeve body 5, wherein the two fixing grooves 2 located on the upper and lower sides are arranged opposite each other, and the two fixing grooves 2 located on the left and right sides are arranged opposite each other.

[0037] The sleeve body 5 is provided with a positioning hole 3. There is one positioning hole 3. The positioning hole 3 is located in the central area surrounded by four model holes 4. The positioning hole 3 is a cylindrical through hole that penetrates the two opposite end faces of the sleeve body 5.

[0038] A method for manufacturing a silicon nitride four-cavity sleeve includes:

[0039] S1. Silicon nitride powder is mixed with alumina sintering aid, and a dispersant and pure water are added for ball milling dispersion to obtain a mixed slurry. The mixed slurry is then spray-dried and granulated to obtain silicon nitride granulated powder. The amount of alumina sintering aid added is 2 wt.% of the mass of silicon nitride powder. The dispersant includes ammonium polyacrylate and tetramethylammonium hydroxide. The amount of ammonium polyacrylate added is 1 wt.% of the mass of silicon nitride powder, and the amount of tetramethylammonium hydroxide added is 3 wt.% of the mass of silicon nitride powder. Silicon nitride grinding stones are used for ball milling dispersion. The mass ratio of silicon nitride powder to silicon nitride grinding stones is 1:2. The solid content of the mixed slurry is 55%. The ball milling time is 6 hours. The inlet air temperature for spray drying and granulation is 220℃, the outlet air temperature is 120℃, and the peristaltic pump speed is 30 r / min.

[0040] S2. Silicon nitride granulated powder is mixed with an organic system containing monomers, crosslinking agents, dispersants, catalysts, and initiators to prepare a silicon nitride slurry. The monomer in the organic system is acrylic acid, the crosslinking agent is N,N-methyleneacrylamide, the dispersants are tetramethylammonium hydroxide and ammonium polyacrylate, the catalyst is tetramethylethylenediamine, and the initiator is sodium persulfate. The mass ratio of monomer, crosslinking agent, dispersant, and catalyst is 16:2:1:1.

[0041] S3. After sequentially performing vacuum degassing, vibration degassing, and sieve degassing on the silicon nitride slurry, it is injected into a paraffin mold with a four-cavity sleeve for integral sealing and gel molding. After demolding by water bath heating, it undergoes staged drying with a combination of sealing and opening, and is then trimmed to obtain a silicon nitride four-cavity sleeve preform. Vacuum degassing, vibration degassing, and sieve degassing are performed sequentially. Vacuum degassing removes air bubbles from the slurry, vibration degassing further removes residual air bubbles, and sieve degassing removes agglomerated particles. Integral sealing and gel molding involves injecting the silicon nitride slurry into the paraffin mold and sealing it for 18 hours. Staged drying involves demolding by water bath heating, first sealing it in a sealed bag and drying it at 50°C for 12 hours, then opening it and drying it at 90°C for 12 hours.

[0042] S4. The silicon nitride four-cavity sleeve green blank is subjected to negative pressure degreasing, micro-positive pressure sintering, and segmented pressurized gas pressure sintering under nitrogen atmosphere in sequence. The furnace pressure during micro-positive pressure sintering is 35 mbar. During segmented pressurized gas pressure sintering, the furnace pressure is adjusted sequentially to 8±0.1 bar, 10±0.1 bar, and 55±0.1 bar as the temperature increases. After holding sintering, cooling, and depressurization, it is finely ground to obtain the silicon nitride four-cavity sleeve. Negative pressure degreasing involves raising the temperature from room temperature to 320℃ within 90 minutes, then raising it to 370℃ within 30 minutes, and then raising it to 450℃ within 60 minutes and holding it at that temperature for 30 minutes. Micro-positive pressure sintering involves raising the temperature from 450℃ to 1000℃ within 82 minutes after negative pressure degreasing, while adjusting the furnace pressure to 35 mbar. The segmented pressurized gas pressure sintering process involved first performing micro-positive pressure sintering, then heating from 1000℃ to 1450℃ at a rate of 3℃ / min, with the nitrogen pressure inside the furnace increased to 8±0.1 bar and held for 50 min. Subsequently, the temperature was increased from 1450℃ to 1600℃ over 60 min, with the furnace pressure adjusted to 10±0.1 bar and held for 30 min. Then, the temperature was increased from 1600℃ to 1880℃ over another 100 min, with the furnace pressure adjusted to 55±0.1 bar and held for 60 min. Finally, the temperature was reduced from 1880℃ to 1400℃ at a rate of 3℃ / min under a pressure of 40±0.1 bar and held for 100 min, after which the furnace was cooled and the pressure was released to room temperature and atmospheric pressure.

[0043] This embodiment adopts a preparation method that combines powder pretreatment, slurry defoaming, overall sealing molding, staged drying, and segmented degreasing and sintering. This forms a process route with complete step connections and detailed process control, which is suitable for scenarios with high requirements for the stability, consistency and repeatability of the preparation process. It is also suitable as a preferred solution for formal production or process finalization.

[0044] Example 2

[0045] A silicon nitride four-cavity sleeve, comprising:

[0046] The sleeve body 5 is a special ceramic sintered body made primarily of silicon nitride. The sleeve body 5 has four model holes 4, each a cylindrical through-hole penetrating two opposite end faces of the sleeve body 5, arranged in two rows and two columns at even intervals. The alumina sintering aid content in the sleeve body 5 is 2 wt.%. The axes of the model holes 4 are parallel to each other, the axis of the positioning hole 3 is parallel to the axis of the model holes 4, and the axes of the two feed inlets 1 are parallel to each other and perpendicular to the axis of the model holes 4.

[0047] The sleeve body 5 is provided with a feed port 1. There are two feed ports 1. The feed ports 1 are cylindrical through holes that penetrate the two opposite side end faces of the sleeve body 5. The feed ports 1 are arranged side by side at equal intervals and are located between two model holes 4 in a corresponding row.

[0048] The sleeve body 5 is provided with four fixing grooves 2. The fixing grooves 2 are formed on the outer peripheral wall of the sleeve body 5 and are located on the upper, lower, left, and right sides of the sleeve body 5, respectively. The fixing grooves 2 are respectively located at the middle of the four sides of the outer peripheral wall of the sleeve body 5, wherein the two fixing grooves 2 located on the upper and lower sides are arranged opposite each other, and the two fixing grooves 2 located on the left and right sides are arranged opposite each other.

[0049] The sleeve body 5 is provided with a positioning hole 3. There is one positioning hole 3. The positioning hole 3 is located in the central area surrounded by four model holes 4. The positioning hole 3 is a cylindrical through hole that penetrates the two opposite end faces of the sleeve body 5.

[0050] A method for manufacturing a silicon nitride four-cavity sleeve includes:

[0051] S1. Silicon nitride powder is mixed with alumina sintering aid, and a dispersant and pure water are added for ball milling dispersion to obtain a mixed slurry. The mixed slurry is then spray-dried and granulated to obtain silicon nitride granulated powder. The amount of alumina sintering aid added is 2 wt.% of the mass of silicon nitride powder. The dispersant includes ammonium polyacrylate and tetramethylammonium hydroxide. The amount of ammonium polyacrylate added is 1 wt.% of the mass of silicon nitride powder, and the amount of tetramethylammonium hydroxide added is 3 wt.% of the mass of silicon nitride powder. Silicon nitride grinding stones are used for ball milling dispersion. The mass ratio of silicon nitride powder to silicon nitride grinding stones is 1:2. The solid content of the mixed slurry is 55%. The ball milling time is 6 hours. The inlet air temperature for spray drying and granulation is 220℃, the outlet air temperature is 120℃, and the peristaltic pump speed is 30 r / min.

[0052] S2. Silicon nitride granulated powder is mixed with an organic system containing monomers, crosslinking agents, dispersants, catalysts, and initiators to prepare a silicon nitride slurry. The monomer in the organic system is acrylic acid, the crosslinking agent is N,N-methyleneacrylamide, the dispersants are tetramethylammonium hydroxide and ammonium polyacrylate, the catalyst is tetramethylethylenediamine, and the initiator is sodium persulfate. The mass ratio of monomer, crosslinking agent, dispersant, and catalyst is 16:2:1:1.

[0053] S3. After sequentially performing vacuum degassing, vibration degassing, and sieve degassing on the silicon nitride slurry, it is injected into a paraffin mold with a four-cavity sleeve and left to stand for 18 hours. After demolding by water bath heating, it is dried at 50°C for 6 hours, then dried at 90°C for 12 hours, and trimmed to obtain a silicon nitride four-cavity sleeve green body. Vacuum degassing, vibration degassing, and sieve degassing are performed sequentially. Vacuum degassing is used to remove air bubbles in the slurry, vibration degassing is used to further remove residual air bubbles in the slurry, and sieve degassing is used to remove agglomerated particles in the slurry. Overall sealing and gel molding involves injecting the silicon nitride slurry into the paraffin mold and sealing it entirely for 18 hours. Staged drying involves demolding by water bath heating, first sealing it in a sealing bag and drying it at 50°C for 12 hours, then opening it and drying it at 90°C for 12 hours.

[0054] S4. The silicon nitride four-cavity sleeve green blank is subjected to negative pressure degreasing, micro-positive pressure sintering, and segmented pressurized gas pressure sintering under nitrogen atmosphere in sequence. The furnace pressure during micro-positive pressure sintering is 35 mbar. During segmented pressurized gas pressure sintering, the furnace pressure is adjusted sequentially to 8±0.1 bar, 10±0.1 bar, and 55±0.1 bar as the temperature increases. After holding sintering, cooling, and depressurization, it is finely ground to obtain the silicon nitride four-cavity sleeve. Negative pressure degreasing involves raising the temperature from room temperature to 320℃ within 90 minutes, then raising it to 370℃ within 30 minutes, and then raising it to 450℃ within 60 minutes and holding it at that temperature for 30 minutes. Micro-positive pressure sintering involves raising the temperature from 450℃ to 1000℃ within 82 minutes after negative pressure degreasing, while adjusting the furnace pressure to 35 mbar. The segmented pressurized gas pressure sintering process involved first performing micro-positive pressure sintering, then heating from 1000℃ to 1450℃ at a rate of 3℃ / min, with the nitrogen pressure inside the furnace increased to 8±0.1 bar and held for 50 min. Subsequently, the temperature was increased from 1450℃ to 1600℃ over 60 min, with the furnace pressure adjusted to 10±0.1 bar and held for 30 min. Then, the temperature was increased from 1600℃ to 1880℃ over another 100 min, with the furnace pressure adjusted to 55±0.1 bar and held for 60 min. Finally, the temperature was reduced from 1880℃ to 1400℃ at a rate of 3℃ / min under a pressure of 40±0.1 bar and held for 100 min, after which the furnace was cooled and the pressure was released to room temperature and atmospheric pressure.

[0055] This embodiment does not employ a fully sealed gel molding process or a phased drying method involving sealing followed by opening. Instead, it uses static molding and a shortened direct drying process. By adjusting the molding stage to static molding and the drying stage to a more direct, short-time drying method, a preparation method with a shorter cycle and simpler operation can be formed. This method is suitable for rapid trial production, preliminary process verification, and applications requiring compressed molding and drying cycles.

[0056] Example 3

[0057] A silicon nitride four-cavity sleeve, comprising:

[0058] The sleeve body 5 is a special ceramic sintered body made primarily of silicon nitride. The sleeve body 5 has four model holes 4, each a cylindrical through-hole penetrating two opposite end faces of the sleeve body 5, arranged in two rows and two columns at even intervals. The alumina sintering aid content in the sleeve body 5 is 2 wt.%. The axes of the model holes 4 are parallel to each other, the axis of the positioning hole 3 is parallel to the axis of the model holes 4, and the axes of the two feed inlets 1 are parallel to each other and perpendicular to the axis of the model holes 4.

[0059] The sleeve body 5 is provided with a feed port 1. There are two feed ports 1. The feed ports 1 are cylindrical through holes that penetrate the two opposite side end faces of the sleeve body 5. The feed ports 1 are arranged side by side at equal intervals and are located between two model holes 4 in a corresponding row.

[0060] The sleeve body 5 is provided with four fixing grooves 2. The fixing grooves 2 are formed on the outer peripheral wall of the sleeve body 5 and are located on the upper, lower, left, and right sides of the sleeve body 5, respectively. The fixing grooves 2 are respectively located at the middle of the four sides of the outer peripheral wall of the sleeve body 5, wherein the two fixing grooves 2 located on the upper and lower sides are arranged opposite each other, and the two fixing grooves 2 located on the left and right sides are arranged opposite each other.

[0061] The sleeve body 5 is provided with a positioning hole 3. There is one positioning hole 3. The positioning hole 3 is located in the central area surrounded by four model holes 4. The positioning hole 3 is a cylindrical through hole that penetrates the two opposite end faces of the sleeve body 5.

[0062] A method for manufacturing a silicon nitride four-cavity sleeve includes:

[0063] S1. Silicon nitride powder is mixed with alumina sintering aid, and a dispersant and pure water are added for ball milling dispersion to obtain a mixed slurry. The mixed slurry is then spray-dried and granulated to obtain silicon nitride granulated powder. The amount of alumina sintering aid added is 2 wt.% of the mass of silicon nitride powder. The dispersant includes ammonium polyacrylate and tetramethylammonium hydroxide. The amount of ammonium polyacrylate added is 1 wt.% of the mass of silicon nitride powder, and the amount of tetramethylammonium hydroxide added is 3 wt.% of the mass of silicon nitride powder. Silicon nitride grinding stones are used for ball milling dispersion. The mass ratio of silicon nitride powder to silicon nitride grinding stones is 1:2. The solid content of the mixed slurry is 55%. The ball milling time is 6 hours. The inlet air temperature for spray drying and granulation is 220℃, the outlet air temperature is 120℃, and the peristaltic pump speed is 30 r / min.

[0064] S2. Silicon nitride granulated powder is mixed with an organic system containing monomers, crosslinking agents, dispersants, catalysts, and initiators to prepare a silicon nitride slurry. The monomer in the organic system is acrylic acid, the crosslinking agent is N,N-methyleneacrylamide, the dispersants are tetramethylammonium hydroxide and ammonium polyacrylate, the catalyst is tetramethylethylenediamine, and the initiator is sodium persulfate. The mass ratio of monomer, crosslinking agent, dispersant, and catalyst is 16:2:1:1.

[0065] S3. After sequentially performing vacuum degassing, vibration degassing, and sieve degassing on the silicon nitride slurry, it is injected into a paraffin mold with a four-cavity sleeve for integral sealing and gel molding. After demolding by water bath heating, it undergoes staged drying with a combination of sealing and opening, and is then trimmed to obtain a silicon nitride four-cavity sleeve preform. Vacuum degassing, vibration degassing, and sieve degassing are performed sequentially. Vacuum degassing removes air bubbles from the slurry, vibration degassing further removes residual air bubbles, and sieve degassing removes agglomerated particles. Integral sealing and gel molding involves injecting the silicon nitride slurry into the paraffin mold and sealing it for 18 hours. Staged drying involves demolding by water bath heating, first sealing it in a sealed bag and drying it at 50°C for 12 hours, then opening it and drying it at 90°C for 12 hours.

[0066] S4. The silicon nitride four-cavity sleeve green blank is subjected to negative pressure degreasing, micro-positive pressure sintering, and segmented pressurized gas pressure sintering under nitrogen atmosphere in sequence. The furnace pressure during micro-positive pressure sintering is 35 mbar. During segmented pressurized gas pressure sintering, the furnace pressure is adjusted sequentially to 8±0.1 bar, 10±0.1 bar, and 55±0.1 bar as the temperature increases. After holding sintering, cooling, and depressurization, it is finely ground to obtain the silicon nitride four-cavity sleeve. Negative pressure degreasing involves slowly heating from room temperature to 450℃ at a rate of 1℃ / min and holding at that temperature for 30 min. Micro-positive pressure sintering involves heating from 450℃ to 1000℃ over 82 min after negative pressure degreasing, while adjusting the furnace pressure to 35 mbar. The segmented pressurized gas pressure sintering process involved first performing micro-positive pressure sintering, then heating from 1000℃ to 1450℃ at a rate of 3℃ / min, with the nitrogen pressure inside the furnace increased to 8±0.1 bar and held for 50 min. Subsequently, the temperature was increased from 1450℃ to 1600℃ over 60 min, with the furnace pressure adjusted to 10±0.1 bar and held for 30 min. Then, the temperature was increased from 1600℃ to 1880℃ over another 100 min, with the furnace pressure adjusted to 55±0.1 bar and held for 60 min. Finally, the temperature was reduced from 1880℃ to 1400℃ at a rate of 3℃ / min under a pressure of 40±0.1 bar and held for 100 min, after which the furnace was cooled and the pressure was released to room temperature and atmospheric pressure.

[0067] In this embodiment, the negative pressure degreasing stage no longer uses a segmented heating method, but instead directly heats to 450℃ at a rate of 1℃ / min and holds at that temperature for 30 minutes. By adjusting the negative pressure degreasing stage to a continuous heating and holding method at a fixed heating rate, a preparation method with more direct program settings and relatively simplified heat treatment control is formed. This method is suitable for application scenarios that aim to reduce the complexity of the degreasing process, simplify equipment temperature settings, and conduct degreasing process optimization verification.

[0068] Example 4

[0069] This embodiment investigates the effects of different molding and drying regimes and negative pressure degreasing regimes on the preparation effect of silicon nitride four-cavity sleeves, and sets up three experimental groups: group A, group B, and group C.

[0070] Group A adopted a process of integral sealed molding, staged drying and segmented negative pressure degreasing. Group B kept all other process conditions the same, but only adjusted the molding and drying regime. Group C kept all other process conditions the same, but only adjusted the negative pressure degreasing regime.

[0071] All three experiments used silicon nitride four-cavity sleeves as the target product for preparation.

[0072] 1. Raw material weighing and powder pretreatment

[0073] Group A weighed 1 kg of silicon nitride powder, added alumina sintering aid at a rate of 2 wt.% of the silicon nitride powder mass, and then added ammonium polyacrylate and tetramethylammonium hydroxide, with the amount of ammonium polyacrylate being 1 wt.% and the amount of tetramethylammonium hydroxide being 3 wt.%.

[0074] After adding pure water, the solid content of the slurry was controlled to be 55%. Silicon nitride ball milling was used for dispersion, with a silicon nitride powder to silicon nitride ball milling stone mass ratio of 1:2, and a milling time of 6 hours. After ball milling, the slurry was spray-dried and granulated under the following conditions: inlet air temperature 220℃, outlet air temperature 120℃, and peristaltic pump speed 30 r / min.

[0075] Groups B and C used the same raw material ratios and powder pretreatment conditions as Group A.

[0076] 2. Slurry preparation and defoaming treatment

[0077] Group A took the prepared silicon nitride granulated powder and mixed it with an organic system to prepare silicon nitride slurry. In the organic system, the monomer is acrylic acid, the crosslinking agent is N,N-methyleneacrylamide, the dispersant is tetramethylammonium hydroxide and ammonium polyacrylate, the catalyst is tetramethylethylenediamine, and the initiator is sodium persulfate. The mass ratio of monomer, crosslinking agent, dispersant and catalyst is 16:2:1:1.

[0078] Both Group B and Group C were prepared with the same organic system composition and proportions as Group A.

[0079] After the slurry in Group A was prepared, it underwent vacuum defoaming, vibration defoaming, and sieving defoaming in sequence to remove air bubbles and agglomerated particles from the slurry. Groups B and C underwent defoaming treatment in the same order as Group A.

[0080] 3. Injection molding

[0081] Group A injected the defoamed silicon nitride slurry into a four-cavity sleeve paraffin mold, and sealed the entire mold for 18 hours after injection, so that the slurry could be molded under relatively closed conditions.

[0082] Group B injected the defoamed silicon nitride slurry into the same mold. After injection molding, the entire mold was not sealed, but was left to stand for 18 hours under normal conditions to form the final product.

[0083] Group C will inject the defoamed silicon nitride slurry into the same mold and seal it as Group A for 18 hours.

[0084] In this step, Group B is the molding method comparison group.

[0085] 4. Demolding and drying

[0086] After the A-group molding is completed, the green body is demolded using a water bath heating method. After demolding, the green body is first placed in a sealed bag and dried at 50°C for 12 hours. Then, the sealed bag is opened and the green body is dried at 90°C for another 12 hours.

[0087] Group B also used water bath heating to demold, but instead of staged sealing and drying after demolding, it was directly dried at 50℃ for 6 hours, and then transferred to 90℃ for 6 hours.

[0088] Group C uses the same demolding and drying methods as Group A.

[0089] In this step, Group B is the drying regime comparison group.

[0090] 5. Green body trimming and negative pressure degreasing

[0091] Group A's dried green blanks underwent surface finishing to remove burrs and uneven areas, while Groups B and C were finished in the same manner.

[0092] The green blanks of Group A, after being trimmed, underwent segmented negative pressure degreasing treatment, specifically: the temperature was raised from room temperature to 320°C within 90 minutes, then raised to 370°C within 30 minutes, and then raised to 450°C within 60 minutes and held at that temperature for 30 minutes.

[0093] Group B used the same negative pressure degreasing procedure as Group A.

[0094] Group C uses a continuous heating negative pressure degreasing method, that is, heating from room temperature to 450℃ at a heating rate of 1℃ / min and holding at that temperature for 30min.

[0095] In this step, Group C is the comparison group for the defatting treatment.

[0096] 6. Micro-positive pressure sintering and segmented pressurized gas pressure sintering

[0097] After completing negative pressure degreasing, Group A was heated from 450℃ to 1000℃ within 82 minutes, while the furnace pressure was adjusted to 35mbar for micro-positive pressure sintering.

[0098] Both Group B and Group C used the same micro-positive pressure sintering conditions as Group A.

[0099] After the micro-positive pressure sintering was completed, Group A was heated from 1000℃ to 1450℃ at a rate of 3℃ / min. During the heating process, the nitrogen pressure in the furnace was increased to 8±0.1 bar and held for 50 min. Then, after 60 min, the temperature was increased to 1600℃, and the furnace pressure was adjusted to 10±0.1 bar and held for 30 min. After another 100 min, the temperature was increased to 1880℃, and the furnace pressure was adjusted to 55±0.1 bar and held for 60 min. Then, the temperature was decreased to 1400℃ at a rate of 3℃ / min under a pressure of 40±0.1 bar and held for 100 min. Finally, the furnace was cooled and the pressure was released to room temperature and atmospheric pressure.

[0100] Both Group B and Group C adopted the same segmented pressurized gas pressure sintering process as Group A.

[0101] After the sintering of the three groups of experiments was completed, the samples were finely ground to obtain silicon nitride four-cavity sleeves.

[0102] 7. Experimental Testing

[0103] Density and thermal shock resistance tests were conducted on the finished silicon nitride four-cavity sleeves prepared from groups A, B, and C, respectively.

[0104] The density test was performed using the water displacement method. First, the mass of the sample in its dry state was measured, and then the apparent mass and suspended mass of the sample after immersion in the liquid were measured. The bulk density of the sample was calculated based on Archimedes' principle, and the results were expressed in g / cm³.

[0105] The thermal shock resistance test employed a high-temperature heating-cooling cycle method. The sample was heated to a set temperature, then removed and cooled. The test temperature was gradually increased, and the highest temperature the sample could withstand before cracking or failure was taken as the thermal shock resistance result, expressed in °C. Three groups of samples were tested under the same conditions.

[0106] The test results are as follows: the density of sample A is 3.326 g / cm³ and the thermal shock resistance is 860℃; the density of sample B is 3.145 g / cm³ and the thermal shock resistance is 790℃; and the density of sample C is 3.261 g / cm³ and the thermal shock resistance is 800℃.

[0107] 8. Comparative Analysis

[0108] Compared to Group B, Group A maintained the same raw material system, slurry system, defoaming method, degreasing regime, and sintering regime, with only the injection molding method and drying regime being adjusted. Test results showed that Group A, which used integral sealed molding combined with staged drying, outperformed Group B, which used static molding and a shorter drying time, indicating that the molding and drying regimes have a significant impact on the final performance of the samples.

[0109] Compared to Group C, Group A maintained the same raw material system, slurry system, defoaming method, injection molding method, drying regime, and sintering regime, with only the negative pressure debinding regime being adjusted. Test results showed that Group A, which used segmented heating and negative pressure debinding, outperformed Group C, which used continuous heating and negative pressure debinding, indicating that the negative pressure debinding procedure has a significant impact on the final performance of the samples.

[0110] Compared with group B, group C's test results were better than group B, indicating that under the experimental conditions of this group, the changes in molding and drying regimes had a more significant impact on the sample performance.

[0111] Based on the combined results of the three sets of experiments, the process of overall sealing molding, staged drying and staged negative pressure degreasing is more suitable as the preparation process of silicon nitride four-cavity sleeves.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A silicon nitride four-cavity sleeve, characterized in that, include: The sleeve body (5) is a special ceramic sintered body made of silicon nitride as the main material; the sleeve body (5) is provided with model holes (4), the number of model holes (4) is 4, the model holes (4) are cylindrical through holes that penetrate the two opposite end faces of the sleeve body (5), and the model holes (4) are arranged in two rows and two columns with equal spacing. The sleeve body (5) is provided with a feed port (1). There are two feed ports (1). The feed port (1) is a cylindrical through hole that passes through the two opposite side ends of the sleeve body (5). The feed ports (1) are arranged side by side at equal intervals and are located between two model holes (4) in a corresponding row. The sleeve body (5) is provided with a fixing groove (2), and there are 4 fixing grooves (2). The fixing grooves (2) are opened on the outer peripheral wall of the sleeve body (5) and are respectively located on the upper side, lower side, left side and right side of the sleeve body (5). The sleeve body (5) is provided with a positioning hole (3). The number of positioning holes (3) is one. The positioning hole (3) is located in the central area surrounded by four model holes (4). The positioning hole (3) is a cylindrical through hole that penetrates the two opposite end faces of the sleeve body (5).

2. The silicon nitride four-cavity sleeve according to claim 1, characterized in that: The alumina sintering aid content in the sleeve body (5) is 2wt.%, the axes of the model holes (4) are parallel to each other, the axis of the positioning hole (3) is parallel to the axis of the model hole (4), and the axes of the two feed ports (1) are parallel to each other and perpendicular to the axis of the model hole (4).

3. A silicon nitride four-cavity sleeve according to claim 1, characterized in that: The fixing grooves (2) are respectively located at the middle of the four sides of the outer peripheral wall of the sleeve body (5), wherein the two fixing grooves (2) located on the upper and lower sides are arranged opposite to each other, and the two fixing grooves (2) located on the left and right sides are arranged opposite to each other.

4. A method for manufacturing a silicon nitride four-cavity sleeve, used to prepare a silicon nitride four-cavity sleeve as described in any one of claims 1-3, characterized in that, include: S1. Mix silicon nitride powder with alumina sintering aid, add dispersant and pure water, and ball mill to disperse the mixture to obtain a mixed slurry. Then, spray dry and granulate the mixed slurry to obtain silicon nitride granulated powder. S2. The silicon nitride granulated powder is mixed with an organic system containing monomers, crosslinking agents, dispersants, catalysts and initiators to prepare silicon nitride slurry; S3. After the silicon nitride slurry is subjected to vacuum degassing, vibration degassing and sieve degassing in sequence, it is injected into a paraffin mold with a four-cavity sleeve for overall sealing and gel molding. After demolding by water bath heating, it is dried in stages by sealing and then opening, and then trimmed to obtain a silicon nitride four-cavity sleeve green blank. S4. The silicon nitride four-cavity sleeve green blank is subjected to negative pressure degreasing, micro-positive pressure sintering, and segmented pressurized gas pressure sintering under nitrogen atmosphere in sequence. The furnace pressure of the micro-positive pressure sintering is 35 mbar. During the segmented pressurized gas pressure sintering process, the furnace pressure is adjusted to 8±0.1 bar, 10±0.1 bar and 55±0.1 bar in sequence as the temperature rises. After heat preservation sintering, cooling and depressurization, it is finely ground to obtain the silicon nitride four-cavity sleeve.

5. The method for manufacturing a silicon nitride four-cavity sleeve according to claim 4, characterized in that: The amount of alumina sintering aid added is 2 wt.% of the mass of the silicon nitride powder. The dispersant includes ammonium polyacrylate and tetramethylammonium hydroxide. The amount of ammonium polyacrylate added is 1 wt.% of the mass of the silicon nitride powder, and the amount of tetramethylammonium hydroxide added is 3 wt.% of the mass of the silicon nitride powder.

6. The method for manufacturing a silicon nitride four-cavity sleeve according to claim 4, characterized in that: The ball milling dispersion uses silicon nitride grinding stones, the mass ratio of silicon nitride powder to silicon nitride grinding stones is 1:2, the solid content of the mixed slurry is 55%, the ball milling time is 6 hours, the inlet air temperature of the spray drying granulation is 220℃, the outlet air temperature is 120℃, and the peristaltic pump speed is 30 r / min.

7. The method for manufacturing a silicon nitride four-cavity sleeve according to claim 4, characterized in that: The monomer in the organic system is acrylic acid, the crosslinking agent is N,N-methyleneacrylamide, the dispersant in the organic system is tetramethylammonium hydroxide and ammonium polyacrylate, the catalyst is tetramethylethylenediamine, the initiator is sodium persulfate, and the mass ratio of the monomer, crosslinking agent, dispersant and catalyst is 16:2:1:

1.

8. The method for manufacturing a silicon nitride four-cavity sleeve according to claim 4, characterized in that: The vacuum defoaming, vibration defoaming, and sieving defoaming are performed sequentially. The vacuum defoaming is used to remove air bubbles from the slurry, the vibration defoaming is used to further remove residual air bubbles from the slurry, and the sieving defoaming is used to remove agglomerated particles from the slurry.

9. The method for manufacturing a silicon nitride four-cavity sleeve according to claim 4, characterized in that: The integral sealing gel molding process involves injecting the silicon nitride slurry into the paraffin mold and then sealing it for 18 hours. The staged drying process involves demolding the mold after heating in a water bath, first sealing it in a sealing bag and drying it at 50°C for 12 hours, then opening it and drying it at 90°C for 12 hours.

10. A method for manufacturing a silicon nitride four-cavity sleeve according to claim 4, characterized in that: The negative pressure degreasing process involves raising the temperature from room temperature to 320°C within 90 minutes, then raising it to 370°C within 30 minutes, and finally raising it to 450°C within 60 minutes and holding it at that temperature for 30 minutes. The micro-positive pressure sintering process involves raising the temperature from 450°C to 1000°C within 82 minutes after the negative pressure degreasing process, while adjusting the gas pressure inside the furnace to 35 mbar. The segmented pressurized gas pressure sintering process involves raising the temperature from 1000°C to 1450°C at a rate of 3°C / min after the micro-positive pressure sintering process, while pressurizing the nitrogen gas inside the furnace during the heating process. The temperature was raised to 8±0.1 bar and held for 50 min; then, after 60 min, the temperature was raised from 1450℃ to 1600℃, and the furnace pressure was adjusted to 10±0.1 bar and held for 30 min; then, after 100 min, the temperature was raised from 1600℃ to 1880℃, and the furnace pressure was adjusted to 55±0.1 bar and held for 60 min; then, under a pressure of 40±0.1 bar, the temperature was lowered from 1880℃ to 1400℃ at a rate of 3℃ / min and held for 100 min, and then cooled with the furnace and the pressure was released to room temperature and atmospheric pressure.

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