Silicon nitride implant and method of making same

Abstract

The present application belongs to the technical field of silicon nitride material preparation, and particularly relates to a silicon nitride implant and a preparation method thereof, the preparation method comprising the following steps: mixing silicon nitride powder, a sintering aid and ethanol, and obtaining a ceramic formula powder after drying treatment; mixing the ceramic formula powder with a composition to obtain a mixture; the composition comprises organic glass, polystyrene, high-density polyethylene, microcrystalline wax powder and a dispersing agent; cooling and granulating the mixture to obtain a ceramic feedstock; printing the ceramic feedstock through a fused deposition printing device to obtain a silicon nitride implant body; and performing degassing and sintering treatment on the silicon nitride implant body to obtain a silicon nitride implant.

Description

Technical Field

[0001] This invention belongs to the field of silicon nitride material preparation technology, specifically relating to a silicon nitride implant and its preparation method. Background Technology

[0002] In recent years, the repair and reconstruction of injuries and defects has been a major challenge in biomedicine. Bioimplantation carries risks of rejection and infection, placing high demands on its sourcing, surgeon technique, and postoperative management, while also requiring greater dimensional accuracy. Silicon nitride, with its high fracture toughness and compressive strength similar to human bone, meets the basic mechanical requirements of implants and exhibits excellent biocompatibility, mechanical properties, and osseointegration. Therefore, silicon nitride implants have become a hot research topic.

[0003] Silicon nitride implants prepared using existing technologies generally suffer from a lack of structural diversity and numerous defects. Therefore, the inventors conceived of using fused deposition modeling (FDM) technology to address this issue. However, due to the high requirements of FDM for ceramic feedstock, the resulting silicon nitride implant blanks exhibit poor interlayer bonding strength, making them prone to cracking or delamination, and resulting in poor mechanical properties. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing silicon nitride implants, comprising the following steps:

[0005] Silicon nitride powder, sintering aid and ethanol are mixed and dried to obtain ceramic formula powder;

[0006] The ceramic formula powder is mixed with the composition to obtain a mixture; the composition includes plexiglass, polystyrene, high-density polyethylene, microcrystalline wax powder and dispersant;

[0007] The mixture is cooled and granulated to obtain a ceramic feedstock;

[0008] A silicon nitride implant preform is obtained by printing a ceramic feed using a fused deposition modeling (FDM) printer.

[0009] Silicon nitride implant blanks are subjected to debinding and sintering processes to obtain silicon nitride implants.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: the melting and softening temperature of plexiglass is 140-160℃, the melting and softening temperature of high-density polyethylene is 125-135℃, the melting and softening temperature of polystyrene is 80-100℃, and the melting temperature of microcrystalline wax powder is 65-75℃. The temperature distribution of each component in the composition has a clear orientation gradient, a wide melting temperature range, and high high-temperature viscosity, which can obtain silicon nitride ceramic feedstock with high solid content. The synergistic effect of each component is conducive to improving the adhesion of ceramic formula powder. In the subsequent fused deposition printing process, it can improve the bonding strength between powders, thereby improving the interlayer bonding force of the green body, alleviating or avoiding the phenomenon of cracking of the green body. This results in silicon nitride implants with diversified structures, fewer pore defects, high density, and small deformation, exhibiting good comprehensive performance.

[0011] Preferably, the silicon nitride powder comprises 85-95 parts by weight, and the sintering aid comprises 5-15 parts; the particle size of the silicon nitride powder is 0.5-2 μm.

[0012] Preferably, the sintering aid includes any one or more of yttrium oxide, ytterbium oxide, and aluminum oxide.

[0013] Preferably, the drying temperature of the drying process is 60-80℃, and the drying time is not less than 24 hours; after drying, the powder is passed through a 60-mesh sieve to obtain ceramic formula powder.

[0014] Preferably, by weight, the mixture contains 70-82 parts of ceramic formula powder and 18-30 parts of composition;

[0015] The ceramic formula powder and the composition are mixed by intensive mixing, with the mixing temperature being 180-210℃ and the mixing time being no less than 4 hours.

[0016] Preferably, by weight, the composition comprises 35-50 parts of plexiglass, 10-20 parts of polystyrene, 10-15 parts of high-density polyethylene, 10-15 parts of microcrystalline wax powder, and 3-10 parts of dispersant.

[0017] The beneficial effects of this preferred solution are as follows: Acrylic glass primarily serves as a skeletal support, preventing deformation of the green body during molding; polystyrene and high-density polyethylene reinforce the green body, preventing breakage and defects; microcrystalline wax powder acts as a lubricant, wetting the ceramic powder and increasing its adhesion to the composition; the dispersant prevents powder agglomeration, which could lead to uneven coating of the composition and ceramic formulation powder. Therefore, all components in this technical solution work synergistically and are indispensable. If the proportions of each component in the composition exceed the range of this technical solution, the composition may fail to completely coat the ceramic formulation powder, or the green body may crack and delaminate, severely affecting the strength of the green body.

[0018] Preferably, the dispersant includes any one or more of stearic acid, oleic acid, and carboxystearic acid.

[0019] Preferably, the printing parameters of the fused deposition modeling (FDM) printing equipment include:

[0020] The nozzle diameter is 0.3–0.8 mm, the slice thickness is 0.2–0.5 mm, the printing flow rate is 80–130%f, the printing speed is 80–150%v, and the printing temperature is 150–180℃.

[0021] The beneficial effects of this preferred solution are as follows: by setting the printing parameters to adjust its printing melt viscosity, combined with the ceramic feed formulation system, it can improve the interlayer bonding strength of the printed green body and increase the interlayer bonding force, which is conducive to preparing silicon nitride implants with diverse structures and good mechanical properties.

[0022] Preferably, the adhesive removal process includes:

[0023] First stage: Increase the temperature from room temperature to 210-230℃ at a heating rate of 5℃ / h, and hold for 2-5 hours;

[0024] Second stage: Increase the temperature from the first stage holding temperature to 600-700℃ at a heating rate of 10℃ / h, and hold for 3-6 hours.

[0025] The advantages of this preferred solution are: in the first stage, the plastic matrix is ​​subjected to low-temperature component removal treatment, and in the second stage, the plastic matrix is ​​subjected to high-temperature component removal treatment.

[0026] Preferably, the sintering process includes:

[0027] First stage: At a heating rate of 180-240℃ / h and a pressure of 3-5MPa, the temperature is raised from room temperature to 1400-1500℃ and held for 1-3 hours;

[0028] Second stage: At a heating rate of 150-180℃ / h and a pressure of 5-10MPa, the temperature is raised from the holding temperature of the first stage to 1720-1780℃ and held for 2-4 hours.

[0029] The advantages of this preferred solution are: pre-growth of the crystal is achieved in the first stage, and complete phase transition is achieved in the second stage, resulting in a silicon nitride implant with low deformation and high precision.

[0030] The present invention also designed a silicon nitride implant, which was prepared using the above-described preparation method.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: the silicon nitride implant blank prepared by the above preparation method has strong interlayer bonding force and has the advantages of structural diversity, good wire plasticity and small deformation. Attached Figure Description

[0032] Figure 1 This is a flowchart of a method for preparing silicon nitride implants according to an embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0034] Example 1

[0035] This embodiment provides a method for preparing a silicon nitride implant, including the following steps:

[0036] (1) According to the weight proportions, take 85 parts of silicon nitride powder with an average particle size of 0.5 μm, 6 parts of alumina powder, 4 parts of ytterbium oxide and 5 parts of yttrium oxide and put them into a ball mill. Use ethanol as solvent to grind and mix them. The ball milling time is 24 h to obtain a ceramic slurry with high solid content, good fluidity and uniform suspension. The particle size D of the slurry exiting the mill is... 50 ≤0.5um. The ceramic slurry is dried in a 60℃ oven for more than 24 hours until constant weight, and then passed through a 60-mesh sieve to obtain the ceramic formula powder.

[0037] (2) Feed preparation: 70 parts by weight of ceramic formula powder and 30 parts by weight of composition are placed in a mixer at 180°C and mixed for 4 hours. After cooling and granulation, ceramic feed is obtained. The composition includes plexiglass, polystyrene, high-density polyethylene, microcrystalline wax powder and oleic acid in a weight ratio of 50:10:10:10:3.

[0038] (3) Fused deposition modeling: A complete model of the silicon nitride implant is established using modeling software. The model is selected on the slicing software of the FDM printing equipment. The printer nozzle diameter is 0.3 mm, the slice thickness is 0.2 mm, the printing flow rate is 80% f, the printing speed is 80% v, and the printing temperature is 180℃ to obtain the silicon nitride implant blank.

[0039] (4) Thermal debinding of silicon nitride implant blank:

[0040] First stage: Increase the temperature from room temperature to 220℃ at a heating rate of 5℃ / h, and hold for 5 hours;

[0041] Second stage: Increase the temperature from 220℃ to 650℃ at a rate of 10℃ / h, and hold for 3 hours.

[0042] (5) The silicon nitride implant blank obtained in step (4) is subjected to gas pressure sintering to obtain a silicon nitride implant. The gas pressure sintering includes the following two stages:

[0043] First stage: At a heating rate of 180℃ / h and a pressure of 3MPa, the temperature is raised from room temperature to 1450℃ and held for 1 hour.

[0044] Second stage: At a heating rate of 150℃ / h and a pressure of 5MPa, the temperature is increased from 1450℃ to 1780℃ and held for 2 hours.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Example 1 is that:

[0047] The weight ratio of plexiglass, polystyrene, high-density polyethylene, microcrystalline wax powder, and oleic acid in the composition is 28:23:20:16:13.

[0048] The silicon nitride implant blank prepared in this comparative example has obvious ceramic powder particles in its cross-section, and the particles are not completely encapsulated with the composition, resulting in a loose filling.

[0049] Example 2

[0050] This embodiment provides a method for preparing a silicon nitride implant, including the following steps:

[0051] (1) According to the weight proportions, take 90 parts of silicon nitride powder with an average particle size of 1μm, 4 parts of lanthanum oxide powder, 4 parts of yttrium oxide and 2 parts of ytterbium oxide and put them into a ball mill. Use ethanol as solvent to grind and mix them. The ball milling time is 24h to obtain a ceramic slurry with high solid content, good fluidity and uniform suspension. The particle size D of the slurry exiting the mill is... 50 ≤0.5um. The ceramic slurry is dried in a 70℃ oven for more than 24 hours until constant weight, and then passed through a 60-mesh sieve to obtain the ceramic formula powder.

[0052] (2) Feed preparation: 76 parts by weight of ceramic formula powder and 24 parts by weight of composition are placed in a mixer at 195°C and mixed for 4 hours. After cooling and granulation, ceramic feed is obtained. The composition includes plexiglass, polystyrene, high-density polyethylene, microcrystalline wax powder and carboxystearic acid in a weight ratio of 40:15:12:13:10.

[0053] (3) Fused deposition modeling: A complete model of the silicon nitride implant is established using modeling software. The model is selected on the slicing software of the FDM printing equipment. The printer nozzle diameter is 0.5 mm, the slice thickness is 0.35 mm, the printing flow rate is 100% f, the printing speed is 100% v, and the printing temperature is 165℃ to obtain the silicon nitride implant blank.

[0054] (4) Thermal debinding of silicon nitride implant blank:

[0055] First stage: Increase the temperature from room temperature to 210℃ at a heating rate of 5℃ / h, and hold for 3 hours;

[0056] Second stage: Increase the temperature from 210℃ to 700℃ at a rate of 10℃ / h, and hold for 5 hours.

[0057] (5) The silicon nitride implant blank obtained in step (4) is subjected to gas pressure sintering to obtain a silicon nitride implant. The gas pressure sintering includes the following two stages:

[0058] First stage: At a heating rate of 210℃ / h and a pressure of 4MPa, the temperature is increased from room temperature to 1400℃ and held for 2 hours.

[0059] Second stage: At a heating rate of 160℃ / h and a pressure of 8MPa, the temperature is increased from 1400℃ to 1750℃ and held for 3 hours.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 2 is that:

[0062] The weight ratio of plexiglass, polystyrene, high-density polyethylene, microcrystalline wax powder and carboxystearic acid in the composition is 70.5:9:9:9:2.5.

[0063] The silicon nitride implants prepared in this comparative example have poor interlayer bonding, resulting in preform cracking and delamination.

[0064] Example 3

[0065] This embodiment provides a method for preparing a silicon nitride implant, including the following steps:

[0066] (1) According to the weight proportions, take 95 parts of silicon nitride powder with an average particle size of 2μm, 2 parts of ytterbium oxide powder, 1 part of alumina and 2 parts of yttrium oxide and put them into a ball mill. Use ethanol as solvent to grind and mix them. The ball milling time is 24h to obtain a ceramic slurry with high solid content, good fluidity and uniform suspension. The particle size D of the slurry exiting the mill is... 50 ≤0.5um. The ceramic slurry is dried in an oven at 80℃ for more than 24 hours until constant weight, and then passed through a 60-mesh sieve to obtain the ceramic formula powder.

[0067] (2) Feed preparation: 82 parts by weight of ceramic formula powder and 18 parts by weight of composition are placed in a mixer at 210°C and mixed for 4 hours. After cooling and granulation, ceramic feed is obtained. The composition includes plexiglass, polystyrene, high-density polyethylene, microcrystalline wax powder and carboxystearic acid in a weight ratio of 35:20:15:15:8.

[0068] (3) Fused deposition modeling: A complete model of the silicon nitride implant is established using modeling software. The model is selected on the slicing software of the FDM printing equipment. The printer nozzle diameter is 0.8 mm, the slice thickness is 0.5 mm, the printing flow rate is 130%f, the printing speed is 150%v, and the printing temperature is 150℃ to obtain the silicon nitride implant blank.

[0069] (4) Thermal debinding of silicon nitride implant blank:

[0070] First stage: Increase the temperature from room temperature to 230℃ at a heating rate of 5℃ / h, and hold for 2 hours;

[0071] Second stage: Increase the temperature from 230℃ to 600℃ at a rate of 10℃ / h, and hold for 3 hours.

[0072] (5) The silicon nitride implant blank obtained in step (4) is subjected to gas pressure sintering to obtain a silicon nitride implant. The gas pressure sintering includes the following two stages:

[0073] First stage: At a heating rate of 240℃ / h and a pressure of 5MPa, the temperature is increased from room temperature to 1500℃ and held for 3 hours.

[0074] Second stage: At a heating rate of 180℃ / h and a pressure of 10MPa, the temperature is increased from 1500℃ to 1720℃ and held for 4 hours.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of producing a silicon nitride implant, characterized by, The method comprises the following steps: mixing silicon nitride powder, sintering aids and ethanol, and obtaining ceramic formula powder after drying treatment; mixing the ceramic formula powder and a composition to obtain a mixture; the composition comprises organic glass, polystyrene, high-density polyethylene, microcrystalline wax powder and a dispersant; cooling and granulating the mixture to obtain ceramic feedstock; printing the ceramic feedstock by a fused deposition printing device to obtain a silicon nitride implant body; performing degassing and sintering treatment on the silicon nitride implant body to obtain a silicon nitride implant; the sintering aids comprise any one or several of yttrium oxide, ytterbium oxide and aluminum oxide; the drying temperature of the drying treatment is 60-80℃, and the drying time is not less than 24h; sieve the ceramic formula powder through a 60-mesh sieve after drying treatment; in terms of weight fraction, the ceramic formula powder in the mixture is 70-82 parts, and the composition is 18-30 parts; the mixing mode of the ceramic formula powder and the composition is internal mixing, the internal mixing temperature is 180-210℃, and the internal mixing time is not less than 4h; in terms of weight fraction, the organic glass in the composition is 35-50 parts, the polystyrene is 10-20 parts, the high-density polyethylene is 10-15 parts, the microcrystalline wax powder is 10-15 parts, and the dispersant is 3-10 parts; the printing parameters of the fused deposition printing device include: nozzle diameter of 0.3-0.8mm, slice thickness of 0.2-0.5mm, and printing temperature of 150-180℃; the sintering treatment comprises: first stage: increasing the temperature from room temperature to 1400-1500℃ at a temperature increasing rate of 180-240℃ / h under a pressure of 3-5MPa, and keeping the temperature for 1-3h; second stage: increasing the temperature from the temperature keeping temperature of the first stage to 1720-1780℃ at a temperature increasing rate of 150-180℃ / h under a pressure of 5-10MPa, and keeping the temperature for 2-4h.

2. The method of claim 1, wherein the silicon nitride implant is prepared by a method comprising: depositing a silicon nitride film on a substrate; and implanting nitrogen ions into the silicon nitride film. in terms of weight fraction, the silicon nitride powder is 85-95 parts, and the sintering aids are 5-15 parts; the particle size of the silicon nitride powder is 0.5-2μm.

3. The method for preparing a silicon nitride implant according to claim 1, characterized in that, the dispersant comprises any one or more of stearic acid, oleic acid and carboxylic stearic acid.

4. The method of claim 1, wherein the silicon nitride implant is prepared by a method comprising: depositing a silicon nitride film on a substrate; and implanting nitrogen ions into the silicon nitride film to form the silicon nitride implant. the degassing treatment comprises: first stage: increasing the temperature from room temperature to 210-230℃ at a temperature increasing rate of 5℃ / h, and keeping the temperature for 2-5h; second stage: increasing the temperature from the temperature keeping temperature of the first stage to 600-700℃ at a temperature increasing rate of 10℃ / h, and keeping the temperature for 3-6h.

5. A silicon nitride implant, characterized by, The silicon nitride implant is prepared by the method of any one of claims 1-4. The silicon nitride implant is prepared by the method of any one of claims 1-4.

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