Silicon nitride ceramic bone nail and preparation method thereof
Silicon nitride ceramic bone nails are prepared through injection molding and sintering processes, which solves the biocompatibility and manufacturing complexity problems of metal bone nail materials and realizes silicon nitride ceramic bone nails with high biocompatibility and low shrinkage, which are suitable for bone tissue simulation and cell stimulation.
Patent Information
- Application Number
- CN202410264792.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-08
- Publication Date
- 2025-09-09
AI Technical Summary
Existing metal bone screw materials have poor corrosion resistance, no effect on osteoblasts, and trace biological toxicity. In addition, traditional silicon nitride bone screws are complex to manufacture, have large shrinkage in finished products, and require secondary processing, which prolongs the product cycle and increases the risk of contamination.
Silicon nitride ceramic bone nails were prepared by mixing powder, plasticizing powder and injection molding. Through injection molding and sintering processes, combined with bioactivators and surfactants, the shrinkage rate was controlled at 5%-10%, and the porosity reached 20% in the second sintering stage to simulate the bone tissue structure.
The prepared silicon nitride ceramic bone screw has a near-net-shape size, does not require secondary processing, has a high porosity, increases biocompatibility, facilitates the flow of body fluids, promotes cell formation of bone tissue, and reduces production costs and cycles.
Smart Images
Figure CN120607407A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of silicon nitride materials, and in particular relates to a silicon nitride ceramic bone nail and a preparation method thereof. Background Art
[0002] Most bone screws currently used in clinical practice are made of metal. Metal nails have drawbacks such as poor corrosion resistance, no effect on osteoblast adhesion and growth, and trace biotoxicity. Furthermore, metal materials can wear or corrode after implantation, generating toxic metal ions or particles that can easily lead to inflammatory cascades. Silicon nitride, with its excellent biocompatibility and high antibacterial properties, has become a promising alternative to metal nails. However, the traditional manufacturing process for silicon nitride nails is complex, resulting in a shrinkage of approximately 20% in the finished product. Post-molding requires secondary processing at a machining center, significantly delaying the product cycle and increasing the risk of contamination. Summary of the Invention
[0003] In a first aspect, the present invention provides a method for preparing a silicon nitride ceramic bone nail, comprising the following steps:
[0004] Silicon nitride, bioactivator and surfactant are mixed evenly to obtain mixed powder.
[0005] The mixed powder, pore-forming agent and plasticizer are kneaded to obtain plasticized powder,
[0006] The plasticized powder is granulated to obtain plasticized granules,
[0007] The plasticized particles are subjected to injection molding to obtain green blanks.
[0008] The green blank is sintered to obtain a silicon nitride ceramic bone screw.
[0009] Compared with existing technologies, the present invention offers the following advantages: the silicon nitride ceramic bone screws produced by this method achieve near-net product dimensions after sintering, with a shrinkage rate of only 5%-10%, eliminating the need for secondary processing. Furthermore, the porosity of the silicon nitride ceramic bone screws can reach 20%, enabling better bone tissue simulation, increased biocompatibility, and facilitated fluid flow, increasing the surface area in contact with proteins and fluids in the human body. Bioactivators can also induce soft tissue cells to form bone tissue. The use of injection molding to produce silicon nitride ceramic bone screws allows for industrialized, large-scale production, reducing production costs and cycle times, and promoting the development of bioceramics.
[0010] Preferably, the silicon nitride and the pore-forming agent are dried at a temperature not lower than 100° C. for a drying time not less than 5 hours.
[0011] The dried silicon nitride and the bioactivator are ball-milled and mixed for 30 minutes or more, and a surfactant is added and ball-milled for 2 hours or more to obtain a mixed powder;
[0012] The dried pore-forming agent is kneaded with the mixed powder and the plasticizer at a temperature of 160-200°C.
[0013] Preferably, the plasticized particles are subjected to injection molding using an injection molding device.
[0014] The parameters of the injection molding equipment are set as follows: temperature of 170-250° C., injection pressure of 80-120 MPa.
[0015] Preferably, the sintering process includes a first sintering stage and a second sintering stage, and the first sintering stage and the second sintering stage are carried out under an inert protective atmosphere.
[0016] The first sintering stage: the temperature is raised from room temperature to 110-130°C at a heating rate of 30°C / h, kept at this temperature for 4-6 hours, then raised to 340-360°C, kept at this temperature for another 5-10 hours, then raised to 600-700°C, and kept at this temperature for another 5-10 hours to obtain the semi-finished product;
[0017] The second sintering stage: sintering the semi-finished product under the conditions of a pressure of 0.8-10 MPa and a temperature of 1680-1800° C. to obtain a silicon nitride ceramic bone screw.
[0018] The beneficial effects of this preferred solution are: the first sintering stage is degreasing sintering, the second sintering stage is forming sintering, and the sintering process is combined with the formulation system, so that the size of the prepared silicon nitride ceramic bone nail after sintering is close to the net product size, the shrinkage rate is only 5%-10%, and no secondary processing is required.
[0019] Preferably, the pore-forming agent includes any one or more of starch, walnut powder, and sweet potato powder, and the bioactivator includes any one or two of magnesium powder and magnesium oxide.
[0020] The beneficial effects of this preferred embodiment are as follows: During the second sintering stage, the degreased silicon nitride body decomposes, producing Si3N4 impurities. As the holding time increases, the Si3N4 decomposes, and the resulting Si and Mg ions have strong adsorption properties in a nitrogen atmosphere, combining to form MgSiN2, which continues to grow along the surface of the pores left after the pore-forming agent evaporates. As the surface temperature of the silicon nitride body increases, the Si and Mg ions are further away from the body surface. At lower temperatures, the gas activity decreases, making it more susceptible to gas adsorption. The ion concentration order is: N ions > Si ions > Mg ions. This promotes the growth of MgSiN2 along the tip, forming columnar MgSiN2 crystals, which improves the porosity of the silicon nitride ceramic bone screw and reduces shrinkage.
[0021] Preferably, the pore-forming agent includes charcoal, and the bioactivator includes any one or more of calcium oxide, silicon dioxide, and yttrium oxide.
[0022] The beneficial effects of this preferred embodiment are as follows: in the second sintering stage, under nitrogen conditions, the nano-carbon powder reacts with SiO2 on the surface of the Si3N4 pores (pores generated after the pore-forming agent evaporates) or with the Si3N4 particles themselves to form extremely fine SiC particles, which are pinned to the grain boundaries of the silicon nitride, effectively increasing the strength of the silicon nitride ceramic bone nail. During the growth process, the silicon nitride whiskers first form α-Si3N4 whiskers according to the VS growth mechanism. As the temperature rises, they react with the sintering aid to form a liquid phase. The α-Si3N4 whiskers dissolve in the liquid phase, and the reaction raw materials continuously transfer into the liquid phase to reach saturation, and then β-Si3N4 is precipitated. The whisker-like silicon nitride is interwoven between the SiC particles, which can enhance the "bridging" effect on the silicon nitride ceramic, which is beneficial to improving the strength of the sample.
[0023] Preferably, the surfactant includes any one or more of stearic acid, zinc stearate, aluminum stearate, beeswax, and mineral oil.
[0024] The beneficial effects of this preferred solution are as follows: a surfactant is added during ball milling to form a film on the surface of silicon nitride and the pore-forming agent, which can act as a bridge when kneading the plasticizer and the mixed powder, allowing the two to be better combined, reducing agglomeration, adjusting the fluidity of the slurry, and enhancing the strength of the plasticized powder.
[0025] Preferably, the plasticizer includes any one or more of polystyrene, polypropylene, polyethylene, silane, diethyl titanate, polyvinyl alcohol, and paraffin.
[0026] Preferably, a sintering aid is added in the second sintering stage, and the sintering aid includes yttrium oxide and / or calcium oxide.
[0027] Preferably, by weight, the silicon nitride is 85-95 parts, the bioactivator is 0.1-2 parts, the surfactant is 0.5-2 parts, the pore-forming agent is 0.5-4 parts, and the plasticizer is 5-10 parts.
[0028] In a second aspect, the present invention further provides a silicon nitride ceramic bone screw, which is prepared using the above-mentioned preparation method.
[0029] Compared with existing technologies, the present invention offers the following advantages: the sintered silicon nitride ceramic bone screws are close to the net product dimensions, with a shrinkage rate of only 5%-10%, eliminating the need for secondary processing. The porosity of the silicon nitride ceramic bone screws can reach 20%, enabling better simulation of bone tissue, increasing biocompatibility, facilitating the flow of body fluids, and increasing the surface area in contact with proteins and fluids in the human body. Bioactivators can also induce soft tissue cells to form bone tissue. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 The figure is a flow chart of a method for preparing a silicon nitride ceramic bone screw according to an embodiment of the present invention. DETAILED DESCRIPTION
[0031] In order to make the objectives, technical solutions and advantages of the present invention more clear, 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.
[0032] Example 1
[0033] This embodiment provides a method for preparing a silicon nitride ceramic bone nail, such as Figure 1 As shown, the following steps are included:
[0034] Step 1: Dry 85 parts of silicon nitride and 0.5 parts of a pore-forming agent in an oven at a temperature of not less than 100° C. and a drying time of not less than 5 hours, wherein the pore-forming agent comprises charcoal.
[0035] Step 2: The dried silicon nitride is ball-milled with 0.1 parts of a bioactivator and mixed for 30 minutes or more. 0.5 parts of a surfactant are then added and mixed for 2 hours or more to obtain a mixed powder. The bioactivator comprises calcium oxide and silicon dioxide, and the surfactant comprises stearic acid and zinc stearate.
[0036] Step 3: Fully knead the dried pore-forming agent, the mixed powder, and 5 parts of plasticizer in a kneader to obtain plasticized powder, wherein the kneading temperature is 160° C. The plasticizer includes polystyrene, polyvinyl alcohol, and paraffin.
[0037] Step 4: Granulate the plasticized powder using a granulator to obtain uniform plasticized particles.
[0038] Step 5: Using an injection molding device to perform injection molding on the plasticized particles to obtain a green blank, wherein the parameters of the injection molding device are set as follows: temperature of 170° C. and injection pressure of 80 MPa.
[0039] Step 6: First Sintering Stage: The green blank is sintered in an atmosphere pressure sintering furnace under a nitrogen atmosphere. Specifically, the temperature is raised from room temperature to 110°C at a rate of 30°C / h. After holding for 4 hours, the temperature is then raised from 110°C to 340°C. After holding for another 5 hours, the temperature is then raised from 340°C to 600°C and held for 5 hours to obtain a degreased semi-finished product.
[0040] Step 7: Second sintering stage: Place the degreased semi-finished product into an atmosphere pressure sintering furnace, apply a pressure of 1 MPa under a nitrogen protective atmosphere, and sinter at a temperature of 1680° C. to obtain a silicon nitride ceramic bone screw.
[0041] Example 2
[0042] This embodiment provides a method for preparing a silicon nitride ceramic bone nail, such as Figure 1 As shown, the following steps are included:
[0043] Step 1: Dry 90 parts of silicon nitride and 2.5 parts of a pore-forming agent in an oven at a temperature of not less than 100° C. and a drying time of not less than 5 hours. The pore-forming agent includes starch, walnut powder, and sweet potato powder.
[0044] Step 2: Ball-mill the dried silicon nitride with 1 part of a bioactivator for at least 30 minutes, then add 1.5 parts of a surfactant and ball-mill for at least 2 hours to obtain a mixed powder. The bioactivator includes magnesium powder and magnesium oxide, and the surfactant includes aluminum stearate and beeswax.
[0045] Step 3: Fully knead the dried pore-forming agent, the mixed powder, and 7 parts of plasticizer in a kneader to obtain plasticized powder, wherein the kneading temperature is 180° C. The plasticizer includes polystyrene, polypropylene, and polyethylene.
[0046] Step 4: Granulate the plasticized powder using a granulator to obtain uniform plasticized particles.
[0047] Step 5: Using an injection molding device to perform injection molding on the plasticized particles to obtain a green blank, wherein the parameters of the injection molding device are set as follows: temperature of 200° C. and injection pressure of 100 MPa.
[0048] Step 6: First Sintering Stage: The green blank is sintered in an atmosphere pressure sintering furnace under a nitrogen atmosphere. Specifically, the temperature is raised from room temperature to 120°C at a rate of 30°C / h. After holding for 5 hours, the temperature is then raised from 120°C to 350°C. After holding for another 7 hours, the temperature is then raised from 350°C to 650°C and held for 7 hours to obtain a degreased semi-finished product.
[0049] Step 7: Second sintering stage: Place the degreased semi-finished product into an atmosphere pressure sintering furnace, apply a pressure of 5 MPa under a nitrogen protective atmosphere, and sinter at a temperature of 1750° C. to obtain a silicon nitride ceramic bone screw.
[0050] Example 3
[0051] This embodiment provides a method for preparing a silicon nitride ceramic bone nail, such as Figure 1 As shown, the following steps are included:
[0052] Step 1: Dry 95 parts of silicon nitride and 4 parts of a pore-forming agent in an oven at a temperature of not less than 100° C. and a drying time of not less than 5 hours, wherein the pore-forming agent includes starch.
[0053] Step 2: Ball-mill the dried silicon nitride with 2 parts of a bioactivator for 30 minutes or longer, then add 2 parts of a surfactant and ball-mill for 2 hours or longer to obtain a mixed powder. The bioactivator includes magnesium powder, and the surfactant includes zinc stearate and aluminum stearate.
[0054] Step 3: Fully knead the dried pore-forming agent, the mixed powder, and 10 parts of a plasticizer in a kneader to obtain a plasticized powder, wherein the kneading temperature is 200° C. The plasticizer includes polystyrene and paraffin.
[0055] Step 4: Granulate the plasticized powder using a granulator to obtain uniform plasticized particles.
[0056] Step 5: Using an injection molding device to perform injection molding on the plasticized particles to obtain a green blank, wherein the parameters of the injection molding device are set as follows: temperature of 250° C. and injection pressure of 120 MPa.
[0057] Step 6: First Sintering Stage: The green blank is sintered in an atmosphere pressure sintering furnace under a nitrogen atmosphere. Specifically, the temperature is raised from room temperature to 130°C at a rate of 30°C / h. After holding for 6 hours, the temperature is then raised from 130°C to 360°C. After holding for another 10 hours, the temperature is then raised from 360°C to 700°C and held for 10 hours to obtain a degreased semi-finished product.
[0058] Step 7: Second sintering stage: Place the degreased semi-finished product into an atmosphere pressure sintering furnace, apply a pressure of 10 MPa under a nitrogen protective atmosphere, and sinter at a temperature of 1800° C. to obtain a silicon nitride ceramic bone screw.
[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions described in the above embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements 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 for preparing a silicon nitride ceramic bone nail, characterized in that: The following steps are involved: Silicon nitride, bioactivator and surfactant are mixed evenly to obtain mixed powder. The mixed powder, pore-forming agent and plasticizer are kneaded to obtain plasticized powder, The plasticized powder is granulated to obtain plasticized granules, The plasticized particles are subjected to injection molding to obtain green blanks. The green blank is sintered to obtain a silicon nitride ceramic bone screw.
2. The method for preparing a silicon nitride ceramic bone nail according to claim 1, wherein: The silicon nitride and the pore-forming agent are dried at a temperature not lower than 100° C. for a drying time not lower than 5 hours. The dried silicon nitride and the bioactivator are ball-milled and mixed for 30 minutes or more, and a surfactant is added and ball-milled for 2 hours or more to obtain a mixed powder; The dried pore-forming agent is kneaded with the mixed powder and the plasticizer at a temperature of 160-200°C.
3. The method for preparing a silicon nitride ceramic bone nail according to claim 1, wherein: The plasticized particles are subjected to injection molding using an injection molding device, The parameters of the injection molding equipment are set as follows: temperature of 170-250° C., injection pressure of 80-120 MPa.
4. The method for preparing a silicon nitride ceramic bone nail according to claim 1, wherein: The sintering process includes a first sintering stage and a second sintering stage, wherein the first sintering stage and the second sintering stage are performed under an inert protective atmosphere. The first sintering stage: the temperature is raised from room temperature to 110-130°C at a heating rate of 30°C / h, kept at this temperature for 4-6 hours, then raised to 340-360°C, kept at this temperature for another 5-10 hours, then raised to 600-700°C, and kept at this temperature for another 5-10 hours to obtain the semi-finished product; The second sintering stage: sintering the semi-finished product under the conditions of a pressure of 0.8-10 MPa and a temperature of 1680-1800° C. to obtain a silicon nitride ceramic bone screw.
5. The method for preparing a silicon nitride ceramic bone nail according to claim 1, wherein: The pore-forming agent includes any one or more of starch, walnut powder, and sweet potato powder; the bioactivator includes any one or two of magnesium powder and magnesium oxide.
6. The method for preparing a silicon nitride ceramic bone nail according to claim 1, wherein: The pore-forming agent includes charcoal, and the bioactivator includes any one or more of calcium oxide, silicon dioxide, and yttrium oxide.
7. The method for preparing a silicon nitride ceramic bone nail according to claim 1, wherein: The surfactant includes any one or more of stearic acid, zinc stearate, aluminum stearate, beeswax, and mineral oil; The plasticizer includes any one or more of polystyrene, polypropylene, polyethylene, silane, diethyl titanate, polyvinyl alcohol, and paraffin.
8. The method for preparing a silicon nitride ceramic bone nail according to claim 4, wherein: In the second sintering stage, a sintering aid is added, wherein the sintering aid includes yttrium oxide and / or calcium oxide.
9. The method for preparing a silicon nitride ceramic bone nail according to claim 1, wherein: By weight, the silicon nitride is 85-95 parts, the bioactivator is 0.1-2 parts, the surfactant is 0.5-2 parts, the pore-forming agent is 0.5-4 parts, and the plasticizer is 5-10 parts.
10. A silicon nitride ceramic bone screw, characterized in that: The silicon nitride ceramic bone nail is prepared using the preparation method described in any one of claims 1-9.