Preparation method of titanium-based bioactive bone implant composite material with hierarchical porous structure

Abstract

The application discloses a preparation method of a multi-level pore structure titanium-based bioactive bone implant composite material, and belongs to the technical field of biomedical materials. According to the method, TC4 titanium alloy powder, ZrO2 powder, hydroxyapatite powder and NaCl powder are mixed at a certain proportion, granulated by multi-component binder system compounding, and then a green body is prepared by a 3D printing process. After the green body is catalytically degreased by warm water and oxalic acid, the titanium-based bioactive bone implant composite material with a multi-level pore structure is prepared by performing step-by-step thermal degreasing and low-temperature pre-sintering-high-temperature densification sintering under the protection of argon. The composite material prepared by the application has a unique three-level through-pore structure, i.e., millimeter-level pores generated by the gap between the filling paths of the 3D printing, sub-millimeter-level pores left after the water removal of the NaCl pore-forming agent, and micron-level pores generated due to the difference in the thermal expansion coefficients of HA and the matrix. The mechanical properties and the structural bionic design of the composite material meet the adaptability requirements of human bone tissues.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, specifically to a method for preparing a multi-level porous titanium-based bioactive bone implant composite material. Background Technology

[0002] TC4 has become a preferred orthopedic implant material due to its excellent biocompatibility and mechanical properties. However, the elastic modulus of traditional dense TC4 is much higher than that of human bone tissue, which can easily lead to stress shielding effects and surrounding bone resorption after long-term implantation. Porous structure design can reduce the elastic modulus; however, existing pore-forming techniques have significant limitations. While space-occupying and foaming methods can prepare macroporous structures larger than 300 μm, it is difficult to simultaneously construct micron and submicron level secondary pores. This pore uniformity results in insufficient specific surface area, severely restricting protein adsorption and cell adhesion. Studies have confirmed that micropores smaller than 50 μm play a crucial regulatory role in osteoblast adhesion and differentiation, but current technologies have not yet achieved the precise and coordinated construction of multi-level pores in titanium matrices.

[0003] To enhance bioactivity, hydroxyapatite composite modification has become a common method. However, there is a significant difference in the coefficient of thermal expansion between hydroxyapatite and the TC4 matrix, which induces microcrack formation during sintering. Simultaneously, the high-temperature environment causes hydroxyapatite to decompose into bioinert phases such as tricalcium phosphate, resulting in deterioration of the material's mechanical properties and a decrease in bioactivity. Traditional thermal debinding processes are prone to green body collapse due to the concentrated decomposition of the binder. The introduction of hydroxyapatite particles further increases the feed viscosity significantly, substantially increasing the printing defect rate.

[0004] Traditional one-stage sintering processes typically involve directly heating the green body to a high temperature for sintering. While simple, this method has significant drawbacks in titanium-based composite systems. Firstly, prolonged exposure to high temperatures accelerates the decomposition of hydroxyapatite, leading to its transformation into bioinert phases such as β-tricalcium phosphate (β-TCP), thus reducing the material's bioactivity. Secondly, due to the significant difference in thermal expansion coefficients between hydroxyapatite and the TC4 matrix, one-stage high-temperature sintering easily causes interfacial stress concentration, inducing microcracks and even macroscopic cracking, severely impacting the material's mechanical properties and structural integrity. While current fibrillation (FDM) technology still faces technical bottlenecks in its application to metal-ceramic composite systems, existing solutions attempting to prepare porous titanium using FDM have yet to overcome the challenge of synergistically optimizing matrix densification and hydroxyapatite activity.

[0005] Therefore, there is an urgent need to develop a method for preparing orthopedic implant materials with a porous structure, good bioactivity, and suitable elastic modulus. Summary of the Invention

[0006] To address the challenges of constructing multi-level pores, decomposing hydroxyapatite, and interfacial cracking in bone implant materials, this invention provides a method for preparing a multi-level porous titanium-based bioactive bone implant composite material. The composite material prepared by this method has a well-connected structure, and its mechanical properties and biomimetic structural design meet the compatibility requirements of human bone tissue.

[0007] The preparation method of the multi-level porous titanium-based bioactive bone implant composite material of the present invention specifically includes the following steps:

[0008] (1) Mix hydroxyapatite powder and ZrO2 powder and ball mill to obtain ceramic powder.

[0009] (2) Mix TC4 titanium alloy powder, ceramic powder and NaCl powder evenly to obtain mixed powder.

[0010] (3) Add the binder to the mixed powder, knead it, crush and granulate it after kneading to obtain granules.

[0011] (4) The particles are 3D printed (e.g., fused deposition modeling) to obtain green bodies.

[0012] (5) Degrease the green body to obtain a degreased green body.

[0013] (6) The degreased green body is sintered to obtain a multi-level porous titanium-based bioactive bone implant composite material.

[0014] Preferably, in step (1) of the present invention, the particle size of the hydroxyapatite powder is 100-200 nm and the particle size of the ZrO2 powder is 15-45 μm.

[0015] Preferably, in step (1) of the present invention, the mass ratio of hydroxyapatite powder to ZrO2 powder is 3-2:2-3.

[0016] Preferably, the ball milling conditions in step (1) of the present invention are: ball milling for 2-6 hours at a rotation speed of 200-400 rpm.

[0017] Preferably, in step (2) of the present invention, the particle size of TC4 titanium alloy powder is 15-45 μm and the particle size of NaCl powder is 300-500 μm.

[0018] Preferably, in step (2) of the present invention, the mass ratio of TC4 titanium alloy powder to ceramic powder is 90-95:5-10, and the volume ratio of NaCl powder is 20-30% of the total volume of TC4 titanium alloy and ceramic powder.

[0019] Preferably, in step (2) of the present invention, the uniform mixing is achieved by adding TC4 titanium alloy powder, ceramic powder and NaCl powder into a powder mixer and mixing for 8-24 hours at a speed of 50-80 rpm.

[0020] Preferably, the components and mass percentages of the adhesive in step (3) of the present invention are: 38% polyoxymethylene, 35% polyethylene glycol, 25% polymethyl methacrylate and 2% stearic acid.

[0021] Preferably, the loading amount of mixed powder in step (3) of the present invention is 50-60%.

[0022] Preferably, the conditions for intensive mixing in step (3) of the present invention are: intensive mixing temperature of 170-190℃ and intensive mixing time of 1-3h.

[0023] Preferably, the diameter of the particles in step (3) of the present invention is 2-4 mm.

[0024] Preferably, the 3D printing parameters in step (4) of this invention are: nozzle diameter 0.5-0.8 mm, printing temperature 170℃-190℃, layer thickness 0.1-0.4 mm, printing speed 15-45 mm / s, and flow rate 80%. 120%, with a fill density of 60%-80%, a grid pattern, and a 90-degree difference in fill angle between adjacent layers.

[0025] Preferably, the degreasing in step (5) of the present invention includes water degreasing, catalytic degreasing and thermal degreasing. Specifically, water degreasing is: treatment in water at 40-60℃ for 18-24h; catalytic degreasing is: degreasing in oxalic acid vapor at 120-150℃ for 1-3h; thermal degreasing is: thermal degreasing is carried out under the protection of argon atmosphere by step heating and holding, first heating to 200℃ at a heating rate of 10℃ / min, and then heating through two heating-holding stages at a heating rate of 1℃ / min. The first stage is held at 380℃ for 60-90min, and the second stage is held at 500℃ for 60-90min.

[0026] Preferably, the sintering conditions in step (6) of the present invention are as follows: under argon protection, the temperature is increased to 700-800℃ at 5-10℃ / min and held for 1-2 hours, and then increased to 1200-1300℃ at 5-10℃ / min and held for 1-2 hours.

[0027] Preferably, the cooling conditions in step (6) of the present invention are to cool down to 500°C at a rate of 5°C / min, and then allow it to cool naturally to room temperature.

[0028] Mechanism of the invention:

[0029] This invention achieves the effective construction of a three-tiered pore structure at the millimeter, sub-millimeter, and micrometer scale through the synergistic effect of 3D printing path filling gaps, NaCl pore-forming, and the difference in thermal expansion coefficients between the matrix and the ceramic phase. Specifically, the 3D-printed filling path directly forms millimeter-scale pores (1-2 mm), providing macroscopic channels for cell migration and tissue ingrowth; the NaCl pore-forming agent leaves sub-millimeter-scale pores (300–500 μm) after water removal, enhancing interpore connectivity and promoting nutrient transport; and the difference in thermal expansion coefficients between the matrix and hydroxyapatite generates micrometer-scale pores (10-30 μm) during sintering, further increasing the specific surface area and facilitating biomolecule adsorption and early cell attachment. The synergistic effect of these three factors not only achieves cross-scale pore coupling but also structurally simulates the multi-level pore characteristics of natural bone tissue, thereby significantly improving the material's bioactivity and bone integration capacity.

[0030] Compared with the prior art, the present invention provides a method for preparing a multi-level porous titanium-based bioactive bone implant composite material, which has the following beneficial effects:

[0031] (1) Achieving precise control of multi-level pore structure

[0032] By precisely controlling the millimeter-level pore distribution with a pore size of 1-2 mm through 3D printing filling path design, the elastic modulus of the material is significantly reduced, improving the mechanical compatibility between the implant and bone tissue. After the NaCl pore-forming agent is dissolved and removed by water desorption process, sub-millimeter-level pores with a pore size of 300-500 μm are formed, which is conducive to the ingrowth of new bone tissue into the pores, vascularization, and the formation of bone interconnection structures. Based on the difference in thermal expansion coefficient between hydroxyapatite and TC4 matrix, micron-level pores with a pore size of 10-30 μm are generated, increasing the specific surface area of ​​the material, enhancing the protein adsorption capacity, promoting osteoblast attachment, proliferation and differentiation, and guiding bone tissue growth on the surface.

[0033] (2) Significantly improves the stability of hydroxyapatite phase and the interfacial bonding strength

[0034] By introducing a ZrO2 interface buffer layer and a stepped sintering process, the problems of high-temperature decomposition of hydroxyapatite and mismatch between its thermal expansion coefficient and that of TC4 are effectively solved. The thermal expansion coefficient of ZrO2 is between that of the TC4 matrix and hydroxyapatite, which significantly buffers the stress concentration caused by the difference in thermal expansion. The synchronously generated transition phases such as CaZrO3 significantly enhance the bonding force of the ceramic / metal interface and avoid the risk of ceramic layer peeling off during the service of the implant. The 700-800℃ pre-sintering stage promotes the formation of sintering necks in TC4, shortens the high-temperature sintering time, and greatly inhibits the transformation of hydroxyapatite into bioinert phases such as β-TCP. Ultimately, a high retention rate of the active phase of hydroxyapatite is achieved, which improves the osteoinductive ability of the material.

[0035] (3) Excellent biocompatibility and mechanical properties

[0036] The composite material prepared by this invention has suitable porosity and elastic modulus. The high porosity provides an ideal three-dimensional space and huge surface area for cell adhesion, bone tissue ingrowth and vascularization, which greatly promotes bioactivity and bone integration. At the same time, the elastic modulus of the composite material can match that of human bone, effectively eliminating the stress shielding effect and maintaining sufficient mechanical strength under high porosity. Attached Figure Description

[0037] Figure 1 This is a process flow diagram for preparing the composite material according to the present invention.

[0038] Figure 2 This is a schematic diagram of the printing path for preparing the composite material according to the present invention.

[0039] Figure 3 This is a flow chart of the thermal degreasing and two-stage sintering process curves for preparing the composite material in Example 1 of the present invention.

[0040] Figure 4 This is a physical image of the green body and composite material in Embodiment 1 of the present invention.

[0041] Figure 5 This is a metallographic micrograph of the tertiary pore structure of the composite material prepared in Example 1 of the present invention.

[0042] Figure 6 This is a stress-strain curve obtained from the compression test of the composite material prepared in Example 2 of the present invention.

[0043] Figure 7 These are SEM images (a) and EDS surface scans of the composite material prepared in Example 3 of this invention, (b) is a Zr Lα1 surface scan, and (c) is a P Kα1 surface scan. Detailed Implementation

[0044] 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.

[0045] The 3D printing method in the embodiments and comparative examples of this invention is fused deposition modeling.

[0046] Example 1

[0047] The specific steps for preparing a hierarchical porous titanium-based bioactive bone implant composite material are as follows:

[0048] (1) Hydroxyapatite powder (particle size 200nm) and ZrO2 powder (particle size 25μm) were mixed and ball-milled in a mass ratio of 3:2, with a ball milling speed of 300rpm and a ball milling time of 4h to obtain ceramic powder.

[0049] (2) Add TC4 powder (particle size 25μm), ceramic powder and NaCl powder (particle size 500μm) to a powder mixer and stir to mix. The mass ratio of TC4 titanium alloy powder to ceramic powder is 95:5, and the volume ratio of NaCl powder is 20% of the volume of the mixed powder of TC4 titanium alloy and ceramic. The powder mixer speed is 50rpm and the mixing time is 24h to obtain mixed powder.

[0050] (3) Add the mixed powder to the binder (the components and mass percentages of the binder are: 38% polyoxymethylene, 35% polyethylene glycol, 25% polymethyl methacrylate and 2% stearic acid), the mixed powder loading is 60%, and then mix it in an intensive manner at a temperature of 170°C for 3 hours. After mixing, crush and granulate to obtain particles with a diameter of 3 mm.

[0051] (4) The particles are formed into a green body by fused deposition modeling. The printing parameters are: nozzle diameter 0.5 mm, printing temperature 170 ℃, layer thickness 0.1 mm, printing speed 15 mm / s, flow rate 120%, infill density 70%, infill pattern is a grid, and the infill angle of adjacent layers differs by 90° (printing path diagram is shown in the figure). Figure 2 (As shown).

[0052] (5) Degreasing the green billet, including water degreasing, catalytic degreasing and thermal degreasing, specifically: the green billet is placed in water at 50℃ for 20h; then degreasing in oxalic acid vapor at 120℃ for 3h; then thermal degreasing is carried out in a tube furnace under the protection of argon atmosphere by step heating and holding. First, the temperature is raised to 200℃ at a heating rate of 10℃ / min, and then the temperature is raised to 1℃ / min through two heating-holding stages. The first stage is held at 380℃ for 90min, and the second stage is held at 500℃ for 90min.

[0053] (6) The defatted green body is placed in a tube furnace for sintering. Under argon protection, the temperature is increased to 750°C at 10°C / min and held for 1 hour. Then the temperature is increased to 1250°C at 10°C / min and held for 2 hours. Then the temperature is decreased to 500°C at 5°C / min and then naturally cooled to room temperature to obtain a multi-level porous titanium-based bioactive bone implant composite material.

[0054] The process flow chart for hot degreasing and two-stage sintering in this embodiment is as follows: Figure 3As shown; the multi-level porous titanium-based bioactive bone implant composite material prepared in this embodiment has a porosity of 52.8%, an elastic modulus of 9.84 GPa, and a maximum compressive strength of 350.3 MPa; the metallographic micrograph of the tertiary porous structure of this composite material is shown in the figure. Figure 5 As shown, the composite material has a three-tiered pore structure of macropores, mesopores, and micropores. The figure shows a macropore structure with a size of up to 1251.76 μm. In bone implant materials, such macropores are beneficial for simulating the macroporous environment of natural bone, providing sufficient space for bone tissue ingrowth, promoting integration between bone and implant, and also facilitating the transport of nutrients and metabolites. There are also mesopores with a size of 327.16 μm, which act as a transition between macropores and micropores, further optimizing the hierarchical structure of pores. This can assist in the migration and proliferation of osteocytes and promote the growth and extension of bone tissue from the macroporous region into the interior of the material. There are also micropores of different sizes, such as 10.42 μm, 23.12 μm, and 31.11 μm. Micropores have a large specific surface area, which is beneficial for the interaction between the material and the biological environment. For example, they can enhance the bioactivity of the material, promote the deposition of osteoid minerals such as hydroxyapatite, and also provide microscopic sites for cell adhesion and differentiation.

[0055] Example 2

[0056] The specific steps for preparing a hierarchical porous titanium-based bioactive bone implant composite material are as follows:

[0057] (1) Hydroxyapatite powder (particle size 100nm) and ZrO2 powder (particle size 15μm) were mixed and ball-milled in a mass ratio of 2:3, with a ball milling speed of 200rpm and a ball milling time of 6h to obtain ceramic powder.

[0058] (2) Add TC4 powder (particle size 15μm), ceramic powder and NaCl powder (particle size 300μm) to a Y-type powder mixer and stir to mix. The mass ratio of TC4 titanium alloy powder to ceramic powder is 9:1, and the volume ratio of NaCl powder is 22% of the volume of the mixed powder of TC4 titanium alloy and ceramic. The mixing speed of the powder mixer is 60rpm and the mixing time is 12h to obtain mixed powder.

[0059] (3) Add the mixed powder to the binder (the components and mass percentages of the binder are: 38% polyoxymethylene, 35% polyethylene glycol, 25% polymethyl methacrylate and 2% stearic acid), the mixed powder loading is 55%, and then mix it in an intensive manner at a temperature of 180°C for 2 hours. After mixing, crush and granulate to obtain particles with a diameter of 2 mm.

[0060] (4) The particles are printed into a green body by fused deposition modeling. The printing parameters are: nozzle diameter 0.6 mm, printing temperature 180 ℃, layer thickness 0.2 mm, printing speed 35 mm / s, flow rate 100%, filling density 80%, filling pattern is grid, and the filling angle of adjacent layers differs by 90°.

[0061] (5) Degreasing the green billet includes water degreasing, catalytic degreasing and thermal degreasing. Specifically, the green billet is placed in water at 40℃ for 24 hours; then degreased in oxalic acid vapor at 125℃ for 2 hours; and then thermal degreasing is carried out in a tube furnace under the protection of argon atmosphere by step heating and holding. First, the temperature is raised to 200℃ at a heating rate of 10℃ / min, and then the temperature is raised to 1℃ / min for two heating-holding stages. The first stage is held at 380℃ for 60 minutes, and the second stage is held at 500℃ for 60 minutes to obtain the degreased green billet.

[0062] (6) The degreased green body was placed in a tube furnace for sintering. Under argon protection, the temperature was increased to 700℃ at 5℃ / min and held for 2h. Then the temperature was increased to 1200℃ at 5℃ / min and held for 1.5h. Then the temperature was decreased to 500℃ at 5℃ / min and allowed to cool naturally to room temperature to obtain a multi-level porous titanium-based bioactive bone implant composite material.

[0063] The stress-strain curve of the composite material prepared in this embodiment ( Figure 6 The results show that the stress of the composite material can reach more than 300 MPa, which has a certain ability to resist compressive failure. The elastic strain energy can reach about 4%, indicating that the material has a certain plastic deformation capacity during compression rather than brittle fracture. It can adapt by deformation when bearing load, which helps to better match the deformation needs of human bones under movement and other conditions for bone implant materials.

[0064] The multi-level porous titanium-based bioactive bone implant composite material prepared in this embodiment has a porosity of 56.4% and an elastic modulus of 8.52 GPa.

[0065] Example 3

[0066] The specific steps for preparing a hierarchical porous titanium-based bioactive bone implant composite material are as follows:

[0067] (1) Hydroxyapatite powder (particle size 150 nm) and ZrO2 powder (particle size 45 μm) were mixed and ball-milled in a mass ratio of 1:1, with a ball milling speed of 400 rpm and a ball milling time of 2 h to obtain ceramic powder.

[0068] (2) Add TC4 powder (particle size 45μm), ceramic powder and NaCl powder (particle size 400μm) to a powder mixer and stir to mix. The mass ratio of TC4 titanium alloy powder to ceramic powder is 92:8, and the volume ratio of NaCl powder is 30% of the volume of the mixed powder of TC4 titanium alloy and ceramic. The powder mixer speed is 80rpm and the mixing time is 8h to obtain mixed powder.

[0069] (3) Add the mixed powder to the binder (the components and mass percentages of the binder are: 38% polyoxymethylene, 35% polyethylene glycol, 25% polymethyl methacrylate and 2% stearic acid), the mixed powder loading is 50%, and then mix it in an intensive manner at a temperature of 190°C for 1 hour. After mixing, crush and granulate to obtain particles with a diameter of 4 mm.

[0070] (4) The particles are printed by fused deposition modeling. The printing parameters are: nozzle diameter 0.8 mm, printing temperature 190℃, layer thickness 0.4 mm, printing speed 45 mm / s, flow rate 80%, filling density 60%, filling pattern is grid, and the filling angle of adjacent layers differs by 90°.

[0071] (5) The green blanks are desalted, degreased and sintered in sequence. Specifically, the green blanks are placed in 60℃ water for desalting and water degreasing treatment for 18h; then degreased in 150℃ oxalic acid vapor for 1h; then heated and held in a tube furnace under the protection of argon atmosphere in a stepped heating and holding method with a heating rate of 2℃ / min, divided into two holding stages. The first stage is held at 380℃ for 70min, and the second stage is held at 500℃ for 70min.

[0072] (6) The degreased green body is placed in a tube furnace for sintering. Under argon protection, the temperature is increased to 800℃ at 8℃ / min and held for 1.5h. Then the temperature is increased to 1300℃ at 8℃ / min and held for 1h. Then the temperature is decreased to 500℃ at 5℃ / min and allowed to cool naturally to room temperature to obtain a multi-level porous titanium-based bioactive bone implant composite material.

[0073] The multi-level porous titanium-based bioactive bone implant composite material prepared in this embodiment has a porosity of 74.89%, an elastic modulus of 3.2 GPa, and a maximum compressive strength of 229.8 MPa.

[0074] The SEM and EDS surface scans of the composite material prepared in this embodiment are as follows: Figure 7As shown, the SEM image reveals regions of different gray levels and some black holes or defect structures. These different gray levels correspond to the distribution of α and β phases in the TC4 alloy, while the black parts are pores in the material. This porous structure is beneficial for biomaterials, such as cell adhesion, proliferation, and nutrient transport. It has positive significance in fields such as bone implant materials, as it can provide space for bone tissue growth.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is that ZrO2 was not added; all other conditions are the same as in Example 1. The specific steps for preparing the composite material are as follows:

[0077] (1) The hydroxyapatite powder (particle size 200nm) was ball-milled at a speed of 300rpm for 4h to obtain the ball-milled hydroxyapatite powder.

[0078] (2) Add TC4 powder (particle size 25μm), ball-milled hydroxyapatite powder and NaCl powder (particle size 500μm) to a powder mixer and stir to mix. The mass ratio of TC4 titanium alloy powder to ball-milled hydroxyapatite powder is 95:5, and the volume ratio of NaCl powder is 20% of the total volume of TC4 titanium alloy and ball-milled hydroxyapatite powder. The powder mixer speed is 50rpm and the mixing time is 24h to obtain mixed powder.

[0079] (3) Add binder to the mixed powder (the components and mass percentages of the binder are: 38% polyoxymethylene, 35% polyethylene glycol, 25% polymethyl methacrylate and 2% stearic acid), the mixed powder loading is 60%, and it is mixed in an intensive manner at a temperature of 170°C for 3 hours; after intensive mixing, it is crushed and granulated to obtain particles with a diameter of 3 mm.

[0080] (4) The particles are printed into a green body by fused deposition modeling. The printing parameters are: nozzle diameter 0.5 mm, printing temperature 170℃, layer thickness 0.1 mm, printing speed 15 mm / s, flow rate 120%, filling density 70%, filling pattern is grid, and the filling angle of adjacent layers differs by 90°.

[0081] (5) Degreasing the green billet, including water degreasing, catalytic degreasing and thermal degreasing, specifically: the green billet is placed in water at 50℃ for 20h; then degreasing in oxalic acid vapor at 120℃ for 3h; then thermal degreasing is carried out in a tube furnace under the protection of argon atmosphere by step heating and holding. First, the temperature is raised to 200℃ at a heating rate of 10℃ / min, and then the temperature is raised to 1℃ / min through two heating-holding stages. The first stage is held at 380℃ for 90min, and the second stage is held at 500℃ for 90min.

[0082] (6) The degreased green body is placed in a tube furnace for sintering. Under argon protection, the temperature is increased to 750°C at 10°C / min and held for 1 hour. Then the temperature is increased to 1250°C at 10°C / min and held for 2 hours. Then the temperature is decreased to 500°C at 5°C / min and then naturally cooled to room temperature to obtain the composite material.

[0083] This comparative example, without the addition of ZrO2, has a porosity of 58.3%, an elastic modulus of 6.28 GPa, and a maximum compressive strength of 134.7 MPa. Compared with Example 1, its porosity is significantly increased, while its elastic modulus and compressive strength are significantly reduced, making it difficult to meet the basic requirements for bone implant materials. The addition of ZrO2 plays a role in buffering and reinforcing the interface between HA and TC4, reducing the porosity caused by the difference in thermal expansion coefficients between HA and TC4.

[0084] Comparative Example 2

[0085] The difference between this comparative example and Example 1 is that a one-step sintering method was used; all other conditions were the same as in Example 1. The composite material was prepared using the following specific steps:

[0086] (1) Hydroxyapatite powder (particle size 200nm) and ZrO2 powder (particle size 25μm) were mixed and ball-milled in a mass ratio of 3:2, with a ball milling speed of 300rpm and a ball milling time of 4h to obtain ceramic powder.

[0087] (2) Add TC4 powder (particle size 25μm), ceramic powder and NaCl powder (particle size 500μm) to a powder mixer and stir to mix. The mass ratio of TC4 titanium alloy powder to ceramic powder is 95:5, and the volume ratio of NaCl powder is 20% of the volume of the mixed powder of TC4 titanium alloy and ceramic. The powder mixer speed is 50rpm and the mixing time is 24h to obtain mixed powder.

[0088] (3) Add the mixed powder to the binder (the components and mass percentages of the binder are: 38% polyoxymethylene, 35% polyethylene glycol, 25% polymethyl methacrylate and 2% stearic acid), the mixed powder loading is 60%, and then mix it in an intensive manner at a temperature of 170°C for 3 hours. After mixing, crush and granulate to obtain particles with a diameter of 3 mm.

[0089] (4) The particles are printed into a green body by fused deposition modeling. The printing parameters are: nozzle diameter 0.5 mm, printing temperature 170℃, layer thickness 0.1 mm, printing speed 15 mm / s, flow rate 120%, filling density 70%, filling pattern is grid, and the filling angle of adjacent layers differs by 90°.

[0090] (5) Degreasing the green billet, including water degreasing, catalytic degreasing and thermal degreasing, specifically: the green billet is placed in water at 50℃ for 20h; then degreasing in oxalic acid vapor at 120℃ for 3h; then thermal degreasing is carried out in a tube furnace under the protection of argon atmosphere by step heating and holding. First, the temperature is raised to 200℃ at a heating rate of 10℃ / min, and then the temperature is raised to 1℃ / min through two heating-holding stages. The first stage is held at 380℃ for 90min, and the second stage is held at 500℃ for 90min.

[0091] (6) The degreased green body is placed in a tube furnace for sintering. Under argon protection, the temperature is increased to 1250℃ at 10℃ / min and held for 2 hours. Then the temperature is decreased to 500℃ at 5℃ / min and allowed to cool naturally to room temperature to obtain the composite material.

[0092] This comparative example uses a one-step sintering method without a low-temperature sintering process. Its porosity is 61.6%, its elastic modulus is 6.02 GPa, and its maximum compressive strength is 101.3 MPa. Compared with Example 1, its performance is significantly degraded. This is due to the obstacle to the densification of ceramics by sintering. One-step sintering cannot achieve complete densification.

[0093] This invention utilizes 3D printing path design and NaCl pore-forming agent to construct a multi-level porous structure in TC4 implants. The porosity and elastic modulus effectively match the human bone modulus, eliminating stress shielding. By introducing a ZrO2 interface layer and a stepped sintering process, thermal mismatch stress is significantly alleviated, interfacial bonding is enhanced, and the decomposition of hydroxyapatite is inhibited, thus achieving high-activity phase retention. The composite material prepared by this invention possesses both excellent biocompatibility and mechanical properties.

[0094] 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 method for preparing a multi-level porous structure titanium-based bioactive bone implant composite material, characterized in that, Specifically, the following steps are included: (1) Mix hydroxyapatite powder and ZrO2 powder and ball mill to obtain ceramic powder; (2) Mix TC4 titanium alloy powder, ceramic powder and NaCl powder evenly to obtain mixed powder; (3) Add the binder to the mixed powder, knead it, crush and granulate it after kneading to obtain granules; (4) The particles are 3D printed to obtain a green body; (5) Degrease the green body to obtain a degreased green body; (6) The defatted green body is sintered and cooled to obtain a multi-level porous titanium-based bioactive bone implant composite material. The hydroxyapatite powder in step (1) has a particle size of 100-200 nm and the ZrO2 powder has a particle size of 15-45 μm; the mass ratio of hydroxyapatite powder to ZrO2 powder is 2-3:2-3. The particle size of the TC4 titanium alloy powder in step (2) is 15-45 μm, and the particle size of the NaCl powder is 300-500 μm; the mass ratio of TC4 titanium alloy powder to ceramic powder is 90-95:5-10, and the volume ratio of NaCl powder is 20-30% of the total volume of TC4 titanium alloy and ceramic powder.

2. The method for preparing the multi-level porous titanium-based bioactive bone implant composite material according to claim 1, characterized in that, The conditions for ball milling in step (1) are: ball milling for 2-6 hours at a speed of 200-400 rpm.

3. The method for preparing the multi-level porous titanium-based bioactive bone implant composite material according to claim 1, characterized in that, The uniform mixing in step (2) involves adding TC4 titanium alloy powder, ceramic powder, and NaCl powder into a powder mixer and mixing for 8-24 hours at a speed of 50-80 rpm.

4. The method for preparing the multi-level porous titanium-based bioactive bone implant composite material according to claim 1, characterized in that, In step (3), the mixed powder loading is 50-60%; the components and mass percentages of the binder are: 38% polyoxymethylene, 35% polyethylene glycol, 25% polymethyl methacrylate and 2% stearic acid.

5. The method for preparing the multi-level porous titanium-based bioactive bone implant composite material according to claim 1, characterized in that, The conditions for intensive mixing in step (3) are: intensive mixing temperature of 170-190℃, intensive mixing time of 1-3h; and the diameter of the particles is 2-4mm.

6. The method for preparing the multi-level porous titanium-based bioactive bone implant composite material according to claim 1, characterized in that, The 3D printing parameters mentioned in step (4) are: nozzle diameter 0.5-0.8mm, printing temperature 170℃-190℃, layer thickness 0.1-0.4mm, printing speed 15-45mm / s, flow rate 80%-120%, infill density 60%-80%, infill pattern is a grid, and the infill angle of adjacent layers differs by 90 degrees.

7. The method for preparing the multi-level porous titanium-based bioactive bone implant composite material according to claim 1, characterized in that, The degreasing in step (5) includes water degreasing, catalytic degreasing and thermal degreasing. Specifically, water degreasing is performed by treating the product in water at 40-60℃ for 18-24 hours. Specifically, catalytic degreasing is performed by degreasing the product in oxalic acid vapor at 120-150℃ for 1-3 hours. Specifically, thermal degreasing is performed by using a stepped heating and holding method under the protection of argon atmosphere. First, the temperature is raised to 200℃ at a heating rate of 10℃ / min, and then the temperature is raised to 1℃ / min for two heating-holding stages. The first stage is held at 380℃ for 60-90 minutes, and the second stage is held at 500℃ for 60-90 minutes.

8. The method for preparing the multi-level porous titanium-based bioactive bone implant composite material according to claim 1, characterized in that, The sintering conditions described in step (6) are as follows: under argon protection, the temperature is increased to 700-800℃ at 5-10℃ / min and held for 1-2 hours, and then increased to 1200-1300℃ at 5-10℃ / min and held for 1-2 hours.

9. The method for preparing the multi-level porous titanium-based bioactive bone implant composite material according to claim 1, characterized in that, The cooling conditions described in step (6) are to cool down to 500°C at a rate of 5°C / min, and then allow it to cool naturally to room temperature.

Images