A porous metal material

Abstract

The present application relates to a kind of porous metal materials.The cavity wall of the hole surrounded by is connected open hole, and the cavity wall is axial hollow structure, and the cavity wall has hole in radial direction, and the porosity of the porous metal material is uniformly distributed or gradient distribution, and the gradient distribution can be gradient change along one direction, or it can be three-dimensional gradient change, and the cavity wall radial hole is single-stage hole.The porous metal material of the present application has good mechanical properties, high three-dimensional pore connectivity, and good transfer performance.

Description

Technical Field

[0001] This invention relates to the field of porous materials, specifically porous metallic materials. Background Technology

[0002] Porous materials are materials containing a large number of pores. They can be broadly classified into two categories: natural porous materials and artificial porous materials. Natural porous materials are very common, such as bones used by animals and humans to support their bodies, leaves used by plants for photosynthesis, and wood. Artificial porous materials can be classified according to their material composition into porous metallic materials, porous ceramic materials, and porous polymer materials.

[0003] Porous metallic materials are among the fastest-growing porous materials in recent years. Compared to dense metallic materials, porous metals possess many superior properties, such as low density, large specific surface area, good energy absorption, high heat exchange and dissipation capacity, excellent permeability, renewability, and good processability. Their applications cover almost all uses of porous materials. For example, the uniform permeability of porous metals can be used to manufacture various filters, separators, and fluid distributors; their large specific surface area can be used to manufacture various porous electrodes, catalysts, catalyst supports, capacitors, electrolytic cell anodes, and heat exchangers; and their combined strength, toughness, and biocompatibility can be used to manufacture porous artificial bones. Porous metallic materials are a new type of functional material possessing both functional and structural properties. They are mainly prepared through methods such as powder sintering, fiber sintering, deposition, and organic foam impregnation. Commonly used porous metallic materials include metals and alloys such as nickel, titanium, aluminum, stainless steel, and tantalum.

[0004] Porous metallic materials exhibit pore structures comprising open and closed pores. Open pores are interconnected, while closed pores are not. Open-pore porous metallic materials offer significant advantages in applications such as porous electrodes, capacitors, electrolytic cell anodes, and artificial bones. Currently, open-pore porous metallic materials are typically prepared using chemical vapor deposition (CVD) or powder sintering. CVD-prepared porous materials have cavity walls composed of a carbon core and a metal material covering the carbon core, such as nickel, titanium, or tantalum. Powder sintering-prepared porous materials have solid cavity walls. The pores in these materials are limited to those enclosed by the cavity walls, and the open-pore connectivity is relatively low.

[0005] The organic foam impregnation method, proposed by Schwartzwalder in 1963, involves impregnating ceramic slurry with organic foam, followed by drying and firing to obtain porous foam ceramics. This method is simple and has significant advantages in preparing high-porosity materials, particularly interconnected open-cell materials. However, collapse is a major challenge in the firing process of the foam impregnation method, and solving this problem is crucial. In a sense, the process approach and methods of the green body preparation stage in the foam impregnation method differ from those in powder sintering. Although both methods rely on firing to achieve a certain degree of pore structure modification, fundamentally, foam impregnation and powder sintering are different porous material preparation processes. The initial green body preparation directly determines the conditions for subsequent firing processes. Green body-firing and pore structure modification form a complete process, not a arbitrarily fragmented combination.

[0006] The preparation of porous metal materials using the organic foam impregnation method typically involves immersing a porous polymer in a slurry, followed by drying and heating to the polymer burn-off temperature, sintering the metal powder particles together to obtain a rigid porous metal structure with high porosity. To achieve high mechanical properties, the metal grains need to be fused together. During sintering, the removal rate of the binder and polymer must be carefully controlled; too rapid a rate will cause bubbles, while too slow a rate will lead to localized collapse. Therefore, porous metal materials prepared using the organic foam impregnation method generally do not ideally have axial through-holes or radial pores in the cavity walls. Measures are taken to avoid the formation of these pores to prevent affecting mechanical strength.

[0007] However, the presence of axial through-holes and radial pores in the cavity wall increases the permeability of the material. Therefore, there is an urgent need to prepare porous metallic materials that simultaneously possess excellent hierarchical pore structure distribution and high mechanical strength. The applicant previously disclosed (CN108452385A) a hierarchical porous material prepared by cross-weaving two diameters of polymer filaments into a mesh, simultaneously injecting slurry, and then sintering. This material has through-channels within the cavity wall and pores with smaller diameters than the pores enclosed by the cavity wall. The pore structure on the cavity wall is a hierarchical pore structure graded according to the material's pore size, with at least two grades. The prepared porous tantalum material has a through-hole diameter of 550 μm, an equivalent diameter of 90 μm for the through-channels within the cavity wall, and two grades of pores smaller than the pores enclosed by the cavity wall. The largest grade pore has a diameter of 20 μm, and on the cavity wall of the 20 μm pore, there are even smaller pores, i.e., the smallest grade pores, with a diameter of 400 nm. The porous materials prepared by this method can achieve rapid and uniform distribution of cells and tissue fluid within the porous material. However, the method of cross-weaving polymer filaments into a web requires relatively large diameter polymer filaments. For small-diameter polymer filaments, the production operation and control of this method are quite difficult. The compressive strength of the multi-level porous material prepared in this patent is about 20 MPa. In order to meet more application scenarios, the preparation process, pore structure, pore size distribution, and cavity wall thickness of the multi-level porous material still need further improvement.

[0008] The applicant previously disclosed (CN108452386A) a porous tricalcium phosphate material prepared using polyurethane foam with an edge diameter of 25μm-50μm, achieving a compressive strength of 3.74MPa; and a porous niobium material prepared using polyurethane foam with an edge diameter of 50μm-90μm, achieving a compressive strength of 25.3MPa. The through-pore diameter was 300μm-600μm, the equivalent diameter of the channels penetrating the cavity wall was 40μm-70μm, and the first-order pores on the cavity wall had a diameter of 10μm-20μm. Smaller pores, i.e., minimum-order pores, with a diameter of 400nm-700nm, were also present on the cavity wall surrounding the 10μm-20μm pores. This patent used a foam impregnation method to prepare multi-level porous materials, but the pore structure and pore size distribution were still not sufficiently optimized. The two-level pores on the cavity wall limited the compressive strength, and it could only produce materials with a uniform porosity distribution, failing to adjust and fully simulate the morphology of bone tissue.

[0009] The applicant has previously prepared porous materials with gradient distributions. For example, CN108201635A discloses a porous metal material layer as a gradient porous metal material layer. Although the porous metal material in this patent adopts a gradient structure, its gradient is mainly formed by welding or powder sintering. The resulting porous material has interfaces between the gradient pores, and true integrated, interface-free fusion has not yet been achieved. Moreover, the aforementioned prepared gradient porous materials do not achieve multi-level pore distribution, have low three-dimensional pore connectivity, and the overall performance of the material is still not ideal. Summary of the Invention

[0010] The purpose of this invention is to provide a porous metal material with good mechanical properties, high three-dimensional pore connectivity, and good fluid transfer performance. The porous metal material has high three-dimensional pore connectivity within its internal cavity walls, resulting in good fluid transfer performance. The axially continuous hollow pores and radial pores in the cavity walls further promote material diffusion and improve the fluid transfer performance within the porous metal material.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A porous metal material has interconnected open pores enclosed by a cavity wall. The cavity wall has an axially hollow structure and radial pores. The porosity of the porous metal material is uniformly distributed or gradient distributed. The gradient distribution can be a gradient change along one direction or a three-dimensional gradient change. The radial pores of the cavity wall are single-level pores.

[0013] Three-dimensional gradient variation refers to changes in multiple directions within three-dimensional space. Single-level is the opposite of multi-level; multi-level refers to a specific multi-scale aperture structure, while single-level refers to a structure without multi-scale apertures.

[0014] Preferably, the porosity of the porous metal material is a gradient distribution, which is a fusion structure of interface-free gradient pores, and the gradient distribution is a radial thickness gradient change of the cavity wall.

[0015] The gradient distribution of this invention does not require connection by means of electric welding or other methods.

[0016] The gradient distribution can be asymptotic gradient change, non-asymptotic gradient change, or a combination of asymptotic and non-asymptotic gradient changes.

[0017] Non-gradient porosity refers to abrupt changes in porosity, which can fully simulate the morphology of cortical and cancellous bone tissues in the human body, achieving a high degree of biomimicry. Gradient porosity refers to continuous changes in porosity, which can fully simulate the pore structure of different regions of a type of bone tissue.

[0018] Optionally, the gradient distribution can be an asymptotic gradient change, a non-asymptotic gradient change, or a combination of asymptotic and non-asymptotic gradient changes in multiple directions in three-dimensional space.

[0019] The size of the openings enclosed by the cavity wall is 100-1500μm, the size of the hollow holes in the cavity wall is 5-90μm, and the size of the radial holes in the cavity wall is 0.2-15μm.

[0020] Optionally, the size of the opening formed by the cavity wall can be selected as 200-800μm, and further selected as 400-500μm, the size of the hollow hole in the cavity wall can be selected as 4-20μm, and the size of the radial hole in the cavity wall can be selected as 5-10μm.

[0021] The distance between the radial holes in the cavity wall is 2-15 μm, and optionally 4-8 μm.

[0022] The porosity of the porous metallic material is 30-90%. Optionally, the porosity is 30-50%, 50-70%, 70-80%, or 80-90%. When the porosity is distributed in a gradual and / or non-gradual gradient along one direction or along multiple directions in three-dimensional space, the porosity of the region with the largest porosity in the porous metallic material is preferably 70-90%, more preferably 75-85%, and the porosity of the region with the smallest porosity is 30-60%, more preferably 35-50%.

[0023] When the porosity gradient distribution is used, the radial thickness gradient of the cavity wall is preferred.

[0024] The radial thickness of the cavity wall is 50-1000 μm.

[0025] The surface roughness of porous metal materials is 15-21 μm, and the roughness of the outer surface of the cavity wall is 2-10 μm.

[0026] Optionally, porous metal materials with non-gradually varying porosity include 2-4 layers of porous metal structures with different porosities.

[0027] Optionally, the porosity of the porous metal material varies non-gradually. The porous metal material is divided into an upper part and a lower part. The upper part provides a first surface with a porosity of 30-60%, and the lower part provides a second surface with a porosity of 70-90%. The length ratio of the upper part to the lower part is 1:1.5 to 3.

[0028] Optionally, the porosity of the porous metal material varies non-gradually. The porous metal material is divided into an upper part and a lower part. The upper part provides a first surface with a porosity of 30%, and the lower part provides a second surface with a porosity of 70%. The length ratio of the upper part to the lower part is 1:1.5.

[0029] Optionally, the porosity of the porous metal material varies non-gradually. The porous metal material is divided into an upper part and a lower part. The upper part provides a first surface with a porosity of 25%, and the lower part provides a second surface with a porosity of 90%. The length ratio of the upper and lower parts is 1:3.

[0030] Optionally, the porosity of the porous metal material varies non-gradually. The porous metal material is divided into an upper part, a middle part, and a lower part. The upper part provides a first surface with a porosity of 20-40%, the middle part has a porosity of 45-60%, and the lower part provides a second surface with a porosity of 75-90%. The length ratio of the upper, middle, and lower parts is 1:1.5 to 2:2.5 to 3.

[0031] Optionally, in each layer of a porous metallic material with a non-gradually varying porosity, such as the upper, middle, and lower layers, the porosity may be uniformly distributed or combined with a gradual gradient variation.

[0032] The metal of this invention is a metal or metal alloy with excellent electrical conductivity or biocompatibility, specifically a metal or metal alloy such as nickel, titanium, tantalum, or niobium, preferably tantalum, niobium, or a tantalum-niobium alloy.

[0033] The axial hollow holes in the cavity wall of porous metal materials are continuous internal pores.

[0034] The method for preparing the porous metal material of this invention is the foam impregnation method.

[0035] Specifically, the double-roller pressing foam impregnation method is adopted.

[0036] Specifically, multi-level porous metal materials were prepared at low cost by controlling the composition and proportion of raw materials and the operating conditions of the preparation process through processes such as surface treatment, slurry impregnation, roller pressing, liquid film breaking, cross-linking curing, and three-stage sintering.

[0037] Specifically, metal powder with a particle size of 5-20 μm is mixed and stirred evenly with a dispersant aqueous solution. While stirring, PVA aqueous solution, defoamer, and glyoxal are added sequentially to prepare a metal powder slurry. The polymer scaffold used has an edge diameter of 5-90 μm. After cleaning the surface of the polymer scaffold, it is immersed in the dispersant aqueous solution for surface treatment. The polymer scaffold is then removed and dried. After drying, the surface-treated polymer scaffold is immersed in the metal powder slurry, and gently squeezed to ensure it fully absorbs the slurry. Once saturated, the polymer scaffold is removed and placed in a roller mill for pressing. During pressing, the distance between the rollers remains constant, squeezing out excess metal powder slurry. This process of immersion and roller pressing is repeated 3-5 times. The preform is then removed, and high-pressure gas is used to blow air onto the surface to break the surface liquid film. The preform is then left to stand in the air to allow the PVA in the preform to cross-link and solidify. This process allows for control of the pore size of porous metal materials. The metal powder slurry is fully filled into the polymer scaffold through roller extrusion, and excess slurry is removed. The cross-linking and curing process then solidifies the metal powder slurry, preventing agglomeration.

[0038] Then, the green body is placed in a vacuum drying oven to dry at a temperature of 60℃-80℃ for 4-6 hours. After drying, the green body is sintered under vacuum conditions by slowly raising the temperature from room temperature to 580-680℃ at a rate of 2-4℃ / min and holding for 6-8 hours. Then, the temperature is raised slowly to 1300-1600℃ at a rate of 2-4℃ / min and held for 6-8 hours. Then, the temperature is raised to 1800-2100℃ at a rate of 6-8℃ / min and held for 6-8 hours. Finally, the green body is cooled in the furnace.

[0039] For high-melting-point metals such as tantalum and niobium, this invention employs a three-stage sintering method. In the first stage, sintering at 580-680℃, the polymer scaffold, defoamer, and dispersant decompose and are removed through a vacuum system. In the second stage, sintering at 1300-1600℃, the porous metal material is pre-sintered and formed. In the third stage, sintering at 1800-2100℃, the porous metal material undergoes high-temperature sintering to further increase its mechanical strength. The high sintering temperature of this invention is well-matched with the hierarchical porous structure, resulting in porous metal materials with excellent mechanical properties.

[0040] The dispersant used in this invention is stearic acid, polyethylene glycol 400, or chitosan. Adding a dispersant to the metal powder slurry and surface-treating the polymer scaffold with the dispersant can ensure uniform dispersion of the metal powder. Even when using a polymer scaffold with a smaller ridge diameter, agglomeration of the metal powder can still be minimized, resulting in porous metal materials with high mechanical strength.

[0041] This invention, by appropriately controlling the heating rate and sintering temperature, creates continuous through-holes inside the cavity wall and pores of suitable diameter in the radial direction of the cavity wall, thereby increasing the mass transfer capacity.

[0042] The defoamer used in this invention is an organosilicon defoamer, preferably a trimethylsiloxy-terminated polydimethylsiloxane.

[0043] The porosity distribution of the porous metal material of this invention is mainly achieved by adjusting the radial thickness distribution of the cavity wall. Specifically, the porosity distribution of the porous metal material is adjusted by changing the shape of the polymer scaffold and the distance between the rollers during rolling. Preferably, the rollers are arranged in parallel. When preparing a porous metal material with a uniform porosity distribution, the polymer scaffold is a structure with two parallel surfaces, such as a cube or cuboid, and the rollers contact the two parallel surfaces during rolling. When preparing a porous metal material with a gradually increasing porosity gradient, the polymer scaffold can be a structure where the distance between the two opposite sides in contact with the rollers gradually changes. When the distance between the two opposite sides gradually changes along one direction, a porous metal material with a gradually increasing porosity gradient along one direction can be prepared. When the distance between the two opposite sides gradually changes along multiple directions, a porous metal material with a gradually increasing porosity gradient (three-dimensional gradually increasing gradient) along multiple directions can be prepared. Optionally, the polymer scaffold is a trapezoidal structure with two inclined sides. During rolling, the rollers can contact the two sides of the trapezoid, and through extrusion, the thickness distribution of the metal powder slurry layer on the inner surface of the polymer scaffold changes, thereby changing the thickness distribution of the cavity wall of the finally sintered porous metal material and causing a change in porosity. When preparing porous metal materials with non-gradually varying (abrupt) porosity distribution, the polymer scaffold can be a structure where the distance between the two opposite sides in contact with the rollers does not change gradually. When the distance between the two opposite sides changes non-gradually in one direction, porous metal materials with non-gradually varying porosity in one direction can be prepared. When the distance between the two opposite sides changes non-gradually in multiple directions, porous metal materials with non-gradually varying porosity in multiple directions (three-dimensional non-gradually varying porosity) can be prepared. Optionally, the polymer scaffold can be convex, have multiple stepped shapes on the sides, etc. When preparing porous metallic materials that combine gradual and non-gradual porosity changes, the polymer scaffold can be a structure where the distance between the two opposing sides in contact with the rollers simultaneously exhibits both non-gradual and gradual changes. When the distance between the two opposing sides exhibits both gradual and non-gradual changes along one direction, a porous metallic material combining gradual and non-gradual porosity changes along one direction can be prepared. When the distance between the two opposing sides exhibits both gradual and non-gradual changes, and these changes occur in multiple directions, a porous metallic material combining three-dimensional gradual and non-gradual porosity changes can be prepared.

[0044] Beneficial effects:

[0045] 1. The porous metal material provided by this invention includes three types of pores, particularly axially hollow pores and radial pores in the cavity wall. In the prior art, to avoid poor mechanical properties, pores within the cavity wall and on the surface are generally undesirable. However, this invention, by employing metal powder of specific sizes and polymer scaffolds, and by precisely controlling the preparation process, yields a material that not only possesses excellent mechanical properties but also, due to the presence of axially hollow pores and radial pores of specific sizes in the cavity wall, improves the three-dimensional connectivity of the pores and the fluid transport capacity. The porous metal material contains at least two continuous channels: a three-dimensionally interconnected channel enclosed by the cavity wall and axially hollow pores in the cavity wall.

[0046] 2. The porous metal material with a progressively gradient porosity provided by the present invention is a fusion structure of interface-free gradient pores, which solves the problems of interfaces between gradient pores with different porosities in the prior art, the failure to achieve true integrated interface-free fusion, unevenness at the interface, pore blockage and cracking.

[0047] 3. By controlling the pore size, distribution, and / or wall thickness of porous metal materials within the scope of this invention, the three-dimensional connectivity and transmission performance of the pores in porous metal materials can be improved, as well as their mechanical properties.

[0048] 4. The high surface roughness of the cavity wall can improve capillary force and enhance the fluid flow within the pores.

[0049] 5. The porous metal material of this invention can be used as a porous electrode, capacitor, electrolytic cell anode, artificial bone, etc. Because the porous metal material of this invention has advantages such as good mechanical properties, high three-dimensional pore connectivity, and good transport performance, when used as an electrode material, it has good supporting performance and strong conductivity. Moreover, due to the combination of the three types of pores, the mass transfer capacity is strong, resulting in high diffusion coefficients for both reactants and products, thus improving the reaction rate. When the porous metal material of this invention is used as a bone tissue material, its high surface roughness can increase the friction coefficient with cortical bone and cancellous bone, improving early implantation stability. Furthermore, the porous metal material has strong permeability, facilitating the transport of body fluids and nutrient cells within the material, and its high fluidity promotes tissue growth and osteoconductivity.

[0050] 6. The gradient porous metal material prepared by the method of the present invention, especially the three-dimensional gradient porous metal material, can highly mimic the bone tissue structure and has many advantages such as strong bone fusion and regeneration ability and good matching with autologous bone after implantation.

[0051] 7. The purity of the porous metal material of the present invention is ≥99%; the mechanical properties of the porous metal material can be adjusted within a wide range by adjusting the process parameters, with a compressive strength of 30-90 (MPa) and an elastic modulus of 1.8-3.8 (GPa). Attached Figure Description

[0052] Figure 1 This is a microstructure diagram of the radial holes in the porous tantalum cavity wall of the present invention;

[0053] Figure 2 This is a schematic diagram of the polymer support structure of the ladder-like structure of the present invention;

[0054] Figure 3 A schematic diagram of a polymer scaffold with multiple stepped shapes on its side;

[0055] Figure 4 To adopt Figure 3 A schematic diagram of a porous metal material with non-gradually varying porosity prepared by a polymer scaffold; Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0057] Example 1

[0058] Mix 80g of tantalum powder with a particle size of 10μm with 20ml of polyethylene glycol 400 aqueous solution (0.1M) and stir until homogeneous. While stirring, add 50ml of PVA aqueous solution (0.2M), 0.1g of trimethylsiloxy-terminated polydimethylsiloxane and 0.3g of glyoxal in sequence to prepare tantalum powder slurry. After cleaning the surface of a cubic polyurethane polymer scaffold with an edge diameter of 30 μm, it was immersed in a 1M polyethylene glycol 400 aqueous solution for surface treatment. The scaffold was then removed and dried. After drying, the surface-treated scaffold was immersed in tantalum powder slurry, and gently squeezed to ensure full absorption of the slurry. Once saturated, the saturated scaffold was removed and placed in a roller mill for pressing. During pressing, the distance between the rollers remained constant, squeezing out excess tantalum powder slurry. This process of slurry immersion and roller pressing was repeated five times. The preform was then removed, and high-pressure gas was used to blow air onto its surface to break the surface liquid film. It was then left to stand in air to allow the PVA in the preform to cross-link and cure. After full curing, the preform was placed in a vacuum drying oven at 60℃ for 4 hours. After drying, the green body is sintered under vacuum conditions by slowly heating from room temperature to 580°C at a heating rate of 2°C / min and holding for 6 hours. Then, it is sintered by slowly heating to 1500°C at a heating rate of 2°C / min and holding for 6 hours. Then, it is sintered by slowly heating to 1900°C at a heating rate of 6°C / min and holding for 6 hours. Finally, it is cooled in the furnace.

[0059] The prepared porous tantalum material has a porosity of 75%, a compressive strength of 65 MPa, and an elastic modulus of 2 GPa. The size of the openings enclosed by the cavity walls is 200-500 μm, the size of the hollow pores in the cavity walls is approximately 30 μm, and the size of the radial pores in the cavity walls is 5-10 μm. The distance between the radial pores in the cavity walls is 3-6 μm. The radial thickness of the cavity walls is approximately 150 μm. The surface roughness of the porous metal material is 18 μm. The outer surface roughness of the cavity walls is 4 μm. Figure 1 The microstructure of radial holes in the cavity wall of a porous tantalum is shown. The radial holes are nearly circular and the surface of the hole walls is smooth.

[0060] When the prepared porous tantalum is used as the anode diffusion layer in an electrolytic cell, the conventional anode catalyst layer is hot-pressed together with the porous tantalum. Compared with the commonly used carbon paper anode diffusion layer, the porous tantalum anode diffusion layer significantly improves the mass transfer capacity of water and oxygen. When assembling an electrolytic cell using conventional methods, the oxygen volume concentration in the anode-side chamber can reach 28% after 30 minutes of electrolysis with the porous tantalum anode diffusion layer, while the oxygen volume concentration in the anode-side chamber is only 18% after 30 minutes of electrolysis with the conventional carbon paper anode diffusion layer.

[0061] When the prepared porous tantalum is used as an artificial bone tissue material, it exhibits strong permeability and good fluid and nutrient flow. The coefficient of friction between porous tantalum and cortical bone is 1.79, and the coefficient of friction between porous tantalum and cancellous bone is 0.97. In comparison, the coefficient of friction between trabecular metal from ZIMMER (USA) and cortical bone is 1.36, and the coefficient of friction between trabecular metal and cancellous bone is 0.93. The porous tantalum of this invention has a high coefficient of friction and stronger adhesion to autologous bone and peripheral ligament tissue, ensuring greater early stability and a higher success rate for implanted products.

[0062] Example 2

[0063] Using the process and raw materials of Example 1, the shape of the polyurethane polymer scaffold was changed to a trapezoidal platform, as shown in the schematic diagram. Figure 2 As shown, during rolling, the rollers contact both sides of the stepped platform, resulting in porous tantalum with a progressively increasing porosity gradient. The stepped platform support is subjected to varying degrees of compression from top to bottom by the rollers, causing the slurry layer thickness to gradually decrease from the upper to the lower surface. This means the radial thickness of the tantalum slurry coating on the polymer support cavity wall gradually decreases, leading to a gradual increase in porosity of the porous tantalum from top to bottom. The prepared porous tantalum has a porosity of 70% on the upper surface side and a cavity wall radial thickness of approximately 200 μm, while the corresponding lower surface side has a porosity of 90% and a cavity wall radial thickness of approximately 100 μm.

[0064] Example 3

[0065] Using the process and raw materials of Example 1, the shape of the polyurethane polymer scaffold was changed to have multiple stepped shapes on the sides, as shown in the schematic diagram. Figure 3As shown. During rolling, the two sides of the roller contact support result in porous tantalum with a non-gradual porosity distribution. After the upper surface is cut into a regular shape with the longitudinal edge flush, the porosity distribution is shown in the schematic diagram. Figure 4 As shown, the porous tantalum has a first surface at the top with a porosity of 35%, a middle porosity of 60%, and a second surface at the bottom with a porosity of 85%.

[0066] Example 4

[0067] The process and raw materials used in Example 1 were employed, the difference being that the metal used was titanium with a particle size of 5 μm, and the amount added was 80 g. The dried preform was sintered under vacuum conditions, slowly heated from room temperature to 580 °C at a heating rate of 2 °C / min, and held for 6 hours. Then, the temperature was further slowly increased to 1250 °C at a heating rate of 2 °C / min and held for 6 hours. The prepared porous titanium had a porosity of 78%, a compressive strength of 60 MPa, and an elastic modulus of 1.8 GPa. The size of the openings enclosed by the cavity walls was 300-550 μm, the size of the hollow pores in the cavity walls was approximately 30 μm, and the size of the radial pores in the cavity walls was 0.2-5 μm. The distance between the radial pores in the cavity walls was 2-5 μm. The radial thickness of the cavity walls was approximately 130 μm. The surface roughness of the porous metal material was 15 μm. The outer surface roughness of the cavity walls was 2 μm.

[0068] Example 5

[0069] The process and raw materials used in Example 1 were employed, the difference being that the metal used was niobium, with a particle size of 15 μm, and an addition amount of 80 g. A cubic polyurethane polymer scaffold with an edge diameter of 60 μm was used. After drying, the preform was sintered under vacuum conditions, slowly heated from room temperature to 620 °C at a heating rate of 3 °C / min and held for 6 hours. Then, the temperature was further slowly increased to 1400 °C at a heating rate of 3 °C / min and held for 6 hours. Finally, the temperature was increased to 1850 °C at a heating rate of 6 °C / min and held for 6 hours, followed by furnace cooling. The prepared porous niobium had a porosity of 82%, a compressive strength of 56 MPa, and an elastic modulus of 1.4 GPa. The size of the openings enclosed by the cavity walls was 500-800 μm, the size of the hollow pores in the cavity walls was approximately 60 μm, and the size of the radial pores in the cavity walls was 5-10 μm. The distance between the radial pores in the cavity walls was 2-8 μm. The radial thickness of the cavity walls was approximately 140 μm. The surface roughness of the porous metal material is 16 μm. The surface roughness of the outer surface of the cavity wall is 8 μm.

[0070] Example 6

[0071] The process and raw materials used in Example 1 were employed, the difference being that the metal was a mixture of 40g of tantalum with a particle size of 20μm and 40g of niobium with a particle size of 20μm, and a cubic polyurethane polymer scaffold with an edge diameter of 80μm was used. After drying, the preform was sintered under vacuum conditions by slowly heating from room temperature to 680℃ at a heating rate of 4℃ / min and holding for 6 hours. Then, the temperature was further slowly increased to 1600℃ at a heating rate of 4℃ / min and held for 6 hours. Finally, the temperature was further increased to 1800℃ at a heating rate of 6℃ / min and held for 6 hours, followed by furnace cooling. The prepared porous tantalum-niobium alloy had a porosity of 84%, a compressive strength of 52MPa, and an elastic modulus of 1.3GPa. The size of the openings enclosed by the cavity walls was 600-1000μm, the size of the hollow pores in the cavity walls was approximately 80μm, and the size of the radial pores in the cavity walls was 3-10μm. The distance between the radial pores in the cavity walls was 3-10μm. The radial thickness of the cavity wall is approximately 145 μm. The surface roughness of the porous metal material is 20 μm. The roughness of the outer surface of the cavity wall is 10 μm.

Claims

1. A porous metallic material, characterized in that: The cavity wall forms a continuous open hole, the cavity wall is an axially hollow structure, and the cavity wall has pores in the radial direction. The porous metal material has a porosity gradient distribution, which can be a gradient change along one direction or a three-dimensional gradient change. The pores in the radial direction of the cavity wall are single-level pores. The porosity distribution of the porous metal material is achieved by adjusting the radial thickness distribution of the cavity wall. The porous metal material is prepared by the following method: Metal powder with a particle size of 5-20 μm is mixed with a dispersant aqueous solution and stirred until homogeneous. While stirring, PVA aqueous solution, defoamer, and glyoxal are added sequentially to prepare a metal powder slurry. A polymer scaffold with an edge diameter of 5-90 μm is used. After cleaning the surface of the polymer scaffold, it is immersed in the dispersant aqueous solution for surface treatment. The polymer scaffold is then removed and dried. After drying, the surface-treated polymer scaffold is immersed in the metal powder slurry, and the polymer scaffold is gently squeezed to allow it to... After fully absorbing the metal powder slurry and reaching saturation, the polymer scaffold soaked in the slurry is removed and placed into a roller mill for rolling. During the rolling process, the distance between the rollers remains constant, squeezing out excess metal powder slurry. This process of soaking in slurry and rolling is repeated 3-5 times. The preform is then removed, and high-pressure gas is used to blow air onto the surface of the preform to break the liquid film on the surface. The preform is then left to stand in the air to allow the PVA in the preform to cross-link and solidify. The porosity distribution of the porous metal material can be adjusted by changing the shape of the polymer scaffold and the distance between the rollers during rolling. Then, the green body is placed in a vacuum drying oven for drying at a temperature of 60℃-80℃ for 4-6 hours. After drying, the green body is sintered under vacuum conditions at a heating rate of 2-4℃ / min from room temperature to 580-680℃ and held for 6-8 hours. Then, the heating rate is increased to 1300-1600℃ at a heating rate of 2-4℃ / min and held for 6-8 hours. Then, the heating rate is increased to 1800-2100℃ at a heating rate of 6-8℃ / min and held for 6-8 hours. Finally, the green body is cooled in the furnace.

2. The porous metal material according to claim 1, characterized in that: The gradient distribution is a fusion structure of interface-free gradient holes, and / or the gradient distribution is a radial thickness gradient variation of the cavity wall.

3. The porous metal material according to claim 1 or 2, characterized in that: The gradient distribution can be asymptotic gradient change, non-asymptotic gradient change, or a combination of asymptotic and non-asymptotic gradient changes.

4. The porous metal material according to claim 1, characterized in that: Three-dimensional gradient change refers to changes in multiple directions in three-dimensional space.

5. The porous metal material according to claim 1, characterized in that: The gradient distribution can be an asymptotic gradient change, a non-asymptotic gradient change, or a combination of asymptotic and non-asymptotic gradient changes in multiple directions in three-dimensional space.

6. The porous metal material according to claim 1, characterized in that: The size of the opening formed by the cavity wall is 100-1500μm, the size of the axial hollow structure of the cavity wall is 5-90μm, and the size of the radial hole in the cavity wall is 0.2-15μm.

7. The porous metal material according to claim 1, characterized in that: The distance between the radial holes in the cavity wall is 2-15 μm.

8. The porous metal material according to claim 1, characterized in that: The porosity of porous metallic materials is 30-90%.

9. The porous metal material according to claim 1, characterized in that: The radial thickness of the cavity wall is 50-1000 μm.

10. The porous metal material according to claim 1, characterized in that: The surface roughness of the porous metal material is 15-21 μm, and the roughness of the outer surface of the cavity wall is 2-10 μm.

Images