A method for preparing a porous gradient structure material

Abstract

The application discloses a kind of preparation methods of porous gradient structure material, comprising the following steps: screening different diameter and density of matrix granular material and pore-forming agent particle, layering is placed in container, then container is excited and handled, and pore-forming agent particle is penetrated in the matrix granular material by vibration, while the pore-forming agent particle is gradient distribution in the vertical direction of the matrix granular material, cold-pressed preforming, sintering forming, i.e. the porous gradient structure material is obtained;Compared with prior art, the process of the application combines granular vibration mechanics and powder metallurgy technology, realizes the gradient distribution of pore-forming agent particle in matrix granular material and its solidification, and the technology has the advantages of simple equipment, convenient operation, strong controllability of void gradient and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of porous materials technology, and in particular to a method for preparing porous gradient structure materials. Background Technology

[0002] Porous gradient structure materials have broad application needs in numerous scientific and technological fields, including aerospace, chemical engineering, and biomedicine, and possess extensive application potential. For example:

[0003] (1) At present, the elastic modulus of human artificial metal implants is usually higher than that of natural bone. When implanted into the human body, stress will be transferred to the bone around the implant, resulting in stress shielding effect. Porous gradient materials can reduce stress shielding effect and have better biomechanical properties. (2) Porous gradient materials can also be used as a heat storage structure to improve the melting and solidification efficiency of phase change materials. (3) As a special structural and functional material, porous gradient structure materials have unique advantages in heat exchange, sound absorption, lubrication and other fields.

[0004] Existing technologies for preparing porous gradient materials mainly include methods such as adding pore-forming agents, additive manufacturing, centrifugal deposition, and template methods. However, these existing methods have limitations, such as the inability to effectively achieve porous gradient structures and uneven pore gradient changes. 3D printing technology for preparing porous gradient materials is complex, expensive, inefficient, and only suitable for a limited number of material types.

[0005] Therefore, traditional methods for preparing porous gradient structure materials can no longer meet their application requirements. For example, the traditional method of adding pore-forming agents has the problem of uneven pore gradient changes, additive manufacturing methods are relatively expensive, and centrifugal deposition methods are only applicable to liquid materials.

[0006] Therefore, existing methods for preparing porous gradient structure materials still need further improvement. Summary of the Invention

[0007] This invention proposes a method for preparing porous gradient structure materials, which solves the technical problems of uneven pore gradient changes in the existing pore-forming agent method, the high cost of additive manufacturing methods, and the limitation of centrifugal deposition method to liquid materials.

[0008] To address the above problems, the present invention proposes the following technical solution:

[0009] This invention provides a method for preparing porous gradient structure materials, comprising the following steps:

[0010] Matrix particles and pore-forming agent particles of different diameters and densities were screened and layered in a container.

[0011] The container is then subjected to vibration treatment, which causes the pore-forming agent particles to penetrate into the matrix granular material. Simultaneously, the pore-forming agent particles are distributed in a gradient along the vertical direction of the matrix granular material.

[0012] The porous gradient structure material is obtained by cold pressing preforming and sintering.

[0013] Based on this technical solution, and more preferably, the volume of the pore-forming agent particles accounts for (30-40)% of the volume of the porous gradient structure material.

[0014] Based on this technical solution, and further preferably, the layered placement in the container specifically includes: placing the matrix particulate material at the bottom of the container and placing the pore-forming agent particles on top of the matrix particulate material.

[0015] Based on this technical solution, and further preferably, the container is subjected to vibration treatment, which causes the pore-forming agent particles to penetrate into the matrix particle material through vibration, wherein the dimensionless acceleration of the vibration is (1-8) m / s². 2 .

[0016] Based on this technical solution, and even more preferably, the decomposition temperature of the pore-forming agent particles is lower than the sintering temperature of the matrix particle material.

[0017] Based on this technical solution, and further preferably, the matrix particulate material includes ceramic material and metal material, and the pore-forming agent particles include PVA, PVC or PMMA.

[0018] Based on this technical solution, and further preferably, the matrix particle material includes ceramic materials, metal or alloy materials, such as Ti6Al4V, and the pore-forming agent particles include PMMA.

[0019] Based on this technical solution, and further preferably, the diameter ratio of the matrix particle material to the pore-forming agent particles is greater than 2, and the density ratio is less than 4.

[0020] Based on this technical solution, and more preferably, the conditions for cold pressing preforming are 200-400MPa and 1200℃.

[0021] Based on this technical solution, and further preferably, the sintering process specifically includes two sintering processes. The first sintering temperature is 800°C, which is used to completely decompose the pore-forming agent particles. The second sintering temperature is 1350°C, which is used to form a dense body to obtain the final sample. The second sintering temperature is lower than the melting point of the matrix particle material.

[0022] Compared with the prior art, the technical effects achieved by the present invention include:

[0023] This invention uses vibration to create a gradient distribution of pore-forming agent particles in the matrix particle material, and then uses powder sintering technology to prepare a porous gradient material with a uniformly changing porous gradient. This provides a convenient way to prepare porous gradient structures on a large scale and greatly reduces the cost of preparing porous gradient materials.

[0024] This invention allows for the selection of matrix materials and pore-forming agent particles according to application requirements. By changing the diameter of the pore-forming agent particles, a porous gradient structure with different pore sizes can be prepared, thereby altering the mechanical properties of the finished product. Attached Figure Description

[0025] Figure 1 This is a flowchart of the preparation method of the porous gradient structure material described in Embodiment 1 of the present invention;

[0026] Figure 2 This is a flowchart of the preparation method for the matrix particle material Ti6Al4V and the pore-forming agent particle PMMA in Example 3 of the present invention.

[0027] Figure 3 This is a simulation of the pore-forming agent particles permeating into the matrix particulate material in Example 3 of the present invention;

[0028] Figure 4 This is the vertical distribution of porosity under various vibration states in Embodiment 4 of the present invention;

[0029] Figure 5 This is an electron microscope image of the porous gradient structure material prepared in Example 4 of the present invention. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below 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 based on the technology to which the claims of the present invention pertain without creative effort are within the scope of protection of the present invention.

[0031] It should be understood that the terminology used in this specification of embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. As used in this specification of embodiments of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0032] Example 1

[0033] This embodiment provides a method for preparing porous gradient structure materials, such as... Figure 1 Specifically, it includes the following steps:

[0034] S1. Screening matrix particulate materials and pore-forming agent particles of different diameters and densities;

[0035] The matrix particle material is Ti6Al4V, and the pore-forming agent particles are PMMA;

[0036] In the specific screening process, the diameter ratio and density ratio of the matrix particles to the pore-forming agent particles affect the efficiency and effect of the final gradient formation. When the diameter of the matrix particles is similar to that of the pore-forming agent particles, the pore-forming agent particles cannot penetrate into the middle of the matrix particles; when the density ratio of the matrix particles to the pore-forming agent particles is relatively large, the pore-forming agent particles also cannot penetrate into the middle of the matrix particles. Therefore, the diameter ratio of the matrix particles to the pore-forming agent particles is greater than 2, the density ratio is less than 4, and the volume of the pore-forming agent particles accounts for 40% of the porous gradient structure material. Then, the material is placed in layers in a container. The layering in the container specifically includes placing the matrix particles at the bottom of the container and placing the pore-forming agent particles on top of the matrix particles.

[0037] S2. The container is then subjected to vibration treatment. The vibration causes the pore-forming agent particles to penetrate into the matrix particle material, and the pore-forming agent particles are distributed in a gradient in the vertical direction of the matrix particle material.

[0038] The main reason why the matrix particles are on top during vibration is the penetration of pore-forming agent particles. However, the wall effect will affect the particle penetration process. It is necessary to reduce particle convection by increasing the vibration frequency and the diameter of the container to achieve the desired result.

[0039] The dimensionless acceleration of the vibration satisfies the following formula:

[0040] r=Aω 2 / g, ω=2πf

[0041] Where A is the amplitude, ω is the angular frequency, g is the gravitational acceleration, and f is the frequency. The container is then subjected to vibration treatment, which causes the pore-forming agent particles to penetrate the matrix particle material through vibration. The dimensionless acceleration r of the vibration ranges from (1-8) m / s². 2 When r is greater than 1, the pore-forming agent gradually seeps downward, forming a gradient distribution of pore-forming agent particles in the matrix particle material.

[0042] S3. Cold pressing preforming, wherein the conditions for cold pressing preforming are 400MPa, 1200℃, and sintering to obtain the porous gradient structure material.

[0043] The sintering process specifically includes two sintering processes. The first sintering stage is used to completely decompose the pore-forming agent particles, and the second sintering stage is used to form a dense body to obtain the final sample. The temperature of the second sintering stage is lower than the melting point of the matrix particle material. The first sintering temperature is 800℃ for 2 hours, and the second sintering temperature is 1350℃ for 2 hours, thus obtaining the porous gradient structure material.

[0044] Example 2

[0045] This embodiment provides a method for preparing porous gradient structure materials, specifically including the following steps:

[0046] S1. Screening matrix particulate materials and pore-forming agent particles of different diameters and densities, wherein the matrix particulate material is Ti6Al4V and the pore-forming agent particles include PMMA;

[0047] In the specific screening process, the diameter ratio and density ratio of the matrix particles to the pore-forming agent particles affect the efficiency and effect of the final gradient formation. When the diameter of the matrix particles is similar to that of the pore-forming agent particles, the pore-forming agent particles cannot penetrate into the middle of the matrix particles; when the density ratio of the matrix particles to the pore-forming agent particles is relatively large, the pore-forming agent particles also cannot penetrate into the middle of the matrix particles. Therefore, the diameter ratio of the matrix particles to the pore-forming agent particles is 3, the density ratio is 2, and the volume of the pore-forming agent particles accounts for 30% of the porous gradient structure material. Then, the material is placed in layers in a container. The layering in the container specifically includes placing the matrix particles at the bottom of the container and placing the pore-forming agent particles on top of the matrix particles.

[0048] S2. The container is then subjected to vibration treatment. Vibration causes the pore-forming agent particles to penetrate into the matrix particle material. The main reason for the matrix particle material being on top during vibration is the penetration of the pore-forming agent particles. However, the wall effect will affect the particle penetration process. It is necessary to increase the vibration frequency and the diameter of the container to reduce particle convection, thereby achieving the purpose. At the same time, the pore-forming agent particles are distributed in a gradient in the vertical direction of the matrix particle material.

[0049] The dimensionless acceleration of the vibration satisfies the following formula:

[0050] r=Aω 2 / g, ω=2πf

[0051] Where A is the amplitude, ω is the angular frequency, g is the gravitational acceleration, and f is the frequency. The container is then subjected to vibration treatment, which causes the pore-forming agent particles to penetrate into the matrix particle material through vibration. The dimensionless acceleration r of the vibration is 2. When r is greater than 1, it promotes the gradual penetration of the pore-forming agent, forming a gradient distribution of the pore-forming agent particles in the matrix material powder.

[0052] S3. Cold pressing preforming, wherein the conditions for cold pressing preforming are 300MPa, 1200℃, and sintering forming, wherein the sintering forming includes two heat preservation processes, the first heat preservation is 600℃ for 2h, and the second heat preservation is 1350℃ for 2h, thereby obtaining the porous gradient structure material.

[0053] Example 3

[0054] This embodiment provides a method for preparing porous gradient structure materials, specifically including the following steps:

[0055] S1. Screen matrix particles and pore-forming agent particles of different diameters and densities. The matrix particles are Ti6Al4V, and the pore-forming agent particles are PMMA. Place them in layers in a container. Figure 2 It can be seen that the vibrator 1 can provide the power for the penetration of the pore-forming agent particles 2, mainly by controlling the amplitude and frequency to change the input energy. The input energy needs to be within a certain range. If the input energy is too large, the particle vibration behavior will be more chaotic. If the input energy is too small, it will not be enough for the pore-forming agent particles 2 to penetrate into the matrix particle material. Therefore, the dimensionless acceleration r of the vibration related to the amplitude and frequency needs to be within (1-8) m / s². 2 Within the range.

[0056] The diameter of the pore-forming agent particles 2 needs to be selected according to the required pore size, and the decomposition temperature of the pore-forming agent particles 2 needs to be lower than the sintering temperature required for the matrix particle material. This has the advantage of promoting the pore-forming agent particles 2 to better penetrate into the matrix particle material 3.

[0057] The matrix particle material 3 needs to be selected according to the specific application, and the diameter ratio and density ratio of the matrix particle material 3 to the pore-forming agent particles 2 need to meet certain requirements, namely:

[0058] d 基体颗粒材料3 / d 成孔剂颗粒2 >2, ρ 基体颗粒材料3 / ρ 成孔剂颗粒2 <4;

[0059] That is, the diameter ratio of the two should be greater than 2, and the density ratio should be less than 4; when the diameter ratio of the matrix particles to the pore-forming agent particles is larger, the matrix particles are more likely to appear on top, and when the density ratio is smaller, the matrix particles are more likely to appear at the bottom of the container.

[0060] S2. The container is subjected to vibration treatment. The vibration causes the pore-forming agent particles 2 to penetrate into the matrix particle material 3. The main reason why the matrix particle material 3 is on top during the vibration is the penetration of the pore-forming agent particles 2. However, the wall effect will affect the particle penetration process. It is necessary to increase the vibration frequency and the diameter of the container to reduce particle convection, thereby achieving the purpose. At the same time, the pore-forming agent particles 2 are distributed in a gradient in the vertical direction of the matrix particle material 3.

[0061] The initial states of the matrix particulate material 3 and the pore-forming agent particles 2 are as follows: Figure 2 As shown in Figure 4, the pore-forming agent particles 2 and the matrix particle material 3 are placed in layers before starting. To avoid wall effects, the diameter of the container can be increased. The content of the pore-forming agent depends on the porosity of the desired porous structure material.

[0062] The permeation process of pore-forming agent particles 2 is as follows Figure 2 As shown in Figure 5, when the dimensionless acceleration r of the vibration is at (1-8) m / s², 2 Under the conditions of vibration within a certain range and with a certain amplitude and frequency, the container is subjected to vibration treatment. The particles inside the container first become dense, and then the pore-forming agent particles 2 gradually begin to penetrate to the bottom, showing a gradient distribution in the vertical direction.

[0063] The final distribution of pore-forming agent particles 2 in the container is as follows: Figure 2 As shown in Figure 6, the content of pore-forming agent particles 2 gradually decreases from top to bottom, which means that the porosity of the final porous structure material gradually decreases.

[0064] S3. Cold pressing preforming, wherein the conditions for cold pressing preforming are 200MPa, 1200℃, and sintering forming, wherein the sintering forming includes two heat preservation processes, the first heat preservation is 700℃ for 2h, and the second heat preservation is 1350℃ for 2h, thereby obtaining the porous gradient structure material.

[0065] Cold-pressed preforming of matrix granular materials, such as Figure 2 As shown in Figure 7, the mixed particles are transferred into a mold and cold-pressed under a certain pressure. The pressure applied to different particles is different.

[0066] Cold-pressed preforms, such as Figure 2 As shown in Figure 8, the cold-pressed preformed mixed particles are transferred to a sintering furnace and shaped under a certain sintering curve. There are two main sintering processes. The temperature in the first sintering stage is relatively low, and the main purpose is to completely decompose the pore-forming agent. The temperature in the second sintering stage depends on the relative melting point of the matrix material powder, and is generally lower than the melting point of 400 degrees. The purpose of this process is to form a dense body, thereby obtaining the final sample.

[0067] Figure 3This embodiment simulates the process of pore-forming agent particles penetrating into the matrix particle material. As can be seen, during the simulated vibration process, before vibration, the matrix particle material Ti6Al4V powder is placed at the bottom of the container, and the pore-forming agent particles PMMA are placed above the matrix particle material Ti6Al4V powder; after vibration, the pore-forming agent particles PMMA gradually penetrate downwards, and the distribution of pore-forming agent particles PMMA in the vertical direction of the matrix particle material Ti6Al4V powder is a gradient distribution.

[0068] Example 4

[0069] This embodiment proposes a method for preparing porous gradient structure materials. When the matrix particle material is Ti6Al4V powder and the pore-forming agent particles are PMMA particles, the method further includes the following steps:

[0070] S1. Screen matrix particulate materials and pore-forming agent particles of different diameters and densities, and place them in layers in a container;

[0071] The initial state of the Ti6Al4V matrix powder and the PMMA pore-forming agent particles is as follows: before starting, the pore-forming agent particles and the matrix powder are placed in layers. To avoid wall effects, the diameter of the container can be increased. The content of the pore-forming agent depends on the porosity of the required sample. The diameter of the pore-forming agent particles needs to be selected according to the pore size of the required porous structure material, and the decomposition temperature of the pore-forming agent needs to be lower than the sintering temperature required for the matrix powder. This has the advantage of promoting better penetration of the pore-forming agent particles into the matrix powder. The matrix powder material needs to be selected according to the specific application, including ceramic materials, metals, or alloy materials.

[0072] In this embodiment, Ti6Al4V powder is selected as the matrix particle material, and the diameter ratio of Ti6Al4V powder to PMMA particles must be greater than 2, and the density ratio must be less than 4. Ti6Al4V粉末 / d PMMA颗粒 >2, ρ Ti6Al4V粉末3 / ρ PMMA颗粒 <4; because when the diameter ratio of the matrix particles to the pore-forming agent particles is larger, the matrix particles are more likely to appear on top, and when the density ratio is smaller, the matrix particles are more likely to appear at the bottom of the container.

[0073] S2. The container is then subjected to vibration treatment to allow the pore-forming agent particles to penetrate into the matrix particle material. In this embodiment, a vibrator is used for vibration treatment. The advantage of this is that it can provide power for the penetration of the pore-forming agent particles. The vibrator mainly changes the input energy by controlling the amplitude and frequency, as shown in the following formula:

[0074] r=Aω 2 / g, ω=2πf

[0075] Where A is the amplitude, ω is the angular frequency, g is the acceleration due to gravity, and f is the frequency.

[0076] Meanwhile, the input energy needs to be within a certain range, because excessive input energy will lead to chaotic particle vibration behavior, while insufficient input energy will not allow the pore-forming agent particles to penetrate into the matrix particle material. Therefore, the dimensionless acceleration r related to amplitude and frequency needs to be greater than 1 and less than 8. The penetration process of the pore-forming agent particles is carried out when the dimensionless acceleration r is (1-8) m / s². 2 Under the conditions of vibration within a certain range and with a certain amplitude and frequency, the container is subjected to vibration treatment. The particles inside the container first become dense, and then the pore-forming agent particles gradually begin to penetrate to the bottom. At the same time, the pore-forming agent particles are distributed in a gradient in the vertical direction of the matrix particle material. Finally, the distribution of the pore-forming agent in the container shows that the content of pore-forming agent particles gradually decreases from the top to the bottom, which means that the porosity of the final sample gradually decreases.

[0077] S3. Cold pressing preforming and sintering forming to obtain the porous gradient structure material;

[0078] The cold pressing preforming process involves transferring the mixed particles into a mold and cold pressing them under a certain pressure. The pressure applied to different particles varies; in this embodiment, the pressure applied to the Ti6Al4V powder is 200 MPa.

[0079] After cold pressing and preforming, the mixed particles are transferred to a sintering furnace for sintering treatment. They are shaped under a certain sintering curve. The sintering process mainly consists of two stages. The sintering temperature in the first stage is relatively low, mainly to allow the pore-forming agent to decompose completely. The sintering temperature in the second stage depends on the relative melting point of the matrix material powder, and is generally below 400 degrees Celsius. The purpose of this heat preservation process is to form a dense body, thereby obtaining the final sample.

[0080] Figure 4 The vertical distribution of porosity under various vibration conditions in this embodiment shows that the porosity change process is uniform and gradual, forming a porous gradient structure with a gradually increasing porosity change rate. This simulation result confirms that adding vibration can make the pore-forming agent exhibit a gradient distribution in the matrix material powder.

[0081] Figure 5 This is an electron microscope image of the porous gradient structure material prepared in this embodiment. SEM observation shows that the pores exhibit a gradient distribution in the vertical direction.

[0082] In summary, the present invention proposes a method for preparing porous gradient structure materials. By changing the particle diameter of the pore-forming agent, porous gradient structures with different pore sizes are prepared, thereby changing the mechanical properties of the finished product. This provides a convenient way for large-scale preparation of porous gradient structures and greatly reduces the cost of preparing porous gradient materials.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a porous gradient structure material, characterized in that, Includes the following steps: Matrix particles and pore-forming agent particles of different diameters and densities are screened and layered in a container. This layering includes placing the matrix particles at the bottom of the container and the pore-forming agent particles on top of them. The container is then subjected to vibration treatment, which causes the pore-forming agent particles to penetrate into the matrix particle material. Simultaneously, the pore-forming agent particles are distributed in a gradient along the vertical direction of the matrix particle material, with the content of the pore-forming agent particles gradually decreasing from the top to the bottom of the container. Cold pressing preforming and sintering molding yield the porous gradient structure material with uniformly varying porosity in the gradient distribution direction. The diameter ratio of the matrix particles to the pore-forming agent particles is greater than 2, and the density ratio is less than 4. The container is then subjected to vibration treatment, which causes the pore-forming agent particles to penetrate into the matrix particle material through vibration, wherein the dimensionless acceleration of the vibration... r satisfy: ， ， in, A For amplitude, ω Angular frequency, g It is the acceleration due to gravity. f For frequency, r The range is 1-8.

2. The method for preparing porous gradient structured materials as described in claim 1, characterized in that, The volume of the pore-forming agent particles accounts for 30-40% of the volume of the porous gradient structure material.

3. The method for preparing porous gradient structured materials as described in claim 1, characterized in that, The decomposition temperature of the pore-forming agent particles is lower than the sintering temperature of the matrix particle material.

4. The method for preparing porous gradient structured materials as described in claim 1, characterized in that, The matrix particulate material includes ceramic or metallic materials, and the pore-forming agent particles include PVA, PVC, or PMMA.

5. The method for preparing porous gradient structured materials as described in claim 1, characterized in that, The matrix particulate material includes Ti6Al4V, and the pore-forming agent particulate material includes PMMA.

6. The method for preparing porous gradient structured materials as described in claim 5, characterized in that, The conditions for cold pressing preforming are 200-400 MPa and 1200℃.

7. The method for preparing porous gradient structured materials as described in claim 5, characterized in that, The sintering process specifically includes two sintering processes. The first sintering temperature is 800°C, which is used to completely decompose the pore-forming agent particles. The second sintering temperature is 1350°C, which is used to form a dense body to obtain the final sample. The second sintering temperature is lower than the melting point of the matrix particle material.

Images