CN107200583B - A porous material with a continuous gradient of porosity and its preparation method - Google Patents

Abstract

The invention provides a method for preparing a porous material with a continuous gradient of porosity, comprising the following steps: (1) mixing a powder raw material with a volume fraction of 50-70% and deionized water with a volume fraction of 30-50%, Then add sol, and ball mill to obtain slurry A; (2) configure the same hydrosol B as in step (1); (3) add hydrosol B to slurry A to obtain mixed slurry at regular intervals, and maintain the The solid phase content in the mixed slurry changes continuously within the range of 0-70vol%. After adding the hydrosol B each time, it is input to the 3D printer for printing, and the mixed slurry at the nozzle is kept solidified into a gel; ( 4) freezing the formed gel along the direction of the gradient, and forming a porous material with a continuous gradient of porosity after sintering. The beneficial effect of the present invention is that the process is simple, the stability and repeatability are good, and by continuously adjusting the solid phase content of the slurry, combined with 3D printing, a gel with a continuous gradient change in the solid content is formed.

Description

A porous material with a continuous gradient of porosity and its preparation method

technical field

The invention relates to a preparation method of a porous material, in particular to a porous material with a continuous gradient of porosity and a preparation method thereof.

Background technique

The porous material with porosity gradient is an important member of functionally graded materials, and its main feature is that the porosity changes regularly with the sample size. Gradient porous materials were first used in the fields of filtration, gas separation, dust removal, etc. Compared with traditional porous materials with uniform porosity, they can maximize efficiency and save energy consumption. In the field of filtration and separation, with the improvement of filtration precision, the pore size of porous materials is required to be smaller and smaller, but this leads to an increase in the resistance of fluid passing through the material, reducing its permeability. Traditional porous materials can no longer meet the needs of high-precision filtration and separation, and porous materials with a gradient change in porosity along the thickness direction can well solve the contradiction between improving filtration accuracy and increasing transmittance. From the perspective of fluid dynamics, the resistance of continuous pore structure is smaller than that of abrupt gradient pore structure. Therefore, continuous gradient pore structure is a better gradient pore structure, and continuous gradient porous materials have wider application prospects. With the development of research on gradient porous materials, their applications are becoming more and more extensive, such as in the field of biomimetic materials such as composite porous preforms, catalyst carriers, sensors, and artificial bones.

There are many preparation methods for gradient porous materials, mainly including particle grading accumulation process, spraying process, organic foam impregnation process, porous matrix chemical deposition process, foaming process, co-sedimentation method, centrifugation method and filter press molding process. However, the existing preparation methods still have the following main problems: 1. Most of the gradient materials prepared by traditional methods have a step porosity gradient, and it is difficult to achieve a continuous gradient change in porosity, so that the gradient porous materials cannot be maximized. 2. The porosity gradient can be adjusted in a small range, and different gradient forms from low porosity (0%) to high porosity (above 80%) cannot be realized, which limits its application range; 3. There is no one It has a universal preparation method, which can meet the preparation of different gradient porous materials such as metals and ceramics; 4. The traditional method is complex in process, poor in stability and reproducibility of the production process, difficult to control the pore structure of porous materials, and difficult to achieve mass production. In view of this, it is urgent to develop a method for preparing porous materials with a continuous porosity gradient with a wide adjustable range of porosity gradient and good versatility.

In view of the above-mentioned defects, the creator of the present invention has finally obtained the present invention through long-term research and practice.

Contents of the invention

In order to solve the above problems, the technical solution adopted by the present invention is to provide a method for preparing a porous material with a continuous gradient of porosity on the one hand, comprising the following steps: (1) mixing a powder raw material with a volume fraction of 50-70% and Mixing deionized water with a volume fraction of 30-50%, then adding the sol, and ball milling within the temperature range of the sol to obtain the slurry A, wherein the sol can be transformed into a gel under certain conditions, and the sol and the The mass ratio of deionized water is 0.01-0.15:1; (2) configure the same hydrosol B as in the step (1), the mass ratio of the sol in its composition to the deionized water is the same as that of the step (1) (3) at regular intervals, add the hydrosol B to the slurry A to obtain a mixed slurry, and maintain the solid phase content in the mixed slurry within the range of 0-70vol% to continue Change, after each addition of the hydrosol B, the mixed slurry is input into the 3D printer for printing, and the mixed slurry at the nozzle of the 3D printer is kept solidified into a gel; (4) the mixed slurry is solidified into a gel; The gel formed in the above step (3) is subjected to freezing treatment along the direction of the gradient of the solid phase content, the freezing temperature is -196-0°C, and then freeze-dried to obtain a porous material body, which is sintered to form a porous material with a continuous gradient of porosity. Material.

Further, the powder raw material includes Ti, Zr, Al, Si, Cu, Ag, Fe, Ni or Mo any metal powder or ceramic powder or organic material powder that does not react violently with water.

Further, the sol in the step (1) is a temperature-controlled sol, which can be transformed into a gel at a low temperature, and it is a mixture of gelatin, agarose, chitosan and gelatin or a mixture of sodium alginate and gelatin any of the

Further, when adding the gelatin, in the step (1), the temperature during ball milling is 20-95°C; in the step (3), the temperature of the mixed slurry at the nozzle is set at 0-20°C ℃.

Further, when adding the agarose, in the step (1), the temperature during ball milling is 40-95° C.; in the step (3), the temperature of the mixed slurry at the nozzle is set to 0-95° C. 40°C.

Further, the sol in the step (1) is a light-controlled sol, which can be transformed into a gel under UV light, which is a polyethylene glycol hydrosol system modified by ethyl cinnamate or a nitrocinnamic acid modified gel. Polyethylene glycol hydrosol system.

Further, the 3D printer is provided with a UV lamp, and when printing, the UV lamp irradiates the mixed slurry at the nozzle.

Further, the constant temperature environment in the preparation process is maintained by a constant temperature box.

Further, in the step (3), the slurry A is placed in the first container, the hydrosol B is placed in the second container, and the first container is connected to the third container through a first peristaltic pump, The second container is connected to the third container through a second peristaltic pump, the third container is connected to the 3D printer through a third peristaltic pump, and a stirring pump is arranged in the third container, and the printing process is as follows:

S1: input the constant amount of slurry A in the first container to the third container through the first peristaltic pump, turn off the first peristaltic pump, turn on the third peristaltic pump and the 3D printer, After printing the first layer, close the third peristaltic pump and the 3D printer;

S2: Turn on the second peristaltic pump, input a constant amount of the hydrosol B into the third container, turn off the second peristaltic pump, turn on the third peristaltic pump and the 3D printer, and finish printing the first After the second layer, close the third peristaltic pump and the 3D printer;

Afterwards, the step S2 is repeated until the printing of the Nth layer is completed, and N is the actual number of printing layers required.

In another aspect, a porous material with a continuous gradient of porosity produced by the above preparation method is provided.

Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The preparation process of the gradient porous material is simple, and the application field of 3D printing technology is expanded; 2. The present invention ensures that the porous material has a continuous porosity gradient, and improves the gradient porous material. 3. The adjustable range of the porosity gradient is improved, and different gradient forms from low porosity (0%) to high porosity (above 80%) can be realized, expanding the application of gradient porous materials 4. It is suitable for the preparation of various gradient porous materials such as metals and ceramics, and has good versatility; 5. It improves the stability and repeatability of the production process and is suitable for mass production.

Description of drawings

Fig. 1 is the principle diagram of 3D printing of porous material with continuous gradient of porosity according to the present invention;

Fig. 2 is a microstructure diagram of a high-porosity section (80vol%) of a continuous gradient porous B ₄ C ceramic prepared in Example 1 of the present invention;

Fig. 3 is a microstructure diagram of a high-porosity section (80 vol%) of a continuous gradient porous silicon nitride ceramic prepared in Example 3 of the present invention.

Detailed ways

The above and other technical features and advantages of the present invention will be described in more detail below in conjunction with the accompanying drawings.

Embodiment one

A preparation method of a porous material with a continuous gradient of porosity, comprising the following steps:

(1) Mix boron carbide micropowder with a volume fraction of 60% and deionized water with a volume fraction of 40%, then add gelatin, and ball mill in the range of 20-95°C to obtain a uniformly mixed slurry A, wherein the gelatin The mass ratio with the deionized water is 0.05:1;

(2) configure gelatin hydrosol B, the mass ratio of gelatin in its composition and deionized water is identical with the ratio in the described step (1);

(3) At regular intervals, add the gelatin hydrosol B to the slurry A to obtain a mixed slurry, keep the solid phase content in the mixed slurry continuously changing within the range of 0-60vol%, each time After adding the gelatin hydrosol B, input the mixed slurry into the 3D printer for printing, keep the temperature of the mixed slurry at the nozzle of the 3D printer in the range of 0-20°C, so that solidify to form a gel;

As shown in Figure 1, it is the printing schematic diagram of the step (3), the slurry A is placed in the first container 1, the gelatin hydrosol B is placed in the second container 2, the first The container 1 is connected to the third container 5 through the first peristaltic pump 3, the second container 2 is connected to the third container 5 through the second peristaltic pump 4, and the stirring pump 6 is arranged in the third container 5, and the The third container 5 is connected to the 3D printer 8 through the third peristaltic pump 7, and the nozzle 9 of the 3D printer 8 is provided with a heating device, which is used to ensure that the printed mixed slurry has good fluidity, 11 represents the gel formed at the nozzle. The preparation of the above-mentioned slurry A, the delivery of the mixed slurry during 3D printing, and the curing temperature of the mixed slurry at the nozzle are all maintained by the thermostat 10. 3D The setting of parameters during the printing process and the opening and closing of the corresponding equipment are controlled by computer programs. The specific printing process is as follows:

S1: Turn on the first peristaltic pump 3 and the agitating pump 6 at the same time through computer control, adjust the speed of the first peristaltic pump 3 to 1ml/s, and pass 200mL of slurry A in the first container through the first peristaltic pump 3 into the third container 5, turn off the first peristaltic pump 3; then computer control to open the third peristaltic pump 7 and the 3D printer 8, the third peristaltic pump 7 at 0.05mL/s The slurry in the third container 5 is input into the 3D printer 8 at a speed of 20 seconds. After 20 seconds, the 3D printer prints the first layer with a thickness of 0.05mm according to the program and cools to form a corresponding gel. Close the third container 5. Peristaltic pump 7 and described 3D printer 8;

S2: Turn on the second peristaltic pump 4 through computer control, and input the gelatin hydrosol B in the second container 2 into the third container 5 at a speed of 0.5ml/s, and close the second peristaltic pump after working for 2s Two peristaltic pumps; then the computer controls to open the third peristaltic pump 7 and the 3D printer 8, and the third peristaltic pump 7 inputs the slurry in the third container 5 to the 3D printer at a speed of 0.05mL/s. In the printer 8, after 20s, the 3D printer prints the second layer with a thickness of 0.05 mm according to the program and cools to form a corresponding gel, and then closes the third peristaltic pump 7 and the 3D printer 8; then repeats the step S2 , until the printing of the Nth layer is completed, N is the actual number of printing layers required, and a gel with a gradient change of the solid phase content as a power function is formed, wherein the solid phase content of the Nth layer is 60%×(199/200) ^N ;

In the present invention, on the one hand, the program controls the continuous change of the solid content of the slurry during 3D printing, and on the other hand, the solid content of the formed gel does not change. With the progress of 3D printing, the solid content of the successively formed gels The distribution has a continuous gradient change;

(4) Freeze the gel formed in the step (3) along the direction of the gradient at -40°C, and then freeze-dry for 48 hours to obtain a porous material body with a gradient porosity, which is stored at 1900°C, The gradient porous boron carbide material was obtained by sintering for 1 hour under the protection of 0.1 MPa argon atmosphere.

Since the printed gel contains a large amount of liquid water, after freezing, the liquid water in the gel network forms ice crystals and grows continuously, while the powder particles and gel materials are discharged from the ice crystals and piled up in the adjacent between ice crystals. Due to the continuous gradient change of solid phase content, the volume of ice crystals changes continuously. After freeze-drying, the ice crystals sublimate, leaving connected pores with continuous gradient changes in porosity, and obtaining a porous material body with a gradient porosity. Adjusting the freezing process can change the pore structure. (pore size, pore directionality, etc.), to meet different application requirements, in which the xerogel plays a role in strengthening the green body. After sintering, a gradient porous material is formed. The sintering method of the green body is air sintering, normal pressure sintering or atmospheric pressure sintering. The xerogel can be completely discharged by heat treatment in air before sintering.

Further, in the step (1), the optimum temperature during ball milling is 60°C; in the step (3), the optimum temperature for the mixed slurry at the nozzle to solidify into a gel is 5°C, thus the optimum temperature Best Mode A porous B ₄ C ceramic material with a continuous gradient of porosity was prepared as shown in FIG. 2 , and its porosity section was 80 vol%.

Further, the boron carbide micropowder in the step (1) can be replaced by any metal powder or other ceramic powder that does not react violently with water in Ti, Zr, Al, Si, Ag, Cu, Fe, Ni or Mo body or organic material powder, the preparation method of the present invention is suitable for the preparation of various gradient porous materials such as metals and ceramics, and has good versatility.

The process for preparing the continuous gradient porous material of the present invention is simple, the process stability and repeatability are good, and the application field of 3D printing technology is expanded, and at regular intervals, water sol is added to the slurry to continuously adjust the slurry Solid phase content, combined with 3D printing, forms a gel with a continuous gradient change in solid content, realizing the change of different gradient forms from low porosity (0%) to high porosity (above 80%), expanding the range of gradient porous materials application field.

Embodiment two

The method for preparing a porous material with a continuous gradient of porosity as described above, the difference of this embodiment is that,

A preparation method of a porous material with a continuous gradient of porosity, comprising the following steps:

(1) Mix Cu micropowder with a volume fraction of 50% and deionized water with a volume fraction of 50%, then add agarose, and ball mill in the range of 40-95° C. to obtain a uniformly mixed slurry A, wherein the agar The mass ratio of sugar to the deionized water is 0.01:1;

(2) configure agarose hydrosol B, the mass ratio of agarose in its composition to deionized water is the same as the ratio in the step (1);

(3) At regular intervals, add the agarose hydrosol B to the slurry A to obtain a mixed slurry, and maintain the solid phase content in the mixed slurry to continuously change within the range of 0-50vol%, each time After adding the agarose hydrosol B, input the mixed slurry into the 3D printer for printing, keep the temperature of the mixed slurry at the nozzle of the 3D printer in the range of 0-40°C, so that solidify to form a gel;

The concrete printing process of described step (3) is as follows:

S1: Turn on the first peristaltic pump 3 and the stirring pump 6 at the same time, adjust the speed of the first peristaltic pump 3 to 1ml/s, and input the 200mL slurry A in the first container through the first peristaltic pump 3 into In the third container 5, close the first peristaltic pump 3; then open the third peristaltic pump 7 and the 3D printer 8, and the third peristaltic pump 7 pumps the The slurry in the third container 5 is input into the 3D printer 8, and after 20 seconds, the 3D printer prints the first layer with a thickness of 0.05 mm according to the program and cools to form a corresponding gel, and then closes the third peristaltic pump 7 and the The 3D printer 8;

S2: Turn on the second peristaltic pump 4 to input the agarose hydrosol B in the second container 2 into the third container 5 at a speed of 0.5ml/s, and turn off the second peristaltic pump after working for 2s Then the computer controls the opening of the third peristaltic pump 7 and the 3D printer 8, and the third peristaltic pump 7 inputs the slurry in the third container 5 into the 3D printer 8 at a speed of 0.05mL/s After 20s, the 3D printer prints the second layer with a thickness of 0.05 mm according to the program and cools to form a corresponding gel, and then closes the third peristaltic pump 7 and the 3D printer 8; then repeats the step S2 until the first N layer printing is completed, and N is the number of printing layers actually required, forming a gel whose solid phase content changes as a power function gradient, wherein the solid phase content of the Nth layer is 50% × (199/200) ^N ;

(4) Freezing the gel formed in the step (3) along the gradient direction at -80°C, and then freeze-drying for 48 hours to obtain a porous material body with a gradient porosity, which is placed at 900°C, The continuous gradient porous Cu material was obtained by sintering for 1 hour under the protection of 0.1MPa argon atmosphere.

Further, when adding the agarose, in the step (1), the optimal temperature during ball milling is 60°C, and in the step (3), the optimal temperature for the mixed slurry at the nozzle to solidify into a gel The temperature is 5°C.

Further, the Cu micropowder in the step (1) can be replaced by any metal powder or ceramic powder or organic material that does not react violently with water in Ti, Zr, Al, Si, Ag, Fe, Ni or Mo Powder.

The sols added during the preparation of the slurry are not limited to gelatin and agarose, but can also be other types of temperature-controlled sols, as long as they can realize the transformation from a sol state to a gel state under temperature control, such as chitosan A mixture with gelatin or a mixture of sodium alginate and gelatin.

Embodiment Three

The method for preparing a porous material with a continuous gradient of porosity as described above, the difference of this embodiment is that,

A preparation method of a porous material with a continuous gradient of porosity, comprising the following steps:

(1) Mix the silicon nitride micropowder with the volume fraction of 70% and the deionized water with the volume fraction of 30%, then add the polyethylene glycol hydrosol system modified by photosensitive ethyl cinnamate, at room temperature Ball milling obtains a homogeneously mixed slurry A, wherein the mass ratio of the ethyl cinnamate-modified polyethylene glycol hydrosol to the deionized water is 0.15:1;

(2) Configure the polyethylene glycol hydrosol B modified by ethyl cinnamate, the polyethylene glycol hydrosol B modified by ethyl cinnamate in its composition and the mass ratio of deionized water and described step (1) in the same proportion;

(3) At regular intervals, add the polyethylene glycol hydrosol B modified by the ethyl cinnamate in the slurry A to obtain a mixed slurry, and maintain the solid phase content in the mixed slurry at 0 Continuously changing in the range of -70vol%, after adding the polyethylene glycol hydrosol B modified by ethyl cinnamate each time, the mixed slurry is input into the 3D printer for printing, and the 3D printer is provided with a UV lamp, when printing, the UV lamp irradiates the mixed slurry at the nozzle to make it solidify to form a gel;

The concrete printing process of described step (3) is as follows:

S1: Turn on the first peristaltic pump 3 and the stirring pump 6 at the same time, adjust the speed of the first peristaltic pump 3 to 1ml/s, and input the 200mL slurry A in the first container through the first peristaltic pump 3 into In the third container 5, close the first peristaltic pump 3; then open the third peristaltic pump 7 and the 3D printer 8, and the third peristaltic pump 7 pumps the The slurry in the third container 5 is input into the 3D printer 8, and after 20 seconds, the 3D printer prints the first layer with a thickness of 0.05 mm according to the program and cools to form a corresponding gel, and then closes the third peristaltic pump 7 and the The 3D printer 8;

S2: Turn on the second peristaltic pump 4, which inputs the polyethylene glycol hydrosol B modified with ethyl cinnamate in the second container 2 into the third container 5 at a speed of 0.5ml/s, After working for 2s, close the second peristaltic pump; then the computer controls to open the third peristaltic pump 7 and the 3D printer 8, and the third peristaltic pump 7 pumps the third container 5 at a speed of 0.05mL/s. The slurry inside is input into the 3D printer 8, and after 20s, the 3D printer prints the second layer with a thickness of 0.05mm according to the program and cools to form a corresponding gel, and the third peristaltic pump 7 and the 3D printer 8 are turned off ; Then repeat the step S2 until the printing of the Nth layer is completed, N is the actual number of printing layers required to form a gel with a gradient change in the solid phase content as a power function, wherein the solid phase content of the Nth layer is 70% ×(199/200) ^N ;

(4) Freezing the gel formed in the step (3) along the gradient direction, the freezing temperature is -196-0°C, and then freeze-drying for 48 hours to obtain a porous material body with a gradient porosity, which is heated at 1800 ℃, 0.1MPa nitrogen atmosphere under the protection of sintering for 1 hour to obtain a continuous gradient porous silicon nitride material, the prepared porous material was characterized by SEM, and the microstructure of the porous silicon nitride with a continuous gradient of porosity as shown in Figure 3 was obtained , and its porosity section is 80vol%.

In this embodiment, since the polyethylene glycol hydrosol B modified by ethyl cinnamate is in a sol state at room temperature, the temperature of the thermostat used in the preparation process and the temperature of the heating device at the nozzle at the end The temperature was adjusted to room temperature.

Further, the silicon nitride micropowder in the step (1) can be replaced by any metal powder or other ceramics that do not react violently with water in Ti, Zr, Al, Si, Ag, Cu, Fe, Ni or Mo Powder or organic material powder.

Embodiment Four

The method for preparing a porous material with a continuous gradient of porosity as described above, the difference of this embodiment is that,

A preparation method of a porous material with a continuous gradient of porosity, comprising the following steps:

(1) Mixing Fe micropowder with a volume fraction of 60% and deionized water with a volume fraction of 40%, then adding a photosensitive nitrocinnamic acid-modified polyethylene glycol hydrosol system, and ball milling at room temperature to obtain A uniformly mixed slurry A, wherein the mass ratio of the nitrocinnamic acid-modified polyethylene glycol hydrosol system to the deionized water is 0.10:1;

(2) Configure the polyethylene glycol hydrosol system B modified by nitrocinnamic acid, the mass ratio of the polyethylene glycol hydrosol system modified by nitrocinnamic acid in its composition to deionized water and the step ( 1) in the same proportion;

(3) Add the nitrocinnamic acid-modified polyethylene glycol hydrosol system B to the slurry A at regular intervals to obtain a mixed slurry, and maintain the solid phase content in the mixed slurry at Continuously changing in the range of 0-60vol%, after each addition of the nitrocinnamic acid-modified polyethylene glycol hydrosol system B, the mixed slurry is input to the 3D printer for printing, and the 3D printer A UV lamp is provided, and when printing, the UV lamp irradiates the mixed slurry at the nozzle to make it solidify and form a gel;

The concrete printing process of described step (3) is as follows:

S1: Turn on the first peristaltic pump 3 and the stirring pump 6 at the same time, adjust the speed of the first peristaltic pump 3 to 1ml/s, and input the 200mL slurry A in the first container through the first peristaltic pump 3 into In the third container 5, close the first peristaltic pump 3; then open the third peristaltic pump 7 and the 3D printer 8, and the third peristaltic pump 7 pumps the The slurry in the third container 5 is input into the 3D printer 8, and after 20 seconds, the 3D printer prints the first layer with a thickness of 0.05 mm according to the program and cools to form a corresponding gel, and then closes the third peristaltic pump 7 and the The 3D printer 8;

S2: Turn on the second peristaltic pump 4, which inputs the nitrocinnamic acid-modified polyethylene glycol hydrosol system B in the second container 2 into the third container 5 at a speed of 0.5ml/s , close the second peristaltic pump after working for 2s; then the computer controls to open the third peristaltic pump 7 and the 3D printer 8, and the third peristaltic pump 7 pumps the third container at a speed of 0.05mL/s The slurry in 5 is input into the 3D printer 8. After 20s, the 3D printer prints the second layer with a thickness of 0.05mm according to the program and light-cures to form a corresponding gel. Turn off the third peristaltic pump 7 and the 3D printer. Printer 8; then repeat the step S2 until the Nth layer is printed, and N is the number of printing layers actually required to form a gel whose solid phase content changes as a power function gradient, wherein the solid phase content of the Nth layer is 60%×(199/200) ^N ;

(4) Freezing the gel formed in the step (3) along the gradient direction, the freezing temperature is -196°C, and then freeze-drying for 48 hours to obtain a porous material body with a gradient porosity, which is placed at 1000°C, The continuous gradient porous Fe material was obtained by sintering for 1 hour under the protection of 0.1MPa argon atmosphere.

In this embodiment, since the nitrocinnamic acid-modified polyethylene glycol hydrosol system B is in a sol state at room temperature, the temperature of the thermostat used in the preparation process and the heating device at the nozzle at the end The temperature was adjusted to room temperature.

Further, the Fe micropowder in the step (1) can be replaced by any metal powder or ceramic powder or organic material that does not react violently with water in Ti, Zr, Al, Si, Ag, Cu, Ni or Mo Powder.

The sol added when preparing the slurry in the embodiment three to the embodiment four is not only limited to the polyethylene glycol hydrosol hydrosol system modified by ethyl cinnamate or the nitrocinnamic acid modified polyethylene glycol hydrosol system, but also can be It is other kind of photosensitivity sol, which only needs to be able to realize the transformation from sol state to gel state under light.

The hydrosol added in the present invention can also be other types of hydrosol except the temperature-controlled hydrosol and the light-controlled hydrosol in Embodiment 1 to Embodiment 4, as long as the added described sol can be used under certain conditions. It turns into a gel.

In the present invention, in the steps S1 and S2 in Embodiment 1 to Embodiment 4, the control parameters of the computer are not limited to the above parameters, and the parameters can be set according to the actual situation. During the printing process, the following requirements must be met:

S1: input the constant amount of slurry A in the first container to the third container through the first peristaltic pump, turn off the first peristaltic pump, turn on the third peristaltic pump and the 3D printer, After printing the first layer, close the third peristaltic pump and the 3D printer;

S2: Turn on the second peristaltic pump, input a constant amount of the hydrosol B into the third container, turn off the second peristaltic pump, turn on the third peristaltic pump and the 3D printer, and finish printing the first After the second layer, turn off the third peristaltic pump and the 3D printer; then repeat the step S2 until the Nth layer is printed, and N is the actual number of printing layers required. When adding the hydrosol B each time, Maintaining the solid phase content in the mixed slurry in the third container continuously changing within the range of 0-90vol%.

The water-based slurry of the invention has wide applicability, and ceramics, metals or organic materials can be prepared into the water-based slurry, so the method is applicable to the preparation of various porous materials. In addition, the automatic control program is used to realize the continuous change of the solid content of the slurry. The change form can be controlled by the program, and a gradient porous material with any gradient change form can be obtained. Finally, the continuous change of the porosity in the porous material is realized. For example, the porosity shows a linear gradient change, Porous materials such as power function gradient changes can meet different application requirements.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the method of the present invention, some improvements and supplements can also be made, and these improvements and supplements should also be considered Be the protection scope of the present invention.

Claims (10)

1. A method for preparing a porous material with a continuous gradient of porosity, comprising the following steps: (1) Mix the powder raw material with a volume fraction of 50-70% and deionized water with a volume fraction of 30-50%, then add the sol, and ball mill it within the temperature range of the sol to obtain slurry A, wherein the sol It can be transformed into a gel under certain conditions, and the mass ratio of the sol to the deionized water is 0.01-0.15:1; (2) configure the same hydrosol B as in the step (1), the mass ratio of the sol in its composition to deionized water is the same as the ratio in the step (1); (3) adding the hydrosol B to the slurry A at regular intervals to obtain a mixed slurry, and maintaining the solid phase content in the mixed slurry continuously changing within a range greater than 0 and not exceeding 70vol%, After adding the hydrosol B each time, input the mixed slurry into the 3D printer for printing, keeping the mixed slurry at the nozzle of the 3D printer solidified into a gel; (4) Freezing the gel formed in the step (3) along the direction of the gradient of the solid phase content, the freezing temperature is -196-0°C, and then freeze-drying to obtain a porous material body, which is sintered to form pores Porous materials with continuous rate gradients. 2. the preparation method of the porous material with porosity continuous gradient according to claim 1, is characterized in that, comprises the following steps: described powder raw material comprises Ti, Zr, Al, Si, Cu, Ag, Fe, Ni Or any metal powder or ceramic powder or organic material powder in Mo that does not react violently with water. 3. the preparation method of the porous material with porosity continuous gradient according to claim 1, is characterized in that, the sol in described step (1) is the sol of temperature control, and it can change into gel at low temperature, It is any one of gelatin, agarose, a mixture of chitosan and gelatin or a mixture of sodium alginate and gelatin. 4. the preparation method of the porous material with porosity continuous gradient according to claim 3, is characterized in that, when adding described gelatin, in described step (1), the temperature during ball milling is 20-95 ℃; In the above step (3), the temperature of the mixed slurry at the nozzle is set at 0-20°C. 5. The method for preparing a porous material with a continuous gradient of porosity according to claim 3, characterized in that, when adding the agarose, in the step (1), the temperature during ball milling is 40-95°C; In the step (3), the temperature of the mixed slurry at the nozzle is set at 0-40°C. 6. the preparation method of the porous material with continuous gradient of porosity according to claim 1, is characterized in that, the sol in described step (1) is photosensitive sol, and it can change into gel under UV light, It is a polyethylene glycol hydrosol system modified by ethyl cinnamate or a polyethylene glycol hydrosol system modified by nitrocinnamic acid. 7. the preparation method of the porous material with porosity continuous gradient according to claim 6, is characterized in that, described 3D printer is provided with a UV lamp, when printing, described UV lamp irradiates the mixed slurry at nozzle place . 8. The method for preparing a porous material with a continuous gradient of porosity according to any one of claims 1-7, characterized in that the constant temperature environment during the preparation process is maintained by a thermostat. 9. the preparation method of the porous material with porosity continuous gradient according to claim 1, is characterized in that, in described step (3), described slurry A is placed in the first container, described hydrosol B is placed in a second container, the first container is connected to the third container through the first peristaltic pump, the second container is connected to the third container through the second peristaltic pump, and the third container is connected to the third container through the third peristaltic pump. The pump is connected to the 3D printer, and a stirring pump is arranged in the third container, and the printing process is as follows: S1: input the constant amount of slurry A in the first container to the third container through the first peristaltic pump, turn off the first peristaltic pump, turn on the third peristaltic pump and the 3D printer, After printing the first layer, close the third peristaltic pump and the 3D printer; S2: Turn on the second peristaltic pump, input a constant amount of the hydrosol B into the third container, turn off the second peristaltic pump, turn on the third peristaltic pump and the 3D printer, and finish printing the first After the second layer, close the third peristaltic pump and the 3D printer; Afterwards, the step S2 is repeated until the printing of the Nth layer is completed, and N is the actual number of printing layers required. 10. A porous material with a continuous gradient of porosity produced by the method for preparing a porous material with a continuous gradient of porosity according to any one of claims 1, 2, 3, 4, 5, 6, 7, and 9.