CN107553686A - A kind of manufacture method of the fiber reinforcement gradient porous ceramics based on 3D printing - Google Patents

Abstract

The invention discloses a method for manufacturing fiber-reinforced gradient porous ceramics based on 3D printing, which comprises the following steps: designing a three-dimensional solid model in modeling software, performing layered slice processing on the model, and generating a processing route for layer-by-layer printing by a printer ; Place the ceramic powder, fiber powder and binder powder in different powder feeders, mix them evenly online and send them to the powder spreading tank to wait for powder spreading; add bonding ink; the nozzles are selected under the control of the control system Adhesive ink is selectively sprayed on the target area to complete the printing of a layer of cross-section. Then, the workbench carrying the powder bed is lowered to a height of layer thickness to re-spread powder, and the above process is repeated to complete the printing of all cross-sections to form a three-dimensional entity; The green body is placed in a vacuum sintering furnace for sintering enhancement treatment to obtain a fiber-reinforced gradient porous ceramic element. The invention obtains porous ceramics with homogenized mechanical properties and controllable pore distribution by regulating the dual gradient distribution of the fiber material of the reinforcement phase and the pore structure.

Description

A manufacturing method of fiber-reinforced gradient porous ceramics based on 3D printing

technical field

The invention relates to 3D printing rapid prototyping technology, in particular to a manufacturing method of fiber-reinforced gradient porous ceramics based on 3D printing.

Background technique

Due to its asymmetric pore structure, gradient porous ceramics effectively improve the permeability and strength of porous ceramics, and have the characteristics of high filtration precision and large air permeability coefficient. It can greatly improve filtration precision and filtration efficiency in the field of filtration separation, especially suitable for Separation of mixed fluids containing fine particles such as high temperature and corrosiveness, high-temperature flue gas dust removal and fine filtration, etc. Fiber-reinforced ceramic matrix composites have high fracture toughness and flexural strength, and the gradient distribution of fibers is conducive to the regulation of gradient porosity Improve the mechanical properties of ceramic materials and homogenize them to prolong their service life.

At present, the methods for preparing gradient porous ceramics mainly include centrifugal forming technology, gradient arrangement method of pore-forming agent, and particle packing technology. Centrifugal molding technology uses particles with different particle sizes to have different sedimentation speeds during high-speed centrifugation. The large particles contained in the slurry deposit to the outer layer, and the small particles deposit to the inner layer to form a gradient structure. After forming, the pore structure also presents a gradient distribution, but High rotational speed requires high equipment and operating technology; the porogen gradient arrangement method is to arrange aggregates mixed with different particle sizes of porogens from large to small according to the particle size of the porogens, and lay them in the mold layer by layer. Pore-gradient porous ceramics are prepared by pressing, drying and firing, but the shape of the product pores obtained by this process is irregular, and the continuous variation of the pore diameter is poor. It is only suitable for products with simple shapes, and it is difficult to prepare products with complex shapes; particles The stacking process is to use particles of different sizes to stack according to a certain ratio to build a pore gradient structure. However, the above methods have many disadvantages: 1. The pore structure and properties of ceramics are uncontrollable, and the pores and properties cannot be distributed in gradients in the material as required; 2. Conventional processes require molds or pore-forming agents, and the pore distribution is single or random; 3. 1. Gradient porous ceramics prepared by traditional methods have uneven properties due to uneven distribution of pores. 4. The material cannot achieve continuous changes between layers. 5. The current preparation process is limited to laboratory research and cannot be applied to industrial production.

Contents of the invention

The present invention provides a method for manufacturing fiber-reinforced gradient porous ceramics based on 3D printing to solve the above technical problems. The manufacturing method can solve the problems that the pore size and distribution of the gradient porous ceramic prepared by the traditional technology are not easy to control and the materials between the layers are difficult to change continuously.

In order to solve the problems of the technologies described above, the technical solution of the present invention is as follows:

A method for manufacturing fiber-reinforced gradient porous ceramics based on 3D printing, comprising the following steps:

1) Use a computer to design a three-dimensional solid model of a predetermined gradient pore structure in the modeling software, and the three-dimensional printer software performs layered slice processing on the model to generate a processing route for the printer to print layer by layer;

2) Place the ceramic powder, fiber powder and binder powder in different powder feeders, control the powder feeding volume of each powder feeder through the computer, mix them evenly online, and send them to the powder spreading cylinder to wait for powder spreading;

3) Add bonding ink to the 3D printing nozzle;

4) Under the control of the control system, the nozzle selectively sprays the bonding ink in the target area to complete the printing of a layer of cross-section. Then, the workbench carrying the powder bed descends to a height of layer thickness to re-spread powder, and repeats The above process completes the printing of all sections to form a three-dimensional entity, wherein the porosity of each layer of material is different, and the composition ratio of ceramic powder, fiber powder and binder powder in each layer of material is different;

5) placing the green body in a vacuum sintering furnace for sintering enhancement treatment to obtain a fiber-reinforced gradient porous ceramic element.

In the above scheme, the characteristic of the three-dimensional solid model in step 1) is that the functional expression of the porosity distribution along the axial direction of the ceramic element is in the form of a power exponent, and the porosity increases continuously along the axial direction of the ceramic element.

In the above scheme, the pore gradient of the three-dimensional solid model in step 1) is 20%-80%.

In the above scheme, the ceramic powder added in step 2) includes one or a mixture of two or more of alumina, silicon carbide or zirconia ceramic powder in any proportion, the fiber includes carbon fiber or silicon carbide fiber, and the binder is poly vinyl alcohol.

In the above scheme, the particle size range of the ceramic powder in step 2) is 20-150 μm.

In the above solution, the carbon fiber powder has a diameter of 7-8 μm and a length of 24-64 μm; the silicon carbide fiber is in the form of a whisker with a diameter of 0.1-2 μm and a length of 20-300 μm, and its appearance is powdery.

In the above scheme, the components of the bonding ink in step 3) include distilled water, glycerol and polyvinylpyrrolidone.

In the above scheme, the distribution ratio of the components of the bonding ink in step 3) is that the mass fraction of distilled water is 93% to 95%, the mass fraction of glycerin is 1.5% to 3.5%, and the mass fraction of polyvinylpyrrolidone is 1.5% to 3.5%. .

In the above solution, the sintering temperature in step 5) is 1440-1650° C., and the sintering time is 1-3 hours.

The beneficial effects of the present invention are:

1) The fiber-reinforced gradient porous ceramic element of the present invention is mainly used as a filter in the field of high-temperature dust removal.

2) The distribution function of the porosity of the ceramic filter element along the axial direction of the ceramic element is:

ε(x)＝Cexp(K ₁ X ² /4+K ₂ X ³ /6)

d represents the inner diameter of the ceramic filter element (m); L represents the axial length (m); C _f represents the frictional resistance coefficient of the ceramic filter element along the way; ρ represents the density of the gas (kg/m ³ ); δ represents the density of the ceramic filter element Wall thickness (m); Q represents the gas volume flow through the filter element; Represents the outer diameter (m) of the ceramic filter element; μ represents the coefficient; c is the integral constant.

The effect is to make the dust evenly distributed along the filter element, which is beneficial to dust removal, can avoid or reduce the dust bridging phenomenon between the ceramic filter elements, and improve the service life of the filter element. Compared with other methods, the use of 3D printing technology can The initial value of the porosity of the closed end or the open end of the ceramic filter element is given according to the needs, and the pore size, pore shape and pore distribution are precisely controlled. It is the first to prepare materials and pores with controllable internal structure of pores by laying mixed powders with different ratios online. Dual Gradient Porous Ceramics.

3) The invention utilizes the simple operation process of 3D printing, the production cycle is shortened, the pore structure can be accurately controlled, and the manufacture of complex porous ceramics becomes simple and easy. At the same time, fiber and ceramic powder are mixed online to obtain fiber-reinforced ceramic materials in different proportions Porous ceramics with homogeneous mechanical properties that realize the dual gradient distribution of pores and fibers are short-process, reproducible, and low-cost pore material gradient ceramics that can meet industrialization. Therefore, it is important to prepare dual-gradient porous ceramics by 3D printing. significance.

4) The gradient distribution of fiber reinforced materials is conducive to improving the material properties and maintaining the uniform mechanical properties of ceramics.

It is worth noting that the flexural strength of porous ceramic components has a greater relationship with its load-bearing area. The actual load-bearing area of porous ceramics with low porosity is larger, and the theoretical flexural strength is also higher. With the increase of porosity, the actual The bearing area is reduced, and the theoretical flexural strength is greatly reduced. If the fiber content is increased according to the porosity, gradient porous ceramics with relatively uniform mechanical properties will be obtained. Then, when bending force is applied to the ceramic matrix, irregular micro-cracks will not occur inside the matrix.

Test Methods:

1. The test method of porosity is the Archimedes drainage method.

2. The bending strength test method is to use the bending strength tester to measure the average value of the bending strength at three points, the span is 40mm, and the loading speed is 0.5mm/min.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

Figure 2 shows the change in flexural strength of gradient porous alumina ceramics with or without carbon fiber reinforcement.

Figure 3 shows the change in flexural strength of gradient porous silicon carbide ceramics with or without carbon fiber reinforcement.

Figure 4 shows the change in flexural strength of gradient porous silicon carbide ceramics with or without silicon carbide fiber reinforcement.

detailed description

The present invention will be further described below in conjunction with specific examples, and these examples are only for illustrating the present invention, and it does not limit the scope of the present invention in any way.

Example 1

1) Use computer-aided design modeling software: CAD, UG, Pro/E, etc. to design a three-dimensional solid model of gradient pore structure (pore gradient is 20% to 80%) according to the requirements of product pore size, pore distribution, and pore shape. The 3D model was approximated to obtain the STL format file, and the 3D model was discretized into a series of ordered 2D layers along the forming height direction with a layer interval of 0.1 mm. The 3D printer software guided the printer to print layer by layer. In this embodiment, printing of five layers is taken as an example, and Table 1 shows the porosity distribution of the three-dimensional model in this embodiment.

2) To form gradient porous ceramics, the composition ratio requirements of each layer are: from the bottom to the top, the mass fraction of carbon fiber in each layer is: 0%, 13%, 22%, 26%, and 30%, and the mass fraction of polyvinyl alcohol is 8%. , the mass fractions of alumina are: 92%, 79%, 70%, 66%, 62%, respectively.

3) Add bonding ink to the nozzle, wherein the bonding ink is composed of distilled water, glycerol and polyvinylpyrrolidone; the distribution ratio of each component of the bonding ink is that the mass fraction of distilled water is 95%, and the mass fraction of glycerin is 2.5% , the mass fraction of polyvinylpyrrolidone is 2.5%.

4) Under the control of the control system, the nozzle selectively sprays the bonding ink in the target area to complete the printing of a layer of cross-section. Then, the workbench carrying the powder bed descends to a height of layer thickness to re-spread powder, and repeats The above process completes the printing of all sections to form a three-dimensional entity.

5) Put the obtained green body in a vacuum sintering furnace for sintering, the sintering temperature is 1550-1650° C., and the sintering time is 2-3 hours, to obtain carbon fiber reinforced alumina gradient porous ceramics.

Table 1

top

80% 60% 40% 20% 0%

bottom

The test results are: the average porosity of the carbon fiber reinforced alumina ceramics with gradient porous structure is 60.2%. It can be seen from Figure 2 that when no carbon fibers are added, the flexural strength of the alumina gradient ceramic components increases with the porosity It showed an obvious downward trend, from 55Mpa to 19Mpa. After adding carbon fiber, the downward trend slowed down, and the lowest bending strength increased from 19Mpa to 38Mpa. The mechanical properties were higher than before, and the overall mechanical properties were relatively uniform.

Example 2

1) Use computer-aided design modeling software: CAD, UG, Pro/E, etc. to design a three-dimensional solid model of gradient pore structure according to the requirements of product pore size, pore distribution, and pore shape (the pore gradient is 20% to 80%, see Table 1), approximate the 3D model to obtain the STL format file, discretize the 3D model into a series of ordered 2D layers along the forming height direction, the layer interval is 0.1 mm, and the 3D printer software guides the printer to print layer by layer.

2) The component ratio requirements for forming gradient porous ceramics are: from the bottom to the top, the mass fractions of carbon fibers in each layer are: 0%, 11%, 19%, 25%, 30%, the mass fraction of polyvinyl alcohol is 8%, silicon carbide The mass fractions are: 92%, 81%, 73%, 67%, 62%, respectively.

3) Add bonding ink to the nozzle, wherein the bonding ink is composed of distilled water, glycerol and polyvinylpyrrolidone; the distribution ratio of each component of the bonding ink is that the mass fraction of distilled water is 95%, and the mass fraction of glycerin is 2.5% , the mass fraction of polyvinylpyrrolidone is 2.5%.

4) Under the control of the control system, the nozzle selectively sprays the bonding ink in the target area to complete the printing of a layer of cross-section. Then, the workbench carrying the powder bed descends to a height of layer thickness to re-spread powder, and repeats The above process completes the printing of all sections to form a three-dimensional entity.

5) Put the obtained green body in a vacuum sintering furnace for sintering, the sintering temperature is 1400-1600° C., and the sintering time is 1-2 hours, to obtain carbon fiber reinforced silicon carbide gradient porous ceramics.

The test results are: the average porosity of carbon fiber reinforced silicon carbide ceramics with gradient porous structure is 61.3%. It can be seen from Figure 3 that when no carbon fibers are added, the flexural strength of silicon carbide gradient ceramic components increases with the porosity It showed an obvious downward trend, from 40Mpa to 6Mpa. After adding carbon fiber, the downward trend slowed down, and the lowest bending strength increased from 6Mpa to 16Mpa. The mechanical properties were higher than before, and the overall mechanical properties were relatively uniform.

Example 3

1) Use computer-aided design modeling software: CAD, UG, Pro/E, etc. to design a three-dimensional solid model of gradient pore structure (pore gradient is 60% to 70%) according to the requirements of product pore size, pore distribution, and pore shape. The 3D model was approximated to obtain the STL format file, and the 3D model was discretized into a series of ordered 2D layers along the forming height direction with a layer interval of 0.1 mm. The 3D printer software guided the printer to print layer by layer.

2) The composition ratio requirements for forming gradient porous ceramics are as follows: from the bottom to the top, the mass fraction of silicon carbide fibers in each layer is 0%, 16%, 24%, 28%, and 33%, and the mass fraction of polyvinyl alcohol is 8%. Silicon mass fractions are: 92%, 76%, 68%, 64%, 59%.

3) Add bonding ink to the nozzle, wherein the bonding ink is composed of distilled water, glycerol and polyvinylpyrrolidone; the distribution ratio of each component of the bonding ink is that the mass fraction of distilled water is 95%, and the mass fraction of glycerin is 2.5% , the mass fraction of polyvinylpyrrolidone is 2.5%.

4) Under the control of the control system, the nozzle selectively sprays the bonding ink in the target area to complete the printing of a layer of cross-section. Then, the workbench carrying the powder bed descends to a height of layer thickness to re-spread powder, and repeats The above process completes the printing of all sections to form a three-dimensional entity.

5) Put the obtained green body in a vacuum sintering furnace for sintering, the sintering temperature is 1400-1500° C., and the sintering time is 2-3 hours, to obtain silicon carbide fiber reinforced silicon carbide gradient porous ceramics.

The test results are: the average porosity of silicon carbide fiber-reinforced silicon carbide ceramics with gradient porous structure is 62.4%; it can be seen from Figure 4 that when no silicon carbide fibers are added, the bending strength of silicon carbide gradient ceramic elements increases with The increase of porosity shows an obvious downward trend, from 40Mpa to 6Mpa. After adding carbon fiber, the downward trend slows down, and the lowest bending strength increases from 6Mpa to 21Mpa. The mechanical properties are higher than before, and the overall mechanical properties are relatively uniform.

Claims (9)

1. a kind of manufacture method of the fiber reinforcement gradient porous ceramics based on 3D printing, it is characterised in that comprise the following steps：

1) three-dimensional entity model of predetermined gradient pore structure, three-dimensional printer software are designed in modeling software with computer The processing route that printer successively prints is generated after hierarchy slicing processing is carried out to model；

2) ceramic powders, fiber dust are placed in different powder feeders from adhesive powder respectively, controlled by computer each The powder sending quantity of individual powder feeder, delivered to after on-line mixing is uniform in powdering cylinder and wait powdering；

3) added in 3D printing shower nozzle and bond ink；

4) shower nozzle selectively sprays in target area under control of the control system bonds ink, completes beating for a layer cross section Print, then, the workbench for being loaded with powder bed decline the height powdering again of a thickness, constantly repeat said process and complete all sections The printing in face forms 3D solid, wherein, the porosity per layer of material is different, and per layer of material in ceramic powders, Fiber dust is different from the component proportion of adhesive powder；

5) base substrate is placed in vacuum sintering furnace and is sintered enhancing processing, obtain fiber reinforcement gradient porous ceramics element.

2. manufacture method according to claim 1, it is characterised in that the feature of three-dimensional entity model is in step 1)：Its The function expression that porosity is axially distributed along ceramic component is power exponent form, and porosity is axially not along ceramic component Disconnected increase.

3. manufacture method according to claim 1, it is characterised in that the porosity gradient of three-dimensional entity model is in step 1) 20%~80%.

4. manufacture method according to claim 1, it is characterised in that the ceramic powders added in step 2) include oxidation The mixing of one or both of aluminium, carborundum or zirconia ceramics powder any of the above ratio, fiber include carbon fiber or carbon SiClx fiber, binding agent are polyvinyl alcohol.

5. according to the manufacture method described in any one of Claims 1-4, it is characterised in that ceramic powder particle is big in step 2) Small range is 20~150 μm.

6. manufacture method according to claim 5, it is characterised in that a diameter of 7~8 μm of carbon fiber powder, length be 24~ 64μm；Silicon carbide fibre form is whisker, and a diameter of 0.1~2 μm, length is 20~300 μm, and outward appearance is powdered.

7. manufacture method according to claim 1, it is characterised in that ink constituent is bonded in step 3) includes distillation Water, glycerine and polyvinylpyrrolidone.

8. manufacture method according to claim 7, it is characterised in that ink is bonded in step 3) and respectively forms composition proportion and is Distilled water mass fraction is 93%~95%, and glycerine mass fraction is 1.5%~3.5%, polyvinylpyrrolidone quality point Number is 1.5%~3.5%.

9. manufacture method according to claim 1, it is characterised in that the sintering temperature described in step 5) is 1440~1650 DEG C, sintering time is 1~3 hour.