Alumina porous ceramic paste, method of making and additive manufacturing method

Abstract

The application relates to the technical field of porous ceramics, in particular to an alumina porous ceramic paste, a preparation method thereof and an additive manufacturing forming method. The raw materials of the alumina porous ceramic paste include alumina, alumina fiber powder, polycarbosilane, liquid photosensitive resin, a sodium hydroxide solution and anhydrous ethanol, and the raw materials are uniformly mixed through steps. By controlling the mass content of each component, the porous ceramic paste with good dispersibility, high fluidity and stability can be prepared and can be used as the paste for additive manufacturing; meanwhile, the paste forming process is simple, only needs to be heated in a reaction kettle, has the advantages of the particle accumulation method, and saves the mechanical forming process of particles, and is low in cost; through the additive manufacturing forming process using the paste, the prepared porous ceramic has high porosity, and most of the pores are closed pores and the pore distribution is more uniform.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of porous ceramics, in particular to an alumina porous ceramic paste, a preparation method thereof and an additive manufacturing forming method. BACKGROUND

[0002] Porous ceramics, also known as microporous ceramics or foam ceramics, are new ceramic materials with certain size and number of pore structures, which mainly utilize the properties of the pore structures in the materials and the materials themselves to achieve the desired functions. As a new green and environmentally friendly material, it has excellent properties such as high porosity, high permeability, large specific surface area, small bulk density, low thermal conductivity, corrosion resistance, high chemical stability and dimensional stability.

[0003] There are many existing processes for preparing porous ceramics, including organic foam precursor method, pore-forming agent addition method, foaming method, and particle accumulation method. Among them, the organic foam precursor method cannot produce micrometer-sized porous ceramics; the pore structure of the porous ceramics prepared by the pore-forming agent addition method and the foaming method is not uniform, and in some aspects, the pores of the prepared porous ceramics are not continuous and connected, and the foaming method is mostly closed-cell; the porous ceramics prepared by the particle accumulation method have a relatively uniform pore distribution and can form pores of various sizes and connected to each other, but the entire process is relatively complex because it involves particle molding and the addition of a binder for compression molding. Therefore, it is necessary to find a method for preparing porous ceramics to produce porous ceramics with high porosity, uniform voids, and all sealed voids. SUMMARY

[0004] To solve the problems of the existing porous ceramics prepared by the preparation process, the present application provides a preparation method of an alumina porous ceramic paste, comprising the following steps:

[0005] S1, 1000 mesh alumina, 500 mesh alumina fiber powder and a first part of anhydrous ethanol are added to a reaction container, the system temperature is adjusted to 60±2℃, stirring is carried out at a speed of 100r / min for 5-10min, and the first mixture is obtained by stirring and mixing uniformly;

[0006] S2, a first part of polycarbosilane and a sodium hydroxide solution with a concentration greater than 40wt% are added to the first mixture under continuous stirring, and after flocculation and precipitation, a second part of anhydrous ethanol is added, and stirring is continued for 6-8min at a speed of 300r / min to obtain the second mixture;

[0007] S3, after the second mixture is placed for 10 min, a second part of polycarbosilane, a third part of anhydrous ethanol and liquid photosensitive resin are added into the second mixture, the temperature of the system is adjusted to 30±2℃, and stirring is carried out for 10-15 min at a stirring rate of 100 r / min, so that the alumina porous ceramic paste is obtained.

[0008] By introducing the first part of polycarbosilane and the dispersant into the alumina powder and the alumina fiber powder matrix, flocculation and precipitation are carried out, the ceramic powder dispersed in the water phase is aggregated by stirring, and the high porosity porous structure is formed by uniform settlement and accumulation in the liquid phase; and the second part of polycarbosilane is introduced in the process of flocculation, so that the bubbles generated by the second part of polycarbosilane are not broken due to long-term stirring, and the porosity of the porous ceramic prepared by the method is higher than that of the porous ceramic prepared by the flocculation method.

[0009] Further, the raw materials of the paste include the alumina 40wt%-60wt%, the alumina fiber powder 5wt%-10wt%, the polycarbosilane 10wt%-15wt%, the liquid photosensitive resin 5wt%-10wt%, the sodium hydroxide solution with a concentration greater than 40wt% 5wt%-10wt% and the anhydrous ethanol 15wt% in percentage by mass.

[0010] Wherein, the sum of the amounts of the first part of anhydrous ethanol, the second part of anhydrous ethanol and the third part of anhydrous ethanol is the total amount of the anhydrous ethanol; and the sum of the amounts of the first part of polycarbosilane and the second part of polycarbosilane is the total amount of the polycarbosilane.

[0011] Further, in step S2, the mass ratio of the first part of polycarbosilane to the alumina is (5-10):(40-60).

[0012] Further, in step S3, the mass ratio of the second part of polycarbosilane to the alumina is 5:(40-60).

[0013] The application further provides an alumina porous ceramic paste prepared by the preparation method.

[0014] The application further provides an additive manufacturing forming method of alumina porous ceramic, which uses the alumina porous ceramic paste as raw material.

[0015] Further, the additive manufacturing forming method comprises 3D printing to prepare a blank, pre-oxidation of the blank and sintering of the blank, wherein the pre-oxidation temperature is 1000-1200℃.

[0016] During the pre-oxidation sintering, the polycarbosilane in the paste is in a high activity at the temperature, and then is uniformly gasified to form closed pores, and the activity of the alumina powder and the alumina fiber powder is further increased at the temperature, so that the crystal grains are more refined.

[0017] Further, the 3D printing preparation blank comprises the following steps:

[0018] (1) designing a three-dimensional entity model;

[0019] (2) STL file data conversion;

[0020] (3) layering, slicing and model analysis;

[0021] (4) adding a support and analyzing support stress;

[0022] (5) laser scanning and layer-by-layer forming to obtain a product three-dimensional model blank;

[0023] (6) processing the blank excess material and the blank surface;

[0024] The alumina ceramic powder and the alumina fiber powder are uniformly dispersed in the prepared organic polymer solution to prepare the alumina ceramic powder and the alumina fiber powder paste; then the organic polymer in the alumina ceramic powder and the alumina fiber powder paste is precipitated, and after laser solidification of the additive manufacturing, the organic polymer is precipitated into a flocculent porous structure, and all solvents are evaporated by heating to form a ceramic green body, and the flocculent organic polymer is uniformly distributed in the ceramic green body; then the flocculent organic polymer is burned off by continuing to heat to form a porous ceramic green body; and finally high-temperature sintering is performed to form a high-strength porous ceramic.

[0025] Compared with the prior art, the alumina porous ceramic paste provided by the application takes alumina powder and alumina fiber powder as the matrix material, and is prepared by combining polycarbosilane, a sodium hydroxide solution and anhydrous ethanol by controlling the mass content of each component, so that the porous ceramic paste has good dispersibility, high fluidity and stability, and can be used as an additive manufacturing paste; meanwhile, the paste forming process is simple, only needs to be heated in a reaction kettle, has the advantages of the particle packing method, and saves the mechanical forming process of particles, so the cost is low; by using the additive manufacturing paste to form a porous ceramic, the prepared porous ceramic has high porosity, and most of the pores are closed and uniformly distributed. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative work based on these drawings also belong to the protection scope of the present application.

[0027] Figure 1 The electron microscope image of the alumina porous ceramic provided for the embodiment 1 of the present application has a scale of 6 μm;

[0028] Figure 2 The electron microscope image of the alumina porous ceramic provided for the comparative example 1 of the present application has a scale of 6 μm;

[0029] Figure 3 The electron microscope image of the alumina porous ceramic provided for the embodiment 1 of the present application has a scale of 1 μm;

[0030] Figure 4 The electron microscope image of the alumina porous ceramic provided for the comparative example 2 of the present application has a scale of 1 μm;

[0031] Figure 5 The electron microscope image of the alumina porous ceramic provided for the embodiment 1 of the present application has a scale of 4 μm;

[0032] Figure 6 The electron microscope image of the alumina porous ceramic provided for the comparative example 3 of the present application has a scale of 4 μm;

[0033] The drawings show that: 1, alumina; 2, alumina fiber; 3, closed pore; 4, alumina ceramic particle. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present application.

[0035] The present application provides a preparation method of alumina porous ceramic paste, which comprises the following steps:

[0036] S1, 1000 mesh alumina, 500 mesh alumina fiber powder and the first part of anhydrous ethanol are added into a reaction container, the system temperature is adjusted to 60±2℃, stirring for 5-10 min, the stirring rate is 100 r / min, and the first mixture is obtained by stirring and mixing;

[0037] S2, under continuous stirring, a first portion of polycarbosilane and a sodium hydroxide solution with a concentration greater than 40wt% are added to the first mixture, and after flocculation and precipitation, a second portion of anhydrous ethanol is added, and stirring is continued for 6-8min at a stirring rate of 300r / min, to obtain a second mixture; wherein the mass ratio of the first portion of polycarbosilane to alumina is (5-10):(40-60);

[0038] S3, after the second mixture is left to stand for 10min, a second portion of polycarbosilane, a third portion of anhydrous ethanol and a liquid photosensitive resin are added to the second mixture, the system temperature is adjusted to 30±2℃, and stirring is continued for 10-15min at a stirring rate of 100r / min, to obtain the alumina porous ceramic paste; wherein the mass ratio of the second portion of polycarbosilane to alumina is 5:(40-60).

[0039] The raw materials of the alumina porous ceramic paste include, in terms of mass percentage, alumina 40wt%-60wt%, alumina fiber powder 5wt%-10wt%, polycarbosilane 10wt%-15wt%, liquid photosensitive resin 5wt%-10wt%, sodium hydroxide solution with a concentration greater than 40wt% 5wt%-10wt% and anhydrous ethanol 15wt%.

[0040] The application also provides an alumina porous ceramic additive manufacturing forming method, which comprises 3D printing to prepare a blank, pre-oxidation of the blank and sintering of the blank.

[0041] The additive manufacturing forming method adopts the alumina porous ceramic paste as the raw material;

[0042] The pre-oxidation temperature is 1000-1200℃.

[0043] The 3D printing to prepare a blank comprises the following steps:

[0044] (1) designing a three-dimensional solid model;

[0045] (2) STL file data conversion;

[0046] (3) layering, slicing and model analysis;

[0047] (4) adding a support and analyzing the support stress;

[0048] (5) laser scanning and layer-by-layer forming to obtain a three-dimensional model blank of the product;

[0049] (6) treating the excess material of the blank and the surface of the blank.

[0050] The application provides the raw material composition of the alumina porous ceramic in the following examples and comparative examples, as shown in Table 1:

[0051] Table 1 (unit: mass percentage)

[0052] Raw materials Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 1000 mesh alumina 40 50 57 38 40 500 mesh alumina fiber powder 10 8 5 12 10 First portion polycarbosilane 10 6 8 10 15 Second portion polycarbosilane 5 5 5 5 0 Liquid photosensitive resin 10 10 5 10 10 45 wt% sodium hydroxide solution 10 6 5 10 10 First portion anhydrous ethanol 5 5 5 5 5 Second portion anhydrous ethanol 5 5 5 5 5 Third portion anhydrous ethanol 5 5 5 5 5

[0053] The application also provides an alumina porous ceramic additive manufacturing forming method of Examples 1-3 and Comparative Examples 1-2, comprising the following steps:

[0054] S10, preparing an alumina porous ceramic paste;

[0055] S20, preparing a green body by 3D printing, using the alumina porous ceramic paste prepared in S10 as raw material;

[0056] S30, pre-oxidizing and sintering the green body at 1000℃ in an air atmosphere for 20h;

[0057] S40, continuing to sinter the green body pre-oxidized in S30, the sintering temperature is 2000℃, and the time is 40h, to obtain an alumina porous ceramic.

[0058] The preparation method of the alumina porous ceramic paste in S10 comprises the following steps:

[0059] S11, adding 1000 mesh alumina, 500 mesh alumina fiber powder and a first part of anhydrous ethanol into a reaction container, adjusting the system temperature to 60℃, stirring for 5min at a stirring rate of 100r / min, and stirring and mixing uniformly to obtain a first mixture;

[0060] S12, continuously stirring to add a first part of polycarbosilane and 45wt% sodium hydroxide solution into the first mixture, adding a second part of anhydrous ethanol after flocculation and precipitation, continuously stirring for 8min at a stirring rate of 300r / min, to obtain a second mixture;

[0061] S13, after the second mixture is placed for 10min, adding a second part of polycarbosilane, a third part of anhydrous ethanol and liquid photosensitive resin into the second mixture, adjusting the system temperature to 30℃, stirring for 10min at a stirring rate of 100r / min, to obtain the alumina porous ceramic paste.

[0062] Comparative Example 3

[0063] Different from Example 1, the preparation method of the alumina porous ceramic paste in S10 is: adding all raw materials into a reaction container, adjusting the system temperature to 60℃, and stirring and mixing uniformly to obtain the alumina porous ceramic paste, wherein the stirring speed is 300r / min, and the stirring time is 20min. The remaining processing steps are the same as those of Example 1.

[0064] The alumina porous ceramics prepared in Example 1 and Comparative Examples 1-3 are characterized by using electron microscope, and electron microscope images of the alumina porous ceramics prepared in Example 1 at different magnifications are obtained as shown in Figs. Figures 1-6 . Figure 1 、 3 Figs. Figure 2 is an electron microscope image of the alumina porous ceramics provided in Comparative Example 1, Figure 4 is an electron microscope image of the alumina porous ceramics provided in Comparative Example 2, Figure 6 is an electron microscope image of the alumina porous ceramics provided in Comparative Example 3;

[0065] Figure 1 、 3 As can be seen from Figs.

[0066] The difference between Comparative Example 1 and Example 1 is that less alumina and more alumina fiber powder are added. Figure 1 and Figure 2 As can be seen from the comparison, since the alumina in Comparative Example 1 is less, the alumina fibers cannot be completely wrapped, and thus a structure that is disordered and not conducive to forming a uniform closed pore structure is formed.

[0067] The difference between Comparative Example 2 and Example 1 is that all polycarbosilane is added in step S12, and no polycarbosilane is added in step S13. Figure 3 and Figure 4 As can be seen from the comparison, although the alumina porous ceramics prepared in Comparative Example 2 have many internal pores, the pore sizes are not uniform, which has a great impact on the performance of the product.

[0068] The difference between Comparative Example 3 and Example 1 is that all raw materials are mixed at one time. Figure 5 and Figure 6 As can be seen from the comparison, the alumina porous ceramics prepared in Comparative Example 3 have few internal pores and the pore sizes are not uniform, and thus the alumina porous ceramics prepared have low porosity and high density.

[0069] The alumina porous ceramic paste provided in the present application uses alumina powder and alumina fiber powder as base materials, and is combined with polycarbosilane, sodium hydroxide solution and anhydrous ethanol, and by controlling the mass content of each component, a stable porous ceramic paste with good dispersibility and high fluidity is prepared, which can be used as a paste for additive manufacturing; at the same time, the paste forming process is simple, only needs to be heated in a reaction kettle, has the advantages of the particle packing method, but saves the mechanical forming process of the particles, and has low cost; by using the paste for additive manufacturing forming process, the porous ceramics prepared have high porosity, and most of the pores are closed and the pore distribution is more uniform.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a porous alumina ceramic paste, characterized in that: The following steps are involved: S1. Add 1000-mesh alumina, 500-mesh alumina fiber powder, and the first portion of anhydrous ethanol into a reaction vessel, adjust the system temperature to 60±2°C, stir for 5-10 minutes at a stirring rate of 100 r / min, and mix thoroughly to obtain a first mixture; S2. Add the first portion of polycarbosilane and a sodium hydroxide solution having a concentration greater than 40 wt % to the first mixture under continuous stirring to cause flocculation and precipitation, then add the second portion of anhydrous ethanol and continue stirring for 6-8 minutes at a stirring rate of 300 r / min to obtain a second mixture; S3. After the second mixture is allowed to stand for 10 minutes, the second portion of polycarbosilane, the third portion of anhydrous ethanol, and the liquid photosensitive resin are added to the second mixture, the system temperature is adjusted to 30±2° C., and the mixture is stirred for 10-15 minutes at a stirring rate of 100 rpm to obtain the alumina porous ceramic paste; In step S2, the mass ratio of the first portion of polycarbosilane to the alumina is (5-10): (40-60); In step S3, the mass ratio of the second portion of polycarbosilane to the alumina is 5:(40-60); In terms of mass percentage, the raw materials of the paste include 40wt%-60wt% of the alumina, 5wt%-10wt% of alumina fiber powder, 10wt%-15wt% of polycarbosilane, 5wt%-10wt% of liquid photosensitive resin, 5wt%-10wt% of sodium hydroxide solution with a concentration greater than 40wt%, and 15wt% of anhydrous ethanol; The sum of the amounts of the first part of anhydrous ethanol, the second part of anhydrous ethanol and the third part of anhydrous ethanol is the total amount of the anhydrous ethanol; the sum of the amounts of the first part of polycarbosilane and the second part of polycarbosilane is the total amount of the polycarbosilane.

2. A porous alumina ceramic paste, characterized in that: Prepared according to the preparation method of claim 1.

3. A method for additive manufacturing of porous alumina ceramics, characterized by: The alumina porous ceramic paste described in claim 2 is used as the raw material.

4. The additive manufacturing method according to claim 3, wherein: The method comprises preparing a green body by 3D printing, pre-oxidation of the green body and sintering of the green body, wherein the pre-oxidation temperature is 1000-1200°C.

5. The additive manufacturing method according to claim 4, wherein: The 3D printing process for preparing the blank comprises the following steps: (1) Design a three-dimensional solid model; (2) STL file data conversion; (3) Layered slicing and model analysis; (4) Add supports and analyze support forces; (5) Laser scanning is used to form the product layer by layer to obtain a three-dimensional model blank; (6) Process the remaining material and the surface of the blank.

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