Preparation method of aluminum-silicon fiber-based layered porous ceramic with hierarchical structure

Abstract

The invention relates to a preparation method of aluminum-silicon fiber-based layered porous ceramic with a hierarchical structure. The method comprises the following steps: preparing an aluminum-silicon fiber film; preparing an aluminum-silicon sol diluent; cutting the aluminum-silicon fiber film into pieces, dipping the pieces in an aluminum-silicon sol diluent, stacking the pieces, and extruding the pieces to prepare an aluminum-silicon fiber-based layered porous ceramic wet blank; preparing a fiber-based layered porous ceramic green body; and carrying out high-temperature calcination on the fiber-based layered porous ceramic blank and aluminum fluoride to prepare the aluminum-silicon fiber-based layered porous ceramic with the hierarchical structure. The preparation method has the beneficial effects that the aluminum-silicon fiber-based layered porous ceramic with the hierarchical structure is prepared by utilizing an electrostatic spinning-impregnation lamination-fluorine-surrounding calcination process, the process has the advantages of low cost, simplicity, high designability and the like, fine regulation and control of an internal structure of a ceramic material can be realized, a material interface can be increased, a pore structure is complicated, and the preparation process is simple. Therefore, the heat insulation effect is improved, and wide application prospects are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-metallic mineral products in the manufacturing industry, and in particular relates to a method for preparing an aluminum-silicon fiber-based porous ceramic with a hierarchical structure. Background Art

[0002] Oxide (such as mullite, alumina, silica, etc.) fiber-based porous ceramics can present hierarchical and multi-interface structures, have excellent temperature resistance, thermal insulation and mechanical properties, and can serve for a long time in extreme environments such as high temperature. Therefore, they have shown broad application prospects in many fields such as aerospace, energy, chemical industry, and environmental protection. The template method is a commonly used layered structure preparation method, which is mostly used to prepare particle-based porous ceramics, but its applicability to high aspect ratio fiber-based porous ceramic systems is poor. The direct spinning method can obtain fiber-based materials with stacking structures. However, the fiber-based materials prepared by the direct spinning method have the problem that the geometric shape and density cannot be finely controlled, and it is not easy to achieve the microstructure and performance optimization of fiber-based porous ceramics. Therefore, it is urgent to develop a preparation method for a new type of fiber-based porous ceramic that can achieve hierarchical and multi-interface structure design. Summary of the invention

[0003] In order to solve the above problems, the object of the present invention is to provide a method for preparing aluminum-silicon fiber-based porous ceramics with a hierarchical structure.

[0004] In order to achieve the above object, the method for preparing the aluminum-silicon fiber-based porous ceramic with a hierarchical structure provided by the present invention comprises the following steps performed in sequence:

[0005] 1) using an electrospinning device to perform electrospinning, followed by drying, and then calcining in a high-temperature furnace to obtain an aluminum silicon fiber film;

[0006] 2) stirring the aluminum silica sol and deionized water in a container at high speed with a high-speed stirrer to obtain an aluminum silica sol dilution solution;

[0007] 3) cutting the aluminum silicate fiber film obtained in step 1) into aluminum silicate fiber film sheets, and then immersing each sheet in the aluminum silicate sol dilution solution obtained in step 2), and then stacking multiple sheets together and extruding them to form an aluminum silicate fiber-based porous ceramic wet blank;

[0008] 4) placing the aluminum-silicon fiber-based porous ceramic wet blank obtained in step 3) in a refrigerator for pre-freezing, and then drying it using a vacuum freeze dryer to prepare a fiber-based porous ceramic blank;

[0009] 5) The fiber-based porous ceramic body obtained in step 4) is placed in a high-temperature furnace and pre-pressed with a ceramic press block, and then aluminum fluoride is placed around it as a catalytic fluorine source. Thereafter, the fiber-based porous ceramic body and aluminum fluoride are sealed in a container and calcined at high temperature to finally produce an aluminum silicon fiber-based porous ceramic with a hierarchical structure.

[0010] In step 1), the process parameters of the electrospinning equipment are: power supply 10kV, receiving distance 12cm, spinning speed 0.5ml / h, spinning temperature 22°C, ambient humidity 40%-60%; the drying method is drying in an oven at 90°C and 180°C for two hours each; the high-temperature calcination temperature is 600°C.

[0011] In step 2), the mass ratio of the aluminum silica sol to deionized water is 5:17.

[0012] In step 3), the thickness of the aluminum silicon fiber-based porous ceramic wet blank is 70% of the thickness of the wet blank before extrusion.

[0013] In step 4), the pre-freezing temperature is -20°C for 12 hours and the vacuum freeze drying time is 20 hours.

[0014] In step 5), the mass ratio of the fiber-based porous ceramic body to aluminum fluoride is 5:1-5:6; the high-temperature calcination temperature is 1300° C.-1400° C., and the temperature is kept for 2 hours.

[0015] Compared with the prior art, the beneficial effect of the preparation method of the aluminum-silicon fiber-based porous ceramics with a hierarchical structure provided by the present invention is that the aluminum-silicon fiber-based porous ceramics with a hierarchical structure are made by utilizing an electrospinning-impregnation lamination-fluorine calcination process, which has the advantages of low cost, simplicity, and high designability. It can achieve fine control of the internal structure of the ceramic material, increase the material interface, and complicate the pore structure, thereby improving the thermal insulation effect, and therefore has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The scanning electron microscope image of the aluminum silicon fiber-based porous ceramic with a hierarchical structure after calcination at 1300° C. in Example 1, wherein the mass ratio of the fiber-based porous ceramic green body to aluminum fluoride is 5:6;

[0017] Figure 2 The scanning electron microscope image of the aluminum silicon fiber-based porous ceramic with a hierarchical structure after calcination at 1300° C. in Example 2, wherein the mass ratio of the fiber-based porous ceramic green body to aluminum fluoride is 5:4;

[0018] Figure 3The scanning electron microscope image of the aluminum silicon fiber-based porous ceramic with a hierarchical structure after calcination at 1300° C. in Example 3, wherein the mass ratio of the fiber-based porous ceramic body to aluminum fluoride is 5:2;

[0019] Figure 4 The scanning electron microscope image of the aluminum silicon fiber-based porous ceramic with a hierarchical structure after calcination at 1300° C. in Example 4, wherein the mass ratio of the fiber-based porous ceramic green body to aluminum fluoride is 5:1;

[0020] Figure 5 The scanning electron microscope image of the aluminum silicon fiber-based porous ceramic with a hierarchical structure after calcination at 1400° C. in Example 5, wherein the mass ratio of the fiber-based porous ceramic green body to aluminum fluoride is 5:1;

[0021] Figure 6 This is a plane scanning electron microscope image of the aluminum silicon fiber-based porous ceramic with a hierarchical structure after calcination at 1300° C. in Example 6, in which the mass ratio of the fiber-based porous ceramic green body to aluminum fluoride is 5:2;

[0022] Figure 7 This is an instantaneous thermal imaging image of the aluminum-silicon fiber-based porous ceramic with a hierarchical structure in Example 6 heated on a heating platform at 500°C for 5 minutes. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Embodiment 1:

[0025] The method for preparing the aluminum-silicon fiber-based porous ceramic with a hierarchical structure provided in this embodiment comprises the following steps performed in sequence:

[0026] 1) Electrospinning was performed using an electrospinning device, wherein the process parameters of the electrospinning device were: power supply 10 kV, receiving distance 12 cm, spinning speed 0.5 ml / h, spinning temperature 22° C., and ambient humidity 50%; then, the film was dried in an oven at 90° C. and 180° C. for two hours each, and then calcined in a high-temperature furnace at 600° C., with a heating rate of 1° C. / min, and kept warm for 2 hours, and finally cooled to room temperature with the furnace to remove most of the organic matter, thereby obtaining an aluminum silicon fiber film;

[0027] 2) In a container, 10 g of aluminum silica sol (SiO2: 6.0%, Al2O3 ≥ 16%) and 34 g of deionized water were stirred evenly with a high-speed stirrer at a speed of 500 r / min for 30 minutes to obtain an aluminum silica sol dilution solution;

[0028] 3) Cutting the aluminum-silicon fiber film obtained in step 1) into rectangular aluminum-silicon fiber film sheets of 20 mm × 20 mm, and then immersing each sheet in the aluminum-silicon sol dilution obtained in step 2), stacking multiple sheets together, and then extruding them using a clamp to form an aluminum-silicon fiber-based porous ceramic wet blank; the thickness of the aluminum-silicon fiber-based porous ceramic wet blank is 70% of the thickness of the wet blank before extrusion;

[0029] 4) placing the aluminum silicon fiber-based porous ceramic wet body obtained in step 3) in a refrigerator at -20°C for pre-freezing for 12 hours, and drying it in a vacuum freeze dryer for 20 hours to prepare a fiber-based porous ceramic body;

[0030] 5) 0.25 g of the fiber-based porous ceramic body obtained in step 4) is placed in a high-temperature furnace and pre-pressed with 8 g of a ceramic press block, and then 0.3 g of aluminum fluoride as a catalytic fluorine source is placed around it to make the mass ratio of the fiber-based porous ceramic body and aluminum fluoride be 5:6. Thereafter, the fiber-based porous ceramic body and aluminum fluoride are sealed with an inverted crucible with a diameter of 60 mm, a height of 60 mm, and a wall thickness of 4 mm and are calcined at a high temperature of 1300°C, a heating rate of 2°C / min, and maintained for 2 hours. Finally, the mixture is cooled to room temperature with the furnace to finally produce an aluminum silicon fiber-based porous ceramic with a hierarchical structure.

[0031] Example 2

[0032] The difference from Example 1 is that the amount of aluminum fluoride used is 0.2 g, so that the mass ratio of the fiber-based porous ceramic body to aluminum fluoride is 5:4.

[0033] Example 3

[0034] The difference from Example 1 is that the amount of aluminum fluoride used is 0.1 g, so that the mass ratio of the fiber-based porous ceramic body to aluminum fluoride is 5:2.

[0035] Example 4

[0036] The difference from Example 1 is that the amount of aluminum fluoride used is 0.05 g, so that the mass ratio of the fiber-based porous ceramic body to aluminum fluoride is 5:1.

[0037] Example 5

[0038] The difference from Example 1 is that the amount of aluminum fluoride used is 0.05 g, the mass ratio of the fiber-based porous ceramic body to aluminum fluoride is 5:1, and the calcination temperature is 1400°C.

[0039] Example 6

[0040] The difference from Example 1 is that the amount of the fiber-based porous ceramic body is 0.75 g, and the amount of aluminum fluoride is 0.3 g, so that the mass ratio of the fiber-based porous ceramic body to aluminum fluoride is 5:2.

[0041] The above six embodiments prepared six groups of samples, and aluminum silicon fiber-based porous ceramics with a hierarchical structure were prepared by adjusting the mass ratio of the fiber-based porous ceramic body to aluminum fluoride and applying different calcination temperatures.

[0042] The microscopic morphology of the aluminum-silicon fiber-based porous ceramic with a hierarchical structure prepared above was observed and analyzed by scanning electron microscopy. Figure 1 , Figure 2 , Figure 3 as well as Figure 4 It can be found that the hierarchical structure inside the aluminum-silicon fiber-based porous ceramic with a hierarchical structure can be effectively controlled by adjusting the mass ratio of the fiber-based porous ceramic body to aluminum fluoride. When the mass ratio is low, a large number of whiskers are formed inside the aluminum-silicon fiber-based porous ceramic with a hierarchical structure using the fibers as templates; when the mass ratio is high, the fibers inside the aluminum-silicon fiber-based porous ceramic with a hierarchical structure have a porous structure.

[0043] contrast Figure 4 and Figure 5 It can be found that too high calcination temperature will lead to the formation of larger pores on the fiber surface inside the aluminum-silicon fiber-based porous ceramics with a hierarchical structure and the grain size will be too large, which will reduce the temperature resistance and mechanical properties of the fiber.

[0044] contrast Figure 3 and Figure 6 It can be found that when the mass ratio of the fiber-based porous ceramic body and the catalyst is kept unchanged, while increasing the amount of the fiber-based porous ceramic body and the catalyst, the concentration of the catalytic gas will increase during the high-temperature calcination process, and whiskers will be formed inside the aluminum-silicon fiber-based porous ceramic with a hierarchical structure using the fibers as a template.

[0045] The high temperature thermal insulation performance of the aluminum silicon fiber matrix porous ceramic with hierarchical structure prepared above was characterized by observing and taking thermal imaging distribution optical photos of the samples using a CA73N thermal imager of the CHAVVI N ARNOUX brand. The sample prepared in Example 6 was heated on a heating platform at 500°C for 5 minutes to reach thermal equilibrium and thermal imaging pictures were taken, as shown in FIG. Figure 7 As shown in the figure, it can be seen that the temperature of the central area of ​​the upper surface of the aluminum silicon fiber-based porous ceramic with a hierarchical structure is 233.2°C, and the thermal insulation rate is 53.36%, so high-temperature thermal insulation can be effectively achieved.

[0046] In summary, the pore structure of the aluminum-silicon fiber-based porous ceramics with a hierarchical structure prepared by the present invention has a certain degree of adjustability and excellent thermal insulation properties, and the layered porous ceramics with different pore structures can be used in a variety of applications.

Claims

1. A method for preparing an aluminum-silicon fiber-based porous ceramic with a hierarchical structure, characterized in that: The method for preparing the aluminum-silicon fiber-based porous ceramic with a hierarchical structure comprises the following steps performed in sequence: 1) using an electrospinning device to perform electrospinning, followed by drying, and then calcining in a high-temperature furnace to obtain an aluminum silicon fiber film; 2) stirring the aluminum silica sol and deionized water in a container at high speed with a high-speed stirrer to obtain an aluminum silica sol dilution solution; 3) cutting the aluminum silicate fiber film obtained in step 1) into aluminum silicate fiber film sheets, and then immersing each sheet in the aluminum silicate sol dilution solution obtained in step 2), and then stacking multiple sheets together and extruding them to form an aluminum silicate fiber-based porous ceramic wet blank; 4) placing the aluminum-silicon fiber-based porous ceramic wet blank obtained in step 3) in a refrigerator for pre-freezing, and then drying it using a vacuum freeze dryer to prepare a fiber-based porous ceramic blank; 5) The fiber-based porous ceramic body obtained in step 4) is placed in a high-temperature furnace and pre-pressed with a ceramic press block, and then aluminum fluoride is placed around it as a catalytic fluorine source. Thereafter, the fiber-based porous ceramic body and aluminum fluoride are sealed in a container and calcined at high temperature to finally produce an aluminum silicon fiber-based porous ceramic with a hierarchical structure.

2. The method for preparing the aluminum-silicon fiber-based porous ceramic with a hierarchical structure according to claim 1, characterized in that: In step 1), the process parameters of the electrospinning equipment are: power supply 10kV, receiving distance 12cm, spinning speed 0.5ml / h, spinning temperature 22°C, ambient humidity 40%-60%; the drying method is drying in an oven at 90°C and 180°C for two hours each; the high-temperature calcination temperature is 600°C.

3. The method for preparing the aluminum-silicon fiber-based porous ceramic with a hierarchical structure according to claim 1, characterized in that: In step 2), the mass ratio of the aluminum silica sol to deionized water is 5:

17.

4. The method for preparing the aluminum-silicon fiber-based porous ceramic with a hierarchical structure according to claim 1, characterized in that: In step 3), the thickness of the aluminum silicon fiber-based porous ceramic wet blank is 70% of the thickness of the wet blank before extrusion.

5. The method for preparing the aluminum-silicon fiber-based porous ceramic with a hierarchical structure according to claim 1, characterized in that: In step 4), the pre-freezing temperature is -20°C for 12 hours and the vacuum freeze drying time is 20 hours.

6. The method for preparing the aluminum-silicon fiber-based porous ceramic with a hierarchical structure according to claim 1, characterized in that: In step 5), the mass ratio of the fiber-based porous ceramic body to aluminum fluoride is 5:1-5:6; the high-temperature calcination temperature is 1300° C.-1400° C., and the temperature is kept for 2 hours.

Images