Preparation method of biphase mullite nano ceramic fiber material with high thermal stability

Abstract

The invention relates to a preparation method of a biphase mullite nano ceramic fiber material with high thermal stability, and belongs to the technical field of inorganic non-metallic materials, aluminum powder, formic acid, acetic acid and deionized water are subjected to water bath reflux and filtration to prepare aluminum sol, then silica sol is added into the aluminum sol, and the mixture is uniformly stirred to obtain a light white transparent aluminum-silicon composite sol product; adding PVA powder, and stirring to obtain a colorless and transparent spinning solution; under the negative voltage condition, electrostatic spinning is carried out, precursor fibers are obtained, and finally high-temperature sintering is carried out. The preparation method has the characteristics of low production cost, simplicity in operation and the like, and the prepared material can still keep certain bendability even under a high-temperature condition and is not easy to brittle or break.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to a preparation method of a high thermal stability biphasic mullite nano-ceramic fiber. Background Art

[0002] Mullite fibers are widely used in industries such as aerospace, machinery, electronics, electric power, petrochemical, etc. due to their excellent high temperature resistance, thermal shock resistance, creep resistance, high temperature strength, chemical stability and heat insulation performance. The preparation methods mainly include melt spinning method, impregnation method, sol-gel method and electrospinning method, etc. Among them, the mullite fibers prepared by the electrospinning process have the advantages of nano-size, continuity and smooth surface. The mullite nanofibers prepared by this process are divided into two structures: single-phase and biphasic. The biphasic mullite nanofibers are considered as a high-performance high temperature resistant material due to their higher thermal stability, creep resistance and chemical stability. However, the preparation of biphasic mullite nanofibers requires aluminum source and silicon source, and the currently commonly used aluminum source has a high cost, which limits its large-scale application. Therefore, it is particularly important to prepare a low-cost high thermal stability biphasic mullite nano-ceramic fiber material. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a high thermal stability biphasic mullite nano-ceramic fiber material and a preparation method thereof.

[0004] The technical solution of the present invention is as follows:

[0005] A preparation method of a high thermal stability biphasic mullite nano-ceramic fiber material specifically includes the following steps:

[0006] Step 1: First, aluminum powder, formic acid, acetic acid and deionized water are refluxed in a water bath, and after filtration, an aluminum sol is prepared. Then, a silicon sol is added to the aluminum sol and stirred evenly to obtain a light white transparent aluminum-silicon composite sol product;

[0007] Step 2: PVA (polyvinyl alcohol) powder is dissolved in the aluminum-silicon composite sol, and after stirring, a colorless transparent spinning solution is obtained;

[0008] Step 3: The colorless transparent spinning solution prepared in Step 2 is subjected to electrospinning under the condition that the spinning voltage is a negative voltage to obtain precursor fibers;

[0009] Step 4: After the precursor fibers described in Step 3 are dried, they are placed in a sintering furnace for sintering to obtain a high thermal stability biphasic mullite nano-ceramic fiber material, and the average diameter of the fibers is 70 - 150 nm.

[0010] Preferably, in step 1, the mass ratio of aluminum powder, formic acid, acetic acid and deionized water is 1:7-8:7-8:17-18, and the water bath reflux temperature is 75-85°C.

[0011] Preferably, in the light white transparent aluminum-silicon composite sol product in step 1, by atomic ratio, Al:Si = 3:1-1.2.

[0012] Preferably, in step 3, the voltage provided by the spinning electrode is a negative voltage, and the voltage magnitude is -12 to -16 kV.

[0013] Preferably, the drying temperature in step 4 is 40-60°C; the sintering is carried out by heating to 600-1300°C at a heating rate of 5-8°C / min and holding for 1-6 h.

[0014] The beneficial effects of the present invention are as follows:

[0015] 1. Using aluminum powder and silica sol as the main raw materials, biphasic mullite nano-ceramic fibers are prepared by the sol-gel method and electrospinning technology, reducing the preparation cost.

[0016] 2. By adjusting the ratio of aluminum sol to silica sol, process parameters, etc., mullite nano-ceramic fibers and their composites with different performance requirements can be prepared to adapt to different use conditions.

[0017] 3. The spinning solution prepared by the present invention has stable performance and uniform composition, ensuring continuous production.

[0018] 4. The biphasic mullite nano-ceramic fibers have stable performance, are applicable to a wide temperature range, and their composites can be prepared according to different use conditions.

[0019] 5. The microstructure of the fiber material prepared by the method of the present invention can effectively inhibit grain growth during high-temperature sintering, ensuring a fine and uniform grain distribution, showing good flexibility and toughness. Even in a high-temperature environment, the material can still maintain a certain degree of bendability and is not prone to brittle fracture or breakage. These excellent properties make the material have high reliability in high-temperature applications. Description of the Drawings

[0020] Figure 1 is the scanning electron micrograph of the biphasic mullite nanofibers prepared in Example 1.

[0021] Figure 2 is the scanning electron micrograph of the biphasic mullite nanofibers prepared in Example 2.

[0022] Figure 3 is the scanning electron micrograph of the biphasic mullite nanofibers prepared in Example 3.

[0023] Figure 4 It is the scanning electron microscope image of the biphasic mullite nanofibers prepared in Comparative Example 1. Detailed implementation manners

[0024] Example 1

[0025] Step 1: Preparation of precursor sol

[0026] 1.08 g of aluminum powder was added to a mixed solution of 6.03 ml of formic acid, 6.86 ml of acetic acid and 17.28 ml of deionized water, and heated in a water bath at 80 °C. After refluxing for 20 h, it was filtered to obtain a colorless and transparent aluminum sol. Then, an aluminum-silicon composite sol product that was light white and transparent was obtained by mixing an aluminum-silicon sol and a silicon sol at a mass ratio of 27:33 at room temperature and stirring for 1 h.

[0027] Step 2: Preparation of spinning solution

[0028] The aluminum-silicon composite sol and PVA were mixed at a mass ratio of 24:1, and stirred for 4 h under heating in a water bath at 40 °C to obtain a spinning solution with excellent stability.

[0029] Step 3: Electrospinning to prepare precursor fibers

[0030] The colorless and transparent spinning solution prepared in Step 2 was subjected to electrospinning under the spinning process parameters of a spinning voltage of -14 kV, a pushing speed of 1 ml / h, and a receiving distance of 12 cm to obtain spun precursor fibers.

[0031] Step 4: The spun precursor fibers were sintered after drying

[0032] The spun precursor fibers obtained in Step 3 were placed in an oven at 60 °C and kept warm for 5 h, and then taken out and placed in a muffle furnace and heated to 1200 °C at a heating rate of 5 °C / min and kept warm for 1 h. High thermal stability biphasic mullite nano-ceramic fibers were obtained. The scanning electron microscope image of the sample is as Figure 1 shown. The diameter of the obtained high thermal stability biphasic mullite nano-ceramic fibers is between 110 and 200 nm, the fibers are uniform and continuous, and there is no fracture phenomenon.

[0033] Example 2

[0034] Steps 1, 2, and 3 are the same as those in Example 1. The difference lies in the treatment in Step 5: The spun precursor fibers obtained in Step 3 were placed in an oven at 60 °C and kept warm for 5 h, and then taken out and placed in a muffle furnace and heated to 1300 °C at a heating rate of 8 °C / min and kept warm for 1 h. High thermal stability biphasic mullite nano-ceramic fibers were obtained. The scanning electron microscope image of the sample is as Figure 2As shown. The obtained high-thermal-stability biphasic mullite nanoceramic fibers have diameters between 80 and 110 nm, the fibers are uniform and continuous, and there is no fracture phenomenon.

[0035] Example 3

[0036] Step 1 is the same as that in Example 1. The difference lies in the treatment of Step 2. In Step 2, the aluminum-silicon composite sol and PVA are mixed at a mass ratio of 23.5:1.5, and stirred for 4 h under a water bath heating at 40 °C to obtain a spinning solution with excellent stability.

[0037] Step 3: Electrospinning to prepare precursor fibers

[0038] The colorless and transparent spinning solution prepared in Step 2 is subjected to electrospinning under the electrospinning process parameters of a spinning voltage of -14 kV, a pushing speed of 1 ml / h, and a receiving distance of 12 cm to obtain spun precursor fibers.

[0039] Step 4: The spun precursor fibers are sintered after drying

[0040] The spun precursor fibers obtained in Step 3 are placed in an oven at 60 °C and kept warm for 6 h, then taken out and placed in a muffle furnace, and heated to 1300 °C at a heating rate of 8 °C / min and kept warm for 3 h. The obtained high-thermal-stability biphasic mullite nanoceramic fibers have diameters between 90 and 120 nm, the fibers are uniform and continuous, and there is no fracture phenomenon. The scanning electron microscope image of the sample is as Figure 3 shown.

[0041] Example 4

[0042] Steps 1, 2, and 3 are the same as those in Example 1. The difference is that: the spun precursor fibers obtained in Step 3 are placed in an oven at 60 °C and kept warm for 5 h, then taken out and placed in a muffle furnace, and heated to 1200 °C at a heating rate of 5 °C / min and kept warm for 6 h. High-thermal-stability biphasic mullite nanoceramic fibers are obtained. The obtained high-thermal-stability biphasic mullite nanoceramic fibers have diameters between 80 and 110 nm, the fibers are uniform and continuous, and there is no fracture phenomenon.

[0043] Comparative Example 1

[0044] Steps 1, 2, and 3 are the same as those in Example 1. The difference lies in the treatment of Step 4: the spun precursor fibers obtained in Step 3 are placed in an oven at 60 °C and kept warm for 5 h, then taken out and placed in a muffle furnace, and heated to 800 °C at a heating rate of 5 °C / min, taken out and cooled, and then kept warm for 1 h at 1500 °C. Continuous but non-uniform biphasic mullite nanoceramic fibers are obtained. The scanning electron microscope image of the sample is as Figure 4As shown, the prepared fiber has a diameter between 120 and 160 nm, and the flexibility of the fiber decreases. This is because when the sintering temperature is too high, the grain size inside the mullite fiber grows too large, resulting in a significant deterioration of the fiber flexibility.

[0045] Comparative Example 2

[0046] Step 1 is the same as in Example 1. The difference lies in the treatment of Step 2: The aluminum-silicon composite sol and PVA are mixed at a mass ratio of 20:5 and stirred for 12 h under a water bath heating at 40 °C to obtain a colorless and transparent spinning solution. However, the spinning process is not continuous, and the whipping phenomenon during the spinning process is not obvious. The morphology photo of the spun fiber shows that the fiber diameter is relatively thick and the fibers are adhered to each other. This is because when the amount of PVA is too much, the solvent has not completely volatilized when the fiber is deposited on the receiving device, resulting in the fiber adhesion phenomenon, indicating that it is difficult to prepare a high thermal stability biphasic mullite nanoceramic fiber material with a high PVA dosage.

[0047] Comparative Example 3

[0048] Step 1 is the same as in Example 1. The difference lies in the treatment of Step 2: The aluminum-silicon composite sol and PVA are mixed at a mass ratio of 24.5:0.5 and stirred for 4 h under a water bath heating at 40 °C to obtain a colorless and transparent spinning solution. The spinning process is continuous, and an obvious whipping phenomenon is observed. The morphology photo of the spun fiber shows that the fiber diameter is relatively thin and droplets are generated, indicating that it is difficult to prepare a high thermal stability biphasic mullite nanoceramic fiber material with a low PVA dosage.

Claims

1. A method for preparing a high thermal stability dual-phase mullite nano-ceramic fiber material, comprising the following steps: Step 1: First, reflux aluminum powder, formic acid, acetic acid and deionized water in a water bath, filter and prepare aluminum sol, then add silica sol into the aluminum sol, stir evenly to obtain a light white transparent aluminum-silicon composite sol product; Step 2: dissolving polyvinyl alcohol powder in aluminum-silicon composite sol, and stirring to obtain a colorless and transparent spinning solution; Step 3: electrospinning the colorless and transparent spinning solution prepared in step 2 under the condition of a negative spinning voltage to obtain a precursor fiber; Step 4: After drying the precursor fiber described in step 3, sintering is carried out in a sintering furnace to obtain a high thermal stability dual-phase mullite nano-ceramic fiber material, and the average diameter of the fiber is 70-150nm.

2. The method for preparing a high thermal stability dual-phase mullite nano-ceramic fiber material according to claim 1, characterized in that: In the step 1, the mass ratio of aluminum powder, formic acid, acetic acid and deionized water is 1:7-8:7-8:17-18, and the water bath reflux temperature is 75-85°C.

3. The method for preparing a high thermal stability dual-phase mullite nano-ceramic fiber material according to claim 1, characterized in that: In the light white transparent aluminum-silicon composite sol product in step 1, Al:Si=3:1-1.2 in atomic ratio.

4. The method for preparing a high thermal stability dual-phase mullite nano-ceramic fiber material according to claim 1, characterized in that: In the step 3, the voltage provided by the spinning electrode is a negative voltage, and the voltage magnitude is -12 to -16 kV.

5. The method for preparing a high thermal stability dual-phase mullite nano-ceramic fiber material according to claim 1, characterized in that: The drying temperature in step 4 is 40-60° C.; the sintering is performed by heating the temperature to 600-1300° C. at a heating rate of 5-8° C. / min and keeping the temperature for 1-6 hours.

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