CN114703564A - A kind of preparation method of rare earth lanthanum oxide doped high temperature resistant alumina fiber - Google Patents

Abstract

The invention provides a rare earth lanthanum oxide doped alumina fiber and a preparation method thereof. The preparation method comprises the following steps: (1) preparing aluminum sol containing lanthanum oxide; (2) preparing a high-temperature resistant alumina fiber precursor; (3) and (3) preparing the high-temperature resistant alumina fiber. The alumina fiber is prepared by adopting a sol-gel method, the preparation process cost is low, the equipment requirement is low, the application is wide, and the alumina fiber can realize a compact fine grain structure below 200 nm; in addition, the high-temperature stability of the alumina fiber is improved by doping a proper amount of rare earth lanthanum oxide, and after the alumina fiber is subjected to high-temperature long-time heat preservation, the rare earth lanthanum oxide-doped alumina fiber shows better room-temperature tensile strength retention rate, and can be applied to the fields of national defense and military industry, aerospace, civil heat insulation and fire resistance, environmental protection, recycling and the like.

Description

A kind of preparation method of rare earth lanthanum oxide doped high temperature resistant alumina fiber

technical field

The invention belongs to the field of inorganic ceramic materials, in particular to a preparation method of rare earth lanthanum oxide doped high temperature resistant alumina fiber.

Background technique

Alumina fiber is a kind of high-performance inorganic fiber, which is mainly composed of Al ₂ O ₃ . Continuous alumina fiber has various excellent characteristics and excellent cost performance, especially used in military industry, aviation, aerospace, automobile, electric power and other fields, it has huge commercial value and great strategic significance in military industry. Although commercial continuous alumina fibers have been in existence for more than 40 years, the production and preparation technology is mainly monopolized by a few companies such as the United States, Japan, the United Kingdom and Germany. The key technology of fiber preparation has not been disclosed, and the research on continuous alumina ceramic fibers in my country There is a big gap between the development and the international advanced level. The industrial production and application of high-performance continuous alumina fibers in China is still a technical problem. The related exploration is still based on laboratory research and development. Regarding the high thermal stability of continuous alumina fibers research is blank.

Since the creep rate of oxide ceramic fibers increases with decreasing grain size, the creep resistance of commercially fine-grained oxide fibers is low. Current commercial oxide ceramic fibers not only tend to creep under mechanical stress above 1100°C, but are also prone to embrittlement due to grain growth. Therefore, the current commercial oxide ceramic fibers cannot meet the increasing demand for chemical and thermal stability applications, such as long-term use in high temperature, steam and other environments, such as literature [see: CLAUSS B.Fibers for ceramics matrix composites [M]. Wiley-VCH; Ceramic Matrix Composites, 2008.]. Therefore, it is necessary to research and develop a high temperature resistant alumina fiber preparation method.

SUMMARY OF THE INVENTION

In view of the above technical problems, the purpose of the present invention is to provide a high temperature resistant rare earth lanthanum oxide doped alumina fiber and a preparation method thereof; The high temperature stability of rare earth lanthanum oxide doped alumina is significantly improved.

In order to achieve the above object, the present invention adopts the following technical solutions:

The present invention is a rare earth lanthanum oxide doped alumina fiber. The rare earth lanthanum oxide doped alumina fiber is composed of an alumina fiber matrix and rare earth lanthanum oxide dispersed in the alumina matrix.

The present invention provides an alumina fiber doped with rare earth lanthanum oxide. The inventors find that the alumina fiber obtained by doped rare earth lanthanum oxide exhibits a very good retention rate of tensile strength at room temperature after being kept at high temperature for a long time. In the actual exploration process, people also tried many other oxides to de-dope alumina fibers, and finally found that lanthanum oxide doping has the best performance.

In a preferred solution, the doping amount of the rare earth lanthanum oxide is less than or equal to 1% of the mass of the alumina matrix.

The doping amount of rare earth lanthanum oxide needs to be appropriate. If it exceeds 1%, the morphology of part of the prepared alumina will change, such as forming long strips or flakes.

Further preferably, the doping amount of the rare earth lanthanum oxide is 0.2% to 1% of the mass of the alumina matrix.

In a preferred solution, the single-filament tensile strength of the rare earth lanthanum oxide-doped alumina fiber is 1.0-2.5GPa; the strength retention rate can reach more than 80% after heat treatment in an air environment of 1100° C. for 10 hours.

A preparation method of rare earth lanthanum oxide-doped alumina fiber of the present invention comprises the following steps: adding aluminum powder into a carboxylic acid solution in batches to obtain a mixture, reacting, and adding dilute nitric acid and a lanthanum source in the reaction process, After the reaction is completed, an aluminum sol is obtained, and the aluminum sol, the silica sol, the iron sol, and the spinning aid solution are mixed, concentrated to obtain a gel, and dry-spun to obtain a gel precursor fiber, which is obtained by pre-sintering and high-temperature sintering. Alumina fibers doped with rare earth lanthanum oxide.

In a preferred solution, the particle size of the aluminum powder is 1-3 μm.

In a preferred solution, the carboxylic acid in the carboxylic acid solution is selected from at least one of formic acid and acetic acid. In the carboxylic acid solution, the volume ratio of the carboxylic acid to the solvent is 1:5.8-6.2, and the solvent is water .

Further preferably, the acid in the carboxylic acid solution is selected from formic acid and acetic acid, and the volume ratio of formic acid and acetic acid is 1:0.8-1.5.

The inventors found that when the acid in the carboxylic acid solution is selected from formic acid and acetic acid, the prepared aluminum sol has better spinnability.

In a preferred solution, the solid-liquid mass-volume ratio of the aluminum powder to the carboxylic acid is 500 g: 800-1200 ml.

In a preferred solution, the reaction temperature is 80-90° C., and the reaction time is 20-28 h.

In a preferred solution, in the dilute nitric acid, the mass fraction of nitric acid is 1-3 wt%.

In a preferred solution, the liquid-solid volume-to-mass ratio of the dilute nitric acid to the aluminum powder is 1000-1500ml:500g.

In a preferred solution, the dilute nitric acid is added to the mixture by dropwise addition.

In a preferred solution, the lanthanum source is selected from lanthanum nitrate hexahydrate, and the added amount of the lanthanum source is lanthanum oxide/alumina oxide ≦1%, preferably 0.2% to 1%.

In a preferred solution, the lanthanum source is dissolved in water and then added dropwise to the mixture.

In the present invention, the timing of adding the lanthanum source has a great influence on the properties of the final doped alumina fiber. Only in the process of preparing the aluminum sol, the aluminum powder is added to the carboxylic acid in batches, and the aluminum powder is added after the completion of the addition. Then, in the process of the reaction, adding Lanyuan can obtain the doped alumina fibers with the best performance. If Lanyuan is added before the addition of aluminum powder is completed, it will interfere with the hydrolysis of aluminum powder, resulting in the preparation of The alumina sol becomes turbid, and the properties of the final doped alumina fibers will decrease; in addition, if the lanthanum source and silica sol are added together, the obtained fiber cross-sectional structure has a network-like porous structure, and the density is poor. The properties of the doped alumina fibers are degraded.

In a preferred solution, the added amount of the iron sol is 5-10% by weight of the mass of the aluminum sol, preferably 8-10%.

In the present invention, the used iron sol is prepared by the hydrolysis reaction of ammonium bicarbonate and ferric nitrate nonahydrate in a molar ratio of 5:2, the reaction temperature ranges from 40 to 70°C, and the reaction time is 1 to 2 hours.

In the present invention, iron sol is used as a nucleating agent to provide nucleation sites to speed up the crystallization rate and increase the nucleation density of crystal grains, so that the initial crystal grains are finer during crystallization; of course, the amount of iron sol added needs to be effectively controlled. Too much will induce unfavorable elongated or plate-like grains, and too little addition will lead to insufficient nucleation density of grains, and the size of the prepared grains will be too large.

In a preferred solution, the amount of the silica sol added is 0.1-0.5 wt % of the mass of the aluminum sol.

In the present invention, the addition of silica sol as a growth inhibitor is to inhibit the growth rate of alumina grains after the formation of alumina grains and prevent the grains from growing too fast; of course, the addition amount of silica sol also needs to be effectively controlled, and the addition amount of silica sol is too large It will form other phase compositions with alumina, and if it is too small, the effect of inhibiting the formation of alumina grains will not be obvious.

In a preferred solution, the added amount of the spinning aid solution is 3-10 wt % of the mass of the aluminum sol.

In a preferred solution, the spinning aid solution is selected from PVP and/or PVB solutions, and the mass fraction of the spinning aid in the spinning aid solution is 8-12 wt %.

In a preferred solution, the pre-sintering temperature is 20-600° C., preferably 400-600° C., the heating rate is 1-2.5° C./min, and the pre-sintering time is 3-5 h.

In a preferred solution, the high-temperature sintering temperature is 1100-1600° C., preferably 1200-1400° C., and the high-temperature sintering time is 0.017-1 h.

In the present invention, after the pre-sintering is completed, the furnace is cooled, and then the temperature is re-heated for high-temperature sintering. The inventor found that this sintering method has better performance of the final product.

In the present invention, the heat treatment process of the strength retention rate is 10h in an air environment of 1100°C.

Principles and Advantages

In the preparation method of the present invention, a sol-gel method is adopted, and by adding aluminum powder in batches, dilute nitric acid (or hydrochloric acid, etc.) is used as a reaction assistant, and aluminum powder is reacted with formic acid and acetic acid to prepare aluminum carboxylate sol. In the reaction process of forming aluminum carboxylate sol, rare earth lanthanum oxide is added, and then PVP (or PVB, etc.) is used as spinning aid, iron sol as nucleating agent and silica sol as growth inhibitor to prepare alumina fiber.

The beneficial effects of the present invention are:

(1) The present invention innovatively introduces rare earth lanthanum oxide and its corresponding doping method into the alumina fiber. Compared with the undoped rare earth lanthanum oxide, the high temperature stability of the alumina fiber is significantly improved. The high temperature stability of fibers provides an effective research idea.

(2) The current commercial oxide ceramic fibers cannot meet the increasing demands in chemical and thermal stability applications. In view of this problem, the high temperature resistant fine-grained dense-structure alumina fiber prepared by the present invention provides a Effective research ideas and programs.

(3) The present invention adopts the sol-gel method to prepare high-temperature-resistant alumina fiber, which has low equipment requirements, simple operation, and is conducive to industrial application, and can be applied to the fields of national defense, military industry, aerospace and the like.

Description of drawings

FIG. 1 is a microstructure diagram (SEM) of the alumina fiber not doped with rare earth lanthanum oxide in Example 1 at high temperature.

FIG. 2 is a microstructure (SEM) image of the alumina fiber doped with 0.2 wt. % rare earth lanthanum oxide at high temperature in Example 3. FIG.

The alumina grain structure in Figure 1 shows growth and coarsening characteristics (corresponding to the red circle mark) under high temperature heat preservation. At this time, the alumina grains begin to grow abnormally, and the high temperature performance decreases, while the alumina grains in Figure 2 The structure does not have such characteristics, indicating that the high temperature resistance is effectively improved after the addition of rare earth lanthanum oxide.

FIG. 3 is a microstructure diagram (SEM) of the alumina fiber not doped with rare earth lanthanum oxide in Example 8. FIG.

FIG. 4 is a microstructure image (SEM) of the alumina fiber doped with 0.2 wt. % rare earth lanthanum oxide in Example 9. FIG.

FIG. 5 is a microstructure diagram (SEM) of the alumina fiber not doped with rare earth lanthanum oxide in Example 8 at high temperature.

FIG. 6 is a microstructure (SEM) image of the alumina fiber doped with 0.2 wt. % rare earth lanthanum oxide at high temperature in Example 9. FIG.

The alumina grain structure in Figure 5 shows serious growth and coarsening characteristics under high temperature heat preservation. At this time, the alumina grains experience serious abnormal growth and the high temperature performance drops sharply, while the alumina grain structure in Figure 6 has no obvious growth. Such characteristics indicate that the high temperature resistance is effectively improved after the addition of rare earth lanthanum oxide.

FIG. 7 shows the strength retention rate at room temperature after high temperature heat treatment of alumina fibers without lanthanum oxide and doped with 0.2wt.% lanthanum oxide in Example 8 and Example 9,

It can be seen from Figure 7 that the room temperature strength retention rate of alumina fibers doped with 0.2wt.% lanthanum oxide is improved, which also shows that the high temperature resistance performance is effectively improved after the addition of rare earth lanthanum oxide.

Detailed ways

Example 1 (comparative example)

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) In the reaction process, 1200ml (mass fraction is 2wt%) of dilute nitric acid is used as a reaction assistant, and after adding aluminum powder, dilute nitric acid is added dropwise through a separating funnel into the reaction kettle to participate in the reaction.

(3) after the reaction is completed, stop heating, stop stirring, and filter after the aluminum sol to be clarified is cooled to room temperature;

(4) prepare 400g (mass fraction is 5wt%) of PVP spinning aid solution in turn, 5wt% iron sol nucleating agent (prepared by the hydrolysis reaction of ammonium bicarbonate and ferric nitrate nonahydrate in molar ratio 5:2, reaction The temperature is 40°C, the reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor;

(5) weighing 8000g of aluminum sol, 12g of silica sol, 400g of iron sol, and 400g of PVP solution, poured it into a glass concentrating bottle in turn and stirred, and mixed the materials for 12 hours to form a uniform mixed solution;

(6) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability to become a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80μ silk; the length of the tunnel: 3m; the temperature of the tunnel: 120°C; the winding speed of the winder: 60r/min) to obtain the gel precursor fiber;

(7) Alumina fibers are obtained after the gel precursor fibers undergo two-stage sintering processes of pre-sintering and high-temperature sintering. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high-temperature sintering temperature is 1400 °C. ℃, keep warm for 90min.

The fiber prepared in this example has a larger grain size, an average particle size greater than 500 nm, a single filament tensile strength of about 611 MPa, and relatively poor microstructure stability at high temperature (see Figure 1).

Example 2

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) In the reaction process, 1200ml of 2wt% dilute nitric acid was used as a reaction assistant, and after adding the aluminum powder, dilute nitric acid was added dropwise through a separatory funnel into the reaction kettle to participate in the reaction.

(3) weigh 1.849g of lanthanum nitrate hexahydrate (mass ratio is 0.1wt%, and the mass is converted by the molar ratio of lanthanum oxide and alumina) in the reaction process, and stir with a certain amount of deionized water after adding the aluminum powder Dissolve and pour into the reaction kettle to participate in the reaction;

(4) after the reaction is completed, stop heating, stop stirring, and filter after the aluminum sol to be clarified is cooled to room temperature;

(5) prepare 400g successively, 5wt% of PVP spinning aid solution, 5wt% iron sol nucleating agent (made by hydrolysis reaction of ammonium bicarbonate and ferric nitrate nonahydrate in a molar ratio of 5:2, and the reaction temperature is 40° C. , the reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor;

(6) weighing 8000g of aluminum sol, 12g of silica sol, 400g of iron sol, and 400g of PVP solution, poured it into a glass concentrating bottle successively and stirred, and mixed the materials for 12 hours to form a uniform mixed solution;

(7) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability and becomes a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80 μm; the length of the tunnel: 3 m; the temperature of the tunnel: 120 ° C; the winding speed of the winder: 60 r/min) to obtain the gel precursor fiber;

(8) Alumina fibers with high temperature stability are obtained after the pre-sintering and high-temperature sintering of the gel precursor fibers. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high temperature The sintering temperature was 1400°C, and the temperature was kept for 90 minutes.

The fiber prepared in this example has a larger grain size, an average particle size of about 400 nm, and a single-filament tensile strength of about 655 MPa, but the microstructure stability is improved at high temperature.

Example 3

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) In the reaction process, 1200ml of 2wt% dilute nitric acid was used as a reaction assistant, and after adding the aluminum powder, dilute nitric acid was added dropwise through a separatory funnel into the reaction kettle to participate in the reaction.

(3) take by weighing 3.69g of lanthanum nitrate hexahydrate (mass ratio is 0.2wt%, the mass is converted by the molar ratio of lanthanum oxide and alumina) in the reaction process, stir with a certain amount of deionized water after adding the aluminum powder Dissolve and pour into the reaction kettle to participate in the reaction;

(4) after the reaction is completed, stop heating, stop stirring, and filter after the aluminum sol to be clarified is cooled to room temperature;

(5) prepare successively 400g 5wt% PVP spinning aid solution, 5wt% iron sol nucleating agent (made by hydrolysis reaction of ammonium bicarbonate and ferric nitrate nonahydrate in molar ratio 5:2, temperature of reaction is 40 ℃, The reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor;

(6) weighing 8000g of aluminum sol, 12g of silica sol, 400g of iron sol, and 400g of PVP solution, poured it into a glass concentrating bottle successively and stirred, and mixed the materials for 12 hours to form a uniform mixed solution;

(7) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability and becomes a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80 μm; the length of the tunnel: 3 m; the temperature of the tunnel: 120 ° C; the winding speed of the winder: 60 r/min) to obtain the gel precursor fiber;

(8) Alumina fibers with high temperature stability are obtained after the pre-sintering and high-temperature sintering of the gel precursor fibers. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high temperature The sintering temperature was 1400°C, and the temperature was kept for 90 minutes.

The fiber prepared in this example has a larger grain size, an average particle size of about 400 nm, and a single-filament tensile strength of about 587 MPa, but the microstructure stability is improved at high temperature (see Figure 2).

Example 4 (comparative example)

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) take 1200ml of 2wt% dilute nitric acid as a reaction aid in the reaction process, after adding the aluminum powder, add dilute nitric acid dropwise into the reactor through a separatory funnel to participate in the reaction; (3) after the reaction is completed, stop heating and stop stirring , the aluminum sol to be clarified is cooled to room temperature and filtered;

(4) 3.69g of lanthanum nitrate hexahydrate (mass ratio is 0.2wt%, and the mass is converted according to the molar ratio of lanthanum oxide and alumina), 400g of 5wt% PVP spinning aid solution, 5wt% iron sol nucleation solution are prepared in turn agent (prepared by the hydrolysis reaction of ammonium bicarbonate and ferric nitrate nonahydrate in a molar ratio of 5:2, the reaction temperature is 40 ° C, the reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor ;

(5) weighing 8000g of aluminum sol, 3.69g of lanthanum nitrate hexahydrate, 28g of silica sol, 52g of iron sol, 400g of PVP solution, poured into a glass concentrating bottle successively and stirred, and mixed materials for several hours to form a uniform mixed solution;

(6) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability to become a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80 μm; the length of the tunnel: 3 m; the temperature of the tunnel: 120 ° C; the winding speed of the winder: 60 r/min) to obtain the gel precursor fiber;

(7) Alumina fibers with high temperature stability are obtained after the pre-sintering and high-temperature sintering of the gel precursor fibers. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high temperature The sintering temperature was 1400°C, and the temperature was kept for 90 minutes.

In this example, lanthanum nitrate hexahydrate is added together with silica sol, etc., and the obtained fiber cross-sectional structure has a network-like porous structure with poor compactness.

Example 5

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) In the reaction process, 1200ml of 2wt% dilute nitric acid was used as a reaction assistant, and after adding the aluminum powder, dilute nitric acid was added dropwise through a separatory funnel into the reaction kettle to participate in the reaction.

(3) in the reaction process, take by weighing 5.549g of lanthanum nitrate hexahydrate (the mass ratio is 0.3wt%, and the mass is converted by the molar ratio of lanthanum oxide and aluminum oxide), and stir with a certain amount of deionized water after adding the aluminum powder Dissolve and pour into the reaction kettle to participate in the reaction;

(4) after the reaction is completed, stop heating, stop stirring, and filter after the aluminum sol to be clarified is cooled to room temperature;

(5) prepare successively 400g 5wt% PVP spinning aid solution, 5wt% iron sol nucleating agent (made by hydrolysis reaction of ammonium bicarbonate and ferric nitrate nonahydrate in molar ratio 5:2, temperature of reaction is 40 ℃, The reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor;

(6) weighing 8000g of aluminum sol, 12g of silica sol, 400g of iron sol, and 400g of PVP solution, poured it into a glass concentrating bottle successively and stirred, and mixed the materials for 12 hours to form a uniform mixed solution;

(7) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability and becomes a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80 μm; the length of the tunnel: 3 m; the temperature of the tunnel: 120 ° C; the winding speed of the winder: 60 r/min) to obtain the gel precursor fiber;

(8) Alumina fibers with high temperature stability are obtained after the pre-sintering and high-temperature sintering of the gel precursor fibers. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high temperature The sintering temperature was 1400°C, and the temperature was kept for 90 minutes.

The fiber prepared in this example has a larger grain size, an average particle size of about 400 nm, and a single-filament tensile strength of about 684 MPa, but the microstructure stability is improved at high temperature.

Example 6

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) In the reaction process, 1200ml of 2wt% dilute nitric acid was used as a reaction assistant, and after adding the aluminum powder, dilute nitric acid was added dropwise through a separatory funnel into the reaction kettle to participate in the reaction.

(3) in the reaction process, take by weighing 9.459g of lanthanum nitrate hexahydrate (the mass ratio is 0.5wt%, and the mass is converted by the molar ratio of lanthanum oxide and aluminum oxide), and stir with a certain amount of deionized water after adding the aluminum powder Dissolve and pour into the reaction kettle to participate in the reaction;

(4) after the reaction is completed, stop heating, stop stirring, and filter after the aluminum sol to be clarified is cooled to room temperature;

(5) prepare successively 400g 5wt% PVP spinning aid solution, 5wt% iron sol nucleating agent (made by hydrolysis reaction of ammonium bicarbonate and ferric nitrate nonahydrate in molar ratio 5:2, temperature of reaction is 40 ℃, The reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor;

(6) weighing 8000g of aluminum sol, 12g of silica sol, 400g of iron sol, and 400g of PVP solution, poured it into a glass concentrating bottle successively and stirred, and mixed the materials for 12 hours to form a uniform mixed solution;

(7) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability and becomes a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80 μm; the length of the tunnel: 3 m; the temperature of the tunnel: 120 ° C; the winding speed of the winder: 60 r/min) to obtain the gel precursor fiber;

(8) Alumina fibers with high temperature stability are obtained after the pre-sintering and high-temperature sintering of the gel precursor fibers. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high temperature The sintering temperature was 1400°C, and the temperature was kept for 90 minutes.

The fiber prepared in this example has a larger grain size, an average particle size of about 400 nm, and a single-filament tensile strength of about 664 MPa, but the microstructure stability is improved at high temperature.

Example 7

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) In the reaction process, 1200ml of 2wt% dilute nitric acid was used as a reaction assistant, and after adding the aluminum powder, dilute nitric acid was added dropwise through a separatory funnel into the reaction kettle to participate in the reaction.

(3) in the reaction process, take by weighing 18.495g of lanthanum nitrate hexahydrate (the mass ratio is 1.0wt%, and the mass is converted by the molar ratio of lanthanum oxide and aluminum oxide), and stir with a certain amount of deionized water after adding the aluminum powder Dissolve and pour into the reaction kettle to participate in the reaction;

(4) after the reaction is completed, stop heating, stop stirring, and filter after the aluminum sol to be clarified is cooled to room temperature;

(5) prepare successively 400g 5wt% PVP spinning aid solution, 5wt% iron sol nucleating agent (made by hydrolysis reaction of ammonium bicarbonate and ferric nitrate nonahydrate in molar ratio 5:2, temperature of reaction is 40 ℃, The reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor;

(6) weighing 8000g of aluminum sol, 12g of silica sol, 400g of iron sol, and 400g of PVP solution, poured it into a glass concentrating bottle successively and stirred, and mixed the materials for 12 hours to form a uniform mixed solution;

(7) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability and becomes a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80 μm; the length of the tunnel: 3 m; the temperature of the tunnel: 120 ° C; the winding speed of the winder: 60 r/min) to obtain the gel precursor fiber;

(8) Alumina fibers with high temperature stability are obtained after the pre-sintering and high-temperature sintering of the gel precursor fibers. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high temperature The sintering temperature was 1400°C, and the temperature was kept for 90 minutes.

The fiber prepared in this example has a larger grain size, an average particle size of about 400 nm, and a single-filament tensile strength of about 667 MPa, but the microstructure stability is improved at high temperature.

Example 8 (comparative example)

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) In the reaction process, 1200ml of 2wt% dilute nitric acid was used as a reaction assistant, and after adding the aluminum powder, dilute nitric acid was added dropwise through a separatory funnel into the reaction kettle to participate in the reaction.

(3) after the reaction is completed, stop heating, stop stirring, and filter after the aluminum sol to be clarified is cooled to room temperature;

(4) prepare successively 400g 5wt% PVP spinning aid solution, 10wt% iron sol nucleating agent (made by ammonium bicarbonate and ferric nitrate nonahydrate molar ratio 5:2 hydrolysis reaction, temperature of reaction is 40 ℃, The reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor;

(5) weighing 8000g of aluminum sol, 12g of silica sol, 800g of iron sol, and 400g of PVP solution, poured it into a glass concentrating bottle in turn and stirred, and mixed the materials for 12 hours to form a uniform mixed solution;

(6) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability to become a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80 μm; the length of the tunnel: 3 m; the temperature of the tunnel: 120 ° C; the winding speed of the winder: 60 r/min) to obtain the gel precursor fiber;

(7) Alumina fibers are obtained after the gel precursor fibers undergo two-stage sintering processes of pre-sintering and high-temperature sintering. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high-temperature sintering temperature is 1400 °C. ℃, keep warm for 5min;

(8) The alumina fibers prepared in step (7) are subjected to high temperature and short-term heat preservation treatment, and the heat treatment process: heat preservation in an air environment of 1400 ° C for 20 minutes; (9) The alumina fibers prepared in step (7) are subjected to high temperature and long-term heat preservation Treatment, test the strength retention rate after cooling with the furnace, heat treatment process: heat preservation in an air environment of 1100 ° C for 10 hours.

In this example, by increasing the content of iron sol, the prepared fiber has a smaller grain size, with an average particle size of less than 200 nm (see Figure 3), and the highest tensile strength of the monofilament is about 1.36 GPa, but the microstructure stability at high temperature is relatively poor. (see Figure 5), the strength retention rate was about 60% after heat treatment at 1100 °C for 10 h (see Figure 7).

Example 9

(1) Using the sol-gel method, pour 500g of aluminum powder (Aladdin, 1-3 μm) into a reactor containing 6000ml of deionized water in three batches every one hour in turn with 500ml of formic acid (Aladdin), 550ml Acetic acid (Aladdin) is mixed to obtain a mixture, which is reacted at 80 ° C for 40 hours to generate aluminum carboxylate sol;

(2) In the reaction process, 1200ml of 2wt% dilute nitric acid was used as a reaction assistant, and after adding the aluminum powder, dilute nitric acid was added dropwise through a separatory funnel into the reaction kettle to participate in the reaction.

(3) take by weighing 3.69g of lanthanum nitrate hexahydrate (mass ratio is 0.2wt%, and the mass is converted by the molar ratio of lanthanum oxide and alumina) in the reaction process, stir with a certain amount of deionized water after adding the aluminum powder Dissolve and pour into the reaction kettle to participate in the reaction;

(4) after the reaction is completed, stop heating, stop stirring, and filter after the aluminum sol to be clarified is cooled to room temperature;

(5) prepare successively 400g 5wt% PVP spinning aid solution, 10wt% iron sol nucleating agent (made by ammonium bicarbonate and ferric nitrate nonahydrate molar ratio 5:2 hydrolysis reaction, temperature of reaction is 40 ℃, The reaction time is 1.5h), 0.15wt% silica sol (Aladdin, 30wt%) growth inhibitor;

(6) weighing 8000g of aluminum sol, 12g of silica sol, 800g of iron sol, and 400g of PVP solution, poured it into a glass concentrating bottle successively and stirred, and mixed the materials for 12 hours to form a uniform mixed solution;

(7) The mixed solution after stirring is distilled by a rotary evaporator, and it is concentrated to a viscosity with a certain spinnability and becomes a gel, and then the gel is dry-spun (spinning kettle temperature: 50 ° C; The diameter of the spinneret: 80 μm; the length of the tunnel: 3 m; the temperature of the tunnel: 120 ° C; the winding speed of the winder: 60 r/min) to obtain the gel precursor fiber;

(8) Alumina fibers are obtained after the gel precursor fibers undergo two-stage sintering processes of pre-sintering and high-temperature sintering. The pre-sintering temperature is 450 °C, the heating rate is 2 °C/min, the time is 3.6 h, and the high-temperature sintering temperature is 1400 °C. ℃, keep warm for 5min;

(9) The alumina fibers prepared in step (8) are subjected to high temperature and short-term heat preservation treatment, and the heat treatment process: heat preservation in an air environment of 1400 ° C for 20 minutes;

(10) The alumina fiber prepared in step (8) is kept at high temperature for a long time, and the strength retention rate is tested after cooling in the furnace.

In this example, by increasing the content of iron sol, the prepared fibers have a smaller grain size and an average particle size of less than 200 nm (see Figure 4), the highest tensile strength of the monofilament is about 1.37 GPa, and the microstructure stability at high temperature is improved ( See Fig. 6), the strength retention rate is about 87% after heat treatment at 1100 °C for 10 h (see Fig. 7).

The above-mentioned examples only express the embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the present invention. The rare earth lanthanum oxide is used as a dopant to modify the oxide. Aluminum, which can be replaced by other elements with the same effect or rare earth oxides, such as yttrium element or rare earth cerium oxide, etc. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, the specific embodiments of the present invention can be modified or some technical features can be equivalently replaced , which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the claims.

Claims (10)

1. A rare earth lanthanum oxide doped alumina fiber is characterized in that: the rare earth lanthanum oxide doped alumina fiber consists of an alumina fiber matrix and rare earth lanthanum oxide dispersed in the alumina matrix.

2. The rare earth lanthanum oxide doped alumina fiber of claim 1, wherein: the doping amount of the rare earth lanthanum oxide is less than or equal to 1 percent of the mass of the alumina matrix.

3. A method of preparing a rare earth lanthanum oxide doped alumina fibre as claimed in claim 1 or 2, characterized in that: the method comprises the following steps: adding aluminum powder into a carboxylic acid solution in batches to obtain a mixture, reacting, adding dilute nitric acid and a lanthanum source in the reaction process, obtaining aluminum sol after the reaction is finished, mixing the aluminum sol, silica sol, iron sol and a spinning aid solution, concentrating to obtain gel, performing dry spinning to obtain gel precursor fiber, and performing presintering and high-temperature sintering to obtain the rare earth lanthanum oxide doped alumina fiber.

4. The method for preparing the rare earth lanthanum oxide doped alumina fiber according to claim 3, wherein the method comprises the following steps:

the particle size of the aluminum powder is 1-3 mu m.

The carboxylic acid in the carboxylic acid solution is at least one selected from formic acid and acetic acid, the volume ratio of the carboxylic acid to a solvent in the carboxylic acid solution is 1: 5.8-6.2, and the solvent is water;

the solid-liquid mass volume ratio of the aluminum powder to the carboxylic acid is 500 g: 800-1200 ml.

5. The method for preparing the rare earth lanthanum oxide doped alumina fiber according to claim 3, wherein the method comprises the following steps:

the reaction temperature is 80-90 ℃, and the reaction time is 20-28 h.

6. The method for preparing the rare earth lanthanum oxide doped alumina fiber according to claim 3, wherein the method comprises the following steps: in the dilute nitric acid, the mass fraction of nitric acid is 1-3 wt%;

the liquid-solid volume mass ratio of the dilute nitric acid to the aluminum powder is 1000-1500 ml: 500g of the total weight of the mixture is 500g,

and the dilute nitric acid is added into the mixture in a dropwise manner.

7. The method for preparing the rare earth lanthanum oxide doped alumina fiber according to claim 3, characterized in that: the lanthanum source is selected from lanthanum nitrate hexahydrate, the addition amount of the lanthanum source is less than or equal to 1 percent according to lanthanum oxide/aluminum oxide,

the lanthanum source was dissolved in water and added dropwise to the mixture.

8. The method for preparing the rare earth lanthanum oxide doped alumina fiber according to claim 3, wherein the method comprises the following steps: the adding amount of the iron sol is 5-10 wt% of the mass of the aluminum sol;

the adding amount of the silica sol is 0.1-0.5 wt% of the mass of the aluminum sol.

9. The method for preparing the rare earth lanthanum oxide doped alumina fiber according to claim 3, wherein the method comprises the following steps: the addition amount of the spinning auxiliary agent solution is 3-10 wt% of the mass of the alumina sol;

the spinning aid solution is selected from PVP and/or PVB solution, and the mass fraction of the spinning aid in the spinning aid solution is 8-12 wt%.

10. The method for preparing the rare earth lanthanum oxide doped alumina fiber according to claim 3, wherein the method comprises the following steps: the pre-sintering temperature is 20-600 ℃, the heating rate is 1-2.5 ℃/min, and the pre-sintering time is 3-5 h;

the high-temperature sintering temperature is 1100-1600 ℃, and the high-temperature sintering time is 0.017-1 h.

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