阅读说明：本技术 耐高温超轻氧化铝陶瓷纤维及其溶胶-凝胶制备方法 (High-temperature-resistant ultralight alumina ceramic fiber and sol-gel preparation method thereof ) 是由 马小民 张春苏 李富萍 陈卫东 张迎锋 吴南春 于 2020-05-20 设计创作，主要内容包括：本发明公开了一种耐高温超轻氧化铝陶瓷纤维及其溶胶-凝胶制备方法。所述制备方法包括：(1)将铝源、有机硅氧烷、水、酸催化剂充分溶解在有机溶剂中,于一定温度下反应一定时间,再加入钽化合物和铪化学物,搅拌均匀后制备得到纺丝原液；(2)配置一种碱性凝固浴,将纺丝原液连续纺至碱性凝固浴中,经溶胶-凝胶化学转变形成氧化铝凝胶纤维；(3)纺丝结束后经溶剂置换和超临界流体干燥,最后再分步煅烧,制备得到耐高温超轻氧化铝陶瓷纤维。该氧化铝陶瓷纤维含铝量大于95％,含少量硅、钽、铪元素,耐高温性能达到1500℃以上,纤维直径1-500微米,长度为1至500米,密度小于0.3g/cm<Sup>3</Sup>,生产工艺简单,易批量化生产,具有广阔的应用前景。(The invention discloses a high-temperature-resistant ultralight alumina ceramic fiber and a sol-gel preparation method thereof. The preparation method comprises the following steps: (1) fully dissolving an aluminum source, organosiloxane, water and an acid catalyst in an organic solvent, reacting for a certain time at a certain temperature, adding a tantalum compound and a hafnium chemical, and uniformly stirring to prepare a spinning solution; (2) preparing an alkaline coagulating bath, continuously spinning the spinning stock solution into the alkaline coagulating bath, and forming alumina gel fibers through sol-gel chemical transformation; (3) and after spinning is finished, performing solvent replacement and supercritical fluid drying, and finally calcining step by step to prepare the high-temperature-resistant ultralight alumina ceramic fiber. The alumina ceramic fiber contains more than 95 percent of aluminum, a small amount of silicon, tantalum and hafnium elements, has high temperature resistance of more than 1500 ℃, has the fiber diameter of 1-500 micrometers, the length of 1-500 meters and the density of less than 0.3g/cm 3 The production process is simple, the mass production is easy,has wide application prospect.)

1. The preparation method of the high-temperature-resistant ultralight alumina ceramic fiber is characterized by comprising the following synthetic steps of:

(1) fully dissolving an aluminum source, organosiloxane, water and an acid catalyst in an organic solvent, reacting for a certain time at a certain temperature, adding a tantalum compound and a hafnium chemical, and uniformly stirring to prepare a spinning solution;

(2) preparing an alkaline coagulating bath, continuously spinning the spinning stock solution into the alkaline coagulating bath, and forming alumina gel fibers through sol-gel chemical transformation;

(3) and (3) carrying out solvent replacement at room temperature, drying the alumina gel fiber by adopting a supercritical fluid technology, and then calcining step by step to prepare the high-temperature-resistant ultralight alumina ceramic fiber.

2. The method for preparing high temperature resistant ultra-light alumina ceramic fiber according to claim 1, wherein the aluminum source in step (1) comprises any one or a combination of two or more of aluminum powder, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, aluminum sulfide, aluminum isopropoxide and aluminum nitrate nonahydrate; and/or the organic siloxane comprises any one or the combination of more than two of ethyl orthosilicate, methyl triethoxysilane and methyl trimethoxysilane; and/or the dosage of the organic siloxane is 0.2 to 5 percent of the mass of the aluminum source.

3. The method for preparing the high-temperature-resistant ultra-light alumina ceramic fiber according to claim 1, wherein the water in the step (1) is any one of deionized water and distilled water; and/or the amount of said water is not limited; and/or the acid catalyst is one or the combination of more than two of phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, formic acid, propionic acid and oxalic acid; and/or the dosage of the acid catalyst is 1-10% of the mass of the organic siloxane.

4. The method for preparing high temperature resistant ultra-light alumina ceramic fiber according to claim 1, wherein the organic solvent of step (1) comprises any one or a combination of two or more of methanol, ethanol, isopropanol, propanol, butanol, tert-butanol, n-hexane, cyclohexane, n-heptane, acetonitrile, toluene, tetrahydrofuran, benzyl alcohol and perfluoroalkane; and/or the dosage of the organic solvent is 20-200% of the mass of the aluminum source.

5. The method for preparing the high temperature resistant ultra-light alumina ceramic fiber according to claim 1, wherein the reaction temperature in the step (1) is 40 ℃ to the boiling temperature of the solvent; and/or the reaction time is 5-24 hours.

6. The method for preparing the high-temperature-resistant ultra-light alumina ceramic fiber according to claim 1, wherein the tantalum compound in the step (1) is any one or a combination of more than two of tantalum powder, lithium tantalate, tantalum salt and organic tantalum complex; and/or the dosage of the tantalum compound is 0.1-2% of that of the aluminum source; and/or the hafnium compound is any one or the combination of more than two of hafnium oxide, hafnium tetrachloride, hafnium hydroxide, hydrated hafnium oxychloride and a complex formed by hafnium and fluoride; and/or the hafnium compound is 0.1-5% of the aluminum source.

7. The method for preparing the high-temperature-resistant ultra-light alumina ceramic fiber according to claim 1, wherein the solvent used in the alkaline coagulation bath in the step (2) is the same reagent as that used in the step (1); and/or the alkali comprises any one or the combination of more than two of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine and ammonium chloride; and/or the amount of base is not limited.

8. The method for preparing high temperature resistant ultra-light alumina ceramic fiber according to claim 1, wherein the solvent replacement of step (3) comprises: the solvent is any one of methanol, ethanol and acetone; the replacement time is 5-12 hours; the number of times of replacement is 3-4.

9. The method for preparing high temperature resistant ultra-light alumina ceramic fiber according to claim 1, wherein the gel fiber drying method of step (3) is supercritical fluid drying; the supercritical fluid comprises supercritical carbon dioxide, supercritical methanol and supercritical ethanol; the drying time is 5-24 hours; and/or the calcination step is not less than 2 times; and/or the calcining temperature is 800-1300 ℃; and/or the calcination time is 5-100 minutes.

10. A high temperature resistant ultra-light alumina ceramic fiber obtained by the method for preparing a high temperature resistant ultra-light alumina ceramic fiber according to any one of claims 1 to 9, characterized in that: the alumina ceramic fiber contains more than 95 percent of aluminum and a small amount of silicon, tantalum and hafnium elements, has high temperature resistance of more than 1500 ℃, has the fiber diameter of 1-500 micrometers, the length of 1-500 meters and the density of less than 0.3g/cm³。

Technical Field

The invention relates to synthesis and preparation of high-temperature-resistant ceramic fibers, in particular to a sol-gel preparation method of ultra-light alumina ceramic fibers, and belongs to the technical field of preparation of high-performance ceramic fibers.

Background

The alumina ceramic is a ceramic material taking alumina as a main component, has good conductivity, excellent mechanical strength and high temperature resistance, has the characteristics of good wear resistance, high hardness, light weight and the like, and is widely applied to the fields of national defense, aerospace, traffic, petroleum, buildings, automobiles, industry, special equipment and the like. The application in national economy and daily life is more and more extensive. The alumina ceramics are divided into a common type and a high-purity type from the aspect of composition: (1) the common alumina ceramic system is divided into 99 porcelain, 95 porcelain, 90 porcelain, 85 porcelain and other varieties according to different alumina contents, wherein the 99 alumina porcelain material is used for manufacturing a high-temperature crucible, a fire-resistant furnace tube and a special wear-resistant material; the 95 alumina porcelain is mainly used as a corrosion-resistant and wear-resistant part; 85, the ceramic is often mixed with part of talc, so that the mechanical strength is improved, and the ceramic can be sealed with metals such as molybdenum, niobium, tantalum and the like. (2) The high-purity alumina ceramic is a ceramic material with the alumina content of more than 99.9 percent. Structurally, alumina ceramics can be divided into bulk ceramics and ceramic fibers.

The alumina fiber is a novel high-performance inorganic ceramic fiber, and compared with non-oxide fibers such as carbon fiber and silicon carbide fiber, the alumina fiber not only has excellent performances such as high modulus, high strength and high temperature resistance, but also has good high-temperature oxidation resistance, corrosion resistance and electrical insulation, has good surface activity, and is easy to be compounded with polymers, metals and ceramic matrixes to form a plurality of composite materials with excellent performances. The alumina fiber has wide application in the fields of industrial high-temperature furnaces, aerospace, transportation and high and new science and technology. Because the melting point of alumina is as high as 2323 ℃, the melt viscosity is low, and the fiberizability is poor, the alumina fiber can not be prepared by a melting method, and at present, the following methods are mainly used: slurry process, sol-gel process, prepolymerization process, pycnometer process, impregnation process, melt spinning process, etc. The methods have the advantages and the disadvantages, but the use temperature of all the silicon oxide ceramic fibers is limited within 1500 ℃ so far, and the preparation threshold of the continuous filament is extremely high, so that the application of the continuous filament in some domestic important occasions is limited; on the other hand, alumina ceramics are generally used in the high-tech field as structural materials, have high density, are difficult to realize ultra-light weight, have high thermal conductivity, and do not have excellent thermal insulation performance.

Disclosure of Invention

Aiming at the defects and material limitations of the prior art, the invention adopts a sol-gel pore-forming technology and replaces an ultralight technology with mechanics, and mainly aims to provide the high-temperature-resistant ultralight alumina ceramic fiber and the preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows.

According to one aspect of the disclosure, a preparation method of a high-temperature-resistant ultra-light alumina ceramic fiber comprises the following synthesis steps:

(1) fully dissolving an aluminum source, organosiloxane, water and an acid catalyst in an organic solvent, reacting for a certain time at a certain temperature, adding a tantalum compound and a hafnium chemical, and uniformly stirring to prepare a spinning solution;

(2) preparing an alkaline coagulating bath, continuously spinning the spinning stock solution into the alkaline coagulating bath, and forming alumina gel fibers through sol-gel chemical transformation;

(3) and (3) carrying out solvent replacement at room temperature, drying the alumina gel fiber by adopting a supercritical fluid technology, and then calcining step by step to prepare the high-temperature-resistant ultralight alumina ceramic fiber.

According to at least one embodiment of the present disclosure, the aluminum source of step (1) comprises any one or a combination of two or more of aluminum powder, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, aluminum sulfide, aluminum isopropoxide, and aluminum nitrate nonahydrate; and/or the organic siloxane comprises any one or the combination of more than two of ethyl orthosilicate, methyl triethoxysilane and methyl trimethoxysilane; and/or the dosage of the organic siloxane is 0.2 to 5 percent of the mass of the aluminum source.

According to at least one embodiment of the present disclosure, the water in step (1) is any one of deionized water and distilled water; and/or the amount of said water is not limited; and/or the acid catalyst is one or the combination of more than two of phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, formic acid, propionic acid and oxalic acid; and/or the dosage of the acid catalyst is 1-10% of the mass of the organic siloxane.

According to at least one embodiment of the present disclosure, the organic solvent of step (1) includes any one or a combination of two or more of methanol, ethanol, isopropanol, propanol, butanol, tert-butanol, n-hexane, cyclohexane, n-heptane, acetonitrile, toluene, tetrahydrofuran, benzyl alcohol and perfluoroalkane; and/or the dosage of the organic solvent is 20-200% of the mass of the aluminum source.

According to at least one embodiment of the present disclosure, the reaction temperature of step (1) is from 40 ℃ to the boiling temperature of the solvent; and/or the reaction time is 5-24 hours.

According to at least one embodiment of the present disclosure, the tantalum compound of step (1) is any one or a combination of two or more of tantalum powder, lithium tantalate, tantalum salt and organic tantalum complex; and/or the dosage of the tantalum compound is 0.1-2% of that of the aluminum source; and/or the hafnium compound is any one or the combination of more than two of hafnium oxide, hafnium tetrachloride, hafnium hydroxide, hydrated hafnium oxychloride and a complex formed by hafnium and fluoride; and/or the hafnium compound is 0.1-5% of the aluminum source.

According to at least one embodiment of the present disclosure, the solvent used in the alkaline coagulation bath of step (2) is the same reagent as that used in step (1); and/or the alkali comprises any one or the combination of more than two of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine and ammonium chloride; and/or the amount of base is not limited.

According to at least one embodiment of the present disclosure, the gel spinning in the step (2) is wet spinning, and the temperature of the spinning solution is 10-120 ℃.

According to at least one embodiment of the present disclosure, the solvent replacement of step (3) comprises: the solvent is any one of methanol, ethanol and acetone; the replacement time is 5-12 hours; the number of times of replacement is 3-4.

According to at least one embodiment of the present disclosure, the gel fiber drying method of step (3) is supercritical fluid drying; the supercritical fluid comprises supercritical carbon dioxide, supercritical methanol and supercritical ethanol; the drying time is 5-24 hours; and/or the calcination step is not less than 2 times; and/or the calcining temperature is 800-1300 ℃; and/or the calcination time is 5-100 minutes.

According to another aspect of the present disclosure, a high temperature resistant ultra-light alumina ceramic fiber obtained by the preparation method of the high temperature resistant ultra-light alumina ceramic fiber is characterized in that: the alumina ceramic fiber contains more than 95 percent of aluminum and a small amount of silicon, tantalum and hafnium elements, has high temperature resistance of more than 1500 ℃, has the fiber diameter of 1-500 micrometers, the length of 1-500 meters and the density of less than 0.3g/cm³。

Compared with the prior art, the invention has the advantages that:

(1) the high-temperature-resistant and ultra-light alumina ceramic fiber has the components of tantalum, hafnium, silicon oxide and the like, has adjustable content and uniform distribution, can be effectively attached to the periphery of an aluminum crystal body, and inhibits the transformation and growth of crystal forms, so that the service temperature of the aluminum crystal body is increased to more than 1500 ℃, and the density of the aluminum crystal body is only 0.3g/cm at most³The density of the traditional alumina ceramic is less than 8 percent, and the weight reduction capacity reaches more than 92 percent.

(2) The preparation method of the high-temperature-resistant and ultra-light alumina ceramic fiber provided by the invention adopts a sol-gel spinning technology, can realize the regulation and control of the diameter and components of the alumina ceramic fiber, has infinite theoretical length, is mainly limited by spinning equipment, and simultaneously has abundant pore structures due to gel-gel transformation and a supercritical drying technology, and can play great application potential in the field of non-structural materials although the mechanical properties are reduced.

Drawings

FIG. 1 is a scanning electron microscope image of a high temperature resistant ultra-light alumina ceramic fiber according to example 1 of the present invention.

FIG. 2 is a scanning electron microscope image of the high temperature resistant ultra-light alumina ceramic fiber in example 2 of the present invention.

FIG. 3 is a scanning electron microscope image of the refractory ultralight alumina ceramic fiber of example 3 of the present invention.

FIG. 4 is a scanning electron microscope photograph of the refractory ultralight alumina ceramic fiber of example 4 of the present invention.

FIG. 5 is a scanning electron microscope photograph of the refractory ultralight alumina ceramic fiber of example 5 of the present invention.

FIG. 6 is a scanning electron microscope photograph of the refractory ultralight alumina ceramic fiber of example 6 of the present invention.

Detailed Description

In view of the deficiencies in the prior art, the inventors of the present invention have made extensive studies and extensive practices to provide technical solutions of the present invention.

One aspect of the embodiments of the present invention provides a method for preparing a high temperature resistant ultra-light alumina ceramic fiber, comprising three key steps:

(1) fully dissolving an aluminum source, organosiloxane, water and an acid catalyst in an organic solvent, reacting for a certain time at a certain temperature, adding a tantalum compound and a hafnium chemical, and uniformly stirring to prepare a spinning solution;

(2) preparing an alkaline coagulating bath, continuously spinning the spinning stock solution into the alkaline coagulating bath, and forming alumina gel fibers through sol-gel chemical transformation;

(3) and (3) carrying out solvent replacement at room temperature, drying the alumina gel fiber by adopting a supercritical fluid technology, and then calcining step by step to prepare the high-temperature-resistant ultralight alumina ceramic fiber.

In some embodiments, the aluminum source includes any one or a combination of two or more of aluminum powder, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, aluminum sulfide, aluminum isopropoxide, and aluminum nitrate nonahydrate, without being limited thereto.

Further, the organosiloxane includes any one or a combination of two or more of ethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane, and methyltrimethoxysilane, and is not limited thereto.

Furthermore, the dosage of the organic siloxane is 0.2 to 5 percent of the mass of the aluminum source.

Further, the water is any one of deionized water and distilled water, and is not limited thereto.

Further, the amount of the water is not limited.

Further, the acid catalyst is any one or a combination of two or more of phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, formic acid, propionic acid, and oxalic acid, and is not limited thereto.

Further, the dosage of the acid catalyst is 1-10% of the mass of the organic siloxane.

Further, the organic solvent includes any one or a combination of two or more of methanol, ethanol, isopropanol, propanol, butanol, t-butanol, n-hexane, cyclohexane, n-heptane, acetonitrile, toluene, tetrahydrofuran, benzyl alcohol and perfluoroalkane, and is not limited thereto.

Furthermore, the dosage of the organic solvent is 20-200% of the mass of the aluminum source.

Further, the reaction temperature is from 40 ℃ to the boiling point temperature of the solvent.

Further, the reaction time is 5-24 hours.

Further, the tantalum compound is any one or a combination of two or more of tantalum powder, lithium tantalate, a tantalum salt, and an organic tantalum complex, and is not limited thereto.

Further, the dosage of the tantalum compound is 0.1% -2% of that of the aluminum source.

Further, the hafnium compound is any one or a combination of two or more of hafnium oxide, hafnium tetrachloride, hafnium hydroxide, hafnium oxychloride hydrate, and a complex of hafnium and fluoride, and is not limited thereto.

Further, the hafnium compound is 0.1-5% of the aluminum source.

In some embodiments, the base catalyst of the coagulation bath includes any one or a combination of two or more of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine, and ammonium chloride, and is not limited thereto.

Further, the amount of the base is not limited.

Further, the solvent of the coagulation bath and the organic solvent used in step (1) remain the same.

Further, the temperature of the coagulating bath is 10-120 ℃.

In some embodiments, the solvent used for the gel solvent replacement includes methanol, ethanol, acetone, and is not limited thereto.

Further, the number of times of solvent replacement is 3 to 4.

Furthermore, each replacement time is 5-12 hours.

Further, the gel drying method is supercritical drying.

Further, the supercritical drying fluid includes, but is not limited to, supercritical carbon dioxide, supercritical methanol, supercritical ethanol.

Further, the drying time is 5-24 hours.

Further, the calcination step is not less than 2 times.

Further, the calcination temperature is 800-1300 ℃.

Further, the calcination time is 5-100 minutes.

In conclusion, the high-temperature-resistant and ultra-light alumina ceramic fiber is designed and synthesized through the structure, the components and the drying process, the alumina ceramic fiber contains more than 95 percent of aluminum and a small amount of silicon, tantalum and hafnium elements, the high-temperature resistance reaches more than 1500 ℃, the diameter of the fiber is 1-500 micrometers, the length of the fiber is 1-500 meters, and the density of the fiber is less than 0.3g/cm³。

The technical scheme of the invention is further explained in detail by a plurality of embodiments and the accompanying drawings. However, the examples are chosen only for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention.