CN113480299A

CN113480299A - Preparation method of low-cost mullite fiber

Info

Publication number: CN113480299A
Application number: CN202011353265.1A
Authority: CN
Inventors: 张铭霞; 王重海; 刘振; 王雪朋; 齐学礼; 程之强; 吕锋; 何子扬; 李茹; 徐浩南
Original assignee: Shandong Industrial Ceramics Research and Design Institute Co Ltd
Current assignee: Shandong Industrial Ceramics Research and Design Institute Co Ltd
Priority date: 2020-11-26
Filing date: 2020-11-26
Publication date: 2021-10-08
Also published as: CN113860862A

Abstract

The invention discloses a preparation method of low-cost mullite fiber, which comprises the steps of firstly preparing an aluminum carboxylate solution; preparing a silicon additive; and mixing the aluminum carboxylate solution with the silicon additive, reacting to obtain precursor sol, and concentrating and aging to obtain the mullite fiber. The method does not generate harmful gases such as chlorine, nitrogen dioxide, sulfur dioxide and the like in the production process, has low requirement on raw materials, is easy to store, can directly use the commercially available raw materials, solves the technical problem that the commercially available aluminum hydroxide raw materials cannot prepare the spinnable mullite fiber, and has simple preparation process and environmental protection.

Description

Preparation method of low-cost mullite fiber

Technical Field

The invention belongs to the field of inorganic nano material preparation, and particularly relates to a preparation method of low-cost mullite fiber.

Background

The mullite ceramic fiber is an engineering material with excellent comprehensive performance, can be used as a reinforcing component of materials such as ceramics, metals, plastics and the like, has the characteristics of high temperature resistance, corrosion resistance, high strength, good thermal shock resistance, good heat insulation performance and the like, and plays an important role in the fields of industry and aerospace.

In the prior art, a sol-gel method and an inorganic aluminum salt method are mostly adopted to prepare mullite fiber, and the preparation of precursor sol in the sol-gel method is the most critical process. In the prior art, aluminum hydroxide is also used as an aluminum source to prepare mullite fiber, but the process is complicated, the requirement on the activity of the raw material is extremely high, and the prepared mullite fiber does not have spinnability. In most processes for preparing spinnable mullite fiber, aluminum hydroxide and silica sol which are used as main raw materials must be prepared and used at the present time, so that the process flow and the preparation cost are increased, the quality requirements on the prepared aluminum hydroxide and silica sol are met, the activity of commercially available aluminum hydroxide is reduced due to long-time standing from preparation to market, and the silica-alumina sol prepared by using the aluminum hydroxide has no spinnability, so that the spinnable sol meeting the requirements cannot be prepared by using common raw materials which are sold on the same market.

The inorganic aluminum salt method is mainly to use aluminum powder and aluminum salt to prepare aluminum sol through high-temperature reflux, and then add silica sol to prepare mullite fiber, but dangerous hydrogen can be generated in the reaction process, and byproducts precipitated in the reaction process of some aluminum salts containing Cl and N can greatly pollute the environment.

Disclosure of Invention

In order to solve the technical problem, the method utilizes the aluminum carboxylate solution prepared from commercial aluminum hydroxide and organic acid, mixes the aluminum carboxylate solution with the silicon-containing additive, and obtains the spinnable mullite fiber after concentration and aging. The invention adopts the following technical scheme:

the preparation method of the low-cost mullite fiber is characterized by comprising the following steps of:

preparing an aluminum carboxylate solution in which Al is present in the form of multimers of Al8-18OX 12-27; wherein X is one or more of-COOH, -RCOO and-OOC-COOH;

preparing a silicon additive;

mixing the aluminum carboxylate solution with the silicon additive, reacting to obtain precursor sol, concentrating and aging to obtain spinnable mullite sol;

spinning the spinnable mullite sol to obtain mullite precursor fiber;

and (3) placing the mullite precursor fiber in a high-temperature furnace for heat treatment, then coating an organic alcohol or ester coating on the surface of the mullite precursor fiber subjected to heat treatment, and drying for 4-10 hours in a drying oven at 50-100 ℃ to obtain the mullite fiber.

Al_8-18OX_12-27The polymer polymerizes Al and short-chain carboxylic acid groups into long-chain aluminum carboxylates by virtue of coordination of Al and carboxylic acid groups, and the structure is the key point of sol spinnability.

Preferably, the preparing of the aluminum carboxylate solution comprises the steps of:

adding organic carboxylic acid into water at 50-80 ℃ to obtain organic carboxylic acid solution, and adding aluminum hydroxide powder into the organic carboxylic acid solution

Continuously stirring and condensing and refluxing the mixture solution at 100-200 ℃, reacting for 10-30 hours, and concentrating under the conditions that the temperature is 40-100 ℃ and the vacuum degree is 0.09-0.1 MPa to remove carboxylic acid to obtain an aluminum carboxylate solution;

wherein the molar ratio of the aluminum hydroxide powder to the organic carboxylic acid is 1: 1-3;

preferably, the organic carboxylic acid is one or more of formic acid, acetic acid, propionic acid, oxalic acid, malonic acid and citric acid.

Preferably, the method for preparing the silicon additive is as follows: mixing a silicon source and saturated monoacid in a molar ratio of 1: 1-3, performing ultrasonic dispersion for 30-60 min, and filtering and precipitating; adding a high-molecular additive into the clarified liquid, and mixing to obtain a silicon additive; wherein the amount of the polymer auxiliary agent is 0-5% of the mass of the silicon source.

Preferably, the silicon source is one or more of silica sol and liquid silica.

Preferably, the concentration aging temperature is 30-70 ℃; the vacuum degree is 0.09-0.1 MPa; the concentration and aging time is 4-8 h.

Preferably, the polymer auxiliary agent is one or more of lactic acid, glycerol, polyvinyl alcohol, polyethylene glycol, polyethylene oxide and methyl cellulose.

Preferably, the viscosity of the prepared spinnable mullite sol is 100-600 Pa.s.

Preferably, the heat treatment conditions are as follows: introducing oxygen at the room temperature of 600-750 ℃, and introducing nitrogen or air at the temperature of 600-750 ℃ to 1200-1400 ℃.

Preferably, the low cost mullite fiber is made according to the method of any of the preceding.

Compared with the prior art, the invention has the following beneficial effects:

the formation process of the aluminum carboxylate solution mainly comprises the reaction and polymerization of aluminum hydroxide and organic carboxylic acid, wherein three hydroxyl groups (OH) are arranged around Al in the aluminum hydroxide, the hydroxyl groups and carboxyl groups in the carboxylic acid are subjected to coupling reaction at high temperature, so that groups around the Al are changed into Al (HCOO) (RCOO) (OOC-COOH) with Al-O-C bonds, and after long-time high-temperature reflux, along with the continuous coupling of the groups around the Al, the groups around different Al are also coupled, so that-Al-O-C-O-Al-O-C-O-Al-bonds are formed, and finally Al in the aluminum carboxylate solution is Al-Al_8-18OX_12-27(wherein X is (HCOO) (RCOO) (OOC-COOH)), which is also a solHas spinnability. The method has no activity requirement on the used aluminum hydroxide, does not need to be prepared in advance, can directly use the commercially available aluminum hydroxide, reduces the cost of raw materials and simplifies the preparation process.

The production process of the invention does not generate harmful gases such as chlorine, nitrogen dioxide, sulfur dioxide and the like, has low requirement on raw materials, is easy to store, can directly use the commercially available raw materials, has simple preparation process and is green and environment-friendly. As shown in FIG. 5, the spinnable mullite fiber prepared by the invention has stable properties, good stability at room temperature, no obvious viscosity change even if the fiber is stored for 30 days, no gelation phenomenon occurs, the fiber can be stored for a long time, and the fiber does not aggregate and deteriorate.

Drawings

FIG. 1 is a nuclear magnetic resonance image of an aluminum carboxylate solution;

FIG. 2 is a diagram of a continuous ceramic fiber prepared by dry spinning mullite fiber;

FIG. 3 is an infrared test chart of an aluminum carboxylate solution;

FIG. 4 is a graph of the viscosity of a mullite sol;

FIG. 5 is a plot of viscosity versus time for each example-prepared sol;

FIG. 6 is a graph of heat treatment curves for each example;

Detailed Description

In order to better understand the technical scheme of the invention, the invention is further explained by combining the drawings and the specific embodiments in the specification.

Example 1:

adding formic acid and acetic acid into distilled water at 50 ℃, fully stirring and uniformly mixing, and then adding aluminum hydroxide powder. The molar ratio of aluminum hydroxide to formic acid and acetic acid was 1:1, the molar ratio of aluminum hydroxide to formic acid added for the second time was 1: 0.5. then, under the conditions of continuous stirring and condensation reflux at the temperature of 100 ℃, and under the conditions of 40 ℃ and the vacuum degree of 0.09MPa, concentrating the mixture solution to remove carboxylic acid, and reacting for 10 hours to prepare a transparent aluminum carboxylate solution; mixing liquid silicon dioxide and formic acid in a molar ratio of 1:1, performing ultrasonic dispersion for 30min, and filtering and precipitating; adding lactic acid, glycerol, polyvinyl butyral and polyvinyl alcohol into the clarified solution, and mixing;

as can be seen from the nuclear magnetic resonance spectrum of the aluminum carboxylate solution of fig. 1: prepared aluminum carboxylate solution as polymer Al_8- ₁₈OX_12-27Exist in the form of (1). From the infrared test chart of the aluminum carboxylate solution of FIG. 3, it can be seen that the functional group of the polymer exists in the form of a group such as (HCOO) (RCOO) (OOC-COOH).

The amount of the added auxiliary agent is 1 percent of the mass of the silicon dioxide; and mixing the aluminum carboxylate solution and the silicon-containing additive to ensure that the molar ratio of Al2O3 to SiO2 in the solution is 3: 2, and reacting to obtain precursor sol. And (3) concentrating and aging the precursor sol at the temperature of 30 ℃ and the vacuum degree of 0.09MPa to obtain the spinnable mullite sol with the viscosity of 100Pa & s. The viscosity curve of the mullite sol in FIG. 4 shows that the mullite sol prepared by the method has normal rheological property according to the relation curve between the shear rate and the sol viscosity. Then introducing oxygen at the temperature of between room temperature and 600 ℃, introducing nitrogen at the temperature of 1200 ℃, and obtaining the mullite precursor fiber with a heat treatment curve as shown in figure 6. Coating organic alcohol on the surface of the mullite precursor fiber, drying for 4 hours in a drying oven at 50 ℃, and as can be seen from the change curve of the viscosity of the sol prepared in figure 5 along with time, the viscosity of the prepared sol does not change obviously even if the sol is stored for 30 days, the sol does not generate gelation phenomenon, can be stored for a long time, does not aggregate and does not deteriorate; and finally, obtaining the mullite fiber shown in the figure 2 through dry spinning.

Example 2:

adding propionic acid and oxalic acid into distilled water at 65 ℃, fully stirring and uniformly mixing, and then adding aluminum hydroxide powder. The molar ratio of aluminum hydroxide to propionic acid and oxalic acid is 1:2, the molar ratio of aluminum hydroxide to acetic acid is 1: 1. then, continuously stirring and condensing the mixture solution under the conditions of 150 ℃, removing carboxylic acid by concentration under the conditions of 70 ℃ and 0.09MPa of vacuum degree, and reacting for 20 hours to prepare a transparent aluminum carboxylate solution; as can be seen from the nuclear magnetic resonance spectrum of the aluminum carboxylate solution of fig. 1: the prepared aluminum carboxylate solution exists in the form of polymer Al8-18OX 12-27. From the infrared test chart of the aluminum carboxylate solution of FIG. 3, it can be seen that the functional group of the polymer exists in the form of a group such as (HCOO) (RCOO) (OOC-COOH).

Then mixing the silica sol and acetic acid in a molar ratio of 1:2, carrying out ultrasonic dispersion for 45min, and filtering and precipitating; adding polyvinylpyrrolidone, polyethylene glycol and polyacrylic acid into the clarified solution, and mixing; the amount of the added auxiliary agent is 3 percent of the mass of the silicon dioxide; and mixing the aluminum carboxylate solution and the silicon-containing additive to ensure that the molar ratio of Al2O3 to SiO2 in the solution is 3: 2, and reacting to obtain precursor sol. And (3) concentrating and aging the precursor sol at the temperature of 50 ℃ and the vacuum degree of 0.09MPa to obtain the spinnable mullite sol with the viscosity of 350Pa & s. The viscosity curve of the mullite sol in FIG. 4 shows that the mullite sol prepared by the method has normal rheological property according to the relation curve between the shear rate and the sol viscosity. Then, oxygen gas was introduced at room temperature to 750 ℃ and nitrogen gas was introduced at 1400 ℃ and the treatment curve is shown in FIG. 6. Coating organic alcohol on the surface of the mullite precursor fiber, drying for 4 hours in a drying oven at 50 ℃, and as can be seen from the change curve of the viscosity of the sol prepared in figure 5 along with time, the viscosity of the prepared sol does not change obviously even if the sol is stored for 30 days, the sol does not generate gelation phenomenon, can be stored for a long time, does not aggregate and does not deteriorate; and finally, obtaining the mullite fiber shown in the figure 2 through dry spinning.

Example 3:

adding malonic acid and citric acid into distilled water at 80 ℃, fully stirring and uniformly mixing, and then adding aluminum hydroxide powder. The molar ratio of aluminum hydroxide to propionic acid and oxalic acid is 1:3, the molar ratio of aluminum hydroxide to acetic acid is 1: 2. then the mixture solution reacts for 30 hours at the temperature of 200 ℃ under the conditions of continuous stirring and condensation reflux to prepare transparent aluminum carboxylate solution; as can be seen from the nuclear magnetic resonance spectrum of the aluminum carboxylate solution of fig. 1: the prepared aluminum carboxylate solution exists in the form of polymer Al8-18OX 12-27. From the infrared test chart of the aluminum carboxylate solution of FIG. 3, it can be seen that the functional group of the polymer exists in the form of a group such as (HCOO) (RCOO) (OOC-COOH).

Then mixing liquid silicon dioxide and propionic acid in a molar ratio of 1:3, ultrasonically dispersing for 60min, and filtering and precipitating; adding polyoxyethylene, methylcellulose and hydroxyethyl cellulose into the clarified liquid, and mixing; the amount of the added auxiliary agent is 5 percent of the mass of the silicon dioxide; the silicon-containing additive is prepared.

And mixing the aluminum carboxylate solution and the silicon-containing additive to ensure that the molar ratio of Al2O3 to SiO2 in the solution is 3: 2, and reacting to obtain precursor sol. And then concentrating and aging the precursor sol at the temperature of 70 ℃ and the vacuum degree of 0.1MPa to obtain the spinnable mullite sol with the viscosity of 600Pa & s. The viscosity curve of the mullite sol in FIG. 4 shows that the mullite sol prepared by the method has normal rheological property according to the relation curve between the shear rate and the sol viscosity. Then introducing oxygen at 700 ℃ and nitrogen at 1300 ℃, and obtaining the mullite precursor fiber with the heat treatment curve as shown in figure 6. Coating organic alcohol on the surface of the mullite precursor fiber, and finally drying in a drying oven at 100 ℃ for 10h, wherein the change curve of the viscosity of the sol prepared in the figure 5 along with the time can be seen, so that the viscosity of the prepared sol does not obviously change even if the sol is stored for 30 days, the sol does not generate the gelation phenomenon, can be stored for a long time, does not aggregate and does not deteriorate; the mullite fiber shown in figure 2 is obtained by dry spinning.

Example 4:

adding acetic acid, propionic acid and oxalic acid into distilled water at 80 ℃, fully stirring and uniformly mixing, and then adding aluminum hydroxide powder. The molar ratio of aluminum hydroxide to acetic acid, propionic acid and oxalic acid was 1: 2. Then, continuously stirring and condensing the mixture solution under the conditions of 140 ℃, removing carboxylic acid by concentration under the conditions of 100 ℃ and 0.1MPa of vacuum degree, and reacting for 18 hours to prepare a transparent aluminum carboxylate solution; the nuclear magnetic resonance spectrum of the aluminum carboxylate solution in figure 1 can be seen: the prepared aluminum carboxylate solution exists in the form of polymer Al8-18OX 12-27. From the infrared test chart of the aluminum carboxylate solution of FIG. 3, it can be seen that the functional group of the polymer exists in the form of a group such as (HCOO) (RCOO) (OOC-COOH).

Then mixing liquid silicon dioxide and propionic acid in a molar ratio of 1:2, ultrasonically dispersing for 60min, and filtering and precipitating; adding polyoxyethylene and polyvinyl alcohol into the clarified liquid for mixing; the amount of the added auxiliary agent is 1 percent of the mass of the silicon dioxide; the silicon-containing additive is prepared.

And mixing the aluminum carboxylate solution and the silicon-containing additive to ensure that the molar ratio of Al2O3 to SiO2 in the solution is 3: 2, and reacting to obtain precursor sol. And then concentrating and aging the precursor sol at the temperature of 40 ℃ and the vacuum degree of 0.1MPa to obtain the spinnable mullite sol with the viscosity of 500 Pa.s. As shown in the viscosity curve of the mullite sol in fig. 4, the rheological property of the mullite sol prepared by the method can be seen from the viscosity curve of the mullite sol in fig. 4, and the rheological property of the mullite sol prepared by the method can be seen from the relation curve of the shear rate and the sol viscosity. Then introducing oxygen at 700 ℃ and nitrogen at 1300 ℃, wherein the heat treatment curve is shown in fig. 6, so as to obtain mullite precursor fiber, coating organic alcohol on the surface of the mullite precursor fiber, drying for 7h in a drying oven at 70 ℃, and as can be seen from the change curve of the viscosity of the sol prepared in fig. 5 along with the time, the viscosity of the prepared sol has no obvious change even if the prepared sol is stored for 30 days, the sol does not have the gelation phenomenon, can be stored for a long time, and does not agglomerate and deteriorate; the mullite fiber shown in figure 2 is obtained by dry spinning.

Example 5:

adding formic acid, acetic acid and citric acid into distilled water at 80 ℃, fully stirring and uniformly mixing, and then adding aluminum hydroxide powder. The molar ratio of aluminum hydroxide to formic acid, acetic acid and citric acid was 1: 3. Then the mixture solution is reacted for 24 hours under the conditions of continuous stirring and condensation reflux at the temperature of 120 ℃ to prepare transparent aluminum carboxylate solution; as can be seen from the nuclear magnetic resonance spectrum of the aluminum carboxylate solution of fig. 1: the prepared aluminum carboxylate solution exists in the form of polymer Al8-18OX 12-27. From the infrared test chart of the aluminum carboxylate solution of FIG. 3, it can be seen that the functional group of the polymer exists in the form of a group such as (HCOO) (RCOO) (OOC-COOH).

Then mixing the liquid silicon dioxide with acetic acid in a molar ratio of 1:2, carrying out ultrasonic dispersion for 60min, and filtering and precipitating; the silicon-containing additive is prepared.

And mixing the aluminum carboxylate solution and the silicon-containing additive to ensure that the molar ratio of Al2O3 to SiO2 in the solution is 3: 2, and reacting to obtain precursor sol. The viscosity curve of the mullite sol in FIG. 4 shows that the mullite sol prepared by the method has normal rheological property according to the relation curve between the shear rate and the sol viscosity. And then concentrating and aging the precursor sol at the temperature of 60 ℃ and the vacuum degree of 0.1MPa to obtain the mullite fiber with the viscosity of 600Pa & s. Then introducing oxygen at 700 ℃ and nitrogen at 1300 ℃, wherein the heat treatment curve is shown in figure 6, obtaining the mullite precursor fiber, coating the surface of the mullite precursor fiber with an ester coating, and drying for 7h in a drying oven at 70 ℃. As can be seen from the curve of the change of the viscosity of the sol prepared in FIG. 5 with time, the viscosity of the prepared sol has no obvious change even if the sol is stored for 30 days, the sol does not have gelation phenomenon, can be stored for a long time, and does not coagulate and deteriorate; the mullite fiber shown in figure 2 is obtained by dry spinning.

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.

Claims

1. The preparation method of the low-cost mullite fiber is characterized by comprising the following steps of:

preparing an aluminum carboxylate solution in which Al is present as Al_8-18OX_12-27Exists in a multimeric form; wherein X is one or more of-COOH, -RCOO and-OOC-COOH;

preparing a silicon additive;

carrying out dry spinning on the spinnable mullite sol by a special spinning system to obtain mullite precursor fiber;

2. The method of preparing a low cost mullite fiber of claim 1 wherein the preparing of the solution of aluminum carboxylate includes the steps of:

adding organic carboxylic acid into water at 50-80 ℃ to obtain an organic carboxylic acid solution,

adding aluminum hydroxide powder into the organic carboxylic acid solution

3. the method for preparing the low-cost mullite fiber as claimed in claim 2, wherein the organic carboxylic acid is one or more of formic acid, propionic acid, malonic acid and citric acid;

4. the method of preparing a low cost mullite fiber of claim 1 wherein the method of preparing the silicon additive is: mixing a silicon source and saturated monoacid in a molar ratio of 1: 1-3, performing ultrasonic dispersion for 30-60 min, and filtering and precipitating; adding a high-molecular additive into the clarified liquid, and mixing to obtain a silicon additive; wherein the amount of the high molecular auxiliary agent is 0-5% of the mass of the silicon source; the saturated monocarboxylic acid is one or more of formic acid, acetic acid and propionic acid.

5. The method for preparing the low-cost mullite fiber as claimed in claim 4 wherein the silicon source is one or more of silica sol and liquid silica.

6. The method for preparing the low-cost mullite fiber as claimed in claim 4, wherein the polymer auxiliary agent is one or more of lactic acid, glycerin, polyvinyl alcohol, polyethylene glycol, polyethylene oxide and methyl cellulose.

7. The method for preparing the low-cost mullite fiber as claimed in claim 1, wherein the concentration aging temperature is 30 to 70 ℃; the vacuum degree is 0.09-0.1 MPa; the concentration and aging time is 4-8 h.

8. The method for preparing the low-cost mullite fiber according to claim 7, wherein the prepared spinnable mullite sol has a viscosity of 100-600 Pa-s.

9. The method of preparing a low cost mullite fiber of claim 1 wherein the heat treatment conditions are: introducing oxygen at the room temperature of 600-750 ℃, and introducing nitrogen or air at the temperature of 600-750 ℃ to 1200-1400 ℃.

10. The low cost mullite fiber of claims 1-9 wherein the low cost mullite fiber is made according to the process of any one of claims 1 to 9.