A method for preparing an al-mg complex oxide ceramic precursor

Abstract

The application discloses a method for preparing Al-Mg complex oxide ceramic precursor. At least two complexing agents are used to coordinate and stabilize the mixed solution of magnesium and aluminum elements. According to different magnesium and aluminum element ratios, the types, proportions and total adding amounts of the two complexing agents are adjusted, the spinning performance of the precursor is improved, and then Al-Mg complex oxide continuous ceramic fibers with different Al2O3 and MgAl2O4 phase contents are obtained. The softening point of the Al-Mg complex oxide ceramic precursor is between 110 DEG C and 180 DEG C, and the highest ceramic yield is 54%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite fiber materials, and particularly relates to a method for preparing Al-Mg complex oxide ceramic precursors. BACKGROUND

[0002] Continuous alumina ceramic fibers are widely used in aerospace, military, automotive and other fields due to their high strength, high modulus and excellent oxidation resistance. In recent years, with the development of the aerospace field, the actual application demand has higher requirements for the high-temperature performance of alumina fibers, and the research focus of domestic and foreign researchers has also shifted from the process production route to the addition of various oxides and heteroatoms. Magnesium oxide is a cheap and harmless alkaline metal oxide with high melting point, high dielectric constant, corrosion resistance and other characteristics. The melting point of magnesium oxide is 2852℃, which is a highly refractory insulating material. Adding magnesium oxide to alumina fibers can improve their chemical stability and high-temperature performance. The solid solution formed by Al2O3 and MgO is MgAl2O4, which belongs to a spinel compound. The crystal cell structure of MgAl2O4 is cubic, the space group is Fd3m, and the general formula is AB2O4. The main characteristics of MgAl2O4 are as follows: 1. high melting point, low density, and light weight in the same volume; 2. high hardness and three-point bending strength, excellent mechanical properties; 3. high thermal conductivity, small thermal stress in the ceramic at high temperature, and excellent thermal shock resistance; 4. excellent wear resistance and corrosion resistance. In summary, ceramic fibers containing magnesium aluminum spinel have excellent performance and can meet the performance requirements of the aerospace field.

[0003] The Russian Federation Institute of Aviation Science prepared magnesium aluminum spinel continuous polycrystalline fibers by using a sol-gel method. Polyformic acid aluminum and magnesium hydroxyacetate were mixed in a certain stoichiometric ratio, heated and hydrolyzed to form a sol. In order to obtain a stable colloidal system, formic acid, isobutyric acid and ethylene glycol were added as stabilizers. After concentration, a spinning solution with a certain viscosity was obtained (Glass and Ceramics, 2019, 76(11)), and then the fiber was obtained by spinning.

[0004] CN104141180B provides a method for preparing continuous magnesium aluminum spinel fibers. The method uses (MgCO3) 4· Mg(OH) 2· 5H2O, acetic acid, water, anhydrous AlCl3, aluminum powder and citric acid as raw materials, MgAl2O4 sol spinning solution is prepared by a sol-gel method, MgAl2O4 precursor fibers are obtained by high-speed centrifugal spinning and high-speed hot gas blowing stretching, and continuous MgAl2O4 fibers are obtained by heat treatment and sintering.

[0005] CN113968974B The present research group previously improved the strength and high-temperature resistance of the fiber by adding a second-phase grain growth inhibitor, zirconium oxide, to the aluminum oxide fiber. The softening point of the Al-Zr copolymer oxide ceramic precursor is between 80 and 180 DEG C. The precursor composition ratio and softening point can be adjusted, and the average diameter of the obtained fiber is 5 to 30 microns, and the tensile strength is not less than 2.0 GPa. SUMMARY

[0006] The present application provides an oxide ceramic precursor, by introducing a second component magnesium oxide, to obtain Al2O3, MgAl2O4 phase Al-Mg complex oxide continuous ceramic fiber. In the Al-Mg complex oxide continuous ceramic precursor in the present application, magnesium is divalent, and only a single type of complexing agent cannot coordinate and stabilize the mixed solution of magnesium and aluminum elements before hydrolysis and polycondensation. At least two complexing agents are required to coordinate and stabilize the mixed solution of magnesium and aluminum elements. For different ratios of magnesium and aluminum elements, the types, proportions, and total amounts of the two complexing agents are adjusted to improve the spinning performance of the precursor.

[0007] The purpose of the present application is to provide an Al-Mg complex oxide ceramic precursor and a preparation method thereof. At least two complexing agents are used to coordinate and stabilize the mixed solution of magnesium and aluminum elements. For different ratios of magnesium and aluminum elements, the types, proportions, and total amounts of the two complexing agents are adjusted to improve the spinning performance of the precursor, and then Al-Mg complex oxide continuous ceramic fibers with different Al2O3, MgAl2O4 phase contents are obtained. The softening point of the Al-Mg complex oxide ceramic precursor is between 110 and 180 DEG C, and the ceramic yield is up to 54%.

[0008] The present application provides a method for preparing an Al-Mg complex oxide ceramic precursor, comprising the following steps:

[0009] 1) Add an aluminum source and a magnesium source to a solvent and stir at a temperature of 60 to 110 DEG C for 0.5 to 3 h; add a complexing agent mixed solution a or b at a temperature of 60 to 90 DEG C, and continue to reflux for 0.5 to 5 h;

[0010] The complexing agent mixed solution a is a mixed solution of butanedione and acetylacetone;

[0011] The complexing agent mixed solution b is a mixed solution of acetic acid and ethyl acetoacetate;

[0012] 2) Add any one of the mixed solutions c to e to the reaction system obtained in step 1), and reflux for 0.5 to 1.5 h after addition; then remove the solvent and cool to room temperature to obtain the Al-Mg complex oxide ceramic precursor;

[0013] The mixed solution c is composed of water and ethylene glycol methyl ether;

[0014] The mixed solution d is composed of water and ethylene glycol ethyl ether;

[0015] The mixed solution e is composed of water and n-propanol.

[0016] In the step 1) of the above method, the aluminum source is selected from at least one of aluminum isopropoxide, aluminum n-propanol and aluminum ethoxide;

[0017] The magnesium source is selected from at least one of magnesium ethoxide, magnesium methoxide, magnesium acetylacetone, magnesium isopropoxide;

[0018] The mass fraction ratio of the aluminum source and the magnesium source, converted into Al2O3:MgO, is 71.7~99.75:0.25~28.3; specifically, 71.7~99.0:1~28.3, and more specifically, 99:1, 97:3, 71.7:28.3;

[0019] The solvent is selected from at least one of n-propanol, methanol and isopropyl alcohol;

[0020] The molar amount of the complexing agent is 0.3~1 times the total molar amount of the aluminum source and the magnesium source; specifically, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1 times;

[0021] In the complexing agent mixed solution a, the molar ratio of butanedione and acetylacetone is 1:10~30; specifically, 1:20;

[0022] In the complexing agent mixed solution b, the molar ratio of acetic acid and ethyl acetoacetate is 1:10~30; specifically, 1:20, 1:12, 1:16, 1:24, 1:18, 1:10;

[0023] In the step 2), the molar ratio of the total amount of the aluminum source and the magnesium source to water is 1:0.6~1; specifically, 1:0.6;

[0024] In the mixed solution c, the mass ratio of water to ethylene glycol methyl ether is 1:1~10; specifically, 1:4;

[0025] In the mixed solution d, the mass ratio of water to ethylene glycol ethyl ether is 1:1~10; specifically, 1:6;

[0026] In the mixed solution e, the mass ratio of water to n-propanol is 1:1~10; specifically, 1:4, 1:2;

[0027] The adding method of any one of the mixed solutions c-e is dropwise adding; the dropwise adding rate is 0.5~2 drops / s; specifically, 1 drop / s, 2 drops / s, 0.5 drop / s;

[0028] The solvent is removed by vacuum distillation, wherein the temperature of the vacuum distillation is 140~200o C, specifically 200 o C, 140 o C, 180 o C, 170 o C, 160 o C; the time is 0.5-6h, specifically 2h, 3h, 2.5h;

[0029] The softening point of the obtained Al-Mg complex oxide ceramic precursor is between 110-180℃.

[0030] The Al-Mg complex oxide ceramic precursor prepared by the above method also belongs to the protection scope of the present application.

[0031] The application of the Al-Mg complex oxide ceramic precursor in the preparation of fibers also belongs to the protection scope of the present application,

[0032] The fiber is a fiber containing aluminum and magnesium; specifically, it is an Al-Mg complex oxide continuous ceramic fiber containing Al2O3 and MgAl2O4 phases at high temperature (higher than 1250°).

[0033] The mass fraction ratio of the aluminum source and the magnesium source converted into Al2O3:MgO is in the range of 1%-28.3% (excluding 28.3%), and the obtained fiber contains Al2O3 and MgAl2O4 phases at high temperature (higher than 1250°).

[0034] The present application has the following beneficial effects:

[0035] 1) The present application uses two kinds of complexing agents to coordinate and stabilize the mixed solution of magnesium and aluminum elements, and by adjusting the type, ratio and total amount of the complexing agent according to different magnesium and aluminum element ratios, the spinning performance of the precursor is improved.

[0036] 2) The softening point of the Al-Mg complex oxide ceramic precursor is between 110-180 o C, without adding spinning aids, the ceramic yield is as high as 54%, and the pollution to the environment during the spinning process and subsequent sintering process is reduced.

[0037] 3) The composition of the precursor can be adjusted, and by adjusting the ratio of the aluminum source and the magnesium source, Al-Mg complex oxide continuous ceramic fibers with different Al2O3 and MgAl2O4 phase contents can be prepared. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 SEM image of the Al-Mg complex oxide ceramic fiber prepared in Example 1 of the present application.

[0039] Figure 2TG diagram of the Al-Mg complex oxide ceramic precursor prepared in Example 1 of the present application.

[0040] Figure 3 XRD diagram of the Al-Mg complex oxide ceramic fiber prepared in Example 1 of the present application at different temperatures.

[0041] Figure 4 XRD diagram of the Al-Mg complex oxide ceramic fiber prepared in Example 4 of the present application at different temperatures.

[0042] Figure 5 Rheological diagram of the Al-Mg complex oxide ceramic precursor prepared in Example 4 of the present application.

[0043] Figure 6 XRD diagram of the Al-Mg complex oxide ceramic fiber prepared in Example 13 of the present application at different temperatures. DETAILED DESCRIPTION

[0044] The present application will be further described in conjunction with the specific embodiments, and the examples given are only for the purpose of illustrating the present application, but not for limiting the scope of the present application. The examples provided below can serve as a guide for further improvement by those of ordinary skill in the art, and do not in any way constitute a limitation on the present application.

[0045] The experimental methods in the following examples are all conventional methods, and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained commercially, unless otherwise specified.

[0046] Example 1

[0047] Aluminum isopropoxide and magnesium isopropoxide were added to n-propanol, wherein the mass fraction ratio of aluminum isopropoxide:magnesium isopropoxide, converted into Al2O3:MgO, was 99:1, and the mixture was stirred and refluxed at a heating temperature of 110℃ for 2 h; then a complexing agent mixed solution of acetic acid and ethyl acetoacetate, wherein the molar ratio of acetic acid to ethyl acetoacetate was 1:20, was added in an amount of 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide at a heating temperature of 80℃, and the mixture was heated and refluxed for 1.5 h; a mixture of water and n-propanol, wherein the mass ratio of water to n-propanol was 1:4, was added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum isopropoxide and magnesium isopropoxide to water was 1:0.6, and the mixture was refluxed for 1 h after the dropwise addition was completed; the mixture was distilled under reduced pressure at a vacuum degree of 280 mbar at 200℃ for 2 h, and then the temperature was maintained for 3 h before being lowered to room temperature, thereby preparing an Al-Mg complex oxide ceramic precursor.

[0048] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example was 180℃, and the ceramic yield was 54%.

[0049] The Al-Mg complex oxide ceramic precursor was heated to above the softening point 55℃, and after melting into a uniform melt and releasing residual bubbles, melt spinning was carried out, the fiber filament was prepared with a fiber outlet aperture of 0.1 mm, a screw extrusion pressure of 30 MPa, and a collection rate of 8000 r / min; the obtained fiber filament was placed in a constant temperature and humidity box, first heated to 40℃, and then kept at 40% relative humidity for 30 min, then heated to 60℃, and kept at 60% relative humidity for 30 min, then heated to 85℃, and kept at 80% relative humidity for 40 min, and then cooled to room temperature to obtain non-fusible fibers; the obtained non-fusible fibers were placed in a high-temperature furnace, heated to 700℃ at a rate of 1℃ / min, kept for 1 h, the furnace atmosphere was air, and then naturally cooled to room temperature; the obtained inorganic fibers were placed in a high-temperature furnace, heated to 1200℃ at a rate of 10℃ / min, kept for 1 h, the furnace atmosphere was air, and the Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 1.5 GPa were obtained.

[0050] The SEM image of the fiber is shown in the following figure Figure 1 The fiber surface is smooth and defect-free, and the diameter is about 10 μm.

[0051] The thermogravimetric curve of the precursor under a flowing air atmosphere at 10℃ / min is shown in the following figure Figure 2 As can be seen from the figure, the ceramic yield of the precursor is about 53.95%, and the weight loss of the precursor is faster before 600℃, and the weight loss is not obvious after 600℃.

[0052] The XRD pattern of the fiber at different temperatures is shown in the following figure Figure 3 As can be seen from the figure, at 1200℃, the fiber is in an amorphous state, gamma -Al2O3 phase, α -Al2O3 phase, when the temperature is increased to 1250℃, the MgAl2O4 crystalline phase begins to appear, and the crystallinity is improved with the increase of the heat treatment temperature.

[0053] Example 2

[0054] The aluminum isopropoxide and the magnesium methoxide are added into isopropyl alcohol, wherein the mass fraction ratio of the aluminum isopropoxide to the magnesium methoxide, converted into Al2O3:MgO, is 99:1, and the mixture is stirred and refluxed at a heating temperature of 100℃ for 1 hour; then a complexing agent mixed solution of 0.6 times the molar fraction of butanedione and acetylacetone, wherein the molar ratio of butanedione to acetylacetone is 1:20, is added into the mixture at a heating temperature of 70℃ and refluxed for 2 hours; then a mixture of water and ethylene glycol ethyl ether, with a mass ratio of 1:6, is added dropwise at a rate of 2 drops per second, wherein the molar ratio of the total amount of the aluminum isopropoxide and the magnesium methoxide to water is 1:0.6, and the mixture is refluxed for 2 hours after the dropwise addition is completed; the mixture is distilled under reduced pressure at a vacuum degree of 260 mbar for 3 hours at 140℃, and then the mixture is cooled to room temperature after being kept for 3 hours, thereby obtaining the Al-Mg complex oxide ceramic precursor.

[0055] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example is 110℃, and the ceramic yield is 48%.

[0056] The Al-Mg complex oxide continuous ceramic fiber with an average diameter of 10 μm and an average tensile strength of 1.1 GPa is obtained by performing the operations of melt spinning, non-fusion treatment, inorganic sintering, and ceramic sintering on the precursor (the operations are the same as those in Example 1).

[0057] Example 3

[0058] The aluminum n-propoxide and the magnesium methoxide are added into isopropyl alcohol, wherein the mass fraction ratio of the aluminum n-propoxide to the magnesium methoxide, converted into Al2O3:MgO, is 99:1, and the mixture is stirred and refluxed at a heating temperature of 100℃ for 1 hour; then a complexing agent mixed solution of 0.8 times the molar fraction of butanedione and acetylacetone, wherein the molar ratio of butanedione to acetylacetone is 1:20, is added into the mixture at a heating temperature of 70℃ and refluxed for 2 hours; then a mixture of water and ethylene glycol ethyl ether, with a mass ratio of 1:6, is added dropwise at a rate of 1 drop per second, wherein the molar ratio of the total amount of the aluminum n-propoxide and the magnesium methoxide to water is 1:0.6, and the mixture is refluxed for 2 hours after the dropwise addition is completed; the mixture is distilled under reduced pressure at a vacuum degree of 260 mbar for 3 hours at 180℃, and then the mixture is cooled to room temperature after being kept for 3 hours, thereby obtaining the Al-Mg complex oxide ceramic precursor.

[0059] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example is 160℃, and the ceramic yield is 50%.

[0060] The Al-Mg complex oxide continuous ceramic fiber with an average diameter of 10 μm and an average tensile strength of 1.2 GPa is obtained by performing the operations of melt spinning, non-fusion treatment, inorganic sintering, and ceramic sintering on the precursor (the operations are the same as those in Example 1).

[0061] Example 4

[0062] Dissolve aluminum ethoxide and magnesium acetylacetonate in isopropyl alcohol, wherein the mass fraction ratio of aluminum ethoxide: magnesium acetylacetonate, converted into Al2O3:MgO, is 99.75:0.25, and the solution is stirred and refluxed at a heating temperature of 80℃ for 1.5 h; then add a complexing agent solution of acetic acid and ethyl acetoacetate in an amount of 0.7 times the molar fraction of the total amount of aluminum ethoxide and magnesium acetylacetonate, wherein the molar ratio of acetic acid to ethyl acetoacetate is 1:12, and heat and reflux for 1.5 h at a heating temperature of 70℃; then drop in a mixture of water and n-propanol at a mass ratio of 1:2 at a dropping rate of 0.5 drops / s, wherein the molar ratio of the total amount of aluminum ethoxide and magnesium acetylacetonate to water is 1:0.6, and reflux for 1 h after dropping; then perform vacuum distillation at 160℃ and a vacuum degree of 380 mbar for 2.5 h, and then reduce to room temperature after holding for 5 h, to obtain an Al-Mg complex oxide ceramic precursor.

[0063] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example is 127℃, and the ceramic yield is 50%.

[0064] By performing melt spinning, non-fusion treatment, inorganic sintering, and ceramic sintering (same as in Example 1) on the precursor, an Al-Mg complex oxide continuous ceramic fiber with an average diameter of 10 μm and an average tensile strength of 1.2 GPa is obtained.

[0065] The in-situ temperature rising XRD pattern of the powder obtained by hydrolysis of the precursor and inorganic sintering is shown in FIG. 1. Figure 4 As shown in the figure, below 1100℃, only amorphous, gamma -Al2O3 phases exist, and when the temperature is raised to 1100℃, the α -Al2O3 crystalline phase begins to appear, and the crystallinity is improved as the heat treatment temperature is raised.

[0066] The rheological curve of the precursor in an air atmosphere is shown in FIG. 2. Figure 5 As shown in the figure, at 100-200℃, the viscosity of the precursor decreases as the temperature rises, and according to the viscosity-temperature curve of the precursor, a suitable melting temperature is selected for spinning.

[0067] Example 5

[0068] The isopropyl alcohol aluminum and the ethanol magnesium are dissolved in n-propanol, wherein the mass fraction ratio of the isopropyl alcohol aluminum:ethanol magnesium is 99:1, which is converted into the mass fraction ratio of Al2O3:MgO, under the heating temperature of 95℃, the stirring reflux is carried out for 2 hours; then under the heating temperature of 80℃, the complexing agent solution of the acetic acid and the acetyl acetic acid ethyl ester is added, the total amount of the isopropyl alcohol aluminum and the ethanol magnesium is 0.4 times of the molar fraction, the molar ratio of the acetic acid and the acetyl acetic acid ethyl ester is 1:20, the heating reflux is carried out for 2 hours; then the mixed solution of water and ethylene glycol methyl ether is added dropwise at the dropping speed of 1 drop / s, the mass ratio of the water and the ethylene glycol methyl ether is 1:4, the molar ratio of the total amount of the isopropyl alcohol aluminum and the ethanol magnesium and the water is 1:0.6, the dropwise addition is completed, and the reflux is carried out for 2 hours; under the vacuum degree of 170℃ and 220mbar, the reduced pressure distillation is carried out for 2 hours, the temperature is kept for 3 hours, and then the temperature is reduced to the room temperature, so that the Al-Mg complex oxide ceramic precursor is prepared.

[0069] The softening point of the Al-Mg complex oxide ceramic precursor obtained in the embodiment is 150℃, and the ceramic yield is 51%.

[0070] Through the melting spinning, the non-fusion treatment, the inorganic sintering and the ceramic sintering (the operations are the same as those in the embodiment 1) on the precursor, the Al-Mg complex oxide continuous ceramic fiber with the average diameter of 10 μm and the average tensile strength of 1.2 GPa is obtained.

[0071] Embodiment 6

[0072] The isopropyl alcohol aluminum and the isopropyl alcohol magnesium are added into n-propanol, wherein the mass fraction ratio of the isopropyl alcohol aluminum:isopropyl alcohol magnesium is 99:1, which is converted into the mass fraction ratio of Al2O3:MgO, under the heating temperature of 110℃, the stirring reflux is carried out for 2 hours; then under the heating temperature of 80℃, the complexing agent solution of the acetic acid and the acetyl acetic acid ethyl ester is added, the total amount of the isopropyl alcohol aluminum and the isopropyl alcohol magnesium is 1.0 times of the molar fraction, the molar ratio of the acetic acid and the acetyl acetic acid ethyl ester is 1:20, the heating reflux is carried out for 1.5 hours; then the mixed solution of water and ethylene glycol methyl ether is added dropwise at the dropping speed of 1 drop / s, the mass ratio of the water and the ethylene glycol methyl ether is 1:4, the molar ratio of the total amount of the isopropyl alcohol aluminum and the isopropyl alcohol magnesium and the water is 1:0.6, the dropwise addition is completed, and the reflux is carried out for 1 hour; under the vacuum degree of 200℃ and 280mbar, the reduced pressure distillation is carried out for 2 hours, the temperature is kept for 3 hours, and then the temperature is reduced to the room temperature, so that the Al-Mg complex oxide ceramic precursor is prepared.

[0073] The softening point of the Al-Mg complex oxide ceramic precursor obtained in the embodiment is 180℃, and the ceramic yield is 54%.

[0074] Through the melting spinning, the non-fusion treatment, the inorganic sintering and the ceramic sintering (the operations are the same as those in the embodiment 1) on the precursor, the Al-Mg complex oxide continuous ceramic fiber with the average diameter of 10 μm and the average tensile strength of 1.3 GPa is obtained.

[0075] Embodiment 7

[0076] aluminum isopropoxide, magnesium isopropoxide were added into n-propanol, wherein the mass fraction ratio of aluminum isopropoxide:magnesium isopropoxide was 99:1, and the amount of the aluminum isopropoxide and the magnesium isopropoxide was converted into the mass fraction ratio of Al2O3:MgO, and the mixture was stirred and refluxed at a heating temperature of 110°C for 2 hours; then a complexing agent solution of acetic acid and ethyl acetoacetate in an amount of 0.5 times the molar fraction of the total amount of the aluminum isopropoxide and the magnesium isopropoxide was added at a heating temperature of 80°C, wherein the molar ratio of the acetic acid to the ethyl acetoacetate was 1:20, and the mixture was heated and refluxed for 1.5 hours; then a mixture of water and n-propanol in a mass ratio of 1:4 was added dropwise at a dropwise adding rate of 1 drop / s, wherein the molar ratio of the total amount of the aluminum isopropoxide and the magnesium isopropoxide to the water was 1:0.6, and the mixture was refluxed for 1 hour after the dropwise adding was completed; the mixture was distilled under reduced pressure at a vacuum degree of 280 mbar and at a temperature of 200°C for 2 hours, and then the mixture was cooled to room temperature after being kept at the temperature for 3 hours, thereby obtaining an Al-Mg complex oxide ceramic precursor.

[0077] The softening point of the Al-Mg complex oxide ceramic precursor obtained in the example was 180°C, and the ceramic yield was 54%.

[0078] The Al-Mg complex oxide continuous ceramic fiber with an average diameter of 10 μm and an average tensile strength of 1.4 GPa was obtained by performing melt spinning, non-fusible treatment, inorganic sintering, and ceramic sintering on the precursor (the operations were the same as those in the example 1).

[0079] Example 8

[0080] aluminum isopropoxide, magnesium isopropoxide were added into n-propanol, wherein the mass fraction ratio of aluminum isopropoxide:magnesium isopropoxide was 99:1, and the amount of the aluminum isopropoxide and the magnesium isopropoxide was converted into the mass fraction ratio of Al2O3:MgO, and the mixture was stirred and refluxed at a heating temperature of 110°C for 2 hours; then a complexing agent solution of acetic acid and ethyl acetoacetate in an amount of 0.5 times the molar fraction of the total amount of the aluminum isopropoxide and the magnesium isopropoxide was added at a heating temperature of 80°C, wherein the molar ratio of the acetic acid to the ethyl acetoacetate was 1:20, and the mixture was heated and refluxed for 1.5 hours; then a mixture of water and n-propanol in a mass ratio of 1:4 was added dropwise at a dropwise adding rate of 1 drop / s, wherein the molar ratio of the total amount of the aluminum isopropoxide and the magnesium isopropoxide to the water was 1:0.6, and the mixture was refluxed for 1 hour after the dropwise adding was completed; the mixture was distilled under reduced pressure at a vacuum degree of 280 mbar and at a temperature of 200°C for 2 hours, and then the mixture was cooled to room temperature after being kept at the temperature for 3 hours, thereby obtaining an Al-Mg complex oxide ceramic precursor.

[0081] The softening point of the Al-Mg complex oxide ceramic precursor obtained in the example was 180°C, and the ceramic yield was 54%.

[0082] The Al-Mg complex oxide continuous ceramic fiber with an average diameter of 10 μm and an average tensile strength of 0.9 GPa was obtained by performing melt spinning, non-fusible treatment, inorganic sintering, and ceramic sintering on the precursor (the operations were the same as those in the example 1).

[0083] Example 9

[0084] aluminum isopropoxide and magnesium isopropoxide were added into n-propanol, wherein the mass fraction ratio of aluminum isopropoxide to magnesium isopropoxide was 99:1 in terms of Al2O3:MgO, and the mixture was stirred and refluxed at a heating temperature of 110°C for 2 hours; then a complexing agent solution of acetic acid and ethyl acetoacetate in an amount of 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide was added at a heating temperature of 80°C, wherein the molar ratio of acetic acid to ethyl acetoacetate was 1:12, and the mixture was heated and refluxed for 1.5 hours; then a mixture of water and n-propanol in a mass ratio of 1:4 was added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum isopropoxide and magnesium isopropoxide to water was 1:0.6, and the mixture was refluxed for 1 hour after the dropwise addition was completed; the mixture was subjected to reduced pressure distillation at 200°C and a vacuum degree of 280 mbar for 2 hours, and then was cooled to room temperature after being kept warm for 3 hours, thereby obtaining an Al-Mg complex oxide ceramic precursor.

[0085] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example was 180°C, and the ceramic yield was 54%.

[0086] The Al-Mg complex oxide continuous ceramic fiber with an average diameter of 10 μm and an average tensile strength of 1.1 GPa was obtained by subjecting the precursor to melt spinning, non-fusion treatment, inorganic sintering, and ceramic sintering (the same as in Example 1).

[0087] Example 10

[0088] aluminum isopropoxide and magnesium isopropoxide were added into n-propanol, wherein the mass fraction ratio of aluminum isopropoxide to magnesium isopropoxide was 99:1 in terms of Al2O3:MgO, and the mixture was stirred and refluxed at a heating temperature of 110°C for 2 hours; then a complexing agent solution of acetic acid and ethyl acetoacetate in an amount of 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide was added at a heating temperature of 80°C, wherein the molar ratio of acetic acid to ethyl acetoacetate was 1:16, and the mixture was heated and refluxed for 1.5 hours; then a mixture of water and n-propanol in a mass ratio of 1:4 was added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum isopropoxide and magnesium isopropoxide to water was 1:0.6, and the mixture was refluxed for 1 hour after the dropwise addition was completed; the mixture was subjected to reduced pressure distillation at 200°C and a vacuum degree of 280 mbar for 2 hours, and then was cooled to room temperature after being kept warm for 3 hours, thereby obtaining an Al-Mg complex oxide ceramic precursor.

[0089] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example was 180°C, and the ceramic yield was 54%.

[0090] The precursor is subjected to melt spinning, non-melting treatment, inorganic sintering, and ceramic sintering (same as the operation in Example 1) to obtain Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 1.2 GPa.

[0091] Example 11

[0092] Aluminum isopropoxide and magnesium isopropoxide are added to n-propanol, wherein the mass fraction ratio of aluminum isopropoxide to magnesium isopropoxide is 99:1 in terms of Al2O3:MgO, and the mixture is stirred and refluxed at a heating temperature of 110°C for 2 h; then a complexing agent solution of acetic acid and acetylacetate ethyl ester in an amount of 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide is added at a heating temperature of 80°C, wherein the molar ratio of acetic acid to acetylacetate ethyl ester is 1:24, and the mixture is heated and refluxed for 1.5 h; then a mixture of water and n-propanol with a mass ratio of 1:4 is added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum isopropoxide and magnesium isopropoxide to water is 1:0.6, and the mixture is refluxed for 1 h after the dropwise addition is completed; the mixture is subjected to reduced-pressure distillation at 200°C and a vacuum degree of 280 mbar for 2 h, and then the mixture is cooled to room temperature after being kept warm for 3 h to obtain an Al-Mg complex oxide ceramic precursor.

[0093] The Al-Mg complex oxide ceramic precursor obtained in this example has a softening point of 180°C and a ceramic yield of 54%.

[0094] The precursor is subjected to melt spinning, non-melting treatment, inorganic sintering, and ceramic sintering (same as the operation in Example 1) to obtain Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 1.2 GPa.

[0095] Example 12

[0096] Aluminum isopropoxide and magnesium isopropoxide are added to n-propanol, wherein the mass fraction ratio of aluminum isopropoxide to magnesium isopropoxide is 99:1 in terms of Al2O3:MgO, and the mixture is stirred and refluxed at a heating temperature of 110°C for 2 h; then a complexing agent solution of acetic acid and acetylacetate ethyl ester in an amount of 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide is added at a heating temperature of 80°C, wherein the molar ratio of acetic acid to acetylacetate ethyl ester is 1:24, and the mixture is heated and refluxed for 1.5 h; then a mixture of water and n-propanol with a mass ratio of 1:4 is added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum isopropoxide and magnesium isopropoxide to water is 1:0.6, and the mixture is refluxed for 1 h after the dropwise addition is completed; the mixture is subjected to reduced-pressure distillation at 200°C and a vacuum degree of 280 mbar for 2 h, and then the mixture is cooled to room temperature after being kept warm for 3 h to obtain an Al-Mg complex oxide ceramic precursor.

[0097] The softening point of the Al-Mg complex oxide ceramic precursor obtained in the embodiment is 180℃, and the ceramic yield is 54%.

[0098] By performing melt spinning, non-fusion treatment, inorganic sintering, and ceramic sintering on the precursor (the same as the operation in Embodiment 1), Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 1.4 GPa are obtained.

[0099] Embodiment 13

[0100] Aluminum isopropoxide and magnesium isopropoxide are added to n-propanol, wherein the mass fraction ratio of aluminum isopropoxide:magnesium isopropoxide, converted into Al2O3:MgO, is 97:3, and the mixture is stirred and refluxed at a heating temperature of 110℃ for 2 h; then a complexing agent solution of acetic acid and ethyl acetoacetate, wherein the molar ratio of acetic acid to ethyl acetoacetate is 1:18, is added in an amount of 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide at a heating temperature of 80℃, and the mixture is heated and refluxed for 1.5 h; then a mixture of water and n-propanol with a mass ratio of 1:4 is added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum isopropoxide and magnesium isopropoxide to water is 1:0.6, and the mixture is refluxed for 1 h after the dropwise addition is completed; the mixture is distilled under reduced pressure at a vacuum degree of 280 mbar at 200℃ for 2 h, and then the temperature is maintained for 3 h before the mixture is cooled to room temperature, thereby obtaining an Al-Mg complex oxide ceramic precursor.

[0101] The softening point of the Al-Mg complex oxide ceramic precursor obtained in the embodiment is 180℃, and the ceramic yield is 54%.

[0102] By performing melt spinning, non-fusion treatment, inorganic sintering, and ceramic sintering on the precursor (the same as the operation in Embodiment 1), Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 1.5 GPa are obtained.

[0103] Figure 6 XRD patterns of the obtained Al-Mg complex oxide ceramic fibers at different temperatures. The XRD patterns of the fibers at different temperatures are shown in FIG. 4. Figure 6 As can be seen from the figure, at 1200℃, the fiber is in an amorphous state, gamma the Al2O3 phase, α the Al2O3 phase, and when the temperature is increased to 1250℃, the MgAl2O4 crystalline phase begins to appear, and the crystallinity of the MgAl2O4 is higher than that in Embodiment 1, and the crystallinity is improved as the heat treatment temperature is increased.

[0104] Embodiment 14

[0105] The isopropyl alcohol aluminum and the isopropyl alcohol magnesium are added into the n-propanol, wherein the mass fraction ratio of the isopropyl alcohol aluminum:isopropyl alcohol magnesium, converted into Al2O3:MgO, is 71.7:28.3, and the stirring reflux is carried out at a heating temperature of 110 ℃ for 2 h; then a complexing agent solution of acetic acid and ethyl acetoacetate, wherein the molar ratio of the acetic acid and the ethyl acetoacetate is 1:10, is added in an amount of 0.6 times the molar fraction of the total amount of the isopropyl alcohol aluminum and the isopropyl alcohol magnesium at a heating temperature of 80 ℃, and the heating reflux is carried out for 1.5 h; then a mixture of water and n-propanol, wherein the mass ratio of the water and the n-propanol is 1:4, is added dropwise at a dropwise adding rate of 1 drop / s, wherein the molar ratio of the total amount of the isopropyl alcohol aluminum and the isopropyl alcohol magnesium and the water is 1:0.6, and the dropwise adding is completed, and the reflux is carried out for 1 h; the reduced pressure distillation is carried out at 160 ℃ and a vacuum degree of 280 mbar for 2 h, and the temperature is kept for 3 h and then reduced to room temperature, so as to prepare the Al-Mg complex oxide ceramic precursor.

[0106] The softening point of the Al-Mg complex oxide ceramic precursor obtained in the example is 180 ℃, and the ceramic yield is 54%.

[0107] The Al-Mg complex oxide continuous ceramic fiber with an average diameter of 10 μm and an average tensile strength of 1.4 GPa is obtained by carrying out the melt spinning, the non-fusion treatment, the inorganic sintering and the ceramic sintering on the precursor (the operations are the same as those in the example 1).

[0108] Comparative Example 1

[0109] The n-propanol aluminum and the methanol magnesium are added into the isopropyl alcohol, wherein the mass fraction ratio of the n-propanol aluminum:methanol magnesium, converted into Al2O3:MgO, is 99:1, and the stirring reflux is carried out at a heating temperature of 100 ℃ for 1 h; then the butanedione is added in an amount of 0.8 times the molar fraction of the total amount of the n-propanol aluminum and the methanol magnesium at a heating temperature of 70 ℃, and the heating reflux is carried out for 2 h; then a mixture of water and ethylene glycol ethyl ether, wherein the mass ratio of the water and the ethylene glycol ethyl ether is 1:6, is added dropwise at a dropwise adding rate of 1 drop / s, wherein the molar ratio of the total amount of the n-propanol aluminum and the methanol magnesium and the water is 1:0.6, the dropwise adding is completed, and the reflux is carried out for 2 h; the reduced pressure distillation is carried out at 180 ℃ and a vacuum degree of 260 mbar for 3 h, and the temperature is kept for 3 h and then reduced to room temperature, so as to prepare the Al-Mg complex oxide ceramic precursor.

[0110] The softening point of the Al-Mg complex oxide ceramic precursor obtained in the example is 160 ℃, and the ceramic yield is 50%.

[0111] The precursor was subjected to melt spinning, non-fusible treatment, inorganic sintering, and ceramic sintering (same as in Example 1) to obtain Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 0.9 GPa. Compared with Example 3, the same ratio of magnesium and aluminum elements, the use of a single composition of complexing agent resulted in a significant decrease in the average tensile strength of the obtained Al-Mg complex oxide continuous ceramic fibers.

[0112] Comparative Example 2

[0113] Aluminum n-propylate and magnesium methoxide were added to isopropanol, wherein the mass fraction ratio of aluminum n-propylate and magnesium methoxide was 99:1 in terms of Al2O3:MgO, and the mixture was stirred and refluxed at a heating temperature of 100℃ for 1 h; then 0.8 times the molar fraction of acetylacetone was added to the mixture, and the mixture was heated and refluxed at a heating temperature of 70℃ for 2 h; then a mixture of water and ethylene glycol ethyl ether with a mass ratio of 1:6 was added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum n-propylate and magnesium methoxide to water was 1:0.6, and the mixture was refluxed for 2 h after the dropwise addition was completed; the mixture was subjected to vacuum distillation at 180℃ and a vacuum degree of 260 mbar for 3 h, and then the mixture was cooled to room temperature after being kept warm for 3 h, thereby obtaining an Al-Mg complex oxide ceramic precursor.

[0114] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example was 160℃, and the ceramic yield was 50%.

[0115] The precursor was subjected to melt spinning, non-fusible treatment, inorganic sintering, and ceramic sintering (same as in Example 1) to obtain Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 0.9 GPa. Compared with Example 3, the same ratio of magnesium and aluminum elements, the use of a single composition of complexing agent resulted in a significant decrease in the average tensile strength of the obtained Al-Mg complex oxide continuous ceramic fibers.

[0116] Comparative Example 3

[0117] Aluminum isopropylate and magnesium isopropylate were added to n-propyl alcohol, wherein the mass fraction ratio of aluminum isopropylate to magnesium isopropylate was 99:1 in terms of Al2O3:MgO, and the mixture was stirred and refluxed at a heating temperature of 110℃ for 2 h; then 0.6 times the molar fraction of acetic acid was added to the mixture, and the mixture was heated and refluxed at a heating temperature of 80℃ for 1.5 h; then a mixture of water and n-propyl alcohol with a mass ratio of 1:4 was added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum isopropylate and magnesium isopropylate to water was 1:0.6, and the mixture was refluxed for 1 h after the dropwise addition was completed; the mixture was subjected to vacuum distillation at 200℃ and a vacuum degree of 280 mbar for 2 h, and then the mixture was cooled to room temperature after being kept warm for 3 h, thereby obtaining an Al-Mg complex oxide ceramic precursor.

[0118] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example is 180℃, and the ceramic yield is 54%.

[0119] By performing melt spinning, non-fusible treatment, inorganic sintering, and ceramic sintering on the precursor (same as the operation in Example 1), Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 1.1 GPa are obtained. Compared with Example 1, the use of a single-component complexing agent under the same magnesium-aluminum element ratio significantly reduces the average tensile strength of the obtained Al-Mg complex oxide continuous ceramic fibers.

[0120] Comparative Example 4

[0121] Aluminum isopropoxide and magnesium isopropoxide are added to n-propanol, wherein the mass fraction ratio of aluminum isopropoxide: magnesium isopropoxide, converted into Al2O3:MgO, is 99:1, and the stirring reflux is performed at a heating temperature of 110℃ for 2 h; then 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide, ethyl acetoacetate, is added at a heating temperature of 80℃, and the heating reflux is performed for 1.5 h; then a mixture of water and n-propanol with a mass ratio of 1:4 is added dropwise at a rate of 1 drop / s, wherein the molar ratio of the total amount of aluminum isopropoxide and magnesium isopropoxide to water is 1:0.6, and the dropwise addition is performed for 1 h; then the pressure is reduced to 280 mbar under a vacuum degree of 200℃, and the reduced pressure distillation is performed for 2 h; then the temperature is kept for 3 h and then reduced to room temperature, thereby obtaining an Al-Mg complex oxide ceramic precursor.

[0122] The softening point of the Al-Mg complex oxide ceramic precursor obtained in this example is 180℃, and the ceramic yield is 54%.

[0123] By performing melt spinning, non-fusible treatment, inorganic sintering, and ceramic sintering on the precursor (same as the operation in Example 1), Al-Mg complex oxide continuous ceramic fibers with an average diameter of 10 μm and an average tensile strength of 1.1 GPa are obtained. Compared with Example 1, the use of a single-component complexing agent under the same magnesium-aluminum element ratio significantly reduces the average tensile strength of the obtained Al-Mg complex oxide continuous ceramic fibers.

[0124] The application has been described in detail. For those skilled in the art, without departing from the purpose and scope of the application, and without unnecessary experiments, the application can be implemented in a wider range under the same parameters, concentrations and conditions. Although the application gives a special example, it should be understood that further improvements can be made to the application. In summary, according to the principle of the application, this application intends to include any changes, uses or improvements of the application, including changes made by conventional techniques known in the art, which are outside the scope disclosed in this application.

Claims

1. A method for preparing Al-Mg multiphase oxide ceramic precursors, comprising the following steps: 1) Add aluminum source and magnesium source to solvent, stir and reflux at 60~110℃ for 0.5~3 h; add complexing agent mixture a or b at 60~90℃, and continue reflux for 0.5~5 h; The complexing agent mixture solution a is a mixture of dimethyl ethyl ketone and acetylacetone; The complexing agent mixed solution b is a mixed solution of acetic acid and ethyl acetoacetate; 2) Add any one of the mixed solutions c to e to the reaction system obtained in step 1), and reflux for 0.5 to 1.5 h after the addition is complete; then remove the solvent and cool to room temperature to obtain the Al-Mg multiphase oxide ceramic precursor. The mixture c is composed of water and ethylene glycol methyl ether; The mixture d is composed of water and ethylene glycol ethyl ether; The mixture e is composed of water and n-propanol; The amounts of aluminum and magnesium sources used, converted to an Al2O3:MgO mass fraction ratio of 71.7~99.75:0.25~28.3; The molar amount of the complexing agent is 0.3 to 1 times the total molar amount of the aluminum source and magnesium source; In the complexing agent mixed solution a, the molar ratio of dimethyl ethyl ketone to acetylacetone is 1:10~30; In the complexing agent mixed solution b, the molar ratio of acetic acid and ethyl acetoacetate is 1:10~30.

2. The method according to claim 1, characterized in that: In step 1), the aluminum source is selected from at least one of aluminum isopropoxide, aluminum n-propoxide, and aluminum ethoxide; The magnesium source is selected from at least one of magnesium ethanol, magnesium methanol, magnesium acetylacetone, and magnesium isopropoxide.

3. The method according to claim 1, characterized in that: In step 2), the molar ratio of the total amount of aluminum source and magnesium source to water is 1:0.6~1; In the mixture c, the mass ratio of water to ethylene glycol methyl ether is 1:1~10; In the mixture d, the mass ratio of water to ethylene glycol ethyl ether is 1:1~10; In the mixture e, the mass ratio of water to n-propanol is 1:1~10.

4. An Al-Mg multiphase oxide ceramic precursor prepared by the method described in any one of claims 1-3.

5. The Al-Mg multiphase oxide ceramic precursor according to claim 4, characterized in that: The softening point of the Al-Mg multiphase oxide ceramic precursor is between 110 and 180°C.

6. The application of the Al-Mg multiphase oxide ceramic precursor according to claim 4 or 5 in the preparation of fibers.

7. The application according to claim 6, characterized in that: The fiber is a fiber containing aluminum and magnesium.

8. The application according to claim 7, characterized in that: The fiber is an Al-Mg multiphase oxide continuous ceramic fiber containing Al2O3 and MgAl2O4 phases.

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