Al-mg complex oxide continuous ceramic fiber and method for manufacturing the same

Abstract

The application discloses an Al-Mg complex oxide continuous ceramic fiber and a preparation method thereof. The preparation method comprises the following steps: 1) melting and spinning Al-Mg complex oxide ceramic precursors to obtain fiber filaments; 2) performing infusibilization treatment on the fiber filaments to obtain infusibilized fibers; and 3) sequentially performing inorganization and ceramization on the infusibilized fibers to obtain Al-Mg complex oxide continuous ceramic fibers. The preparation method of the Al-Mg complex oxide continuous ceramic fiber is simple in process, friendly to the environment and convenient for large-scale production. The crystal form of the Al-Mg complex oxide continuous ceramic fiber comprises a mixture of alpha-Al2O3, gamma-Al2O3 and MgAl2O4, and the proportion can be adjusted. The average diameter of the Al-Mg complex oxide continuous ceramic fiber is 5-20 microns, and the tensile strength is not less than 1.0 GPa.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite fiber materials, and relates to an Al-Mg complex oxide continuous ceramic fiber and a preparation method thereof. BACKGROUND

[0002] Ceramic fiber materials have the advantages of high-temperature resistance, stable chemical performance, oxidation resistance and low thermal conductivity, and are widely used in the fields of aerospace, metallurgy, chemical industry, high-temperature furnaces and the like. For example, the ceramic fiber materials are used in components of rockets, airplanes, spaceships and automobile engines, heat exchangers and the like, and can be used as inner linings of high-temperature furnaces to realize the light-weight and large-size of furnace structures and are ideal energy-saving and efficiency-improving materials. With the rapid development of modern industry, the requirement for high-temperature resistance of refractory materials is also increasing. In order to improve the high-temperature use performance of ceramic fiber materials, some people have prepared a series of complex oxide ceramic fibers by a sol-gel method or a carboxylate method. Magnesia-alumina spinel is an oxide ceramic material with high melting point (2135℃), small thermal expansion coefficient, low thermal conductivity, good thermal shock resistance and strong corrosion resistance. The magnesia-alumina spinel is not corroded by concentrated inorganic acid, hydrofluoric acid, phosphoric acid and caustic alkali at room temperature, and is resistant to the action of slag, molten metal, salts and carbon at high temperature, and has high refractoriness and high-temperature strength. The magnesia-alumina spinel fiber can be applied to a wider range of fields due to its advantages in shape and size. In the field of high-temperature thermal insulation materials, the spinel fiber is expected to be used to manufacture thermal insulation felt and become the latest ultra-light high-temperature resistant fiber at home and abroad. In the field of reinforcing materials, the magnesia-alumina spinel fiber is expected to be used as a reinforcing material for metal-based and ceramic-based composite materials, and the resin-based composite material reinforced by the magnesia-alumina spinel fiber is expected to replace glass fiber and carbon fiber in some fields.

[0003] Nanjing University of Science and Technology prepared continuous MgAl2O4 fibers by a sol-gel method. A fiber precursor spinning solution was obtained by polymerizing an aluminum chloride solution and a magnesium citrate solution. The precursor spinning solution was prepared into continuous magnesia-alumina spinel fibers with small diameter and certain toughness through centrifugal spinning and heat treatment in an air atmosphere. The precursor fibers were heated to 600℃ at a rate of 3℃ / min, then heated to 1000℃ at a rate of 5℃ / min and kept for 2h in the air atmosphere. The diameter of the fibers after the heat treatment is 5-8μm (Acta Crystallographica Section B: Structural Crystallography, 2014, 43(12):3191-3196).

[0004] CN1919762B Zhengzhou University provides a method for preparing transparent MgAl2O4 fibers: Alumina powder, metallic aluminum powder, magnesium oxide powder, and metallic magnesium powder are used as matrix raw materials, mixed in a mass percentage ratio of 50-80:0-30:10-20:0-20, and then calcined in a nitrogen atmosphere furnace to synthesize transparent MgAl2O4 fibers. This preparation method has disadvantages such as short fiber length, large fiber diameter, and high brittleness. Furthermore, the electric furnace used requires a special atmosphere in its structural design, making it difficult to scale up the equipment. Summary of the Invention

[0005] The purpose of this invention is to provide an Al-Mg multiphase oxide continuous ceramic fiber and its preparation method. The Al-Mg multiphase oxide continuous ceramic fiber is prepared by polymer melt spinning, a process that is environmentally friendly. The resulting Al-Mg multiphase oxide continuous ceramic fiber is a mixture of α-Al₂O₃, γ-Al₂O₃, and MgAl₂O₄ in an adjustable ratio; its average diameter is 5–20 μm, and its tensile strength is not less than 1 GPa.

[0006] The method for preparing Al-Mg multiphase oxide continuous ceramic fibers provided by the present invention includes the following steps:

[0007] 1) The Al-Mg multiphase oxide ceramic precursor was melt-spun to obtain fiber filaments;

[0008] 2) The fiber filaments are subjected to a non-melting treatment to obtain non-melting fibers;

[0009] 3) The infusible fibers are sequentially subjected to inorganic and ceramic sintering to obtain the Al-Mg multiphase oxide continuous ceramic fibers.

[0010] In step 1) of the above method, the softening point of the Al-Mg multiphase oxide ceramic precursor is 110-180℃; specifically, it can be 180℃.

[0011] The Al-Mg multiphase oxide ceramic precursor was prepared by the following method:

[0012] Aluminum and magnesium sources were added to a solvent and refluxed under stirring at 60–110 °C for 0.5–3 h. Then, a mixed solution of acetic acid and ethyl acetoacetate was added at 60–90 °C and refluxed for another 0.5–5 h. A complexing agent solution of acetic acid and ethyl acetoacetate in 0.6 molar fractions of the total amount of aluminum and magnesium sources was added and refluxed for another 0.5–5 h. A mixture of water and n-propanol in a mass ratio of 1:4 was then added dropwise and refluxed for 1 h after the addition was complete. The mixture was then distilled under reduced pressure and cooled to room temperature to obtain the Al-Mg multiphase oxide ceramic precursor.

[0013] 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, it can be 99.75:0.25, 99:1, 97:3, 95:5, 71.7:28.3;

[0014] The aluminum source is aluminum isopropoxide; the magnesium source is magnesium isopropoxide;

[0015] The solvent is n-propanol;

[0016] In the mixed solution of acetic acid and ethyl acetoacetate, the molar ratio of acetic acid to ethyl acetoacetate is 1:20;

[0017] The mixed solution of acetic acid and ethyl acetoacetate is 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide;

[0018] The molar ratio of the total amount of aluminum source and magnesium source to water is 1:0.6;

[0019] The temperature of the melt spinning is higher than the softening point of the precursor; specifically, it can be 210-235°C, and more specifically, it can be 235°C, 220°C, or 210°C;

[0020] In the melt spinning, the pore size of the spinning hole can be 0.1-1 mm; specifically, it can be 0.1 mm, 0.2 mm, or 0.25 mm;

[0021] The screw extrusion force is 5-30 MPa; specifically, it can be 20 MPa, 25 MPa, or 30 MPa;

[0022] The spinning rate is 1000-8000 r / min; specifically, it can be 4000 r / min or 8000 r / min;

[0023] The operation of the non-melting treatment in step 2) is as follows: the fiber filament is placed in a constant temperature and humidity box, first heated to 35-50°C (such as 40°C) at a relative humidity of 35-50% (such as 40%), and then heated to 55-70°C (such as 60°C) at a relative humidity of 55-70% (such as 60%) for 10-60 min (such as 20 min or 30 min), and then heated to 75-90°C (such as 85°C) at a relative humidity of 75-95% (such as 80%) for 10-60 min (such as 40 min), and then cooled to room temperature.

[0024] In the inorganicization step in step 3), the inorganicization temperature is 550-850°C; specifically, it can be 650°C, 700°C, 800°C, or 900°C;

[0025] The rate of increasing from room temperature to the inorganicization temperature is 0.5-4°C / min; specifically, it can be 1°C / min.

[0026] The inorganic time is 0.5h-4h; specifically, 1h;

[0027] The inorganic atmosphere is air;

[0028] The cooling to room temperature is natural cooling;

[0029] In the ceramic step, the ceramic temperature is 1100-1500℃; specifically, 1200℃, 1300℃, 1400℃;

[0030] The rate from room temperature to ceramic temperature is 10-30℃ / min; specifically, 10℃ / min;

[0031] The ceramic time is 0.5h-2h; specifically, 1h;

[0032] The ceramic atmosphere is air.

[0033] In addition, the Al-Mg complex oxide continuous ceramic fiber prepared by the above method and the application of the Al-Mg complex oxide continuous ceramic fiber in preparing a material with at least one of structural reinforcement and high-temperature insulation also belong to the protection scope of the present application.

[0034] The tensile strength of the Al-Mg complex oxide continuous ceramic fiber is not less than 1.0Gpa; specifically, 1.0GPa, 1.1GPa, 1.3GPa, 1.4GPa, 1.5GPa;

[0035] The crystal phase of the Al-Mg complex oxide continuous ceramic fiber is selected from at least two of α-Al2O3 phase, γ-Al2O3 phase and MgAl2O4 phase.

[0036] The average diameter of the Al-Mg complex oxide continuous ceramic fiber is 5-20μm; specifically, 10μm, 12μm, 14μm, 16μm.

[0037] The present application has the following beneficial effects:

[0038] 1) The preparation method of the Al-Mg complex oxide continuous ceramic fiber provided by the present application adopts melt spinning to form fibers, which is simple in process, friendly to environment and convenient for large-scale production.

[0039] 2) The crystal form of the Al-Mg complex oxide continuous ceramic fiber provided by the present application is a mixture of α-Al2O3, γ-Al2O3 and MgAl2O4, and the proportion is adjustable.

[0040] 3) The average diameter of the Al-Mg complex oxide continuous ceramic fiber provided by the present application is 5-20μm, and the tensile strength is not less than 1.0GPa. Attached Figure Description

[0041] Figure 1 This is a SEM image of the Al-Mg multiphase oxide continuous ceramic fiber prepared in Example 1 of the present invention.

[0042] Figure 2 The images show the XRD patterns of the Al-Mg multiphase oxide continuous ceramic fibers prepared in Example 1 of this invention at different temperatures.

[0043] Figure 3 This is a rheological diagram of the precursor prepared in Example 2 of the present invention.

[0044] Figure 4 This is the TG image of the precursor prepared in Example 2 of the present invention.

[0045] Figure 5 This is a SEM image of the Al-Mg multiphase oxide continuous ceramic fiber precursor prepared in Example 2 of the present invention.

[0046] Figure 6 The images show the XRD patterns of the Al-Mg multiphase oxide continuous ceramic fibers prepared in Example 2 of this invention at different temperatures.

[0047] Figure 7 The images show the XRD patterns of the Al-Mg multiphase oxide continuous ceramic fibers prepared in Example 3 of this invention at different temperatures. Detailed Implementation

[0048] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0050] Example 1

[0051] Preparation of Al-Mg multiphase oxide continuous ceramic fibers

[0052] The precursor is synthesized as follows: aluminum isopropoxide and magnesium isopropoxide are added to n-propanol, the mass ratio of aluminum isopropoxide to magnesium isopropoxide is 99:1, the mixture is stirred and refluxed at 110℃ for 2 hours; then a complexing agent solution of acetic acid and acetylacetate ethyl ester is added, the molar ratio of acetic acid to acetylacetate ethyl ester is 1:20, the amount of the complexing agent solution is 0.6 times the total amount of aluminum isopropoxide and magnesium isopropoxide, the mixture is heated and refluxed at 80℃ for 1.5 hours; then a mixture of water and n-propanol is added dropwise at a rate of 1 drop per second, the mass ratio of water to n-propanol is 1:4, the molar ratio of the total amount of aluminum isopropoxide and magnesium isopropoxide to water is 1:0.6, the mixture is refluxed for 1 hour after the dropwise addition is completed; the mixture is distilled under reduced pressure at 200℃ and a vacuum degree of 280 mbar for 2 hours, the mixture is cooled to room temperature after being kept at 200℃ for 3 hours, and an Al-Mg complex oxide ceramic precursor is obtained, the softening point of the precursor is 180℃, and the ceramic yield is 54%;

[0053] 2) melt spinning: the Al-Mg complex oxide ceramic precursor with a softening point of 180℃ and a mass ratio of Al2O3 to MgO of 99:1 is heated to 235℃, the precursor is melted into a uniform melt and the residual bubbles are removed, then melt spinning is performed at 235℃, the spinning hole diameter is 0.1 mm, the screw extrusion pressure is 30 MPa, and the fiber is collected at a speed of 8000 r / min, and a fiber precursor is obtained;

[0054] 3) infusibilization: the fiber precursor is placed in a constant temperature and humidity box, the temperature is first increased to 40℃, the fiber precursor is kept at 40% relative humidity for 30 minutes, then the temperature is increased to 60℃, the fiber precursor is kept at 60% relative humidity for 30 minutes, then the temperature is increased to 85℃, the fiber precursor is kept at 80% relative humidity for 40 minutes, and the fiber precursor is cooled to room temperature to obtain an infusibilized fiber;

[0055] 4) inorganization: the infusibilized fiber is placed in a high-temperature furnace, the temperature is increased to 700℃ at a rate of 1℃ / min, the fiber is kept at 700℃ for 1 hour, the atmosphere in the furnace is air, and the fiber is naturally cooled to room temperature;

[0056] 5) ceramicization: the inorganic fiber is placed in a high-temperature furnace, the temperature is increased to 1200℃ at a rate of 10℃ / min, the fiber is kept at 1200℃ for 1 hour, the atmosphere in the furnace is air, and an Al-Mg complex oxide continuous ceramic fiber is obtained.

[0057] The average diameter of the fiber is 10 μm; the crystal phase composition is a mixture of amorphous phase, γ-Al2O3 phase, α-Al2O3 phase and MgAl2O4 phase, and the tensile strength of the fiber is 1.5 GPa.

[0058] 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.

[0059] The XRD images of the fiber at different temperatures are shown in the following figures:Figure 2 From the figure, it can be seen that at 1200℃, it is amorphous, γ-Al2O3 phase, α-Al2O3 phase, when the temperature rises to 1250℃, MgAl2O4 crystalline phase begins to appear, and the crystallinity increases with the increase of the heat treatment temperature.

[0060] Example 2

[0061] Preparation of Al-Mg complex oxide continuous ceramic fiber

[0062] 1) Precursor synthesis: aluminum isopropoxide, magnesium isopropoxide were added to n-propanol, wherein the mass fraction ratio of aluminum isopropoxide: magnesium isopropoxide was 99.75:0.25, converted into Al2O3:MgO, under the heating temperature of 110℃, stirring reflux for 2h; then under the heating temperature of 80℃, add 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide of acetic acid and acetylacetate ethyl ester complexing agent solution, wherein the molar ratio of acetic acid and acetylacetate ethyl ester is 1:20, heating reflux for 1.5h; then drop 1 drop / s of the mixed solution of water and n-propanol with a mass ratio of 1:4, wherein the molar ratio of the total amount of aluminum isopropoxide, magnesium isopropoxide and water is 1:0.6, drop for 1h; under the condition of 200℃, 280mbar vacuum degree, reduced pressure distillation for 2h, keep warm for 3h, then reduce to room temperature, to obtain Al-Mg complex oxide ceramic precursor, the softening point is 180℃, the ceramic yield is 54%;

[0063] 2) Melt spinning: the Al-Mg complex oxide ceramic precursor with a softening point of 180℃ and a mass fraction ratio of Al2O3:MgO of 99.75:0.25 was heated to 235℃, and after it was melted into a uniform melt and the residual bubbles were removed, melt spinning was carried out at a temperature of 235℃, the spinning hole was 0.1mm, the screw extrusion pressure was 30MPa, and the fiber filament was obtained at a speed of 8000r / min;

[0064] The rheological curve of the precursor in air atmosphere is shown in Figure 3 From the figure, it can be seen that the viscosity of the precursor decreases with the increase of the temperature at 100-200℃, according to the viscosity-temperature curve of the precursor, the appropriate melting temperature for spinning is selected.

[0065] The thermogravimetric curve of the precursor in flowing air atmosphere at 10℃ / min is shown in Figure 4 From the figure, it can be seen that the ceramic yield of the precursor is about 54%, the weight loss of the precursor is fast before 600℃, and the weight loss is not obvious after 600℃.

[0066] The SEM image of the fiber filament is shown in Figure 5 .

[0067] 3) non-melting: the obtained fiber filament is placed in a constant temperature and humidity box, first heated to 40℃, kept at 40% relative humidity for 20 min, then heated to 60℃, kept at 60% relative humidity for 20 min, then heated to 85℃, kept at 80% relative humidity for 30 min, and cooled to room temperature to obtain non-melting fiber;

[0068] 4) inorganic: the obtained non-melting fiber is placed in a high-temperature furnace, heated to 650℃ at a rate of 1℃ / min, kept for 1h, and the furnace atmosphere is air;

[0069] 5) ceramic: the obtained inorganic fiber is placed in a high-temperature furnace, heated to 1200℃ at a rate of 10℃ / min, kept for 1h, and the furnace atmosphere is air, to obtain the Al-Mg complex oxide continuous ceramic fiber provided by the application.

[0070] The average diameter of the obtained fiber is 10μm; the crystal phase composition is a mixture of amorphous phase, γ-Al2O3 phase and α-Al2O3 phase, and the tensile strength of the fiber is 1.4GPa.

[0071] The XRD patterns of the fiber prepared at different temperatures are shown in the following figure Figure 6 As can be seen from the figure, below 1100℃, there are only amorphous phase and γ-Al2O3 phase, when the temperature rises to 1100℃, α-Al2O3 crystalline phase begins to appear, and the crystallinity increases with the increase of the heat treatment temperature.

[0072] Example 3

[0073] Preparation of Al-Mg complex oxide continuous ceramic fiber

[0074] 1) precursor synthesis: aluminum isopropoxide and magnesium isopropoxide are added to n-propanol, wherein the mass fraction ratio of aluminum isopropoxide: magnesium isopropoxide is 97:3 after conversion to Al2O3:MgO, and the mixture is stirred and refluxed at a heating temperature of 110℃ for 2h; then 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide is added to the mixture, which is a complexing agent solution of acetic acid and acetylacetate ethyl ester, wherein the molar ratio of acetic acid to acetylacetate ethyl ester is 1:20, and the mixture is heated and refluxed at a heating temperature of 80℃ for 1.5h; 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 1h after the dropwise addition is completed; the mixture is reduced pressure distilled at 200℃ and a vacuum degree of 280mbar for 2h, and then cooled to room temperature after keeping for 3h, to obtain an Al-Mg complex oxide ceramic precursor, the softening point of which is 180℃, and the ceramic yield is 54%;

[0075] 2) melt spinning: the Al-Mg complex oxide ceramic precursor with a softening point of 180℃ and a mass ratio of Al2O3:MgO of 97:3 is heated to 235℃, after it is melted into a uniform melt and residual bubbles are removed, melt spinning is carried out at a temperature of 235℃, the fiber outlet aperture is 0.1mm, the screw extrusion pressure is 25MPa, and the fiber is collected at a speed of 8000r / min to obtain a fiber precursor;

[0076] 3) non-melting: the obtained fiber precursor is placed in a constant temperature and humidity box, first heated to 40℃, kept at a relative humidity of 40% for 30min, then heated to 60℃, kept at a relative humidity of 60% for 30min, then heated to 85℃, kept at a relative humidity of 85% for 40min, and cooled to room temperature to obtain a non-melting fiber;

[0077] 4) inorganic: the obtained non-melting fiber is placed in a high-temperature furnace, heated to 700℃ at a rate of 1℃ / min, kept for 1h, the furnace atmosphere is air, and then naturally cooled to room temperature;

[0078] 5) ceramic: the obtained inorganic fiber is placed in a high-temperature furnace, heated to 1300℃ at a rate of 10℃ / min, kept for 1h, the furnace atmosphere is air, and the Al-Mg complex oxide continuous ceramic fiber provided by the application is obtained.

[0079] The average diameter of the obtained fiber is 10μm; the crystal phase composition is a mixture of amorphous phase, γ-Al2O3 phase, α-Al2O3 phase and MgAl2O4 phase, and the tensile strength of the fiber is 1.5GPa.

[0080] The XRD patterns of the fiber at different temperatures are shown in the following figure Figure 7 It can be seen from the figure that at 1200℃, it is amorphous phase, γ-Al2O3 phase and α-Al2O3 phase, when the temperature rises to 1250℃, MgAl2O4 crystalline phase begins to appear, and the crystallinity of MgAl2O4 is higher than that of Example 1, and the crystallinity increases with the increase of heat treatment temperature.

[0081] Example 4

[0082] Preparation of Al-Mg complex oxide continuous ceramic fiber

[0083] 1) Precursor synthesis: 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 71.7:28.3, and the mixture is stirred and refluxed at a heating temperature of 110℃ for 2h; 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, is added at a heating temperature of 80℃, wherein the molar ratio of acetic acid to ethyl acetoacetate is 1:20, and the mixture is heated and refluxed for 1.5h; then a mixture of water and n-propanol, in 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 1h after the dropwise addition is completed; the mixture is distilled under reduced pressure at a vacuum degree of 280mbar and at a temperature of 200℃ for 2h, and then the temperature is maintained for 3h before the mixture is cooled to room temperature, thereby obtaining an Al-Mg complex oxide ceramic precursor, which has a softening point of 180℃ and a ceramic yield of 54%;

[0084] 2) Melt spinning: the Al-Mg complex oxide ceramic precursor, which has a softening point of 180℃ and a mass fraction ratio of Al2O3:MgO of 71.7:28.3, is heated to 235℃, and then melt spinning is performed at a temperature of 235℃ after the precursor is melted into a uniform melt and residual bubbles are removed, wherein the spinning hole diameter is 0.1mm, the screw extrusion pressure is 30MPa, and the fiber is collected at a rate of 8000r / min, thereby obtaining a fiber precursor;

[0085] 3) Infusibilization: the fiber precursor is placed in a constant-temperature and constant-humidity box, and then the temperature is increased to 40℃, the relative humidity is set to 40%, and the fiber precursor is maintained at the temperature and humidity for 30min; then the temperature is increased to 60℃, the relative humidity is set to 60%, and the fiber precursor is maintained at the temperature and humidity for 30min; then the temperature is increased to 85℃, the relative humidity is set to 80%, and the fiber precursor is maintained at the temperature and humidity for 40min; and then the fiber precursor is cooled to room temperature, thereby obtaining an infusibilized fiber;

[0086] 4) Inorganization: the infusibilized fiber is placed in a high-temperature furnace, and then the temperature is increased to 700℃ at a rate of 1℃ / min, the furnace atmosphere is air, the fiber is maintained at the temperature for 1h, and then the fiber is naturally cooled to room temperature;

[0087] 5) Ceramization: the inorganic fiber is placed in a high-temperature furnace, and then the temperature is increased to 1200℃ at a rate of 10℃ / min, the furnace atmosphere is air, and the fiber is maintained at the temperature for 1h, thereby obtaining the Al-Mg complex oxide continuous ceramic fiber provided by the application.

[0088] The average diameter of the fiber is 10μm; the crystal phase composition is a mixture of amorphous phase, γ-Al2O3 phase, α-Al2O3 phase, and MgAl2O4 phase; and the tensile strength of the fiber is 1.4GPa.

[0089] Example 5

[0090] Preparation of Al-Mg complex oxide continuous ceramic fiber

[0091] 1) Precursor synthesis: 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 2h; subsequently, 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℃, wherein the molar ratio of acetic acid to ethyl acetoacetate was 1:20, and the mixture was heated and refluxed for 1.5h; 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 1h after the dropwise addition was completed; the mixture was subjected to reduced pressure distillation at 200℃ and a vacuum degree of 280mbar for 2h, and was cooled to room temperature after being kept warm for 3h, thereby obtaining an Al-Mg complex oxide ceramic precursor, which had a softening point of 180℃ and a ceramic yield of 54%;

[0092] 2) Melt spinning: the Al-Mg complex oxide ceramic precursor, which had a softening point of 180℃ and a mass fraction ratio of Al2O3:MgO of 99:1, was heated to 235℃, and was subjected to melt spinning at 235℃ after being melted into a uniform melt and releasing residual bubbles, with a spinning hole diameter of 0.2mm, a screw extrusion pressure of 20MPa, and a take-up rate of 4000r / min, thereby obtaining a fiber precursor;

[0093] 3) Infusibilization: the fiber precursor was placed in a constant temperature and humidity box, was warmed to 40℃, was kept warm at a relative humidity of 40% for 30min, was warmed to 60℃, was kept warm at a relative humidity of 60% for 30min, was warmed to 85℃, was kept warm at a relative humidity of 80% for 40min, and was cooled to room temperature, thereby obtaining an infusibilized fiber;

[0094] 4) Inorganization: the infusibilized fiber was placed in a high-temperature furnace, was warmed to 800℃ at a rate of 1℃ / min, was kept warm for 1h in an air atmosphere, and was naturally cooled to room temperature;

[0095] 5) Ceramization: the inorganic fiber was placed in a high-temperature furnace, was warmed to 1300℃ at a rate of 10℃ / min, was kept warm for 1h in an air atmosphere, and was obtained as an Al-Mg complex oxide continuous ceramic fiber.

[0096] The obtained fiber had an average diameter of 14μm, a crystal phase composition of a mixture of amorphous, γ-Al2O3 phase, α-Al2O3 phase and MgAl2O4 phase, and a tensile strength of 1.1GPa.

[0097] Example 6

[0098] Preparation of an Al-Mg complex oxide continuous ceramic fiber

[0099] 1) Precursor synthesis: 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 2h; subsequently, a complexing agent 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 1.5h; then, a mixture of water and n-propanol, 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 isopropoxide and magnesium isopropoxide to water was 1:0.6, and the mixture was refluxed for 1h after the dropwise addition was completed; the mixture was subjected to reduced-pressure distillation at 200℃ and a vacuum degree of 280mbar for 2h, and then was cooled to room temperature after being kept warm for 3h, thereby obtaining an Al-Mg complex oxide ceramic precursor, which had a softening point of 180℃ and a ceramic yield of 54%;

[0100] 2) Melt spinning: the Al-Mg complex oxide ceramic precursor, which had a softening point of 180℃ and a mass fraction ratio of Al2O3:MgO of 99:1, was heated to 220℃, and after the precursor was melted into a uniform melt and the residual bubbles were removed, melt spinning was performed at a temperature of 220℃, with a spinning hole diameter of 0.1mm, a screw extrusion pressure of 30MPa, and a take-up speed of 4000r / min, thereby obtaining a fiber precursor;

[0101] 3) Infusibilization: the fiber precursor was placed in a constant-temperature and constant-humidity box, and was first warmed to 40℃, kept warm at a relative humidity of 40% for 30min, then warmed to 60℃, kept warm at a relative humidity of 60% for 30min, then warmed to 85℃, kept warm at a relative humidity of 80% for 40min, and finally cooled to room temperature, thereby obtaining an infusibilized fiber;

[0102] 4) Inorganization: the infusibilized fiber was placed in a high-temperature furnace, and was warmed to 700℃ at a rate of 1℃ / min, kept warm for 1h, and then naturally cooled to room temperature in an air atmosphere;

[0103] 5) Ceramization: the inorganic fiber was placed in a high-temperature furnace, and was warmed to 1200℃ at a rate of 10℃ / min, kept warm for 1h, and then obtained as an Al-Mg complex oxide continuous ceramic fiber.

[0104] The obtained fiber had an average diameter of 12μm, a crystal phase composition of a mixture of amorphous, γ-Al2O3 phase, α-Al2O3 phase and MgAl2O4 phase, and a tensile strength of 1.3GPa.

[0105] Example 7

[0106] Preparation of an Al-Mg complex oxide continuous ceramic fiber

[0107] 1) Precursor synthesis: 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 2h; subsequently, a complexing agent solution of acetic acid and ethyl acetoacetate, wherein the molar ratio of acetic acid to ethyl acetoacetate was 1:20, was added at a heating temperature of 80℃, and the mixture was heated and refluxed for 1.5h; then, a mixture of water and n-propanol, 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 isopropoxide and magnesium isopropoxide to water was 1:0.6, and the mixture was refluxed for 1h after the dropwise addition was completed; the mixture was subjected to reduced pressure distillation at 200℃ and a vacuum degree of 280mbar for 2h, and then was cooled to room temperature after being kept warm for 3h, thereby obtaining an Al-Mg complex oxide ceramic precursor, with a softening point of 180℃ and a ceramic yield of 54%;

[0108] 2) Melt spinning: the Al-Mg complex oxide ceramic precursor, with a softening point of 180℃ and a mass fraction ratio of Al2O3:MgO of 99:1, was heated to 210℃, and after the precursor was melted into a uniform melt and residual bubbles were removed, melt spinning was performed at a temperature of 210℃, with a spinning hole diameter of 0.1mm, a screw extrusion pressure of 30MPa, and a winding speed of 4000r / min, thereby obtaining a fiber precursor;

[0109] 3) Infusibilization: the fiber precursor was placed in a constant temperature and humidity box, and was first heated to 40℃, kept warm at a relative humidity of 40% for 30min, then heated to 60℃, kept warm at a relative humidity of 60% for 30min, and then heated to 85℃, kept warm at a relative humidity of 80% for 40min, and finally cooled to room temperature, thereby obtaining an infusibilized fiber;

[0110] 4) Inorganization: the infusibilized fiber was placed in a high-temperature furnace, heated to 700℃ at a rate of 1℃ / min, kept warm for 1h, and then naturally cooled to room temperature;

[0111] 5) Ceramization: the inorganic fiber was placed in a high-temperature furnace, heated to 1400℃ at a rate of 10℃ / min, kept warm for 1h, and then obtained as an Al-Mg complex oxide continuous ceramic fiber.

[0112] The average diameter of the obtained fiber was 14μm; the crystal phase composition was a mixture of amorphous phase, γ-Al2O3 phase, α-Al2O3 phase and MgAl2O4 phase, and the tensile strength of the fiber was 1.1GPa.

[0113] Example 8

[0114] Preparation of an Al-Mg complex oxide continuous ceramic fiber

[0115] 1) Precursor synthesis: 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 97:3, and the mixture was stirred and refluxed at a heating temperature of 110℃ for 2h; subsequently, a complexing agent solution of acetic acid and ethyl acetoacetate, wherein the molar ratio of acetic acid to ethyl acetoacetate was 1:20, was added at a heating temperature of 80℃, and the mixture was heated and refluxed for 1.5h; then, a mixture of water and n-propanol, 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 isopropoxide and magnesium isopropoxide to water was 1:0.6, and the mixture was refluxed for 1h after the dropwise addition was completed; the mixture was subjected to reduced pressure distillation at 200℃ and a vacuum degree of 280mbar for 2h, and then was cooled to room temperature after being kept warm for 3h, thereby obtaining an Al-Mg complex oxide ceramic precursor, with a softening point of 180℃ and a ceramic yield of 54%;

[0116] 2) Melt spinning: the Al-Mg complex oxide ceramic precursor, with a softening point of 180℃ and a mass fraction ratio of Al2O3:MgO of 97:3, was heated to 235℃, and then was subjected to melt spinning at 235℃ after being melted into a uniform melt and releasing residual bubbles, with a spinning hole diameter of 0.25mm, a screw extrusion pressure of 30MPa, and a winding speed of 8000r / min, thereby obtaining a fiber precursor;

[0117] 3) Infusibilization: the fiber precursor was placed in a constant temperature and humidity box, and was subjected to temperature rising and humidity rising in sequence, i.e., rising to 40℃ and keeping warm at a relative humidity of 40% for 30min, rising to 60℃ and keeping warm at a relative humidity of 60% for 30min, and rising to 85℃ and keeping warm at a relative humidity of 85% for 40min, and then was cooled to room temperature, thereby obtaining an infusibilized fiber;

[0118] 4) Inorganization: the infusibilized fiber was placed in a high-temperature furnace, and was heated to 900℃ at a rate of 1℃ / min, kept warm for 1h, and then was naturally cooled to room temperature in an air atmosphere;

[0119] 5) Ceramization: the inorganic fiber was placed in a high-temperature furnace, and was heated to 1200℃ at a rate of 10℃ / min, kept warm for 1h, and then was obtained as an Al-Mg complex oxide continuous ceramic fiber.

[0120] The obtained fiber had an average diameter of 16μm, and a crystal phase composition of a mixture of amorphous phase, γ-Al2O3 phase, α-Al2O3 phase and MgAl2O4 phase, and a tensile strength of 1.0GPa.

[0121] Comparative Example 1

[0122] Preparation of Al-Mg complex oxide continuous ceramic fiber

[0123] Precursor synthesis: aluminum isopropoxide, magnesium isopropoxide were added to n-propanol, wherein the mass fraction ratio of aluminum isopropoxide: magnesium isopropoxide was 99:1, corresponding to Al2O3:MgO, under a heating temperature of 110°C, stirring reflux for 2h; then a solution of acetylacetate ethyl ester was added, which was 0.6 times the molar fraction of the total amount of aluminum isopropoxide and magnesium isopropoxide, under a heating temperature of 80°C, heating reflux for 1.5h; then a mixture of water and n-propanol was added at a rate of 1 drop / s, wherein the mass ratio of water to n-propanol was 1:4, and the molar ratio of the total amount of aluminum isopropoxide, magnesium isopropoxide, and water was 1:0.6, and after the drop was completed, reflux was performed for 1h; under a vacuum degree of 280mbar at 200°C, the pressure was reduced for 2h, and after 3h of incubation, the temperature was reduced to room temperature, to obtain an Al-Mg complex oxide ceramic precursor, with a softening point of 180°C and a ceramic yield of 54%;

[0124] 2) Melt spinning: the Al-Mg complex oxide ceramic precursor with a softening point of 180°C and a mass fraction ratio of Al2O3:MgO of 99:1 was heated to 235°C, and after it was melted into a uniform melt and the residual bubbles were removed, melt spinning was performed at a temperature of 235°C, with a fiber outlet aperture of 0.1mm, a screw extrusion pressure of 30MPa, and a take-up rate of 8000r / min, to obtain a fiber precursor;

[0125] 3) Non-melting: the obtained fiber precursor was placed in a constant temperature and humidity box, first heated to 40°C, incubated at a relative humidity of 40% for 30min, then heated to 60°C, incubated at a relative humidity of 60% for 30min, then heated to 85°C, incubated at a relative humidity of 80% for 40min, and cooled to room temperature to obtain a non-melting fiber;

[0126] 4) Inorganizing: the obtained non-melting fiber was placed in a high-temperature furnace, heated to 700°C at a rate of 1°C / min, incubated for 1h, with an air atmosphere in the furnace, and then naturally cooled to room temperature;

[0127] 5) Ceramization: the obtained inorganic fiber was placed in a high-temperature furnace, heated to 1200°C at a rate of 10°C / min, incubated for 1h, with an air atmosphere in the furnace, to obtain an Al-Mg complex oxide continuous ceramic fiber.

[0128] An Al-Mg complex oxide continuous ceramic fiber with an average diameter of 10μm and an average tensile strength of 1.1GPa was obtained. Compared with Example 1, the use of a single composition complexing agent resulted in a significant decrease in the average tensile strength of the obtained Al-Mg complex oxide continuous ceramic fiber.

[0129] The application has been described in detail. For those skilled in the art, the application can be implemented in a wider range under the same parameters, concentrations and conditions without departing from the spirit and scope of the application and without unnecessary experiments. Although the application gives a special example, it should be understood that the application can be further improved. In summary, according to the principle of the application, the application intends to include any change, use or improvement of the application, including the change made by the conventional technology known in the art, which is out of the range disclosed in the application.

Claims

1.A method for preparing Al-Mg complex oxide continuous ceramic fiber, comprising the following steps: 1) melt spinning Al-Mg complex oxide ceramic precursor to obtain fiber filaments; 2) infusibilizing the fiber filaments to obtain infusibilized fibers; 3) inorganicizing and sintering the infusibilized fibers in sequence to obtain the Al-Mg complex oxide continuous ceramic fiber; the Al-Mg complex oxide ceramic precursor is prepared by the following method: adding aluminum source and magnesium source into solvent, stirring and refluxing at a heating temperature of 60-110 ℃ for 0.5-3 h; then adding a complexing agent mixed solution of acetic acid and ethyl acetoacetate in a molar fraction of 0.6 times the total amount of aluminum source and magnesium source at a heating temperature of 60-90 ℃, heating and refluxing for 0.5-5 h; then dropping a mixed solution of water and n-propanol with a mass ratio of 1:4, and refluxing for 1 h after dropping; and then reducing pressure to distill and reducing to room temperature to obtain the Al-Mg complex oxide ceramic precursor; the temperature for inorganicizing in the step 3) is 550-850 ℃; the time for inorganicizing is 0.5 h-4 h; and the atmosphere for inorganicizing is air; in the step 1) of melt spinning, the softening point of the Al-Mg complex oxide ceramic precursor is 110-180 ℃; the mass fraction ratio of the aluminum source and the magnesium source, converted into Al 2 O 3 : MgO, is 71.7-99.75: 0.25-28.3; the molar ratio of acetic acid and ethyl acetoacetate in the mixed solution of acetic acid and ethyl acetoacetate is 1:20; and the molar ratio of the total amount of aluminum source and magnesium source to water is 1:0.6; the temperature for melt spinning is higher than the softening point of the precursor, and is 210-235 ℃; in the melt spinning, the pore diameter of the spinning hole is 0.1-1 mm; the screw extrusion force is 5-30 MPa; and the spinning rate is 1000-8000 r / min; the operation of the step 2) of infusibilizing is as follows: placing the fiber filaments in a constant temperature and humidity box, first increasing the temperature to 35-50 ℃, maintaining the temperature at 35-50% relative humidity for 10-60 min, then increasing the temperature to 55-70 ℃, maintaining the temperature at 55-70% relative humidity for 10-60 min, then increasing the temperature to 75-90 ℃, maintaining the temperature at 75-95% relative humidity for 10-60 min, and cooling to room temperature; in the step 3) of inorganicizing, the rate of increasing the temperature from room temperature to the inorganicizing temperature is 0.5-4 ℃ / min; in the step of sintering, the temperature for sintering is 1100-1500 ℃; the rate of increasing the temperature from room temperature to the sintering temperature is 10-30 ℃ / min; the time for sintering is 0.5 h-2 h; and the atmosphere for sintering is air; 8.Al-Mg complex oxide continuous ceramic fiber prepared by the method of any one of claims 1-7; the tensile strength of the Al-Mg complex oxide continuous ceramic fiber is not less than 1.0 GPa; and the average diameter of the Al-Mg complex oxide continuous ceramic fiber is 5-20 μm. ​ ​ ​ ​ ​ ​ ​ ​ 2. The method of claim 1, wherein: ​ 3. The method of claim 1, wherein: ​ ​ ​ 4. The method of claim 1, wherein: ​ ​ ​ ​ 5. The method of claim 1, wherein: ​ 6. The method of claim 1, wherein: ​ 7. The method of claim 1, wherein: ​ ​ ​ ​ ​ 9. The fiber according to claim 8, characterized in that: ​ the crystal phase of the Al-Mg complex oxide continuous ceramic fiber is selected from α - an Al2O3 phase, ​ - at least two of an Al2O3 phase and a MgAl2O4 phase; ​

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