Ceramic fiber composite material as well as preparation method and application thereof

Abstract

The invention discloses a ceramic fiber composite material as well as a preparation method and application thereof, and the ceramic fiber composite material comprises the following components in percentage by weight: 40-80% of gamma-alumina-based ceramic fiber, 10-50% of thermoplastic fiber, 0-20% of pore forming agent and 2-10% of polyvinyl alcohol, the preparation method of the ceramic fiber composite material comprises the following steps: preparing slurry from gamma-alumina-based ceramic fibers and thermoplastic fibers, carrying out suction filtration or compression molding on the slurry to obtain a wet blank, carrying out high-temperature drying to obtain a green body, and sintering to obtain the fiber composite material with high porosity, high hydrogen fluoride filtration efficiency and good mechanical strength. The gamma-alumina-based ceramic fiber is used as a matrix, the low-temperature thermoplastic chopped fiber and the thermoplastic fiber micro powder are used as bonding materials, the organic or inorganic pore-forming agent is used as a pore-forming material, and the polyvinyl alcohol is used as a wet and green body molding agent, so that the mechanical strength of the filtering material is improved while the efficient hydrogen fluoride gas filtering effect is ensured.

Description

Technical Field

[0001] The present invention relates to a ceramic fiber composite material, a preparation method and an application thereof, and belongs to the technical field of high-temperature filter materials. Background Art

[0002] Power lithium batteries are the core of new energy vehicles, and their safe and efficient transportation is the key to ensuring the high-quality development of the industrial supply chain. Power lithium batteries have potential dangerous characteristics of combustion and explosion and belong to Class 9 dangerous goods (GB6944) during transportation. With the arrival of the retirement tide of new energy vehicles, the proportion of high-risk transportation of waste recycled batteries is increasing rapidly, and the transportation safety problem is becoming increasingly prominent. A large amount of toxic hydrogen fluoride gas will be released during the combustion and explosion process of power lithium batteries. For example, the concentration of hydrogen fluoride gas generated by the combustion of lithium iron phosphate batteries for 5 minutes is greater than 2000 ppm / Ah. Direct emission will pose a great threat to human health and the surrounding environment. Therefore, it is urgent to set up a high-temperature hydrogen fluoride gas filtration system in the transportation protection packaging. Among them, as the core component, the filter material should have high-efficiency hydrogen fluoride adsorption performance, good pressure relief performance and excellent mechanical strength at high temperature, which is an important development direction of this filter material.

[0003] In the industrial dry fluoride removal process, the filter material usually adopts activated carbon, zeolite, γ-aluminum oxide, calcium oxide particles, etc. However, a large amount of heat, flue gas and explosive particles are usually generated during the combustion and explosion process of lithium batteries. Traditional fluoride removal materials are difficult to balance the requirements of high pressure relief and high hydrogen fluoride filtration under this working condition. In addition, the specific gravity of traditional materials is relatively large, increasing the costs of production, installation and transportation. Therefore, it is urgent to develop a high-temperature resistant, light-weight, high-strength filter material with both high hydrogen fluoride adsorption and low filtration resistance.

[0004] Summary of the Invention

[0005] Object of the Invention: The first object of the present invention is to provide a ceramic fiber composite material with low resistance, high temperature resistance, light weight and high strength for filtration. The second object of the present invention is to provide a preparation method of the ceramic fiber composite material. The third object of the present invention is to provide the application of the ceramic fiber composite material in removing hydrogen fluoride gas, so as to solve the problem that the fluoride removal material cannot be applied to the filtration system of the power lithium battery protection packaging.

[0006] Technical Solution: The ceramic fiber composite material of the present invention is characterized in that it comprises the following components in percentage by weight: 40-80% of γ-aluminum oxide-based ceramic fibers, 10-50% of thermoplastic fibers, 0-20% of pore-forming agent, and 2-10% of polyvinyl alcohol (PVA).

[0007] Further, the γ-aluminum oxide-based ceramic fiber is an active material for filtering hydrogen fluoride gas. On the basis of ensuring good pressure relief effect, it can provide excellent hydrogen fluoride filtration efficiency. The composition of the γ-aluminum oxide-based ceramic fiber by weight percentage includes: 75-95% of γ-Al2O3, 5-25% of amorphous SiO2. The diameter of the γ-aluminum oxide-based ceramic fiber is 9-12 μm, and the upper limit of the working temperature is 1000 °C.

[0008] Further, the thermoplastic fiber is used to improve the integrity of the material after sintering. The composition of the thermoplastic fiber by weight percentage includes: SiO2 > 52%, Al2O3 > 45%, P2O5 + CaO + Na2O + K2O + B2O3 < 3%. The melting point of the thermoplastic fiber is 700-900 °C, and the diameter of the thermoplastic fiber is 11-15 μm. By adjusting the chemical composition ratio, the melting point of the thermoplastic fiber can be regulated as required within the range of 700-900 °C.

[0009] Furthermore, the thermoplastic fiber can be divided into two types: chopped fiber and fiber micropowder according to length. The length range of the chopped fiber is 500 μm - 3 mm, and the length range of the fiber micropowder is 100 - 400 μm.

[0010] Further, the pore former is an organic pore former and / or an inorganic pore former.

[0011] Further, the organic pore former is one or both of polymethyl methacrylate (PMAA) or potato starch.

[0012] Further, the inorganic pore former is one or several of CaCO3, NaCl or CaSO4.

[0013] Further, the particle size of the pore former is 50 - 500 μm.

[0014] Further, polyvinyl alcohol (PVA) is used to improve the uniformity of the material slurry and the integrity of the wet and green embryos. During the stirring process, PVA can increase the viscosity of the liquid phase and achieve uniform dispersion of the fiber and the pore former. During the pressing and suction filtration forming process, PVA can be used as a binder for the embryo body to improve the strength of the material before firing.

[0015] The preparation method of the ceramic fiber composite material described in the present invention includes the following steps:

[0016] (1) Disperse polyvinyl alcohol in water, add γ-aluminum oxide-based ceramic fiber and thermoplastic fiber, and stir to form a slurry;

[0017] (2) Filter the slurry by suction or press it into shape to obtain a wet embryo; or, add a pore former to the slurry, continue stirring, and then filter it by suction or press it into shape to obtain a wet embryo;

[0018] (3) Heat and dry the wet embryo to obtain a green embryo, and perform high-temperature sintering on the green embryo to obtain a ceramic fiber composite material.

[0019] Furthermore, in step (1), when the content of the thermoplastic fiber is greater than 30%, ultrasonic stirring can be adopted. The ultrasonic stirring is carried out for more than 10 minutes, and the rotation speed of the ultrasonic stirring is 1000 revolutions per minute.

[0020] Furthermore, in step (2), during suction filtration forming: select a filter membrane with a pore size of 50 μm, carry out vacuum suction filtration at a pressure of 0.05 MPa to 0.1 MPa, and the suction filtration ends when no liquid drips out within 30 seconds.

[0021] Furthermore, in step (2), during compression forming: pour the slurry into a mold, carry out pressing with a constant pressure of 0.1 MPa to 10 MPa, and keep it for more than 10 minutes.

[0022] Furthermore, in step (3), the temperature for heat drying is 50 - 80 °C, and the time for heat drying is more than 24 hours.

[0023] Furthermore, in step (3), the specific sintering temperature and duration are adjusted according to the melting point of the thermoplastic fiber. The sintering temperature is the melting point T of the thermoplastic fiber + 10 °C to T + 100 °C.

[0024] Even further, during the sintering process, the temperature rising rate is 3 °C / min, the sintering temperature is 700 - 900 °C, and the sintering time is 2 to 4 hours.

[0025] Furthermore, when a pore-forming agent is used, in step (3), the sintering temperature is 10 °C to 20 °C higher than the melting point of the pore-forming agent, and after maintaining it for more than 2 hours, continue to heat up to the melting point T of the thermoplastic fiber + 10 °C to T + 100 °C for sintering, which can avoid the generation of excessive gas leading to micro-defects or micro-cracks inside the composite material.

[0026] Application of the ceramic fiber composite material described in the present invention in removing hydrogen fluoride gas.

[0027] The present invention uses γ-aluminum oxide-based ceramic fibers as the main raw material, thermoplastic fibers as the binder material, organic or inorganic pore-forming agents as the pore-forming material, and polyvinyl alcohol as the green body plasticizer to prepare a porous ceramic fiber composite material. When the γ-aluminum oxide-based ceramic fibers are less than 40%, and the thermoplastic fibers are more than 50%, the HF adsorption efficiency of the sintered sample decreases significantly; while when the thermoplastic fibers are less than 10%, and the γ-aluminum oxide-based ceramic fibers are more than 80%, the flexural strength of the sintered sample decreases significantly; and when the pore-forming agent is too high (more than 20%), the structural integrity of the material is damaged, and the flexural performance and adsorption efficiency decrease sharply. When the polyvinyl alcohol is less than 2%, the suction filtration deposition is uneven and the green body structure collapses; when the polyvinyl alcohol is more than 10%, a large number of bubbles are generated during the suction filtration process, resulting in the filter membrane being blocked.

[0028] It can balance high strength and high porosity, and can effectively reduce the bulk density of the material. The ceramic fiber composite material provided by the present invention can efficiently adsorb hydrogen fluoride gas on the basis of ensuring good pressure relief performance of the protective packaging.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0030] (1) The present invention uses γ-aluminum oxide-based ceramic fibers as the matrix material, which can exhibit excellent hydrogen fluoride adsorption ability within 1000°C. Glass fibers are used as thermoplastic fibers to bind the γ-aluminum oxide-based ceramic fibers, enhancing the mechanical properties of the ceramic fiber composite material within 800°C.

[0031] (2) The present invention adjusts the pore size distribution of the filter material by controlling and adjusting the length and diameter of the fibers, the particle size distribution of the pore-forming agent, and the ratio of the ceramic fibers, thermoplastic fibers, and pore-forming agent. The pore size gradually decreases along the flow direction of the gas flow, realizing the fine filtration of the fine particles generated during the combustion and explosion process of lithium batteries, and finally realizing the efficient filtration of high-temperature flue gas. Description of the Drawings

[0032] Figure 1 It is a flowchart for preparing the ceramic fiber composite material in Example 1;

[0033] Figure 2 It is a physical diagram and a scanning electron microscope diagram of the ceramic fiber composite material prepared by the suction filtration method in Example 1, where a is the physical diagram and b is the scanning electron microscope diagram;

[0034] Figure 3 It is a physical diagram and a scanning electron microscope diagram of the ceramic fiber composite material prepared by the pressing method in Example 2, where a is the physical diagram and b is the scanning electron microscope diagram;

[0035] Figure 4 It is a physical diagram of the pressure filtration mold required for the pressing method process. Detailed Embodiments

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0037] The following embodiments are only used to more clearly illustrate the technical solution of the present invention and should not be used to limit the protection scope of the present invention.

[0038] The chemical composition of γ-aluminum oxide-based ceramic fiber is calculated by weight percentage: 85% γ-Al2O3 and 15% amorphous SiO2. The diameter of the γ-aluminum oxide-based ceramic fiber is 9-12 μm, and the upper limit of the working temperature is 1000 °C.

[0039] The chemical composition of the thermoplastic fiber (glass fiber) is calculated by weight percentage: SiO2 > 52%, Al2O3 > 45%, P2O5 + CaO + Na2O + K2O + B2O3 < 3%.

[0040] Pore former: PMMA with a pore size range of 100um - 200um.

[0041] Example 1

[0042] (1) Raw material preparation: Cut the γ-aluminum oxide-based ceramic fiber and the thermoplastic fiber short to 1 - 2 mm to obtain γ-aluminum oxide short-cut fiber and thermoplastic short-cut fiber; mix 0.5 g of PVA particles with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0043] (2) Preparation of ceramic fiber composite slurry: First, add 5 g of PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and successively add 5 g of γ-aluminum oxide short-cut fiber and 1.25 g of thermoplastic short-cut fiber in mass ratio to solution A, and obtain a ceramic fiber composite slurry after high-speed stirring and dispersion.

[0044] (3) Filtration molding: Install a filter membrane with a pore size of 50 μm in the filtration device, add the ceramic fiber composite slurry to the filtration device, and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet embryo.

[0045] (4) Drying: Put the filtered wet embryo into a vacuum oven and dry it at 60 °C for 24 h to obtain a green embryo of the ceramic fiber composite.

[0046] (5) Sintering: Place the green embryo of the ceramic fiber composite in a muffle furnace, heat it to 900 °C at a rate of 3 °C per minute, and keep it for 120 minutes, then cool it naturally with the furnace to obtain a ceramic fiber composite (with a diameter of about 36.5 mm and a thickness of about 13.3 mm). The preparation process is as Figure 1 shown.

[0047] Figure 2 The physical diagram and scanning electron microscope diagram of the ceramic fiber composite material prepared by the suction filtration method in Example 1, where a is the physical diagram and b is the scanning electron microscope diagram; from Figure 2 It can be seen that the material is uniformly white, with obvious fiber synapses at the edge, relatively thin texture, and has certain light transmission performance. Microscopically, the fibers are randomly arranged.

[0048] Example 2:

[0049] The experimental process is the same as that in Example 1, except that the wet blank is formed by pressing, that is, the pressure is increased during forming.

[0050] (1) Raw material preparation: Both γ-aluminum oxide-based ceramic fibers and thermoplastic fibers are cut into short lengths of 1 - 2 mm to obtain γ-aluminum oxide short-cut fibers and thermoplastic short-cut fibers; 0.5 g of PVA particles are mixed with 4.5 g of ultrapure water to obtain a 10% PVA solution. (2) Preparation of ceramic fiber composite material slurry: First, 5 g of the PVA solution is added to 200 g of ultrapure water at a speed of 400 revolutions per minute and mixed for 30 minutes to obtain a uniform solution A. Solution A is added to a high-speed disperser, and 5 g of γ-aluminum oxide short-cut fibers and 1.25 g of thermoplastic short-cut fibers with a mass ratio to solution A are added in sequence. After high-speed stirring and dispersion, a ceramic fiber composite material slurry is obtained.

[0051] (3) Pressing forming: The ceramic fiber composite material slurry is poured into a customized mold (as Figure 4 shown), and the sample is pressed with a constant pressure of 1 MPa and kept for 10 minutes to obtain a wet blank.

[0052] (4) Drying: The wet blank is placed in a vacuum oven and dried at 60 °C for 24 h to obtain a green body of the ceramic fiber composite material.

[0053] (5) Sintering: The green body of the ceramic fiber composite material is placed in a muffle furnace, heated to 900 °C at a rate of 3 °C per minute, and kept for 120 minutes, and then naturally cooled with the furnace to obtain a ceramic fiber composite material (with a diameter of about 36.2 mm and a thickness of about 8.3 mm).

[0054] Figure 3 The physical diagram and scanning electron microscope diagram of the ceramic fiber composite material prepared by the pressing method in Example 2, where a is the physical diagram and b is the scanning electron microscope diagram, from Figure 3 It can be seen that the material is uniformly white, with curling at the edge, relatively thick texture, the material shows brittleness, and microscopically, the fibers are randomly arranged.

[0055] Example 3:

[0056] The experimental process is the same as that of Example 1, except for the thermoplastic fiber micropowder.

[0057] (1) Raw material preparation: Cut both γ-aluminum oxide-based ceramic fibers and thermoplastic fibers into short lengths of 1 - 2 mm to obtain γ-aluminum oxide short-cut fibers and thermoplastic short-cut fibers; Grind another part of the thermoplastic fibers to 100 μm - 400 μm to obtain thermoplastic fiber micropowder, and mix 0.5 g of PVA particles with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0058] (2) Preparation of ceramic fiber composite slurry: First, add 5 g of the PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and sequentially add 5 g of γ-aluminum oxide short-cut fibers, 1.25 g of thermoplastic short-cut fibers, and 4 g of thermoplastic fiber micropowder with respect to the mass ratio of solution A, and obtain a ceramic fiber composite slurry after high-speed stirring and dispersion.

[0059] (3) Vacuum filtration forming: Install a filter membrane with a pore size of 50 μm in the vacuum filtration device, add the ceramic fiber composite slurry to the vacuum filtration device, and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet embryo.

[0060] (4) Drying: Place the pressed wet embryo in a vacuum oven and dry it at 60 °C for 24 h to obtain a green embryo of the ceramic fiber composite.

[0061] (5) Sintering: Place the green embryo of the ceramic fiber composite in a muffle furnace, heat it to 900 °C at a rate of 3 °C per minute, hold for 120 minutes, and then cool it naturally with the furnace to obtain the ceramic fiber composite.

[0062] Example 4:

[0063] The experimental process is the same as that of Example 1, except for the addition of the pore-forming agent PMMA.

[0064] (1) Raw material preparation: Cut both γ-aluminum oxide-based ceramic fibers and thermoplastic fibers into short lengths of 1 - 2 mm to obtain γ-aluminum oxide short-cut fibers and thermoplastic short-cut fibers; Mix 0.5 g of PVA particles with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0065] (2) Preparation of ceramic fiber composite slurry: First, add 5 g of PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and sequentially add 5 g of γ-aluminum oxide short-cut fibers, 1.25 g of thermoplastic short-cut fibers, and 1.25 g of PMMA with a pore size range of 100 μm - 200 μm to solution A. After high-speed stirring and dispersion, ceramic fiber composite slurry B is obtained.

[0066] (3) Filtration molding: Install a filter membrane with a pore size of 50 μm in the filtration device. Add the ceramic fiber composite slurry to the filtration device and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet embryo.

[0067] (4) Drying: Place the pressed sample in a vacuum oven and dry it at 60 °C for 24 h to obtain a green body of the ceramic fiber composite.

[0068] (5) Sintering: Place the green body of the ceramic fiber composite in a muffle furnace, heat it to 200 °C at a rate of 3 °C per minute and hold for 120 minutes, then heat it to 900 °C at a rate of 3 °C per minute and hold for 120 minutes, and then cool it naturally in the furnace to obtain the ceramic fiber composite.

[0069] Example 5:

[0070] The experimental process is the same as that of Example 1, except that the content of thermoplastic short-cut fibers is appropriately increased.

[0071] (1) Raw material preparation: Cut both γ-aluminum oxide-based ceramic fibers and thermoplastic fibers short to 1 - 2 mm to obtain γ-aluminum oxide short-cut fibers and thermoplastic short-cut fibers; mix 0.5 g of PVA particles with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0072] (2) Preparation of ceramic fiber composite slurry: First, add 5 g of PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and sequentially add 5 g of γ-aluminum oxide short-cut fibers and 2.5 g of thermoplastic short-cut fibers to solution A. After high-speed stirring and dispersion, the ceramic fiber composite slurry is obtained.

[0073] (3) Filtration molding: Install a filter membrane with a pore size of 50 μm in the filtration device. Add the ceramic fiber composite slurry to the filtration device and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet embryo.

[0074] (4) Drying: The wet embryo after suction filtration was placed in a vacuum oven and dried at 60 °C for 24 h to obtain a green body of the ceramic fiber composite material.

[0075] (5) Sintering: The green body of the ceramic fiber composite material was placed in a muffle furnace, heated to 900 °C at a rate of 3 °C per minute, held for 120 minutes, and then naturally cooled in the furnace to obtain the ceramic fiber composite material.

[0076] Example 6:

[0077] The experimental process was the same as that of Example 1, except that the content of the thermoplastic short fibers was appropriately increased.

[0078] (1) Preparation of raw materials: The γ-aluminum oxide-based ceramic fibers and thermoplastic fibers were both cut into 1 - 2 mm to obtain γ-aluminum oxide short fibers and thermoplastic short fibers; 0.5 g of PVA particles were mixed with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0079] (2) Preparation of the ceramic fiber composite slurry: First, 5 g of the PVA solution was added to 200 g of ultrapure water at a speed of 400 revolutions per minute and mixed for 30 minutes to obtain a uniform solution A. Solution A was added to a high-speed disperser, and 5 g of γ-aluminum oxide short fibers and 5.25 g of thermoplastic short fibers with a mass ratio to solution A of 5 g were added in sequence. After high-speed stirring and dispersion, a ceramic fiber composite slurry was obtained.

[0080] (3) Suction filtration molding: A filter membrane with a pore size of 50 μm was installed in the suction filtration device. The ceramic fiber composite slurry was added to the suction filtration device, and the sample was vacuum suction filtered at a pressure of 0.05 MPa. When no liquid dripped out within 30 seconds, it was stopped to obtain a wet embryo.

[0081] (4) Drying: The wet embryo after suction filtration was placed in a vacuum oven and dried at 60 °C for 24 h to obtain a green body of the ceramic fiber composite material.

[0082] (5) Sintering: The green body of the ceramic fiber composite material was placed in a muffle furnace, heated to 900 °C at a rate of 3 °C per minute, held for 120 minutes, and then naturally cooled in the furnace to obtain the ceramic fiber composite material.

[0083] Comparative Example 1:

[0084] The experimental process was the same as that of Example 1, except that a large amount of thermoplastic fiber micropowder was added.

[0085] (1) Preparation of raw materials: The γ-aluminum oxide-based ceramic fibers were cut into 1 - 2 mm to obtain γ-aluminum oxide short fibers, the thermoplastic fibers were ground to 100 - 400 μm to obtain thermoplastic fiber micropowder, and 0.5 g of PVA particles were mixed with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0086] (2) Preparation of ceramic fiber composite slurry: First, add 5 g of PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and sequentially add 5 g of short-cut γ-alumina fibers and 25 g of thermoplastic fiber micropowders with a mass ratio to solution A, and obtain a ceramic fiber composite slurry after high-speed stirring and dispersion.

[0087] (3) Vacuum filtration molding: Install a filter membrane with a pore size of 50 μm in the vacuum filtration device, add the ceramic fiber composite slurry to the vacuum filtration device, and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet blank.

[0088] (4) Drying: Place the wet blank after vacuum filtration into a vacuum oven and dry it at 60 °C for 24 h to obtain a green blank of the ceramic fiber composite.

[0089] (5) Sintering: Place the green blank of the ceramic fiber composite in a muffle furnace, heat it to 900 °C at a rate of 3 °C per minute, hold for 120 minutes, and then cool naturally with the furnace to obtain the ceramic fiber composite.

[0090] Comparative Example 2:

[0091] The experimental process is the same as that of Example 1, except that a large amount of thermoplastic short-cut fibers are added.

[0092] (1) Raw material preparation: Cut both γ-alumina-based ceramic fibers and thermoplastic fibers to 1 - 2 mm to obtain short-cut γ-alumina fibers and thermoplastic short-cut fibers; mix 0.5 g of PVA particles with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0093] (2) Preparation of ceramic fiber composite slurry: First, add 5 g of PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and sequentially add 5 g of short-cut γ-alumina fibers and 11.66 g of thermoplastic short-cut fibers with a mass ratio to solution A, and obtain a ceramic fiber composite slurry after high-speed stirring and dispersion.

[0094] (3) Vacuum filtration molding: Install a filter membrane with a pore size of 50 μm in the vacuum filtration device, add the ceramic fiber composite slurry to the vacuum filtration device, and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet blank.

[0095] (4) Drying: Place the sample after vacuum filtration into a vacuum oven and dry it at 60 °C for 24 h to obtain a green blank of the ceramic fiber composite.

[0096] (5) Sintering: Place the green body of the ceramic fiber composite material in a muffle furnace, heat it to 900 °C at a rate of 3 °C per minute, hold for 120 minutes, and then cool it naturally in the furnace to obtain the ceramic fiber composite material.

[0097] Comparative Example 3:

[0098] The experimental process is the same as that of Example 1, except that a small amount of thermoplastic short fibers are added.

[0099] (1) Raw material preparation: Cut both γ-aluminum oxide-based ceramic fibers and thermoplastic fibers into 1 - 2 mm lengths to obtain γ-aluminum oxide short fibers and thermoplastic short fibers; mix 0.5 g of PVA particles with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0100] (2) Preparation of ceramic fiber composite material slurry: First, add 5 g of the PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and successively add γ-aluminum oxide short fibers with a mass ratio of 5 g to solution A and 0.5 g of thermoplastic short fibers, and obtain the ceramic fiber composite material slurry after high-speed stirring and dispersion.

[0101] (3) Vacuum filtration forming: Install a filter membrane with a pore size of 50 μm in the vacuum filtration device, add the ceramic fiber composite material slurry to the vacuum filtration device, and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet green body.

[0102] (4) Drying: Place the filtered sample in a vacuum oven and dry it at 60 °C for 24 h to obtain the green body of the ceramic fiber composite material.

[0103] (5) Sintering: Place the green body of the ceramic fiber composite material in a muffle furnace, heat it to 900 °C at a rate of 3 °C per minute, hold for 120 minutes, and then cool it naturally in the furnace to obtain the ceramic fiber composite material.

[0104] Comparative Example 4:

[0105] The experimental process is the same as that of Example 1, except that a large amount of pore-forming agent is added.

[0106] (1) Raw material preparation: Cut both γ-aluminum oxide-based ceramic fibers and thermoplastic fibers into 1 - 2 mm lengths to obtain γ-aluminum oxide short fibers and thermoplastic short fibers; mix 0.5 g of PVA particles with 4.5 g of ultrapure water to obtain a 10% PVA solution.

[0107] (2) Preparation of ceramic fiber composite slurry: First, add 5 g of PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and sequentially add 5 g of γ-aluminum oxide short-cut fibers, 1.25 g of thermoplastic short-cut fibers, and 2.5 g of PMMA with a pore size range of 100 μm - 200 μm to solution A. After high-speed stirring and dispersion, ceramic fiber composite slurry B is obtained.

[0108] (3) Vacuum filtration forming: Install a filter membrane with a pore size of 50 μm in the vacuum filtration device. Add the ceramic fiber composite slurry to the vacuum filtration device, and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet embryo.

[0109] (4) Drying: Place the pressed sample in a vacuum oven and dry it at 60 °C for 24 h to obtain a green body of the ceramic fiber composite.

[0110] (5) Sintering: Place the green body of the ceramic fiber composite in a muffle furnace, heat it to 200 °C at a rate of 3 °C per minute and hold for 120 minutes, then heat it to 900 °C at a rate of 3 °C per minute and hold for 120 minutes, and then cool it naturally in the furnace to obtain the ceramic fiber composite.

[0111] The overall structure of the sintered sample is damaged.

[0112] Comparative Example 5:

[0113] The experimental process is the same as that of Example 1, except that the added PVA content is reduced.

[0114] (1) Raw material preparation: Cut γ-aluminum oxide-based ceramic fibers and thermoplastic fibers short to 1 - 2 mm to obtain γ-aluminum oxide short-cut fibers and thermoplastic short-cut fibers; mix 0.05 g of PVA particles with 0.45 g of ultrapure water to obtain a 10% PVA solution.

[0115] (2) Preparation of ceramic fiber composite slurry: First, add 0.5 g of PVA solution to 200 g of ultrapure water at a speed of 400 revolutions per minute and mix for 30 minutes to obtain a uniform solution A. Add solution A to a high-speed disperser, and sequentially add 5 g of γ-aluminum oxide short-cut fibers and 1.25 g of thermoplastic short-cut fibers with a mass ratio to solution A, and perform high-speed stirring and dispersion to obtain the ceramic fiber composite slurry.

[0116] (3) Vacuum filtration forming: Install a filter membrane with a pore size of 50 μm in the vacuum filtration device. Add the ceramic fiber composite slurry to the vacuum filtration device, and perform vacuum filtration on the sample at a pressure of 0.05 MPa. Stop when no liquid drips out within 30 seconds to obtain a wet embryo.

[0117] (4) Drying: The wet embryo after suction filtration was placed in a vacuum oven and dried at 60 °C for 24 h to obtain a green body of the ceramic fiber composite material.

[0118] The structure of the green body collapsed and became powdery.

[0119] Comparative Example 6:

[0120] The experimental process was the same as that of Example 1, except that the added PVA content increased.

[0121] (1) Raw material preparation: The γ-aluminum oxide-based ceramic fibers and the thermoplastic fibers were both cut into 1 - 2 mm to obtain γ-aluminum oxide short-cut fibers and thermoplastic short-cut fibers; 1 g of PVA particles were mixed with 9 g of ultrapure water to obtain a 10% PVA solution.

[0122] (2) Preparation of the ceramic fiber composite material slurry: First, 10 g of the PVA solution was added to 200 g of ultrapure water at a speed of 400 revolutions per minute and mixed for 30 minutes to obtain a uniform solution A. Solution A was added to a high-speed disperser, and 5 g of γ-aluminum oxide short-cut fibers and 1.25 g of thermoplastic short-cut fibers with a mass ratio to solution A were added in sequence. After high-speed stirring and dispersion, a ceramic fiber composite material slurry was obtained.

[0123] (3) Suction filtration molding: A filter membrane with a pore size of 50 μm was installed in the suction filtration device, the ceramic fiber composite material slurry was added to the suction filtration device, and the sample was vacuum-filtered at a pressure of 0.05 MPa. When no liquid dripped out within 30 seconds, it was stopped to obtain a wet embryo.

[0124] A large number of bubbles were generated during the suction filtration process, resulting in the blockage of the filter membrane and the inability to obtain a wet embryo.

[0125] The density, porosity, filtration resistance performance at a wind speed of 110 L / min, flexural strength, and hydrogen fluoride adsorption performance of the ceramic fiber composites prepared in the above Examples 1 - 6 and Comparative Examples 1 - 4 were tested.

[0126] Density and porosity test: GB / T25995-2010 "Test Methods for Density and Apparent Porosity of Fine Ceramics"

[0127] Filtration resistance test: ISO29463 "High-Efficiency Filters and Filter Media for Removing Particles from Air"

[0128] Flexural strength: GB / T6569-2006 "Test Methods for Bending Strength of Fine Ceramics"

[0129] Hydrogen fluoride adsorption performance test: A combustion and explosion experiment was conducted on a 5 Ah lithium iron phosphate battery in a closed space. A ceramic fiber composite material with a thickness of 2 mm and a diameter of 36 mm was placed at the outlet of the space. The HF filtration efficiency was calculated based on the change in the HF concentration in the air flow before and after passing through the sample during the measurement experiment. The results are shown in Table 1.

[0130] Table 1 Comprehensive performance test of ceramic fiber composite materials

[0131]

[0132] As can be seen from Table 1, by comparing Example 1 and Example 2: with the increase in the pressure during the green body forming process, the HF filtration efficiency of the ceramic fiber composite material decreases, while the flexural strength and the filtration resistance at a constant flow rate increase. By comparing Example 3 and Example 6: doping with fiber micropowder can significantly improve the flexural strength of the material. By comparing Example 1 and Example 4: although doping with the pore-forming agent PMMA can increase the porosity, the HF filtration efficiency of the ceramic fiber composite material decreases, the flexural strength slightly decreases, and the filtration resistance at a constant flow rate decreases.

[0133] From Comparative Examples 1 and 2, it can be seen that too high a content of thermoplastic fibers will cause a sharp decrease in the porosity of the ceramic fiber composite material and a significant reduction in the HF adsorption effect. From Comparative Example 3, it can be obtained that when the content of thermoplastic fibers is lower than the limit, the flexural strength of the composite material decreases significantly. From Comparative Example 4, it can be obtained that when the content of the pore-forming agent exceeds the limit, the structural integrity of the material is damaged, and the flexural performance and adsorption efficiency decrease sharply. From Comparative Examples 5 and 6, it can be obtained that when the content of polyvinyl alcohol is too low, the suction filtration deposition is uneven and the green body structure collapses; when the content of polyvinyl alcohol is higher than a certain value, a large number of bubbles are generated during the suction filtration process, resulting in the blockage of the filter membrane.

Claims

1. A ceramic fiber composite material, characterized in that: The invention comprises the following components by weight percentage: 40-80% of gamma-alumina-based ceramic fiber, 10-50% of thermoplastic fiber, 0-20% of pore-forming agent and 2-10% of polyvinyl alcohol.

2. The ceramic fiber composite material according to claim 1, characterized in that: The components of the γ-alumina-based ceramic fiber include, by weight percentage, 75-95% of γ-Al2O3 and 5-25% of amorphous SiO2. The diameter of the γ-alumina-based ceramic fiber is 9-12 μm.

3. The ceramic fiber composite material according to claim 1, characterized in that: The components of the thermoplastic fiber include, by weight percentage: SiO2>52%, Al2O3>45%, P2O5+CaO+Na2O+K2O+B2O3<3%, the melting point of the thermoplastic fiber is 700-900°C, and the diameter of the thermoplastic fiber is 11-15 μm.

4. The ceramic fiber composite material according to claim 1, characterized in that: The pore former is an organic pore former and / or an inorganic pore former. The organic pore former is one or both of polymethyl methacrylate and potato starch. The inorganic pore former is one or more of CaCO3, NaCl and CaSO4. The particle size of the pore former is 50-500 μm.

5. The method for preparing the ceramic fiber composite material according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) dispersing polyvinyl alcohol in water, adding γ-alumina-based ceramic fibers and thermoplastic fibers, and stirring to form a slurry; (2) filtering the slurry by suction or pressing to obtain a wet embryo; Alternatively, a pore-forming agent is added to the slurry, stirring is continued, and then suction filtration or pressure molding is performed to obtain a wet embryo; (3) The wet embryo is heated and dried to obtain a green embryo, and the green embryo is sintered at a high temperature to obtain a ceramic fiber composite material.

6. The preparation method according to claim 5, characterized in that: In step (1), when the content of thermoplastic fiber is greater than 30%, ultrasonic stirring can be used, and the ultrasonic stirring time is more than 10 minutes, and the rotation speed of ultrasonic stirring is 1000 revolutions / min.

7. The preparation method according to claim 5, characterized in that: In step (2), during the filtration process: select a filter membrane with a pore size of 50 μm, perform vacuum filtration at a pressure of 0.05 MPa to 0.1 MPa, and terminate the filtration process when no liquid drips out within 30 seconds.

8. The preparation method according to claim 5, characterized in that: In step (2), during compression molding: pour the slurry into a mold, press at a constant pressure of 0.1 MPa to 10 MPa, and maintain for more than 10 minutes.

9. The preparation method according to claim 5, characterized in that: In step (3), the heating and drying temperature is 50-80°C, the heating and drying time is more than 24 hours, and the sintering temperature is the melting point of the thermoplastic fiber T+10°C~T+100°C. When a pore-forming agent is used, the sintering temperature is 10°C~20°C higher than the melting point of the pore-forming agent, and is maintained for more than 2 hours and then continued to be heated to the melting point of the thermoplastic fiber T+10°C~T+100°C for sintering.

10. Use of the ceramic fiber composite material according to any one of claims 1 to 4 in removing hydrogen fluoride gas.

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