Self-supporting strontium manganate nanofiber membrane for high-temperature insulation and preparation method thereof

Abstract

This invention discloses a self-supporting strontium manganate nanofiber membrane for high-temperature insulation and its preparation method. The preparation method includes: 1) adding manganese salt, strontium salt, and catalyst sequentially to a solvent, stirring for a period of time, then adding itaconic acid, followed by a free radical polymerization initiator, and continuing to heat and stir until homogeneous to obtain a precursor solution; 2) spinning the precursor solution into a precursor fiber membrane using electrospinning technology; 3) directly placing the precursor fiber membrane into a high-temperature calcination furnace at a certain temperature for calcination, removing it after a period of time, and cooling it in room temperature air to obtain a self-supporting strontium manganate nanofiber membrane. This invention can prepare a strontium manganate nanofiber membrane with both excellent flexibility and infrared shielding performance, resulting in a self-supporting strontium manganate nanofiber membrane with advantages such as low gas-solid thermal conductivity, high infrared reflectivity, good high-temperature insulation, good thermal shock resistance, and high structural stability.

Description

Technical Field

[0001] This invention belongs to the field of textile materials technology, specifically relating to a self-supporting strontium manganate nanofiber membrane for high-temperature insulation and its preparation method. Background Technology

[0002] Ceramic fiber materials possess advantages such as excellent high-temperature resistance, strong oxidation resistance, good resistance to mechanical vibration, and excellent thermal and chemical stability, making them widely used in thermal protection fields such as aerospace, defense, weaponry, chemical metallurgy, and nuclear power generation. Existing ceramic fibers are generally in the micrometer range; further refining their diameter to the nanometer range can significantly reduce the pore size between fibers, increasing the restriction on gas molecule movement and effectively reducing gas thermal conductivity. However, current ceramic fiber insulation materials generally have low infrared reflectivity, resulting in insufficient ability to block radiative heat transfer under high-temperature conditions, limiting further improvements in their high-temperature thermal insulation performance. Strontium manganate has attracted much attention due to its excellent infrared reflectivity, high-temperature resistance, low thermal conductivity, and low toxicity. Processing it into nanofibers can simultaneously reduce gas thermal conduction, solid thermal conduction, and radiative thermal conduction, potentially leading to the development of highly efficient ceramic nanofiber insulation materials that combine low gas-solid thermal conductivity with high infrared shielding performance. The main methods for preparing ceramic nanofiber materials include hydrothermal synthesis, sol-gel method, spinning method, solid-liquid-gas phase method and electrospinning method. Among them, electrospinning method has become one of the main technologies for preparing ceramic nanofiber materials due to its advantages such as simple manufacturing equipment, wide range of spinnable raw materials and good fiber structure tunability.

[0003] Currently, there are few reports on the preparation of strontium manganate nanofibers using electrospinning technology, both domestically and internationally. MATEC Web of Conferences 67 (2016) 06093 reported the preparation of strontium manganate nanofibers using manganese acetate tetrahydrate and strontium nitrate as metal sources and polyvinylpyrrolidone as a polymer template, employing electrospinning and calcination methods. China Synthetic Fiber Industry 39 (2016) 58-60 reported the preparation of strontium manganate nanofibers using the same method. Ceramics International 44 (2018) 21982–21992 reported the preparation of strontium manganate nanofibers using manganese acetate and strontium acetate as metal sources and polyvinylpyrrolidone as a polymer template, employing electrospinning and high-temperature calcination methods. While the aforementioned literature successfully prepared strontium manganate nanofibers using electrospinning, the addition of large amounts of polymers to the precursor solutions resulted in low inorganic component content in the precursor fibers, leading to low yields of strontium manganate fibers after calcination. Furthermore, the polymers in the precursor fibers were prone to instability and decomposition during calcination, resulting in poor fiber continuity and numerous defects in individual fibers, making it difficult to obtain self-supporting strontium manganate nanofibers.

[0004] Therefore, developing a self-supporting strontium manganate nanofiber membrane with high strontium manganate content, good flexibility, high infrared reflectivity, good high-temperature insulation, and high structural stability is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation, which solves the problems of existing technologies that require the addition of polymers, resulting in poor fiber continuity, numerous defects in individual fibers, and brittle fiber membranes. Simultaneously, it addresses the issues of insufficient radiative heat transfer insulation capacity and difficulty in further improving the high-temperature insulation performance of existing ceramic fiber materials, thus producing a highly efficient ceramic nanofiber insulation material that combines low gas-solid thermal conductivity with high infrared shielding performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation includes the following steps:

[0008] Step 1: Manganese salt, strontium salt, and catalyst are added to the solvent in sequence and stirred for 5-90 min. Itaconic acid is then added and stirred for another 10-120 min. Subsequently, a free radical polymerization initiator is added and the mixture is heated and stirred for another 5-90 min to prepare the precursor solution.

[0009] Step 2: The precursor solution is spun into a precursor fiber membrane using electrospinning technology;

[0010] Step 3: Calcine the precursor fiber membrane and then cool it in room temperature air to obtain a self-supporting strontium manganate nanofiber membrane.

[0011] The manganese salt is one of manganese acetate tetrahydrate, manganese nitrate tetrahydrate, manganese chloride tetrahydrate, or manganese sulfate monohydrate.

[0012] The strontium salt is one of strontium nitrate, strontium chloride, or strontium acetate;

[0013] The catalyst is one of hydrochloric acid, nitric acid, formic acid, acetic acid, or oxalic acid;

[0014] The free radical polymerization initiator is one of ammonium persulfate, azobisisobutyronitrile, or diacyl peroxide;

[0015] The solvent is one of water, methanol, ethanol, n-propanol, acetone, or N,N-dimethylformamide.

[0016] Further, in step 1, the molar ratio of manganese salt to strontium salt is 1:1, the molar ratio of manganese salt to catalyst is 1:0.01-0.1; the total mass ratio of manganese salt and strontium salt to solvent is 10g:10-70mL, the molar ratio of manganese salt to itaconic acid is 1:0.1-2, the molar ratio of manganese salt to free radical polymerization initiator is 1:0.01-0.3; and the heating and stirring temperature is 50-100℃.

[0017] Furthermore, in step 1, the precursor solution has a dynamic viscosity of 0.1–14 Pa·s and an electrical conductivity of 5–80 mS / m.

[0018] Furthermore, the solvent specifically comprises:

[0019] When the manganese salt is manganese acetate tetrahydrate, the strontium salt is strontium nitrate, and the solvent is one of water, ethanol, acetone, or N,N-dimethylformamide;

[0020] When the manganese salt is manganese nitrate tetrahydrate, the strontium salt is strontium nitrate, and the solvent is one of water, ethanol, acetone, or N,N-dimethylformamide;

[0021] When the manganese salt is manganese chloride tetrahydrate, the strontium salt is strontium nitrate, and the solvent is one of water, ethanol, or N,N-dimethylformamide;

[0022] When the manganese salt is manganese sulfate monohydrate, the strontium salt is strontium nitrate, and the solvent is water or N,N-dimethylformamide;

[0023] When the manganese salt is manganese acetate tetrahydrate, the strontium salt is strontium chloride, and the solvent is one of water, methanol, ethanol, acetone, or N,N-dimethylformamide;

[0024] When the manganese salt is manganese nitrate tetrahydrate, the strontium salt is strontium chloride, and the solvent is one of water, methanol, ethanol, n-propanol, or N,N-dimethylformamide;

[0025] When the manganese salt is manganese chloride tetrahydrate, the strontium salt is strontium chloride, and the solvent is one of water, methanol, ethanol, n-propanol, or N,N-dimethylformamide;

[0026] When the manganese salt is manganese sulfate monohydrate, the strontium salt is strontium chloride, and the solvent is water or N,N-dimethylformamide;

[0027] When the manganese salt is manganese acetate tetrahydrate and the strontium salt is strontium acetate, the solvent is one of water, ethanol or N,N-dimethylformamide;

[0028] When the manganese salt is manganese nitrate tetrahydrate, the strontium salt is strontium acetate, and the solvent is one of water, ethanol, or N,N-dimethylformamide;

[0029] When the manganese salt is manganese chloride tetrahydrate, the strontium salt is strontium acetate, and the solvent is one of water, ethanol, or N,N-dimethylformamide;

[0030] When the manganese salt is manganese sulfate monohydrate, the strontium salt is strontium acetate, and the solvent is water or N,N-dimethylformamide.

[0031] Furthermore, the electrospinning process parameters in step 2 are as follows: spinning ambient temperature is 10-50℃, relative humidity is 10-80%, injection speed is 0.1-10mL / h, voltage is 10-60kV, and the distance between the spinneret and the receiving device is 3-45cm.

[0032] Further, step 3 specifically involves placing the precursor fiber membrane directly into a muffle furnace at a temperature of 600–1200°C for calcination, holding it at that temperature for 10–360 minutes, and then removing it and cooling it in ambient air to obtain a self-supporting strontium manganate nanofiber membrane.

[0033] The self-supporting strontium manganate nanofiber membrane prepared by this invention has an average fiber diameter of 10–600 nm and a relative standard deviation of 0.1–12%, an internal grain size of 2–75 nm, a flexibility of 0–100 mN, an average infrared reflectance of ≥92% in the near-infrared band, and a thermal conductivity of 0.026–0.116 W / (m·K) in the temperature range of 25–1200℃. The fiber diameter range represents the fiber thickness; smaller fiber diameters result in better single-fiber flexibility and improved membrane flexibility. The relative standard deviation can be used to characterize the uniformity of fiber diameter distribution; a smaller relative deviation value indicates better fiber uniformity. The grain size is closely related to the mechanical properties of single fibers; smaller grain sizes result in higher single-fiber mechanical properties and better membrane flexibility.

[0034] The first step of this invention involves dissolving manganese salt, strontium salt, and a catalyst sequentially in their respective solvents. Under the action of the catalyst, the manganese and strontium salts hydrolyze and condense into short chains of manganese oxide and strontium oxide. After stirring for a period of time, itaconic acid is added. The carboxyl groups on the surface of the itaconic acid molecules are covalently linked to the hydroxyl groups on the manganese oxide and strontium oxide short chains, effectively improving the viscoelasticity of the mixed solution. Subsequently, a free radical polymerization initiator is added to the mixed solution, and the solution is heated. Under the action of the initiator, itaconic acid molecules polymerize with manganese and strontium hydroxyl groups via free radicals, forming entangled polymer-like chains, further improving the spinnability and fiber continuity of the precursor solution. Electrospinning technology is then used to process the precursor solution into precursor fibers with good fiber continuity and uniform size. In the subsequent calcination process, the precursor fiber membrane was directly placed in a high-temperature calcination furnace at a certain temperature and calcined. After holding at that temperature for a period of time, it was removed and rapidly cooled in ambient air. This avoided secondary grain growth and crystal transformation during the cooling process, resulting in self-supporting strontium manganate nanofibers with small grain size and few fiber defects. Because no large amount of polymer was introduced into the precursor solution, the inorganic component content in the precursor fiber was relatively high. This prevented the intact skeletal structure of the single fiber from being destroyed by the decomposition of a large amount of organic components during calcination, ultimately yielding self-supporting strontium manganate nanofibers.

[0035] Beneficial effects:

[0036] (1) The preparation method of the present invention utilizes the free radical polymerization between itaconic acid molecules and manganese hydroxyl and strontium hydroxyl to form entangled polymer-like chains, which effectively improves the spinnability and fiber continuity of the precursor solution.

[0037] (2) The preparation method of the present invention is different from the traditional preparation method of strontium manganate fiber materials. It does not require the addition of polymer, the precursor fiber has a high strontium manganate content, good fiber continuity, few single fiber defects, and the preparation process is simple, highly operable and easy to industrialize.

[0038] (3) The self-supporting strontium manganate nanofiber membrane prepared by the present invention has excellent properties such as good flexibility, high infrared reflectivity and good high temperature insulation. It is expected to obtain a high-efficiency ceramic fiber thermal insulation material with both low gas-solid thermal conductivity and high infrared shielding performance. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0040] Example 1

[0041] A method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation, comprising the following steps:

[0042] (1) Manganese acetate tetrahydrate, strontium nitrate, and hydrochloric acid were dissolved in water and stirred for 60 min. Itaconic acid was added and stirred for another 60 min. Then ammonium persulfate was added and the mixture was heated and stirred at 80 °C for 90 min to prepare a precursor solution. The molar ratio of manganese salt to strontium salt in the precursor solution was 1:1; the molar ratio of manganese salt to hydrochloric acid was 1:0.02; the ratio of manganese salt, strontium salt, and solvent was 10 g:40 mL; the molar ratio of manganese salt to itaconic acid was 1:1; and the molar ratio of manganese salt to ammonium persulfate was 1:0.2. The mixture was stirred evenly to obtain a homogeneous and stable precursor solution with a dynamic viscosity of 7.2 Pa·s and a conductivity of 63.4 mS / m.

[0043] (2) The above precursor solution was spun into a precursor fiber membrane using electrospinning technology. The process parameters for electrospinning were: ambient temperature 25℃, relative humidity 50%, injection speed 1.5mL / h, voltage 44kV, and distance between the receiving device and the spinneret 28cm.

[0044] (3) The precursor fiber membrane was directly placed in a muffle furnace at 600℃ and calcined. After holding for 240 minutes, it was taken out and cooled in room temperature air to finally obtain a self-supporting strontium manganate nanofiber membrane.

[0045] The performance of the self-supported strontium manganate nanofiber membrane prepared above was tested. Referring to the national standard GB / T34520.2-2017 "Test Methods for Continuous Silicon Carbide Fibers Part 2: Single Fiber Diameter", the average diameter of the strontium manganate nanofibers was measured to be 350 nm, with a relative standard deviation of 2.9%. According to GB / T 23413-2009 "Determination of Grain Size and Microstrain of Nanomaterials - X-ray Diffraction Line Broadening Method", the strontium manganate grain size inside the fiber was measured to be 34 nm. Referring to the national standard GB / T8942-2016 "Determination of Paper Softness", the softness of the self-supported strontium manganate nanofiber membrane was measured to be 62 mN. According to the national standard GB / T 18319-2019 "Test Methods for Photothermal Storage Performance of Textiles", the average infrared reflectance of the self-supported strontium manganate nanofiber membrane in the near-infrared band was measured to be 92.6%. According to 5990-2006 "Test Method for Thermal Conductivity of Refractory Materials (Hot Wire Method)," the thermal conductivity of self-supporting strontium manganate nanofiber membranes in the range of 25 to 1200℃ was measured to be 0.026 to 0.114 W / (m·K).

[0046] Example 2

[0047] A method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation, comprising the following steps:

[0048] (1) Manganese nitrate tetrahydrate, strontium nitrate, and nitric acid were dissolved in water and stirred for 30 min. Itaconic acid was added and stirred for another 60 min. Then ammonium persulfate was added and the mixture was heated and stirred at 70 °C for 60 min to prepare a precursor solution. The molar ratio of manganese salt to strontium salt in the precursor solution was 1:1; the molar ratio of manganese salt to nitric acid was 1:0.03; the ratio of manganese salt, strontium salt, and solvent was 10 g:45 mL; the molar ratio of manganese salt to itaconic acid was 1:0.5; and the molar ratio of manganese salt to ammonium persulfate was 1:0.25. The mixture was stirred evenly to obtain a homogeneous and stable precursor solution with a dynamic viscosity of 7.6 Pa·s and a conductivity of 35.8 mS / m.

[0049] (2) The above precursor solution was spun into a precursor fiber membrane using electrospinning technology. The process parameters for electrospinning were: ambient temperature 28℃, relative humidity 45%, injection speed 3mL / h, voltage 56kV, and distance between the receiving device and the spinneret 30cm.

[0050] (3) The precursor fiber membrane was directly placed in a muffle furnace at 800℃ and calcined. After holding for 60 minutes, it was taken out and cooled in room temperature air to finally obtain a self-supporting strontium manganate nanofiber membrane.

[0051] The performance was determined using the same testing method as in Example 1. The average diameter of the strontium manganate nanofibers was 420 nm, the relative standard deviation of the diameter was 3.7%, the strontium manganate grain size inside the fiber was 28 nm, the flexibility of the self-supporting strontium manganate nanofiber membrane was 42 mN, the average infrared reflectance of the self-supporting strontium manganate nanofiber membrane in the near-infrared band was 93.4%, and the thermal conductivity in the range of 25 to 1200 °C was 0.027 to 0.108 W / (m·K).

[0052] Example 3

[0053] A method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation, comprising the following steps:

[0054] (1) Manganese chloride tetrahydrate, strontium nitrate, and oxalic acid were dissolved in a mixed solvent of water / ethanol. The mixture was stirred for 30 min, and itaconic acid was added and stirred for another 50 min. Then, azobisisobutyronitrile was added, and the mixture was heated and stirred at 90 °C for 40 min to prepare a precursor solution. The molar ratio of manganese salt to strontium salt in the precursor solution was 1:1; the molar ratio of manganese salt to oxalic acid was 1:0.03; the ratio of manganese salt, strontium salt, and solvent was 10 g:50 mL; the volume ratio of water to ethanol was 3:1; the molar ratio of manganese salt to itaconic acid was 1:0.8; and the molar ratio of manganese salt to azobisisobutyronitrile was 1:0.15. The mixture was stirred evenly to obtain a homogeneous and stable precursor solution with a dynamic viscosity of 6.1 Pa·s and a conductivity of 32.7 mS / m.

[0055] (2) The above precursor solution was spun into a precursor fiber membrane using electrospinning technology. The process parameters for electrospinning were: ambient temperature 23℃, relative humidity 30%, injection speed 2.5mL / h, voltage 45kV, and distance between the receiving device and the spinneret 26cm.

[0056] (3) The precursor fiber membrane was directly placed in a muffle furnace at 900℃ and calcined. After holding at the temperature for 60 minutes, it was taken out and cooled in room temperature air to finally obtain a self-supporting strontium manganate nanofiber membrane.

[0057] The performance was determined using the same testing method as in Example 1. The average diameter of the strontium manganate nanofibers was 380 nm, the relative standard deviation of the diameter was 2.4%, the strontium manganate grain size inside the fiber was 43 nm, the flexibility of the self-supporting strontium manganate nanofiber membrane was 72 mN, the average infrared reflectance of the self-supporting strontium manganate nanofiber membrane in the near-infrared band was 92.8%, and the thermal conductivity in the range of 25 to 1200 °C was 0.028 to 0.115 W / (m·K).

[0058] Example 4

[0059] A method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation, comprising the following steps:

[0060] (1) Manganese sulfate monohydrate, strontium nitrate, and hydrochloric acid were dissolved in water and stirred for 25 min. Itaconic acid was added and stirred for another 30 min. Then ammonium persulfate was added and the mixture was heated and stirred at 90 °C for 30 min to prepare a precursor solution. The molar ratio of manganese salt to strontium salt in the precursor solution was 1:1; the molar ratio of manganese salt to hydrochloric acid was 1:0.035; the ratio of manganese salt, strontium salt, and solvent was 10 g:43 mL; the molar ratio of manganese salt to itaconic acid was 1:1.5; and the molar ratio of manganese salt to ammonium persulfate was 1:0.75. The mixture was stirred evenly to obtain a homogeneous and stable precursor solution with a dynamic viscosity of 7.3 Pa·s and a conductivity of 52.8 mS / m.

[0061] (2) The above precursor solution was spun into a precursor fiber membrane using electrospinning technology. The process parameters for electrospinning were: ambient temperature 27℃, relative humidity 46%, injection speed 3mL / h, voltage 48kV, and distance between the receiving device and the spinneret 20cm.

[0062] (3) The precursor fiber membrane was directly placed in a muffle furnace at 750°C and calcined. After holding for 180 minutes, it was taken out and cooled in room temperature air to finally obtain a self-supporting strontium manganate nanofiber membrane.

[0063] The performance was determined using the same testing method as in Example 1. The average diameter of the strontium manganate nanofibers was 330 nm, the relative standard deviation of the diameter was 2.5%, the strontium manganate grain size inside the fiber was 38 nm, the flexibility of the self-supporting strontium manganate nanofiber membrane was 62 mN, the average infrared reflectance of the self-supporting strontium manganate nanofiber membrane in the near-infrared band was 93.7%, and the thermal conductivity in the range of 25 to 1200 °C was 0.026 to 0.109 W / (m·K).

[0064] Example 5

[0065] A method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation, comprising the following steps:

[0066] (1) Manganese acetate tetrahydrate, strontium chloride, and formic acid were dissolved in water and stirred for 60 min. Itaconic acid was added and stirred for another 40 min. Then ammonium persulfate was added and the mixture was heated and stirred at 80 °C for 50 min to prepare a precursor solution. The molar ratio of manganese salt to strontium salt in the precursor solution was 1:1; the molar ratio of manganese salt to formic acid was 1:0.06; the ratio of manganese salt, strontium salt, and solvent was 10 g:60 mL; the molar ratio of manganese salt to itaconic acid was 1:1.2; and the molar ratio of manganese salt to ammonium persulfate was 1:0.6. The mixture was stirred evenly to obtain a homogeneous and stable precursor solution with a dynamic viscosity of 8.2 Pa·s and a conductivity of 37.5 mS / m.

[0067] (2) The above precursor solution was spun into a precursor fiber membrane using electrospinning technology. The process parameters for electrospinning were: ambient temperature 29℃, relative humidity 53%, injection speed 4mL / h, voltage 46kV, and distance between the receiving device and the spinneret 16cm.

[0068] (3) The precursor fiber membrane was directly placed in a muffle furnace at 850°C and calcined. After holding at the temperature for 60 minutes, it was taken out and cooled in room temperature air to finally obtain a self-supporting strontium manganate nanofiber membrane.

[0069] The performance was determined using the same testing method as in Example 1. The average diameter of the strontium manganate nanofibers was 390 nm, the relative standard deviation of the diameter was 2.7%, the strontium manganate grain size inside the fiber was 36 nm, the flexibility of the self-supporting strontium manganate nanofiber membrane was 58 mN, the average infrared reflectance of the self-supporting strontium manganate nanofiber membrane in the near-infrared band was 92.6%, and the thermal conductivity in the range of 25 to 1200 °C was 0.026 to 0.113 W / (m·K).

[0070] Example 6

[0071] A method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation, comprising the following steps:

[0072] (1) Manganese nitrate tetrahydrate, strontium chloride, and oxalic acid were dissolved in a mixed solvent of water / N,N-dimethylformamide. The mixture was stirred for 40 min, and itaconic acid was added and stirred for another 40 min. Then, diacyl peroxide was added, and the mixture was heated and stirred at 90 °C for 90 min to prepare a precursor solution. The molar ratio of manganese salt to strontium salt in the precursor solution was 1:1; the molar ratio of manganese salt to oxalic acid was 1:0.03; the ratio of manganese salt, strontium salt, and solvent was 10 g:55 mL; the volume ratio of water to N,N-dimethylformamide was 1:1; the molar ratio of manganese salt to itaconic acid was 1:1.8; and the molar ratio of manganese salt to diacyl peroxide was 1:0.9. The mixture was stirred evenly to obtain a homogeneous and stable precursor solution with a dynamic viscosity of 7.9 Pa·s and a conductivity of 61.5 mS / m.

[0073] (2) The above precursor solution was spun into a precursor fiber membrane using electrospinning technology. The process parameters for electrospinning were: ambient temperature 32℃, relative humidity 48%, injection speed 2.5mL / h, voltage 47kV, and distance between the receiving device and the spinneret 23cm.

[0074] (3) The precursor fiber membrane was directly placed in a muffle furnace at 700℃ and calcined. After holding for 180 minutes, it was taken out and cooled in room temperature air to finally obtain a self-supporting strontium manganate nanofiber membrane.

[0075] The performance was determined using the same testing method as in Example 1. The average diameter of the strontium manganate nanofibers was 410 nm, the relative standard deviation of the diameter was 3.7%, the strontium manganate grain size inside the fiber was 49 nm, the flexibility of the self-supporting strontium manganate nanofiber membrane was 86 mN, the average infrared reflectance of the self-supporting strontium manganate nanofiber membrane in the near-infrared band was 93.4%, and the thermal conductivity in the range of 25 to 1200 °C was 0.027 to 0.113 W / (m·K).

[0076] Examples 7-12

[0077] The preparation steps for Examples 7-12 are the same as those for Example 1. The parameters of the precursor solution, electrospinning and calcination parameters, and the performance parameters of the self-supporting strontium manganate fiber membrane are shown in the table below (Note: Stirring time 1 is the stirring time after adding manganese salt, strontium salt, and catalyst to the solvent; stirring time 2 is the stirring time after adding itaconic acid; and stirring time 3 is the stirring time after adding the free radical polymerization initiator).

[0078]

Claims

1. A method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation, characterized in that: Includes the following steps: Step 1: Manganese salt, strontium salt, and catalyst are added to the solvent in sequence and stirred for 5-90 min. Itaconic acid is then added and stirred for another 10-120 min. Subsequently, a free radical polymerization initiator is added and the mixture is heated and stirred for another 5-90 min to prepare the precursor solution. The molar ratio of manganese salt to strontium salt is 1:1, and the molar ratio of manganese salt to catalyst is 1:0.01~0.1; the total mass ratio of manganese salt and strontium salt to solvent is 10g:10~70mL, the molar ratio of manganese salt to itaconic acid is 1:0.1~2, and the molar ratio of manganese salt to free radical polymerization initiator is 1:0.01~0.3; the heating and stirring temperature is 50~100℃; the dynamic viscosity of the precursor solution is 0.1~14Pa·s, and the conductivity is 5~80mS / m; The manganese salt is one of manganese acetate tetrahydrate, manganese nitrate tetrahydrate, manganese chloride tetrahydrate, or manganese sulfate monohydrate; the strontium salt is one of strontium nitrate, strontium chloride, or strontium acetate; the catalyst is one of hydrochloric acid, nitric acid, formic acid, acetic acid, or oxalic acid; the free radical polymerization initiator is one of ammonium persulfate, azobisisobutyronitrile, or diacyl peroxide; the solvent is one of water, methanol, ethanol, n-propanol, acetone, or N,N-dimethylformamide; specifically, when the manganese salt is manganese acetate tetrahydrate and the strontium salt is strontium nitrate, the solvent is one of water, ethanol, acetone, or N,N-dimethylformamide; when the manganese salt is manganese nitrate tetrahydrate and the strontium salt is strontium nitrate, the solvent is one of water, ethanol, acetone, or N,N-dimethylformamide; when the manganese salt is manganese chloride tetrahydrate and the strontium salt is strontium nitrate, the solvent is one of water, ethanol, or N,N-dimethylformamide. When the manganese salt is manganese sulfate monohydrate and the strontium salt is strontium nitrate, the solvent is water or N,N-dimethylformamide; when the manganese salt is manganese acetate tetrahydrate and the strontium salt is strontium chloride, the solvent is water, methanol, ethanol, acetone, or N,N-dimethylformamide; when the manganese salt is manganese nitrate tetrahydrate and the strontium salt is strontium chloride, the solvent is water, methanol, ethanol, n-propanol, or N,N-dimethylformamide; when the manganese salt is manganese chloride tetrahydrate and the strontium salt is strontium chloride, the solvent is water, methanol, ethanol, n-propanol, or N,N-dimethylformamide; when the manganese salt is manganese sulfate monohydrate and the strontium salt is strontium chloride, the solvent is water or N,N-dimethylformamide; when the manganese salt is manganese acetate tetrahydrate and the strontium salt is strontium acetate, the solvent is water, ethanol, or N,N-dimethylformamide. When the manganese salt is manganese nitrate tetrahydrate and the strontium salt is strontium acetate, the solvent is one of water, ethanol, or N,N-dimethylformamide; when the manganese salt is manganese chloride tetrahydrate and the strontium salt is strontium acetate, the solvent is one of water, ethanol, or N,N-dimethylformamide; when the manganese salt is manganese sulfate monohydrate and the strontium salt is strontium acetate, the solvent is water or N,N-dimethylformamide; Step 2: The precursor solution is spun into a precursor fiber membrane using electrospinning technology; Step 3: Calcine the precursor fiber membrane and then cool it in room temperature air to obtain a self-supporting strontium manganate nanofiber membrane. The calcination parameters are as follows: place the precursor fiber membrane directly into a muffle furnace at a temperature of 600~1200℃ for calcination, hold for 10~360 min, and then remove it and cool it in room temperature air to obtain a self-supporting strontium manganate nanofiber membrane.

2. The method for preparing a self-supporting strontium manganate nanofiber membrane for high-temperature insulation according to claim 1, characterized in that, The process parameters for electrospinning in step 2 are as follows: spinning ambient temperature is 10~50℃, relative humidity is 10~80%, injection speed is 0.1~10mL / h, voltage is 10~60kV, and the distance between the spinneret and the receiving device is 3~45cm.

3. A high-temperature insulation self-supporting strontium manganate nanofiber membrane prepared by the method according to any one of claims 1 or 2.

Images