Superfine high-entropy zirconate-silicon oxide flexible fiber membrane and preparation method thereof

Abstract

The invention discloses a superfine high-entropy zirconate-silicon oxide flexible fiber membrane and a preparation method thereof, and belongs to the field of preparation of new ceramic fiber materials, the chemical formula of the fiber membrane is RE2Zr2O7-SiO2, the fiber membrane is formed by wrapping high-entropy rare earth zirconate nanoparticles with amorphous silicon oxide, and the fiber membrane has an RE / Zr-O-Si amorphous interface; the RE is composed of five rare earth metal elements. The high-entropy zirconate-silicon oxide fiber membrane prepared through the method is uniform in component, good in flexibility, capable of being bent and folded, extremely high in purity, small and uniform in diameter and compact in structure, the grain size of high-entropy zirconate at the high temperature is within 10 nm, and the high-entropy zirconate-silicon oxide fiber membrane has good anti-sintering performance.

Description

Technical Field

[0001] The present invention relates to an ultra-fine high-entropy zirconate-silica flexible fiber membrane and a preparation method thereof, belonging to the field of preparation of new ceramic fiber materials. Background Art

[0002] Zirconia materials have characteristics such as high temperature resistance, high strength, wear resistance, high melting point, low thermal conductivity, and high thermal expansion coefficient, and are indispensable thermal protection materials in thermal protection systems of aerospace and modern advanced industries, etc. However, a single zirconia material is extremely prone to phase change in a service environment with alternating hot and cold, and is accompanied by a volume change of 3-7%. It is difficult for zirconia materials to be stably applied in the long term. In addition, the growth rate of single zirconia particles at high temperature is relatively fast, and the coarsening of grains will further reduce its heat insulation performance, which seriously limits the application of zirconia materials in the field of thermal protection. Rare earth zirconate materials have lower thermal conductivity and better corrosion resistance compared to single zirconia materials. However, rare earth zirconate materials have strong chemical bonds, poor mechanical properties, and low toughness, and it is difficult to fully meet the application requirements of thermal protection materials.

[0003] High-strength ceramic fibers usually have excellent self-supporting properties, and their flexible and rigid products have characteristics such as low density, high porosity, and low thermal conductivity. Preparing rare earth zirconate ceramics into fibers can not only maintain the excellent properties of rare earth zirconates themselves, but may also be expected to further reduce the thermal conductivity of rare earth zirconate materials. However, the growth of grains at high temperature will cause shrinkage deformation, embrittlement and breakage of polycrystalline fibers, resulting in a decrease in their strength and toughness. How to prepare rare earth zirconate ceramic fibers with good anti-sintering performance and maintain high strength and flexibility at high temperature is a very challenging problem.

[0004] Chinese Patent Application CN109868526A discloses a method for preparing yttrium zirconate nanofibers from a zirconium-yttrium polymer precursor. Acetylacetone and triethylamine are reacted, and then triethylamine salt is removed with acetone to obtain a spinnable zirconium-yttrium acetylacetone polymer precursor. This method has expensive raw materials, cumbersome steps, and the application of acetone makes the preparation process have certain risks. Moreover, the fiber diameter prepared by this method is 500 nm, the grain growth rate is relatively fast, the anti-sintering performance is poor, and the fiber flexibility is also poor. Summary of the Invention

[0005] Aiming at the deficiencies of zirconate fiber materials in the prior art, such as low anti-sintering performance, poor flexibility, and complex preparation processes, the first object of the present invention is to provide an ultra-fine high-entropy zirconate-silica flexible fiber membrane. Through the high-entropy modification and crystal phase adjustment of zirconate, and the introduction of silica into high-entropy zirconate fibers, a flexible fiber membrane material with amorphous silica-coated ultra-fine high-entropy rare-earth zirconate nanoparticles is obtained, and an RE / Zr-O-Si amorphous interface is formed, enabling the zirconate fibers of the present invention to have better anti-sintering performance and flexibility, and can be used as structural reinforcement materials, high-temperature refractory materials, fire insulation materials, chemical corrosion-resistant materials, and catalyst carriers.

[0006] The second object of the present invention is to provide a preparation method for the ultra-fine high-entropy zirconate-silica flexible fiber membrane. The present invention adopts a simple electrospinning-calcination method, which can synthesize an ultra-fine high-entropy zirconate-silica flexible fiber membrane with uniform composition, high oxide content, and nano-scale at low temperature.

[0007] To achieve the above technical objects, the present invention provides an ultra-fine high-entropy zirconate-silica flexible fiber membrane with the chemical formula RE 2 Zr 2 O 7 -SiO 2 , which is composed of amorphous silica-coated high-entropy rare-earth zirconate nanoparticles and has an RE / Zr-O-Si amorphous interface; the RE is composed of five rare-earth metal elements.

[0008] The key to the technical solution of the present invention lies in the high-entropy structural design of rare-earth zirconate, which makes up for the deficiencies of single rare-earth zirconate in terms of low toughness, heat insulation, and anti-sintering performance. Specifically, the present invention introduces amorphous silica with high damage tolerance into high-entropy rare-earth zirconate fibers to obtain a fiber morphology with amorphous silica-coated ultra-fine high-entropy zirconate nanoparticles. This coating structure plays an important role in improving the performance of the fiber material of the present invention. Through this coating structure, a larger crystal phase-amorphous interface area can be obtained, which can effectively hinder the grain growth and phase transformation of high-entropy rare-earth zirconate. At the same time, through the A-site high-entropy design of the zirconate material, the high-entropy rare-earth zirconate grains can simultaneously have a fluorite phase and a pyrochlore phase, greatly ensuring the high-temperature performance and anti-sintering performance of the material. The introduction of glassy SiO 2 will lead to the formation of RE / Zr-O-Si bonds, which can further increase the crystallization temperature of high-entropy zirconate particles and play a role in refining high-entropy zirconate grains. Moreover, amorphous SiO 2The heterogeneous interface between the crystalline high-entropy zirconate can further significantly improve the high-temperature stability and anti-sintering performance of the material. In addition, this encapsulated amorphous silica, as a soft interface, can buffer the stress generated inside the high-entropy zirconate through local plastic deformation and viscoelastic energy dissipation; the formation of RE / Zr-O-Si also results in a strong bonding interface between the amorphous silica and the high-entropy rare-earth zirconate, which effectively improves the flexibility of the high-entropy zirconate fiber membrane.

[0009] As a preferred embodiment, the chemical formula is (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ). 2 Zr 2 O 7 -SiO 2 . When La, Sm, Gd, Dy, Yb, and Zr are used for high-entropy alloy design, the material has better anti-sintering performance and toughness, which is mainly based on the fact that the selected rare-earth elements include both light rare earths (La, Sm, and Gd) and heavy rare earths (Dy and Yb), and their size disorder degree is as high as 8.911, which is easy to form a duplex structure. Through the high-entropy effect, lattice distortion effect, retarded diffusion effect, and "cocktail" effect of the high-entropy material, a large number of grain boundaries and heterogeneous interfaces are contained in the fibers prepared by the present invention, and these grain boundaries and heterogeneous interfaces can synergistically further significantly improve the high-temperature stability and anti-sintering performance of the material with the RE / Zr-O-Si amorphous surface.

[0010] As a preferred embodiment, the grain size of the high-entropy rare-earth zirconate nanoparticles is 5-10 nm. The high-entropy rare-earth zirconate nanoparticles of the present invention have obvious advantages in grain size after introducing silica to form an encapsulated state. The fine nanocrystals have a higher specific surface area, and the high-density grain boundaries can effectively improve the strength and toughness of the material.

[0011] As a preferred embodiment, the molar ratio of La, Sm, Gd, Dy, Yb, and Zr is 1:1:1:1:1:5.

[0012] As a preferred embodiment, the diameter of the ultrafine high-entropy zirconate-silica flexible fiber membrane is 100-300 nm. This shows that the precursor spinning solution prepared by the present invention has good spinnability. The small fiber diameter can improve the breaking strength and flexibility of the fiber, and the fine fibers are more likely to form a dense and disordered packing structure, reducing the thermal conductivity of the fiber.

[0013] The present invention also provides a method for preparing an ultrafine high-entropy zirconate-silica flexible fiber membrane, which includes the following steps:

[0014] (1) Weigh five rare earth metal salts respectively according to the design ratio, mix them with Zr salt, dissolve them with an organic solvent, and then add a spinning aid to obtain a RE-Zr precursor spinning solution.

[0015] (2) Add a silicon source and water to the RE-Zr precursor spinning solution to hydrolyze the silicon source and obtain a RE-Zr-Si precursor spinning solution.

[0016] (3) Electrospun the RE-Zr-Si precursor spinning solution to obtain precursor fibers.

[0017] (4) Heat-treat the precursor fibers in an oxygen-containing atmosphere to obtain the product.

[0018] In the process of preparing the RE-Zr-Si precursor spinning solution in the present invention, no complex reaction is experienced, and the uniform mixing of alloy elements and Si elements at the atomic and molecular levels is directly achieved. The prepared high-entropy zirconate-silica fibers have a more uniform composition, and the combination of electrospinning technology and heat treatment process further promotes the formation of amorphous interfaces and coating morphologies.

[0019] Experiments have found that if the silicon source, water and metal salts are directly added synchronously, too long stirring time will lead to too high hydrolysis degree of the silicon source and easy gelation, so that the alloy elements and Si elements cannot achieve uniform mixing at the atomic level, and fiber breakage is likely to occur in the subsequent spinning process.

[0020] As a preferred solution, the organic solvent is at least one of anhydrous methanol, anhydrous ethanol, acetone and N, N-dimethylformamide (DMF); more preferably DMF. The selected organic solvent in the present invention can fully dissolve and mix the rare earth metal salts.

[0021] As a preferred solution, the spinning aid is at least one of polyethylene oxide and polyvinylpyrrolidone; polyethylene oxide has a higher viscosity than polyvinylpyrrolidone, which is likely to cause nozzle blockage and is not conducive to spinning. And polyvinylpyrrolidone is easily soluble in various solvents, and the solution preparation is more flexible. Therefore, the present invention further preferably uses polyvinylpyrrolidone.

[0022] As a preferred solution, the Zr salt is ZrOCl 2 and its hydrates. The zirconium salt raw material used in the present invention is easily available and can be uniformly mixed with five rare earth metal salts in an organic solvent, greatly simplifying the process steps.

[0023] As a preferred solution, the silicon source is at least one of tetraethyl orthosilicate, methyltrimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane and γ-chloropropyltriethoxysilane.

[0024] As a preferred solution, the mass ratio of the total mass of the five rare earth metal salts and Zr salt to the mass of the organic solvent is 1:(1.6~3.3); within the solvent range selected by the present invention, the five rare earth metal salts and Zr salt can be fully dissolved, which facilitates the subsequent spinning process.

[0025] As a preferred solution, the amount of silicon source added is (0.05-0.4) in a molar ratio of Si to Zr: 1, and the mass ratio of water to silicon source is (0.5-2) : 1. In the present invention, if the Si content is too low, the fiber flexibility is poor, while if the Si content is too high, silicate is easily formed, which reduces the strength of the fiber.

[0026] As a preferred solution, the content of the spinning aid is 5-11% of the total mass of the five rare earth metal salts, the Zr salt and the organic solvent.

[0027] As a preferred solution, in step (1), after adding the spinning aid, stirring and aging for 24 to 72 hours are required. The stirring process can ensure that the rare earth salt and the zirconium salt are fully mixed, the spinning aid is fully dissolved, and the generation of slag balls is avoided during the spinning process.

[0028] As a preferred solution, the electrospinning parameters are: relative humidity of 30-60%, temperature of 25-45°C, spinning voltage of 12-18KV, receiving distance of 10-20cm, propulsion speed of 0.3-0.7ml / h; the receiving device is a metal roller with a rotation speed of 100-500r / min. The precursor fiber prepared under the electrospinning parameters of the present invention has the characteristics of uniform diameter, good continuity and good flexibility, and the propulsion speed of the spinning solution of the present invention has an important influence on the uniformity of the fiber. When the propulsion speed is too fast, beaded precursor fibers are easily formed, and the fiber diameter and composition are uneven, resulting in the inability to effectively form the morphology structure of amorphous silicon oxide-encapsulated high-entropy rare earth zirconate nanoparticles in the subsequent heat treatment process.

[0029] As a preferred solution, the heating program of the heat treatment is: heating from room temperature to 1000-1200°C at a rate of 1-5°C / min, keeping the temperature for 120-300min; then reducing the temperature to 400-500°C at a rate of 2-3°C / min, and then cooling with the furnace. The linear heating of the present invention is conducive to the formation of uniform morphology, while the slow heating rate and a certain holding time are conducive to the full bonding of RE / Zr-O-Si, and finally forming the morphological characteristics of high entropy zirconate particles wrapped with silicon dioxide.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention for the first time provides a preparation scheme for a high-entropy zirconate-silica flexible fiber membrane. The prepared high-entropy zirconate-silica fiber has a small and controllable diameter, good continuity, foldability, and excellent flexibility.

[0032] (2) The process for preparing a spinnable rare-earth-zirconium-silicon precursor spinning solution in the present invention is simple, and the precursor has stable properties and can be stored for a long time.

[0033] (3) The high-entropy zirconate-silica fiber membrane prepared in the present invention has a uniform composition, extremely high purity, a small and uniform diameter, a dense structure, and the grain size of the high-entropy zirconate is within 10 nm at high temperatures, having good anti-sintering performance.

[0034] (4) The present invention does not require a complex heat treatment process or atmosphere protection, and the preparation process is simple and easy for batch production.

[0035] (5) By performing high-entropy modification and crystal phase adjustment on zirconate, and introducing silica into the high-entropy zirconate fiber at the same time, the present invention obtains a flexible fiber membrane material with amorphous silica coating ultrafine high-entropy rare-earth zirconate nanoparticles, and forms a RE / Zr-O-Si amorphous interface, enabling the zirconate fiber of the present invention to have better anti-sintering performance and flexibility, and can be used as a structural reinforcement material, a high-temperature refractory material, a fire-fighting heat insulation material, a chemical corrosion-resistant material, and a catalyst support. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the process flow chart for preparing the high-entropy zirconate-silica fiber membrane of the present invention.

[0037] Figure 2 is the XRD pattern of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 -SiO 2 fiber membrane prepared in Example 1.

[0038] Figure 3 is the optical photograph of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 -SiO 2 precursor fiber membrane prepared in Example 1.

[0039] Figure 4The folding diagram of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 -SiO 2 fiber membrane prepared in Example 1.

[0040] Figure 5 The low-magnification SEM image of the fibers of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 -SiO 2 fiber membrane prepared in Example 1 ( Figure 5 (a)) and the high-magnification SEM image ( Figure 5 (b)).

[0041] Figure 6 The TEM images of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 -SiO 2 fibers prepared in Example 1 ( Figure 6 (a)), the partial enlarged view ( Figure 6 (b)), the HADDF image ( Figure 6 (c)), the elemental distribution map of La ( Figure 6 (d)), the elemental distribution map of Sm ( Figure 6 (e)), the elemental distribution map of Gd ( Figure 6 (f)), the elemental distribution map of Dy ( Figure 6 (g)), the elemental distribution map of Yb ( Figure 6 (h)), the elemental distribution map of Zr ( Figure 6 (i)), the elemental distribution map of Si ( Figure 6 (j)) and the elemental distribution map of O ( Figure 6 (k)).

[0042] Figure 7 The (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 )2 Zr 2 O 7 -SiO 2 fiber ( Figure 7 (a)) and the heat insulation performance of the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 fiber ( Figure 7 (b)).

[0043] Figure 8 For the (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 -SiO 2 fiber prepared in Example 1, its high-temperature stability. Specific embodiments

[0044] To further illustrate the present invention, the content of the present invention will be described in detail below in conjunction with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments either.

[0045] Example 1

[0046] (1) Weigh equimolar amounts of 5 rare earth nitrate particles of La(NO 3 ) 3 ·6H 2 O, Sm(NO 3 ) 3 ·6H 2 O, Gd(NO 3 ) 3 ·6H 2 O, Dy(NO 3 ) 3 ·6H 2 O, Yb(NO 3 ) 3 ·5H 2 O and mix them evenly, denoted as D RE ;

[0047] (2) Weigh the corresponding amount of ZrOCl according to the molar ratio of RE:Zr being 1:1 2 ·8H 2 O, mix it well with D RE , and label it as D RE-Zr .

[0048] (3) According to the mass ratio of the mixed salt D RE-Zr to the solvent being 1:2.7, weigh the corresponding amount of N,N-dimethylformamide (DMF), and dissolve the mixed salt D RE-Zr in DMF, stir for 5 h until D RE-Zr is fully dissolved, and label it as S RE-Zr .

[0049] (4) According to the content of the spinning aid being 7% of the mass of the S RE-Zr solution, weigh the corresponding amount of polyvinylpyrrolidone (PVP), add it to the S RE-Zr solution, stir until fully dissolved, and the stirring aging time is 48 h to obtain the RE-Zr precursor spinning solution, labeled as A1.

[0050] (5) According to the molar ratio of silicon to zirconium being 0.25:1, and in accordance with the mass ratio of water to the silicon source being 1:1, weigh tetraethyl orthosilicate and water, add them to A1, stir well for 8 h to ensure the full hydrolysis of tetraethyl orthosilicate, and obtain the RE-Zr-Si precursor spinning solution A.

[0051] (6) Electrospinning of the precursor spinning solution A in step 5 is carried out under the electrospinning conditions of a temperature of 35 °C, a relative humidity of 40%, a rotation speed of the drum receiving device of 250 r / min, a spinning voltage of 16 KV, a receiving distance of 15 cm, and a propulsion speed of 0.35 ml / h to obtain the precursor fiber membrane B. The prepared precursor fibers have the characteristics of uniform fiber diameter, good fiber continuity, and dense structure, as Figure 3 shown, with a diameter of 100 - 300 nm.

[0052] (7) Heat-treat the precursor fiber membrane B spun in step 6 in an air atmosphere at 1100 °C for 2 h to obtain the high-entropy zirconate-silica fiber. The fiber structure is dense, the fiber diameter is small, and the zirconate particle size is within 10 nm, having good anti-sintering performance. The heat treatment procedure is as follows: heat from room temperature to 1100 °C at a heating rate of 5 °C / min, then hold for 2 h, then cool at a cooling rate of 2 °C / min to 500 °C, and then cool with the furnace to room temperature.

[0053] The prepared (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr2 O 7 -SiO 2 The fiber has good heat insulation performance and flexibility. The heat insulation performance of the fiber with a thickness of 8 mm was tested with a butane flame (1380 °C). After heat treatment for 300 s, its back temperature was only 224 °C. The grain size of the high-entropy zirconate was 5 - 10 nm. After heat treatment at 1100 °C for 10 h, the grain size increased slightly to 30 - 50 nm, indicating that the prepared fiber has good anti-sintering performance. In addition, the fiber also has good high-temperature phase stability and still maintains the fluorite and pyrochlore biphasic structure after heat treatment at 1200 °C for 10 h. And it is shown by Figure 3 and Figure 4 that the fiber has good flexibility and can be bent and folded. It can be clearly seen from Figure 6 that the high-entropy rare-earth zirconate nanoparticles are wrapped by amorphous silica and have a RE / Zr-O-Si amorphous interface.

[0054] Example 2

[0055] (1) Weigh equimolar amounts of 5 kinds of rare-earth nitrate particles of La(NO 3 ) 3 ·6H 2 O, Sm(NO 3 ) 3 ·6H 2 O, Gd(NO 3 ) 3 ·6H 2 O, Dy(NO 3 ) 3 ·6H 2 O, Yb(NO 3 ) 3 ·5H 2 O and mix them evenly, denoted as D RE ;

[0056] (2) Weigh the corresponding amount of ZrOCl 2 ·8H 2 O according to the molar ratio of RE:Zr being 1:1, and mix it fully with D RE , denoted as D RE-Zr .

[0057] (3) According to the mass ratio of the mixed salt D RE-Zr to the solvent being 1:2, weigh the corresponding amount of N,N-dimethylformamide (DMF), dissolve the mixed salt D RE-Zr in DMF, and stir for 5 h until D RE-Zr is fully dissolved, denoted as S RE-Zr .

[0058] (4) According to the content of the spinning aid being SRE-Zr 5% of the solution mass, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to S RE-Zr solution and stir until completely dissolved. The stirring and aging time is 48 h to obtain the RE-Zr precursor spinning solution, denoted as A1.

[0059] (5) According to the molar ratio of silicon to zirconium being 0.25:1, and in accordance with the mass ratio of water to silicon source being 1:1, weigh tetraethyl orthosilicate and water and add them to A1, stir thoroughly for 8 h to ensure the complete hydrolysis of tetraethyl orthosilicate, and obtain the RE-Zr-Si precursor spinning solution A.

[0060] (6) Electrospin the precursor spinning solution A in step 5 under the electrospinning conditions of a temperature of 30 °C, a relative humidity of 40%, a rotation speed of the roller receiving device of 250 r / min, a spinning voltage of 15.5 KV, a receiving distance of 15 cm, and a feeding speed of 0.35 ml / h to obtain the precursor fiber B.

[0061] (7) Sinter the precursor fiber B spun in step 6 in an air atmosphere. The heat treatment procedure is as follows: heat from room temperature to 1000 °C at a heating rate of 5 °C / min, then hold for 2 h, then cool to 500 °C at a cooling rate of 2 °C / min, and then cool to room temperature with the furnace to obtain the nano high-entropy zirconate fiber.

[0062] The prepared (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 -SiO 2 fibers have good heat insulation performance and flexibility. The heat insulation performance of the fiber with a thickness of 8 mm is tested with a butane flame (1380 °C). After heat treatment for 300 s, its back temperature is 228 °C. The grain size of the high-entropy zirconate is 5 - 10 nm. After heat treatment at 1100 °C for 10 h, the grain size slightly increases to 20 - 50 nm, indicating that the prepared fibers have good anti-sintering performance. In addition, the fibers also have good high-temperature phase stability and still maintain the fluorite and pyrochlore double-phase structure after heat treatment at 1200 °C for 10 h.

[0063] Example 3

[0064] (1) Weigh equimolar amounts of LaCl 3 ·6H 2 O, SmCl 3 ·6H 2 O, GdCl 3 ·6H 2 O, DyCl 3·6H 2 O, YbCl 3 ·6H 2 Five kinds of rare earth chloride particles of O were evenly mixed and denoted as D RE ;

[0065] (2) Weigh the corresponding amount of ZrOCl according to the molar ratio of RE:Zr being 1:1 2 ·8H 2 O, and mix it fully with D RE and denote it as D RE-Zr .

[0066] (3) According to the mass ratio of the mixed salt D RE-Zr and the solvent being 1:2.7, weigh the corresponding amount of N,N-dimethylformamide (DMF), and dissolve the mixed salt D RE-Zr in DMF, stir for 5 h until D RE-Zr is fully dissolved, and denote it as S RE-Zr .

[0067] (4) According to the content of the spinning aid being 7% of the mass of the S RE-Zr solution, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to the S RE-Zr solution, stir until fully dissolved, and the stirring aging time is 48 h to obtain the RE-Zr precursor spinning solution, denoted as A1

[0068] (5) According to the molar ratio of silicon to zirconium being 0.1:1, and in accordance with the mass ratio of water to the silicon source being 1.5:1, weigh tetraethyl orthosilicate and water and add them to A1, stir fully for 5 h to ensure the full hydrolysis of tetraethyl orthosilicate, and obtain the RE-Zr-Si precursor spinning solution A

[0069] (6) Electrospinning of the precursor spinning solution A in step 5 was carried out under the electrospinning conditions of a temperature of 40 °C, a relative humidity of 40%, a rotational speed of the drum receiving device of 300 r / min, a spinning voltage of 16 KV, a receiving distance of 12 cm, and a feeding speed of 0.5 ml / h to obtain the precursor fiber B

[0070] (7) The precursor fiber B spun in step 6 was heat-treated in an air atmosphere, and the heat treatment program was: heating from room temperature to 1100 °C at a heating rate of 5 °C / min, then holding for 2 h, and then cooling at a cooling rate of 2 °C / min to 500 °C, and then furnace cooling to room temperature to obtain the nano high-entropy zirconate fiber

[0071] The prepared (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr2 O 7 -SiO 2 The fiber has good heat insulation performance and flexibility. The heat insulation performance of the fiber with a thickness of 8 mm was tested with a butane flame (1380 °C). After heat treatment for 300 s, its back temperature was 242 °C. After heat treatment at 1100 °C for 10 h, the grain size increased slightly to 30 - 60 nm, indicating that the prepared fiber has good anti-sintering performance. In addition, the fiber also has good high-temperature phase stability and still maintains the fluorite and pyrochlore double-phase structure after heat treatment at 1200 °C for 10 h.

[0072] Example 4

[0073] (1) Weigh equimolar amounts of 5 rare earth nitrate particles of La(NO 3 ) 3 ·6H 2 O, Sm(NO 3 ) 3 ·6H 2 O, Gd(NO 3 ) 3 ·6H 2 O, Dy(NO 3 ) 3 ·6H 2 O, Yb(NO 3 ) 3 ·5H 2 O and mix them evenly, denoted as D RE ;

[0074] (2) Weigh the corresponding amount of ZrOCl 2 ·8H 2 O according to the molar ratio of RE:Zr being 1:1, and mix it well with D RE , denoted as D RE-Zr .

[0075] (3) According to the mass ratio of the mixed salt D RE-Zr to the solvent being 1:2.7, weigh the corresponding amount of N,N-dimethylformamide (DMF), dissolve the mixed salt D RE-Zr in DMF, and stir for 5 h until D RE-Zr is fully dissolved, denoted as S RE-Zr .

[0076] (4) According to the content of the spinning aid being 7% of the mass of the S RE-Zr solution, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to the S RE-Zr solution and stir until fully dissolved. The stirring and aging time is 48 h to obtain the RE-Zr precursor spinning solution, denoted as A1.

[0077] (5) According to the molar ratio of silicon to zirconium being 0.4:1, and in accordance with the mass ratio of water to silicon source being 1:1, weigh tetraethyl orthosilicate and water and add them to A1, stir well for 5 h to ensure the complete hydrolysis of tetraethyl orthosilicate, and obtain the RE-Zr-Si precursor spinning solution A.

[0078] (6) Electrospin the precursor spinning solution A in step (5) under the electrospinning conditions of a temperature of 35 °C, a relative humidity of 30%, a rotational speed of the drum receiving device of 250 r / min, a spinning voltage of 18 kV, a receiving distance of 15 cm, and a feeding speed of 0.35 ml / h to obtain the precursor fiber B.

[0079] (7) Heat-treat the precursor fiber B spun in step (6) in an air atmosphere. The heat-treatment procedure is as follows: heat from room temperature to 1200 °C at a heating rate of 5 °C / min, then hold for 2 h, then cool to 500 °C at a cooling rate of 2 °C / min, and then cool to room temperature in the furnace to obtain the nano high-entropy zirconate fiber.

[0080] The prepared (La 0.2 Sm 0.2 Gd 0.2 Dy 0.2 Yb 0.2 ) 2 Zr 2 O 7 -SiO 2 fibers have good heat insulation performance and flexibility. The heat insulation performance of the fibers with a thickness of 8 mm was tested with a butane flame (1380 °C). After heat treatment for 300 s, the back temperature was only 235 °C. After heat treatment at 1100 °C for 10 h, the grain size increased slightly, being 40 - 70 nm, indicating that the prepared fibers have good anti-sintering performance. In addition, the fibers also have good high-temperature phase stability and still maintain the fluorite and pyrochlore biphasic structure after heat treatment at 1200 °C for 10 h.

[0081] Comparative Example 1

[0082] (1) According to the molar ratio of Yb:Zr being 1:1, weigh the corresponding amounts of Yb(NO 3 ) 3 ·5H 2 O and ZrOCl 2 ·8H 2 O raw materials, and mix them well, denoted as D Yb-Zr .

[0083] (2) According to the mass ratio of the mixed salt D Yb-Zr and the solvent being 1:2.7, weigh the corresponding amount of N,N-dimethylformamide (DMF), dissolve the mixed salt D Yb-Zr in DMF, and stir for 5 h until D Yb-ZrFully dissolve and denote as S Yb-Zr .

[0084] (3) According to the content of the spinning aid being S Yb-Zr which is 7% of the solution mass, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to S RE-Zr solution and stir until fully dissolved. The stirring and aging time is 48 h to obtain the Yb-Zr precursor spinning solution, denoted as A1.

[0085] (4) According to the molar ratio of silicon to zirconium being 0.25:1 and in accordance with the mass ratio of water to silicon source being 1:1, weigh tetraethyl orthosilicate and water and add them to A1, and stir thoroughly for 8 h to ensure the full hydrolysis of tetraethyl orthosilicate to obtain the Yb-Zr-Si precursor spinning solution A.

[0086] (5) Electrospin the precursor spinning solution A in step 4 under the spinning conditions of a temperature of 35 °C, a relative humidity of 40%, a rotational speed of the drum receiving device of 250 r / min, a spinning voltage of 16 KV, a receiving distance of 15 cm, and a propulsion speed of 0.35 ml / h to obtain the precursor fiber B.

[0087] (6) Heat-treat the precursor fiber B spun in step 5 in an air atmosphere at 1100 °C for 2 h to obtain ytterbium zirconate-silica fiber. The heat-treatment procedure is as follows: heat from room temperature to 1100 °C at a heating rate of 5 °C / min, then hold for 2 h, then cool at a cooling rate of 2 °C / min to 500 °C, and then cool in the furnace to room temperature.

[0088] Compared with Example 1, the structure of the ytterbium zirconate-silica fiber is relatively dense, but the ytterbium zirconate particle size is relatively large, being 20 - 40 nm, and the anti-sintering performance is poor. After heat-treatment at 1100 °C for 10 h, the grain size rapidly increases to 150 - 200 nm, and the flexibility of the fiber membrane is poor.

[0089] Comparative Example 2

[0090] Steps 1 - 4 and steps 6 - 7 of this comparative example are the same as those of Example 1, and the difference lies only in the following steps:

[0091] (5) According to the molar ratio of silicon to zirconium being 0:1, no silicon source is introduced into the RE-Zr precursor spinning solution.

[0092] Compared with Example 1, the obtained high-entropy zirconate fiber has poor flexibility, and the size of the high-entropy zirconate grains is relatively large, within 20 nm. After heat-treatment at 1100 °C for 10 h, the grain size increases to 50 - 80 nm. Compared with Example 1, the anti-sintering performance decreases. In addition, the heat insulation performance also decreases. For the butane flame test of a thickness of 8 mm of (La 0.2 Sm 0.2 Gd 0.2 Dy0.2 Yb 0.2 ) 2 Zr 2 O 7 The heat insulation performance of the fiber, with the back temperature being 259 °C.

[0093] Comparative Example 3

[0094] Steps 1 to 5 and Step 7 of this comparative example are the same as those of Example 1, with the difference only being the following steps:

[0095] (6) The precursor spinning solution A in Step 5 was electrospun under the spinning conditions of a temperature of 35 °C, a relative humidity of 40%, a rotational speed of the drum receiving device of 250 r / min, a spinning voltage of 16 kV, a receiving distance of 15 cm, and a propulsion speed of 1 ml / h to obtain a precursor fiber membrane B.

[0096] Compared with Example 1, the propulsion speed of the spinning solution was too fast, the diameter of the prepared nanofibers increased, about 400 nm, and beaded fibers appeared, making it difficult to form fibers with a uniform diameter.

[0097] Comparative Example 4

[0098] Steps 1 to 2 and Steps 5 to 7 of this comparative example are the same as those of Example 1, with the difference only being the following steps:

[0099] (3) According to the mass ratio of the mixed salt D RE-Zr and the solvent being 1:2.7, weigh the corresponding amount of N,N-dimethylformamide (DMF), and dissolve the mixed salt D RE-Zr in DMF, and stir for 0.5 h until D RE-Zr dissolves, denoted as S RE-Zr .

[0100] (4) According to the content of the spinning aid being 7% of the mass of the S RE-Zr solution, weigh the corresponding amount of polyvinylpyrrolidone (PVP) and add it to the S RE-Zr solution and stir until it is fully dissolved. The stirring and aging time is 6 h to obtain a precursor spinning solution.

[0101] Compared with Example 1, the aging time of the precursor spinning solution was changed, the mixed salt was difficult to dissolve and mix evenly, and the spinning aid was not fully dissolved. The viscosity of the spinning solution was low and the spinnability was poor. There were a large number of slag balls during the electrospinning process, and the fibers were short and had low strength.

Claims

1. An ultrafine high entropy zirconate-silicon oxide flexible fiber membrane, characterized in that: The chemical formula is RE2Zr2O7-SiO2, which is composed of amorphous silicon oxide wrapped with high-entropy rare earth zirconate nanoparticles and has a RE / Zr-O-Si amorphous interface; the RE is composed of five rare earth metal elements.

2. The ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to claim 1, characterized in that: The chemical formula is (La 0.2 Sm 0.2 G 0.2 Dy 0.2 Yb 0.2 )2Zr2O7-SiO2.

3. The ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to claim 2, characterized in that: The grain size of the high entropy rare earth zirconate nanoparticles is 5-10 nm.

4. The ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to claim 3, characterized in that: The molar ratio of La, Sm, Gd, Dy, Yb and Zr is 1:1:1:1:1:

5.

5. The method for preparing an ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Weighing five kinds of rare earth metal salts according to the designed proportions, mixing them with Zr salt, dissolving them in an organic solvent, and then adding a spinning aid to obtain a RE-Zr precursor spinning solution; (2) adding a silicon source and water to the RE-Zr precursor spinning solution to hydrolyze the silicon source and obtain a RE-Zr-Si precursor spinning solution; (3) electrospinning the RE-Zr-Si precursor spinning solution to obtain precursor fibers; (4) The precursor fiber is heat treated in an oxygen-containing atmosphere to obtain a fiber.

6. The method for preparing an ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to claim 5, characterized in that: The organic solvent is at least one of anhydrous methanol, anhydrous ethanol, acetone and N,N-dimethylformamide; The spinning aid is at least one of polyethylene oxide and polyvinyl pyrrolidone; The Zr salt is ZrOCl2 and its hydrate; The silicon source is at least one of ethyl orthosilicate, methyltrimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane and γ-chloropropyltriethoxysilane.

7. The method for preparing an ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to claim 6, characterized in that: The mass ratio of the total mass of the five rare earth metal salts and the Zr salt to the organic solvent is 1:(1.6-3.3); The amount of the silicon source added is such that the molar ratio of Si to Zr is (0.05-0.4):1; and the mass ratio of water to the silicon source is (0.5-2):

1.

8. The method for preparing an ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to claim 5, characterized in that: In step (1), after adding the spinning aid, stirring and aging are required for 24 to 72 hours.

9. The method for preparing an ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to claim 8, characterized in that: The electrospinning parameters are: relative humidity of 30-60%, temperature of 25-45°C, spinning voltage of 12-18KV, receiving distance of 10-20cm, propulsion speed of 0.3-0.7ml / h; the receiving device is a metal roller with a rotation speed of 100-500r / min.

10. The method for preparing an ultrafine high entropy zirconate-silicon oxide flexible fiber membrane according to claim 8 or 9, characterized in that: The heating procedure of the heat treatment is: heating from room temperature to 1000-1200°C at a rate of 1-5°C / min, keeping the temperature for 120-300min; then decreasing the temperature to 400-500°C at a rate of 2-3°C / min, and then cooling in the furnace.

Images