Zirconia / silicon carbide / silica nanofiber and preparation method and application thereof
Zirconia/silicon carbide/silicon oxide nanofibers were prepared by electrospinning and heat treatment to form a layered ring structure, which solved the problems of brittleness and thermal conductivity of zirconia fibers and achieved nanofiber materials with high flexibility and low thermal conductivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA BUILDING MATERIALS ACADEMY CO LTD
- Filing Date
- 2023-12-15
- Publication Date
- 2026-05-29
AI Technical Summary
Existing methods for preparing zirconia fibers are insufficient for producing continuous nanofibers, and their high brittleness and poor temperature resistance limit their flexibility and thermal conductivity in practical applications.
Zirconia/silicon carbide/silicon oxide nanofibers were prepared using electrospinning technology. By adding a liquid silicon source to a zirconium sol solution, zirconium/silicon carbide/silicon oxide nanofibers were formed. Oxygen-free sintering and heat treatment were used to form a layered ring structure, which improved the flexibility of the fibers and reduced their thermal conductivity.
The prepared zirconia/silicon carbide/silicon oxide nanofibers have high flexibility, low density and low thermal conductivity, can be bent more than 40 times and have a resilience of more than 90%, making them suitable for aerospace and other fields.
Smart Images
Figure CN117702307B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanofiber materials technology, and in particular to a zirconium oxide / silicon carbide / silicon oxide nanofiber, its preparation method, and its application. Background Technology
[0002] Zirconia fibers possess excellent physicochemical properties such as high strength, high temperature resistance, corrosion resistance, and good biocompatibility, making them widely applicable in fields such as environment, energy, and biological tissue scaffolds. Currently, the main methods for preparing ZrO2 fibers include impregnation, mixed spinning, and sol-gel methods. However, ZrO2 fibers prepared by these methods exhibit poor continuity, and their diameters are mostly on the order of micrometers, which limits the practical applications of ZrO2 fibers.
[0003] Electrospinning technology can directly prepare continuous nanofibers and has become the main method for preparing flexible ZrO2 nanofiber membranes due to its advantages such as simple equipment, controllable process, and wide variety of spinnable materials. Literature reports that the Key Laboratory of Excited State Physics at the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, has disclosed a method for preparing one-dimensional titanium-doped zirconium oxide nanofibers by combining electrospinning and high-temperature calcination. After high-temperature calcination, the fiber diameter is greatly reduced due to the decomposition of the template agent and polyvinylpyrrolidone (PVP) at high temperatures. Scanning electron microscopy reveals monoclinic fibers with a diameter of approximately 100 nm. However, these titanium-doped zirconium oxide fibers are relatively brittle and have poor temperature resistance, and are generally used as photocatalysts. Some literature reports that the overall performance of a product can be improved by three-dimensionally overlapping multiple nanofibers. However, this method of improving product performance by using three-dimensionally overlapping multiple fibers has very limited effect on product performance. It is still difficult to obtain a ZrO2 fiber with strong comprehensive performance that has both high elasticity and flexibility as well as low density and low thermal conductivity. This limits the practical application of zirconium oxide fiber and greatly affects its promotion and application. Summary of the Invention
[0004] The main objective of this invention is to provide a zirconia / silicon carbide / silicon oxide nanofiber, its preparation method, and its application. The technical problem to be solved is how to provide a zirconia / silicon carbide / silicon oxide nanofiber that has both high elasticity and high flexibility, as well as low density and low thermal conductivity, with strong comprehensive performance, which greatly expands the application of zirconia fibers and makes them more suitable for practical use.
[0005] The objective of this invention and the technical problem it solves are achieved by the following technical solution. A method for preparing zirconium oxide / silicon carbide / silicon oxide nanofibers according to this invention includes the following steps:
[0006] S11 Adds a liquid silicon source to the zirconium sol solution and stirs it evenly to obtain a spinning solution;
[0007] S12 Electrospinning the spinning solution and drying it to obtain a nanofiber precursor.
[0008] S13 oxygen-free sintering yields zirconium oxide / silicon carbide nanofibers; wherein the zirconium oxide serves as the fiber center; and a silicon carbide layer is coated on the outside of the zirconium oxide.
[0009] S14 heat treatment oxidizes the surface of the silicon carbide layer near the outer side to obtain zirconium oxide / silicon carbide / silicon oxide nanofibers.
[0010] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.
[0011] Preferably, in the aforementioned preparation method, the preparation steps of the zirconium sol solution are as follows: zirconium acetate, yttrium acetate, polyvinylpyrrolidone and deionized water are mixed and stirred evenly at 25-70°C; wherein the mass ratio of zirconium acetate, yttrium acetate, polyvinylpyrrolidone and deionized water is 1:0.03-0.08:0.01-0.06:0.05-0.06.
[0012] Preferably, in the aforementioned preparation method, the liquid silicon source is liquid polycarbosilane; the mass ratio of the liquid silicon source to the zirconium acetate is 0.1 to 0.5:1; after adding the liquid silicon source, the mixture is stirred for 10 to 30 minutes to obtain the spinning solution.
[0013] Preferably, in the aforementioned preparation method, the oxygen-free sintering involves sintering the nanofiber precursor in a nitrogen atmosphere.
[0014] Preferably, in the aforementioned preparation method, the sintering temperature of the oxygen-free sintering is 800–1500°C, and the sintering time is 0.5–2 h.
[0015] Preferably, in the aforementioned preparation method, the heat treatment involves first cooling the zirconium oxide / silicon carbide nanofibers to room temperature after oxygen-free sintering, then placing them in a muffle furnace and heating them to 800-1000°C at a rate of ≥10°C / min, without holding the temperature, and directly cooling them to room temperature with the furnace.
[0016] The objective of this invention and the technical problem it solves are achieved by the following technical solution. A zirconium oxide / silicon carbide / silicon oxide nanofiber according to this invention comprises:
[0017] Zirconia nanofibers are disposed at the center of the zirconium oxide / silicon carbide / silicon oxide nanofibers;
[0018] A silicon carbide coating layer is applied to the outer side of the zirconium oxide nanofibers;
[0019] A silicon oxide coating layer is applied to the outside of the silicon carbide coating layer.
[0020] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.
[0021] Preferably, the aforementioned zirconium oxide / silicon carbide / silicon oxide nanofibers have a diameter of 100–200 nm and a density of 0.03–0.05 g / cm³. 3 It has a thermal conductivity of 0.02 to 0.03 W / (m·K), can be bent ≥40 times, and has a springback of ≥90% after 100 compressions.
[0022] Preferably, the aforementioned zirconium oxide / silicon carbide / silicon oxide nanofibers are prepared by the aforementioned preparation method.
[0023] The objective of this invention and the technical problem it solves are achieved by the following technical solution: An application of the aforementioned zirconium oxide / silicon carbide / silicon oxide nanofibers in the field of aerospace technology, according to this invention.
[0024] By employing the above technical solution, the zirconium oxide / silicon carbide / silicon oxide nanofiber, its preparation method, and its application provided by the present invention have at least the following advantages:
[0025] The zirconia / silicon carbide / silicon oxide nanofibers provided by this invention are prepared by adding a silicon source to a zirconium sol and using a sol-gel method to prepare a high-nanofiber spinning solution, which is then prepared into a nanofiber precursor by electrospinning. The dried fiber precursor is then subjected to oxygen-free sintering. During sintering, zirconium oxide is first sintered and crystallized to form a zirconia fiber core composed of zirconium oxide grains. Then, polycarbosilane is sintered and crystallized to form a silicon carbide layer composed of silicon carbide grains, which uniformly coats the outer surface of the zirconia fiber core. Finally, the fiber core is heat-treated to gradually oxidize the silicon carbide layer from the outside to the inside, that is, the outer portion of the silicon carbide layer is converted into a silicon oxide layer, forming a zirconia / silicon carbide / silicon oxide nanofiber composed of a zirconia fiber core, a silicon carbide-coated middle layer, and a silicon oxide-coated outer layer. The layered, ring-structured composite fiber of this invention increases the complexity of the fiber, resulting in high flexibility and elasticity in the zirconia / silicon carbide / silicon oxide nanofibers. Bending tests show they can be bent ≥40 times, and compression tests show a resilience rate ≥90% after 100 cycles. Furthermore, the complex structure of the zirconia / silicon carbide / silicon oxide nanofibers leads to a complex heat transfer path, resulting in a thermal conductivity as low as 0.02–0.03 W / (m·K), providing excellent thermal insulation. As can be seen from the above, the composite fiber of this invention overcomes the inherent brittleness of nanofibers and can handle a wider range of working conditions.
[0026] Furthermore, the preparation method of the present invention uses the sol-gel method to add silicon carbide raw materials such as polycarbosilane to the zirconium oxide spinning solution to prepare a multi-component spinning solution in one spinning process. Then, a two-step high-temperature heat treatment process is used to prepare high-performance zirconium oxide / silicon carbide / silicon oxide nanofibers. The process steps are simple and do not require supercritical drying to prepare nanowires as in the prior art. It is cost-effective and highly efficient.
[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the structure of the zirconium oxide / silicon carbide / silicon oxide nanofibers of the present invention;
[0029] Figure 2 This is a process flow diagram of the zirconium oxide / silicon carbide / silicon oxide nanofibers of the present invention;
[0030] Figure 3 The image shows a SEM image of zirconia / silicon carbide / silicon oxide nanofibers obtained in Example 1 of this invention. Detailed Implementation
[0031] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation methods, structures, features, and effects of a zirconium oxide / silicon carbide / silicon oxide nanofiber, its preparation method, and its applications according to the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.
[0032] This invention proposes a zirconium oxide / silicon carbide / silicon oxide nanofiber, as shown in the attached figure. Figure 1 As shown, it includes:
[0033] Zirconia nanofiber 1 is disposed at the center of zirconia / silicon carbide / silicon oxide nanofiber;
[0034] A silicon carbide coating layer 2 is applied to the outer side of the zirconium oxide nanofibers;
[0035] The silicon oxide coating layer 3 is coated on the outside of the silicon carbide coating layer.
[0036] In the above technical solution, the zirconium oxide / silicon carbide / silicon oxide nanofibers are nested rings from the inside out, forming a zirconium oxide / silicon carbide / silicon oxide nanocomposite fiber. This structural design of the composite fiber increases the structural complexity of the single fiber, thereby improving the flexibility of the nanofiber, while reducing the thermal conductivity of the fiber.
[0037] By cutting the zirconium oxide / silicon carbide / silicon oxide nanofibers obtained in the examples along a radial cross section and then performing elemental distribution analysis on the cut surface of the fibers, the results showed that the elements at the core were zirconium and oxygen, the elements in the middle layer were carbon and silicon, and the elemental distribution in the outermost layer was silicon and oxygen. This result indicates that the zirconium oxide / silicon carbide / silicon oxide nanofibers of the present invention form a nested ring structure of zirconium oxide nanofibers, silicon carbide coating layer and silicon oxide coating layer, rather than a three-dimensional overlapping structure of several fibers in the traditional sense.
[0038] The tests showed that the zirconium oxide / silicon carbide / silicon oxide nanofibers of the embodiments of the present invention have a diameter of 100-200 nm and a density of 0.03-0.05 g / cm³. 3 The thermal conductivity is 0.02~0.03W / (m·K). The flexibility test results show that it can be bent ≥40 times, with an optimal value of 50 times; the rebound after 100 compressions is ≥90%, with an optimal value of 95%; the test results show that the composite fiber filament has a nanometer-scale diameter, low density, and low thermal conductivity, and has excellent heat insulation and temperature resistance performance; moreover, it has good flexibility and elasticity, and has excellent mechanical properties.
[0039] This invention proposes a method for preparing zirconium oxide / silicon carbide / silicon oxide nanofibers, as shown in the appendix. Figure 2 As shown, it includes the following steps:
[0040] The first step is to prepare a zirconium sol solution. In one embodiment of the invention, the zirconium sol is preferably prepared according to the following raw materials and proportions: zirconium acetate, yttrium acetate, polyvinylpyrrolidone, and deionized water are mixed and stirred evenly at 25–70°C. When the zirconium sol is prepared at a temperature below 25°C, its production efficiency is low and the cost is uneconomical; while when the zirconium sol is prepared at a temperature above 70°C, the reaction becomes too vigorous, leading to uncontrolled preparation and difficulty in ensuring consistent quality. Therefore, the present invention preferably prepares the zirconium sol at 25–70°C; more preferably 40–60°C; and even more preferably 45–55°C.
[0041] The raw material ratio for preparing zirconium sol is zirconium acetate, yttrium acetate, polyvinylpyrrolidone (PVP), and deionized water in a mass ratio of 1:0.03–0.08:0.01–0.06:0.05–0.06; more preferably, the mass ratio of zirconium acetate, yttrium acetate, PVP, and deionized water is 1:0.05:0.03:0.05–0.06; and even more preferably, the molar ratio of zirconium acetate to deionized water is 1:1. Polyvinylpyrrolidone, as a synthetic water-soluble polymer, possesses the general properties of water-soluble polymers, including colloidal protection, film-forming properties, adhesiveness, hygroscopicity, solubilization, and coagulation. By strictly controlling the addition ratio of the above raw materials, this invention can ensure that the prepared zirconium sol has a stable structure and good performance.
[0042] Next, a liquid silicon source is added to the zirconium sol solution and stirred until homogeneous to obtain the spinning solution. The temperature control during stirring is the same as that required during the preparation of the zirconium sol.
[0043] The preferred liquid silicon source is liquid polycarbosilane; this is because liquid silicon sources are easily dispersed in zirconium sol and because they allow silicon to be uniformly distributed in the spinning solution. When adding the liquid silicon source, the mass ratio of liquid silicon source to zirconium acetate is preferably controlled at 0.1–0.5:1. As seen in the ring structure of the zirconium oxide / silicon carbide / silicon oxide nanofibers of the present invention, silicon is first coated on the outer surface of zirconium oxide in the form of silicon carbide, and then on the surface of silicon carbide in the form of silicon oxide. Since zirconium acetate is the sole source of zirconium in the zirconium sol, adjusting the amount of silicon source added based on the amount of zirconium acetate added can effectively control the ratio of silicon to zirconium. The added silicon content should not be too low, because if the amount of silicon added is too small, the amount of silicon carbide generated during the subsequent sintering process will be insufficient, making it difficult to completely coat the outer surface of the zirconia fiber, thus making it difficult to realize the inventive concept of forming a ring-shaped composite fiber. Alternatively, even if the silicon carbide layer completely coats the zirconia layer, if the thickness of the formed silicon carbide layer is too thin, all the silicon carbide may be oxidized to silicon oxide during the subsequent heat treatment, resulting in only a two-layer structure with a silicon oxide layer on the surface of the zirconia fiber, making it difficult to realize the inventive concept of forming a three-layer ring-shaped composite fiber. Therefore, the mass ratio of liquid silicon source to zirconium acetate should not be less than 0.1:1. The added silicon content should not be too high, because if too much silicon is added, it will increase the material cost of the fiber. On the other hand, it will take longer to ensure that the polycarbosilane can be completely sintered to form a silicon carbide layer, and the production efficiency will also be reduced. Furthermore, the composite fiber of the present invention can achieve the improvement of the composite fiber as long as it can form a nested ring structure, while the thickness of the coating layer has little impact on the performance. Therefore, the present invention preferably has a mass ratio of liquid silicon source to zirconium acetate of no more than 0.5:1.
[0044] After adding the liquid silicon source to the zirconium sol, it is preferable to stir for 10–30 minutes to obtain the spinning solution. If the stirring time is too short, the liquid silicon source will be difficult to disperse evenly in the zirconium sol, resulting in uneven composition at different locations and affecting its performance. After ensuring that the liquid silane is evenly dispersed and reacted, there is no need for excessive stirring to ensure high production efficiency and good cost performance.
[0045] The next step is to electrospin the spinning solution. The equipment and process for electrospinning can be any commonly used electrospinning equipment and process in this technical field, as long as it can achieve uniform spinning of the spinning solution. The preferred electrospinning steps of this invention are as follows: the spinning solution is drawn into the syringe of the electrospinning equipment, the voltage of the electrospinning equipment is set to 30KV, the injection speed is 0.09mm / min, and the spinning distance is 15cm, thus preparing the spinning solution into fiber filaments.
[0046] The next step is to dry the fibers to obtain the nanofiber precursor. Drying can be performed using a blower commonly used in the art, without the complexity and lower cost of the supercritical drying process used in existing nanowire preparation techniques. Preferably, the nanofiber precursor is dried by placing it in a blower drying oven at approximately 60°C for 12–24 hours to ensure complete drying.
[0047] In the dried nanofiber precursor, zirconium exists in the form of zirconium oxide, while silicon is mixed in as polycarbosilane.
[0048] Next, the nanofiber precursor is subjected to oxygen-free sintering to obtain zirconia / silicon carbide nanofibers. The structure of these zirconia / silicon carbide nanofibers features zirconia as the fiber center, with a silicon carbide layer coating the outer surface of the zirconia. Here, oxygen-free sintering means that the sintering environment does not contain oxygen, to prevent silicon carbide from being oxidized to silicon oxide during sintering. A nitrogen atmosphere can be used, as is commonly used in the art. In some embodiments of the present invention, a preferred operation is to place the dried nanofiber precursor in a vacuum furnace, then evacuate the furnace to remove air, minimizing or avoiding oxygen retention, and then introduce nitrogen into the vacuum furnace. Generally, the nitrogen atmosphere is controlled at approximately one atmosphere; however, this is not specifically limited in the present invention. During the oxygen-free sintering process, due to the difference in properties between zirconium oxide and polycarbosilane, zirconium oxide is first sintered to form zirconium oxide fibers composed of zirconium oxide grains, which do not contain silicon. At this time, silicon is uniformly present around the zirconium oxide fibers. As the oxygen-free sintering continues, silicon and carbon are gradually sintered into silicon carbide grains, and the formed silicon carbide grains uniformly coat the outside of the zirconium oxide fibers, forming a two-layer structure of nanofibers with a silicon carbide layer on the surface of the zirconium oxide fibers.
[0049] To effectively form the nested ring structure of silicon carbide-coated zirconia, the sintering temperature of the oxygen-free sintering is preferably controlled at 800–1500°C. If the sintering temperature is below 800°C, silicon carbide cannot crystallize, making it difficult to form a crystalline structure; while if the sintering temperature is above 1500°C, the silicon carbide fiber size will be too large, and the grain size will be too coarse, resulting in the silicon carbide not being able to fully coat the surface of the zirconia fibers, making it difficult to form a nested ring structure. To ensure both sufficient reaction to form the silicon carbide coating and good production efficiency, the sintering time of the oxygen-free sintering is preferably 0.5–2 hours.
[0050] Finally, the zirconia / silicon carbide nanofibers obtained by oxygen-free sintering are heat-treated to oxidize the outer surface of the silicon carbide layer, resulting in zirconia / silicon carbide / silicon oxide nanofibers. Preferably, the heat treatment is performed in an air atmosphere to utilize the oxygen in the air to oxidize the silicon carbide into a silicon oxide layer. The heat treatment process involves first cooling the oxygen-free sintered zirconia / silicon carbide nanofibers to room temperature, and then rapidly heating them to 800–1000°C in a muffle furnace; for ease of description, this temperature is defined as the peak temperature. At this peak temperature, no holding time is performed, and the fibers are directly cooled to room temperature in the furnace. The technical purpose of the heat treatment is to oxidize the outer surface of the silicon carbide coating on the zirconia surface into a silicon oxide layer. If the heating rate is too low, the oxidation reaction may be inefficient, affecting production efficiency and resulting in uneconomical costs. Therefore, a faster heating rate is better. However, due to the limitations of the muffle furnace itself, which currently has a maximum adjustable heating rate of 10°C / min, this invention preferably uses a heating rate of ≥10°C / min. If the peak temperature of the heat treatment is below 800℃, the oxidation reaction of silicon carbide is difficult to occur, and the silicon carbide layer cannot be converted into a silicon oxide layer. If the peak temperature of the heat treatment is above 1000℃, the oxidation reaction of silicon carbide may be too rapid, making the reaction difficult to control. This could result in an excessively thick silicon oxide layer, or even the complete oxidation of all silicon carbide into a silicon oxide layer. This would prevent the formation of a three-layered interlocking structure, resulting only in a two-layered nested structure with a silicon oxide layer covering a zirconium oxide fiber core, thus failing to achieve the inventive concept of this invention. The present invention further preferably uses a peak heat treatment temperature of 850–950℃; even more preferably, 900℃.
[0051] The zirconium oxide / silicon carbide / silicon oxide nanofibers of the present invention are preferably prepared by the preparation method of the zirconium oxide / silicon carbide / silicon oxide nanofibers of the present invention.
[0052] The present invention also proposes an application of the aforementioned zirconium oxide / silicon carbide / silicon oxide nanofibers in the field of aerospace technology.
[0053] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.
[0054] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by those skilled in the art to which this invention pertains.
[0055] Example 1
[0056] This embodiment prepares a zirconium oxide / silicon carbide / silicon oxide nanofiber, and the specific steps are as follows:
[0057] 1) Weigh 100 parts zirconium acetate, 5 parts yttrium acetate, 3 parts polyvinylpyrrolidone K90, and 5.5 parts deionized water; mix the measured zirconium acetate, yttrium acetate, polyvinylpyrrolidone K90, and deionized water together and stir evenly in an environment of about 50°C.
[0058] 2) Weigh 10 portions of liquid polycarbosilane; add the measured polycarbosilane to the solution obtained in step 1), and stir for 20 minutes at about 50°C to obtain the spinning solution.
[0059] 3) The spinning solution obtained in step 2) is drawn into the syringe of the electrospinning equipment. The electrospinning parameters are set to a voltage of 30KV, a injection speed of 0.09mm / min, and a spinning distance of 15cm. Electrospinning is carried out under these process parameters.
[0060] 4) Place the fiber obtained in step 3) into a forced-air drying oven and dry it at a temperature of about 60°C for 24 hours to obtain the nanofiber precursor.
[0061] 5) Place the nanofiber precursor obtained in step 4) into a vacuum furnace, evacuate the air in the vacuum furnace, and then introduce nitrogen into the vacuum furnace to make the pressure in the vacuum furnace one atmosphere; raise the temperature to 1200℃ and hold for 1 hour to obtain the precursor.
[0062] 6) Cool the zirconia / silicon carbide nanofibers obtained in step 5) to room temperature; then place them in a muffle furnace and heat them to 900°C at a rate of 10°C / min without stopping. Then let them cool to room temperature with the furnace to obtain zirconia / silicon carbide / silicon oxide nanofibers.
[0063] The SEM images of the zirconia / silicon carbide / silicon oxide nanofibers obtained in this embodiment are attached. Figure 3 As shown, the fiber was cut along a radial section, and then the elemental distribution of the cut surface was analyzed. The results showed that the elements at the core were zirconium and oxygen, the elements in the middle layer were carbon and silicon, and the elements in the outermost layer were silicon and oxygen.
[0064] Testing revealed that the zirconium oxide / silicon carbide / silicon oxide nanofibers obtained in this embodiment of the invention have a diameter of 100 nm and a density of 0.05 g / cm³. 3 It has a thermal conductivity of 0.03 W / (m·K), can be bent 45 times, and has a springback of 91% after 100 compressions.
[0065] Example 2
[0066] The process steps are the same as in Example 1, except that: 3 parts yttrium acetate, 1 part polyvinylpyrrolidone K90, and 5.5 parts deionized water are added, and the mixing temperature is approximately 30°C. 30 parts of liquid polycarbosilane are added, and the mixing temperature is approximately 30°C for 30 minutes. The drying time of the nanofiber precursor is 12 hours. The oxygen-free sintering temperature is 800°C, and the holding time is 2 hours. The peak temperature of the heat treatment is 800°C.
[0067] Testing revealed that the zirconium oxide / silicon carbide / silicon oxide nanofibers obtained in this embodiment of the invention have a diameter of 150 nm and a density of 0.04 g / cm³. 3 It has a thermal conductivity of 0.02 W / (m·K), is flexible enough to be bent 50 times, and has a 95% springback after 100 compressions.
[0068] Example 3
[0069] The process steps are the same as in Example 1, except that: 8 parts of yttrium acetate, 6 parts of polyvinylpyrrolidone K90, and 5.5 parts of deionized water are added, and the mixing temperature is approximately 65°C. The amount of liquid polycarbosilane added is 50 parts, and the mixing temperature is approximately 65°C for 10 minutes. The drying time of the nanofiber precursor is 18 hours. The oxygen-free sintering temperature is 1500°C, and the holding time is 0.5 hours. The peak temperature of the heat treatment is 1000°C.
[0070] Testing revealed that the zirconium oxide / silicon carbide / silicon oxide nanofibers obtained in this embodiment of the invention have a diameter of 200 nm and a density of 0.03 g / cm³. 3 It has a thermal conductivity of 0.03 W / (m·K), can be bent 42 times, and has a 90% springback after 100 compressions.
[0071] Comparative Example 1
[0072] The process steps are the same as in Example 1, except that the amount of liquid polycarbosilane is 8 parts. Testing showed that the zirconium oxide / silicon carbide / silicon oxide nanofibers obtained in this comparative example have a diameter of 123 nm and a density of 0.04 g / cm³. 3 It has a thermal conductivity of 0.05 W / (m·K), is flexible enough to be bent 30 times, and has a springback of 85% after 100 compressions.
[0073] Comparative Example 2
[0074] The process steps are the same as in Example 1, except that the oxygen-free sintering temperature is 750℃. Testing showed that the zirconia / silicon carbide / silicon oxide nanofibers obtained in this comparative example have a diameter of 260 nm and a density of 0.045 g / cm³. 3 It has a thermal conductivity of 0.055 W / (m·K), is flexible enough to be bent 25 times, and has an 80% springback after 100 compressions.
[0075] Comparative Example 3
[0076] The process steps are the same as in Example 1, except that the oxygen-free sintering temperature is 1550℃. Testing showed that the zirconia / silicon carbide / silicon oxide nanofibers obtained in this comparative example have a diameter of 500 nm and a density of 0.05 g / cm³. 3 It has a thermal conductivity of 0.06 W / (m·K), is flexible enough to be bent 20 times, and has a springback of 75% after 100 compressions.
[0077] Comparative Example 4
[0078] The process steps are the same as in Example 1, except that the peak temperature of the heat treatment is 750℃. Testing showed that the zirconia / silicon carbide / silicon oxide nanofibers obtained in this comparative example have a diameter of 200 nm and a density of 0.04 g / cm³. 3 It has a thermal conductivity of 0.05 W / (m·K), is flexible enough to be bent 30 times, and has an 80% springback after 100 compressions.
[0079] Comparative Example 5
[0080] The process steps are the same as in Example 1, except that the peak temperature of the heat treatment is 1050℃. Testing showed that the zirconia / silicon carbide / silicon oxide nanofibers obtained in this comparative example have a diameter of 300 nm and a density of 0.048 g / cm³. 3 It has a thermal conductivity of 0.057 W / (m·K), is flexible enough to be bent 25 times, and has an 80% springback after 100 compressions.
[0081] Comparative Example 6
[0082] Zirconia nanofibers, silicon carbide nanofibers, and zirconia nanofibers with a diameter of approximately 100 nm were mixed in the same proportions as in the example to form three-dimensionally overlapping fibers. The density of the zirconia / silicon carbide / silicon oxide nanofibers obtained in this comparative example was measured to be 0.04 g / cm³. 3 It has a thermal conductivity of 0.065 W / (m·K), is flexible enough to be bent 30 times, and has a springback of 85% after 100 compressions.
[0083] As can be seen from the test data of the examples and comparative examples, when the proportion of liquid silicon source added is low, the prepared fibers have a high thermal conductivity, a low number of bends, a small rebound after 100 compressions, and are brittle with poor thermal insulation. For example, in Comparative Example 1, this may be because the amount of liquid silicon added is small, so the silicon carbide layer formed during oxygen-free sintering may not be able to fully cover the zirconium oxide layer. Or even if it can fully cover the zirconium oxide layer, the thin silicon carbide may be completely oxidized to a silicon oxide layer during heat treatment, preventing the formation of the three-layered ring-structured composite fiber of the present invention. When the oxygen-free sintering temperature is low, the prepared fibers have a large diameter, are brittle, and have poor thermal insulation. For example, in Comparative Example 2, this is because at low sintering temperatures, silicon carbide cannot crystallize and is difficult to form a crystalline structure. When the oxygen-free sintering temperature is too high, the prepared fibers are coarser in diameter, more brittle, and have poor thermal insulation, as seen in Comparative Example 3. This is because a high sintering temperature causes the silicon carbide fibers to become too large and the grain size too coarse, resulting in insufficient silicon carbide to fully coat the surface of the zirconia fibers, making it difficult to form a nested ring structure. When the heat treatment temperature is too low, the prepared fibers are also coarser in diameter, more brittle, and have poor thermal insulation, as seen in Comparative Example 4. This is because a low peak heat treatment temperature makes it difficult for the silicon carbide oxidation reaction to occur, preventing the silicon carbide layer from being converted into a silicon oxide layer. When the heat treatment temperature is too high, the prepared fibers are even coarser in diameter, more brittle, and have poor thermal insulation, as seen in Comparative Example 5. This is because a high temperature may cause the silicon carbide oxidation reaction to be too rapid, making the reaction difficult to control. This could result in an excessively thick silicon oxide layer, or even the complete oxidation of the silicon carbide into a silicon oxide layer, preventing the formation of a nested ring structure of the three materials. When zirconia nanofibers, silicon carbide nanofibers, and silicon oxide nanofibers are mixed to form a three-dimensional overlapping composite fiber, the fiber is brittle and has poor thermal insulation, as shown in Comparative Example 6. The possible reason is that the three fibers do not form a layered ring structure, but are mixed together in a physical contact manner. They are difficult to play a synergistic role in performance and cannot improve the brittleness and thermal insulation.
[0084] The numerical range described in this invention includes all values within this range, and also includes any range value composed of any two values within this range. Different values of the same indicator appearing in all embodiments of this invention can be arbitrarily combined to form a range value.
[0085] The technical features in the claims and / or specification of this invention can be combined, and the combination is not limited to the combinations obtained through reference in the claims. Technical solutions obtained by combining the technical features in the claims and / or specification are also within the scope of protection of this invention.
[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A method for preparing zirconium oxide / silicon carbide / silicon oxide nanofibers, characterized in that, Includes the following steps: S11. A liquid silicon source is added to the zirconium sol solution and stirred until homogeneous to obtain a spinning solution; the liquid silicon source is liquid polycarbosilane; the preparation steps of the zirconium sol solution are as follows: zirconium acetate, yttrium acetate, polyvinylpyrrolidone and deionized water are mixed and stirred until homogeneous at 25~70 °C; the mass ratio of the liquid silicon source to the zirconium acetate is 0.1~0.5:1; S12 Electrospinning the spinning solution and drying it to obtain a nanofiber precursor. S13 oxygen-free sintering yields zirconium oxide / silicon carbide nanofibers; wherein the zirconium oxide serves as the fiber center. A silicon carbide layer is coated on the outside of the zirconium oxide; the sintering temperature of the oxygen-free sintering is 800~1500℃; S14 heat treatment oxidizes the surface of the silicon carbide layer near the outer side to obtain zirconium oxide / silicon carbide / silicon oxide nanofibers; the heat treatment is carried out after oxygen-free sintering, the zirconium oxide / silicon carbide nanofibers are first cooled to room temperature, and then placed in a muffle furnace and heated to 800~1000℃ at a rate of ≥10℃ / min, without heat preservation, and directly cooled to room temperature with the furnace.
2. The preparation method according to claim 1, characterized in that, The mass ratio of zirconium acetate, yttrium acetate, polyvinylpyrrolidone, and deionized water is 1:0.03~0.08:0.01~0.06:0.05~0.
06.
3. The preparation method according to claim 2, characterized in that, After adding the liquid silicon source, stir for 10-30 minutes to obtain the spinning solution.
4. The preparation method according to claim 1, characterized in that, The oxygen-free sintering involves sintering the nanofiber precursor in a nitrogen atmosphere.
5. The preparation method according to claim 4, characterized in that, The sintering time is 0.5~2h.
6. A zirconium oxide / silicon carbide / silicon oxide nanofiber, prepared by the preparation method according to any one of claims 1 to 5, characterized in that, It includes: Zirconia nanofibers are disposed at the center of the zirconium oxide / silicon carbide / silicon oxide nanofibers; A silicon carbide coating layer is applied to the outer side of the zirconium oxide nanofibers; A silicon oxide coating layer is applied to the outside of the silicon carbide coating layer.
7. The zirconium oxide / silicon carbide / silicon oxide nanofibers according to claim 6, characterized in that, Its diameter is 100~200nm, and its density is 0.03~0.05g / cm³. 3 It has a thermal conductivity of 0.02~0.03W / (m·K), can be bent ≥40 times, and has a springback of ≥90% after 100 compressions.
8. An application of the zirconium oxide / silicon carbide / silicon oxide nanofibers according to claim 6 or 7 in the field of aerospace technology.