Yttrium-zirconium ceramic fiber aerogel with grain boundary segregation phenomenon and high infrared reflectivity

Abstract

The invention discloses yttrium-zirconium ceramic fiber aerogel with a grain boundary segregation phenomenon and high infrared reflectivity, and belongs to the field of oxide ceramic fiber aerogel thermal insulation materials. The preparation method comprises the following steps: preparing polyacetylacetonate yttrium-zirconium precursor powder according to a molar ratio of yttrium to zirconium of 10: 1-2: 1, mixing the polyacetylacetonate yttrium-zirconium precursor powder with a polymer spinning aid and a solvent according to a mass ratio of (10-30): 1: (20-40) to obtain a spinning solution, carrying out centrifugation or electrostatic spinning to form a layered aerogel precursor, heating to 900 DEG C at a speed of 3-5 DEG C / min, carrying out heat preservation for 2 hours, and carrying out cooling crystallization. The aerogel has a zirconium element grain boundary segregation phenomenon, the fiber diameter is 1-4 microns, the average near-infrared reflectivity exceeds 95%, the volume shrinkage rate in a 1500 DEG C long-term environment is smaller than or equal to 5%, and the aerogel has excellent high-temperature thermal stability and heat insulation performance and can meet the heat prevention and insulation requirements in extreme high-temperature scenes.

Description

Technical Field

[0001] This invention belongs to the field of oxide ceramic fiber aerogel thermal insulation materials, specifically relating to a yttrium-zirconium ceramic fiber aerogel with high infrared reflectivity exhibiting grain boundary segregation. Background Technology

[0002] The development and progress of advanced industries such as aerospace, clean energy, and energy conservation and emission reduction require reliable thermal insulation materials that exhibit high thermal stability and insulation performance under extreme high-temperature conditions to ensure the function and safety of critical systems. Ceramic aerogels, due to their high-temperature resistance, high porosity, and low thermal conductivity, have proven to be among the most promising thermal insulation materials. However, due to grain growth effects at high temperatures, their insufficient structural stability often leads to degradation of insulation performance, potentially resulting in catastrophic consequences. Existing research shows that crystal / phase structure design and entropy stabilization design can significantly improve the thermal stability of ceramic aerogels below 1400℃. However, these strategies mainly focus on structural stabilization within the grains, while grain boundaries, another key factor in improving ceramic thermal stability, have received little attention due to their more complex structure and more difficult control methods. This greatly restricts further improvements in the thermal stability of ceramic aerogels at high and ultra-high temperatures. Therefore, to improve the operating temperature of ceramic aerogels and expand their application prospects, research on the design and control of ceramic grain boundaries is urgently needed. Summary of the Invention

[0003] To address the problem that traditional oxide ceramic fiber aerogels suffer from significant grain growth at extreme high temperatures (≥1500℃), leading to aerogel structural collapse and loss of thermal insulation performance, the present invention aims to provide a yttrium-zirconium ceramic fiber aerogel with high infrared reflectivity exhibiting grain boundary segregation. The significant grain boundary segregation in the aerogel effectively hinders the growth of ceramic grains at high temperatures, while the yttrium oxide component generates high near-infrared reflectivity, enabling the aerogel to meet the thermal insulation requirements under ultra-high temperature environments of 1500℃.

[0004] The technical solution adopted in this invention is as follows: a yttrium-zirconium ceramic fiber aerogel with high infrared reflectivity exhibiting grain boundary segregation is prepared according to the following steps:

[0005] Step 1: Using polyyttrium acetylacetonate as the matrix, polyzirconium acetylacetonate is combined to prepare polyyttrium acetylacetonate-zirconium precursor powder; wherein, the yttrium:zirconium is mixed according to the molar ratio of yttrium:zirconium, and the ratio is yttrium:zirconium = 2:1 to 10:1.

[0006] Step 2: Dissolve the precursor powder in a polymer spinning aid solution to obtain a clear and transparent spinning solution; according to the mass ratio, precursor powder: polymer spinning aid: solvent = (10~30): 1: (20~40);

[0007] The polymeric spinning aid can be one or more of polyvinylpyrrolidone, polyethylene oxide, polyethylene glycol, polyvinyl alcohol, and polyvinyl butyral in any proportion; the solvent can be one or more of methanol, ethanol, glacial acetic acid, and deionized water in any proportion.

[0008] Step 3: Prepare a layered fiber aerogel precursor by centrifugal spinning or electrospinning of the spinning solution;

[0009] Step 4: The aerogel precursor is subjected to high-temperature crystallization treatment in air atmosphere. The steps are as follows: heat up to 900℃ at a rate of 3-5℃ / min, hold for 2 hours, and then cool down to 25℃ at a rate of 3-5℃ / min to form a three-dimensional layered yttrium-zirconium ceramic fiber aerogel.

[0010] Furthermore, in step two, the average molecular weight of the polymeric spinning aid is 5800–3000000.

[0011] Furthermore, in step two, the resulting spinning solution is prepared at a temperature of 20–30°C and a viscosity of 2–15 Pa·s.

[0012] Furthermore, in step three, the aerogel precursor is prepared by centrifugal spinning or electrospinning, while the ambient temperature is maintained at 20-30℃ and the ambient humidity is maintained at 20-40%.

[0013] Furthermore, in step three, the aerogel precursor is prepared by centrifugal spinning at a speed of 5000–12000 rpm.

[0014] Furthermore, in step three, the aerogel precursor is prepared by electrospinning, with the electrospinning voltage maintained at 15-25kV.

[0015] Furthermore, in step three, the fiber aerogel precursor prepared by centrifugal spinning or electrospinning is a three-dimensional layered structure, with a single layer being a dense fiber membrane and interlayer fibers overlapping and entangled with each other.

[0016] Furthermore, in step four, the equipment used for high-temperature crystallization of the aerogel precursor can be a tunnel furnace, a box furnace, or an atmosphere sintering furnace.

[0017] Furthermore, as described above, the yttrium-zirconium ceramic fiber aerogel exhibits a significant phenomenon of zirconium atom segregation and enrichment at the grain boundaries, which can effectively hinder the growth of ceramic grains at high temperatures. This is reflected in the fact that the zirconium element signal intensity within 5 nm on both sides of the grain boundary measured by energy dispersive spectroscopy (EDS) is 10-30% higher than that in the internal region of the grain.

[0018] Furthermore, as described above, the diameter of the yttrium-zirconium ceramic fiber aerogel is 1 μm to 4 μm.

[0019] Furthermore, as described above, the yttrium-zirconium ceramic fiber aerogel has an average near-infrared reflectance of over 95%.

[0020] Furthermore, as described above, the yttrium-zirconium ceramic fiber aerogel exhibits a volume shrinkage rate of no more than 5% in an environment with an environment of not less than 24 hours and a temperature of 1500°C.

[0021] Advantages and benefits of the present invention: The preparation method of the present invention is simple and efficient. The yttrium-zirconium ceramic fiber aerogel prepared has excellent high-temperature thermal stability, which significantly improves the upper limit of the service temperature of existing ceramic fiber aerogels. At the same time, it also has extremely low high-temperature thermal conductivity and ultra-high near-infrared reflectivity, which further improves the thermal insulation performance of the obtained aerogel and has broad application prospects. Attached Figure Description

[0022] Figure 1 This is a density measurement image of the yttrium-zirconium ceramic fiber aerogel in the example.

[0023] Figure 2 The images shown are solid representations and SEM images of the yttrium-zirconium ceramic fiber aerogel in the embodiments. (a) shows an aerogel block placed on a flower, (b) is an SEM image of the aerogel layered structure, and (c) is an SEM image of the fiber overlap and entanglement within a single layer of aerogel.

[0024] Figure 3 The images shown are high-resolution images and elemental distribution characterization diagrams of the grain boundaries of yttrium-zirconium ceramic fibers in the embodiments. Among them, (a) and (c) are high-resolution images and EDS elemental distribution diagrams of double and triple grain boundaries, respectively, and (b) and (d) are net intensity distribution data of yttrium and zirconium obtained by scanning the elemental distribution lines of double and triple grain boundaries, respectively.

[0025] Figure 4 The figures show the thermal conductivity, near-infrared reflectance, and thermal stability data of the yttrium-zirconium ceramic fiber aerogel in the examples. (a) shows the thermal conductivity data for 100-1000℃, and (b) shows the near-infrared reflectance data.

[0026] Figure 5 The diagram illustrates the thermal insulation performance of yttrium-zirconium ceramic fiber aerogel in the embodiment. (a) shows the front optical image and the back infrared optical image of the aerogel thermal insulation test, and (b) shows the temperature-time relationship curves of the front and back sides during the aerogel thermal insulation test. Detailed Implementation

[0027] The present invention will be further described below with reference to examples and accompanying drawings. The described embodiments are only some embodiments of the present invention, and all other embodiments obtained based on the present invention are within the protection scope of the present invention:

[0028] Example 1:

[0029] A high infrared reflectivity yttrium-zirconium ceramic fiber aerogel exhibiting grain boundary segregation is prepared by the following steps:

[0030] S1: Prepare polyacetylacetone yttrium-zirconium precursor powder by mixing yttrium and zirconium in a molar ratio of 6:1.

[0031] S2: The precursor powder, PVP and methanol are mixed and stirred at 60°C in a mass ratio of 15:1:30 until the solution is golden yellow, clear and transparent, and a spinning solution with a viscosity of 4 Pa·s is obtained.

[0032] S3: Add the spinning solution to a centrifugal spinning box with an outlet diameter of 0.3 mm, set the centrifugal spinning speed to 5000 rpm, and perform centrifugal spinning under the conditions of ambient temperature of 25℃ and ambient humidity of 20-40% to prepare a layered fiber aerogel precursor.

[0033] S4: High-temperature crystallization treatment of aerogel precursor is carried out using a box furnace: the temperature is increased to 900℃ at a rate of 3-5℃ / min, held for 2 hours, and then cooled to 25℃ at a rate of 3-5℃ / min to form a three-dimensional layered yttrium-zirconium oxide ceramic fiber aerogel.

[0034] Example 2:

[0035] A high infrared reflectivity yttrium-zirconium ceramic fiber aerogel exhibiting grain boundary segregation is prepared by the following steps:

[0036] S1: Prepare polyacetylacetone-yttrium-zirconium precursor powder by mixing yttrium and zirconium in a molar ratio of 10:1.

[0037] S2: The precursor powder, PVP and methanol are mixed and stirred at 60°C in a mass ratio of 10:1:20 until the solution is golden yellow, clear and transparent, and a spinning solution with a viscosity of 15 Pa·s is obtained.

[0038] S3: Add the spinning solution to a centrifugal spinning box with a fiber outlet diameter of 0.3 mm, set the centrifugal spinning speed to 12000 rpm, and perform centrifugal spinning under the conditions of ambient temperature of 25℃ and ambient humidity of 30-40% to prepare a precursor for forming layered fiber aerogel.

[0039] S4: High-temperature crystallization treatment of aerogel precursor is carried out using a box furnace: the temperature is increased to 900℃ at a rate of 3-5℃ / min, held for 2 hours, and then cooled to 25℃ at a rate of 3-5℃ / min to form a three-dimensional layered yttrium-zirconium oxide ceramic fiber aerogel.

[0040] Example 3:

[0041] A high infrared reflectivity yttrium-zirconium ceramic fiber aerogel exhibiting grain boundary segregation is prepared by the following steps:

[0042] S1: Prepare polyacetylacetone-yttrium-zirconium precursor powder by mixing yttrium and zirconium in a molar ratio of 2:1.

[0043] S2: The precursor powder, PVP and methanol are mixed and stirred at 60°C in a mass ratio of 30:1:40 until the solution is golden yellow, clear and transparent, and a spinning solution with a viscosity of 2 Pa·s is obtained.

[0044] S3: The spinning solution is pushed into an electrospinning needle with an inner diameter of 0.2 mm at a rate of 1.5 ml / h. The distance between the electrospinning needle and the collector is 0.6 m. The electrospinning voltage is set to 21 kV. Electrospinning is carried out under the conditions of ambient temperature of 25℃ and ambient humidity of 30-40% to prepare a precursor for forming layered fiber aerogel.

[0045] S4: High-temperature crystallization treatment of aerogel precursor is carried out using a box furnace: the temperature is increased to 900℃ at a rate of 3-5℃ / min, held for 2 hours, and then cooled to 25℃ at a rate of 3-5℃ / min to form a three-dimensional layered yttrium-zirconium oxide ceramic fiber aerogel.

[0046] Example 4:

[0047] like Figure 1-2 As shown, the yttrium-zirconium ceramic fiber aerogel prepared by centrifugal spinning combined with high-temperature annealing has an extremely low density (30–50 mg·cm³). -3 Aerogel blocks have a layered microstructure, with a single layer being a dense fibrous membrane, and interlayer fibers overlapping and entangled with each other. The diameter of a single fiber is 1μm to 4μm.

[0048] Example 5:

[0049] like Figure 3 As shown, the elemental distribution of yttrium-zirconium ceramic fiber aerogel prepared by centrifugal spinning combined with high-temperature annealing was characterized by energy dispersive spectroscopy (EDS). The results showed that the obtained yttrium-zirconium ceramic fiber aerogel exhibited obvious segregation and enrichment of zirconium atoms at the grain boundaries. Whether at double or triple grain boundaries, the zirconium element signal intensity within 5 nm on both sides of the grain boundary was about 20% higher than that in the grain interior region, demonstrating obvious atomic segregation and enrichment behavior.

[0050] Example 6:

[0051] like Figure 4-5 As shown, the thermal properties of yttrium-zirconium ceramic fiber aerogel prepared by centrifugal spinning combined with high-temperature annealing were characterized, and the results were: 50 mg·cm⁻¹ -3The thermal conductivity of yttrium-zirconium ceramic fiber aerogel at 1000℃ is only 89 mW·m. -1 ·K -1 The aerogel exhibits an average near-infrared reflectance exceeding 95%; its volume shrinkage does not exceed 5% in a long-term environment of 1500℃; and at a front temperature of approximately 1300℃, a 3cm thickness can reduce the back temperature to below 100℃. These properties demonstrate that the yttrium-zirconium ceramic fiber aerogel prepared through centrifugal spinning combined with high-temperature annealing possesses excellent extreme high-temperature thermal stability and outstanding thermal insulation capabilities.

Claims

1. A yttrium-zirconium ceramic fiber aerogel with high infrared reflectivity exhibiting grain boundary segregation, characterized in that, It was prepared according to the following steps: Step 1: Using polyyttrium acetylacetonate as the matrix, polyzirconium acetylacetonate is combined to prepare polyyttrium acetylacetonate-zirconium precursor powder; wherein, the yttrium:zirconium is mixed according to the molar ratio of yttrium:zirconium, and the ratio is yttrium:zirconium = 2:1 to 10:

1. Step 2: Dissolve the precursor powder in a polymer spinning aid solution to obtain a clear and transparent spinning solution; the mass ratio is precursor powder: polymer spinning aid: solvent = (10-30): 1: (20-40); Step 3: Prepare a layered fiber aerogel precursor by centrifugal spinning or electrospinning of the spinning solution; Step 4: The aerogel precursor is subjected to high-temperature crystallization treatment in air atmosphere. The steps are as follows: the temperature is increased to 900°C at a rate of 3-5°C / min, held for 2 hours, and then cooled to 25°C at a rate of 3-5°C / min to form a three-dimensional layered yttrium-zirconium ceramic fiber aerogel.

2. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: In step two, the average molecular weight of the polymeric spinning aid is 5,800 to 3,000,000; the polymeric spinning aid is one or more of polyvinylpyrrolidone, polyethylene oxide, polyethylene glycol, polyvinyl alcohol, and polyvinyl butyral in any proportion; the solvent is one or more of methanol, ethanol, glacial acetic acid, and deionized water in any proportion.

3. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: In step two, the temperature of the resulting spinning solution is 20–30°C, and the viscosity is 2–15 Pa·s.

4. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: In step three, aerogel precursors are prepared by centrifugal spinning or electrospinning, with the ambient temperature maintained at 20–30°C and the ambient humidity maintained at 20–40%. When preparing aerogel precursors by centrifugal spinning, the spinning speed is 5000–12000 rpm. When preparing aerogel precursors by electrospinning, the electrospinning voltage is maintained at 15–25 kV.

5. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: In step three, the fiber aerogel precursor prepared by centrifugal spinning or electrospinning is a three-dimensional layered structure, with a single layer being a dense fiber membrane and interlayer fibers overlapping and entangled with each other.

6. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: In step four, the equipment used for high-temperature crystallization of the aerogel precursor is a tunnel furnace, box furnace, or atmosphere sintering furnace.

7. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: The zirconium signal intensity within 5 nm on both sides of the grain boundary measured by energy dispersive spectroscopy is 10–30% higher than that in the grain interior region.

8. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: The fiber diameter is 1μm to 4μm.

9. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: It has an average near-infrared reflectance of over 95%.

10. The yttrium-zirconium ceramic fiber aerogel with grain boundary segregation as described in claim 1, characterized in that: In an environment of not less than 24 hours and a temperature of 1500℃, the volume shrinkage rate of the aerogel does not exceed 5%.

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