CN116751072B - Intermediate entropy oxide nanofiber aerogel for nuclear power pipeline and preparation method thereof - Google Patents

Abstract

The invention discloses a medium entropy oxide nanofiber aerogel for nuclear power pipelines and a preparation method thereof. The composition is (Si _x Ti _1‑x‑8y Zr _7y Gd _y )O _2‑0.5y , and the fiber channels are arranged in a unidirectional layered structure. Tetraethyl orthosilicate, n-butyl titanate, zirconium oxynitrate, and gadolinium nitrate are used as precursors of silicon, titanium, zirconium, and gadolinium, respectively, and medium entropy oxide nanofibers are prepared by electrostatic spinning, homogenization, and freeze drying. Under the synergistic effect of medium entropy effect, lattice distortion, and hysteresis diffusion, the fiber obtains excellent mechanical properties, and excellent infrared shading effect, high temperature resistance, and neutron shielding performance are obtained by regulating Ti, Zr, and Gd components, so that the medium entropy oxide nanofiber aerogel realizes high temperature resistance, radiation resistance, sound insulation and noise reduction, and thermal insulation performance integration, meeting the thermal insulation and noise reduction requirements of nuclear power pipelines.

Description

Medium entropy oxide nanofiber aerogel for nuclear power pipeline and preparation method thereof

Technical Field

The invention belongs to the field of aerogel preparation, and particularly relates to a medium entropy oxide nanofiber aerogel for nuclear power pipelines and a preparation method thereof.

Background Art

Correctly selecting insulation materials for high-temperature nuclear power pipelines can not only improve the thermal economy of nuclear power but also reduce the investment cost of building sodium-cooled fast reactors, which has a great driving effect on the development of nuclear energy.

During the operation of fast reactors, nuclear power pipelines are often in a high temperature (100-600℃) and partial nuclear irradiation (a small amount of γ irradiation and neutron irradiation) environment. The fast and complex liquid flow in the pipeline will also produce a lot of noise, which is extremely harmful to the health of workers. Therefore, the thermal insulation materials of nuclear power pipelines are required to be resistant to high temperature, resistant to radiation, thermal insulation, sound insulation and noise reduction.

Common pipeline insulation materials (glass wool, asbestos, silica aerogel felt, etc.) have defects such as insufficient high temperature resistance, high high temperature thermal conductivity, poor radiation resistance, and poor low-frequency sound insulation performance, which are difficult to meet the actual application needs of nuclear power pipelines. Therefore, the development of nuclear power pipeline insulation materials with excellent thermal insulation effect, sound insulation and noise reduction performance, high thermal stability, and radiation resistance is of great significance to promote the development of nuclear energy.

The Chinese invention patent with application number CN202211373904.X discloses a thermal insulation, sound-absorbing silica aerogel composite material and its preparation method, which is composed of a silica aerogel felt and a fireproof slurry layer coated on the surface of the aerogel felt. The advantages of this invention are that the interior of the fiber felt is fully filled with silica aerogel to ensure the thermal insulation performance of the composite material, and the aerogel fireproof slurry is coated and used in combination with glass fiber mesh cloth to effectively improve the thermal insulation performance and mechanical strength of the aerogel felt composite material. However, it also has defects such as complex manufacturing process, poor low-frequency sound insulation performance, and poor radiation resistance.

The Chinese invention patent with application number CN201810540419.4 discloses a method for preparing a highly efficient thermal insulation aerogel felt, which is prepared by impregnating a silica sol mixed with zinc oxide nanoparticles and titanium dioxide nanoparticles with a fiber felt. The invention has the advantage of improving the mechanical strength of the aerogel felt while having a strong thermal insulation effect, but it has the disadvantages of insufficient radiation resistance and uneven distribution of nanoparticles, which affects the overall performance of the aerogel.

Summary of the invention

The purpose of the present invention is to provide a medium entropy oxide nanofiber aerogel for nuclear power pipelines and a preparation method thereof.

A medium-entropy oxide nanofiber aerogel for nuclear power pipelines, characterized in that the medium-entropy oxide nanofiber aerogel composition is (Si _x Ti _1-x-8y Zr _7y Gd _y )O _2-0.5y , wherein 0.2≤x≤0.78, 0.01≤y≤0.1, 0.69R≤mixing entropy＝-R[xlnx+(1-x-8y)ln(1-x-8y)+7yln(7y)+ylny]≤1.60R; the average diameter of the nanofibers is 60-80nm, the average thickness of the single-layer fiber membrane is 120-150μm, the average aspect ratio is 800-1600, the porosity is 75-99%, and the density is 25-60kg/m ³ .

A medium entropy oxide nanofiber aerogel for nuclear power pipelines and a preparation method thereof, characterized in that the preparation method comprises the following sequential steps:

(1) using tetraethyl orthosilicate as a precursor of silicon, n-butyl titanate as a precursor of titanium, zirconyl nitrate as a precursor of zirconium, and gadolinium nitrate as a precursor of gadolinium, and uniformly mixing the precursors with an acid catalyst, deionized water, and ethanol to prepare an aerogel precursor solution, wherein the acid catalyst is one or more of hydrochloric acid, phosphoric acid, nitric acid, and acetic acid, and the molar ratio of tetraethyl orthosilicate, n-butyl titanate, zirconyl nitrate, gadolinium nitrate, acid catalyst, deionized water, and ethanol is x:(1-x-8y):7y:y:(0.002-0.02)x:(1-5)x:(1-20)x;

(2) mixing the aerogel precursor solution prepared in step (1) with the polyvinyl alcohol solution in a mass ratio of 1: (0.5-1), and stirring for 4-6 hours to obtain a polyvinyl alcohol system spinning solution;

(3) spinning the spinning solution of step (2) by electrospinning technology, removing the precursor nanofiber after spinning, wherein the spinning temperature is 20-25°C, the humidity is 20%-60%, the perfusion speed is 0.1-10mL/h, the voltage is 8-35kV, and the distance between the receiving device and the spinneret is 10-30cm; obtaining a medium entropy oxide nanofiber membrane by high temperature heat treatment, wherein the heat treatment temperature is 600-800°C and the heat preservation time is 2-4h;

(4) preparing SiO ₂ sol by a molar ratio of tetraethyl orthosilicate, water, ethanol and phosphoric acid of 1:(4-10):(8-15):(0.01-0.1);

(5) dissolving polyacrylamide powder in water to prepare a polyacrylamide solution with a mass fraction of 0.01 to 0.05 wt%, then cutting 0.1 to 0.5 g of the medium entropy oxide nanofiber membrane into small pieces and soaking them in 100 to 200 g of the polyacrylamide solution, and adding the _SiO2 sol prepared in step (4) at the same time, dispersing the above mixed fiber solution by a high-pressure homogenizer to obtain a sol-mixed dispersion;

(6) placing the medium entropy nanofiber membrane dispersed colloidal solution into a liquid nitrogen bath for freezing, causing ice crystals in the solution to rapidly nucleate and grow, converting the solution from a liquid state to a solid state, and obtaining a frozen block after the solvent in the dispersion is completely solidified, and then placing the frozen block in a freeze dryer, and controlling the temperature and vacuum degree to allow the solvent to directly sublimate from a solid state to a gaseous state to remove the solvent ice crystals without destroying the pore structure of the material, thereby obtaining a fiber aerogel, wherein the freezing temperature is -60 to -40°C, and the vacuum degree is 0.005 to 0.01Pa;

(7) Placing the fiber aerogel in a high temperature furnace for high temperature calcination to obtain a medium entropy oxide nanofiber aerogel material, wherein the heat treatment temperature is 600-800°C and the insulation time is 2-4 hours.

Beneficial Effects

Compared with existing materials and technologies, the present invention has the following beneficial effects: (1) multi-component nanofiber aerogel has a significant mesentropy effect, and a higher configurational entropy is beneficial to stabilizing the fiber structure and improving the fiber mechanical properties; (2) under the synergistic effect of the mesentropy oxide lattice distortion and the hysteresis diffusion effect, grain growth is inhibited, thermal radiation reflection is improved, and high-temperature thermal conductivity is reduced; (3) by regulating the Ti, Zr and Gd components, the high temperature resistance, thermal stability and radiation resistance of the nanofiber aerogel are significantly improved; (4) the freeze-drying process can effectively avoid the destruction of the gel pore structure caused by the existence of the gas-liquid interface surface tension during the drying process, maintain the nanoporous structure of the aerogel, inhibit gas thermal convection, and significantly improve the thermal insulation performance.

DETAILED DESCRIPTION

The present invention is further described below by way of examples, but these examples shall not be used to limit the scope of protection of the present invention.

Example 1

A method for preparing medium entropy oxide nanofiber aerogel for nuclear power pipelines comprises the following steps in sequence:

(1) uniformly mixing tetraethyl orthosilicate, n-butyl titanate, zirconyl nitrate, gadolinium nitrate, hydrochloric acid, deionized water and ethanol to obtain a precursor solution, wherein the molar ratio of tetraethyl orthosilicate, n-butyl titanate, zirconyl nitrate, gadolinium nitrate, hydrochloric acid, deionized water and ethanol is 1:0.5:0.875:0.125:0.02:2:5;

(2) mixing the aerogel precursor solution prepared in step (1) with the polyvinyl alcohol solution in a mass ratio of 1:1, and stirring for 6 hours to obtain a polyvinyl alcohol system spinning solution;

(3) using electrospinning technology to spin the spinning solution of step (2), and removing the precursor nanofiber after spinning, wherein the spinning temperature is 25°C, the humidity is 40%, the perfusion rate is 0.7 mL/h, the voltage is 15 kV, and the distance between the receiving device and the spinneret is 20 cm, and a medium entropy oxide nanofiber membrane is obtained by high-temperature heat treatment, wherein the heat treatment temperature is 800°C and the insulation time is 2 h;

(4) preparing _SiO2 sol with tetraethyl orthosilicate, water, ethanol and phosphoric acid, wherein the ratio of tetraethyl orthosilicate: water: ethanol: phosphoric acid is 1: 4: 8: 0.02;

(5) Dissolve the polyacrylamide powder in water to prepare a polyacrylamide solution with a mass fraction of 0.01 wt%. Then cut 0.3 g of the medium entropy oxide nanofiber membrane into small pieces and soak them in 100 g of the polyacrylamide solution, and add the SiO ₂ sol prepared in step (4) at the same time, and disperse the fiber dispersion liquid by a high-pressure homogenizer to obtain a sol-mixed dispersion liquid;

(6) placing the medium entropy nanofiber membrane dispersed colloidal solution into a liquid nitrogen bath for freezing, causing ice crystals in the solution to rapidly nucleate and grow, converting the solution from a liquid state to a solid state, and obtaining a frozen block after the solvent in the dispersion is completely solidified. The frozen block is then placed in a freeze dryer, and the solvent is directly sublimated from a solid state to a gas state by controlling the temperature and vacuum degree to remove the solvent ice crystals without destroying the pore structure of the material, thereby obtaining a fiber aerogel, wherein the freezing temperature is -50°C and the vacuum degree is 0.005Pa;

(7) The fiber aerogel is placed in a high-temperature furnace for high-temperature calcination to obtain a medium-entropy oxide nanofiber aerogel material, wherein the heat treatment temperature is 800°C and the insulation time is 2h.

The molecular formula of the nanofiber aerogel prepared in this embodiment is (Si _0.4 Ti _0.2 Zr _0.35 Gd _0.05 )O _1.975 , the mixing entropy is 1.21R, the thermal conductivity at 800° C. is (0.0316±0.002) W/(m·K), and compared with pure SiO ₂ aerogel, the radiation resistance of the aerogel composite material is improved by 25%.

Example 2

A method for preparing medium entropy oxide nanofiber aerogel for nuclear power pipelines comprises the following steps in sequence:

(1) uniformly mixing tetraethyl orthosilicate, n-butyl titanate, zirconyl nitrate, gadolinium nitrate, hydrochloric acid, deionized water and ethanol to obtain a precursor solution, wherein the molar ratio of tetraethyl orthosilicate, n-butyl titanate, zirconyl nitrate, gadolinium nitrate, hydrochloric acid, deionized water and ethanol is 1:0.7:0.7:0.1:0.02:2:6;

(2) mixing the aerogel precursor solution prepared in step (1) with the polyvinyl alcohol solution in a mass ratio of 1:1, and stirring for 6 hours to obtain a polyvinyl alcohol system spinning solution;

(3) using electrospinning technology to spin the spinning solution of step (2), and removing the precursor nanofiber after spinning, wherein the spinning temperature is 25°C, the humidity is 40%, the perfusion rate is 0.7 mL/h, the voltage is 15 kV, and the distance between the receiving device and the spinneret is 20 cm, and a medium entropy oxide nanofiber membrane is obtained by high-temperature heat treatment, wherein the heat treatment temperature is 800°C and the insulation time is 2 h;

(4) preparing _SiO2 sol with tetraethyl orthosilicate, water, ethanol and phosphoric acid, wherein the ratio of tetraethyl orthosilicate: water: ethanol: phosphoric acid is 1: 4: 8: 0.02;

(5) Dissolve the polyacrylamide powder in water to prepare a polyacrylamide solution with a mass fraction of 0.01 wt%. Then cut 0.3 g of the medium entropy oxide nanofiber membrane into small pieces and soak them in 100 g of the polyacrylamide solution, and add the SiO ₂ sol prepared in step (4) at the same time, and disperse the fiber dispersion liquid by a high-pressure homogenizer to obtain a sol-mixed dispersion liquid;

(6) placing the medium entropy nanofiber membrane dispersed colloidal solution into a liquid nitrogen bath for freezing, causing ice crystals in the solution to rapidly nucleate and grow, converting the solution from a liquid state to a solid state, and obtaining a frozen block after the solvent in the dispersion is completely solidified. The frozen block is then placed in a freeze dryer, and the solvent is directly sublimated from a solid state to a gas state by controlling the temperature and vacuum degree to remove the solvent ice crystals without destroying the pore structure of the material, thereby obtaining a fiber aerogel, wherein the freezing temperature is -50°C and the vacuum degree is 0.005Pa;

(7) The fiber aerogel is placed in a high-temperature furnace for high-temperature calcination to obtain a medium-entropy oxide nanofiber aerogel material, wherein the heat treatment temperature is 800°C and the insulation time is 2h.

The molecular formula of the nanofiber aerogel prepared in this embodiment is (Si _0.4 Ti _0.28 Zr _0.28 Gd _0.04 )O _1.98 , the mixing entropy is 1.21R, the thermal conductivity at 600° C. is (0.0348±0.002) W/(m·K), and compared with pure SiO ₂ aerogel, the radiation resistance of the aerogel composite material is improved by 28%.

Finally, it should be noted that the above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an act that infringes the scope of protection of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments in any form based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims (2)

1. The medium entropy oxide nanofiber aerogel for the nuclear power pipeline is characterized by comprising the component (Si _xTi_1-x-8yZr_7yGd_y)O_2-0.5y), wherein x is more than or equal to 0.2 and less than or equal to 0.78,0.01 and less than or equal to 0.1,0.69R, mixed entropy is more than or equal to 20 and less than or equal to-R xlnx + (1-x-8 y) ln (1-x-8 y) +7yln (7 y) + ylny ] < 1.60R, the average diameter of the nanofiber aerogel is 60-80 nm, the average length-diameter ratio is 800-1600, the porosity is 75-99%, and the density is 25-60 kg/m ³.

2. The method for preparing the medium entropy oxide nanofiber aerogel for the nuclear power pipeline according to claim 1, which is characterized by comprising the following sequential steps:

(1) Tetraethyl orthosilicate is used as a silicon precursor, n-butyl titanate is used as a titanium precursor, zirconyl nitrate is used as a zirconium precursor, gadolinium nitrate is used as a gadolinium precursor solution, the precursor, an acid catalyst, deionized water and ethanol are uniformly mixed to prepare an aerogel precursor solution, wherein the acid catalyst is one or more of hydrochloric acid, phosphoric acid, nitric acid and acetic acid, and the molar ratio of the tetraethyl orthosilicate, the n-butyl titanate, the zirconyl nitrate, the gadolinium nitrate, the acid catalyst, the deionized water and the ethanol is x: (1-x-8 y): 7y: y: (0.002-0.02) x: (1-5) x: (1-20) x;

(2) Mixing the aerogel precursor solution prepared in the step (1) with a polyvinyl alcohol solution according to the following steps of 1: mixing the components according to the mass ratio of (0.5-1), and stirring for 4-6 hours to obtain a polyvinyl alcohol system spinning solution;

(3) Spinning the spinning solution in the step (2) by adopting an electrostatic spinning technology, and taking down precursor nanofiber after spinning, wherein the spinning temperature is 20-25 ℃, the humidity is 20-60%, the filling speed is 0.1-10 mL/h, the voltage is 8-35 kV, the distance between a receiving device and a spinning nozzle is 10-30 cm, and the intermediate entropy oxide nanofiber membrane is obtained through high-temperature heat treatment, the heat treatment temperature is 600-800 ℃, and the heat preservation time is 2-4 h;

(4) Tetraethyl orthosilicate, water, ethanol and phosphoric acid were formulated as a SiO ₂ sol, wherein tetraethyl orthosilicate: water: ethanol: phosphoric acid = 1: (4-10): (8-15): (0.01-0.1);

(5) Dissolving polyacrylamide powder in water to prepare a polyacrylamide solution with the mass fraction of 0.01-0.05 wt%, cutting 0.1-0.5 g of medium entropy oxide nanofiber membrane into small pieces, soaking the small pieces in 100-200 g of polyacrylamide solution, adding the SiO2 sol prepared in the step (4), and dispersing the solution by a high-pressure homogenizer to obtain a sol mixed dispersion;

(6) Putting the dispersion liquid mixed by the sol obtained in the step (5) into a liquid nitrogen bath for freezing, quickly nucleating and growing ice crystals in the solution, converting the solution into a solid state from the liquid state, obtaining frozen blocks after the solvent in the dispersion liquid is completely solidified, then putting the frozen blocks into a freeze dryer, and directly sublimating the solvent from the solid state into a gaseous state by controlling the temperature and the vacuum degree to remove the solvent ice crystals without damaging the pore structure of the material, thereby obtaining the fiber aerogel, wherein the freezing temperature is-60 to-40 ℃ and the vacuum degree is 0.005-0.01 Pa;

(7) And (3) placing the fiber aerogel in a high-temperature furnace for high-temperature calcination to obtain the medium-entropy oxide nanofiber aerogel material, wherein the heat treatment temperature is 600-800 ℃, and the heat preservation time is 2-4 hours.