Preparation method of radiation-resistant lead-doped rare earth oxide composite aerogel

Abstract

The invention belongs to the technical field of aerogel preparation, and particularly relates to a preparation method of radiation-resistant lead-doped rare earth oxide composite aerogel, which comprises the following steps: dissolving rare earth nitrate or rare earth chlorine salt in a water-alcohol mixed liquid phase system with a certain volume ratio, fully stirring to form a homogeneous phase system, and drying to obtain the radiation-resistant lead-doped rare earth oxide composite aerogel. Then a certain amount of lead nitrate is added, the mass fraction of generally added lead is 0.01%-8%, rare earth is one or more of cerium, samarium, europium, erbium, lanthanum, yttrium and ytterbium, alcohol is one or more of methanol, ethanol and isopropanol, and the volume ratio of water is 10%-90%. According to the invention, pulverization and slag falling of the aerogel material can be effectively weakened through lead doping and silicon deposition, the stability of the composite material is effectively improved, the requirements of heat preservation and radiation shielding of a nuclear reactor loop system in the nuclear industry can be met, and effective support is provided for energy conservation, consumption reduction and safe and stable operation of a nuclear reactor in the nuclear industry.

Description

Technical Field

[0001] The invention belongs to the technical field of aerogel preparation, and in particular relates to a method for preparing a radiation-resistant lead-doped rare earth oxide composite aerogel. Background Art

[0002] The nuclear reactor loop system is in a high temperature, high radiation (neutron and gamma ray) environment during operation. In order to reduce the heat loss of thermal pipelines and promote energy conservation and consumption reduction, it is usually necessary to use thermal insulation materials on the outer surface of thermal pipelines and equipment for insulation measures. However, due to its special radiation environment, the insulation material should have good radiation resistance. In addition, extreme factors such as nuclear irradiation in nuclear reactors often greatly accelerate the corrosion and failure of nuclear industry equipment, so the insulation material also needs to have radiation shielding performance. The use of rare earth aerogel materials with a large thermal neutron absorption cross-section not only improves the thermal insulation performance of the insulation material, but also shields the radiation generated by the nuclear reaction, protecting the safe and stable operation of nuclear industry equipment and facilities.

[0003] Conventional non-metallic thermal insulation materials such as rock wool, expanded perlite, microporous calcium silicate, glass fiber, aluminum silicate, etc. in the nuclear industry will lose strength and become brittle after a certain dose of irradiation, forming powder or shrinking agglomerates, resulting in the formation of "empty shells" in some insulation layers, greatly reducing thermal insulation performance. Aerogel has the advantage of low thermal conductivity and the best thermal insulation effect among solid materials. Although conventional silicon-based, aluminum-based and zirconium-based aerogels have good thermal insulation performance, their radiation shielding effect is insufficient. Rare earth-based aerogels alone (CN110563435B, CN113526912B and CN112320809B) have thermal insulation and radiation resistance, but their mechanical strength is insufficient and they are easy to pulverize during high-temperature treatment. CN114907091B discloses a method for preparing a rare earth-silicon-based aerogel composite material with a surface coated with an anti-radiation coating, wherein the method comprises doping a soluble rare earth into a silica gel and impregnating a sparingly soluble rare earth salt on the surface of the gel under pressure. However, the sparingly soluble rare earth salt is not generated by an atomic or molecular reaction when impregnated on the surface of the aerogel, and has insufficient bonding force and is easy to pulverize. The present invention improves the mechanical strength of the aerogel by introducing doping elements and preparing a protective layer for the aerogel, thereby solving the problem of pulverization and slag falling caused by insufficient radiation resistance of the current material. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a radiation-resistant lead-doped rare earth oxide composite aerogel, which can solve the problem of pulverization and slagging caused by insufficient radiation resistance of current materials.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for preparing a radiation-resistant lead-doped rare earth oxide composite aerogel, the preparation method comprising the following steps:

[0007] Step 1. dissolving rare earth nitrate or rare earth chloride in a mixed liquid phase system of water and alcohol in a certain volume ratio, stirring sufficiently to form a homogeneous system, and then adding a certain amount of lead nitrate, and the mass fraction of the lead added is usually 0.01% to 8%, wherein the rare earth is one or more of cerium, samarium, europium, erbium, lanthanum, yttrium, and ytterbium, the alcohol is one or more of methanol, ethanol, and isopropanol, and the volume ratio of water is 10% to 90%;

[0008] Step 2. Maintaining the temperature below 25° C., quickly add the three-dimensional network inducer and the proton capture agent in step (1), stir evenly, let the mixture stand to form a rare earth oxide gel, and then age for 12 to 24 hours. The skeleton reinforcing agent is one or more of citric acid, polyacrylic acid, propylene oxide, ethylene oxide, formamide, and butylene oxide.

[0009] Step 3. Add an alcohol solution of an organic silicon salt, a zirconium salt, a titanium salt, or a soluble rare earth nitrate salt in step (2) to deposit silicon or zirconium on the surface of the wet gel in step (2) to protect the rare earth oxide. The deposition conditions are as follows: the device containing the gel is sealed and kept at a temperature of 40 to 70° C. in a forced air drying oven for 12 to 24 hours to finally obtain a protective layer with a thickness of 2 to 20 nm.

[0010] The alcohol selected is consistent with the alcohol used in step (1). For silicon salt, if methanol is used, methyl orthosilicate is used as the silicon source, and if ethanol is used, ethyl orthosilicate is used as the silicon source. For titanium salt, organic titanium salts such as tetrabutyl titanate or tetraisopropyl titanate are used. For zirconium salt, zirconyl acetate, zirconyl nitrate or zirconyl chloride is used.

[0011] Step 4. After step (3), the alcohol solvent is replaced, and the alcohol solvent is replaced every 24 hours. The solvent exchange is performed 3 to 5 times, wherein the type of alcohol used in the solvent exchange is the same as the alcohol used in (1);

[0012] Step 5. The gel of step (4) is dried by supercritical drying, wherein the supercritical drying method is CO2 supercritical drying or ethanol supercritical drying. The CO2 supercritical drying process is as follows: under the protection of CO2 supercritical fluid, the alcohol solvent in the three-dimensional network of the wet gel is replaced by CO2 to obtain an aerogel. The alcohol solvent is methanol, and the drying temperature is 40 to 50°C; the alcohol solvent is ethanol, and the drying temperature is 40 to 60°C; the alcohol solvent is isopropanol, and the drying temperature is 50 to 80°C, the autoclave pressure is controlled to be 8 to 15 MPa, and the drying time is 5 to 15 hours; the ethanol supercritical drying process is as follows: the drying temperature is 260 to 320°C, the autoclave pressure is controlled to be 8 to 12 MPa, and the reaction time is 5 to 15 hours;

[0013] Step 6. The aerogel dried in step (5) is heat treated in a nitrogen atmosphere, and the heat treatment conditions are: 0-200°C, heating rate 2°C / min, maintained for 2 hours; 200-500°C, heating rate 2°C / min, maintained for 2 hours;

[0014] Step 7. The tap density of the prepared aerogel composite material is 0.134 to 0.422 g / cm 3 According to the rare earth raw material in step (1) and the deposition material and time in step (3), the thermal conductivity at 500°C ranges from 0.022W / (m·K) to 0.047W / (m·K); the specific surface area of ​​the aerogel ranges from 200m 2 / g to 560m 2 / g.

[0015] The technical effects achieved by the present invention are:

[0016] The key to the present invention is that the doped metal forms a relatively stable skeleton structure in the rare earth oxide aerogel, thereby improving the internal structural stability of the rare earth oxide aerogel. At the same time, the doped lead material can also shield γ radiation;

[0017] The formed aerogel is then coated and protected by surface deposition, and the rare earth oxide-based aerogel is externally coated, which effectively enhances the internal and external skeleton structure strength of the rare earth oxide aerogel and reduces the powdering and slag of the aerogel under long-term strong irradiation;

[0018] The rare earth oxide-based composite aerogel material of the present invention not only has good radiation resistance and heat preservation properties, but also has good stability and long-term use performance in a strong radiation environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a schematic diagram of a process flow of preparing a lead-doped rare earth oxide composite aerogel according to a method for preparing a radiation-resistant lead-doped rare earth oxide composite aerogel. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0021] Example 1

[0022] (1) Dissolve 17.37 g of cerium nitrate hexahydrate and 4.33 g of lanthanum nitrate hexahydrate in a mixture of 8 mL of water and 72 mL of ethanol in a certain volume ratio, stir thoroughly to make them completely dissolved, and then add a certain amount of 1.66 g of lead nitrate.

[0023] (2) Maintaining the temperature below 25°C, quickly add 3.84g of anhydrous citric acid in step (1) and stir for 30 minutes. While maintaining the solution temperature below 25°C, add 30mL of propylene oxide. After rapid stirring for 2 minutes, transfer to a mold. Fully soak the glass fiber felt, then seal it with a plastic bag and wait for it to gel. After gelling, age it at room temperature and seal it for 12 hours.

[0024] (3) A mixture of 20 mL of ethanol and 20 mL of ethyl orthosilicate was added to the mixture in step (2) and silicon deposition was performed for 24 hours (35° C.).

[0025] (4) After step (3), the ethanol solvent was replaced, and the alcohol solvent was replaced every 24 hours. The solvent exchange was performed 5 times.

[0026] (5) Drying the gel of step (4) by supercritical drying. The supercritical drying method is CO2 supercritical drying, and the process is: the drying temperature is 40°C, and the pressure of the autoclave is controlled at 15MPa;

[0027] (6) The aerogel dried in step (5) is subjected to heat treatment in a nitrogen atmosphere. Heat treatment conditions: 0-200°C, heating rate 2°C / min, maintained for 2 hours; 200-500°C, heating rate 2°C / min, maintained for 2 hours.

[0028] Example 2

[0029] In step (1) of Example 1, lead nitrate was not added, and the other steps remained the same.

[0030] Example 3

[0031] In step (1) of Example 1, the addition of 20 mL of tetraethyl orthosilicate was replaced by the addition of 20 mL of ethanol, and the other steps remained the same.

[0032] The aerogel materials prepared in Example 1, Example 2 and Example 3 were 60 Coγ source was used for irradiation, with a total radiation dose of 50 kGy and a dose rate of 300 Gy / h. In practice, the shielding effect of each material against γ rays can reach more than 90%. The results of each example material before and after irradiation are summarized as follows:

[0033]

[0034] The results show that lead-doped rare earth oxide composite aerogel has good anti-γ radiation shielding performance. Lead doping and silicon deposition can effectively reduce the powdering and slagging of aerogel materials, effectively improve the stability of composite materials, meet the needs of thermal insulation and radiation shielding of nuclear reactor loop systems in the nuclear industry, and provide effective support for energy saving and consumption reduction and safe and stable operation of nuclear industry reactors.

[0035] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for preparing radiation-resistant lead-doped rare earth oxide composite aerogel, characterized in that: The preparation method comprises the following steps: Step 1. dissolving rare earth nitrate or rare earth chloride in a mixed liquid phase system of water and alcohol in a certain volume ratio, stirring sufficiently to form a homogeneous system, and then adding a certain amount of lead nitrate, and the mass fraction of the lead added is usually 0.01% to 8%, wherein the rare earth is one or more of cerium, samarium, europium, erbium, lanthanum, yttrium, and ytterbium, the alcohol is one or more of methanol, ethanol, and isopropanol, and the volume ratio of water is 10% to 90%; Step 2. Maintaining the temperature below 25° C., quickly add the three-dimensional network inducer and the proton capture agent in step (1), stir evenly, let the mixture stand to form a rare earth oxide gel, and then age for 12 to 24 hours. The skeleton reinforcing agent is one or more of citric acid, polyacrylic acid, propylene oxide, ethylene oxide, formamide, and butylene oxide. Step 3. Add an alcohol solution of an organic silicon salt, a zirconium salt, a titanium salt, or a soluble rare earth nitrate salt in step (2) to deposit silicon or zirconium on the surface of the wet gel in step (2) to protect the rare earth oxide. The deposition conditions are as follows: the device containing the gel is sealed and kept at a temperature of 40 to 70° C. in a forced air drying oven for 12 to 24 hours to finally obtain a protective layer with a thickness of 2 to 20 nm. The alcohol selected is consistent with the alcohol used in step (1). For silicon salt, if methanol is used, methyl orthosilicate is used as the silicon source, and if ethanol is used, ethyl orthosilicate is used as the silicon source. For titanium salt, organic titanium salts such as tetrabutyl titanate or tetraisopropyl titanate are used. For zirconium salt, zirconyl acetate, zirconyl nitrate or zirconyl chloride is used. Step 4. After step (3), the alcohol solvent is replaced, and the alcohol solvent is replaced every 24 hours. The solvent exchange is performed 3 to 5 times, wherein the type of alcohol used in the solvent exchange is the same as the alcohol used in (1); Step 5. The gel of step (4) is dried by supercritical drying, wherein the supercritical drying method is CO2 supercritical drying or ethanol supercritical drying. The CO2 supercritical drying process is as follows: under the protection of CO2 supercritical fluid, the alcohol solvent in the three-dimensional network of the wet gel is replaced by CO2 to obtain an aerogel. The alcohol solvent is methanol, and the drying temperature is 40 to 50°C; the alcohol solvent is ethanol, and the drying temperature is 40 to 60°C; the alcohol solvent is isopropanol, and the drying temperature is 50 to 80°C, the autoclave pressure is controlled to be 8 to 15 MPa, and the drying time is 5 to 15 hours; the ethanol supercritical drying process is as follows: the drying temperature is 260 to 320°C, the autoclave pressure is controlled to be 8 to 12 MPa, and the reaction time is 5 to 15 hours; Step 6. The aerogel dried in step (5) is heat treated in a nitrogen atmosphere, and the heat treatment conditions are: 0-200°C, heating rate 2°C / min, maintained for 2 hours; 200-500°C, heating rate 2°C / min, maintained for 2 hours; Step 7. The tap density of the prepared aerogel composite material is 0.134 to 0.422 g / cm 3 According to the rare earth raw material in step (1) and the deposition material and time in step (3), the thermal conductivity at 500°C ranges from 0.022W / (m·K) to 0.047W / (m·K); the specific surface area of ​​the aerogel ranges from 200m 2 / g to 560m 2 / g.

Images