Radioactive composite film carrier for isotope battery and preparation method thereof

Abstract

The invention provides a radioactive composite film for an isotope battery, the radioactive composite film comprises a radioactive source film layer, the radioactive source film layer comprises a polymer film-forming material and a radioactive substance, the radioactive substance is selected from strontium nitrate, strontium chloride or a mixture of the two; and the radiation-resistant polymer coating is positioned on one side of the radioactive source film layer and covers the radioactive source film layer. According to the radioactive composite film body, the high polymer material is adopted as a carrier of radioactive substances, the self-absorption effect of the radioactive substances can be effectively reduced, and the utilization rate of the radioactive substances is increased.

Description

Technical Field

[0001] The present application relates to the technical field of thin-film radioactive source preparation technology, and in particular to a radioactive composite thin-film carrier for isotope batteries and a preparation method thereof. Background Art

[0002] Micro-electromechanical systems (MEMS) are small mechanical and electromechanical components manufactured using microelectronics processing technology. They have been widely used in military and civilian fields due to their small size, high precision, low energy consumption, good stability, and easy integration. With the development of MEMS technology, MEMS devices have put forward higher requirements for energy supply, such as easy miniaturization, high energy density, high stability, and strong environmental adaptability. However, traditional solar cells, chemical fuel cells, and lithium-ion batteries cannot meet these requirements well.

[0003] An isotope battery is a device that converts isotope decay energy into electrical energy. It has unique advantages such as long life, high energy density, stable and reliable performance, good environmental tolerance, easy integration and miniaturization. It is suitable for power supply under extreme environmental conditions and is an ideal energy supply solution for micro devices such as MEMS. In order to improve the stability and reliability of isotope batteries and effectively utilize the decay energy of radioactive isotopes, the radioactive isotopes need to be in close contact with the substrate non-metallic functional materials, and the self-absorption effect of the carrier material on the decay particles needs to be reduced. Constructing a thin-film radioactive source is a relatively effective strategy. At present, the main methods for preparing thin-film radioactive sources include ceramic / enamel method, powder metallurgy method, electroplating method, deposition method and the like.

[0004] The widely used ceramic method mainly uses titanium oxide and silicon dioxide as the matrix material. The radioactive source solution is dripped onto the matrix material and sintered at high temperature to form a ceramic body or glass. This preparation method requires high-temperature sintering, and the operations and process involved are complicated. The radioactive sources prepared by the powder metallurgy method are generally millimeter-level, and use metals with high atomic numbers such as gold and silver as carriers. The radioactive sources are severely absorbed and have low utilization rates. The electroplating method and the deposition method are respectively limited by factors such as delicate operating conditions, nuclide loading efficiency, and nuclide distribution uniformity. The resulting thin-film radioactive sources cannot meet the application requirements of isotope batteries.

[0005] Therefore, a new thin-film radiation source and a new process for preparing the same are needed to solve at least one of the above problems. Summary of the invention

[0006] In view of this, the main purpose of the present application is to provide a radioactive composite thin film carrier for isotope batteries and a preparation method thereof. The radioactive composite thin film carrier of the present application has a small self-absorption effect of radioactive substances, a high utilization rate of radioactive substances, a uniform distribution of radioactive substances, high stability and high adhesion to the substrate, and a simple preparation method with low energy consumption.

[0007] To this end, the present application provides a radioactive composite film for an isotope battery, the radioactive composite film comprising:

[0008] A radiation source film layer, the radiation source film layer comprising a polymer film-forming material and a radioactive substance, wherein the radioactive substance is selected from strontium nitrate, strontium chloride or a mixture of the two; and

[0009] The radiation-resistant polymer coating is located on one side of the radiation source film layer and covers the radiation source film layer.

[0010] In some embodiments, the polymer film-forming material is polyethylene oxide, polyvinyl alcohol, or a mixture of the two;

[0011] The radiation-resistant polymer coating comprises a radiation-resistant polymer material, and the radiation-resistant polymer material is selected from polymethyl methacrylate, polyethyl methacrylate or a mixture of the two.

[0012] In some embodiments, the radioactive composite film has a thickness of 10-500 μm and an area of ​​1-100 cm 2 .

[0013] The present application also provides a method for preparing a radioactive composite film for an isotope battery, comprising the following steps:

[0014] S1, preparing a radioactive source film-forming solution, wherein the radioactive source film-forming solution comprises an aqueous solution of a polymer film-forming material and a radioactive substance, wherein the radioactive substance is selected from strontium nitrate, strontium chloride or a mixture of the two;

[0015] S2, dropping the radioactive source film-forming liquid onto the center of the plane of the substrate, shaking to spread the radioactive source film-forming liquid, and drying to form a radioactive source film layer;

[0016] S3, adding the radiation-resistant polymer coating film-forming liquid dropwise to the above-mentioned radiation source film layer, shaking to spread the radiation-resistant polymer coating film-forming liquid, and drying to form the radiation-resistant polymer coating.

[0017] In some embodiments, step S1 comprises:

[0018] Prepare a polymer film-forming material solution: heat and dissolve the polymer film-forming material in ultrapure water at 60-90° C., wherein the polymer film-forming material is polyethylene oxide, polyvinyl alcohol or a mixture of the two.

[0019] Prepare the radioactive substance solution: dissolve the radioactive substance in ultrapure water, and

[0020] Prepare the radioactive source film-forming solution: mix the above-mentioned polymer film-forming material solution and the radioactive substance solution.

[0021] In some embodiments, the polymer film-forming material solution comprises 5 to 10 parts by weight of the polymer film-forming material and 100 to 200 parts by weight of the ultrapure water; and / or

[0022] The concentration of the radioactive substance solution is 1-500 g / L.

[0023] In some embodiments, the volume ratio of the radioactive substance solution to the polymer film-forming material solution is 1:5-3:5.

[0024] In some embodiments, in step S2, the amount of the radioactive source film-forming liquid added is 50 to 1000 μL / cm 2 .

[0025] In some embodiments, the drying comprises heating at 90-150° C. or irradiating with an infrared lamp to evaporate the solvent, and then naturally cooling and drying at room temperature.

[0026] In some embodiments, the radiation-resistant polymer coating film-forming liquid comprises a radiation-resistant polymer material and a solvent, and the radiation-resistant polymer material is selected from polymethyl methacrylate, polyethyl methacrylate or a mixture thereof; and / or

[0027] The solvent is selected from dichloromethane, chloroform or a mixture of the two solvents.

[0028] In some embodiments, the concentration of the radiation-resistant polymer coating film-forming liquid is 5 to 30 g / L.

[0029] In some embodiments, the dropwise addition volume of the radiation-resistant polymer coating film-forming liquid is 0.5 to 1.0 mL.

[0030] In some embodiments, the substrate is one of quartz glass, high borosilicate glass, transparent alumina ceramics, and transparent yttrium aluminum garnet ceramics.

[0031] In some embodiments, the flat surface of the substrate is a smooth mirror surface or a concave surface.

[0032] The radioactive composite thin film carrier of the present application uses polymer materials as carriers of radioactive substances, which can effectively reduce the self-absorption effect of radioactive substances and improve the utilization rate of radioactive substances. The polymer film-forming material with rich oxygen-containing groups used in the present application is conducive to the uniform and stable dispersion of radioactive substances in the polymer material, and the polymer film-forming material has good viscosity properties to the substrate. In addition, the radioactive composite thin film carrier of the present application also includes a layer of radiation-resistant polymer coating, which is conducive to reducing the impact of high-temperature irradiation and improving the stability and safety of radioactive substances. The method of the present application does not require high-temperature calcination. During the preparation process, the film-forming solution can spread by itself, the process flow is simple, and the operability is strong. And the soluble preparation of the radioactive composite thin film carrier can be achieved by adjusting the concentration, ratio and other conditions of the radioactive substance solution and the polymer film-forming material solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a scanning electron microscope image of the radioactive composite thin film carrier prepared in Example 1 of the present application and its element distribution map.

[0034] Figure 2 This is a comparison chart of the states of the radioactive composite thin film carrier prepared in Example 1 of the present application before and after irradiation by a linear electron accelerator. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other in the absence of conflict. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0036] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs. In the event of a conflict, this specification takes precedence.

[0037] It should be noted that in the embodiments of the present application, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a method or device including a series of elements includes not only the elements explicitly recorded, but also other elements not explicitly listed, or also includes elements inherent to the implementation of the method or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the presence of other related elements in the method or device including the element.

[0038] Among many energy-type radioactive isotopes, strontium-90 has good economic efficiency (its raw materials can be produced from spent fuel, easy to mass-produce, and can be equipped in large quantities), long life (half-life of up to 28.9 years, stable and efficient energy supply, and service life of up to 5-10 years), high energy density (strontium nitrate has a specific power of up to 6700μW / Ci), and has become the preferred raw material for the radioactive source of micro-isotope batteries. In order to improve the stability and reliability of isotope batteries and effectively utilize the decay energy of strontium-90, the radioactive isotope needs to be in close contact with the substrate non-metallic functional material, and reduce the self-absorption effect of the carrier material on the decay particles.

[0039] Constructing a thin-film radioactive source is an effective strategy. The applicant has found through literature research that polymer materials have good film-forming properties and can form micrometer or even nanometer sizes, making them a good carrier. Among them, the main body of the peelable film used for radioactive pollution purification is polymer material, which proves that polymer film materials have good adsorption and bonding effects on radioactive isotopes.

[0040] In view of this, the present application provides a radioactive composite film for isotope batteries, the radioactive composite film radiation source film layer, the radiation source film layer includes a polymer film-forming material and a radioactive substance, wherein the radioactive substance is selected from strontium nitrate, strontium chloride or a mixture of the two; and a radiation-resistant polymer coating, the radiation-resistant polymer coating is located on one side of the radiation source film layer and covers the radiation source film layer.

[0041] In the present application, the radioactive composite film includes a radioactive source film layer and a radiation-resistant polymer coating. The radioactive source film layer includes a polymer film-forming material and a radioactive substance. The polymer film-forming material has good film-forming properties, can form a micron or even nanometer size, and can be suitable for use in micro-electromechanical systems. On the one hand, compared with the traditional process of using titanium dioxide, metal gold-silver, etc. as a carrier, the use of polymer film-forming materials as carriers of radioactive substances can reduce the problem of radiation source absorption; on the other hand, the radioactive material elements are evenly distributed therein, which is conducive to enhancing energy conversion efficiency, reducing material costs, and improving battery performance. Strontium-90 has the advantages of good economy, long aging, and high energy density. Strontium nitrate, strontium chloride or a mixture of the two is used as a radioactive substance. The material is easy to mass produce and is the preferred raw material for the radioactive source of a micro-isotope battery. The radiation-resistant polymer coating covers the radioactive source film layer, which can reduce the impact of high-intensity irradiation on the radioactive composite film carrier and improve the stability and safety of the radioactive source film.

[0042] In some embodiments, the polymer film-forming material is polyethylene oxide, polyvinyl alcohol or a mixture of the two. Polyethylene oxide and polyvinyl alcohol have abundant oxygen-containing functional groups, and have good adsorption effects on radioactive sources in the form of ions in radioactive substances, which is beneficial to improving the stable adsorption and uniform distribution of radioactive substances in the radioactive source film layer, and the above-mentioned polymer film-forming materials have good radiation resistance and stable chemical properties, which is beneficial to improving the service life of the radioactive composite film. In addition, the above-mentioned polymer film-forming materials have good film-forming properties and good adhesion to the substrate, which is beneficial to improving the stability of the radioactive composite film carrier.

[0043] In some embodiments, the radiation-resistant polymer coating comprises a radiation-resistant polymer material, and the radiation-resistant polymer material is selected from polymethyl methacrylate, polyethyl methacrylate, or a mixture thereof. The above polymer materials have radiation resistance, and by forming a radiation-resistant polymer coating to cover the radiation source film layer, the radiation source film layer can be protected from the influence of high-intensity radiation, thereby improving the service life and safety performance of the radiation source film layer. In addition, the above radiation-resistant polymer material is a commercial material, has good economic efficiency, and the raw materials are easily available. Moreover, as a protective coating, the film formation is stable, the drying is fast, and the film is easy to form.

[0044] In some embodiments, the radioactive composite film has a thickness of 10-500 μm and an area of ​​1-100 cm 2. By making the thickness and area of ​​the radioactive composite film within the above range, it is beneficial to improve the mechanical properties of the radioactive composite film, improve the transmission efficiency of radioactive particles, and improve the utilization rate of the radiation source, thereby improving the performance of the isotope battery. Under the conditions of the same amount of radioactive material, the larger the area of ​​the radioactive composite film, the smaller its thickness, which is beneficial to the transmission of radioactive particles and enhances the efficiency of the utilization of radioactive decay energy. In addition, the thickness and area of ​​the radioactive composite film within the above range make the radioactive composite film carrier suitable for micro-electromechanical systems.

[0045] On the other hand, the present application also provides a method for preparing a radioactive composite film for an isotope battery, comprising the following steps:

[0046] S1, preparing a radioactive source film-forming solution, wherein the radioactive source film-forming solution comprises an aqueous solution of a polymer film-forming material and a radioactive substance, wherein the radioactive substance is selected from strontium nitrate, strontium chloride or a mixture of the two;

[0047] S2, dropping the radioactive source film-forming liquid onto the center of the plane of the substrate, shaking to spread the radioactive source film-forming liquid, and drying to form a radioactive source film layer;

[0048] S3, adding the radiation-resistant polymer coating film-forming liquid dropwise to the above-mentioned radiation source film layer, shaking to spread the radiation-resistant polymer coating film-forming liquid, and drying to form the radiation-resistant polymer coating.

[0049] The method of the present application prepares a film-forming liquid with polymer film-forming materials and radioactive substances using water as a solvent, drips the liquid onto the plane of the substrate, and then shakes the liquid to allow it to self-spread. After drying, a radioactive source film layer is formed. Then, the radiation-resistant polymer coating film-forming liquid is spread on the radioactive source film layer using a similar method to form a film. In the present application, water is mainly used as a solvent to reduce the use of organic solvents, which is environmentally friendly and inexpensive. The high-temperature calcination process is avoided by the self-spreading and drying of the polymer film-forming material, which saves energy costs and is simple to operate. The preparation process of the present application does not require high-temperature calcination, has a simple process flow, and is highly operable, providing technical support for the large-scale production and industrial application of thin-film radioactive sources.

[0050] In some embodiments, step S1 comprises:

[0051] Prepare a polymer film-forming material solution: heat and dissolve the polymer film-forming material in ultrapure water at 60-90° C., wherein the polymer film-forming material is polyethylene oxide, polyvinyl alcohol or a mixture of the two.

[0052] Prepare the radioactive substance solution: dissolve the radioactive substance in ultrapure water, and

[0053] Prepare the radioactive source film-forming solution: mix the above-mentioned polymer film-forming material solution and the radioactive substance solution.

[0054] By separately preparing a polymer film-forming material solution and a radioactive substance solution and then mixing them, it is possible to controllably prepare a film having different loading amounts of radioactive source substances as well as the thickness and size of the film by adjusting the concentration of the polymer film-forming material solution and the concentration of the radioactive substance solution as well as the mixing ratio of the two solutions.

[0055] In some embodiments, the polymer film-forming material solution includes 5 to 10 parts by weight of the polymer film-forming material, and 100 to 200 parts by weight of the ultrapure water; the concentration of the radioactive substance solution is 1-500 g / L. As a result, it is beneficial for the radioactive source film layer film-forming liquid to self-spread and form a film on the substrate surface. In addition, due to the adjustment of the loading amount of the radioactive substance. Exemplarily, the polymer film-forming material may include, for example, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight or a range of any two of them, and, for example, 100 parts by weight, 120 parts by weight, 140 parts by weight, 160 parts by weight, 180 parts by weight, 200 parts by weight or a range of any two of them, of ultrapure water. For example, the concentration of the radioactive substance solution can be 1 g / L, 10 g / L, 50 g / L, 100 g / L, 200 g / L, 300 g / L, 400 g / L, 500 g / L, or a value between any two of these values. It is understood that in the process of preparing the polymer film-forming material solution, the polymer film-forming material is completely dissolved to form a clear and transparent solution.

[0056] In some embodiments, the volume ratio of the radioactive substance solution to the polymer film-forming material solution is 1:5-3:5. When the volume ratio of the radioactive substance solution to the polymer film-forming material solution is within the above range, the resulting mixed solution will not be too concentrated or too dilute, which is conducive to self-spreading film formation and faster and earlier molding; in addition, it is also conducive to operation in an actual hot chamber, wherein a volume ratio that is too small requires too high operating accuracy, which can easily cause large errors in solution concentration; a volume ratio that is too large can only obtain a dilute solution, which is not conducive to obtaining a stably formed film. Exemplarily, the volume ratio of the radioactive substance solution to the polymer film-forming material solution can be 1:5, 2:5, 3:5, or a ratio between the ranges consisting of any two of them.

[0057] In some embodiments, the mixing time of the polymer film-forming material solution and the radioactive substance solution is 0.5-2 hours. This is conducive to uniform dispersion of the radioactive substance in the polymer film-forming material. Exemplarily, the mixing time can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, or a value between any two of these values.

[0058] In some embodiments, the polymer film-forming material includes polyethylene oxide, polyvinyl alcohol or a mixture thereof.

[0059] In an embodiment where the polymer film-forming material includes both polyethylene oxide and polyvinyl alcohol, the preparation of the polymer film-forming solution material solution includes: heating and dissolving 5 to 10 parts of polyethylene oxide in 100 to 200 parts of ultrapure water at 60-90°C to obtain a polyethylene oxide solution; heating and dissolving 5 to 10 parts of polyvinyl alcohol in 100 to 200 parts of ultrapure water at 60-90°C to obtain a polyvinyl alcohol solution; and mixing the polyethylene oxide solution and the polyvinyl alcohol solution in a volume ratio of 5:0.1 to 5:1 to obtain the polymer film-forming material solution.

[0060] In some embodiments, the weight average molecular weight of the polyethylene oxide is 100,000 to 500,000; the weight average molecular weight of the polyvinyl alcohol is 1,000 to 50,000. If the molecular weight of the polymer film-forming material is too small, it is difficult to form a film, the mechanical properties are extremely poor, and it is extremely easy to break; if the molecular weight of the polymer film-forming material is too large, it is difficult to form a solution and cannot self-spread. By making the weight average molecular weight of polyethylene oxide or polyvinyl alcohol respectively within the above range, it is beneficial to obtain a film with certain mechanical properties.

[0061] In some embodiments, the substrate is one of quartz glass, high borosilicate glass, transparent alumina ceramics, and transparent yttrium aluminum garnet ceramics. The above substrate is light-transmissive and has relatively little effect on the transmission of radioactive particles, which is conducive to improving the transmission efficiency of radioactive particles. In addition, the above substrate is easy to obtain a smooth surface, which is conducive to the spreading of the film-forming liquid of the radiation source film layer.

[0062] In some embodiments, the plane of the substrate is a smooth mirror surface or a concave surface, which is conducive to the self-spreading of the radioactive source film-forming liquid on the substrate surface, which is conducive to the self-spreading of the radioactive source film-forming liquid on the substrate surface.

[0063] In some embodiments, in step S2, the amount of the radioactive source film-forming liquid added is 10-1000 μL, thereby enabling controllably forming radioactive source films of different areas, and the larger the amount of radioactive source film-forming liquid added, the larger the radioactive source film formed.

[0064] In some embodiments, in step S2, the drying includes heating at 90-150° C. or irradiating with an infrared lamp to evaporate the solvent, and then naturally cooling and drying at room temperature.

[0065] In some embodiments, the drying time is 30 to 120 minutes.

[0066] In some embodiments, the natural cooling and drying time is 60 to 240 minutes.

[0067] In some embodiments, in step S3, the radiation-resistant polymer coating film-forming liquid includes a radiation-resistant polymer material and a solvent, wherein the radiation-resistant polymer material is selected from polymethyl methacrylate, polyethyl methacrylate or a mixture of the two; and the solvent is selected from dichloromethane, chloroform or a mixture of the two solvents. The above-mentioned radiation-resistant polymer material has good radiation resistance, which is beneficial to reducing the impact of high-intensity radiation on the radiation source film layer. The above-mentioned solvent is used to prepare the radiation-resistant polymer coating film-forming liquid, so that the radiation-resistant polymer coating film-forming liquid can achieve self-spreading on the radiation source film layer.

[0068] In some embodiments, the drop volume of the radiation-resistant polymer coating film-forming liquid is 0.5-1.0 mL, so that the prepared radiation-resistant polymer coating can completely cover the radiation source film layer, thereby protecting the radiation source film layer.

[0069] In some embodiments, in step S3, drying is achieved by natural cooling and drying to form a polymer coating. In some embodiments, the natural cooling and drying time is 10-30 minutes.

[0070] In the above preparation method, only the embodiment of forming a radioactive composite film on the surface of one side of the substrate is described. It can be understood that those skilled in the art can form a radioactive composite film on one side or both sides of the substrate as needed. In the embodiment of forming a radioactive composite film on both sides of the substrate, the preparation method includes forming a radioactive composite film on one side of the substrate, drying it to form a film, and then forming a radioactive composite film on the other side using the same method; or forming a radioactive source film layer on both sides of the substrate, drying it to form a film, and then forming a radiation-resistant polymer coating on the radioactive source film layer. Based on the teachings of this application, those skilled in the art can adjust the order of steps of the preparation method, and the embodiments obtained thereby belong to the scope of this application.

[0071] The following will describe the implementation of the present application in detail with reference to specific examples. It should be understood that the following specific examples are exemplary and should not be construed as limiting the present application.

[0072] Example

[0073] Example 1

[0074] (1) Weigh 8.0 g of polyethylene oxide with a weight average molecular weight of 500,000 and add it to a round-bottom flask containing 100 mL of ultrapure water, heat it to 90° C., and stir it at 90° C. for 6 hours until it is completely dissolved; after cooling, add water to make up to the 100 mL mark, and stir evenly to obtain a polyethylene oxide aqueous solution.

[0075] (2) Weigh 2.0 g of polyvinyl alcohol with a weight average molecular weight of 1750 and add it to a round-bottom flask containing 25 mL of ultrapure water, heat it to 90° C., and stir it at 90° C. for 6 hours until it is completely dissolved; after cooling, add water to make up to the 25 mL mark, and stir evenly to obtain a polyvinyl alcohol aqueous solution.

[0076] (3) Use a pipette to transfer 5 mL of polyethylene oxide aqueous solution and 0.2 mL of polyvinyl alcohol aqueous solution respectively, and mix them evenly to obtain a polymer film-forming material solution.

[0077] (4) Add 3 mL of strontium-90 aqueous solution (5 g / L) to the mixed polymer film-forming material solution and mix well to obtain the radiation source film-forming solution.

[0078] (5) Use a pipette to quantitatively transfer 0.7 mL of the above-mentioned radioactive source film-forming liquid and drop it drop by drop onto the center of a 25×25 mm transparent yttrium aluminum garnet ceramic substrate. Shake the solution appropriately to spread the droplets evenly to the edge of the substrate.

[0079] (6) Drying with an infrared lamp, with the infrared lamp and the substrate at a vertical distance of 20 cm, and the drying time is 60 minutes. As the heating time increases, the water gradually evaporates, and then the film is left to cool naturally at room temperature to obtain a radiation source film layer.

[0080] (7) Using dichloromethane as solvent, prepare a polymethyl methacrylate solution with a concentration of 10 g / L, transfer 0.5 mL to cover the dried film, and let it stand and dry for 10 min to form a radiation-resistant polymer coating. In this way, a radioactive composite film carrier is prepared. In the radioactive composite film carrier, the radioactive composite film includes a radiation source film layer and a radiation-resistant polymer film layer. After testing, the area of ​​the radioactive composite film is about 400 mm 2 , with a diameter of about 20 mm and a film thickness of about 100 μm.

[0081] The prepared radioactive composite film was tested for performance according to the following method:

[0082] (1) Scanning electron microscopy test and element distribution analysis.

[0083] Thermo Scientific Apreo 2S scanning electron microscope was used for testing. The process was as follows: first, the conductive adhesive was attached to the copper stage, the radioactive composite film or the radioactive composite film and substrate were bonded to the conductive adhesive, and then the sample was subjected to necessary gold spraying treatment. Finally, it was placed in the scanning electron microscope sample transition chamber, and then pushed into the interior, and vacuumed until the vacuum degree reached <1.5×10 -3 After Pa, the electron gun was turned on and the acceleration voltage was adjusted to 5-20 kV for microscopic morphology characterization. In addition, the surface micromorphology of the radioactive composite film and the distribution of the three elements C, O, and Sr were observed with the ULTIM Max 65 spectrometer.

[0084] (2) Linear electron accelerator irradiation:

[0085] A linear electron accelerator is used for irradiation, the irradiation conditions are 2-5MeV, and the irradiation time is 10-1200s.

[0086] The radioactive composite film prepared in Example 1 was subjected to scanning electron microscopy and element distribution analysis. The test results are shown in Figure 1 .Depend on Figure 1 It can be seen that the obtained composite film has good flatness from both macroscopic and microscopic observations, and the Sr element is evenly distributed on the polymer film carrier, with a loading amount of about 9.8wt% (theoretical loading ~10wt%).

[0087] The radioactive composite film prepared in Example 1 was irradiated by a linear electron accelerator, and the states of the radioactive composite film before and after irradiation were compared and photographed. The comparison photographs are shown in Figure 2 .from Figure 2 It can be seen that under the conditions of 2-5MeV (voltage of 83-98kV), the irradiation time was 10-1200s with a current of 10-200μA respectively. By comparing the apparent morphology of the composite film before and after irradiation, there was no obvious morphological change, indicating that under the current irradiation intensity, the composite film prepared in Example 1 has good radiation tolerance and is suitable for the loading of the radioactive isotope materials involved.

[0088] Comparative Example 1

[0089] A radioactive composite thin film carrier is prepared by a method similar to that of Example 1, except that polyimide is used as the polymer film-forming material.

[0090] Experiments have found that polyimide is not miscible with aqueous solutions containing strontium-90, and a uniform dispersion effect cannot be achieved. In addition, after film formation, it is difficult to redissolve for post-processing.

[0091] Comparative Example 2

[0092] A radioactive composite thin film carrier was prepared by a method similar to that of Example 1, except that polydopamine was used as the polymer film-forming material.

[0093] Experiments have found that the radioactive composite film formed by polydopamine has poor mechanical properties and is easily deliquescent, and the thickness of the resulting film cannot meet high load requirements.

[0094] Comparative Example 3

[0095] A radioactive composite thin film carrier is prepared by a method similar to that of Example 1, except that epoxy resin is used as the polymer film-forming material.

[0096] The experiment found that the prepared radioactive source film-forming liquid was difficult to dry into a film.

[0097] Comparative Example 4

[0098] A radioactive composite thin film carrier is prepared by a method similar to that of Example 1, except that polyimide is used as the radiation-resistant polymer material.

[0099] Experiments have shown that the resulting radiation-resistant polymer coating has poor light transmittance, which is not conducive to particle transmission.

[0100] The above description is only a preferred embodiment of the present application, and does not limit the patent scope of the present application. All equivalent structural changes made by using the contents of the present application specification and drawings under the inventive concept of the present application, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A radioactive composite film for isotope battery, characterized in that: The radioactive composite film comprises: A radiation source film layer, the radiation source film layer comprising a polymer film-forming material and a radioactive substance, wherein the radioactive substance is selected from strontium nitrate, strontium chloride or a mixture of the two; and The radiation-resistant polymer coating is located on one side of the radiation source film layer and covers the radiation source film layer.

2. The radioactive composite film according to claim 1, wherein: The polymer film-forming material is polyethylene oxide, polyvinyl alcohol or a mixture of the two; The radiation-resistant polymer coating comprises a radiation-resistant polymer material, and the radiation-resistant polymer material is selected from polymethyl methacrylate, polyethyl methacrylate or a mixture of the two.

3. The radioactive composite film according to claim 1 or 2, wherein: The thickness of the radioactive composite film is 10-500 μm, and the area of ​​the film is 1-100 cm 2 .

4. A method for preparing a radioactive composite film for an isotope battery, comprising the following steps: S1, preparing a radioactive source film-forming solution, wherein the radioactive source film-forming solution comprises an aqueous solution of a polymer film-forming material and a radioactive substance, wherein the radioactive substance is selected from strontium nitrate, strontium chloride or a mixture of the two; S2, dropping the radioactive source film-forming liquid onto the center of the plane of the substrate, shaking to spread the radioactive source film-forming liquid, and drying to form a radioactive source film layer; S3, adding the radiation-resistant polymer coating film-forming liquid dropwise to the above-mentioned radiation source film layer, shaking to spread the radiation-resistant polymer coating film-forming liquid, and drying to form the radiation-resistant polymer coating.

5. The preparation method according to claim 4, wherein Step S1 includes: Prepare a polymer film-forming material solution: heat and dissolve the polymer film-forming material in ultrapure water at 60-90° C., wherein the polymer film-forming material is polyethylene oxide, polyvinyl alcohol or a mixture of the two. Prepare the radioactive substance solution: dissolve the radioactive substance in ultrapure water, and Prepare the radioactive source film-forming solution: mix the above-mentioned polymer film-forming material solution and the radioactive substance solution.

6. The preparation method according to claim 4 or 5, wherein: The polymer film-forming material solution comprises 5 to 10 parts by weight of the polymer film-forming material and 100 to 200 parts by weight of the ultrapure water; and / or The concentration of the radioactive substance solution is 1-500 g / L; Preferably, the volume ratio of the radioactive substance solution to the polymer film-forming material solution is 1:5-3:

5.

7. The preparation method according to claim 4 or 5, wherein: In step S2, The amount of the radioactive source film-forming liquid added is 50 to 1000 μL / cm 2 ; Preferably, the drying comprises heating at 90-150° C. or irradiating with an infrared lamp to evaporate the solvent, and then naturally cooling and drying at room temperature.

8. The preparation method according to claim 4 or 5, wherein: The radiation-resistant polymer coating film-forming liquid comprises a radiation-resistant polymer material and a solvent, wherein the radiation-resistant polymer material is selected from polymethyl methacrylate, polyethyl methacrylate or a mixture thereof; and / or The solvent is selected from dichloromethane, chloroform or a mixture of the two solvents; Preferably, the concentration of the radiation-resistant polymer coating film-forming liquid is 5 to 30 g / L.

9. The preparation method according to claim 4 or 5, wherein: The dropwise addition volume of the radiation-resistant polymer coating film-forming liquid is 0.5 to 1.0 mL.

10. The preparation method according to claim 4 or 5, wherein: The substrate is one of quartz glass, high borosilicate glass, transparent alumina ceramics, and transparent yttrium aluminum garnet ceramics; Preferably, the plane of the substrate is a smooth mirror surface or a concave surface.

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