Boron-10 isotope enriched boron nitride neutron scintillator screen of meter-scale oversize dimensions

Abstract

This invention belongs to the field of neutron scintillation screen technology, specifically relating to a meter-scale ultra-large boron-10 isotope-enriched boron nitride neutron scintillation screen. The invention mixes boron-10 isotope-enriched, luminescent boron nitride, a binder, and a solvent to form a homogeneous slurry; then, the slurry is coated onto a substrate using a blade coating or spray coating method to form a wet film; finally, after curing, a meter-scale neutron scintillation screen is obtained. This invention achieves integrated neutron absorber and luminescent center at the atomic scale, fundamentally solving the problem of non-radiative recombination loss caused by energy interface transport in traditional physical hybrid scintillators, while overcoming the limitations of chemical vapor deposition methods. 10 The fabricated scintillation screen faces challenges such as difficulty in enriching boron, substrate dependence, difficulty in large-area fabrication, and high toxicity of raw materials. It exhibits high neutron detection efficiency, high light yield, and excellent optical uniformity, providing an advanced material solution for the large-scale application of thermal neutron detection.

Description

Technical Field

[0001] This invention belongs to the field of neutron scintillation screen technology, specifically relating to a boron nitride neutron scintillation screen with a meter-scale ultra-large size enriched with boron-10 isotope. Background Technology

[0002] Thermal neutrons are indispensable for nuclear reactor safety monitoring, non-destructive testing, and scientific research. Scintillation detection, due to its ability to measure intensity and create images, has become one of the most widely used techniques. The core of this method lies in using specific materials to convert neutron signals into visible light. Among these materials, the isotope boron-10 (… 10 B) Due to its high thermal neutron absorption cross-section of 3840 barn, it is considered an ideal neutron absorbing material. The alpha particles produced by its nuclear reactions and... 7 Li ions can transfer energy to the luminescent center, thereby achieving efficient conversion of neutrons into photons.

[0003] Currently, boron-based neutron scintillator technology is mainly represented by existing technologies such as patent applications with publication numbers CN102313754A, CN102352076A, and CN102382385A. The core of these technologies is to incorporate neutron-absorbing materials (such as those containing boron) into the neutron scintillator. 10 A hybrid approach involving compounds of type B and luminescent materials (such as ZnS:Ag) is used to prepare thermal neutron scintillators via a mixture of these materials and a film-forming device, atomizer, or tablet press. In this composite structure, neutrons are... 10 After alpha particles are generated from alpha absorption, they travel a relatively long distance and excite luminescent materials to emit light. This process results in most of the energy being dissipated as heat through non-radiative recombination, causing significant energy loss and thus significantly reducing the effective neutron detection efficiency. This is why current technologies generally employ neutron-absorbing materials (such as those containing...) 10 The fundamental reason for the route of combining compounds of B with externally added luminescent materials (such as ZnS:Ag) is that commonly used commercial compounds containing B are... 10 Compound B has extremely low luminescence efficiency and cannot directly output an effective light signal after absorbing neutrons.

[0004] Unlike the aforementioned approach that mixes neutron-absorbing and luminescent materials, our previous work employed a chemical vapor deposition (CVD) technique to grow luminescent boron nitride thin films. Relevant patents include: Chinese patent application CN119932521A, which discloses a micrometer-resolution boron nitride neutron scintillation screen and its fabrication method, using sapphire as a substrate and depositing a luminescent boron nitride thin film via CVD; and Chinese patent application CN119932523A, which also discloses a method for fabricating a boron nitride neutron scintillation screen using CVD. These two technologies successfully integrated the neutron absorption and luminescence centers, allowing the thin film to emit light directly without the need for additional luminescent materials. The limitation of this method is that it did not utilize… 10 The B enrichment process is limited by the high toxicity of the precursor raw materials used, strong substrate dependence, and equipment limitations in the preparation area. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a meter-scale ultra-large boron-10 isotope-enriched boron nitride neutron scintillation screen. This invention directly synthesizes carbon-doped luminescent boron nitride powder, which is both a neutron absorber and a highly efficient luminescent material, eliminating the need for external luminescent materials. This fundamentally solves the problem of weak intrinsic luminescence of boron nitride, eliminating the need for luminescent materials and reducing non-radiative recombination. This powder material can be used to prepare scintillation screens using blade coating or spray coating processes. While achieving high isotope enrichment, it overcomes the equipment limitations of chemical vapor deposition (CVD) thin film preparation, enabling the direct fabrication of meter-scale ultra-large scintillation screens.

[0006] A strategy combining high-temperature solid-state sintering with various slurry film-forming technologies is employed. First, enrichment is utilized... 10 Boric acid from B reacts with melamine and organic polymers to form a precursor, which is then used to synthesize luminescent carbon-doped h- through a high-temperature sintering process. 10 BN powder fundamentally ensures the material's high neutron absorption capacity and luminescence properties. Subsequently, various mature slurry processing technologies, including blade coating and spray coating, are flexibly selected according to actual application requirements to prepare this functional powder into large-area (meter-scale), continuous, dense thin films. This comprehensive solution solves the problems of strong substrate dependence and equipment limitations in CVD technology, while also ensuring raw material safety and low cost. It overcomes the limitations of existing CVD thin film growth routes, such as substrate dependence, difficulty in large-area production, and high raw material toxicity. 10 B-enrichment is difficult and other problems exist.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing a boron-10 isotope-enriched boron nitride neutron scintillation screen with a diameter of meters, the preparation route of which is as follows: Figure 1 As shown, the preparation method includes the following steps: (1) Preparation of luminescent boron nitride: Melamine was mixed with boron-10 enriched boric acid, and an organic polymer was added as a carbon source. The mixture was then mixed to obtain a solution. The solution was heated and evaporated to obtain a solid precursor powder. Subsequently, high-temperature solid-state sintering was performed to obtain carbon-doped h- 10 The sintered product of BN was finally ultrasonically immersed in deionized water or a weak acid solution, centrifuged, and the solid was collected and dried to obtain carbon-doped h- 10 BN luminescent powder.

[0008] (2) Slurry molding of meter-scale scintillator screen: carbon doped h- 10 BN luminescent powder, binder and solvent are mixed to form a uniform slurry; then the slurry is coated onto the substrate by scraping or spraying to form a wet film; finally, after curing, a neutron scintillation screen with a size of meter is obtained.

[0009] Furthermore, in step (1), the polymer includes polyethylene glycol, polyacrylamide, methylcellulose, polyvinyl alcohol, etc.

[0010] Further, in step (1), the carbon doping h- 10 BN luminescent powder can also be replaced with oxygen, fluorine, rare earth elements, or combinations thereof doped with h- 10 BN luminescent powder.

[0011] Furthermore, the molar ratio of melamine, boron-10 enriched boric acid, and polyethylene glycol is 2:1:1 to 1:1:1.

[0012] Further, in step (1), the heating and stirring temperature is 80~100 ℃, and the heating and stirring time is 1~2 h.

[0013] Further, in step (1), the drying temperature is 60~90 ℃ and the drying time is 12~24 h.

[0014] Further, in step (1), the heating treatment refers to a programmed heating to 900-1200 ℃ at a heating rate of 5-10 ℃ / min, and holding at this temperature for 2-6 h.

[0015] Furthermore, in step (1), the ultrasonic immersion time is 0.5~1 h.

[0016] Further, in step (2), the binder is a binder such as polyvinyl alcohol, cellulose, urea-formaldehyde resin, polystyrene, epoxy resin, etc., and the carbon-doped h- 10 The mass ratio of BN luminescent powder to binder is 90:10 to 95:5.

[0017] Furthermore, in step (2), the heating and curing temperature is 50 ℃, and the heating and curing time is 10~30 min.

[0018] Further, in step (2), the solvent includes at least one of deionized water, anhydrous ethanol, N-methylpyrrolidone, and chlorobenzene.

[0019] Further, in step (2), the mixing process includes at least one of heating and stirring, homogenizing, or ultrasonic dispersion.

[0020] Further, in step (2), the substrate is a substrate with a small thermal neutron absorption cross section, including at least one of aluminum plate, alumina plate, and titanium alloy plate.

[0021] Furthermore, in step (2), the curing method includes at least one of room temperature air drying, heat curing, and ultraviolet curing.

[0022] A second aspect of the present invention provides a boron-10 isotope-enriched boron nitride neutron scintillation screen of meter size prepared by the above-described preparation method.

[0023] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a meter-scale ultra-large boron-10 isotope-enriched boron nitride neutron scintillation screen. A precursor is synthesized from boron-10-enriched boric acid, melamine, and ethylene glycol via a solution method, followed by high-temperature solid-state sintering to prepare a carbon-doped h- 10 Boron-10 isotope-enriched boron nitride neutron scintillator of this invention simultaneously realizes the functions of neutron absorbing material and luminescent center, fundamentally solving the non-radiative recombination loss problem in composite scintillators of neutron absorbing and luminescent materials, and overcoming the limitations of chemical vapor deposition methods. 10 The fabricated scintillation screen faces challenges such as difficulty in enriching boron, substrate dependence, difficulty in large-area fabrication, and high toxicity of raw materials. It exhibits high neutron detection efficiency, high luminous efficiency, and excellent optical uniformity, providing an advanced material solution for the large-scale application of thermal neutron detection.

[0024] Specifically, the present invention has the following advantages: (1) The present invention prepares carbon-doped h- 10 This single scintillator material, BN, solves the problem of intrinsic h-BN not emitting light. 10 By introducing carbon luminescent centers into the BN lattice and utilizing enriched boron-10 as a highly efficient neutron absorber, neutron absorption and luminescence are simultaneously achieved at the atomic scale, fundamentally solving the problem of traditional physical hybrid structures (containing...) 10The energy loss problem in the mixture of B compounds as neutron absorbers and ZnS:Ag phosphors as luminescent materials.

[0025] (2) This invention adopts a solution precursor-high temperature sintering-slurry forming technical route, which solves the problem of CVD technology on 10 B suffers from problems such as low enrichment, substrate dependence, difficulty in large-area fabrication, and high toxicity of raw materials. This proposed solution offers a simple process, safe raw materials, and allows for the direct use of enriched materials. 10 The B source provides a pathway for the large-scale, controllable fabrication of meter-sized, high-performance neutron scintillation screens. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the fabrication process of the boron-10 isotope-enriched boron nitride neutron scintillation screen of the present invention, which has a meter-scale size.

[0027] Figure 2 This is an optical photograph of the sintered product in Example 1.

[0028] Figure 3 The carbon-doped h- in Example 1 10 Optical photograph of BN luminescent powder.

[0029] Figure 4 The carbon-doped h- in Example 1 10 Photoluminescence spectrum of BN luminescent powder.

[0030] Figure 5 An optical photograph of the boron nitride neutron scintillation screen enriched with boron-10 isotopes at a size of meter size, as shown in Example 1.

[0031] Figure 6 This is a schematic diagram of the thermal neutron imaging process in Example 1.

[0032] Figure 7 This is a photograph of the aircraft blades in Example 1.

[0033] Figure 8 The image shows the neutron imaging results of the aircraft blades in Example 1. Detailed Implementation

[0034] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0036] Example 1: Preparation, characterization, and testing of a meter-sized boron-10 isotope-enriched boron nitride neutron scintillation screen. (1) First, accurately weigh melamine and boric acid enriched with boron-10 ( 10 B abundance >99%, purchased from Liaoning Honghao Chemical Industry Co., Ltd., and polyethylene glycol (PEG, average molecular weight 20000) were placed in a reaction vessel at a molar ratio of 2:1:1. An appropriate amount of deionized water was added, and the mixture was stirred continuously at 80 ℃ for 2 hours to form a homogeneous and clear precursor solution. The temperature was then raised to 90 ℃ for solvent evaporation. After the solution transformed into a milky white colloid, it was transferred to an 80 ℃ forced-air drying oven for 24 hours to obtain a solid precursor powder.

[0037] (2) The obtained precursor powder was placed in a crucible and then placed in a muffle furnace. The temperature was programmed to rise to 1000 °C at a heating rate of 5 °C / min and held at this temperature for 6 hours to complete the synthesis of hexagonal boron nitride and the lattice doping of carbon atoms. After the sintering process was completed, the furnace was allowed to cool to room temperature to obtain a white sintered product, such as... Figure 2 As shown.

[0038] (3) The sintered product was purified by three cycles of ultrasonic-centrifugation with deionized water. Each ultrasonic treatment lasted 30 minutes, and the centrifugation parameters were set to 8000 rpm for 3 minutes. Finally, carbon-doped h- 10 BN luminescent powder. This powder appears white in a macroscopic state, like... Figure 3 As shown, it exhibits bright blue emission characteristics under 266 nm excitation. Photoluminescence spectrum ( Figure 4 Tests showed that a sharp emission peak appeared at about 350 nm and a broad, flat emission peak appeared between 400 and 600 nm.

[0039] (4) To prepare a large-area scintillation screen, take 18 g of purified carbon-doped h- 10 BN luminescent powder was mixed with 2 g of polyvinyl alcohol (PVA, type 2488) binder, and 200 mL of anhydrous ethanol was added. The mixture was then ultrasonically treated for 30 minutes to form a stable and homogeneous slurry system. A precision coating device was used to form a film on an aluminum substrate with a 200 μm gap. The wet film was then dried at 50 °C for 20 minutes to complete the curing process, ultimately obtaining a smooth, uniformly thick, independent scintillator screen. Figure 5 As shown. Figure 6The diagram illustrates a neutron imaging test. Thermal neutrons generated by the reactor are extracted through a beam tube, pass through the imaging object, and bombard a scintillator to produce visible light. This light is then redirected by a mirror to a camera, which records the image, ultimately yielding a clear image. This scintillator screen can identify internal details (cracks, etc.) of aircraft blades in neutron imaging tests. Figure 7 and Figure 8 As shown.

[0040] Example 2: Preparation of a boron-10 isotope-enriched boron nitride neutron scintillation screen with a meter-scale size (1) Accurately weigh melamine and boric acid enriched with boron-10 ( 10 B abundance >99%, purchased from Liaoning Honghao Chemical Industry Co., Ltd., and polyacrylamide (PAM, average molecular weight 15000) were placed in a flask at a molar ratio of 1:1:1. A suitable amount of a mixed solvent of deionized water and anhydrous ethanol (volume ratio 1:1) was added, and the mixture was stirred continuously at 90 °C for 1.5 hours to form a homogeneous and viscous precursor solution. The temperature was then raised to 90 °C for evaporation. After the solvent evaporated and the system became a milky white paste, it was transferred to a 70 °C forced-air drying oven and dried for 18 hours to obtain a solid precursor powder.

[0041] (2) The precursor powder was placed in a quartz crucible and then placed in a tube furnace. The temperature was increased to 1100 °C at a rate of 8 °C / min and held at this temperature for 4 hours to complete the carbon doping h- 10 Synthesis of BN. After sintering, the product was cooled to room temperature in the furnace to obtain a white sintered product.

[0042] (3) The sintered product was ultrasonically soaked in deionized water for 1 hour, followed by centrifugation (6000 rpm, 5 minutes) to remove impurities. After washing with deionized water three times, it was dried in a vacuum drying oven at 60 ℃ for 12 hours to obtain carbon-doped h- 10 BN luminescent powder. This powder emits bright blue-violet light when excited at 266 nm.

[0043] (4) Take 19 g of the above-mentioned luminescent powder and mix it with 1 g of epoxy resin binder. Add 180 mL of N-methylpyrrolidone solvent and disperse the mixture for 20 minutes (3000 rpm) using a spin coater to form a uniform, bubble-free slurry. Apply the slurry to an alumina substrate using a spraying process (spraying distance 30 cm) to form a uniform wet film. Then heat and cure the film at 50 °C for 30 minutes to finally obtain a meter-scale scintillation screen with dimensions of 1.0 m × 1.0 m and a thickness of 80 μm. This scintillation screen has excellent surface flatness and good optical uniformity, making it suitable for neutron imaging scenarios.

[0044] Example 3: Preparation of a boron-10 isotope-enriched boron nitride neutron scintillation screen with a meter-scale size (1) Accurately weigh melamine, boron-10 enriched boric acid (10B abundance >99%, purchased from Liaoning Honghao Chemical Industry Co., Ltd.), and methylcellulose (MC), and place them in a reaction vessel at a molar ratio of 1.5:1:1. Add an appropriate amount of deionized water and stir at a constant temperature of 100 °C for 1 hour to form a transparent precursor solution. Then, allow it to cool naturally to room temperature, pour it into a petri dish, and dry it in an 85 °C forced-air drying oven for 20 hours to obtain a solid precursor powder.

[0045] (2) The precursor powder was placed in a muffle furnace and heated to 900 °C at a rate of 10 °C / min. The temperature was then maintained at this temperature for 2 hours to complete the carbon doping h- 10 Synthesis of BN. After sintering, the product was rapidly cooled to room temperature to obtain a white sintered product, which was then ground to obtain well-dispersed powder particles.

[0046] (3) The sintered product was ultrasonically soaked in deionized water for 0.5 hours and purified by two ultrasonic-centrifugal cycles (5000 rpm, 4 minutes) to remove unreacted impurities. Then it was dried in an 80 ℃ forced-air drying oven for 16 hours to obtain carbon-doped h- 10 BN luminescent powder.

[0047] (4) Take 18.5 g of the above luminescent powder and mix it with 1.5 g of cellulose binder, add anhydrous ethanol, and disperse it by ultrasonication for 40 minutes to form a stable slurry. Apply the slurry to the alumina substrate by a blade coating method (blank coating speed 5 cm / s, gap 600 μm) to form a wet film, and then let it air dry naturally at room temperature for 48 hours to complete the curing. Finally, a meter-scale scintillator screen with a size of 1.1m×1m and a thickness of 120 μm is obtained.

[0048] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing a boron-10 isotope-enriched boron nitride neutron scintillation screen with a size of meter-scale, characterized in that, The preparation method includes the following steps: Boron nitride enriched with boron-10 isotope and possessing luminescent properties is mixed with a binder and a solvent to form a uniform slurry. The slurry is then coated onto a substrate by a scraping or spraying method to form a wet film. Finally, after curing, a neutron scintillation screen with a size on the order of meters is obtained.

2. The method for preparing a meter-sized boron-10 isotope-enriched boron nitride neutron scintillation screen according to claim 1, characterized in that, The boron-10 isotope-enriched luminescent boron nitride has a crystal structure of at least one of hexagonal boron nitride, cubic boron nitride, rhombohedral boron nitride, and wurtzite boron nitride; and its physical form is at least one of nanosheets, quantum dots, micron particles, and secondary particles formed by their aggregation.

3. The method for preparing a meter-sized boron-10 isotope-enriched boron nitride neutron scintillation screen according to claim 1, characterized in that, The boron-10 isotope-enriched boron nitride with luminescent properties is a material whose luminescence performance is controlled by elemental doping; the doping element is at least one of carbon, oxygen, fluorine and rare earth elements.

4. The method for preparing a meter-sized boron-10 isotope-enriched boron nitride neutron scintillation screen according to claim 1, characterized in that, The adhesive is at least one of polyvinyl alcohol, cellulose, urea-formaldehyde resin, polystyrene, and epoxy resin.

5. The method for preparing a meter-sized boron-10 isotope-enriched boron nitride neutron scintillation screen according to claim 1, characterized in that, The solvent is at least one of deionized water, anhydrous ethanol, N-methylpyrrolidone, and chlorobenzene.

6. The method for preparing a meter-sized boron-10 isotope-enriched boron nitride neutron scintillation screen according to claim 1, characterized in that, The substrate is a substrate with a small thermal neutron absorption cross section, and is at least one of aluminum plate, alumina plate, and titanium alloy plate.

7. The method for preparing a meter-sized boron-10 isotope-enriched boron nitride neutron scintillation screen according to claim 1, characterized in that, The mixing process is at least one of heating and stirring, dispersion using a homogenizer, or ultrasonic dispersion.

8. The method for preparing a meter-sized boron-10 isotope-enriched boron nitride neutron scintillation screen according to claim 1, characterized in that, The curing method is at least one of the following: room temperature air drying, heat curing, and ultraviolet curing.

9. A boron-10 isotope-enriched boron nitride neutron scintillation screen with a meter-sized diameter prepared by the preparation method according to any one of claims 1 to 8.

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