Sub-micron resolution, boron-10 isotope enriched boron nitride neutron scintillator screen

Abstract

This invention belongs to the field of nuclear radiation detection and nanomaterials technology, specifically relating to a submicron-resolution boron-10 isotope-enriched boron nitride neutron scintillator. Addressing the technical bottleneck of severe light scattering in existing physically hybrid scintillators, this invention innovatively employs anodized aluminum nanopore templates as a confined reaction vessel and optical waveguide structure. A precursor solution enriched with boron-10 isotopes is filled into the template pores, and a hexagonal boron nitride scintillator with a nanoarray structure and boron-10 isotope enrichment is generated through in-situ reaction at high temperature. This structure strictly confines the generation and propagation of scintillating light within independent nanopillars, fundamentally suppressing transverse light scattering by utilizing the waveguide effect of the pore walls. Thus, while ensuring the macroscopic thickness of the scintillator and high neutron absorption efficiency, it achieves micron- to submicron-level spatial resolution.

Description

Technical Field

[0001] This invention belongs to the field of nuclear radiation detection and nanomaterials technology, specifically relating to a boron nitride neutron scintillation screen with submicron resolution and boron-10 isotope enrichment. Background Technology

[0002] Neutron imaging, as a powerful non-destructive testing technique, possesses high sensitivity and excellent penetration capability for light elements (such as hydrogen, lithium, and carbon). It can clearly reveal the internal structure of lightweight materials encased in high atomic number materials (such as metal shells), which is difficult to achieve with traditional techniques such as X-rays. Therefore, it plays an irreplaceable role in cutting-edge fields such as materials science, nuclear safety, and aerospace. However, these applications often place extremely high demands on spatial resolution.

[0003] Currently, the spatial resolution of mainstream commercial scintillators (such as LiF / ZnS:Ag) and their improved technologies faces a severe bottleneck. Traditional technical approaches, such as those disclosed in Chinese patent applications with publication numbers CN102313754A, CN102382385A, CN102352076A, CN119592323A, and CN104538078A, all involve combining a neutron-absorbing material (containing lithium or boron) with a luminescent center to obtain a composite neutron scintillator. This method has the following problems: (1) The random mixing of micron-scale luminescent particles and neutron-absorbing particles results in an uneven internal structure, severe light scattering at the particle interface, chaotic propagation paths, and divergent directions, leading to a decrease in resolution. (2) The neutron absorption and luminescence processes are spatially separated. Nuclear reaction products must pass through a non-luminescent matrix to excite luminescent centers. This process is accompanied by significant non-radiative recombination energy loss. (3) The randomness and uncertainty of the energy transfer path cause the photon emission position to deviate from the original neutron interaction point, which limits its spatial resolution.

[0004] To improve resolution, Tang et al. (Molecules, 2023, 28(4): 1815-26) achieved a 12μm resolution by thinning the Gd2O2S:Tb,F scintillator to 2.5μm; similarly, 10 The B / CsI:Tl stack structure (IEEE Transactions on Nuclear Science, 2020, 67(8): 1929-33.) also achieved a resolution of 9 μm by using ultrathin layers.

[0005] On the other hand, Chinese patent application CN119932521A and others have explored the route for preparing boron nitride thin films by chemical vapor deposition (CVD), which is expected to improve optical uniformity and thus enhance resolution. However, this process is costly, the raw materials are highly toxic, and the low enrichment of boron-10 isotopes results in weak neutron absorption.

[0006] In summary, existing technologies (such as physical mixing and tableting) employ the stacking or mixing of micron-sized particles. This structure inevitably generates numerous particle interfaces and internal structural inhomogeneities. When the scintillation light generated by neutron reactions propagates between these interfaces, multiple scattering occurs, causing chaotic photon propagation paths and directional divergence, thus limiting the theoretical limit of spatial resolution. Simultaneously, this technical solution assigns the two key functions of neutron absorption and photon emission to physically separated material units (such as...) 10 Compound B reacts with ZnS:Ag, leading to a nuclear reaction that produces charged particles (α / 7 Li) must travel along a random and inefficient path in a non-luminescent medium to excite luminescent centers. During this process, most of the energy is dissipated through non-radiative recombination. Thin-film scintillators such as boron nitride are prepared by CVD. Theoretically, this method can yield more uniform and transparent films to reduce scattering, but it faces challenges such as the high toxicity of raw materials and the difficulty in effectively enriching boron-10 isotopes, resulting in weak neutron absorption.

[0007] Therefore, developing a new type of scintillator that can fundamentally suppress light scattering from a physical structure while maintaining high neutron sensitivity has become the key to propelling thermal neutron imaging technology toward the era of microscopic resolution. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a submicron resolution boron-10 isotope-enriched boron nitride neutron scintillation screen. This solves the problem of low resolution caused by severe light scattering and energy transfer path loss in micron-scale multiphase composite scintillators, as well as the difficulty in enriching the isotope boron-10.

[0009] Specifically, this invention employs a synthesis strategy assisted by a dual-channel porous anodic alumina (AAO) template or a microfiber template: a precursor solution enriched with the isotope boron-10 is uniformly dispersed in the ordered nanopores of the porous AAO template or microfiber template, and the AAO template or microfiber template is used as a reaction vessel. Through subsequent high-temperature sintering, a hexagonal boron nitride scintillator with a highly ordered nanoarray structure and enriched boron-10 isotope is prepared.

[0010] This innovative technology integrates a high-neutron absorption cross section (achieved through boron-10) and a highly efficient luminescent center (achieved through carbon in the crystal lattice) within the same continuous lattice at the atomic scale. This fundamentally eliminates the long-range, random transport of α-ions in non-luminescent media and minimizes non-radiative recombination energy loss, thereby achieving a breakthrough in light yield and energy conversion efficiency, laying the physical foundation for high-resolution detection. Furthermore, utilizing a micro / nano structure substrate as a reaction vessel, a nanoarray structure and a hexagonal boron nitride scintillator enriched with boron-10 isotopes were fabricated. This enables the confinement of luminescent units and guidance of the light path at the nanoscale, suppressing light scattering at its source through physical structure, aiming to achieve micrometer- or even sub-micrometer-level spatial resolution in neutron imaging.

[0011] 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 carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes, the method comprising the following steps: A precursor solution containing boron-10 isotope-enriched boron, nitrogen, and carbon sources was filled into a micro / nano structure substrate with a pore array. The substrate was then sintered to allow the precursor to react within the pores, generating carbon-doped hexagonal boron nitride enriched with boron-10 isotope and featuring a nanopillar array structure.

[0012] Furthermore, the boron source is boric acid enriched with boron-10 isotopes, and the abundance of boron-10 isotopes is not less than 20%.

[0013] Furthermore, the nitrogen source is at least one of melamine and urea, and the carbon source is at least one of polyethylene glycol, polyvinyl alcohol, cellulose, urea-formaldehyde resin, polystyrene, and epoxy resin.

[0014] Furthermore, the mass ratio of the boron source, nitrogen source and carbon source is (1~2):(1~2):1, and the solvent of the precursor solution is deionized water or anhydrous ethanol.

[0015] Furthermore, the micro / nano structure substrate is an AAO template or a micro-fiber template.

[0016] Furthermore, the pore size of the micro / nano structure substrate channel is 50-300 nanometers, and the thickness of the substrate is 20-200 micrometers.

[0017] Furthermore, the filling method is as follows: immerse the micro / nano structure substrate in the precursor solution, heat and dry it, then vacuum dry it, then slowly restore the pressure to normal, use the pressure difference to drive the solution to completely fill the pores, then heat and dry it, so that the precursor solution fills and solidifies in the nanopores.

[0018] Furthermore, the in-situ reaction refers to the precursor undergoing a direct chemical reaction within each nanopore during the sintering process to generate carbon-doped, boron-10-enriched hexagonal boron nitride with uniform size and directional arrangement.

[0019] Furthermore, the heating drying refers to drying at 60~90 ℃ for 6~12 hours, the vacuum drying time is 30~60 minutes, and the temperature rise drying refers to drying at 80 ℃ for 6~12 hours.

[0020] Further, the sintering temperature is 900~1200 °C, and the time is 6~10 hours. The precursor reacts in situ within each nanopore to generate a carbon-doped, boron-10-enriched hexagonal boron nitride nanopillar array neutron scintillator with uniform size and directional arrangement. A second aspect of the invention provides a carbon-doped, boron-10-enriched hexagonal boron nitride nanoarray composite scintillator prepared by the above-described method. Utilizing its nanoconfinement effect, the luminescent units are isolated and confined within independent channels, physically suppressing transverse light scattering. This achieves micron- or sub-micron-level spatial resolution in neutron imaging applications, with the scintillator having a spatial resolution better than 1 μm.

[0021] The third aspect of the present invention provides an application of the above-mentioned carbon-doped boron-10 isotope-enriched hexagonal boron nitride nanoarray composite scintillator in neutron imaging. The carbon-doped boron-10 isotope-enriched hexagonal boron nitride nanoarray composite scintillator serves as a neutron scintillator screen, and an amplification optical path is added to the imaging system. The two work together to achieve high-resolution neutron imaging.

[0022] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention achieves the integration of a neutron absorber (boron-10) and a luminescent center (C) at the atomic scale by using hexagonal boron nitride enriched with boron-10 isotopes through carbon doping. This completely eliminates the energy loss path of charged particles passing through non-luminescent media in traditional physical hybrid structures, directly and efficiently converting nuclear reaction energy into photon emission. Its technological advancement lies in suppressing non-radiative recombination to the maximum extent from a physical mechanism perspective, laying the material foundation for high-resolution detection.

[0023] (2) The high-temperature reaction synthesis method based on nanoconfined space (using an AAO template or a nanoarray structure of a microfiber template as the reaction vessel) is a key structural innovation of this invention. The waveguide effect of the nanopores confines the scintillator within the nanoscale, which reduces lateral light scattering that causes image blurring from the structural source. The transmission and emission processes of scintillating light after neutron incident on the composite neutron scintillator and the nanoarray scintillator are as follows: Figure 1 As shown. Therefore, this technology enables spatial resolution at the micrometer and even submicrometer levels.

[0024] (3) The preparation method of the present invention (such as the precursor solution method combined with controllable sintering) has significant process feasibility and advantages. Compared with CVD technology, which requires toxic precursors, single crystal substrates and is difficult to achieve boron-10 isotope enrichment, the technical solution of the present invention has safe raw materials, low cost, mild process and can achieve high boron-10 isotope enrichment. Attached Figure Description

[0025] Figure 1 This study describes the scintillation light transmission and emission process after neutron incident on a composite neutron scintillation screen and a nanoarray scintillation screen.

[0026] Figure 2 This is a flowchart illustrating the fabrication process of the nanoarray composite neutron scintillator in Example 1.

[0027] Figure 3 The images show SEM images (a) of the unfilled AAO template in Example 1 and (b) of the AAO template filled with carbon-doped boron-10 isotope-enriched hexagonal boron nitride.

[0028] Figure 4 The photoluminescence spectrum of the nanoarray composite neutron scintillator in Example 1 is shown.

[0029] Figure 5 This is a schematic diagram of a high-resolution neutron imaging testing system.

[0030] Figure 6 Neutron imaging results for resolving the card. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] Example 1: Preparation of Nanoarray Composite Neutron Scintillator Weigh 5 g of boron-10 isotope-enriched boric acid, 5 g of melamine, and 5 g of PEG into a 1 L beaker. Add 500 ml of deionized water, heat to 80 °C, and continuously stir magnetically for 1 hour to obtain a clear and transparent precursor solution. Place a 3 cm × 3 cm AAO template in acetone, ethanol, and deionized water, respectively, and ultrasonically clean for 15 minutes each. Dry with nitrogen gas. Completely immerse this cleaned AAO template in the precursor solution. Then, transfer the entire system to a drying oven, evaporate and concentrate at 85 °C for 6 h, and place it in a vacuum desiccator under vacuum for 30 minutes. Then, slowly restore atmospheric pressure, using the pressure difference to completely fill the pores. Finally, place the micro / nanostructure substrate in an 80 °C oven for 8 hours to allow the precursor solution to fill and solidify within the nanopores.

[0034] The dried anodized aluminum template was placed in a muffle furnace. The furnace temperature was increased to 1100 °C at a heating rate of 5 °C / min and maintained at this temperature for 8 hours for sintering. After the reaction, the furnace was programmed to cool to below 200 °C at a rate of 2 °C / min, and then allowed to cool naturally to room temperature. The sample was removed, and carbon-doped h- 10 BN nanoarray neutron scintillator. The fabrication flowchart is shown below. Figure 2 As shown.

[0035] Test Example 1: Characterization and Testing of Nanoarray Composite Neutron Scintillators like Figure 3 As shown, by comparing the SEM images of the unfilled and filled AAO templates in Example 1, it can be seen that the pores of the AAO template are densely filled, forming a highly ordered array of nanopillars with a diameter of about 200 nm that matches the pore size.

[0036] The photoluminescence (PL) spectrum of the nanoarray composite neutron scintillator prepared in Example 1 was tested at an excitation wavelength of 266 nm, as shown below. Figure 4 As shown, a strong and broad emission peak was observed at 440 nm, which confirms the effectiveness of carbon doping and its characteristics as a luminescent center.

[0037] The standard resolution test card was placed close to the nanoarray composite neutron scintillator prepared in Example 1, and combined with... Figure 5 The magnified optical path structure of the neutron imaging system. The obtained neutron imaging images are shown below. Figure 6 As shown, the scintillation screen, working in conjunction with the amplification optical path, can clearly resolve a linewidth of 800 nm, demonstrating the outstanding advantages of this method in achieving ultra-high spatial resolution.

[0038] 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 carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes, characterized in that, The preparation method includes the following steps: A precursor solution containing boron-10 isotope-enriched boron, nitrogen, and carbon sources was filled into a micro / nano structure substrate with a pore array. The substrate was then sintered to allow the precursor to react within the pores, generating carbon-doped hexagonal boron nitride enriched with boron-10 isotope and featuring a nanopillar array structure.

2. The method for preparing a carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes according to claim 1, characterized in that, The boron source is boric acid enriched with boron-10 isotopes, and the abundance of boron-10 isotopes is not less than 20%.

3. The method for preparing a carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes according to claim 1, characterized in that, The nitrogen source is at least one of melamine and urea, and the carbon source is at least one of polyethylene glycol, polyvinyl alcohol, cellulose, urea-formaldehyde resin, polystyrene, and epoxy resin.

4. The method for preparing a carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes according to claim 1, characterized in that, The mass ratio of the boron source, nitrogen source and carbon source is (1~2):(1~2):1, and the solvent of the precursor solution is deionized water or anhydrous ethanol.

5. The method for preparing a carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes according to claim 1, characterized in that, The micro / nano structure substrate is an anodic aluminum oxide template or a microfiber template.

6. The method for preparing a carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes according to claim 1 or 5, characterized in that, The pore size of the micro / nano structure substrate is 50-300 nanometers, and the thickness of the substrate is 20-200 micrometers.

7. The method for preparing a carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes according to claim 1, characterized in that, The filling method is as follows: the micro / nano structure substrate is immersed in the precursor solution, heated and dried, then vacuum dried, then restored to normal pressure, and the solution is driven to fill the pores by the pressure difference. Then the temperature is raised and dried, so that the precursor solution fills and solidifies in the nanopores.

8. The method for preparing a carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes according to claim 1, characterized in that: The in-situ reaction refers to the direct chemical reaction of the precursor within each nanopore during high-temperature sintering, generating uniformly sized, directionally arranged carbon-doped hexagonal boron nitride enriched with boron-10 isotopes.

9. A carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes, prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The spatial resolution of the scintillator is better than 1 μm.

10. An application of a carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes as described in claim 9 in neutron imaging, characterized in that, The carbon-doped hexagonal boron nitride nanoarray composite scintillator enriched with boron-10 isotopes serves as a neutron scintillator screen, and an amplification optical path is added to the imaging system. The two work together to achieve neutron imaging.

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