Three-dimensional X-ray imaging optical thin film and preparation method thereof

Abstract

The invention discloses a three-dimensional X-ray imaging optical thin film and a preparation method thereof, and belongs to the technical field of X-ray imaging. The optical thin film is formed by compounding In < 3 + >-doped CaSb2O6 fluorescent powder and a polydimethylsiloxane (PDMS) flexible polymer, the thickness is 100-500 microns, and the optical thin film has high stretchability (greater than or equal to 100%) and excellent bending stability. A 0.8-0.988 eV deep trap is introduced through In < 3 + > doping, long-acting storage (larger than or equal to 72 h) of carriers is achieved, and radiation recombination luminescence is achieved through thermal excitation of the carriers at the high temperature (such as 433 K). The film supports a three-dimensional imaging mode of first writing and then reading, internal structure information of an object is recorded through 360-degree rolling of X-rays or rolling of the object to be detected, trap information is released through programmed heating, and non-overlapping three-dimensional imaging is achieved. The method is simple in process and low in cost, can be widely applied to the fields of aero-engine blade detection, pipeline welding seam evaluation, medical intervention navigation, information encryption and the like, and has the advantages of good high-temperature stability, long cycle life (more than or equal to 50 times) and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of X-ray imaging technology, in particular to an optical film with three-dimensional imaging capability, anti-thermal quenching performance and delay reading function, as well as its preparation method, three-dimensional imaging strategy and various uses in industrial nondestructive testing, medical intervention, security and anti-counterfeiting. BACKGROUND

[0002] Traditional two-dimensional X-ray flat panel detectors (CsI: Tl, etc.) can only obtain integral projections along the ray direction when detecting complex geometric workpieces, and cannot distinguish longitudinal information, resulting in missed detection or misjudgment of defects.

[0003] In addition, the existing X-ray imaging technology (such as flat panel detector) also has the following bottlenecks: Two-dimensional overlapping imaging: unable to distinguish the longitudinal information of the internal structure of complex objects, resulting in misjudgment of damage detection; Real-time reading limitation: relying on continuous X-ray excitation, unable to realize "storage first-reading later" to reduce dose; Thermal quenching sensitivity: the fluorescence intensity sharply decays under high temperature environment, which is difficult to adapt to high temperature working conditions such as aircraft engine blades and oil and gas pipelines.

[0004] Therefore, it has become a technical problem to be solved in the field to develop a flexible optical film that can maintain high brightness and long storage life in the normal temperature to high temperature range, and can display the internal structure of three-dimensional objects in the form of two-dimensional images. In view of the above problems, a three-dimensional X-ray imaging optical film based on CaSb2O6: In 3+ fluorescent powder realizes anti-thermal quenching, long afterglow storage and high-temperature thermal excitation multi-dimensional imaging through defect state regulation.

[0005] In the present application, "trap" refers to a defect energy level in a material that can capture and store X-ray excited carriers; "writing" refers to the process of X-ray excited carriers being captured by traps; "reading" refers to the process of recording images by thermal excitation to make carriers recombine and emit light. SUMMARY

[0006] OBJECT The present application aims to provide an optical film with three-dimensional X-ray imaging function, anti-thermal quenching performance and delay reading capability, to solve the problems of two-dimensional overlap, poor thermal stability and large real-time radiation dose in the prior art.

[0007] TECHNICAL SCHEME To achieve the above-mentioned application purposes, the present application adopts the following specific technical schemes, which strictly correspond to each requirement in the claims: (1) Material composition and performance.

[0008] The three-dimensional X-ray imaging optical film is composed of a fluorescent powder material and a flexible polymer matrix. The chemical composition of the fluorescent powder material is CaSb2O6:xIn 3+ , wherein the doping concentration x ranges from 0.08% to 0.4% (mole percent). Through this doping, a trap energy level with a depth of 0.8-0.988 eV is introduced in the CaSb2O6 matrix, which is characterized by thermoluminescence test (heating rate 5 K / s). According to what is well known to those skilled in the art, the calculation formula of trap energy level E t is: E t = T m / 500, wherein T m is the temperature value corresponding to the maximum value of the thermoluminescence spectrum peak intensity. Preferably, x = 0.4%, at which the trap concentration and image storage life (≥72 h) reach the best balance.

[0009] The flexible polymer is polydimethylsiloxane (PDMS), and the mass ratio of PDMS to fluorescent powder is 1:1. The composite system endows the optical film with excellent mechanical properties, the thickness of which can be adjusted in the range of 100-500 μm, the tensile rate of which can be ≥100%, and the X-ray excitation luminescence performance and image storage function of which do not significantly decay after being repeatedly bent for 100 times.

[0010] (2) Anti-thermal quenching and high-temperature enhancement mechanism.

[0011] The material releases carriers to emit light under high-temperature thermal excitation environment after being charged by X-rays. This phenomenon is due to the thermal activation effect between the deep trap introduced by In 3+ and the luminescent center. At high temperatures, the carriers trapped by the deep trap obtain enough energy and are more effectively transferred to the luminescent center through the thermal activation process, thereby compensating for the increase in non-radiative transition probability caused by the increase in temperature, realizing luminescence. At room temperature, the stored carriers can be saved for a long time and can store images for ≥72 h after the X-rays are turned off, because the trap energy level is relatively deep and far away from room temperature (~300 K, 0.6eV), avoiding the interference of thermal disturbance at room temperature.

[0012] (3) Preparation method of the optical film.

[0013] The preparation method of the optical film comprises the following steps: a) Synthesis of phosphor: The phosphor material is composed of CaCO3, Sb2O3, In(CH3COO)3 with a molar ratio of 1:1:x, where the doping concentration x ranges from 0.08% to 0.4% (mole percent). The mixture is uniformly mixed by wet milling for 30 minutes using anhydrous ethanol as the dispersion medium. The mixed precursor is placed in an alumina crucible and heated to 1300°C at a rate of 5°C / min in an air atmosphere, and then sintered for 1-3 hours.

[0014] b) Thin film formation: The above phosphor is mixed with the PDMS precursor at a mass ratio of 1:1, and a curing agent accounting for 10% of the mass of PDMS is added. After thorough stirring, the bubbles are removed in a vacuum environment. The mixed slurry is coated on a clean quartz glass or flexible PET substrate by spin coating or blade coating.

[0015] c) Curing: The coated film is placed on a heating stage at 60°C for 2 hours to allow the PDMS to fully crosslink, resulting in a flexible and uniform optical film.

[0016] (4) Three-dimensional imaging method The three-dimensional X-ray imaging method is shown in the accompanying Figure 1 The specific steps are as follows: a) Information writing: The optical film is placed or attached to the inside or surface of the object to be measured (such as an aero-engine blade or pipe weld). A micro-focus X-ray source (typical parameters: 50 kV voltage, dose rate 6.6 mGy / s) is used to irradiate the X-ray source or the object to be measured by 360° rolling or rotating, with an irradiation time of usually 60 seconds. During this process, the structural information at different depths inside the object is recorded and stored in the film in the form of carrier trapping by traps according to the projection angle.

[0017] b) Information reading: After turning off the X-ray source, the film is moved to a dark room. Through a program of temperature rise (such as from room temperature to 433 K at a constant rate), thermal excitation promotes the release and luminescence of the trapped carriers. The luminescence images at different temperatures (corresponding to different trap depths / space information) are recorded using a CCD or CMOS camera. By algorithm, these two-dimensional projections from different "depths" can be reconstructed to obtain the non-overlapping three-dimensional structural information inside the object.

[0018] (5) Application and cycle stability The optical film can be widely used in: a) Crack detection of aero-engine blades: The film can be directly attached to the inner wall of the blade for online detection at a working temperature of 433 K or even higher, with consistent imaging clarity at room temperature.

[0019] b) Assessment of oil and gas pipeline welds: A thin film can be pre-placed at the weld and read after a delay following a single exposure, reducing the radiation dose to operators.

[0020] c) Medical interventional catheter navigation: Utilizing its flexibility, it can be integrated into the catheter tip to perform imaging navigation of internal structures such as blood vessels.

[0021] d) Optical information encryption: Utilizing its long persistence storage characteristics, information can be "written first and then decrypted".

[0022] The film exhibits excellent cycling stability, supporting at least 50 cycles of "X-ray writing - 365 nm UV erasure (30-second irradiation)" with an intensity decay rate of less than 5%.

[0023] Beneficial effects Compared with the prior art, the present invention has the following significant advantages: (1) For the first time, three core functions, namely “three-dimensional imaging, thermal quenching and delayed reading”, are integrated into a single thin film; (2) Flexible films can be directly placed inside complex curved surfaces such as engine blades and pipe welds, filling the gap of traditional rigid detectors; (3) The process is simple, the cost is low, and it is easy to achieve large-scale preparation.

[0024] (4) Stable operation under high temperature conditions (≥433 K), suitable for online detection of defects in aero engines. Attached Figure Description

[0025] Figure 1 Schematic diagram of three-dimensional X-ray imaging method; Figure 2 CaSb₂O₆:xIn 3+ XRD patterns of different doping concentrations; Figure 3 CaSb₂O₆:xIn 3+ TL shift spectra at different doping concentrations; Figure 4 CaSb2O6: 0.4% In 3+ Scanning electron microscope image of the phosphor; Figure 5 CaSb2O6: 0.4% In 3+ Thermoluminescence (TL) curves under different X-ray irradiation times; Figure 6 CaSb2O6: 0.4% In 3+ Optical spectra at different X-ray doses; Figure 7 CaSb2O6: 0.4% In 3+TL intensity map after 72 hours; Figure 8 CaSb2O6:0.4% In 3+ Emission spectra at different temperatures (room temperature - 433 K, intensity vs. wavelength); Figure 9 Photos of the imaging stability of the prepared optical thin film in the rolled and stretched state of the flexible film; Figure 10 Comparison of two-dimensional imaging and three-dimensional imaging. DETAILED DESCRIPTION

[0026] The application will be further described below in connection with specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not used to limit the protection scope of the application. In addition, it should be understood that after reading the disclosure of the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the protection scope defined by the application.

[0027] Example 1: CaSb2O6:0.4 %In 3+ Synthesis of phosphor CaCO3 1.000 g, Sb2O3 2.915 g, In(CH3COO)3 0.0117 g (corresponding to 0.4 % In 3+ ) were weighed, wet-milled in 5 mL anhydrous ethanol for 30 min; the mixture was placed in an alumina crucible and sintered at 1300 °C in air atmosphere for 1 h, and after cooling, the white CaSb2O6:0.4 %In 3+ phosphor was obtained by grinding. The XRD was consistent with the standard card PDF #46-1496, and no impurity phase was present, as shown in Figure 2 . Figure 3 TL shift map for CaSb2O6:xIn 3+ , it can be seen that as the doping concentration increases, the TL peak gradually shifts to a deep energy level. Figure 4 SEM image of CaSb2O6:0.4% In 3+ material, it can be seen that the example exhibits the common morphology of inorganic powder, and In 3+ has been successfully doped into the sample. Figure 5 The TL map of the sample under the same dose and different X-ray irradiation times is shown, which shows that the sample has a storage effect on X-rays, and at the same time shows that the stored carriers can be released again under thermal stimulation. Figure 6 The sample exhibits blue light emission around 460 nm under different X-ray power irradiation. At the same time, the sample was tested for storage time after X-ray irradiation, and the TL map showed that after 72 hours, the TL intensity could still be detected.

[0028] Example 2: CaSb2O6: 0-0.32 % In 3+ Synthesis of phosphor CaCO3 1.000 g, Sb2O32.915 g, In(CH3COO)30-0.0094 g (corresponding to 0% - 0.32 % In 3+ ) were weighed, and 5 mL of anhydrous ethanol was added for wet grinding for 30 min; the mixture was placed in an alumina crucible and sintered at 1300 °C in air for 1 h. After cooling, the white CaSb2O6: 0.08% - 0.32 % In 3+ phosphor was obtained by grinding. XRD was consistent with standard card PDF #46-1496, and no impurities were observed, as shown in Figure 2 .

[0029] Example 3: Preparation of optical thin film CaCO3 1.000 g, Sb2O32.915 g, In(CH3COO)30.0117 g (corresponding to 0.4 % In 3+ ) were weighed, and 5 mL of anhydrous ethanol was added for wet grinding for 30 min; the mixture was placed in an alumina crucible and sintered at 1300 °C in air for 1 h. After cooling, the white CaSb2O6: 0.4 % In 3+ phosphor was obtained by grinding. XRD was consistent with standard card PDF #46-1496, and no impurities were observed. Polydimethylsiloxane (PDMS) solvent and CaSb2O6: 0.4 % In 3+ were mixed in a weight ratio of 1:1 to prepare a solution. Then, a curing agent and PDMS were added to the solution in a weight ratio of 1:10. The solution was stirred at room temperature for 1 hour. The glass substrate was then ultrasonically cleaned, and the glass substrate was sequentially ultrasonically cleaned with alcohol, acetone, and deionized water for 30 min each, and then placed in a drying box for drying. The prepared precursor solution was coated on the substrate, and a thin film was formed by scraper movement, and then placed on a heating platform for annealing treatment at 50 °C for 6 hours. After annealing, the optical thin film was obtained. The thin film was placed on a temperature control platform, and the emission spectrum (λ ex = 300 nm) was measured at different temperature points. The results showed that the integral intensity at 433 K was 3.72 times that at 298 K, and there was no obvious quenching, as shown in Figure 8 . Figure 9 The film was shown to be stable in curling and stretching.

[0030] Example 4: Verification of three-dimensional X-ray imaging Test object: curled metal sheet (outer diameter 16 mm, wall thickness 1 mm, to test three-dimensional imaging quality).

[0031] Steps: Attaching the thin film to the crimped metal inner wall; Placing the sample to be tested under the microfocus X-ray source (50 kV, 6.6 mGy / s) for 360° rotation irradiation for 60 s; Turning off the X-ray, and the thin film is left in the dark box for 5 min; Unfolding the optical film and heating to 433 K, while recording optical images using a camera; The three-dimensional image has no background overlap compared with the two-dimensional image, as shown in Figure 10 . Figure 10 The three-dimensional image shown is reconstructed by the following steps: recording luminescence images at different temperatures, extracting trap release signals of each layer, and reconstructing the three-dimensional structure using back projection algorithms (such as FDK or iterative reconstruction).

[0032] Example 5: Delayed reading and cycle stability After the thin film is written by X-ray, it is placed at room temperature for 72 h, and still has a strong thermoluminescence spectrum; irradiation with a 365 nm LED for 30 s can completely erase it, and repeated writing / erasing cycles for 50 times, the luminescence intensity attenuation is <5%.

[0033] Example 6: High temperature working condition simulation Placing the thin film in the high temperature heating table to simulate the working state of the engine aluminum alloy blade inside, after continuous operation at 433 K for 2 h, immediately perform X-ray imaging, the crack image has the same clarity as at room temperature, verifying the high temperature reliability.

[0034] The above describes the embodiments of the present application. However, the present application is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An optical thin film with three-dimensional X-ray imaging function, characterized in that: a) Composed of phosphor and flexible polymer; b) The phosphor is CaSb2O6:xIn 3+ ; c) The flexible polymer is polydimethylsiloxane (PDMS); d) The optical thin film has a deep trap of 0.8–0.988 eV, enabling it to store images for ≥72 h after X-ray shutdown and to reread the images under thermal excitation conditions; e) The imaging clarity of the optical thin film is consistent with that at room temperature when operating in a high-temperature environment.

2. The optical thin film according to claim 1, characterized in that: The phosphor is CaSb2O6:xIn 3+ Where 0.08%≤x≤0.4%, preferably, x is 0.

4.

3. The three-dimensional X-ray imaging optical thin film according to claim 1 or 2, characterized in that, The deep trap energy level was obtained by thermoluminescence testing at a heating rate of 5 K / s.

4. The three-dimensional X-ray imaging optical thin film according to claim 1 or 2, characterized in that, After being charged with X-rays, the optical thin film emits light under subsequent high-temperature thermal excitation.

5. The three-dimensional X-ray imaging optical thin film according to claim 1 or 2, characterized in that, After the optical film operates continuously at a high temperature of 433 K for 2 hours, the imaging clarity is consistent with that at room temperature.

6. The method for preparing the optical thin film according to any one of claims 1-5, characterized in that: a) Mix CaCO3, Sb2O3, and In(CH3COO)3 in a molar ratio, wet mill with ethanol for 30 min, and sinter at 1300 ℃ for 1-3 h to obtain CaSb2O6:xIn 3+ The preferred phosphor has a sintering time of 1 hour. b) Mix the obtained phosphor with PDMS at a mass ratio of 1:1, degas under vacuum, and spin-coat the mixture into a film. c) Curing at 60 ℃ for 2 h yields a flexible optical film.

7. A three-dimensional X-ray imaging method, characterized in that, The optical thin film of any one of claims 1-5 comprises: a) Place the optical thin film as described in claims 1-4 inside the object being tested; b) Irradiate the image with an X-ray source at a dose rate of 6.6 mGy / s for 60 s to complete the image information writing; c) After turning off the X-rays, the trap information is read by heating the device through a program to achieve non-overlapping three-dimensional imaging.

8. The three-dimensional X-ray imaging method according to claim 7, characterized in that, The rolling irradiation is a 360° rotating irradiation.

9. The use of the optical thin film according to claims 1-5 in crack detection of aero-engine blades, evaluation of weld seams in oil and gas pipelines, navigation of medical interventional catheters, or encryption of optical information.

10. The use according to claim 8, characterized in that, The optical film supports ≥50 write / erase cycles with an intensity decay of <5%.

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