GOS scintillation ceramic capable of regulating and controlling pore distribution based on grain boundary as well as preparation method and application of GOS scintillation ceramic

Abstract

The invention relates to a GOS scintillation ceramic based on grain boundary regulation and control of pore distribution and a preparation method and application thereof, the preparation method comprises the following steps: adding gadolinium oxysulfide and a dispersant, and preparing fully dispersed gadolinium oxysulfide slurry; in a strong magnetic field environment greater than 1T, forming by using a slurry suction mold, and preferentially arranging c axes of the gadolinium oxysulfide particles along the magnetic field direction; demolding and drying a formed wet blank; pre-sintering the dried green body at the temperature of between 800 and 1,200 DEG C; and sintering at 1750-1900 DEG C by adopting spark plasma sintering (SPS) to finally prepare the gadolinium oxysulfide scintillation ceramic with directionally arranged grains, namely the GOS scintillation ceramic based on grain boundary regulation and control of pore distribution. Compared with the prior art, the method has the advantages that the magnetic field orientation technology and the advanced spark plasma sintering (SPS) technology are combined, the preparation process is systematically optimized, and the material performance and the production efficiency are both improved.

Description

Technical Field

[0001] The invention belongs to the field of scintillation ceramics, and relates to a GOS scintillation ceramic based on grain boundary regulation of pore distribution, and a preparation method and application thereof. Background Art

[0002] Gadolinium oxysulfide (GOS) ceramic scintillator has the advantages of high X-ray conversion efficiency, short afterglow, good irradiation stability, no moisture absorption, no dissociation, etc. For example, CN114031403A discloses a method for preparing gadolinium oxysulfide scintillator ceramics, which uses vacuum hot pressing sintering or spark plasma sintering to sinter Gd in one step. 2 O 2 S scintillating powder is sintered to efficiently obtain gadolinium oxysulfide scintillating ceramics doped with at least one element of Pr, Eu, Tb, Sm, Yb, and Tm, thereby ensuring that the finished gadolinium oxysulfide scintillating ceramics have fine grain size and high density.

[0003] However, traditional gadolinium oxysulfide (GOS) scintillating ceramics have low transmittance due to light reflection, refraction and birefringence effects at the grain boundaries. The optical transmittance of GOS ceramics is greatly reduced due to the disordered grain structure, which affects its application in radiation detection, medical imaging and particle physics experiments. Summary of the invention

[0004] The purpose of the present invention is to provide a GOS scintillating ceramic based on grain boundary regulation of pore distribution and its preparation method and application, combining the strong magnetic field induced preferential orientation technology to achieve grain boundary control of multiple pores, and the spark plasma sintering (SPS) process, successfully achieving high densification of ceramic materials and consistent arrangement of grain optical axes, fundamentally reducing the reflection, refraction and birefringence effects of light at the grain boundary, and reducing large-scale pores, while optimizing small-scale pore structures, thereby improving light output. This method not only significantly improves the light transmittance of GOS ceramics, but also reduces production costs by optimizing the process flow, and achieves efficient and energy-saving one-time molding.

[0005] The purpose of the present invention can be achieved by the following technical solutions: The first object of the present invention is to provide a method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution, the preparation method comprising the following steps: S1. Add gadolinium oxysulfide and a dispersant to prepare a fully dispersed gadolinium oxysulfide slurry; S2, in a strong magnetic field environment greater than 1 T, using a slurry absorption mold to shape the gadolinium oxysulfide slurry obtained in step S1, so that the c-axis of the gadolinium oxysulfide particles is preferentially arranged along the magnetic field direction, to obtain a molded wet blank; S3, demoulding and drying the formed wet blank obtained in step S2 to obtain a dried blank; S4, pre-sintering the dried green body obtained in step S3 at 800-1200° C. to remove the dispersant and organic matter, thereby obtaining a pre-sintered ceramic; S5, sintering the pre-fired ceramic obtained in step S4 at 1750-1900° C. by spark plasma sintering (SPS), and finally preparing gadolinium oxysulfide scintillation ceramic with oriented grain arrangement, that is, the GOS scintillation ceramic with pore distribution regulated by grain boundaries.

[0006] Furthermore, the preparation method comprises the following steps: 1. Raw material preparation Use gadolinium oxysulfide powder with a purity of ≥99.995% as the base material, add an appropriate amount of sintering aid (such as LiF or KCl) according to the mass ratio to promote densification and grain refinement during the sintering process, and also add a dispersant. After mixing the above raw materials, prepare a fully dispersed gadolinium oxysulfide slurry to ensure uniform distribution of particles and suspension stability.

[0007] 2. Magnetic field forming The prepared gadolinium oxysulfide slurry is injected into the slurry absorption mold and placed in a 10T-20T strong magnetic field environment for molding. Since the magnetic susceptibility of the gadolinium oxysulfide grains in the a-axis and b-axis directions is similar, but the magnetic susceptibility is higher in the c-axis direction, the magnetic field can induce the c-axis of the particles to preferentially align along the magnetic field direction. During the slurry absorption process, as the water is discharged, the gadolinium oxysulfide particles in the slurry gradually form a directional wet blank on the mold surface.

[0008] 3. Pre-burning treatment The wet blank is demolded and dried, and then pre-sintered at 800-1200°C. The main purpose of this step is to remove the dispersant and other organic matter in the slurry, provide a pure material environment for subsequent sintering, and retain the preferred orientation structure of the particles.

[0009] 4. Spark plasma sintering (SPS) The pre-sintered green body is sintered under optimized spark plasma sintering conditions (temperature 1750-1900℃, pressure 50-100 MPa, heating rate 10-50℃ / min, holding time 0.5-3 hours). The rapid heating and efficient sintering characteristics of the SPS process significantly shorten the sintering time, while maintaining the preferred orientation of the particles and further improving the density of the ceramic.

[0010] Furthermore, the method for preparing the fully dispersed gadolinium oxysulfide slurry is ball milling, and the ball milling time is 10 to 30 hours.

[0011] Furthermore, the dispersant is anhydrous ethanol.

[0012] Furthermore, the added amount of the dispersant is 0.5wt% of the added amount of gadolinium oxysulfide.

[0013] Furthermore, in step S1, a sintering aid is also added.

[0014] Furthermore, the added amount of the sintering aid is 0.1-1wt% of the added amount of gadolinium oxysulfide.

[0015] Furthermore, the sintering aid is one or more of LiF and KCl.

[0016] Furthermore, in step S2, the magnetic induction intensity of the strong magnetic field is 10T-20T.

[0017] Furthermore, the spark plasma sintering is performed at a heating rate of 10-50°C / min, a holding time of 0.5-3 hours, and a pressure of 50-100 MPa.

[0018] Furthermore, the linear transmittance of the GOS scintillating ceramic based on grain boundary regulation of pore distribution is increased by more than 20% compared with disordered grain ceramics.

[0019] Furthermore, in step S3, the drying condition is: drying at 60° C. for 10 to 20 hours.

[0020] Furthermore, in step S4, the pre-burning time is 1 to 5 hours.

[0021] Furthermore, in step S1, at least one element selected from Pr, Eu, Tb, Sm, Yb and Tm is doped, and the doping amount is 0.1-1wt% of the added amount of gadolinium oxysulfide.

[0022] The second object of the present invention is to provide a GOS scintillation ceramic with pore distribution regulated by grain boundaries, wherein the compressive strength of the GOS scintillation ceramic with pore distribution regulated by grain boundaries is 400-500 MPa.

[0023] The third object of the present invention is to provide an application of GOS scintillation ceramics based on grain boundary regulation of pore distribution, and to use the gadolinium oxysulfide scintillation ceramics for radiation detection, medical imaging, and particle physics research.

[0024] The optical axes of all or part of the grains of the gadolinium oxysulfide scintillating ceramic are arranged in the same direction, thereby effectively avoiding or reducing the birefringence effect of light between adjacent grains and significantly improving the linear transmittance. The size, distribution and state of the grain boundaries directly affect the performance of the overall material. In particular, the arrangement of the grains in the material and the characteristics of the grain boundaries determine the microstructure and pore distribution of the material. By precisely controlling the orientation of the grains and the distribution of the grain boundaries, the formation of pores and the pore structure can be optimized while improving the strength of the material. By controlling the grain boundaries, the formation of large-scale pores can be effectively suppressed, and the distribution of small-scale pores can be optimized, thereby improving the density and uniformity of the material, and further improving its mechanical properties and radiation transmittance. The preparation method includes placing a fully dispersed gadolinium oxysulfide slurry in a strong magnetic field to form a green blank with a preferred orientation, and then optimizing the sintering temperature and pressure conditions through a spark plasma sintering process (SPS) to achieve one-time molding, avoiding the high cost and complexity of the traditional hot isostatic pressing (HIP) process. The preparation method of the invention is simple, efficient and energy-saving, and the prepared gadolinium oxysulfide scintillation ceramic can be widely used in the fields of radiation detection, medical imaging, particle physics research, etc.

[0025] Compared with the prior art, the present invention has the following characteristics: 1) The GOS scintillating ceramics based on grain boundary regulation of pore distribution provided by the present invention, in order to fundamentally solve the long-standing technical problem of low light transmittance of traditional gadolinium oxysulfide (GOS) scintillating ceramics caused by light reflection, refraction and birefringence effects at grain boundaries, the present invention proposes a new method for preparing GOS scintillating ceramics with oriented grain arrangement. This method systematically optimizes the preparation process by combining magnetic field orientation technology and advanced spark plasma sintering (SPS) technology, thereby achieving a dual improvement in material performance and production efficiency.

[0026] 2) The GOS scintillating ceramics provided by the present invention, which regulate the pore distribution based on grain boundaries, use a strong magnetic field (magnetic induction intensity ≥ 1T, usually 10T-20T) to apply directional control to the GOS particles, so that the optical axis of the grains is preferentially oriented along the direction of the magnetic field, thereby significantly reducing or avoiding the scattering and interference of light at the grain boundaries. And by making the optical axis passing through the grains along the direction of the magnetic field, thereby controlling the grain boundaries, it is possible to effectively reduce large-scale pores, while optimizing the small-scale pore structure, making the material more uniform and improving its mechanical properties, and increasing the light output of the material. Due to the disordered grain structure, the optical transmittance of GOS ceramics is greatly reduced, which affects its application effect in the fields of radiation detection, medical imaging, and particle physics experiments. The present invention uses magnetic field orientation technology to significantly improve the consistency of the c-axis direction of the particles, successfully solving the above problems.

[0027] 2) The GOS scintillating ceramics provided by the present invention, which are based on grain boundary regulation of pore distribution, further use the SPS process to optimize the sintering process, and achieve high densification and grain refinement of ceramic materials by accurately controlling key parameters such as sintering temperature, pressure and holding time. The rapid heating and short-time high-pressure sintering characteristics of the SPS process not only significantly reduce the sintering temperature (usually between 1750-1900°C), but also avoid the high energy consumption, high cost and multi-step processing complexity commonly seen in the traditional hot isostatic pressing (HIP) process, successfully achieving one-time molding, and significantly improving production efficiency and material performance stability.

[0028] 2) Compared with the traditional method, the innovative point of the method of the present invention is that the synergistic effect of the magnetic field and the preferred orientation of particles is fully considered in the preparation process, and the high-efficiency sintering characteristics of the SPS process are combined to maximize the optical properties and mechanical strength of GOS ceramics by systematically optimizing the entire process from raw material preparation to final sintering. The overall process has significant advantages in energy saving and low cost. The prepared GOS ceramic material exhibits comprehensive characteristics of oriented grain arrangement, high density, and excellent light transmittance, and can be widely used in radiation detection, X-ray medical imaging, high-energy particle detection and other fields.

[0029] In summary, the present invention successfully prepared gadolinium oxysulfide scintillating ceramics with preferential grain orientation, and the consistency of its optical axis direction significantly improved the optical performance, avoided the interference of traditional ceramic grain boundaries on light, and significantly improved the transmittance. In addition, the present invention combines the advantages of strong magnetic field induction and SPS technology, which not only solves the high cost and complexity of traditional hot isostatic pressing (HIP) process, but also realizes the prospect of energy-saving and environmentally friendly industrial application. The material can be widely used in radiation detection, medical imaging, high-energy particle research and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the XRD pattern of the GOS scintillating ceramic prepared in Example 1 based on grain boundary regulation of pore distribution.

[0031] Figure 2 This is a photo of the GOS scintillating ceramic prepared in Example 1 based on grain boundary regulation of pore distribution. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the accompanying drawings and the following embodiments are only used to illustrate the present invention, rather than to limit the present invention. It should be pointed out that for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0033] Any features such as preparation methods, materials, structures or composition ratios that are not clearly described in this technical solution shall be deemed as common technical features disclosed in the prior art.

[0034] Gadolinium oxysulfide powder is commercially available gadolinium oxysulfide phosphor with a purity of ≥99.995%.

[0035] Example 1

[0036] This embodiment provides a GOS scintillation ceramic for regulating pore distribution based on grain boundaries, comprising the following steps: Weigh 5g of gadolinium oxysulfide powder and add 0.5% (0.025g) of LiF sintering aid according to the mass ratio. Use anhydrous ethanol as the dispersion medium (dispersant), add 0.5% (0.025g) of anhydrous ethanol according to the mass ratio, and perform high-speed ball milling in a ball mill. The ball milling time is set to 12 hours and the ball-to-material ratio is 5:1. Zirconia beads with a diameter of 4mm are used during the ball milling process to ensure that the slurry is fully dispersed and the particle size distribution is uniform. Inject the prepared slurry into a specially designed (specifically: the mold is designed as multiple parallel chambers, multiple micro-channels are designed at the bottom of the mold, a magnet is placed in the mold, a heating belt is set outside the mold or a heating element is embedded in the mold, and the mold surface can be coated with an aluminum oxide coating material) slurry absorption mold, and the mold is placed in a strong magnetic field environment of 10T for molding. The direction of the magnetic field is perpendicular to the mold base, and the c-axis of the particles tends to be arranged along the magnetic field direction by utilizing the characteristic that the magnetic susceptibility of gadolinium oxysulfide grains in the c-axis direction is significantly higher than that of the a-axis and b-axis. During the slurry absorption process, excess dispersion medium is gradually discharged under vacuum conditions to form a wet green body structure. After molding, the wet green body is demolded from the mold and placed in a drying oven, and slowly dried at 60°C for 12 hours to prevent cracks or deformation. The dried green body is then placed in a muffle furnace and pre-fired at 900°C in an air atmosphere for 1 hour. The pre-fired green body is finally sintered using a spark plasma sintering device. The specific parameters are: sintering temperature 1800°C, sintering pressure 80 MPa, heating rate 20°C / min, and holding time 1 hour. The rapid heating and high pressure conditions of SPS sintering effectively inhibit excessive grain growth while maintaining the preferential orientation of the grains. The sintering process is completed in an argon protective atmosphere to obtain GOS scintillating ceramics with pore distribution regulated by grain boundaries, such as Figure 1 , 2 shown.

[0037] Example 2

[0038] This embodiment provides a GOS scintillation ceramic for regulating pore distribution based on grain boundaries, comprising the following steps: Weigh 15g of high-purity (≥99.995%) gadolinium oxysulfide powder and add 0.3% (0.045g) of KCl as a sintering aid. Mix the above raw materials with 0.075g of anhydrous ethanol and place them in a ball mill for full dispersion. The ball milling time is set to 24 hours, the ball-to-material ratio is 8:1, and the ball milling medium is 6mm in diameter. Zirconia beads. During the ball milling process, ensure that the slurry is evenly dispersed and the particle size is controlled in the micron range. Inject the prepared gadolinium oxysulfide slurry into the slurry absorption mold and place it in a superconducting magnet with a magnetic induction intensity of 20T for molding. The direction of the magnetic field is perpendicular to the bottom of the mold. The c-axis of the gadolinium oxysulfide particles tends to be preferentially arranged along the magnetic field direction by taking advantage of the fact that the magnetic susceptibility of the gadolinium oxysulfide particles in the c-axis direction is greater than that of the a-axis and b-axis. During the slurry absorption process, the dispersion medium in the slurry is gradually removed under a vacuum environment, and the preferential orientation state of the particles is maintained during the formation of the wet blank. After the formed wet blank is demolded from the mold, it is slowly dried in a 60°C drying oven for 16 hours to prevent cracking or deformation. The dried blank is then placed in an air atmosphere and pre-fired in a muffle furnace at 1000°C for 2 hours. The pre-firing treatment can effectively remove the residual organic dispersant in the slurry and enhance the mechanical stability of the blank while retaining the preferred orientation of the particles. The pre-fired blank is finally sintered using a spark plasma sintering device. The sintering conditions are set as follows: sintering temperature 1900°C, pressure 100 MPa, heating rate 20°C / min, holding time 2 hours, and the entire process is completed in an argon protective atmosphere to obtain GOS scintillating ceramics with pore distribution regulated by grain boundaries.

[0039] Comparative Example 1 This comparative example provides a gadolinium oxysulfide scintillation ceramic, which is different from Example 1 in that in this comparative example, the mold is placed in an environment without an external magnetic field for molding to obtain the gadolinium oxysulfide scintillation ceramic.

[0040] Comparative Example 2 This comparative example provides a gadolinium oxysulfide scintillation ceramic, which is different from Example 1 in that, in this comparative example, a conventional hot isostatic pressing (HIP) process is used to perform final sintering on the pre-sintered green body, and the conditions of the conventional hot isostatic pressing (HIP) process are as follows: the sintering temperature is set at about 1550°C, the pressure is set at about 150MPa, the sintering time is usually 3 hours, the heating rate is controlled at 7°C / min, the cooling rate is 15°C / min, and the process is carried out under argon gas to obtain the gadolinium oxysulfide scintillation ceramic.

[0041] The gadolinium oxysulfide scintillating ceramic with preferred orientation obtained in Example 1 has a compressive strength of 445 MPa, a flexural strength of 197 MPa, a surface hardness of 8HV level, high mechanical strength, a light transmittance of 64%, and excellent optical properties.

[0042] The gadolinium oxysulfide scintillating ceramic with preferred orientation obtained in Example 2 has a compressive strength of 392 MPa, a flexural strength of 221 MPa, a surface hardness of 9HV level, high mechanical strength, a light transmittance of 59%, and excellent optical properties.

[0043] The gadolinium oxysulfide scintillating ceramic obtained in Comparative Example 1 has a preferred orientation and has a compressive strength of 342 MPa, a flexural strength of 160 MPa, a surface hardness of 8 HV level, and a light transmittance of 51%.

[0044] The gadolinium oxysulfide scintillating ceramic obtained in Comparative Example 2 has a preferred orientation and has a compressive strength of 342 MPa, a flexural strength of 181 MPa, a surface hardness of 9 HV level, and a light transmittance of 48%.

[0045] Through the process flow of this application, the present invention successfully prepared gadolinium oxysulfide scintillating ceramics with preferential grain orientation, and the consistency of its optical axis direction significantly improved the optical performance, avoided the interference of traditional ceramic grain boundaries on light, and significantly improved the transmittance. In addition, the present invention combines the advantages of strong magnetic field induction and SPS technology, which not only solves the high cost and complexity of traditional hot isostatic pressing (HIP) process, but also realizes the prospect of energy-saving and environmentally friendly industrial application. This material can be widely used in radiation detection, medical imaging, high-energy particle research and other fields.

[0046] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution, characterized in that: The preparation method comprises the following steps: S1. Add gadolinium oxysulfide and a dispersant to prepare a dispersed gadolinium oxysulfide slurry; S2, in a strong magnetic field environment greater than 1 T, using a slurry absorption mold to shape the gadolinium oxysulfide slurry obtained in step S1, so that the c-axis of the gadolinium oxysulfide particles is preferentially arranged along the magnetic field direction, to obtain a molded wet blank; S3, demoulding and drying the formed wet blank obtained in step S2 to obtain a dried blank; S4, pre-firing the dried green body obtained in step S3 at 800-1200° C. to obtain a pre-firing ceramic; S5, sintering the pre-fired ceramic obtained in step S4 at 1750-1900° C. by spark plasma sintering to finally prepare gadolinium oxysulfide scintillation ceramic with oriented grain arrangement, that is, the GOS scintillation ceramic with pore distribution regulated by grain boundaries.

2. The method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution according to claim 1, characterized in that: The dispersant is anhydrous ethanol; The added amount of the dispersant is 0.5wt% of the added amount of gadolinium oxysulfide.

3. The method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution according to claim 1, characterized in that: In step S1, a sintering aid is also added; The amount of the sintering aid added is 0.1-1wt% of the amount of gadolinium oxysulfide added; The sintering aid is one or more of LiF and KCl.

4. The method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution according to claim 1, characterized in that: In step S2, the magnetic induction intensity of the strong magnetic field is 10T-20T.

5. The method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution according to claim 1, characterized in that: The spark plasma sintering adopts a heating rate of 10-50°C / min, a holding time of 0.5-3 hours, and a pressure of 50-100 MPa.

6. The method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution according to claim 1, characterized in that: The linear transmittance of the GOS scintillating ceramics based on grain boundary regulation of pore distribution is increased by more than 20% compared with disordered grain ceramics.

7. The method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution according to claim 1, characterized in that: In step S3, the drying condition is: drying at 60° C. for 10 to 20 hours.

8. The method for preparing GOS scintillating ceramics based on grain boundary regulation of pore distribution according to claim 1, characterized in that: In step S4, the pre-burning time is 1 to 5 hours.

9. A GOS scintillating ceramic with pore distribution regulated by grain boundaries obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The compressive strength of the GOS scintillating ceramic based on grain boundary regulation of pore distribution is 400-500 MPa.

10. An application of GOS scintillating ceramics based on grain boundary controlled pore distribution obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The gadolinium oxysulfide scintillating ceramic is used for radiation detection, medical imaging, and particle physics research.

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