High-lead-equivalent lutetium oxide transparent ceramic as well as preparation method and application thereof

Abstract

The invention provides high-lead-equivalent lutetium oxide transparent ceramic as well as a preparation method and application thereof, and belongs to the technical field of transparent ceramic preparation. The element composition of the high-lead-equivalent lutetium oxide transparent ceramic provided by the invention is (Lu < 1-x > Hf < x >) 2O3, x is 0.03-0.05, and the preparation method of the high-lead-equivalent lutetium oxide transparent ceramic comprises the step of preparing lutetium oxide powder and hafnium oxide through a solid phase method. The high-lead-equivalent lutetium oxide transparent ceramic provided by the invention has the characteristics of high lead equivalent, high density, high transmittance and good shielding performance, and can be well used as a radiation shielding material.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of transparent ceramics, and particularly relates to a high lead equivalent lutetium oxide transparent ceramic, a preparation method thereof and an application thereof. Background Art

[0002] A radiation shielding material is a material used to absorb or attenuate ionizing radiation (such as X-rays, γ-rays, neutron radiation, etc.), and is widely used in the nuclear industry, medical treatment, aerospace, military and other fields. Transparent ceramic materials are a type of ceramic materials with optical transparency, and have characteristics such as high strength, high temperature resistance and corrosion resistance. Compared with glass and single crystals, they have better mechanical properties, thermal stability and corrosion resistance, and the manufacturing process is relatively simple. Currently, they are an ideal radiation shielding window material.

[0003] Although traditional radiation shielding materials (such as lead glass) and existing transparent ceramic materials (such as Al2O3, YAG) have excellent light transmittance, their lead equivalent is relatively low and their radiation shielding performance is insufficient. It is necessary to increase the thickness to improve the protection ability, resulting in a significant increase in the volume and cost of the equipment.

[0004] Introducing PbO (20 - 60wt%) into silicate or phosphate glass to form a lead-containing crystal phase (such as PbF2), which has both X / γ-ray shielding and visible light transparency (light transmittance 70 - 85%), and can be used for medical CT observation windows and nuclear facility windows.

[0005] However, due to the excessive lead content in mainstream lead-containing shielding materials, there is an environmental pollution risk in the production and waste disposal links, and it conflicts with the restrictive requirements of international environmental protection regulations (such as RoHS) for the use of lead. Although the environmental protection performance of existing lead-free alternative materials (such as Bi2O3-based composites) has been improved, their shielding performance has been significantly reduced, and they cannot meet the requirements of high-energy ray protection scenarios (such as medical CT, industrial flaw detection) at the same thickness.

[0006] In addition, the lutetium oxide (Lu2O3) ceramics prepared by traditional sintering processes have problems such as grain boundary impurity segregation (such as Si, Ca residues) and pores, resulting in a decrease in the light transmittance, deterioration of the mechanical properties and a decrease in the lead equivalent of the material. Lattice oxygen vacancy defects further cause the discoloration of the material in a radiation environment, reducing its long-term stability and restricting its application in harsh scenarios.

[0007] Therefore, how to provide a transparent ceramic material that can achieve a high lead equivalent under lead-free conditions, and has a high ceramic density, high transmittance and good shielding performance has become an urgent technical problem to be solved. Summary of the Invention

[0008] The present invention is to solve the above technical problems, and thus provides a high lead equivalent lutetium oxide transparent ceramic and its preparation method and application. The technical object of the present invention is to solve the problems that when lead is added to existing transparent ceramics, it is easy to result in a high lead content, but when lead is reduced, it cannot meet the high lead equivalent, and at the same time, its transmittance is low, the ceramic density is low, and the shielding performance is not high enough. It provides a lutetium oxide transparent ceramic with a high lead equivalent and its preparation method, realizes the simplification of the preparation process, and the prepared lutetium oxide ceramic still has a high lead equivalent without adding lead, and at the same time its optical quality is extremely excellent.

[0009] In order to achieve the above technical object, the technical solution adopted by the present invention is as follows:

[0010] One of the objects of the present invention is to provide a high lead equivalent lutetium oxide transparent ceramic, and the element composition of the transparent ceramic is (Lu 1-x Hf x )2O3, where x = 0.03 - 0.05.

[0011] The high lead equivalent lutetium oxide transparent ceramic provided by the present invention has a high lead equivalent without adding lead, and the transparent ceramic has a high density, a high transmittance, and good shielding performance. As shown in the comparative example of the present invention, when the value range of x is not within the parameters defined by the present invention (such as x = 0.01, or x = 0.07 - 0.09), it will cause a significant decline in the performance of the lutetium oxide transparent ceramic.

[0012] The second object of the present invention is to provide a preparation method of the high lead equivalent lutetium oxide transparent ceramic as described above, including the following steps:

[0013] (1) Preparation of precursor powder: Using lutetium oxide powder as the raw material, adding hafnium oxide to the lutetium oxide, adopting the solid-phase method, through ball milling, mixing, drying and sieving, and then through a first high-temperature calcination, the calcined powder is ball milled, mixed, dried and sieved again, and finally through a second high-temperature calcination to obtain the precursor powder; the addition amount of hafnium oxide is 3 - 5 at% of the lutetium oxide atomic number;

[0014] (2) Green body forming: Using a two-step pressure forming process of dry pressing and cold isostatic pressing to form the precursor powder obtained in step (1) into a ceramic green body;

[0015] (3) Ceramic sintering: Placing the ceramic green body prepared in step (2) in a vacuum environment, sintering at 1860 °C for 8 hours to obtain a pure phase ceramic, and annealing and polishing the pure phase ceramic to obtain a lutetium oxide transparent ceramic material.

[0016] Through component optimization and process innovation, the present invention dopes 1 - 9 at% of HfO2 in the Lu2O3 matrix, and utilizes Hf 4+ and Lu 3+The ionic radius matching forms a solid solution, significantly reducing the grain boundary migration energy barrier and promoting the densification of the ceramic. The high density characteristic of HfO2 further increases the density of the ceramic body. Combining the high atomic number characteristics of Lu (Z = 71) and Hf (Z = 72), through the synergistic effect of the photoelectric effect and Compton scattering, the high lead equivalent radiation shielding performance under lead-free conditions is achieved. At the same time, the present invention adopts a two-step ball milling process to optimize the powder quality: the raw materials are crushed to the sub-micron level through primary milling to reduce hard agglomeration; and then through secondary ball milling, the powder is further refined, and combined with vacuum sintering, a nearly fully dense transparent ceramic material is obtained.

[0017] In addition, the present invention compensates for oxygen vacancies through HfO2 doping, and combined with vacuum sintering and air annealing processes, effectively reduces lattice defects, suppresses radiation-induced discoloration phenomena, and improves the long-term stability of the material. Oxygen vacancy control significantly reduces the light transmittance attenuation rate of the material in a radiation environment, meeting the high requirements for the long-term stability of materials in scenarios such as nuclear facilities and medical equipment.

[0018] The core innovation of the present invention lies in the synergistic optimization of HfO2 doping and the two-step ball milling-sintering process, breaking through the limitations of traditional Lu2O3 ceramics in terms of densification, shielding performance, and environmental stability, and realizing the quantifiable production of lead-free high-shielding transparent ceramics. Under lead-free conditions, the present invention simultaneously achieves high transparency and high lead equivalent, solving the contradiction of "shielding and transparency cannot be achieved simultaneously" in traditional materials. In addition, the design that abandons lead-containing components complies with environmental protection regulations, and the optimized solid-phase sintering process reduces energy consumption and equipment dependence, and the product yield and batch stability are significantly improved, providing a reliable technical support for the wide application of high-performance radiation shielding materials.

[0019] Furthermore, the temperature of the first high-temperature calcination in step (1) is 1300 °C, and the calcination time is 4 hours.

[0020] Furthermore, the temperature of the second high-temperature calcination in step (1) is 600 °C, and the calcination time is 5 hours.

[0021] Furthermore, the purity of the lutetium oxide powder in step (1) is 99.99%.

[0022] Furthermore, the ball milling process in step (1) is to ball mill in a planetary ball mill at 300 r / min for 20 hours.

[0023] Furthermore, in step (2), 5 MPa dry pressing and 250 MPa cold isostatic pressing are carried out. The time of dry pressing is not limited and can be 5-10 minutes, and the pressing time of cold isostatic pressing is 15 minutes.

[0024] Furthermore, the vacuum degree of the vacuum environment in step (3) is 10 -4Pa.

[0025] Furthermore, the annealing process described in step (3) is annealing in air at 1300 °C for 4 hours in a muffle furnace.

[0026] The third object of the present invention is to provide the application of the above-mentioned lutetium oxide transparent ceramic with high lead equivalent in the preparation of radiation shielding materials.

[0027] The beneficial effects of the present invention are as follows:

[0028] (1) A lutetium oxide transparent ceramic provided by the present invention achieves the effect of high lead equivalent without adding lead, and well solves the safety risk problem existing in the existing lead-containing transparent ceramics;

[0029] (2) The lutetium oxide transparent ceramic with high lead equivalent provided by the present invention has the characteristics of high density, high transmittance and good shielding performance of ceramics, and can be well applied to radiation shielding materials. Description of the Drawings

[0030] Figure 1 Lutetium oxide transparent ceramics with hafnium oxide addition amounts of 1-9 at% prepared in the examples and comparative examples.

[0031] Figure 2 X-ray diffraction patterns of the lutetium oxide transparent ceramics prepared in the examples and comparative examples of the present invention.

[0032] Figure 3 Transmittance of the lutetium oxide transparent ceramics prepared in the examples and comparative examples.

[0033] Figure 4 Lead equivalent of the lutetium oxide transparent ceramics prepared in the examples and comparative examples.

[0034] Figure 5 Vickers hardness of the lutetium oxide transparent ceramics prepared in the examples and comparative examples.

[0035] Figure 6 Gamma shielding efficiency of the lutetium oxide transparent ceramics prepared in the examples and comparative examples. Detailed Embodiments

[0036] In order to make the objects, technical solutions and advantages of the present invention clearer, the following describes the present invention in detail with reference to the examples. It should be noted that the following examples are only used to explain and illustrate the present invention, and are not used to limit the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above-mentioned inventive content still fall within the protection scope of the present invention.

[0037] Example 1

[0038] A high lead equivalent lutetium oxide transparent ceramic material, the composition of the lutetium oxide transparent ceramic being (Lu 1-x Hf x )2O3 (x = 0.03).

[0039] The preparation method of the above high lead equivalent lutetium oxide transparent ceramic includes: precursor powder preparation, green body forming, and ceramic sintering, specifically as follows:

[0040] (1) Precursor powder preparation: Using lutetium oxide powder as the raw material, adding hafnium oxide to the lutetium oxide, adopting the solid-phase method, through ball milling, mixing, drying and sieving, and then calcining at 1300 °C for 4 hours. The calcined powder is ball milled, mixed, dried and sieved again, and finally calcined at 600 °C for 5 hours to obtain the precursor powder: the addition amount of hafnium oxide accounts for 3 at% (atomic ratio) of lutetium oxide;

[0041] (2) Green body forming: Using a two-step pressure forming process of dry pressing (5 MPa, 5 minutes) and cold isostatic pressing (250 MPa, 15 minutes) to form the precursor powder obtained in step (1) into a ceramic green body;

[0042] (3) Ceramic sintering: Placing the ceramic green body obtained in step (2) in a vacuum environment at 1860 °C and a vacuum degree of 10 -4 Pa and sintering for 8 hours to obtain a pure-phase ceramic, and annealing and polishing the pure-phase ceramic to obtain the lutetium oxide transparent ceramic material.

[0043] Example 2

[0044] A high lead equivalent lutetium oxide transparent ceramic material, the composition of the lutetium oxide transparent ceramic being (Lu 1-x Hf x )2O3 (x = 0.05).

[0045] The preparation method of the above high lead equivalent lutetium oxide transparent ceramic includes: precursor powder preparation, green body forming, and ceramic sintering, specifically as follows:

[0046] (1) Precursor powder preparation: Using lutetium oxide powder as the raw material, adding hafnium oxide to the lutetium oxide, adopting the solid-phase method, through ball milling, mixing, drying and sieving, and then calcining at 1300 °C for 4 hours. The calcined powder is ball milled, mixed, dried and sieved again, and finally calcined at 600 °C for 5 hours to obtain the precursor powder: the addition amount of hafnium oxide is 5 at% of the lutetium oxide atoms;

[0047] (2) Green body forming: Using a two-step pressure forming process of dry pressing (5 MPa, 8 minutes) and cold isostatic pressing (250 MPa, 15 minutes) to form the precursor powder obtained in step (1) into a ceramic green body;

[0048] (3) Ceramic sintering: Place the ceramic green body obtained in step (2) in a vacuum environment and sinter at 1860 °C and a vacuum degree of 10 -4 Pa for 8 hours to obtain a pure-phase ceramic. Anneal and polish the pure-phase ceramic to obtain a lutetium oxide transparent ceramic material.

[0049] Comparative Example 1

[0050] Prepare a lutetium oxide transparent ceramic (Lu 1-x Hf x )2O3 (x = 0.01) according to the method of Example 1, where the addition amount of hafnium oxide is 1 at% of the number of lutetium oxide atoms.

[0051] Comparative Example 2

[0052] Prepare a lutetium oxide transparent ceramic (Lu 1-x Hf x )2O3 (x = 0.07) according to the method of Example 1, where the addition amount of hafnium oxide is 7 at% of the number of lutetium oxide atoms.

[0053] Comparative Example 3

[0054] Prepare a lutetium oxide transparent ceramic (Lu 1-x Hf x )2O3 (x = 0.09) according to the method of Example 1, where the addition amount of hafnium oxide is 9 at% of the number of lutetium oxide atoms.

[0055] Comparative Example 4

[0056] Prepare a lutetium oxide transparent ceramic according to the method of Example 1, without adding hafnium oxide, and directly prepare Lu2O3 ceramic, that is, x = 0.

[0057] Test Example

[0058] (I) Perform performance tests on the lutetium oxide transparent ceramics prepared in the examples and comparative examples. The specific contents and methods of the tests are as follows:

[0059] (1) Transmittance

[0060] Use an ellipsometer (UVISEL / PLUS; Horiba, Japan) to measure the refractive index in the range of 200 to 2000 nm. Use a UV-Vis-NIR spectrometer (Lambda-750, PerkinElmer, USA) to measure the optical transmittance of the ceramic sample before and after radiation exposure in the wavelength range of 200 nm to 2000 nm.

[0061] (2) Lead equivalent

[0062]

[0063] Where (μ / ρ) m and (μ / Φ) Pb are the mass attenuation coefficient of the material and the mass attenuation factor of lead, respectively; ρ m and ρ Pb are the density of the material and the density of lead, respectively; d m is the unit thickness of the material.

[0064] (3) Vickers hardness

[0065] The hardness of the samples was measured using a Vickers hardness tester (HV-5, Ribo Instruments, Chongqing, China). A load of 1 kg was applied to the ceramic surface through a diamond indenter, resulting in an indentation. The Vickers hardness was then obtained from the test load and the length of the indentation diagonal. The calculation formula is as follows:

[0066]

[0067] Here, HV represents the Vickers hardness, F represents the applied load, and d1 and d2 correspond to the lengths of the indentation diagonals.

[0068] (4) Density

[0069] The density was measured using Archimedes' principle, with deionized water as the immersion medium.

[0070] (5) Shielding efficiency

[0071] The γ-ray shielding effectiveness of the samples was evaluated using a comprehensive experimental platform for β / γ detection. 137 A Cs radiation source emits γ-rays with an energy of 0.662 MeV and is located 200 mm away from the ceramic sample. To obtain a collimated narrow γ-ray beam, a collimator with an aperture of 3 mm is inserted between the radiation source and the ceramic sample. The γ-ray detector is located behind the ceramic sample. To counteract scattered radiation and minimize external interference, the entire measurement device is surrounded by a 10-cm-thick lead plate.

[0072] (6) γ-ray absorption coefficient

[0073] It is obtained by measuring the material density and the mass attenuation coefficient, and the calculation method is as follows:

[0074]

[0075] (2) The test results are shown in Figures 1-6 .

[0076] From Figure 1It can be seen that the transmittance of Lu2O3 ceramics without HfO2 is only about 9% in the visible and infrared bands. After adding a small amount of HfO2 (x = 0.03) as a sintering aid, the transmittance increases significantly to about 81% at 1600 nm, which is very close to the theoretical limit of 81.5%.

[0077] From Figure 2 It can be seen that the lead equivalent of Lu2O3 ceramics without HfO2 is about 0.77 mmPb. After adding HfO2 to the sample and sintering, the lead equivalent of Lu2O3 ceramics increases to a maximum of 0.84 mmPb.

[0078] From Figure 3 It can be seen that the hardness of Lu2O3 transparent ceramics without Hf is only 5.25 GPa. When the Hf content reaches 3 at%, the hardness increases significantly to 9.57 GPa.

[0079] From Figure 4 It can be seen that due to the presence of many pores inside, the ceramics without HfO2 have a relatively low density of about 8.75 g / cm 3 . After adding HfO2, the pores are effectively eliminated, and the density of the sample increases to a maximum of 9.55 g / cm 3 , exceeding the theoretical density value of pure Lu2O3 TC (9.42 g / cm 3 ). This is because Hf with a higher atomic number enters the lattice. This result shows that using HfO2 as a sintering aid avoids the problem of density reduction of ceramics caused by traditional sintering aids.

[0080] From Figure 5 It can be seen that Lu2O3 transparent ceramics without HfO2 can only shield about 40% of γ-rays at a thickness of 1 cm, and most of the rays still penetrate the sample. When the HfO2 content x ≥ 0.03 in the sample, the shielding efficiency remains at about 60%. Adding HfO2 significantly improves the shielding performance of Lu2O3 transparent ceramics against γ-rays.

[0081] From Figure 6 It can be seen that the γ-ray linear absorption coefficient of Lu2O3 ceramics with x = 0 is relatively low, less than 0.5. After adding HfO2 to the sample, the shielding effect of the sample against γ-rays is improved. When x = 0.03, the γ-ray absorption coefficient reaches the maximum value (about 0.9).

[0082] In addition, as can be seen from the above figures, when using the lutetium oxide transparent ceramics prepared in Example 1 and Example 2, the properties of the obtained ceramics are significantly better than those of the ceramics obtained in Comparative Examples 1-4.

Claims

1. A high lead equivalent lutetium oxide transparent ceramic, characterized in that, The elemental composition of the transparent ceramic is (Lu 1-x Hf x )2O3, where x = 0.03 - 0.

05.

2. The preparation method of the high lead equivalent lutetium oxide transparent ceramic according to claim 1, characterized in that, It includes the following steps: (1) Preparation of precursor powder: Using lutetium oxide powder as the raw material, adding hafnium oxide to the lutetium oxide, adopting the solid-phase method, through ball milling, mixing, drying and sieving, and then through a first high-temperature calcination. The calcined powder is ball milled, mixed, dried and sieved again, and finally through a second high-temperature calcination to obtain the precursor powder; the addition amount of the hafnium oxide is 3-5 at% of the number of lutetium oxide atoms; (2) Green body forming: Using a two-step pressure forming process of dry pressing and cold isostatic pressing to form the precursor powder obtained in step (1) into a ceramic green body; (3) Ceramic sintering: Placing the ceramic green body obtained in step (2) in a vacuum environment, sintering at 1860 °C for 8 hours to obtain a pure-phase ceramic, and annealing and polishing the pure-phase ceramic to obtain a lutetium oxide transparent ceramic material.

3. The preparation method according to claim 2, characterized in that, In step (1), the temperature of the first high-temperature calcination is 1300 °C, and the calcination time is 4 hours.

4. The preparation method according to claim 2, characterized in that, In step (1), the temperature of the second high-temperature calcination is 600 °C, and the calcination time is 5 hours.

5. The preparation method according to claim 2, characterized in that, In step (1), the purity of the lutetium oxide powder is 99.99%.

6. The preparation method according to claim 2, wherein In step (1), the ball milling process is ball milling at 300 r / min for 20 hours in a planetary ball mill, and the sieving is through a 200-mesh sieve.

7. The preparation method according to claim 2, wherein, In step (2), dry pressing is carried out, and the dry pressing pressure is 5 MPa; the cold isostatic pressing pressure is 250 MPa, and the cold isostatic pressing time is 15 minutes.

8. The preparation method according to claim 2, characterized in that The degree of vacuum of the vacuum environment described in step (3) is 10 -4 Pa.

9. The preparation method according to claim 2, wherein In step (3), the annealing treatment process is air annealing at 1300 °C for 4 hours in a muffle furnace.

10. Use of the high lead equivalent lutetium oxide transparent ceramic described in claim 1 or the high lead equivalent lutetium oxide transparent ceramic prepared by the method described in any one of claims 2-9 in the preparation of radiation shielding materials.

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