High-density nano-microporous tritium breeding-neutron multiplication composite functional ceramic material as well as preparation method and application thereof

Abstract

The invention discloses a high-density nano-microporous tritium breeding-neutron multiplication composite functional ceramic material as well as a preparation method and application thereof, and relates to the field of nuclear fusion engineering. The material is composed of high-density microporous lead lithium titanate ceramic pellets doped with titanium dioxide nanotubes, has high density and a nanoscale microporous structure, and is structurally a doped structure of Li2TiO3 and Li2PbO3 monoclinic crystals and the titanium dioxide nanotubes. According to the invention, the problem of low tritium desorption rate of traditional lithium titanate ceramic pellets is solved, and by regulating the doping ratio (0.1%-0.7%) of the titanium dioxide nanotubes, a nanoscale microporous structure is formed while high density is maintained, so that the mechanical property and the tritium desorption rate of the ceramic pellets can be synergistically improved. The prepared ceramic pellet has excellent mechanical strength, thermal stability and tritium release performance, and is suitable for a tritium breeding agent in a fusion reactor solid water-cooled cladding.

Description

Technical Field

[0001] The present invention relates to the field of nuclear fusion engineering, and specifically relates to a highly dense nano-porous tritium breeding-neutron multiplication composite functional ceramic material, a preparation method thereof, and an application in a tritium breeder for a solid-state water-cooled blanket of a fusion reactor. Background Art

[0002] Nuclear fusion energy is regarded as an ideal choice to solve the future energy crisis, and the deuterium-tritium reaction is the most feasible fusion reaction. However, tritium is extremely scarce in nature, and it is necessary to realize the self-sustaining cycle of tritium in a fusion reactor through a tritium breeder. Lithium-based ceramic materials are considered to be ideal tritium breeders due to their excellent thermal stability and chemical inertness. Lithium lead titanate (Li2Pb x Ti 1-x O3) ceramics have been widely studied as solid tritium breeders for fusion reactors due to their high tritium breeding efficiency and good thermal stability. However, the existing lithium lead titanate ceramic pellets have the problem of low tritium desorption rate. The highly dense structure makes it difficult for tritium to be released, which affects its application efficiency in fusion reactors. Summary of the Invention

[0003] To solve the technical problem that the highly dense structure makes it difficult for tritium to be released, the present invention proposes to dope titanium dioxide nanotubes into lithium lead titanate (Li2Pb x Ti 1-x O3) ceramic powder, and prepare ceramic pellets with a high density and a nano-porous structure through a mechanical ball milling method and a polymer-assisted sedimentation method. This method significantly improves the tritium desorption rate while maintaining the high density of the material, and solves the deficiencies of the existing technology.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] First, the present invention proposes a highly dense nano-porous tritium breeding-neutron multiplication composite functional ceramic material, which is composed of highly dense microporous lithium lead titanate ceramic pellets doped with titanium dioxide nanotubes, and has a high density and a nano-porous structure; the chemical formula of the highly dense microporous lithium lead titanate ceramic pellets is TiO2 / Li2Pb x Ti 1-x O3, where x = 0 to 0.7; the highly dense microporous lithium lead titanate ceramic pellets are a doping structure of monoclinic crystals of Li2TiO3 and Li2PbO3 and titanium dioxide nanotubes in terms of structure.

[0006] As a preferred technical solution of the present invention, the average diameter of the highly dense microporous lithium lead titanate ceramic pellets is 1.3 mm to 1.5 mm, the sphericity is 1.007 to 1.074, the crushing load is 15.9 N to 27.5 N, and the porosity is 18.6% to 31.1%.

[0007] Secondly, the present invention provides a method for preparing a highly dense nano-microporous tritium breeding-neutron multiplication composite functional ceramic material, and the steps are as follows:

[0008] (1) Load Li2TiO3 powder and PbO powder into a ball milling jar filled with absolute ethanol according to the proportion of Li, Ti, and Pb elements in Li2Pb x Ti 1-x O3, and complete the assembly under the argon atmosphere in the glove box; place the ball milling jar on a planetary ball mill for ball milling to obtain the lithium lead titanate powder;

[0009] (2) Dope titanium dioxide nanotubes into the prepared lithium lead titanate powder at a ratio of 0.1% - 0.7%, load the doped powder into a ball milling jar filled with absolute ethanol, and complete the assembly under the argon atmosphere in the glove box; place the ball milling jar on a planetary ball mill for ball milling to obtain the microporous lithium lead titanate ceramic powder;

[0010] (3) Disperse the microporous lithium lead titanate ceramic powder, polymerizable monomer, and polyvinyl alcohol in deionized water, ball mill in a ball milling jar, and add an appropriate amount of ammonium persulfate as an initiator to obtain the microporous lithium lead titanate ceramic slurry;

[0011] (4) After dropping the microporous lithium lead titanate ceramic slurry into silicone oil through a peristaltic pump, the slurry forms highly spherical droplets during the falling process, and the spherical droplets complete polymerization with the polymerizable monomer during the falling process to form a gel ball blank, that is, the microporous lithium lead titanate ceramic small ball blank;

[0012] (5) Wash and dry the microporous lithium lead titanate ceramic small ball blank, and sinter it in an air atmosphere to finally obtain a highly dense microporous lithium lead titanate ceramic small ball.

[0013] As a preferred technical solution of the present invention, in the preparation method:

[0014] The ball milling parameters in steps (1) and (2) are as follows: the ball milling speed is 100 rpm, the ball-to-powder ratio is 10:1, the ball milling time is 10 h, after each 30 min of ball milling, stop for 20 min and adjust the forward and reverse directions. The powder after ball milling treatment needs to be placed in an oven at 70 °C for drying for 12 h to evaporate all the absolute ethanol and obtain the dried powder.

[0015] The polymerizable monomer in step (3) is prepared by mixing acrylamide and N,N-methylenebisacrylamide according to a molar ratio of 5:1, and the addition amount of the polymerizable monomer and the microporous lithium lead titanate ceramic powder is configured according to a mass ratio of 10:9, and the addition amount of the initiator is 1 wt.% of the polymerizable monomer.

[0016] In step (5), the heating rate is 3 °C / min to 10 °C / min, and after heating to 923 K to 1123 K, the sintering time is 3 h to 6 h.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. By doping titanium dioxide nanotubes into lithium lead titanate (Li2Pb x Ti 1-x O3) powder, ceramic balls with high density and nano-scale microporous structure are prepared by mechanical ball milling and polymer-assisted sedimentation method.

[0019] 2. The present invention solves the problem of low tritium desorption rate of traditional lithium titanate ceramic balls. By adjusting the doping ratio of titanium dioxide nanotubes (0.1% - 0.7%), a nano-scale microporous structure is formed while maintaining high density. Therefore, the mechanical properties and tritium desorption rate of the ceramic balls can be improved synergistically. The prepared ceramic balls have excellent mechanical strength, thermal stability and tritium release performance, and are suitable as tritium breeders in the solid-state water-cooled blanket of fusion reactors. Brief Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of the preparation of high-density microporous lithium lead titanate ceramic balls of the present invention.

[0021] Figure 2 is a scanning electron microscope image of lithium lead titanate powder doped with 0.1% titanium dioxide nanotubes.

[0022] Figure 3 is a scanning electron microscope image and element distribution image of lithium lead titanate powder doped with 0.5% titanium dioxide nanotubes.

[0023] Figure 4 is the X-ray diffraction (XRD) pattern of lithium lead titanate (Li2Pb 0.3 Ti 0.7 O3) powder doped with titanium dioxide (TiO2) nanotubes before and after sintering. Detailed Embodiments

[0024] The following further elaborates on the present invention in combination with embodiments and drawings.

[0025] Example 1

[0026] (1) Preparation of lithium lead titanate ceramic powder:

[0027] According to Li2Pb x Ti 1-xThe proportions of Li, Ti, and Pb elements in O3 (x = 0.3) were used to load Li2TiO3 powder and PbO powder into a ball milling jar filled with absolute ethanol. Assembly was completed under an argon atmosphere in a glove box. The ball milling jar was placed on a planetary ball mill for ball milling. The ball milling speed was 100 rpm, the ball-to-powder ratio was 10:1, and the ball milling time was 10 h. After each 30 min of ball milling, the machine was stopped for 20 min to adjust the forward and reverse directions. The powder obtained from ball milling was transferred to a beaker and then dried in an oven at 70 °C for 12 h to completely evaporate the absolute ethanol, obtaining dry lithium lead titanate ceramic powder.

[0028] (2) Preparation of microporous lithium lead titanate (Li2Pb 0.3 Ti 0.7 O3) ceramic powder:

[0029] Doped into the prepared lithium lead titanate powder according to the proportion of 0.1% doping amount of titanium dioxide nanotubes. The doped powder was loaded into a ball milling jar filled with absolute ethanol. Assembly was completed under an argon atmosphere in a glove box. The ball milling jar was placed on a planetary ball mill for ball milling. The ball milling speed was 100 rpm, the ball-to-powder ratio was 10:1, and the ball milling time was 10 h. After each 30 min of ball milling, the machine was stopped for 20 min to adjust the forward and reverse directions. The powder obtained from ball milling was transferred to a beaker and then dried in an oven at 70 °C for 12 h to completely evaporate the absolute ethanol, obtaining the dried powder and obtaining microporous lithium lead titanate ceramic powder with a doping amount of 0.1% titanium dioxide nanotubes.

[0030] (3) Preparation of microporous lithium lead titanate (Li2Pb 0.3 Ti 0.7 O3) ceramic slurry:

[0031] The powder after ball milling and mixing was placed in a mortar for grinding. The ground powder, 5 wt.% polyvinyl alcohol (analytical pure, Sinopharm Group), and polymerizable monomers (acrylamide and N,N'-methylenebisacrylamide formulated according to a molar ratio of 5:1, Macklin reagent) were dispersed in deionized water and ball milled in a ball milling jar for 60 min. Ammonium persulfate (Xi Ya reagent) with an addition amount of 1 wt.% of the monomer was added as an initiator to obtain the required slurry. Among them, the addition amount of the polymerizable monomer and the proportion of the microporous lithium lead titanate ceramic powder were configured according to a mass ratio of 10:9.

[0032] (4) Preparation of microporous lithium lead titanate (Li2Pb 0.3 Ti 0.7 O3) ceramic small blank bodies:

[0033] The polymer-assisted sedimentation method realized microporous lithium lead titanate (Li2Pb 0.3 Ti 0.7Preparation of O3) ceramic microspheres. After the ball-milled ceramic slurry is dropped into silicone oil through a peristaltic pump, highly spherical droplets are formed during the falling process of the slurry. The spherical droplets complete polymerization with polymerizable monomers during the falling process to form gel sphere blanks.

[0034] (5) Sintering of microporous lithium lead titanate (Li2Pb 0.3 Ti 0.7 O3) ceramic microspheres:

[0035] Take out the microporous lithium lead titanate (Li2Pb 0.3 Ti 0.7 O3) ceramic microsphere blanks, wash and dry them, then transfer them into a corundum crucible and calcine them in a muffle furnace. The sintering parameters are that the sample is heated from room temperature to 1123K at a heating rate of 5°C / min. After sintering for 3h, it is cooled with the furnace to obtain the sintered highly dense microporous lithium lead titanate (Li2Pb 0.3 Ti 0.7 O3) ceramic microspheres.

[0036] Example 2

[0037] The difference between this example and Example 1 is only that the amount of titanium dioxide nanotube doping is doped into the prepared lithium lead titanate powder at a ratio of 0.5%.

[0038] Example 3

[0039] The difference between this example and Example 1 is only that the amount of titanium dioxide nanotube doping is doped into the prepared lithium lead titanate powder at a ratio of 0.7%.

[0040] Example 4

[0041] The difference between this example and Example 1 is only that in step (1), the ratio of Li2TiO3 powder to PbO powder is adjusted to prepare Li2Pb 0.5 Ti 0.5 O3 ceramic powder.

[0042] Example 5

[0043] The difference between this example and Example 1 is that the ratio of Li2TiO3 powder to PbO powder is adjusted to prepare Li2Pb 0.5 Ti 0.5 O3 ceramic powder. At the same time, the amount of titanium dioxide nanotube doping is doped into the prepared lithium lead titanate powder at a ratio of 0.5%.

[0044] Example 6

[0045] The difference between this example and Example 1 is that the ratio of Li2TiO3 powder to PbO powder is adjusted to prepare Li2Pb 0.5 Ti 0.5O3 ceramic powder. At the same time, titanium dioxide nanotubes are doped into the prepared lithium lead titanate powder at a doping ratio of 0.7%.

[0046] Analysis of the preparation of highly dense microporous lithium lead titanate ceramic balls samples:

[0047] Take the highly dense microporous lithium lead titanate ceramic ball samples, and use a scanning electron microscope (Scanning Electron Microscopy, SEM) to analyze the surface structure of the samples, use XRD to analyze the crystal grain composition of the samples. Based on Archimedes' principle, use an electronic density balance (FA2104J) to measure the density of the samples, and use an automatic mercury injection instrument (MAC Auto-pore V9620, mercury temperature: 20.96 °C) to evaluate the open porosity of the samples. Use a universal testing machine (WANCEE TM105D) to measure the crushing load of the balls, the load is 5 kN, and the test rate is 0.25 mm / min. Use an X-ray diffractometer (X, Pert MPD, CuKα) to perform a phase analysis on the sintered ceramic balls. The ball samples need to be first crushed and ground into powders smaller than 100 μm before testing. The X-ray uses CuKα, the tube voltage is 40 kV, the current is 100 mA, the 2θ range: 10 - 80°, and the scanning speed: 10° / min. Use a thermal field emission scanning electron microscope (Zeiss SIGM) to analyze its microstructure.

[0048] It can be seen from Figure 1 that the ceramic balls are overall regular spherical in shape, with a smooth outer surface and a uniform internal structure. Their color is light yellow, which is consistent with the composition and sintering process of the ceramic material. The balls contain micropores inside, and these micropores show a relatively regular distribution inside the balls, with uniform pore sizes, mainly concentrated between the nanometer scale and the micrometer scale. The formation of the micropores is due to the doping of titanium dioxide nanotubes during the preparation of the ceramic material. The titanium dioxide nanotubes coexist with the ceramic powder during the sintering process, and finally leave these microporous structures inside the ceramic balls.

[0049] It can be seen from Figure 2 that the lithium lead titanate powder is composed of irregularly shaped particles, with different particle sizes and a relatively dispersed distribution. The surfaces of some particles are relatively smooth, while some particles show a certain degree of roughness and unevenness. Agglomeration phenomena can be observed between some particles, which may be caused by the interaction forces between particles during the powder preparation process. Overall, the structure of the powder is relatively loose and no tight agglomerates are formed. This microstructure has a certain impact on the subsequent ceramic forming and sintering processes.

[0050] It can be seen from Figure 3It can be seen that the lithium lead titanate powder particles exhibit a relatively regular polyhedron shape, the particle size distribution is relatively uniform, and the agglomeration phenomenon between particles is significantly reduced, showing good dispersibility. The surface of each particle is relatively smooth and has a clear crystal plane structure, indicating that after increasing the doping content of titanium dioxide nanotubes, the powder is mixed more uniformly. The optimization of this microstructure helps to improve the densification and mechanical properties of the subsequent ceramic materials.

[0051] It can be seen from the elemental distribution images that red, green, and blue represent the distributions of oxygen element, lead, and titanium respectively. The green bright spots are relatively evenly distributed throughout the field of view, indicating that the lead element has good dispersibility in the powder and there is no obvious aggregation or segregation phenomenon. The blue bright spots also show a relatively uniform distribution, indicating that the titanium element is also well-dispersed in the powder and forms a relatively uniform composite structure with the lead element. The red bright spots are relatively few, but their dispersion in the powder can still be observed, indicating that the oxygen element coexists with the lead and titanium elements to a certain extent and forms stable chemical bonding.

[0052] From Figure 4 it can be seen that the unsintered sample ( Figure 4 a) shows the obvious presence of Li2TiO3, PbO, and TiO2 phases. Among them, the presence of the PbO impurity phase indicates that the raw materials were not fully reacted during the ball milling process, and the characteristic peaks of TiO2 confirm that the nanotubes have been successfully incorporated into the matrix. The broadening of the Li2TiO3 diffraction peaks reflects the grain refinement or lattice strain caused by ball milling.

[0053] After sintering treatment ( Figure 4 b), significant changes occur in the spectrum: the PbO impurity phase completely disappears, and at the same time, new diffraction peaks of Li2PbO3 appear, indicating that the sintering process promotes the full reaction of PbO with the matrix to form the designed target composite phase. The characteristic peaks of TiO2 still exist but the intensity decreases, indicating that the nanotubes are structurally stable during the sintering process, without obvious phase transformation or agglomeration, and are uniformly dispersed in the ceramic matrix. In addition, the diffraction peaks of Li2TiO3 become sharper, showing the characteristics of increased crystallinity and grain growth after sintering.

[0054] These results confirm that the TiO2 nanotubes have been successfully incorporated into the lithium lead titanate matrix, and phase purification and structure optimization have been achieved through the sintering process.

[0055] Performance testing of the microporous lithium lead titanate ceramic balls prepared in Examples 1 - 6

[0056]

[0057] In the present invention, by doping titanium dioxide nanotubes (TiO2) and optimizing lithium lead titanate (Li2Pb x Ti1-x With respect to the chemical composition of (O3), a tritium breeding-neutron multiplication composite functional ceramic material with both high density and nanoscale microporous structure was successfully prepared. The regulation of the doping ratio of titanium dioxide nanotubes is the key to balancing the mechanical strength and tritium desorption rate of the material. When the TiO2 doping amount is 0.5% (Examples 2 and 5), the ceramic balls exhibit the best comprehensive performance: the crushing load reaches 25.5 - 28.7 N (meeting the mechanical requirements of the fusion reactor blanket); the porosity is 24.9% - 26.7% (significantly enhancing the tritium diffusion channels). Excessive doping (such as 0.7%) will lead to too high porosity, although the tritium desorption rate is increased, but the mechanical strength decreases significantly. The optimization of the lead content (x value) further enhances the neutron multiplication function of the material: Li2Pb 0.5 Ti 0.5 O3 (Examples 4 - 6) while maintaining the pore structure, improves the neutron multiplication efficiency by the introduction of Pb, but the TiO2 doping amount needs to be controlled to maintain the strength. Through comprehensive comparison, it is found that the ceramic balls with the best comprehensive performance are prepared by mixing TiO2 nanotubes with a doping amount of 0.5% and Li2Pb 0.5 Ti 0.5 O3 powder.

[0058] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements or use similar methods to replace the specific embodiments described, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all fall within the protection scope of the present invention.

Claims

1. A highly dense nano-microporous tritium breeding-neutron multiplication composite functional ceramic material, characterized in that, It is composed of highly dense microporous lead titanate lithium ceramic balls doped with titanium dioxide nanotubes, and has a high density and a nanoscale microporous structure; the chemical formula of the highly dense microporous lead titanate lithium ceramic balls is TiO2 / Li2Pb x Ti 1-x O3, where x = 0 to 0.7; the highly dense microporous lead titanate lithium ceramic balls are a doped structure of monoclinic crystals of Li2TiO3 and Li2PbO3 and titanium dioxide nanotubes in terms of structure.

2. The highly dense nano-porous tritium breeding-neutron multiplication composite functional ceramic material according to claim 1, wherein The average diameter of the highly dense microporous lithium lead titanate ceramic spheres is 1.3 mm to 1.5 mm, the sphericity is 1.007 to 1.074, the crushing load is 15.9 N to 27.5 N, and the porosity is 18.6% to 31.1%.

3. A method for preparing the highly dense nano-microporous tritium-breeding and neutron-multiplication composite functional ceramic material as claimed in claim 1 or 2, characterized in that, The steps are as follows: (1) According to the ratio of Li, Ti, and Pb elements in Li2Pb x Ti 1-x O3, load Li2TiO3 powder and PbO powder into a ball milling jar filled with absolute ethanol, complete the assembly under an argon atmosphere in a glove box; place the ball milling jar on a planetary ball mill for ball milling to obtain the lithium lead titanate powder. (2) Dope titanium dioxide nanotubes into the prepared lithium lead titanate powder at a ratio of 0.1% to 0.7%, load the doped powder into a ball milling tank filled with anhydrous ethanol, and complete the assembly under the argon atmosphere in a glove box; place the ball milling tank on a planetary ball mill for ball milling to obtain microporous lithium lead titanate ceramic powder; (3) Disperse the microporous lithium lead titanate ceramic powder, polymerizable monomer, and polyvinyl alcohol in deionized water, perform ball milling in a ball milling tank, and add an appropriate amount of ammonium persulfate as an initiator to obtain a microporous lithium lead titanate ceramic slurry; (4) After dropping the microporous lithium lead titanate ceramic slurry into silicone oil through a peristaltic pump, high-sphericity droplets are formed during the falling process of the slurry, and the spherical droplets complete polymerization with the polymerizable monomer during the falling process to form a gel sphere blank, that is, a microporous lithium lead titanate ceramic sphere blank; (5) Wash and dry the microporous lithium lead titanate ceramic sphere blank, and sinter it in an air atmosphere to finally obtain highly dense microporous lithium lead titanate ceramic spheres.

4. The method according to claim 3, wherein The ball milling parameters in the above steps (1) and (2) are: the ball milling speed is 100 rpm, the ball-to-powder ratio is 10:1, the ball milling time is 10 h, and after each 30 min of ball milling, stop for 20 min and adjust the forward and reverse directions.

5. The method according to claim 3, wherein The powder after ball milling treatment in the above steps (1) and (2) needs to be placed in an oven at 70 °C for drying for 12 h to completely evaporate the anhydrous ethanol and obtain the dried powder.

6. The method according to claim 3, characterized in that The polymerizable monomer in the above step (3) is prepared by mixing acrylamide and N,N'-methylenebisacrylamide in a molar ratio of 5:1, and the addition amount of the polymerizable monomer to the microporous lithium lead titanate ceramic powder is configured according to a mass ratio of 10:9, and the addition amount of the initiator is 1 wt.% of the polymerizable monomer.

7. The method according to claim 3, characterized in that The heating rate in the above step (5) is 3 °C / min to 10 °C / min, and after heating to 923 K to 1123 K, the sintering time is 3 h to 6 h.

8. The application of the composite functional ceramic material as claimed in claim 1 or 2 and the composite functional ceramic material prepared by the method as claimed in any one of claims 3 to 7 as a tritium breeder in a solid-state water-cooled blanket of a fusion reactor.

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