Strontium titanate / boron nitride nanotube composite ceramic compact, and preparation method and application thereof
By employing a method for preparing strontium titanate/boron nitride nanotube composite ceramic cores, the performance degradation problem of strontium titanate ceramic cores under high-temperature irradiation was solved, achieving efficient improvement in thermal conductivity and mechanical properties, and extending battery life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- THE 404 COMPANY LIMITED CHINA NAT NUCLEAR
- Filing Date
- 2024-08-16
- Publication Date
- 2026-08-04
AI Technical Summary
Existing strontium titanate ceramic cores exhibit performance degradation under high temperature and irradiation conditions, leading to reduced heat transfer efficiency and service life. Furthermore, carbon nanotubes are easily oxidized in existing reinforcement methods, and the poor dispersibility of boron nitride results in limited performance improvement.
Strontium titanate and boron nitride nanotube composite ceramic cores were prepared by surface modification and wet stirring techniques. The boron nitride nanotubes accounted for 0.1% to 3% of the mass. The cores were prepared by spark plasma sintering to ensure that the boron nitride nanotubes were uniformly dispersed in the strontium titanate ceramic matrix.
It improves the thermal conductivity and mechanical properties of ceramic cores, enhances high-temperature oxidation resistance and radiation stability, and extends the service life and performance of high-power radioisotope thermal source batteries.
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Figure CN119118658B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of composite ceramic preparation technology, and in particular to a strontium titanate / boron nitride nanotube composite ceramic core, its preparation method, and its application. Background Technology
[0002] Radionuclides extracted from high-level radioactive waste 90 Sr can be used to prepare isotope thermal batteries, and the main component of the thermal source chip is strontium titanate (Sr). 90 SrTiO3) ceramics. High-power radioisotope thermal batteries face harsh environments such as high temperatures and intense radiation during long-term service, leading to irradiation damage to the battery core, degradation of its physical and mechanical properties and structural stability, thus limiting its heat transfer efficiency and lifespan, severely restricting the development of high-power radioisotope thermal batteries. How to effectively improve… 90 The high-temperature resistance, thermal conductivity, mechanical properties, and radiation resistance of SrTiO3 ceramic chips are crucial for ensuring the efficient and safe use of high-power radioisotope thermal source batteries.
[0003] Existing ceramic material performance enhancement technologies mainly involve introducing secondary strengthening phases into single ceramics to prepare composite ceramics. One technical document (Preparation and Performance Study of Strontium Titanate-Based Thermoelectric Composites [D]. Donghua University, 2022) discloses a method for preparing a carbon nanotube (CNT) and strontium titanate (SrTiO3) ceramic composite. This method involves combining CNTs and SrTiO3 via heterogeneous deposition followed by discharge plasma sintering. A drawback is that at high temperatures, the carbon in the CNTs reacts with oxygen in the SrTiO3 lattice. Therefore, when high-power radioisotope thermoelectric battery cells operate under high-temperature conditions for extended periods, the CNT structure will be damaged by oxygen, rendering CNT strengthening technology ineffective. 90 The reduced reinforcing properties of SrTiO3 ceramic chips negatively impact the lifespan and performance of nuclear batteries.
[0004] Technical documents ( 90 Design, simulation and radiation optimization of Sr isotope battery radiation source [J]. Isotopes, 2024, 37(1):49-54.), discloses a composite ceramic core block in which boron nitride powder with one-tenth of the original powder mass is added to the strontium titanate powder formulation. According to the experiment, the thermal resistance of the core block is significantly reduced after adding boron nitride, which has a positive effect on improving the thermoelectric conversion performance of the battery. However, the method shows that the dispersion of boron nitride is not good, which reduces the strengthening effect of boron nitride on strontium titanate ceramic. Moreover, the mass ratio of boron nitride in this technical literature is too large, which leads to a significant increase in the volume of the core block. Summary of the Invention
[0005] The purpose of this invention is to provide a strontium titanate / boron nitride nanotube composite ceramic core, its preparation method, and its application, effectively improving... 90 Thermal conductivity and mechanical properties of SrTiO3 ceramic core.
[0006] The objective of this invention can be achieved through the following technical solutions:
[0007] On one hand, the present invention provides a strontium titanate / boron nitride nanotube composite ceramic core, wherein the composite ceramic core is prepared by strontium titanate and boron nitride nanotubes, and the mass percentage of boron nitride nanotubes in the strontium titanate / boron nitride nanotube composite ceramic core is 0.1% to 3%.
[0008] Preferably, the boron nitride nanotubes have an average diameter of 50 nm and a length of 10-20 μm, and the strontium titanate has an average particle size of 200 nm.
[0009] Secondly, the present invention also provides a method for preparing the above-mentioned strontium titanate / boron nitride nanotube composite ceramic core, comprising the following steps:
[0010] S1: Boron nitride nanotubes were functionalized using an alkaline solution to obtain surface-modified boron nitride nanotubes;
[0011] S2: Strontium titanate is uniformly dispersed in anhydrous ethanol to obtain a slurry of strontium titanate, and the mixture is stirred continuously.
[0012] S3: Surface-modified boron nitride nanotubes are uniformly dispersed in anhydrous ethanol to obtain a surface-modified boron nitride nanotube slurry, which is then added to a strontium titanate slurry to obtain a strontium titanate / boron nitride nanotube slurry, and stirred continuously.
[0013] S4: Heat and stir the strontium titanate / boron nitride nanotube slurry to obtain strontium titanate / boron nitride nanotube composite powder;
[0014] S5: The strontium titanate / boron nitride nanotube composite powder is pressed into a core blank and sintered to obtain a strontium titanate / boron nitride nanotube composite ceramic core.
[0015] Preferably, in step S1, the alkaline solution includes a sodium hydroxide solution, the concentration of which is 5-6 mol / L, and the ratio of the amount of boron nitride nanotubes to the sodium hydroxide solution is (10-100 mg): 15 mL.
[0016] More preferably, in step S1, the specific process of functionalization is as follows: boron nitride nanotubes are ultrasonically dispersed in a sodium hydroxide solution, placed in a hydrothermal reactor lined with polytetrafluoroethylene, reacted at 110-180℃ for 12-24 hours, centrifuged, filtered, washed until neutral, and dried at 70-90℃ for 12-24 hours. Step S1 utilizes the high temperature and high pressure conditions of sodium hydroxide solution in the reactor to functionalize the boron nitride nanotubes, causing hydroxyl groups to bond to the boron atoms on the surface of the boron nitride nanotubes, thereby obtaining surface-modified boron nitride nanotubes.
[0017] More preferably, in step S1, the specific process of functionalization is as follows: boron nitride nanotubes are ultrasonically dispersed in a sodium hydroxide solution, then placed in a hydrothermal reactor lined with polytetrafluoroethylene, reacted at 110-180℃ for 12-24 hours, removed and centrifuged and filtered, the boron nitride nanotubes are washed with deionized water until neutral, and then dried in a drying oven at 80℃ to obtain the modified boron nitride nanotubes.
[0018] Preferably, in step S2, the stirring is performed using a top-mounted electric stirrer at a speed of 300–1200 rpm. The top-mounted electric stirrer effectively mixes the strontium titanate and boron nitride nanotube slurry, ensuring that they do not separate during the wet mixing process.
[0019] More preferably, in step S2, the strontium titanate powder is placed in a beaker, anhydrous ethanol is added and ultrasonically dispersed, and then the strontium titanate slurry is transferred to another large beaker and continuously stirred with a top-mounted electric stirrer.
[0020] Preferably, in step S3, the dispersion includes ultrasonic dispersion, the ultrasonic dispersion time is 2-3 hours, and during the ultrasonic dispersion process, the temperature of the surface-modified boron nitride nanotube slurry does not exceed 60°C.
[0021] Preferably, in step S3, the surface-modified boron nitride nanotube slurry is added dropwise to the strontium titanate slurry at a rate of 1-5 ml per second.
[0022] More preferably, in step S3, a pipette is used to drop the surface-modified boron nitride nanotube slurry into the strontium titanate slurry.
[0023] Preferably, in step S4, the heating and stirring continues until the solvent in the strontium titanate-boron nitride nanotube slurry is dried. Before obtaining the strontium titanate / boron nitride nanotube composite powder, the solvent-dried strontium titanate / boron nitride nanotube slurry is further dried in a vacuum drying oven. The drying temperature of the vacuum drying oven is 80-120°C, and the drying time is 20-30 hours.
[0024] Preferably, in step S5, the sintering method includes discharge plasma sintering, the sintering temperature is 1050-1200℃, the sintering pressure is 80-100MPa, and the temperature is held for 3-5 minutes after reaching the sintering temperature; after the holding period, the temperature is lowered to 700-900℃ and the pressure is removed and held for 5-10 minutes.
[0025] Thirdly, the present invention also provides an application of the above-mentioned strontium titanate / boron nitride nanotube composite ceramic core, including its application in a high-power radioactive isotope heat source battery core.
[0026] Boron nitride nanotubes (BNNTs) have a similar structure to CNTs. Besides high thermal conductivity and excellent mechanical properties, they exhibit superior high-temperature oxidation resistance compared to CNTs. Furthermore, the light elements such as boron in BNNTs can effectively reduce bremsstrahlung generated by the interaction between β particles and the core matrix, thereby reducing the radiation dose emitted by the heat source core to the environment. Therefore, they can be used in the field of isotope heat source oxide ceramic cores for high-temperature oxidizing environments. To this end, this invention provides a strontium titanate / boron nitride nanotube composite ceramic core, its preparation method, and its applications.
[0027] Compared with the prior art, the present invention has the following beneficial effects:
[0028] (1) This invention uses SrTiO3 ceramic as the main body and constructs a BNNT network in the ceramic matrix. BNNT, which has excellent mechanical and thermal properties, serves as a reinforcing phase, which improves the density and uniformity of the ceramic core and fully ensures the thermal and mechanical properties of the composite ceramic core.
[0029] (2) BNNT has better thermochemical stability than CNT and can be used in harsh environments with high temperature and chemical activity, so its strengthening effect in high-power radioactive isotope heat source battery cells is better.
[0030] (3) In the process of preparing strontium titanate ceramic core, the present invention improves the uniform dispersion of boron nitride nanotubes in strontium titanate ceramic powder by modifying the surface of boron nitride nanotubes with hydroxyl groups and by using wet stirring and mixing technology, thus maintaining the structural integrity of boron nitride nanotubes.
[0031] (4) The present invention can not only disperse boron nitride nanotubes well in the strontium titanate ceramic matrix by improving the wet mixing method, but also avoid the damage of boron nitride caused by ball milling. By using high crystal quality boron nitride nanotubes with optimized mass ratio, the thermal conductivity of the core will be further increased and the thermal resistance of the core will be reduced. Under the premise of ensuring that the volume of the heat source core does not increase significantly, it has a more positive effect on improving the thermoelectric conversion performance of the battery.
[0032] (5) The preparation method and process conditions of the strontium titanate / boron nitride nanotube composite ceramic core of the present invention are simple and easy to implement, which is conducive to its widespread use. Attached Figure Description
[0033] Figure 1 This is a scanning electron microscope image of the composite powder obtained by wet mixing of boron nitride nanotubes modified by hydrothermal reaction with sodium hydroxide solution and strontium titanate powder in Example 1.
[0034] Figure 2 The thermal conductivity comparison diagram shows the SrTiO3-1wt.%BNNT, SrTiO3-2wt.%BNNT, and SrTiO3-3wt.%BNNT composite ceramic cores prepared in Examples 1-3, and the SrTiO3 single-phase ceramic core prepared in the comparative example.
[0035] Figure 3 The image shows a hardness comparison between the SrTiO3-2wt.%BNNT composite ceramic core prepared in Example 2 and the SrTiO3 single-phase ceramic core prepared in the comparative example. Detailed Implementation
[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.
[0037] This invention provides a strontium titanate / boron nitride nanotube composite ceramic core, which is prepared using strontium titanate and boron nitride nanotubes. The mass percentage of boron nitride nanotubes in the strontium titanate / boron nitride nanotube composite ceramic core is 0.1% to 3%. The boron nitride nanotubes have an average diameter of 50 nm and a length of 10-20 μm, and the strontium titanate has an average particle size of 200 nm.
[0038] The above-mentioned strontium titanate / boron nitride nanotube composite ceramic core was prepared by the following method:
[0039] (1) Boron nitride nanotubes are ultrasonically dispersed in a 5-6 mol / L sodium hydroxide solution, wherein the ratio of boron nitride nanotubes to sodium hydroxide solution is (10-100 mg): 15 mL; then the solution is placed in a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 110-180℃ for 12-24 hours. The solution is then removed, centrifuged and filtered, and the boron nitride nanotubes are washed with deionized water until neutral. The boron nitride nanotubes are then dried in a drying oven at 70-90℃ for 12-24 hours to functionalize the boron nitride nanotubes, thereby bonding hydroxyl groups to the boron atoms on the surface of the boron nitride nanotubes to obtain surface-modified boron nitride nanotubes.
[0040] (2) Place the SrTiO3 powder into a beaker, add anhydrous ethanol and ultrasonically disperse it. Then transfer the SrTiO3 slurry to another large beaker and stir it continuously with a top-mounted electric stirrer.
[0041] (3) Mix the boron nitride nanotubes obtained in step (1) with anhydrous ethanol and ultrasonically disperse for 2-3 hours while keeping the temperature below 60°C. Use a pipette to slowly add the boron nitride nanotube dispersion to the SrTiO3 slurry in step (2) at a rate of 1-5 ml per second, and continue stirring and mixing.
[0042] (4) Heat and stir the SrTiO3-BNNT slurry until it is dry, then stop stirring. Take out the dried powder and put it into a vacuum drying oven for further drying. The drying temperature of the vacuum drying oven is 80-120℃ and the drying time is 20-30h to obtain SrTiO3-BNNT composite powder;
[0043] (5) The SrTiO3-BNNT composite powder prepared in step (4) is loaded into a mold for core block pressing and molding. The core block is sintered in a discharge plasma sintering furnace to obtain SrTiO3-BNNT composite ceramic core. The sintering temperature is 1050-1200℃ and the sintering pressure is 80-100MPa. After reaching the sintering temperature, the temperature is held for 3-5 minutes. After the holding period, the temperature is lowered to 700-900℃ and the pressure is removed and held for 5-10 minutes to obtain strontium titanate / boron nitride nanotube composite ceramic core.
[0044] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.
[0045] The boron nitride nanotubes and strontium titanate used in the following examples were selected from Beijing Deco Island Gold Technology Co., Ltd.
[0046] The following detailed description is based on specific embodiments.
[0047] Example 1
[0048] (1) Mix 0.1g boron nitride nanotubes with 15ml of 5mol / L sodium hydroxide solution in a beaker and sonicate for 30min to obtain a mixed solution.
[0049] (2) The mixed solution obtained in step (1) was placed in a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 120°C for 24 hours. After the hydrothermal reaction was completed, the solution was centrifuged at 8000 rpm and repeatedly washed with deionized water. The last wash was with anhydrous ethanol. The solution was then placed in an oven and dried at 80°C for 24 hours to obtain surface-modified boron nitride nanotubes.
[0050] (3) Put 6g of SrTiO3 powder into a beaker, add anhydrous ethanol and ultrasonically disperse it. Immediately transfer the SrTiO3 slurry into the beaker and stir it continuously with a top-mounted electric stirrer.
[0051] (4) Divide the boron nitride nanotubes obtained in step (2) into two equal portions of 0.03g each and place them in two beakers containing 150ml of anhydrous ethanol. Disperse them ultrasonically for 2 hours. During the ultrasonic dispersion, use an ice pack to keep the water temperature below 60℃. Then, add the mixture to the SrTiO3 slurry stirred in step (3) using a plastic pipette and continue stirring and mixing.
[0052] (5) Heat the stirred SrTiO3-1wt.%BNNT slurry on a heating table until it is dry, then stop stirring. Take out the powder dried on the heating table and put it into a vacuum drying oven for further overnight drying. The drying temperature of the drying oven is 90℃.
[0053] (6) The SrTiO3-1wt.%BNNT composite powder prepared in step (5) is loaded into a graphite mold and vacuum sintered at 1100℃ and 100MPa for 3 minutes. Then, the temperature is lowered to 800℃ and held at pressureless temperature for 5 minutes to remove the core stress, thus obtaining the SrTiO3-1wt.%BNNT composite ceramic core.
[0054] Example 2
[0055] By changing the amount of modified boron nitride nanotubes, the mass percentage of boron nitride nanotubes in the strontium titanate / boron nitride nanotube composite ceramic core was 2%, while the rest remained the same as in Example 1, thus preparing a SrTiO3-2wt.%BNNT composite ceramic core.
[0056] Example 3
[0057] By changing the amount of modified boron nitride nanotubes, the mass percentage of boron nitride nanotubes in the strontium titanate / boron nitride nanotube composite ceramic core was 3%, while the rest remained the same as in Example 1, thus preparing a SrTiO3-3wt.%BNNT composite ceramic core.
[0058] Comparative Example
[0059] SrTiO3 powder was loaded into a graphite mold and vacuum sintered at 1100℃ and 100MPa for 3 minutes. Then, the temperature was lowered to 800℃ and held at pressureless temperature for 5 minutes to remove the core stress, thus preparing an undoped SrTiO3 single-phase ceramic core.
[0060] Performance testing
[0061] Figure 1 This is a scanning electron microscope image of the composite powder obtained by wet mixing of boron nitride nanotubes (BNNT) modified by hydrothermal reaction with sodium hydroxide solution and strontium titanate powder in Example 1. It can be clearly seen that BNNT is uniformly dispersed in SrTiO3 ceramic powder.
[0062] Figure 2 The graph shows a comparison of the thermal conductivity of the SrTiO3-1wt.%BNNT, SrTiO3-2wt.%BNNT, and SrTiO3-3wt.%BNNT composite ceramic cores prepared in Examples 1-3, and the SrTiO3 single-phase ceramic core prepared in the comparative example. It can be seen that doping SrTiO3 ceramics with a mass percentage of 1-3wt.% BNNT can significantly improve the thermal conductivity of the SrTiO3 ceramic core.
[0063] Figure 3 The chart shows a hardness comparison between the SrTiO3 single-phase ceramic core prepared in the comparative example and the SrTiO3-2wt.%BNNT composite ceramic core prepared in Example 2. It can be seen that 2wt.% (approximately 7vol.%) of BNNT in the SrTiO3 ceramic can significantly improve the hardness of the SrTiO3 ceramic core.
[0064] In summary, the incorporation of boron nitride nanotubes into strontium titanate ceramic powder can significantly enhance the thermal conductivity and mechanical properties of the composite ceramic core.
[0065] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention should be within the protection scope of the present invention.
Claims
1. A strontium titanate / boron nitride nanotube composite ceramic core, characterized in that, The composite ceramic core is prepared using strontium titanate and boron nitride nanotubes, wherein the mass percentage of boron nitride nanotubes in the strontium titanate / boron nitride nanotube composite ceramic core is 0.1% to 3%. The composite ceramic core uses SrTiO3 ceramic as the matrix and constructs a BNNT network in the ceramic matrix. BNNT serves as a reinforcing phase, which improves the density and uniformity of the composite ceramic core and fully guarantees the thermal conductivity and mechanical properties of the composite ceramic core. The boron nitride nanotubes have an average diameter of 50 nm and a length of 10-20 µm; the strontium titanate has an average particle size of 200 nm. The method for preparing the composite ceramic core includes the following steps: S1: Boron nitride nanotubes were functionalized using an alkaline solution to obtain surface-modified boron nitride nanotubes; S2: Strontium titanate is uniformly dispersed in anhydrous ethanol to obtain a slurry of strontium titanate, and the mixture is stirred continuously. S3: Surface-modified boron nitride nanotubes are uniformly dispersed in anhydrous ethanol to obtain a surface-modified boron nitride nanotube slurry, which is then added to a strontium titanate slurry to obtain a strontium titanate / boron nitride nanotube slurry, and stirred continuously. S4: Heat and stir the strontium titanate / boron nitride nanotube slurry to obtain strontium titanate / boron nitride nanotube composite powder; S5: The strontium titanate / boron nitride nanotube composite powder is pressed into a core blank and sintered to obtain a strontium titanate / boron nitride nanotube composite ceramic core. In step S1, the alkaline solution includes a sodium hydroxide solution with a concentration of 5-6 mol / L, and the ratio of boron nitride nanotubes to sodium hydroxide solution is (10-100 mg): 15 mL. In step S3, the dispersion includes ultrasonic dispersion, the ultrasonic dispersion time is 2-3 h, and during the ultrasonic dispersion process, the temperature of the surface-modified boron nitride nanotube slurry does not exceed 60 ℃; the surface-modified boron nitride nanotube slurry is added dropwise to the strontium titanate slurry at a rate of 1-5 ml per second; In step S5, the sintering method includes discharge plasma sintering, the sintering temperature is 1050-1200 ℃, the sintering pressure is 80-100 MPa, and the temperature is held for 3-5 min after reaching the sintering temperature; after the holding period, the temperature is lowered to 700-900 ℃ and the pressure is removed and held for 5-10 min.
2. The method for preparing a strontium titanate / boron nitride nanotube composite ceramic core according to claim 1, characterized in that, In step S1, the specific process of functionalization is as follows: boron nitride nanotubes are ultrasonically dispersed in sodium hydroxide solution, placed in a hydrothermal reactor lined with polytetrafluoroethylene, reacted at 110-180 ℃ for 12-24 h, centrifuged, filtered and washed until neutral, and dried at 70-90 ℃ for 12-24 h.
3. The method for preparing a strontium titanate / boron nitride nanotube composite ceramic core according to claim 1, characterized in that, In step S2, the stirring is carried out by a top-mounted electric stirrer at a speed of 300~1200 rpm.
4. The method for preparing a strontium titanate / boron nitride nanotube composite ceramic core according to claim 1, characterized in that, In step S4, the heating and stirring continue until the solvent in the strontium titanate / boron nitride nanotube slurry is dried. Before obtaining the strontium titanate / boron nitride nanotube composite powder, the solvent-dried strontium titanate-boron nitride nanotube slurry is further dried in a vacuum drying oven. The drying temperature of the vacuum drying oven is 80~120 ℃, and the drying time is 20~30 h.
5. An application of the strontium titanate / boron nitride nanotube composite ceramic core as described in claim 1, characterized in that, This includes applications in high-power radioactive isotope heat source battery cells.