CN-121974697-A - Boron carbide powder enriched with boron-10 isotope and preparation method thereof

CN121974697ACN 121974697 ACN121974697 ACN 121974697ACN-121974697-A

Abstract

A boron carbide powder rich in boron-10 isotopes and a preparation method thereof relate to the technical field of advanced ceramic material preparation. The method takes boric acid enriched with boron-10 as a boron source, creatively adopts a composite carbon source composed of high-activity carbon black and nano carbon material, introduces a removable reaction medium, and combines optimized three heat treatment processes of compression molding, dehydration, medium-temperature activation and high-temperature carbothermal reduction by precisely controlling the molar ratio of boron to carbon. The method effectively solves the problems of incomplete reaction, low product purity, poor microcosmic uniformity, low isotope utilization rate and the like in the traditional carbothermic reduction method, and can efficiently synthesize the boron carbide powder with high purity, high boron-10 enrichment degree and uniform grain morphology. The method has simple and controllable process and provides a reliable way for preparing the high-performance boron carbide material for the core.

Inventors

SONG JINGHONG
LIU HUAN
XU LUWEN

Assignees

山东千明新材料有限公司

Dates

Publication Date: 20260505
Application Date: 20260206

Claims (10)

1. The preparation method of boron carbide powder enriched with boron-10 isotope is characterized by comprising the following steps: (1) Preheating a boron source enriched with boron-10, and uniformly mixing the boron source, a composite carbon source and a removable reaction medium, wherein the molar ratio of boron atoms in the boron source to carbon atoms in the composite carbon source is controlled to be 6.5-7.5:6.5-7.5; (2) Pressing and molding the uniformly mixed powder to obtain a blank; (3) And (3) carrying out heat treatment on the obtained blank body in a protective atmosphere sequentially through a dehydration stage, a medium-temperature activation stage and a high-temperature carbothermic reduction stage, and finally obtaining the boron carbide powder enriched with the boron-10 isotope through cooling and post treatment.
2. The method for preparing boron carbide powder enriched in boron-10 isotopes of claim 1, wherein in the step (2), the boron source is boric acid enriched with 10 B, and the preheating treatment is dehydration pretreatment of the boron source for 1-3 hours under the conditions of 200-300 ℃ and vacuum or inert atmosphere; the composite carbon source consists of a main carbon material and a reinforced carbon material, wherein the main carbon material is carbon black, and the reinforced carbon material is at least one of carbon nano tubes or graphene; the removable reaction medium is an alkali or alkaline earth metal halide.
3. The method for preparing boron carbide powder enriched in boron-10 isotopes of claim 2, wherein the mass ratio of the reinforced carbon material in the composite carbon source is 5% -15%.
4. The method for preparing boron carbide powder enriched in boron-10 isotopes of claim 2, wherein the removable reaction medium is sodium chloride or potassium fluoride and the addition amount is 3% -10% of the total mass of the raw materials.
5. The method for preparing boron carbide powder enriched in boron-10 isotopes according to claim 1, wherein the molding pressure in the compression molding in the step (2) is 70-90 MPa, and the dwell time is 2-5 min.
6. The preparation method of boron carbide powder enriched with boron-10 isotopes according to claim 1, wherein in the step (3), the dehydration stage is to heat a green body to 500-600 ℃ and keep the temperature for 0.5-2 h under an inert atmosphere, the medium-temperature activation stage is to heat the green body to 800-1000 ℃ and keep the temperature for 0.2-1 h under a reducing atmosphere containing hydrogen, and the high-temperature carbothermic reduction stage is to heat the green body to 1650-1750 ℃ and keep the green body for 0.5-2 h under the reducing atmosphere.
7. The method for preparing boron carbide powder enriched in boron-10 isotopes of claim 6, wherein the reducing atmosphere is a mixture of argon and hydrogen, and the volume fraction of hydrogen is 1% -5%.
8. The method of claim 1, wherein the post-treatment in step (3) comprises dissolving and removing the removable reaction medium with a solvent.
9. A boron carbide powder enriched with boron-10 isotopes is characterized in that the boron carbide powder is prepared by the preparation method of any one of claims 1-8, the boron carbide powder is pure phase B 4 C, the abundance retention rate of the boron-10 isotopes is not lower than 92%, and powder grains are in a granular shape or a short rod shape, and the grain size distribution is 1-10 mu m.
10. The boron carbide powder enriched in boron-10 isotopes of claim 9, wherein the mass percentage of elemental iron in the powder is less than 0.05%.

Description

Boron carbide powder enriched with boron-10 isotope and preparation method thereof Technical Field The invention relates to the technical field of advanced ceramic material preparation, in particular to boron carbide powder enriched with boron-10 isotopes and a preparation method thereof. Background Boron carbide (B 4 C) is one of the most rigid artificial materials known to have excellent properties of high hardness, low density, high melting point, and extremely high thermal neutron absorption cross section. Wherein the absorption capacity of the boron-10 isotope is mainly attributed to the boron-10 isotope, and the absorption cross section of the boron-10 isotope for thermal neutrons is up to 3837 target. These characteristics make B 4 C an irreplaceable function in the high-end fields of control rods and shielding assemblies, light-weight armor protection, superhard wear-resistant parts and the like of nuclear reactors. Particularly for nuclear energy application, the preparation of the B 4 C powder with high 10 B isotope enrichment degree, high purity and uniform microstructure is a key for improving the safety and efficiency of a nuclear reactor. Currently, the main method for industrially preparing B 4 C powder is a carbothermal reduction method, namely, B 4 C is synthesized by taking a boron source (such as boric acid and boron oxide) and a carbon source (such as graphite and carbon black) as raw materials and carrying out reduction reaction under a high-temperature inert atmosphere. However, this conventional process still faces a serious set of challenges in pursuing high 10 B enrichment and high product quality. In order to pursue chemical stability, graphite is mostly used as a carbon source in the conventional process. However, graphite has a regular crystal structure and low reactivity, and the solid-solid reaction with boron oxide (B 2O3) is difficult to be completely carried out, which tends to result in residual unreacted free carbon in the product. When graphite is used as a carbon source, the reaction is incomplete. Residual carbon can seriously affect the subsequent sintering densification and final mechanical properties of the B 4 C ceramic. The commonly used boron source (such as boric acid) can be dehydrated to generate B 2O3 in the heating process, if the dehydration process is improperly controlled, the rapid volatilization of moisture can easily lead to the damage of a blank structure, and the B 2O3 is easy to volatilize at high temperature, so that the molar ratio of boron to carbon deviates from a preset value, and the fluctuation of components and the formation of boron-rich or carbon-rich non-metering phases are caused. In addition, there are significant differences in the microscopic morphology and reaction paths of the different carbon sources, directly leading to non-uniformity in the morphology of the final product. B 4 C powder grains obtained by taking graphite as a carbon source are irregular, the size distribution is wide, and lamellar graphite residues are accompanied. Such non-uniform microstructures can present difficulties in subsequent sintering, affecting the reliability of the product properties. 10 The B isotope is an expensive strategic resource and it is important how to keep it in the final product to a maximum during the synthesis. The traditional process can cause precious 10 B loss due to the problems of incomplete reaction, volatilization of B 2O3 and the like, so that the enrichment efficiency is reduced, and the raw material cost is increased. The thermionic mass spectrometer test shows that the abundance retention of 10 B from feedstock to product is still in room for improvement, even in the optimized process. The carbothermic reduction method requires a reaction temperature of up to 1700-1800 ℃ and has huge energy consumption. More importantly, the process is essentially a solid-solid phase reaction, with the contact area and mass transfer rate between the reactants being critical factors limiting the rate and completeness of the reaction. The traditional method is difficult to effectively solve the problem of large mass transfer resistance at high temperature, and the problem is often compensated by prolonging the heat preservation time or improving the temperature, so that the energy consumption and the volatilization risk of B 2O3 are further increased. In summary, the prior art has the common problems of low purity of the product, poor micro-uniformity, non-ideal isotope utilization rate, high reaction energy consumption and the like. Disclosure of Invention The invention aims to solve the technical problems of overcoming the defects of the prior art and providing boron carbide powder enriched with boron-10 isotopes, which realizes uniform mixing of molecular level, obviously improves reaction dynamics, and can obtain high-purity, high-uniformity and high- 10 B enrichment degree B 4 C powder under relatively mild conditions, and a preparation met