硼酸铋纳米结构的制备及其中子-γ防护性能研究

发布时间：2018-04-13 13:31

本文选题：硼酸铋 + 溶胶凝胶法　；参考：《西南科技大学》2017年硕士论文

【摘要】：近年来,随着核能和核技术的迅猛发展,人类越来越频繁活动于各类射线的环境中。面对有较强穿透能力的中子和γ射线给人体带来的伤害,传统的辐射防护材料已经无法完全满足屏蔽的具体需求。因此,为了迎接进一步的挑战,研发对中子和γ射线屏蔽效果好且力学性能优良的新型辐射防护材料已经成为材料研发的主要方面。本文以Bi_2(NO_3)_(3.5)H)2O和H)3BO)3作为原料,通过溶胶凝胶法成功制备出硼酸铋晶体,并通过调节反应条件,制备了不同形貌的硼酸铋纳米结构。研究表明,Bi/B摩尔比对产物物相有很大影响,当n(Bi):n(B)=1:2时,产物为六方晶系的Bi_6B_(10)O_(24)晶体。烧结温度和时间对硼酸铋形貌有一定影响,并得出当在530℃下烧结5 h时可以得到厚度为十几纳米的硼酸铋片状结构,当烧结温度为600℃,时间为3 h时可以得到分散性较好,尺寸为100~300 nm的硼酸铋纳米颗粒。初步探究了不同形貌的硼酸铋纳米结构的形成机制,并发现助剂柠檬酸和EDTA在硼酸铋纳米结构的形成和形貌的控制方面均起到了重要作用。通过γ谱仪对制备得到的硼酸铋纳米粉体进行γ射线屏蔽性能测试,并运用蒙特卡罗(MCNP5)程序对其热中子的屏蔽性能进行模拟后发现,硼酸铋纳米粒子对中子和γ射线的屏蔽性能均随着粉体含量的增大而增大;并且当粉体含量相同时,对γ射线的质量衰减系数随着射线能量的增大而降低,同时由于铋弱吸收区的存在,材料在105.3 keV处表现出最高的屏蔽性能。另外,不同形貌的硼酸铋纳米粉体对热中子和γ射线的屏蔽性能均要高于Bi2O3和B2O3混合物的屏蔽性能,并且片状结构的硼酸铋与颗粒状硼酸铋相比对γ射线表现出更好的屏蔽性能,但是二者对热中子的吸收性能差异甚微,表明材料对中子和γ射线的屏蔽性不仅与材料密度有关,还与粒子尺寸和形貌有关,将填料粒子纳米化,并提高粒子形貌的规整度后有利于材料对中子和γ射线的屏蔽性能的提高。
[Abstract]:In recent years, with the rapid development of nuclear energy and technology, human beings are more and more frequent activities in various types of radiation environment. In the face of neutron and gamma ray has a strong ability to penetrate to the harm of radiation protection materials, the traditional has been unable to fully meet the specific needs of shielding. Therefore, in order to meet the challenges of further research. The neutron and gamma ray shielding effect is good and the new radiation protection material with excellent mechanical properties and has become the main aspect of material development. Based on the Bi_2 (NO_3) _ (3.5)) H 2O and H 3BO) 3) as raw materials by the sol-gel method successfully prepared bismuth borate crystal, and by adjusting the reaction conditions boric acid, bismuth nanostructures with different morphologies were prepared. The results show that the molar ratio of Bi/B phase has a great influence on the product, when n (Bi): n (B) =1:2, is the product of the six party system of Bi_6B_ (10) O_ (24) crystal. The sintering temperature and time on boron Have a certain effect of bismuth morphology, obtained when sintering at 530 DEG C for 5 h from bismuth borate sheet structure thickness is 10 nm, when sintering temperature is 600 DEG C, time of 3 h can be obtained with good dispersion, size of bismuth borate nano particles 100~300 nm. A preliminary study of the formation mechanism of boric acid bismuth nanostructures with different morphologies, and found that the additives of citric acid and EDTA control on the formation and morphology of bismuth borate nano structure has played an important role. The gamma ray shielding performance test by gamma spectrometry bismuth borate nano powder was prepared by using Monte Carlo (MCNP5), and the shielding performance of program the thermal neutron simulation found that the shielding properties of bismuth borate nanoparticles on the neutron and gamma ray were increase with the powder content; and when the powder content is the same, the quality of gamma ray attenuation coefficient with With the increase of the X-ray energy decreases at the same time, due to the existence of weak absorption of bismuth, exhibits the highest shielding performance at 105.3 keV. In addition, shielding shielding properties of bismuth borate nano powders with different morphologies of thermal neutrons and gamma rays were higher than that of Bi2O3 and B2O3 mixture, and bismuth borate flake the structure and the granular bismuth borate compared to gamma ray shielding showed better performance, but the two of the thermal neutron absorption properties showed little difference, shielding materials for neutron and gamma ray is not only related to the density of the material, is also related to the particle size and morphology, the nano filler particles, and improve particle morphology the regularity is conducive to shielding materials for neutron and gamma ray enhancement.

【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ135.32;TB383.1

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