摘要
金属铍具有耐高温、耐腐蚀特点,是国防军工和航空航天等领域不可替代的金属材料.然而,由于缺乏铍元素微区无损定量分析技术,制约了诸如铍元素在矿物中赋存状态、铍超常富集机制等相关基础研究和找矿勘查技术的发展.虽然电子探针具有矿物微区定量分析的优势,但是目前还没有有效的对超轻元素Be的分析技术.本研究.选择日本电子两种不同型号的电子探针(JEOL JXA-8800和JXA-8100),配置不同分光晶体(LDEB和LDE3H),对绿柱石中铍的定量分析方法进行了研究,结果以加速电压10kV、束流20 nA、分光晶体为LDE3H、Base=1,win-dow=5、slit为open、微分模式(differential)、峰位测量时间为50s、背景测量25s、标样为金属Be为最佳条件.该方法测试绿柱石中Be的检测限低于250ppm(1ppm=1μg/g),BeO的标准误差σ==0.52wt%.此外,对造成铍测试困难的原因、分析过程中出现的现象、条件设置等,在理论上进行了剖析.这不仅为同行电子探针测试Be元素提供了较成熟的测试经验,而且也为铍资源的相关研究和找矿勘查提供了技术支撑.
Beryllium(Be) is resistant to high temperatures and corrosion, and thus is an important strategic resource for use in defense and military industries. Beryllium is also used in nuclear reactors as a neutron reflector or moderator. At present, there are numerous unresolved research questions regarding Be resources, including the mechanisms of Be mineralization, Be occurrence in minerals, and Be separation and extraction from ores. Therefore, it is important to be able to measure Be contents of minerals in situ by electron probe microanalysis(EPMA). However, given that Be is an ultra-light element, it is the most difficult element to measure by EPMA. The objectives of this research were to:(1) develop robust techniques for EPMA of Be-bearing minerals to support research into Be resources;and(2) advance the techniques for the measurement of ultra-light elements.In this study, beryl samples from the Xuebaoding deposit in Sichuan Province, China, were selected for Be analysis by EPMA. Data from two different electron microprobes(JEOL JXA-8800 and JXA-8100) with different crystals(LDEB and LDE3H, respectively) were compared. Our results show that the LDE3H crystal is better for Be analysis than the LDEB crystal, as the interplanar spacing of the former(2 d=20 nm) is much larger than that of the latter(2 d=14 nm). Under appropriate measurement conditions, satisfactory Be data can be obtained with the LDE3 H crystal. The highest peak count for the Be Kа line in the Be metal sample was obtained at an accelerating voltage of 10 kV(higher than at 3, 5, or 15 kV).The highest peak-to-background ratio for the Be Kа line in the beryl sample was also obtained at an accelerating voltage of 10 kV, a probe current of 100 nA, and beam size of 10 μm. The highest peak-to-background ratio for the Be Kа line in the beryl sample was obtained at a probe current of 20 nA(higher than at 10, 50, 100, or 200 nA) with an accelerating voltage of 10 kV and beam size of 10 μm. Thus, the optimum analytical conditions are as follows: accelerating voltage=10 kV;beam current=20 nA;beam size=0–10 μm;PHA(gain)=128;base=1;window=5;slit open;differential mode;standard=Be metal;thickness of carbon film for Be metal standard and beryl sample=15 nm;background=avoidance of interference peaks of other elements close to the Be peak position in high order;ZAF correction.Based on the chemical characteristics of Be, we also investigated why Be is challenging to measure by EPMA, and considered the chemical peak shift during analysis and the selection and optimization of the analytical conditions. The peak shifts for different Be minerals are caused mainly by the hybridization of atomic orbits between Be and O atoms. The absorption effect is the main reason why Be analyses are challenging by EPMA. The absorption effect is mainly due to O atoms, as well as other elements in minerals, such as Si, Na, Mg, and Li. A uniformly and accurately controlled carbon film thickness for the standard and samples is a key factor. A digital coating instrument(LEICA-EM-ACE200) was used in this work to ensure a precise finish. A compilation of published Be data obtained with JEOL, Shimadzu, and Cameca EMPA instruments shows that each has different crystals(LDE3H, LSA300, and PC3, respectively) and conditions for optimal Be analysis. In addition, the optimal peak position, accelerating voltage, and beam current vary for different Be Bearing minerals analyzed with the same EPMA instrument. However, a low beam current and accelerating voltage generally minimize the absorption effect on Be.
作者
张文兰
车旭东
王汝成
谢磊
李晓峰
张迪
Wenlan Zhang;Xudong Che;Rucheng Wang;Lei Xie;Xiaofeng Li;Di Zhang(State Key Laboratony for Mineral Deposits Research,School of Earth Sciehces and Engineering.Nanjing Universiny Nanjing 210023.China;Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Bejing 100029,China;Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;State Key Laboratory of Lithospheric Evolution,Instiute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2020年第28期3205-3216,共13页
Chinese Science Bulletin
基金
中国科学院地质与地球物理研究所重点自主部署项目(IGGCAS-201902)
国家自然科学基金(91855209,41572058)
第二次青藏高原综合科学考察研究(2019QZKK0802)资助
关键词
电子探针
定量分析
超轻元素铍
绿柱石
分析条件
吸收效应
electron probe microanalysis(EPMA)
quantitative analysis
ultralight beryllium element
beryl
analytical condition
absorption effect
