【作者】 杨健；

【导师】 葛良全；

【作者基本信息】 成都理工大学 ， 核资源与核勘查工程， 2011， 博士

【摘要】 在微米级,亚微米级尺度上观察和测定矿物组份,对地学研究和矿产资源勘查都具有重大意义。作为一种重要的分析手段,微束微区X射线荧光矿物探针旨在将大面积扫描与微区分析结合,能在微米级尺度范围内,满足对矿物成份和元素分布的分析测定,并可进一步推广应用到金属学、电子科学、医学、生物学和环境监测等领域。本文从X射线与物质的相互作用基本原理出发,在研究微束X射线荧光技术的矿物微区分析关键技术之基础上,设计并研制微束微区X射线荧光矿物探针仪,主要研究内容与取得的研究成果如下:1、研制国内首台微束微区X射线荧光矿物探针。实现了微束照射(光斑直径约30μm-50μm)和微区激发;微区的精密定位与控制;微区的显微放大与成像;微区特征X射线能谱信息的准确获取,矿物微区多元素定性、定量分析等。仪器的主要技术指标达到并部分超过国外同类技术产品。2、微束X射线源的设计与实现。设计了X射线聚束光路,建立了微束X光学器件与微区X射线荧光分析技术的关联性。设计的微束X射线源采用牛津公司先进的低功率侧窗型微焦斑(70μm)X射线光管和具有国际先进水平的国产毛细管X射线透镜组合,实测微区空间分辨率对NiKα线焦斑直径为34μm,有效的提高了目标元素特征X射线荧光的激发效率、减小了背景散射,为微束微区多元素定性和高灵敏度定量测量奠定了基础。3、针对X射线微束的能量及强度分布特征,进行三维机械微动平台的精密设计,研究三维机械精密微动平台空间微米尺度定位技术,以提高探针系统在微区内对目标点及面的扫描分析的运动精度。在三维微动平台整体结构布局研究的基础上,建立高精密电机驱动,高精度精密串联机械传动元件为主的机械传动系统动力学模型,以Hertz接触理论,对微动台机械传动链的轴向传动刚度进行理论推导,分析了平台在低速运动下的不平稳现象及定位误差产生的原因。结合参数化建模和有限元分析法,对滚珠丝杠螺母副等重要零部件进行静态特性分析,对机械结构进行优化设计。设计的三维微动平台整体尺寸小于180mm3,在几十毫米行程范围内,实现平均最小步距1.5μm,定位精度达到±1μm,无低速爬行现象。保证了仪器分析的空间分辨率及定量定性分析的精度。4、基于X射线微束源和微区分析要求的特殊性,研究矿物分析微区信息(包括微区图像信息和特征X射线能谱信息)的获取技术。矿物探针采用20~40倍光学放大镜和300万像素CCD工业数码相机组成显微成像系统,以Si-PIN半导体为X射线探测器,实现对矿物微区图像和目标元素特征X射线的实时采集。同时,显微成像系统与三维微动平台的联动操作,使矿物待分析微区在空间中被精确定位。在理论分析和物理实验基础上获得了最优的源-样-探-CCD几何设计,为降低微束微区X射线荧光分析的检出限,提高元素分析的灵敏度、精确度提供了技术保证。5、对矿物探针的主要技术指标展开测试,提出了科学的微束微区X射线矿物探针焦斑的微分实验测定方法和积分实验测定方法。在微米尺度上,对铬镍丝(直径10μm)步进测量NiKαX射线特征峰面积,实现对微区焦斑的微分曲线测定;对铜片步进测量CuKαX射线特征峰面积,实现对微区焦斑的积分曲线测定。在一定的置信水平下对微分曲线和积分曲线概率分析获取系统的焦斑直径。实测结果表明:在0.317的置信水平下,微束微区X射线荧光矿物探针的焦斑直径为34μm。6、开展了矿物微束微区X射线荧光分析的初步试验。对块状锌矿石(闪锌矿)和铁矿石(黄铁矿)光片样品进行了微束微区荧光分析试验。结果显示:微束微区X荧光矿物探针系统可以将10μm~30μm粒径大小的矿物颗粒从基体中有效的区分出来,对单矿物中元素含量分析的准确度达到4.21 %(RSD)。微束微区X射线荧光矿物探针仪适用于地质样品,显晶或隐晶矿物成分,粉晶材料,块状、薄片、光片材料的微区多元素定性定量分析,具有低成本、制样简单,分析速度快的特点。对微束微区X射线荧光矿物探针仪的研制和关键技术的探讨将加快此类仪器的国产化步伐,填补我国在低成本,自动化,高精度,微米级区域内X射线荧光矿物探针研制和野外应用研究方面的空白,打破国内市场被国外仪器垄断的局面,提高我国矿产资源勘查的装置水平与技术水平。更多还原

【Abstract】 Observation and determination for mineral components at micro-level and sub-micro level are of great significance in the field of geosciences and mineral resources exploration. As an important analytical tool, micro-beam and micro-area X-ray fluorescence (Micro-XRF) mineral probe which aims to combine both a large area of scanning and micro-area analysis is capable of meeting the requirements for the analysis and detection of mineral composition and elements distribution at micrometer scale, it can also be further extended to the metal study, electronics science, medicine, biology, environmental monitoring and other fields. From the basic principle of X-ray interaction with matter, setting out to study the key analytical technology of micro-beam X-ray fluorescence for the minerals, the dissertation elaborates the design and development of a kind of micro-beam and micro-area X-ray fluorescence (Micro -XRF) mineral probe. The main contents and the innovative research results are as follows:1. Developed the first micro-beam and micro-area X-ray fluorescence mineral probe at home. Implemented micro-beam irradiation (spot diameter is about 30μm ~50μm) and micro-area excitation; micro-area precision positioning and control; microscopic magnification and imaging; obtaining accurate information of characteristic X-ray energy spectrum for micro-area analysis, multi-elements qualitative and quantitative analysis for minerals within micro-area. The major technical indicators have reached that of similar foreign products, part of them surpass the foreign advanced level.2. Design and Implementation of Micro-beam X-ray source. Designed X-ray optical path and established the technical association between the focusing X-ray optics and micro-area X-ray fluorescence analysis . The micro-beam X-ray source combined both the Oxford advanced side’s window low-power X-ray tube with 70μm micro-spot and Monolithic X-ray Lens made in china which have reached the international advanced level. The measured spatial resolution on NiKαline spot diameter is 34μm, which effectively raised the target element characteristic X-ray fluorescence excitation efficiency, reduced the background scattering, then laid the foundation for micro-beam and micro-area multi-element qualitative analysis and highsensitivity quantitative measurement. 3. Designed a kind of three-dimensional precision micro-displacement stage targeting at the distribution characteristic of micro-beam X-ray energy and intensity. Research into its space micrometer precision positioning technology in order to improve the moving stability and accuracy for the mechanical components under the low speed effectively. Based on exploring the three-dimensional layout of the overall structure, built up a dynamic model for the mechanical transmission system in series which consists of high-precision motor and high precision mechanical transmission components. Using Hertz contact theory to execute the theoretical derivation for transmission chain rigidity of mechanical transmission system. Analyzed the reasons of unstability at low speed and the positioning errors of micro-platform. At the same time, used parametric modeling software combined with finite element analysis method to optimize the design of the mechanical structure. The three-dimensional micro-displacement stage, which was designed less than 180mm3 in overall size and achieved ten to tens of millimeter stroke in spatial orientation with±1μm positioning accuracy and 1.5μm average step, can provide a precise movement for the target point positioning and the surface scanning in Micro-probe system.4. Considering on the special requirements of micro-beam sources and micro-area analysis, studied the access technology of information from the micro-area on mineral sample(including image information and energy spectrum characteristic information of X-ray). Adopting Si-PIN semiconductor detector and a microscopic magnification systems which consists the 20 to 40 times optical magnifier and 300 million pixel CCD industrial digital camera, the Mineral probe can collect the information of the micro-area image and characteristic X-ray energy spectrum of target elements in real-time. Meanwhile, the micro-area to be analyzed can be precisely located in space when linking the operation of microscopic magnification systems and the three-dimensional moving platform. Obtained the optimal source - sample - probe-CCD geometric design based on the theoretical analysis and physical experiments, which reduced detection limits of micro-beam and micro-area X-ray fluorescence analysis, improved the sensitivity of elemental analysis and provided technical guarantee of the accuracy.5. Carried out the testing for the main technical indicators of mineral probe. Presented scientific differential and integral experimental methods to measure the focal spot size of micro-beam and micro-area X-ray mineral probe. In the micron scale, measuring the NiKαX-ray characteristics peak area of nickel-chromium wire (diameter 10μm) by step moving can get the differential curve of the spot , however measuring the CuKαX-ray characteristics peak area of copper slice by step can get the integral curve of spot. Under a certain level of confidence, analyzing the differential curve and the integral curves further will finally access the spot size of the instrument. The test results showed that at 0.317 confidence level, the focal spot diameter of micro-beam and micro-area X-ray fluorescence minaral probe is 34μm.6. Developed preliminary mineral tests on the micro-beam and micro-area X-ray fluorescence mineral probe system, which operated on the sample of massive zinc ore (sphalerite) and iron ore (pyrite). The results showed that micro-beam and micro-area X-ray fluorescence mineral probe system can effectively distinguish mineral particles varying from 10μm to 30μm from matrix. The analysis accuracy for elements content in single mineral is 4.21% (RSD).With the characteristic of lower costs, simple sample preparation, fast speed of analysis, the micro-beam and micro-area X-ray fluorescence mineral probe instrument is satisfactory for qualitative and quantitative multi-element micro-area analysis, which can be used in the geological mineral samples, crystalline or cryptocrystalline mineral composition, powder materials, massive, thin, tinsel materials. Hence, developing the micro-beam and micro-area X-ray fluorescence mineral probes and investigating the key technologies of them will accelerate the pace of manufacturing domestic silimar production, fill the empty of development the low-cost, automated, high precision Micro-XRF and application in the mineral exploration within micro-region at home; Meanwhile, break the monopoly situation by foreign device at domestic market. All of that will improve the equipment level and technical level of mineral exploration at home.更多还原