Characterisation of rare earth minerals with field emission scanning electron microscopy

Abstract

Rare earth elements are becoming increasingly in demand, due to their prevalence in both renewable energy devices and high end electronics. The characterisation of the composition and morphology of the various phases that have valuable rare earth elements in the ores are needed in conjunction with the study of their physicochemical properties to optimise industrial process to extract the minerals containing the rare earth elements. Rare earth bearing minerals contain many elements with overlapping X-ray peaks (L- and M-lines) with an energy dispersive spectrometry detector, requiring a high degree of X-ray energy resolution. A program was developed to obtain the intensity of each peak by deconvolution of the X-ray spectrum. Low accelerating voltage of less than 5 kV and small beam diameter of less than 10 nm of a cold field emission scanning electron microscope allow x-ray microanalysis on the nanometre scale. A 100 nm wide phase was observed at 4 kV on a backscattered electron micrograph. Furthermore, a small beam diameter of less than 10 nm was used for identification of small phases of a few micrometres.

Les éléments de terre rare sont de plus en plus en demande, grâce à leur prévalence tant dans les dispositifs d’énergie renouvelable que dans l’électronique de haute gamme. On a besoin de caractériser la composition et la morphologie des différentes phases qui contiennent des terres rares de valeur dans les minerais, en combinaison avec l’étude de leurs propriétés physico-chimiques, afin d’optimiser le procédé industriel d’extraction des minéraux contenant les terres rares. Les minéraux porteurs de terre rare contiennent plusieurs éléments ayant des pics de rayons x qui se chevauchent (lignes L et M) avec un détecteur de spectroscopie à dispersion d’énergie, nécessitant une haute résolution énergétique. On a développé un programme visant à obtenir l’intensité de chaque pic par déconvolution du spectre de rayons x. Un faible voltage d’accélération de moins que 5 kV et un faisceau à faible diamètre de moins que 10 nm d’un microscope électronique à balayage par cathode froide permettent la microanalyse des rayons x à l’échelle du nanomètre. On a observé une phase de 100 nm de largeur à 4 kV sur une micrographe d’électrons rétrodiffusés. De plus, on a utilisé un faisceau de faible diamètre de moins que 10 nm pour l’identification de petites phases de quelques μm.     

Sequence Algebra, Sequence Decision Diagrams and Dynamic Fault Trees

A large attention has been focused on the Dynamic Fault Trees in the past few years. By adding new gates to static (regular) Fault Trees, Dynamic Fault Trees aim to take into account dependencies among events. Merle et al. proposed recently an algebraic framework to give a formal interpretation to these gates.In this article, we extend Merle et al.'s work by adopting a slightly different perspective. We introduce Sequence Algebras that can be seen as Algebras of Basic Events, representing failures of non-repairable components. We show how to interpret Dynamic Fault Trees within this framework. Finally, we propose a new data structure to encode sets of sequences of Basic Events: Sequence Decision Diagrams. Sequence Decision Diagrams are very much inspired from Minato's Zero-Suppressed Binary Decision Diagrams. We show that all operations of Sequence Algebras can be performed on this data structure.     

Fault management in process control: eye movements and action

Operators controlled a simulated thermal hydraulic system based on Crossman's waterbath task. They were required to keep the system at set points for temperature, level and flow rates. The system was subjected to disturbances and to failures, which the operators were required to manage. Behavioural data were collected in the form of keystroke commands, and in addition eye movements were measured. Evidence for ‘cognitive lockup’ and for a preference for serial fault management were found. Fixation durations do not change, but faulty subsystems are examined more frequently. During lockup other subsystems may be examined but action on them is delayed. Eye movements give considerable additional insight into the nature of process control information processing compared with traditional measures of operator performance.     

Study on electrothermally actuated cantilever array for nanolithography

Nanolithography is a patterning technique for the fabrication of nano-scale structures.A promising method of nanolithography known as scanning probe lithography has particularly extensive applications for its high resolution,high reliability,and simple operation.In this paper,a novel electrothermally actuated cantilever with integrated heater,thermal conductor and actuator for scanning probe lithography is proposed.Cantilevers are designed in an 8×4 array.Analytical models are presented to simulate the temp...     

8279集成芯片在铝电解智能槽控机上的应用

8279芯片是专用数码显示器接口芯片,能对显示器自动扫描,并大大减轻CPU的负担。因此,在单片机应用系统中,获得了广泛的应用。主要阐述了8279芯片的主要结构、原理以及在铝电解智能槽控机的硬件组成、应用软件上的初始化、软件构成。     

基于PLC技术的VIGAN卸船机控制系统故障诊断

本文根据VIGAN卸船机控制系统分析了基于PLC技术的故障诊断设计。     

A new and accurate fault location algorithm for combined transmission lines using Adaptive Network-Based Fuzzy Inference System

This paper presents a new and accurate algorithm for locating faults in a combined overhead transmission line with underground power cable using Adaptive Network-Based Fuzzy Inference System (ANFIS). The proposed method uses 10 ANFIS networks and consists of 3 stages, including fault type classification, faulty section detection and exact fault location. In the first part, an ANFIS is used to determine the fault type, applying four inputs, i.e., fundamental component of three phase currents and zero sequence current. Another ANFIS network is used to detect the faulty section, whether the fault is on the overhead line or on the underground cable. Other eight ANFIS networks are utilized to pinpoint the faults (two for each fault type). Four inputs, i.e., the dc component of the current, fundamental frequency of the voltage and current and the angle between them, are used to train the neuro-fuzzy inference systems in order to accurately locate the faults on each part of the combined line. The proposed method is evaluated under different fault conditions such as different fault locations, different fault inception angles and different fault resistances. Simulation results confirm that the proposed method can be used as an efficient means for accurate fault location on the combined transmission lines.     

超短脉冲激光对无机硅材料的损伤

通过控制作用于材料表面的激光能量和脉冲数量,实验研究了800nm,50fs,1kHz激光作用下融石英玻璃和硅片的破坏机制和损伤规律,计算了材料的损伤阈值与脉冲能量以及脉冲数量的依赖关系,并采用简化的理论模型计算了熔石英玻璃材料的损伤阈值与激光脉宽以及光子能量之间的依赖关系。对这两种无机硅材料在飞秒脉冲作用后的微区结构改变进行了扫描电子显微镜(SEM)测试,研究了其形貌特征。结果表明,硅片是由缺陷中的导带电子作为种子电子引发雪崩电离导致材料损伤,而熔石英玻璃是由多光子电离激发出导带电子引发雪崩电离导致材料损伤。     

新型光学成像技术及其在生物医学中的应用

本文介绍了在生物医学中有广泛应用前景的共焦扫描光学显微镜、扫描近场光学显微术和光学相干微术三种新型成像技术的基本原理和应用。     

扫描隧道显微镜中的扫描驱动器

概述了扫描隧道显微镜的工作原理,给出了采用压电材料的扫描控制方案及获取样品表面形貌信号的方法,介绍了系统中的ｚ扫描驱动器,ｘｙ扫描驱动器（扫描平台）及其非线性修正方法。