Preparation of Samples with Both Hard and Soft Phases for Electron Backscatter Diffraction: Examples from Gold Mineralization
Abstract Preparation of high-quality polished sample surfaces is an essential step in the collection of microanalytical data on the microstructures of minerals and alloys. Poorly prepared samples can yield insufficient or inconsistent results and, in the case of gold, potentially no data due to the “beilby” layer. Currently, preparation of ore samples is difficult as they commonly contain both hard and soft mineral phases. The aim of our research is to produce suitably polished sample surfaces, on all phases, for electron backscatter diffraction analysis. A combination of chemical–mechanical polishing (CMP) and broad ion-beam polishing (BIBP) was used to tackle the problem. Our results show that it is critical to perform CMP first, as it produces a suitable polish on the hard mineral phases but tends to introduce more damage to the soft mineral surfaces. BIBP is essential to produce a high-quality polish to the soft phases (gold). This is a highly efficient method of sample preparation and is important as it allows the complete quantification of ore textures and all constituent mineral phases, including soft alloys.
Computer-aided determination of crystal-lattice orientation from electron channeling patterns in the SEM
The paper presents the major steps of a mathematical procedure that permits the simulation of Electron Channeling Pattern @CP) maps of any mineral species for which unit-cell constants, the atomic species and their equivalent positions are known. The basis of calculation is the Bragg equation, the structure factor d and the atomic scattering factors of the atomic species. Simulated spherical ECP maps for chromite and quartz are presented and compared to traditional ECP maps, which were constructed from ECP photomicrographs, good results. The fraction of the ECP sphere that covers all possible orientations of a crystal is discussed for all 32 point groups. It is shown that Lauegroup symmetry is the determining factor, which results in a loss of "resolution" in certain point groups. The ECP simulation leads to the creation of a software package CHANNEL, which permits rapid ECP-pattern recognition and lattice-orientation determination, in principle without the need for previous construction of an ECP map.
Application of Automatic Tracking Correlation Filtering in Motored Spindle Dynamic Balancing
According to the information characteristics of the dynamic imbalance signal and the definition of correlation function,the principles and algorithm of relevant filter with automatic tracking is given.In labview development system,based on the principles of relevant filter with automatic tracking,the graphics programming of extracting the dynamic imbalance signal is developed.With this programming,the vibration signal including different frequency harmonic signals and noise is processed by simulation and on-site experiment.The results show that: through relevant filter with automatic tracking,the dynamic imbalance signal under different rotating speed can be extracted accurately,and it can meet the requirement of motored spindle dynamic balancing measurement.