Determination of Nanocluster Sizes from Dark-Field Scanning Transmission Electron Microscopy Images

2008 ◽  
Vol 112 (6) ◽  
pp. 1759-1763 ◽  
Author(s):  
Norihiko L. Okamoto ◽  
Bryan W. Reed ◽  
Shareghe Mehraeen ◽  
Apoorva Kulkarni ◽  
David Gene Morgan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Dark Field ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Microscopy Images

scholarly journals Identification of interstratified mica and pyrophyllite monolayers within chlorite using advanced scanning/transmission electron microscopy

2019 ◽  
Vol 104 (10) ◽  
pp. 1436-1443
Author(s):  
Guanyu Wang ◽  
Hejing Wang ◽  
Jianguo Wen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Clay Minerals ◽  
Scanning Transmission Electron Microscopy ◽  
Dark Field ◽  
Chemical Compositions ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

Abstract Interstratified clay minerals reflect the weathering degree and record climatic conditions and the pedogenic processes in the soil. It is hard to distinguish a few layers of interstratified clay minerals from the chlorite matrix, due to their similar two-dimensional tetrahedral-octahedral-tetrahedral (TOT) structure and electron-beam sensitive nature during transmission electron microscopy (TEM) imaging. Here, we used multiple advanced TEM techniques including low-dose high-resolution TEM (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging combined with energy-dispersive spectroscopic (EDS) mapping to study interstratified layers in a chlo-rite sample from Changping, Beijing, China. We demonstrated an interstratified mica or pyrophyllite monolayer could be well distinguished from the chlorite matrix by projected atomic structures, lattice spacings, and chemical compositions with advanced TEM techniques. Further investigation showed two different transformation mechanisms from mica or pyrophyllite to chlorite: either a 4 Å increase or decrease in the lattice spacing. This characterization approach can be extended to the studies of other electron-beam sensitive minerals.

A further investigation of the complex M3 murataite structure using Hf substitution and STEM-EELS techniques

2019 ◽  
Vol 75 (3) ◽  
pp. 442-448
Author(s):  
Ryosuke S. S. Maki ◽  
Peter E. D. Morgan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Radioactive Waste ◽  
Scanning Transmission Electron Microscopy ◽  
Dark Field ◽  
Site Preference ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

Many members of the complex crystalline fluorite supercell structures (e.g. zirconolite, pyrochlore and murataite polytypes) have been considered/studied for possible long-term radioactive-waste immobilization. The eight-coordinated sites in these crystals are of particular importance because they are preferred for the accommodation of trivalent rare earths and actinides present in radioactive waste from fuel element processing. The fluorite-type supercell structures include the murataites, M3, M5, M7, M8, having those numbers of repeating fluorite sub-cell units. One simple technique, as shown here, namely the substitution of Hf into the Zr site, is very helpful for structural analysis in these very complex cases in order to further illuminate the site preference of the Zr ion. Three M3 murataite samples, Ca-Mn-Ti-Zr-Al-Fe-O (regular M3), Ca-Ti-Zr-Al-Fe-O (Mn-free M3) and Ca-Mn-Ti-Hf-Al-Fe-O (Hf-substituted M3) are investigated and, through techniques described for larger cells, show that the Zr is very likely not to be hosted in the [6] Ti site in the M3 murataite structure, as suggested by Pakhomova et al. [(2013), Z. Kristallogr. Cryst. Mater. 228, 151–156], but more likely replaces the [8] Ca1 site and less likely the [8] Ca2 site. This adjusted site preference for each cation from the powder X-ray diffraction (PXRD) and scanning transmission electron microscopy electron energy-loss spectroscopy (STEM-EELS) methods, agrees well with the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image.

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