Chapter 4—Selected Area Electron Diffraction Analysis of Extraction Replica and Thin Foil Specimens in the Transmission Electron Microscope

2009 ◽  
pp. 41-41-32
Author(s):  
1997 ◽  
Vol 3 (S2) ◽  
pp. 755-756
Author(s):  
D. C. Dufner ◽  
R. A. Zingaro ◽  
A. P. Murphy ◽  
C. D. Moody

Since the early 1980s, Se toxicity in wildlife has created a great deal of interest and concern. Reservoirs, marshes, and wetlands in which excessive amounts of Se have been found are considered to be the source of their toxicity problems. Thus, an effective and inexpensive treatment of Se-contaminated waters which significantly lowers the concentration of this element is needed. One such method for removing selenites and selenates from water utilizes iron (II) hydroxide as a reducing agent. In this work, the reduction products are analyzed in the transmission electron microscope (TEM) using electron diffraction and energy-dispersive spectroscopy (EDS) to determine the presence of Se.A “standard” aqueous solution was prepared by the addition of KOH to distilled water to pH 8.8. Sufficient quantities of Na2SeO3 or Na2SeO4 were weighed and dissolved in the “standard” solution to yield SeO3-2 or SeO4-2 ions. A weighed quantity of Fe(NH4)2(SO4)2 was then added to the SeO3-2 or SeO4-2 “standard” solution to form a precipitate of iron hydroxide.


2002 ◽  
Vol 757 ◽  
Author(s):  
D. E. Janney

ABSTRACTArgonne National Laboratory has developed an electrometallurgical process for conditioning spent sodium-bonded metallic reactor fuel prior to disposal. A waste stream from this process consists of stainless steel cladding hulls that contain undissolved metal fission products such as Tc, Ru, Rh, Pd, and Ag; a small amount of undissolved actinides (U, Np, Pu) also remains with the hulls. These wastes will be immobilized in a waste form whose baseline composition is stainless steel alloyed with 15 wt% Zr (SS-15Zr). Scanning electron microscope (SEM) observations of simulated metal waste forms (SS-15Zr with up to 11 wt% actinides) show eutectic intergrowths of Fe-Zr-Cr-Ni intermetallic phases with steels. The actinide elements are almost entirely in the intermetallics, where they occur in concentrations ranging from 1–20 at%. Neutron- and electron-diffraction studies of the simulated waste forms show materials with structures similar to those of Fe2Zr and Fe23Zr6.Dissolution experiments on simulated waste forms show that normalized release rates of U, Np, and Pu differ from each other and from release rates of other elements in the sample, and that release rates for U exceed those for any other element (including Fe). This paper uses transmission electron microscope (TEM) observations and results from energy-dispersive X-ray spectroscopy (EDX) and selected-area electron-diffraction (SAED) to characterize relationships between structural and chemical data and understand possible reasons for the observed dissolution behavior.Transmission electron microscope observations of simulated waste form samples with compositions SS-15Zr-2Np, SS-15Zr-5U, SS-15Zr-11U-0.6Rh-0.3Tc-0.2Pd, and SS-15Zr-10Pu suggest that the major actinide-bearing phase in all of the samples has a structure similar to that of the C15 (cubic, MgCu2-type) polymorph of Fe2Zr, and that materials with this structure exhibit significant variability in chemical compositions. Material whose structure is similar to that of the C36 (dihexagonal, MgNi2-type) polymorph of Fe2Zr was also observed, and it exhibits less chemical variability than that displayed by material with the C15 structure. The TEM data also demonstrate a range of actinide concentrations in materials with the Fe23Zr6 (cubic, Mn23Th6-type) structure.Microstructures similar to those produced during experimental deformation of Fe-10 at% Zr alloys were observed in intermetallic materials in all of the simulated waste form samples. Stacking faults and associated dislocations are common in samples with U, but rarely observed in those with Np and Pu, while twins occurred in all samples. The observed differences in dissolution behavior between samples with different actinides may be related to increased defect-assisted dissolution in samples with U.


Author(s):  
H. Rager ◽  
M. Schosnig ◽  
A.K. Schaper ◽  
A. Kutoglu ◽  
W. Treutmann

This paper deals with transmission electron microscope experiments of Ca,Sr-åkermanite solid solutions at temperatures between 100 K and 375 K. The aim of the investigations was to study the compositional and temperature dependence of phase transitions from the normal to the incommensurately modulated structure of(Ca


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