Electron microprobe

Summary

An electron microprobe (EMP), also known as an electron probe microanalyzer (EPMA) or electron micro probe analyzer (EMPA), is an analytical tool used to non-destructively determine the chemical composition of small volumes of solid materials. It works similarly to a scanning electron microscope: the sample is bombarded with an electron beam, emitting x-rays at wavelengths characteristic to the elements being analyzed. This enables the abundances of elements present within small sample volumes (typically 10-30 cubic micrometers or less) to be determined, when a conventional accelerating voltage of 15-20 kV is used. The concentrations of elements from lithium to plutonium may be measured at levels as low as 100 parts per million (ppm), material dependent, although with care, levels below 10 ppm are possible. The ability to quantify lithium by EPMA became a reality in 2008. History The electron microprobe, also known as the electron probe microanalyzer, developed utilizing t

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Melt inclusions (MIs) hosted in euhedral olivine have been proposed to represent droplets of primary melt, protected from processes occurring near Earth's surface during eruption. The complex zoning of phosphorus (P) in some olivines and the presence of a P-depleted zone around MIs indicate a complex history for the host-MI system. We analyzed P in olivine and MIs from two mid-oceanic ridge basalt (MORB) samples from the Mid-Atlantic Ridge (MAR) by electron probe microanalyzer, secondary ion mass spectrometry (SIMS), and NanoSIMS. Phosphorus dendrites in olivine suggest an initial fast olivine growth followed by a stage of slower growth. Dissolution textures around some MIs were identified and were probably caused by adiabatic decompression melting. Based on diffusion modeling of P in olivine, we infer that olivine beneath the MAR remains in the system (1) for days to weeks after crystallization of P-rich lamellae, and (2) for a few hours after recrystallization of dissolved olivine. Dissolution and reprecipitation of olivine containing boundary layers suggests that most MIs might be affected by late post-entrapment processes.

Geological Soc Amer, Inc2017

Phase equilibria in the Au-Cu-Ge ternary system, including the solid state phase relations at 450 degrees C as well as four vertical sections, were studied by means of scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Based on the present experimental results and the available information in the literature, a thermodynamic description of the Au-Cu-Ge ternary system has been developed using the CALPHAD (CALculation of PHAse Diagram) method. A consistent set of thermodynamic parameters for each phase was derived. The calculated phase diagrams and thermodynamic properties are in reasonable agreement with the experimental data obtained in the present study as well as those reported in the literature. (C) 2013 Elsevier B.V. All rights reserved.

Elsevier Science Sa2014

Experimental investigation and thermodynamic modeling of the Au-Ge-Ni system

Shan Jin, Christian Leinenbach

Phase equilibria in the Au-Ge-Ni ternary system were studied by means of scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. The phase relations in the solid state at 600 A degrees C as well as a vertical section at Au72Ge28-Ni were established. No ternary compound was found at 600 A degrees C. On the basis of the experimental phase equilibria data, a thermodynamic model of the Au-Ge-Ni ternary system was developed using the CALPHAD method. Thermodynamically calculated phase diagrams are shown at 600 A degrees C, in two vertical sections and the liquidus projection. Reasonable agreement between the calculations and the experimental results was achieved.

Springer Wien2012