Electron probe microanalysers

There are three types of electron microscopes commonly used for microanalysis. These are the scanning electron microscope (SEM) with X-ray detectors, the electron probe microanalyser (EPMA), which is essentially a purpose built analytical microscope of the SEM type, and transmission microscopes (TEM and STEM) fitted with X-ray detectors. In a TEM, compositional information may also be obtained by... 

Wollast, R., and Burny, F. Study of bone mineralization at the microscopic level using an electron probe microanalyser. Calc. Tiss. Res. 8, 73-82 (1971). 

It was in 1949, at the first European conference on electron microscopy in DelO. that R. Castaing described the electron probe microanalyser he had designed under the guidance of A. Guinier. In his thesis (1951), Castaing also described the basic physical principles that were subsequently to make the microprobe a tool for quantitative microanalysis. Current electron microprobe analysers differ little in their basic principle from that originally described by Castaing. Of course, improvements have been made over the years, notably the enhancement of detection systems and the automation of the equipment. 

A6. Andersen, C. A., An introduction to the electron probe microanalyser and its application to biochemistry. Methods Biochem. Anal. 15, 147-270 (1967). 

The spatial distributions of catalytic metals and contaminant poisons in auto exhaust catalysts were delineated by electron probe line scans. Element concentrations were characterized by element sensitivities, i.e. in counts per second (cps). The electron probe microanalyses (EPM) were qualitative or semiqualitative in nature. Accurate correlation between element sensitivity and element concentration requires rather sophisticated instrument calibration. A quantitative evaluation of the EPM findings is beyond the scope of this paper. In general, it can be stated that element concentration is directly proportional to element sensitivity. Furthermore, the proportionality constant between element concentration and element sensitivity varies greatly from element to element. 

The authors report the syntheses of Th2(P04)2HP04-H20 and Th(0H)P04 from aqueous solutions under hydrothermal conditions at temperatures around 150°C. A combination of techniques (SEM, XRD, IR, electron probe microanalyses, DTA and TGA) are used. It is indicated that the dissolution reactions of Tli4(P04)4P207 in water results in the formation of Th2(P04)2HP04-H20. No original thermodynamic data were obtained in this study. 

Early electron probe microanalysers were usually stand-alone instruments, but the instrumentation currently produced normally takes the form of an add-on option to a scanning electron microscope (SEM) (see Scanning electron microscopy), the same beam being used to create the visible image and to generate X-rays. Thus, an area of interest may be subjected to both topographical and compositional investigation. 

Electron probe microanalyser (EPMA) Electron beam is allowed to probe the sample resulting interactions, emits characteristics x-ray of elements present in the sample recorded in WDX-spectra and the needed information can be extracted from the data. ... 

Figure 2. Electron-probe microanalyses of a deactivated catalyst semiquantitative vanadium and sulfur concentration profiles...

Moreover, thin (less than 2 pm thickness) and pinhole-free Pd-Cu alloy composite membranes with a diffusion barrier have been fabricated on mesoporous stainless steel supports (MSSS) by vacuum electro-deposition (Nam and Lee, 2001). The deposition film was fabricated by multilayer coating and diffusion treatment and the formation of Pd-Cu alloys was achieved by annealing the as-deposited membranes at 450°C in nitrogen atmosphere. To improve the structural stability of Pd alloy/Ni-MSSS composite membranes, a thin intermediate layer of silica by sol-gel method was introduced as a diffusion barrier between Pd-Cu active layer and a modified MSSS substrate. The composition and phase structures of the alloy film were studied by energy dispersive analysis (EDS) and XRD the typical Pd-Cu plating had a composition of 63% Pd and 37%Cu and the atomic inter-diffusion of Pd and Cu resulted in Pd-Cu alloys in an fee structure. The electron probe microanalyser (EPMA) profiling analysis indicated that the improved membranes were structurally stable. The Pd-Cu alloy composite membrane obtained in this study yielded excellent separation performance with H2 permeance of 2.5 x 10 cm /(cm cmHg s) and Hj/Nj selectivity above 70000 at 450°C. 

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