Biomedical subjects

D Eyidi

Publications and source records attributed to D Eyidi.

3 recordsLinked to original sources

PubMed2006

Short note on parallel illumination in the TEM.

Parallel illumination conditions are required for several experiments in the transmission electron microscope (TEM). The image rotation induced by the helical trajectory of electrons passing through the magnetic field of the TEM lenses inevitably induces an inclination of the beam relative to the optical axis in the object plane--even for an electron which travels parallel to the optical axis in the far field. This angle (shear angle) is vectorially added to the convergence angle; it depends both on the distance to the optical axis and the magnetic field. By using a beam tilt compensation method, the minimum shear angle is found to be of the order of 1 mrad for a field of view of 2 microm in a 200 kV TEM. In practice, "parallel illumination" can only be obtained for fields of view 1 microm.

Journal Article↗

PubMed2003

Phase analysis of superconducting polycrystalline MgB(2).

Superconducting MgB(2) ceramics were prepared and yield superconducting transition temperatures of about 39 K. For covering the various length scales on which inhomogeneities appear in MgB(2), electron-probe micro-analysis (EPMA) and analytical transmission electron microscopy (TEM) were applied for a phase analysis. Particularly useful were the preliminary electron spectroscopic imaging (ESI) results in the TEM. It could be shown by EPMA that the microstructure consists of a Mg-B-O matrix and boron-rich secondary phases of composition close to MgB(12). It was unclear in which form oxygen was present in the superconducting matrix. By combining the acquisition of B-K and O-K edge jump ratio images and energy-dispersive X-ray spectroscopy in the TEM, we could prove that the matrix consists of superconducting MgB(2) and MgO. Most of the MgO precipitates and grains appear with diameters between 20 and 300 nm. The size distribution of MgO was inhomogeneous and oxygen-rich areas of dimensions >1 microm were also observed. Edge jump ratio images obtained by ESI were analysed for determining the signal values and effects of multiple inelastic scattering.

Boron Compounds↗

PubMed2002

A simple, quick and reliable method for TEM cross-section preparation of ceramic oxide films on thin metal substrates.

We present a preparation method of cross-sectional thin foils for transmission electron microscopy (TEM). Samples are 0.1-1 m thick ceramic oxide films (CeO2, CeO2-YBa2Cu3O7 and CeO2-ZrO2/YO2-YBa2Cu3O7) epitaxially grown on 30-100 m highly textured nickel substrates. This method includes gluing the sample between a copper oxide dummy and a silicon dummy, followed by mechanical polishing and conventional ion milling. TEM cross-sectional samples obtained with this selection of dummies are electron-transparent up to a few tens of m parallel to the film surface. Several layer structures were analyzed by TEM and the results are shown. The preparation technique described here can be applied to any type of oxide film deposited on thin metal substrates.

Journal Article↗