Biomedical subjects
Publications and source records attributed to C A Volkert.
We report a macroscopic shrinkage by up to 30 vol % during electrochemical dealloying of Ag-Au. Since the original crystal lattice is maintained during the process, we suggest that the formation of nanoporous gold in our experiments is accompanied by the creation of a large number of lattice defects and by local plastic deformation.
In this paper, synthetic fluorapatite-gelatine composite particles are prepared for transmission electron microscopy (TEM) studies using two methods based on focused ion beam (FIB) milling. TEM studies on the FIB-prepared specimens are compared with TEM observations on samples prepared using an ultramicrotome. The results show that ultramicrotome slicing causes significant cracking of the apatite, whereas the ion beam can be used to make high-quality, crack-free specimens with no apparent ion beam-induced damage. The TEM observations on the FIB-prepared samples confirm that the fluorapatite composite particles are composed of elongated, preferentially orientated grains and reveal that the grain boundaries contain many small interstices filled with an amorphous phase.
Small amounts of alloying elements can significantly retard electromigration in conductor lines. This phenomenon is experimentally well established but is still lacking a fundamental explanation. An atomic-level mechanism for this behavior is proposed here which is based on a kinetic analysis of diffusion in crystalline interfaces. It predicts a reduction or reversal of the flux of host atoms for physically reasonable parameters and can account for the observed effect of copper on electromigration in aluminum conductor lines.