14 research outputs found
Time-of-flight measurements of the neutron spectrum in a sub-critical fast reactor assembly
Comparison of tetracycline and minocycline in the treatment of non-gonococcal urethritis.
Investigation into the inhibitory effect of flurofamide on animal ureaplasmas and its use in the treatment of ureaplasma-infected sheep
Mechanical behavior of a bulk nanostructured iron alloy
Bulk, fully dense materials were prepared from Fe-10Cu with grain diameters between 45 run and 1.7 yum. The materials were prepared by ball milling of powders in a glove box, followed by hot isostatic pressing (hipping) or powder forging. Larger grain sizes were obtained by thermal treatment of the consolidated powders. The bulk materials were relatively clean, with oxygen levels below 1500 wpm and other contaminants less than 0.1 at. pet. The mechanical behavior of these materials was unique. At temperatures from 77 to 470 K, the first and only mechanism of plastic deformation was intense shear banding, which was accompanied by a perfectly plastic stress-strain response (absence of strain hardening). There was a large tension-compression asymmetry in the strength, and the shear bands did not occur on the plane of maximum shear stress or the plane of zero extension. This behavior, while unusual for metals, has been observed in amorphous polymers and metallic glasses. On the other hand, the fine-grained Fe-10Cu materials behaved like coarse-grained iron in some respects, particularly by obeying the Hall-Petch equation with constants reasonably close to those of pure iron and by exhibiting low-temperature mechanical behavior which was very similar to that of steels. Transmission electron microscopy (TEM) studies found highly elongated grains within shear bands, indicating that shear banding occurred by a dislocation-based mechanism, at least at grain sizes above 100 nm. Similarities and differences between the fine-grained Fe-10Cu and metals, polymers, metallic glasses, radiation-damaged metals, and quench-damaged metals are discussed
Heterogeneous nucleation and microstructure formation in colloidal model systems with various interactions
Recent studies of crystal nucleation and further microstructure formation in colloidal model systems are reviewed. Homogeneous as well as different heterogeneous nucleation scenarios will be discussed. We focus on the crystallization process of one component colloidal model systems with hard sphere like interaction, long range electrostatic interaction and depletion force induced attractive interaction. Heterogeneous crystallization on flat and smooth substrates, on structured substrates, induced by different kind of seed particles as well as inoculation adding a larger amount of seeds will be presented