Sigma-phase in Fe-Cr and Fe-V alloy systems and its physical properties

A review is presented on physical properties of the sigma-phase in Fe-Cr and Fe-V alloy systems as revealed both with experimental -- mostly with the Mossbauer spectroscopy -- and theoretical methods. In particular, the following questions relevant to the issue have been addressed: identification of sigma and determination of its structural properties, kinetics of alpha-to-sigma and sigma-to-alpha phase transformations, Debye temperature and Fe-partial phonon density of states, Curie temperature and magnetization, hyperfine fields, isomer shifts and electric field gradients.Comment: 26 pages, 23 figures and 83 reference

Core-shell latices based on conductive polymers

A poly(butyl methacrylate) (PBMA) latex was coated with a thin polypyrrole (PPy) layer in a chemical in situ polymerization. Ammonium persulfate and Fenton's reagent were used as the oxidants. The influence of reaction time on the conversion of pyrrole and on the conductivity of the resulting coated latices was investigated. Furthermore, the influence of the reaction atmosphere was investigated. It was found that the ammonium persulfate-oxidized reaction was quite insensitive towards the reaction atmosphere, whereas the Fenton's reagent oxidized system was very sensitive. In the latter system, when kept in air the conductivity reached a maximum after 30 minutes. In a nitrogen reaction atmosphere the conductivity gradually increased. The maximum conductivity, which was about 20 times as high as in air, was reached after 90 minutes and remained stable