Growth Rate and Morphology of Nb3Sn Layers in ITER-Type Bronze-Processed Wires Under Different Diffusion Annealing Regimes
The Nb3Sn-based bronze-processed multifilamentary composites have been fabricated at the Bochvar Institute of Inorganic Materials, Moscow, Russia, and studied by electron microscopy to determine the relationships between their structural parameters and annealing duration at different temperatures (575 °C, 650 °C, 750 °C). The structure of superconducting layers during their formation is characterized by thickness, average size of equiaxed grains, and by the fraction ratio of columnar and equiaxed grains. It was found that at high diffusion annealing temperatures (above 650 °C), the superconducting layers grow much faster, but the average size of equiaxed Nb3Sn grains even under a short exposure (10 h) is much larger than after a long low-temperature annealing. It is shown that to ensure the best current-carrying capacity of Nb3Sn-based wires in high magnetic fields, it is necessary to take into account different trends: on the one hand, the possibility of approaching the Nb3Sn phase stoichiometry and providing its maximum amount and on the other hand to avoid the undesirable growth of grains resulting in a lower pinning force.
The Nb3Sn layers formation at diffusion annealing of Ti-doped multifilamentary Nb/Cu–Sn composites
The structure and morphology of superconducting Nb3Sn layers in multifilamentary Nb–Ti/Cu–Sn and Nb/Cu–Sn–Ti composite wires after various regimes of the diffusion annealing have been studied by transmission and scanning electron microscopy. The effect of the doping mode and Ti concentration on the thickness, structure and morphology of Nb3Sn layers is pronounced even after the first (low-temperature) stage of the diffusion annealing. After various regimes of the annealing the wires with doped bronze matrix (Nb/Cu–Sn–0.24Ti) demonstrate wider zones of fine equiaxed Nb3Sn grains with narrow grain size distributions compared to those with Ti-doped Nb filaments, which is of great importance for an attainment of the highest critical current densities Jc.
Within and Inter-Institutional Differences Between Death Certifiers on Autopsy Conclusions
This study seeks to establish whether medico-legal practitioners differ in their autopsy conclusions within and across medico-legal institutions. Data include 459 violent deaths (homicides, suicides, and accidents) autopsy reports written by more than 20 death certifiers from four medico-legal institutions in two countries (France and the United States). Multinomial models show that compared with accidental deaths, weapon use and decedents’ characteristics both influence a homicide verdict, but not a suicide one. In addition, French practitioners are more likely than Americans to reach a conclusion of homicide or suicide compared with accident, and homicides are more likely to be certified by male practitioners.