Citizen Brown, Race for Profit : race et citoyenneté aux xxe et xxie siècles. Présentations d’ouvrages

Organisées tous les deux ans, les rencontres de la Society of American City and Regional Planning History (SACRPH) rassemblent sur plusieurs jours près de deux cents spécialistes de l’aménagement urbain états-unien et international. Pour leur dix-huitième édition, elles se sont tenues dans le quartier de Crystal City d’Arlington, dans la banlieue de Washington, DC (et dont on pourra retrouver une présentation vidéo d’introduction ici, et le programme complet des interventions ici). Des acteu..

Comparative Study on Electrical Conductivity of CeO2-Doped AlN Ceramics Sintered by Hot-Pressing and Spark Plasma Sintering

International audienceAluminum nitride (AlN) ceramics were prepared by both Hot-pressing (HP) and Spark-Plasma-Sintering (SPS) using cerium oxide as the sintering aid. The characterization of AlN raw powder denoted the presence of an amorphous layer that led to the formation of aluminum oxide. During the sintering process, CeO2 introduced as a sintering aid was reduced into Ce2O3. The latter reacted with aluminum oxide to form a transient liquid phase that promotes sintering by both HP and SPS. A reactional path leading to the formation of secondary phases, such as CeAlO3 and CeAl11O18, has been proposed according to the pseudo-binary Al2O3 – Ce2O3. Ceramics obtained from HP and SPS are presented as similar, except for the secondary-phase distribution. The influences of secondary phase composition and distribution on electrical conductivity were evaluated by leakage current measurements. The mechanism of DC conduction and the global conductivity of ceramics were discussed according to the sintering process and the number of secondary phases