β-SiC powders were synthesised by carbothermic reduction of carbon-black doped silica gel. The morphological characteristics of the resulting powders depend on the morphology of precursor carbon black as well as the reaction conditions. A model for particle coarsening during carbothermic reduction is presented, suggesting that surface diffusion may be responsible for the formation of polycrystalline aggregates, while at higher reaction temperatures volume diffusion is operative. Processing consisting of decarburization, HF treatment and sedimentation but no milling is required to convert crude reaction products into sinterable powders. After doping with boron and carbon they can be sintered to 98–99% of theoretical density which, in general, is better than or comparable to results obtained with commercial β-SiC powders which were also included in the present study.

Developpement d'un processus de consolidation de ceramiques a hautes performances par pressage isostatique chaud (HIP) sans conteneur. Presentation d'un four HIP muni d'un systeme dilatometrique pour la mesure du retrait au frittage. Optimisation de la densification de materiaux a base de Si 3 N 4 .

Calcines of precipitated zirconia powders were studied by HREM and ED. Aggregates of originally amorphous particles form nonperfect crystallites which scatter single crystal ED reflection into subreflections. This scattering was attributed to the lattice strain.

The Brew-Instron apparatus was used in order to investigate the temperature dependence of bend strength of SiC based refractories in the range from room temperature up to 1400°C. The results obtained show that the strength of the samples strongly depends on the type and amount of bonding phase used (silicate, nitride) as well as on the grain size and the grain size distribution of the SiC phase. Nitride bonded materials are superior to silicate bonded and by decreasing the SiC grain size the high-temperature strength can be markedly increased. The extend of deformation is governed mainly by the SiC grain size, whereas the amount of binder phase does not influence it significantly. The results are discussed with reference to other methods which are used to characterize the performance of the refractories.

A study was made, using the optical microscopy and x-ray diffraction techniques, of the reactions of uranium oxysulfide with boron, silicon, lanthanum, and yttrium in the temperature range 1000–1700°C. Boron and silicon cannot be employed as reducing agents in the synthesis of uranium monosulfide from uranium oxysulfide. It was established that in the operation of a reactor UOS present in sulfide fuel is a harmful impurity because it reacts with lanthanides forming in the course of fission.

The reactions of uranium oxysulphide with selected oxysulphides of rare earths (La, Gd, Yb) and Y were investigated. Several new phases, identified as uranium-rare earth oxysulphides were found. The chemical compositions and lattice constants of those compounds were determined.

Uranium monosulphide, doped with various amounts of UOS, and in certain cases with BaS, was sintered at temperatures 1500–1950°C in an argon atmosphere. The additions of both UOS and BaS result in the formation of liquid phase, which was determined to be an US-UOS or US-BaUS2 eutectic respectively. The presence of liquid phase greatly enhances the sintering of US in the temperature interval studied.

Phase equilibria in the systems USCaS, USSrS and USBaS have been investigated by X-ray diffraction, metallography and electron-probe microanalysis. New ternary sulphides, CaUS2, SrUS2 and BaUS2, which appeared in the corresponding systems, formed eutectic mixtures with primary solid solutions. Eutectic melting temperatures were determined for the systems USCaS and USSrS and tentative phase diagrams constructed. Detailed crystal structure analyses of CaUS2 and SrUS2 were carried out.

Proton spin–lattice relaxation times of four UO2·xH2O hydrates–hydroxides have been measured at 23 Mc/sec in the temperature range from + 50 to − 140°C. The observed relaxation rate is explained as being due to reorienting water molecules and to Sz (U4+)I+ (H) coupling.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation J. Zupan, M. Komac, D. Kolar; Magnetic Susceptibility of Boron Nitride. J. Appl. Phys. 1 December 1970; 41 (13): 5337–5338. https://doi.org/10.1063/1.1658674 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioJournal of Applied Physics Search Advanced Search |Citation Search