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[en] Short communication. 1 ref

[en] MgO and Co_1-xO powders in 9:1 and 1:9 molar ratio (denoted as M₉C₁ and M₁C₉, respectively) were sintered and homogenized at 1600 deg. C followed by annealing at 850 deg. C and 800 deg. C, respectively to form defect clusters and precipitates. Analytical electron microscopic observations indicated the protoxide remained as rock salt structure with complicated planar diffraction contrast for M₉C₁ sample, however with spinel paracrystal precipitated from the M₁C₉ sample due to the assembly of charge- and volume-compensating defects of the 4:1 type, i.e., four octahedral vacant sites surrounding one Co³⁺-filled tetrahedral interstitial site. The spacing of such defect clusters is 4.5 times the lattice spacing of the average spinel structure of Mg-doped Co_3-δO₄, indicating a higher defect cluster concentration than undoped Co_3-δO₄. The {111} faulting of Mg-doped Co_3-δO₄/Co_1-xO in the annealed M₁C₉ sample implies the possible presence of zinc blend-type defect clusters with cation vacancies assembled along oxygen close packed (111) plane

[en] The chiral constituent quark model is applied to predict the magnetic M1 and electric E2 amplitudes of the Δ↔γN transition. It is found that the one-meson-exchange quark-quark potential due to the chiral fields enhances the E2/M1 ratio by a factor of about 2. The predicted M_1⁺ amplitude and the E2/M1 ratio ≅-1.0% are within the range determined from a recent analysis of the data of pion photoproduction. copyright 1997 The American Physical Society

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[en] Confocal and electron microscopic observations of willemite (α-Zn₂SiO₄) crystalline ware glaze, fired to 1270 deg. C and then aged at 1080 deg. C for 5 h, indicated the glaze decomposed as (Zn, Ti, Ca)-rich and (Si, Al, K, Na)-rich regions, from which willemite crystallites and amorphous droplets were formed, respectively. Under the constraint of the glaze thickness, the willemite crystallites further developed into plate-like spherulites, which consists of lath-like crystals growing at the order of [0 0 0 1]>><1 0 1-bar 0>><2 1-bar 1-bar 0> and viable for coalescence over {2 1bar 1-bar 0} habit plane. The impinged plate-like spherulites formed a flat interface at the early stage of crystallization, but irregular interface in late stage due to weaving, truncation and lateral coalescence of the crystals. The {2 1-bar 1-bar 0}-specific coalescence can be rationalized by Brownian-type motion/rotation of the crystals until parallel epitaxy is reached

[en] Oxides of RO + R₃O₄ + R₂O₃ or RO + R₃O₄ (where R represents cations) coexist on the high aluminum activity coatings on Rene 80 and pure nickel during high temperature oxidation at 1093⁰C. Electron diffraction studies indicate that they have the same crystallographic relationships to the γ phase as ((anti 111)_γRO,R3O4//(0001)_R2O3) (01anti 1)_γ,RO,R3O4//(1anti 210)_R2O3. However, the preferred orientation relationships disappear when the oxide particles are greater than a certain critical size. The γ phase (ordered or disordered) is formed by the degradation of the β phase in the coating and obeys the Bain relationship to the β phase. Ni₂Al was also identified in the degraded coating on Rene 80. (orig.)