Mathematical models of degradation-relaxation kinetics are considered for jammed thick-film systems composed of screen-printed spinel Cu0.1Ni0.1Co1.6Mn1.2O4 and conductive Ag or Ag-Pd alloys. Structurally intrinsic nanoinhomogeneous ceramics due to Ag and Ag-Pd diffusing agents embedded in a spinel phase environment are shown to define governing kinetics of thermally induced degradation under 1...

Nanocrystalline magnesium ferrite is synthesized by high-energy ball milling. The formation of nanocrystalline ferrite phase is observed after 3 h of milling and its content increases with milling time. The structural and microstructural evolution of the nanophase have been studied by X-ray powder diffraction and the Rietveld method. After 3 h of milling, ferrite phase (mixed spinel) nucleates ...

Context. Microscopic presolar grains extracted from primitive meteorites have extremely anomalous isotopic compositions revealing the stellar origin of these grains. Multiple elements in single presolar grains can be analysed with sensitive mass spectrometers, providing precise sets of isotopic compositions to be matched by theoretical models of stellar evolution and nucleosynthesis. Aims. The ...

Dunitic xenoliths from late Palaeogene, alkaline basalt flows on Ubekendt Ejland, West Greenland contain olivine with 100 · Mg/(Mg + Fe), or Mg#, between 92.0 and 93.7. Orthopyroxene has very low Al2O3 and CaO contents (0.024–1.639 and 0.062–0.275 wt%, respectively). Spinel has 100 · Cr/ (Cr + Al), or Cr#, between 46.98 and 95.67. Clinopyroxene is absent. The osmium isotopic composition of oliv...

Transparent polycrystalline spinel ceramic was fabricated without any sintering aids by spark plasma sintering method of a mixture of Al2O3 and MgO powders for only 10min soak at 1250°C. Densification, microstructure and optical transparency of spinel were examined. The spinel exhibits an in-line transmission of 55% for a visible-wavelength of 470nm and high hardness value of 2040 HV.

Minor element variations in MgAl2O4 spinel from the type B1 calcium-aluminum-rich inclusion (CAI) Allende TS-34 confirm earlier studies in showing correlations between the minor element chemistry of spinels with their location within the inclusion and with the chemistry of host silicate phases. These correlations result from a combination of crystallization of a liquid produced by re-melting ev...

The magnetic properties of spinel nanoparticles are determined by crystal chemistry issues such as cation distribution and oxidation states. The cation distribution and oxidation state of Mn-Fe spinel nanoparticles have been systematically studied at various temperatures by using neutron diffraction and electron energy loss spectroscopy, respectively. The Mn-Fe spinel nanoparticles prepared by ...

High pressure/temperature annealing experiments are used to determine diffusivities of H and D in non-stoichiometric spinel, a low-pressure analogue for nominally anhydrous minerals in Earth’s mantle. Data are fitted to the following Arrhenius law: Diffusivity (m/s) = 4 ± 1 × 10 exp(−54 ± 2 kJ mol/RT). At low temperatures, H and D diffusion in non-stoichiometric spinel is charge balanced by flu...

[1] We present details of the identification of sites that show an absorption band at visible wavelengths and a strong 2 m band using the SELENE Spectral Profiler. All the sites exhibiting the visible feature are found on the regional dark mantle deposit (DMD) at Sinus Aestuum. All the instances of the visible feature show a strong 2 m band, suggestive of Feand Cr-rich spinels, which are differ...