Correction: Crystal structure and microstructural changes of molybdenum nitrides traces during catalytic reaction by in situ X-ray diffraction studies. (Correction)

X-ray diffraction was used to study changes in the crystal structure and microstructure of molybdenum nitrides during ammonia decomposition. In addition, electron microscopy was employed to analyse morphological changes of the nitrides caused by the catalytic reaction. Molybdenum nitride catalysts (MoxNy) were prepared via high temperature ammonolysis of molybdenum oxide (MoO3) at 650 °C and 800 °C. The materials are nanocrystalline and highly porous, the samples produced at 650 °C still contain the partly reduced precursor (MoO2). In situ X-ray diffraction studies performed on a laboratory instrument equipped with a catalysis reaction chamber reveal significant compositional and structural changes taking place during the reaction. Ball milling, known to enhance the activity of catalysts, has a deleterious effect on the molybdenum nitride specimens: it gives an initial boost due to the reduction of size and increase in dislocation content, but it also favours the formation of the less active hexagonal MoN

The origin of black magnetic spherules through a study of their chemical, physical and mineralogieal characteristics

The origin of black magnetic spherules sampled in air,<br />and in ancient and recent marine sediments has been investigated.<br />Experiments were performed reproducing in laboratory the same processes undergone by the cosmic dust during its flight through the atmosphere.<br />Spherules similar in size, shape, chemical and mineralogieal characteristics to the natural ones have been obtained. It has been tested that hollow spherules can be also produced in the high atmosphere.<br />The bubble formed inside some black magnetic spherules by the decrease of solubility of oxygen at the melting point can be sometimes ejected from the rear side of the spherule producing secondary particles less than 10 pim is size.<br />The volcanic origin of black magnetic spherules has been excluded.<br />In fact ferromagnetic volcanic particulate matter present mineralogic,<br />chemical and structural characteristics different from that of black magnetic spherules.<br />Also the use of some parameters is suggested to discriminate industrial<br />ferromagnetic spherules from black magnetic spherules of extraterrestrial origin.<br />Samples from sediments old enough to exclude industrial contamination<br />allow to calculate the earth accretion in cosmic dust

Crystal structure and microstructural changes of molybdenum nitrides traced during catalytic reaction by in situ X-ray diffraction studies

X-ray diffraction was used to study changes in the crystal structure and microstructure of molybdenum nitrides during ammonia decomposition. In addition, electron microscopy was employed to analyse morphological changes of the nitrides caused by the catalytic reaction. Molybdenum nitride catalysts (MoxNy) were prepared via high temperature ammonolysis of molybdenum oxide (MoO3) at 650 °C and 800 °C. The materials are nanocrystalline and highly porous, the samples produced at 650 °C still contain the partly reduced precursor (MoO2). In situ X-ray diffraction studies performed on a laboratory instrument equipped with a catalysis reaction chamber reveal significant compositional and structural changes taking place during the reaction. Ball milling, known to enhance the activity of catalysts, has a deleterious effect on the molybdenum nitride specimens: it gives an initial boost due to the reduction of size and increase in dislocation content, but it also favours the formation of the less active hexagonal MoN