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Characterization of autocatalytic decomposition reactions is important
for the safe handling and storage of energetic materials. Isothermal differential
scanning calorimetry (DSC) has been widely used to detect autocatalytic decomposition
of energetic materials. However, isothermal DSC tests are time consuming and
the choice of experimental temperature is crucial. This paper shows that an
automatic pressure tracking calorimeter (APTAC) can be a reliable and efficient
screening tool for the identification of autocatalytic decomposition behavior
of energetic materials.
Hydroxylamine nitrate (HAN) is an important
member of the hydroxylamine family. High concentrations of HAN are used as
liquid propellants, and low concentrations of HAN are used primarily in the
nuclear industry for decontamination of equipment. Because of its instability
and autocatalytic decomposition behavior, HAN has been involved in several
incidents. 相似文献
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Several magnetic and optical processes contribute to the magneto-optical response of nickel thin films after excitation by a femtosecond laser pulse. We achieved a first complete identification by explicitly measuring the time-resolved Kerr ellipticity and rotation, as well as its temperature and magnetic field dependence in epitaxially grown (111) and (001) oriented Cu/Ni/Cu wedges. The first hundreds of femtoseconds the response is dominated by state filling effects. The true demagnetization takes approximately 0.5-1 ps. At the longer (sub-ns) time scales the spins are found to precess in their anisotropy field. Simple and transparent models are introduced to substantiate our interpretation. 相似文献
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The test of the validity of the Fromhold-Cook theory of metal oxidation for the O2/Fe system in the tunnel regime is impeded by the growth of a passivating Fe2+/Fe3+ double layer at T=150 degrees C. However, during an intermediate anneal step at 200 degrees C, the Fe3+ is reduced to Fe2+. The oxidation rate of this annealed layer is in agreement with the Fromhold-Cook theory. At room temperature, the ionic current is rate limiting. For T>150 degrees C, the thermionic emission of electrons is rate limiting for oxygen coverages larger than 13x10(15) atoms/cm(2). 相似文献
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The kinetics of hydrogen uptake of thin films of FeTi deposited on Si substrates and covered with 20 nm Pd were studied. The films serve as a model system for powdered FeTi, with grains that are (partly) covered with Pd, which serves as a protection for severe oxidation. Two FeTi compositions near the 50/50 composition were studied. The hydrogen uptake kinetics as a function of temperature and pressure were measured by probing the differential pressure between a small hydriding reaction chamber and a reference chamber. Both compositions showed first order kinetics for the largest portion of the uptake. Using results of additional measurements in which the thickness of the layers was varied, a model is proposed in which the uptake proceeds via fast channels through the film, followed by slower diffusion into the bulk. Finally, the influence of oxidation was studied. An FeTi-oxide underneath the Pd layer is a barrier for H diffusion. It was found that by annealing the H uptake rate could be increased. This is probably due to the decomposition of the oxide. Samples partly covered with Pd and partly by FeTi-oxides, obtained by decomposing the fully covered structure by air annealing at 250 °C, showed uptake throughout the entire FeTi film with an even faster rate than in a fully covered film. Some explanation with simple models of the observed phenomena is given. 相似文献
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E. M. B. Heller J. F. Suyver A. M. Vredenberg D. O. Boerma 《Applied Surface Science》1999,150(1-4):227-234
The hydrogen storage material FeTi has the disadvantage to lose its sorption capacity in contact with impurities such as O2 and H2O. A possibility to overcome this problem is to coat it with an anti-corrosive layer which is permeable for hydrogen. In this study we prepared FeTi layers covered with a (4 or 20 nm) thin Pd layer. We used ion beam and sputter profiling techniques, X-ray photoelectron spectrometry and scanning probe techniques to investigate the response of these bi-layers upon annealing up to 300°C in vacuum, air and 10−5 mbar O2. The layered structure remains intact up to 150°C. At 200°C in air and O2, Fe and (some) Ti move towards the Pd surface where they form oxide regions. At higher temperatures thicker oxide regions, presumably along the Pd grains, are formed. These processes are more pronounced for the case of 4 nm Pd. A model is presented to explain the observed phenomena. We conclude that up to 150°C 4 nm of Pd is sufficient to act as a protective layer. For a temperature of 200°C, 20 nm Pd may still provide sufficient protection against oxidation. 相似文献