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Coating of LiBH4 and Its Effect on the Decomposition of RDX and AP

Ding X., Shu Y., Chen Z., Liu N., Gou B., Zhang J., Wu M., Xie G., Dang T.

Central European Journal of Energetic Materials

2017

Vol. 14, no. 1

134--151

The novel fuel additive LiBH4 was introduced as an energetic component for its outstanding hydrogen content, perfect burning performance and high reactivity. In order to limit the hygroscopicity and to improve the stability in the air, LiBH4 was coated on the surface with wax and polyester carbonate. The final product was characterized by scanning electron microscopy (SEM), X-ray photoelectron energy spectroscopy (XPS) and Raman spectroscopy, while the stability in air was investigated by regular checking of variations in weight. The results show that a uniform coating layer was formed on the surface of the LiBH4, and the coverage was estimated from the boron content as approximately 82%. A healing effect was confirmed on defective surfaces exposed to air; the coating layer improves the relative stability by 50.7%. Furthermore, LiBH4 as an additive to promote the thermal decomposition of 1,3,5-trinitro-1,3,5-trazinane (RDX) and ammonium perchlorate (AP) was explored by differential scanning calorimetry (DSC), in which the catalytic effects of pure LiBH4 and coated LiBH4 were compared, and indicated that the coating does not decrease the reactivity of LiBH4. It is suggested that surface coating with some inert materials is a simple and effective method for improving the storage and performance of LiBH4, while ensuring its reactivity.

Effect of surface modification of [alfa]-Ti on internal friction

Łunarska E., Chernyayeva O., Zachariasz R.

Advances in Materials Science

2008

Vol. 8, nr 1(15)

107-115

The measurements of the internal friction were done using the RAK -3 relaxator at the bending mode oscillation of the acoustic frequency. The annealed a-Ti and a-Ti with the surface modified by the pulse mechanical grinding, by the plasma assisted formation of the layer of Ti-AI intermetallics and by the electrochemical hydrogen charg-ing have been studied. The Young modulus and the attenuation of samples were measured at the heating of specimens between 200 and 600 K. In the studied temperature range, some relaxation processes occurred in the modified specimens. The values of the Young modulus and of the internal friction background have been also found to depend on the state of the Ti surface. The possible effects of the phase composition and the stress state on the obtained results have been discussed.

Nanocrystalline magnesium and its properties of hydrogen sorption

David E.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 20, nr 1-2

87-90

Purpose: The goal of this paper is to study the possibility of obtaining of magnesium and magnesium hydride in nanocrystalline form and then to activate these materials for to be used in efficient systems of hydrogen storage. Design/methodology/approach: The magnesium hydride (MgH2) was directly synthesized from mechanically grinded magnesium powder obtained through ball milling of Mg(BM), and hydrogen of high purity. The MgH2 was then chemical activation by surface modification of nanocrystalline Mg with nickel ultrafine particles addition. The hydrogen sorption properties of the nanocrystalline Mg were investigated by a conventional pressure-volume-temperature technique, X-ray diffraction, and scanning electron microscopy (SEM). Findings: We found that the mechanical activation improved significantly the kinetics of hydrogen absorption in nanocrystalline magnesium, increasing sorption rates by up to 2 orders of magnitude. A profound effect of the powder particle size on the hydrogen desorption characteristics has been also observed. It was also determined that the Mg2Ni compound absorbed hydrogen quickly and showed excellent hydrogen sorption properties at 300 degrees centigrade. Research limitations/implications: The reduction of the particle size of magnesium and the creation of fresh surfaces by mechanical ball milling help the kinetics but does not affect the thermodynamics. Practical implications: Further examination to obtain improved properties of hydrogen sorption process of magnesium based materials and investigations of achievement of new systems for hydrogen solid storage. Originality/value: This work contains new aspects, which show the conditions of obtaining of nanocrystalline metal clusters with size under 30nm and represents new approach of improvement of hydrogen sorption process in light metals, such as magnesium, that can provide promising results for hydrogen storage applications.