Application of introduced nano-diamonds for the study of carbon condensation during detonation of high explosives

This paper describes the experimental studies of the formation of nano-diamonds during detonation of TNT/RDX 50/50 mixture with small-angle x-ray scattering (SAXS) method at a synchrotron radiation beam on VEPP-3 accelerator. A new experimental method with introduction of nano-diamonds into the explosive has been applied. Inclusion of the diamonds obtained after detonation into the TNT and RDX explosives allows modelling of the case of instant creation of nano-diamonds during detonation.Comment: Latex, 4 pages, 2 figures (proc. of SR-2008

The "In Situ" Research of the Synthesis of NiMoO4

The formation of the crystal structure of the NiMoO4 high temperature phase in the solid phase reaction NiO+α-MoO3→β-NiMoO4 at 600 C has been "in situ" studied with the high temperature synchrotron technique. We have performed the measurements of the Extended X-ray Absorption Fine Structure (EXAFS) and the X-ray Absorption Near Edge Structure (XANES) at the K-edge of Ni atom in during the -niMoO4synthesis. The analysis of the XANES data and the Fourier transformants of the EXAFS data has led us to the conclusion that at the initial stage of synthesis the nearest oxygen surrounding of Ni atoms in the final production reaction has got an unique geometry that differs from the octahedral oxygen surrounding of Ni atoms in the both structures of NiO and β-NiMoO4. At the initial stage of the β-NiMoO4 synthesis there is not the final product of the synthesis, but the formation of the β-NiMoO4 crystal structure takes place essentially later, contrary to how it has been considered so far. We have concluded that at the original stage of the β-NiMoO4 synthesis the some intermediate phase is formed that is characterized with the low concentration of nickel and the low symmetrical geometry for the nearest oxygen surrounding of Ni atoms

XANES Registration by Electron Beam Position Scanning for Time-Resolved Experiment

A new method of XANES registration has been designed and realised at VEPP-3. Traditionally, the monochromator rotation is used for the energy scanning. In this new method, the position of the monochromator is fixed, but the position of the electron beam is changed by the magnetic field. As a result, the angle SRbeam/ monochromator is changed thus changing the energy of the monochromatic beam. We registered test-XANES spectra of Ag by electron beam position scanning and then used this method to investigate fast Ag reduction from organometallic compounds. Depending on the type of monochromator and on the energy interval, XAFS spectra may be measured now within 6-20 s. Traditional QEXAFS has a natural limit, depending on the mass of the crystal of the monochromator, holder and translation stage. The mass of the electrons in the bunch is very small and there is no limit for fast scanning. The use of an undulator as synchrotron radiation source can improve the time resolution of this method by several orders of magnitude and reach nanosecond region

Control of particle size via chemical composition: Structural and magnetic characterization of Ni–Co alloy nanoparticles encapsulated in lamellar mixed oxides

International audienc

Atomic displacement effects in near-edge resonant “forbidden” reflections.

A survey of atomic displacement effects in the resonant scattering of synchrotron radiation is presented. It is shown that the dynamical displacements, associated with thermal vibrations, provide the thermal-motion-induced (TMI) “forbidden” reflections, while static displacements (e.g. induced by impurities) provide the point-defect-induced (PDI) “forbidden” reflections. Both kinds of reflections occur owing to perturbation of valent electrons wave functions by atomic displacements. The results of numerical calculations of TMI forbidden reflections in Ge and ZnO are compared with experimental data