Yu. A. Zakharov

Explosive decomposition of heavy-metal azides

A real-time investigation of the explosive decomposition of heavy-metal azides is reported. A multichannel instrument configuration designed specifically for the goals of the study is described; it is capable of measuring the transient conductivity and the spectral and kinetic characteristics of the luminescence and absorption of exploding samples with nanosecond time resolution. New phenomena are discovered and analyzed in detail: the predetonation conductivity and predetonation luminescence of heavy-metal azides. The conductivity of silver azide in the predetonation state is used to make an experimentally justified decision as to whether the explosion is driven by a thermal or chain mechanism, in favor of the latter. The sum-total of the new data provides the basis for the development of an experimentally justified model of predetonation luminescence and the explosive decomposition process of heavy-metal azides, including the following principal stages: hole trapping by a cation vacancy, reconstruction of the center as a result of chemical reaction with the formation of a quasi-local hole state in the valence band, hole detrapping from the reconstructed center, carrier multiplication as a result of impact ionization by hot holes, and reconstruction of a local state in the bandgap, thereby establishing conditions for repetition of the investigated chain of processes.

Explosive luminescence of silver azide

Spectroscopic-kinetic investigations of the luminescence accompanying the explosive decomposition of silver azide are performed. A new phenomenon is observed: predetonation luminescence. A comparison of the predetonation luminescence spectrum with the band structure is in agreement with a model in which the exothermic reaction 2N30→N6 provides the energy for the explosion.

Preexplosion phenomena in heavy metal azides

The paper reports results of investigation of the explosive decomposition of heavy metal azides in real time. The characteristics of the detected predetonation effects — the preexplosion conductance and luminescence of heavy metal azides — are described. The obtained value of the preexplosion conductivity of silver azide indicates that the process is of a chain nature. A model for the development of explosion of heavy metal azides is developed including multiplication of active particles (holes) by a first-order reaction and chain termination by a second-order reaction.

The effect of magnetic field on the shape of etch pits of paracetamol crystals

Abstract In the present study we investigate the effect of magnetic field on the shape of etch pits of the crystals of p-hydroxyacetanilide (paracetamol), which is widely used in pharmacy as antipyretic, antiphlogistic medicine. It was discovered that the magnetic field (H=0.5 T, τ=15 min) changes the morphology of etch pits and shifts dislocations in paracetamol crystal. Activation energy of the changes induced by the action of the magnetic field was determined to be 63 kJ/mol, which is comparable with the energy of hydrogen bonds in crystal lattice.

Study of silver azide explosive decomposition by spectroscopic methods with high temporal resolution

Predetonation conductivity and luminescence have been observed when the decomposition of silver azide whiskers was initiated by a laser pulse. Conductivity kinetics and luminescence spectra have been investigated. Experimental results show that the explosion occurs by a chain mechanism and a model of elementary steps of the chain reaction is proposed within the framework of band model.

The control of the solid phase decomposition of silver azide by noncontact electric field

Abstract The results of the experimental research of a new phenomenon — the decomposition of silver azide whiskers in case of unipolar injection of positive holes in crossed electric fields — are presented. In crossed electric fields the gas evolution is observed from the crystal face which is close to the negatively charged condenser plate and it depends on the intensity of the noncontact electric field E : at 2 E −1 the external gas evolution rate is changed from 10 −12 to 10 −7 cm 3 s −1

Determination of the surface structure peculiarities of nanoscale metal particles via small-angle X-ray scattering

The typical distortions of the particle size distribution functions are calculated from the smallangle X-ray diffraction for nanoscale transition metal powders and their mutual binary systems. The abnormal negative distribution functions are established to be caused by the presence of a thin nanoscale (oxide or hydroxide) shell at the metal nanoparticle surface with the electronic (scattering) density inferior to the electronic density of the nucleus. The analysis of the intensity and position of the abnormal minimum and maximum of the distribution function using computer modeling of the inhomogeneous particle scattering and experimental methods allows assuming the structure of the diffracting particles and evaluating the nucleus size and the relative outer shell density.

Radiation resistance of ionic and ionic-molecular crystals

The factors that determine the stability of ionic and ionic-molecular crystals in ionizing radiation fields are analyzed. The concepts of the fundamental reactivity (stability) of a solid (the ability of the ideal crystal lattice of the material, in which only intrinsic point defects—interstitial ions and vacancies—are present, to undergo radiation-chemical degradation) and the structure-sensitive reactivity determined by the presence of structural and extrinsic defects are introduced. Data on the radiation resistance of crystalline solids (alkali halides, silver halides, and silver azide) are summarized. It is pointed out that the AgHal crystalline matrix should be resistant toward radiation and alkali halide and AgN3 crystals should not.