Self-propagating high-temperature synthesis of intermetallide/oxide nanocomposite powders using mechanocomposite precursors

It was found that mechanical activation of a mixture containing iron, aluminum, and oxide iron resulted in mechanochemical reduction of iron oxide and formation of a Fe/Al/Al₂O₃ nanostructural mechanocomposite. High-temperature self-propagating synthesis (SHS) using this composite as a precursor yielded a FeAl/Al₂O₃ composite, which retained the morphology and dimensional characteristics of the precursor. During mechanical activation of a mixture of iron, aluminum, and chromium oxide, complete reduction of the latter did not occur but SHS also led to the formation of an intermetallide/oxide nanocomposite, in which chromium atoms were incorporated in the structure of iron aluminide.     

Electric fields with annular features in corpuscular optics

A new class of axisymmetric Laplace potentials with an annular feature that can be described by elementary functions is introduced. The possibilities of employing these potentials in the synthesis of energy-analyzing systems and lenses are discussed. Equipotential portraits of electric fields with annular features are presented. Pis’ma Zh. Tekh. Fiz. 25, 23–27 (May 12, 1999)     

The field-induced ion evaporation effect in the bipartition of charged droplets

A physical mechanism explaining the formation of a cluster phase during the electrostatic bipartition of droplets unstable with respect to their own charge is suggested. The mechanism assumes the possibility of the field-induced evaporation of ions from the surface of droplets of a micron size formed in the final stage of a droplet decay cascade.     

Effect of long-term annealing on accumulation of impurities

The occurrence of changes in impurity accumulation after a long-term annealing preceding the in-diffusion of impurities is shown experimentally. Atoms of Au as acceptors affecting the resistivity and photoconductivity decay time were used as indicators in studies of these changes.     

Ignition of petn particles by a gas-detonation wave

Ignition ofPETN particles by a gas-detonation wave in a gas suspension has been studied experimentally. The critical pressure at which the total rate ofPETN decomposition increases sharply has been found using a method of multiwave pyrometry with variation in the pressure of the initial gas mixture from 0.1 to 0.4MPa. It is shown that this can occur owing to a large increase in thePETN surface area because of the fragmentation of melting particles in a high-enthalpy flow of gas. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 2, pp. 133–138, March–April, 1997.     

Electrostatic mechanism of a wavy microrelief formation on a semiconductor surface sputtered by an ion beam

It is shown that modeling of a physical mechanism of the formation of an ordered wavy microrelief on the semiconductor surface under the action of a high-energy ion beam can be considered as an electrostatic problem.     

Methods for measuring amplitudes of signals from Cherenkov counters

Measurements of the pulse heights in the T0 start trigger detector of the ALICE experiment are necessary both for time-amplitude offline correction of start signal T0 used in the time-of-flight TOF detector and for monitoring the state of the Cherenkov counters in the detector. A high amplitude resolution is not required for these tasks; what is needed is fast encoding and interfacing with the data readout system in which only time channels are available. Therefore, amplitudes are measured in the detector by pulse-height-to-time conversion using two independent methods, one of which involves quasi-logarithmic charge-to-time converter (QTC) and the other employs two—leading-edge (LED) and constant-fraction (CFD)—timing discriminators. The main characteristics of both methods and results of calibrations of the appropriate devices using a pulsed laser are presented.     

A mean timer of the T0 start trigger detector of the ALICE experiment

A mean timer module generating signals of an accurate time mark, which does not depend on the point of the ion collision along the beam axis in the vacuum tube of the accelerator, has been developed and tested on the beam of the accelerator at CERN. This signal is used as a start signal of the time-of-flight particle identification system of the ALICE experiment. The module is a component of the T0 start trigger detector developed at the Moscow Engineering Physics Institute (MEPhI) along with other institutes. Tests of the module at CERN have shown that the accuracy of the time compensation is not worse than ±10 ps, completely meeting the experimental conditions.     

Vibrational instability of the charged interface of immiscible electrically conductive liquids

This paper shows that, in an electrostatic field normal to the flat interface of two viscous electrically conductive liquids, an oscillatory instability of the interface with periodically increasing amplitude can be produced when the electrical conductivity of the upper liquid is substantially greater than that of the lower one. Results are obtained by numerical analysis of the dispersion equation. Pis’ma Zh. Tekh. Fiz. 23, 32–36 (November 12, 1997)