Currently available methods of industrial nanodiamond synthesis

The main theoretical aspects of detonation decomposition of powerful mixed explosives with a negative oxygen balance accompanied by the formation of nanodiamonds (ultrafine-dispersed diamonds, UDDs) are described. The basic UDD synthesis parameters are considered, and the expediency of using trotyl-hexogen alloys is shown. The conditions of diamond phase conservation in the detonation products are specified. Various versions of industrial detonation synthesis of UDDs are considered. The most efficient technology of chemical cleaning of UDDs (with nitric acid at high temperatures and pressures) for producing UDDs with the highest purity is described.

     

Microstructure and mechanical characteristics of nanodiamond-SiC compacts

Superhard nanodiamond-SiC ceramics are prepared by infiltrating liquid Si into porous nanodiamond compacts under pressure. Synthesized samples are 2.2 mm thick and 3–4 mm in diameter. The effect of particle size of dynamically synthesized nanodiamond powders on silicon infiltration and SiC phase formation is studied. It is established that silicon does not penetrate into the pores of nanodiamond powders if the original particle size is smaller than 0.5–1.0 μm. The critical pore size for infiltration is 100–200 nm. A study of the microstructure of the samples showed the presence of the nanometer-and submicron-scale SiC phase. The ultrasound velocities are measured in the prepared compacts, and the elastic moduli are calculated. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 4, 2004, pp. 734–736. Original Russian Text Copyright ? 2004 by Ekimov, Gromnitskaya, Mazalov, Pal’, Pichugin, Gierlotka, Palosz, Kozubowski.     

Pretransition state and structural transition in a deformed crystal

Physics of the Solid State - It is shown theoretically that a deformed crystal exhibiting structural instability can be treated as a quantum system of pseudospins. The quantum behavior of atoms...     

Destruction and stabilization of the electromagnetic transparency of a semiconductor superlattice

Three types of transparency of a semiconductor superlattice, namely, self-induced, induced, and selective transparency, were studied. The conditions of their existence and the causes of their destruction were revealed. It was shown that the state of self-induced transparency, which is unstable in a harmonic field, can be stable in a biharmonic field.     

Optical properties of CdF<Subscript>2</Subscript> in a wide energy range

For either of the two reflection spectra of cadmium difluoride that are known from experiments, a complete set of the fundamental optical functions is calculated in the energy range 4–45 eV with the Kramers-Kronig relationships. The basic features of the optical spectra are established, and a hypothesis for their origin is suggested based on the known theoretical results for the band structure.     

Magnetization vector field in a uniaxial ferromagnetic film

Technical Physics - Analytical models for the magnetization vector field B m in a uniaxial ferromagnetic film are studied. Some of them are found to closely approximate B m even if the quality...     

Attenuation of electromagnetic waves in a semiconductor superlattice in a magnetic field

Magnetoplasma waves and inhomogeneous (complex) waves in an infinite semiconductor superlattice in a magnetic field are studied, and dispersion curves are obtained. It is shown analytically and numerically that, in periodic structures, among inhomogeneous waves, there are many complex waves for which the imaginary part of the wave vector is greater than the real part. The effect of dissipation in a medium on the dispersion curves of magnetoplasma waves is examined. The dependence of the minimum phase velocity on the collision frequency and the magnetic field strength is studied.