Vol 25, No 2 (2016)

Suggested is a theoretical model of the ETE process in gasless SHS systems placed in a hollow dielectric cylinder with an electroconducting outer shell placed in a cylindrical metallic casing. Maximum temperature, time of inert heating, and induction period of ETE were calculated as a function of inlayed electric power. The results may turn helpful in analysis of experimental data aiming at elucidating the kinetic parameters of high-temperature ETE reactions.

Li_0.35–0.5xMg_xZn_0.3Fe_2.35–0.5xO₄ nanoparticles (x = 0, 0.14, 0.28, 0.42, 0.56, and 0.70) were prepared by low-cost combustion synthesis at relatively low temperature. Thick films of Li–Mg–Zn ferrite were prepared by screen printing method and characterized by XRD and microwave characteristics at microwave frequencies (within X- and Ku-bands) by overlay technique using λ/2 rejection filter. The influence of magnesium content x on the resonance frequency, quality factor, effective dielectric constant, complex permittivity, complex permeability, microwave conductivity, and penetration depth was explored.

We successfully prepared superconducting powders of magnesium diboride doped with carbon nanotubes by the method of combustion synthesis under high Ar pressure. Powders of magnesium, boron, and multi-walled carbon nanotubes (MWCNT) were used as starting materials. X-ray diffraction analysis showed the presence of MgB₂ and MgO in combustion products. The temperature dependence of magnetization showed a sharp superconducting transition at around 38.5 K. The critical current density can be estimated from the hysteresis of magnetization curve by using the Bean’s formula. MgB₂ doped with MWCNT (1%) showed the best value of high critical current density, 1.4 × 10⁸ A/cm² at 5 K, in zero magnetic fields.

Investigated were the combustion synthesis of Eu-doped Ca–α-SiAlONs and their luminescence properties. Experimentally established were (a) green compositions ensuring maximal extent of conversion, (b) influence of elemental composition on phase composition and microstructure of synthesized Ca–α-SiAlONs, and (c) influence of elemental composition on the excitation and emission spectra of Ca–α-SiAlON luminophors.

The paper shows the investigation results of structure and phase formation of boron, aluminum and silicon nitride particles in gaseous nitrogen of high pressure (10–40 MPa) under the terms of thermocoupled high- and low-exothermic reactions (so-called chemical furnaces). In this case the high-exothermic reaction is an additional heat source for the low-exothermic one. The reactions are separated in space and chemically independent. The nitriding terms which are close to extreme ones (high burning temperatures of aluminum, boron and silicon, high heating rates, etc.) provide the reagent evaporation and promote gastransport reactions with the combustion mechanism transition from the solid-phase to gas-phase or vaporliquid due to volatile intermediate products of nitriding and impurities. As a result, the SHS products contain not only well-known forms of nitride particles (nano-fibers, nano-filaments, nano-plates, nano-whiskers, etc.) but such structures as BN nano-tubes with various types of morphology and cubic modifications of BN and AlN as well. It is to be studied additionally.