The recombination instability of current in a nonlinear regime in gold-compensated germanium

We report on the first results of the experimental verification of a theoretical one-dimensional model describing the recombination instability of current in gold-compensated germanium in a two-parametric space. The experiment revealed various regimes of the system functioning in the voltage-emission parameter space, the formation of subdomains, and the order-disorder transitions via intermittency or by a nonstandard evolution scenario.     

Solid-state equilibria and thermodynamic properties of compounds in the Bi-Te-I system

The Bi-Te-I system has been studied by differential thermal analysis, x-ray diffraction, and emf measurements in the temperature range 300–400 K using concentration cells of the type (?)Bi(s) | glycerol + KI + BiI₃ | Bi-Te-I(s)(+). The results have been used to construct the 300-K section of the Bi-Te-I phase diagram. The existence of the ternary compounds BiTeI, Bi₂TeI, and Bi₄TeI_1.25 has been confirmed, and the position of the phase fields involving these compounds has been accurately determined. Using emf data, we have evaluated the partial thermodynamic functions (Δ\(\bar G\), Δ\(\bar H\), and Δ\(\bar S\)) of the bismuth in the alloys studied, the standard thermodynamic functions of formation of the ternary compounds, and their standard entropies.     

Influence of salts of alkylphenol sulfonic acid on the corrosion of St3 steel in HCl–kerosene systems

We study the influence of salts of alkylphenol sulfonic acid on the corrosion of St3 steel in a 0.1 N HCl–kerosene system. All salts have inhibiting properties beginning with a concentration of 25 mg/liter and, in some cases, completely inhibit corrosion. It is shown that the protective effect increases with temperature. Within the range of concentrations of the inhibitor 25–200 mg/liter, the activation energy of corrosion becomes 5–6 times higher. Thus, the investigated compounds inhibit corrosion of St3 steel as a result of chemical adsorption. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 5, pp. 69–74, September–October, 2008.     

Heat-transfer phenomena in alloys

The phonon heat conductivity k _ph in Bi_{1 − x} Sb _x (x = 0.04–0.12) alloys is investigated in the temperature range of 6–60 K. The results are compared with the theory of solids at low temperatures, and the basic sources of phonon scattering are revealed. It is shown that phonon scattering at local mass changes dominates over other sources. The dependences of k _ph on composition are considered at temperatures of 60 and 90 K, and it is found that the normal N processes substantially affect the phonon scattering under these conditions. The donor-impurity effect on heat conductivity of Bi_0.88Sb_0.12 is considered, and the heat resistance caused by the phonon scattering at impurity centers is singled out.     

Immobilization of disperse red 1 onto polydiethyleneglycol-bis-allylcarbonate (CR-39) radiation grafted with poly(acryloyl chloride)

Abstract Acryloyl chloride (AC) was radiation grafted from 30% solution of monomer in toluene onto polydiethyleneglycol-bis-allylcarbonate (CR-39) by their simultaneous -iradiation. The grafting process was more efficient at dose rate of 4.4 kGy/h as compared with 0.4 kGy/h, and grafting values of 15-18% were achieved at 2.2-5.5 kGy. Subsequent immobilization of disperse red 1 (DR1) onto the grafted polymer was carried out from 0.02 M solution of this dye in dichloroethane, and the immobilized DR1 yield increased with the grafted polyAC value. Surfaces of the starting and modifed CR-39 were characterized with the FTIR-ATR spectroscopy and atomic force microscopy. An essential difference in chemical structure and topography of the CR-39 surface before and after the DR1 immobilization has been shown. The colourless plates of CR-39 became red after the DR1 immobilization, and the color intensity increased with the dye content. Changes in visible absorption spectra of the immobilzed DR1 caused by the photoinduced trans-cis isomerization of this dye were discussed.     

Thermal transport in MWCNT sheets and yarns

Laser flash and self-heating 3ω techniques were employed to determine the anisotropic thermal conductivity and thermal diffusivity of a highly oriented, free-standing multiwalled carbon nanotube (MWCNT) sheet and a yarn drawn from a sidewall of the MWCNT forest grown by chemical-vapor deposition. Normalized to ideal high density structure the thermal conductivity and the thermal diffusivity along the alignment are 50 ± 5 W/m K and 45 ± 5 mm²/s, respectively, and are mostly limited by dangling terminals of bundles, intrinsic defects of individual nanotubes and phonon scattering within the bundles, which form the supporting matrix of the MWCNT sheet. The high degree of tube–tube overlap substantially decreases the electrical and thermal interconnection resistance, which usually dominates in randomly deposited mat-like nanotube assemblies. The extremely high surface area of the MWCNT sheet leads to excessive radial heat radiation that does not allow transferring the heat energy along the MWCNT sheet by means of phonons to distances >2 mm. On the other hand, the high surface area and negligible heat capacitance make it a perfect material for bolometric sensing (r = 38 V/W) and heat dissipation.     

Optimal design of alkane pyrolysis processes: propane pyrolysis

A two-stage optimal design procedure is suggested for alkane pyrolysis processes and is applied to propane pyrolysis. The first stage considers only hydrocarbon decomposition, the primary reaction in the process. A mathematical model consisting of an overall stoichiometric, an empirical rate, and a heat-balance and hydrodynamic equation is constructed. This model is analyzed for a varied tube diameter and a fixed propane conversion to optimize the design parameters of the propane pyrolysis reactor. At the second stage, the main reaction is considered together with secondary and tertiary reactions and a complete model taking into account recycling of the unreacted raw material is constructed. The optimum inlet temperature and recycle ratio are determined as a function of the total feed rate. An economic optimality criterion is suggested, and final process optimization is carried out.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 38, No. 6, 2004, pp. 693–698.Original Russian Text Copyright © 2004 by Aliev, Tairov, Guseinova, Kalaushina, Shakhtakhtinskii.