Open Access
Access granted
Subscription Access
Vol 488, No 1 (2019)
- Year: 2019
- Articles: 7
- URL: https://journals.rcsi.science/0012-5016/issue/view/9272
Physical Chemistry
Changes in the Mechanical Properties of Powder Aluminum Matrix Composites Modified by Microadditives of Hybrid Materials Based on Multiwall Carbon Nanotubes Decorated with Titanium Carbide Nanoparticles
Abstract
Bulk composite materials based on AMg2 aluminum alloy reinforced with 0.05 wt % multiwall carbon nanotubes (MWCNT) or MWCNT decorated with TiC nanoparticles were produced by powder metallurgy. A comparative analysis of the structural and phase composition and properties of the powder composites was made. It was determined that the compressive offset yield strength of the MWCNT-hybrid-filled aluminum matrix composite exceeds that of the MWCNT-filled aluminum matrix composite.
113-116
Debonding of a Metal Coating from a Track-Etched Membrane
Abstract
The tensile behavior of a metal nanocoating on a track-etched membrane based on a polyethylene terephthalate film was investigated. Near cylindrical pores in the substrate, conical debondings of the coating were detected for the first time. Nanopores initiate multiple cracking of the coating, and short microcracks mutually inhibit their growth. As a consequence, long cracks crossing the entire coating do not form, and the coating remains continuous and electrically conductive at high strains.
117-119
CeF4 Complexes in Organic Solvents
Abstract
The first complexes of cerium tetrafluoride in solutions have been studied by 19F NMR and IR spectroscopy. The temperature dependence of the 19F NMR spectra has been explored, and conclusion has been made that dynamic equilibrium between the molecular adduct and singly charged ionic forms, including geometric isomers, exists in solution. The statistical probability for the formation of [CeF4(dmso)4] stereoisomers of square antiprism configuration has been calculated, and their assignment to possible stereoisomers have been made on the basis of relative intensities of the 19F NMR signals. Quantum-chemical calculations of the structure of one of the possible isomers have been performed for the [CeF4(dmso)4] molecular adduct, [CeF3(dmso)5]+ cation, and [CeF5(dmso)3]– anion to show their thermodynamic stability.
120-124
Kinetics of Chemical Processes in the Human Brain: Modeling of the BOLD fMRI Signal
Abstract
A kinetic model is presented that describes the pulse of the oxygen level increase in the excited nervous tissue of the human brain in response to an external signal. The model is based on biochemical data and describes experimental data on the hemodynamic impulse response. The model predicts the dynamic behavior of process participants preceding the oxygen pulse and determining the BOLD signal level.
125-128
Deflagration-to-Detonation Transition in Air Mixtures of Polypropylene Pyrolysis Products
Abstract
A new method to determine fuel detonability has been proposed, which is based on measuring the length and time of a deflagration-to-detonation transition (DDT) in a calibration pulsed-detonation wind tunnel (CPDWT). The fuel was polypropylene granules (PG). A test stand was designed and built, which included the CPDWT and a gas generator to obtain PG pyrolysis products (PGPP) at a decomposition temperature to 800°C. Experiments for studying DDT in PGPP–air mixtures were carried out. It was shown that the detonability of PGPP is close to that of a stoichiometric mixture of autogas liquefied petroleum gas with air under normal conditions.
129-133
Influence of Vibrations in the Interfacial Layer on the Wettability of an Adhered Material of Interfacial Formations in Systems with d and f Elements
Abstract
The effect of local vibration in an interfacial layer of a heterogeneous liquid system on the wettability of the material of interfacial formations based on a d- or f-metal di-(2-ethylhexyl)phosphate salt adhered to glass has been studied. It has been demonstrated that, in the field of mechanical vibrations, one can obtain a hydrophobic material with a desired wetting angle value. It has been established that the influence of mechanical vibrations is caused by changes in the hydrodynamic situation in the transition region and is a result of complex interplay mainly between hydrodynamic and coagulation processes in the interfacial layer of the di-(2-ethylhexyl)phosphoric acid–solvent/aqueous solution of a d- or f-metal salt system. The wettability of the material of interfacial formations adhered to glass turns out to depend on the parameters of the force field (vibration frequency and amplitude), the design features of the experimental setup, and the composition of the system.
134-137
Nonequilibrium Thermodynamics and Stoichiography in Studying Solid-Phase Processes of Fabrication of Functional Materials
Abstract
The application of general principles of nonequilibrium thermodynamics and stoichiography allows obtaining novel information on the solid-phase transformations of multielement and heterophase substances and materials. Without solid-phase standards, the use of stoichiography makes it possible to detect, identify, and quantify known and unknown crystalline and amorphous phases of constant or variable composition. For the first time, reliable results are presented concerning the evolution of solid products in the course of preparation of the Mo–V–Te–Nb–O catalyst of propane ammoxidation.
138-141