Vol 11, No 1 (2017)

Nanostructured powders of pseudoalloys of immiscible Cu and Mo metals are prepared by highenergy ball milling (HEBM). Mechanical alloying in an Activator-2S planetary ball mill for 60 min provides a uniform distribution of refractory Mo particles in a moldable Cu matrix on submicron and nanoscopic levels. Nanostructured Cu–Mo powders are consolidated by spark plasma sintering (SPS) in a temperature range of 700–950°C at a pressure of 50 MPa for 10 min. The effect of preparation conditions on the microstructure, crystal structure, and properties (density, hardness, electric resistivity) of the nanostructured Cu–Mo pseudoalloys is studied. It is shown that a combination of HEBM and SPS provides the formation of a high-density (97%) nanostructured consolidated Cu–Mo composite with a hardness of 3.68–3.88 GPa and an electric resistivity of 6.1–6.2 μΩ cm; these parameters made the composite promising for use as an electric-contact material.

Laser atom-molecule reaction interaction through polarizability and dipole moment contribution leads to potential energy surface barrier reshaping and bound states along the reaction path. The polarizability is maximum in the transition state. We will show here by using gauge representation (electric field gauge) for wave length λ = 20.6 μm, intensity I = 1 × 10¹² W/cm², I = 5 × 10¹² W/cm², I = 1 × 10¹³ W/cm², I = 3 × 10¹³ W/cm², that we can create laser induced potential energy surface barrier reshaping in the transition state region (–1–0.5 a. u.). We illustrate such effects for the LiH + CH₃ ↔ Li + CH₄ reaction with a barrier using ab-initio methods for calculating the reaction path, polarizability and dipole moment contribution of the atom-molecule reaction.

A method for calculating transition probabilities based on an earlier developed trajectory approach is tested by the example of evaluating the probability of photoionization of the hydrogen atom exposed an ultrashort optical pulse.

The heterogeneous relaxation of vibrationally excited CO molecules (v= 4, 5) on a molybdenum glass wall in He–CO–O₂ discharges has been investigated. The probability of heterogeneous relaxation for CO(v < 3) has been measured for the first time.

The available quantum calculations of inelastic cross sections were analyzed for processes in collisions Mg + H and Mg⁺ + H^–. The cross sections with large values were obtained with high accuracy. These processes are of particular interest for astrophysics.

Specific features of complexation in solutions of a strong dibasic acid in the H₂SO₄–2-pyrrolidone (Pyr) system (in the range of compositions of 0–100% H₂SO₄) are studied using multiple frustrated total internal reflection IR spectroscopy. The conclusions drawn on the structure of the complexes formed in such solutions are confirmed by quantum-chemical calculations of the mPyr · nH₂SO₄ (m, n = 1, 2) heteroassociates and by comparison of their calculated and measured vibrational spectra. It is found that, in the investigated solutions, four types of acid–base complexes, with various degrees of proton transfer in the OHO bridge, are formed: (AHA)^– anions with quasi-symmetric H-bonds, solvated by acid molecules, or entering into the composition of PyrH⁺ · (AHA)^– ion pairs; quasi-ion pairs with incomplete proton transfer to the base molecule of 1: 1 and 2: 2 compositions; and 2Pyr · H₂SO₄ complexes with two O–H···O bridges of molecular type. The main differences in the mechanisms of the acid–base interactions in the H₂SO₄–Pyr system as compared to the CH₃SO₃H–Pyr system result from the participation of two OH-groups of H₂SO₄ molecule in these interactions. Therefore, two types of quasi-ion pairs and complexes of 2Pyr · H₂SO₄ composition are formed.

A numerical solution for the polarization of two-level atoms that interact with a polyharmonic field was obtained. An analytical solution for the particular case of a symmetrical position of carrier frequency relative to transition frequency is possible. The results showed that nonlinear effects occur in a polarization spectrum at the small amplitudes of comb components and small frequency distances between them. Consequently, it is necessary to take into account nonlinear effects in comb spectroscopy.

A method taking into account valence (non-Rydberg) and dissociative configurations has been developed for calculation of potential energy surfaces of the NO molecule in an intense IR radiation field. The resonance rovibronic structure of the Rydberg molecule–laser field quantum system has been analyzed within the steady-state formalism of the radiation collision matrix using multi-channel quantum defect theory. Special conditions for field control of predissociation involving intermediate Rydberg and valence states have been formulated.

The Bridgman–Stockbarger method is used to prepare single-crystal TlCdI₃ samples doped with bismuth. The material exhibits a broadband photoluminescence in the near-IR range with a maximum intensity at a wavelength of 1175 nm. The properties of bismuth-doped TlCdI₃ were compared with previously studied chlorides and bromides containing Bi⁺ impurity centers. It is demonstrated that the luminescence center in TlCdI₃ is not the monovalent bismuth cation.

The influence of the addition of nitrogen to a He–CO mixture on plasma-chemical processes in a discharge under conditions characteristic of the active medium of a sealed-off CO laser was studied. It was found that the addition of nitrogen noticeably decreased the rate of CO dissociation and the concentrations of C atoms and C₂ and C₃O₂ molecules formed in a discharge in the course of plasma-chemical reactions.

A previously proposed method for accurate description of resonance radiation transport in solving self-consistent problems is applied to a model of the contraction of the positive column of a glow discharge in argon. The exact solution to the problem and the solution obtained within the framework of the traditional approximation of local effective transition probability according to Biberman are compared. The influence of radiation transport on various plasma parameters is demonstrated

Requirements to the modeling of the effects of temperature differential and ionizing radiation on the current–voltage characteristics of high electron mobility transistors (HEMTs) were formulated. The results of modeling of the effects of temperature differential on the current–voltage characteristics of HEMTs were described. The results of analysis of the effects of ionizing radiation on the current–voltage characteristics of HEMTs were given. The results of modeling of the effects of ionizing radiation on the current–voltage characteristics of HEMTs were presented.

A new organogelator, L-phenylalanine dihydrazide derivative (BOC-Phe-HdHz) has been designed, synthesized and characterized. In addition, the gelling behaviors of BOC-Phe-HdHz were studied. The organogelator has been shown to be capable of forming stable thermoreversible organogels in various organic solvents at extremely low concentrations (<3 wt %). The gel–sol phase transition temperatures (T_GS) were determined as a function of gelator concentration and the corresponding enthalpies (ΔH_g) were extracted. SEM revealed that the gelator self-assembled into different supramolecular network structures in different gels. FT-IR confirmed that hydrogen bonding and hydrophobic interaction were the driving forces for the supramolecular assembly process. XRD was measured in three different states of the gelator: solid powder, gel and xerogel. In addition, XRD and molecular modeling studies have been carried out and provided more information of the possible packing modes for the formation of organogelator aggregates.

The ignition of a metallized composite propellant by a local energy source of limited heat content is studied. The main characteristic of the process (ignition delay time) is calculated over a wide range of initial temperatures of the source (800–1500 K) for the actual inhomogeneous structure of the propellant with consideration of the presence of fine metal particles and for an effective heterogeneous structure with thermophysical properties calculated by formulas based on the rule of additivity of the thermophysical properties of the components. The thermal conductivity of the propellant is also calculated by approximate expressions proposed by Maxwell, Frick, Bruggeman, Meredith, Xiao, Hamilton, Cross, Behrens, Misnar, Peterson, Hermans, and Nielsen for polymeric materials containing finely dispersed inclusions with a higher thermal conductivity as compared to the polymer matrix. It is found that the expressions proposed by these authors yield values of the ignition delay time and the minimum initial temperature of the heat source required to initiate combustion that differ from those predicted by the model with account of the real heterogeneous structure by up to 75 and 15%, respectively.

The interaction between curcumin (CUR) and bovine serum albumin (BSA) in physiological buffer (pH 7.4) was investigated by fluorescence and UV-vis absorption spectroscopy at 298, 306 and 313 K. The results revealed that CUR could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The binding constant K and number of binding sites n of CUR with BSA were measured by fluorescence quenching method. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS), were calculated to be–64.11 kJ mol^–1 < 0 and–95.53 J mol–1 K^–1 < 0, which respectively indicated that the interaction of CUR with BSA was driven mainly by the van der Waals force or hydrogen bond formation. The UV and AFM results found that the CUR and BSA could interact to form complex structures.

The dynamic adsorption of nitrogen dioxide on Zeolon 900H, Zeolon 900K, Zeolon 900Na, Zeolon 200H, Zeolon 500H, H/ZSM-5, Na/ZSM-5, and CaA zeolites is studied. Breakthrough curves C/C₀ = σ(t) (C₀ is the initial concentration of NO₂ at the adsorption column inlet and C is the breakthrough concentration at the column outlet) is measured over a temperature range of 290–430 K. It has been shown that the time dependence of C/C₀ is described by the Wheeler–Jonas equation. The parameters of this equation, the adsorption constant rate k_v and dynamic adsorption capacity (DAC) are determined by fitting the theoretical curves to the experimental data for the aforementioned zeolites at 290–430 K. The Hertz–Knudsen equation is used to obtain theoretical temperature dependence of k_v. For this dependence, the curve fitting method is also used to determine the adsorption activation energy E_ad. It is found that the activation energy ranges within 300–500 cal/mol, which shows that the adsorption of NO₂ on these zeolites is a physical process, with the electronic structure of the molecules being perturbed only slightly during the adsorption process. A theoretical formula for calculating the time of protective action of the sorbent is derived. It is shown that the DAC and the corresponding protective action time for the studied sorbents depend on the temperature and increase in the series Zeolon 900Na < Na/ZSM-5 < Zeolon 900K < H/ZSM-5 < Zeolon 500H < Zeolon 200H < Zeolon 900H for gas mask filters at room temperature (293 K), and increase in the series CaA < H/ZSM-5 < Zeolon 900H < Zeolon 500H < Na/ZSM-5 < Zeolon 200H < Zeolon 900K < Zeolon 900Na for systems of purification of flue gases from thermal power plants at 350 K.

Polytetrafluoroethylene–polystyrene composite films are prepared by polymerizing styrene in a stretched polytetrafluoroethylene (PTFE) matrix immersed into a styrene monomer solution at 90°C. The kinetics of the thermal polymerization of styrene sorbed into the pores formed in the matrix is studied. A model of the polymerization process is proposed capable of describing the kinetics of polystyrene (PS) accumulation in the film, which, in particular suggests that the polymerization occurs in the bulk of growing PS inclusions at a constant concentration of monomer in them and that the formation of active sites most efficiently proceeds at their interface with the matrix. Stretched PTFE–PS composites containing up to 70 wt % PS in the matrix are prepared.

The dependence of the initial rate of NO₃ uptake on a methane soot coating at two temperatures (256 and 297 K) and NO₃ concentrations of 2.4 × 10¹² to 3.6 × 10¹³ cm^–3 is studied using a flow reactor with a movable insert and mass-spectrometric detection. It is found that, in this concentration range, the uptake of NO₃, unlike that of NO₂ and N₂O₅, occurs by the impact recombination mechanism. It is demonstrated that, before being deactivated, each active surface site destroys ~100 and ~150 NO₃ radicals at 297 K and 256 K, respectively. The uptake coefficient calculated per specific BET surface of the soot coating depends on the exposure time as γ(t) = γ₀exp(−t/τ), where γ₀ and τ are NO₃-concentration-dependent parameters. Based on the Langmuir concept of adsorption, the elementary parameters that control the uptake process are determined, such as the desorption rate constant k_d = ν_dexp(−Q_ad/RT) at ν_d = 3 × 10⁹ s^–1 and the heat of adsorption, Qad = 42.6 kJ mol^–1, as well as the rate constant of the bimolecular heterogeneous reaction of deactivation of active surface sites, k_r = A_rexp(–Ea/RT), with A_r = 1.1 × 10^–11 cm³ s^–1 and E_a = 9.5 kJ mol^–1.

Studies on the formation of spiral structures are always of interest to researchers. When potassium sulfate is heated in water and subjected to swirling in a beaker, the crystals formed a multi-arm spiral structure when allowed to settle. The spiral structure was either clockwise or anti-clockwise depending on the rotation of the swirl. The spiral formation requires heat to maintain integrity of the structure. The multi-arm spiral structure of potassium sulfate was stable if left undisturbed at room temperature.