Study of the process of PbS nanocrystal formation in lead stearate and behenate Langmuir-Blodgett films by electron diffraction and x-ray reflectometry

Special features of the formation of PbS nanocrystals in Langmuir-Blodgett (LB) films of lead stearate and behenate under the action of H₂S are studied. It is shown that structural transformations in a multilayered LB film can be controlled using electron diffraction patterns of the oblique-texture type and x-ray reflectometry data.     

Nanocomposite: Antimony Sulfide in Channels of Single-Walled Carbon Nanotubes

A nanocomposite of antimony sulfide Sb₂S₃ embedded into the channels of single-walled carbon nanotubes (SWCNTs) has been prepared for the first time by the capillary wetting method and has been characterized by X-ray powder diffraction, transmission electron microscopy (TEM), transmission scanning electron microscopy (TSEM), and X-ray energy dispersive (EDX) spectroscopy. Antimony sulfide fills the channels of almost all SWCNTs. Channel filling is continuous along the entire length of the tube up to 1 μm. The diameters of filled SWCNTs fall in the range 0.6–3.5 nm. The periodicity of Sb₂S₃ crystal clusters observed on electron microscopic images is 2.0–2.2 nm along the nanotube axis and 2.5–3.5 nm in the transverse direction. A structural model of a Sb₂S₃ cluster is suggested.     

The system for the monitoring of the photomultiplier dark noise in the Borexino neutrino detector

Monitoring the dark noise of photomultiplier tubes (PMT) is important for maintaining the operation of the Borexino detector. For this purpose, a dark noise monitoring system was developed on the basis of the CAN network and the DeviceNet upper-level protocol. The system consists of a set of CAN controllers, which digitize PMT signals and transmit data over the CAN to the host computer. The software creates a DeviceNet protocol stack, ensuring data collection and transmission. The user interface is built on the basis of dynamic WEB pages.     

Evaluation of cross-peak volumes in 2D-spectra using 1D-fitting of line shapes

An interactive technique for the evaluation of cross-peak volumes in 2D-spectra is presented, based on a 1D nonlinear curve-fitting procedure. The effects of applied window functions, truncation of time domain data and cross-peak overlap on the evaluated cross-peak volumes are considered. The technique is applied to crowded NOESY spectra of the 34–65 and 163–231 fragments of bacterioopsin ofHalobacterium halobium. For these spectra 284 and 546 cross-peak volumes were measured with high accuracy.     

Dependence of the temperature of stochastically heated electrons on the flux density of pulsed laser radiation on a target

Electron dynamics in the field of focused picosecond multimode laser radiation was considered by numerical methods. It was found that the electron energy during stochastic perturbation of its trajectory can exceed the energy of oscillatory motion in a plane wave by several orders of magnitude. The electron distribution function was studied based on 2D numerical simulation. An analytical expression for the distribution function of relativistic electrons as ideal gas was derived. The distribution function in the radiation flux density range of 10¹⁴–10¹⁷ W/cm² was compared with an analytical expression of the equilibrium distribution; a temperature characteristic for electrons stochastically heated by the laser field was introduced. The dependence of the electron temperature on the radiation flux density was determined.     

Thermal stability of organic layered systems based on lead stearate

The structural variation in multilayer Langmuir-Blodgett films of lead stearate caused by heat treatment under different conditions in the temperature range 20–100°C is investigated by X-ray reflectometry and high-resolution electron diffraction. Successive annealing of the samples is shown to not alter the initial layered structure at temperatures of 60, 80, and 100°C; partial disturbance of the layered structure occurs upon successive annealing at 80°C and 100°C. Significant disturbance of the structure is observed when the films are heated immediately to 100°C. In all these cases, the orthorhombic (pseudomonoclinic) lattice, with the lattice constants: a = 0.496, b = 0.738, c = 9.60 nm, α = β = γ = 90°, space group P2/1b, formed by transferring monolayers onto the substrate is retained in the crystalline domains of the film.     

Simulation of the adhesion properties of the polyethylene/carbon nanotube interface

The properties of a polyethylene matrix in contact with carbon nanoinclusions, such as carbon nanotubes and graphene plates, are studied via the molecular-dynamics method. Ultimate shear stresses for the polyethylene/graphene interface are calculated, and the effect of the filler aspect ratio on the nanocomposite elastic modulus is considered.     

Electron microscopy study of the microstructure of Ni–W substrate surface

The surface microstructure of Ni–W alloy tapes, which are used as substrates to form films of high-temperature superconductors and photovoltaic devices, has been studied. Several samples of a Ni₉₅W₅ tape (Evico) annealed under different conditions were analyzed using scanning electron microscopy, energy-dispersive X-ray microanalysis, electron diffraction, and electron energy-loss spectroscopy. NiWO₄ precipitates are found on the surface of annealed samples. The growth of precipitates at a temperature of 950°С is accompanied by the formation of pores on the surface or under an oxide film. Depressions with a wedge-shaped profile are found at the grain boundaries. Annealing in a reducing atmosphere using a specially prepared chamber allows one to form a surface free of nickel tungstate precipitates.