Structure and optical properties of the silver/polyacrylonitrile nanocomposites

Small-angle X-ray scattering is used to prove the formation of silver nanoparticles with sizes of 5–11 nm in siver/polyacrylonitrile nanocomposites synthesized via photopolymerization of a mixture containing silver, acrylonitrile, and photoinitiator. Optical spectra of nanocomposites obtained under different conditions are studied. The absorption spectra exhibit maxima at wavelengths of 420–450 nm related to the surface plasmon resonance of silver nanoparticles. IR spectra of the nanocomposites prove the formation of polyacrylonitrile in the course of the photopolymerization of monomer. The formation of metal nanoimpurities in polymer matrix leads to an increase in the intensity of photoluminescence and Raman scattering of polyacrylonitrile.     

Reduced OFF-axis haze in polymer-dispersed liquid crystals

Polymer-dispersed liquid crystals (PDLCs) are composite materials formed by micron-sized droplets of liquid crystals (LCs) dispersed in a polymer matrix, which can be turned from an opaque state to a transparent one by application of a suitable electric field. PDLCs have been proposed in applications related to the control of light transmittance on large surfaces (light shutters, displays, rear mirrors). Despite several advantages, PDLCs’ main drawback is haze, i.e. the fast decay of transmission at large viewing angles. In this paper, a method for achieving highly transparent PDLC devices over a wide range of viewing angles is proposed. The method is based on the use of PDLCs with tilted elongated LC droplets and driven by opportune electric fields, which are experimentally calculated and able to ensure an almost constant value for OFF-axis transmittance.     

X-ray fluorescence analysis of Ni–Fe–Mn/Cr systems

We have developed a procedure for x-ray fluorescence determination of the constituent composition and thickness of two-layer Ni–Fe–Mn/Cr films deposited on Polikor, an aluminum oxide ceramic. We have calculated correction coefficients taking into account interelement interference effects in this system. We have experimentally determined the density of the materials making up the composition of the films. We have established and present the metrological characteristics of the procedure developed.     

Calculation of radial distribution function from incomplete experimental diffraction data

A method for calculating atomic radial distribution functions for amorphous materials has been suggested. The method is based on the principle of the maximum informational entropy. Under the condition of a limited amount of the experimental diffraction data, the method allows one to obtain the unique solution and considerably reduces the errors caused by series termination, which are inherent in traditional computational methods based on the Fourier transform. A criterion of using the method of optimum information is formulated, and the reliability of the data obtained are quantitatively estimated. The advantages of the method are demonstrated on the computation of the short-range order in hydrogenated amorphous silicon.     

X-ray fluorescence analysis of the systems Fe–Ni–Mo/Cr

A procedure has been developed for the X-ray fluorescence determination of the thickness of Fe-No-Mo/Cr two-layer films supported on polycor. Correction coefficients have been calculated that take into account the effects of the mutual influence of the elements in this system. The density of the materials in the films has been experimentally determined. The performance characteristics of the developed procedure are provided.     

Determination of Traces of Toxic Elements in Dimethylaminoborane upon Their Concentration for Atomic Emission Analysis

A technique of atomic emission determination of traces of toxic elements in dimethylaminoborane with detection limits of n·10^–5–10^–8 wt. % has been developed. To reduce the detection limits, a technique of separation of the basic component in the form of boron fluoride, with concentration of microimpurities on a graphite collector, was used.     

Polymer Membranes Dispersed Liquid Crystal (PMDLC): a new electro-optical device

Polymer Dispersed Liquid Crystals (PDLCs) are liquid crystal dispersions in a polymer matrix, which look like opaque in their OFF state, when no electric field is applied, and transparent in their ON state. They are generally obtained by a phase separation process, such as Thermal, Solvent- and Polymerization-Induced Phase Separation (TIPS, SIPS and PIPS, respectively), between two transparent conductive glass substrates. In this paper, a new electro-optical device, formed by a porous polymer membrane imbibed with liquid crystal by capillary suction, is presented (Polymer Membranes Dispersed Liquid Crystals, PMDLC). Polymer membrane surfaces were made conductive before liquid crystal loading by magnetron sputtering of a thin layer of conductive indium tin oxide. The morphology and the electro-optical response of these devices were investigated and the observed transmittances and relaxation times were found to be similar to those of conventional PDLCs. In addition, PMDLCs showed interesting flexibility as no solid conductive substrate is required and economic convenience as there is no loss of liquid crystal in the polymer matrix.     

Determination of the Elemental Composition of Chalcogenide Powders by the X‐Ray Fluorescence Method

A procedure of xray spectral fluorescence analysis of the elemental composition of As _x S_100–x chalcogenide powder samples is developed and its metrological characteristics are established. In determining the content of the components in an As₅₀S₅₀ sample, the relative standard deviation was 0.0030 for As and 0.0035 for S. The results of the xray spectral fluorescence analysis are in good agreement with the data of a gravimetric method.