On shift and resolubility of relaxation maxima with change in properties of the boundary polymer layer in composite materials

Temperature dependencies of viscoelastic functions of the three-component models of composite materials in the transition state temperature range of polymer binder have been studied. On the basis of theoretical calculations for the models, a conclusion has been made about the conditions for shift of the relaxation maxima along the temperature axis. Also conditions for their resolubility on tan δ curves were determined for materials such as filled polymers as well as anisotropic laminated and reinforced plastics with deformation of the components in series. These effects are due to the change in properties of the boundary layer of the polymer. They are entirely dependent on the concentration ratio between the boundary layer and the bulk of the binder polymer and on the difference in their glass temperatures T_g. Concentration of the high-modulus filler affects T_g of the composition. This is due to the change in the ratio of concentrations of the polymer in the boundary layer and in the bulk. With parallel deformation of the components of the three-component model, resolubility and shift of the relaxation maxima depend not only on the above factors, but also on the reinforcing filler concentration.     

Electrical properties and transport mechanisms in phase change memory thin films of quasi-binary-line GeTe–Sb<Subscript>2</Subscript>Te<Subscript>3</Subscript> chalcogenide semiconductors

The temperature dependences of the resistivity and current–voltage (I–V) characteristics of phase change memory thin films based on quasi-binary-line GeTe–Sb₂Te₃ chalcogenide semiconductors Ge₂Sb₂Te₅, GeSb₂Te₅, and GeSb₄Te₇ are investigated. The effect of composition variation along the quasibinary line on the electrical properties and transport mechanisms of the thin films is studied. The existence of three ranges with different I–V characteristics is established. The position and concentration of energy levels controlling carrier transport are estimated. The results obtained show that the electrical properties of the thin films can significantly change during a shift along the quasi-binary line GeTe–Sb₂Te₃, which is important for targeted optimization of the phase change memory technology.     

Rheological,mechanical, and adhesive properties of thermoplastic-LCP blends filled by glass fibers

Rheological, mechanical, and adhesive properties have been studied of two-phase polymer blends containing a liquid crystal copolyester of poly(ethylelene terephthalate) and p-hydroxybenzoic acid plus isotactic polypropylene (PP) with varying compositions and concentrations of glass fibers. Perfect fibrillation of the disperse LC-phase into the PP-matrix in capillary flow was observed at LCP concentrations >20 wt% and temperatures >488 K. This effect leads to a decrease of blend viscosity and a reinforcing of the extrudate's mechanical characteristics. At the same time, more essential reinforcement is achieved by the simultaneous addition of the reinforcing agents both of the LCP and glass fibers. Processing of PP is not impaired. It was found that the adhesive strength increases substantially when the amount of LCP in the blend exceeds a definite level, corresponding to a phase inversion. The results are explained by the formation near the interface of two adhesion layers: the first is composed of pure LCP having a higher surface tension, whereas the second layer represents the blend of various compositions. At small amounts of LCP, the adhesion failure proceeds in the interphase between the LCP and the blend. After the phase inversion, where adhesion strongly increases, the failure of adhesion joints proceeds near the interface between LCP and the glass.     

Sorption characteristics of materials of the filtration barrier in upper aquifers contaminated with radionuclides

Sorption and desorption characteristics of natural materials (apatite, vermiculite, haydite, wood sawdust, perlite, zeolite produced by Tseolit-Treid, shungite) were studied, and the possibility of using them in filtration barriers in upper aquifers contaminated with cesium, strontium, uranium, and technetium was discussed. Changes in the sorption properties of the materials under the action of natural groundwater microflora were evaluated. Under the conditions of the barrier operation, microbiological action does not significantly affect the sorption characteristics of the materials studied.