Effect of modification on the physical, mechanical and relaxation properties of the polymer - nanodispersed graphite system

The paper analyzes the physical, mechanical and relaxation properties of the polychlortrifluoroethylene (PCTFE) - modified nanodispersed graphite (TEG) system. It has been shown that the modification of the surface of conducting carbon nanoplates with ultradispersed dielectric silicon dioxide (SiO2) (30%) leads to a nontrivial effect - an increase in the electrical conductivity of the PCTFE - 2.5% TEG/30% SiO2 composite by more than two orders of magnitude in comparison with the PCTFE - TEG composites, containing unmodified carbon nanoplates. The functionalization of carbon nanoplates was carried out by treating the particle surface with an active solution of chlorosilane in an organic solvent, that in case of hydrophobization of the filler surface, leads to an increase in the system percolation threshold. It is shown that the method of hydrolyzation of the filler surface can be highly effective due to a directed change in some, in particular, shielding, properties of polymer composites based on nanocarbon. It is established that the modification of the nanofiller (dispersed thermoexpanded graphite) increases the intermolecular interaction of the filler-matrix. Depending on the concentration of the filler, the structure of the matrix and the system as a whole demonstrates dynamic transformations in the size of the heterogeneity of the structure. Ultrasonic studies of composites have shown that the smallest size of structure inhomogeneity is achieved in the range of concentrations of percolation development, and the change in the size of system structure inhomogeneity is associated with the transition from inhomogeneity as the size of crystallites activated by nanofiller at low concentrations associated with coagulation of nanoparticles at concentrations exceeding the percolation threshold. Thus, in the case of nanofillers, it is impractical to use concentrations that significantly exceed the percolation threshold, as this leads to coagulation of the filler particles and the relative loosening of the matrix.

Spatially-resolved electronic structure of stripe domains in IrTe2 through electronic structure microscopy

Phase separation in the nanometer- to micrometer-scale is characteristic for correlated materials, for example, high temperature superconductors, colossal magnetoresistance manganites, Mott insulators, etc. Resolving the electronic structure with spatially-resolved information is critical for revealing the fundamental physics of such inhomogeneous systems yet this is challenging experimentally. Here by using nanometer- and micrometer-spot angle-resolved photoemission spectroscopies (NanoARPES and MicroARPES), we reveal the spatially-resolved electronic structure in the stripe phase of IrTe2. Each separated domain shows two-fold symmetric electronic structure with the mirror axis aligned along 3 equivalent directions, and 6 × 1 replicas are clearly identified. Moreover, such electronic structure inhomogeneity disappears across the stripe phase transition, suggesting that electronic phase with broken symmetry induced by the 6 × 1 modulation is directly related to the stripe phase transition of IrTe2. Our work demonstrates the capability of NanoARPES and MicroARPES in elucidating the fundamental physics of phase-separated materials.

Radiotechnical Signal Processing Techniques for Polymer Materials Structure Analysis

Paper describes new approach to material structure analysis by means of ultrasound probing. Short-time Fourier transform and time-frequency analysis used to determine structure inhomogeneity present and perform structure condition assessment. Experimental results show possibilities of polymer materials structure assessment.

On Reliability of Stainless Maraging Steel

The investigation results on the problem of the reliability of high-strength low-carbon maraging steel products have been generalized. The influence of a method for remelting on the reliability behavior is shown and the ways for the reliability behavior improvement are suggested. The study of the reasons for decreasing KCU during heat treatment shows that in addition to the precipitation of phases causing brittleness at cooling, chromium zones at heating, and formation of chemical and structure inhomogeneity in the two-phase region, the main reason is the remelting method with the parameters which predetermine the variation in grain size in the structure, a small number of interstitial elements (IE), retained austenite in the structure, and lower level of KCU of the steel prepared by VAR both after quenching and after TST. Shows influence of the quenching temperature on the amount of retained austenite and level of impact strength (KCU), of the time of aging on the work of the crack development (KCV) at the temperature of maximal development of brittleness in steel 08Cr15Ni5Cu2Ti and on the position of brittleness transition temperature prepared by ESR and VAR. After cooling down to the liquid nitrogen temperature, the VAR-steel is less liable to brittle fracture after maximal strengthening aging and more reliable after 1.5h-aging (KCV is twice as much as that in ESR-steel despite the low KCU level). The science-based regimes are developed for stamped semi-finished items from steel 08Cr15Ni5Cu2Ti allowing guaranteeing the proper quality and reliability of functioning of the items made from them.

Structure Inhomogeneity and Failure Analysis of Modern Pipe Steels

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.