Time programming of material’s properties via self-irradiation phenomena

We consider theoretically programming of ageing processes in materials over large time intervals via the introduction of small quantities of unstable nuclei in a material’s structure. Incorporation of minuscule amounts of radio-active species (e.g. carbon-14, tritium) in the structure of polymers, such as polytetrafluoroethylene, can be used for presetting self-decomposition of plastic products to a certain term. Radio-decay of unstable nuclei embedded in conductive polymers and dielectrics might enable the design of electrical resistors and capacitors with time-dependent characteristics. Relaxation of internal mechanical stresses, amorphization and swelling driven by self-irradiation can be used for programming configurations of mechanical systems over large terms (from years to thousands of years). Implementations of the time-programmed materials and their possible applications are discussed.     

Investigation of bulk metallic glass structure by means of electron irradiation

The sensitivity of radiation effects on structural features in metallic glasses (MG) provides a way of investigating the structure and structural defects of MG through the studies of accumulation and relaxation processes of radiation damages in the glasses. In particular, it is a way to verify the validity of models proposed for the MG structure. Currently, there are two theoretical structural models of MG, based on completely different concepts. On the one hand, the model of random closely packed spheres + free volume approach is based on the idea of “the ultimate disorder”. On the other hand, in the polycluster model the idea of altering and distorted short-range order is used. Each of the models implies fairly different kinds of primary radiation damages, relaxation kinetics, and other properties. We have studied the accumulation and recovery kinetics of radiation defects in ZrTiCuNiBe and ZrTiCuNiAl bulk metallic glasses irradiated with 2.5 MeV electrons at T ～ 80 K. Electrical resistance measurements of the irradiated samples were performed. Dose dependences at ～80 K and the recovery spectrum of irradiation-induced electrical resistance in the 85–300 K temperature range were obtained. The data suggest that the point defects are stable in the metallic glasses, and the defect mobility is a thermally activated process. The results obtained are evidently in accord with the polycluster model of the MG structure.     

Refined model of elastic nanoindentation of a half-space by the blunted Berkovich indenter accounting for tangential displacements on the contact surface

Elastic contact between a non-ideal Berkovich indenter and a half-space is investigated. The derived mathematical model of the contact allows for tangential displacements of the boundary points of the half-space. The tip of the blunted indenter is simulated as a smooth surface. The boundary element method is implemented in the model for numerical simulation of nanoindentation. The relative deviation function is introduced and calculated to quantify the influence of the tangential displacements on the load–displacement curves. A simple expression is derived for the impact of the tangential displacements on the values of the reduced Young’s modulus determined due to nanoindentation studies. The refined model was successfully applied to simulate the experimental load–displacement curves gained by elastic nanoindentations of flat LiF and KCl samples. Such values of the indenter bluntness (the varying parameter) were found that the simulated load–displacement curves coincided with those of the experimental data at displacements higher than 7.5 nm. The model neglecting tangential displacements gives slightly differing values for the parameter of the indenter bluntness.

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Molecular nanostructures of alcohols adsorbed in micropores of active carbons

Quantitative topological analysis of molecular nanostructures of alcohols adsorbed in a model pore of active carbon depending on the micropore width and temperature is carried out. The analysis is performed using a method (MDTG) that we suggested earlier. It is based on a combination of molecular-dynamic calculations and graph theory and allows detecting and recording all molecular nanostructures observed in each shot of the molecular-dynamic path; averaging the data for any amount of such shots thus obtaining “average” concentrations of associates (dimers, trimers, etc.); and then determining concentrations and characteristics of isomers (e.g., chains, branched chains, cycles, etc.), bond widths, angles, etc., in each group of associates.     

Experimental Evaluation of Food-Grade Semi-Refined Carrageenan Toxicity

The safety of food additives E407 and E407a has raised concerns in the scientific community. Thus, this study aims to assess the local and systemic toxic effects of the common food additive E407a in rats orally exposed to it for two weeks. Complex evaluations of the effects of semi-refined carrageenan (E407a) on rats upon oral exposure were performed. Local effects of E407a on the intestine were analyzed using routine histological stains and CD68 immunostaining. Furthermore, circulating levels of inflammatory markers were assessed. A fluorescent probe O1O (2- (2′-OH-phenyl)-5-phenyl-1,3-oxazole) was used for evaluating the state of leukocyte cell membranes. Cell death modes of leukocytes were analyzed by flow cytometry using Annexin V and 7-aminoactinomycin D staining. Oral administration of the common food additive E407a was found to be associated with altered small and large intestinal morphology, infiltration of the lamina propria in the small intestine with macrophages (CD68⁺ cells), high systemic levels of inflammation markers, and changes in the lipid order of the phospholipid bilayer in the cell membranes of leukocytes, alongside the activation of their apoptosis. Our findings suggest that oral exposure to E407a through rats results in the development of intestinal inflammation.     

Synthesis of novel silica-gel-supported thiosemicarbazide and its properties for solid phase extraction of mercury

A new thiosemicarbazidе-modi?ed silica gel (SG-THSC) sorbent was prepared. The sorbent was quantified by adsorption of mercury ions on silica gel, desorption and then spectrophotometry detection of mercury ions. The retention parameters (sample flow rate, eluent type, sample volume, presence of foreign ions, shaking time, sample flow rate and volume, eluent condition, interfering substances) were investigated. The quantitative recovery (>95%) of Hg(II) ions could be obtained by use of 5 mL of 6 mol L^?1 HCl. The adsorption capacity of SG-THSC was found to be 98.3 mg g^–1 at optimum pH. The maximum preconcentration factor was 400. The technique detection limit was 70 ng L^–1, and the relative standard deviation was lower than 4.0% (n = 6). The studied sorbent was applied to preconcentrate the trace Hg(II) from the mineralised residues of fish and seawater samples.     

New diurethane plasticizers for polyurethane thermoplastics and perspective functional composites

A method to synthesize low‐molecular‐mass diurethane compounds via reaction between diisocyanates and various primary and secondary alcohols was presented. A number of diurethanes with the melting points below 100^oC were revealed. These diurethanes can be used as fusible plasticizers for thermoplastic polyurethanes (TPU) and for high‐filled composites based thereupon. TPU based on oligotetramethyleneoxide diol and on 4,4′‐diphenylmethane diisocyanate and containing 30% of fusible diurethanes were produced. In the presence of such plasticizers, a 3‐order increase in magnitude of the melt flow index was demonstrated. Data evincing significantly larger strength values of TPU and of tungsten‐containing high‐filled composites (94.2 wt %), comparing with thermoplastics plasticized with low‐molecular‐mass liquids, were presented. The mechanism of this phenomenon attributed to the partial crystallization of diurethanes in TPU compositions was described. Samples of low‐toxic thermoplastic polyurethane having density value of 9.4 g/cm³ and meant for protection of various facilities from radioactive radiation, instead of highly toxic metallic, lead, were prepared. Issues of improving the frost resistance of this new type of TPU were considered. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41481.