Doklady Rossijskoj akademii nauk. Himiâ, nauki o materialah.

In this work, the phenomena of copper-induced formation of NHC-R and NHC=O particles in the Chan–Evans–Lam arylation reaction system of aniline are discussed for the first time. The considered combinations between NHC and arylboronic acid residues have been demonstrated using 5 different arylboronic acids and three Cu/NHC complexes. It is also shown that the formation of the azolone NHC=O is due to copper-mediated oxygen transfer from the atmosphere to the carbene center of the NHC. Using a set of experimental physicochemical methods of analysis, as well as with the help and methods of quantum chemistry, it is shown for the first time that the degradation pathway of Cu/NHC complexes through the formation of NHC–R is controlled kinetically, and through the formation of NHC=O - thermodynamically, which makes a significant contribution to the understanding of the observed phenomena.

The kinetics of oxygen sorption from air by Y_0.8Ca_0.2BaCo_4-xFe_xO_7+δ (x = 0, 1) is studied by nonisothermal thermogravimetric measurements. The activation energy is calculated by model-free methods of Friedman, Starink and Vyazovkin. The master plot and Coates–Redfern methods are applied to determine the mechanism of oxygen intake. The results show the activation energies and frequency factors are 189 and 197 kJ mol^–1 and 4.7 × 10¹³ and 2.3 × 10¹⁴ min^–1 in Y_0.8Ca_0.2BaCo₄O_7+δ and Y_0.8Ca_0.2BaCo₃FeO_7+δ, respectively. The arguments are given in proof of oxygen sorption determined by the volume random nucleation and growth of the oxygen-rich nuclei.

Titanium and its alloys have a number of unique properties, such as high specific strength, corrosion resistance, non-toxicity and biocompatibility with human tissues. Due to these properties, they are widely used to create prosthetic joints for the human body. However, the material used for implants, VT6 (Ti–6Al–4V), can cause a stress shielding effect due to a higher elastic modulus (110 GPa) compared to human bone (<30 GPa). In addition, Al and V ions released from the VT6 alloy can cause health problems such as Alzheimer's disease, osteomalacia and neuropathy. Therefore, the development of titanium-based materials that are non-toxic and have mechanical properties corresponding to natural bone is an urgent task. In this paper, we study Ti–38Zr–9Nb (at. %) alloy ingots and plates obtained from them. Particular attention is paid to the homogeneity of the chemical composition, microstructure, phase composition and mechanical properties. The ingots obtained as a result of the work are suitable for further pressure processing. Homogenizing annealing at a temperature of 1000°C for two hours destroys the dendritic structure of the alloy. After homogenizing annealing, the α'-phase completely dissolves in the β-phase, which is the main one for using the alloy in implants. The microstructure of the plates is uniform and consists of polyhedral β-grains. The grain size after rolling is approximately 100 μm. X-ray phase analysis showed that the alloy consists of metastable β-Ti stabilized by Nb and Zr. The Ti-38Zr-9Nb alloy has good mechanical properties, which make it a suitable material for medical purposes.

The fragility of ice limits its use as construction material, the road and crossings base in winter period in hard-to-reach northern regions. To strengthen it, various dispersed additives are introduced. However, the approaches proposed to date are labor-intensive, dispersions settle and can be poorly wetted. Here we suggest to strength ice using nano/microfibrillar cellulose aerogels. Their advantages over currently used materials include low specific gravity (0.1–0.001 g cm^–3), large volume (up to 99 vol. %) of interconnected pores, hydrophilicity and biodegradability. The ice nanocomposites were formed in one step by simple impregnation of aerogels with water and subsequent freezing. The volume of the ice matrix included a homogeneous three-dimensional network of intertwined nano/microfibrils. The enhancement of the mechanical strength of ice by aerogels was due to a change in the mechanism of failure from brittle to plastic. Unlike ice, the composites did not undergo a breakdown into pieces after reaching yield stress. The three-dimensional network of nano/microfibrils of cellulose prevented the formation and development of macrocracks, which are associated with the rapid breaking of ice. Destruction occurred through a gradually increasing number of microcracks.

For the first time, the maximum synergistic effect of reducing the flammability of epoxy resin according to the oxygen index was established using a non-stoichiometric mixture of melamine and ammonium hydrophosphate. The synergetics of the mixture is due to the formation of heat-resistant ceramic-like structures as a result of thermal degradation of the components. In the present work, the effect of increasing the resistance up to (80 ± 10)% to impulse loads followed by rapid failure (mechanical or rheological explosion) was established for the first time for a polymer composite based on cured epoxy resin with 20% content of phosphorus-nitrogen-containing flame retardants (P,N-antipyrenes) due to the introduction of 0.5–1.5% organobentonite nanoparticles. It is also recorded that the electric current pulses arising from the ultrafast destruction of the “matrix” composite differ in frequency characteristics from the composite with the introduced nanoparticles of organobentonite. For a polymeric composite, one band of radio frequency radiation with a maximum at 2.4 MHz is fixed, and for a composite with introduced organobentonite nanoparticles, bands of radio frequency radiation with maxima at 2.4, 20.9 and 25.3 MHz. A probable mechanism of the observed effect is proposed.