On chemical and diffusional interactions between PCBN and superalloy Inconel 718: Imitational experiments

During a metal cutting process, chemical wear can become the dominant mechanism of tool degradation under the high temperatures and contact pressures that arise between the tool and the metal workpiece. This study focuses on the chemical and diffusional interactions between superalloy Inconel 718 and cubic boron nitride (cBN) tool material with and without TiC binder. It covers thermodynamic modeling and experimental tests in the pressure range of 0.1 Pa to 2.5 GPa at temperatures up to 1600 °C. The methods used include diffusion couples under both vacuum and high pressure, transmission electron microscopy (TEM) analysis and in-situ synchrotron observations. It is shown that cBN is prone to diffusional dissolution in the metal and to reactions with niobium, molybdenum, and chromium from Inconel 718. Adding TiC binder changes the overall degradation process because it is less susceptible to these interaction mechanisms.     

An approach to Y2O3:Eu optical nanostructured ceramics

Y₂O₃:Eu³⁺ (1 at.%) translucent nanostructured ceramics with total forward transmission achieving ∼70% of the theoretical limit has been obtained by the transformation-assisted consolidation of custom-made cubic Y₂O₃:Eu³⁺ nanopowders under high pressure (HP). Sintering under the pressure of 7.7 GPa and temperatures in the 100-500 °C range leads to the partial cubic-to-monoclinic phase transition that results in two-phase Y₂O₃:Eu³⁺ nanoceramics. The average grain size of ceramics d ≤ 50 nm for both Y₂O₃:Eu³⁺ polymorph is comparable with crystallite size of initial nanopowders (d ∼ 40 nm), indicating that the grain growth factor is near unity. The phase compositions, morphology, densities, preliminary optical and luminescent properties of synthesized nanostructured ceramics have been studied.     

Structural features of boron nitride dense phase formation from rhombohedral modification under high static pressure

The real structure of boron nitride (BN) polycrystals after high-pressure treatment was investigated by X-ray and transmission electron microscopy methods. Different stages of boron nitride polycrystal evolution under high quasistatic pressure and high temperature were fixed, involving rhombohedral boron nitride twinning, one-dimensionally disordered structure, 2H, 4H, 3C dense phase formation and 3C-BN recrystallization. A new structural scheme of BN_r-BN_w transition is proposed.     

Pharmacokinetic characteristics of 6-azacytidine

Pharmacokinetics of 6-azacytidine, an antitumour drug, is studied by ion-pair reversed-phase highly effective liquid chromatography. The survey of the drug elimination from blood is of a two-phase character: the first phase--with a biological half-life of 5.5 min (for rats) and 6.5 min (for rabbits); the second phase--1.2 and 2.5 h, respectively. For a 24 h period 75% of the drug is excreted unchanged in the urine.     

Superhard pcBN tool materials with Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript> MAX-phase binder: Structure,properties, application

Superhard cutting tool materials were sintered in cBN–(Ti₃SiC₂–TiC) system via high pressure–high temperature method. Sintering was performed under the pressure 8 GPa in the 1400–2400°C temperature range. The initial mixtures of three compositions were chosen with 90, 80 and 60 vol % cBN. The mixtures were prepared by mixing cBN (1–3 μm) and Ti₃SiC₂–TiC (< 2 μm). It was found, that upon sintering, the compositions of the obtained samples differed from the initial mixtures in all cases as a result of chemical reactions. Microstructure observations, phase composition estimation, and mechanical properties of the obtained tool materials were carried out. The results indicate that both the varying cBN content and the applied sintering conditions have a direct effect on the structure, properties, and kinetics of reactions.     

Biological treatment of storm wastewater at industrial enterprise using the immobilized microorganisms and hydrobionts

The possibility of effective treatment of storm-and-industrial wastewater has been shown in principle by using microorganisms, hydrobiocenoses and higher aquatic plants attached to installations in the form of floating rafts equipped with VIYA type carriers submerged into water with hydrobionts–water purifiers immobilized on these carriers.     

The Influence of VC–Al Additive on Wear Resistance of cBN-based Composites

The paper addresses wear resistance of cBN–VC–Al cutting tool material under the conditions of high-speed continuous turning of AISI 316L stainless steel.     

Crystal-oriented mechanism of dynamic recrystallization nucleation in cubic boron nitride

Structural transformations occurring at 8 GPa and 2400 °C in twinned cubic boron nitride (cBN) with a triplex texture [112] have been explored by electron microscopy using the thin foil procedure. The following reconstructions have been established: destruction of the texture that occurs by rotation about the [220] axis, fragmentation of twinned grains, detwinning of large fragments by rotation about the [110] axis and formation of nuclei of a primary recrystallization from fragments with no twins.     

Y3Al5O12 translucent nanostructured ceramics—Obtaining and optical properties

Y₃Al₅O₁₂ nanostructured ceramics with total transmittance of 63% at λ = 1064 nm has been obtained by low-temperature high-pressure sintering. According to high-resolution transmission electron microscopy ceramics is near pore-free and consists of close-packed grains of 20–40 nm in size. The transmittance spectrum in the visible and IR wavelength range, stationary X-ray excited luminescence and thermally stimulated luminescence were studied to characterize Y₃Al₅O₁₂ nanostructured ceramics in comparison to single crystals of the same composition. The observed differences in the optical and luminescent properties were interpreted as a consequence of high defectivity level of nanoceramics arising from its non-equilibrium character, extremely large concentration of grain boundaries and surface states.