Effect of Doping on Helium Behavior and Bubble Structure Development in Nickel and Vanadium Alloys

Transmission electron microscopy and thermal desorption spectrometry are used to study the behavior of ion-implanted helium and formation of a gas bubble structure in fcc and bcc metals as a function of the concentration of the alloying elements (aluminum in nickel and titanium in vanadium). It is shown that during post-radiation annealing of room-temperature irradiated samples alloying in both types of alloys substantially decreases the size and increases the density of the bubbles formed. In nickel–aluminum alloys, with post-radiation uniform heating, the thermal desorption peaks shift to high temperature with increasing aluminum content and, conversely, in vanadium–titanium alloys a shift to low temperature with increasing titanium concentration occurs, though the effective gas release activation energy increases in both alloys with increasing concentration of the alloying element. The data obtained are discussed from the standpoint of the influence of doping on the mechanisms of growth and migration of bubbles.     

Nucleation of normal phase in the dynamic resistive state in submicron Bi2212 bridges

The resistive state above the Larkin-Ovchinnikov (LO) instability current has been experimentally studied. Analysis of the stepwise I–V curves of thin superconducting bridges ≤1 μm wide, etched from the Bi₂Sr₂Ca₁Cu₂O_y (Bi2212) whiskers, reveals the following scenario of vortex dynamics: first, a pair of current-induced Abrikosov vortices enter the bridge, then they are accelerated by the current above the critical velocity of the LO instability and approach the limiting velocity of the normal phase propagation, of the order of 10⁷ cm/s. Each vortex leaves a tail of normal phase behind itself, which is equivalent to a phase slip line. At low temperatures the tails cover the whole width of the bridge—the I–V curves between the steps become Ohmic.     

Investigation of the Adhesion of Potassium Chloride to the Structural Materials of Equipment Surface

Chemical and Petroleum Engineering - The results of experimental studies of the adhesion of wetted fine fractions of flotation potassium chloride to the surface of various materials in the drying...     

Studying viscoelastic properties of liquid crystals during nematic-isotropic phase transition by low-frequency ultrasound probing of small-volume samples

The velocity of propagation and the coefficient of absorption of ultrasound in liquid crystals (LCs) in the vicinity of the phase transition from a nematic phase (N) to the isotropic liquid (I) has been studied in samples with a volume of 0.15 cm³ using an acoustic resonance technique at frequencies in the range from 0.68 to 1.63 MHz. An analysis of the results of acoustic measurements provides information on the characteristics of phase transition and critical anomalies in the viscous properties of LCs in the N-I phase transition region. The proposed acoustic method offers good prospects for the rapid investigation of small volumes of mesogenic compounds.     

Radiogenic 234U and 210Po in humus acids of dyctionemic shale

Radiochemical analysis is made of different fractions of humic and fulvic acids separated from organic matter of graptolitic argillite (dyctionemic shale) of the Baltic basin. The relation between the decalcination of humates and fulvates and the isotopic composition of U is studied. The tightness of binding to humus substances, including humin, is different for ²³⁸U and ²³⁴U, which is probably due to preferential stabilization of the radiogenic uranium in the oxidation state +4. Based on the experiments on precipitation of humates at pH 0–2, it is suggested that the thiol groups of humic acids are involved in chemical binding of ²¹⁰Po. Experiments on partial decalcination of humates in 1 M HNO₃ revealed stronger binding of the radiogenic Po as compared to ^208,209Po. The results were interpreted in terms of the known models.     

Corrosive and mechanical strength of welded joints in steels at elevated temperatures

This paper presents the experimental data on the effect of an aqueous medium upon the resistance to fatigue crack initiation and growth in pressure vessel steels and their welded joints, which find applications in power equipment. The tendency to crack extension for these materials under long-term loading is also evaluated.