Machine-Learning Based Interatomic Potential for Studying the Properties of Crystal Structures

Russian Microelectronics - In the process of modeling multilayer semiconductor nanostructures, an important role is played by the rapid acquisition of accurate values of the characteristics of the...     

Investigation of Characteristics of Electrostatically Actuated MEMS Switch with an Active Contact Breaking Mechanism

The electrostatically actuated MEMS switch with resistive contact is presented. The movable electrode is a beam suspended on its torsion hinges. The contact material is platinum. The switch has an active breaking mechanism making it possible to protect it against stiction and provide a low actuation voltage. The measuring technique for the operating characteristic in the “hot” mode under a low direct current is described. The pull-in voltage and the breaking voltage, the switching time, and the dependence of the contact resistance on the number of actuation cycles are measured. The wear of contact surfaces is investigated. The operation of the switch in a bistable mode is demonstrated, in which the closed condition is maintained without applying the actuation voltage and the state transition occurs due to the active contact breaking mechanism.     

A Study of the Structure of Steel – Titanium Joints Formed by Diffusion Welding with the Use of Ultrafine Nickel Powder

Metal Science and Heat Treatment - The structure and phase composition of welded joints of austenitic steel 08Kh17N10T and titanium alloy PT-3V formed by diffusion welding with an intermediate...     

Specific features of low-temperature phase transformations in nitrogen-Containing Cr-Mn-based steels

Physical and mechanical properties of nitrogen-containing austenitic steels of different alloying systems have been studied at temperatures from −196 to 700°C in the quenched state. It has been found that nitrogen-containing Cr-Mn-based steels undergo a paramagnetic to antiferromagnetic ordering (with a manifestation of invar properties), the ΔE effect, and a resistivity anomaly. It has been shown that the behavior of the temperature dependence of the yield stress in nitrogen austenite is determined by several factors. Along with specific features of the dislocation structure determined by a low energy of stacking faults, the strengthening of nitrogen austenite is influenced by its magnetic state.     

Morphology of multiscale defect structures and plastic strain localization during impact perforation of A6061 alloy targets

Mechanisms of plastic strain localization (PSL) and fracture localization (FL) during dynamic (impact) loading accompanied by “plug” formation are related to structural transitions in the ensemble of defects. A characteristic feature of these transitions in the A6061 alloy is the multiscale character of the resulting structures. It is established that two bands featuring multiscale invariance can exist, namely, the PSL and FL bands, the lengths of which depend on the impact velocity. The length of a deformed layer, in which strain is localized, has a clear tendency of growing toward the free surface of the target. The passage from the PSL to FL band is characterized by a sharp increase in the Hurst exponent.     

Effect of grain boundary on the character of pulse-train-induced cleavage fracture in copper crystal

The process of pulse-train-induced cleavage fracture in a copper crystal with grain boundary was studied by methods of computer simulation. It is demonstrated that trains of isolated compression pulses induced in the material favor the tendency to fracture propagation along the grain boundary.     

Features of high-temperature diffusion in concrete at the 4th block of the Chernobyl NPP

The element distribution and structural-phase changes in core samples taken from concrete wall in one of the rooms of the Chernobyl Nuclear Power Plant subjected to penetration of lava-like fuel-containing mass were studied by γ-ray activation and crystal-optical methods and IR spectrometry. High-temperature diffusion processes in concrete that occurred in the course of the Chernobyl accident (1986) were simulated using the developed numerical model describing concrete as a porous multiphase system occurring on the local level in the thermodynamic equilibrium with the matrix voids filled with water and gas. Comparison of theoretical results with profiles of the content of particular elements and with characteristics of newly formed minerals shows that the high-temperature fluid cloud saturated with aggressive reduction gases played the decisive role in the processes occurring during the first stage of the accident.     

Carrier-free production of Tc at an electron accelerator

We report on the results of studies of the ⁹⁵Tc isotope production conditions in a poorly investigated ⁹⁶Ru(γ,N)⁹⁵Tc reaction at a relatively inexpensive electron accelerator. Based on the analytical model it is demonstrated the possibility for estimating the effective and peak cross-sections and the isotope yield for a given reaction in a thick production target without preliminary determination of its excitation function. For this purpose we compared specific activities of two small samples that were activated under the same conditions using the reference reaction ⁶⁸Zn(γ,p)⁶⁷Cu and the one under investigation. The experiment on simultaneous photo-activation of natural zinc and ruthenium targets was performed followed by the investigation of their isotope composition. The specific activity of the radionuclide was measured and cross-sections for the ⁹⁶Ru(γ,N)^95g,mTc reactions were determined. The yields of desired isomers and admixtures in the natural ruthenium targets of different size were estimated. It is shown, in particular, that the operating conditions of the NSC KIPT accelerator KUT-30 can provide ^95gTc yields up to 120 mCi/h.     

Efficiency Of Amorphous Aluminosilicophosphate Protective Coatings For Niobium And Niobium Alloys

Results of optimization of the composition and technology of depositing amorphous aluminosilicophosphate coatings for protecting niobium and niobium-base alloys from the action of oxygen of the ambient at an elevated temperature and the resulting loss of plasticity are presented. Forced and long-duration thermal tests of specimens with coatings have been conducted and proved the effectiveness of the designed coatings. Experimental data on temperature dependences of the thermal conductivity and the rate of loss of mass of the material of the coatings in vacuum are presented.