Interconnection of structural characteristics with dynamic properties of A5083 aluminum alloy

In this work, the resistance of high-strain rate deformation and fracture during shock-wave compression of aluminum alloy A5083 previously obtained in two structural states by torsion under high pressure or dynamic pressing is studied. It is shown by electron microscopy that sub-microcrystalline structures differ in the size of grain–subgrains, dislocation density, and ratio of low-angle and high-angle boundaries. It is established that, at the same grain size, the sub-microcrystalline alloy exhibits higher dynamic properties, and after dynamic pressing, it has higher spall strength

Electrochemical synthesis of nickel-aluminium oxide system from metals obtained by ore processing

Separate and combined electrochemical oxidation of aluminium and nickel has been conducted by alternating current of industrial frequency. Concentration increase of electrolyte solution (sodium chloride) in the range from 3 to 25 wt. % and current density from 0.5 to 1.5 A/cm{2} was found to result in the increasing metal oxidation rate, excluding aluminium oxidation which oxidation rate is independent of the electrolyte solution concentration. At the current density of 1.5 A/cm{2} the products of separate oxidation of nickel and aluminium are nickel oxyhydroxides, nickel hydroxides and aluminium oxyhydroxide (boehmite), respectively. In addition to these compounds, the nickel-aluminium oxide hydrate is included in the products of nickel and aluminium co-oxidation. Its content grows with the increasing electrolyte solution concentration. Varying the concentration and current density within the limits indicated, the nickel-aluminium oxide system with nickel oxide content from 3 to 10 wt. % is produced

ПОДБОР ПАРАМЕТРОВ ПОЛИКАПИЛЛЯРНОЙ КОЛОНКИ ДЛЯ ПОРТАТИВНЫХ ГАЗОАНАЛИЗАТОРОВ ПО ИНДЕКСАМ КОВАЧА

Short straight multicapillary columns (MCC) allow for fast gas chromatographic separation. However, their limited efficiency makes it difficult to use them for the analysis of multicomponent mixtures. Therefore, it is important to preliminarily evaluate the possibility of separation of target substances, based on the available information about their characteristics, in particular, by retention indices (RI). The paper provides an example of the choice of MCC and chromatographic conditions for the separation of explosives in stationary phases OV-5 and SE-54. To find the correspondence of the retention indices of the target substances with their retention factors k on the studied MCCs, the retention times of C10−C19 n-alkanes were experimentally determined at different column temperatures. Then the dependences of the calculated lnk on the quantity of carbon atoms m in n-alkanes CmH2m+2  were plotted and approximated by linear functions ln k = a + bm and their coefficients a and b were found for each temperature. From where, it was easy to calculate the retention factors of the target substances by their RI, assuming that RI = m·100, as well as to estimate the MCC efficiency required to separate neighboring peaks to obtain the desired level of separation. Based on the obtained equations, the explosives retention factors for MCCs at different temperatures were calculated and their required efficiency for separating adjacent peaks was estimated. The retention factors experimentally determined for some explosives on the MCCs at 140 °C turned out to be quite close to the theoretically calculated ones. In the future, the similar approach can be used to predict the possibility of gas chromatographic separation of mixtures of dangerous substances such as narcotic drugs.Key words: fast gas chromatography, multicapillary column, chromatographic column selection, retention indices, explosivesDOI: http://dx.doi.org/10.15826/analitika.2022.26.1.003A.P. Efimenko1, I.I. Naumenko2, E.V.Kirillova3, A.A. Shorokhov31Multichrom ltd., Arbusova str. 4a,  b. 1, Novosibirsk, 630117,Russian Federation2Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyga 3, Novosibirsk, 630090,Russian Federation 3«SPO «Analitpribor», Babushkina str. 3, Smolensk, 214031, Russian FederationКороткие прямые поликапиллярные колонки (ПКК) позволяют проводить быстрые газохроматографические разделения, однако их ограниченная эффективность требует тщательного подбора ПКК при анализе многокомпонентных смесей. Поэтому при решении конкретной аналитической задачи актуально предварительно оценить возможность разделения целевых веществ, опираться на доступные сведения об их характеристиках, в частности, на индексы удерживания (RI). В настоящей работе приведен пример подбора ПКК и условий хроматографирования для разделения смесей взрывчатых веществ (ВВ) на неподвижных фазах (НФ) OV-5 и SE-54, выбранных нами из-за того, что известные индексы удерживания ВВ в основном определены на НФ подобного состава. Для нахождения соответствия индексов удерживания целевых веществ с их фактором удерживания k на исследуемых ПКК экспериментально были определены времена удерживания н-алканов С10 – С19 при различных температурах колонок, после чего построены зависимости рассчитанных ln k от числа атомов углерода m в н-алканах CmH2m+2 и аппроксимацией линейной функцией ln k = a + bm для каждой температуры найдены коэффициенты аппроксимации a и b. Откуда легко можно было вычислить факторы удерживания целевых веществ по их RI, считая, что RI = m·100, а также оценить эффективность ПКК, достаточную для разделения соседних пиков целевых веществ с необходимой степенью разделения. На основании полученных уравнений рассчитаны факторы удерживания ВВ для ПКК при разных температурах и оценена необходимая эффективность для разделения соседних пиков. Экспериментально определенные для некоторых ВВ факторы удерживания на ПКК с исследуемыми НФ при 140 оС оказались достаточно близки к теоретически рассчитанным. В дальнейшем подобный подход может быть использован для прогноза возможности газохроматографического разделения смесей опасных веществ или соединений, обращение с которыми имеет законодательные ограничения.Ключевые слова: экспрессная газовая хроматография, поликапиллярные колонки, подбор хроматографических колонок, индексы удерживания, взрывчатые веществаDOI: http://dx.doi.org/10.15826/analitika.2022.26.1.00

Thermal stability of hafnium bronze subjected to dynamic channel angular pressing

Thermal stability of the structure of Cu-0.8%Hf alloy subjected to severe plastic deformation by 2 passes of dynamic channel angular pressing (DCAP) has been investigated. It is demonstrated that after such deformation the microstructure of the hafnium bronze is non-uniform, where areas of cell structure are neighboring with thin-lamellar structure of twinning type. Such structure indicates the action of two deformation mechanisms, dislocation sliding and twinning. It has been revealed that doping with hafnium has considerably affected susceptibility of copper to relaxation processes under the DCAP and following annealing. It has been found that the microstructure formed under the deformation can be retained at the annealing up to 500 C without noticeable changes, and the microhardness changes only slightly in this temperature range. At the same time, at heating up to 600 C and higher the relaxation processes are developed in the structure which is accompanied with a drastic drop of microhardness. © Published under licence by IOP Publishing Ltd.The work has been done under the State Assignment of FASO of Russia (topic Function , No. 19-119012990095-0) with partial support of the Program of Fundamental Research of Ural Branch of RAS (Project No. 18 10 2 37)

A transverse current rectification in graphene superlattice

A model for energy spectrum of superlattice on the base of graphene placed on the striped dielectric substrate is proposed. A direct current component which appears in that structure perpendicularly to pulling electric field under the influence of elliptically polarized electromagnetic wave was derived. A transverse current density dependence on pulling field magnitude and on magnitude of component of elliptically polarized wave directed along the axis of a superlattice is analyzed.Comment: 12 pages, 6 figure

Direct Observation of Martensitic Phase-Transformation Dynamics in Iron by 4D Single-Pulse Electron Microscopy

The in situ martensitic phase transformation of iron, a complex solid-state transition involving collective atomic displacement and interface movement, is studied in real time by means of four-dimensional (4D) electron microscopy. The iron nanofilm specimen is heated at a maximum rate of ∼10^(11) K/s by a single heating pulse, and the evolution of the phase transformation from body-centered cubic to face-centered cubic crystal structure is followed by means of single-pulse, selected-area diffraction and real-space imaging. Two distinct components are revealed in the evolution of the crystal structure. The first, on the nanosecond time scale, is a direct martensitic transformation, which proceeds in regions heated into the temperature range of stability of the fcc phase, 1185−1667 K. The second, on the microsecond time scale, represents an indirect process for the hottest central zone of laser heating, where the temperature is initially above 1667 K and cooling is the rate-determining step. The mechanism of the direct transformation involves two steps, that of (barrier-crossing) nucleation on the reported nanosecond time scale, followed by a rapid grain growth typically in ∼100 ps for 10 nm crystallites

Dynamic Strength of Submicrocrystalline Copper and Copper Alloys Obtained by High-Speed Pressing

The mechanical properties of copper with a purity of 99,8 wt. % and alloys Cu–0,03 wt. %Zr and Cu–0,1wt. %Cr with submicrocrystalline structure obtained by dynamic channel-angular pressing was studied. The tests were carried out under shock-wave compression with pressure up to 7 GPа and strain rate 10 5 s–1.Исследованы механические свойства меди чистотой 99,8 мас. % и сплавов Cu–0,03 мас. %Zr и Cu–0,1 мас. %Cr с субмикрокристаллической структурой, полученной методом динамического канально-углового прессования. Испытания проводились в условиях ударного сжатия с давлением до 7 ГПа и скоростью деформации 10 5 с–1.Работа выполнена в рамках государственного задания по теме «Структура» № АААА-А18-118020190116-6 и Программе Президиума РАН «Конденсированное вещество и плазма при высоких плотностях энергии»

Effect of temperature on resonant electron transport through stochastic conduction channels in superlattices

We show that resonant electron transport in semiconductor superlattices with an applied electric and tilted magnetic field can, surprisingly, become more pronounced as the lattice and conduction electron temperature increases from 4.2 K to room temperature and beyond. It has previously been demonstrated that at certain critical field parameters, the semiclassical trajectories of electrons in the lowest miniband of the superlattice change abruptly from fully localized to completely unbounded. The unbounded electron orbits propagate through intricate web patterns, known as stochastic webs, in phase space, which act as conduction channels for the electrons and produce a series of resonant peaks in the electron drift velocity versus electric-field curves. Here, we show that increasing the lattice temperature strengthens these resonant peaks due to a subtle interplay between the thermal population of the conduction channels and transport along them. This enhances both the electron drift velocity and the influence of the stochastic webs on the current-voltage characteristics, which we calculate by making self-consistent solutions of the coupled electron transport and Poisson equations throughout the superlattice. These solutions reveal that increasing the temperature also transforms the collective electron dynamics by changing both the threshold voltage required for the onset of self-sustained current oscillations, produced by propagating charge domains, and the oscillation frequency

STRUCTURE AND PROPERTIES OF COPPER AND ALLOYS UNDER EXTREME LOADING

The dynamic properties of technical copper and copper alloys with a submicrocrystalline (SMC) structure formed by the dynamic channel.angular pressing methodwere studied. The tests were carried out undershock.wave compressionwithintensity 6–7GPa·and speed deformation of (0.9–2.0)·10 5 s–1 . The effect of the dispersion and defects of SMC structure on its resistance to highspeed deformation and fractureto is estimated.Исследованы структура и динамические свойства технической меди и низколегированных сплавов на основе меди с субмикрокристаллической (СМК) структурой, полученной методом динамического канально.углового прессования. Испытания проводились в условиях ударного сжатия с давлением 6–7 ГПа и скоростью деформации (0,9–2,0)·10 5 с–1. Проведена оценка влияния дисперсности и дефектности СМК.структуры на ее сопротивление высокоскоростному деформированию и разрушению.Работа выполнена в рамках государственного задания по теме «Структура» № АААА-А18-118020190116-6 и при частичной поддержке УрО РАН (проект № 18-10-2-39)