Structure and solidification of the (Fe0.75B0.15Si0.1)100-xTax (x=0-2) melts: experiment and machine learning

Fe-B-Si system is a matrix for synthesis of new functional materials with exceptional magnetic and mechanical properties. Progress in this area is associated with the search for optimal doping conditions. This theoretical and experimental study is aimed to address the influence of Ta alloying on the structure of undercooled (Fe0.75B0.15Si0.1)100-xTax (x=0-2) melts, their undercoolability and the processes of structure formation during solidification. Small concentration of Ta complicates standard ab initio and machine learning investigations. We developed a technique for fast and stable training of machine learning interatomic potential (MLIP) in this case and uncovered the structure of the undercooled melts. Molecular dynamic simulations with MLIP showed that at Ta concentration of 1 at.% there is a sharp change in the chemical short-range ordering in the melt associated with a change in the interaction of Ta atoms. This effect leads to a restructuring of the cluster formation in the system. At the same time, our experimental investigation shows that melts with a Ta content of 1 at.% have the greatest tendency to undercoolability. Alloying with Ta promotes the formation of primary crystals of Fe2B, and at a concentration of more than 1.5 at.% Ta, also of FeTaB. Herewith, near 1 at.% Ta, the crystallization of the melt proceeds nontrivially: with the formation of two intermediate metastable phases Fe3B and Fe2Ta Laves phase. Also, the highest tendency to amorphization under conditions of quick quenching is exhibited by a melt with a Ta concentration of 1 at.%. The results not only provide understanding of optimal alloying of Fe-B-Si materials but also promote a machine learning method for numerical design of metallic alloys with a small dopant concentration.Comment: 26 pages, 10 figure

Импульсный режим воздействия полупроводникового лазера с длиной волны 445 нм в фонохирургии: экспериментальное исследование

The study presents the results of an experimental study devoted to the choice of the most optimal mode of pulsed contact laser exposure of semiconductor laser with a wavelength of 445 nm in phonosurgery, which implies maximum preservation of anatomically and functionally significant structures of the larynx combined with a radical approach to the pathological process. From the standpoint of the mucoundular theory of voice formation, wave-like oscillations of the vocal folds are possible due to the mobility of the cover layer of the vocal fold (epithelium, superficial layer of the lamina propria) relative to its body (deep layer of the lamina propria, vocal muscle). Thus, any injury at the level of the integumentary layer is associated with the risk of excessive scarring and loss of the ability to wave-like sliding. Pig vocal folds, according to a number of authors, have a structure similar to human ones in terms of both histological structure and acoustic parameters, which justifies the rationality of their use as an experimental model. In a series of experiments using a 445 nm laser, contact pulsed impacts on a biological model were carried out with pulse durations of 10, 20, 50, and 100 ms, followed by evaluation of the following parameters based on the data of histological sections: the depth and width of the ablation crater, the width of the zone of lateral thermal damage. Thus, the most optimal for phonosurgical interventions modes of pulsed laser exposures with a wavelength of 445 nm are described.В работе представлены результаты экспериментального исследования, посвященного выбору наиболее оптимального режима импульсного контактного лазерного воздействия полупроводникового лазера с длиной волны 445 нм в хирургии голосовых складок (фонохирургии). Эндоларингеальная фонохирургия подразумевает собой максимальную сохранность анатомически и функционально значимых структур гортани в сочетании с радикальностью в отношении патологического процесса. С позиции мукоундулярной теории голосообразования волнообразные колебания голосовых складок возможны за счет подвижности покровного слоя голосовой складки (эпителий, поверхностный слой собственной пластинки) относительно ее тела (глубокий слой собственной пластинки, голосовая мышца). Таким образом, любая травматизация на уровне покровного слоя сопряжена с риском его избыточного рубцевания и потерей способности к волнообразному скольжению. Голосовые складки свиньи, по данным ряда авторов, имеют схожее строение с человеческими как по гистологическому строению (толщина слоев, соотношение коллагеновых и эластических волокон), так и по акустическим параметрам, что обосновывает рациональность их использования в качестве экспериментальной модели. В серии экспериментов с использованием лазера 445 нм проведены контактные импульсные воздействия на биологическую модель с длительностью импульсов 10, 20, 50 и 100 мс с последующей оценкой по данным гистологических срезов следующих параметров: глубина и ширина кратера абляции, ширина зоны бокового термического повреждения. Таким образом, описаны наиболее оптимальные для фонохирургических вмешательств режимы импульсных воздействий лазера с длиной волны 445 нм

Phase selection and microstructure of slowly solidified Al-Cu-Fe alloys

The search for effective methods to fabricate bulk single-phase quasicrystalline Al-Cu-Fe alloys is currently an important task. Crucial to solving this problem is to understand the mechanisms of phase formation in this system. Here we study the crystallization sequence during solidification as well as the conditions of solid phase formation in slowly solidified Al-Cu-Fe alloys in a wide range of compositions. We have also constructed concentration dependencies of undercoolability by differential thermal analysis method. These experimental results are compared with data on chemical short-range order in the liquid state determined from ab initio molecular dynamic simulations. We observe that the main features of interatomic interaction in the Al-Cu-Fe alloys are similar for both liquid and solid states and they change in the vicinity of i-phase composition. In the concentration region, where the i-phase is formed from the melt, both the undercoolability and the crystallization character depend on the temperature of the melts before cooling. © 2019 Elsevier B.V.This work was supported by supercomputer of IMM UB RAS and computing resources of the federal collective usage center Complex for Simulation and Data Processing for Mega-science Facilities at NRC “Kurchatov Institute” Russian Science Foundation (grant RNF 18-12-00438 ). The experimental study was perfomed using equipment of the Shared Use Centre of Physical and Physicochemical Methods of Analysis and Study of the Properties and Surface Characteristics of Nanostructures, Materials, and Products, UdmFRC UB RAS. AIMD simulations have been carried out using ”Uran” http://ckp.nrcki.ru

Crystal chemistry of fluorcarletonite, a new mineral from the Murun alkaline complex (Russia)

This paper reports the first description of the crystal structure and crystal chemical features of fluorcarletonite, a new mineral from the Murun potassium alkaline complex (Russia), obtained by means of single-crystal and powder X-ray diffraction (XRD), electron microprobe analysis (EMPA), thermogravimetry (TG), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. The crystal structure of fluorcarletonite, KNa4Ca4Si8O18(CO3)4(F,OH)⚫ H2O, a rare phyllosilicate mineral, contains infinite double-silicate layers composed of interconnected four- and eight-membered rings of SiO4 tetrahedra and connected through the interlayer K-, Na- and Ca-centered polyhedra and CO3 triangles. The X-ray diffraction analysis confirms the mineral to be tetragonal, P4∕mbm, a=13.219(1)&thinsp;Å, c=16.707(2)&thinsp;Å, V=2919.4(6)&thinsp;Å3 (powder XRD data), a=13.1808(5)&thinsp;Å, c=16.6980(8)&thinsp;Å, V=2901.0(3)&thinsp;Å3 (single-crystal XRD data, 100&thinsp;K). The EMPA (average from 10 analyses) gave the following composition (wt&thinsp;%): SiO2 44.1(6), CaO 20.0(3), Na2O 11.1(3), K2O 4.5(2), F 1.3(5), TiO2 0.1(1) and Al2O3 0.03(3). The TG–DSC analysis confirmed the presence of H2O and CO2 (weight losses of 1.17&thinsp;% and 14.9&thinsp;%, respectively). The FTIR spectrum acquired in the range from 4000 to 400&thinsp;cm−1 reveals the presence of H2O, CO3 and OH groups. The average formula of fluorcarletonite calculated from the results of EMPA and crystal structure refinement is K1.04Na3.89Ca3.87Ti0.01Si7.99Al0.01O18(CO3)3.86(F0.72OH0.28)⚫1.11H2O.</p