Materials Science Physics Research Articles

Molecule Based Materials for Quantum Cellular Automata: A Short Overview and Challenging Problems

AbstractIn this review we shortly summarize in an accessible way the physical and nanoscale material science aspects of the promising field of molecular quantum cellular automata (QCA). QCA is a revolutionary paradigm in quantum electronics with promising application in the conceptually new computing scheme which can be referred to as “computing with molecules”. This scheme of devices have vitally important advantages compared with conventional schemes of quantum computing in which the binary information is stored in the eigenvectors of a two‐level quantum system and therefore their practical application is strongly limited by the requirement of coherence. Molecular QCA promise nanometer‐scale units with ultra‐high device densities, as well as room temperature operation with extremely small heat release. Molecular materials provide at the same time options to control the key properties of the active molecules by chemical means. Hereunder we summarize the background of the electronic and vibronic problems in QCA cells represented by the tetrameric mixed‐valence (MV) complexes and organic molecules proposed for implementation as four‐site molecular QCA. We discuss the basic model of the molecular cell that include the following ingredients: 1) intracell Coulomb repulsion energy of the electrons in different electronic distributions among the redox sites; 2) electron transfer between redox sites which changes electronic distributions; 3) interaction of the itinerant electrons with molecular vibrations which is referred to as the vibronic interactions; 4) intercell Coulomb interaction by mean of which the binary information is transmitted from cell to cell. On the basis of this model we will study the cell polarization, adiabatic picture of the switching cycle describing interaction between the “input” and “output” molecular cells, non‐linear cell‐cell response function whose shape describes the action of molecular logic gates. Along with developed and current problems, we discuss new challenging trends of research in this fascinating area.

The Structural Formation in Differentially-Hardened 100-Meter-Long Rails during Long-Term Operation

By using modern physical-materials science methods, the roll surface of structural-phase states and mechanical properties has been analyzed at a distance ranging from 0 to 22 mm with respect to the central axis and to the fillet of differentially-quenched DT 350 grade 100-meter-long rails. These rails have been manufactured at Evraz United West Siberian Metallurgical Plant after long-term operation on an experimental test ring (passed gross tonnage amounting to 1411 million tons). According to chemical composition, the rail metal satisfies the requirements of TU (Engineering Specifications) 0921-276–01124323–2012 for steel E76HF grade steel. The impact strength and hardness on the head’s roll surface and throughout the cross section meet the TU (Engineering Specifications) requirements. The microstructure of the rail metal is represented by finely dispersed lamellar pearlite—1.5 points of scale No. 7 according to GOST (State Standard) 8233—with inclusions of excess ferrite along the grain boundaries. The interlamellar distance in the railhead ranges from 0.10 to 0.15 μm. The long-term operation of the rails is accompanied by the formation of a gradient structure presented by a regular change in hardness, microhardness, and impact strength throughout the railhead section. The microhardness at a depth of 2 mm counted from the roll surface amounts to 1481–1486 MPa. At a depth of 10 mm, the microhardness decreases to 1210–1385 MPa, which is caused by an increase in the interlamellar distance and by a decrease in the level of metal cold-work strengthening in the course of long-term operation. It has been suggested that this could be caused by an increase in the interlamellar distance and by a decrease in the level of cold-work strengthening in the course of long-term operation.

Formation of Gradient Structure in Rails at Long-Term Operation

Abstract It has been shown by the methods of physical material science that long-term operation of rails is accompanied by the formation of the gradient structural constituents consisting in the regular change in relative content of lamellar pearlite, fractured pearlite and structure of ferrite-carbide mixture in cross-selection of rail head. As the distance to the surface of rails increases the relative content of metal volume with the structure of lamellar pearlite decreases and that with the structure of fractured pearlite and ferrite-carbide mixture increases. It has been established that the characteristic feature of ferrite-carbide mixture structure is a nanodimentional range of grains, subgrains and particles of the carbide phase forming it. The dimension of grains and subgrains forming the given type of structure varies within the limits of 40-70 nm. The size of carbide phase particles located along the boundaries of grains and subgrains varies within the limits of 8-20 nm.

Вплив температури спікання на фазовий склад та механічні властивості композитів на основі $c$BN з добавками сполук ванадію

The influence of the sintering temperature on the mechanical properties of cBN-based ceramic composites with binders in form of vanadium compounds is investigated by methods of physical material science. Two compositions are selected for the study cBN–VC–Al and cBN–VN–Al with 60% vol. of cBN. Samples are obtained by high pressure high temperature sintering (HPHT) in toroid type apparatus with central hole 30. Sintering is conducted in temperature range of 1600–2450°C under pressure of 7.7 GPa. Sintering in the temperature range of 1600–1850°C induces the beginning of the interaction between components of the mixture and significant change in the elastic properties of the samples in both systems. As found, the maximum values of microhardness are achieved at 2150°C—40 GPa for a system with a carbide binder and 30 GPa in a system with vanadium nitride. The highest level of tool wear resistance during high-speed machining of steels is shown the samples of both groups sintered in the temperature range of 2000–2150°С. (Less)

Structural Phase State of Surface Alloyed Y2O3 Silumin After Electron beam Processing

The structure, phase composition and tribological properties of surface layers of hypoeutectic silumin after the complex processing including the electroexplosion alloying with the yttrium oxide powder in different regimes and the subsequent electron beam processing have been analyzed by the methods of modern physical material science. With respect to the initial silumin the ≈20-fold increase in the wear resistance and ≈1.5-fold decrease in the friction coefficient have been detected. The complex processing is accompanied by the formation of the multiphase submicro—nanocrystalline layer up to 80 μm in thickness enriched by yttrium and oxygen atoms responsible for the multiple increase in the wear resistance. At the complex processing according to the first regime of electroexplosion alloying (EEA) (Y2O3 powder mass—0.0589 g, discharge voltage—2.8 kV) with the subsequent electron beam irradiation, the major phase of the modified layer is the solid solution based on Al (≈71.2 mass %), the remaining phases are SiO2, YAlO3, YSi2. The 1.5-fold increase in the mass of Y2O3 powder at EEA and 1.1-fold decrease in the discharge voltage is accompanied by the increase in the quantity of phases, the significant (more than 2.5-fold) decrease in the content of the solid solution based on Al, the ≈2.2-fold increase in the content of silicon oxide, the presence of yttrium oxide and metallic yttrium.

Nanostructure formation of hypoeutectic silumin by electronion-plasma methods

The structure, phase composition and defect substructure of the surface layers of hypoeutectic silumin after the complex processing including the electroexplosion ion plasma alloying by the yttrium oxide powder and the subsequent electron beam processing have been analyzed by the methods of modern physical material science. The complex processing is accompanied by the dissolution of the silicon inclusions and intermetallides and the formation of the submicro- and nanodimensional structure. The modified layer (70 μm) is multielemental and it has the structure of high velocity cellular crystallization.

Effect of the Density of Electron Beam Energy on the Structure and Mechanical Characteristics of Surface Layers of Hypoeutectic Silumin

The structural phase states and mechanical properties of hypoeutectic silumin subjected to electron beam treatment with energy density of 10–35 J cm−2 are studied according to modern physical materials science. Treating silumin with an electron beam that has an energy density of 25 J cm−2 leads to the formation of a cellular structure in a layer that is up to 40 μm thick. The increase in the hardness of the surface layer of silumin is apparently due to the formation of a high-speed cellular crystallization structure of submicron size with nanoscale layers of the second phase distributed along the cell boundaries.

Structure and properties of layer, surfaced on HARDOX 450 steel by boron containing wire

Analysis of structure phase states and properties of the layers formed on HARDOX 450 low alloy steel by welded-on wires with boron content of 4.5 and 6.5 % wt. was made by the methods of modern physical material science. In the initial state HARDOX 450 steel has the structure of tempered martensite, in the volume and along the boundaries of crystals of it the cementite particles are located. The particles located in the volume have acicular shape and those along boundaries are mainly round. The presence of extinction bend contours has been revealed, indicative of the curvature torsion of crystal lattice of the material’s portion. They originate and finish on the interfaces of martensite crystals. Scalar density of chaotically located dislocations and forming the netlike substructure is 6.2·1010 cm–2. The layer welded on HARDOX 450 steel has microhardness increasing by more than two-fold that of the base. Analysis of state diagrams of Fe – C, Fe – B, B – C systems and polythermal cross–sections in Fe – C – B system has shown that the rapid cooling of Fe23C6 – Fe23B6 alloys from liquid state would facilitate the formation of multiphase structural states. It is stated by the methods of transmission electron diffraction microscopy that the reasons for the high microhardness level of the surface layers are the following: formation of iron borides and crystals of ultafine-dispersion (up to 100 nm) packet martensite with high level (~1011 cm–2 ) of scalar density of dislocations; presence of nanodimentional particles of iron and boron carbides in the volume and on the boundaries of martensite crystals; high level of curvature torsion of crystal lattice of iron borides and α-phase grains, caused by the internal stress fields along interphase (interface of iron boride crystals and α-phase grains) and intraphase boundaries (interface of iron borides and martensite crystals packet). Increase in boron concentration from 4.5 to 6.5 % is accompanied by the sufficient increase (by 1.2 – 1.5 times) in hardness of welded layer. It is caused by the increase of dimensions and relative content of iron boride regions by 1.5 – 2.0 times.

Earth science education: The current state of play

Earth science education: The current state of play

Formation and Evolution of Structure and Phase Composition of Hypoeutectoid Silumin on Electron Beam Processing

The structural phase states and silumin’s defect substructure of silumin hypoeutectoid composition subjected to electron beam processing with the following parameters: energy density—25 J/cm2, pulse duration—150 µs, number of pulses—3, pulsed repetition rate—0.3 Hz were analyzed by methods of modern physical material science. The irradiation of the surface leads to the melting of the surface layer, the structure formation of high-speed cellular crystallization of submicron dimentions and the repeated precipitation of the second phase particles. The cells formation of two types: those free from precipitations of the second phase and those containing the lamellar eutectic Al–Si was revealed. The cells are separated by the second phase interlayers containing the particles of Cu15Si14Al4Cu9, silicon and copper. As the distance from the surface of irradiation increases the layer containing the second phase inclusions of quasi—equilibrium shape are defined along with the crystallization cells. It is indicative of the occurance of the globularization processes of silumin’s structure on electron beam processing.

The Structure and Properties of a Weld-Deposited Layer onto Steel Hardox 450 Using a Boron-Containing Wire

By using the methods of modern physical material science, the structure-phase states and properties of the layers formed on low-alloyed steel Hardox 450 with the use of welding wires with a boron content amounting to 4.5 and 6.5 wt % have been analyzed. In the initial state, steel Hardox 450 has the structure of tempered martensite in the bulk and along the boundaries of crystals in which cementite particles are located. The particles located in the bulk are needle-shaped and those located along boundaries are mainly round-shaped. The revealed extinction bend contours indicate a torsion curvature of the crystal lattice in this area of the material. They begin and finish at the interfaces of the martensite crystals. The scalar density of chaotically arranged dislocations forming a reticulate-type substructure is 6.2 × 1010 cm–2. The weld-deposited layer onto steel Hardox 450 has more than two-fold microhardness than that of the base metal. The analysis of state diagrams for the Fe–C, Fe–B, and B–C systems and of polythermal cross-sections in the Fe–C–B system has shown that a rapid cooling of Fe23C6–Fe23B6 alloys from the liquid state facilitates the formation of multiphase structural states. It has been established by means of transmission electron diffraction microscopy that the reasons for the high microhardness level of the surface layers consist in the following factors: the formation of iron borides and the crystals of ultrafine packet martensite (up to 100 nm) having a high level (~1011 cm–2) of scalar dislocation density; the presence of nanosized particles of iron and boron carbides in the bulk and along the boundaries of martensite crystals; and a high torsion curvature level in the crystal lattice of iron borides and α-phase grains caused by internal stress fields along interphase boundaries (the interface between iron boride crystals and α-phase grains) and intraphase boundaries (the interface between iron borides and martensite crystals in the packet). Increasing boron concentration from 4.5 to 6.5% is accompanied by a sufficient (1.2–1.5-fold) increase in the hardness of the weld-deposited layer. It is caused by a 1.5–2.0-fold increase in the size and relative content of iron boride areas.

Bouncing Droplets: A Hands-On Activity To Demonstrate the Properties and Applications of Superhydrophobic Surface Coatings

Here we report a hands-on activity addressed to master’s students in Physical Chemistry and Materials Science courses on the properties and applications of superhydrophobic surfaces. This simple and intuitive experience can also be used to teach undergraduate and high school students, thanks to its application-oriented approach and tangible results. Superhydrophobicity was achieved by the functionalization of oxide powders with alkylsilanes and their subsequent deposition on a glass substrate. The film’s superhydrophobicity was assessed by different application tests and compared with the behaviors of model hydrophobic, hydrophilic, and superhydrophilic surfaces. Its antistain properties were tested with both model dye solutions and everyday liquids. Films were fouled with graphite and dye powders to compare the self-cleaning capabilities of the different surfaces, and single droplet transport was achieved by adding magnetic particles. This engaging and adaptable experience introduces students to basic concepts of surface science in an intuitive and tangible way.

Modification of surface layer of hypoeutectic silumin by electroexplosion alloying followed by electron beam processing

The analysis of structure, phase composition and tribological properties of surface layers of hypoeutectic silumin after complex treatment including the electroexplosion alloying by yttrium oxide powder in different modes and subsequent electron beam processing was done by the methods of modern physical material science. The complex treatment is accompanied by the formation of multi–phase submicro – nanocrystalline layer up to 80 μm thick enriched by yttrium atoms and being responsible for the increase in wear resistance. It is shown that Y atom concentration in the modified layer depends on electroexplosion alloying (EEA) mode. The distribution of Y atoms in the layer depends on the mode of EEA as well.

Experimental Study of Two-Beam X-Ray Diffractometry Using Synchrotron Radiation

A new scheme of two-beam X-ray diffractometry on the “X-Ray Crystallography and Physical Materials Science” (XCPM) beamline at the Kurchatov Synchrotron Radiation Source (KSRS) has been experimentally investigated. The scheme includes a standard double-crystal monochromator and a narrow slit installed in front of the sample. Measurements have been performed for the Si 111 and 311 reflections in the monochromator and the Si 111 and 220 reflections in the sample crystal. It is shown that this scheme allows one to obtain a near-proper diffraction reflection curve even in the case of symmetric diffraction if the Bragg angle for the monochromator exceeds the Bragg angle for the crystal sample by a factor of 2 or more. The experimental results coincide well with the theory.

The story of the creation method of assessing damage of steels on the basis of mechanical spectroscopy

Against the background of the formation and development of one of the promising methods of physical materials science – mechanical spectroscopy - the history of the discovery of Tula metal physicists N.N. Sergeev and V.S. Ageev previously unknown effect of inelastic behavior of steels. Their first attempt of theoretical description of the mechanism of its formation is described. Set out the further fate of the detected effect in the interplay with the lives of its researchers. The history of the renovation of the forgotten for almost 30 years of discovery is proposed. A multi-faceted program of large-scale study of the mechanism of undeservedly forgotten effect, implemented in decades by the followers of the pioneers, is presented in detail. Disputes with skeptics are described. The main alternative ideas as the reasons of scientific disputes around the nature of effect are stated. Answers to critical questions are given, which allowed the authors to convince skeptics of the reality of the discovered phenomenon and to create a new direction in the study of steels and alloys – a method of assessing their damage by the results of mechanical spectroscopy. The examples of industrial application of the created direction are described. The areas of application of the method of application of the complex of inelastic effects developed by the authors on the basis of the revived method for a multiscale description of structural changes in steels and alloys in the course of external destructive effects of different nature are listed. New ways of development and improvement of the method proposed by the authors in the study of products obtained both by standard ingot technology and in the conditions of additive 3D printing technologies are described.

Nanostructurisation of hypoeutectic silumin by electroexplosion alloying and subsequent electron beam processing

The structure, phase composition and defect substructure of the surface layers of hypoeutectic silumin after the complex processing including the electroexplosion alloying (EEA) by the yttrium oxide powder and the subsequent electron beam processing have been analysed by the methods of modern physical materials science. The complex processing is accompanied by the dissolution of the silicon inclusions and intermetallides and the formation of the submicro- and nanodimensional structures. The modified layer (70 μm) is multielemental and it has the structure of high velocity cellular crystallisation.

Особливості формування структури та фазового складу в процесі реакційного спікання кубічного нітриду бору зі сполуками Ti, Cr, V

Influence of sintering temperature on both phase composition and structure of ceramic matrix composites based on cubic boron nitride with binders in a form of Al and the Ti, Cr, V carbides are investigated by methods of physical materials science. As the object of study, three cBN–TiC–Al, cBN–Cr3C2–Al, cBN–VC–Al compositions containing 60% vol. cBN are selected. The composites are obtained by high-pressure high-temperature (HPHT) sintering in high-pressure apparatus AVTT-30 in the temperature range of 1600– 2450°C under pressure of 7.7 GPa. In the process of HPHT sintering of composites in the cBN–TiC–Al and cBN–Cr3C2–Al systems, the formation of titanium and chromium diborides is found at the temperatures of sintering Тsint ≥ 1850°С and Тsint ≥ 2150°С, respectively, simultaneously with the formation of alu-minium nitride. (Less)

Switching of Monomer Fluorescence, Charge-Transfer Fluorescence, and Room-Temperature Phosphorescence Induced by Aromatic Guest Inclusion in a Supramolecular Host.

Crystal engineering of three-component crystals with guest-dependent photoluminescence switching, including (i) crystallization-induced emission enhancement, (ii) intermolecular charge-transfer emission, and (iii) room-temperature phosphorescence under ultraviolet irradiation, was demonstrated. This strategy was based on the confinement of aromatic guests in a supramolecular host (denoted as EBPDI-TPFB) composed of 5,5'-(ethyne-1,2-diyl)bis(2-pyridin-3-yl-isoindoline-1,3-dione (EBPDI) with two tris(pentafluorophenyl)borane (TPFB) molecules linked by B-N dative bonds that acted as Lewis pairs. The single-crystal X-ray structures of complexes with eight different guests were collected, revealing that the size and/or shape of the supramolecular host EBPDI-TPFB was modulated by the included guest molecules. The excellent guest inclusion ability of EBPDI-TPFB allowed systematic photoluminescence regulation of the complexes, which exhibited multicolor emissions in the crystalline state. Photoluminescence switching characteristics of the complexes were observed upon removing the guests or mechanical grinding of the crystals. These results indicated that using the host-guest chemistry of multicomponent crystals not only facilitates crystallization, but also can reveal hidden optical functions by combining molecules of interest, which should contribute to the fields of physical chemistry and materials science.

Erratum to: A Mobile Measurement System for the Coupled Monitoring of Atmospheric and Soil Parameters

In this article the true affiliation is A. V. Bazarov a* , N. B. Badmaev b, c , S. A. Kurakov d, e, and B.-M. N. Gonchikov b a Institute of Physical Materials Science, Siberian Branch, Russian Academy of Sciences, ul. Sakh’yanovoi 6, Ulan-Ude, 670047 Russia b Institute of General and Experimental Biology, Siberian Branch, Russian Academy of Sciences, ul. Sakh’yanovoi 6, Ulan-Ude, 670047 Russia c Buryat State University, ul. Smolina 24a, Ulan-Ude, 670047 Russia d Institute of Monitoring of Climatic and Ecological Systems, Siberian Branch, Russian Academy of Sciences, pr. Akademicheskii 10/3, Tomsk, 634055 Russia e Tomsk State University of Control Systems and Radio-electronics, pr. Lenina 40, Tomsk 634055 Russia * e-mail: alebazaro@gmail.com Received June 27, 2016 In this article techical mistakes were found. Below the correct variant of the table on page 273 is provided.

Study of the surface relief, structure and phase composition of the silumin composite layer obtained by the method of electric explosion alloying by Al-Y2O3 system

The studies of the surface relief, structure and phase composition of silumin surface layer modified by the electric explosion of the aluminium conductor with the weighed sample of yttrium oxide were done by the methods of modern physical material science (atomic-force and transmission electron microscopy) in the research. It is stated that the multi-layer structure which consist of the highly porous coating inhomogeneous in thickness, the liquid phase alloying layer and the thermal effect layer, is formed in the top layer. It is revealed that the top layer possesses a submicro- and nanodimentional multi-phase structure. The particles of silicon, Y2O3, YSi2 and Y2Si2O7 are the hardening phases of this structure. It consists of the cellular crystallization structure being characterized by the inhomogeneity in the distribution of the alloying elements.