Formation of Quasicrystals and Related Structures in Systems of Aluminum with Transition Metals. Part 1. Binary Systems Formed by Aluminum with 3d Metals

Quasiperiodic phases (quasicrystals) with symmetries forbidden by classic crystallography have been observed in systems of aluminum with transition metals. In binary systems, these phases are metastable; they were obtained for the first time by rapid solidification of melts. We consider the formation of the quasicrystals and we refine the phase diagrams for binary systems A – 3d-M (from V to Ni) in which quasicrystals have been observed.     

过渡金属-Na二元合金形成焓的EAM模型计算

运用嵌入原子方法（EAM）研究了过渡金属W、Nb、Ta与碱金属Na组成的3个二元合金的形成焓。计算结果与HumeRethory理论符合得较好，EAM模型用于过渡金属（W，Nb，Ta）与碱金属（Na）组成的合金系统的形成焓计算是合适的。     

Wetting and Contact Interaction in Systems Formed by Nitrides of Group IV Transition Metals with Chromium-Nickel Alloy

Wetting and contact interaction have been examined for the nitrides TiN_0.98 and ZrN_0.87 in contact with chromium -nickel alloys of various compositions at 1500-1900°C in purified argon at an excess pressure of 0.35·10⁵ Pa; the methods used have been sessile drop, microstructure, x-ray diffraction, electron-probe microanalysis, and hardness measurement. Wetting is accompanied by interaction of the liquid and substrate with the release from the nitrides of nitrogen and also by the dissolution of Ni and Cr in the nitrides, which increases the lattice constants and raises the microhardness, while leading to the formation of intermetallides and solid solutions.     

Metal Chemistry of Scandium in Binary Systems Formed with Platinum-Group Metals as the Basis for Construction Multicomponent Systems Based on Those Metals

Major trends are considered in the physicochemical interaction in binary systems formed by scandium with the platinum metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum) from the characteristic features of the phase diagrams and the use of metal-chemical factors governing the formation of intermetallides with various stoichiometry and structure types in those systems (the size, electron-concentration and electronegativity factors). The values for those factors have been established that are favorable to the formation of phases with Sc:Pt´ stoichiometry (Pt´ is a platinum metal), namely: 1:3 (structure type AuCu₃, 1:1 (CsCl type), 11:4 (Zr₁₁Os₄ type), and 44:7 (Mg₄₄Rh₇ type). Published data and the authors' own evidence on the structure of bounding binary systems have been used with evidence on the physicochemical interactions in the Sc Ru Rh system in forecasting the type of phase equilibria occurring in systems of Sc Pt´ Pt´ ´ type (where Pt´, Pt´´ = Ru, Rh, Pd, Ir).     

Physicochemical Interactions in Systems Formed by Trivalent REM with Group IVp Elements. Part 2. Phase Diagrams

A major aspect is considered of the physicochemical interaction in binary systems formed by REM with group IV p elements, namely the phase diagrams. The general regularities and the differences between these phase diagrams are considered for REM – X systems (X = Si, Ge, Sn, and Pb), particularly the relationship between the phase diagram topology and the crystallochemistry of the compounds formed. A comparison is performed for predicted and experimentally constructed phase diagrams.     

Compaction and Structure Formation during Sintering of Composite Materials Based on Nitrides of Groups IV and V Transition Metals. Part 5. Sintering of Composite Materials of the Systems (TiN,ZrN)

Features of sintering in argon and structure formation of materials of the systems (TiN, ZrN) – Ni are studied. It is shown that sintering is accompanied by the release of nitrogen from nitrides, reciprocal dissolution of nickel in nitrides and also Ti and Zr in nickel, formation of nickel intermetallics, and an increase in the microhardness of solid phase grains. The main reason for the quite high porosity of sintered TiN – Ni and ZrN – Ni composites are the accumulation of nitrogen released from the nitrides within closed volumes with formation of closed pores. Sintering of materials is accompanied by the growth and faceting of solid phase grains due to dissolution and recrystallization through a liquid phase, and also an increase in metal phase content.     

Physicochemical Interactions in Systems Formed by Trivalent REM with Group IV p Elements. Part 1. Intermetallic Compounds

A systems approach has been used in the analysis of the number, stoichiometry, and crystal structures of compounds formed by REM with group IV p elements. General trends and differences between the intermetallides have been identified. The existence and crystal structures are predicted for certain compounds not observed by experiment.     

The Influence of 3d and 4d Transition Metals on the Glass Forming Ability of Ternary FeCo-Based Alloys

Thermodynamic modeling was used to determine enthalpies of formation and other thermodynamic parameters describing glass forming ability of Fe-Co-TM (TM = V, Nb, Cr, Mo) alloys. FeCo-based alloys are considered as candidates for applications as high magnetic flux density materials due to their high magnetic saturation and low magnetic anisotropy. Nevertheless, mechanical properties, especially the lack of ductility, are their main weakness. Therefore, further optimization by vitrification, further heat treatment and alloying should be considered. As the most crucial step is the synthesis of amorphous precursors, discussion is concentrated on the effect of transition metal substitution on the glass forming ability. The highest glass forming ability was reported for Fe-Co-Nb alloys. It can be also noted that the driving force for vitrification can be improved by substitution of Fe by other transition elements, as glass forming ability parameter ∆P_HS reaches the lowest values for Fe-less compositions.

     

Characterization of Ti6Al4V for Integral Transition Structures in FRP–Aluminum Compounds

Components in hybrid design become more and more important in terms of their lightweight potential. In this context, the demand for weight saving in aerospace industry leads to increase numbers of applications of fiber reinforced composites for primary structural components. In consequence, the use of FRP‐metal compounds is necessary. In the context of the investigations of the researcher group named “Black‐Silver” (“Schwarz Silber”, FOR 1224) founded by the DFG (German Research Foundation) material optimized interface structures for advanced carbon fiber reinforced plastic (CFRP)–aluminum compounds are currently being studied. Within their work the researcher group focussed on three concepts realizing the transition structures: the usage of wires (titanium), foils (titanium), and fibers (glass fiber) as transition elements between CFRP and aluminum. For the connection of the aluminum sheet and the transition element die‐casting and laser beam welding are basically used. The paper concentrates on the characterization of suitable materials for transition structures. Due to their high strength and low density (in comparison to steel) and the resulting potential in view on light‐weight design Ti‐alloys were investigated. Because of the increased availability of Ti‐wires compared to Ti‐foils in suitable thickness the former were used for the basic investigations on Ti‐alloys which are suitable for integral transition structures.     

Physicochemical Interaction in Systems Formed by Trivalent REM with Group IV p-Elements. IV. Phase Thermodynamics

The available data are analyzed on the enthalpies of formation of intermetallic compounds in binary systems of rare-earth metals with group IV p-elements. Consideration is given to effects of metallochemical factors on these enthalpies of formation. For REM silicides and germanides, the dominant effect comes from the size factor, while for the plumbides, it comes from the electronegativity. The effects of these factors tend to balance for compounds containing tin. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 60–66, May–June, 2005.     

Ab Initio Calculation of 4f→5d Transition Energy and Electronic Structure of Ce3+ Doped in LiYF4 Crystal

The electronic structures of LiYF4:Ce3 and LiYF4 crystals simulated by an embedded (in a microcrystal containing 1938 ions) cluster CeY4Li8F24, and Y5Li8F24 respectively, were computed by the ab initio self-consistent relativistic DV-Xa(discrete variational Xa) method. The ground-state calculation showed that only the lowest 5d level Ed of Ce3 ion lies around the BCB (bottom of the conduction band) while the lowest 4f levels is 2.5 eV lower than BCB. The CB states consist of 4p of Y mixed with 5d of Ce, even for the wavefunctions (WFS) of Ed under BCB there are still 24% of Y-4p and 9% of F-2p as components. Furthermore, transition state (TS) calculation was performed in this work to obtain the 4f→5d transition energies Efd, to improve the calculation of Ref.[6] in which a small CeF8 cluster embedded in an array of point charge was used and the results of ground-state calculation were roughly used to compare directly with the observed 4f→5d transition energies. The ionic radius of Ce3 is larger than that of Y3 , for modeling approximately the lattice relaxation, we simply let the eight fluorine ions of the nearest-neighbor and next-nearest-neighbor move out radially and simultaneously. As results, the CeY4Li8F24 cluster with 4.56% outward relaxation of the eight fluorines has the lowest total energy and gave satisfactory 4f→5d energies Efd, but the calculated ground-state Ed is 0.68 eV higher than BCB. For another cluster with 7.36% outward relaxation the Ed is 0.43 eV lower than BCB, which makes the observation of fine structure (including zero-phonon line) of the lowest 5d band understandable easier, but the splits between the transition energies Efd were not as good as the former. Therefore, we consider the relaxation is somehow around 4.56%～7.36% outward, not as large as 10%.     

Z-->B transition in poly[d(G-m5C)2] induced by interaction with 4',6-diamidino-2-phenylindole

The Z form of poly[d(G-m5C)2], in presence of Mg2+ ion, is found to be transformed into B form upon interaction with 4',6-diamidino-2-phenylindole (DAPI). The Z-->B transformation is complete at a mixing ratio of about 0.07 DAPI per DNA base pairs, i.e., each DAPI molecule may be related to the conversion of 6-7 base pairs. An interaction between DAPI and poly[d(G-m5C)2] in its Z form at low drug: DNA ratios is suggested from optical dichroism and time-resolved luminescence anisotropy results. The spectroscopic behaviour of DAPI indicates that the Z conformation of DNA does not provide normal binding sites for DAPI, such as groove or intercalation sites, but that the initial association may be of external nature.     

Physicochemical Interactions in Systems Formed by Trivalent REM with Group IV p-Elements. Part 3. Coefficients in Equations Relating Transformation Temperature to REM Melting Point (T - T R)

A study has been made on the coefficients in linear equations relating phase transition temperatures to melting point for rare-earth metals (R) namely T - T_R. The coefficient B is related to the metallicity of the chemical bonds in the compounds. The relationship is derived between the coefficient B for the compounds R₅X₃ (X are p elements of groups III–V), which have structures of Mn₅Si₃ type, and the c/a ratios and the number of the group for element X. As that number increases, c/a and B decrease, which may indicate a reduction in the relative contribution of the metallic term in the chemical bonding.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 55–64, March–April, 2005.     

Molecular dynamics studies of axis bending in d(G5-(GA4T4C)2-C5) and d(G5-(GT4A4C)2-C5): effects of sequence polarity on DNA curvature

Gel retardation studies and other experiments indicate that DNA sequences containing the d(GA4T4C)n motif are curved, whereas those of identical composition but with a reverse sequence polarity, the d(GT4A4C)n motif, are straight. Hydroxyl radical cleavage experiments show that d(GA4T4C)n shows a unique signature, whereas d(GT4A4C)n behaves normally. To explain these results at a molecular level, molecular dynamics (MD) simulations were performed on the DNA duplexes d(G5-(GA4T4C)2-C5) and d(G5-(GT4A4C)2-C5) to 3.0 and 2.5 ns, respectively. The MD simulations are based on the Cornell force field implemented in the AMBER 4.1 modeling package and performed in a neutral solution of anionic DNA with K+, Cl- and Mg2+ at concentrations roughly comparable to a ligase buffer. Long range interactions were treated by the particle mesh Ewald method. Analysis of the results shows that the calculated dynamical structure of d(G5-(GA4T4C)2-C5) exhibits strong gross curvature, consistent with the observed behavior. The most significant locus of curvature in the MD structure is found at the central C15-G16 step, with an average roll angle of 12.8(+/-6.40)deg. The d(G5-(GT4A4C)2-C5) MD structure exhibited significantly less gross curvature. Analysis of results indicates that the reduction in gross curvature in the d(G5-(GT4A4C)2-C5) trajectory originates from the effect of the T10-A11 and T20-A21 steps, which showed average roll angles of 12.5(+/-5)deg. These three steps, T10-A11, C15-G16 and T20-A21, are half-helix turns away from one another, and their contributions to concerted bending cancel out. The A-tracts in the MD structure are essentially straight. The dynamical structure of d(G5-(GA4T4C)2-C5) exhibited minor groove deformation comprised of expansion at the 5' end of A-tracts and progressive narrowing towards the 3' end, consistent with and elaborating the interpretation of hydroxyl radical chemical probing results.     

Oxidation Processes for Alloys in the Ni – Zr System. Part 2. Phase Composition of Scale Formed on Ni7Zr2

We have used x-ray and metallographic layer-by-layer phase analysis to study the structure and composition of scale formed on the alloy Ni₇Zr₂ during its oxidation in air over a period of 1 h and 10 h in the temperature range 500-1200°C. In the scale we find NiO, the cubic and monoclinic modifications of ZrO₂, and also Ni and Ni₅Zr. The phase components are nonuniformly distributed over the thickness of the scale. The outer scale consists of the oxides NiO and ZrO₂, while the composition of the inner scale includes Ni and Ni₅Zr in addition to monoclinic ZrO₂. Cubic ZrO₂ is formed on the surface of the specimen in the initial stages of its oxidation at 500-700°C. For T ≥ 900°C, on the surface of the scale we find both modifications of ZrO₂, while the nickel phase is itself a solid solution Ni(Zr). We note that the mechanisms for the formation of low-temperature (T ≤ 800°C) and high-temperature (T ≥ 900°C) scales are different. It is hypothesized that these differences are determined mainly by the fact that at high temperatures, diffusion of zirconium ions toward the outer boundary of the scale is superimposed on diffusion of oxygen toward the scale – alloy boundary.     

Formation of metallic phase on reducing-gas injection in multicomponent oxide melt. Part 2. Density and surface properties

The density and surface tension of melts of ferronickel (0–100% Ni) and oxidized nickel ore are measured by the sessile-drop method, as well as the interface tension at their boundary in the temperature range 1550–1750°C. The composition of the nickel ore is as follows: 14.8 wt % Fetot, 7.1 wt % FeO, 13.2 wt % Fe₂O₃, 1.4 wt % CaO, 16.2 wt % MgO, 54.5 wt % SiO₂, 4.8 wt % Al₂O₃, 1.5 wt % NiO, and 1.2 wt % Cr₂O₃. In the given temperature range, the density of the alloys varies from 7700 to 6900 kg/m³; the surface tension from 1770 to 1570 mJ/m²; the interface tension from 1650 to 1450 mJ/m², the density of the oxide melt from 2250 to 1750 kg/m³; and its surface tension from 310 to 290 mJ/m². The results are in good agreement with literature data. Functional relationships of the density, surface tension, and interphase tension with the melt temperature and composition are derived. The dependence of the alloy density on the temperature and nickel content corresponds to a first-order equation. The temperature dependence of the surface tension and interphase tension is similar, whereas the dependence on the nickel content corresponds to a second-order equation. The density and surface tension of the oxide melt depend linearly on the temperature. The results may be used to describe the formation of metallic phase when carbon monoxide is bubbled into oxide melt.     

熔炼法制备的AB5-AB2复合合金的晶体结构和电化学性能

选择AB2 型Laves相合金Zr0 .9Ti0 .1 (Mn0 .35Ni0 .55V0 .1 5) 2 作为添加剂与稀土基AB5型合金进行熔炼处理 ,制备了AB5 AB2 复合合金。XRD表明 ,制备的AB5 AB2 复合合金具有AB5合金的CaCu5主相结构 ,同时含有少量的AB2 合金的C14型Laves相存在。并且 ,随着AB2 含量的增加 ,复合合金中的第二相含量逐渐增加。通过复合处理 ,AB5合金的放电容量、循环寿命和倍率放电性能均得到明显提高。AB5 x ?2 复合合金电极的最大放电容量由x =0时的 3 2 2mAh·g- 1 升高到x =1时的 3 3 1mAh·g- 1 。AB5 1?2 复合合金电极 ,在 15 0 0mA·g- 1电流密度下的放电容量从 62mAh·g- 1 提高到 185mAh·g- 1 ,经 3 0 0次充 /放电循环后的容量保持率从 44 .2 4%提高到 78.5 1%。