Ordering effect on the mechanical,electronic and magnetic properties of the β-based non-canonical approximant phases: β-Al50Cu33Fe17, η-Al50Cu44Fe6 and φ-Al47.5Cu49.5Fe3

Abstract

Using transmission electron microscopy and X-ray diffraction, we established that the ordered η1-Al₅₀Cu₄₄Fe₆ and φ-Al_47.5Cu_49.5Fe₃ (Fmm2) alloys with nano-sized domain structure are formed by slowly cooling, whereas β-solid solutions with a short-range order were found in quenched states. The φ′-modification which exhibits the additional long-period superstructure was also observed in Al_47.5Cu_49.5Fe₃. The studies of low temperature magnetic susceptibility and heat capacity did not reveal any another phase transitions in these alloys. The indentation test showed that hardness and Young’s modulus consistently grow as β-Al₅₀Cu₃₃Fe₁₇ → η1-Al₅₀Cu₄₄Fe₆ → (φ+φ′)-Al_47.5Cu_49.5Fe₃ and approach to those in icosahedral phase. The same trend in the Young’s modulus was obtained for alloys containing β-solid solution with a short-range order. Ab initio calculations, however, predicted the opposite tendency in cubic β-Al₅₀Cu_50?xFe_x with a decrease in x, which was explained by the weakening of the covalent Fe 3d – Al sp bonding. This discrepancy between the results for β- and ordered phases, we related to a crucial effect of ordering which is accompanied by a progressive distortion of cubic local structure in the series β-Al₅₀Cu₃₃Fe₁₇ → η1-Al₅₀Cu₄₄Fe₆ → φ-Al_47.5Cu_49.5Fe_3. As we demonstrated for η-Al(Cu, Fe), these distortions lead to the strengthening of the both covalent Fe–Al and Cu–Al bonds and the higher modules.     

Nuclear-physical analysis of the contamination on the surface of a COMPLAST panel after 12-year exposure at the ISS

Using methods of X-ray fluorescence analysis (XRFA), the Rutherford backscattering of ions (RBS) and spectral X-ray microanalysis (SXRM) in combination with scanning electron microscopy (SEM), we study the elemental composition and structure of contaminants on the surface of a metallic panel with samples of different materials exposed to outer space for 12 years. It turns out that the main elements of the contaminants are C, O, Si, S, Ca, Fe, and Zn. Since these elements are the constituents of materials located on the panel, they are present as a result of destruction of the materials under the action of outer-space factors. X-ray phase analysis (XRPA) of the contaminants shows that carbon is present in the form of an amorphous graphite phase with a small addition of crystalline graphite, while the other components are in an amorphous state. Crystalline silicium dioxide and other silicium compounds are not found.     

Lamellar structure and nanomechanical properties of quasicrystalline Al-Cu-Fe alloys

The kinetics of structural phase transformations in quasicrystal-forming Al-Cu-Fe alloys with compositions in the region of stability of the icosahedral (i) phase has been investigated. It has been shown that, depending on the development of metastable transformations i → pentagonal phases P1 and P2, a homogeneous lamellar structure (i + P1 + P2) or a polygrain i-phase is formed in the alloys. The P-h diagrams obtained upon nanoindentation, atomic force microscopy, and scanning electron microscopy of indentations have demonstrated signs of elasto-plastic deformation of the alloys with lamellar and polygrain icosahedral structures. It has been found that, in contrast to the polygrain icosahedral alloys with a normal size effect of nanoindentation, the alloys with a lamellar structure are characterized by a nonmonotonic dependence of the hardness (H) on the maximum load (P _max) and exhibit the effect of strain hardening in the range of loads 50 mN ≤ P _max < 500 mN. The strain hardening is considered as the result of resistance exerted by boundaries of the lamellar structure to the development of plastic deformation.     

Induction of Mesomorphic Properties in Non-Mesogenic Octa(decyloxy) phthalocyanines

Abstract

As it is well known [1, 2], non-peripheral substituted octa (alkoxy)-phthalocyanines (Pc) do not exhibit neither thermotropic nor lyotropic mesomorphism (in binary mixtures with organic solvents). In this work we induced an enantiotropic mesophase due to charge-transfer (CT) interactions in mixtures of PC derivatives I-III (viscous or oil-like liquids) with a strong electron acceptor 2,4,7-trinitro-9-fluorenone (TNF). Decreasing of number and length of substituents and modification of chemical structure of phthalocyanine macrocycle by introduction of four sulfur atoms (compound IV) resulted in crystallinity of this compound. In contact preparation of IV with TNF a wide area of CT-complex showing the monotropic mesomorphic phase is found out. All above mentioned CT-complexes do not form any lyomesophases in binary mixtures with number of organic solvents.     

Thermodynamic properties of tetraphenylantimony benzophenoxymate in the region of 0–450 K

Heat capacity of tetraphenylantimony benzophenoxymate Ph₄SbONCPh₂ is measured for first time using adiabatic calorimeter in the range from 6K to 350K and differential scanning calorimeter in the range from 330 K to 450 K. In the range of 400–450 K is revealed a melting accompanied with partial decomposition of the substance. Standard thermodynamic functions of crystalline Ph₄SbONCPh₂ in the range from T → 0 K to 440 K are calculated. Enthalpy of combustion of this compound is measured in a combustion calorimeter with isothermal cover and static bomb. Standard thermodynamic formation functions of crystalline Ph₄SbONCPh₂ at 298.15 K are calculated. Fractal dimension D is revealed.     

Synthesis and structure of tetraphenylantimony 1-adamantanecarboxylate and triphenylantimony bis(1-adamantanecarboxylate)

Reaction of pentaphenylantimony with triphenylantimony bis(1-adamantylcarboxylate) yielded the solvate of tetraphenylantimony 1-adamantylcarboxylate with benzene. Triphenylantimony bis(1-adamantylcarboxylate) was prepared from triphenylantimony and 1-adamantylcarboxylic acid in the presence of hydrogen peroxide in ether. X-ray studies showed that in the first and in the second product antimony atom has the distorted trigonal bipyramide coordination (OSbO and CSbO trans-angles are 179.42° and 174.58°, respectively). Sb-O interatomic distances are 2.154 and 2.202 Å, respectively. The carbonyl group oxygen atom is coordinated with the central atom, Sb?O interatomic distances are 2.570 and 3.396 Å, respectively.     

Enthalpies of reaction of calcium chloride and sodium oxalate in an aqueous NaCl solution

The heats of mixing of dilute aqueous solutions of calcium chloride and sodium oxalate with additions of 1–5 wt % NaCl at 298.15 K and the heats of dilution of calcium chloride solutions were measured. Increasing the sodium chloride content in a solution noticeably increases the time of precipitation of calcium oxalate. A fine precipitate of CaC₂O₄ formed in solutions containing 3 and 5 wt % NaCl is difficult to remove from the parts of a calorimeter cell. The enthalpies of precipitation of CaC₂O₄ depend slightly on the content of the “background electrolyte,” whereas the enthalpies of dilution, owing to ion association, significantly decrease in magnitude and become positive in a 5% NaCl solution. The “standard” enthalpy of precipitation in water, determined by extrapolation of the experimental values to the zero concentration of the background electrolyte, differs noticeably from the enthalpy of precipitation in water.     

The thermodynamic properties of crystalline pentasodium hafnium <Emphasis Type="Italic">tris</Emphasis>(phosphate)

The temperature dependence of the heat capacity of crystalline pentasodium hafnium tris(phosphate) was studied over the temperature range 6–650 K. The experimental data were used to calculate the thermodynamic functions of Na₅Hf(PO₄)₃ from 0 to 650 K and the fractal dimension at 20–50 K. The standard entropy of formation from simple substances at 298.15 K was calculated from the absolute entropy value. The thermodynamic properties of Na₅M(PO₄)₃ (M = Ti, Zr, and Hf) phosphates were compared.     

TDDFT Study on the Electronic Excitations and First Hyperpolarizabilities of Mixed-metal Carbonyl Clusters W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2（L = dppe/dppf）

Mixed-metal carbonyl clusters of W2Ir2（CO）10（η^5-C5H4Me）2 1 and W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2 （L = dppe 2, dppf 3） have been studied by TDDFT method focusing on their electronic and nonlinear optical properties. These three clusters exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The origin of β is discussed by the new proposed orbital-pair decomposition scheme by Barandes et al. The result suggests that the β values of the two clusters are mainly originated from d-d electron transition within the metal skeleton, and d-p （π＊） electron transition from metals to carbonyls and phenyl. The additional coordination by the electron donor group, ferrocene, makes cluster 3 own much larger β values, and the relatively longer range charge transfer from d orbitals of ferrocene to d orbirals of Ir and W is responsible for the enhanced β values.