THE SIZE DEPENDENCIES OF PROPERTIES OF MO-W ALLOY OF EQUIATOMIC COMPOSITION

Основываясь на параметрах парного потенциала межатомного взаимодействия Ми-Леннард-Джонса для Mo и W были рассчитаны параметры потенциала для сплава замещения Mo - W эквиатомного состава. Получены размерные зависимости для уравнения состояния, модуля упругости, коэффициента теплового расширения, изобарной теплоемкости, поверхностной энергии и производной поверхностной энергии по температуре. Также получены температурные зависимости коэффициента теплового расширения изобарной теплоемкости для макро- и нанокристаллов сплава Mo - W. Было показано, что температурная зависимость коэффициента теплового объемного расширения для нанокристалла лежит выше, чем зависимость для макрокристалла, также обнаружено, что с уменьшением размера уменьшается модуль упругости, коэффициент теплового объемного расширения возрастает, а удельная поверхностная энергия нанокристалла сплава Mo - W уменьшается. Based on the parameters of the Mie-Lennard-Jones pair-wised potential of the interatomic interaction for Mo and W , the potential parameters for an equiatomic Mo - W substitution alloy were calculated. Size dependences for the equation of state, modulus of elasticity, coefficient of thermal expansion, isobaric heat capacity, surface energy and surface energy temperature derivative were obtained. Temperature dependencies of coefficient of thermal expansion and isobaric heat capacity for macro- and nano-crystals of Mo - W alloy were also obtained. It was shown that the temperature dependence of the thermal expansion coefficient for a nanocrystal is higher than that for a macrocrystal. It was also found that with a decrease in size, the elastic modulus decreases, the thermal volume expansion coefficient increases, and the specific surface energy of the alloy nanocrystal Mo - W decreases.

In situ scanning electron microscopy observations of filler material transport in branched carbon microtubes by Joule heating

Y-branched or side-by-side-branched carbon microtubes with metal filler material were fabricated, and material transport in the branched microtubes with Joule heating was investigated using in situ scanning electron microscopy with micro-electrode probes. When a voltage and electric current were applied, the material enclosed in the microtubes moved from its original position. The movement was not related to the direction of the electric current; therefore, it is concluded that the movement was not due to electromigration, but rather a temperature gradient, volume expansion and increased vapor pressure by Joule heating. In Y-branched microtubes, a part of the metal filler material moved from one branch to another branch, which would be useful for microfluidic flow switching. A cylindrical filler material was also observed to be expelled from a branch while its shape was maintained, and this phenomenon is presumably caused by vaporization-induced high pressure and could find application in micro-mechanical manipulators such as punching needles. In side-by-side-branched carbon microtubes, Joule heating caused thermal volume expansion to fill the spaces in the branches that were initially empty. The microtubes then reverted to a state almost identical to the initial state with empty spaces when the electric current was turned off. These results suggest that thermal volume expansion could be employed for flow switching.

Perovskite R{\bar 3}c phase AgCuF3: multiple Dirac cones, 100% spin polarization and its thermodynamic properties

Very recently, experimentally synthesized R{\bar 3}c phase LaCuO3 was studied by Zhang, Jiao, Kou, Liao & Du [J. Mater. Chem. C (2018), 6, 6132–6137], and they found that this material exhibits multiple Dirac cones in its non-spin-polarized electronic structure. Motivated by this study, the focus here is on a new R{\bar 3}c phase material, AgCuF3, which has a combination of multiple Dirac cones and 100% spin polarization properties. Compared to the non-spin-polarized system LaCuO3, the spin-polarized Dirac behavior in AgCuF3 is intrinsic. The effects of on-site Coulomb interaction, uniform strain and spin–orbit coupling were added to examine the stability of its multiple Dirac cones and half-metallic behavior. Moreover, the thermodynamic properties under different temperatures and pressures were investigated, including the normalized volume, thermal volume expansion coefficient, heat capacity at constant volume and Debye temperature. The thermal stability and the phase stability of this material were also studied via ab initio molecular dynamic simulations and the formation energy of the material, respectively.

Geochemical evidence for oil and gas expulsion in Triassic lacustrine organic-rich mudstone, Ordos Basin, China

Forty-six core samples were collected from a deep well that penetrated organic-rich layers of the Chang 7, 8, and 9 members of the Yanchang Formation (Fm) in the Ordos Basin. Tests for total organic content (TOC), Rock-Eval pyrolysis, X-ray diffraction (XRD) mineralogy, and molecular composition of gases released from rock crushing were conducted. Analytical results indicate that TOC and clay contents are elevated. The organic matter (OM)-rich mudstone in the Triassic Yanchang Fm suggests good-to-excellent source potential for oil generation. Its thermal maturity is in the oil window. Strong petroleum expulsion occurred from the upper part of the approximately 13 m (42.6 ft) thick Chang 7 member, and for the Chang 8 and Chang 9 members, resulting in low free oil and low methane ([Formula: see text]) concentration in these OM-rich intervals. A combination of sandstone and thin organic-rich mudstone layers is a perfect hybrid lithology stacking pattern for petroleum expulsion. The thickness for effective source rock, approximately 10–12 m (32.8–39.3 ft), varied with sandstone/mudstone lithology stacking pattern. In contrast, limited or no oil expulsion occurred in the lower part of Chang 7 member, a 25 m (82 ft) thick organic-rich interval, which is indicated by high free oil and high [Formula: see text] concentration. A [Formula: see text]-TOC plot can be used to differentiate generated gas, retained gas in OM-rich mudstones, and migrated gas in permeable sandstone beds. We have developed a conceptual model for petroleum expulsion from OM-rich thin versus OM-rich thick layers. Compaction and thermal volume expansion of oil generated from OM may play an important role in petroleum expulsion in OM-rich mudstones. The estimated petroleum expulsion efficiency is approximately 70% and 35% for thin and thick OM-rich mudstone layers, respectively. The redistributed OM in clay-dominated rock assemblage likely forms the preferred migration path to petroleum expulsion.

Synthesis, Photoisomerization and Thermo-Optic Property of Azo Optically Active Polymer

A novel azobenzene optically polymer (P-DA) was synthesized based on the azo chromophore molecule, chiral reagent L(-)-tartaric acid, acryloyl chloride and methacrylate. The P-DA was characterized by FT-IR, UV-Vis spectroscopy, 1H NMR, DSC and TGA. The P-DA had high thermal stability up to its glass-transition temperature (Tg) of 110 oC and 5 % heat weight loss temperature of 199 oC. The UV-induced trans/cis photoisomerization and reflex-isomerization behaviors were investigated. The results indicated that the P-DA solution could undergo photochromism after irradiated by 365 nm UV light. The optical parameters: refractive index (n), the dielectric constant (ε) and thermal volume expansion coefficient (β) of P-DA were obtained. The thermo-optic coefficients are one order of magnitude larger than those of the inorganic materials, such as SiO2 (1.1×10−5 oC -1 and LiNbO3 (4×10−5 oC -1) and was larger than the organic material such as polystyrene (-1.23×10-4 oC -1) and PMMA (-1.20×10-4 oC -1). The conclusion had a little significance to develop optical communication.