Mssbauer studies on the shape effect of Fe_(84.94)Si_(9.68)Al_(5.38) particles on their microwave permeability

Ball milling for long time (such as 10, 20, and 30 h) can transform Fe 84.94 Si 9.68 Al 5.38 alloy powders with irregular shapes into flakes. X-ray diffraction (XRD) and Mssbauer measurements have proven that the unmilled particles and the flakes obtained by milling for 10 h have the same D0 3 -type superlattice structure. The flakes obtained by milling for 20 h and 30 h have the same disorder α-Fe(Si, Al) structure. There are more than 6 absorption peaks in the transmission Mssbauer spectra (TMSs) for the particles with D0 3 -type superlattice structure, which can be fitted with 5 sextets representing 5 different Fe-site environments. However, only 6 TMS absorption peaks have been found for particles with a disorder α-Fe(Si, Al) structure, which can be fitted with the distributions of Mssbauer parameters (Bhf, isomer shift). The TMS results show that the flaky particles have a stronger tendency to possess the planar magnetic anisotropy. As the result, the flakes have larger microwave permeability values than particles with irregular shapes. The conversion electron Mssbauer spectra (CEMSs) also show the significantly different Fe-sites environments between the alloy surface and the inside.     

Inclusive(π,η) Reactins on Nuclei

By assuming that the ηN reaction is dominated by the N(1535)resonance,the A(π,η)X inclusive reaction is studied in the framework of the DWBA model,and double differential cross sections are calculated for the ¹²C(π,η)X inclusive reaction.A good agreement between our theoretical result and the experimental datais achieved,and it is found that the interaction between N and N is attractive.The Pauli blocking effect is not obvious for the η production process.     

Order-disorder transition on Si(001): c(4 × 2) to (2 × 1)

A phase transition between c(4 × 2) and (2 × 1) structures on the clean Si(001) surface has been observed at about 200 K by low energy electron diffraction. From the temperature dependence of the width and intensity of the diffraction spots this transition is concluded to be a second order order-disorder transition. The transition proceeds by a single stage, which is in strong contrast with the case of Ge(001) for which a two-stage transition has been reported.     

Carbon monoxide chemisorption on Cu(100)-c(2 × 2)Pd

Chemisorption of carbon monoxide on Cu(100)-c(2 × 2)Pd was investigated using ultraviolet photoelectron spectroscopy. Adsorption was found to occur molecularly with a saturation coverage at 100 K which is approximately the same as that on Cu(100). Desorption spectra indicate that the CO-surface bond strength for the majority of the molecules is intermediate to that for the pure metals. The 4σ satellite, characteristic of photoemission from CO on Cu, was not observed.     

Two-dimensional Ir cluster lattice on a graphene moiré on Ir(111)

Lattices of Ir clusters have been grown by vapor phase deposition on graphene moirés on Ir(111). The clusters are highly ordered, and spatially and thermally stable below 500 K. Their narrow size distribution is tunable from 4 to about 130 atoms. A model for cluster binding to the graphene is presented based on scanning tunneling microscopy and density functional theory. The proposed binding mechanism suggests that similar cluster lattices might be grown of materials other than Ir.     

Surface structure of β-FeSi2(101) epitaxially grown on Si(111)

The surface morphology and structure of -FeSi₂(101) films epitaxially grown on Si(111) has been studied by means of Scanning Tunneling Microscopy (STM). The films are formed by large crystallites which are single domain. Each crystallite has only one of the three possible azimuthal orientations with respect to the substrate. A large density of planar defects, however, is detected on top of each crystallite. They are assigned to intrinsic stacking faults and their existence seems hard to avoid. This high density of intrinsic defects casts serious doubts on the use of -FeSi₂ as an optoelectronic material.     

A note on ■_c(3055)~ and ■_c(3123)~

The Babar Collaboration announced two new excited charmed baryons■_c(3055)~ and■_c(3123)~ . We study their strong decays assuming they are D-wave states.Some assignments are excluded by comparing our numerical results with the experimental values of the total widths of ■_c(3055)~ and■_c(3123)~ .We also suggest some possible decay modes,which will be helpful to determine the properties of■_c(3055)~ and■_c(3123)~ .     

Bicovariant differential calculi on Sμ U(2)

Bicovariant, differential calculi on S U(2) are investigated and the nonexistence of three-dimensional calculus and the uniqueness of 4D_± calculi are proved. Formulae for the external product, external derivative, and classical limit are presented.     

Investigation on Self-Q-Switched Er~(3 )-Doped Fiber Lasers

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Investigation on (EC/DMC)(70−x)wt% to LiBETI(x)wt% impact on PVdF-co-HFP/octadecylamine-MMT(montmorillonite) nano clay composite electrolytes

The composition dependence of plasticizer (ethylenecarbonate(EC)/dimethyl carbonate(DMC))_(70?x)wt% to Lithium bis(perfluoroethanesulfonyl)imide(LIBETI)_(x)wt% salt (where x?=?1.5, 3.0, 4.5, 6.0 wt%) on PVdF-co-HFP (25 wt%)/surface modified octadecylamine containing montmorrillonite (ODA-MMT) nano clay (5 wt%) matrix has been investigated by AC impedance, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and dielectric and cyclic voltammetry studies. The enhanced conductivity 2.1?×?10^?5 Scm^?1 is noted in salt rich phase (EC/DMC)_(70–6)wt% /LiBETI_(x=6)wt% (VK4). In XRD, 2θ at 20.9° confirms β-phase. In FTIR studies, vibrational bands 838, 522 and 611 cm^?1 confirm β-phase of PVdF due to clay intercalation. In DSC studies, the melting of α-phase crystallites is noted between 140–150 °C. In SEM studies, one of the membranes presents fern leaf texture confirming swelling of clay. The increase in dielectric constant and dielectric loss with decrease in frequency is attributed to high contribution of charge accumulation at the electrode–electrolyte interface. In cyclic voltammetry studies, salt-rich phase membrane (VK4) shows good cyclability than other membranes.     

Dangling-bond logic gates on a Si(100)-(2 × 1)-H surface

Atomic-scale Boolean logic gates (LGs) with two inputs and one output (i.e. OR, NOR, AND, NAND) were designed on a Si(100)-(2 × 1)-H surface and connected to the macroscopic scale by metallic nano-pads physisorbed on the Si(100)-(2 × 1)-H surface. The logic inputs are provided by saturating and unsaturating two surface Si dangling bonds, which can, for example, be achieved by adding and extracting two hydrogen atoms per input. Quantum circuit design rules together with semi-empirical elastic-scattering quantum chemistry transport calculations were used to determine the output current intensity of the proposed switches and LGs when they are interconnected to the metallic nano-pads by surface atomic-scale wires. Our calculations demonstrate that the proposed devices can reach ON/OFF ratios of up to 2000 for a running current in the 10 μA range.     

STM study of Pd growth on TiO2(100)-(1 × 3)

STM has been used to study the initial growth of palladium on TiO₂(100)-(1 × 3). The results demonstrate that STM is capable of imaging individual atoms which form part of a supported metal cluster. The data were obtained from small (35Ådiameter by 8Åhigh) clusters at a dispersed-equivalent coverage of about 0.01 ML. At higher coverages the clusters coalesce.     

Calculation on the CO2 influences on the structure,stability of (MgO)m (m = 1–6) clusters

ABSTRACT

The concentration of carbon dioxide (CO₂) has a significant influence on the morphology of thermal decomposition products of magnesite. So, structures, stabilities and adsorption mechanisms of (MgO)_m (m?=?1–6) clusters by one or two CO₂ molecules were calculated by the GGA-PW91 method. The results show that the stability of the considered clusters is (MgO)_m(CO₂)₂ clusters > (MgO)_m(CO₂) clusters > (MgO)_m clusters by the average binding energy. Certain low-lying isomers of (MgO)_m(CO₂) and (MgO)_m(CO₂)₂ clusters which have an isolated O atom are deviating from the cluster center which possess higher kinetic activity. (MgO)_m clusters prefer to adsorb a CO₂ molecule, while (MgO)₃(CO₂) clusters prefer to adsorb a CO₂ molecule rather than the neighbors. Magnesite is difficult to transit to (MgCO₃)₂ clusters at room temperature. However, magnesite will spontaneously transit to (MgO)₂ clusters and further transit to MgO crystal which need to adsorb more energy at 700?K.     

Similarities in the decomposition and dehydrogenation of cyclohexene on (4 × 4)-CMo(110) and Pt(111)

The decomposition and dehydrogenation of cyclohexene have been used as probing reactions to directly compare the surface reactivities of carbon-modified Mo(110) and Pt(111). By using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS), we find that the dominant decomposition pathway of cyclohexene can be converted from complete decomposition to atomic carbon and hydrogen on clean Mo(110) to partial dehydrogenation to benzene and hydrogen on (4 × 4)-CMo(110). The latter reaction mechanism is very similar to that observed on Pt(111). Furthermore, in contrast to the near identical catalytic properties that are commonly observed for bulk molybdenum carbide and nitride powder materials, we find that the reactivities of carbon-modified and nitrogen-modified Mo(110) surfaces are qualitatively different.     

(Information) Paradox Regained? A Brief Comment on Maudlin on Black Hole Information Loss

We discuss some recent work by Tim Maudlin concerning Black Hole Information Loss. We argue, contra Maudlin, that there is a paradox, in the straightforward sense that there are propositions that appear true, but which are incompatible with one another. We discuss the significance of the paradox and Maudlin’s response to it.     

Cesium adsorption on the β2-GaAs(001) surface

The results of first-principles calculations of the cesium adsorption energy on the β2-GaAs(001) surface performed within approaches of the density functional theory are presented for two possible terminations of the surface. It is shown that, among the considered high-symmetry positions, the energy-preferred position for cesium is position T ₃ when the surface layer contains arsenic and position T ₄ for gallium terminated surface. Cesium introduces insignificant perturbations in the positions of surface-layer atoms, and surface dimers do not break even in the case of adsorption at the dimer bridge and top positions. It is shown that cesium bonding to the GaAs (001) substrate can be explained by sp hybridization of arsenic and gallium orbitals as well as by formation of cesium states mixed with delocalized states of a clean surface. At low coverage, more preferable adsorbate sites are those with nearest neighbor arsenic atoms for both surface terminations.