BaFe 2 As 2 exhibits properties characteristic of the parent compounds of the newly discovered iron (Fe)-based high-T C superconductors. By combining the real space imaging of scanning tunneling microscopy/spectroscopy (STM/S) with momentum space quantitative Low Energy Electron Diffraction (LEED) we have identified the surface plane of cleaved BaFe 2 As 2 crystals as the As terminated Fe-As layer -the plane where superconductivity occurs. LEED and STM/S data on the BaFe 2 As 2 (001) surface indicate an ordered arsenic (As) -terminated metallic surface without reconstruction or lattice distortion. It is surprising that the STM images the different Fe-As orbitals associated with the orthorhombic structure, not the As atoms in the surface plane.
Thermally stable hematite (alpha-Fe(2)O(3)) hollow nanowires were synthesized by a vacuum-pyrolysis route from beta-FeOOH nanowires for the first time. The products can catalyze the oxidation of almost 100% carbon monoxide at 320 degrees C, exhibiting excellent catalytic performances despite their small BET surface area.
diffusion coefficient of methane in coal is a key parameter
for the prediction of coalbed methane production. The apparent diffusion
coefficient is different from the true diffusion coefficient, which
would result in the deviation of methane production. In this study,
the particle method using the unipore model and the counterdiffusion
method is adopted to measure the methane diffusion coefficients. The
results indicated that the true diffusion coefficient obtained by
the counterdiffusion experiment decreases first and then increases
with increasing methane pressure. The apparent diffusion coefficients
obtained by the particle method with two different grain sizes are
lower than the true diffusion coefficient. The relationship between
the apparent diffusion coefficient and the true diffusion coefficient
is analyzed, and the desorption capacity factor (DCF) is proposed
to reflect the gap between them. The apparent diffusion coefficient
is closer to the true diffusion coefficient when the DCF is small.
When using the particle method to estimate the methane diffusion coefficient,
experiments with large coal particles and a small methane concentration
gradient should be adopted.
Self-healable, transparent, and antifogging polysaccharide films composed of acrylamide-modified chitosan (AMCS) and alginate aldehyde (ADA) were fabricated via layer-by-layer (LBL) assembly. The Schiff base linkage formed between amino groups of AMCS and aldehyde groups of ADA was used to construct the films. Fourier transform infrared spectroscopy and X-ray photoelectron spectra revealed that the films were cross-linked through Schiff base bonds. Ultraviolet− visible spectroscopy and field emission scanning electron microscope characterizations demonstrated that the films exhibited linear growth during the LBL process. The films showed a repetitive self-healing property, and the repeated damage-healing of the films was thickness-dependent. The films can heal the scratches that penetrated to the underlying substrates. Besides the excellent self-healing property, the films showed an antifogging property due to the hydrophilic nature of the two polysaccharides. The antifogging ability of the film was thickness-dependent. Also, the films could regain their transmittance and fog-resistant property after mechanical abrasion due to their self-healing capability. These self-healable and fog-resistant polymeric films have potential applications in food packaging.
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