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961.
962.
Yu Wu Tullio Toccoli Jian Zhang Norbert Koch Erica Iacob Alessia Pallaoro Salvatore Iannotta Petra Rudolf 《Applied Physics A: Materials Science & Processing》2009,95(1):21-27
Organic molecular beam deposition is studied systematically at thermal and hyperthermal regimes aiming at investigating the
role of molecular kinetic energy on the growth mechanism of pentacene submonolayers on SiO
x
/Si. We show that the kinetic energy of the impinging molecule (E
k
) plays a crucial role in determining island structure and shape, distribution of island sizes, the crystalline quality of
the first monolayer, and even the growth mode of subsequent layers. With increasing E
k
, the island structure changes from fractal to nonfractal, the shape becomes more anisotropic and the island size more uniform,
pointing to correlated island growth. Moreover, while 3D island growth is observed for thermal organic molecular beam deposition,
supersonic molecular beam deposition gives rise to layer-by-layer growth, at least for the first two layers. When E
k
≥5.0 eV, the first monolayer is composed of large single crystalline domains which can extend over up to 10 μm, inferred from
comparing atomic force micrographs of height and net transverse shear force. In these growth conditions both the high surface
diffusivity and energy redistribution play a major role. We propose a mechanism where the energy dissipation occurring during
the molecule–surface collision leads to the reorientation of whole islands during island coalescence, resulting in the elimination
of grain boundaries. 相似文献
963.
G.?A.?Petrakovski? L.?N.?Bezmaternykh D.?A.?Velikanov A.?M.?Vorotynov O.?A.?Bayukov M.?Schneider 《Physics of the Solid State》2009,51(10):2077-2083
High-quality single crystals of ludwigites Cu2 MBO5 (M = Fe3+, Ga3+) have been grown, and the magnetic, resonance, and Mössbauer studies have been performed. It is established that the Cu2FeBO5 and Cu2GaBO5 compounds are antiferromagnets with Néel temperatures of 32 and 3.4 K, respectively. A model of the magnetic structure of the compounds is proposed. It is shown that the magnetic properties of the ludwigites are substantially dependent on the degree of ion distribution over crystallographic positions. 相似文献
964.
Bernd Schneider 《Nachrichten aus der Chemie》2009,57(10):1005-1007
965.
966.
Low-energy cluster beam deposition was used to deposit mass-selected Aun clusters (n = 4, 6, 13 and 20) on amorphous carbon (a-C) substrates. The resulting samples were stored at room temperature under ambient conditions for time periods up to 32 months to analyze the coarsening behaviour of the clusters. Cluster-size distributions were measured in regular time intervals by transmission electron microscopy (TEM). The TEM experiments show a significant increase of the average cluster size with time analogous to classical surface Ostwald ripening (OR). The coarsening of Au clusters can be well described by steady-state diffusion-limited kinetics. The derived surface mass-transport diffusion coefficients at room temperature range between 1.1 and 3.8·10−25 m2 s−1 for our samples. A detailed analysis of values suggests that, the rate of the surface OR for mass-selected Aun clusters increases with the cluster size in the sequence: Au4 ≈ Au6 < Au13 < Au20 for the investigated range of Au clusters. Given that the initial, on-surface cluster-size distributions are nominally monodisperse, classical OR with cluster coarsening based only on the Gibbs-Thomson effect cannot explain the observed coarsening. The activation of the coarsening process is rationalized by initial variations of the cluster sizes due to the deposition process itself and/or the interaction of the clusters with the substrate. Moreover, the presence of initial deposited Au clusters as different isomers with slightly different chemical potential on the substrate, may also initiate the coarsening by surface OR. Furthermore, we find that the coarsening is most pronounced for the paucidispersed sample with Aum (10 ? m ? 20) clusters. A possible explanation of this behaviour is the presence of an initial distribution of different cluster sizes directly after deposition. 相似文献
967.
968.
969.
The creation of anoxic granulated biomass has been monitored in a laboratory USB (Upflow Sludge Blanket) reactor with the
volume of 3.6 L. The objective of this research was to verify the possibilities of post-denitrification of residual NO3-N concentrations in treated wastewater (denitrification of 10-20 mg L−1 NO3-N) and to determine the maximum hydraulic and mass loading of the granulated biomass reactor. G-phase from biodiesel production
and methanol were both tested as external organic denitrification substrates. The ratio of the organic substrate COD to NO3-N was 6. Only methanol was proven as a suitable organic substrate for this kind of reactor. However, the biomass adaptation
to the substrate took over a week. The cultivation of anoxic granulated biomass was reached at hydraulic loading of over 0.35
m h−1. The size of granules was smaller when compared with results found and described in literary reports (granules up to 1 mm);
however, settling properties were excellent and denitrification was deemed suitable for the USB reactor. Sludge volume indexes
of granules ranged from 35-50 mL g−1 and settling rates reached 11 m h−1. Maximum hydraulic and mass loadings in the USB reactor were 0.95 m3 m−2 h−1 and 6.6 kg m−3 d−1. At higher loading levels, a wash-out of the biomass occurred.
Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May
2008. 相似文献
970.
Jnos Madarsz Petra Bombicz Czugler Mtys Ferenc Rti Gbor Kiss Gyrgy Pokol 《Thermochimica Acta》2009,490(1-2):51-59
Detailed study on identification and thermal decomposition of solid title compounds 1 and 2 crystallized from the used aqueous ammonia solutions of Pd(NH3)2(NO2)2 and Pt(NH3)2(NO2)2, has been carried out. Beyond the composition of complexes 1 and 2, their trans square planar configuration have already been recognized by reference IR spectra and powder XRD patterns, nevertheless their exact molecular and crystal structure as of trans-Pd(NH3)2(NO2)2 (1, Pd-NN) and trans-Pt(NH3)2(NO2)2 (2, Pt-NN) has been determined by single crystal X-ray diffraction (R = 0.0515 and 0.0341), respectively. Despite their compositional and configuration analogy, they crystallize in different crystal systems and space groups. The crystals of 1 (Pd-NN) are triclinic (space group No. 2, P-1, a = 5.003(1) Å, b = 5.419(1) Å, c = 6.317(1) Å, α = 91.34(2)°, β = 111.890(10)°, γ = 100.380(10)°), while those of 2 (Pt-NN) are monoclinic (space group No. 5, C2, a = 7.4235(16) Å, b = 9.130(2) Å, c = 4.4847(10) Å, β = 99.405(7)°).The pyrolytic processes of 1 and 2 (which might be sensitive to shock and heat) have been followed by simultaneous thermogravimetric and differential thermal analysis (TG/DTA), while the evolved gaseous species have been traced in situ by online coupled TG/DTA–EGA–MS and TG–EGA–FTIR instruments in He and air. Pd and Pt powders, forming as final solid products in single step, are captured and checked by TG and XRD. Whilst the unified evolved gas analyses report evolution of N2, H2O, NH3, N2O, NO, and NO2 gases as gaseous product components in the exothermic decomposition of both trans-Pd(NH3)2(NO2)2 (1) and trans-Pt(NH3)2(NO2)2 (2) starting from ca. 230 and 220 °C, in sealed crucibles with a pinhole on the top, respectively. 相似文献