Late Quaternary aeolian dust input variability on the Chinese Loess Plateau: inferences from unmixing of loess grain-size records

IEECAS SKLLQG

ENVIRONMENTAL EVOLUTION OF ORDOS DESERT IN CHINA SINCE 1.1MA B. P. AS INDICATED BY YULIN STRATIGRAPHICAL SECTION AND ITS GRAIN-SIZE ANALYSIS RESULTS

IEECAS SKLLQG

Changes in grain-size and sedimentation rate of the Neogene Red Clay deposits along the Chinese Loess Plateau and implications for the palaeowind system

IEECAS SKLLQG

The influence of the microstructure evolution on the surface morphology in the annealing process of helium-implanted spinel

Single-crystalline spinel (MgAl2O4) specimens were implanted with helium ions of 100 keV at three successively increasing fluences of (0.5, 2.0 and 8.0) x 10(16) ions/cm(2) at room temperature. The specimens were subsequently annealed in vacuum at different temperatures ranging from 500 to 1100 degrees C. Different techniques, including Fourier transformed infrared spectroscopy (FTIR), thermal desorption spectrometry (TDS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the specimens, It was found that the absorbance peak in the FTIR due to the stretching vibration of the Al-O bond shifts to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with an increase of annealing temperature. The absorbance peak shift has a linear relationship with the fluence increase in the as-implanted state, while it does not have a linear relationship with the fluence increase after the annealing process. Surface deformation occurred in the specimens implanted with fluences of 2.0 and 8.0 x 10(16) ions/cm(2) in the annealing process. The phenomena described above can be attributed to differences in defect formation in the specimens. (C) 2008 Elsevier B.V. All rights reserved.

Annealing effects in silicon implanted with helium

Silicon samples were implanted with helium and analyzed by atomic force microscopy (AFM) and Raman spectroscopy before and after annealing in the range of 523-1273 K. After annealing at 523 K, the amorphous area induced by He-ion implantation at room temperature was partially recovered and grain sizes became larger. The surface morphology was analyzed through AFM measurements and it was observed that root mean square of the surface roughness alters upwards and then downwards with annealing temperature. (C) 2008 Elsevier B.V. All rights reserved.

Surface morphology of He-implanted single-crystalline silicon

Single-crystalline Si (100) samples were implanted with 30 keV He2+ ions to doses ranging from 2.0x10(16) to 2.0x10(17) ions/cm(2) and subsequently thermally annealed at 800 degrees C for 30min. The morphological change of the samples with the increase of implantation dose was investigated using atomic force microscopy (AFM). It was found that oblate-shaped blisters with an average height around 4.0nm were found on the 2.0 x 10(16) ions /cm(2) implanted sample surface; spherical-shaped blisters with an average height wound 10.0nm were found on the 5.0 x 10(16) ions/cm(2) implanted sample surface; strip-shaped and conical cracks were observed on the sample He-implanted to a dose of 1.0 X 10(17) ions /cm(2). Exfoliations occurred on the sample surface to a dose of 2.0 x10(17) ions /cm(2). Mechanisms underlying the surface change were discussed.

Segmented All-Platinum Nanowires with Controlled Morphology through Manipulation of the Local Electrolyte Distribution in Fluidic Nanochannels during Electrodeposition

Synthesis of segmented all-Pt nanowires is achieved by a template-assisted method. The combination of a suitably chosen electrolyte/template system with pulse-reverse electrodeposition allows the formation of well-defined segments linked to nanowires. Manipulation of the morphology is obtained by controlling the electrokinetie effects on the local electrolyte distribution inside the nanochannels during the nanowire growth process, allowing a deviation from the continuously cylindrical geometry given by the nanoporous template. The length of the segments can be adjusted as a function of the cathodic pulse duration. Applying constant pulses leads to segments with homogeneous shape and dimensions along most of the total wire length. X-ray diffraction demonstrates that the preferred crystallite orientation of the polycrystalline wires varies with the average segment length. The results are explained considering transitions in texture formation with increasing thickness of the electrodeposit. A mechanism of segment formation is proposed based on structural characterizations. Nanowires with controlled segmented morphology are of great technological importance, because of the possibility to precisely control their substructure as a means of tuning their electrical, thermal, and optical properties. The concept we present in this work for electrodeposited platinum and track-etched polycarbonate membranes can be applied to other selected materials as well as templates and constitutes a general method to controlled nanostructuring and synthesis of shape controlled nanostructures.

Influence of drying method on morphology and properties of asymmetric cellulose hollow fiber membrane

Using a dry/wet spinning process, asymmetric cellulose hollow fiber membranes (CHFM) were prepared from a dope composed of cellulose/N-methylmorpholine-N-oxide/water. The formation mechanism for the finger-like macrovoids at the inner portion of as-spun fibers was explained. Naturally drying and three solvent exchange drying methods were tried to investigate their influence on morphology and properties of CHFM. It was found that the ethanol-hexane exchange drying was an appropriate method to minimize morphology change of the as-spun CHFM, whereas the naturally drying caused the greatest shrinkage of the fibers that made the porous membrane become dense. The result, CHFM from ethanol-hexane exchange drying performed the highest gas permeation rate but gas permeation of the naturally dried membrane could not be detectable. The resultant CHFM from the ethanol-hexane exchange drying also showed acceptable, mechanical properties, thus it was proposed to be an appropriate method for gas separation purpose. The experimental results supported the proposed drying mechanism of CHFM. The free water would evaporate or be replaced by a solvent that subsequently would evaporate but the bonded water would remain in the membrane. What dominated the changes of membrane morphology during drying should be. the molecular affinities of cellulose-water, water-solvent and solvent-solvent. (C) 2004 Elsevier B.V. All rights reserved.

Morphology observation of carbon deposition by CH4 decomposition over Ni-based catalysts

We found a novel morphology variation of carbon deposition derived from CH4 decomposition over NI-based catalysts. By altering the chemical composition and particle size of Ni-based catalysts, carbon filaments, nanofibres and nanotubes were observed over conventional Ni/y-Al2O3, Ni-Co/gamma-Al2O3 and nanoscale Ni-Co/gamma-Al2O3 catalysts, respectively. The simple introduction of Co into a conventional Ni/gamma-Al2O3 catalyst can vary the carbon deposition from amorphous filamentous carbon to ordered carbon fibres. Moreover, carbon nanotubes with uniform diameter distribution can be obtained over nanosized Ni-Co/gamma-Al2O3 catalyst particles. In addition, the oxidation behaviour of the different deposited carbon was studied by using a temperature-programmed oxidation technique. This work provides a simple strategy to control over the size and morphology of the carbon deposition from catalytic decomposition of CH4.