Platinum supported mesoporous silica spheres by optmized microfluidic sol-gel synthesize scheme

Droplet based microfluidics is used to perform sol-gel reactions. The chemicals are dispensed, mixed, and pre-processed inside a microfluidic device allowing for long operation times without any clogging. Using this approach and optimizing all reaction and processing parameters we generate mesoporous silica particles with a very high surface area of 820 m2 g−1 and a narrow pore radius distribution of around 2.4 nm. To take full advantage of the possibilities offered by this microfluidic synthesis route, we produced platinum supported silica microspheres (as high as 7 mol. %) for heterogeneous catalysis

Unraveling Crystal Growth in GeSb Phase-Change Films in between the Glass-Transition and Melting Temperatures

The study of crystal growth in phase-change thin films is of crucial importance to improve our understanding of the extraordinary phase transformation kinetics of these materials excellently suited for data storage applications. Here, we developed and used a new method, based on isothermal heating using laser illumination in combination with a high-speed optical camera, to measure the crystal growth rates, in a direct manner over 6 orders of magnitude, in phase-change thin films composed of several GeSb alloys. For Ge8Sb92 and Ge9Sb91, a clear non-Arrhenius temperature dependence for crystal growth was found that is described well on the basis of a viscosity model incorporating the fragility of the supercooled liquid as an important parameter. Using this model, the crystal growth rate can be described for the whole range between the glass transition temperature of about 380 K and the melting temperature of 880 K, excellently explaining that these phase-change materials show unique and remarkable behavior that they combine extremely low crystal growth rates at temperatures below 380 K required for 10 years of data retention and very fast growth rates of 15 m s(-1) at temperatures near the melting point required for bit switching within tens of nanoseconds

Fabrication of anti-sticking patterned metallic stamp for imprinting

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Crystallization of Ge2Sb2Te5 thin films by nano- and femtosecond single laser pulse irradiation

The amorphous to crystalline phase transformation of Ge(2)Sb(2)Te(5) (GST) films by UV nanosecond (ns) and femtosecond (fs) single laser pulse irradiation at the same wavelength is compared. Detailed structural information about the phase transformation is collected by x-ray diffraction and high resolution transmission electron microscopy (TEM). The threshold fluences to induce crystallization are determined for both pulse lengths. A large difference between ns and fs pulse irradiation was found regarding the grain size distribution and morphology of the crystallized films. For fs single pulse irradiated GST thin films, columnar grains with a diameter of 20 to 60 nm were obtained as evidenced by cross-sectional TEM analysis. The local atomic arrangement was investigated by high-resolution Cs-corrected scanning TEM. Neither tetrahedral nor off-octahedral positions of Ge-atoms could be observed in the largely defect-free grains. A high optical reflectivity contrast (~25%) between amorphous and completely crystallized GST films was achieved by fs laser irradiation induced at fluences between 13 and 16 mJ/cm(2) and by ns laser irradiation induced at fluences between 67 and 130 mJ/cm(2). Finally, the fluence dependent increase of the reflectivity is discussed in terms of each photon involved into the crystallization process for ns and fs pulses, respectively