TY - JOUR A1 - Sarfraz, Adnan A1 - Schlegel, Moritz-Caspar A1 - Wright, J. A1 - Emmerling, Franziska T1 - Advanced gas hydrate studies at ambient conditions using suspended droplets N2 - We report the spontaneous formation of a clathrate hydrate in a suspended droplet at ambient conditions. A novel method for producing and stabilizing clathrates for analytical studies is described. KW - Clathrates KW - Thermography KW - Acoustic levitator KW - Dichloromethane PY - 2011 DO - https://doi.org/10.1039/c1cc13049h SN - 0022-4936 SN - 1359-7345 VL - 47 IS - 33 SP - 9369 EP - 9371 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-24480 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sarfraz, Adnan T1 - Crystallization and Morphological Diversity of Caffeine on Surfaces: Needles and Hexagons T2 - Tag der Chemie CY - Berlin, Germany DA - 2010-06-16 PY - 2010 AN - OPUS4-21209 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schlegel, Moritz-Caspar A1 - Wenzel, Klaus-Jürgen A1 - Sarfraz, Adnan A1 - Panne, Ulrich A1 - Emmerling, Franziska T1 - A wall-free climate unit for acoustic levitators N2 - Acoustic levitation represents the physical background of trapping a sample in a standing acoustic wave with no contact to the wave generating device. For the last three decades, sample holders based on this effect have been commonly used for contact free handling of samples coupled with a number of analytical techniques. In this study, a wall-free climate unit is presented, which allows the control of the environmental conditions of suspended samples. The insulation is based on a continuous cold/hot gas flow around the sample and thus does not require any additional isolation material. This provides a direct access to the levitated sample and circumvents any influence of the climate unit material to the running analyses. KW - Acoustic levition PY - 2012 DO - https://doi.org/10.1063/1.4705968 SN - 0034-6748 SN - 1089-7623 VL - 83 IS - 5 SP - 055101-1 EP - 055101-3 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-25881 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schlegel, Moritz-Caspar A1 - Sarfraz, Adnan A1 - Müller, Urs A1 - Panne, Ulrich A1 - Emmerling, Franziska T1 - First seconds in a building's life - In situ synchrotron X-ray diffraction study of cement hydration on the millisecond timescale N2 - Setting cement: Highly dynamic hydration processes that occur during the first seconds of cement hydration were studied by time-resolved synchrotron X-ray diffraction. Polycarboxylate ether additives were found to influence the formation of the initial crystalline hydration products on a molecular level. KW - Cement hydration KW - Colloidal suspensions KW - In situ analysis KW - X-ray diffraction KW - SyXRD KW - High resolution KW - In-situ PY - 2012 DO - https://doi.org/10.1002/anie.201200993 SN - 1433-7851 SN - 1521-3773 SN - 0570-0833 VL - 51 IS - 20 SP - 4993 EP - 4996 PB - Wiley-VCH CY - Weinheim AN - OPUS4-26287 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sarfraz, Adnan A1 - Simo, A. A1 - Fenger, R. A1 - Christen, W. A1 - Rademann, K. A1 - Panne, Ulrich A1 - Emmerling, Franziska T1 - Morphological diversity of caffeine on surfaces: needles and hexagons N2 - A systematic crystal morphology study on the pharmaceutical model compound caffeine has been conducted on different surfaces: silicon, silver, soda lime glass, and silver subsurface ion-exchanged soda-lime silicate (SIMO) glasses. The morphology of the solid caffeine deposits has been investigated using environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Needle-shaped caffeine crystals have been observed by drop-casting and also by applying the rapid expansion of supercritical solutions (RESS) technique using supercritical carbon dioxide. The aspect ratio of the crystalline needles typically vary between 10 and 100, but have been observed as large as 500. The XRD data of the RESS products indicate unambiguously the presence of the thermodynamically most stable polymorph of caffeine known as the β-form. Under defined conditions we observe a unique, surface-mediated morphology for caffeine crystals with nearly perfect hexagonal shape. The relative fraction of the hexagons was seen to strongly increase especially when SIMO glasses were used. These hexagons have a distinct upper size limit depending on the solvent and substrate being used. The size distribution analysis of the hexagons yielded an average perimeter of typically 10 µm. The mechanism of the formation process of this new hexagonal motif is explained in terms of the spinodal dewetting of the thin film of caffeine solution on the surface. KW - Caffeine KW - Silicon KW - Silver KW - Ion exchanged soda lime silicate glass KW - ESEM KW - AFM KW - X-ray diffraction KW - RESS KW - Carbon dioxide KW - Supercritical fluids PY - 2012 DO - https://doi.org/10.1021/cg101358q SN - 1528-7483 VL - 12 IS - 2 SP - 583 EP - 588 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-25457 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sarfraz, Adnan T1 - In-situ study of the crystallization of metal (IV) phosphonates T2 - Bessy User Meeting 2011 CY - Berlin, Germany DA - 2011-11-29 PY - 2011 AN - OPUS4-25124 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sarfraz, Adnan T1 - Study of the crystallization of metal (IV) phosphonates: X-ray diffraction and thermal analysis T2 - Tag der Chemie CY - Berlin, Germany DA - 2011-07-13 PY - 2011 AN - OPUS4-24220 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schlegel, Moritz-Caspar A1 - Sarfraz, Adnan A1 - Müller, Urs A1 - Panne, Ulrich A1 - Emmerling, Franziska T1 - Erste Sekunden im Leben eines Bauwerks - In-situ-Synchrotron-Röntgenbeugungsuntersuchungen der Zementhydratation mit Millisekunden-Auflösung N2 - Höchst dynamische Hydratationsprozesse in den ersten Sekunden bei der Entstehung eines Bauwerkes lassen sich mithilfe von Synchrotron-Röntgenbeugung mit einer sehr hohen Zeitauflösung nachverfolgen. Der Schwerpunkt lag dabei auf der Beeinflussung der Bildung erster kristalliner Hydratationsprodukte während des Frühstadiums der Zementhydratation. KW - SyXRD KW - High resolution KW - In-situ KW - Colloidal suspension KW - Cement hydration KW - In-situ-Analyse KW - Kolloidale Suspensionen KW - Röntgenbeugung KW - Zementhydratation PY - 2012 DO - https://doi.org/10.1002/ange.201200993 SN - 0044-8249 SN - 0932-2140 SN - 1521-3757 VL - 124 IS - 20 SP - 5078 EP - 5081 PB - Wiley-VCH CY - Weinheim AN - OPUS4-26284 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gorelik, T.E. A1 - Sarfraz, Adnan A1 - Kolb, U. A1 - Emmerling, Franziska A1 - Rademann, Klaus T1 - Detecting crystalline nonequilibrium phases on the nanometer scale N2 - The use of Automated electron Diffraction Tomography (ADT) is presented as a novel approach for crystallization studies at the nanometer scale for nonequilibrium phases. Here, ADT was applied to elucidate the structural identity of the recently reported hexagonal morphology of caffeine crystals, which grow only on specific surfaces. Caffeine was crystallized from solution on a specially treated TEM carbon grid. The analysis of ADT data revealed that the lattice parameters of these hexagons match those of the high temperature α-form of caffeine. Furthermore, it was observed that in this hexagonal morphology, the α-form remained stable for a prolonged period of time. The stabilization of hexagons can be interpreted in terms of enhanced interactions with the supporting surfaces. KW - Electron diffraction KW - Polymorphism caffeine KW - ADT PY - 2012 DO - https://doi.org/10.1021/cg300377j SN - 1528-7483 VL - 12 IS - 6 SP - 3239 EP - 3242 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-26285 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -