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In papermaking, the formation of bonds between single pulp fibers is influenced by the hardness of the fibers in their wet state. In this work, transversal hardness and modulus of pulp fibers have been studied via atomic force microscopy-based nanoindentation in dependence on relative humidity (RH). Additionally, the change in hardness of cellulose and xylan/cellulose model films was also investigated as a function of swelling in the presence of water and calcium chloride (CaCl2) solution. The hardness of pulp fibers is decreasing slowly from 240 MPa at 5% RH to 90 MPa at 80% RH and exhibits a distinct decrease to 2.7 MPa at the fully wet state. The hardness in water is reduced by a factor of almost 100 compared with the dry state; therefore, a form change is easily possible and facilitates the formation of hydrogen bonds on the fiber surfaces. The investigations on the model films reveal that pure cellulose hardens in the CaCl2 solution, compared with distilled water, whereas xylan on cellulose is becoming softer.

The typically elongated shape of droplets on chemically microstriped surfaces has been suggested to depend strongly on the kinetics during deposition. Here, we unequivocally establish the importance of impact kinetics by comparing the geometry of pico- to microliter droplets deposited from an inkjet nozzle with those obtained by conventional deposition from a syringe. For large Weber numbers, the strongly enhanced spreading during the impact in combination with direction-dependent pinning of the contact line gives rise to more spherical droplets with a low aspect ratio. The impact energy can be minimized by the prolonged firing of small picoliter droplets to form larger droplets or, as shown in the past, by using high-viscosity liquids. In the first case, the impact energy is absorbed by the liquid already present, therewith reducing the impact diameter and consequently forming markedly more elongated droplets

Im vorliegenden Beitrag wird das Forschungsrating des Wissenschaftsrats (RWR) im Fach Soziologie behandelt. Mit dieser Pilotstudie versuchte der Wissenschaftsrat ein Verfahren zu testen, welches eine differenzierte Bewertung der Forschungseinrichtungen in Deutschland ermoglicht. Zwei Thesen werden gegen das RWR vorgebracht und anschliesend anhand empirischer Daten gepruft. Einerseits wird vermutet, dass die Ergebnisse aufgrund der impliziten Bewertungen durch Gutachter weder objektiv, reliabel noch valide sind. Andererseits wird gefragt, ob sich die Ergebnisse des RWR mit Hilfe eines kostengunstigeren, auf wenigen quantitativen Indikatoren basierenden Modells der Forschungsqualitat reproduzieren lassen. Hierfur werden Daten des RWR und eine Befragung zur Reputation deutscher Forschungsstandorte ausgewertet. Daruber hinaus wurden mit Mitgliedern der Bewertungsgruppe Interviews durchgefuhrt. Im Ergebnis zeigt sich, dass Probleme hinsichtlich der Gutekriterien, insbesondere der Auswertungsobjektivitat, nicht ausgeschlossen werden konnen. Das Fazit bezuglich der Reliabilitat, beschrankt auf die innere Konsistenz der quantitativen Indikatoren, fallt insgesamt positiv aus. Eine Reproduktion der Ergebnisse mit ausschlieslich quantitativen Daten gelingt nicht in befriedigender Art und Weise. Dies wird als Anzeichen eher geringer Validitat interpretiert. Es wird gefolgert, dass hinsichtlich des Umfangs und der Qualitat der erhobenen Daten sowie der Standardisierung der Auswertung Verbesserungsbedarf besteht.

Experimentally we explore the potential of using pre-defined motion of a receding contact line to control the deposition of nanoparticles from suspension. Stripe-patterned wettability gradients are employed, which consist of alternating hydrophilic and hydrophobic stripes with increasing macroscopic surface energy. Nanoparticle suspensions containing nanorods and nanospheres are deposited onto these substrates and left to dry. After moving over the pattern and evaporation of the solvent, characteristic nanoparticle deposits are found. The liquid dynamics has a pronounced effect on the spatial distribution. Nanoparticles do not deposit on the hydrophobic regions; there is high preference to deposit on the wetting stripes. Moreover, the fact that distributed nanoparticle islands are formed suggests that the receding of the contact line occurs in a stick-slip like fashion. Furthermore, the formation of liquid bridges covering multiple stripes during motion of the droplet over the patterns is modeled. We discuss their origin and show that the residue after drying, containing both nanoparticles and the stabilizing surfactant, also resembles such dynamics. Finally, zooming into individual islands reveals that highly selective phase separation occurs based on size and shape of the nanoparticles.

This review features the potential of modern high spatial resolution methods in materials science and engineering by presenting a selection of scientific examples covering bulk materials, as well as hard coatings, semiconductors, and mesoporous thin films. Complementary techniques are employed to study microstructure and/or texture and stresses in multiphase Mo-, Al-, and Mg-base alloys, in several nitride- and boride-based hard coatings, in silicon, as well as in mesoporous silica films. Although far from being comprehensive, the chosen examples aim at underlining the importance of modern electron microscopy based methods and of scattering/diffraction techniques at large scale neutron and synchrotron radiation facilities for modern materials research. In addition, atom probe tomography, Raman scattering and atomic force microscopy are also highlighted.

The optical quality and photonic properties of all-polymer distributed Bragg reflectors are related to the morphology of the layers and the optical responses of the materials. We introduce the X-ray reflectivity method to determine the thickness, the interface- and surface-roughness of cellulose acetate and polystyrene layers which are two polymers often used in the domain of spin casted multilayer systems. Atomic force microscopy and spectroscopic ellipsom-etry were used as complementary techniques for investigating the surface roughness and the film thickness. The shrinkage and the change of interface roughness of the polymers were investigated up to temperatures of 200 °C Up to 170 °C the interface roughness stays constant at about 1 nm while it increases up to 2nm at 200 °C. The thickness of the polystyrene layer remains constant up to 170 °C, well above its glass transition temperature T g . For cellulose acetate a monothonic decrease is observed with increasing temperature. It could be shown, that the change in the optical response of a thermally treated distributed Bragg reflector is related to the change of the layer thickness of cellulose acetate. Spectra of (PS CA) 20 PS distributed Bragg reflectors (DBR) are in a good agreement with calculated spectra with parameters optained from of the X-ray reflectivity measurements.

Tapping mode atomic force microscopy (AFM) is employed for dynamic plowing lithography of exfoliated graphene on silicon dioxide substrates. The shape of the graphene sheet is determined by the movement of the vibrating AFM probe. There are two possibilities for lithography depending on the applied force. At moderate forces, the AFM tip only deforms the graphene and generates local strain of the order of 0.1%. For sufficiently large forces the AFM tip can hook graphene and then pull it, thus cutting the graphene along the direction of the tip motion. Electrical characterization by AFM based electric force microscopy, Kelvin probe force microscopy and conductive AFM allows us to distinguish between the truly separated islands and those still connected to the surrounding graphene.