Flux-assisted spreading of an Al–7 wt%Si alloy on TiC

The effect of a K–Al–F-based flux was investigated on the wettability of TiC by an Al–7 wt%Si alloy in the interval of temperatures between 660 and 900 °C in Ar and in atmospheric air. Null spreading was observed without flux whereas perfect wetting was enabled by the flux in both atmospheres. The liquid flux, which provides a locally protective atmosphere by spreading on the surfaces of the substrate and eventually on the Al alloy, dissolves the aluminium oxide covering the molten alloy enabling thus direct contact between the liquid alloy and the TiC substrate. The low tensions for the solid/flux and liquid metal/flux interfaces facilitate spontaneous spreading and instantaneous wetting. Meanwhile, the flux is displaced to the lateral periphery of the substrate and to the surface of the liquid. Under the resolution of the scanning electron microscope, microstructural examination of the interfaces did not reveal reaction products. Rapid infiltration of the alloy into TiC/flux compacts, at low temperatures, correlated well with the flux-assisted spreading kinetics observed.     

Thermal spreading of MoO3 in H–ZY

This work provides a structural, optical and kinetics approach to the molybdenum oxo-species formed during thermally driven migration on H–ZY starting from mechanical mixtures with MoO₃. The samples were characterized as a function of time of treatment by UV–vis diffuse reflectance, X-ray diffraction, N₂ adsorption and scanning transmission electron microscopy (STEM). Local analysis of elemental compositions obtained from linear scan of characteristic X-ray signal show a direct evidence of molybdenum presence into the zeolite crystals. Ultraviolet absorption spectra were used to determine both the kinetics of the spreading and the speciation of MoO_x in the H–ZY. Besides MoO₃, three surface molybdenum oxo-species were identified according to the edge energy (E_g) values of bulk molybdenum oxide reference compounds. This study shows that the tetrahedral species prevailed on H–ZY. This is consistent with limitations in the migration and growth of MoO_x in the channel structure of the zeolite. Kinetic study suggest that migration of MoO_x in the H–ZY at low temperature (ca. 723 K) occurs across the formation and diffusion of hydrated species such as MoO₂(OH)₂, which interact with the zeolite and form monomeric and dimeric structures (like (MoO₄)²⁻ and (Mo₂O₇)²⁻). Migration of MoO_x species in the H–ZY studied is significant even at 723 K and after very short periods of treatment (<5 min).     

Investigation of effects of Argenine–Glycine–Aspartate (RGD) and nano-scale titanium coatings on cell spreading and adhesion

This paper examines the effects of physical and chemical surface modifications on the biocompatibility of silicon surfaces that are relevant to implantable silicon Bio-micro-electro-mechanical systems (BioMEMS). Two types of surface modifications were explored. The first involved the deposition of nano-scale biocompatible layers of pure titanium on silicon, while the second explored the covalent attachment of the binding peptide Argenine–Glycine–Aspartic acid (RGD) for improved cell adhesion. Improvements in biocompatibility were assessed through examination of cell areas after culture, as well as the measurements of adhesion strengths, as determined by shear assay techniques. The titanium nanolayers and the RGD coating resulted in improvements in biocompatibility. Increased cell spreading areas and improved adhesion strength were obtained from short and long-term studies of Human Osteosarcoma (HOS) cells cultured on the coated surfaces. RGD functionalization resulted in the greatest improvement in cell spreading area and adhesion strength for short culture times. The effects of the titanium, while less than those of RGD for short culture times, appeared to be greater after 48 h of culture.     

Jet printing of colloidal solutions – Numerical modeling and experimental verification of the influence of ink and surface parameters on droplet spreading

Ink jet printing of functional materials promises an efficient route for the manufacturing of future low cost and large-area electronics applications. The effect of capillary flow of thin liquid films, the control of droplet spreading by suitably influencing the wetting properties of surfaces, the rheology of the ink and the process design play a relevant role in improvement of ink jet printed patterns. This work presents the experimentally based numerical study of the shape of single ink jetted droplets controlled by homogeneous contact angle distributions. The dynamics of the fluid on the substrate surface is treated in the frame of the lubrication theory using the concept of a precursor film and modeling the equilibrium contact angle by a disjoining pressure. The model describes the spreading of axisymmetric droplets considering different material and process parameter configurations. It is shown that the spreading process can be modeled separately from the drying process within a certain range of contact angles.