Effect of thermoplastic morphology on mechanical properties in laser-assisted joining of polyamide 6 with aluminum

This paper examined the joining zone between semi-crystalline polyamide 6 and aluminum EN AW 6082 in laser-based joining and evaluated the mechanical properties of the joint. The joint tests were carried out in overlap configuration and a characterized in terms of energy per unit length. The mechanical properties were examined to the point of cohesive failure. An increasing energy per unit length resulted in a reduced crosshead displacement in short-term testing and a decreased fatigue strength. Further material testing was carried out locally at various positions within the joining zone. The mechanical properties were correlated with results of a hardness test, thermoplastic morphology, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). By combining the findings with heat-treated samples at elevated temperatures, secondary crystallization was identified and evidenced as a primary effect among the changes in mechanical properties due to the heat treatment of the thermoplastic material

Deformation behavior of gold/copper multilayer systems

Two sets of Au/Cu multilayers with a total thickness of 2 µm were deposited with magnetron sputtering onto Si/SiO2 with an individual layer thickness of 250 nm and 25 nm. Subsets of the samples were treated with rapid thermal annealing (RTA) at temperatures of 300°C and 400°C for 60 s each to allow inter-diffusion and alloying at the Au/Cu interfaces. The mechanical behavior was evaluated by nanoindentation with a Vickers indenter at maximum loads of 20 mN to 500 mN. Cross sections of the nanoindentations were prepared by focused ion beam technique to investigate the deformation phenomena of the multilayer structure by scanning electron microscopy. In comparison of both, the 25 nm and the 250 nm structure, respectiveley, the latter shows a delamination near the indenter edge normal vector to the substrate surface, whereas the thin layers show buckling and shear banding as deformation mechanisms and no delamination occurs. The Martens hardness HM determined at a depth of 10 % of the total multilayer thickness increases from 1.8 GPa to 2.2 GPa with the annealing at 300°C for the 250 nm layers and to 2.9 GPa with the reduction of the layer thickness to 25 nm. X-ray diffraction patterns reveal a strong texture in \u3c111\u3e direction normal to the substrate surface and the formation of a Au-Cu solid solution phase during annealing. The decrease in individual layer thickness leads to a classic increase of the Martens hardness due to dislocation pile-up and a significant change in deformation behavior from dislocation plasticity to shear banding, which Li et al. [1] describe as buckling-assisted grain boundary sliding. After annealing, a notable increase of the hardness is observed for the 250 nm layers, while for the 25 nm layers it does not change significantly. Subsequent TEM investigations shall provide information on the processes in the layers and at the layer interfaces. Please click Additional Files below to see the full abstract

Ti3SiC2-formation during Ti–C–Si multilayer deposition by magnetron sputtering at 650 °C

Titanium Silicon Carbide films were deposited from three separate magnetrons with elemental targets onto Si wafer substrates. The substrate was moved in a circular motion such that the substrate faces each magnetron in turn and only one atomic species (Ti, Si or C) is deposited at a time. This allows layer-by-layer film deposition. Material average composition was determined to Ti0.47Si0.14C0.39 by energy-dispersive X-ray spectroscopy. High-resolution transmission electron microscopy and Raman spectroscopy were used to gain insights into thin film atomic structure arrangements. Using this new deposition technique formation of Ti3SiC2 MAX phase was obtained at a deposition temperature of 650 °C, while at lower temperatures only silicides and carbides are formed. Significant sharpening of Raman E2g and Ag peaks associated with Ti3SiC2 formation was observed

Silicon carbide formation in reactive silicon-carbon multilayers

An alternative low thermal budget silicon carbide syntheses route is presented. The method is based on self-propagating high-temperature synthesis of binary silicon-carbon-based reactive multilayers. With this technique, it is possible to obtain cubic polycrystalline silicon carbide at relatively low annealing temperatures by a solid state reaction. The reaction starts above 600 °C. The transformation process proceeds in a four-step process. The reaction enthalpy was determined to be (-70 ± 4) kJ/mol

Robert Bosch Stiftung - Kooperation der Gesundheitsberufe : die Idee des Memorandums

Die Aufgaben der Gesundheitsversorgung wurden mit dem zunehmenden Alter der Patienten, dem gewandelten Krankheitsspektrum, aber auch durch die geänderten Bedürfnisse der Nutzer sowie den verstärkten Einsatz von Medizintechnik immer aufwändiger und komplexer. Arbeitsteilung, Fragmentierung und Spezialisierung waren über viele Jahre unsere Antworten auf solche Herausforderungen. Den Effekt dieses vermeintlichen Fortschritts formulierte Hans Georg Gadamer (1994) in einem Aufsatz zum Thema „Über die Verborgenheit der Gesundheit“: „So viel ist jedenfalls klar“, schreibt er, der Begriff der „Ganzheit“ ist ein kunstvoller Ausdruck – der durch seinen Gegenbegriff, die „Spezialisierung“, überhaupt erst „notwendig […] geworden ist“. Hier setzt unser Memorandum an, es will einen Beitrag auf dem Weg zurück in die Zukunft einer neuen Ganzheit der Gesundheitsversorgung leisten