Fabrication of nanoparticle-containing films and nano layers for alloying and joining
Nanoparticles (NPs) can improve mechanical properties of construction elements. However, the integration is not trivial due to the nanoscopic nature of the particles and the different material properties of particle and device: new processing routes have to be found for homogeneous incorporation. Therefore, a wet chemical synthesis is established to incorporate various ceramic NPs such as TiO2, TiC, SiC, and WC in copper films in desired concentrations. Depending on the kind and concentration of NPs, hardness and wear resistance of copper are enhanced. The resulting metal matrix composite films are thus of high interest for various applications such as reinforced electrical contacts and in aerospace and automotive technology. The energy released in an exothermic reaction of a reactive multilayer system (RMS) can be used as a precise and well-defined local heat source for joining the surface of polymers. In this case, a RMS consisting of alternating layers of nickel and aluminum is used. The design of the RMS is adjusted in a way that despite the intensive but very short reaction no damaging of the polymers occurs. The joining process takes only milliseconds and does not require any pre- or post-treatment of the polymers. With the optimal joining parameters, e.g., the joining load, for fiber non-reinforced polymers tensile strengths can be achieved, which lead to a material failure by tensile attempts. Preliminary tests of fiber reinforced polymers result in a tensile strength that is characteristic for adhesive polymer bonding. Model simulations show that only the first few micrometers of the materials surface are in a liquid state for a very short period of time. In addition to the applied joining load, the materials composition and specifically the resulting solidification process of the liquid polymer phase result in a strong bond between polymer samples that have to be joined. Materials with different thermal expansion coefficients are difficult to join thermally. Among them is the joining of solar cells. It is conventionally carried out by heating the whole assembly. Due to the thermal differences between tabbing wire and silicon, deformations as well as changes in the microstructure can occur. In the worst case, damage of the whole assembly is possible. Upon inspection of the joining process, the high energy consumption of the process itself is also critical.