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In the last decade, microsystem engineering has rapidly developed. Nowadays microsystems have a very broad scope of applications, which range from electronics and aerospace to chemistry, optics, biology and medicine. Within this framework, the joining technique plays a crucial role. Therefore the development of new concepts for joining hybrid microstructures is one of the main tasks within the collaborative research center, assembly of hybrid microsystems. Active soldering and transient liquid phase (TLP) bonding processes are two innovative and trend-setting technologies in the field of joining dissimilar materials and have been specifically adapted to the requirements of the microsystems. IntroductionThe use of innovative materials and the adaptation of manufacturing methods in the field of microcomponents has contributed vastly to the enormous success of microsystem engineering. Within this framework the fabrication of hybrid structures is receiving increasingly more interest.The joining processes used at present in microsystem engineering are strongly limited concerning the number of suitable joining materials, as well as their use at higher temperatures. The two processes active soldering and transient liquid phase (TLP) bonding are innovative and ground-breaking in the field of joining dissimilar materials [1,2,5].In order to overcome the restrictions of common joining processes of hybrid microcomponents, these bonding techniques have been transferred from the macro-into the microtechnology and adapted to the special requirements of the microsystems. For this purpose, new filler metals have been developed and produced, which are constantly optimised and modified according to the specific requirements of the microstructures being joined.Investigated filler metals have been evaluated and characterized with regard to fundamental parameters in the field of microsystem technology. One of these parameters is the process temperature, since too high soldering temperatures are disadvantageous for numerous applications in the microtechnology.Regarding the mechanical characteristics of the filler metals, not only the strength has been particularly considered but also the ductility of the joint. Moreover, the material behaviour regarding chemical attack has been examined and evaluated for possible areas of improvement. Objectives and methodology Active soldersActive solders are metallic alloys, which contain ''surface active'' elements (e.g. titanium, zirconium) in small quantities, able to reduce the surface energy between nonmetallic material and molten filler metal, thus improving the wetting behaviour.On the contrary to the usual active filler metals, which require a minimum process temperature of 850°C and must be used either under vacuum or in inert gas atmosphere, the active solders can wet metallic and nonmetallic substrates in an air atmosphere in a temperature range of 200°C-400°C.This extraordinary result is due to traces of rare earth metals (cerium, praseodymium, neodymium), which are alloyed in the matrix...

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Quasicrystalline phases improve many alloy properties such as thermomechanical stability, thermal and electrical conductivity, and tribological performance. High hardness, however, is accompanied by brittleness, an undesired property in many applications. Reduced brittleness can be achieved by embedding quasicrystalline phases in a more ductile material, forming a metal-matrix composite that retains some quasicrystalline properties. This study evaluates thermally sprayed coatings made from different compositions of such composites. The coatings assessed were produced by arc-wire, HVOF, and atmospheric plasma spraying using various forms of feed material, including blended, agglomerated, chemical encased, and attrition-milled powders and filled wires. The investigation involved metallurgical analysis, proving the existence of quasicrystal content and assessing the matrix phase, and tests showing how sliding wear is influenced by the composition of quasicrystalline phases.