Ink jet printing techniques are used for an increasing number of materials and applications. Properties of the used inks have great influence on process stability and accuracy as well as the resulting part properties. Inks containing ceramic particles have been applied in various studies and applications. The criteria identifying suitable inks vary depending on the applied printing technology. In this study, inks for application in a piezoelectric print head were investigated. Alumina inks with solid loadings up to 21 vol.-% were prepared and characterized. The Influence of different solid loadings, dispersant concentrations and binding agents was examined. The prepared inks show sufficient stability and fit literature recommendations for successful drop ejection. Considering rheological aspects, two inks with light shear-thinning behaviour and viscosities of 18 mPas and 23 mPas at high shear rates were recommended for upcoming printing tests. The Re/We 1/2 ratio can be used for predetermination of print ability but the influence of the surface tension is not sufficiently taken into account using the presented calculations. So further printing experiments are essential for clarification of the calculations and obtained print ability values. Keywords: Suspension / particle processing / materials processing / rheology / alumina /
Inkjet printing of conductive silver lines on solid or flexible substrates for the fabrication of electronic components has been reported in a variety of ways over more than the last decade. Numerous publications highlight the importance of the silver source for the feasibility of the process as well as the resulting properties of the printed structures. In previous work [1] we reported the first experimental attempt to realize such conductive silver components inside a structure printed with a custom three dimensional powder printer. Aim of this study was to combine the functionality of directly printed functional elements with the geometrical flexibility of powder-based three-dimensional printing. While functionality in the printed glass/metallic compound is achieved in principle, an inhomogeneous microstructure with differentiated silver and glass areas is observed. In this article the silver source for the printing process is varied in order to achieve a homogeneous compound in desired areas. Three different metallic sources were used, namely a diluted screen-printing paste, a silver nitrate solution and silver particles formed by a previously reported polyol process. Ink were formulated from mentioned silver sources and printed with a glass powder. The fabricated samples are investigated in terms of their microstructure evolution and part functionality. The microstructure evolution is discussed in regard to the selected silver source. Additionally, the thermal treatment of the structures is optimized in order to ensure the optimum microstructure and part functionality. The reported experiments present the further development for a unique and novel method for fabricating glass/metal compounds by powder-based three-dimensional printing, allowing for the expansion of the process into novel applications.
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