Ink jet printing techniques are applied with an increasing number of materials. In particular, solid freeform fabrication (SFF) methods for ceramic materials have attracted great interest in recent years. Methods such as stereo lithography, selective laser sintering and three dimensional printing produce complex geometries or parts with material gradients directly from a digital model.
The technological approach for such production methods can be divided into two categories: direct ceramic ink jet printing and three dimensional printing. In the former, an ink containing ceramic particles is printed onto a substrate and part build-up is conducted through stacking of printed layers. In the latter, binder solutions are printed into a powder bed and bind the loose powder.
Now, D. A. Polsakiewicz and W. Kollenberg at the Bonn-Rhine-Sieg University of Applied Science in Germany have investigated inks for application in a piezoelectric print head with high solid content. They prepared and characterized alumina inks and examined the influence of different solid loadings, dispersant concentrations and binding agents. Their paper appears in Materials Science and Engineering Technology (doi:10.1002/mawe.201100780).
Polsakiewicz and Kollenberg found that a binary mixture of water and ethylene glycol can serve as a solvent system for alumina particles and solvent properties can be adjusted by varying composition. As their results reveal, viscosity as well as shear-thinning behavior increased with raising solid content. Rheological behavior of the inks was not affected by small changes in particle size or specific surface area. However, surface tension values varied depending on the powder used. Supplementary experiments are necessary to confirm and understand these results.
Moreover, further printing experiments are essential for clarification of an interesting assumption. The researchers suppose that higher solid loadings could also be possible without increasing the viscosity. But attention must be given to increasing shear-thinning characteristics for higher solid loadings.
Martin Grolms is a writer for MaterialsViews.com