TY - JOUR A1 - Zocca, Andrea A1 - Franchin, Giorgia A1 - Elsayed, Hamada A1 - Gioffredi, Emilia A1 - Bernardo, Enrico A1 - Colombo, Paolo T1 - Direct Ink Writing of a Preceramic Polymer and Fillers to Produce Hardystonite (Ca2ZnSi2O7) Bioceramic Scaffolds JF - Journal of the American Ceramic Society N2 - The direct ink writing of an ink composed of a preceramic polymer and fillers was used to produce hardystonite (Ca2Zn-Si2O7) bioceramic scaffolds. Suitable formulations were developed for the extrusion of fine filaments (350 µm diameter) through a nozzle. The preceramic polymer was employed with the double purpose of contributing to the rheology of the ink by increasing its viscosity and of forming the hardystonite phase upon heat treatment by reacting with the fillers. A control of the rheology is essential when spanning features have to be produced, and therefore the main rheological characteristics of the inks were measured (flow curves, dynamic oscillation tests, viscosity recovery tests) and compared to models reported in the literature. Highly porous scaffolds (up to 80% total porosity) were produced and heat treated in air or in nitrogen atmosphere. The influence of the heat-treatment atmosphere on the morphology, crystalline phase assemblage, and compressive strength of the scaffolds was investigated. KW - Porous materials KW - Bioceramics KW - Polymer precursor KW - Processing PY - 2016 DO - https://doi.org/10.1111/jace.14213 VL - 6 IS - 99 SP - 1960 EP - 1967 PB - Wiley-Blackwell AN - OPUS4-38114 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Elsayed, H. A1 - Zocca, Andrea A1 - Franchin, G. A1 - Bernardo, E. A1 - Colombo, P. T1 - Hardystonite bioceramics from preceramic polymers JF - Journal of the European Ceramic Society N2 - In this work, we demonstrated that the hardystonite (Ca2ZnSi2O7) bioceramics can be produced withhigh phase purity, starting from different preceramic polymers and suitable fillers (precursors for CaOand ZnO) after heating at 1200◦C in air. Open-celled hardystonite foams were easily prepared from a filler-containing silicone resin using hydrazine as foaming agent. The fabrication of cellular structures using a preceramic polymer and fillers was possible because the polymeric melt allowed for the entrapment of the gases generated by the decomposition of hydrazine, and the simultaneous cross-linking of the preceramic polymer enabled the retention of the foam structure. Samples with a well-developed hierarchical porous structure, with an open porosity ranging from ∼65 to ∼81 vol% and an average cell window size ranging from 150 to 500 µm were produced. The hardystonite components possessed a compressive strength ranging from ∼1.4 to ∼2.1 MPa. KW - Bioceramics KW - Silicate KW - Hardystonite KW - Preceramic Polymers PY - 2016 DO - https://doi.org/10.1016/j.jeurceramsoc.2015.10.034 SN - 0955-2219 VL - 2016/36 SP - 829 EP - 835 PB - Elsevier Ltd. AN - OPUS4-37445 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zocca, Andrea A1 - Gomes, Cynthia A1 - Linow, Ulf A1 - Marx, Heidi A1 - Melcher, J A1 - Colombo, P A1 - Günster, Jens T1 - Structural optimization of printed structures by self-organized relaxation JF - Rapid Prototyping Journal N2 - Purpose – This paper aims to present an additive manufacturing-based approach in which a new strategy for a thermally activated local melting and material flow, which results in densification of printed structures, is introduced. Design/methodology/approach – For enabling this self-organized relaxation of printed objects by the viscous flow of material, two interconnected structures are printed simultaneously in one printing process, namely, Structure A actually representing the three dimensional object to be built and Structure B acting as a material reservoir for infiltrating Structure A. In an additional process step, subsequent to the printing job, an increase in the objects’ temperature results in the melting of the material reservoir B and infiltration of structure A. Findings – A thermally activated local melting of the polymethylsilsesquioxane results in densification of the printed structures and the local formation of structures with minimum surface area. Originality/value – The present work introduces an approach for the local relaxation of printed three-dimensional structures by the viscous flow of the printed material, without the loss of structural integrity of the structure itself. This approach is not restricted only to the materials used, but also offers a more general strategy for printing dense structures with a surface finish far beyond the volumetric resolution of the 3D printing process. KW - Printing KW - 3D PY - 2016 DO - https://doi.org/10.1108/RPJ-07-2014-0087 SN - 1355-2546 VL - 22 IS - 2 SP - 344 EP - 349 PB - Emerald AN - OPUS4-37447 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -