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 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 U6 - 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 - TY - JOUR A1 - Dombrowski, Felix A1 - Hoffmann, Rita A1 - Ploska, Ute A1 - Marx, Heidi A1 - Berger, Georg T1 - Investigations on degradable and figuline calcium alkaline phosphate cements with multimodal particle size distribution N2 - The paper presented here deals with rheological and hardening properties during the setting reaction, and density and compressive strength after the final setting of a figuline composite consisting of Ca2KNa(PO4)2 and 2wt% medium gel strength gelatin. Compared to the composite with monomodal particle size distribution (d50=7.18µm; span=3.9) and its properties during and after setting reaction, the goal of this work is to increase the resulting product compressive strength by mixing different particle sizes in order to obtain bi- and trimodal distributions. For the bimodal powder mixtures the ratio in diameter (dcourse/dsmall) was chosen with 7/1 and volume ratio dcourse/dsmall was 70/30%. For the trimodal powder mixtures the ratio in diameter (dcourse/dmedium/dsmall) was chosen with 70/7/1 and volume ratio dcourse/dmedium/dsmall was set to 44/28/28%.After establishing an adequate crushing and sieving process the tap density and powder density of each fraction was determined. Subsequently, the different particle sizes were mixed and the densities and the Hausner ratio were determined again. The mixtures show an increase in both densities especially the tap density increased significantly. Rheological investigations show that the graphs of storage and loss moduli of the multimodal powder mixtures respectively are similar. The characteristic setting times show a slight decrease compared with the monomodal composite but not significantly different data. When comparing the resulting compressive strength of cylindrical samples, which were stored direct after reaching the initial setting time under physiological conditions, the studies illustrated in all cases for the multimodal mixtures a significant increase in compressive strength and a higher density. KW - Calcium alkaline phosphate cement KW - Gelatin KW - Compressive strength KW - Figuline KW - Particle size PY - 2012 U6 - https://doi.org/10.4028/www.scientific.net/KEM.493-494.355 SN - 1013-9826 VL - 493-494 SP - 355 EP - 360 PB - Trans Tech Publ. CY - Aedermannsdorf AN - OPUS4-24925 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dombrowski, Felix A1 - Marx, Heidi A1 - Ploska, Ute A1 - Nicolaides, Dagmar A1 - Stiller, M. A1 - Knabe, C. A1 - Berger, Georg T1 - Solubility and ingrowth behaviour of degradable and figuline calcium alkaline phosphate cements N2 - The thrust of the investigations presented here is to point out the degradation behaviour in vitro and the ingrowth behaviour in vivo of four different calcium alkaline phosphate cements. Two of the figuline and mouldable composites consist of the crystalline phase Ca2KNa(PO4)2 and two of the crystalline phase Ca10[K/Na](PO4)2 each containing 2wt% medium gel strength porcine gelatin. Furthermore A-TCP was added to both Ca10[K/Na](PO4)2 cements as a hardening supporting reactant. The testing material groups differ in small amorphous portions containing either silica phosphate (GB9), magnesium potassium phosphate (GB14) or diphosphates (401545 and 401545(70)). The respective composites show a monomodal particle size distribution (d50~7µm; span~4) and an average total porosity around 28vol%.For the solubility studies cylindrical samples (d=6mm; h=12mm) were stored in a 0.1mol TRIS buffer solution and incubated at 37°C for maximum 50 weeks. The storage solution was analysed and renewed every week. The results are plotted cumulative. For the in vivo studies critical size defects were dissected to mandibles in a sheep model in which a 1cm³ area of the bottom of the mandibles was surgically resected and replaced with the figuline cements whereas the mouldability allows the reconstruction of the original outer contour without draining off even when replacing upside down. KW - Calcium alkaline phosphate cement KW - Gelatin KW - Figuline KW - Solubility KW - Ingrowth behavior PY - 2012 U6 - https://doi.org/10.4028/www.scientific.net/KEM.493-494.387 SN - 1013-9826 VL - 493-494 SP - 387 EP - 390 PB - Trans Tech Publ. CY - Aedermannsdorf AN - OPUS4-24924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marx, Heidi A1 - Berger, Georg A1 - Breitwieser, M. T1 - Prüftechnik für anorganischen Biozement KW - Gillmoore-Needle-Test KW - Initiale Abbindezeit KW - Finale Abbindezeit KW - Härtetest KW - Biozemente PY - 2007 SN - 0016-3538 VL - 51 IS - 2 SP - 106 EP - 108 PB - GIT-Verlag CY - Darmstadt AN - OPUS4-14582 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Berger, Georg A1 - Gildenhaar, Renate A1 - Pauli, Jutta A1 - Marx, Heidi T1 - Preparation and Characterization of New Self-Setting Calcium Phosphate Cements Based on Alkali Containing Orthophosphates KW - P-31-NMR Investigation KW - Ca2KNa(PO4)2 KW - Calcium Alkali Orthophosphates KW - Calcium Phosphate Cement KW - Self-Setting Cement PY - 2005 SN - 1013-9826 VL - 284-286 SP - 121 EP - 124 PB - Trans Tech Publ. CY - Aedermannsdorf AN - OPUS4-5493 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -