TY - JOUR A1 - Blaeß, Carsten A1 - Müller, Ralf T1 - Sintering and foaming of bioactive glasses N2 - Sintering, crystallization, and foaming of 44.8SiO2–2.5P2O3–36.5CaO–6.6Na2O–6.6K2O–3.0CaF2 (F3) and 54.6SiO2–1.7P2O3–22.1CaO–6.0Na2O–7.9K2O–7.7MgO (13–93) bioactive glass powders milled in isopropanol and CO2 were studied via heating microscopy, differential thermal analysis, vacuum hot extraction (VHE), Infrared spectroscopy, and time-of-flight secondary ion mass spectrometry. Full densification was reached in any case and followed by significant foaming. VHE studies show that foaming is driven by carbon gases and carbonates were detected by Infrared spectroscopy to provide the major foaming source. Carbonates could be detected even after heating to 750◦C, which hints on a thermally very stable species or mechanical trapping. Otherwise, dark gray compact colors for milling in isopropanol indicate the presence of residual carbon as well. Its significant contribution to foaming, however, could not be proved and might be limited by the diffusivity of oxygen needed for carbon oxidation to carbon gas. KW - Bioactive Glass KW - Crystallization KW - Foaming KW - Sintering PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-552454 SN - 0002-7820 SP - 1 EP - 11 PB - Wiley online library AN - OPUS4-55245 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Blaeß, Carsten A1 - Wilbig, Janka A1 - Müller, Ralf A1 - Nawaz, Q. A1 - Boccaccini, A.R. T1 - 3D printing of crystallizing bioactive glasses N2 - Artificial bone replacement by individual customized three-dimensional resorbable bioactive glass has not yet been widely established in the clinical use. This is mainly due to the antagonism of sintering ability and suitable bioactivity. Competitive crystallization often prevents the generation of dense sintered bodies, especially for additive manufactured 3D structures. Previous studies of the fluoride-containing glass F3 have shown its potential to combine both sintering ability and suitable bioactivity. Furthermore, the occurring sintering blockade by surface crystallization of Na2CaSi2O6 was tunable by glass particle size. In this study the glasses F3, F3-Cu with 1 mol% CuO added at the expense of CaO and the well-known 13-93 were chosen to determine the influence of surface crystallization on 3D printed sinter bodies. For this purpose, grain size fractions in range of smaller 32 µm to 315 µm in fraction size of 6-20 µm were sieved from jaw crushed glass frit as well as glass cubes were cut from casted blocks for all glasses. Sintering behavior of both pressed and printed powder compacts was observed via heating microscopy. Crystallization was determined by DTA and crystallization progress was monitored on fractured sinter bodies and polished cubes via electron and laser scanning microscopy as well as with diffractometry. Depending on grain size the formation of crystalline support framework along former grain boundaries shows the capability to stabilize fully densified sinter bodies before softening. Beside of this, the generation of complex hierarchic porosity was possible as well. T2 - ICG Berlin 2022 CY - Berlin, Germany DA - 03.07.2022 KW - Bioactive Glass KW - Crystallization KW - Sintering KW - 3D printing PY - 2022 AN - OPUS4-55253 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Blaeß, Carsten T1 - Viskose Rissschließung in Gläsern und Glasmatrixkompositen N2 - Um die Langzeitbeständigkeit von Hochtemperatur-Festoxidbrennstoffzellen (SOFC) sicherzustellen, ist das grundlegende Verständnis der viskosen Schließung oder Heilung von Rissen, als Folge wechselnder thermischer oder mechanischer Belastung, in Gläsern und teilkristallinen Materialien ein entscheidender Faktor. In Glas ist die Rissheilung hauptsächlich durch viskoses Fließen bestimmt. In teilkristallinen Schmelzen bewirkt der kristalline Volumenanteil die Erhöhung der effektiven Viskosität. Um die Auswirkungen des kristallinen Volumenanteils auf die Rissheilung zu ergründen, wurden Glasmatrixkomposite mit variierten inerten kristallinen Fülleranteilen, die während der Wärme-behandlung konstant blieben, hergestellt. Verwendet wurde ein kristallisationsträges Natrium-Calcium-Silicatglas und ZrO2 als inerter Füller. Komplexe, reproduzierbare Rissstrukturen wurden durch Vickers-Eindrücke erzeugt und die viskose Rissschließung während isothermer Wärmebehandlungs-schritte mittels Laser-Scanning-Mikroskopie verfolgt. Die Untersuchungen zeigen, dass, verglichen zum füllerfreien Glas, der kristalline Phasenanteil die effektive Viskosität erhöht und dadurch großräumiges Fließen verlangsamt. Dies verzögert das Aufweiten der Risse. Dieser Effekt erschwert die Rissverkürzung und führt oftmals zu großen gerundeten Kavitäten und dadurch zu einer verzögerten Rissschließung. Wird dieses Aufweiten verringert, ist zunächst ein lokales viskoses Fließen der Restglasphase weiterhin gegeben, sodass sich die Risse sogar schneller schließen. Für kristalline Anteile > 27 Vol% bildet sich dann ein stabiles Perkolationsgerüst aus, das die weitere Rissschließung auch lokal unterbindet. Nur innerhalb größerer glasiger Bereiche ist hierbei noch eine Rissschließung zu beobachten. Ein Optimum der Risslängenverkürzung konnte bei 17 Vol% beobachtet werden. T2 - 94. Glastechnische Tagung CY - Online meeting DA - 10.05.2021 KW - Glas KW - Hochtemperaturbrennstoffzelle KW - Glasmatrixkomposit KW - Rissheilung PY - 2021 AN - OPUS4-54245 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Blaeß, Carsten A1 - Müller, Ralf T1 - Master curve for viscous crack healing N2 - A novel method to generalize kinetic data of viscous crack healing in glasses is proposed. The method assumes that crack healing progress is proportional to the healing time, t, and indirect proportional to viscosity, n. This way, crack length and crack width data, normalized to the initial crack length and plotted versus t/n, allow to compare crack healing progress for different cracks and healing temperatures in a master curve. Crack healing experiments conducted in this study demonstrate the applicability of this method for a commercial microscope slide glass. KW - Crack healing KW - Glass KW - Master curve KW - Vickers indentation PY - 2018 U6 - https://doi.org/10.1016/j.matlet.2017.12.082 SN - 0167-577X SN - 1873-4979 VL - 216 SP - 110 EP - 112 PB - Elsevier AN - OPUS4-44300 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Blaeß, Carsten A1 - Müller, Ralf A1 - Feldmann, Ines A1 - Brauer, D.S. T1 - Sintering ability of fluoride-containing bioactive glass powder N2 - Sintered bioactive glass scaffolds of defined shape and porosity, e.g. made via additive manufacturing, must provide sufficient bioactivity and sinterability. As higher bioactivity is often linked to high corrosion and crystallization tendency, a certain compromise between sintering ability and bioactivity is therefore required. Groh et al. developed a fluoride-containing bioactive glass (F3), which allows fiber drawing and shows a bioactivity well comparable to that of Bioglass®45S5. To study whether and to what extent the sinterability of F3 glass powder is controlled by particle size, coarse and fine F3 glass powders (300-310µm and 0-32µm) were prepared by crushing, sieving and milling. Sintering, degassing and phase transformation during heating were studied with heating microscopy, vacuum hot extraction (VHE), DTA, XRD, and SEM. For the coarse glass powder, sintering proceeds slowly and is limited by surface crystallization of primary Na2CaSi2O6 crystals. Although the crystallization onset of Na2CaSi2O6 is shifted to lower temperature, full densification is attained for the fine powder. This finding indicate that certain porosity might be tuned via particle size variation. Above 900°C, intensive foaming is evident for the fine powder. VHE studies revealed that carbon species are the main foaming source. T2 - 92. Glastechnische Tagung CY - Bayreuth, Germany DA - 28.05.2018 KW - Sintering KW - Bioactive glass KW - Crystallization PY - 2018 AN - OPUS4-45568 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Blaeß, Carsten A1 - Müller, Ralf T1 - Effects of microstructure on crack healing in glass matrix composites N2 - Crack healing in glass ceramic solid oxide fuel cell (SOFC) sealants is of utmost importance as cracks caused by thermal cycling remain a bottleneck in developing durable SOFC. Whereas no or low crystal volume fraction seems most favorable for viscous crack healing, it does not for load bearing and undesired diffusion. On the other hand, crystals or filler particles can make the sealant less prone to these disadvantages but it could increase the effective composite viscosity and retard crack healing. Against this background, the influence of crystal volume fraction, phi, on viscous crack healing in glass matrix composites prepared from soda lime silicate glass and zirconia filler particles was studied. Vickers indention induced radial cracks were healed isothermally during interrupted annealing steps and monitored with optical microscopy. Due to the slow crystallization of the glass under study, phi could be kept constant during crack healing. For bulk glass samples (phi = =), the decrease in radial crack length was retarded by an initial increase in crack width due to crack rounding. Up to phi = 0.15 the increase in effective viscosity retarded this crack broadening thereby yielding faster crack healing. For phi > 0.15, crack broadening was progressively suppressed but the same was true for crack healing, which was fully prevented above phi = 0.3. Results indicate that optimum micro structures can prevent crack broadening limited by the global effective composite viscosity and this way promote crack healing limited by local glass viscosity. T2 - 93. Glastechnische Tagung CY - Nürnberg, Germany DA - 12.05.2019 KW - Crack healing KW - Glass matrix composite KW - Vickers indentation PY - 2019 AN - OPUS4-48543 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Blaeß, Carsten A1 - Müller, Ralf A1 - Poologasundarampilai, G. A1 - Brauer, D. S. T1 - Sintering and concomitant crystallization of bioactive glasses N2 - The sintering of bioactive glasses allows for the preparation of complex structures, such as three‐dimensional porous scaffolds. Such 3D constructs are particularly interesting for clinical applications of bioactive glasses in bone regeneration, as the scaffolds can act as a guide for in‐growing bone cells, allowing for good Integration with existing and newly formed tissue while the scaffold slowly degrades. Owing to the pronounced tendency of many bioactive glasses to crystallize upon heat treatment, 3D scaffolds have not been much exploited commercially. Here, we investigate the influence of crystallization on the sintering behavior of several bioactive glasses. In a series of mixed‐alkali glasses an increased CaO/alkali metal oxide Ratio improved sintering compared to Bioglass 45S5, where dense sintering was inhibited. Addition of small amounts of calcium fluoride helped to keep melting and sintering temperatures low. Unlike glass 13‐93, these new glasses crystallized during sintering but this did not prevent densification. Variation in bioactive glass particle size allowed for fine‐tuning the microporosity resulting from the sintering process. KW - Bioactive glass KW - Crystallization KW - Scaffolds KW - Sintering PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-485458 SN - 2041-1286 VL - 10 IS - 4 SP - 449 EP - 462 PB - Wiley AN - OPUS4-48545 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Blaeß, Carsten A1 - Müller, Ralf T1 - Viscous healing of Vickers indentation–induced cracks in glass N2 - AbstractViscous healing of cracks induced by the Vickers indentation in a soda lime magnesium silicate, a soda borosilicate, and a soda aluminosilicate glass (NAS) was studied by laser scanning microscopy. Plots of the crack length, width, and depth normalized to the initial crack length versus time over viscosity merge into single master curves of each of these quantities for each glass. Despite glass properties do not differ strikingly from each other, however, these master curves strongly differ among the glasses. This finding was attributed to a different interplay of various crack healing phenomena. Lateral cracks were found to be responsible for the bulging of the sample surface around the Vickers imprint, which in turn promotes radial crack widening as the main cause of healing delay. The most rapid healing of lateral cracks was observed in NAS in which bulging and crack widening were least pronounced. KW - Crack healing KW - Glass KW - Vickers indentation PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-587295 SN - 0002-7820 VL - 106 IS - 10 SP - 5795 EP - 5805 PB - Wiley AN - OPUS4-58729 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Blaeß, Carsten A1 - Müller, Ralf A1 - Boccaccini, A. R. T1 - Sintering and crystallization kinetics of bioactive glass 13-93 N2 - This study investigates the sintering and crystallization behavior and kinetic of the bioactive glass (BG) 13–93 with nominal composition (in mol%): 54.6 SiO2 - 1.7 P2O3 - 22.1 CaO - 6.0 Na2O - 7.9 K2O - 7.7 MgO. Sintering and crystallization were investigated non-isothermally for various particle size fractions smaller than 315 μm as well as for bulk samples. Densification was not hindered by the presence of crystalline phases across all particle size fractions. Afterwards, wollastonite was found as the dominant crystal phase at higher temperature which resorb primary surface precipitation-like quartz crystallites. The growth direction shifts into volume when the sample surface is nearly covered. The crystal growth rate of wollastonite was calculated from the crystalline surface layer thickness measured during heating. The findings of this study are relevant for the high temperature processing of BG 13–93. KW - Bioactive glass KW - Sintering KW - Crystallization PY - 2024 U6 - https://doi.org/10.1016/j.jnoncrysol.2023.122790 SN - 0022-3093 VL - 627 SP - 1 EP - 7 PB - Elsevier AN - OPUS4-59337 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nawaz, Q. A1 - Blaeß, Carsten A1 - Mueller, Ralf A1 - Boccaccini, A.R. T1 - Processing and cytocompatibility of Cu-doped and undoped fluoride-containing bioactive glasses N2 - Sintered or additive-manufactured bioactive glass (BG) scaffolds are highly interesting for bone replacement applications. However, crystallization often limits the high-temperature processability of bioactive glasses (BGs). Thus, the BG composition must combine high bioactivity and processability. In this study, three BGs with nominal molar (%) compositions 54.6SiO2-1.7P2O3-22.1CaO-6.0Na2O-7.9K2O-7.7MgO (13–93), 44.8SiO2-2.5P2O3-36.5CaO-6.6Na2O-6.6K2O-3.0CaF2 (F3) and 44.8SiO2-2.5P2O3-35.5CaO-6.6Na2O-6.6K2O-3.0CaF2-1.0CuO (F3–Cu) were investigated. The dissolution and ion release kinetics were investigated on milled glass powder and crystallized particles (500–600 μm). All glasses showed the precipitation of hydroxyapatite (HAp) crystals after 7 days of immersion in simulated body fluid. No significant differences in ion release from glass and crystalline samples were detected. The influence of surface roughness on cytocompatibility and growth of preosteoblast cells (MC3T3-E1) was investigated on sintered and polished BG pellets. Results showed that sintered BG pellets were cytocompatible, and cells were seen to be well attached and spread on the surface after 5 days of incubation. The results showed an inverse relation of cell viability with the surface roughness of pellets, and cells were seen to attach and spread along the direction of scratches. KW - Bioactive glass KW - Crystallization KW - Solubility KW - Cytocompatibility KW - Surface roughness PY - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-598257 SN - 2666-5395 VL - 18 SP - 1 EP - 8 PB - Elsevier Ltd. AN - OPUS4-59825 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -