TY - JOUR A1 - Fritsch, Tobias A1 - Kurpiers, J. A1 - Roland, S. A1 - Tokmoldin, N. A1 - Shoaee, S. A1 - Ferron, T. A1 - Collins, B. A. A1 - Janietz, S. A1 - Vandewal, K. A1 - Fritsch, D. T1 - On the Interplay between CT and Singlet Exciton Emission in Organic Solar Cells with Small Driving Force and Its Impact on Voltage Loss N2 - The interplay between free charge carriers, charge transfer (CT) states and singlet excitons (S1) determines the recombination pathway and the resulting open circuit voltage (VOC) of organic solar cells. By combining a well-aggregated low bandgap polymer with different blend ratios of the fullerenes PCBM and ICBA, the energy of the CT state (ECT) is varied by 130 meV while leaving the S1 energy of the polymer (ES1) unaffected. It is found that the polymer exciton dominates the radiative properties of the blend when ECT approaches ES1, while the VOC remains limited by the non-radiative decay of the CT state. It is concluded that an increasing strength of the exciton in the optical spectra of organic solar cells will generally decrease the non-radiative voltage loss because it lowers the radiative VOC limit (VOC,rad), but not because it is more emissive. The analysis further suggests that electronic coupling between the CT state and the S1 will not improve the VOC, but rather reduce the VOC,rad. It is anticipated that only at very low CT state absorption combined with a fairly high CT radiative efficiency the solar cell benefit from the radiative properties of the singlet excitons. KW - Organic Solar Cell KW - Open Circuit Voltage KW - Voltage Loss KW - Ternary PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552518 DO - https://doi.org/10.1002/aenm.202200641 SN - 1614-6832 SP - 1 EP - 11 PB - Wiley-VCH CY - Weinheim AN - OPUS4-55251 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Vermesan, O. A1 - Blystad, L.-C. A1 - Bahr, R. A1 - Froelich, B. A1 - Ullate, L.G. A1 - Martinez, O. A1 - Fritsch Yusta, C. A1 - Guey, J.-L. A1 - Fleury, G. A1 - Liang, K. A1 - Mercier, D. A1 - Schoeb, P. A1 - Mc Hugh, Jarlath T1 - High temperature phased array ultrasonic system with integrated front end electronics T2 - IEEE Ultrasonics Symposium CY - Rotterdam, Netherlands DA - 2005-09-18 PY - 2005 SN - 0-7803-9382-1 VL - 1 SP - 186 EP - 189 PB - IEEE Operations Center CY - Piscataway, NJ AN - OPUS4-10993 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Winkler, T. A1 - Hoenig, E. A1 - Huber, G. A1 - Janssen, R. A1 - Fritsch, D. A1 - Gildenhaar, Renate A1 - Berger, Georg A1 - Morlock, M.M. A1 - Schilling, A.F. T1 - Osteoclastic bioresorption of biomaterials: Two- and three-dimensional imaging and quantification N2 - Purpose: Bioresorbable materials have been developed in the hope that the body will replace them with newly formed tissue. The first step of this remodeling process in bone is the bioresorption of the material by osteoclasts. The aim of this study was to analyze osteoclastic resorption of biomaterials in vitro using the commonly used two-dimensional methods of light-microscopy (LM) and scanning electron microscopy (SEM) in comparison with infinite focus microscopy (IFM), a recently developed imaging method allowing for three-dimensional surface analysis. Methods: Human hematopoietic stem cells were cultivated in the presence of the cytokines M-CSF and RANK-L for 4 weeks directly on dentin and a calcium phosphate cement. Osteoclast development was surveyed with standard techniques. After removal of the cells, resorption was characterized and quantified by LM, SEM and IFM. Results: Osteoclast cultures on the biomaterials presented the typical osteoclast-specific markers. On dentin samples LM, SEM as well as IFM allowed for discrimination of resorption. Quantification of the resorbed area showed a linear correlation between the results (LM vs. SEM: r=0.996, p=0.004; SEM vs. IFM: r=0.989, p=0.011; IFM vs. LM: r=0.995). It was not possible to demarcate resorption pits on GB14 using LM or SEM. With IFM, resorption on GB14 could be visualized and quantified two- and three-dimensionally. KW - Biomaterial KW - Three-dimensional KW - IFM KW - Osteoclast KW - Dentin KW - Calcium phosphate PY - 2010 SN - 0391-3988 VL - 33 IS - 4 SP - 198 EP - 203 PB - Wichtig Ed. CY - Milano [u.a.] AN - OPUS4-21621 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Winkler, T. A1 - Hoenig, E. A1 - Gildenhaar, Renate A1 - Berger, Georg A1 - Fritsch, D. A1 - Janssen, R. A1 - Morlock, M.M. A1 - Schilling, A.F. T1 - Volumetric analysis of osteoclastic bioresorption of calcium phosphate ceramics with different solubilities N2 - Commonly, to determine osteoclastic resorption of biomaterials only the resorbed area is measured. The depth of the resorption pit, however, may also be important for the performance of a material. To generate such data we used two calcium phosphate ceramics (Ca10 and Ca2). The solubility of the materials was determined according to DIN EN ISO 10993-14. They were scanned three-dimensionally using infinite focus microscopy and subsequently cultivated for 4 weeks in simulated body fluid without (control) or with human osteoclasts. After this cultivation period osteoclasts number was determined and surface changes were evaluated two- and three-dimensionally. Ca10 and Ca2 showed solubilities of 11.0 ± 0.5 and 23.0 ± 2.2 mg g-1, respectively. Both materials induced a significant increase in osteoclast number. While Ca10 did not show osteoclastic resorption, Ca2 showed an increased pit area and pit volume due to osteoclastic action. This was caused by an increased average pit depth and an increased number of pits, while the average area of single pits did not change significantly. The deduced volumetric osteoclastic resorption rate (vORR) of Ca2 (0.01–0.02 µm3 µm-2 day-1) was lower than the remodelling speed observed in vivo (0.08 µm3 µm-2 day-1), which is in line with the observation that implanted resorbable materials remain in the body longer than originally expected. Determination of volumetric indices of osteoclastic resorption might be valuable in obtaining additional information about cellular resorption of bone substitute materials. This may help facilitate the development of novel materials for bone substitution. KW - Biodegradation KW - Surface analysis KW - Simulated body fluid KW - Osteoclasts KW - Calcium phosphate ceramics PY - 2010 DO - https://doi.org/10.1016/j.actbio.2010.04.015 SN - 1742-7061 VL - 6 IS - 10 SP - 4127 EP - 4135 PB - Elsevier CY - Amsterdam AN - OPUS4-22554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano Munoz, Itziar A1 - Fritsch, Tobias A1 - Mishurova, Tatiana A1 - Trofimov, Anton A1 - Apel, D. A1 - Ulbricht, Alexander A1 - Kromm, Arne A1 - Hesse, René A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - On the interplay of microstructure and residual stress in LPBF IN718 N2 - The relationship between residual stresses and microstructure associated with a laser powder bed fusion (LPBF) IN718 alloy has been investigated on specimens produced with three different scanning strategies (unidirectional Y-scan, 90° XY-scan, and 67° Rot-scan). Synchrotron X-ray energy-dispersive diffraction (EDXRD) combined with optical profilometry was used to study residual stress (RS) distribution and distortion upon removal of the specimens from the baseplate. The microstructural characterization of both the bulk and the nearsurface regions was conducted using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). On the top surfaces of the specimens, the highest RS values are observed in the Y-scan specimen and the lowest in the Rot-scan specimen, while the tendency is inversed on the side lateral surfaces. A considerable amount of RS remains in the specimens after their removal from the baseplate, especially in the Y- and Z-direction (short specimen Dimension and building direction (BD), respectively). The distortion measured on the top surface following baseplate thinning and subsequent removal is mainly attributed to the amount of RS released in the build direction. Importantly, it is observed that the additive manufacturing microstructures challenge the use of classic theoretical models for the calculation of diffraction elastic constants (DEC) required for diffraction-based RS analysis. It is found that when the Reuß model is used for the calculation of RS for different crystal planes, as opposed to the conventionally used Kröner model, the results exhibit lower scatter. This is discussed in context of experimental measurements of DEC available in the literature for conventional and additively manufactured Ni-base alloys. KW - L-PBF IN718 material KW - Effect of scanning strategies KW - Near-surface X-ray diffraction KW - Residual stress in AM KW - Distortion upon baseplate removal PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-519460 DO - https://doi.org/10.1007/s10853-020-05553-y SN - 0022-2461 VL - 56 IS - 9 SP - 5845 EP - 5867 PB - Springer AN - OPUS4-51946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silvestroni, L. A1 - Kupsch, Andreas A1 - Müller, B. R. A1 - Ulbricht, Alexander A1 - Wieder, Frank A1 - Fritsch, Tobias A1 - Sciti, D. A1 - Bruno, Giovanni T1 - Determination of short carbon fiber orientation in zirconium diboride ceramic matrix composites N2 - In fiber-reinforced components, the fiber alignment and orientation have paramount influence on the thermomechanical properties of the resulting composite, for both short and continuous fiber. Here we present the case of an ultra-refractory matrix intended for extreme environment applications, ZrB2, reinforced with 20 vol% and 50 vol% short carbon fibers. In both cases, fibers tend to align perpendicular to the uniaxial pressure applied during shaping and sintering of a pellet, although the fiber tilt across the pellet thickness is difficult to determine. Moreover, for high volume fractions of reinforcement, the spatial distribution of the fibers is heterogeneous and tends to have domains of preferential orientations. We compare the information on the fiber distribution as collected by scanning electron microscopy images, X-ray computed tomography and synchrotron X-ray refraction radiography (SXRR). The three techniques prove to be complementary. Importantly, we demonstrate that SXRR yields the most statistically significant information due to the largest field of view, yet with a sensitivity down to the nanometer, and that can be successfully applied also to heavy matrix materials, such as zirconium boride. KW - Ceramic matrix composites KW - Synchrotron X-ray refraction radiography KW - X-ray computed tomography KW - Scanning electron microscopy KW - High-temperature ceramics PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597712 DO - https://doi.org/10.1016/j.jeurceramsoc.2024.02.048 SN - 0955-2219 VL - 44 IS - 8 SP - 4853 EP - 4862 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-59771 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -