TY - JOUR A1 - Westwood, S. A1 - Josephs, R. A1 - Choteau, T. A1 - Daireaux, A. A1 - Stoppacher, N. A1 - Wielgosz, R. A1 - Davies, S. A1 - do Rego, E. A1 - Wollinger, W. A1 - Garrido, B. A1 - Fernandes, J. A1 - Lima, J. A1 - Oliveira, R. A1 - de Sena, R. A1 - Windust, A. A1 - Huang, T. A1 - Dai, X. A1 - Quan, C. A1 - He, H. A1 - Zhang, W. A1 - Wei, C. A1 - Li, N. A1 - Gao, D. A1 - Liu, Z. A1 - Lo, M. A1 - Wong, W. A1 - Pfeifer, Dietmar A1 - Koch, Matthias A1 - Dorgerloh, Ute A1 - Rothe, Robert A1 - Philipp, Rosemarie A1 - Hanari, N. A1 - Rezali, M. A1 - Arzate, C. A1 - Berenice, M. A1 - Caballero, V. A1 - Osuna, M. A1 - Krylov, A. A1 - Kharitonov, S. A1 - Lopushanskaya, E. A1 - Liu, Q. A1 - Lin, T. A1 - Fernandes-Whaley, M. A1 - Quinn, L. A1 - Nhlapo, N. A1 - Prevoo-Franzsen, D. A1 - Archer, M. A1 - Kim, B. A1 - Baek, S. A1 - Lee, S. A1 - Lee, J. A1 - Marbumrung, S. A1 - Kankaew, P. A1 - Chaorenpornpukdee, K. A1 - Chaipet, T. A1 - Shearman, K. A1 - Gören, A. A1 - Gündüz, S. A1 - Yilmaz, H. A1 - Un, I. A1 - Bilsel, G. A1 - Clarkson, C. A1 - Bedner, M. A1 - Camara, J. A1 - Lang, B. A1 - Lippa, K. A1 - Nelson, M. A1 - Toman, B. A1 - Yu, L. T1 - Mass fraction assignment of folic acid in a high purity material - CCQM-K55.d (Folic acid) Final Report N2 - The comparison required the assignment of the mass fraction of folic acid present as the main component in the comparison sample. Performance in the comparison is representative of a laboratory's measurement capability for the purity assignment of organic compounds of medium structural complexity [molecular weight range 300–500] and high polarity (pKOW < −2). Methods used by the eighteen participating NMIs or DIs were based on a mass balance (summation of impurities) or qNMR approach, or the combination of data obtained using both methods. The qNMR results tended to give slightly lower values for the content of folic acid, albeit with larger associated uncertainties, compared with the results obtained by mass balance procedures. Possible reasons for this divergence are discussed in the report, without reaching a definitive conclusion as to their origin. The comparison demonstrates that for a structurally complex polar organic compound containing a high water content and presenting a number of additional analytical challenges, the assignment of the mass fraction content property value of the main component can reasonably be achieved with an associated relative standard uncertainty in the assigned value of 0.5% KW - CCQM key comparison KW - Purity assessment KW - Folic acid PY - 2018 UR - https://www.bipm.org/utils/common/pdf/final_reports/QM/K55/CCQM-K55.d.pdf DO - https://doi.org/10.1088/0026-1394/55/1A/08013 VL - 55 IS - Technical Supplement, 2018 SP - 08013, 1 EP - 38 PB - Institute of Physics Publishing (IOP) ; Bureau International des Poids et Mesures AN - OPUS4-44999 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, M. A1 - Zhang, T. A1 - Wang, J. A1 - Cheng, Z. A1 - Yang, J. A1 - Qiao, X. A1 - Wen, J. A1 - Resch-Genger, Ute A1 - Ou, J. T1 - Fluorescence temperature sensing of NaYF4:Yb3+/Tm3+@NaGdF4:Nd3+/Yb3+ nanoparticles at low and high temperatures N2 - NaYF4:Yb3+/Tm3+@NaGdF4:Nd3+/Yb3+ upconversion nanoparticles (UCNPs) were prepared using a solvothermal method, and the effects of key factors such as the content of sensitiser Nd 3+ and Yb3+ on their luminescence properties were investigated. The nanoparticles are homogeneous in size and well dispersed. Under 808 nm excitation, it can produce strong upconversion fluorescence. At the same time, the nanoparticles have good temperature-sensing properties at the thermally coupled energy levels of 700 nm and 646 nm for Tm3+. Using its fluorescence intensity ratio (FIR), accurate temperature measurements can be performed, and it has been found that it exhibits different temperature sensing properties in low and high-temperature regions. The maximum relative sensitivity was found to be 0.88% K-1 and 1.89% K-1 for the lowtemperature region of 285 K-345 K and the high-temperature region of 345 K-495 K. The nanoparticles were applied to the internal temperature measurement of lithium batteries and the actual high-temperature environment, respectively, and were found to have good temperature measurementt performance. KW - Fluorescence KW - Sensor KW - Temperature KW - Ratiometric KW - Lanthanide KW - Quantum yield KW - Integrating sphere spectroscopy KW - Absolute fluorescence KW - Quality assurance KW - Nano KW - Particle KW - Application KW - Upconversion nanoparticle PY - 2022 DO - https://doi.org/10.1088/1361-6528/ac84e4 SN - 1361-6528 VL - 33 IS - 34 SP - 1 EP - 15 PB - IOP Publishing CY - Bristol AN - OPUS4-55454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Li, Changchao A1 - Jin, Ling N. A1 - Bank, Michael S. A1 - Fan, Chunlan A1 - Gillings, Michael R. A1 - Zhao, Tingting A1 - Han, Yong A1 - Chen, Tian A1 - Gao, Meng A1 - Zhu, Dong A1 - Chen, Qinglin A1 - Zhu, Guibing A1 - Wang, Jie A1 - Wang, Lei A1 - Liu, Jian A1 - Yuan, Xianzheng A1 - Huang, Qishen A1 - Wang, Xiaofei A1 - Jahnke, Annika A1 - Brahney, Janice A1 - Allen, Steve A1 - Arp, Hans Peter H. A1 - Oberbeckmann, Sonja A1 - Bergmann, Melanie A1 - Pointing, Stephen B. A1 - Zhang, Daizhou A1 - Rillig, Matthias C. T1 - Potential planetary health impacts of the airborne plastisphere N2 - Microplastics are a ubiquitous yet long-overlooked component of airborne particulate matter. The surface of these plastic particles provides a unique niche for microorganisms, collectively known as the plastisphere. The plastisphere in aquatic and terrestrial ecosystems harbors microbial communities with distinct compositions, structures, and functional profiles, posing potential planetary health risks. The characteristics, fate, and impacts of the microbiome associated with airborne microplastics, however, remain largely unknown. In this review, we fill the knowledge gaps by exploring how airborne microplastics serve as key habitats for microorganisms and the potential planetary health implications. We show that microplastics are expected to carry and sustain microorganisms over long distances and timescales in air, potentially dispersing pathogens, antibiotic-resistance genes, and other bioactive agents across ecosystems. These interactions may perturb ecological processes and biological health on a planetary scale. Interdisciplinary research and innovative methodologies are urgently required to better understand and mitigate the airborne plastisphere risks. KW - Microplastics KW - Microbiome KW - Plastisphere PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-645551 DO - https://doi.org/10.1016/j.oneear.2025.101446 SN - 2590-3322 VL - 8 IS - 10 SP - 1 EP - 17 PB - Elsevier B.V. AN - OPUS4-64555 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vogel, F. A1 - Cheng, J. A1 - Liang, S. B. A1 - Ke, C. B. A1 - Cao, S. S. A1 - Zhang, X. P. A1 - Zizak, I. A1 - Manzoni, Anna Maria A1 - Yu, J. M. A1 - Wanderka, N. A1 - Li, W. T1 - Formation and evolution of hierarchical microstructures in a Ni-based superalloy investigated by in situ high-temperature synchrotron X-ray diffraction N2 - Hierarchical microstructures are created when additional γ particles form in γ’ precipitates and they are linked to improved strength and creep properties in high-temperature alloys. Here, we follow the formation and evolution of a hierarchical microstructure in Ni86.1Al8.5Ti5.4 by in situ synchrotron X-ray diffraction at 1023 K up to 48 h to derive the lattice parameters of the γ matrix, γ’ precipitates and γ particles and misfits between phases. Finite element method-based computer simulations of hierarchical microstructures allow obtaining each phase's lattice parameter, thereby aiding peak identification in the in situ X-ray diffraction data. The simulations further give insight into the heterogeneous strain distribution between γ’ precipitates and γ particles, which gives rise to an anisotropic diffusion potential that drives the directional growth of γ particles. We rationalize a schematic model for the growth of γ particles, based on the Gibbs-Thomson effect of capillary and strain-induced anisotropic diffusion potentials. Our results highlight the importance of elastic properties, elastic anisotropy, lattice parameters, and diffusion potentials in controlling the behavior and stability of hierarchical microstructures. KW - XRD KW - Superalloy KW - Finite element method KW - Transmission electron microscopy PY - 2022 DO - https://doi.org/10.1016/j.jallcom.2022.165845 SN - 0925-8388 VL - 919 SP - 1 EP - 17 PB - Elsevier CY - Lausanne AN - OPUS4-55394 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhao, J. A1 - Hu, Y. A1 - wei Lin, S. A1 - Resch-Genger, Ute A1 - Zhang, R. A1 - Wen, J. A1 - Kong, X. A1 - Qin, A. A1 - Ou, J. T1 - Enhanced luminescence intensity of near-infraredsensitized sensitized upconversion nanoparticles via Ca²+ doping for a nitric oxide release platform N2 - Light-induced NO release based on exogenous NO donors has attracted substantial attention in clinical applications; the induction light source usually converts near-infrared light to blue or ultraviolet light. However, the low efficiency of near-infrared light-assisted chemical light energy conversion remains a challenge, especially for NaYF4:Yb3+/Tm3+ photoconverting near-infrared light to ultraviolet (UV) and blue light. In this paper, a luminescence-enhanced strategy is reported by doping Ca2+ into NaYF4:Yb3+/Tm3+ and coating it with NaGdF4 through a two-step solvothermal method. Then, UCNPs modified with methyl-b-cyclodextrin (M-b-CD) are loaded on a ruthenium nitrosyl complex [(3)Ru(NO)(Cl)] as nitric oxide release-molecules (NORMs). X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) data demonstrated that Ca2+ was successfully doped into NaYF4:Yb3+/Tm3+ nanoparticles as the core, and a pure hexagonal phase, NaYF4, was obtained from the doping of Ca2+. TEM revealed that the crystallinity was significantly improved after Ca2+ doping, and the core–shell structure was successfully synthesized, with NaGdF4 directionally grown on the NaYF4:Ca/Yb/Tm core. Fluorescence tests showed that, especially in the ultraviolet and blue light excitation wavelength regions, the UC emission intensity of the Ca-doped NaYF4:Yb3+/Tm3+@NaGdF4 core–shell UCNPs increased by 302.95 times vs. NaYF4:Yb3+/Tm3+ UCNPs. Finally, the release of NO was tested by the Griess method. Under 980 nm irradiation, the cell viability distinctly decreased with increasing UCNPs@M-b-CD-NORMs concentration. This study Shows that NORM release of NO is triggered by enhanced up-converted UV and blue light, which can be used for the development of UV photo-sensitive drugs. KW - Nano KW - Nanomaterial KW - Upconversion nanoparticle KW - Lanthanide KW - Photoluminescence KW - Quantum yield KW - Photophysics KW - Lifetime KW - Sensor KW - Surface chemistry KW - Single particle KW - Brightness KW - NIR KW - PDT PY - 2020 DO - https://doi.org/10.1039/d0tb00088d VL - 8 IS - 30 SP - 6481 EP - 6489 PB - Journal of Materials Chemistry B AN - OPUS4-51262 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, M. A1 - Zhang, R. A1 - Fa, X. A1 - Yang, J. A1 - Cheng, Z. A1 - Qiao, X. A1 - Ou, J. A1 - Würth, Christian A1 - Resch-Genger, Ute T1 - Core−Shell NaYF4:Yb3+/Tm3+@NaGdF4:Ce3+/Eu3+ Nanoparticles for Upconversion and Downconversion Dual-Mode Fluorescence-Based Temperature Sensing N2 - NaYF4 as the core and NaGdF4 as the outer layer were used to obtain NaYF4:Yb3+/Tm3+@NaYF4:Ce3+/Eu3+ nanoparticles. Physical and morphological investigations indicated that the obtained nanoparticles were prepared in a hexagonal shape, with the NaGdF4 shell layer uniformly encapsulated on the NaYF4 core. Strong Tm3+ upconversion emission peaks were observed for a 980-nm-laser-excited sample, while strong Eu3+ downconversion emission peaks were observed for a 254-nm-laser-excited sample. By zonal doping of Tm3+ and Eu3+, their fluorescence intensity can be significantly increased; more importantly, simultaneous temperature measurements with dual-mode upconversion/downconversion can be achieved. The temperature measurement properties of the dual mode were also investigated, and it was discovered that the upconversion 3F3 → 3H6 and 1G4 → 3F4 thermocouple energy levels gave the best temperature measurements with maximum absolute and relative sensitivities of 0.0877 K−1 and 1.95% K−1, respectively, which are better than the current temperature measurement sensitivities of most rare-earth-based materials. This material was prepared as fiber-optic temperature-sensing probes to detect the temperature in the environment in real time and was found to perform excellently for temperature measurement. KW - Upconversion nanoparticle KW - Lanthanide KW - Sensing; temperature KW - Photophysics PY - 2022 DO - https://doi.org/10.1021/acsanm.2c01611 VL - 5 IS - 7 SP - 9266 EP - 9276 PB - American Chemical Society AN - OPUS4-55363 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Huang, K. A1 - Liu, H. A1 - Kraft, Marco A1 - Shikha, S. A1 - Zheng, X. A1 - Agren, H. A1 - Würth, Christian A1 - Resch-Genger, Ute A1 - Zhang, Y. T1 - A protected excitation-energy reservoir for efficient upconversion luminescence N2 - Lanthanide-doped upconversion nanoparticles (UCNPs) are of great interest for biomedical applications. Currently, the applicability of UCNP bionanotechnology is hampered by the generally low luminescence intensity of UCNPs and inefficient energy Transfer from UCNPs to surface-bound chromophores used e.g. for photodynamic therapy or analyte sensing. In this work, we address the low-Efficiency issue by developing versatile core-Shell nanostructures, where high-concentration sensitizers and activators are confined in the core and Shell Region of representative hexagonal NaYF2:Yb,Er UCNPs. After Doping concentration optimization, the sensitizer-rich core is able to harvest/accumulate more excitation energy and generate almost one order of Magnitude higher luminescence intesity than conventional homogeneously doped nanostructures. At the same time, the activator Ions located in the Shell enable a ~6 times more efficient resonant energy Transfer from UCNPs to surface-bound acceptor dye molecules due to the short distance between donor-acceptor pairs. Our work provides new insights into the rational design of UCNPs and will greatly encrease the General applicability of upconversion nanotechnologies. KW - Fluorescence KW - Lanthanide KW - Upconversion KW - Brightness KW - Quantification KW - Nanoparticle KW - Absolute fluorometry KW - NIR KW - IR KW - Quantum yield KW - Integrating sphere spectroscopy KW - Method KW - Energy transfer KW - Shell KW - Particle architecture PY - 2017 DO - https://doi.org/10.1039/c7nr06900f SN - 2040-3372 SN - 2040-3364 VL - 10 IS - 1 SP - 250 EP - 259 PB - The Royal Society of Chemistry AN - OPUS4-43893 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Qu, R. A1 - Maaß, Robert A1 - Liu, Z. A1 - Tönnies, D. A1 - Tian, L. A1 - Ritchie, R. A1 - Zhang, Z. A1 - Volkert, A. T1 - Flaw-insentive fracture of a micrometer-sized brittle metallic glass N2 - Brittle materials, such as oxide glasses, are usually very sensitive to flaws, giving rise to a macroscopic fracture strength that is much lower than that predicted by theory. The same applies to metallic glasses (MGs), with the important difference that these glasses can exhibit certain plastic strain prior to catas- trophic failure. Here we consider the strongest metallic alloy known, a ternary Co 55 Ta 10 B 35 MG. We show that this macroscopically brittle glass is flaw-insensitive at the micrometer scale. This discovery emerges when testing pre-cracked specimens with self-similar geometries, where the fracture stress does not de- crease with increasing pre-crack size. The fracture toughness of this ultra-strong glassy alloy is further shown to increase with increasing sample size. Both these findings deviate from our classical under- standing of fracture mechanics, and are attributed to a transition from toughness-controlled to strength- controlled fracture below a critical sample size. KW - Metallic glass KW - Fracture toughness KW - Size effect KW - Small-scale PY - 2021 DO - https://doi.org/10.1016/j.actamat.2021.117219 VL - 218 PB - Elsevier Ltd. AN - OPUS4-53097 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhou, X. A1 - Mathews, P. A1 - Berkels, B. A1 - Delis, W. A1 - Saood, S. A1 - Alhassan, A. A1 - Keuter, P. A1 - Schneider, J. A1 - Korte-Kerzel, S. A1 - Sandlöbes, S. A1 - Raabe, D. A1 - Neugebauer, j. A1 - Dehm, G. A1 - Hickel, Tilmann A1 - Scheu, C. A1 - Zhang, S. T1 - Materials Design by Constructing Phase Diagrams for Defects N2 - Phase transformations and crystallographic defects are two essential tools todrive innovations in materials. Bulk materials design via tuning chemicalcompositions is systematized using phase diagrams. It is shown here that thesame thermodynamic concept can be applied to manipulate the chemistry atdefects. Grain boundaries in Mg–Ga system are chosen as a model system,because Ga segregates to the boundaries, while simultaneously improving thestrength and ductility of Mg alloys. To reveal the role of grain boundaries,correlated atomic-scale characterization and simulation to scope and buildphase diagrams for defects are presented. The discovery is enabled bytriggering phase transformations of individual grain boundaries through localalloying, and sequentially imaging the structural and chemical changes usingatomic-resolution scanning transmission electron microscopy. Ab initiosimulations determined the thermodynamic stability of grain boundaryphases, and found out that increasing Ga content enhances grain boundarycohesion, relating to improved ductility. The methodology to trigger, trace,and simulate defect transformation at atomic resolution enables a systematicdevelopment of defect phase diagrams, providing a valuable tool to utilizechemical complexity and phase transformations at defects. KW - Automatic pattern recognition KW - Defect phase diagram KW - Density functional theory KW - Grain boundary complexion KW - Transmission electron microscopy PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618063 DO - https://doi.org/10.1002/adma.202402191 SN - 1521-4095 SP - 1 EP - 9 PB - Wiley AN - OPUS4-61806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, K. A1 - Mezhov, Alexander A1 - Schmidt, Wolfram T1 - Effect of agitation during the early‑age hydration on thixotropy and morphology of cement paste N2 - The effect of agitation during the earlyage hydration on thixotropy and morphology of cement paste prepared with and without superplasticizers (SP) is investigated by applying penetration test, small amplitude oscillatory shear sweep test (SAOS), isothermal calorimetric test, scanning electron microscopy (SEM) and energy dispersive X-ray analyses (EDX). The results show that the agitation of cement paste during the induction period increases the heat flow rate and destroys existing structures of samples without changing the mineral composition of samples. Yet, if the agitation is applied during the acceleration period, the heat flow rate is significantly lowered and the morphology and mineral composition of samples undergo irreversible change, freshly formed syngenite is destroyed and no longer restored. The penetration force and the static yield stress grow linearly during the induction period and exponentially during the acceleration period. Agitation during the induction period destroys the structure, which causes the static yield stress and the penetration force values becoming nearly equal to zero. However, during the acceleration period, even after agitation the static yield stress and the penetration force exhibit high residual values, which indicates the impact of hydration to the structural build-up. KW - Hydration · Thixotropy KW - Agitation KW - Morphology KW - Structural build-up PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-621189 DO - https://doi.org/10.1617/s11527-024-02504-w VL - 57 SP - 1 EP - 13 PB - Springer Nature Switzerland AG CY - Schweiz AN - OPUS4-62118 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, W.-H. A1 - Qin, J. A1 - Lu, D.-G. A1 - Thöns, Sebastian A1 - Havbro Faber, M. T1 - Vol-informed decision-making for SHM system arrangement N2 - Structural health monitoring systems have been widely implemented to provide real-time continuous data support and to ensure structural safety in the context of structural integrity management. However, the quantification of the potential benefits of structural health monitoring systems has not yet attracted widespread attention. At the same time, there is an urgent need to develop strategies, such as optimizing the monitoring period, monitoring variables, and other factors, to maximize the potential benefits of structural health monitoring systems. Considering the continuity of structural health monitoring information, a framework is developed in this article to support decision-making for structural Health monitoring systems arrangement in the context of structural integrity management, which integrates the concepts of value of information and risk-based inspection planning based on an approach which utilizes a conjugate prior probability distribution for updating of the probabilistic models of structural performances based on structural health Monitoring information. An example considering fatigue degradation of steel structures is investigated to illustrate the application of the proposed framework. The considered example shows that the choice of monitoring variables, the Monitoring period, and the monitoring quality may be consistently optimized by the application of the proposed framework and approach. Finally, discussions and conclusions are provided to clarify the potential benefits of the proposed Framework with a special view to practical applications of structural health monitoring systems. KW - Value of information KW - Structural health monitoring systems arrangement strategy KW - Structural integrity management KW - Rskbased inspection KW - Structural health monitoring information model PY - 2020 DO - https://doi.org/10.1177/1475921720962736 SN - 1475-9217 VL - 21 IS - 1 SP - 37 EP - 58 PB - SAGE Journals CY - USA AN - OPUS4-53064 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Gluth, Gregor A1 - Gaggl, M. A1 - Zhang, W. A1 - Hillemeier, B. A1 - Behrendt, F. ED - Udomkichdecha, W. ED - Böllinghaus, Thomas ED - Manonukul, A. ED - Lexow, J. T1 - Membranes made of hardened cement paste for processing wood gas - Influence of paste composition and separation factors N2 - The efficiency of wood gasification can be improved by applying membrane based gas separation operations in several of its sub-processes. In the present study the use of membranes made of hardened cement pastes for this purpose was investigated to provide a low cost alternative to conventional membrane materials. The pastes were tested for their diffusional properties in a Wicke-Kallenbach cell and analyzed with regard to their pore structure. The use of low water to binder ratios and slag and/or pozzolans led to a finer pore structure and higher separation factors; in particular, an approximately linear dependence of the separation factors on the threshold radii was observed. The results implicated that Knudsen diffusion is the prevailing diffusion mechanism in the membranes. Deviations from the theoretically expected separation factors were found, which may be ascribed to concentration polarization and channeling effects. KW - Hardened cement paste KW - Pore structure KW - Diffusion KW - Gas separation PY - 2014 SN - 978-3-319-11339-5 SN - 978-3-319-11340-1 DO - https://doi.org/10.1007/978-3-319-11340-1_20 SP - 199 EP - 209 PB - Springer AN - OPUS4-32065 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tehranchi, Ali A1 - Zhang, S. A1 - Zendegani, A. A1 - Hickel, Tilmann A1 - Neugebauer, J. A1 - Scheu, C. T1 - Metastable defect phase diagrams as roadmap to tailor chemically driven defect formation N2 - Thermodynamic bulk phase diagrams have become the roadmap used by researchers to identify alloy compositions and process conditions that result in novel materials with tailored properties. Recent experimental studies show that changes in the alloy composition can drive not only transitions in the bulk phases present in a material, but also in the concentration and type of defects they contain. Defect phase diagrams in combination with density functional theory provide a natural route to study these chemically driven defects. Our results reveal, however, that direct application of equilibrium bulk thermodynamics can fail to reproduce experimentally observed defect formation. Therefore, we extend the concept to metastable defect phase diagrams to account for kinetic limitations that prevent the system from reaching equilibrium. We apply this concept to successfully explain the formation of large concentrations of planar defects in supersaturated Fe-Nb solid solutions. We then utilize it to design suitable conditions for synthesis, which we subsequently realized experimentally, successfully validating the formation of the predicted defects in Mg-Al-Ca alloys. The concept offers new avenues for the design of materials performance by tailoring defect structures. KW - Metastable defect phase diagram KW - Ab initio thermodynamics KW - Chemical potential KW - Laves phases KW - Transmission electron microscopy PY - 2024 DO - https://doi.org/10.1016/j.actamat.2024.120145 SN - 1359-6454 VL - 277 SP - 1 EP - 9 PB - Elsevier Ltd. AN - OPUS4-61803 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, K. A1 - Mezhov, Alexander A1 - Schmidt, Wolfram T1 - Effect of Polycarboxylate Superplasticizer in Ordinary Portland Cement and Sulfate Resistant Cement N2 - Polycarboxylate superplasticizers (PCE) are the most widely used admixtures in today’s cementitious construction materials. The molecular structure has a decisive influence on the effectiveness of PCE, which also can be tailored to serve in a different cementitious system. The current study investigates the influence of the backbone charge density of PCE on the rheology, hydration kinetics, and adsorption behavior of ordinary Portland cement (OPC) and sulfate-resistant cement (SRC). The results indicate that regardless of the PCE type, OPC requires a higher amount of PCE to be adsorbed to induce changing of rheological parameters and hydration kinetics. Regardless of the cement type, the PCE with a higher charge density exhibits higher adsorption behavior, corresponding to lower viscosity measurement. Compared to OPC, SRC is more sensitive to the introduction of both PCEs and has a lower saturation dosage, indicating that SRC generally provides better workability properties regardless of the PCE. KW - Polycarboxylate superplasticizers (PCE) KW - Sulfate resistant cement (SRC) KW - Rheological KW - Adsorption KW - Cement hydration PY - 2023 DO - https://doi.org/10.1061/JMCEE7.MTENG-15033 SN - 0899-1561 VL - 35 IS - 6 SP - 1 EP - 12 PB - ASCE Libary AN - OPUS4-58244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, Kun A1 - Kong, Deyu A1 - Schmidt, Wolfram A1 - Mezhov, Alexander T1 - Influence of hydroxypropylation of starch on rheological properties of cement paste modified by superplasticizers N2 - Starch is often used as a viscosity modifying agent (VMA) in self-compacting concrete (SCC) and highly flowable concrete. In this paper, starches possessing different degrees of hydroxypropyl substitution (DS) were used to study the shear rheological properties and hydration kinetics of cement paste in the presence of and without polycarboxylate superplasticizer (PCE). The starch with the highest DS increases the yield stress and the plastic viscosity stronger than others. Regardless of the dosage and DS of starch the structural build-up is not affected specifically by the starch during the induction period. During the acceleration period starches reduce the structural build-up, but with the highest DS this effect was less prominent than for the other modifications. In the presence of PCE the addition of starch notably increases the yield stress, whereas the influence on the plastic viscosity is limited. Yet, the combined application of PCE and starch allows to control rheological properties and maintain the structural build-up rate. KW - Modified starch KW - PCE KW - Structural build-up KW - Rheological properties KW - Cement hydration PY - 2025 DO - https://doi.org/10.1016/j.conbuildmat.2025.143646 SN - 1879-0526 VL - 495 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam AN - OPUS4-64168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, K. A1 - Mezhov, Alexander A1 - Schmidt, Wolfram T1 - Chemical and thixotropic contribution to the structural build-up of cementitious materials N2 - The structural build-up of fresh cement paste is often considered as a purely thixotropic phenomenon in literature even though cementitious materials undergo a non-reversible hydration process that can have an influence on the structuration process. In the current paper a method is proposed to validate the impact of the non-reversible structural build-up. It is shown that fresh cement paste samples lose their structural gain almost completely due to thixotropy while the structural build-up due to hydration can be observed but occurs in a significantly lower order of magnitude over the course of the first hours of hydration. In addition, it is shown, that the chemical component of the structural build-up accelerates with the onset of the acceleration period of hydration, while its contribution in the entire structural build-up remains constant. KW - Thixotropy KW - Structural build-up KW - Penetration test KW - Rheological properties PY - 2022 DO - https://doi.org/10.1016/j.conbuildmat.2022.128307 SN - 0950-0618 VL - 345 IS - 128307 SP - 1 EP - 10 PB - Elsevier Ltd. AN - OPUS4-58248 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhang, K. A1 - Mezhov, Alexander A1 - Schmidt, Wolfram T1 - Thixotropic and chemical structural build-up of cement pastes with superplasticizer under different storage conditions N2 - Synopsis: The paper presents the results of a study on the influence of agitation on the structural build-up of fresh cement pastes using a penetration test. It first presents results about the influence of the penetrating shape’s geometry on the influence on the cement paste specimen. Then, results are shown for the load-deflection curves depending upon time and agitation before testing. Based on the observation of the force required to penetrate the sample, conclusions on the structural build-up can be made. The observations were made over the course of time with samples that were left at rest and partly agitated before testing at different time steps. The setup allows to identify the contribution of the chemical reaction to the structural build-up process. The presence of superplasticizer obviously reduces the load that cement paste can withstand, while the loss of thixotropy is found notably lower than that of neat cement pates T2 - 13th International Conference on Superplasticizers and Other Chemical Admixtures in Concrete CY - Milan, Italy DA - 10.07.2022 KW - Thixotropy KW - Superplasticizer KW - Structural build-up KW - Texture analyzer KW - Penetration test PY - 2022 DO - https://doi.org/10.14359/51736058 VL - 354 SP - 13 EP - 24 PB - ACI Special Publications AN - OPUS4-58324 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhang, K. A1 - Schmidt, Wolfram A1 - Mezhov, Alexander T1 - Influence of the hydroxypropylation of starch on its performance as viscosity modifying agent N2 - Synopsis: Starch is a commonly used viscosity modifying agent (VMA). The performance of starch as VMA depends on its origin (e.g. potato, corn, cassava, etc.) and corresponding molecular properties, such as molecular weight, ratio between amylose and amylopectin etc. Depending upon the application, the efficiency of starch can be enhanced by hydroxypropylation. The maximum degree of substitution (DoS) cannot be greater than 3.0, which is the number of hydroxy groups per glucose monomer in the polymer. In the current research three potato starches exhibiting the DoS of 0.4, 0.6 and 0.8 were utilised. The influence of the modified starch on the rheological properties and hydration of cement paste, as well as the viscosity of the pore solution were investigated. Our findings show that the starch with the highest DoS increases the dynamic yield stress the most, while the plastic viscosity is less dependent on the DoS. Additionally, starch with the highest DoS retards hydration to lower degree than other starches. T2 - 13th International Conference on Superplasticizers and Other Chemical Admixtures in Concrete CY - Milan, Italy DA - 10.07.2022 KW - Potato starch KW - Rheological KW - Cement hydration KW - Pore solutions PY - 2022 DO - https://doi.org/10.14359/51736074 VL - 354 SP - 209 EP - 218 PB - ACI Special Publications AN - OPUS4-58320 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mezhov, Alexander A1 - Schmidt, Wolfram A1 - Zhang, H. A1 - Diesendruck, Ch. E. T1 - The effect of the charge density of a comb polyphosphate superplasticizer on the structural build-up of cement paste N2 - Synopsis: Lately, there has been rising attention to superplasticizers (SP) based on polyphosphate esters. However, the influence of the molecular structure of the polyphosphate polymers on time-dependent properties such as structural build-up has not been examined yet intensively. To investigate this effect, three comb polyphosphate superplasticizers with different charge densities were synthesised by free radical polymerisation. Our findings indicate that SP with the lowest and medium charge densities extend the induction period more strongly than the SP with the highest charge density. The reduction of the structural build-up rate is linearly dependent on the dosage and concentration of the functional group of polyphosphate SP in the cementitious system. This study proposes a mathematical equation expressing the relationship between the structural build-up rate during the induction period and the molecular structure of the polyphosphate SP. T2 - 13th International Conference on Superplasticizers and Other Chemical Admixtures in Concrete CY - Milan, Italien DA - 10.07.2022 KW - Admixture KW - Superplasticizer KW - Polyphosphate KW - Structural build-up PY - 2022 DO - https://doi.org/10.14359/51736079 VL - 354 SP - 255 EP - 262 PB - ACI Special Publications AN - OPUS4-58321 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mezhov, Alexander A1 - Zhang, K. A1 - Schmidt, Wolfram T1 - Interactions of Biobased Rheology Modifying Agents with Superplasticizer in Cement Paste N2 - Organic admixtures are an indispensable component of modern concrete. Thus, their purposeful application is not only technically and economically viable but in addition an inevitable tool to make concrete more environmentally friendly. In this context, the use of polysaccharides has increasingly gained interest in the built environment as sustainable resource for performance enhancement. However, due to its origin, biopolymers possess a vast variety of molecular structures which can result in incompatibilities with other polymers present in concrete, such as superplasticizers. The present study highlights effects of the joint application of different types of starches and polycarboxylates with respect to their influence on cement hydration and structural build-up of cement pastes. KW - Polysaccharides KW - Superplasticizers KW - Hydration KW - Cement PY - 2022 DO - https://doi.org/10.4028/www.scientific.net/CTA.1.563 SN - 2674-1237 SP - 563 EP - 568 PB - Trans Tech Publications Ltd, Switzerland CY - Basel, Switzerland. AN - OPUS4-58325 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhang, Zeyu A1 - Kruschwitz, Sabine A1 - Weller, Andreas A1 - Halisch, M. A1 - Prinz, Carsten T1 - Enhanced pore space analysis by use of μ-CT, MIP, N2 - We investigate the pore space of rock samples with respect to different petrophysical parameters using various methods, which provide data upon pore size distributions, including micro computed tomography (μ-CT), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and spectral induced polarization (SIP). The resulting cumulative distributions of pore volume as a function of pore size are compared. Considering that the methods differ with regard to their limits of resolution, a multiple length scale characterization of the pore space geometry is proposed, that is based on a combination of the results from all of these methods. The findings of this approach are compared and discussed by using Bentheimer sandstone. Additionally, we compare the potential of SIP to provide a pore size distribution with other commonly used methods (MIP, NMR). The limits of resolution of SIP depend on the usable frequency range (between 0.002 and 100 Hz). The methods with similar resolution show a similar behavior of the cumulative pore volume distribution in the overlapping pore size range. The methods μ-CT and NMR provide the pore body size while MIP and SIP characterize the pore throat size. Using this difference, the average pore body to throat ratio is determined to be about three for the Bentheimer sandstone. Our study shows that a good agreement between the pore radii distributions can only be achieved if the curves are adjusted considering the resolution and pore volume in the relevant range of pore radii. The MIP curve with the widest range in resolution should be used as reference T2 - Annual Symposium of the Society of Core Analysts 2017 CY - Vienna, Austria DA - 27.08.2017 KW - Spectral induced polarization KW - Mercury intrusion porosimetry KW - µ-CT KW - Nuclear magnetic resonance KW - Bentheimer Sandstone PY - 2017 SP - 086, 1 EP - 086, 8 AN - OPUS4-43082 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zhang, Zeyu A1 - Kruschwitz, Sabine A1 - Prinz, Carsten A1 - Halisch, M. A1 - Weller, Andreas T1 - Porenraumanalyse mittels MIP, NMR, SIP, BET, CT und Auflichtmikroskopie N2 - In der Vergangenheit wurde immer wieder diskutiert, ob die Porenhalsverteilung poröser silikatischer Medien maßgeblich die Relaxationszeit in Messergebnissen der Spektralen Induzierten Polarisation (SIP) bestimmt und dementsprechend auch neuere Ansätze, Porenweitenverteilungen aus diesen Daten abzuleiten, zuverlässig sein können. Systematische Studien an Gesteinen mit sehr unterschiedlichen Porenverteilungen zeigten, dass in Materialien mit engen Porenhälsen (z.B. < 5 μm) vor allem oder zusätzlich zum vermuteten Porenhalspeak niederfrequente Relaxationen zu beobachten sind, deren Ursache noch unklar ist. Unter Einbeziehung der Methoden Röntgen-Computertomografie (μ-CT), Quecksilberporosimetrie (MIP), Stickstoffabsortion, Nukleare Magnetische Resonanz, SIP und Auflichtmikroskopie untersuchen wir den Porenraum hinsichtlich der Parameter Porosität, Permeabilität und innere Oberfläche und bestimmen die geometrischen Eigenschaften wie Porenweitenverteilungen oder fraktale Dimension durch verschiedene Algorithmen. Dabei ist zu berücksichtigen, dass sich die Methoden hinsichtlich der Grenzen ihres Auflösungsvermögens unterscheiden. Mit einer Zusammenführung der Ergebnisse aller Methoden kann eine mehrere Längenskalen überdeckende Charakterisierung der Porenraumgeometrie erfolgen. Die Anwendung und Auswertung der verschiedenen Methoden werden am Beispiel von Baumberger Kalksandstein und Bentheimer Sandstein verglichen und diskutiert. T2 - 77. Jahrestagung der Deutschen Geophysikalischen Gesellschaft CY - Potsdam, Germany DA - 27.03.2017 KW - Spektral Induzierte Polarisation KW - Fraktale Dimension KW - MIP KW - Sandstein PY - 2017 AN - OPUS4-43246 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -