TY - JOUR A1 - Agudo Jácome, Leonardo A1 - Nörtershäuser, P. A1 - Somsen, C. A1 - Dlouhý, A. A1 - Eggeler, G. T1 - On the nature of gamma' phase cutting and its effect on high temperature and low stress creep anisotropy of Ni-base single crystal superalloys N2 - The creep anisotropy of the single crystal superalloy LEK 94 deformed in tension along [0 0 1] and [1 1 0] directions at 1293 K and 160 MPa was investigated. Elementary microstructural processes which are responsible for a higher increase in creep rates with strain during [1 1 0] as compared to [0 0 1] tensile loading were identified. [1 1 0] tensile creep is associated with a higher number of γ' phase cutting events, where two dislocations with equal Burgers vectors of type <1 1 0> jointly shear the γ' phase. The resulting <2 2 0>-type superdislocation can move by glide. In contrast, during [0 0 1] tensile loading, two dislocations with different <1 1 0>-type Burgers vectors must combine for γ' phase cutting. The resulting <2 0 0>-type superdislocations can only move by a combination of glide and climb. The evolution of dislocation networks during creep determines the nature of the γ' phase cutting events. The higher [1 1 0] creep rates at strains exceeding 2% result from a combination of a higher number of cutting events (density of mobile dislocations in γ') and a higher superdislocation mobility (<2 2 0> glide) in the γ' phase. KW - Ni-base single crystal superalloys KW - Creep KW - Anisotropy KW - Dislocation KW - Rafting PY - 2014 DO - https://doi.org/10.1016/j.actamat.2014.01.021 SN - 1359-6454 SN - 1873-2453 VL - 69 SP - 246 EP - 264 PB - Elsevier Science CY - Kidlington AN - OPUS4-30387 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mieller, Björn A1 - Rabe, Torsten T1 - Surface characteristics of LTCC substrates fabricated by pressure-assisted sintering N2 - Plane LTCC substrates can be produced in zeroshrinkage technology by pressure-assisted sintering. The application of axial pressure during sintering supports densification, enhances cofiring of different materials, and restrains deformation. However, the sintered surfaces are affected by the release tapes and by the setters used in the pressure-assisted sintering process. In this study, the effect of release tape particle size on the surface properties of sintered substrates was investigated. Moreover, the substitution of release tape by the use of a vitreous carbon setter was tested. Surface roughness and sheet resistances of metallic thin films on the respective samples were determined. It was found that the roughness of the substrates is not directly correlated with the adequacy of the surface for thin-film deposition. Compared with a freely sintered sample with an average roughness (Ra) of 0.31 μm, pressure-assisted sintering created smoother surfaces using finegrained release tapes (Ra = 0.18 μm) and rougher surfaces using coarse release tapes (Ra = 0.46 μm). Still, sheet resistances were higher on all sinter-pressed samples. The vitreous carbon setter created unusual trenched surface structures, characterized by varying roughness values and intermediate sheet resistances on the LTCCs tested. PY - 2013 DO - https://doi.org/10.4071/imaps.385 SN - 1551-4897 N1 - Geburtsname von Mieller, Björn: Brandt, B. - Birth name of Mieller, Björn: Brandt, B. VL - 10 IS - 4 SP - 144 EP - 149 CY - Washington, DC AN - OPUS4-30331 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Battig, Alexander A1 - Abdou-Rahaman Fadul, Naïssa A1 - Frasca, Daniele A1 - Schulze, Dietmar A1 - Schartel, Bernhard T1 - Multifunctional graphene nanofiller in flame retarded polybutadiene/chloroprene/carbon black composites N2 - To curtail flammability risks and improve material properties, flame retardants (FRs) and fillers are mixed into rubbers. High loadings of aluminum trihydroxide (ATH) and carbon black (CB) are the most used FRs and reinforcing additive, respectively, in rubbers. To reduce loading without losing mechanical properties, partial substitution of ATH as well as CB by low amounts of multilayer graphene (MLG) nanoparticles is investigated. The high aspect ratio MLG is made of ten graphene sheets. In polybutadiene/chloroprene (BR/CR) nanocomposites 3 phr MLG replaced 15 phr CB and/or 3 phr ATH. Material and mechanical properties as well as fire behavior of the nanocomposites are compared to BR/CR with 20 phr CB both with and without 50 phr ATH. MLG appears as a promising nanofiller to improve the functional properties: replacement of CB improved rheological, curing, and mechanical properties; substitution of ATH improved nanocomposite properties without affecting flame retardancy. KW - Nanocomposites KW - Rubber KW - Multilayer graphene KW - Carbon black KW - Polybutadiene/chloroprene KW - Graphene PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-523468 DO - https://doi.org/10.1515/epoly-2021-0026 SN - 1618-7229 VL - 21 IS - 1 SP - 244 EP - 262 PB - De Gruyter AN - OPUS4-52346 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Musl, O. A1 - Sulaeva, I. A1 - Sumerskii, I. A1 - Mahler, A.K. A1 - Rosenau, T. A1 - Falkenhagen, Jana A1 - Potthast, A. T1 - Mapping of the Hydrophobic Composition of Lignosulfonates N2 - Lignosulfonates are industrial biorefinery products that are characterized by significant variability and heterogeneity in their structural composition. Typically, they exhibit high dispersities in molar mass (molar mass distribution-MMD) and in functionalities (functionality-type distribution - FTD), which crucially affect their material usage. In terms of FTD, state-of-the-art Lignin analytics still rely mainly on the determination of functional group contents, which are statistical averages with limited explanatory power. In contrast, our online hydrophobic interaction chromatography−size-exclusion chromatography 2D-LC approach combines the determination of both MMD and FTD in a single measurement to provide a comprehensive picture of the characteristic composition of industrial lignosulfonates information hitherto inaccessible by state-of-the-art lignin analytics. In this way, the complex inter - relationships between these two important structural parameters can be studied in an unprecedented manner. In this study, we reveal the considerable differences in terms of hydrophobic composition and its dispersity present in a range of different industrial lignosulfonates - data desperately needed in tailoring and refining of lignosulfonate composition for material usage. KW - Lignosulfonates KW - Amphiphilicity KW - Hydrophobic interaction chromatography KW - Two-dimensional chromatography (2D-LC) KW - Charge-to-size-ratio PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538612 DO - https://doi.org/10.1021/acssuschemeng.1c06469 VL - 9 IS - 49 SP - 16786 EP - 16795 PB - ASC Publications AN - OPUS4-53861 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Suárez Ocano, Patricia A1 - Fries, S. G. A1 - Lopez-Galilea, I. A1 - Darvishi Kamachali, Reza A1 - Roik, J. A1 - Agudo Jácome, Leonardo T1 - The AlMo0.5NbTa0.5TiZr refractory high entropy superalloy: Experimental findings and comparison with calculations using the CALPHAD method N2 - Detailed microstructural characterization of the AlMo0.5NbTa0.5TiZr refractory high entropy superalloy in the as-cast state is reported for first time and compared with the state annealed at 1400 oC for 24 h. The former shows a dendritic structure, with a mixture of A2/B2 phases < 20 nm in both the dendritic and interdendritic regions. A mostly amorphous phase, rich in Al and Zr, is found within the interdendritic region. The annealed state reproduced the combination of A2/B2/Al-Zr-rich phases reported previously. Calculations from two relevant ThermoCalc databases were compared with the experimental results. Equilibrium calculations were compared with results for the annealed alloy, whereas solidification paths calculated using Scheil-Gulliver model were used for comparison with the as-cast alloy. A previously hypothesized spinodal decomposition during cooling as the mechanism responsible for the patterned A2/B2 microstructure is confirmed via the CALPHAD calculations, pointing to its use as an efficient design tool for such alloys. Finally, the comparison between the experimental and computational findings allowed better understanding the solidification path and equilibrium stability of this alloy, giving a base to make better decisions on the field of new refractory superalloy design. KW - CALPHAD database analysis KW - Refractory superalloys KW - Chemically complex alloy KW - Characterization KW - Microstructure PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-545906 DO - https://doi.org/10.1016/j.matdes.2022.110593 SN - 1873-4197 VL - 217 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam AN - OPUS4-54590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Battig, Alexander A1 - Müller, Patrick A1 - Bertin, Annabelle A1 - Schartel, Bernhard T1 - Hyperbranched Rigid Aromatic Phosphorus-Containing Flame Retardants for Epoxy Resins N2 - A rigid aromatic phosphorus-containing hyperbranched flame retardant structure is synthesized from 10-(2,5 dihydroxyphenyl)-10H-9-oxa- 10-phosphaphenanthrene-10-oxide (DOPO-HQ), tris(4-hydroxyphenyl)phosphine oxide (THPPO), and 1,4-terephthaloyl chloride (TPC). The resulting poly-(DOPO-HQ/THPPO-terephthalate) (PDTT) is implemented as a flame retardant into an epoxy resin (EP) at a 10 wt% loading. The effects on EP are compared with those of the monomer DOPO-HQ and triphenylphosphine oxide (OPPh3) as low molar mass flame retardants. The glass transition temperature, thermal decomposition, flammability (reaction to small flame), and burning behavior of the thermosets are investigated using differential scanning calorimetry, thermogravimetric analysis, pyrolysis combustion flow calorimetry, UL 94-burning chamber testing, and cone calorimeter measurements. Although P-contents are low at only 0.6 wt%, the study aims not at attaining V-0, but at presenting a proof of principle: Epoxy resinswith PDTT show promising fire performance, exhibiting a 25% reduction in total heat evolved (THE), a 30% reduction in peak heat release rate (PHRR) due to flame inhibition (21% reduction in effective heat of combustion (EHC)), and an increase in Tg at the same time. This study indicates that rigid aromatic hyperbranched polymeric structures offer a promising route toward multifunctional flame retardancy. KW - Hyperbranched KW - Aromatic KW - Phosphorus KW - Phosphine oxide KW - DOPO KW - Flame retardant KW - Xpoxy resin KW - Rigid PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-525910 DO - https://doi.org/10.1002/mame.202000731 SN - 1439-2054 VL - 306 IS - 4 SP - 731 PB - Wiley AN - OPUS4-52591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dudziak, Mateusz A1 - Topolniak, Ievgeniia A1 - Silbernagl, Dorothee A1 - Altmann, Korinna A1 - Sturm, Heinz T1 - Long-time behavior of surface properties of microstructures fabricated by multiphoton lithography N2 - The multiphoton lithography (MPL) technique represents the future of 3D microprinting, enabling the production of complex microscale objects with high precision. Although the MPL fabrication parameters are widely evaluated and discussed, not much attention has been given to the microscopic properties of 3D objects with respect to their surface properties and time-dependent stability. These properties are of crucial importance when it comes to the safe and durable use of these structures in biomedical applications. In this work, we investigate the surface properties of the MPL-produced SZ2080 polymeric microstructures with regard to the physical aging processes during the post-production stage. The influence of aging on the polymeric microstructures was investigated by means of Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). As a result, a time-dependent change in Young’s Modulus, plastic deformation, and adhesion and their correlation to the development in chemical composition of the surface of MPL-microstructures are evaluated. The results presented here are valuable for the application of MPL-fabricated 3D objects in general, but especially in medical technology as they give detailed information of the physical and chemical time-dependent dynamic behavior of MPL-printed surfaces and thus their suitability and performance in biological systems. KW - Multiphoton lithography KW - Additive manufacturing KW - Microfabrication KW - SZ2080 negative photo-resist KW - Young´s modulus KW - Aging KW - Surface properties KW - X-ray photoelectron spectroscopy KW - Atomic force microscopy KW - Force-distance-curve PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542166 DO - https://doi.org/10.3390/nano11123285 SN - 2079-4991 VL - 11 IS - 12 SP - 1 EP - 12 PB - MDPI CY - Basel AN - OPUS4-54216 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sommer, Konstantin A1 - Agudo Jácome, Leonardo A1 - Hesse, René A1 - Bettge, Dirk T1 - Revealing the nature of melt pool boundaries in additively manufactured stainless steel by nano-sized modulation N2 - In the current study, the 3D nature of the melt pool boundaries (MPBs) in a 316 L austenitic steel additively manufactured by laser-based powder bed fusion (L-PBF) is investigated. The change of the cell growth direction and its relationship to the MPBs is investigated by transmission electron microscopy. A hitherto unreported modulated substructure with a periodicity of 21 nm is further discovered within the cell cores of the cellular substructure, which results from a partial transformation of the austenite, which is induced by a Ga+ focused ion beam. While the cell cores show the modulated substructure, cell boundaries do not. The diffraction pattern of the modulated substructure is exploited to show a thickness ≥200 nm for the MPB. At MPBs, the cell walls are suppressed, leading to continuously connecting cell cores across the MPB. This continuous MPB is described either as overlapping regions of cells of different growing directions when a new melt pool solidifies or as a narrow planar growth preceding the new melt pool. KW - Additive manufacturing KW - Austenitic steel 316L KW - Melt pool boundary KW - Microstructural characterization KW - Transmission electron microscopy PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-547295 DO - https://doi.org/10.1002/adem.202101699 SN - 1527-2648 VL - 24 IS - 6 SP - 1 EP - 11 PB - Wiley-VCH CY - Weinheim AN - OPUS4-54729 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chan, Yin Yam A1 - Ma, C. A1 - Zhou, F. A1 - Hu, Y. A1 - Schartel, Bernhard T1 - A liquid phosphorous flame retardant combined with expandable graphite or melamine in flexible polyurethane foam N2 - A systematic series of flexible polyurethane foams (FPUF) with different concentrations of flame retardants, bis([dimethoxyphosphoryl]methyl) phenyl phosphate (BDMPP), and melamine (MA) or expandable graphite (EG) was prepared. The mechanical properties of the FPUFs were evaluated by a universal testing machine. The pyrolysis behaviors and the evolved gas analysis were done by thermogravimetric analysis (TGA) and TGA coupled with Fourier-transform infrared (TG-FTIR), respectively. The fire behaviors were studied by limiting oxygen index (LOI), UL 94 test for horizontal burning of cellular materials (UL 94 HBF), and cone calorimeter measurement. Scanning electronic microscopy (SEM) was used to examine the cellular structure's morphology and the postfire char residue of the FPUFs. LOI and UL 94 HBF tests of all the flame retarded samples show improved flame retardancy. BDMPP plays an essential role in the gas phase because it significantly reduces the effective heat of combustion (EHC). This study highlights the synergistic effect caused by the combination of BDMPP and EG. The measured char yield from TGA is greater than the sum of individual effects. No dripping phenomenon occurs during burning for FPUF-BDMPP-EGs, as demonstrated by the result of the UL 94 HBF test. EG performs excellently on smoke suppression during burning, as evident in the result of the cone calorimeter test. MA reduces the peak heat release rate (pHRR) significantly. The synergistic effect of the combination of BDMPP and EG as well as MA offers an approach to enhance flame retardancy and smoke suppression. KW - Bis([dimethoxyphosphoryl]methyl) phenyl phosphate KW - Expandable graphite KW - Flexible polyurethane foam KW - melamine KW - phosphorous flame retardant PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-541840 DO - https://doi.org/10.1002/pat.5519 SN - 1099-1581 VL - 33 IS - 1 SP - 326 EP - 339 PB - Wiley AN - OPUS4-54184 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Manzoni, Anna Maria A1 - Mohring, Wencke A1 - Hesse, René A1 - Agudo Jácome, Leonardo A1 - Stephan-Scherb, C. T1 - Early material damage in equimolar CrMnFeCoNi in mixed oxidizing/sulfiding hot gas atmosphere N2 - The challenges to use more varied fuels at medium and high temperatures above 500 °C need to be addressed by tuning the materials toward a better resistance against increased corrosion. As a first step the corrosion processes need to be better understood, especially in the case of the unavoidable and highly corrosive sulfur-based gases. Herein, oxidation/sulfidation of an equimolar CrMnFeCoNi high-entropy alloy is studied at an early stage after hot gas exposure at 600 °C for 6 h in 0.5% SO2 and 99.5% Ar. The oxidation process is studied by means of X-ray diffraction, scanning and transmission electron microscopy, and supported by thermodynamic calculations. It is found that the sulfur does not enter the bulk material but interacts mainly with the fast-diffusing manganese at grain boundary triple junctions at the alloy surface. Submicrometer scaled Cr–S–O-rich phases close to the grain boundaries complete the sulfur-based phase formation. The grains are covered in different Fe-, Mn-, and Cr-based spinels and other oxides. KW - High entropy alloy KW - Sulfiding KW - Corrosion KW - Transmission electron microscopy PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543495 DO - https://doi.org/10.1002/adem.202101573 SN - 1527-2648 SP - 1 EP - 8 PB - Wiley-VCH CY - Weinheim AN - OPUS4-54349 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -