TY - JOUR A1 - Mair, Georg A1 - Becker, B. A1 - Gesell, Stephan A1 - Wang, Bin T1 - Monte-Carlo-analysis of minimum load cycle requirements for composite cylinders for hydrogen N2 - Hydrogen is an attractive energy carrier that requires high effort for safe storage. For ensuring safety, storage cylinders must undergo a challenging approval process. Relevant standards and regulations for composite cylinders used for the transport of hydrogen and for its onboard storage are currently based on deterministic (e.g. ISO 11119-3) or to some respect semi-probabilistic criteria (UN GTR No. 13; with respect to burst strength). This paper provides a systematic analysis of the load cycle properties resulting from these regulations and standards. Their characteristics are compared with the probabilistic approach of the Federal Institute for Materials Research and Testing BAM. The most important aspect of comparing different concepts is the rate for accepting designs with potentially unsafe or critical safety properties. This acceptance rate is analysed by operating Monte-Carlo simulations over the available range of production properties. T2 - ICHS 2017 CY - Hamburg, Germany DA - 11.09.2017 KW - Safety assessment KW - Failure rate KW - Ageing KW - Degradation KW - End of life KW - Production scatter PY - 2018 DO - https://doi.org/10.1016/j.ijhydene.2018.09.185 SN - 0360-3199 VL - 44 IS - 17 SP - 8833 EP - 8841 PB - Elsevier Ltd AN - OPUS4-46341 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Paul, Andrea A1 - Wander, Lukas A1 - Becker, Roland A1 - Goedecke, Caroline A1 - Braun, Ulrike T1 - High-throughput NIR spectroscopic (NIRS) detection of microplastics in soil N2 - The increasing pollution of terrestrial and aquatic ecosystems with plastic debris leads to the accumulation of microscopic plastic particles of still unknown amount. To monitor the degree of contamination analytical methods are urgently needed, which help to quantify microplastics (MP). Currently, time-costly purified materials enriched on filters are investigated both by micro-infrared spectroscopy and/or micro-Raman. Although yielding precise results, these techniques are time consuming, and are restricted to the analysis of a small part of the sample in the order of few micrograms. To overcome these problems, here we tested a macroscopic dimensioned NIR process-spectroscopic method in combination with chemometrics. For calibration, artificial MP/soil mixtures containing defined ratios of polyethylene, polyethylene terephthalate, polypropylene, and polystyrene with diameters < 125 µm were prepared and measured by a process FT-NIR spectrometer equipped with a fiber optic reflection probe. The resulting spectra were processed by chemometric models including support vector machine regression (SVR), and partial least squares discriminant analysis (PLS-DA). Validation of models by MP mixtures, MP-free soils and real-world samples, e.g. and fermenter residue, suggest a reliable detection and a possible classification of MP at levels above 0.5 to 1.0 mass% depending on the polymer. The benefit of the combined NIRS chemometric approach lies in the rapid assessment whether soil contains MP, without any chemical pre-treatment. The method can be used with larger sample volumes and even allows for an online prediction and thus meets the demand of a high-throughput method. KW - Microplastics KW - Soil KW - Chemometrics KW - PLS-DA KW - Support vector machines KW - Near Infrared Spectroscopy PY - 2018 DO - https://doi.org/10.1007/s11356-018-2180-2 SN - 1614-7499 SN - 0944-1344 VL - 26 IS - 8 SP - 7364 EP - 7374 PB - Springer AN - OPUS4-45405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Prewitz, M. A1 - Gaber, M. A1 - Müller, Ralf A1 - Marotzke, C. A1 - Holtappels, Kai T1 - Polymer coated glass capillaries and structures for high-pressure hydrogen storage: Permeability and hydrogen tightness N2 - The hydrogen tightness of high-pressure hydrogen storage is a Basic criterion for long-term storage. The H2 permeation coefficients of epoxy resin and a glass lacquer were determined to enable the geometric optimization of a glass capillary storage. It was found that the curing conditions have no significant influence on the H2 permeation coefficient of resin. The H2 permeation coefficient of epoxy resin is only about three orders of Magnitude greater than that of borosilicate glass. This suggests that the initial pressure of 700 bar takes about 2.5 years to be halved in capillary array storage. Therefore, a high-pressure hydrogen storage tank based on glass capillaries is ideally suited for long-term storage in mobile applications. KW - Permeability KW - Glass capillaries KW - Coating KW - Hydrogen storage KW - Long-term calculation KW - Epoxy resin PY - 2018 DO - https://doi.org/10.1016/j.ijhydene.2017.12.092 SN - 0360-3199 VL - 43 IS - 11 SP - 5637 EP - 5644 PB - Elsevier AN - OPUS4-44327 LA - eng 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 DO - 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 - JOUR A1 - Martin-Sanchez, Pedro Maria A1 - Gebhardt, Christopher A1 - Toepel, Jörg A1 - Barry, J. A1 - Munzke, N. A1 - Günster, Jens A1 - Gorbushina, Anna T1 - Monitoring microbial soiling in photovoltaic systems: A qPCR-based approach N2 - Soiling of photovoltaic (PV) systems compromises their performance causing a significant power loss and demanding periodical cleaning actions. This phenomenon raises great concerns in the solar energy field, thus leading to notable research efforts over the last decades. Soiling is caused by a dual action of dust deposition and biofouling. However, surprisingly, the microbiological contribution to PV soiling is often overlooked or underestimated. In this study, a variety of qPCR-based methods have been developed to quantify the microbial load of fungi, bacteria and phototrophs on PV panels. These protocols were evaluated by comparison with culturedependent methods, and were implemented with real solar plants for two years. The results show that the developed molecular methods are highly sensitive and reliable to monitor the microbial component of the soiling. Fungal biomass was clearly dominant in all analysed PV modules, while bacteria and phototrophs showed much lower abundance. Light microscopy and qPCR results revealed that melanised microcolonial fungi and phototrophs are the main biofilm-forming microorganisms on the studied solar panels. In particular, the fungal qPCR protocol is proposed as a useful tool for monitoring of PV soiling, and investigating the microbial contribution to specific soiling cases. KW - Solar panels KW - PV modules KW - Real-time qPCR KW - Bacteria KW - Fungi KW - Phototrophs PY - 2018 DO - https://doi.org/10.1016/j.ibiod.2017.12.008 SN - 0964-8305 VL - 129 SP - 13 EP - 22 PB - Elsevier Science AN - OPUS4-43892 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kalinka, Gerhard A1 - Sahin, M. A1 - Schlögl, S. A1 - Wang, J. A1 - Kaynak, B. A1 - Mühlbacher, I. A1 - Ziegler, W. A1 - Kern, W. A1 - Grützmacher, H. T1 - Tailoring the interfaces in glass fiber-reinforced photopolymer composites N2 - The present work provides a comparative study on the interface and adhesion properties of surface modified single glass fibers embedded in an acrylate matrix. To facilitate a covalent bonding at the fibermatrix interface, the fibers are functionalized with selected organosilanes that comprise either passive (unsaturated C¼C bonds of methacrylate moieties) or photoactive functionalities (photocleavable bis(acyl)phosphane oxide groups). Immobilization of the functional silanes is carried out by a classic silanization reaction involving a condensation reaction across the surface hydroxyl groups of the inorganic glass fibers. The change of the physico-chemical properties of the fibers due to desizing and subsequent surface modification is monitored by X-ray photoelectron spectroscopy and zeta potential measurements. In addition, scanning electron microscopy is used to follow the changes in surface morphology. After the modification step, the desized and modified single fibers are embedded in a photocurable acrylate resin formulation. By performing single fiber pull-out tests, maximum pull-out force, friction strength and apparent interfacial shear strength are determined as a function of the coupled silanes. The results reveal that the attached organosilanes lead to a significant increase in adhesion strength, whilst the performance of the photo-cleavable organosilane is superior to the passive methacryl-functional derivative. KW - Photocleavable organosilanes KW - Fiber-matrix interface KW - Photopolymer composites KW - Single fiber pull-out test KW - Surface modification PY - 2018 DO - https://doi.org/10.1016/j.polymer.2018.03.020 SN - 0032-3861 VL - 141 SP - 221 EP - 231 PB - Elsevier Ltd. CY - New York AN - OPUS4-44784 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scheuerlein, C. A1 - Finn, Monika A1 - Meyer, Christian A1 - Lackner, F. A1 - Savary, F. A1 - Rehmer, Birgit T1 - Thermomechanical Behavior of the HL-LHC 11 Tesla Nb3Sn Magnet Coil Constituents During Reaction Heat Treatment N2 - The knowledge of the temperature-induced changes of the superconductor volume and of the thermomechanical behavior of the different coil and tooling materials is required for predicting the coil geometry and the stress distribution in the coil after the Nb3Sn reaction heat treatment. In this paper, we have measured the Young’s and shear moduli of the HL-LHC 11 T Nb3Sn dipole magnet coil and reaction tool constituents during in situ heat cycles with the dynamic resonance method. The thermal expansion behaviors of the coil components and of a free standing Nb3Sn wire were compared based on dilation experiments. KW - Superconducting magnet KW - Young`s modulus KW - Thermal expansion KW - Stress-strain-behavior PY - 2018 DO - https://doi.org/10.1109/TASC.2018.2792485 SN - 1051-8223 SN - 1558-2515 VL - 28 IS - 3 SP - 4003806 - 1 EP - 4003806 - 6 PB - IEEE Council on Superconductivity CY - New York AN - OPUS4-44020 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wisniewski, W. A1 - Thieme, C. A1 - Müller, Ralf A1 - Reinsch, Stefan A1 - Groß-Barsnick, S.-M. A1 - Rüssel, C. T1 - Oriented surface nucleation and crystal growth in a 18BaO·22CaO·60SiO2 mol% glass used for SOFC seals N2 - A glass of the composition 37BaO·16CaO·47SiO2 wt% produced on an industrial scale is crystallized at 970 °C for times ranging from 15 min to 2 h. The crystallization at the immediate surface as well as the crystal growth into the bulk are analyzed using scanning electron microscopy (SEM) including energy dispersive X-ray spectroscopy (EDXS) and electron backscatter diffraction (EBSD) as well as X-ray diffraction in the Θ–2Θ setup (XRD). The immediate surface shows the oriented nucleation of walstromite as well as the formation of wollastonite and an unknown phase of the composition BaCaSi3O8. All three phases also grow into the bulk where walstromite ultimately dominates the kinetic selection and grows throughout the bulk due to a lack of bulk nucleation. Walstromite shows systematic orientation changes as well as twinning during growth. A critical analysis of the XRD-patterns acquired from various crystallized samples indicates that their evaluation is problematic and that phases detected by XRD in this system should be verified by another method such as EDXS. KW - Glass KW - Surface nucleation KW - Orientation KW - EBSD PY - 2018 DO - https://doi.org/10.1039/c7ce02008b VL - 20 IS - 6 SP - 787 EP - 795 PB - Royal Society of Chemistry AN - OPUS4-44405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Agea Blanco, Boris A1 - Meyer, Christian A1 - Müller, Ralf A1 - Günster, Jens T1 - Sand erosion of solar glass: Specific energy uptake, total transmittance, and module efficiency N2 - Surface roughness, R Z , normal transmittance, Τ N , total transmittance, Τ T , and photovoltaic (PV) module efficiency, η S , were measured for commercial solar glass plates and PV test modules identically sandblasted with different loads of quartz sand (200 – 400 μ m), impact inclination angles, and sand particle speed. Measured data are presented versus the specific energy uptake during sand blasting, E (J/m2). Cracks, adhering particles, and scratch ‐ like textures probably caused by plastic flow phenomena could be observed after sand blasting. Their characteristic size was much smaller than that of sand particles. After blasting and subsequent cleaning, the glass surface was still covered with adhering glass particles. These particles, cracks, and scratch ‐ like textures could not be removed by cleaning. For sand blasting with α = 30° inclination angle and E = 30 000 J/m2, normal transmittance, total transmittance, and relative module efficiency decreased by 29%, 2% and ∽ 2%, respectively. This finding indicates that diffusive transmission of light substantially contributes to PV module efficiency and that the module efficiency decrease caused by sand erosion can be better estimated from total than by normal transmittance measurements. KW - Transmittance KW - Efficiency KW - Photovoltaic modules KW - Roughness KW - Sand blasting PY - 2018 DO - https://doi.org/10.1002/er.3930 SN - 1099-114X SN - 0363-907X VL - 42 IS - 3 SP - 1298 EP - 1307 PB - Wiley & Sons, Ltd. AN - OPUS4-44157 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rockenhäuser, Christian A1 - Schriever, Sina A1 - von Hartrott, P. A1 - Piesker, Benjamin A1 - Skrotzki, Birgit T1 - Comparison of long-term radii evolution of the S-phase in aluminum alloy 2618A during ageing and creep N2 - A study was made on the effect of creep loading on the precipitate radii evolution of the aluminum alloy 2618A. The overageing process of the alloy was investigated under load at a temperature of 190 °C with stresses between 79 and 181 MPa and compared to stress free isothermal ageing. The precipitates responsible for strength were characterized using dark-field transmission electron microscopy (DFTEM). This allows the experimental Determination of radii distributions of the rod-shaped Al2CuMg precipitates and the evaluation regarding their mean precipitate radius. It was found that the mean precipitate radius enables the comparison of the different microstructural conditions of crept and uncrept samples. The mean precipitate radii of the samples experiencing creep are significantly higher than those of undeformed samples. It was shown that the acquired radii distributions are viable to determine averaged particle radii for comparison of the aged samples. A ripening process including pipe diffusion along dislocations describes the data on coarsening very well for the creep samples. KW - Aluminum alloys KW - Electron microscopy KW - Aging KW - Creep KW - Microstructure KW - S-Phase PY - 2018 DO - https://doi.org/10.1016/j.msea.2018.01.033 SN - 0921-5093 VL - 716 SP - 78 EP - 86 PB - Elsevier B. V. AN - OPUS4-44090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Behrens, H. A1 - Bauer, U. A1 - Reinsch, Stefan A1 - Kiefer, P. A1 - Müller, Ralf A1 - Deubener, J. T1 - Structural relaxation mechanisms in hydrous sodium borosilicate glasses N2 - Borosilicate glasses (16Na2O–10B2O3–74SiO2, NBS) with water contents up to 22 mol% H2O were prepared to study the effect of water on structural relaxation using DTA, viscometry and internal friction measurements. The results show that the glass transition temperature Tg of DTA and the isokom temperature T12, of viscometry are in excellent agreement, confirming the equivalence of enthalpy and viscous relaxation for NBS glass. Combining Tg data with water speciation data demonstrates that OH groups are mainly responsible for the decrease of Tg with increasing hydration, while molecular water plays only a minor role. Internal friction spectra at 7.125 Hz confirm the decisive influence of water on mechanical relaxation. The temperature range of α-relaxation (glass transition) strongly decreases while two β-relaxation peaks (sub-Tg) progressively appear with increasing water content. A high temperature β-relaxation peak, attributed to the presence of OH groups, shifts from 670 to 450 K as total water content increases from 0.01 to 5 wt%. A low temperature β-relaxation peak, attributed to molecular water, appears at 380 K and 330 K in glasses containing 3 and 5 wt% H2O, respectively. These findings suggest that relaxation mechanism of different hydrous species at low temperature may contribute to fatigue of stressed glasses. KW - Borosilicate glass KW - Water KW - Relaxation KW - Internal friction KW - Glass transition PY - 2018 DO - https://doi.org/10.1016/j.jnoncrysol.2018.05.025 VL - 497 SP - 30 EP - 39 PB - Elsevier B.V. AN - OPUS4-45608 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadammal, Naresh A1 - Kailas, Satish A1 - Szpunar, Jerzy A1 - Suwas, Satyam T1 - Development of microstructure and texture during single and multiple pass friction stir processing of a strain hardenable aluminium alloy N2 - In the present study, microstructure and texture development during single and multiple pass friction stir processing (FSP) of a strain hardenable wrought AlMg alloy (AA5086) was investigated. Subtle differences were observed while comparing with heat treatable alloys in the nucleation mechanism of the recrystallized microstructure observed in the nugget zone. Strain induced boundary migration was the dominant mechanism of microstructure evolution in the alloy, which influenced the crystallographic texture development by weakening it. Micro-texture measurements reveal variations in the crystallographic texture along the thickness of the sample. Recrystallization texture components were observed in the nugget zone indicative of a pronounced static recrystallization in the alloy as compared to the heat treatable alloys. Bulk texture measurements within the nugget zone of the optimally processed sample reveal a relatively dominant C component of shear texture. Average grain size in the nugget zone remained the same and the bulk crystallographic texture components were retained during multiple-pass FSP. The lower strain energies involved and the enhanced recovery processes due to the high temperature materials processing of the alloy during FSP resulted in a stable microstructure and texture. In summary, FSP could be promoted as a competent and suitable secondary processing technique for the bulk production of ultra-fine-grained materials in strain hardenable aluminium alloys. KW - Friction stir processing KW - Aluminium alloys KW - Electron back-scattered diffraction KW - Crystallographic texture KW - Dynamic recrystallization PY - 2018 UR - https://www.sciencedirect.com/science/article/pii/S1044580317336136 DO - https://doi.org/10.1016/j.matchar.2018.03.044 SN - 1044-5803 SN - 1873-4189 VL - 140 SP - 134 EP - 146 PB - Elsevier B.V CY - Amsterdam, The Netherlands AN - OPUS4-45125 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Thiede, Tobias A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Klaus, Manuela A1 - Genzel, Christoph A1 - Haberland, Christoph A1 - Bruno, Giovanni T1 - The influence of the support structure on residual stress and distortion in SLM Inconel 718 parts N2 - The effect of support structure and of removal from the base plate on the residual stress state in selective laser melted IN718 parts was studied by means of synchrotron X-ray diffraction. The residual stresses in subsurface region of two elongated prisms in as-built condition and after removal from the base plate were determined. One sample was directly built on a base plate and another one on a support structure. Also, the distortion on the top surface due to stress release was measured by contact profilometry. High tensile residual stress values were found, with pronounced stress gradient along the hatching direction. In the sample on support, stress redistribution took place after removal from the base plate, as opposed to simple stress relaxation for the sample without support. The sample on support structure showed larger distortion compared to sample without support. We conclude that the use of a support decreases stress values but stress-relieving heat treatments are still needed. KW - Additive manufacturing KW - SLM KW - Residual stress KW - Synchrotron X-ray diffraction KW - IN718 PY - 2018 DO - https://doi.org/10.1007/s11661-018-4653-9 SN - 1073-5623 VL - 49A IS - 7 SP - 3038 EP - 3046 PB - Springer Sciences & Business Media CY - New York, NY AN - OPUS4-45100 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Elsayed, H. A1 - Zocca, Andrea A1 - Schmidt, J. A1 - Günster, Jens A1 - Colombo, P. A1 - Bernardo, E. T1 - Bioactive glass-ceramic scaffolds by additive manufacturing and sinter-crystallization of fi ne glass powders N2 - Wollastonite (CaSiO 3 ) – diopside (CaMgSi 2 O 6 ) glass-ceramic scaffolds have been successfully fabricated using two different additive manufacturing techniques: powder-based 3D printing (3DP) and digital light processing (DLP), coupled with the sinter-crystallization of glass powders with two different compositions. The adopted manufacturing process depended on the balance between viscous flow sintering and crystallization of the glass particles, in turn in fluenced by the powder size and the sensitivity of CaO – MgO – SiO 2 glasses to surface nucleation. 3DP used coarser glass powders and was more appropriate for low temperature firing (800 – 900 °C), leading to samples with limited crystallization. On the contrary, DLP used finer glass powders, leading to highly crystallized glass-ceramic samples. Despite the differences in manufacturing technology and crystallization, all samples featured very good strength-to-density ratios, which bene fit theiruse for bone tissue engineering applications. The bioactivity of 3D-printed glass-ceramics after immersion in simulated body fluid and the similarities, in terms of ionic releases and hydroxyapatite formation with already validated bioactive glass-ceramics, were preliminarily assessed. KW - 3D-Printing KW - Bio Ceramic KW - Additive manufacturing PY - 2018 DO - https://doi.org/10.1557/jmr.2018.120 SN - 2044-5326 SN - 0884-2914 VL - 33 IS - 14 SP - 1960 EP - 1971 PB - Cambridge University Press AN - OPUS4-45718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Günster, Jens A1 - Zocca, Andrea A1 - Lima, Pedro A1 - Acchar, W. T1 - 3D printing of porcelain by layerwise slurry deposition N2 - The Layerwise Slurry Deposition is a technology for the deposition of highly packed powder layers. A powder bed is achieved by depositing and drying layers of a ceramic suspension by means of a doctor blade. This deposition technique was combined with the binder jetting technology to develop a novel Additive Manufacturing technology, named LSD-print. The LSD-print was applied to a porcelain ceramic. It is shown that it was possible to produce parts with high definition, good surface finish and at the same time having physical and mechanical properties close to those of traditionally processed porcelain, e.g. by slip casting. This technology shows high future potential for being integrated alongside traditional production of porce-lain, as it is easily scalable to large areas while maintaining a good definition. Both the Layerwise Slurry Deposition method and the binder jetting technologies are readily scalable to areas as large as > 1 m2. KW - Binder jetting KW - Additive Manufacturing KW - 3D printing KW - Porcelain PY - 2018 DO - https://doi.org/10.1016/j.jeurceramsoc.2018.03.014 SN - 0955-2219 VL - 38 IS - 9 SP - 3395 EP - 3400 PB - Elsevier Ltd. AN - OPUS4-45713 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chi, Jinchun A1 - Zocca, Andrea A1 - Agea Blanco, Boris A1 - Melcher, J. A1 - Sparenberg, M. A1 - Günster, Jens T1 - 3D Printing of Self-Organizing Structural Elements for Advanced Functional Structures N2 - A shape evolution approach based on the thermally activated self-organization of 3D printed parts into minimal surface area structures is presented. With this strategy, the present communication opposes currently established additive manufacturing strategies aiming to stipulate each individual volumetric element (voxel) of a part. Instead, a 3D structure is roughly defined in a 3D printing process, with all its advantages, and an externally triggered self-organization allows the formation of structural elements with a definition greatly exceeding the volumetric resolution of the printing process. For enabling the self-organization of printed objects by viscous flow of material, functionally graded structures are printed as rigid frame and melting filler. This approach uniquely combines the freedom in design, provided by 3D printing, with the mathematical formulation of minimal surface structures and the knowledge of the physical potentials governing self-organization, to overcome the paradigm which strictly orrelates the geometrical definition of 3D printed parts to the volumetric resolution of the printing process. Moreover, a transient liquid phase allows local programming of functionalities, such as the alignment of functional particles, by means of electric or magnetic fields. KW - Additive Manufacturing KW - Self-Assembly KW - 3D-Printing KW - Polymeric Materials PY - 2018 DO - https://doi.org/10.1002/admt.201800003 SN - 2365-709X VL - 3 IS - 5 SP - 1800003-1 EP - 1800003-7 PB - Wiley-VCH CY - Weinheim AN - OPUS4-45714 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bernardino, R. A1 - Wirth, C. A1 - Stares, S.L. A1 - Salmoria, G.V. A1 - Hotza, D. A1 - Günster, Jens T1 - Manufacturing of SiO2-Coated b-TCP Structures by 3D Printing using a Preceramic Polymer as Printing Binder and Silica Source N2 - Tricalcium phosphate (b-TCP) can be used as bone graft, exhibiting suitable bioabsorption and osteoconduction properties. The presence of silica may induce the formation of a hydroxyapatite layer, enhancing the integration between implant and bone tissue. Preceramic polymers present silicon in their composition, being a source of SiO2 after thermal treatment. Using the versatility of 3D printing, b-TCP and a polysiloxane were combined to manufacture a bulkb-TCP with a silica coating. For the additive manufacturing process, PMMA powder was used as passive binder for the b-TCP particles, and polymethylsilsesquioxane (MK), dissolved in an organic solvent, was used both as a printing binder (ink) and as the source of SiO2 for the coating. Five distinct coating compositions were printed with increasing amounts of MK. The structures were then submitted to heat treatment at 1180 °C for 4 h. XRD and FTIR showed no chemical reaction between the calcium phosphate and silica. SEM allowed observation of a silicon-based ating on the structure surface. Mechanical strength of the sintered porous structures was within the range of that of trabecular bones. KW - Tricalcium Phosphate KW - 3D-Printing KW - Preceramic polymer KW - Bone regeneration PY - 2018 DO - https://doi.org/10.4416/JCST2017-00056 VL - 9 IS - 1 SP - 37 EP - 41 PB - Göller Verlag CY - 76532 Baden-Baden AN - OPUS4-45715 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pelegrina, J. L. A1 - Olbricht, Jürgen A1 - Yawny, A. A1 - Eggeler, G. T1 - Temperature-induced transformations and martensitic reorientation processes in ultra-fine-grained Ni rich pseudoelastic NiTi wires studied by electrical resistance N2 - Temperature-induced, stress-induced martensitic phase transitions and martensite reorientation process in Ni rich (50.9 at.%) NiTi pseudoelastic NiTi wires with ultra-fine grained (UFG) microstructure were studied by electrical resistance measurements. Measurements of the electrical resistance as a function of temperature at different constant mechanical loads accompanied by complementary experiments with variable loads at constant temperature were performed. Results show that the transformation mechanisms in UFG microstructures exhibit a higher level of complexity when compared with those characterizing the behavior of other microstructures (e.g., recrystallized or larger grains size). It was found that a threshold stress level below 150 MPa delimits the transition from a homogeneous (low stress) to localized but reversible Lüders type transformation (high stress) when the transformations are induced under constant applied stress and that reorientation processes require stresses of 100 MPa in the present UFG wires. Even though the strain evolutions do not always show two distinct yielding events during cooling or heating, electrical resistance measurements proved that a two-step transformation involving R-phase and B19' martensite was always present in the extended range of temperatures and stresses investigated here. KW - Shape memory alloys KW - NiTi KW - Martensitic transformation KW - Electrical resistance PY - 2018 DO - https://doi.org/10.1016/j.jallcom.2017.12.009 SN - 0925-8388 VL - 735 SP - 2574 EP - 2583 PB - Elsevier AN - OPUS4-43549 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schilling, Markus A1 - Niebergall, Ute A1 - Alig, I. A1 - Oehler, H. A1 - Lellinger, D. A1 - Meinel, Dietmar A1 - Böhning, Martin T1 - Crack propagation in PE-HD induced by environmental stress cracking (ESC) analyzed by several imaging techniques N2 - Different imaging techniques were employed to monitor Full Notch Creep Test (FNCT) experiments addressing environmental stress cracking in more detail. The FNCT is a well-established test method to assess slow crack growth and environmental stress cracking of polymer materials, especially polyethylene. The standard test procedure, as specified in ISO 16770, provides a simple comparative measure of the resistance to crack growth of a certain material based on the overall time to failure when loaded with a well-defined mechanical stress and immersed in a liquid medium promoting crack propagation. Destructive techniques which require a direct view on the free fracture surface, such as light microscopy and laser scanning microscopy, are compared to non-destructive techniques, i.e. scanning acoustic microscopy and xray micro computed tomography. All methods allow the determination of an effective crack length. Based on a series of FNCT specimens progressively damaged for varied Durations under standard test conditions, the estimation of crack propagation rates is also enabled. Despite systematic deviations related to the respective Imaging techniques, this nevertheless provides a valuable tool for the detailed evaluation of the FNCT and its further development. KW - Environmental stress cracking (ESC) KW - Slow crack growth (SCG) KW - Full notch creep test (FNCT) KW - X-ray computed tomography (CT) KW - Laser scanning microscopy (LSM) KW - Scanning acoustic microscopy (SAM) PY - 2018 DO - https://doi.org/10.1016/j.polymertesting.2018.08.014 SN - 0142-9418 SN - 1873-2348 VL - 70 SP - 544 EP - 555 PB - Elsevier AN - OPUS4-45766 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Epishin, A. A1 - Fedelich, Bernard A1 - Nolze, Gert A1 - Schriever, Sina A1 - Feldmann, Titus A1 - Farzik Ijaz, M. A1 - Viguier, B. A1 - Poquillon, D. A1 - Le Bouar, Y. A1 - Ruffini, A. A1 - Finel, A. T1 - Creep of single crystals of nickel-based superalloys at ultra-high homologous temperature N2 - The creep behavior of single crystals of the nickel-based superalloy CMSX-4 was investigated at 1288 °C, which is the temperature of the hot isostatic pressing treatment applied to this superalloy in the industry. It was found that at this super-solvus temperature, where no gammaPrime-strengthening occurs, the superalloy is very soft and rapidly deforms under stresses between 4 and 16 MPa. The creep resistance was found to be very anisotropic, e.g., the creep rate of [001] crystals was about 11 times higher than that of a [111] crystal. The specimens of different orientations also showed a very different necking behavior. The reduction of the cross-sectional area psi of [001] crystals reached nearly 100 pct, while for a [111] crystal psi = 62 pct. The EBSD analysis of deformed specimens showed that despite such a large local strain the [001] crystals did not recrystallize, while a less deformed [111] crystal totally recrystallized within the necking zone. The recrystallization degree was found to be correlated with deformation behavior as well as with dwell time at high temperature. From the analysis of the obtained results (creep anisotropy, stress dependence of the creep rate, traces of shear deformation, and TEM observations), it was concluded that the main strain contribution resulted from <01-1>{111} octahedral slip. T2 - 3rd European Conference on Superalloys (‘Eurosuperalloys 2018’) CY - Oxford, UK DA - 9.9.2018 KW - Single-crystal KW - Superalloy KW - Creep KW - Isostatic hot pressing (HIP) PY - 2018 DO - https://doi.org/10.1007/s11661-018-4729-6 SN - 1073-5623 SN - 1543-1940 VL - 49A IS - 9 SP - 3973 EP - 3987 PB - Springer Sciences & Business Media CY - New York, NY AN - OPUS4-45660 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sharatchandra Singh, W. A1 - Stegemann, Robert A1 - Kreutzbruck, Marc A1 - Mukhopadhyay, C. K. A1 - Purnachandra Rao, B. T1 - Mapping of Deformation-Induced Magnetic Fields in Carbon Steels Using a GMR Sensor Based Metal Magnetic Memory Technique N2 - Giant magneto-resistive (GMR) sensor based metal magnetic memory (MMM) technique is proposed for mapping of deformation-induced self-magnetic leakage fields (SMLFs) in carbon steel. The specimens were subjected to different amounts of tensile deformation and the deformation-induced SMLFs were measured using a GMR sensor after unloading the specimens. 3D-nonlinear finite element modeling was performed to predict stress–strain state in a steel specimen under tensile load. The experimentally obtained SMLF images were correlated with the finite element model predicted stress–strain states. Studies reveal that the MMM technique can detect the plastic deformation with signal-to-noise ratio better than 20 dB. The technique enables the mapping of plastic deformation in carbon steels for the evaluation of the severity of deformation. The study also reveals that deformation-induced SMLF is influenced by the presence of initial surface residual stress, introduced by shot peening. The intensity of SMLF signal is found to increase with increase in tensile load and decrease with shot peening. KW - GMR KW - Metal Magnetic Memory KW - 3D-finite element modeling KW - Plastic deformation KW - Carbon steel PY - 2018 DO - https://doi.org/10.1007/s10921-018-0470-8 SN - 0195-9298 VL - 37 IS - 2 SP - 21 PB - Springer US AN - OPUS4-45667 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Karl, D. A1 - Kamutzki, F. A1 - Zocca, Andrea A1 - Görke, O. A1 - Günster, Jens A1 - Gurlo, A. T1 - Towards the colonization of Mars by in-situ resource utilization: Slip cast ceramics from Martian soil simulant N2 - Here we demonstrate that by applying exclusively Martian resources a processing route involving suspensions of mineral particles called slurries or slips can be established for manufacturing ceramics on Mars. We developed water-based slurries without the use of additives that had a 51 wt. % solid load resembling commercial porcelain slurries in respect to the particle size distribution and rheological properties. These slurries were used to slip cast discs, rings and vases that were sintered at temperatures between 1000 and 1130 °C using different sintering schedules, the latter were set-up according the results of hot-stage microscopic characterization. The microstructure, porosity and the mechanical properties were characterized by SEM, X-ray Computer tomography and Weibull analysis. Our wet processing of minerals yields ceramics with complex shapes that show similar mechanical properties to porcelain and could serve as a technology for future Mars colonization. The best quality parts with completely vitrificated matrix supporting a few idiomorphic crystals are obtained at 1130 °C with 10 h dwell time with volume and linear shrinkage as much as ~62% and ~17% and a characteristic compressive strength of 51 MPa. KW - Ceramic KW - Mars PY - 2018 DO - https://doi.org/10.1371/journal.pone.0204025 SN - 1932-6203 VL - 13 IS - 10 SP - e0204025, 1 EP - 7 PB - Public Library of Science CY - San Francisco, Kalifornien, Vereinigte Staaten AN - OPUS4-46612 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - de Camp, N. V. A1 - Kalinka, Gerhard A1 - Bergeler, J. T1 - Light-cured polymer electrodes for non-invasive EEG recordings N2 - We invented the first non-metallic, self-adhesive and dry biosignalling electrode. The PEDOT polymer electrode changes its aggregate state and conductivity by a light curing procedure. The electrode can be applied as a gel underneath hair without shaving. With the aid of blue light, the electrode can be hardened within a few seconds at the desired location on the scalp. The cured polymer electrode is highly conductive and can be applied on a very small location. Unlike other EEG electrodes, our electrode does not lose conductivity upon drying. Furthermore, our electrode strongly bonds to Skin and does not require any additional adhesive. Short circuits due to an outflow of gel are prevented with this technique. Therefore, the PEDOT polymer electrode is extremely well suited for applications that, up to now, have been challenging, such as non-invasive EEG recordings from awake and freely moving animals, EEG recordings from preterm babies in the neonatal intensive care unit or long-term recordings in the case of sleep monitoring or epilepsy diagnostics. We addressed two technical questions in this work. First, is the EEG recorded with polymer electrodes comparable to a standard EEG? Second, is it possible to record full-band EEGs with our electrodes? KW - Light curing KW - Polymer KW - Electric conductivity PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-459803 UR - https://rdcu.be/7aPD DO - https://doi.org/10.1038/s41598-018-32304-6 SN - 2045-2322 VL - 8 IS - 14041 SP - 1 EP - 9 PB - Nature Publishing Group CY - London AN - OPUS4-45980 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Cabeza, S. A1 - Mishurova, Tatiana A1 - Nadammal, Naresh A1 - Thiede, Tobias A1 - Bruno, Giovanni T1 - Residual Stresses in Selective Laser Melted Samples of a Nickel Based Superalloy N2 - Additive Manufacturing (AM) through the Selective Laser Melting (SLM) route offers ample scope for producing geometrically complex parts compared to the conventional subtractive manufacturing strategies. Nevertheless, the residual stresses which develop during the fabrication can limit application of the SLM components by reducing the load bearing capacity and by inducing unwanted distortion, depending on the boundary conditions specified during manufacturing. The present study aims at characterizing the residual stress states in the SLM parts using different diffraction methods. The material used is the nickel based superalloy Inconel 718. Microstructure as well as the surface and bulk residual stresses were characterized. For the residual stress analysis, X-ray, synchrotron and neutron diffraction methods were used. The measurements were performed at BAM, at the EDDI beamline of -BESSY II synchrotronand the E3 line -BER II neutron reactor- of the Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. The results reveal significant differences in the residual stress states for the different characterization techniques employed, which indicates the dependence of the residual state on the penetration depth in the sample. For the surface residual stresses, longitudinal and transverse stress components from X-ray and synchrotron agree well and the obtained values were around the yield strength of the material. Furthermore, synchrotron mapping disclosed gradients along the width and length of the sample for the longitudinal and transverse stress components. On the other hand, lower residual stresses were found in the bulk of the material measured using neutron diffraction. The longitudinal component was tensile and decreased towards the boundary of the sample. In contrast, the normal component was nearly constant and compressive in nature. The transversal component was almost negligible. The results indicate that a stress re-distribution takes place during the deposition of the consecutive layers. Further investigations are planned to study the phenomenon in detail. T2 - European Conference on Residual Stresses - ECRS10 CY - Leuven, Belgium DA - 11.09.2018 KW - Additive Manufacturing KW - Selective Laser Melting KW - Residual Stresses PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-459818 SN - 978-1-94529-189-0 SN - 978-1-94529-188-3 DO - https://doi.org/10.21741/9781945291890-41 SN - 2474-395X SN - 2474-3941 VL - 6 SP - 259 EP - 264 PB - Materials Research Forum LLC CY - Millersville, PA 17551, USA AN - OPUS4-45981 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Deubener, J. A1 - Allix, M. A1 - Davis, M.J. A1 - Duran, A. A1 - Höche, T. A1 - Honma, T. A1 - Komatsu, T. A1 - Krüger, S. A1 - Mitra, I. A1 - Müller, Ralf A1 - Nakane, S. A1 - Pascual, M.J. A1 - Schmelzer, J.W. A1 - Zanotto, E.D. A1 - Zhou, S. T1 - Updated definition of glass-ceramics N2 - Glass-ceramics are noted for their unusual combination of properties and manifold commercialized products for consumer and specialized markets. Evolution of novel glass and ceramic processing routes, a plethora of new compositions, and unique exotic nano- and microstructures over the past 60 years led us to review the Definition of glass-ceramics. Well-established and emerging processing methods, such as co-firing, additive manufacturing, and laser patterning are analyzed concerning the core requirements of processing glass-ceramics and the Performance of the final products. In this communication, we propose a revised, updated definition of glass-ceramics, which reads “Glass-ceramics are inorganic, non-metallic materials prepared by controlled crystallization of glasses via different processing methods. They contain at least one type of functional crystalline phase and a residual glass. The volume fraction crystallized may vary from ppm to almost 100%”. KW - Glass-ceramics definition PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-464711 DO - https://doi.org/10.1016/j.jnoncrysol.2018.01.033 SN - 0022-3093 SN - 1873-4812 VL - 501 SP - 3 EP - 10 PB - Elsevier B.V. AN - OPUS4-46471 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kotaka, M. A1 - Honma, T. A1 - Komatsu, T. A1 - Shinozaki, K. A1 - Affatigato, M. A1 - Müller, Ralf T1 - Control of self-powdering phenomenon in ferroelastic β′-Gd2(MoO4)3 crystallization in boro-tellurite glasses N2 - Glasses with compositions of 21Gd2O3-63MoO3-(16-x)B2O3-xTeO2 (mol%) (x= 0, 2, 4, 8) were prepared using a conventional melt quenching technique, and the crystallization behavior of ferroelastic β′-Gd2 MoO4)3 Crystals was examined to clarify the mechanism of self-powdering phenomenon and to design bulk crystallized glasses. It was found that the self-powdering phenomenon appeared significantly during the crystallization at temperatures near the crystallization peak temperature, but the phenomenon is suppressed in the crystallization at temperatures much higher than the glass transition temperature. It was also found that the substitution of TeO2 for B2O3 in the base glasses suppresses the self-powdering phenomenon and consequently bulk crystallized glasses were obtained in the glass with x=8 mol%. The densities at room temperature of the base glasses are d =4.755–4.906 g/cm3, being much higher than the value of d=4.555 g/cm3 for β′-Gd2(MoO4)3 crystal. It is proposed that the stresses in the inside of crystals induced by large density differences (i.e., large molar volume differences) between the glassy phase and crystals might be relaxed effectively in the glasses containing TeO2 with weak TeeO bonds and fragile character. KW - Glass crystallization stress PY - 2018 DO - https://doi.org/10.1016/j.jnoncrysol.2017.12.006 SN - 0022-3093 SN - 1873-4812 VL - 501 SP - 85 EP - 92 PB - Elsevier B.V. AN - OPUS4-46472 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Häberle, Nicolas A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Falkenberg, Rainer A1 - Kahlcke, Ole T1 - Application of multi-phase viscoplastic material modelling to computational welding mechanics of grade-s960ql steel N2 - The sound numerical prediction of welding-induced thermal stresses, residual stresses, and distortions strongly depends on the accurate description of a welded material’s thermomechanical deformation behaviour. In this work, we provide experimental data on the viscoplastic deformation behaviour of a grade-s960ql steel up to a temperature of 1000 ◦C. In addition, a multi-phase viscoplastic material model is proposed, which accounts for the experimentally observed isothermal deformation behaviour of grade-s960ql steel base and austenitised material, as well as for athermal contributions that originate from solid-state phase transformations. The multi-phase viscoplastic and a classic rateindependent isotropic hardening material model were applied in the numerical simulations of both-ends-fixed bar Satoh tests and a single-pass gas metal arc weld. The influence of material modelling choices on the agreement between numerical simulation and experimental results is discussed, and recommendations for further work are given. KW - Residual stress KW - Viscoplasticity KW - Material modeling KW - Grade S960QL steel PY - 2018 DO - https://doi.org/10.1016/j.crme.2018.08.001 VL - 346 IS - 11 SP - 1018 EP - 1032 PB - Elsevier Masson SAS AN - OPUS4-46512 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Prasetiadi, A. E. A1 - Jost, M. A1 - Schulz, Baerbel A1 - Quibeldey, M. A1 - Rabe, Torsten A1 - Follmann, R. A1 - Jakoby, R. T1 - Liquid-crystal-based amplitude tuner and tunable SIW filter fabricated in LTCC technology N2 - Tunable microwave devices will play an important role in future wireless systems, in which high-frequency bands, e.g. millimeter waves, will become promising, due to its huge spectrum availability. At such frequency bands, liquid crystals (LCs) exhibit low microwave loss, which is excellent compared with the other tuning elements. In this paper, LC-based microwave components are fabricated by using low temperature co-fired ceramic technology, allowing the integration of the LC into microwave structures. The first component, the Amplitude tuner, controls the signal’s amplitude by using the interference concept, which exhibits a tunable attenuation range from 11 dB to 30 dB at 30 GHz. The second component is a 3-pole tunable bandpass filter, which is realized by using a substrate integrated waveguide topology, enabling a device with comparatively high-quality factors (Q-factors). The measurement results show Q-factors in the range of 68 to 100 for a frequency tuning of 29.4–30.1 GHz, i.e. a tuning range of 700 MHz, accompanied by an insertion loss 2 dB to 4 dB. KW - Passive components and circuits KW - Filters KW - Microwave technology PY - 2018 DO - https://doi.org/10.1017/S1759078718000600 SN - 1759-0787 VL - 10 IS - 5-6 SP - 674 EP - 681 PB - Cambridge University Press AN - OPUS4-46985 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thiede, Tobias A1 - Cabeza, S. A1 - Mishurova, Tatiana A1 - Nadammal, N. A1 - Kromm, Arne A1 - Bode, Johannes A1 - Haberland, C. A1 - Bruno, Giovanni T1 - Residual stress in selective laser melted Inconel 718: Influence of the removal from base plate and deposition hatch length N2 - The residual stress distribution in IN718 elongated prisms produced by Selective Laser Melting was studied by means of neutron (bulk) and laboratory X-ray (surface) diffraction. Two deposition hatch lengths were considered. A horizontal plane near the top surface (perpendicular to the building direction) and a vertical plane near the lateral surface (parallel to the building direction) were investigated. Samples both in as-built (AB) condition and removed (RE) from the base plate were characterized. While surface stress fields seem constant for AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e. with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the baseplate. KW - Residual stress KW - Additive manufacturing KW - Neutron diffraction KW - Selective laser melting KW - Laboratory X-ray diffraction KW - Coordinate measurement machine KW - IN718 PY - 2018 DO - https://doi.org/10.1520/MPC20170119 SN - 2379-1365 VL - 7 IS - 4 SP - 717 EP - 735 PB - ASTM International CY - USA, West Conshohocken AN - OPUS4-46673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kirner, Sabrina V. A1 - Slachciak, Nadine A1 - Elert, Anna Maria A1 - Griepentrog, Michael A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Sahre, Mario A1 - Dörfel, Ilona A1 - Sturm, Heinz A1 - Pentzien, Simone A1 - Koter, Robert A1 - Spaltmann, Dirk A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Tribological performance of titanium samples oxidized by fs-laser radiation, thermal heating, or electrochemical anodization N2 - Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms. KW - Femtosecond laser KW - Titanium KW - Oxidation KW - Friction PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-445609 DO - https://doi.org/10.1007/s00339-018-1745-8 SN - 0947-8396 SN - 1432-0630 VL - 124 IS - 4 SP - 326, 1 EP - 10 PB - Springer-Verlag AN - OPUS4-44560 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eggeler, G. A1 - Wieczorek, N. A1 - Fox, F. A1 - Berglund, S. A1 - Bürger, D. A1 - Dlouhý, A. A1 - Wollgramm, P. A1 - Neuking, K. A1 - Schreuer, J. A1 - Agudo Jácome, Leonardo A1 - Gao, S. A1 - Hartmaier, A. A1 - Laplanche, G. T1 - On shear testing of single crystal Ni-base superalloys N2 - Shear testing can contribute to a better understanding of the plastic deformation of Ni-base superalloy single crystals. In the present study, shear testing is discussed with special emphasis placed on its strengths and weaknesses. Key mechanical and microstructural results which were obtained for the high-temperature (T ≈ 1000 °C) and low-stress (τ ≈ 200 MPa) creep regime are briefly reviewed. New 3D stereo STEM images of dislocation substructures which form during shear creep deformation in this regime are presented. It is then shown which new aspects need to be considered when performing double shear creep testing at lower temperatures (T < 800 °C) and higher stresses (τ > 600 MPa). In this creep regime, the macroscopic crystallographic [11−2](111) shear system deforms significantly faster than the [01−1](111) system. This represents direct mechanical evidence for a new planar fault nucleation scenario, which was recently suggested (Wu et al. in Acta Mater 144:642–655, 2018). The double shear creep specimen geometry inspired a micro-mechanical in-situ shear test specimen. Moreover, the in-situ SEM shear specimen can be FIB micro-machined from prior dendritic and interdendritic regions. Dendritic regions, which have a lower γ′ volume fraction, show a lower critical resolved shear stress. T2 - EuroSuperalloys 2018 CY - Oxford, UK DA - 09.09.2018 KW - Superalloy single crystals KW - Shear testing KW - Creep mechanisms KW - In-situ SEM micro shear deformation KW - Transmission electron microscopy PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-456591 DO - https://doi.org/10.1007/s11661-018-4726-9 SN - 1073-5623 SN - 1543-1940 VL - 49A IS - 9 SP - 3951 EP - 3962 PB - Springer US CY - New York AN - OPUS4-45659 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Sophie A1 - Mieller, Björn A1 - Delorme, F. A1 - Chen, C. A1 - Bektas, M. A1 - Moos, R. A1 - Rabe, Torsten T1 - Influence of Reaction-Sintering and Calcination Conditions on Thermoelectric Properties of Sm-doped Calcium Manganate CaMnO3 N2 - A wide range of solid-state synthesis routes for calcium manganate is reported in the literature, but there is no systematic study about the influence of the solid-state synthesis conditions on thermoelectric properties. Therefore, this study examined the influence of calcination temperature and calcination cycles on the Seebeck coefficient, electrical conductivity, and thermal conductivity. Higher calcination temperatures and repeated calcination cycles minimized the driving force for sintering of the synthesized powder, leading to smaller shrinkage and lower densities of the sintered specimens. As the electrical conductivity increased monotonously with increasing density, a higher energy input during calcination caused deterioration of electrical conductivity. Phase composition and Seebeck coefficient of sintered calcium manganate were not influenced by the calcination procedure. The highest thermoelectric properties with the highest power factors and figures of merit were obtained by means of reaction-sintering of uncalcined powder. KW - Thermoelectric oxides KW - Calcination KW - Solid-state-synthesis KW - Power factor KW - Reaction-sintering PY - 2018 DO - https://doi.org/10.4416/JCST2018-00017 SN - 2190-9385 VL - 9 IS - 3 SP - 289 EP - 300 PB - Göller Verlag AN - OPUS4-46224 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bresch, Sophie A1 - Mieller, Björn A1 - Selleng, Christian A1 - Stöcker, T. A1 - Moos, R. A1 - Rabe, Torsten T1 - Influence of the calcination procedure on the thermoelectric properties of calcium cobaltite Ca3Co4O9 N2 - Calcium cobaltite is one of the most promising oxide p-type thermoelectric materials. The solid-state reaction (or calcination, respectively), which is well known for large-scale powder synthesis of functional materials, can also be used for the synthesis of thermoelectric oxides. There are various calcination routines in literature for Ca3Co4O9 powder synthesis, but no systematic study has been done on the influence of calcination procedure on thermoelectric properties. Therefore, the influence of calcination conditions on the Seebeck coefficient and the electrical conductivity was studied by modifying calcination temperature, dwell time, particle size of raw materials and number of calcination cycles. This study shows that elevated temperatures, longer dwell times, or repeated calcinations during powder synthesis do not improve but deteriorate the thermoelectric properties of calcium cobaltite. Diffusion during calcination leads to idiomorphic grain growth, which lowers the driving force for sintering of the calcined powder. A lower driving force for sintering reduces the densification. The electrical conductivity increases linearly with densification. The calcination procedure barely influences the Seebeck coefficient. The calcination procedure has no influence on the phase formation of the sintered specimens. KW - Thermoelectrics KW - Calcination KW - Calcium Cobaltite KW - Solid-State-Synthesis KW - Reaction-sintering PY - 2018 DO - https://doi.org/10.1007/s10832-018-0124-3 SN - 1385-3449 SN - 1573-8663 VL - 40 IS - 3 SP - 225 EP - 234 PB - Springer AN - OPUS4-44336 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Agudo Jácome, Leonardo A1 - Pöthkow, K. A1 - Paetsch, O. A1 - Hege, H.-C. T1 - Three-dimensional reconstruction and quantification of dislocation substructures from transmission electron microscopy stereo pairs N2 - A great amount of material properties is strongly influenced by dislocations, the carriers of plastic deformation. It is therefore paramount to have appropriate tools to quantify dislocation substructures with regard to their features, e.g., dislocation density, Burgers vectors or line direction. While the transmission electron microscope (TEM) has been the most widely-used equipment implemented to investigate dislocations, it usually is limited to the two-dimensional (2D) observation of three-dimensional (3D) structures. We reconstruct, visualize and quantify 3D dislocation substructure models from only two TEM images (stereo pairs) and assess the results. The reconstruction is based on the manual interactive tracing of filiform objects on both images of the stereo pair. The reconstruction and quantification method are demonstrated on dark field (DF) scanning (S)TEM micrographs of dislocation substructures imaged under diffraction contrast conditions. For this purpose, thick regions (> 300 nm) of TEM foils are analyzed, which are extracted from a Ni-base superalloy single crystal after high temperature creep deformation. It is shown how the method allows 3D quantification from stereo pairs in a wide range of tilt conditions, achieving line length and orientation uncertainties of 3% and 7°, respectively. Parameters that affect the quality of such reconstructions are discussed. KW - Dislocation KW - Diffraction contrast KW - Scanning transmission electron microscopy (STEM) KW - Stereoscopy KW - Visualization PY - 2018 DO - https://doi.org/10.1016/j.ultramic.2018.08.015 SN - 0304-3991 VL - 195 SP - 157 EP - 170 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-46355 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Höhne, Patrick A1 - Mieller, Björn A1 - Rabe, Torsten T1 - Slurry development for spray granulation of ceramic multicomponent batches N2 - The granules commonly yielded by spray drying procedures exhibit a hard shell and an irregular, dimpled shape, which is often described as donut-like morphology. Sintered parts produced from such granules suffer from microstructural defects and reduced mechanical properties resulting from these disadvantageous granule properties. Using the example of alumina, zirconia and zirconia-toughened alumina (ZTA) batches, this paper shows that the morphology of the granules can be tuned by adjusting slurry stability. High zeta potential is essential to optimally disperse the particles. But to achieve spherical and soft granules the electrostatic repulsion forces between the particles should be reduced before spray granulation. Electrostatic repulsion forces were changed with the addition of nitric acid. Measurements of zeta potential and viscosity, as well as sedimentation investigations with an optical centrifuge were used for precise slurry assessment as a major precondition for optimal and reproducible adjustment of slurries before spray drying. Sedimentation analysis using an optical centrifuge was performed to investigate different influences like that of additive composition, solids content or pH-value on the sedimentation behavior. Adequately flocculated slurries lead to homogeneous, soft granules that can be easily deformed and pressed. The fraction of donut-shaped particles and the rigidity of granules were reduced. Consequently, the sintered parts produced from these granulates show improvements regarding porosity, pore size distribution, sintered density and biaxial strength. KW - Slurry optimization KW - Optical centrifugation KW - Destabilization KW - Spray drying KW - Biaxial strength PY - 2018 DO - https://doi.org/10.4416/JCST2018-00022 SN - 2190-9385 VL - 9 IS - 3 SP - 327 EP - 336 PB - Göller Verlag AN - OPUS4-46225 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mujica Roncery, L. A1 - Agudo Jácome, Leonardo A1 - Aghajani, A. A1 - Theisen, W. A1 - Weber, S. T1 - Subsurface characterization of high-strength high-interstitial austenitic steels after impact wear N2 - The microstructure of the subsurface after impact wear of three high-strength high interstitial austenitic steels has been analysed using transmission electron microscopy (TEM) in alloys with C and N as interstitial elements. In all cases, a nanocrystalline region followed by a transition zone and a cold-worked area are present. Additionally, microhardness and nano-scratching tests were conducted to study the wear-related properties of the impact subsurface and the base material. The results of the microstructural analysis reveal that the following mechanisms are involved during impact wear: abrasion (ploughing), microcrack formation associated with contact fatigue, entrapment and adhesion of SiO2 particles. The analysis of the wear-related properties indicates that the subsurface acts as a self-protective layer that prevents the deterioration of the substrate. KW - Impact wear KW - TEM KW - Nano-scratch test KW - High interstitial austenitic steel PY - 2018 DO - https://doi.org/10.1016/j.wear.2018.02.016 SN - 0043-1648 VL - 402-403 SP - 137 EP - 147 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-44290 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schulz, T. A1 - Reimann, T. A1 - Bochmann, A. A1 - Vogel, A. A1 - Capraro, B. A1 - Mieller, Björn A1 - Teichert, S. A1 - Töpfer, J. T1 - Sintering behavior, microstructure and thermoelectric properties of calcium cobaltite thickfilms for transversal thermoelectric multilayer generators N2 - The sintering behavior and the thermoelectric performance of Ca3Co4O9 multilayer laminates were studied, and a multilayer thermoelectric generator was fabricated. Compacts and multilayer samples with anisotropic microstructure and residual porosity were obtained after conventional sintering at 920 °C, whereas dense and isotropic multilayer samples were prepared by firing at 1200 °C and reoxidation at 900 °C. A hot-pressed sample has a dense and anisotropic microstructure. Samples sintered at 920 °C exhibit low electrical conductivity due to the low density, whereas the Seebeck coefficient is not sensitive to preparation conditions. However, thermal conductivity of multilayers is very low, and, hence acceptable ZT values are obtained. A ransversal multilayer thermoelectric generator (TMLTEG) was fabricated by stacking layers of Ca3Co4O9 green tapes, AgPd conductor printing, and co-firing at 920 °C. The TMLTEG has a power output of 3 mW at ΔT =200 K in the temperature interval of 25 °C to 300 °C. KW - Thermoelectric oxide KW - Calcium cobaltite KW - Pressure-assisted sintering KW - Multilayer PY - 2018 DO - https://doi.org/10.1016/j.jeurceramsoc.2017.11.017 SN - 0955-2219 SN - 1873-619X VL - 38 IS - 4 SP - 1600 EP - 1607 PB - Elsevier Ltd. AN - OPUS4-43983 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonntag, Nadja A1 - Skrotzki, Birgit A1 - Stegemann, Robert A1 - Löwe, Peter A1 - Kreutzbruck, M. T1 - The role of surface topography on deformation-induced magnetization under inhomogeneous elastic-plastic deformation N2 - It is widely accepted that the magnetic state of a ferromagnetic material may be irreversibly altered by mechanical loading due to magnetoelastic effects. A novel standardized nondestructive testing (NDT) technique uses weak magnetic stray fields, which are assumed to arise from inhomogeneous deformation, for structural health monitoring (i.e., for detection and assessment of damage). However, the mechanical and microstructural complexity of damage has hitherto only been insufficiently considered. The aim of this study is to discuss the phenomenon of inhomogeneous “self-magnetization” of a polycrystalline ferromagnetic material under inhomogeneous deformation experimentally and with stronger material-mechanical focus. To this end, notched specimens were elastically and plastically deformed. Surface magnetic states were measured by a three-axis giant magnetoresistant (GMR) sensor and were compared with strain field (digital image correlation) and optical topography measurements. It is demonstrated that the stray fields do not solely form due to magnetoelastic effects. Instead, inhomogeneous plastic deformation causes topography, which is one of the main origins for the magnetic stray field formation. Additionally, if not considered, topography may falsify the magnetic signals due to variable lift-off values. The correlation of magnetic vector components with mechanical tensors, particularly for multiaxial stress/strain states and inhomogeneous elastic-plastic deformations remains an issue. KW - Magnetic stray fields KW - Magnetomechanical effect KW - Damage KW - Topography KW - Multiaxial deformation KW - Notch KW - Plastic deformation KW - Metal magnetic memory KW - Digital image correlation KW - Structural steel PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-457878 DO - https://doi.org/10.3390/ma11091518 SN - 1996-1944 VL - 11 IS - 9 SP - 1518, 1 EP - 26 PB - MDPI CY - Basel, Switzerland AN - OPUS4-45787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonntag, Nadja A1 - Cabeza, S. A1 - Kuntner, M. A1 - Mishurova, Tatiana A1 - Klaus, M. A1 - Kling e Silva, L. A1 - Skrotzki, Birgit A1 - Genzel, Ch. A1 - Bruno, Giovanni T1 - Visualisation of deformation gradients in structural steel by macroscopic magnetic domain distribution imaging (Bitter technique) N2 - Abstract While classically used to visualise the magnetic microstructure of functional materials (e.g., for magnetic applications), in this study, the Bitter technique was applied for the first time to visualise macroscopic deformation gradients in a polycrystalline low-carbon steel. Spherical indentation was chosen to produce a multiaxial elastic–plastic deformation state. After removing the residual imprint, the Bitter technique was applied, and macroscopic contrast differences were captured in optical microscopy. To verify this novel characterisation technique, characteristic “hemispherical” deformation zones evolving during indentation were identified using an analytical model from the field of contact mechanics. In addition, near-surface residual stresses were determined experimentally using synchrotron radiation diffraction. It is established that the magnetic domain distribution contrast provides deformation-related information: regions of different domain wall densities correspond to different “hemispherical” deformation zones (i.e., to hydrostatic core, plastic zone and elastic zone, respectively). Moreover, the transitions between these three zones correlate with characteristic features of the residual stress profiles (sign changes in the radial and local extrema in the hoop stress). These results indicate the potential of magnetic domain distribution imaging: visualising macroscopic deformation gradients in fine-grained ferromagnetic material with a significantly improved spatial resolution as compared to integral, mean value-based measurement methods. KW - Bitter technique KW - Deformation KW - Expanding cavity model KW - Indentation KW - Magnetic domain distribution KW - Residual stress PY - 2018 DO - https://doi.org/10.1111/str.12296 SN - 1475-1305 VL - 54 IS - 6 SP - e12296, 1 EP - 15 PB - Wiley AN - OPUS4-46569 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mueller, Axel A1 - Becker, Roland A1 - Dorgerloh, Ute A1 - Simon, Franz-Georg A1 - Braun, Ulrike T1 - The effect of polymer aging on the uptake of fuel aromatics and ethers by microplastics N2 - Microplastics are increasingly entering marine, limnic and terrestrial ecosystems worldwide, where they sorb hydrophobic organic contaminants. Here, the sorption behavior of the fuel-related water contaminants benzene, toluene, ethyl benzene and xylene (BTEX) and four tertiary butyl ethers to virgin and via UV radiation aged polypropylene (PP) and polystyrene (PS) pellets was investigated. Changes in material properties due to aging were recorded using appropriate polymer characterization methods, such as differential scanning calorimetry, Fourier transform infrared spectroscopy, gel permeation chromatography, X-ray photoelectron spectroscopy, and microscopy. Pellets were exposed to water containing BTEX and the ethers at 130-190 mg/L for up to two weeks. Aqueous sorbate concentrations were determined by headspace gas chromatography. Sorption to the polymers was correlated with the sorbate's Kow and was significant for BTEX and marginal for the ethers. Due to substantially lower glass transition temperatures, PP showed higher sorption than PS. Aging had no effect on the sorption behavior of PP. PS sorbed less BTEX after aging due to an oxidized surface layer. KW - BTEX KW - Polypropylene KW - Polystyrene KW - Sorption KW - Degradation PY - 2018 DO - https://doi.org/10.1016/j.envpol.2018.04.127 SN - 0269-7491 VL - 240 SP - 639 EP - 646 PB - Elsevier CY - Amsterdam AN - OPUS4-44990 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Le, Quynh Hoa A1 - Bäßler, Ralph A1 - Knauer, S A1 - Jaeger, P A1 - Kratzig, Andreas A1 - Bettge, Dirk A1 - Kranzmann, Axel T1 - Droplet corrosion of CO2 transport pipeline steels in simulated oxyfuel flue gas N2 - The research focus of this study was set on the corrosion process of condensate as droplets on the surface of carbon steels (X52, X70) martensitic steel UNS S41500, and super austenite UNS N08031 in CO2 atmosphere with impurities at 278 K (to simulate the offshore transportation condition in a buried pipeline). The possibility of dew/droplet formation on the steel surface and wetting behavior of corresponding materials were evaluated by contact angle measurement in dense CO2 at 278 K. To observe the effect of impurities (SO2 and O2) on droplet corrosion process, exposure tests were carried out in the mixed atmosphere with a drop, 1 ‑ 10 µL in volume, of CO2 saturated ultra-pure water on steel surface. Comparable exposure tests were carried out with the same gas mixture and the same volume of water, as vapor, to observe the droplet formation and the corrosion process that follows. Effects of surface roughness on the droplet formation and its corrosion process were further studied and showed no significant role upon long time exposure. The results from droplet experiments were compared to those from the bulk electrolyte for the further recommendation on the quality control of gas stream along with the use of carbon steels as transport pipelines in CCS - Carbon Capture and Storage system. KW - CCUS, supercritical/dense phase CO2, carbon steels, martensitic steel, superaustenite steel, droplet corrosion PY - 2018 UR - http://corrosionjournal.com/doi/abs/10.5006/2927 DO - https://doi.org/10.5006/2927 SN - 0010-9312 SN - 1938-159X VL - 74 IS - 12 SP - 1406 EP - 1420 PB - NACE International CY - Houston, Texas, USA AN - OPUS4-46903 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -