TY - JOUR A1 - Hennig, Andreas A1 - Dietrich, Paul A1 - Hemmann, Felix A1 - Thiele, T. A1 - Borcherding, H. A1 - Hoffmann, Angelika A1 - Schedler, U. A1 - Jäger, Christian A1 - Resch-Genger, Ute A1 - Unger, Wolfgang T1 - En route to traceable reference standards for surface group quantifications by XPS, NMR and fluorescence spectroscopy N2 - The fluorine content of polymer particles labelled with 2,2,2-trifluoroethylamine was reliably quantified with overlapping sensitivity ranges by XPS and solid-state NMR. This provides a first step towards reference materials for the metrological traceability of surface group quantifications. The extension of this concept to fluorescence spectroscopy is illustrated. KW - Polymer beads KW - Poly(acrylic acid)-grafted particles KW - XPS KW - SEM KW - Surface analysis KW - Fluorescent dye labeling KW - NMR PY - 2015 DO - https://doi.org/10.1039/c4an02248c SN - 0003-2654 SN - 1364-5528 VL - 140 IS - 6 SP - 1804 EP - 1808 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-32794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jäger, Christian T1 - Comparison of 19F qNMR, absolute fluorescence, and absorption measurement of dye concentrations in fluorescent PS particles T2 - 53rd Experimental Nuclear Magnetic Resonance Conference CY - Miami, FL, USA DA - 2012-04-15 PY - 2012 AN - OPUS4-25718 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fichera, Mario Augusto A1 - Braun, Ulrike A1 - Schartel, Bernhard A1 - Sturm, Heinz A1 - Knoll, Uta A1 - Jäger, Christian T1 - Solid-state NMR investigations of the pyrolysis and thermo-oxidative decomposition products of a polystyrene/red phosphorus/magnesium hydroxide system N2 - Thermal, thermo-oxidative and fire residues of high impact polystyrene/magnesium hydroxide/red phosphorus (HIPS/Mg(OH)2/Pr) are investigated by solid-state NMR and compared with the results for the binary subsystem Mg(OH)2/Pr. The influences of oxygen, nitrogen and temperature are discussed. For a thermal decomposition and pyrolysis during combustion, the main pyrolysis of HIPS takes place while the remaining residue is a rather intact polymer, with a major share of the embedded Pr still present. Subsequently, mainly amorphous phosphates and a slight amount of crystalline Mg3(PO4)2 and Mg2P2O7 are formed at the highest temperatures. Only with increasing mass loss does the remaining polystyrene structure decompose and graphitic structures occur. The influence of oxygen on the decomposition mechanism is most obvious for the binary system Mg(OH)2/Pr. Pr vanishes more rapidly and crystalline, oxygen-rich magnesium phosphates are formed. In HIPS/Mg(OH)2/Pr systems the polymer acts as a barrier to reaction by the embedded particles, so that major characteristics of an anaerobic decomposition are found. Significant amounts of phosphorus are retained in the condensed phase through a reaction of Pr with Mg(OH)2 to mostly amorphous phosphates. This formation of amorphous inorganic magnesium phosphates can act as an additional physical barrier. This study outlines some advanced approaches for controlling the condensed-phase mechanisms of phosphorus and underlines that solid-state NMR is a most powerful tool for investigating the organic and inorganic residues. KW - HIPS KW - Red phosphorus KW - Magnesium hydroxide KW - Solid-state NMR KW - Flame retarded polymers PY - 2007 SN - 0165-2370 SN - 1873-250X VL - 78 IS - 2 SP - 378 EP - 386 PB - Elsevier CY - Amsterdam AN - OPUS4-14517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Seto, J. A1 - Ma, Y. A1 - Davis, S.A. A1 - Meldrum, F. A1 - Gourrier, A. A1 - Kim, Y.-Y. A1 - Schilde, U. A1 - Sztucki, M. A1 - Burghammer, M. A1 - Maltsev, Sergey A1 - Jäger, Christian A1 - Cölfen, H. T1 - Structure-property relationships of a biological mesocrystal in the adult sea urchin spine N2 - Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature’s demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials. KW - Calcium carbonate biomineralization KW - Echinoderm skeleton KW - Hierarchical structuring KW - Mesocrystal KW - Skeletal elements PY - 2012 DO - https://doi.org/10.1073/pnas.1109243109 SN - 0027-8424 SN - 1091-6490 VL - 109 IS - 10 SP - 3699 EP - 3704 PB - National Academy of Sciences CY - Washington, DC AN - OPUS4-27726 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kowalke, J. A1 - Arnold, C. A1 - Ponomarev, I. A1 - Jäger, Christian A1 - Kroll, P. A1 - Brendler, E. A1 - Kroke, E. T1 - Structural Insight into Layered Silicon Hydrogen Phosphates Containing [SiO6] Octahedra Prepared by Different Reaction Routes N2 - The layered silicophosphate Si(HPO4)(2) was prepared via a novel synthesis approach using silicon nanopowder and ortho-phosphoric acid at 150 degrees C providing a polycrystalline product. Silicophosphate compounds with sixfold coordinated silicon atoms obtained from pyrophosphoric acid H4P2O7 and tetraalkoxysilanes via a sol-gel route exhibit the same short-range order. The solid products were analyzed with XRD, elemental analysis (ICP-AES), and detailed NMR spectroscopic studies, including H-1, C-13, Si-29, and P-31 MAS-, P-31-Si-29-REDOR, HETCOR, and CP-RFDR experiments. DFT calculations support the structure of Si(HPO4)(2) consisting of layers of [SiO6] octahedra linked by [O3P(OH)] tetrahedra. The OH groups point to the neighboring layers and may be substituted by ethoxy or other groups. KW - Silicon KW - Phosphorus KW - Sol-gel processes KW - NMR spectroscopy KW - Computational chemistry PY - 2019 DO - https://doi.org/10.1002/ejic.201801321 IS - 6 SP - 828 EP - 836 PB - ChemPubSoc AN - OPUS4-48058 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Greiser, Sebastian A1 - Jäger, Christian A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten T1 - Einkomponentige alkaliaktivierte Bindemittel und Mörtel mit hohem Widerstand gegen Schwefelsäureangriff N2 - Einkomponentige alkaliaktivierte Bindemittel (AAB), d. h. AAB, bei denen der Aktivator als Feststoff im Bindemittel vorliegt, weisen Vorteile hinsichtlich der praktischen Anwendung im Bauwesen gegenüber konventionellen AAB auf. Einkomponentige AAB lassen sich als Gemische aus reaktiver Silica und Natriumaluminat herstellen, wobei die Reaktionsprodukte von der eingesetzten Silica und den Verhältnissen Na2O/Al2O3/SiO2/H2O abhängen: Während Mikrosilica und ähnliche Reststoffe zu zeolithreichen Produkten führen, erhält man aus Reisschalenasche vollständig amorphe Gele (sog. «Geopolymere »). Mörtel auf Basis solcher Bindemittel entsprechen den Anforderungen von DIN 19573:2016-03 hinsichtlich des Widerstands gegen Schwefelsäureangriff (Prüfung bei pH = 1 für 70 d) und sind damit potentiell als Reparatursysteme für Abwasserinfrastruktur geeignet. Untersuchungen mittels 29Si-MAS-NMR und 1H-29Si-Kreuzpolarisations(CP)-MAS-NMR sowie REM-Aufnahmen von erhärteten und dem Schwefelsäureangriff ausgesetzten AAB zeigen, dass der hohe Säurewiderstand v. a. auf die Fällung von Silicagel an der Grenzfläche Mörtel/Säure zurückzuführen ist, wodurch der Korrosionsfortschritt in darunterliegenden Schichten verlangsamt wird. T2 - Tagung Bauchemie der GDCh-Fachgruppe Bauchemie CY - Aachen, Germany DA - 30.09.2019 KW - Alkaliaktivierte Bindemittel KW - Biogene Schwefelsäurekorrosion KW - Abwasserinfrastruktur KW - Reparatursysteme PY - 2019 SP - 107 EP - 113 PB - Gesellschaft Deutscher Chemiker CY - Frankfurt am Main AN - OPUS4-49264 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Greiser, Sebastian A1 - Jäger, Christian A1 - Kühne, Hans-Carsten ED - Wang, J. ED - Kriven, W. ED - Fey, T. ED - Colombo, P. ED - Weber, W.J. ED - Amoroso, J. ED - Fahrenholtz, W.G. ED - Shimamura, K. ED - Halbig, M. ED - Kirihara, S. ED - Wu, Y. ED - Shurgart, K. T1 - One-part geopolymers and aluminosilicate gel-zeolite composites: factors influencing microstructure and engineering properties N2 - Mixing and curing of geopolymers and related alkali-activated materials without storage and handling of highly alkaline solutions possesses advantages regarding safety and economic viability. One possible approach is to produce these materials from solid silica feedstocks and solid sodium aluminate, and subsequent mixing with water. We present a comparison between geopolymers and aluminosilicate gel-zeolite composites synthesized by this route from different silica feedstocks (by-product silica from chlorosilane production, microsilica, rice husk ash) and with different SiO2/Al2O3 ratios, using results from XRD, NMR, SEM, thermal analysis, mechanical and acid resistance testing. The use of rice husk ash favors formation of a fully amorphous geopolymer with high strength. Utilization of the other silica feedstocks leads to formation of aluminosilicate gel-zeolite composites, the amount and kind of zeolites depending on the feedstock and the SiO2/Al2O3 ratio. These composites show beneficial dehydration behavior, viz. no distinct dehydration step of thermal strain, with the phase assemblage after heating to 1000°C controlled by the starting composition. Mortars produced from both, the geopolymers as well as the composites, exhibit high resistance to sulfuric acid attack, making them promising materials for the construction and the repair of industrial and sewer structures. T2 - 42nd International Conference on Advanced Ceramics and Composites CY - Daytona Beach, FL, USA DA - 21.01.2018 KW - Alkali-activated materials KW - One-part geopolymers KW - Sulfuric acid resistance KW - High-temperature resistance PY - 2019 DO - https://doi.org/10.1002/9781119543381.ch17 VL - 39 IS - 3 SP - 183 EP - 196 PB - John Wiley & Sons AN - OPUS4-47282 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Patrick A1 - Gluth, Gregor A1 - Lindemann, Mathias A1 - Greiser, Sebastian A1 - Jäger, Christian A1 - Brouwers, H.J.H. ED - Bernal, S.A. ED - Provis, J.L. T1 - Structural investigations on one-part geopolymers after different drying regimes T2 - 34th Cement and concrete science conference CY - Sheffield, UK DA - 2015-09-14 KW - Geopolymers KW - One-part mix PY - 2015 SP - 37 EP - 40 AN - OPUS4-34554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, Patrick A1 - Gluth, Gregor A1 - Jäger, Christian A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten T1 - Sulfuric acid resistance of one-part alkali-activated mortars N2 - One-part alkali-activated (geopolymer) mortars based on three different silica-rich starting materials and sodium aluminate, with and without ground granulated blast furnace slag (GGBFS) addition, were tested regarding sulfuric acid resistance according to DIN 19573:2016-03 (70 days at pH = 1). Corresponding pastes were characterized by XRD, SEM, chemical analysis, 29Si MAS NMR and 1H-29Si CPMAS NMR after water storage and after acid exposure. The mortars exhibited a high resistance against sulfuric acid attack, with the best ones conforming to the requirements of DIN 19573:2016-03. The analytical results showed that this was due to precipitation of silica gel at the acid-mortar interface, which formed a mechanically stable layer that protected the subjacent mortar and thus inhibited further degradation. The addition of GGBFS decreased the acid resistance via formation of expansive calcium sulfate phases. KW - Alkali activated materials KW - Acid resistance KW - Nuclear magnetic resonance KW - One-part geopolymers PY - 2018 DO - https://doi.org/10.1016/j.cemconres.2018.04.009 SN - 0008-8846 VL - 109 SP - 54 EP - 63 PB - Elsevier Ltd. AN - OPUS4-44722 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Patrick A1 - Gluth, Gregor A1 - Greiser, Sebastian A1 - Jäger, Christian A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten T1 - Investigations on one-part geopolymers synthesized from different silica sources N2 - One-part geopolymers, synthesized from three different silica sources and sodium aluminate, were investigated regarding their microstructure and the evolution of their compressive strength on curing at slightly elevated temperatures. The effect of thermal treatment was studied up to 1000 °C and for the investigation of the chemical durability specific samples were treated with sulfuric acid (H2SO4, pH = 1). Depending on the silica feedstock, different degrees of reaction were observed. One of the silicas had a significantly higher reactivity. For two of the silicas, significant amounts of zeolites occurred as reaction products besides geopolymeric gel, whereas the more reactive silica source lead to the formation of a rather fully condensed geopolymeric network. The composites indicated promising behavior on heating in so far as no distinct shrinkage step occurred in the temperature range of dehydration. Up to 400 °C the residual strength of those mixes increased. Above 800 °C the samples underwent new phase formation. After exposure to sulfuric acid (pH 1; 70 d) specimens showed a residual compressive strength of about 77 % of the reference, indicating high acid resistance. T2 - 6th International Conference on Non-Traditional Cement & Concrete CY - Brno, Czech Republic DA - 19.06.2017 KW - Geopolymers KW - Zeolites KW - Thermal properties KW - Acid resistance KW - Chemical durability PY - 2017 SN - 978-80-214-5507-8 SP - 299 EP - 306 AN - OPUS4-40774 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, Patrick A1 - Greiser, Sebastian A1 - Gluth, Gregor A1 - Jäger, Christian A1 - Brouwers, H.J.H. T1 - Degree of reaction and phase content of silica-based one-part geopolymers investigated using chemical and NMR spectroscopic methods N2 - One-part geopolymers were synthesized from two different silica materials (a silica-rich residue from chlorosilane production and a commercial microsilica) and sodium aluminate at three different SiO2/Al2O3 ratios and a nominal water/solids ratio of 0.5. The degree of reaction of the silica in the cured geopolymers (i.e. the fraction of silica dissolved to form aluminosilicates and minor products) was determined using two different methods: chemical attack with HCl to dissolve the reaction products and evaluation of peak areas of 29Si MAS NMR spectra. It was found that the degree of reaction of the silica decreases with increasing the silica content of the starting mix, and that it is almost constant after 1 day of curing and almost independent from the kind of starting silica. From the results of the NMR-based method, the mean SiO2/Al2O3 ratio of the reaction products (aluminosilicates and minor products) can be estimated to be ca. 2.0, nearly independent of the starting composition of the geopolymers. The dissolution method is biased, but of sufficient precision to be useful for following changes of the degree of reaction. Major crystalline phases in the cured geopolymers are zeolite A and/or hydrosodalite. Depending on the starting composition, the relative amounts of these zeolites vary; additionally, sodalite (only for the residue from chlorosilane production with >1 wt% Cl-), faujasite, and zeolite EMT can appear in the geopolymers. The 29Si and 27Al MAS NMR results indicate mainly Si(4Al) and Al(4Si) sites, in line with the presence of zeolite A, hydrosodalite, sodalite, and geopolymeric gel of comparatively low SiO2/Al2O3 ratio. KW - Geopolymers KW - One-part mix KW - 29Si MAS NMR KW - 27Al MAS NMR KW - Silica KW - Degree of reaction PY - 2015 DO - https://doi.org/10.1007/s10853-015-9232-5 SN - 0022-2461 SN - 1573-4803 VL - 50 IS - 20 SP - 6768 EP - 6778 PB - Springer Science + Business Media B.V. CY - Norwell, Mass. AN - OPUS4-33826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Greiser, Sebastian A1 - Sturm, Patrick A1 - Gluth, Gregor A1 - Hunger, M. A1 - Jäger, Christian T1 - Differentiation of the solid-state NMR signals of gel, zeolite phases and water species in geopolymer-zeolite composites N2 - Geopolymer-zeolite composites were synthesized using a silica-rich industrial byproduct from chlorosilane production and sodium aluminate. Pastes were cured at 80 °C and 80% RH, and subsequently dried in two different climates: at 23 °C and 50% RH, and under vacuum. 1H MAS, 23Na MAS and 29Si MAS NMR and XRD measurements were performed after the drying procedures as well as after subsequent aging. Zeolite Na-A was found beside traces of faujasite-type zeolite and zeolite EMT as major crystalline phases in the cured composites; the fraction of geopolymeric gel in the reaction products was determined to be ~18% on a molar basis. Various water species could be distinguished using 1H MAS and 1H-29Si CP MAS NMR, applying rotorsynchronized echo experiments. The largest fraction of the pore water resides in the α-cages of the zeolite Na-A and in the geopolymeric gel; in addition, water exists in the β-cages of the zeolites and adsorbed at sodium ions. The water species in α-cages and in the pores of the geopolymeric gel exhibit slightly different chemical shifts of 4.7 ppm and 4.9 ppm, respectively, in the 1H MAS NMR spectra. Changes of the water content in the geopolymer pores of differently dried samples were observed and led to slightly varied chemical shifts in the 29Si MAS NMR spectra too. Measurements after more than 500 days revealed no significant aging effects of the composites, which confirm their chemical stability. KW - Geopolymers KW - Aluminosilicate inorganic polymers KW - Zeolite Na-A KW - Spectroscopy KW - Drying PY - 2017 DO - https://doi.org/10.1016/j.ceramint.2016.11.004 SN - 0272-8842 VL - 43 IS - 2 SP - 2202 EP - 2208 PB - Elsevier AN - OPUS4-38694 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Greiser, Sebastian A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Brouwers, H.J.H. A1 - Jäger, Christian ED - Bílek, V. ED - Kersner, Z. T1 - 27Al-1H and 27Al-29Si Double resonance NMR of one-part geopolymers N2 - The production and processing of ordinary Portland cement are responsible for nearly 5% of the world C02 emissions. Due to the world’s increasing requirement for building materials, this air pollution is growing up in the next decades. Alternative cement such as geopolymers can reduce these emissions effectively, Conventional geopolymer binders, produced ffom fly ash or metakaolin as aluminosilicate source and water-glass or alkali hydroxide Solutions as activator, are often used and studied. It is known that under appropriate conditions the starting materials form a three-dimensional aluminosilicate structure and create a gel-like matrix, In our case, a silica source from wastewater treatment of chlorosilane production and solid sodium aluminate as starting materials are initiated to harden by water. This procedure is known as “just add water” or “one-part” geopolymer formulation. These composites have significant advantages for use on construction site, but their Chemical structure is not extensively analyzed. In this work, a well known one-part geopolymer is investigated by 'H and 27A1 magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Furthermore, it is shown that overlapping NMR lines can resolved with echo experiments and T2 - NTCC2014 - International conference on non-traditional cement and concrete CY - Brno, Czech Republic DA - 16.06.2014 KW - Geopolymers KW - One-part formulation KW - Zeolite Na-A KW - NMR KW - REDOR PY - 2014 SN - 978-80-214-4867-4 SP - 91 EP - 94 PB - Novpress AN - OPUS4-31224 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Greiser, Sebastian A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Jäger, Christian T1 - Correction: 29Si{27Al}, 27Al{29Si} and 27Al{1H} double-resonance NMR spectroscopy study of cementitious sodium aluminosilicate gels (geopolymers) and gel–zeolite composites N2 - Correction for ‘29Si{27Al}, 27Al{29Si} and 27Al{1H} double-resonance NMR spectroscopy study of cementitious sodium aluminosilicate gels (geopolymers) and gel–zeolite composites’ by Sebastian Greiser et al., RSC Adv., 2018, 8, 40164–40171, https://doi.org/10.1039/C8RA09246J. PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-635365 DO - https://doi.org/10.1039/d3ra90078a SN - 2046-2069 VL - 13 IS - 37 SP - 26148 PB - Royal Society of Chemistry (RSC) CY - London AN - OPUS4-63536 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hemmann, Felix A1 - Agirrezabal-Telleria, Iker A1 - Jäger, Christian A1 - Kemnitz, E. T1 - Quantification of acidic sites of nanoscopic hydroxylated magnesium fluorides by FTIR and 15N MAS NMR spectroscopy N2 - Lewis and Brønsted sites were quantified in a series of weak acidic hydroxylated magnesium fluorides by Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance spectroscopy (NMR) with pyridine as probe molecule. Molar extinction coefficients, which are necessary for quantitative FTIR measurements, were calculated by an easy approach. It utilizes the fact that both signals, used for the quantification by FTIR, are caused by the same deformation vibration mode of pyridine. Comparison of quantitative FTIR experiments and quantification by NMR shows that concentrations of acidic sites determined by FTIR spectroscopy have to be interpreted with caution. Furthermore, it is shown that the transfer of molar extinction coefficients from one catalyst to another may lead to wrong results. Molar extinction coefficients and concentrations of acidic sites determined by FTIR spectroscopy are affected by grinding and probably the particle size of the sample. High temperature during FTIR experiments has further impact on the quantification results. KW - Acidity KW - Fluoride catalyst KW - Infrared spectroscopy KW - Adsorption of pyridine KW - Molar extinction coefficient determination PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-351448 DO - https://doi.org/10.1039/C5RA15116C SN - 2046-2069 VL - 5 IS - 109 SP - 89659 EP - 89668 PB - RSC Publishing CY - London AN - OPUS4-35144 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hemmann, Felix A1 - Jäger, Christian A1 - Kemnitz, E. T1 - Comparison of acidic site quantification methods for a series of nanoscopic aluminium hydroxide fluorides N2 - Quantitative determination of acidic surface sites is highly important for the characterization of solid acids because the activity of a catalyst is often related to the concentration of these sites. A recently developed method using 15N Nuclear Magnetic Resonance spectroscopy (NMR) for the quantification of acidic Lewis and Brønsted sites has been tested for a series of nanoscopic aluminum hydroxide fluorides. Comparison with other methods for the quantitative determination of acidic sites shows that this 15N NMR quantification method is a promising technique for the comprehensive investigation of acidic sites. Three different acidic sites, one Brønsted and two Lewis sites, can be distinguished by their 15N chemical shifts of pyridine and simultaneously quantified under conditions corresponding to catalytic reaction conditions. Determination of the individual concentrations of acidic sites allows further insight into the catalytic process. It was found that the concentration of Brønsted sites correlates with catalyzed conversion of citronellal to isopulegol in the investigated series of catalysts. Additionally, investigations indicate that one of the Lewis sites become blocked during the reaction of citronellal. KW - Solid acids KW - TOF KW - NH3-TPD KW - Progressive catalyst poisoning KW - FTIR KW - Quantitative NMR KW - Solid state NMR PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-323280 DO - https://doi.org/10.1039/c4ra09477h SN - 2046-2069 VL - 4 IS - 100 SP - 56900 EP - 56909 PB - RSC Publishing CY - London AN - OPUS4-32328 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Greiser, Sebastian A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Jäger, Christian T1 - 29Si{27Al}, 27Al{29Si} and 27Al{1H} double-resonance NMR spectroscopy study of cementitious sodium aluminosilicate gels (geopolymers) and gel-zeolite composites N2 - The influence of starting materials and synthesis route on the properties and the structure of cementitious sodium aluminosilicate gels is not fully understood, partly due their amorphous nature and the fact that they often contain residual reactants, which can make the results of single-pulse NMR spectroscopy applied to these materials difficult to interpret or ambiguous. To overcome some of these limitations, 29Si{27Al} TRAPDOR NMR as well as 27Al{29Si} and 27Al{1H} REDOR NMR spectroscopy were applied to materials synthesized by the one-part alkali-activation route from three different amorphous silica starting materials, including rice husk ash. The latter led to formation of a fully amorphous sodium aluminosilicate gel (geopolymer), while the materials produced from the other silicas contained amorphous phase and crystalline zeolites. Application of the double-resonance NMR methods allowed to identify hydrous alumina gel domains in the rice husk ash-based material as well as significantly differing amounts of residual silica in the three cured materials. Four-coordinated Al existed not only in the aluminosilicate gel framework but also in a water-rich chemical environment with only a small amount of Si in proximity, likely in the alumina gel or possibly present as extra-framework Al in the aluminosilicate gel. The results demonstrate how the employment of different silica starting materials determines the phase assemblage of one-part alkali-activated materials, which in turn influences their engineering properties such as the resistance against chemically/biologically aggressive media. KW - Alkali-activated materials KW - Solid-state NMR KW - Aluminium hydroxide KW - Rice husk ash PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-469353 DO - https://doi.org/10.1039/C8RA09246J SN - 2046-2069 VL - 8 IS - 70 SP - 40164 EP - 40171 PB - Royal Society of Chemistry (RSC) CY - London AN - OPUS4-46935 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kervarec, M.-C. A1 - Kemnitz, E. A1 - Scholz, G. A1 - Rudic, S. A1 - Jäger, Christian A1 - Braun, T. A1 - Michalchuk, Adam A1 - Emmerling, Franziska T1 - A HF Loaded Lewis-Acidic Aluminium Chlorofluoride for Hydrofluorination Reactions N2 - The very strong Lewis acid aluminium chlorofluo-ride (ACF) was loaded with anhydrous HF. The interactionbetween the surface of the catalyst and HF was investigatedusing a variety of characterization methods, which revealed he formation of polyfluorides. Moreover, the reactivity ofthe HF-loaded ACF towards the hydrofluorination of alkyneswas studied. KW - Aluminium KW - HF KW - Hydrofluorination KW - Metal fluorides PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-508360 DO - https://doi.org/10.1002/chem.202001627 VL - 26 SP - 1 PB - Wiley Online Libary AN - OPUS4-50836 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fischer, Franziska A1 - Greiser, Sebastian A1 - Peifer, Dietmar A1 - Jäger, Christian A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Mechanochemically Induced Conversion of Crystalline Benzamide Polymorphs by Seeding N2 - Benzamide has been known for its polymorphism for almost 200 years.Three polymorphic forms are described. To date,itwas only possible to crystallizeametastable form in amixture together with the thermodynamically most stable form I. Acomplete transformation of form Iinto the metastable form III by mechanochemical treatment has been achieved. Catalytic amounts of nicotinamide seeds were used to activate the conversion by mechanochemical seeding. NMR experiments indicated that the nicotinamide molecules were incorporated statistically in the crystal lattice of benzamide form III during the conversion. The transformation pathway was evaluated using in situ powder X-ray diffraction. KW - Nicotinamide KW - Benzamide KW - In situ reactions KW - Mechanochemistry KW - Polymorphs PY - 2016 DO - https://doi.org/10.1002/anie.201607358 VL - 128 IS - 46 SP - 14493 EP - 14497 PB - WILEY-VCH CY - Weinheim AN - OPUS4-38472 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wawrzyn, Eliza A1 - Schartel, Bernhard A1 - Seefeldt, Henrik A1 - Karrasch, Andrea A1 - Jäger, Christian T1 - What reacts with what in bisphenol A polycarbonate/silicon rubber/bisphenol A bis(diphenyl phosphate) during pyrolysis and fire behavior? N2 - The pyrolysis and flame retardancy of a bisphenol A polycarbonate/silicon rubber/bisphenol A bis(diphenyl phosphate) (PC/SiR/BDP) blend were investigated and compared to those of PC/BDP and PC/SiR. The impact modifier SiR consists mainly of poly(dimethylsiloxane) (PDMS > 80 wt %). The pyrolysis of PC/SiR/BDP was studied by thermogravimetry (TG), TG–FTIR to analyze the evolved gases, and a Linkam hot stage cell within FTIR as well as 29Si NMR and 31P NMR to analyze the solid residue. The fire performance was determined by PCFC, LOI, UL 94, and a cone calorimeter under different external irradiations. The fire residues were studied by using ATR-FTIR as well as the additional binary systems PC + PDMS, PC + BDP, and BDP + PDMS, focusing on the specific chemical interactions. The decomposition pathways are revealed, focusing on the competing interaction between the components. Fire retardancy in PC/SiR/BDP is caused by both flame inhibition in the gas phase and inorganic-carbonaceous residue formation in the condensed phase. The PC/SiR/BDP does not work as well superimposing the PC/SiR and PC/BDP performances. PDMS reacts with PC and BDP, decreasing BDP's mode of action. Nevertheless, the flammability (LOI > 37%, UL 94 V-0) of PC/SiR/BDP equals the high level of PC/BDP. Indeed, SiR in PC/SiR/BDP is underlined as a promising impact modifier in flame-retarded PC/impact modifier blends as an alternative to highly flammable impact modifiers such as acrylonitrile–butadiene–styrene (ABS), taking into account that the chosen SiR leads to PC blends with a similar mechanical performance. KW - PC KW - BDP KW - PDMS KW - Flame retardancy KW - Flammability KW - Decomposition KW - Pyrolysis PY - 2012 DO - https://doi.org/10.1021/ie201908s SN - 0888-5885 SN - 1520-5045 VL - 51 IS - 3 SP - 1244 EP - 1255 PB - American Chemical Society CY - Washington, DC AN - OPUS4-25460 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -