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Robert E. Dinnebier - One of the best experts on this subject based on the ideXlab platform.
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dehydration of the sorel Cement Phase 3mg oh 2 mgcl2 8h2o studied by in situ synchrotron x ray powder diffraction and thermal analyses
Zeitschrift für anorganische und allgemeine Chemie, 2014Co-Authors: Tomče Runčevski, Robert E. Dinnebier, Daniela FreyerAbstract:Dehydration is an important process which affects the chemical, physical and mechanical properties of materials. This article describes the thermal dehydration and decomposition of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O, studied by in situ synchrotron X-ray powder diffraction and thermal analyses. Attention is paid on the determination of the chemical composition and crystal structure of the lower hydrates, identified as the Phases 3Mg(OH)2·MgCl2·5.4H2O and 3Mg(OH)2·MgCl2·4.6H2O. The crystal structure of 3Mg(OH)2·MgCl2·4.6H2O is solved and refined by the Rietveld method and a structural model for the 3Mg(OH)2·MgCl2·5.4H2O Phase is given. These Phases show statistical distribution of water molecules, hydroxide and chloride anions positioned as ligands on the magnesium octahedra. A structural scheme of the temperature induced transformations in the thermal range from 25 to 500 °C is presented.
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structural characterization of a new magnesium oxysulfate hydrate Cement Phase and its surface reactions with atmospheric carbon dioxide
Journal of the American Ceramic Society, 2013Co-Authors: Tomče Runčevski, Chengyou Wu, Hongfa Yu, Bo Yang, Robert E. DinnebierAbstract:A new magnesium oxysulfate hydrate Phase, 5Mg(OH)2·MgSO4·7H2O was synthesized and structurally characterized. The new Phase crystallizes in the form of microsized needles and its crystal structure was solved using X-ray powder diffraction. The crystal packing is made of infinite triple MgO6 chains, intercalated with sulfate groups, water molecules, and hydroxide anions. Using vibrational spectroscopy [infrared (IR) and Raman] and Rietveld refinement, the arrangement of water molecules and hydroxide anions were observed to be statistically distributed and dynamically disordered. The high-temperature behavior and decomposition were studied by thermal analyses and in situ X-ray powder diffraction. The high-temperature measurements reveal the presence of five decomposition stages from the new Phase to the production of MgO. After the reactions with atmospheric carbon dioxide were analyzed using micro-Raman spectroscopy, two new carbonate Phases were detected on the surface of the material.
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Dehydration of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O studied by in situ Synchrotron X-ray Powder Diffraction and Thermal Analyses
Zeitschrift für anorganische und allgemeine Chemie, 2013Co-Authors: Tomče Runčevski, Robert E. Dinnebier, Daniela FreyerAbstract:Dehydration is an important process which affects the chemical, physical and mechanical properties of materials. This article describes the thermal dehydration and decomposition of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O, studied by in situ synchrotron X-ray powder diffraction and thermal analyses. Attention is paid on the determination of the chemical composition and crystal structure of the lower hydrates, identified as the Phases 3Mg(OH)2·MgCl2·5.4H2O and 3Mg(OH)2·MgCl2·4.6H2O. The crystal structure of 3Mg(OH)2·MgCl2·4.6H2O is solved and refined by the Rietveld method and a structural model for the 3Mg(OH)2·MgCl2·5.4H2O Phase is given. These Phases show statistical distribution of water molecules, hydroxide and chloride anions positioned as ligands on the magnesium octahedra. A structural scheme of the temperature induced transformations in the thermal range from 25 to 500 °C is presented.
Tomče Runčevski - One of the best experts on this subject based on the ideXlab platform.
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dehydration of the sorel Cement Phase 3mg oh 2 mgcl2 8h2o studied by in situ synchrotron x ray powder diffraction and thermal analyses
Zeitschrift für anorganische und allgemeine Chemie, 2014Co-Authors: Tomče Runčevski, Robert E. Dinnebier, Daniela FreyerAbstract:Dehydration is an important process which affects the chemical, physical and mechanical properties of materials. This article describes the thermal dehydration and decomposition of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O, studied by in situ synchrotron X-ray powder diffraction and thermal analyses. Attention is paid on the determination of the chemical composition and crystal structure of the lower hydrates, identified as the Phases 3Mg(OH)2·MgCl2·5.4H2O and 3Mg(OH)2·MgCl2·4.6H2O. The crystal structure of 3Mg(OH)2·MgCl2·4.6H2O is solved and refined by the Rietveld method and a structural model for the 3Mg(OH)2·MgCl2·5.4H2O Phase is given. These Phases show statistical distribution of water molecules, hydroxide and chloride anions positioned as ligands on the magnesium octahedra. A structural scheme of the temperature induced transformations in the thermal range from 25 to 500 °C is presented.
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structural characterization of a new magnesium oxysulfate hydrate Cement Phase and its surface reactions with atmospheric carbon dioxide
Journal of the American Ceramic Society, 2013Co-Authors: Tomče Runčevski, Chengyou Wu, Hongfa Yu, Bo Yang, Robert E. DinnebierAbstract:A new magnesium oxysulfate hydrate Phase, 5Mg(OH)2·MgSO4·7H2O was synthesized and structurally characterized. The new Phase crystallizes in the form of microsized needles and its crystal structure was solved using X-ray powder diffraction. The crystal packing is made of infinite triple MgO6 chains, intercalated with sulfate groups, water molecules, and hydroxide anions. Using vibrational spectroscopy [infrared (IR) and Raman] and Rietveld refinement, the arrangement of water molecules and hydroxide anions were observed to be statistically distributed and dynamically disordered. The high-temperature behavior and decomposition were studied by thermal analyses and in situ X-ray powder diffraction. The high-temperature measurements reveal the presence of five decomposition stages from the new Phase to the production of MgO. After the reactions with atmospheric carbon dioxide were analyzed using micro-Raman spectroscopy, two new carbonate Phases were detected on the surface of the material.
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Dehydration of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O studied by in situ Synchrotron X-ray Powder Diffraction and Thermal Analyses
Zeitschrift für anorganische und allgemeine Chemie, 2013Co-Authors: Tomče Runčevski, Robert E. Dinnebier, Daniela FreyerAbstract:Dehydration is an important process which affects the chemical, physical and mechanical properties of materials. This article describes the thermal dehydration and decomposition of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O, studied by in situ synchrotron X-ray powder diffraction and thermal analyses. Attention is paid on the determination of the chemical composition and crystal structure of the lower hydrates, identified as the Phases 3Mg(OH)2·MgCl2·5.4H2O and 3Mg(OH)2·MgCl2·4.6H2O. The crystal structure of 3Mg(OH)2·MgCl2·4.6H2O is solved and refined by the Rietveld method and a structural model for the 3Mg(OH)2·MgCl2·5.4H2O Phase is given. These Phases show statistical distribution of water molecules, hydroxide and chloride anions positioned as ligands on the magnesium octahedra. A structural scheme of the temperature induced transformations in the thermal range from 25 to 500 °C is presented.
Barbara Lothenbach - One of the best experts on this subject based on the ideXlab platform.
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The crystal structure of Magnesium Silicate Hydrate (M-S-H) andits relation with talc-like clay mineral
2016Co-Authors: Cédric Roosz, Pierre Henocq, Sylvain Grangeon, Stephane Gaboreau, Philippe Vieillard, Barbara Lothenbach, Valérie Montouillout, Philippe Blanc, Eric GiffautAbstract:In the framework of a geological disposal of radioactive waste, Cement-based materials will be highly used; the deep geological disposal facilitywill imply large amounts of concrete in the clayrock formation. In this context, low pH Cementitious materials are considered, especiallyfor sealingrequirements, in order to minimize chemical interactions at the interfaces between Cementitious materials and the clay surrounding rock formations and/or engineered clay materials. The target is to reach a concrete pore solutionpH more compatible with the clay materials or rock formation (pH ~7-7.5) for reducing the detrimental impact of the alkali plume from the Cement-based materials. Recent studies 1–3 have proposed low-pH formulations based on ternary and quaternary mixes of Portland Cement with supplementary Cementitious materials (SCMs) such as blast furnace slag (BFS) andfly ash (FA).For these formulations, the pHis controlledby low C/S C-S-H. However, if forOrdinary Portland Cement (OPC) concrete formulations, the hydration products are well characterized with suitable constrained kinetic/thermodynamic models 4 [4], , the mineralogical control of elements in solution have to be discussed for low pH formulations because of their higheraluminum and magnesium contents 5. In particular, for the hydration of MgO, which is mainly introduced by the BFS, Zhang et al. 6 have mentioned the precipitation of brucite (MgOH 2) which reacted with the silica fume to produce a magnesium silicate hydrate (M-S-H). The calculated pH in equilibrium with this mineralogical assemblage is around 10.5 and satisfies the requirement of low pH condition. The occurrence of M-S-H has been mentioned in many environments 6–9 , and was described as low crystalline Phases according to the low intensity and broad peaks signals. Despite this abundance of M-S-H evidences and characterizations, the structure of M-S-H is not well known. Some authors have explained the precipitation of such Mg-silicate hydrates according to Ca/Mg isomorphic substitution in the calcium silicate hydrates (C-S-H). The present study aims to determine this crystal structure and to define their nature (Cement Phase or phyllosilicate). Two low temperature synthesis of M-S-H have been made, with Mg/Si ratios of 0.6 and 1.2, close to the talc composition (Mg 3 Si 4 O 10 OH 2) and consistent to the Ca/Si ratio of the C-S-H Phases. Crystal chemistry of M-S-H was determined by combining TGA, electron probe micro-analysis (EPMA), TEM, NMR and powder X-ray diffraction. These experimental investigations of poorly crystalline Mg-silicates showed a 2:1 magnesium phyllosilicate-like structure with short range stacking order, identified as a talc-like structure. All the talc structure crystallographic evidences described in previous studies are in agreement with the characterization of the talc synthesis performed for short synthesis time
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The crystal structure of Magnesium Silicate Hydrate (M-S-H) and its relation with talc-like clay mineral
2016Co-Authors: Cédric Roosz, Pierre Henocq, Sylvain Grangeon, Stephane Gaboreau, Philippe Vieillard, Barbara Lothenbach, Valérie Montouillout, Philippe Blanc, Eric GiffautAbstract:In the framework of geological disposal of radioactive waste, Cement materials are foreseen to be used in the mechanical stability of the installations and to limit radionuclide transfer through the rock formation. In order to fill these requirements, the behavior of various concrete formulations is currently studied. In this context, low pH Cementitious materials are considered as alternatives to classical high performance concretes in order to minimize chemical interactions at the interfaces between Cement materials and the clay surrounding rock formations and/or engineered clay materials. The additive of supplementary Cementitious materials such as blastfurnace slag and fly ash induces pozzolanic reactions with the precipitation of low Ca/Si (C/S) ratio of calcium silicate hydrates (C-S-H) to reach a lower equilibrium pH of the pore solution (pH ~10). It follows that the control of the pH will be governed by the C-S-H with lower C/S ratio. However, if in Ordinary Portland Cement (OPC) and/or standard concrete formulations the hydration products are well characterized with well constrained kinetic/thermodynamic models; for low pH formulation, the mineralogical control of elements in solution have to be discussed, if we consider that concentrations of elements in solution like Aluminum and magnesium are higher than for OPC. In particular for the hydration of MgO, which is mainly introduced by the BFS, Zhang, Cheeseman and Vandeperre have mentioned the precipitation of brucite (MgOH2) which reacted with the silica fume to produce a magnesium silicate hydrate (M-S-H). The calculated pH in equilibrium with this mineralogical assemblage is around 10.5 and satisfies the requirement of low pH condition. The occurrence of M-S-H has been mentioned in many environments, and was described as low crystalline Phases according to the low intensity and broad peaks signals. Despite this abundance of M-S-H evidences and characterizations, the structure of M-S-H is not well known. Some authors have tried to explain the precipitation of such Mg-silicate hydrates according to Ca/Mg isomorphic substitution in the calcium silicate hydrates (C-S-H). The present study aims at determining this structure, to define their nature (Cement Phase or phyllosilicate). Two low temperature synthesis of M-S-H with a Mg/Si ratio of 0.6 and 1.2, close to the talc composition (Mg3Si4O10OH2) and consistent to the Ca/Si of the C-S-H Phases. Crystal chemistry of M-S-H was determined by combining TGA, electron probe micro-analysis (EPMA), TEM, NMR and powder X-raydiffraction. Characterizations of these poorly crystalline Mg-silicates reveal a 2:1 magnesium phyllosilicate-like structure with short range stacking order, described as a talc-like structure. All the talc structure crystallographic evidences described in previous studies are in agreement with the characterization of the talc synthesis performed for short synthesis time. In that case, the M-S-H particles are displaying a low cristallinity and a small size. XRD patterns were successfully modeled according the modeling approach developed by, thus providing meaningful and accurate structural information, including structure defects, despite the weak modulation of the profiles. A full structure model is thus proposed for M-S-H.
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The crystal structure of Magnesium Silicate Hydrate (M-S-H) andits relation with talc-like clay mineral
2016Co-Authors: Cédric Roosz, Pierre Henocq, Sylvain Grangeon, Stephane Gaboreau, Philippe Vieillard, Barbara Lothenbach, Valérie Montouillout, Philippe Blanc, Eric GiffautAbstract:In the framework of a geological disposal of radioactive waste, Cement-based materials will be highly used; the deep geological disposal facilitywill imply large amounts of concrete in the clayrock formation. In this context, low pH Cementitious materials are considered, especiallyfor sealingrequirements, in order to minimize chemical interactions at the interfaces between Cementitious materials and the clay surrounding rock formations and/or engineered clay materials. The target is to reach a concrete pore solutionpH more compatible with the clay materials or rock formation (pH ~7-7.5) for reducing the detrimental impact of the alkali plume from the Cement-based materials. Recent studies 1–3 have proposed low-pH formulations based on ternary and quaternary mixes of Portland Cement with supplementary Cementitious materials (SCMs) such as blast furnace slag (BFS) andfly ash (FA).For these formulations, the pHis controlledby low C/S C-S-H. However, if forOrdinary Portland Cement (OPC) concrete formulations, the hydration products are well characterized with suitable constrained kinetic/thermodynamic models 4 [4], , the mineralogical control of elements in solution have to be discussed for low pH formulations because of their higheraluminum and magnesium contents 5. In particular, for the hydration of MgO, which is mainly introduced by the BFS, Zhang et al. 6 have mentioned the precipitation of brucite (MgOH 2) which reacted with the silica fume to produce a magnesium silicate hydrate (M-S-H). The calculated pH in equilibrium with this mineralogical assemblage is around 10.5 and satisfies the requirement of low pH condition. The occurrence of M-S-H has been mentioned in many environments 6–9 , and was described as low crystalline Phases according to the low intensity and broad peaks signals. Despite this abundance of M-S-H evidences and characterizations, the structure of M-S-H is not well known. Some authors have explained the precipitation of such Mg-silicate hydrates according to Ca/Mg isomorphic substitution in the calcium silicate hydrates (C-S-H). The present study aims to determine this crystal structure and to define their nature (Cement Phase or phyllosilicate). Two low temperature synthesis of M-S-H have been made, with Mg/Si ratios of 0.6 and 1.2, close to the talc composition (Mg 3 Si 4 O 10 OH 2) and consistent to the Ca/Si ratio of the C-S-H Phases. Crystal chemistry of M-S-H was determined by combining TGA, electron probe micro-analysis (EPMA), TEM, NMR and powder X-ray diffraction. These experimental investigations of poorly crystalline Mg-silicates showed a 2:1 magnesium phyllosilicate-like structure with short range stacking order, identified as a talc-like structure. All the talc structure crystallographic evidences described in previous studies are in agreement with the characterization of the talc synthesis performed for short synthesis time
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Identification of the Thermodynamically Stable Fe‐Containing Phase in Aged Cement Pastes
Journal of the American Ceramic Society, 2015Co-Authors: Marika Vespa, Erich Wieland, Rainer Dähn, Barbara LothenbachAbstract:Current developments in Cement chemistry increasingly rely on predictive thermodynamic modeling of the Phase composition in Cementitious composites with the aim of linking the performance of the material with the Phase composition of the material. This approach requires identification of the Cement Phases that form in hydrating Cementitious materials using standard techniques, such as X-ray diffraction (XRD) and thermal analysis (DTA, TGA), but also state-of-the-art synchrotron-based techniques, in particular for those cases in which the signals of solid solutions overlap in XRD and TGA measurements. In this study, two ordinary Portland Cements, with different chemical compositions and subject to different hydration times (~10, ~50 yr), were investigated aiming at identifying the most stable Fe-containing Cement Phase in the Cement pastes. The Fe-containing Cement Phases and their solid solutions with the Al analogues in the complex Cement matrix were analyzed with X-ray absorption spectroscopy, indicating the formation of a mixed Fe–Al siliceous hydrogarnet as the major Fe-containing Phase. The presence of this Phase after long hydration periods and upon selective dissolution of the pastes further indicates that, independent of the chemical compositions of Cements, formation of the mixed Fe–Al siliceous hydrogarnet is thermodynamically favored in aged pastes, which is supported by published thermodynamic calculations.
Uwe Gbureck - One of the best experts on this subject based on the ideXlab platform.
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Dual setting α-tricalcium phosphate Cements
Journal of Materials Science: Materials in Medicine, 2013Co-Authors: Thibault Christel, Juergen Groll, Meinard Kuhlmann, Elke Vorndran, Uwe GbureckAbstract:An extension of the application of calcium phosphate Cements (CPC) to load-bearing defects, e.g. in vertebroplasty, would require less brittle Cements with an increased fracture toughness. Here we report the modification of CPC made of alpha-tricalcium phosphate (α-TCP) with 2-hydroxyethylmethacrylate (HEMA), which is polymerised during setting to obtain a mechanically stable polymer-ceramic composite with interpenetrating organic and inorganic networks. The Cement liquid was modified by the addition of 30–70 % HEMA and ammoniumpersulfate/tetramethylethylendiamine as initiator. Modification of α-TCP Cement paste with HEMA decreased the setting time from 14 min to 3–8 min depending on the initiator concentration. The 4-point bending strength was increased from 9 MPa to more than 14 MPa when using 50 % HEMA, while the bending modulus decreased from 18 GPa to approx. 4 GPa. The addition of ≥50 % HEMA reduced the brittle fracture behaviour of the Cements and resulted in an increase of the work of fracture by more than an order of magnitude. X-ray diffraction analyses revealed that the degree of transformation of α-TCP to calcium deficient hydroxyapatite was lower for polymer modified Cements (82 % for polymer free Cement and 55 % for 70 % HEMA) after 24 h setting, while the polymerisation of HEMA in the Cement liquid was quantitative according to FT-IR spectroscopy. This work demonstrated the feasibility of producing fracture resistant dual-setting calcium phosphate Cements by adding water soluble polymerisable monomers to the liquid Cement Phase, which may be suitable for an application in load-bearing bone defects.
Daniela Freyer - One of the best experts on this subject based on the ideXlab platform.
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dehydration of the sorel Cement Phase 3mg oh 2 mgcl2 8h2o studied by in situ synchrotron x ray powder diffraction and thermal analyses
Zeitschrift für anorganische und allgemeine Chemie, 2014Co-Authors: Tomče Runčevski, Robert E. Dinnebier, Daniela FreyerAbstract:Dehydration is an important process which affects the chemical, physical and mechanical properties of materials. This article describes the thermal dehydration and decomposition of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O, studied by in situ synchrotron X-ray powder diffraction and thermal analyses. Attention is paid on the determination of the chemical composition and crystal structure of the lower hydrates, identified as the Phases 3Mg(OH)2·MgCl2·5.4H2O and 3Mg(OH)2·MgCl2·4.6H2O. The crystal structure of 3Mg(OH)2·MgCl2·4.6H2O is solved and refined by the Rietveld method and a structural model for the 3Mg(OH)2·MgCl2·5.4H2O Phase is given. These Phases show statistical distribution of water molecules, hydroxide and chloride anions positioned as ligands on the magnesium octahedra. A structural scheme of the temperature induced transformations in the thermal range from 25 to 500 °C is presented.
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Dehydration of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O studied by in situ Synchrotron X-ray Powder Diffraction and Thermal Analyses
Zeitschrift für anorganische und allgemeine Chemie, 2013Co-Authors: Tomče Runčevski, Robert E. Dinnebier, Daniela FreyerAbstract:Dehydration is an important process which affects the chemical, physical and mechanical properties of materials. This article describes the thermal dehydration and decomposition of the Sorel Cement Phase 3Mg(OH)2·MgCl2·8H2O, studied by in situ synchrotron X-ray powder diffraction and thermal analyses. Attention is paid on the determination of the chemical composition and crystal structure of the lower hydrates, identified as the Phases 3Mg(OH)2·MgCl2·5.4H2O and 3Mg(OH)2·MgCl2·4.6H2O. The crystal structure of 3Mg(OH)2·MgCl2·4.6H2O is solved and refined by the Rietveld method and a structural model for the 3Mg(OH)2·MgCl2·5.4H2O Phase is given. These Phases show statistical distribution of water molecules, hydroxide and chloride anions positioned as ligands on the magnesium octahedra. A structural scheme of the temperature induced transformations in the thermal range from 25 to 500 °C is presented.