The Experts below are selected from a list of 43218 Experts worldwide ranked by ideXlab platform
Jason Graetz - One of the best experts on this subject based on the ideXlab platform.
-
In Situ Hydrothermal Synthesis of LiFePO4Studied by Synchrotron X-Ray Diffraction
The Journal of Physical Chemistry Letters, 2011Co-Authors: Jiajun Chen, Jianming Bai, Haiyan Chen, Jason GraetzAbstract:The development of high capacity, safe lithium battery materials requires new tools to better understand how reaction conditions affect nucleation and crystallization, particle size, morphology, and defects. We present a general approach for studying the synthesis of Li battery electrode materials in real time. The formation of LiFePO{sub 4} was investigated by time-resolved in situ Synchrotron X-Ray Diffraction under hydrothermal conditions, and the reaction kinetics were determined by changes of the Bragg reflections. We provide the first evidence in support of a dissolution-reprecipitation process for the formation of LiFePO{sub 4}, which occurs at temperatures as low as 105 C and appears to be a three-dimensional diffusion-controlled process. Lattice parameters and their evolution were monitored in situ, as well as the formation of antisite defects and their subsequent elimination under various synthesis conditions. The ability to characterize and tailor synthesis reactions in situ is essential for rapid optimization of the synthesis procedures and, ultimately, the development of new battery electrodes.
-
In Situ Hydrothermal Synthesis of LiFePO4 Studied by Synchrotron X-Ray Diffraction
2011Co-Authors: Jiajun Chen, Jianming Bai, Haiyan Chen, Jason GraetzAbstract:The development of high capacity, safe lithium battery materials requires new tools to better understand how reaction conditions affect nucleation and crystallization, particle size, morphology, and defects. We present a general approach for studying the synthesis of Li battery electrode materials in real time. The formation of LiFePO4 was investigated by time-resolved in situ Synchrotron X-Ray Diffraction under hydrothermal conditions, and the reaction kinetics were determined by changes of the Bragg reflections. We provide the first evidence in support of a dissolution–reprecipitation process for the formation of LiFePO4, which occurs at temperatures as low as 105 °C and appears to be a three-dimensional diffusion-controlled process. Lattice parameters and their evolution were monitored in situ, as well as the formation of antisite defects and their subsequent elimination under various synthesis conditions. The ability to characterize and tailor synthesis reactions in situ is essential for rapid optimiz...
J.d. Almer - One of the best experts on this subject based on the ideXlab platform.
-
Hydride reorientation in Zr2.5Nb studied by Synchrotron X-Ray Diffraction
Acta Materialia, 2012Co-Authors: M.a. Vicente Alvarez, Javier R. Santisteban, P. Vizcaino, A.d. Banchik, A. V. Flores, J.d. AlmerAbstract:Abstract The crystallographic texture and stress state of hydride platelets of two different orientations precipitated in Zr2.5Nb pressure tubes were studied by Synchrotron X-Ray Diffraction experiments using an 80 keV photon beam and an area detector in transmission geometry. Circumferential and radial hydrides with platelet normals along the tube radial and circumferential directions, respectively, were precipitated in tube material loaded up to H contents of 130 wt.ppm. This macroscopic hydride orientation was controlled by application of a load along the tube hoop direction during hydride precipitation. The experiments show that both circumferential and radial platelets are composed of δ-hydrides precipitated in α-Zr grains from a wide range of orientations, but with a clear preference for Zr crystals with their c -axes at an angle of ∼15–20° from the hoop direction. Some moderate differences between the crystallographic texture of the two hydrides result from application of the load during precipitation. The results are explained in terms of an autocatalytic nucleation process and the Zr2.5Nb microstructure. A careful stress analysis revealed that both hydride types are compressed by the matrix on the plane of the platelet, with the largest stresses always found along the axial direction of the tube. Determination of the stress state of the hydride could be exploited as a Diffraction signature of the hydride orientation.
-
Hydride precipitation and stresses in zircaloy-4 observed by Synchrotron X-Ray Diffraction
Acta Materialia, 2010Co-Authors: Javier R. Santisteban, M.a. Vicente-alvarez, P. Vizcaino, A.d. Banchik, J.d. AlmerAbstract:Abstract The grain stresses within hydrides precipitated in rolled zircaloy-4 plates were determined by Synchrotron X-Ray Diffraction experiments using an 80 keV photon beam and a high-speed area detector placed in transmission geometry. Results showed large compressive stresses (360 ± 20 MPa) in the hydrides along the plate rolling direction. The origin of these stresses was investigated by performing hydride dissolution/precipitation in situ for thermal cycles between room temperature and 400 °C. A large stress hysteresis was observed, with a steady decrease on heating and an abrupt change on cooling. The observed stresses are explained by the constraint imposed by grain boundaries on the growth of hydride platelets on the rolling–transverse plane of the rolled plates.
-
Load transfer in bovine plexiform bone determined by Synchrotron X-Ray Diffraction
Journal of Materials Research, 2008Co-Authors: Riaz Akhtar, Mark R. Daymond, J.d. Almer, Paul MummeryAbstract:High-energy Synchrotron X-Ray Diffraction (XRD) has been used to quantify load transfer in bovine plexiform bone. By using both wide-angle and small-angle XRD, strains in the mineral as well as the collagen phase of bone were measured as a function of applied compressive stress. We suggest that a greater proportion of the load is borne by the more mineralized woven bone than the lamellar bone as the applied stress increases. With a further increase in stress, load is shed back to the lamellar regions until macroscopic failure occurs. The reported data fit well with reported mechanisms of microdamage accumulation in bovine plexiform bone.
Maximilian Fichtner - One of the best experts on this subject based on the ideXlab platform.
-
Thermal decomposition of AlH3 studied by in situ Synchrotron X-Ray Diffraction and thermal desorption spectroscopy
Journal of Alloys and Compounds, 2007Co-Authors: Jan Petter Maehlen, Volodymyr A. Yartys, Roman V. Denys, Maximilian Fichtner, Ch. Frommen, Boris M. Bulychev, Philip Pattison, Hermann Emerich, Yaroslav Filinchuk, Dmitry ChernyshovAbstract:The thermal decomposition of alane was investigated by application of Synchrotron X-Ray Diffraction (SR-XRD) and thermal desorption spectroscopy (TDS). Two polymorphs were studied, α- and γ-AlH3. Activation energies, anisotropic volume expansions, and phase transformation paths were found. In addition, the crystal structure data, including structure of hydrogen sublattice, and small charge transfer from the aluminium towards the hydrogen sites were observed during a high-resolution SR-XRD study of α-AlH3.
-
Thermal decomposition of Mg(AlH4)2 studied by in situ Synchrotron X-Ray Diffraction
Journal of Alloys and Compounds, 2005Co-Authors: A. Fossdal, Maximilian Fichtner, H.w. Brinks, Bjørn C. HaubackAbstract:Abstract The thermal decomposition of Mg(AlH4)2 was studied by in situ Synchrotron X-Ray Diffraction. The reaction proceeds in two steps. The first reaction step involves decomposition of magnesium alanate to magnesium hydride and the solid solution Al1−x/2Mgx/2: ( 1 − x / 2 ) Mg(AlH4)2→(1−(3/2)x)MgH2+2Al1−x/2Mgx/2+(3+(3/2)x)H2. No evidence of intermediate phases was found. The second step proved to be more complex. For simplicity this step can be written as: ( 1 − ( 3 / 2 ) x ) MgH2+2Al1−x/2Mgx/2→AlxMgy+(1−(3/2)x)H2, where AlxMgy represents either two cubic Al–Mg solid solution phases or the ordered β -Al3Mg2 phase.
P Dierickx - One of the best experts on this subject based on the ideXlab platform.
-
Ageing of 100Cr6 steel: Synchrotron X-Ray Diffraction and dimensional analysis investigation
Materials Science and Technology, 2016Co-Authors: V Lejay, C Sidoroff, M Perez, C. Le Bourlot, P DierickxAbstract:Thermal ageing of 100Cr6 with different initial austenitisings was studied using the combination of Synchrotron X-Ray Diffraction and dimensional variation measurements. Synchrotron X-Ray Diffraction provided the phase volume fractions and their carbon content through the analysis of the lattice parameters. Dimensional measurements were obtained in situ in a quench dilatometer also used to realise the heat treatment. The combined analysis of these data provides a better understanding of phase evolutions. For the different austenitising treatments investigated, the dimensional variations were found to be easily linked to the phase parameters measured by X-Ray Diffraction.This paper is part of a Themed Issue on Recent developments in bearing steels.
-
Ageing of 100Cr6 steel: Synchrotron X-Ray Diffraction and dimensional analysis investigation
Materials Science and Technology, 2015Co-Authors: V Lejay, Christophe Le Bourlot, C Sidoroff, M Perez, P DierickxAbstract:Thermal ageing of 100Cr6 with different initial austenitisings was studied using the combination of Synchrotron X-Ray Diffraction and dimensional variation measurements. Synchrotron X-Ray Diffraction provided the phase volume fractions and their carbon content through the analysis of the lattice parameters. Dimensional measurements were obtained in situ in a quench dilatometer also used to realise the heat treatment. The combined analysis of these data provides a better understanding of phase evolutions. For the different austenitising treatments investigated, the dimensional variations were found to be easily linked to the phase parameters measured by X-Ray Diffraction.
Brendan J. Kennedy - One of the best experts on this subject based on the ideXlab platform.
-
Unusual thermal expansion of Sr2IrO4: A variable temperature Synchrotron X-Ray Diffraction study
Journal of Solid State Chemistry, 2015Co-Authors: Ben Ranjbar, Brendan J. KennedyAbstract:Abstract The structure of Sr2IrO4 has been studied between 20 and 1273 K using Synchrotron X-Ray Diffraction. Sr2IrO4 undergoes an apparently continuous transition from I41/acd to I4/mmm near 1123 K. The cooperative tilting of the corner sharing IrO6 octahedra in I41/acd results in highly anisotropic and unusual thermal expansion behavior with negative thermal expansion along the c-axis.
-
Anisotropic thermal expansion in Sr2RhO4 – A variable temperature Synchrotron X-Ray Diffraction study
Solid State Sciences, 2015Co-Authors: Ben Ranjbar, Brendan J. KennedyAbstract:Abstract Synchrotron X-Ray Diffraction studies of Sr 2 RhO 4 , between 100 and 1273 K, demonstrate the presence of anisotropic thermal expansion that is significantly impacted by the progressive reduction in the size of the cooperative tilting of the corner sharing RhO 6 octahedra. The tilting results in negative thermal expansion along the c -axis, demonstrating the importance of soft phonon modes. This anisotropy in thermal expansion is reflected in the changes in the individual Rh–O bond distances. Near 850 K Sr 2 RhO 4 undergoes an apparently continuous transition from I 4 1 / acd to I 4/ mmm and above this temperature the material displays typical positive thermal expansion.
