scholarly journals Study of hydrogen storage of the TiFe alloy by neutron powderdiffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C1767-C1767
Author(s):  
Catherine Gosselin ◽  
Jacques Huot ◽  
Roxana Flacau
Keyword(s):  
Neutron Diffraction ◽  
Hydrogen Storage ◽  
Room Temperature ◽  
Low Cost ◽  
Sorption Property ◽  
Metal Hydrides ◽  
Structural Difference ◽  
Neutron Diffraction Study ◽  
Point Of View ◽  
Practical Applications

Metal hydrides are interesting materials from a fundamental as well as practical point of view. Hydrogen storage applications have been the main driving force of research on these materials but lately, uses such as thermal storage are considered. In this presentation, we will review the use of neutron diffraction for the development of new metal hydrides. A good candidate for hydrogen storage applications is the low cost intermetallic compound TiFe which operates near room temperature (RT) under mild pressure conditions. However, the biggest disadvantage of TiFe alloy synthesized by conventional metallurgical method is it poor activation characteristics [1]. The alloy reacts with hydrogen only after complicated activation procedure involving exposure to high temperature (~4000C) and high pressure for several days. In the '90, some researches showed that the change in the nanocristallinity can modify the sorption property of the TiFe[2]. Other research works found that palladium increase the contaminant resistance. However, addition of palladium is too expansive for practical applications [3]. Recently, we found that, when doping TiFe with Zr and Zr7Ni10, the activation could be easily done at room temperature. We present here a neutron diffraction study of these compounds that shows the structural difference between the activated compound and the one cycled under hydrogen.

scholarly journals Study of hydrogen storage materials by neutron powder diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C939-C939
Author(s):  
Jacques Huot ◽  
Catherine Gosselin ◽  
Thomas Bibienne ◽  
Roxana Flacau
Keyword(s):  
Neutron Diffraction ◽  
Hydrogen Storage ◽  
Room Temperature ◽  
Cast Alloy ◽  
Metal Hydrides ◽  
Structural Difference ◽  
Neutron Diffraction Study ◽  
Point Of View ◽  
Scattering Lengths ◽  
The One

Metal hydrides are interesting materials from a fundamental as well as practical point of view. Hydrogen storage applications have been the main driving force of research on these materials but lately uses such as thermal storage are considered. In this presentation we will review the use of neutron diffraction for the development of new metal hydrides. Two systems will be presented: BCC solid solution alloys and FeTi alloy. Ti-based BCC solid solutions are promising material for hydrogen storage applications which need high volumetric capacity and room temperature operation. One system that has been considered is Ti-V-Cr. Using only X-ray diffraction for structural identification does not provide information about hydrogen localization. Therefore, neutron diffraction is essential for complete determination of this class of hydrides. We will present examples of Ti-V-Cr compounds doped with Zr-Ni alloy. The peculiarity of this type of alloy is that, for neutron diffraction, the scattering lengths of the elements almost cancel. Therefore, the neutron pattern of as-cast alloy shows very small Bragg peaks but the advantage is that the hydride for is very easy to see and analyze. Another good candidate for hydrogen storage applications is the intermetallic compound TiFe which operates at around room temperature (RT) under mild pressure conditions. However one disadvantage of TiFe alloy synthesized by conventional metallurgical method is its poor activation characteristics. The alloy reacts with hydrogen only after complicated activation procedure involving exposure to high temperature (~4000C) and high pressure for several days. Recently we found that by doping this alloy with Zr and Zr7Ni10 the activation could be easily done at room temperature. We present here a neutron diffraction study of these compounds that shows the structural difference between the activated compound and the one cycled under hydrogen.

scholarly journals Study of Ti-V-Cr metal hydrides by neutron powder diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C1762-C1762
Author(s):  
Thomas Bibienne ◽  
Roxana Flacau ◽  
Jean-Louis Bobet ◽  
Jacques Huot
Keyword(s):  
Neutron Diffraction ◽  
Raw Materials ◽  
Cast Alloy ◽  
Metal Hydrides ◽  
Point Of View ◽  
X Ray ◽  
Practical Applications ◽  
Slow Kinetics ◽  
Melt Synthesis

Metal hydrides are interesting materials from a fundamental as well as practical point of view. In particular, Ti-based BCC solid solutions are considered as promising candidates for mobile applications because of their high volumetric capacities and room temperature operation. However, the slow kinetics of the first hydrogenation, the so-called activation step, is an important hurdle in the use of these alloys for practical applications. It has recently been shown that doping a Ti-V-Cr composition with Zr7Ni10 leads to a fast activation kinetic without heating treatment [1]. We studied the effect of this doping on two new Ti-V-Cr compositions: 52Ti-12V-36Cr and 42Ti-21V-37Cr. Two different doping methods were investigated: i) a single-melt synthesis where the raw materials (i.e. Ti, V, Cr, Zr and Ni) chunks were mixed and arc-melted; ii) co-melt synthesis where 52Ti-12V-36Cr and 7Zr-10Ni were arc-melted independently and thereafter re-melted together. Using only X-ray diffraction for structural identification does not provide information about hydrogen localization. Therefore, neutron diffraction is essential for complete determination of this class of hydrides. The peculiarity of the present alloys is that, for neutron diffraction, the scattering lengths of the elements almost cancel. Therefore, the neutron pattern of as-cast alloy shows very small Bragg peaks but the advantage is that the hydride is very easy to see and analyze. We performed in-situ neutron diffraction experiments during dehydrogenation of these materials to see the transition from the dihydride to monohydride. These measurements were complementary to X-ray and synchrotron radiation diffraction and enabled a better crystal structure determination of these alloys

scholarly journals Twinning in MAPbI3 at room temperature uncovered through Laue neutron diffraction

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Joachim Breternitz ◽  
Michael Tovar ◽  
Susan Schorr
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Neutron Diffraction ◽  
Room Temperature ◽  
Point Of View ◽  
Temperature Structure ◽  
Theoretical Point ◽  
Laue Diffraction ◽  
The Past ◽  
Halide Perovskites

Abstract The crystal structure of MAPbI3, the signature compound of the hybrid halide perovskites, at room temperature has been a reason for debate and confusion in the past. Part of this confusion may be due to twinning as the material bears a phase transition just above room temperature, which follows a direct group–subgroup relationship and is prone to twinning. Using neutron Laue diffraction, we illustrate the nature of twinning in the room temperature structure of MAPbI3 and explain its origins from a group-theoretical point-of-view.

A neutron diffraction study of potassium dihydrogen phosphate by Fourier synthesis

1953 ◽  
Vol 220 (1142) ◽  
pp. 397-421 ◽  
Keyword(s):  
Neutron Diffraction ◽  
Room Temperature ◽  
Potassium Dihydrogen Phosphate ◽  
Neutron Diffraction Study ◽  
Data Series ◽  
Dihydrogen Phosphate ◽  
Fourier Synthesis ◽  
Potassium Dihydrogen ◽  
Atomic Nuclei ◽  
Specific Assessment

Projections of the distribution of atomic nuclei in potassium dihydrogen phosphate at room temperature have been obtained by Fourier synthesis of single-crystal neutron diffraction data. Series termination effects have been examined and corrected for, either by specific assessment of the diffraction rings or by difference syntheses. The parameters so obtained are confirmed by least-squares analyses and give a reliability index of 7%. Hydrogen peaks occur midway between two oxygen atoms and appear circular when viewed along the O—H—O bond, but elliptical when viewed across it. The PO 4 tetrahedra are much more nearly regular than previously supposed, and the O—H—O bonds are inclined at not more than ½º to the xy -plane.

Metallographic and numerical characterization of MgH2-Mg system

2008 ◽  
Vol 1127 ◽  
Author(s):  
Annalisa Aurora ◽  
Massimo Celino ◽  
Fabrizio Cleri ◽  
Daniele Mirabile Gattia ◽  
Simone Giusepponi ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Density Functional ◽  
Low Cost ◽  
Secondary Emission ◽  
Point Of View ◽  
Atomic Diffusion ◽  
Cross Sectional ◽  
Conducting Phase ◽  
Practical Applications ◽  
Operation Temperature

ABSTRACTThe remarkable ability of magnesium to store significant quantities of hydrogen has fostered intense research efforts in the last years in view of its future applications where light and safe hydrogen-storage media are needed. Magnesium material, characterized by light weight and low cost of production, can reversibly store about 7.7 wt% hydrogen. However, further research is needed since Mg has a high operation temperature and slow absorption kinetics that prevent the use in practical applications. For these reasons a detailed study of the interface between Mg and MgH2 is needed. Further insights are gained by characterizing the Mg-MgH2 system from both the experimental and the numerical point of view.The study of the MgH2-Mg phase transformation in powder samples has been performed to gain detailed metallographic information. A method for studying this phase transformation by cross sectional samples scanning electron microscopy observation of partially transformed material has been developed. This method exploits the peculiar features of this system where the MgH2 phase is insulating and the Mg is a metallic conducting phase. This difference can induce a contrast between the two phases owing to the different secondary emission yield. Further insights are gained by characterizing Mg-MgH2 interfaces by means of accurate first-principle molecular dynamics simulations based on the density-functional theory. Extensive electronic structure calculations are used to characterize the equilibrium properties and the behavior of the surfaces in terms of total energy considerations and atomic diffusion.

Neutron Diffraction Study of Duplex Stainless Steel during Loading at 200°C

2008 ◽  
Vol 571-572 ◽  
pp. 175-180
Author(s):  
Rim Dakhlaoui ◽  
Andrzej Baczmanski ◽  
Chedly Braham ◽  
Sebastian Wroński ◽  
Krzysztof Wierzbanowski ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Room Temperature ◽  
Compressive Loading ◽  
Diffraction Method ◽  
Neutron Diffraction Study ◽  
Shear Stresses ◽  
Duplex Steel ◽  
Consistent Model ◽  
Influence Of Temperature On ◽  
Tension And Compression

In this work, the influence of temperature on the mechanical properties of duplex steel is studied by performing monotonic “in situ” tension and compression at 200oC. The lattice strains in both phases were measured using the time-of-flight neutron diffraction method (at the ISIS spallation neutron source, STFC Rutherford Appleton Laboratory, UK). A thermal-elastic selfconsistent model was used to predict the expansion of the interplanar spacings during heating to 200°C. Subsequently, the variation of phase stresses during tensile and compressive loading at room temperature (20°C) and at 200°C were theoretically calculated by the elastoplastic self-consistent model. Comparing the model data with experimental results the critical resolved shear stresses and work hardening parameters were determined individually in each phase of the DSS. Finally, the yield stresses in each phase of the studied steel have been estimated. It was found that both yield points (of austenite and ferrite) are lower at 200°C than those at room temperature.

Neutron Diffraction Study on Intermetallic Er5Mg24 and Tm5Mg24

2004 ◽  
Vol 443-444 ◽  
pp. 263-266 ◽  
Author(s):  
Wolfgang Schäfer ◽  
K.H.J. Buschow
Keyword(s):  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Neutron Diffraction Study ◽  
Neutron Powder Diffraction ◽  
Magnetic Exchange ◽  
Lattice Constants ◽  
Group I ◽  
Temperature Lattice ◽  
Curie Temperatures

Neutron powder diffraction on the binary intermetallics Er5Mg24 and Tm5Mg24 confirms their isostructural and pure crystallization in the Ti5Re24-type structure (space group I 4 3m, Z = 2)with rare earths located in 2a(0,0,0) and 8c(x,x,x) and Mg in two different 24g(x,y,x) sites. Room temperature lattice constants are 11.263(2) Å and 11.215(1) Å for the Er and Tm compound, respectively. Atomic positions have been refined. Both compounds order ferromagnetically below Curie temperatures of 17.5(5) K and 7.5(5) K for Er5Mg24 and Tm5Mg24, respectively. The magnitudes of the Er moments at 4.2 K are 7.5(2) µB and 4.4(2)µB on the 2a and the 8c sites, respectively. The Tm moments which have been refined from 2 K measurements amount to 3.0(3)µB and 2.8(2) µB, respectively. The temperature dependencies of the magnetic Bragg intensities reveal distinct deviations from Brillouin curves for J = 15/2 (Er) and J = 6 (Tm) systems and indicate a complex magnetic exchange.

Sign in / Sign up

Export Citation Format

Share Document