Etude cristallographique et magnétique de composés intermétalliques à base d’éléments de terre rare, de cobalt et d’éléments p, dérivant de la structure CaCu5

This study is devoted to the structural and magnetic properties of intermetallic compounds of rare earth elements, cobalt and p elements, deriving from the CaCu5 type structure.The RCo5-xMx (M = Al, Ga and Si) phases preserve the CaCu5 structure, whereas the Rn+1Co3n+5B2n compounds form various superstructures. A preferential occupation of Al, Ga and Si atoms for the 3g site of the CaCu5 structure was established by means of neutron diffraction. The iron for cobalt substitution in the PrCo4Al and PrCo4Ga compounds shows a preferential occupation for the 3g site.The presence of M elements in the RCo5-xMx compounds modifies significantly the magnetic phase diagrams. X-ray absorption spectroscopy measurements performed for CeCo5-xMx and Cen+1Co3n+5B2n demonstrate that cerium shows an intermediate valence state.Hydrogen insertion in Y2Co7 induces an orthorhombic distortion for the Y2Co7H6 hydride. A metamagnetic transition is observed in this hydride.Ce travail est consacré à l’étude des propriétés structurales et magnétiques des composés intermétalliques à base d’éléments de terre rare, de cobalt et d’éléments p dérivant de la structure CaCu5. Les phases RCo5-xMx (M = Al, Ga et Si) conservent la structure CaCu5, tandis que les composés Rn+1Co3n+5B2n présentent des surstructures variées. Une occupation préférentielle des atomes Al, Ga, Si pour le site 3g de la structure CaCu5 a été démontrée par diffraction neutronique. La substitution du fer au cobalt dans les composés PrCo4Al et PrCo4Ga s’effectue préférentiellement dans le site 3g de la structure. La présence d’éléments M dans les phases RCo5-xMx modifie sensiblement les diagrammes de phase magnétiques. Les mesures de spectroscopie d’absorption X réalisées pour les composés CeCo5-xMx et Cen+1Co3n+5B2n ont établit que le cérium est dans un état de valence intermédiaire. L’insertion de l’hydrogène dans Y2Co7 conduit à une distorsion orthorhombique pour Y2Co7H6 et provoque l’apparition d’une transition métamagnétique

Стратегия хирургического лечения местнораспространенных опухолей малого таза с применением эвисцераций. Сообщение1. Синдромы кишечной непроходимости, кровотечения и сдавления мочевых путей

Представлен обзор и анализ методов хирургической коррекции синдромов кишечной непроходимости, кровотечения и сдавления мочевых путей при местнораспространенных опухолях малого таза. Обобщен 10−летний опыт хирургического лечения данной патологии в Институте общей и неотложной хирургии. Приведена классификация основных методов оперативных пособий, направленных на достижение гемостаза и деривации мочи и кала.The methods of surgical correction of syndromes of intestinal obstruction, hemorrhage and urinary tract compression at local tumors of the small pelvis are reviewed and analyzed. The 10−year experience of surgical treatment for this pathology at Institute for General and Urgent Surgery is generalized. Main methods of operative treatment aimed at achievement of hemostasis and urine and feces derivation are presented

Ultrasmall MgH_2 Nanoparticles Embedded in an Ordered Microporous Carbon Exhibiting Rapid Hydrogen Sorption Kinetics

MgH_2 nanoparticles with different average sizes have been prepared as ordered microporous carbon by tuning the Mg amount from 15 to 50 wt %. Ultrasmall particles with mean sizes of 1.3 and 3.0 nm have been obtained for 15 and 25 wt % Mg contents, respectively. The hydrogen desorption properties strongly depend on the nanoparticle size, as evidenced by different thermal analysis techniques. The onset temperature of hydrogen desorption for MgH_2 nanoparticles below 3 nm occurs at a temperature about 245 K lower than for microcrystalline material. Two distinct hydrogen desorption peaks are noticed for nanoparticles with mean sizes of 1.3 and 3.0 nm, as confirmed by TDS and HP-DSC. 1H NMR investigations suggest the presence of two MgH_2 populations with enhanced hydrogen mobility, as compared to the microcrystalline hydride. The short hydrogen diffusion path and the enhanced hydrogen mobility may explain the increased desorption kinetics of these ultrasmall nanoparticles

Materials for hydrogen-based energy storage - past, recent progress and future outlook

Globally, the accelerating use of renewable energy sources, enabled by increased efficiencies and reduced costs, and driven by the need to mitigate the effects of climate change, has significantly increased research in the areas of renewable energy production, storage, distribution and end-use. Central to this discussion is the use of hydrogen, as a clean, efficient energy vector for energy storage. This review, by experts of Task 32, “Hydrogen-based Energy Storage” of the International Energy Agency, Hydrogen TCP, reports on the development over the last 6 years of hydrogen storage materials, methods and techniques, including electrochemical and thermal storage systems. An overview is given on the background to the various methods, the current state of development and the future prospects. The following areas are covered; porous materials, liquid hydrogen carriers, complex hydrides, intermetallic hydrides, electrochemical storage of energy, thermal energy storage, hydrogen energy systems and an outlook is presented for future prospects and research on hydrogen-based energy storage

EC Participation in the IEA HIA - Task 22

Contribution under the European Commission Update in the section of IEA HIA Member Reports: Task 22 participation.JRC.F.2-Cleaner energ

Microstructural Modifications Induced by Hydrogen Absorption in Mg5Ga2 and Mg6Pd

We have recently proposed a new method to design one-dimensional structures of MgH2 in the nano- and micrometers ranges by hydrogen induce disproportionation of bulk Mg24Y5. The present study confirms the same behavior in hydrogenated Mg5Ga2 and Mg6Pd. Single-crystalline one-dimensional structures and micro-particles of MgH2 are formed by hydrogen absorption and subsequent partial disproportionation of Mg5Ga2 and Mg6Pd. The MgH2 whiskers and particles grow in different morphologies for different alloying partners. Growth mechanisms are proposed in relation to the morphology and the chemical surface composition of original compounds.JRC.F.2-Cleaner energie

Uncovering the Effect of Al Addition on the Hydrogen Storage Properties of the Ternary TiVNb Alloy

The effect of Al addition on the structure, microstructure and hydrogen storage properties of the ternary TiVNb alloy was investigated from small amounts to equimolar composition. Alx(TiVNb)1−x (x = 0.05, 0.175 and 0.25) alloys are bcc single-phase materials with decreasing lattice parameters with increasing Al content. Al addition progressively decreases the hydrogen storage capacity but also destabilizes fcc dihydride formation for alloys with x ≤ 0.10. Among the different compositions, the most promising alloy was found to be that with x = 0.05 Al content that exhibited high initial storage capacity (2.96 wt.%), a less stable hydride (ΔH = −52 kJ/mol H2 and ΔS = −141 J/K∙mol H2), better desorption properties (desorption onset temperature around 100 °C) and enhanced reversible capacity during cycling (2.83 wt.%) compared to the ternary TiVNb. In situ and ex situ synchrotron X-ray powder diffraction, together with thermal desorption experiments, showed improved desorption properties with Al addition, together with a two-step reaction with hydrogen. These findings highlight the use of small quantities of lightweight Al in refractory multi-principal element alloys as a promising approach for enhancing the solid-state hydrogen storage performance of bcc-type alloys

A Round Robin Characterisation of the Hydrogen Sorption Properties of a Carbon Based Material

A Round Robin exercise has been carried out in the frame of the European project NESSHY (Novel and Efficient Solid State HYdrogen storage systems) to evaluate the hydrogen physisorption on a commercial microporous carbon material. Fourteen laboratories have measured pressure¿composition¿isotherms at 77 K and ambient temperature following a test protocol. The dispersion of isotherms increases with pressure. Four similar isotherms measured by different methods from different laboratories are proposed as standard hydrogen sorption behaviour. The hydrogen capacities are 1.40(0.1) and 0.07(0.01) wt.% for 1 MPa hydrogen pressure at 77 K and ambient temperature, respectively. A statistical evaluation of the results is applied in order to point out laboratories that might need a corrective action. Tentative recommendations for optimising the acquisition of physisorption isotherm data and a check list for data reporting are proposed. The authors advise this carbon material as being suitable for benchmarking of laboratories in this field.JRC.F.2-Cleaner energ

Effect of Cr/Mn Addition in TiVNb on Hydrogen Sorption Properties: Thermodynamics and Phase Transition Study

High-entropy alloys (HEAs) are a promising class of materials that can grant remarkable functional performances for a large range of applications due to their highly tunable composition. Among these applications, recently, bcc HEAs capable of forming fcc hydrides have been proposed as high-capacity hydrogen storage materials with improved thermodynamics compared to classical metal hydrides. In this context, a single-phase bcc (TiVNb)0.90Cr0.05Mn0.05 HEA was prepared by arc melting to evaluate the effect of combined Cr/Mn addition in the ternary TiVNb. A thermodynamic destabilization of the fcc hydride phase was found in the HEA compared to the initial TiVNb. In situ neutron and synchrotron X-ray diffraction experiments put forward a fcc → bcc phase transition of the metallic subnetwork in the temperature range of 260–350 °C, whereas the H/D subnetwork underwent an order → disorder transition at 180 °C. The absorption/desorption cycling demonstrated very fast absorption kinetics at room temperature in less than 1 min with a remarkable total capacity (2.8 wt.%) without phase segregation. Therefore, the design strategy consisting of small additions of non-hydride-forming elements into refractory HEAs allows for materials with promising properties for solid-state hydrogen storage to be obtained