Hydro-Québec

About: Hydro-Québec is a government organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Electric power system & Dielectric. The organization has 2596 authors who have published 4433 publications receiving 100878 citations.

Nanocrystalline Ni-Mo alloys and their application in electrocatalysis

Abstract: The structural and electrocatalytic properties of metastable Ni-Mo alloys have been investigated for the hydrogen evolution reaction in alkaline solutions. Amorphous and nanocrystalline phases have been prepared by mechanically alloying the elemental components under various milling conditions. Fcc nanocrystals are formed when the Mo concentration is smaller than 30 at. %. The nanocrystalline state becomes unstable with respect to the amorphous phase when the Mo content in the solid solution exceeds 30 at. %. The electroactive phase for the hydrogen evolution reaction in alkaline solutions is the nanocrystalline supersaturated solid solution. The presence of oxygen during the milling process improves the properties of the alloys.

Structural and magnetic characterization of granular Y1Ba2Cu3O7−δ nanocrystalline powders

Abstract: High energy ball milling has been used to produce nanocrystalline Y1Ba2Cu3O7-δ powders. These powders are being used as starting materials for manufacturing superconducting textured wires by a solid state recrystallization process. Magnetic and microstructural characterizations were performed as a function of milling time. The milling reduces the average crystal size and creates low and high-angle grain boundaries which increase the granularity of the superconductor. As a result, the long-range order on the oxygen sublattice and on the yttrium and barium sites is destroyed. A transition from orthorhombic to tetragonal and finally to a cubic metastable phase is observed. Total loss of superconductivity occurs after about 1 h of milling. Prior to this time, superconductivity can partially be restored by room-temperature aging. High-temperature heat treatment of the nanocrystalline phase produces a tetragonal structure with c = 3a.

Kinetics of the production of chain-end groups and methanol from the depolymerization of cellulose during the ageing of paper/oil systems. Part 3: extension of the study under temperature conditions over 120 °C

Abstract: To go further in our assessment of methanol for the monitoring of the cellulosic insulation condition in electrical transformers, two of the paper/oil systems [one comprising a standard wood Kraft paper and the other, a thermally-upgraded Kraft paper (TU paper)] discussed in Parts 1 and 2 (Gilbert et al. in Cellulose 16:327–338. doi:10.1007/s10570-008-9261-1, 2009; Cellulose 17:253–269. doi:10.1007/s10570-009-9365-2, 2010) were reinvestigated under accelerated ageing conditions (T between 130 and 210 °C). The experimental data were tracked by testing two mathematical models, one that takes into account the inhomogeneous nature of the polymer by decreasing with time a pseudo-zero rate constant by a first-order process and the other, by simultaneously operating a separate first-order law for the three main categories of 1,4-β-glycosidic bonds in the polymer structure. These additional results provide evidence that the degradation proceeds via a random opening of these bonds in both the amorphous and crystalline regions, with the influence of a pyrolysis-like mechanism even at relatively low temperatures. Very good dependence with the temperature (lnk vs 1/T) is noted for the rate constants of the production of chain-end groups and the formation of methanol, confirming the importance of carrying out the ageing tests beyond the LODP of the specimens (leveling-off value of the degree of polymerization). The grouping of some of these data with those published in Part 2 for an identical system reveals that the degradation is governed by a single reaction pattern over 70–210 °C. The Arrhenius law applied to this data grouping shows an activation energy of 95 ± 4 kJ mol−1 with a frequency factor (lnAa) of 22 ± 1 for the depolymerization, while for the formation of CH3OH, the respective values are 122 ± 6 kJ mol−1 and 33 ± 2. Finally, the kinetic parameters obtained under accelerated ageing conditions over 150–210 °C show that the stabilizing substances of the TU-Kraft paper modify the bond opening mechanism by blocking the effect of the acid and water generated by the oil decomposition. When they are present in the fibrous structure, the activation energy of the reaction goes up to 148 ± 14 kJ mol−1 with a frequency factor of 33 ± 4 for the depolymerization and 133 ± 11 kJ mol−1 with a frequency factor of 33 ± 3 for the formation of CH3OH.