Conservatoire national des arts et métiers

About: Conservatoire national des arts et métiers is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Orthogonal frequency-division multiplexing. The organization has 3573 authors who have published 7127 publications receiving 141430 citations. The organization is also known as: CNAM & Conservatoire des arts et métiers.

Photoinduced coupled proton and electron transfers. 2. 7-hydroxyquinolinium ion

Abstract: The hydroxyl group of 7-hydroxyquinoline in acidic media (i.e., of 7-hydroxyquinolinium cation, 7-HQ(C)) undergoes photoinduced deprotonation even in strongly acidic media. It occurs from dilute perchloric acid solutions up to 8 mol L-1 concentration, which is evidence of an outstanding photoacidity. Excited-state proton ejection was shown to be reversible at acid concentrations greater than 1 mol L-1. Below this value, the proton ejection was not balanced by the proton recombination. Concerning the rates of the excited-state reactions, (i) the proton ejection rate constants k1 increased upon acid dilution, attaining at high dilution the limiting value of (k1)0 = 5.5 × 1010 s-1. k1 was shown to vary with the water activity according to k1 = (k1)0(aH2O)4. The number 4 is then a key number for the ability of water to accept a proton from 7-HQ(C*). (ii) The proton recombination rate constant varies from 3 × 109 to 4 × 1010 s-1 when the acid concentration ranges from 1 to 5 mol L-1. This observation can tenta...

Effects of interstitial oxygen on microstructure and mechanical properties of Ti-48Al-2Cr-2Nb with fully lamellar and duplex microstructures

Abstract: The effect of added oxygen in the range of 1000 to 4000 wt ppm on the microstructures of a Ti-48Al-2Cr-2Nb alloy has been investigated and compared to the microstructures for a high-purity alloy. For specimens cooled from theα phase, interstitial oxygen stabilizes the lamellar microstructure with respect toγ grains, with higher than equilibrium values for theα 2 volume fraction. For specimens cooled from theα +γ phase field, the lamellar microstructure still tends to be favored by oxygen, but it is found that the phase volume fractions are not significantly different from equilibrium values. This suggests that interstitial O essentially reduces the kinetics of theα toα +γ transformation. Thus, interstitial oxygen will have a strong effect on microstructures obtained by continuous cooling fromα, but significantly less on those, such as the duplex microstructure, obtained by long treatment in theα +γ phase field. In general, increased O content is well correlated with reduced ductility. Finally, the role of interstitial oxygen on this phase transformation is discussed.