Polytetrahedral Clusters

By studying the structures of clusters bound by a model potential that favours polytetrahedral order, we find a previously unknown series of `magic numbers' (i.e. sizes of special stability) whose polytetrahedral structures are characterized by disclination networks that are analogous to hydrocarbons.Comment: 4 pages, 4 figure

Solution synthesis of core-shell Co9S8@MoS2 catalysts

SSCI-VIDE+ECI2D+AHD:CGE:PAFInternational audienceCore-shell Co9S8@MoS2 unsupported catalysts have been prepared by a solution reaction in ethylene glycol. First, using a cobalt sulfide seed, amorphous core-shell CoS@MoSx (x = 3-4) was prepared. Then, after thermal treatment, 20-50 nm-sized particles were obtained, in which MoS2 was crystallized at the exterior of the Co9S8 core. The solids show high catalytic activity in hydrodesulphurization, with an exceptionally high thermal stability. Thus, the high catalytic activity was preserved even after thermal treatment at 750 degrees C. A symmetric synergy model has been proposed with the catalytic sites located at the interface between the cobalt sulfide crystallites and the stacks of MoS2 slabs

Structural and electrochemical studies of Pt-Sn nanoparticulate catalysts

Structural and stability studies of bimetallic Pt-Sn (3:1) nanoparticles were performed in situ via X-ray diffraction at wide angles (WAXS). The homemade bimetallic catalyst (Pt-Sn) ccomp (ccomp = from carbonyl complex) was synthesized in mild conditions from a Pt-carbonyl chemical precursor. A relatively narrow size distribution (2.4 ± 0.9 nm) of such a bimetallic catalyst supported onto carbon Vulcan XC72 was obtained at room temperature. Its electrochemical behavior was compared to that of a commercial catalyst. The WAXS study revealed that such a catalyst, prepared via the carbonyl route, has a certain degree of surface disorder (high Debye parameter, B), which enhances the electrocatalytic activity for hydrogen adsorption. Furthermore, WAXS also demonstrated that the structural stability of this bimetallic catalyst is maintained at the annealing temperature employed (500 C), although the particle size increases from 1.6 to 2.2 nm. Electrochemical underpotential deposition studies, via copper deposition, also provide information concerning the state of the nanoparticulate surface of the various platinum-based catalysts investigated

A review on potentials and challenges of nanolubricants as promising lubricants for electric vehicles

The most remarkable difference between electric vehicles (EVs) and conventional ones is the fuel burning dependency of the internal combustion engine, while the emerging EVs operate on electric motors. These alternations create staggering shifts in both lubricants' market demand and performance specifications. Lubricants for electrical powertrain constitutes greases, transmission oils, and lubricants for auxiliary systems and do not rely on engine oils as internal combustion vehicles. The new standards will be more focused on lubricants' electrical properties such as breakage voltage and conductivity, coupled with tribological performance under high rpm, corrosion resistance and thermal management benchmarks. This paper thematically reviews the different studies performed with nanolubricants, and how they match EVs' operational requirements. Conclusions from this study can be considered as guidelines for the potential application of nanolubricants in EVs and possible future research that can be accomplished on the topic

Réclamation de la commune d'Aire,... pour l'établissement d'une école centrale, à la Convention nationale ([Reprod.]) / [signé : A. Papegay et Dassenoy]

Collection : Les archives de la Révolution française ; 9.1.342Appartient à l’ensemble documentaire : NordPdeC

Structural and electrochemical studies of Pt-Sn nanoparticulate catalysts

Structural and stability studies of bimetallic Pt-Sn (3:1) nanoparticles were performed in situ via X-ray diffraction at wide angles (WAXS). The homemade bimetallic catalyst (Pt-Sn) ccomp (ccomp = from carbonyl complex) was synthesized in mild conditions from a Pt-carbonyl chemical precursor. A relatively narrow size distribution (2.4 ± 0.9 nm) of such a bimetallic catalyst supported onto carbon Vulcan XC72 was obtained at room temperature. Its electrochemical behavior was compared to that of a commercial catalyst. The WAXS study revealed that such a catalyst, prepared via the carbonyl route, has a certain degree of surface disorder (high Debye parameter, B), which enhances the electrocatalytic activity for hydrogen adsorption. Furthermore, WAXS also demonstrated that the structural stability of this bimetallic catalyst is maintained at the annealing temperature employed (500 C), although the particle size increases from 1.6 to 2.2 nm. Electrochemical underpotential deposition studies, via copper deposition, also provide information concerning the state of the nanoparticulate surface of the various platinum-based catalysts investigated