Hydrogen evolution kinetics on Ni cathodes modified by spontaneous deposition of Ag or Cu

Nickel modification by spontaneous deposition of transition metals such as Ag and Cu is shown as an economic and simple alternative for the activation of hydrogen evolution reaction（HER） on cathodes in alkaline media. The kinetics of HER is studied on Ni/Ag and Ni/Cu catalysts by cyclic voltammetry and electrochemical impedance spectroscopy（EIS） using a rotating disk electrode（RDE）. Freshly synthesized catalysts, as well as catalysts subjected to a short chronoamperometric ageing procedure, are analyzed and the kinetic and thermodynamic parameters of the HER are obtained. The nickel surface modified with transition metals with an outer shell electronic configuration [xd;（x+1）s;], such as Cu(3d;4s;)and Ag(4d;5s;), shows an improved activity for the HER compared to bare nickel. Furthermore, the Ni/Cu catalyst presents a decreased onset potential. The hydrogen evolution rate, measured as current density at –1.5 V（vs. SCE）, is similar on Ni/Cu and Ni/Ag electrodes.

Surface Tension and Foam Stability Prediction of Polydimethylsiloxane-Polyol Systems

The Gibbs elasticity modulus represents an important tool to predict the foamability for transient and permanent foams like polyurethane flexible systems. Elasticity is related to foamability and so is used as a synonymous for the purpose of this paper. In this article we propose a method and a thermodynamic model to analyze the espumability of silicone surfactants in polyol binary mixtures using surface tension data. The present work describes foamability through the Gibbs elasticity modulus expressed in terms of first and second derivatives of surface pressure vs bulk composition. Furthermore, the Gibbs adsorption equation and the corresponding novel surface equation of state based on a modification of the Langmuir isotherm resulted in an elasticity equation with analytical solution. It is shown that according to foam model systems of surfactant solution in polyol used at commercial processes, optimum concentration level of surfactant obtained at this article by Gibbs adsorption equation and maximus on elasticity modulus finally match.

Development of a Low Cost Pulsed Laser Deposition System for Thin Films Growth

.Pulsed Laser Deposition (PLD) is a powerful technique to grow thin films. Oxides, Magnetics and superconducting materials have been obtained by PLD and theirs properties are strongly dependent of deposition parameters. The construction of a simple and cheap PLD system that is suitable for growing various thin films, including magnetic materials, controlling some deposition parameters is presented. The design characteristics and construction are presented for each one of the devices that compose this PLD system. The equipment has the possibility of carrying out films deposition using up to five targets under controlled atmosphere and substrate temperature. The system also allows controlling the cool off sample time after growing up films at high temperatures. A wide range of relative speeds between target and substrate axial rotation can be externally controlled. With the configuration and the dimensions adopted in their construction, a PLD system of great experimental flexibility is achieved, at a very low cost regarding the commercial systems. To evaluate their performance and effectiveness, the deposition characteristics of a BaFe12O19 film on (0001) sapphire substrate is presented.