Fast-Scan Cyclic Voltammetry - Scanning Electrochemical Microscopy

The use of fast scan cyclic voltammetry (FSCV) to generate images in scanning electrochemical microscopy is demonstrated. In the FSCV-SECM method a cyclic voltammogram is acquired at each grid point of the scanned area. Thus, each point in the SECM image is a data array rather than a single value. This provides a significant increase in the amount of data collected per scan and provides the ability to make images of multiple analytes per scan. In addition, the use of cyclic voltammetry allows images based on adsorptive as well as diffusional processes. In this paper, we describe the FSCV-SECM experiment and equipment, we show that FSCV-SECM can resolve multiple chemical species in a single scan, and we demonstrate that cathodic-stripping voltammetry can be used to image the concentration profiles of halide ions

The Activity of Silicon Carbide Particles in Al-Based Metal Matrix Composites Revealed by Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) is used to image variations in electrochemical activity over the surface of an aluminum-based metal matrix composite (MMC) in contact with buffered or unbuffered neutral solutions. The composite consists of an Al - 13.5% Si - 9% Mg alloy matrix and reinforcing silicon carbide particles (SiCp). Feedback mode SECM imaging using ferrocenemethanol as a redox mediator in 0.1 M NaCl solution and in buffer solution (pH 6.8) revealed that the SiC particles are electrochemically active. The data suggest that the electronic conductivity at these sites is higher than that of the Al2O3 film covering the alloy matrix surface. The reduction of dissolved oxygen on the silicon carbide particles was investigated by in situ SECM images of samples and current vs. tip-substrate distance curves. The results with samples of SiCp/Al composites immersed in distilled water alone or in either 0.1 M NaCl or boric acid/borax buffer containing ferrocenemethanol as mediator demonstrate that the silicon carbide particles are conductive and act as local cathodes for the reduction of oxygen

Videojuego para el repaso de fracciones “Tséem Took y la princesa de Uxmal Versión 1.1”

Se expone el diseño de un videojuego didáctico conformado de varias actividades, con el propósito de que los estudiantes de primaria, en especial los educandos de sexto grado, refuercen el estudio de la noción de fracción. Este juego es creado considerando un avatar, cuya acción de movimiento para el usuario es en tercera persona. Los escenarios son creados por herramientas de modelado en 2D, 3D y exportado a un formato que entienda el motor de juegos XNA.A videogame with several activities for students in the primary level is proposed. Our objective is to help students of the sixth year in the learning of the math fractions. The videogame is supported by a didactic analysis. The videogame includes an avatar who is manipulated by the user in the third person view. Virtual scene considers different types of 2D and 3D objects and it was developed using the XNA game engine.Facultad de Informátic

THERMOGRAVIMETRIC APPROACH FOR ASSESSING THE OXIDATION LEVEL OF A BIODIESEL SAMPLE

Biodiesel, unlike diesel, is highly susceptible to autoxidation. This autoxidation is a major concern for a biodiesel producer. Various methods have been developed to estimate the degree of oxidative stability of biodiesel. These methods are useful to compare and estimate the oxidative stability between different biodiesel samples. However, an absolute value of the oxidative state will be more useful. In this study, we describe a method of estimating a figure that can be used as an indicator of the oxidation level. This indicator was determined from the thermal decomposition curve of biodiesel, as obtained from the thermogravimetric test. Biodiesel from waste cooking oil was oxidized at 80, 100 and 120 ºC using different exposure areas (19.6, 63.6, and 153.9 cm2). The percentage of oxidation, measured from low (80 ºC, 19.6 cm2) to highly aggressive conditions (120 ºC, 153.9 cm2), was in the range of 0.4 ± 0.1 and 23.5 ± 3.3. Kinematic viscosity was also measured for the oxidized samples, and a strong correlation (R2=0.96) was observed between the percentage of oxidation products and kinematic viscosity. In addition, the oxidative effect of temperature and area of exposure on the biodiesel samples was confirmed by ultraviolet spectroscopy

Inhibition Effect of Glycerol on the Corrosion of Copper in NaCl Solutions at Different pH Values

The inhibitory effect of glycerol on copper corrosion in aerated NaCl (0.5 M) solutions at three pH values (4, 7, and 10) was evaluated. Inhibition efficiency was assessed with conventional electrochemical techniques: open circuit potential, potentiodynamic polarization, and electrochemical impedance analysis. Glycerol reduced the corrosion rate of copper in NaCl solutions. The best inhibition effect (η≈83%) was produced in alkaline (pH 10) chloride media. This effect can be ascribed to increased viscosity and the presence of copper-glycerol complexes