Corrosion experiments with everyday used metals

La corrosión que sufren los metales en un ambiente húmedo es un fenómeno muy importante desde un punto de vista tecnológico, pues sus propiedades mecánicas empeoran sustancialmente al sufrir corrosión. En este trabajo se proponen varias experiencias sencillas para poner de manifiesto este fenómeno utilizando reactivos y materiales fácilmente accesibles. Todas estas experiencias pueden ser realizadas por estudiantes de química de bachillerato como actividades complementarias para realizar en casa, pues ayudaran a despertar su interés por la experimentación en química

Convierta cobre en plata y en oro

Esta experiencia resulta bastante sorprendente y, además, puede llevarse a cabo con reactivos y materiales fácilmente accesibles y asequibles. Se puede realizar al estudiar las reacciones de oxidación-reducción con alumnos de bachillerato, si bien, dada su espectacularidad podría llevarse a cabo frente a un público menos selecto (para alumnos de niveles inferiores o incluso para el gran público) como demostración en un espectáculo de química recreativa

Experiencias sorprendentes de química con indicadores de pH caseros

En este trabajo se describen varias experiencias sencillas relacionadas con las reacciones ácido-base. Todas ellas pueden realizarse con utensilios de cocina y usando sustancias baratas que pueden encontrarse fácilmente en un supermercado, una farmacia o en casa. En concreto, se describe la forma de obtener algunos indicadores de pH a partir de extractos vegetales o de medicamentos. Además, se proponen varias experiencias en las que se hace uso de estos indicadores con el fin de estudiar las reacciones ácido-base. Todas estas experiencias están enfocadas a alumnos de enseñanza secundaria

Experimentos de química recreativa con sulfato de cobre pentahidratado

En este trabajo se proponen varias experiencias sencillas usando sales de sulfato de cobre pentahidratado. Todas ellas pueden realizarse en casa con utensilios de cocina y usando sustancias baratas, la mayoría de las cuales pueden encontrarse en un supermercado. Las experiencias propuestas permiten estudiar el proceso de cristalización del sulfato de cobre pentahidratado, reacciones de oxidación-reducción, de formación de precipitados e, incluso, reacciones de formación de complejos. Estas experiencias pretenden despertar el interés de los alumnos por la químic

Degradación del almidón mediante la amilasa salival

Esta sencilla experiencia requiere de reactivos y materiales fácilmente accesibles y asequibles.Se puede realizar con alumnos de secundaria o de bachillerato al estudiar las reacciones con catalizadores en química o bien cuando se estudian las enzimas enbiología

Experiencias sobre corrosión en metales de uso cotidiano

La corrosión que sufren los metales en un ambiente húmedo es un fenómeno muy importante desde un punto de vista tecnológico, pues sus propiedades mecánicas empeoran sustancialmente al sufrir corrosión. En este trabajo se proponen varias experiencias sencillas para poner de manifiesto este fenómeno utilizando reactivos y materiales fácilmente accesibles. Todas estas experiencias pueden ser realizadas por estudiantes de química de bachillerato como actividades complementarias para realizar en casa, pues ayudarán a despertar su interés por la experimentación en química.Palabras clave: Experiencias de química; Corrosión; Demostraciones de química.Corrosion experiments with everyday used metalsThe corrosion of metals in a humid environment is a very important subject from a technological point of view, because the mechanical properties of metals substantially worsen with corrosion. In this paper we propose several simple experiments to demonstrate this phenomenon using very accessible reagents and materials. All these experiences can be performed by high school chemistry students as complementary homework activities, since they will help them to arouse their interest in experimenting on chemistry.Keywords: Chemistry experiments; Corrosion; Chemical demonstrations

Irradiation of carbon nanotubes with carbon projectiles: A molecular dynamics study

The irradiation of carbon based nanostructures with ions and electrons has been shown to be an appropriate tool to tailor their properties. The defects induced in the nanostructures during irradiation are able to modify their mechanical and electronic properties. Here we simulate the irradiation of carbon nanotubes with carbon ions using a molecular dynamics code. We use the Tersoff potential joined smoothly to the Universal Ziegler-Biersack-Littmark potential at short distances. We study the number of defects produced after irradiation with a single carbon ion finding a saturation with its energy at ∼ 3 keV. We observe, after continuum irradiation with low energy ions, the formation of bumps in the irradiated region. For larger energy ions we find that the diameter of the nanotube shrinks as shown in previous works.This work has been financially supported by Project FIS2010-17225 by the Spanish Ministerio de Ciencia e Innovación

Calculated energy loss of swift He, Li, B, and N ions in SiO2, Al2O3, and ZrO2

We have calculated the electronic stopping power and the energy-loss straggling parameter of swift He, Li, B, and N ions moving through several oxides, namely SiO2, Al2O3, and ZrO2. The evaluation of these stopping magnitudes was done in the framework of the dielectric formalism. The target properties are described by means of a combination of Mermin-type energy-loss functions that characterize the response of valence-band electrons, together with generalized oscillator strengths to take into account the ionization of inner-shell electrons. We have considered the different charge states that the projectile can have, as a result of electron capture and loss processes, during its motion through the target. The electron density for each charge state was described using the Brandt-Kitagawa statistical model and, for He and Li ions, also hydrogenic orbitals. This procedure provides a realistic representation of both the excitation properties of the target electrons and the projectile charge density, yielding stopping powers that compare reasonably well with available experimental data above a few tens of keV/amu.This work was supported by the Spanish Comisión Interministerial de Ciencia y Tecnología (BFM2003-04457-C02-01 and BFM2003-04457-C02-02). S.H.A. thanks the Fundación Cajamurcia for financial support and J.M.F.V. expresses his gratitute for a travel grant from the Universitat d’Alacant

Simulation of swift boron clusters traversing amorphous carbon foils

We use a simulation code to study the interaction of swift boron clusters (Bn+, n=2–6, 14) with amorphous carbon foils. We analyze different aspects of this interaction, such as the evolution of the cluster structure inside the target, the energy and angle distributions at the detector or the stopping power ratio. Our simulation code follows in detail the motion of the cluster fragments through the target and in the vacuum until reaching a detector, taking into account the following interactions: (i) wake force, (ii) Coulomb repulsion among cluster fragments, (iii) stopping force, and (iv) elastic scattering with the target nuclei. Electron capture and loss by each fragment is also included in the code, affecting the above-mentioned interactions. The clusters size grows inside the foil due mainly to the Coulomb explosion but this increase is less pronounced in the plane transversal to the beam direction because of the alignment effect of the wake forces. We obtain an enhancement of the stopping power ratio that increases with the projectile energy and with the number of molecular constituents. Our results agree very well with the available experimental data for the thicker foils (≳10 μg∕cm2) and are compatible (within the experimental error bars) for the thinner foils.This work has been financially supported by the Spanish Ministerio de Educación y Ciencia (Contract Nos. BFM2003-04457-C02-01 and BFM2003-04457-C02-02). S.H.A. thanks the Fundación CajaMurcia for financial support and C.D.D. thanks the Spanish Ministerio de Educación y Ciencia for support under the Ramón y Cajal Program

Collision cascade effects near an edge dislocation dipole in alpha-Fe: Induced dislocation mobility and enhanced defect clustering

Collision cascades near a 1/2⟨111⟩{110} edge dipole in alpha-iron have been studied using molecular dynamics simulations for a recoil energy of 20 keV and two temperatures, 20 K and 300 K. These simulations show that the collision cascade induces the migration of the dislocations through glide along its slip plane. The motion of the dislocations starts at the peak of the collision cascade and expands a time scale much longer than the cascade duration, until restoring the equilibrium distance of the dipole, regardless of the damage produced by the cascade. At the initial stages, kinks are formed at the dislocation that enhance glide. When defects reach the dislocations, jogs are produced. We show that the initial dislocation motion is triggered by the shock wave of the collision cascade. The cascade morphology is also strongly influenced by the presence of the dislocations, having an elongated form at the peak of the displacement, which demonstrates the strong interaction of the dislocations with the cascade even at the early stages. Finally, we show that larger vacancy clusters are formed in the presence of dislocations compared to isolated cascades and that these clusters are larger for 300 K compared to 20 K.This work was partly supported by the Generalitat Valenciana through PROMETEO2017/139. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. EM gratefully acknowledges support from the U.S. DOE, Office of Science, Office of Fusion Energy Sciences, and Office of Advanced Scientific Computing Research through the Scientific Discovery through Advanced Computing (SciDAC) project on Plasma-Surface Interactions (award no. DE-SC0008875)