Development and testing of galvanic anodes for cathodic protection

Aquest treball resumeix els resultats obtinguts en un projecte de recerca dut a terme en el nostre laboratori i relacionat amb l'assaig electroquímic dels ànodes de sacrifici emprats en protecció catòdica, així com en el desenvolupament de nous ànodes d'alumini -Al- lliures d'indi -In- i de mercuri -Hg. Les aportacions més importants han estat fetes en els aspectes següents: 1. Mecanisme de corrosió durant els assaigs electroquímics. 1.1. Al. Assaig electroquímic d'ànodes de sacrifici de Al. 1.2. Mg. Mecanisme de dissolució dels ànodes de sacrifici de Mg durant l'assaig electroquímic. 1.3. Zn. L'impedància electroquímica com a eina d'assaig dels ànodes de sacrifici de Zn aplicats per projecció tèrmica sobre el formigó. 2. Augment de l'eficiència electroquímica dels ànodes de Mg mitjançant el tractament tèrmic i el control de la seva microestructura. 3. Disseny i desenvolupament de nous ànodes de Al sense In ni Hg. Aquests nous ànodes de Al-Zn-Mg-Li són proposats com una alternativa als actualment en ús. El sistema Al-Mg-Zn ha estat escollit a causa de la presència de precipitats en la matriu de l'alumini, que poden ser capaços de trencar la pel·lícula passiva, però mantenen una alta eficiència electroquímica.This paper summarizes the results obtained in the research project carried out in our laboratory related to the testing of sacrificial anodes used in cathodic protection (CP) systems and the development of new In/Hg-free aluminium-alloy anodes. The main contributions are in the following subjects: 1. Corrosion mechanism during electrochemical testing. 1.1. Al. Electrochemical testing of Al sacrificial anodes. 1.2. Mg. Dissolution mechanism of Mg sacrificial anodes under electrochemical testing. 1.3. Zn. EIS testing of thermal spray Zn anodes for concrete applications. 2. Improving the efficiency of Mg sacrificial anodes by microstructure control and heat treatments. 3. Design and development of new Al-alloy anodes In/Hg free. The evaluation of an Al-Zn-Mg-Li alloy as a potential candidate for Al-sacrificial anode was studied. The Al-Zn-Mg system was particularly selected due to the presence of precipitates in _-Al matrix which are capable of breaking down passive films whilst presenting good electrochemical efficiencies. The effect of Li additions on superficial activation of the anode by means of precipitation of AlLi type compounds was also examined

Absolute single photoionization cross-sections of Br3+: Experiment and theory

Absolute single photoionization cross section measurements for Br3+ ions are reported in the photon energy range 44.79-59.54 eV at a photon energy resolution of 21 ±3 meV. Measurements were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged-beams technique. Numerous resonance features in the experimental spectrum are assigned and their energies and quantum defect values are tabulated. The cross-section measurements are also compared with Breit-Pauli R-matrix calculations with suitable agreement over the photon energy range investigated. Analysis of the measured spectrum including Rydberg resonance series identifications produced a new emperical determination of the ionizational potential of Br3+ of 46.977 ± 0.050 eV, which is 805 meV lower than the most recently published value of 47.782 eV. This disparity between our determination and the earlier published value is similar to an 843 meV shift in the accepted ionization potential published for iso-electronic Se2+ as part of this same research program

DISTRIBUCIÓN HORIZONTAL Y VERTICAL DE HUEVECILLOS DE MOSCA PINTA (Aeneolamia spp.) EN CAÑA DE AZÚCAR (Saccharum spp.) EN LA REGION CENTRAL DE VERACRUZ

The spittlebug (Aeneolamia spp.) has become an endemic plague in recent years, damaging sugar cane (Saccharum spp.) fields in the central region of Veracruz, México, where the losses are quite significant and various control strategies have been used. A preventive measure has been the control of hibernating eggs during the dry season, through the use of mechanized tasks based on phytosanitary rakes, whose incorporation is justified in areas of high incidence of eggs, or where the economic threshold of the damage is found. Three agro-climate zones in the area of influence of the Central Motzorongo sugar plant were studied, and in each zone one site, cycle and variety were selected, which showed a high egg infestation, to evaluate three raking distances, from the center of the stump to the mid-furrow (0-15 cm, 15-30 cm, 30-45 cm) and five depths (1,2,3,4,5 cm), and the egg extraction was done previously through the soil sampling technique with a metallic frame of 15X15X5. It was determined that there was no significant difference in terms of percentages of concentration of eggs between the distances evaluated; however, between depths, in all sampling zones, it was found that the highest average concentration is located in the first 3 cm of depth (90.39 %) as preventive control of the plague.Dado que la mosca pinta (Aeneolamia spp.), se ha convertido en los últimos años una plaga endémica y dañina al cultivo de la caña de azúcar (Saccharum spp.) en la región Centro de Veracruz, México, donde las pérdidas son muy significativas y se han empleado diversas estrategias de control. Una medida preventiva, ha sido el control de huevecillos hibernantes durante la época seca, mediante el uso de labores mecanizadas a base de rastras fitosanitarias, cuya incorporación se justifica en áreas con alta incidencia de huevecillos, o donde se registra el umbral económico de daño. Se estudiaron tres zonas agroclimáticas del área de influencia del ingenio azucarero Central Motzorongo, y en cada zona se seleccionó un sitio, ciclo, y variedad que registrara alta infestación de huevos, para evaluar tres distancias de paso de rastra, a partir del centro de la cepa hacia el entresurco (0-15 cm, 15-30 cm, 30-45 cm) y cinco profundidades (1,2,3,4,5 cm), y mediante la técnica de muestreo de suelo con marco metálico de 15X15X5 se realizó la extracción de huevecillos previamente. Se determinó que no hubo diferencia estadística significativa en cuanto a porcentajes de concentración de huevecillos entre las distancias evaluadas, sin embargo, entre profundidades en todas zonas de muestreo, se registró que la mayor concentración promedio se ubica en los primeros 3 cm de profundidad (90.39%) como control preventivo de la plaga

Mechanisms of Spontaneous and Amplified Spontaneous Emission in CH3 NH3 Pb I3 Perovskite Thin Films Integrated in an Optical Waveguide

In this paper, the physical mechanisms responsible for optical gain in CH3NH3PbI3 (MAPI) polycrystalline thin films are investigated experimentally and theoretically. Waveguide structures composed by a MAPI film embedded in between PMMA and silica layers are used as an efficient geometry to confine emitted light in MAPI films and minimize the energy threshold for amplified spontaneous emission (ASE). We show that photogenerated exciton density at the ASE threshold is as low as (2.4-12)×1016cm-3, which is below the Mott transition density reported for this material and the threshold transparency condition deduced with the free-carrier model. Such a low threshold indicates that the formation of excitons plays an important role in the generation of optical gain in MAPI films. The rate-equation model including gain is incorporated into a beam-propagation algorithm to describe waveguided spontaneous emission and ASE in MAPI films, while using the optical parameters experimentally determined in this work. This model is a useful tool to design active photonic devices based on MAPI and other metal-halide semiconductors