Crystal and magnetic structure of substituted lanthanum cobaltites

The crystal and magnetic structures of the lanthanum cobaltites La0.6Sr0.4CoO3, La0.6Sr0.4Co0.9Fe0.1O3 and La0.6Ba0.4Co0.9Fe0.1O3 have been studied by neutron powder diffraction at temperatures of 2, 300 and 900 K. All compounds undergo a phase transition from cubic to rhombohedral structure. Below the room temperature La0.6Sr0.4CoO3 becomes ferromagnetic while for the components with 10% Fe substituted for Co, we found an antiferromagnetic order

Impact of the final thermal sealing of combined zinc/cerium oxide protective coating primers formed on low carbon steel

The final sealing possesses a proven beneficial effect on the protective properties of anodic oxide films on aluminum. In this sense, the present research is devoted to the evaluation of the impact of this procedure on the barrier ability of combined Zn/Ce oxide layers deposited on low carbon steel samples. For this purpose, four samples were submitted to galvanic zinc deposition, followed by spontaneous formation of cerium oxide primer layer (CeOPL). Afterwards, two of the samples underwent thermal sealing in boiling water in order to enhance their barrier ability. Its evaluation was performed by two electrochemical methods: electrochemical impedance spectroscopy (EIS) and potentiodynamic scanning (PDS) after 24 hours of exposure to a diluted model corrosive medium (MCM). Other instrumental methods were used in order to describe the effect of this final procedure on the color characteristics and hydrophobicity of the films. The results were collected from multiple tests, followed by statistical data treatment. In addition, the surfaces of the obtained films were submitted to direct observation by scanning electron microscopy (SEM), coupled with energy dispersion X-ray (EDX). Their composition was determined by means of X-ray Photoelectron Spectroscopy (XPS). The acquired data have revealed a detrimental effect of the final sealing in boiling water. It was expressed by the loss of the barrier properties of the Zn/CeOPL films, combined with additional decolorization and hydrophilization. Finally, the mechanism of this detrimental effect was determined by further SEM, EDX and XPS analyses

Evaluation of the electrochemical performance of Ag containing AAO layers after extended exposure to a model corrosive medium

The coating procedure appears to be an indispensable finishing stage in the production of Al based industrial products, engineering facilities and equipment. For this reason, there is an ever-increasing interest towards the elaboration of reliable corrosion protective layers with apparent coverage, adhesion, and barrier properties. In this sense, both the for­ma­ti­on of anodized aluminum oxide (AAO) layer and its further modification with silver enable the elaboration of advanced (Al-O-Ag) films with extended beneficial charac­te­ris­tics. The present research activities are aimed at the determination of the corrosion pro­tective properties of electrochemically synthesized Al-O-Ag layers on the technically pure AA1050 alloy. The structures and compositions of the obtained Al-O-Ag layers were characterized by X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The research activities were accomplished by means of two independent electrochemical characteri­za­tion methods: electrochemical impedance spectroscopy (EIS) and potentio­dynamic scan­ning (PDS). The electrochemical measurements were performed after 24, 168 and 672 hours of exposure to 3.5 % NaCl solution used as a model corrosive medium (MCM), in order to determine the barrier properties and durability of the elaborated Al-O-Ag layers. The analysis of the obtained results has undoubtedly shown that the proposed electro­chemical Al-O-Ag layer formation can successfully be used for the creation of self-standing layers with apparent corrosion protective properties. Besides, Al-O-Ag system can be used as a basis for development of efficient protective layers suitable for application in biologically contami­nated media.</p

crystal and magnetic structure of substituted lanthanum cobaltites

The crystal and magnetic structures of the lanthanum cobaltites La0.6Sr0.4CoO3, La0.6Sr0.4Co0.9Fe0.1O3 and La0.6Ba0.4Co0.9Fe0.1O3 have been studied by neutron powder diffraction at temperatures of 2, 300 and 900 K. All compounds undergo a phase transition from cubic to rhombohedral structure. Below the room temperature La0.6Sr0.4CoO3 becomes ferromagnetic while for the components with 10% Fe substituted for Co, we found an antiferromagnetic order

Characterization of Siloxane-poly(methyl methacrylate) Hybrid Films Obtained on a Tinplate Substrate Modified by the Addition of Organic and Inorganic Acids

Tinplate is used to food packaging and other types of packages. The corrosion resistance of the tinplate has been study due the necessity of an alternative to high environmental impact of chromatization process. Therefore protective coatings as hybrid films base elaborations with different acids are studied to improve the barrier effect against corrosion. The objective of this work is characterize hybrid films deposited on a tinplate from a sol made up of the alkoxide precursors 3-(trimethoxysilylpropyl) methacrylate (TMSM), tetraethoxysilane (TEOS) and poly(methyl methacrylate) (PMMA) together with one of three acids (acetic, hydrochloric or nitric acid) and to verify their action against the corrosion of the substrate. The films were obtained by a dip-coating process and cured for 3 hours at 160 °C. The film hydrophobicity was determined by contact angle measurements, and the morphology was evaluated by SEM. FTIR measurements were performed to characterize the chemical structures of the films. The electrochemical behavior of the coatings was evaluated by techniques open circuit potential monitoring (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results demonstrate that the siloxane-PMMA films improve the protective properties of the tinplate, with the films obtained by acetic acid addition exhibiting the greatest improvement

Assessment of Nd2-XSrXNiO4-d as a cathodic material for Solid Oxide Fuel Cell applications

The features and performance of each device and equipment is directly related to its composing materials. The efficiency and durability of the Solid Oxide Fuel Cells (SOFC) also depend on their composing elements. Other important factors for the SOFC behavior are the working conditions (compositions, and humidity of the fuel and oxidant gaseous mixtures, temperature, pressure, etc.). These facts predetermine the necessity for detailed investigation of the behavior of each composing layer of SOFC. For this reason, the electrical characteristics of Nd2-xSrxNiO4-d as SOFC cathodic material were evaluated by high temperature electrochemical methods, durability tests, and posterior XRD and SEM characterization. As a result, the optimal composition and working conditions for the investigated material in assembled SOFC were determined. The obtained material reveals excellent durability and compatibility with the rest SOFC components