Copper-cobalt alloy coatings were deposited on mild steel substrates using sodium citrate electrolytes at room temperature and under direct current. A set of cathodic polarization curves was plotted by varying the mechanical stirring speed of the solution (0-400 rpm), using a range of current densities during the electrodeposition experiments. Factorial design was used to verify the influence of these deposition parameters on the cathodic efficiency, the copper and cobalt content in the coating, the corrosion current density of the coating/substrate system, and the efficiency of the coating in protecting the substrate. The electroplating experiments showed that, with the studied bath composition, high stirring speed and low current density lead to greater cathodic current efficiency and copper-rich coatings. On the other hand, high current density and low stirring speed yields coatings with high cobalt content and a lower cathodic efficiency. Our results show that the studied parameters affect the corrosion current density and the coating efficiency of the coating/ substrate system in opposite ways. The best results were obtained increasing the current density and decreasing the mechanical stirring speed. Additionally, three samples were produced in selected deposition conditions. The coatings morphologies were compact, and their grain sizes seemed to enlarge with increasing stirring speed and decreasing current density.

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Zn-Co alloy coatings were produced on carbon steel, at room temperature, from citrate baths

In the present work, cysteine and allyl alcohol were added to citrate baths as additives to Cu-Zn coatings on steel substrates. In order to verify the effects of the deposition parameters (current density, mechanical stirring speed, and additives) on the coating composition, electrochemical behavior, morphology, and microstructure properties of Cu-Zn coatings, the electrodeposition of the alloy was carried out using an experimental composite design 2 3 , in which these parameters were considered the entry variables and the measured properties were the response variables. The confidence level was 95% and the results were shown as response surface diagrams. It was possible to verify that the current density affected the zinc content in the coating, while the coating produced from cysteine-contained bath presented the worse anticorrosive performance. In a general way, it was possible to observe that the studied parameters affected the morphology, grain size, and the electrochemical behavior of these coatings, although only a few response variables were statistically influenced by them.

Synthesis and Characterization of Two Novel Fibrous TitaniumPhospates Ti2O(PO4)2·2H2O.-Studies on the synthesis of Ti phosphates under hydrothermal conditions from TiCl4 using relatively low concentrations of H3PO4 lead to the novel phases ρ-TiP and π-TiP of the title formula. Characterization by XRD, IR, 31P MAS NMR, and TGA show that both compounds have different structures. According to the powder XRD data, the structure of ρ-TiP consists of a framework with two types of tunnels along the c axis formed by Ti in octahedral coordination and PO4 tetrahedra. Due to the absence of n-alkylamine intercalation for both compounds and similarities in the thermal decomposition behavior, a framework structure is also suggested for π-TiP. Both compounds are weak acid cation exchangers. -(BORTUN, A. I.; KHAINAKOV, S. A.; BORTUN, L. N.; POOJARY, D. M.; RODRIGUEZ, J.; GARCIA, J. R.; CLEARFIELD, A.; Chem. Mater. 9 (1997) 8, 1805-1811; Dep. Chem., Tex. A&M Univ., College Station, TX 77843, USA; EN)

RESUMO -A produção de óxidos metálicos in situ pode originar novos materiais, com maior dureza, resistência à abrasão e propriedades eletrocatalíticas. Óxidos de metais de transição, tais como Ni e Co, apresentam propriedades eletrocatalíticas que os tornam atrativos para aplicação nas reações de redução do O 2 e desprendimento de Cl 2, O 2 e H 2 . Neste trabalho, o processo de formação de óxidos de Co ou de Ni foi estudado empregando curvas voltamétricas cíclicas levantadas sobre grafite, a partir de banhos contendo íons Ni(II) ou Co(II) (0,10 mol/L), na ausência ou presença de citrato de sódio (0,10 mol/L), em diferentes valores de pH e velocidades de varredura (v), variando-se o potencial entre -2,0 V ESS e 2,0 V ESS . Observou-se que, para os íons não complexados, os comportamentos encontrados, para cada um dos íons metálicos, foram aproximadamente similares entre si, independente das variáveis estudadas. Por outro lado, em presença de citrato, tanto v quanto o pH influenciaram na intensidade dos picos relacionados aos óxidos de Co ou Ni.Área temática: Engenharia de Materiais e Nanotecnologia

(PO 4 ) 3 . The partially disordered distribution of Cd and Na between the A(1) and M(1) sites results from the similar ionic radii of Cd 2+ (0.95 Å) and Na + (1.02 Å) [7]. The Rietveld refinements of the Na 2 (Mn 1-x Mg x )Fe 2+ Fe 3+ (PO 4 ) 3 alluaudite-type compounds are still in progress.[1] Moore P.B., Am. Mineral, 1971Mineral, , 56, 1955 The large number of open-framework metal phosphates which have been recently synthesized and studied is a consequence of their potential applications in the areas of catalysis, sorption and separation processes. The zinc phosphates constitute one of the largest families of open-framework materials that have been studied during the past few years. This is mainly due to their similarity with the zeolites: the total charge of the divalent zinc phosphates is the same as the aluminosilicate zeolites. In fact, several zinc phosphates possess zeolitic structures. Hydrothermal methods have been extensively used in the synthesis of this kind of compounds, employing organic amines as templates which act as structure-directing or space-filling agents. In many cases, the location and definite identification of those extra-framework organic species is problematical; their high degree of disorder makes impossible to study the role of N--H···O bonds in establishing or stabilizing the structure. We report here the hydrothermal synthesis and full structural determination of an organically templated zincophosphate [H 3 N(CH 2 ) 3 NH 3 ][H 0.2 ZnPO 4 ]. The structure of this compound, which has the same tetrahedral connectivity than that in the zeolite edingtonite family, was reported by Harrison et al. six years ago. Nevertheless, the position of the organic template could then not be determined. In this work a complete study of the framework-template interactions is analyzed. E-mail: boujrhal@yahoo.fr Keywords: Phosphates, Microstructure, structure defectThe Moroccan sedimentary phosphates are essentially constituted by apatite, mineral which finds application in all domains; like medicine, nuclear wastes, biology and geology. These phosphates contain some ppm of uranium undergoes spontaneous fission since its geological formation. This spontaneous fission causes the (irradiation) defects in the structure, by recoil of the fission products. This work focuses on the exam of the micro/nanostructure, the local structure and the irradiated defect in the structure of several grains of phosphate by electron microscopy observations. Several STEM imaging and X cartographies are obtained, the Scanning Electron Microscope (SEM) shows the internal morphology of the grains and its qualitative analysis, where as, the Transmission Electron Microscope (TEM) gives the quantitative analysis and the structure of the material studied here. This electronic microscopy offers the possibility to observe the sample during its analysis; it was possible to put in evidence the heterogeneities in the grains and to characterize all the precipitate zones seeming to be homogeneous. On the other hand, the SEM was a...

In this work, Ni-Co oxides coatings were produced using electrochemical techniques (chronopotentiometry and/or linear voltammetry) and solutions containing Ni 2+ and Co 2+ ions in the molar ratio 1: 2, sodium citrate as the ligand, and different pH values (7.5 and 10.5). Energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), Raman spectroscopy (LRS) and electrochemical impedance spectroscopy (EIS) were used to characterize these coatings. The results showed that both pH values favored the production of Ni-Co oxide phases, independent of the electrochemical technique used. The EDS analysis indicated that it was possible to produce of oxides coating presenting different Ni:Co ratios using electrodeposition process. However, the morphology, the microstructure and the electrocatalytic ability of the coatings depended on both the pH and on the electrochemical technique used to produce them. The coatings produced using pH 10.5 were suitable to be used as electrocatalysts for the oxygen evolution reaction (OER).