Thermal study of the solid-state reactions on Pt-15%Rh/Hg system

Thermogravimetry (TG), energy dispersive X-ray microanalysis (EDX), scanning electron microscopy (SEM), mapping surface and X-ray diffraction (XRD) were used for the study of solid-state reaction on Pt-15%Rh with electrodeposited mercury. The results suggest when heated the mercury film react with the Pt-15%Rh alloy to form intermetallics having different thermal stabilities indicated by three mass loss steps. The first mass loss step occurs between room temperature and 184 degrees C only the bulk Hg is removed and PtHg4, PtHg2 and RhHg2 were characterized by XRD. The second step, between 184 and 271 degrees C, was attributed to PtHg4 decomposition with formation of PtHg2 stabilized by RhHg2. The third step, between 271 and 340 degrees C, was attributed to decomposition of a solid-solution of PtHg2/RhHg2. The fourth step, between 340 and 600 degrees C, was ascribed to: (1) a thermal decomposition of PtHg2, formed by a PtHg eutectoid reaction (similar to 340 degrees C) on the surface and (2) Hg removal from a solid solution of Pt-15%Rh(Hg). (C) 2013 Elsevier B.V. All rights reserved.

SVET, SKP and EIS study of the corrosion behaviour of high strength Al and Al-Li alloys used in aircraft fabrication

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da reação de oxidação de metanol sobre fases intermetálicas ordenadas de AuIn, AuSn e AuSb2 em meio alcalino

The present work assessment materials can be used as fuel cells electrocatalysts. The alkaline fuel cell though was less studied, has some advantages compared to the acid configuration. The materials assesment were Au polycrystalline and intermetallics ordered phases of AuIn, AuSn and AuSb2. Your electrocatalytic properties were studied across cyclic voltametry and chronoamperometry techniques in Sodium Hydroxide 0,15M and Metanol 0,15M solution. The results obtained show a more efficiency to intermetallic AuIn as electrocatalyst for the oxidation reaction of methanol in alkaline medium, it showed high levels of current density and on set potential less positive compared to Au polycrystalline. The intermetallic AuSn showed activity just higher concentrations of methanol. Except AuSb2, who represented himself unstable in alkaline media, the intermetallics AuIn and AuSn present a promising future as anode materials for the oxidation in alkaline medium

Estudo da adsorção e oxidação do monóxido de carbono sobre as fases intermetálicas ordenadas AuIn, AuSb2, AuSn, PdSb e PdSn

Aiming to reduce the cost of electrocatalysts and a greater resistance to CO poisoning this work was to study the adsorption and oxidation of carbon monoxide on ordered intermetallic phases AuIn, AuSb2, AuSn, PdSb and PdSn using voltammetric techniques in alkaline electrolyte solution. The results suggest that the AuSn and PdSn intermetallics has some form of resistance to CO poisoning. It is assumed that this behavior is a result of electronic effect and the effect of the third body has been achieved by adding a second metal to Au and Pd. However, further studies should be conducted to confirm this hypothesis as to test these materials as electrocatalysts in the reaction of oxidation of fuels

Comparação dos efeitos de compressão isostática e compressão uniaxial na obtenção da liga NiTi por metalurgia do pó

Several alloys present the shape memory effect and among them, the equiatomic NiTi alloy, nitinol, is the most important one. It is usually used in several engineering applications and also in biomedical devices, in the fabrication of orthodontic wire, stents and Judet staples. Although a considerable amount of these biomedical devices is utilized in Brazil and a fraction of it is already made here, all nitinol used is bought abroad. Thus, it is important to develop the necessary know-how to fabricate NiTi wire and sheet. It would mean less importation with job creation and wealth generation for the country. In this work nitinol was obtained powder metallurgy from elemental powders of Ti and Ni using uniaxial compression and uniaxial compression followed by isostatic compression. The final densities achieved were determined by the Archimedes method. The precipitation of intermetallic secondary phases was studied and the samples were characterized by metallographic analysis, optical microscopy and X-ray diffraction. Results indicated that 50 hours sintering route showed a low amount of intermetallics, and no trace of unreacted powder. XRD and metallography at room temperature indicated B19’ as the predominant phase, which corresponds to martensite. Although density results showed little dispersion, the most dense sample was compacted under uniaxial compression and presented 4.8 g/cm3, corresponding to 20.84% porosity. Density variation was considered normal to the measurement process and independent of the compaction mode

O efeito da ordenação e estrutura geométrica dos materiais PtSn/C e PdSn/C na eletrooxidação do glicerol em meio alcalino

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)