This paper presents a comprehensive interface and electrochemical phenomena review of different anodes for SOFC. In this way, it was possible to select some mixed electronic and ionic conductor materials alternatives to the conventional anode, Ni-YSZ conductor. New materials must present a satisfactory electronic and ionic conductivity at intermediate temperatures, be able to operate under different types of hydrocarbon fuels without deactivation, present stability under redox cycles and thermal expansion compatible with the other materials. Among all new materials, Sr0.86Y0.08TiO3, a Y-doped strontium titanate (YST), presented the highest measured conductivity, of 82 S cm-1 at 800 °C. In addition, this material showed excellent stability time and coefficient of thermal expansion compatible with materials used as cathode, strontium-doped lanthanum manganite and electrolyte, yttria stabilized zirconia. SrTiO3 (ST) compounds synthesized by solid-state reaction method, calcined, and sintered to obtain undoped (ST), 4% (YST04) and 8% (YST08) of Y-dopant and as a heterojunction with yttria-stabilized zirconia (YST08/YSZ). It was observed that calcination under Ar/5%H2 atmosphere has increased the dopant maximum concentration in the SrTiO3 cubic crystal structure when compared to inert atmosphere. When the Y solubility limit was exceeded, a pyrochlore phase Y2Ti2O7 was formed on the intergranular region due to the deficiency of oxygen vacancies, especially in the presence of inert atmosphere.

Abstract In this study, polyetherimide/polyvinylpyrrolidone (PEI/PVP) hollow fiber membranes (HFMs) were synthesized by the phase inversion method. The synthesized PEI/PVP membranes were characterized by morphological analysis and transport properties (hydraulic permeability and solute rejection coefficient). Their performance in uremic solutes separation was also investigated. Urea removal and clearance were measured. Surface properties were analyzed by infrared spectroscopy (FT-IR), water uptake, zeta potential and protein adsorption. The results showed that PEI/PVP membranes had transport properties comparable to those of current high flux clinical membranes, with better removal of medium molecular weight solutes (using lysozyme as a model) and high retention of high molecular weight solutes (using albumin as a model). Surface characterization suggests that PEI/PVP membranes present improved blood compatibility. These results confirm the potential of polyetherimide as an alternative material for producing hollow fiber hemodialyzers, in substitution to polysulfone and polyethersulfone.

A utilização de reatores à membrana nas reações em fase gasosa, alternativamente aos modelos convencionais para a produção de hidrogênio, é de grande interesse científico e tecnológico. Busca-se o desenvolvimento de sistemas catalíticos mais eficientes e, em especial, de membranas com melhores propriedades de transporte de gases. Neste trabalho, foi investigada a produção de membranas poliméricas do tipo fibras ocas, as quais foram posteriormente pirolisadas e destinadas ao preparo de membranas catalíticas seletivas. As membranas foram preparadas pelo processo de inversão de fase, utilizando-se poli(éter imida) como polímero base e poli(vinil pirrolidona) como modificador de viscosidade. A obtenção das membranas de carbono constitui-se de uma etapa inicial de oxidação das membranas secas, seguida da pirólise propriamente dita, em um reator de quartzo. Os polímeros precursores e as membranas poliméricas foram caracterizados por análise térmica. As morfologias das fibras poliméricas e de carbono foram avaliadas por microscopia eletrônica de varredura. As propriedades de transporte das fibras foram determinadas em uma célula de permeação de gases. As fibras poliméricas obtidas apresentaram morfologia caracterizada pela ausência de macrovazios e presença de microporos interconectados. Os testes de permeabilidade gasosa a N2 e CO2 permitiram avaliar a existência de defeitos. As fibras de carbono apresentaram morfologia característica, com aparente resistência mecânica.

The use of membrane reactors for hydrogen production, coupling, this way, the production and separation in a single step, has increased in scientific and technologic importance. The main challenge in this field is to develop catalytic systems more efficient as well as membranes with more suitable gas transport properties. In this work, it was investigated the production of polymeric hollow fibers for preparation of carbon membranes by pyrolysis and further deposition of an active phase to produce catalytic membranes. Precursor membranes were prepared by phase inversion process, using polyetherimide as base polymer and polyvinyl pyrrolidone as macromolecular additive. Carbon membranes were obtained by pyrolysis in a quartz reactor, after an oxidation initial step. Polymeric and carbon membranes were both analyzed by electronic scanning microscopy and permeability tests. The hollow fibers presented a morphology characterized by absence of macrovoids and prevalence of interconnected pores. N2 and CO2 permeability made possible the detection of defects. Carbon membranes presented a typical morphology, with an apparent mechanical resistance, ideal for the intended use as catalyst in natural gas reforming.