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Re-activation of degraded nickel cermet anodes - Nano-particle formation via reverse current pulses
No full textThe Ni/yttria-stabilized-zirconia (YSZ) cermet is the most commonly applied fuel electrode for solid oxide cells (SOCs). Loss of Ni/YSZ electrode activity is a key life-time limiting factor of the SOC. Developing means to mitigate this loss of performance or re-activate a fuel electrode is therefore important. In this work, we report a series of five tests on state-of-the-art Ni/YSZ-YSZ-CGObarrier-LSC/CGO cells. All cells were deliberately degraded via gas stream impurities in CO2/CO or harsh steam electrolysis operation. The cells were re-activated via a variety of reverse current treatments (RCTs). Via electrochemical impedance spectroscopy, we found that the Ni/YSZ electrode performance could be recovered via RCT, but not via constant fuel cell operation. For optimized RCT, we obtained a lower Ni/YSZ electrode resistance than the initial resistance. E.g. at 700 °C we measured fuel electrode resistance of 180 mΩ cm2, 390 mΩ cm2, and 159 mΩ cm2 before degradation, after degradation and after re-activation via RCT, respectively. Post-test SEM revealed that the RCT led to formation of nano-particles in the fuel electrode. Besides the remarkable improvement, the results also showed that RCTs can weaken Ni/YSZ interfaces and the electrode/electrolyte interface. This indicates that finding an optimum RCT profile is crucial for achieving maximum benefit
Monokatoikia Villa Adriana sto Porto Rafti / Casa unifamiliare Villa Adriana a Porto Rafti
No full textDescrizione critica della casa unifamiliare, denominata "Villa Adriana", realizzata in località Porto Rafti, nella costa orientale dell'Attica, in Grecia. Viene evidenziato il rapporto tra costruzione (muratura in calcestruzzo armato) e la composizione dei vari partiti architettonici (interni ed esterni), prestando molta attenzione alla scelta dei materiali e la configurazione della decorazione (nel senso del "decorazioni" vitruviano)
Some results of a modern approach to the Occupational Safety and Health problems
No full textEuropean Directives on OS&H recommend a systematic Risk Analysis of the working activities, whose results should be discussed in some formalized documents. If we consider the Italian situation, at least as resulting from in depth analyses of a number of fatal accidents, the main risk analysis techniques adopted appear based on multi-purpose precompiled forms and Risk matrices deriving from subjective and incomplete assumptions. This is due to a merely formal implementation, heritage of an obsolete prescriptive approach. Hence, the need of a strong contribution to the wide spreading of a Culture of Safety based on study and research in the field of OS&H. Our OS&H research group of Politecnico di Torino, developed and is still working on a well-tested approach covering all phases of Occupational Risk Assessment and Management. The paper deals with some innovative results on Accident Prevention and definition of workers' exposure models in a System Quality approach
Il futuro delle ex-caserme? Non case ma servizi alla città
No full textL'articolo, a firma di Federica Cravero, recensisce la seconda giornata degli incontri "Torino. Argomenti per un futuro possibile" organizzati dal DAD sul tema delle "Caserme dismesse e non: aree di potenziale sperimentazione e sviluppo del territorio". Nell'articolo sono riportate, in forma di intervista, alcune frasi di Paolo Mellano, estratte dalla relazione introduttiva all'incontro
Cyanobacteria and Microalgae: Thermoeconomic Considerations in Biofuel Production
Get PDFIn thermodynamics, the useful work in any process can be evaluated by using the exergy quantity. The analyses of irreversibility are fundamental in the engineering design and in the productive processes' development in order to obtain the economic growth. Recently, the use has been improved also in the thermodynamic analysis of the socio-economic context. Consequently, the exergy lost is linked to the energy cost required to maintain the productive processes themselves. The fundamental role of the fluxes and the interaction between systems and their environment is highlighted. The equivalent wasted primary resource value for the work-hour is proposed as an indicator to support the economic considerations on the biofuel production by using biomass and bacteria. The equivalent wasted primary resource value for the work-hour is proposed as an indicator to support the economic considerations of the biofuel production by using biomass and bacteria. Moreover, the technological considerations can be developed by using the exergy inefficiency. Consequently, bacteria use can be compared with other means of biofuel production, taking into account both the technologies and the economic considerations. Cyanobacteria results as the better organism for biofuel production
Artificial Potential Field and Sliding Mode Strategies for Rendezvous Maneuver and Obstacle Avoidance
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Re-wrap" method (Refractory metals Re= Mo, Nb, Ta and W) for joining of ceramics and CMC
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Preliminary investigations on stone cutting sludge processing for a future recovery
No full textSolid waste management is a key component for the natural stone industry. In recent years, multiwire machines have been overtaking stone gang saw cutting technology. The advantages of these new cutting-edge technologies are high efficiency and performance, flexibility of use, high quality of the cut surfaces, very low environmental impact (low energy consumption, lowest concentration of heavy metals in the sludge, less waste) and lowest noise levels. There are many studies on the separation and recovery of sludge from cutting with the gang saw, but very few on diamond cutting sludges. In accordance with the European Commission's Thematic Strategy on the Prevention and Recycling of Waste (EC raw material strategies), it is important to perform a correct characterization of sludge from cutting with the new technologies, in order to investigate its possible recovery. This paper presents a preliminary investigation of the sludge resulting from different types of silicatic stones with the aim of their valorization. The investigation was conducted on sludge from cutting with diamond wire, diamond saw blades, and mixed sludge resulting from the filter press. The following tests have been performed to characterize the sludge properties: chemical analysis on the solid fraction of sludge, particle size distribution, evaluation of the metals content through image analysis for each particle size, and leaching tests. To assess the possible recovery of the sludge, wet magnetic separation tests with a high gradient magnetic separator were performed in order to obtain two types of secondary materials, namely the mineral fraction and metals fraction. The separation efficiency has been evaluated through DRX and SEM analysis on the two fractions. The results obtained for the different particle size classes have been compared. The magnetic separation of the size class <0.038 mm has a low separation efficiency because of the phenomenon of grain capture by metallic granules: for this reason the metallic fraction of this class must be further processed if it is to be considered as a secondary raw material. On the other hand, the magnetic separation of the other granulometric classes is characterized by good separation efficiency. A good efficiency of the process is a key factor in order to optimize the recovery process and to increase the economic advantages. The study performed is useful for evaluating the possible reuse of both the metal and the mineral parts, through the implementation of a proactive waste management strategy in order to avoid a subsequent environmental degradation