Metallic interconnects represent the main component of a solid oxide fuel cell (SOFC) stack in terms of weight and volume. They are typically made of ferritic stainless steel (FSS) coated on the air ...side. At the stack operating conditions, the interconnect is exposed to a dual atmosphere: air at the cathode side; fuel (a hydrogen-rich mixture) at the anode side. The stacks considered in this study were field operated in reformed natural gas for 5000, 9000 and 20,000 h respectively. The analyzed interconnects are made from CROFER22APU and coated on the air side with Co-Mn base spinel. One interconnect has been studied for each stack by sampling and preparing cross section the inlet and outlet positions. The samples were characterized by SEM-EDXS in order to investigate the evolution of the interconnect at the air side. The interaction between the metal substrate and the coating is investigated highlighting the formation of chromia based thermal grown oxide (at the FSS/coating interface) and the solid-state diffusion of Cr and Fe from the metal into the coating. The microstructural features evolving as a function of time are also quantified.
Filled skutterudites form a wide class of intermetallic compounds thoroughly studied for their promising thermoelectric performance. An electrochemical study was performed on a set of two samples of ...filled skutterudite with composition Sm
0.1
(Fe
0.45
Ni
0.55
)
4
Sb
12
differing for the content of additional phases. The aim of the study is to test their resistance to corrosion by a 0.1 M NaCl solution, with particular reference to the effect of the presence of possible extra phases forming during synthesis. Measurements were carried out by electrochemical impedance spectroscopy and potentiodynamic polarization after reaching equilibrium; corrosion products grown on the sample surface after polarization tests were analyzed by scanning electron microscopy. The polarization resistance resulted in increase with the skutterudite amount within the sample, thus pointing at the role of the extra phases (Fe,Ni)Sb
2
and Sb in promoting a localized attack and in accelerating the corrosion rate. This evidence sets a clear indication toward the need for monophasic skutterudites in order to minimize the action of corroding agents in the perspective of optimizing the device durability.
The Valaisan-type armband (a specific type of bracelet) is a typical metallurgical production from the western area of Switzerland belonging to the classic phase of the Aare-Rhone group (BzA2a, ca. ...2000–1800 BC). This investigation aims to (i) characterize the metal composition, (ii) reconstruct the thermomechanical treatments applied during the manufacturing process, and (iii) gather information on the possible exploitation of the local ores coupling metallography and chemical analysis. The results show that each armband is manufactured from a hammered sheet of copper-based alloy, containing either tin (up to 3.0 wt.%) or a combination of antimony, nickel, and silver. In several cases, it is assumed that minor elements are already part of the original ore, suggesting a conscious selection of copper veins. In other armbands, a direct addition of
cassiterite
(SnO
2
) to the copper matrix is hypothesized based on the material composition and features of the inclusions. Microstructural features are coherent with a procedure that combines mechanical deformation (with a total deformation degree between 70 and 76%), annealing, and quenching, coherently with more recent productions (Late Bronze Age). The analysis of inclusions, rarely performed during metallographic investigations, provides precious evidences on thermal treatments applied during the manufacturing process and shows that annealing was carried out at low temperatures.
Electromethanogenesis is an innovative technology that uses a microbial electrochemical system to produce methane from CO
2
, in a power-to-gas (BEP2G) concept. The results of experimental tests of ...new and cost-effective carbonaceous materials for electrode are presented here. The study aims at optimizing electromethanogenesis processes at laboratory level in mesothermic condition. As part of the experiments, hydrogenotrophic microorganisms (Family Metanobacteriaceae of Archaea domains) were selected from a mixed consortium taken from a biogas digestate and inoculated in double-chamber bioelectrochemical systems. The maximum amount of methane produced was 0.3 - 0.8 mol/m
2
g (normalized to the cathode area) with carbon cloth electrodes. Aiming at improving the methane productivity, innovative materials for the electrodes were now studied, creating porous high-surface composites, and studying nitrogen carbons doped with Cu and hydroxyapatite (Multicomposite Cu@/HAP/C), as chemical catalysts for CO
2
reduction (CO2RR). The description of the procedure for the Multicomposite Cu@/HAP/C production is reported in detail.
Two Venetian types of swords coming from the “Luigi Marzoli” Arms Museum in Brescia were characterized in this study, to understand their manufacturing process and to gather information about their ...provenance. Both the blades and the hilts components are analyzed using a multi-methodological approach, to describe possible differences in the metallurgical features that involved classical metallographic and spectroscopic techniques. Microstructural results indicate a complex process for the manufacturing of the blades, by hot-forging, confirmed by a sequence of different microstructures even on the same sample. Furthermore, an interesting and unusual manufacturing technique is used on one of the pommels, which consists of two hemispheres connected by copper joints. Hypothesis about the ironmaking and the provenience of raw materials are obtained by the features and composition of the inclusions. It is suggested that there is the use of both a direct and an indirect process on the swords. It is likely that the minerals used to obtain iron and copper of the swords come from the mines of the Brescia and Bergamo territories. All the hypotheses are consistent with the historical documents of the time that also give information on the diffusion of such swords in the Brescia area.
The growth of anodic oxide on niobium has been investigated as a function of the applied potential in a solution containing P and Ca-EDTA complexes. Anodizing below and above the breakdown potential ...has been explored via morphological (AFM and SEM) and compositional (XPS and EDX) analysis. Below the breakdown potential, thin (few hundreds of nanometers) and uniform oxide layers are formed, with negligible inclusions of electrolyte ions. Conversely, above the breakdown potential, in the so-called ASD regime, thicker and microporous oxide layers are observed, with a significant enrichment of the matrix with Ca and P. At potentials around 250 V the structure evolves towards a highly inhomogeneous and porous layer with the presence of some fractures, potentially affecting the oxide passivation properties. The corrosion resistance properties of the oxide layers have been investigated by electrochemical methods (OCP, anodic polarization and EIS). Data indicate that the corrosion resistance, initially increasing with the anodizing potential, weakens at potentials around 250 V. A potential of about 200 V represents, therefore, a good tradeoff between morphological and compositional properties and resistance to corrosion, which are important issues in view of osteoconductive properties for orthopaedic implant applications.
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•Anodizing of niobium promotes the growth of a passive, corrosion resistant oxide.•The anodizing potential modulates the oxide layer morphology and composition.•Anodozing in the ASD regimes leads to significant inclusions of Ca and P ions.•The corrosion behaviour is affected by the oxide thickness and porosity.•EIS allowed to distinguish three different contributions to the corrosion process.
The performance of an SOFC stack is related to the evolution over time of the materials during operation. Metallic interconnects (MICs) are exposed to high temperature (ca. 850 °C) and dual ...atmosphere (fuel and air streams), and hence react to form an oxide scale on top. This paper focuses on the fuel side of the MIC and investigates the nature of the oxides formed in SOFC stacks field operated by the SUNFIRE GmbH Company for up to 20,000 h in the frame of the EU-H2020 ADASTRA project. This opportunity supports the understanding on how the metal (i.e., CROFER®22APU) reacts once exposed to the fuel stream by performing investigations on the surface and on the cross-section of the samples by SEM-EDS and micro-Raman spectroscopy. The results show the presence of a layered thermally grown oxide (TGO) rich in Cr at the interface with the metal. On top of the scale, a predominant presence of MnxOy is found supporting the hypothesis of a further reaction of the TGO with selective Cr depletion. The manganese oxides may represent a severe issue due to their very low conductivity.
•Interconnects oxidize when exposed to wet fuel in field operated SOFC stack.•The pH2O/pH2 ratio affects the oxide formation.•The thermal gradient between fuel Inlet and Outlet positions affects the oxide growth rate.•MnxOy formed on top represents a potential issue for stack performances due to its low conductivity.
Two 11th- and 12th-century entrance doors from the Basilica di San Marco in Venice, made of different copper alloys and woods, were non-invasively examined in situ. The chemical composition of the ...metals, the way in which different metal parts were joined together, the tree species used to construct the supporting structures and the age of the wood are determined. A portable ED-XRF instrument and optical microscopes were used. The doors were also photographed to produce high-resolution orthophotos and 3D models. The metal parts of the doors were made of leaded tin-bronze and quaternary Cu-Sn-Zn-Pb alloys and were mounted on a wooden multi-layer structure of larch and silver fir; the dendrochronological dates of some of the larch boards are 1965, teminus post quem.
Two 11th- and 12th-century entrance doors from the Basilica di San Marco in Venice, made of different copper alloys and woods, were non-invasively examined in situ. The chemical composition of the ...metals, the way in which different metal parts were joined together, the tree species used to construct the supporting structures and the age of the wood are determined. A portable ED-XRF instrument and optical microscopes were used. The doors were also photographed to produce high-resolution orthophotos and 3D models. The metal parts of the doors were made of leaded tin-bronze and quaternary Cu-Sn-Zn-Pb alloys and were mounted on a wooden multi-layer structure of larch and silver fir; the dendrochronological dates of some of the larch boards are 1965, teminus post quem.
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