By Jensen Karin Vels
The anode/electrolyte interface ш strong oxide gas cells (SOFC) is understood to reason electric losses. Geometrically uncomplicated Ni yttria-stabilised zirconia (YSZ) interfaces have been tested to realize info at the structural and chemical adjustments taking place in the course of experiments at 1000°C in an environment of ninety seven% H2/3% H20. Electrochemical impedance spectroscopy at open circuit voltage (OCV) and at anodic and cathodic polarisations (100 mV) was once played. A correlation of information with the constitution improvement and the chemical composition used to be tried. Nickel wires with assorted impurity content material (99.8% Ni and 99.995% Ni) have been used to envision the influence of impurities at the polarisation resistance and get in touch with region morphology. The electropolished nickel wires have been pressed opposed to a sophisticated eight mol% YSZ surface.Extensive structural alterations from a flat interface to a lull and valley constitution have been came upon to take place ш the touch zone with the impure nickel twine, and a ridge of impurities was once equipped alongside the rim of the touch sector. Impurity debris within the interfacial sector have been additionally saw. The impurity part was once defined as an alkali silicate glassy part. No modifications have been came across among polarised and non-polarised samples. With natural nickel wires, besides the fact that, the microstructures trusted the polarisation /non-polarisation stipulations. At non-polarised stipulations a hill and valley variety constitution used to be came upon. Anodic polarisation produced an as much as 1 um thick interface layer such as nano-sized YSZ debris with a few Ni current. At cathodic polarisation either a granulated constitution and a lull and valley constitution comparable to the constitution of non-polarised samples have been came upon. Small impurity ridges have been surrounding the touch components on non-polarised and cathodically polarised samples. TOF-SIMS and XPS analyses confirmed the presence of impurities in either the impure and natural touch components. The impedance spectroscopy printed that looking on the impurity content material of the nickel, varied advancements of the polarisation resistance with time happened. At open circuit voltage the samples with impure nickel electrodes confirmed an preliminary bring up towards a excessive consistent polarisation resistance, while the samples with natural nickel electrodes confirmed a substantial lessen to a low consistent polarisation resistance with time. For either forms of nickel the polarisation resistance dropped upon polarisation. the world particular polarisation resistances for the samples with natural electrodes have been nearly 10 occasions less than for samples with impure electrodes. This used to be regularly ascribed to the impurity content material and distribution, either within the 3 part boundary sector and as a roughly non-stop movie overlaying the interfacial quarter. The drop within the Rp upon polarisation will be ascribed to alterations ш the distribution of the impurity part within the interfacial area.
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The anode/electrolyte interface ш sturdy oxide gasoline cells (SOFC) is understood to reason electric losses. Geometrically easy Ni yttria-stabilised zirconia (YSZ) interfaces have been tested to achieve details at the structural and chemical alterations taking place in the course of experiments at 1000°C in an environment of ninety seven% H2/3% H20.
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45 Fig. 11. A, B and C show the contact area on the sample with an impure nickel wire (A1 in fig. 7). D, E and F show the contact area on the sample with a pure nickel wire (B1 in fig. 7). The colour coding indicates the present mixtures of elements. 11D X1 =Mn and X2=Na. 11E X1=Si and X2= Ti. 11F X1= Si and X2= Al. 46 Fig. 12. A) and C) Total ion images of the contact area (B1 in fig. 7) and the YSZ surface outside the contact area, respectively, on sample 232n. The YSZ grains are seen in different colour due to crystallographic orientation.
1000°C) Annealed 4 days in 9 % H2. 00 Ion sputtering was used to remove some layers of atoms. 08. After 10 minutes of sputtering no Si was detected on either of the samples 62 and 63. Equally, all the sodium had disappeared at this level. 2). Only a typical analysis was provided from Johnson Matthey and so the actual composition of the impurity fraction is unknown. The EDS measurements after electropolishing showed no visible or detectable impurity particles on the surface, indicating that the impurities are dispersed evenly in the nickel.
Mn also originates from the nickel wire impurities. The Si/Zr ratios in and outside the contact area are equal for the samples with an impure nickel wire. 2). These differences show that the samples with impure nickel wires probably have received additional Si from the nickel. Impurity particles all over the Ni wire contain a relatively large amount of Si. The Si in the contact area is located preferably into the impurity particles but also as a thin film on the contact area surface. The Na found outside the contact areas on both samples originates mainly from the YSZ.