94 research outputs found
Porous LSCF/Dense 3YSZ Interface Fracture Toughness Measured by Single Cantilever Beam Wedge Test
Sandwich specimens were prepared by firing a thin inter-layer of porous
La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF) to bond a thin tetragonal yttria-stabilised
zirconia (YSZ) beam to a thick YSZ substrate. Fracture of the joint was
evaluated by introducing a wedge between the two YSZ adherands so that the
stored energy in the thin YSZ cantilever beam drives a stable crack in the
adhesive bond and allows the critical energy release rate for crack extension
(fracture toughness) to be measured. The crack path in most specimens showed a
mixture of adhesive failure (at the YSZ-LSCF interface) and cohesive failure
(within the LSCF). It was found that the extent of adhesive fracture increased
with firing temperature and decreased with LSCF layer thickness. The adhesive
failures were mainly at the interface between the LSCF and the thin YSZ beam
and FEM modelling revealed that this is due to asymmetric stresses in the LSCF.
Within the firing temperature range of 1000-1150C, the bonding fracture
toughness appears to have a strong dependence on firing temperature. However,
the intrinsic adhesive fracture toughness of the LSCF/YSZ interface was
estimated to be 11 Jm2 and was not firing temperature dependent within the
temperature range investigated.Comment: 13 figures, 1 table, journal paper publishe
Analyses of microstructural and elastic properties of porous SOFC cathodes based on focused ion beam tomography
Mechanical properties of porous SOFC electrodes are largely determined by
their microstructures. Measurements of the elastic properties and
microstructural parameters can be achieved by modelling of the digitally
reconstructed 3D volumes based on the real electrode microstructures. However,
the reliability of such measurements is greatly dependent on the processing of
raw images acquired for reconstruction. In this work, the actual
microstructures of La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF) cathodes sintered at an
elevated temperature were reconstructed based on dual-beam FIB/SEM tomography.
Key microstructural and elastic parameters were estimated and correlated.
Analyses of their sensitivity to the grayscale threshold value applied in the
image segmentation were performed. The important microstructural parameters
included porosity, tortuosity, specific surface area, particle and pore size
distributions, and inter-particle neck size distribution, which may have
varying extent of effect on the elastic properties simulated from the
microstructures using FEM. Results showed that different threshold value range
would result in different degree of sensitivity for a specific parameter. The
estimated porosity and tortuosity were more sensitive than surface area to
volume ratio. Pore and neck size were found to be less sensitive than particle
size. Results also showed that the modulus was essentially sensitive to the
porosity which was largely controlled by the threshold value.Comment: 21 pages, 14 figures, 2 tables, journal paper published in Journal of
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Microbial network for waste activated sludge cascade utilization in an integrated system of microbial electrolysis and anaerobic fermentation
Background: Bioelectrochemical systems have been considered a promising novel technology that shows an enhanced energy recovery, as well as generation of value-added products. A number of recent studies suggested that an enhancement of carbon conversion and biogas production can be achieved in an integrated system of microbial electrolysis cell (MEC) and anaerobic digestion (AD) for waste activated sludge (WAS). Microbial communities in integrated system would build a thorough energetic and metabolic interaction network regarding fermentation communities and electrode respiring communities. The characterization of integrated community structure and community shifts is not well understood, however, it starts to attract interest of scientists and engineers. Results: In the present work, energy recovery and WAS conversion are comprehensively affected by typical pre-treated biosolid characteristics. We investigated the interaction of fermentation communities and electrode respiring communities in an integrated system of WAS fermentation and MEC for hydrogen recovery. A high energy recovery was achieved in the MECs feeding WAS fermentation liquid through alkaline pretreatment. Some anaerobes belonging to Firmicutes (Acetoanaerobium, Acetobacterium, and Fusibacter) showed synergistic relationship with exoelectrogens in the degradation of complex organic matter or recycling of MEC products (H-2). High protein and polysaccharide but low fatty acid content led to the dominance of Proteiniclasticum and Parabacteroides, which showed a delayed contribution to the extracellular electron transport leading to a slow cascade utilization of WAS. Conclusions: Efficient pretreatment could supply more short-chain fatty acids and higher conductivities in the fermentative liquid, which facilitated mass transfer in anodic biofilm. The overall performance of WAS cascade utilization was substantially related to the microbial community structures, which in turn depended on the initial pretreatment to enhance WAS fermentation. It is worth noting that species in AD and MEC communities are able to build complex networks of interaction, which have not been sufficiently studied so far. It is therefore important to understand how choosing operational parameters can influence reactor performances. The current study highlights the interaction of fermentative bacteria and exoelectrogens in the integrated system
Bacillus subtilis Inhibits Vibrio natriegens-Induced Corrosion via Biomineralization in Seawater
The marine bacterium, Vibrio natriegens, grows quickly in a marine environment and can significantly accelerate the corrosion of steel materials. Here, we present an approach to inhibit V. natriegens-induced corrosion by biomineralization. The corrosion of steel is mitigated in seawater via the formation of a biomineralized film induced by Bacillus subtilis. The film is composed of extracellular polymeric substances (EPS) and calcite, exhibiting stable anti-corrosion activity. The microbial diversity and medium chemistry tests demonstrated that the inhibition of V. natriegens growth by B. subtilis was essential for the formation of the biomineralized film
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