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Freeze-casting uniformity and domains
No full textFreeze-casting is a technique for making centimeter long microchannel structures. Freeze-cast samples are often characterized from 2D cross-sectional images, resulting in weak determination of porosity and surface area as function of height of the sample. Here we analyze a freeze-cast 40 mm long sample of La0.66Ca0.33–xSrxMn1.05O3 (LCSM) for which we have a full X-ray tomography dataset with a voxel size of 23.34 × 23.34 × 23.34 μm3, as well as a high resolution cutout with a voxel size of 2.77 × 2.77 × 2.77 μm3. We analyze the porosity and tortuosity and show that the latter is 1.17 and 1.27 for the solid and pore phase respective in the direction along the microchannels, but 5.12 and 8.83 in the perpendicular direction. We also quantify the domain structure of the freeze-casted pores and show that this is not uniform for the sample, but that the angular orientation and number of domains is preserved throughout the sample.</p
In situ/Operando Synchrotron Radiation Analytical Techniques for CO<sub>2</sub>/CO Reduction Reaction:From Atomic Scales to Mesoscales
No full textElectrocatalytic carbon dioxide/carbon monoxide reduction reaction (CO(2)RR) has emerged as a prospective and appealing strategy to realize carbon neutrality for manufacturing sustainable chemical products. Developing highly active electrocatalysts and stable devices has been demonstrated as effective approach to enhance the conversion efficiency of CO(2)RR. In order to rationally design electrocatalysts and devices, a comprehensive understanding of the intrinsic structure evolution within catalysts and micro-environment change around electrode interface, particularly under operation conditions, is indispensable. Synchrotron radiation has been recognized as a versatile characterization platform, garnering widespread attention owing to its high brightness, elevated flux, excellent directivity, strong polarization and exceptional stability. This review systematically introduces the applications of synchrotron radiation technologies classified by radiation sources with varying wavelengths in CO(2)RR. By virtue of in situ/operando synchrotron radiationanalytical techniques, we also summarize relevant dynamic evolution processes from electronic structure, atomic configuration, molecular adsorption, crystal lattice and devices, spanning scales from the angstrom to the micrometer. The merits and limitations of diverse synchrotron characterization techniques are summarized, and their applicable scenarios in CO(2)RR are further presented. On the basis of the state-of-the-art fourth-generation synchrotron facilities, a perspective for further deeper understanding of the CO(2)RR process using synchrotron radiation analytical techniques is proposed.</p
Low-cost multispectral sensor reveals cold chain breaks, meat type, and storage time in chicken meat samples
No full textA portable and low-cost spectrometric system has been proposed to discriminate cold chain (frozen) interruption during the supply chain, as well as, the sample type among four different tested chicken meat and products (nugget, wing, thigh and drumstick) and the storage time elapsed after the cold chain break. To achieve this, an AS7265x sensor chipset was used and controlled by a custom programmed microcontroller through a Qwiic I2C interface. Communication between the user and the sensor setup was made using a custom programmed interface developed using the Python. Frozen chicken samples were thawed under various temperature-time combinations (4, 8, 16, and 24 h at 4 and 24 °C) and then refrozen at -18 °C. The refrozen samples were stored for up to 60 days. Spectral measurements (410–940 nm) were taken before thawing and at 1, 10, 30 and 60 days of storage after refreezing. The spectra obtained were analysed using Principal Component Analysis and outliers were eliminated using Mahalobobis distance. Several classification models (including Decision Tree, Random Forest, AdaBoost, Support Vector Machine, k-Nearest Neighbors, Gaussian-Naïve Bayes, Multilayer Perceptron, Gaussian Process, Linear and Quadratic Discriminant Analysis and Partial Least Squares Discriminant Analysis) were trained where appropriate. The top models with the highest predictive ability were selected and merged to build Soft Voting Classifiers (SVC) for each feature to be predicted. The SVC models correctly classified the samples with 93%, 92% and 83% accuracy for cold chain interruption, chicken meat/product type and storage time after thaw-refreeze cycle, respectively. In addition, a graphical interface was also developed so that it can be used by end users for food safety concerns. The results showed the potential of the developed low-cost sensor to rapidly detect the potential food safety risks due to cold chain breakage and to trace back the problem by predicting the storage time after refreezing.</p
Multicomponent and Surface Charge Effects on PFOS Sorption and Transport in Goethite-Coated Porous Media under Variable Hydrochemical Conditions
No full textPerfluorooctanesulfonate (PFOS), a toxic anionic perfluorinated surfactant, exhibits variable electrostatic adsorption mechanisms on charge-regulated minerals depending on solution hydrochemistry. This work explores the interplay of multicomponent interactions and surface charge effects on PFOS adsorption to goethite surfaces under flow-through conditions. We conducted a series of column experiments in saturated goethite-coated porous media subjected to dynamic hydrochemical conditions triggered by step changes in the electrolyte concentration of the injected solutions. Measurements of pH and PFOS breakthrough curves at the outlet allowed tracking the propagation of multicomponent reactive fronts. We performed process-based reactive transport simulations incorporating a mechanistic network of surface complexation reactions to quantitatively interpret the geochemical processes. The experimental and modeling outcomes reveal that the coupled spatio-temporal evolution of pH and electrolyte fronts, driven by the electrostatic properties of the mineral, exerts a key control on PFOS mobility by determining its adsorption and speciation reactions on goethite surfaces. These results illuminate the important influence of multicomponent transport processes and surface charge effects on PFOS mobility, emphasizing the need for mechanistic adsorption models in reactive transport simulations of ionizable PFAS compounds to determine their environmental fate and to perform accurate risk assessment
Oxygen defective metal oxides for room temperature electronics
No full textDue to their wide range of important properties, there is increasing interest in developing defective functional metal oxides. Among the various ionic defect species, oxygen defects are of notable significance. These are primarily in the form of oxygen vacancies, although in certain unique structures with relatively high activation energy, oxygen interstitials can also be predominant. Their significance stems largely from their higher mobility than cation defects, offering extensive possibilities for strategic manipulation to modify functional oxides' physical and chemical properties. This feature encompasses potential alterations in electronic and phase structures, thermal transport, and oxygen diffusivity. A deep understanding of the mechanisms underlying the tuning of oxygen defect chemistry is crucial to optimise the figures of merit for each specific application. Moreover, expanding the application of oxygen-deficient oxide devices necessitates developing these functional oxides at room temperature.In the studied materials, the limitation of reduced temperature for oxygen vacancy formation is partially attributed to the low mobility of ionic charge carriers and their mechanical and Coulombic interactions with host crystal structures. Reducing the device dimensions to the nanoscale, such as creating ultrathin films with thicknesses of just a few nanometers or even two-dimensional (2D) materials, can effectively decrease the transport distance for oxygen vacancies while maintaining relatively high performance. This approach provides a strategy to optimise the application of functional oxides at room temperature. However, transitioning to low-dimensional thin films introduces new constraints that impact their physical and chemical performance. For instance, in-plane strain or other structural defects arising from the mismatch between the substrate and the thin film, as well as at the surfaces and interfaces of these low-dimensional thin films, can be critically important factors influencing the properties of the thin films.This thesis aims to fundamentally understand oxygen vacancies in low-dimensional thin film materials fabricated using Pulsed Laser Deposition (PLD) with highly coherent epitaxial characteristics. PLD is adopted as a synthetic method for the superior control of the material's structural and chemical properties, including the possibility of tuning the oxygen defect content in the asdeposited state.Several key targets are outlined for the thesis:(1) Understand the functionalities of oxygen vacancies in correlated oxides, particularly their conductivity as a function of oxygen vacancy content. The coupling between strain and oxygen vacancies is a new freedom to control the film's properties.(2) Explore high-temperature oxygen ionic conductors with mixed electronic and ionic properties in the nanoscale for room-temperature application. We mainly explored ceria based (CeGdO2) properties at room temperature.(3) Topotactic transitions in cobaltite (La,Sr)CoO3-δ perovskites. This class of materials yields exemplary transition of room temperature properties. However, the transition mainly occurs at high temperatures and in large chemical gradients. We mainly studies how to realize the room temperature topotactic transition.(4) Enrich the methodology for generating oxygen vacancies at room temperature in the designed double-layer heterostructure devices. This configuration aids in understanding the structural and chemical mechanisms leading to the kinetics of oxygen vacancy transport at the nanoscale. It also explores how oxygen vacancies can be formed at room temperature, particularly at the heterostructure interfaces
Analysis of model dimensionality, particle shrinkage, boundary layer reactions on particle-scale modelling of biomass char conversion under pulverized fuel combustion conditions
No full textIn this work, the effects of model dimensionality, particle shrinkage, and boundary layer reactions on particle-scale modelling of biomass char conversion under pulverized fuel combustion conditions have been analysed by using six models: zero-dimensional models with constant particle size (0D_Cons) or shrinking particle size (0D_SPM), one-dimensional models with/without considering particle shrinkage (1D_Cons/1D_SPM), and 1D_Cons and 1D_SPM with considering boundary layer reactions (1D_Cons_BH and 1D_SPM_BH). A comparison with existing experimental data shows that the 1D_SPM_BH model with consideration of intra-particle heat and mass transfer, particle shrinkage, and boundary layer reactions is an appropriate model to describe biomass char conversion over a wide range of conditions. The 0D_Cons model is a good approximation for the conditions of small particle size (< 1 mm) at 1273–1473 K, but overestimates the char conversion rate for larger biomass char particle or at high temperatures (regime III). The 0D_SPM model gives a reasonable prediction on char conversion time but predicts a larger contribution of reaction between char and O2 as compared to the 1D_SPM_BH model. The consideration of intra-particle heat and mass transfer in particle-scale modelling (1D_Cons and 1D_SPM) is beneficial to improving the model prediction of char conversion time and the contributions of char oxidation and gasification reactions. The boundary layer reactions have a significant effect on the prediction of char conversion for large particles (> 1 mm) and high temperatures (> 1473 K). An implication for the selection of a particle-scale model in CFD modelling is also given
Thermodynamic modelling of MDEA(aq)-NH<sub>3</sub>(aq)-K<sub>2</sub>CO<sub>3</sub>(aq)-CO<sub>2</sub>(aq) using the Extended UNIQUAC model
No full textThe development of advanced processes for carbon dioxide capture requires reliable thermodynamic models to ensure accurate process design. This work presents an optimized parameter set of the Extended UNIQUAC model for advanced mixed solvent solutions containing CO2-MDEA-NH3-K2CO3 in water. The model was parameterized using vapor–liquid equilibrium, pure component saturation pressure, excess enthalpy, heat of absorption, molar heat capacity, apparent molar heat capacity, and solid–liquid equilibrium. These thermal and equilibrium properties cover temperatures between 253.6 K to 600 K and pressures up to 75.6 bar. The current model represents an extension of previous versions that were suitable for modeling aqueous NH3 and K2CO3 solutions. This parametrization accounts for molecular interactions between MDEA and these two components, which allows for the design of advanced capture processes. This paper demonstrates that the new model parameters are valid within the range of operational conditions typically found in CO2 capture processes
On the determination and interpretation of the lithospheric induced magnetisation
No full textWe present a new technique for reducing the uncertainties inherent in the interpretation of lithospheric magnetic field observations over the Earth. This technique, without involving iterations, provides an improved estimate of the depth-integrated magnetic susceptibility of the crust as compared to previous approaches. Departing from the normal practice of using observations at specific locations, we model directly Gauss coecients of the lithospheric magnetic field and use an a-priori initial lithospheric thickness model to circumvent magnetic annihilators (i.e. magnetisation distributions that cannot be determined from magnetic data since they have no impact on the lithospheric magnetic field). Of the several initial magnetic layer models tested, we prefer the model where magnetic thickness is based on the Moho or the regional estimate of the Curie depth when it is shallower than the Moho because it is physically reasonable and produces the fewest artefacts. The method is applied to a recent high-degree lithospheric magnetic field model called LCS-1 derived from CHAMP and Swarm magnetic satellite data. The technique is appropriate for regions where induced magnetisation dominates over remanent magnetisation. We show that high degrees of the final depth-integrated magnetic susceptibility variation are dependent only on the corresponding high degrees of the LCS-1 magnetic field model. Thus, the depth-integrated magnetic susceptibility variation is an important quantity derived in the study which enables readily qualitative interpretation of regional geology.<br/
Simple pot modification improves catch efficiency and species composition in a tropical estuary mud crab (<i>Scylla serrata</i>) fishery
No full textPots are widely used fishing gear type for targeting different crustacean and fish species. Pot entrance size and design are among the most important technical parameters that influence the catch efficiency of certain species. An optimal pot entrance design should allow an efficient entry for the target species while preventing subsequent escape. The tropical estuary pot fishery targeting mud crab (Scylla serrata) in Vembanad Lake, India, employs rectangular pots with rectangular-shaped entrances. Low catch rates for target species and high bycatch rates are observed in this fishery. This study was carried out to investigate if a simple pot modification by extending the entrance of the traditional pots, can improve the catch efficiency of mud crab. Further, we estimated and compared the catch composition in this small-scale fishery using the traditional and modified entrance pots. The results showed that the catch efficiency for all sizes of mud crab is on average more than six times higher with the modified entrance pots compared to the traditional pots (622% (CI: 344–1867%)). However, significant quantities of juvenile crabs are caught in modified pots. Further, the bycatch ratio was significantly reduced for modified compared to the standard entrance pots in this fishery. These results show that such pot modifications have potential to significantly improve the catches in mud crab pot fisheries without increase in capture of bycatch species. However, additional mechanisms for excluding undersized crabs from pot catches should be investigated
Climate change impacts of conventional sewage sludge treatment and disposal
No full textSewage sludge (SS) management remains a challenge across the world. We quantified the potential climate change impacts of eight conventional technology configurations (TCs) for SS treatment and disposal by considering four different energy exchanges and using a life cycle assessment (LCA) model that employed uncertainty distributions for 104 model parameters. All TCs showed large climate change loads and savings (net values ranging from 123 – 1148 kg CO2-eq/t TS) when the energy exchange was with a fossil-based energy system, whereas loads and savings were approximately three times lower when the energy exchange was with a renewable energy system. Uncertainty associated with the climate change results was more than 100% with fossil-energy exchange and low TS content of SS but was lower for renewable energy. Landfilling had the greatest climate change impact, while thermal drying with incineration had the highest probability of providing better climate change performance than other TCs. The global sensitivity analysis identified nine critical technological parameters. Many of them can be easily measured for relevant SS and technology levels to improve specific estimates of climate change impact. When all scenarios were optimised to the 20% best cases, thermal drying with incineration outperformed the other TCs. This paper contributes to better quantifying the climate change impacts of different technologies used for sludge treatment given changing energy systems and identifies crucial parameters for further technological development