Main obstacles from the shuttle effect and slow conversion rate of soluble polysulfide compromise the sulfur utilization and cycling life for lithium sulfur (Li–S) batteries. In pursuit of a ...practically viable high performance Li–S battery, a separator configuration (CoS2/HPGC/interlayer) as efficient polysulfide trapping barrier is reported. This configuration endows great advantages, particularly enhanced conductivity, promoted polysulfide trapping capability, accelerated sulfur electrochemistry, when using the functional interlayer for Li–S cells. Attributed to the above merits, such cell shows excellent cyclability, with a capacity of 846 mAh g−1 after 250 cycles corresponding to a high capacity retention of 80.2% at 0.2 C, and 519 mAh g−1 after 500 cycles at 1C (1C = 1675 mA g−1). In addition, the optimized separator exhibits a high initial areal capacity of 4.293 mAh cm−2 at 0.1C. Moreover, with CoS2/HPGC/interlayer, the sulfur cell enables a low self‐discharge rate with a very high capacity retention of 97.1%. This work presents a structural engineering of the separator toward suppressing the dissolution of soluble Li2Sn moieties and simultaneously promoting the sulfur conversion kinetics, thus achieving durable and high capacity Li–S batteries.
Separator modification based on CoS2 nanoparticles supported on hierarchical porous graphitic carbon (HPGC) as polysulfide‐trapping shielding (CoS2/HPGC interlayer) is developed for lithium–sulfur batteries. Such synergistic effects of the optimized separator makes CoS2/HPGC interlayer a promising application in high‐capacity and durable lithium–sulfur batteries.
Fluid invasion, displacement of one fluid by another in porous media, is important in a large number of industrial and natural processes. Of special interest is the trapping of gas and oil clusters. ...We study the impact of wettability on fluid pattern formation and capillary trapping in three‐dimensional glass beads packs (dmean = 1 mm) during fluid invasion at capillary numbers of 10−7 using μ‐CT. The invading fluid was water, and the defending fluid was air. The contact angle of the glass beads was altered between 5° and 115° using Piranha cleaning and silanization. We analyzed the front morphology of the invading fluid, the residual gas saturation, the fluid occupation frequency of pores, and the morphology and statistics of the trapped gas clusters. We found a sharp transition (crossover) at a critical contact angle θc = 96°. Below θc the morphology of the displacement front was flat and compact caused by the strong smoothing effect of cooperative filling. Above θc the morphology of the displacement front was fractal and ramified caused by single bursts (Haines jumps). Across this dynamical phase transition the trapping efficiency changes from no trapping to maximal trapping. For θ > θc the experimental results show that invasion percolation governs the fluid displacement. Strong indicators are the universal scaling behavior of the size distribution of large clusters (relative data error εdata < 1%) and their linear surface‐volume relationship (R2 = 0.99).
Key Points
Wettability‐controlled dynamical phase transition in trapping efficiency for 3‐D porous media (1‐mm glass beads)
Trapping efficiency changes from no trapping to maximal trapping: Above the critical contact angle θc smaller pores are occupied by gas
For θ > θc the results show that invasion percolation governs the fluid displacement: universal scaling for the trapped gas clusters
Direct acyl radical formation of linear aldehydes (RCH2-CHO) and subsequent hydroacylation with electron-deficient olefins can be effected with various types of metal and nonmetal catalysts/reagents. ...In marked contrast, however, no successful reports on the use of branched aldehydes have been made thus far because of their strong tendency of generating alkyl radicals through the facile decarbonylation of acyl radicals. Here, use of a hypervalent iodine(III) catalyst under visible light photolysis allows a mild way of generating acyl radicals from various branched aldehydes, thereby giving the corresponding hydroacylated products almost exclusively. Another characteristic feature of this approach is the catalytic use of hypervalent iodine(III) reagent, which is a rare example on the generation of radicals in hypervalent iodine chemistry. PUBLICATION ABSTRACT
We present the use of Au bowtie nanoantenna arrays (BNAs) for highly efficient, multipurpose particle manipulation with unprecedented low input power and low-numerical aperture (NA) focusing. Optical ...trapping efficiencies measured are up to 20× the efficiencies of conventional high-NA optical traps and are among the highest reported to date. Empirically obtained plasmonic optical trapping "phase diagrams" are introduced to detail the trapping response of the BNAs as a function of input power, wavelength, polarization, particle diameter, and BNA array spacing (number density). Using these diagrams, parameters are chosen, employing strictly the degrees-of-freedom of the input light, to engineer specific trapping tasks including (1) dexterous, single-particle trapping and manipulation, (2) trapping and manipulation of two- and three-dimensional particle clusters, and (3) particle sorting. The use of low input power densities (power and NA) suggests that this bowtie nanoantenna trapping system will be particularly attractive for lab-on-a-chip technology or biological applications aimed at reducing specimen photodamage.
3D printing and numerical analysis are combined to design a new class of architected materials that contain bistable beam elements and exhibit controlled trapping of elastic energy. The proposed ...energy‐absorbing structures are reusable. Moreover, the mechanism of energy absorption stems solely from the structural geometry of the printed beam elements, and is therefore both material‐ and loading‐rate independent.
The term ‘biomedical engineering’ refers to the application of the principles and problem-solving techniques of engineering to biology and medicine. Biomedical engineering is an interdisciplinary ...branch, as many of the problems health professionals are confronted with have traditionally been of interest to engineers because they involve processes that are fundamental to engineering practice. Biomedical engineers employ common engineering methods to comprehend, modify, or control biological systems, and to design and manufacture devices that can assist in the diagnosis and therapy of human diseases.
This Special Issue of Fluids aims to be a forum for scientists and engineers from academia and industry to present and discuss recent developments in the field of biomedical engineering. It contains papers that tackle, both numerically (Computational Fluid Dynamics studies) and experimentally, biomedical engineering problems, with a diverse range of studies focusing on the fundamental understanding of fluid flows in biological systems, modelling studies on complex rheological phenomena and molecular dynamics, design and improvement of lab-on-a-chip devices, modelling of processes inside the human body as well as drug delivery applications. Contributions have focused on problems associated with subjects that include hemodynamical flows, arterial wall shear stress, targeted drug delivery, FSI/CFD and Multiphysics simulations, molecular dynamics modelling and physiology-based biokinetic models.
This study investigates fines migration and mineral reactions as a mechanism for CO2 residual trapping. We perform imbibition experiments using a sintered glass core and seven Berea sandstone cores. ...The cores receive four injection stages: water, CO2-saturated water, water-saturated CO2, and finally water or CO2-saturated water. During the second injection stage, the quantity of CO2-saturated water is altered to induce various degrees of fines migration and mineral reactions. These effects are found to yield residual CO2 saturations of 16%, 22% and 23% for zero, 25 and 50 pore volumes of CO2-saturated water injection, respectively. These percentages are 6–7% greater than if neither fines migration nor mineral reactions were present. This is attributed to pore plugging caused by fines migration and mineral reactions, impeding the imbibing water from displacing CO2 in the plugged pores. In addition, CO2-saturated water imbibition is found to increase residual CO2 saturation by 26–30% over that resulting from water imbibition. This is attributed to the CO2 dissolution effect during water imbibition. We therefore conclude that fines migration and mineral reactions is a CO2 residual trapping mechanism during CO2 sequestration.
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•Experiments are performed on glass and Berea cores to study CO2 residual trapping.•Fines migration and mineral reactions lead to plugging of pores.•Pores plugged by fines migration and mineral reactions trap CO2.•Both water and CO2-saturated water imbibition experiments are performed.•Water imbibition yields less residual CO2 due to dissolution.
•Residual trapping ability decreases with porosity and increases with heterogeneity.•Variance in the drainage saturation field best predicts residual gas trapping.•Correlation length and lamination ...direction have no effect on residual trapping.•Mesoscale trapping mechanism can be as important as pore-scale trapping mechanism.•Voxel-level residual trapping amount is correlated with permeability not porosity.
To increase confidence in the long-term security of CO2 geologic storage, reliable predictions of the level of post-injection CO2 residual trapping are needed. In this study, we conduct CO2/water coreflooding experiments at reservoir conditions on nine core samples with different degrees and types of heterogeneity to find the best petrophysical properties for predicting sandstone CO2 residual trapping ability. We are able to extract petrophysical properties such as porosity, permeability, degree of mesoscale heterogeneity, and spatial correlation lengths of petrophysical property fields in different directions using a CT scanner. Experimental results show that CO2 residual trapping ability decreases with porosity and increases with the degree of heterogeneity. A number of metrics for heterogeneity are evaluated, including the Dykstra-Parsons coefficient and the variance in voxel-level CO2 drainage saturation fields as well as the porosity and permeability fields. The variance of the saturation distribution during drainage provides the best predictor of residual gas trapping. By extrapolating the relationship between the degree of heterogeneity and the linear trapping coefficient, we show that pore-scale trapping mechanisms account for 46–97% of the residually trapped CO2 and the mesoscale capillary heterogeneity trapping mechanism accounts for 3–54% of the residually trapped CO2 for the nine sandstone samples tested.
•Optical trapping technique for diverse single particles in air is reviewed.•Technical details of optical trapping for single particles in air are summarized.•Recent applications of single optically ...trapped airborne particles are discussed.
Trapping a single aerosol particle allows detailed investigation of its fundamental properties over extended time periods without external interferences. Optical trapping has developed into a powerful tool to perform such single-particle studies. However, trapping and manipulating a single particle in air, especially an irregularly shaped, absorbing particle, is much more challenging than that of a particle in a liquid solution. Even though the underlying mechanisms are not fully understood, recent experimental developments advanced the technique for trapping single particles in air, making it possible to manipulate and characterize a wide range of single particles. In this paper, we review recently demonstrated optical configurations for trapping and manipulating single airborne particles. Based on different trapping principles, we tentatively categorize them into radiation-pressure traps, photophoretic traps, and universal optical traps (UOTs). Radiation-pressure traps are based on the radiation pressure force resulting from photon momentum transfer; they include the early optical levitation configurations and the well-known optical tweezers. Photophoretic traps are based on the complex photophoretic forces that occur in absorbing particles; they are classified by the optical arrangements and include single-beam, dual-beam, and confocal-beam traps. UOTs can trap a variety of different types of particles, including transparent or absorbing, spherical or irregularly shaped, and liquid or solid particles. In order to evaluate each optical trapping scheme, four key aspects, i.e., simplicity, robustness, flexibility, and efficiency, of an optical trapping configuration are discussed. In addition to the stable optical trapping, optical manipulations from one dimension to three dimensions allow studying various single particles with great flexibility. With the single particle stably trapped and flexibly manipulated in air, other analytical techniques can be used to characterize these particles. Recent updates on optical methods for characterizing and monitoring single particles in air are discussed, such as light scattering, Raman spectroscopy, and cavity ringdown spectroscopy (CRDS).
Artificial photosynthesis of alcohols from CO2 is still unsatisfactory owing to the rapid charge relaxation compared to the sluggish photoreactions and the oxidation of alcohol products. Here, we ...demonstrate that CO2 is reduced to methanol with 100 % selectivity using water as the only electron donor on a carbon nitride‐like polymer (FAT) decorated with carbon dots. The quantum efficiency of 5.9 % (λ=420 nm) is 300 % higher than the previously reported carbon nitride junction. Using transient absorption spectroscopy, we observed that holes in FAT could be extracted by the carbon dots with nearly 75 % efficiency before they become unreactive by trapping. Extraction of holes resulted in a greater density of photoelectrons, indicative of reduced recombination of shorter‐lived reactive electrons. This work offers a strategy to promote photocatalysis by increasing the amount of reactive photogenerated charges via structure engineering and extraction before energy losses by deep trapping.
A modified carbon nitride with O‐containing linkers decorated with carbon dots selectively produces methanol from CO2 and water with the benchmark quantum yield of ca. 6 %. Transient absorption spectroscopic investigation shows that extraction of holes before trapping by the carbon dots is key for the remarkable performance.
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