Synergistic Effect of Graphene Oxide for Impeding the Dendritic Plating of Li

Dendritic growth of lithium (Li) has severely impeded the practical application of Li‐metal batteries. Herein, a 3D conformal graphene oxide nanosheet (GOn) coating, confined into the woven structure of a glass fiber separator, is reported, which permits facile transport of Li‐ions thought its structure, meanwhile regulating the Li deposition. Electrochemical measurements illustrate a remarkably enhanced cycle life and stability of the Li‐metal anode, which is explained by various microscopy and modeling results. Utilizing scanning electron microscopy, focused ion beam, and optical imaging, the formation of an uniform Li film on the electrode surface in the case of GO‐modified samples is revealed. Ab initio molecular dynamics (AIMD) simulations suggest that Li‐ions initially get adsorbed to the lithiophilic GOn and then diffuse through defect sites. This delayed Li transfer eliminates the “tip effect” leading to a more homogeneous Li nucleation. Meanwhile, C? C bonds rupture observed in the GO during AIMD simulations creates more pathways for faster Li‐ions transport. In addition, phase‐field modeling demonstrates that mechanically rigid GOn coating with proper defect size (smaller than 25 nm) can physically block the anisotropic growth of Li. This new understanding is a significant step toward the employment of 2D materials for regulating the Li deposition.     

Experimental and numerical characterization of viscous flow and mixing in an impinging jet contactor

The laminar flow in an impinging jet contactor is examined as a first step toward the development of new technology for fast mixing of viscous fluids. The flow, velocity, and stretching fields in an impinging jet contactor are quantified for low Reynolds number flow using three-dimensional numerical simulations and particle image velocimetry measurements. Computational and experimental velocity fields are in close agreement, as quantified by the velocity probability density functions. Two steady-state flow regimes are found to exist: for jet Reynolds numbers (Re_j) < 10, the jets do not impinge and the velocity field scales linearly with Reynolds number; for Re_j > 10, the jets begin to impinge and recirculation regions form above and below the impingement point. The magnitude of the rate-of-strain tensor is calculated as a function of Re_j. While areas of essentially zero stretching occupy most of the flow domain, very high rates of stretching occur at specific locations in the flow. The maximum and average rates of stretching in the contactor increase roughly linearly as a function of Reynolds number. Mixing simulations show that no mixing occurs for the steady flow in a symmetric-jet contactor. However, mixing is improved substantially by a slight modification of the impinging jet geometry that disrupts geometric symmetry.     

Effect of NR and EPDM on the rheology of HDPE/PP blends

Summary We studied melt-rheological properties of ternary blends of polypropylene and high-density polyethylene with an elastomer (natural rubber or ethylene-propylene-diene), at several blending ratios and shear rates. Measurements made on a cone-plate rheometer are presented and discussed as a function of blend composition. The effect of the shear rate on the viscosity and flow curve is discussed in terms of the exponent of the power low for a non-Newtonian liquid. The addition of an elastomer to the polyolefins blends changes the shape of the viscosity-composition curve; this change is discussed in terms of the possible morphology of the blend. Received: 25 September 1998/Revised version: 8 February 1999/Accepted: 9 February 1999     

Postharvest Heat Treatment for Olive Oil Debittering at the Industrial Scale

To enhance the debittering of olive oil, 500-kg olive fruit (Olea europaea L.) samples in duplicate from different olive cultivars and orchard locations in Spain (Manzanilla olive fruits from Villarrasa during the 2002/2003, 2004/2005 and 2005/2006 seasons, or from Dos Hermanas during the 2004/2005 and 2005/2006 seasons, Picual olive fruits from Cabra during the 2004/2005 season and Verdial olives from Villarrasa during the 2004/2005 and 2005/2006 seasons) were treated by dipping in hot water under different conditions (50–68 °C for 3 or 5 min), which had been previously determined based on laboratory-scale experiments, and subsequently processed for virgin olive oil extraction. Heat treatment produced a change in the intensity of the oil bitterness in all cases, increased the pigment content, decreased stability and reduced the sensory freshness of the oil. Although heat treatment reduced the phenolic content of the oil, this effect was not uniform among the different phenolic compounds and depended on the crop season and olive variety. Therefore, the determination of debittering conditions will require a series of preliminary laboratory-scale experiments.     

Pressure dependence of Raman modes in double wall carbon nanotubes filled with 1D Tellurium

The preparation of highly anisotropic one-dimensional (1D) structures confined into carbon nanotubes (CNTs) in general is a key objective in nanoscience. In this work, capillary effect was used to fill double wall carbon nanotubes (DWCNTs) with trigonal Tellurium. The samples are characterized by high resolution transmission electronic microscopy and Raman spectroscopy. In order to investigate their structural stability and unravel the differences induced by intershell interactions, unpolarized Raman spectra of radial and tangential modes of DWCNTs filled with 1D nanocrystalline Te excited with 514 nm were studied at room temperature and high pressure. Up to 11 GPa we found a pressure coefficient of 3.7 cm⁻¹ GPa⁻¹ for the internal tube and 7 cm⁻¹ GPa⁻¹ for the external tube. In addition, the tangential band of the external and internal tubes broaden and decrease in amplitude. All findings lead to the conclusion that the outer tube acts as a protection shield for the inner tube (at least up 11 GPa). No pressure-induced structural phase transition was observed in the studied range.     

Real-time monitoring of drug concentration in a continuous powder mixing process using NIR spectroscopy

A non-destructive NIR spectroscopic method was used to acquire on-line spectra of a continuous mixing process, and evaluate the performance of this novel system. Partial least squares (PLS) calibration models were developed and used for real-time determination of active ingredient concentration on the blends produced with a continuous mixer. The NIR method was developed for concentrations ranging from 0 to 15% (w/w) of acetaminophen (APAP), the active pharmaceutical ingredient used in the experiments. The calibration model's overall accuracy was 0.41% (w/w), and estimated through the root mean square error of cross validation (RMSECV) for samples predicted using leave-class-out cross validation. In this cross validation, each concentration was defined as a class, and when a sample of a specific concentration was predicted all samples of that concentration were left out of the calibration model. The precision of the calibration model was also estimated at various concentration levels, to facilitate the differentiation between the variation in drug concentration due to the analytical method's measurement uncertainty and the variation in the drug distribution throughout the powder blend. The results obtained are very promising since in three of the five powder mixes, the variation in the drug concentration in the powder blends was similar to that of the analytical method indicating a high degree of blend homogeneity     

Solvent effects in the catalytic hydrotreament of haloaromatics over Pd/Al2O3 in water+organic mixtures

Solvent effects have been studied for the liquid phase (atmospheric pressure, T=303 K) hydrodehalogenation (HDH) of a range of haloarenes in methanol, THF, water+methanol and water+THF promoted by Pd/Al₂O₃. The catalyst has been characterized in terms of temperature programmed reduction, XRD, TEM, BET and pore volume measurements: the active Pd phase is present as nano-scale particles (<1–6 nm, surface area weighted mean diameter=2.4 nm). In the absence of transport limitations, catalyst deactivation and secondary reactions, the following sequence of increasing dehalogenation rate has been established: dichlorophenol(s)<monochlorophenol(s)<dibromophenol<monobromophenol(s). This is consistent with an electrophilic mechanism involving an arenium intermediate. The hydrogenolytic cleavage of C–Br bond(s) is promoted to a greater extent (relative to C–Cl) due to the lower associated bond dissociation energy while the presence of a second halogen substituent has a deactivating effect. Higher initial HDH rates were observed with increasing water content in the solvent mixture and this is principally related to an increase in the dielectric constant of the medium; HDH rate showed a lesser dependence on molar volume. We link the HDH activity dependency on dielectric constant to the capacity of the solvent to stabilize the arenium intermediate. In contrast, reaction selectivity was unaffected by variations in solvent composition, suggesting that each step in the reaction pathway (stepwise or concerted dehalogenation) is influenced to the same extent. Higher HDH rate with increasing solvent dielectric constant and selectivity invariance with solvent composition also extended to the HDH of chlorobenzenes.     

All-carbon N-heterocyclic Carbene-catalyzed (3+2) Annulation using Donor-Acceptor Cyclopropanes

Donor-acceptor cyclopropanes are known to serve as dipole precursors capable of engaging in (3+2) annulations with electron-deficient π-systems. In 2013, the reaction of donor-acceptor cyclopropanes with α,β-unsaturated acyl fluorides in an all-carbon (3+2) annulation was discovered. The reaction proceeds in good yields using the IMes NHC to provide diastereomerically pure β-lactone-fused cyclopentanes bearing four contiguous stereocentres. Subsequent studies demonstrated that N-t-butyl substituted homochiral morpholinone NHCs allowed the reaction to be achieved in up to 98 % ee. In this account, a background to this reaction is introduced, along with a complete account of the strengths, limitations and challenges encountered while developing this chemistry.     

Heat release and engine performance effects of soybean oil ethyl ester blending into diesel fuel

The engine performance impact of soybean oil ethyl ester blending into diesel fuel was analyzed employing heat release analysis, in-cylinder exergy balances and dynamometric tests. Blends with concentrations of up to 30% of soybean oil ethyl ester in volume were used in steady-state experiments conducted in a high speed turbocharged direct injection engine. Modifications in fuel heat value, fuel-air equivalence ratio and combustion temperature were found to govern the impact resulting from the addition of biodiesel on engine performance. For the analyzed fuels, the 20% biodiesel blend presented the best results of brake thermal efficiency, while the 10% biodiesel blend presented the best results of brake power and sfc (specific fuel consumption). In relation to mineral diesel and in full load conditions, an average increase of 4.16% was observed in brake thermal efficiency with B20 blend. In the same conditions, an average gain of 1.15% in brake power and a reduction of 1.73% in sfc was observed with B10 blend.     

Analysis and interpretation of residence time distribution experimental curves in FM01-LC reactor using axial dispersion and plug dispersion exchange models with closed-closed boundary conditions

The liquid phase mixing flow pattern at low (20 < Re < 120) and intermediate liquid flow rate (120 < Re < 400) was studied by means of residence time distribution (RTD) experimental curve in an up-flow Filter Press electrochemical reactor (FM01-LC) bench scale. For this purpose, a plastic turbulence promoter was used with stainless-steel and platinised titanium structural meshes as electrodes in channel configuration. To visualize and determine the mixing flow pattern in the liquid phase, the stimulus-response technique was employed using dextran blue (D_M = 1.058 × 10⁻¹¹ m² s⁻¹, 25 °C, in water) as model tracer. A theoretical analysis and approximation RTD experimental curves with axial dispersion model (ADM) and plug dispersion exchange model (PDE), with “closed-closed vessel” boundary conditions were used in order to establish a better approximation of the axial dispersion, stagnant zones, channelling and by-pass (preference flow) effects present at low and intermediate Re. RTD curves show that the liquid flow pattern in the FM01-LC deviates considerably from axial dispersion model at low Re, where the FM01-LC exhibits large channelling, stagnant zones, and dead zone. The PDE model represents fairly this deviation from ideal flow (less dead zone).