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An efficient and facile approach to synthesize a bi-functional electrocatalyst via combining carbon foam with cobalt-centered zeolitic imidazolate framework (ZIF-67) is reported. The carbon foam was synthesized via dehydration of sugar utilizing zinc nitrate, forming Co3ZnC in the carbon matrix. To obtain Co hybridized and Co particles covered with carbon nanotubes embedded in a carbon matrix (Co-Zn-CNTs), physical mixing of both defines the critical point after pyrolysis. Higher content of N-related species and transition metal species in polyvalent states and well-grown multi-wall carbon nanotubes for charge transfer are achieved after the pyrolysis process. The obtained Co-Zn-CNTs catalyst was employed as cathode and anode for overall water splitting (HER and OER) and showed excellent performances. This development offers a low-cost and straightforward strategy to synthesize catalyst material for large-scale fuel cells and water splitting technologies. This development affords a precise method for effectively improving the electrocatalyst performance derived from the ZIF-67 precursor.

Controlled surface functionalization with azides to perform on surface "click chemistry" is desired for a large range of fields such as material engineering and biosensors. In this work, the stability of an azido-containing self-assembled monolayer in high vacuum is investigated using in situ Fourier transform infrared spectroscopy. The intensity of the antisymmetric azide stretching vibration is found to decrease over time, suggesting the degradation of the azido-group in high vacuum. The degradation is further investigated at three different temperatures and at seven different nitrogen pressures ranging from 1 x 10(-6) mbar to 5 x 10(-3) mbar. The degradation is found to increase at higher temperatures and at lower nitrogen pressures. The latter supporting the theory that the degradation reaction involves the decomposition into molecular nitrogen. For the condition with the highest degradation detected, only 63% of azides is found to remain at the surface after 8 h in vacuum. The findings show a significant loss in control of the surface functionalization. The instability of azides in high vacuum should therefore always be considered when depositing or postprocessing azido-containing layers.

TiO 2 is a Li-ion electrode material based on abundant materials which exhibits high cycle life and requires no stringent high temperature processing. Amorphous TiO 2 is known to reach the theoretical capacity of 1280 mAh/cm 3 . This theoretical limit can only be achieved through nano-scaling of the system or through chlorine modification. In both cases, all the available Ti + I V atoms are reduced to Ti + III , with insertion of Li + ions upon the reductive step. The energy density of batteries containing a TiO 2 anode remains limited by the high oxidation potential (1.8V vs. Li + /Li) and suffer from poor rate performance. Two routes can be followed to improve the performance and applicability of TiO 2 as Li-ion battery electrode. The first approach focuses on increasing the reversible insertion capacity of Li x TiO 2 beyond x = 1, alternatively lowering the insertion potential increases the energy density of the anode. High level chlorine modification of TiO 2 is observed to significantly enhance the Li-ion storage capability of Li x TiO 2 , exceeding x = 1, beyond the current theoretical limit of 1280 mAh/cm 3 or 330 mAh/g. This work focuses on elucidating the reaction mechanism which increases the insertion capacity. A combination of electrochemical techniques, RBS and TOF-SIMS is used on thin-film electrodes. The lithium insertion beyond x > 1, is associated to the conversion of TiO 2 to metallic Ti, similar to the conversion reactions observed in other binary oxides. Through chlorine modification the energy density of the anode is enhanced, both by increasing the capacity of TiO 2 and by introducing a low potential insertion reaction.

We investigated the benzotriazole enabled growth of low Ni content (5–15 at.%) CuNi alloy deposits by characterisation of its morphology and elemental composition as a function of substrate metal (Cu and Ni), charge density, current density, and potential-time response measured during electrodeposition. Alloy deposition starts in favor of Cu, forming a Cu-rich layer on a Ni substrate and Cu-rich islands on a Cu substrate after which aggregates only form on a Cu substrate, due to the ability of benzotriazole (BTAH) to chemically bond to Cu but not to a Ni surface. Furthermore, Ni deposits preferably on grain boundaries, BTAH gets incorporated in the deposit and forms a thin layer between the Cu substrate and the alloy deposit. Based on our findings a growth model for BTAH enabled CuNi growth is proposed which describes that the BTAH working mechanism is twofold. First, the additive shifts the onset potential of Cu2+ reduction closer to the Ni2+ reduction potential by forming a chemisorbed BTAH layer, thereby enabling Cu and Ni co-deposition and, secondly, during deposition it specifically interacts with Cu, thus inhibiting Cu dendrite formation.

High voltage cathodes suffer from degradation phenomena that are challenging to be observed and identified during cell operation. Dense and smooth sputtered thin films electrodes with absence of binders and conductive additives allow a direct study of the active material upon Li insertion and extraction at surface and bulk. Using an operando spectroscopic ellipsometry set-up combined with a customized electrochemical-optical cell (EC-SE), the evolution of the optical absorption and thickness of LiMn2O4 and LiNi0.5Mn1.5O4 thin-film electrodes was monitored upon cycling. Mixed Mn3+/4+ valence in the electrodes and evident layer dissolution associated to Transition Metal (TM) dissolution in the non-aqueous electrolyte at the applied polarization potentials was observed. Our results reaffirm EC-SE as a convenient method to study degradation phenomena in cobalt-free transition metal oxide electrodes.

The combination of good electronic conductivity and optical transparency of indium tin oxide (ITO) have made it an indispensable material for large-area electronics. Similarly, the combination of good electronic and ionic conduction properties of ITO makes it interesting for use in Li-ion batteries. Many of the applications rely on the retention of ITO's significant electronic conductivity over a large range of operating potentials. However, ITO is known to react with Li-ions through conversion and subsequent alloying reactions. Consequently, the use of ITO in Li-ion batteries depends on the properties at the potential of interest. In this work we used an ITO thin-film model system for a systematic study of how the films properties change during the lithiation and delithiation processes. A test structure was designed to measure the electronic conductivity through the film at different stages of the conversion and alloying processes. Changes in the conductivity were complemented by a meticulous physico-chemical characterization at a microscopic scale, combining an array of characterization techniques, including AFM, C-AFM, ERD, RBS, SEM, and XRD. As such, a clear picture of the link between the microscopic observations and changes in the macroscopic conductivity was established.

In this work, we studied the electrochemistry of LMO using thin-film electrodes in LiClO4 and LiPF6 based electrolyte solutions. The thin-film system allows the removal of all passive components, leaving only the LMO with a single well-defined electrode/electrolyte interface, making it an ideal system to study interactions at this interface. We observed a peculiar decomposition reaction when using a LiPF6 salt based electrolyte solution, as soon as the LMO electrode was discharged below 3 V. This decomposition reaction led to the formation of a highly ionically resistive interphase layer, greatly affecting the insertion kinetics into the active material. This was in stark contrast to the LiClO4 based electrolyte solutions, which showed ideal insertion behaviour. Through the combination of elastic recoil detection analysis (ERDA) and X-ray photoelectron spectroscopy (XPS) we determined that the reaction stems from a direct interaction between the LiPF6 salt and tetragonal Li2Mn2O4.

In experimental fluid dynamics, it would be invaluable to have solids with a refractive index similar to that of water, hence simplifying the use of existing facilities to study flows around complex geometries. Here we report a polymer that is refractive-index-matched with water at room temperature and can be cast in thick specimens. We successfully demonstrated its use with three common laser-based diagnostics: laser-induced fluorescence, particle image velocimetry, and molecular tagging velocimetry.

Molecular tagging velocimetry (MTV) is a nonintrusive optical diagnostic with typically three variants in liquids distinguished by the dye that they rely on: phosphorescent, photochromic, or caged. The latter scheme, initially called photo-activated nonintrusive tracking of molecular motion (PHANTOMM), required both a UV and a dedicated blue laser. Here, we demonstrate caged-dye-based MTV with pulsed UV and green lasers for the first time, simplifying its deployment in most experimental fluid dynamics laboratories.

Despite their widespread use in the chemical industries, hydrogenation reactions remain challenging. Indeed, the nature of reagents and catalysts induce intrinsic safety challenges, in addition to demanding process development involving a 3-phase system. Here, to address common issues, we describe a successful process intensification study using a meso-scale flow reactor applied to a hydrogenation reaction of ethyl cinnamate at kilo lab scale with heterogeneous catalysis. This method relies on the continuous pumping of a catalyst slurry, delivering fresh catalyst through a structured flow reactor in a continuous fashion and a throughput up to 54.7 g/h, complete conversion and yields up to 99%. This article describes the screening of equipment, reactions conditions and uses statistical analysis methods (Monte Carlo/DoE) to improve the system further and to draw conclusions on the key influential parameters (temperature and residence time).

Chemical vapor deposition of metal-organic frameworks (MOF-CVD) will facilitate the integration of porous and crystalline coatings in electronic devices. In the two-step MOF-CVD process, a precursor layer is first deposited and subsequently converted to a MOF through exposure to linker vapor. We herein report the impact of different metal oxide and metalcone layers as precursors for zeolitic imidazolate framework ZIF-8 films. ispartof: DALTON TRANSACTIONS vol:50 issue:20 pages:6784-6788 ispartof: location:England status: published

© 2019 Elsevier B.V. Thin film solid state Li 4 Ti 5 O 12 -based batteries are developed by using amorphous Lithium Phosphorus Oxynitride (LiPON) electrolyte deposited by reactive sputtering at different substrate temperatures (T dep ). Such layers maintain their amorphous character even at higher T dep . The stoichiometry, ionic conductivity, thermal stability and overall effect on full battery stacks were investigated. The ionic conductivity falls down by nearly three orders of magnitude for samples deposited at higher temperatures while no significant compositional variations are found, in contrast with previous reports. This is interpreted as the creation of a highly thermally stable LiPON glass with a closed-packed structure which inhibits Li-ion diffusion. The onset of the glass transition (T g ) and the crystallization temperature (T c ) of LiPON shifts to higher temperatures as T dep increases. Galvanostatic (dis)charge measurements on fully operational thin film batteries show a decrease in capacity and a worsened C-rate performance as LiPON T dep increases. Despite the lower ionic conduction, the improved thermal stability reported here using LiPON whose properties can be properly tuned could open interesting scenarios in future advances in solid-state battery systems and new possibilities in high temperature applications. ispartof: SOLID STATE IONICS vol:337 pages:24-32 status: published

While laser melting, deposition, and annealing of semiconductor thin films are well-established, pulsed laser processing of bulk semiconductor material powders has been minimally investigated. This work investigates nanosecond pulsed laser melting of bismuth telluride, a common thermoelectric material. Using both experimental and computational modeling methods, a process window was determined in which melting is achieved before ablation occurs. The process window was determined for Bi2Te3 powder compacts, with melt depths on the order of 20–100 μm. The melted region had a fine-grained, columnar microstructure and showed typical selective laser melting defects such as microcracking. Stroboscopic imaging was used as an in situ imaging technique to observe molten pool features, revealing a teardrop-shaped molten pool with little resolidification between pulses. A simplified thermal model of the nanosecond pulsed laser melting process was developed, and two models for the solid phase thermal conductivity were used to investigate the impact of thermal conductivity on the size, shape, and duration of the molten pool. The results demonstrate the narrow process window available for pulsed laser processing of bulk bismuth telluride powders, and the discussion includes thermal management approaches possible for reducing defects such as microcracking.

The High Temperature Test Facility (HTTF) is a quarter-scale integral-effect facility designed to study pressurized and depressurized conduction cooldowns (PCC and DCC, respectively) in high temperature, gas-cooled reactors (HTGR). This study focuses on DCC and aims to characterize the gas exchange between the reactor core and the reactor cavity to assess the risk for air ingress and subsequent potential for natural circulation core cooldowns. High-resolution velocity profile measurements are performed at the coolant pipe break location over a long time-scale using molecular tagging velocimetry. This non-intrusive, laser-based technique is applied for the first time in the field of nuclear thermal hydraulics, providing new insights for understanding the underlying phenomena at play during a DCC event. Such data are also valuable for validation of numerical simulations such as Reactor Excursion and Leak Analysis Program (RELAP). Results are reported here for various gas mixtures of helium (the coolant) and nitrogen (surrogate for air) to study the effect of density ratio. The short transient (30 s) lock-exchange phase is well captured with helium flow velocity between 0.8 and 2 m/s. The flow is shown to persist over much longer time-scales (hours) at a velocity of about 0.2 m/s, a likely consequence of gas mixing in the hot leg and in the lower plenum of the reactor. Flow visualization at the exit of the hot leg shows shear instabilities, which supports the hypothesis of significant mixing.

In this paper, we report on the fabrication and characterization of functional 3D LiMn2O4 thin-film electrodes giving a footprint capacity of 0.5 mA h cm−2, i.e. surpassing any thin-film electrode reported thus far. Using a novel process based on a solid state reaction between electrolytic manganese dioxide (EMD) and Li2CO3 stacked-layers, crack-free, uniform and continuous lithium manganese oxide (LMO) thin films were fabricated on planar and high aspect ratio microstructured substrates. The fabricated LMO films are shown to have a stoichiometry close to that of spinel LiMn2O4 with a homogeneous elemental distribution throughout the layer. The prepared thin films are electrochemically active reaching a volumetric capacity of 1200 A h L−1, which is close to the theoretical capacity of spinel LiMn2O4. The few hundred nanometer thin-film morphology allows for use of both the 3 V and 4 V regions. The 3D LMO thin-film electrodes had 21 times the capacity of the planar LMO thin film with similar thickness due to the area enhancement and the excellent conformal coating of the high aspect ratio micropillar substrates. An excellent rate performance was demonstrated for both the planar and the high aspect ratio substrates where 48% and 30% of the theoretical LiMn2O4 capacity are maintained at very high C-rates of 20C and 100C, respectively.

Nanostructured metals with large surface area have a great potential for multiple device applications. Although various metal architectures based on metal nanoligaments and nanowires are well known, they typically show a tradeoff between mechanical robustness, high surface area, and high (macro)porosity, which, when combined, could significantly improve the performance of devices such as batteries, electrolyzers, or sensors. In this work, we rationally designed templated networks of interconnected metal nanowires, combining for the first time high porosity of metal foams, narrowly distributed macropores, and a very high surface area of nanoporous dealloyed metals. Thanks to their structural uniformity, the few-micron thick nanowire meshes are also remarkably flexible and durable. We show how the textural properties of the material can be precisely tuned to optimize the nanowire networks for applications in different devices. In an exemplary application in electrolytic production of hydrogen, thanks to its high surface area, a few-micron thick nanomesh outperformed a 300 times thicker nickel foam. Furthermore, thanks to its high porosity, the Pt-doped nanomesh surpassed a microporous Pt/C cloth, demonstrating benefits of the optimally designed nanowire structure for a simultaneous improvement and miniaturization of electrochemical devices. This work extends the potential of interconnected nanowires to multiple new research and industrial applications requiring highly porous and flexible conductive materials with a high surface-to-volume ratio. ispartof: Acs Applied Materials & Interfaces vol:10 issue:51 pages:44634-44644 ispartof: location:United States status: published

Although 2D layered nanomaterials have been intensively investigated towards their application in energy conversion and storage devices, their disadvantages have rarely been explored so far especially compared to their 3D counterparts. Herein, WO3·nH2O (n = 0, 1, 2), as the most common and important electrochemical and electrochromic active nanomaterial, is synthesized in 3D and 2D structures through a facile hydrothermal method, and the disadvantages of the corresponding 2D structures are examined. The weakness of 2D WO3·nH2O originates from its layered structure. X-ray diffraction and scanning electron microscopy analyses of as-grown WO3·nH2O samples suggest a structural transition from 2D to 3D upon temperature increase. 2D WO3·nH2O easily generates structural instabilities by 2D intercalation, resulting in a faster performance degradation, due to its weak interlayer van der Waals forces, even though it outranks the 3D network structure in terms of improved electronic properties. The structural transformation of 2D layered WO3·nH2O into 3D nanostructures is observed via ex situ Raman measurements under electrochemical cycling experiments. The proposed degradation mechanism is confirmed by the morphology changes. The work provides strong evidence for and in-depth understanding of the weakness of 2D layered nanomaterials and paves the way for further interlayer reinforcement, especially for 2D layered transition metal oxides.

Molecular layer deposition (MLD) offers the deposition of ultrathin and conformal organic or hybrid films which have a wide range of applications. However, some critical potential applications require a very specific set of properties. For application as desiccant layers in water barrier films, for example, the films need to exhibit water uptake and swelling and be overcoatable. For application as a backbone for a solid composite electrolyte for lithium ions on the other hand, the films need to be stable against lithium and need to be transformable from a hybrid MLD film to a porous metal oxide film. Magnesium-based MLD films, called "magnesicone", are promising on both these aspects, and thus, an MLD process is developed using Mg(MeCp)(2) as a metal source and ethylene glycol (EG) or glycerol (GL) as organic reactants. Saturated growth could be achieved at 2 to 3 angstrom/cycle in a wide temperature window from 100 to 250 degrees C. The resulting magnesicone films react with ambient air and exhibit water uptake, which is in the case of the GL-based films associated with swelling (up to 10%) and in the case of EG-based magnesicone with Mg(CO)(3) formation, and are overcoatable with an ALD of Al2O3. Furthermore, by carefully tuning the annealing rate, the EG-grown films can be made porous at 350 degrees C. Hence, these functional tests demonstrate the potential of magnesicone films as reactive barrier layers and as the porous backbone of lithium ion composite solid electrolytes, making it a promising material for future applications.

In situ nitrogen doping of aluminum phosphate has been investigated in two different plasma-enhanced atomic layer deposition (PEALD) processes. The first method consisted of the combination of trimethyl phosphate plasma (TMP*) with a nitrogen plasma and trimethyl aluminum (TMA), that is, TMP*-N-2*-TMA. The second method replaces TMP* with a diethylphosphoramidate plasma (i.e., DEPA*-N-2*-TMA) of which the amine group could further aid nitrogen doping and/or eliminate the need for a nitrogen plasma step. At a substrate temperature of 320 degrees C, the TMP*-based process showed saturated growth (0.8 nm/cycle) of a nitrogen-doped (approximately 8 atom %) Al phosphate, while the process using DEPA* showed a similar amount of nitrogen but a significantly higher growth rate (1.4 nm/cycle). In the latter case, nitrogen doping could also be achieved without the nitrogen plasma, but this leads to a high level of carbon contamination. Both films were amorphous as-deposited, while X-ray diffraction peaks related to AlPO4 appeared after annealing in a He atmosphere. For high coating thickness (>2 nm), a significant increase in the Li-ion transmittance was found after nitrogen doping, although the coating has to be electrochemically activated. At lower thickness scales, such activation was not needed and nitrogen doping was found to double the effective transversal electronic conductivity. For the effective transversal ionic conductivity, no conclusive difference was found. When a lithium nickel manganese cobalt oxide (NMC) powder is coated with one ALD cycle of N-doped Al phosphate, the rate capability and the energy efficiency of the electrode improves.

Altres ajuts: ICN2 is supported by the CERCA Programme/Generalitat de Catalunya. In this study, we use transient thermal gratings-a non-contact, laser-based thermal metrology technique with intrinsically high accuracy-to investigate room-temperature phonon-mediated thermal transport in two nanoporous holey silicon membranes with limiting dimensions of 120 nm and 250 nm, respectively. We compare the experimental results with ab initio calculations of phonon-mediated thermal transport according to the phonon Boltzmann transport equation (BTE) using two different computational techniques. We find that the calculations conducted within the Casimir framework, i.e., based on the BTE with the bulk phonon dispersion and diffuse scattering from surfaces, are in quantitative agreement with the experimental data and thus conclude that this framework is adequate for describing phonon-mediated thermal transport in silicon nanostructures with feature sizes of the order of 100 nm.

Li-ion conductivity increases with introduction of an interfacial ice layer in nano-SCE., The transition to solid-state Li-ion batteries will enable progress toward energy densities of 1000 W·hour/liter and beyond. Composites of a mesoporous oxide matrix filled with nonvolatile ionic liquid electrolyte fillers have been explored as a solid electrolyte option. However, the simple confinement of electrolyte solutions inside nanometer-sized pores leads to lower ion conductivity as viscosity increases. Here, we demonstrate that the Li-ion conductivity of nanocomposites consisting of a mesoporous silica monolith with an ionic liquid electrolyte filler can be several times higher than that of the pure ionic liquid electrolyte through the introduction of an interfacial ice layer. Strong adsorption and ordering of the ionic liquid molecules render them immobile and solid-like as for the interfacial ice layer itself. The dipole over the adsorbate mesophase layer results in solvation of the Li+ ions for enhanced conduction. The demonstrated principle of ion conduction enhancement can be applied to different ion systems.

For the first time, MoO3 nanoparticles (NPs) with a size ranging from 1.5 to 60 nm were deposited on spray dried zeolitic imidazolate framework-8 (ZIF-8) by rotary chemical vapor deposition (RCVD) in order to improve its photocatalytic performance. A direct effect of the deposition time on the metal oxide loading was observed. In a time frame between 0.9 and 2.7 ks the metal oxide loading can be increased from 1 to 3 wt%. All the MoO3-NPs/ZIF-8 catalysts were tested towards the methylene blue photodegradation using sunlight. MoO3-NPs/ZIF-8 3 wt% RCVD reached a conversion of 82% and 95% after 180 and 300 min, respectively.

Toxic wastewaters from the textile industry have made its way into rivers and other waterways, posing a serious health treat on both human and wildlife. Herein, this data set presents the potential use of MoO 3 nanoparticles supported on ZIF-8 in the photodegradation of a cationic dye molecule. The data presented in this article report a concise description of experimental conditions for the spray-dried ZIF-8 synthesis and subsequent deposition of MoO 3 nanoparticles via rotary chemical vapor deposition (RCVD). The photodegradation and analysis data reviled that the MoO 3 -NPs@ZIF-8 3 wt% displayed the ability of degrading methylene blue up to 82% and 95% after 180 and 300 min, respectively.

While many naturally occurring polysaccharides have been widely used as drug carriers, there are two main drawbacks in their use: the first is their physical properties such as molecular weight, branching, type of glycosidic linkages and solubility depend on their source and the method of isolation and purification, the second is many of them are contaminated with proteins and protein removal is essential for preventing immune reactions. Synthetic polysaccharides on the other hand can be tailor made from their respective monomers with consistent physical properties and are, free from protein contamination, both being significant advantages in their use. Although, the synthesis of polysaccharides such as polyglucose, polymannose, polygalactose etc., by the polycondensation of their respective monomers have been reported more than half a century ago, their use as drug carriers have not received any attention so far. In this report, we show that polyglucose (PG) having a weight average molar mass of 37,000 g/mol can be synthesized in a single step by the melt polycondensation of glucose in over 70% yield. Oxidation using sodium periodate generated aldehyde functions on the polymer. Amphotericin B, (AmB) a water-insoluble polyene antibiotic was chosen as a model drug to couple onto periodate oxidized PG via imine linkage at ~20 wt% concentration. The drug loading capacity of the conjugates was above 90%. Further reduction using sodium borohydride gave the more stable amine conjugates with any residual aldehyde on the polymer backbone getting reduced to hydroxyl groups. The conjugates were highly soluble in water and stable on storage. At ten times the concentration of AmB, the conjugates produced negligible hemolysis to human blood. The AmB conjugates were then evaluated for their anti-fungal activity against C. albicans and A. fumigatus and anti-leishmanial activity against different strains of L. donovani in culture. The conjugates showed potent anti-fungal and anti-leishmanial activity. The use of synthetic polysaccharides in drug delivery and in other biomedical applications will have many potential advantages.

A thick turbulent annular liquid layer that swirls inside a fixed pipe is studied by means of surface observations and stereoscopic particle image velocimetry in an index-matched nozzle facility. This flow combines the complexities of swirling and free-surface turbulence. The free surface of the layer changes the boundary condition compared to filled swirling pipes and introduces the equivalent of a hollow core. The liquid layer shares similarities with turbulent open-channel flows, with the high centrifugal force across the layer having a similar effect to that of gravity in channel flows. At the surface, the restoring forces are surface tension and centrifugal acceleration. The particular nozzle under study has been envisioned for inertial confinement fusion, but the flow has relevance to systems such as compact separators or liquid rocket fuel injectors. Data are acquired at five downstream locations from the nozzle exit for four Reynolds numbers for subcritical flows. Injection flow rate and fluid kinematic viscosity are controlled independently, which allows adjusting independently the Reynolds and Taylor–Reynolds numbers. This also enables control of the centrifugal force at the free surface to test the effects of turbulence intensity on the free surface in regimes where air entrainment and droplet ejection occur. The swirl number is fixed by the design of the nozzle. From velocimetry data, mean velocity and turbulence statistics are extracted. For all the conditions tested, three flow regimes are identified: developing, developed, and transitional. The developed regime appears self-similar on the mean; the swirl creates a favourable pressure gradient that sustains the axial flow and confines the boundary layer near the wall. Large coherent vortex structures are identified in the layer. A simple model is proposed to describe the layer thickness and the velocity distribution in it. In the transitional regime, helical varicose waves generated by centrifugal instability are observed on the surface. Additionally, wall effects are visible in the bulk of the flow, and the main flow features are large overturning motions.

High-quality zeolite imidazole frameworks (ZIF-8, ZIF-67, and bimetallic Zn/Co-ZIF) were synthesized using the spray-drying technique and the mechanism of crystal growth during the whole process is discussed. It is also demonstrated that the crystallization mechanism for N-donor containing ditopic imidazolate (IM) ligands forming ZIF structures is divergent from MOF formation applying carboxylate ligands, and their formation using the spray dry method occurs via a unique mechanism. An intermediate amorphous phase was obtained after spray drying the feed solution, and the crystallographic ZIF structure was obtained during immersion in a solvent. Several characterization techniques, such as FTIR, XRD, SEM, porosity analysis, elemental analysis etc., were applied to examine the characteristic properties of materials, including, intermediate compounds and final products. The results proved that the spray drying procedure is a facile, continuous and effective synthetic route to produce MOFs (ZIFs) in higher quantities with high-quality properties such as high porosity, a large surface area, more active catalyst sites, etc. applying a minimum amount of time and energy which is unusual in common synthesis methods of MOFs.

This paper asserts that the development of continuum-scale mathematical models utilizing John Newman’s BAND subroutine can be simplified through the use of dual number automatic differentiation. This paper covers the salient features of the BAND algorithm as well as dual numbers and how they can be leveraged to algorithmically linearize systems of partial differential equations; these two concepts can be combined to produce accurate and computationally efficient models while significantly reducing the amount of personnel time necessary by eliminating the time-consuming process of equation linearization. As a result, this methodology facilitates more rapid model prototyping and establishes a more intuitive relationship between the numerical model and the differential equations. By utilizing an existing and validated programming module, dnadmod, these advantages are achieved without burdening the general user with significant additional programming overhead.

Titania (TiO2) offers a high theoretical capacity of 336 mAh g–1 with the insertion of one Li per Ti unit. Unfortunately, the poor ionic and electronic conductivity of bulk TiO2 electrodes limits its practical implementation. Nanosizing titania below ∼20 nm has shown to increase the rate performance and accessible capacity but still not more than 75% of the theoretical capacity at 1 C. In this work, we discovered that chlorine doping of amorphous TiO2 (TiO2–xCl2x) can achieve a high capacity without the need for nanosizing. By in situ doping during atomic layer deposition, an unprecedented 90% of the theoretical capacity was achieved at 1 C for 100 nm thick films. Even at a charging rate of 20 C, 40% of the maximum capacity was accessible for the film with highest Cl-content (x = 0.088). The capacity was found linearly dependent on the chloride content for a Cl/Ti atomic ratio from 0.06 to 0.09. The enhanced insertion kinetics are ascribed to enhanced electronic conductivity and facilitated Li+-ion diffus...

While photobleaching can be detrimental in applications focusing on fluorescence as it lowers the signal strength, it can advantageously provide non-fluorescent tracers in a fluorescent flow and hence be implemented in tracking techniques such as molecular tagging velocimetry (MTV). The photobleaching of rhodamine 6G under a single UV pulse is described with a simple three-level model of fluorescence. It offers a convenient estimate of the order of magnitude of irradiance required to observe significant photobleaching for a uniform beam. In an effort to improve the application to MTV, analytical formulas enable to determine the photobleached signal strength from a Gaussian UV laser beam overlapping with a green laser sheet and imaged from the side, as well as the apparent width of the imaged photobleached line.

The use of Ti phosphate as a functional coating for Li ion battery electrodes has been investigated, as well as the effect of nitrogen doping on its electrochemical properties. First, previous knowledge on PE-ALD of Ti phosphate (using an exposure sequence of trimethylphosphate plasma–oxygen plasma–titaniumisopropoxide) was used to study an altered process using a nitrogen plasma, i.e. TMP* - N2* - TTIP. This enabled the deposition of a nitrogen doped (6 at.%) Ti phosphate with a growth per cycle of 0.4 nm/cycle. Next, a dual-source precursor (diethylphosphoramidate plasma, or DEPA*) was introduced instead of TMP*, allowing for a higher growth rate (0.6 nm/cycle) and a higher nitrogen level (8.6 at.%). The ionic transparency of the phosphate slightly decreased due to nitrogen incorporation, but the effective transversal electronic conductivity showed to be three times higher after nitrogen doping. A 2 nm coating of (un)doped Ti phosphate significantly improved the rate capability of a lithium nickel manganese cobalt oxide (NMC) electrode, increasing the amount of energy that can be stored at high (dis)charging speeds with a factor 10 (at 5C). In addition, the undoped titanium phosphate coating offered increased stability, retaining 84% of the capacity after 100 cycles at 1C with respect to 79% for the uncoated electrode.

Two air entrainment mechanisms driven by vortex instability are reported in the unstable relaxation of a horizontal shear layer below a free surface. This flow is experimentally investigated by means of planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) coupled with surface profilometry. PLIF identifies counter-rotating vortex pairs (CRVP) emanating from the surface following the growth of high steepness two-dimensional millimetre-size waves for Reynolds and Weber numbers based on the momentum thickness of 177 to 222 and 7.59 to 13.9, respectively. High spatio-temporal resolution PIV reveals the role of surface-generated vorticity and flow separation in the highly curved trough of the waves on the injection of a CRVP. Air bubbles are entrapped in the wake of these CRVPs at Reynolds number above 190. PIV data and spanwise PLIF images show two initiation mechanisms: primary vortex instability modulating the spanwise location where the flow separates, resulting in the pinch off of an air ligament, and secondary vortex instability turning a CRVP into$\unicode[STIX]{x1D6FA}$-shaped loops pulling the surface down. Instability wavelengths agree with linear stability analysis, and models for these new air entrainment mechanisms are proposed.

Atomic Layer Deposition (ALD) is an enabling technology which provides coating and material features with significant advantages compared to other existing techniques for depositing precise nanometer-thin two-dimensional (2D) nanostructures. It is a cyclic process which relies on sequential self-terminating reactions between gas phase precursor molecules and a solid surface. ALD is especially advantageous when the film quality or thickness is critical, offering ultra-high aspect ratios. ALD provides digital thickness control to the atomic level by depositing film one atomic layer at a time, as well as pinhole-free films even over a very large and complex areas. Digital control extends to sandwiches, hetero-structures, nano-laminates, metal oxides, graded index layers and doping, and it is perfect for conformal coating and challenging 2D electrodes for various functional devices. The technique’s capabilities are presented on the example of ALD-developed ultra-thin 2D tungsten oxide (WO3) over the large area of standard 4” Si substrates. The discussed advantages of ALD enable and endorse the employment of this technique for the development of hetero-nanostructure 2D semiconductors with unique properties.

Three-dimensional (3D) configuration of high-performance energy storage devices has been the subject of ongoing investigations targeting their integration in autonomous microelectronic systems. In this study we demonstrate a route toward the realization of high capacity cathode material for 3D thin-film lithium-ion (Li-ion) batteries. Electrolytic manganese dioxide (EMD) film can be applied as a Li-ion intercalation electrode upon its conversion to lithium manganese dioxide (LiMn2O4 or LMO) by solid-state reaction. The main challenges of depositing thicker EMD film directly on the current collector often lay in achieving a good film adhesion and preventing oxidation of non-noble current collectors such as TiN, Ni. To improve the adhesion of the EMD films we modify the surface of the current collector by means of thin-film or seed layer coatings, which also prevent the oxidation of the underlying current collector substrate during the anodic deposition process. As a result submicron to micron thick EMD films with good adhesion were deposited on various current collectors. The acidity of the electrolyte solutions was varied depending on the type of the surface coating or current collector used. The mechanism of the EMD film growth and morphology on different substrates was examined. Compatibility of the proposed current collector interface modification for the electrodeposition of conformal thick EMD films on high-aspect ratio microstructures was demonstrated. A method of EMD film conversion to LMO at low-temperature on different substrates was shown as the path toward their application in 3D Li-ion batteries. ispartof: Journal of the Electrochemical Society vol:164 issue:14 pages:D954-D963 status: published

Viscous stress contributes to momentum transfer between two phases, which plays an important role in both industrial applications and environmental processes. Near a wavy interface, the flow is modulated and produces a spatially non-uniform normal and tangential viscous stress. This study presents measurements of these stresses at a liquid–gas interface populated with two-dimensional millimeter scale waves performed with multiphase particle image velocimetry. Large datasets enable conditional phase-averaging of the data based on wave steepness, which increases the precision of the results and allows statistical analysis. For the first time at this scale, the spatial distribution of normal and tangential viscous stress is obtained for a large range of wave steepness (ak = 0–1, with a the amplitude and k the wavenumber). As the steepness increases, the mean shear stress over a wavelength decreases in magnitude, while the normal viscous stress increases. These trends are linear for ak 0.7, flow separation is observed in the gas phase near the troughs and drastically alters the viscous stress distribution.

Titanium phosphate thin films were deposited by a new plasma-enhanced atomic layer deposition process. The process consisted of sequential exposures to trimethyl phosphate (TMP, Me3PO4) plasma, O2 plasma and titanium isopropoxide (TTIP, Ti(OCH(CH3)2)4) vapor, and it was characterized by in situ spectroscopic ellipsometry and ex situ X-ray reflectometry. The growth linearity, growth per cycle (GPC), and density of the resulting thin films were investigated as a function of the pulse times and the substrate temperature. The conformality of the process was characterized by deposition on micropillars. At a substrate temperature of 300 °C and using saturated pulse times, linear growth with a GPC of 0.66 nm per cycle and without nucleation delay was achieved. The as-deposited films were amorphous, while crystalline TiP2O7 was formed upon annealing in air or helium atmospheres. In lithium-ion test cells, the as-deposited films showed insertion and extraction of Li+ around a potential of 2.7 V vs. Li/Li+. Charge/discharge measurements revealed a volumetric capacity of 330 mA h cm−3, together with a good rate capability and minimal capacity fading.

Thermoelectric devices can convert heat to electricity. Recent advancements in the development of semiconductor thermoelectric materials have led to a significant increase in the thermoelectric figure of merit ZT. However, challenges in materials processing and assembly hinder the potential of thermoelectric power generation. An assessment of alternative advanced manufacturing methods for thermoelectric devices reveals the advantages of selective laser melting. While laser melting is a well-established additive manufacturing technique for metals, ceramics, and polymers, this study will provide the first investigations of semiconductor materials melt-processing using a laser. Preliminary experimental results demonstrate the effect of laser processing parameters on the microstructure and densification of the melt line.

Nanostructured electrodes show great promises for application in batteries and could improve their energy and power density. Herein, a carbon-coated 3D Ni nanomesh was used as an air cathode for non-aqueous Li-air (O2 ) battery applications. A 3 μm thick 3D Ni nanomesh was fabricated, showing an excellent surface area/footprint area ratio (90 cm2 :1 cm2 ) and uniformly distributed pores, on which a conformal amorphous carbon coating was applied for the first time. This carbon-coated 3D Ni nanomesh showed an approximately 100 times larger charge-footprint capacity than that of the glassy carbon electrode. Owing to its tunable properties, a capacity higher than 6 mAh cm-2 could be achieved for a carbon-coated 3D Ni nanomesh with a thickness of 100 μm, whereas the practical capacities of current air electrodes are in the range of 2 mAh cm-2 . ispartof: CHEMSUSCHEM vol:12 issue:17 pages:3967-3970 ispartof: location:Germany status: published

ispartof: ADVANCED MATERIALS INTERFACES vol:6 issue:15 status: published