A microstructural zone model for the morphology of sol-gel coatings

The thickness and the morphology of dip-coated single sol-gel layers is easily controlled by varying the sol compositions and the deposition parameters. A thorough study of the microstructure of transparent conducting ZnO: Al coatings deposited on fused silica substrates using X-ray diffraction, X-ray reflectometry and transmission electron microscopy cross-sections as well as of In2O3: Sn, SnO2: Sb, ZnO and TiO2 coatings reported in the literature shows that three basic morphologies can be observed: granular, layered and columnar. In multilayer systems they were found to depend essentially on the single layer thickness (SLT) and on the crystallite size determined from the data of thick films, a parameter called the "intrinsic crystallite size (ICS)". All the results so far analysed are in agreement with a 3-zone model when ICS is plotted against SLT or in a more refined version when q = ICS/SLT is plotted against the homologous temperature T-sintering/T-melting. Comparison with the Movchan-Demchishin and Polley-Carter models proposed for PVD and CVD coatings, respectively, is presented

Synthesis and characterization of aluminum doped zinc oxide nanostructures via hydrothermal route

Stable crystalline aluminum doped zinc oxide (AZO) nanopowders were synthesized using hydrothermal treatment processing. Three different aluminum precursors have been used. The Al-precursors were found to affect the morphology of the obtained nanopowders. AZO nanoparticles based on zinc acetate and aluminum nitrate have been prepared with different Al/Zn molar ratios. XRD investigations revealed that all the obtained powders have single phase zincite structure with purity of about 99%. The effect of aluminum doping ratio in AZO nanoparticles (based on Al-nitrate precursor) on structure, phase composition, and particle size has been investigated. The incorporation of Al in ZnO was confirmed by UV-Vis spectroscopy revealing a blue shift due to Burstein-Moss effect

Enhanced electrochemical energy storage by nanoscopic decoration of endohedral and exohedral carbon with vanadium oxide via atomic layer deposition

Atomic layer deposition (ALD) is a facile process to decorate carbon surfaces with redox-active nanolayers. This is a particularly attractive route to obtain hybrid electrode materials for high performance electrochemical energy storage applications. Using activated carbon and carbon onions as representatives of substrate materials with large internal or external surface area, respectively, we have studied the enhanced energy storage capacity of vanadium oxide coatings. While the internal porosity of activated carbon readily becomes blocked by obstructing nanopores, carbon onions enable the continued deposition of vanadia within their large interparticle voids. Electrochemical benchmarking in lithium perchlorate in acetonitrile (1 M LiClO4) showed a maximum capacity of 122 mAh/g when using vanadia coated activated carbon and 129 mAh/g for vanadia coated carbon onions. There is an optimum amount of vanadia between 50 and 65 wt % for both substrates that results in an ideal balance between redox-activity and electrical conductivity of the hybrid electrode. Assembling asymmetric (charge balanced) full-cells, a maximum specific energy of 38 Wh/kg and 29 Wh/kg was found for carbon onions and activated carbon, respectively. The stability of both systems is promising, with a capacity retention of ∼85–91% after 7000 cycles for full-cell measurements

Influence of structure zone model parameters on the electrical properties of ZnO:Al sol-gel coatings

Structure zone models (Movchan-Demchishin, Thornton, etc.) have been proposed to predict the morphology of metal and metal—oxide films produced by PVD or CVD processes. An original model was proposed for metal—oxide coatings made by the sol—gel process, based on a thorough experimental study of the microstructure of many coatings either obtained at INM or reported by other laboratories. The different morphologies — granular, layered, columnar — were described in terms of a parameter q = ICS/SLT, where ICS is a so-called "intrinsic crystallite size'; and SLT is the single layer thickness and the homologous temperature TH = TSintering/TMelting. The influence of these morphologies and parameters on the electrical properties of transparent conducting ZnO:Al coatings is reported

Improved Capacitive Deionization Performance of Mixed Hydrophobic / Hydrophilic Activated Carbon Electrodes

Capacitive deionization (CDI) is a promising salt removal technology with high energy efficiency when applied to low molar concentration aqueous electrolytes. As an interfacial process, ion electrosorption during CDI operation is sensitive to the pore structure and the total pore volume of carbon electrodes limit the maximum salt adsorption capacity (SAC). Thus, activation of carbons as a widely used method to enhance the porosity of a material should also be highly attractive for improving SAC values. In our study, we use easy-to-scale and facile-to-apply CO2 activation at temperatures between 950 °C and 1020 °C to increase the porosity of commercially available activated carbon. While the pore volume and surface area can be significantly increased up to 1.51 cm3/g and 2113 m2/g, this comes at the expense of making the carbon more hydrophobic. We present a novel strategy to still capitalize the improved pore structure by admixing as received (more hydrophilic) carbon with CO2 treated (more hydrophobic) carbon for CDI electrodes without using membranes. This translates in an enhanced charge storage ability in high and low molar concentrations (1 M and 5 mM NaCl) and significantly improved CDI performance (at 5 mM NaCl). In particular, we obtain stable CDI performance at 0.86 charge efficiency with 13.1 mg/g SAC for an optimized 2:1 mixture (by mass)

Electrospun Hybrid Vanadium Oxide/Carbon Fiber Mats for Lithium- and Sodium-Ion Battery Electrodes

Vanadium oxide nanostructures are constantly being researched and developed for cathodes in lithium- and sodium-ion batteries. To improve the internal resistance and the discharge capacity, this study explores the synthesis and characterization of continuous one-dimensional hybrid nanostructures. Starting from a sol–gel synthesis, followed by electrospinning and controlled thermal treatment, we obtained hybrid fibers consisting of metal oxide crystals (orthorhombic V₂O₅ and monoclinic VO₂) engulfed in conductive carbon. For use as Li-ion battery cathode, a higher amount of carbon yields a more stable performance and an improved capacity. Monoclinic VO₂/C fibers present a specific capacity of 269 mAh·g_VOx^–1 and maintain 66% of the initial capacity at a rate of 0.5 A·g^–1. Orthorhombic V₂O₅/C presents a higher specific capacity of 316 mAh·g_VOx^–1, but a more limited lithium diffusion, leading to a less favorable rate handling. Tested as cathodes for Na-ion batteries, we confirmed the importance of a conductive carbon network and nanostructures for improved electrochemical performance. Orthorhombic V₂O₅/C hybrid fibers presented very low specific capacity while monoclinic VO₂/C fibers presented an improved specific capacity and rate performance with a capacity of 126 mAh·g_VOx^–1

Synthesis and Characterization of Aluminum Doped Zinc Oxide Nanostructures via Hydrothermal Route

Stable crystalline aluminum doped zinc oxide (AZO) nanopowders were synthesized using hydrothermal treatment processing. Three different aluminum precursors have been used. The Al-precursors were found to affect the morphology of the obtained nanopowders. AZO nanoparticles based on zinc acetate and aluminum nitrate have been prepared with different Al/Zn molar ratios. XRD investigations revealed that all the obtained powders have single phase zincite structure with purity of about 99%. The effect of aluminum doping ratio in AZO nanoparticles (based on Al-nitrate precursor) on structure, phase composition, and particle size has been investigated. The incorporation of Al in ZnO was confirmed by UV-Vis spectroscopy revealing a blue shift due to Burstein-Moss effect

Benchmarking immunoinformatic tools for the analysis of antibody repertoire sequences

Antibody repertoires reveal insights into the biology of the adaptive immune system and empower diagnostics and therapeutics. There are currently multiple tools available for the annotation of antibody sequences. All downstream analyses such as choosing lead drug candidates depend on the correct annotation of these sequences; however, a thorough comparison of the performance of these tools has not been investigated. Here, we benchmark the performance of commonly used immunoinformatic tools, i.e. IMGT/HighV-QUEST, IgBLAST and MiXCR, in terms of reproducibility of annotation output, accuracy and speed using simulated and experimental high-throughput sequencing datasets

Niobium carbide nanofibers as a versatile precursor for high power supercapacitor and high energy battery electrodes

This study presents electrospun niobium carbide/carbon (NbC/C) hybrid nanofibers, with an average diameter of 69 ± 30 nm, as a facile precursor to derive either highly nanoporous niobium carbide-derived carbon (NbC–CDC) fibers for supercapacitor applications or niobium pentoxide/carbon (Nb2O5/C) hybrid fibers for battery-like energy storage. In all cases, the electrodes consist of binder-free and free-standing nanofiber mats that can be used without further conductive additives. Chlorine gas treatment conformally transforms NbC nanofiber mats into NbC–CDC fibers with a specific surface area of 1508 m2 g−1. These nanofibers show a maximum specific energy of 19.5 W h kg−1 at low power and 7.6 W h kg−1 at a high specific power of 30 kW kg−1 in an organic electrolyte. CO2 treatment transforms NbC into T-Nb2O5/C hybrid nanofiber mats that provide a maximum capacity of 156 mA h g−1. The presence of graphitic carbon in the hybrid nanofibers enabled high power handling, maintaining 50% of the initial energy storage capacity at a high rate of 10 A g−1 (64 C-rate). When benchmarked for an asymmetric full-cell, a maximum specific energy of 86 W h kg−1 was obtained. The high specific power for both systems, NbC–CDC and T-Nb2O5/C, resulted from the excellent charge propagation in the continuous nanofiber network and the high graphitization of the carbon structure