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Polymer nanoimprinting of submicrometer-scale dimple arrays with structural coloration was demonstrated. Highly ordered aluminum dimple arrays measuring 530–670 nm in diameter were formed on an aluminum substrate via etidronic acid anodizing at 210–270 V and subsequent anodic oxide dissolution. The nanostructured aluminum surface led to bright structural coloration with a rainbow spectrum, and the reflected wavelength strongly depends on the angle of the specimen and the period of the dimple array. The reflection peak shifts gradually with the dimple diameter toward longer wavelength, reaching 800 nm in wavelength at 670 nm in diameter. The shape of the aluminum dimple arrays were successfully transferred to a mercapto-ester ultra-violet curable polymer via self-assembled monolayer coating and polymer replications using a nanoimprinting technique. The nanostructured polymer surfaces with positively and negatively shaped dimple arrays also exhibited structural coloration based on the periodic nanostructure, and reflected light mostly in the visible region, 400–800 nm. This nanostructuring with structural coloration can be easily realized by simple techniques such as anodizing, SAM coating, and nanoimprinting. [ABSTRACT FROM AUTHOR]

Carbonate ions in LiCl–Li 2 O salt are a source of carbon contamination in the electrolytic refining of metal oxides, and their concentration is also an essential information for understanding the CO 2 decomposition process. In this study, the solubility of gaseous CO 2 in molten LiCl–Li 2 O was studied with the goal of developing processes to decompose the oxides effectively. Ar–CO 2 gas mixtures were dissolved in molten salts containing various amounts of Li 2 O, and the solubility of the CO 2 gas was calculated by measuring the mass difference between the molten salts before and after the CO 2 dissolution. The molar amount of dissolved CO 2 gas was almost as large as the molar quantity of Li 2 O when the partial pressure of CO 2 was 1.0 or 0.5 atm for Li 2 O concentrations in the range of 0–60 mol%. This confirms that a large quantity of the oxide ions reacted with the CO 2 gas, resulting in the generation of carbonate ions. [ABSTRACT FROM AUTHOR]

Anodic oxide fabricated by anodizing has been widely used for nanostructural engineering, but the nanomorphology is limited to only two oxides: anodic barrier and porous oxides. Therefore, the discovery of an additional anodic oxide with a unique nanofeature would expand the applicability of anodizing. Here we demonstrate the fabrication of a third-generation anodic oxide, specifically, anodic alumina nanofibers, by anodizing in a new electrolyte, pyrophosphoric acid. Ultra-high density single nanometer-scale anodic alumina nanofibers (1010 nanofibers/cm2) consisting of an amorphous, pure aluminum oxide were successfully fabricated via pyrophosphoric acid anodizing. The nanomorphologies of the anodic nanofibers can be controlled by the electrochemical conditions. Anodic tungsten oxide nanofibers can also be fabricated by pyrophosphoric acid anodizing. The aluminum surface covered by the anodic alumina nanofibers exhibited ultra-fast superhydrophilic behavior, with a contact angle of less than 1°, within 1 second. Such ultra-narrow nanofibers can be used for various nanoapplications including catalysts, wettability control, and electronic devices. [ABSTRACT FROM AUTHOR]

Abstract: Micro-, submicron-, and nano-scale titanium dioxide particles were reduced by reduction with a metallic calcium reductant in calcium chloride molten salt at 1173K, and the reduction mechanism of the oxides by the calcium reductant was explored. These oxide particles, metallic calcium as a reducing agent, and calcium chloride as a molten salt were placed in a titanium crucible and heated under an argon atmosphere. Titanium dioxide was reduced to metallic titanium through a calcium titanate and lower titanium oxide, and the materials were sintered together to form a micro-porous titanium structure in molten salt at high temperature. The reduction rate of titanium dioxide was observed to increase with decreasing particle size; accordingly, the residual oxygen content in the reduced titanium decreases. The obtained micro-porous titanium appeared dark gray in color because of its low surface reflection. Micro-porous metallic titanium with a low oxygen content (0.42wt%) and a large surface area (1.794m2 g−1) can be successfully obtained by reduction under optimal conditions. [Copyright &y& Elsevier]

The self-ordering behavior of anodic porous alumina that was formed by anodizing in selenic acid electrolyte (H2SeO4) at various concentrations and voltages was investigated with SEM and AFM imaging. A high purity aluminum foil was anodized in 0.1-3.0M selenic acid solutions at 273K and at constant cell voltages in the range of 37 to 51V. The regularity of the cell arrangement increased with increasing anodizing voltage and selenic acid concentration under conditions of steady oxide growth without burning. Anodizing at 42-46V in 3.0M selenic acid produced highly ordered porous alumina. By selective dissolution of the anodic porous alumina, highly ordered convex nanostructures of aluminum with diameters of 20nm and heights of 40nm were exposed at the apexes of each hexagonal dimple array. Highly ordered anodic porous alumina with a cell size of 102nm from top to bottom can be fabricated by a two-step selenic acid anodizing process, that includes the first anodizing step, the selective oxide dissolution, and the second anodizing step. [ABSTRACT FROM AUTHOR]

Abstract: In a metallurgical process, gas–liquid flow plays an important role in increasing the efficiency by stirring liquid mechanically or by injecting a gas. Owing to the difficulty of direct observation in a high-temperature system or real furnace experiment, numerical analysis is useful and widely studied. However, flexible treatment of complicated free surface behavior such as fragmentation and coalescence of liquids is still a difficult problem. This paper presents a new particle-based simulation scheme for gas–liquid flow. We improved the numerical stability, which is generally a problem with the particle method, and verified the model’s accuracy for fundamental gas–liquid flow analysis. Because all the phases were discretized as particles in Moving Particle Semi-implicit (MPS) method, the proposed model can track the movement of both the gas and liquid phases directly. A large difference in the real density between the gas and liquid phases makes the gas–liquid interface behavior unstable. This study proposed an optimization of the weakly compressible Poisson equation, an initial particle arrangement, and a smoothed interface density in order to stabilize the multi-density flow analysis. This model guarantees conservation of the fluid volume even for a high-density-ratio flow like that at a gas–liquid interface. Therefore, a gas–liquid interface has been represented with high accuracy. We believe that this scheme is also applicable to phenomena in an actual process that includes many dispersal phases. [Copyright &y& Elsevier]

Abstract: The growth behavior of anodic porous alumina formed via anodizing in a new electrolyte, squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione), is reported for the first time. A high-purity aluminum foil was anodized in a 0.1M squaric acid solution at 293K and a constant applied potential of 100-150V. Anodic oxides grew on the aluminum foil at applied potentials of 100-120V, but a burned oxide film was formed at higher voltage. Anodic porous alumina with a cell size of approximately 200–400nm and sub-100-nm-scale pore diameter was successfully fabricated by anodizing in squaric acid. The cell size of the anodic oxide increased with anodizing time because of the uneven growth of the porous layer. The anodic porous alumina obtained by squaric acid anodizing consists of amorphous Al2O3 containing 5-6 at% carbon from the electrolyte. [Copyright &y& Elsevier]

Highlights: [•] A metallic Ti–Zr alloy was obtained by electroless reduction for capacitor applications. [•] The reduction mechanisms were studied by SEM, XRD, EPMA, and an oxygen analyzer. [•] The alloy was obtained by electroless reduction in the presence of excess calcium reductant. [•] A micro-porous Ti–Zr alloy was successfully obtained. [•] The alloy has a low oxygen content and a large surface area. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new aluminum bulk micromachining through an anodic oxide mask was developed. [•] Laser irradiation of anodized aluminum results in the formation of a locally exposed aluminum pattern. [•] The anodic oxide acted as a resist mask during electrochemical etching. [•] A hemicylindrical microgroove with a flat surface was fabricated by electrochemical etching. [•] Free-standing oxides formed by an undercutting were easily removed by ultrasonication. [Copyright &y& Elsevier]

Abstract: The electrochemical decomposition of CO2 gas in LiCl–Li2O or CaCl2–CaO molten salt was studied to produce carbon. This process consists of the electrochemical reduction of the oxide, Li2O or CaO, and the thermal reduction of CO2 gas by metallic Li or Ca. Two kinds of ZrO2 solid electrolytes were tested as an oxygen ions conductor and removed oxygen ions from the molten salts to the outside of reactor. After the electrolysis in the both salts, the aggregations of nanometer-scale amorphous carbon and rod-like graphite crystals were observed by transmission electron microscope. When 9.7% CO2–Ar mixed gas was blown into LiCl–Li2O or CaCl2–CaO molten salt, the current efficiency was evaluated to be 89.7% or 78.5%, respectively, by the exhaust gas analysis and the supplied charge. When the solid electrolyte with the better ionic conductivity was used, the current and the carbon production became larger. The rate determining step of this proposal was diffusion of oxygen ions in ZrO2 solid electrolyte. [Copyright &y& Elsevier]

Abstract: Metallic nickel powders with low and uniform residual oxygen content were produced from NiO using the molten salt electrolysis of CaO in CaCl2 melt. Suitable amount of CaO for the reduction was in the range of 0.5–3.0mol% CaO. The electrical isolation of NiO from both electrodes could produce metallic Ni in CaCl2 melt. Separating the metal oxides from the cathode confirmed the mechanism of calciothermic reduction that the electrolysis of dissolved CaO in CaCl2 melt produces Ca, and that the dissolved Ca in molten CaCl2 successfully reduces NiO to metallic Ni. An average of about 600ppm oxygen in Ni sample was achieved directly from oxide, when NiO was detached from the cathode. [Copyright &y& Elsevier]

• An aluminum surface was covered with numerous aluminum oxide nanowires by anodizing. • The nanowire morphology was precisely controlled by a two-step anodizing process. • Superhydrophobic aluminum surfaces were fabricated with self-assembled monolayers. • The slippery behavior can be controlled by the morphology of nanowires. • Opposite slipping behaviors were demonstrated by the water dropping experiments. The influence of the nanomorphology of alumina nanowires (ANWs) fabricated by a two-step anodizing process on the superhydrophobicity was investigated through advancing contact angle (ACA) and receding contact angle (RCA) measurements. Aluminum nanobowl specimens were anodized in pyrophosphoric acid to fabricate an ordered ANW structure with an average diameter of 7.1 nm, and the outermost surface of the ANWs was chemically bonded with fluorinated self-assembled monolayers. The growing ANWs bent immediately their own weight, and pyramidal ANW structures were formed as they joined the surrounding nanowires together. The ACA value increased with the number density of pyramidal ANW structures due to the reducing area fraction of ANWs, and an increased superhydrophobicity with a contact angle of approximately 165° was measured on the low-density pyramidal structure with a density of 8.1 × 1011 m−2. Additional anodizing led to complete nanowire bending; thus, the advancing contact angle decreased. The pyramidal nanowire structure exhibited a large slipping property with a contact angle hysteresis (CAH) < 10°, whereas the bent nanowire structure exhibited a decreased slipping property with a CAH > 100°. Superhydrophobic surfaces with opposite water slipping properties were demonstrated by a water dropping experiment. [ABSTRACT FROM AUTHOR]

• A practical multi-interfacial tension model has been considered in the SPH framework. • Obtained results corresponded to the analytical solution of the multi-contact angles. • The model is applicable to the dynamic analysis involving two or more liquid phases. • The contribution of momentum leads to a temporal change of triple line morphology. To analyze the complex droplet transient deformation involving two immiscible phases, a practical multi-interfacial tension model has been introduced in the SPH framework. The attraction, which operates on the interface between the different phases is explicitly defined as London dispersion force using the Fowkes theoretical model, and the interfacial tension can be calculated using the sum of the attraction magnitudes corresponding to the surrounding particles. The analytical solution demonstrated good agreement with the simulated results corresponding to the macroscopic multicontact angles and nature of interphase interfacial forces. This simple model is widely applicable to the dynamic analysis of capillary forces involving two or more liquids, and we demonstrated its application to the simulation of the deformation behavior of a binary droplet that contacts a solid. The solid-liquid-liquid contact angle is not sufficient to predict the equilibrium morphology, and the momentum exchange between the two liquids should be considered. [ABSTRACT FROM AUTHOR]

Scandium sulfides were synthesized from its stable oxide, Sc 2 O 3 , using CS 2 gas. Suitable temperature and time for synthesis were examined experimentally using a constant flow rate of gas mixture of Ar and CS 2. The high rate of evaporation from liquid CS 2 enhanced formation and stoichiometry of sulfides, and eliminated impurity carbon. Most of parts in the sample were converted to Sc 2 S 3 at 1473 ​K for 7.2 ks, and a transient phase of Sc 2 O 2 S was often synthesized after a prolonged time under certain oxygen and sulfur potentials. CS 2 gas is carried out from its liquid by Ar gas flow, and reacts with Sc 2 O 3 to be converted to Sc 2 S 3 with CO/CO 2 gas evolution. From the exhaust the excess amount of CS 2 gas is condensed for recycling. Image 1 • Scandium sulfide(Sc 2 S 3) prepared by CS 2 sulfurization system from scandium oxide(Sc 2 O 3). • Morphology Sc 2 S 3 and intermediates in CS 2 sulfurization system. • Preparation of scandium sulfide with low oxygen level. [ABSTRACT FROM AUTHOR]

A superhydrophilic aluminum surface with fast water evaporation based on nanostructured aluminum oxide was fabricated via anodizing in pyrophosphoric acid. Anodizing aluminum in pyrophosphoric acid caused the successive formation of a barrier oxide film, a porous oxide film, pyramidal bundle structures with alumina nanofibers, and completely bent nanofibers. During the water contact angle measurements at 1 s after the water droplet was placed on the anodized surface, the contact angle rapidly decreased to less than 10°, and superhydrophilic behavior with the lowest contact angle measuring 2.0° was exhibited on the surface covered with the pyramidal bundle structures. As the measurement time of the contact angle decreased to 200–33 ms after the water placement, although the contact angle slightly increased in the initial stage due to the formation of porous alumina, at 33 ms after the water placement, the contact angle was 9.8°, indicating that superhydrophilicity with fast water evaporation was successfully obtained on the surface covered with the pyramidal bundle structures. We found that the shape of the pyramidal bundle structures was maintained in water without separation by in situ high-speed atomic force microscopy measurements. [ABSTRACT FROM AUTHOR]

The anodizing of aluminum in an alkaline sodium tetraborate (Na 2 B 4 O 7) solution was investigated with respect to the nanostructural characterization of anodic porous alumina. Electropolished aluminum specimens were galvanostatically anodized under various conditions in 0.1–0.5 M sodium tetraborate solutions at 293–353 K and a current density of 2.5–400 A m−2. Anodic oxide with numerous flower-like defects was formed by anodizing in a 0.1 M Na 2 B 4 O 7 solution due to the film breakdown with continuous visible sparking. On the other hand, a uniform porous alumina film without any breakdown was successfully obtained by anodizing a more concentrated solution than 0.3 M at 333 K. The anodic oxide was almost pure alumina and consisted of a thin outer layer with numerous small pits and a thick inner layer with typical porous alumina cells. The pore walls possessed continuous bumpy surfaces measuring 10–20 nm in roughness. As the temperature further increased to 353 K, the regularity of the porous alumina improved due to the high current density of more than 150 A m−2 during anodizing. Slippery superhydrophobic and sticky superoleophobic aluminum surfaces could be easily fabricated via high temperature anodizing and subsequent self-assembled monolayer modification. Unlabelled Image • Pure Al plates were galvanostatically anodized in an alkaline sodium tetraborate solution. • Porous alumina was formed in a high concentration solution at high temperature. • The pore walls possessed continuous bumpy surfaces. • The anodic oxide consisted of almost pure alumina. • The regularity was improved by the high current density anodizing at high temperature. [ABSTRACT FROM AUTHOR]

We investigated the transient behavior of immiscible two-liquid interfaces initiated by a single rising gas bubble and characterized by liquid "column" and "film" morphologies. To analyze the effect of the buoyancy force, viscosity, and interfacial tension on these morphologies, the single-solution density was controlled continuously by association with the rising velocity of the bubble. It was observed that the extension of the liquid column further into the upper liquid phase owing to the wake flow under the bubble is driven by the buoyancy force, with the velocity decreasing gradually with the distance between the bubble and the liquid-liquid interface. Based on this mechanism, we determined that a strong dimensionless correlation exists between the lifetime of the column and the physical properties of the two liquid phases. On the other hand, gravitational drainage does not affect the film lifetime. However, marginal pinching is dominant, probably owing to the existence of a surface tension gradient between the film and the meniscus. [ABSTRACT FROM AUTHOR]

The fabrication of sticky and slippery superhydrophobic aluminum was achieved by anodizing in pyrophosphoric acid and modification with self-assembled monolayers (SAMs). In addition, the corresponding sliding behaviors of a water droplet were investigated by contact angle measurements and direct observations. For the formation of anodic alumina nanofibers, 4N aluminum plates were anodized in a concentrated pyrophosphoric acid solution at 25-75 V. The morphology of the anodic oxide successively changed to barrier oxide, porous oxide, nanofibers, bundle structures with many nanofibers, and then weak nanofibers during anodizing. The anodized specimens were immersed in a fluorinated phosphonic acid/ethanol solution to form SAMs on the surface of the anodic oxide. The contact angle hysteresis drastically changed with anodizing time: it increased with the formation of porous oxide, decreased for the nanofibers and bundle structures, and then increased once again for the weak nanofibers. Correspondingly, the adhesion interaction between the water droplet and the aluminum surface also drastically changed to show sticky, slippery, and sticky behaviors with anodizing time. More sticky and slippery aluminum surfaces can be obtained by anodizing at higher voltages. The slippery behavior was further improved through two distinct anodizing processes with the formation of ordered alumina nanofibers. A superhydrophobic aluminum surface with coexisting sticky and slippery properties was fabricated by the selective anodizing method., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We investigated the transient behavior of immiscible two-liquid interfaces initiated by a single rising gas bubble and characterized by liquid "column" and "film" morphologies. To analyze the effect of the buoyancy force, viscosity, and interfacial tension on these morphologies, the single-solution density was controlled continuously by association with the rising velocity of the bubble. It was observed that the extension of the liquid column further into the upper liquid phase owing to the wake flow under the bubble is driven by the buoyancy force, with the velocity decreasing gradually with the distance between the bubble and the liquid-liquid interface. Based on this mechanism, we determined that a strong dimensionless correlation exists between the lifetime of the column and the physical properties of the two liquid phases. On the other hand, gravitational drainage does not affect the film lifetime. However, marginal pinching is dominant, probably owing to the existence of a surface tension gradient between the film and the meniscus.