Various Kinds Of Metals Research Articles

Recent progress in the synthesis and applications of covalent organic framework-based composites.

Covalent organic frameworks (COFs) have historically been of interest to researchers in different areas due to their distinctive characteristics, including well-ordered pores, large specific surface area, and structural tunability. In the past few years, as COF synthesis techniques developed, COF-based composites fabricated by integrating COFs and other functional materials including various kinds of metal or metal oxide nanoparticles, ionic liquids, metal-organic frameworks, silica, polymers, enzymes and carbon nanomaterials have emerged as a novel kind of porous hybrid material. Herein, we first provide a thorough summary of advanced strategies for preparing COF-based composites; then, the emerging applications of COF-based composites in diverse fields due to their synergistic effects are systematically highlighted, including analytical chemistry (sensing, extraction, membrane separation, and chromatographic separation) and catalysis. Finally, the current challenges associated with future perspectives of COF-based composites are also briefly discussed to inspire the advancement of more COF-based composites with excellent properties.

A systematic study on the metallophilicity of ordered five-atomic-layer MXenes using high-throughput automated workflow and machine learning

Dendrite growth is an important issue hindering practical applications of various kinds of metal (e.g. Li, Na, K, Mg, Ca, Fe, Zn, and Al) batteries. To tackle this problem, an effective method is to introduce metallophilic materials as hosts for metal anodes. Due to its high electrical conductivity, ease of assembly, and large compositional space, MXene is an excellent choice for anode host materials. However, how do MXenes’ compositions influence their metallophilicity to different kinds of metals, and how do we find MXenes with the strongest metallophilicity to different kinds of metals? To answer these questions, a density functional theory (DFT) based high-throughput automated workflow (HTAW) is designed and a machine learning (ML) study is performed focusing on the metallophilicity of ordered five-atomic-layer MXenes. For the first time, the metallophilicity of ordered five-atomic-layer MXenes from their entire compositional space to a total of eight kinds of metal anodes is studied. The metallophilicity of ∼10 % of the compositional space is investigated by the HTAW and serves as the dataset for ML study, and the remaining ∼90 % is predicted by the trained ML model. Based on the predictions, a ‘cooperation with neighbor’ mechanism governing MXenes’ metallophilicity is summarized, MXenes with the strongest metallophilicity to the eight kinds of metals are discovered, and the already synthesized -O terminated Cr2TiC2 is found to be a member of them, which represents a readily available subject for further experimental verifications and practical applications.

Dispersity and Mechanical Strength Ni-TiO2 Composites Electrodeposited Via Supercritical CO2 Emulsified Electrolyte

Electrodeposition of metal matrix composites (MMCs) is an effective method to enhance physical and chemical properties of materials by allowing dispersion of nanoparticles into the metal matrix. Various kinds of metals including Au, Cu and Ni have been reported as the metal-matrix depending on their target application. In co-electrodeposition with nanoparticles, uneven distribution of the nanoparticles in the metal matrix caused by aggregation of nanoparticles in the electrolyte would lead to an unevenly local enhancement of the desired property. Therefore, in co-electrodeposition of MMCs, controlling the dispersity, such as the size and space distribution, of the particles in the metal matrix is always a research topic of interest. Supercritical carbon dioxide (SC-CO2) is a state of CO2 exists when the temperature and pressure are above its critical point. SC-CO2 has low surface tension and low viscosity, which are advantageous in co-electrodeposition of metal matrix composite. Dispersed phases in the SC-CO2 emulsified electrolyte would improve transfer of materials in the electrolyte and expect to influence incorporation amount and distribution of suspension particles in the electrolyte then eventually affect the dispersity in the electrodeposited metal matrix. In this study, Ni-TiO2 composite coatings are electrodeposited with SC-CO2 emulsified electrolyte. The effects of SC-CO2 emulsion on the amount and distribution of TiO2 particles incorporated in the Ni matrix, and the mechanical property of the Ni-TiO2 composite coatings are evaluated for applications in miniaturized electronics.Ni-TiO2 composite coatings are deposited on cold-worked Cu plates with 3.5 cm2 in surface area through a two-electrode deposition cell. Ni plates are used as counter electrode. Ni Watts bath-based electrolyte, which composed of NiSO4‧6H2O, NiCl2‧6H2O, and H3BO3, with and without addition of 30 g/L TiO2 nanoparticles are used for the electrodeposition process. Since SC-CO2 molecules are non-polar, 0.2 g/L of sodium dodecyl sulfate (SDS) is added to emulsify SC-CO2 with the Ni electrolyte. Pure Ni and Ni-TiO2 composite coatings fabricated from conventional electrodeposition method without addition of SC-CO2 are prepared as comparisons. Pure Ni coatings are named as Ni-S-# (# represents the concentration of SDS in electrolyte) and the Ni-TiO2 composite coatings prepared by conventional method are named as CV-S-#. For the composite coatings prepared from the SC-CO2 emulsified electrolyte, the samples are designated as SC-S-#. For all electrodeposition processes, the temperature is maintained at 50 °C, the deposition time is 40 min, and the applied current density is 30 mA/cm2. Conventional electrodeposition of pure Ni and Ni-TiO2 composite are conducted under ambient pressure, and 15 MPa is used for the electrodeposition with SC-CO2. Volume fraction of SC-CO2 in the reaction cell is 20 vol.%. Surface morphologies of the as-deposited films are observed with a scanning electron microscope. The element composition are characterized by energy dispersive X-ray spectrometry (EDS). The crystalline structure annd grain size are measured by X-ray diffraction spectrometer (XRD). Local density of TiO2 particles in Ni matrix are quantified by a python-based convolution process from Ti EDS mapping datasets. The Ti local density data is revisualized as heatmap and its coefficient of variation is calculated to evaluate the dispersity of TiO2 in composite coatings. Hardness of the films is evaluated by Vickers hardness measurement.TiO2 content and Vickers hardness of Ni-TiO2 composite coatings fabricated with representative electrodeposition conditions are shown in Fig. 1. Benefit from the accelerated mass transfer in SC-CO2 emulsified electrolyte, a significant increase of TiO2 incorporation amount could be found between SC-S-02 and CV-S-02. As a result of grain refinement and high incorporation amount of TiO2 in Ni-TiO2 composite coatings, the Vickers hardness of SC-S-02 is found at about 1150HV, which is threefold of the hardness of CV-S-02. Rest parts of the data, including the influence of SC-CO2 on surface morphology of Ni-TiO2 composite coatings and grain refinement of Ni matrix, and the effect of SC-CO2 on the improvement of dispersity of TiO2 particles incorporated in Ni matrix, will be presented in the ECS meeting. Figure 1

(Invited) Metal Nanoparticles Modified Nitrogen Containing Carbon Film Electrodes for Chemical Sensing

Electrocatalytic performance of metal nanoparticles (NPs) has been studied to apply for electrochemical devices such as fuel cells and electrochemical sensors. We have developed metal NPs embedded carbon film electrodes by co-sputtering of metal and carbon [1]. Various kinds of metals including Pt, Pd, Au, Ni, Cu and their alloys can be fabricated in the carbon film by using unbalanced magnetron (UBM) sputtering and applied for detecting hydrogen peroxide, glucose [1], heavy metals [2,3] and sugar markers [4, 5]. The electrocatalytic activity of metal NPs can be modulated by changing electronegativity of substrate such as carbon electrodes. Here, we proposed Ni NPs electrodeposited on nitrogen containing carbon film electrodes. Method The carbon films were prepared by unbalanced magnetron sputtering equipment and then treated by N2 plasma. The surface of the films were characterized by XPS. Then NiNP was electrodeposited onto both plasma treated and untreated carbon films by changing the deposition potentials. The fabricated electrodes were potential cycled to sufficiently form surface Ni(OH)2 on the surface of NiNPs, then applied for measuring sugar oxidation such as glucose and oligosaccharide in alkaline solutions with different pH. Results and Discussion The nitrogen containing carbon film electrode show unique electrochemical performances including reduction of overpotentials for oxygen reduction and oxidation of some biochemicals such as NADH and L-ascorbic acid [6]. The films also show excellent biocompatibility to suppress the fouling of proteins during electrochemical measurements [7]. When we deposited NiNPs onto the nitrogen containing carbon film, the size of NiNPs became smaller by decreasing potential from -1000 to -1300 mV. Since the size of NiNPs at N2 plasma treated surface is larger than that at pure carbon film, we adjusted the potential to obtain similar NiNPs size on both N2 plasma treated and untreated carbon surfaces. After deposition, both electrodes were potential cycled between 0 and 0.70 V (vs Ag/AgCl) to form surface Ni(OH)2 , which is confirmed by HR-TEM, and HAADF-STEM-EDS images. The redox reaction peaks of Ni(OH)2 oxidation and NiOOH reduction is almost identical when the scan rate is slow (1 mV/s). However, the oxidation and reduction peaks shifted positive and negative directions, respectively at Ni(OH)2 modified untreated carbon film with increasing potential scan rate up to 100 mV/s. In contrast, peak separation increase at Ni(OH)2 modified N2 plasma treated carbon film is greatly suppressed suggesting fast redox reaction similar to at Ni(OH)2. We applied both NiNPs deposited plasma treated and untreated carbon film electrodes for electrocatalytic oxidation of glucose and maltopentaose (G5) in alkaline media. Higher electrocatalytic oxidation currents of glucose was observed at NiNPs on nitrogen containing carbon film compared with those at NiNPs on untreated carbon film particularly in higher glucose concentration region (> 1mM). Moreover, the electrocatalytic current was started to increase sharply at +0.28 V at the Ni@Ni(OH)2-NP/N-C, while that at Ni@Ni(OH)2-NP/C was started to increased gradually at +0.34 V. These results could be due to the slightly formed NiOOH at the low potential region which cannot be detected as current change.And 60 mV potential difference could be interpreted as electrostatic interaction between G5 and electrode surface.In conclusion, the electrocatalytic activity of NiNPs can be enhanced by modifying NiNPs on the N2 plasma treated carbon films, which shows enhanced current and lower onset potential for electrocatalytically oxidation of G5.

Heavy Metals Toxicity and the Environment Protection

Pollution of environment is one of the most horrible ecological crisis to which we are subjected today. One of the main sources of pollution in the environments is metallic compounds. Metals and metalloids have long been mined and used in numerous applications. This has led to a significant increase of metal pollutions. Metals can accumulate in all environmental matrices at either high or trace levels of concentration. Heavy metals are naturally occurring elements that have a high atomic weight and a density. Therefore amount of various kinds of metals are present in soil, plants, air, lakes, animals, oceanic regions, even in foodstuffs and human beings. Their widespread distribution, especially heavy metals, became serious problems because of their toxicities for animals, human health and the environment. Their toxicity of heavy metals depends on several factors including the dose, route of exposure and chemical species, as well as the age, gender, genetics and nutritional status of exposed individuals. Because of their high degree of toxicity, lead, cadmium, chromium, zinc, nickel, arsenic and mercury rank among the priority metals that are of public health significance. Metals generally enter in the ecosystem in a relatively non-toxic form and generally become intrinsic components of the environment in such a way that it is difficult to remove them from the environment. Some of them are converted into toxic forms through the environmental reactions involving various micro-organisms and non-biological pathways. For example, methylated compounds like dimethyl mercury, (CH3)2Hg, are more toxic than their inorganic forms. In the present investigation more attention has been given to heavy metals like lead, cadmium, nickel and zinc. Although, the term “heavy metals” refer to any metallic element that has a relatively high density and is toxic or poisonous at low concentrations. Examples of heavy metals include Pb, Cd, Hg, As, Cr and Ti etc. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure and molecular mechanisms of toxicity, genotoxicity and carcinogenicity.

(Invited) Metal Nanoparticles Modified Carbon Film Electrodes for Chemical Sensing

Electrocatalytic performance of metal nanoparticles (NPs) has been studied to apply for electrochemical devices such as fuel cells and electrochemical sensors. We have developed metal NPs embedded carbon film electrodes by co-sputtering of metal and carbon [1]. Various kinds of metals including Pt, Pd, Au, Ni, Cu and their alloys can be fabricated in the carbon film by using unbalanced magnetron (UBM) sputtering and applied for detecting hydrogen peroxide, glucose [1], heavy metals [2,3] and sugar markers [4, 5]. The electrocatalytic activity of metal NPs can be modulated by changing electronegativity of neighbor materials. Here, we proposed two electrode structures to modulate the electrocatalytic activity of metal NPs by forming metal NPs on hybrid carbon film electrodes, The electrodes were then applied applied for detecting small organic molecules such as alcohols and sugars.The first electrode structure is Ni(OH)2 NPs electrodeposited on the surface of nitrogen terminated carbon film electrodes. The carbon film was formed by UBM sputtering and the surface was treated by N2 plasma. After treatment, the NiNPs were electrodeposited by applying negative potential(Fig.1 left figure of Electrode Fabrication). The size of NiNPs became smaller by decreasing potential from -1000 to -1300 mV. By taking account of this property, we adjusted the potential to obtain similar NiNPs size on both N2 plasma treated and untreated carbon surfaces. After deposition, the potentials of both electrodes were cycled between 0 and 0.70 V (vs Ag/AgCl) to form surface Ni(OH)2. The redox reaction peaks of Ni(OH)2 oxidation and NiOOH reduction shifted positive and negative directions, respectively at Ni(OH)2 modified untreated carbon film(Fig.1 centor figure of Electrode Fabrication). with increasing potential scan rate. In contrast , peak separation increase at Ni(OH)2 modified N2 plasma treated carbon film is greatly decreased suggesting fast redox reaction. We applied both electrodes for electrocatalytic oxidation of glucose in alkaline media(Fig.1 left of Applications). The oxidation current of glucose at Ni(OH)2 modified N2 plasma treated carbon film electrode shows much larger current than that at Ni(OH)2 modified N2 untreated carbon film electrode. The current of former electrode continued to slightly increase when the glucose concentration is around 7 mM. In contrast, the current of latter electrode was saturated below 3 mM. The other structure we proposed was fabricated by electroplating the Ni onto PdNPs or AuNPs embedded carbon film electrodes. By using the overpotential difference between PdNPs and carbon surface, we successfully electrodeposited NiNPs selectively only on the embedded PdNPs, resulting Ni-Pd heterodimer structure on the electrode surface(Fig.1 right of Electrode Fabrication). The average size of deposited NiNPs onto PdNPs is smaller than that deposited on the pure carbon film electrode because the embedded PdNPs worked as growth core of NiNPs. We cycled the potential in strong alkaline solution to form Ni(OH)2 on the surface of NiNPs. The oxidation peak potential of Ni(OH)2 /Pd heterodimers, which corresponds to surface NiOOH formation reaction, slightly increases with increasing the scan rates from 1 mV/s to 100 mV/s. In contrast, the oxidation peak potential of Ni(OH)2 NP modified pure carbon film(Fig.1 center figure of Electrode Fabrication) shifted more positively (about 0.2 V) with increasing the scan rate, which suggests that the oxidation and reduction cycle of Ni(OH)2 /Pd heterodimer is much faster than that of Ni(OH)2 NP. Both electrodes were applied to electrochemically oxidize methanol. When the concentration of methanol is below 1M, the sensitivity of Ni(OH)2 NP modified carbon film electrode is relatively higher than that at Ni(OH)2 /Pd heterodimer modified carbon film electrode. However, the curent at Ni(OH)2 /Pd heterodimer modified electrodes was superior to that at Ni(OH)2 NP modified electrode when the methanol concentration was higher than 1 M (Fig.1 right figure of Applications). This could be due to the fast regeneration of catalytic sites (NiOOH) resulting in higher turnover rates for methanol oxidation reaction. The above behavior of Ni(OH)2 /Pd heterodimer modified carbon film electrode could be more suitable for energy device such as fuel cell electrode and Ni(OH)2 modified carbon film electrode is more suitable to detect alcohol sensing electrode.In conclusion, the electrocatalytic activity of NiNPs can be largely modulated by changing substrates, suggesting that the design of electrode surfaces are very important to realize high performance electrodes for chemical sensors.

Effect of TiN/TiO2 multilayer coatings on the properties of stainless steel for biomedical applications

A large number of research studies have been focused recently on possible methods for surface modification of metals and alloys. Titanium nitride (TiN) and titanium dioxide (TiO2) films deposited on different substrates have found many applications because of their good mechanical properties, resistance to corrosion, and biocompatibility. The substrates for coating can consist of various kinds of metals and alloys used for manufacturing implants, and endodontic or rotary dental instruments. In this study, stainless steel 304L substrates and endodontic files were coated by a DC-magnetron-sputtered TiN/TiO2 multilayer; the mechanical and biocompatible properties of the newly deposited films were explored.The structure of the coatings was examined by X-ray diffraction (XRD), whereas the hardness was investigated by nanoindentation. The corrosion resistance was evaluated by potentiodynamic polarization tests in Ringer solution. Each endodontic file coated with TiN/TiO2 was used for mechanical preparation of five root canals and, afterwards, their surface morphology was studied by scanning electron microscopy (SEM).Our results confirmed that the TiN/TiO2 multilayer coatings prepared had good stoichiometry and corrosion resistance. Moreover, the pre-coated instruments had a smoother surface and less debris and defects after mechanical preparation of five root canals compared to the non-coated ones. This indicated the usefulness of the coating formed in dental applications.

Biomass-Templated Fabrication of Metallic Materials for Photocatalytic and Bactericidal Applications.

In this paper, we report a simple, feasible and low-cost method to fabricate self-standing metallic materials using cellulose-based biomass as sacrificial templates. This process involves the impregnation of metallic precursors to the cellulose fibers of biomass templates and the transformation of the precursors to corresponding metals or metal oxides (as well as the removal of the cellulose framework) at an elevated temperature. The structures of the metallic materials as fabricated take the form of architectures of biomass templates (e.g., chromatography paper, medical absorbent cotton, catkins of reed, seed balls of oriental plane, and petals of peach blossom), and the various kinds of metals and metal oxides fabricated with these templates include silver, gold, anatase, cupric oxide, zinc oxide, etc. We have demonstrated photocatalytic and bactericidal applications of such metallic materials, and they should find more applications in electronics, catalysis, energy storage, biomedicine and so on.

Power electronics thermal solutions using thermally conductive polyimide films

Increased adoption of hybrid and electrical vehicles as well as renewable energy systems are driving the innovation in power module packaging. Thermal substrate, one of the major components of power modules, is not an exception, and technological advancements are necessary to meet increased reliability requirements. DuPont has developed a thermally conductive polymer film that provides very low thermal resistance and very high insulation. The film can be bonded to conductive and thick metallic layers and this polymer equivalent of DBC shows very high reliability in addition to high performance characteristics. Electrically insulating layers within a power electronics module are critical for separating circuitry from thermal management layers. Electrical insulating substrates typically used in power electronics modules utilize a ceramic layer, comprised most commonly of either Al2O3, AlN, or Si3N4. Thin Cu layers are bonded to either side of the substrate using a direct bond Cu (DBC) or active metal brazing (AMB) process. These processes involve bonding metallization layers to both sides of the ceramic at a high temperature as bonding to only one side would cause deformation during the cooling phase. Typical metal thickness bonded to either side of the ceramic is about 0.3–0.6 mm as the high temperature manufacturing process does not allow very thick metals to be bonded and this limits the heat spreading capability of the thermal substrate. DuPont's new Temprion™ Organic Direct Bond Copper (ODBC) address aforementioned problems, increasing thermal durability and reliability as well as enabling system layer suppression. Temprion™ ODBC's dielectric layer will absorb thermo-mechanical stress from the metals due to CTE mismatch, dramatically improving durability of the system. In addition, various kinds of metals including Cu and Al can be easily bonded to Temprion™ DB films through simple process. There are no thickness limitations on bonding metal sheets and metal attached at the bottom can be used as an integrated heat sink/baseplate. Al2O3 and Si3N4-based substrates were utilized as a baseline for reliability comparison with the DuPont substrates. The industry-standard substrates in used in this study have a thickness of 0.3 and 0.8 mm for the Cu metallization layers and 0.38 and 0.32 mm for the insulating layer respectively for Al2O3 an Si3N4 insulators. DuPont ODBC substrates were fabricated by attaching a polyimide layer to a layer of 0.8-mm-thick Cu. The polyimide and bottom Cu layer cross-sectional footprints are both 50.8 mm × 50.8 mm. The corners of both layers were filleted with various radii (0.5, 1.0, 2.0, and reversed 2.0 mm) to explore the impact of different stress concentrations between the metallization and insulating layers. The top Cu metallization was inset 2.0 mm from the perimeter of the electrically-insulating substrate and bottom Cu metallization.10 samples each of the DuPont ODBC and industry Al2O3 substrates were placed in a thermal shock chamber and cycled between temperature extremes of −40°C and 200°C. Substrates were inspected every 1000 cycles. After 5000 cycles, the ODBC substrates experienced no hipot failures, but preliminary edge delamination was visually observed. Al2O3 substrates all failed after 50 thermal cycles.Five DuPont ODBC samples were placed in a thermal chamber and subjected to an elevated temperature of 175°C. After 2000 hours, no hipot failures were observed, but edge delamination was again observed.Five DuPont ODBC samples were attached to a cold plate with Kapton tape. Heater cartridges were attached to the top of the substrates with Kapton tape and thermocouples were placed in several locations through the package. The heater cartridges were alternated between on and off states to allow for the substrates to cycle between −40°C and +200°C. While the change between the maximum and minimum temperatures is smaller for the power cycling test compared to the thermal cycling test, the heater cartridge and cold plate create a thermal gradient within the samples that is not possible with passive thermal cycling. After 2000 hrs cycles of testing, no hipot failures or edge delamination have been observed. Herein we show that the DuPont ODBC substrate design is a promising alternative to traditional industry substrates based on ceramic insulators. The reliability of the substrate design has been demonstrated under several thermomechanical accelerated tests and the electrical and thermal performance has been measured. Future work will include reliability comparisons to other industry substrates, including thermal shock testing of substrates with HPS, AlN, and Si3N4 ceramic layers. Thermal models will correlate thermal resistance values measured by the transient thermal tester and compare the ODBC substrate performance to industry substrates within a commercialized power electronics module. The modeling will also optimize the thickness of the metallization layers within the ODBC substrates to minimize the junction temperature of the switching devices.

Study of quench effect on heavy metal uptake efficiency by an aluminosilicate-based material

Quench is a widely used technique in organic synthesis or inorganic material treatment but only limited studies have been performed on aluminosilicate. In this work, the quench effect on the textural properties and surface functional groups has been studied by the functionalization of a waste-derived aluminosilicate material. The porous structure has been changed in the presence of a quench reagent. We consider that this difference originated due to the prevention of replacement of potassium atoms in surface ion-exchange sites by hydrogen atoms. Surface characterization including SEM, XPS and FTIR further confirmed the preservation of SiOK functional groups. Meanwhile, due to the differences between the electronegativities of potassium atoms and hydrogen atoms the ion-exchange ability for heavy metals of the quenched samples was significantly enhanced and this has been validated by adsorption experiments with various kinds of metals. The mass balance for leaching calcium and potassium atoms also revealed that the enhanced ion-exchange capacity was caused by the improved liberation of potassium and calcium atoms from the aluminosilicate network. Moreover, the leaching test for metal doped material shows a limited amount of metal leaching under acidic conditions, indicating the potential application of this material in industrial wastewater treatment or catalysis applications.

Effects of Alkali Metal Ions on H2O2 Reduction Current at Pt Electrodes

The hydrogen peroxide reduction reaction (HPRR) has attracted attention because it is involved in the oxygen reduction reaction, which is an important cathode reaction in several fuel cell systems. Thus, it has been widely studied, including effects of electrolyte components and additives on the HPRR at Pt electrodes. Katsounaros and Mayrhofer have reported the influence of the adsorption of (bi)sulfate and halide ions to the HPRR in acidic electrolytes [1]. The strength of the inhibition of the HPRR increases as the degree of the adsorption increases. They also reported [2] that alkali metal cations, e.g., Li+, Na+, and K+, suppress the HPRR in basic electrolytes. The hydrated alkali metal cations and chemisorbed OH species on Pt, denoted as M+(H2O) x and OHads respectively, non-covalently stabilize each other, leading to the formation of quasi-specifically adsorbed hydrated metal ion clusters, OHads-M+(H2O) x clusters, that blocks electrochemical reactions. The suppression becomes large as the strength of the non-covalent interaction increases (K+ < Na+ < Li+), and as a consequence the rest potential decreases in the following order: K+ < Na+ < Li+, as reproduced in Figure 1a. On the other hand, inorganic salts which are composed of the alkali metal cations, e.g., Na2SO4 and K2SO4, are often used as supporting electrolytes for electrochemical reactions. However, as we have reported before [3], the salts generally affect the hydrogen evolution reaction (HER) on various kinds of metals, namely, Pt, Au, Rh, Ag, Cu, Fe, Ni, W, Zn, Sn, and In, in strong acidic solutions. The rate of the HER decreased in the presence of the cations because the transport rate of H+ ions to the electrode surface due to electromigration decreased in the presence of the cations. Thus, the reduction current due to the HER decreased as the concentration of the salts increased. We have reported [4] that the HPRR in acidic electrolytes is also affected when the inorganic salts, Na2SO4 and K2SO4, are added to the electrolytes. The local pH at the electrode surface became basic during the HPRR because of the decrease in the transport rate of H+ in the presence of the alkali metal cations. Furthermore, we have tentatively suggested [5] that the HPRR in acidic electrolytes is affected by the non-covalent interaction between the cations and OHads. Then, in order to verify this, this work focuses on studying how the cations affect the HPRR. Although the rest potential is independent on the kind of alkali metal cations, the HPRR is suppressed due to the presence of the cations. The H2O2 reduction current decreases (in absolute value) in the following order: Li+ < Na+ < K+, as shown in Fig. 1b. This order is in the reverse order of the strength of the non-covalent interaction observed for basic electrolytes. Thus, the suppression cannot be explained on the basis of the non-covalent interaction but rather on the basis of the decrease in the transport rate of H+, which will be discussed in this work. REFERENCES [1] I. Katsounaros, W. B. Schneider, J. C. Meier, U. Benedikt, P. U. Biedermann, A. Cuesta, A. A. Auer and K. J. Mayrhofer, Physical Chemistry Chemical Physics, 15, 8058 (2013). [2] I. Katsounaros and K. J. J. Mayrhofer, Chem. Commun., 48, 6660-6662 (2012). [3] Y. Mukouyama, R. Nakazato, T. Shiono, S. Nakanishi and H. Okamoto, J. Electroanal. Chem., 713, 39 (2014). [4] Y. Mukouyama, H. Kawasaki, D. Hara, M. Kikuchi, Y. Yamada, S. Nakanishi, ECS Trans., 69 (39), 37-45 (2015). [5] Y. Mukouyama, D. Hara, H. Kawasaki, M. Kikuchi, Y. Yamada, S. Nakanishi, ECS Trans., 69 (39), 47-57 (2015). FIGURE CAPTION Figure 1. The current (I) – potential (E) curves for a Pt-plate electrode in basic and acidic solutions measured under potential controlled conditions at a scan rate of 0.01 Vs-1. The basic solutions are 0.05 M alkali hydroxide (denoted as MOH) + 0.01 M H2O2, and the acidic ones are 0.05 M H2SO4 + 0.01 M H2O2 with or without 0.05 M alkali sulfate (denoted as M2SO4). Figure 1

Toward rechargeable&amp;nbsp;lithium&amp;ndash;oxygen&amp;nbsp;batteries: recent advances

Toward rechargeable Li–O2 batteries: recent advances Nobuyuki Imanishi Department of Chemistry, Mie University, Tsu, Mie, Japan Abstract: This review summarizes research and development trends in lithium–oxygen (Li–O2) batteries. Development of a post–lithium-ion battery is highly expected to be a means to solve the global energy problem. The metal–oxygen cell, especially the Li–O2 cell, attracts attention, since it has much larger theoretical energy density than conventional battery systems. First, this review discusses the energy density that a battery should have from the viewpoint of power sources for electric vehicles. Then the fundamental features of various kinds of metal–oxygen batteries are explained and challenges faced by them are described. The remaining part of the review focuses on research subjects of the Li–O2 batteries. Early works which led to the present lithium–oxygen cells are briefly presented. Then, systems using various electrolytes and their major issues are introduced. First, irreversible decomposition of the electrolyte and Li2O2 deposition at oxygen cathode of an organic system are described. The effort that is directed toward the solution of dendritic growth of lithium metal anode is also introduced. Thereafter, new materials, mechanisms, and strategy that were reported recently are described with regard to each of the three electrolyte systems, respectively. These are expected to be breakthroughs to solve the serious problems, such as irreversible decomposition of electrolyte. In conclusion, the issues that should be solved with the direction of future development are mentioned.Keywords: energy density, lithium anode, dendrite, peroxide, superoxide

Electrodeposition and Behavior of Single Metal Nanowire Probes

This paper describes the fabrication of scanning probes with single metal nanowires (NWs) at the probe tip. The porous-template technique can produce NWs of various kinds of metals, with diameters down to 10-20 nm, which compete with multiwall carbon nanotube diameters. Metal NWs are grown by electrodeposition on the scanning probe tip. One NW can be selected to remain by focused ion beam technique. A variety of metals can be chosen as the tip material. Electric potentials of NWs at the probe tip can be measured. Single NW probes can measure surface topographies, electrode potentials, and their mechanical bending properties.

Application of Ultraprecision Microgrooves to Dental Implant and Blood Inspection

Ultraprecision micromachining technology is expected to be a potential tool of producing bio-related parts though it is a traditional one. The characteristic of the ultraprecision micromachining technology is the high possibility of selecting various kinds of metals and creating complicated shapes with high dimensional accuracy and surface quality. The study introduces two cases, dental implants and microchannel chips, by means of ultraprecision microgrooves as applications of ultraprecision micromachining technology. As seen from machined results, it is found that the ultraprecision microgrooving technology has the potential of producing a variety of bio-related parts as well as mechanical parts and optical elements.

Universal Preparation of Novel Metal and Semiconductor Nanoparticle–Glass Composites with Excellent Nonlinear Optical Properties

We report on a simple and universal method for fabricating various kinds of metal and semiconductor (Si, Ge, Bi, and Cu) nanoparticle–glass composites by using metallic Al as a reducing agent in the raw materials of the glass batches. By taking advantage of the redox equilibrium that sets up between the Al reducing agent and various oxides, crystal nuclei such as Si and Ge atom clusters are already formed during the melt-quenching stage. During the subsequent heat-treatment stage, the nanoparticles grow on the nuclei by a process of diffusion. The nanoparticle size can be controlled by heat-treatment temperature and holding time. The fabricated nanoparticle–glass composites exhibit large third-order optical nonlinearities (χ3 up to 10–8 esu) and an ultrafast response time (within picoseconds), which makes them possible to manufacture ultrafast all-optical switches.

Effects of Nickel on Eosinophil Survival

Background: Accessories, watches, coins and other items containing metal sometimes cause contact dermatitis and metal allergy. Among metals, nickel in alloys is ionized by sweat on the surface of the skin and exhibits particularly marked irritancy and allergenicity. Although eosinophils play important roles in allergy, the effects of nickel on eosinophils have not been elucidated. Methods: Eosinophils were prepared from the peritoneal cavity in rats immunized with Ascaris suum extract. Purified rat eosinophils were incubated in the presence of various kinds of metals including nickel. The viability of eosinophils was analyzed using a flow cytometer. Results: When rat eosinophils were incubated for 3 days in the presence of nickel chloride at 30–1,000 μM, the viability of eosinophils was decreased in a concentration-dependent manner. Nickel chloride at 300 μM significantly increased the percentage of annexin V⁺ PI^– eosinophils. The population of annexin V⁺ PI^– eosinophils was also increased by nickel sulfate, cobalt chloride and zinc sulfate. The binding of nickel ions to eosinophils was detected by flow cytometer. Conclusions: Nickel ions bind to eosinophils and decrease the viability of eosinophils through the induction of apoptosis. Nickel ions may exhibit activity which modifies the function of eosinophils in allergy.

Unique Mechanical Properties of Nanostructured Metals

Recently, it becomes possible to fabricate bulk metals having ultrafine grained or nanocrystalline structures of which grain size is in nano-meter dimensions. One of the promising ways to realize bulk nanostructured metals is severe plastic deformation (SPD) above logarithmic equivalent strain of 4. We have developed an original SPD process, named Accumulative Roll Bonding (ARB) using rolling deformation in principle, and have succeeded in fabricating bulk nanostructured sheets of various kinds of metals and alloys. The ARB process and the nanostructured metals fabricated by the ARB are introduced in this paper. The nanostructured metals sometimes perform quite unique mechanical properties, that is rather surprising compared with conventionally coarse grained materials. The unique properties seem to be attributed to the characteristic structures of the nano-metals full of grain boundaries.

Unique Mechanical Properties of Nanostructured Metals

Recently, it becomes possible to fabricate bulk metals having ultrafine grained or nanocrystalline structures of which grain size is in nano-meter dimensions. One of the promising ways to realize bulk nanostructured metals is severe plastic deformation (SPD) above logarithmic equivalent strain of 4. We have developed an original SPD process, named Accumulative Roll Bonding (ARB) using rolling deformation in principle, and have succeeded in fabricating bulk nanostructured sheets of various kinds of metals and alloys. The ARB process and the nanostructured metals fabricated by the ARB are introduced in this paper. The nanostructured metals sometimes perform quite unique mechanical properties, that is rather surprising compared with conventionally coarse grained materials. The unique properties seem to be attributed to the characteristic structures of the nano-metals full of grain boundaries.

Study of Metal Coating on Lead-Free High Refractive Index Glass Prepared from Local Sand

Lead-containing glasses coated with lead metal have been used for decoration in Thailand for a long time, were a high refractive index glass. Due to harmful effects of lead, time degradation of glass and because of many kinds of local raw materials for glass production especially sand, colorless lead-free high refractive index glasses were prepared by using local raw materials. In this work, the various kinds of metals; silver and aluminum, were coated on the surface of the prepared glasses using both chemical and physical methods. The joining interfacial layer between the glass body and the coated layer was studied using a scanning electron microscope and the hardness of the coated glasses was measured by a microhardness tester to compare with those of lead coating. It was found that the structures between the joining interfacial layers were similar. The values of the Knoop hardness were approximately 520±20 kg/mm2. This glass can be used to replace the lead glass for restoration glass or decoration onto the surface of the new wood or the metal carving products.

Fabrication of metal nanodot arrays using a porous alumina membrane as a template

Thin nanodotstructured metal films and heterostructured nanodot arrays (metal nanodot arrays/Si) with a high density and uniform distribution for various kinds of metals (Au, Al, Ag, Pb, Cu, Sn, and Zn) were fabricated by thermal vacuum evaporation using an anodic porous alumina membrane as a template. However, for such metals as Sn, Zn, and Pb with relatively lower melting point as compared with Al it was found that heterostructured nanodot arrays were not formed by a single stage of evaporation. For these metals, we developed a new method termed “two step evaporation method”. The size and the arrays of dots were depended on the pore structure in the anodic porous alumina template. The technique demonstrated in this report is simple and suitable for the preparation of nanodot arrays in the large area for materials which could be vacuum evaporated.