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Lithium-ion batteries (LIBs) are one of the most promising energy storing devices, offering high volumetric and gravimetric energy density compared with other battery technologies [1]. However, LIBs are suffering from safety issues due to the poor chemical stability and the flammability of organic liquid electrolytes. Solid state electrolytes are expected to solve such safety issues. Since the initial study by Murugan et al. in 2007, Li7La3Zr2O12 (LLZO) garnet has received much attention due to its high ionic conductivity (10-3 to 10-4 S cm-1) and stability against Li metal. [2-3]. LLZO is crystallized in both cubic (space group Ia-3d) and tetragonal (space group I41/acd) form. The ionic conductivity of cubic phase is two order magnitudes higher than that of tetragonal phase [3]. However, it is difficult to obtain the cubic phase LLZO because the cubic phase is not stable at room temperature and can be obtained at high sintering temperature (>1200 °C). Therefore, super-valent cation doping, such as Al3+ and Ga3+, is introduced in order to increase the number of vacancies and results in the enhancement of stability of the high conductivity cubic phase at room temperature. Ga3+ is one of the most promising candidates due to its high ionic conductivity. Both grain size and density are important factors in determining the ionic conductivity, but the relationship is not clear in Ga-doped LLZO. In this study, we investigated the correlation between grain size and ionic conductivity in order to understand how to improve the ionic conductivity of Ga-doped LLZO. The grain size of Ga-doped LLZO has been controlled by changing the sintering temperature (1000 °C and 1150 °C for 8 h) and employing the two-step sintering method (1150 °C for 5 min-1000 °C for 8 h). We synthesized the Ga3+-doped LLZO (Li6.1Ga0.3La3Zr2O12) from LiOHH2O, La2O3, ZrO2, and Ga2O3. The 15 wt% excess of LiOHH2O was used to compensate the lithium loss during high temperature sintering. The powders were ball-milled in isopropyl alcohol for 12 h at a milling speed of 250 rpm/min and dried for 12 h. The well-ground powder was calcined at 600 °C for 6 h in alumina crucible and then reground, pelletized, and sintered at temperatures for 8 h covered with mother powders to prevent Li loss during sintering. Li+ evaporation typically leads to the pyrochlore La2Zr2O7 phase formation. The relative density of the pellets was obtained as 93.2, 93.4, and 94.5% for 1000 °C sintered LLZO (Ga-LLZO-1000), 1150 °C sintered LLZO (Ga-LLZO-1150), and two-step sintered LLZO (Ga-LLZO-TS), respectively. The total ionic conductivity of Ga-LLZO-1150 was much higher (1.22 x 10-3 S cm-1) than that of Ga-LLZO-1000 (3.05 x 10-4 S cm-1) although the relative density of both samples was similar. The grain coarsening was observed in Ga-LLZO-1150 with size of >200 µm whereas the grain size of Ga-LLZO-1000 was -4 S cm-1) than Ga-LLZO-1150 (Fig. 1b). In general, the increase of density leads to the higher ionic conductivity of materials because higher density provides more pathways for lithium ions transport across the material. For comparison, the ionic conductivity and the density of undoped and Al-doped LLZO were also measured, and the ionic conductivity of both samples increased with increasing the density or sintering temperature. However, this was not true in Ga-doped LLZO. The conductivity of the specimen with higher density and smaller grain size was lower than that of lower density with larger grain size. Both bulk and grain boundary contribute to the total ionic conductivity. The total ionic conductivity (σt otal) is calculated according to σt otal = d/(A x Rtotal), where d is the pellet thickness, A is the area of the electrode and Rtotal represents the total resistance of the pellet which is the sum of Rbulk and Rgrain boundary. Ga-LLZO-1150 with large grain size has the higher ionic conductivity because the larger grain size leads to an enhancement in the ratio of grain/grain boundaries, resulting the improvement of the total ionic conductivity by reducing the grain boundary resistance. The ionic conductivity of Ga-doped LLZO was more affected by the grain size than the density. Reference [1] J.-M. Tarascon, M. Armand, Nature 414 (2001) 359–367. [2] R. Murugan et al., Angew. Chem. (2007) 119, 7925. [3] H. Buschmann et al., Phys. Chem. Chem. Phys. 13 (2011) 19378–19392. Figure 1

Red-emitting (SrxCa1−x)AlSiN3:Eu2+ (SCASN:Eu2+) phosphors were successfully prepared by spark plasma sintering (SPS) at a relatively low temperature of 1700°C in vacuum (200 mtorr). The synthesized phosphors showed a broad absorption band from near UV to yellow region (300 ~ 600 nm) and exhibited a single broad emission band centered at 626 ~ 653 nm under the excitation of 450 nm. The effects of Sr occupancy and Eu doping concentration on the photoluminescence (PL) properties of SCASN:Eu2+ phosphors were examined. In addition, the temperature dependence of the PL intensity and the emission characteristics of white light-emitting InGaN-based β-sialon:Eu2+/SCASN:Eu2+ LED were compared with those of commercial YAG:Ce3+ phosphor and InGaN-based YAG:Ce3+ LED, respectively.

The need for high performance electrochemical energy storage devices has increased due to the fast development of portable electronics and electric vehicles. For decades, lithium ion batteries (LIBs) have been considered as one of the most attractive examples in many electric applications, because of their high energy density and good power performance. However, its limited resource restricts the application of LIBs for large-scale energy storage systems. Among many other candidates, sodium ion batteries (SIBs) have been demonstrated as a promising alternative for its high abundance in earth crust and sea water. In recent years, there were numerous attempts to find new anode materials for high performance SIBs, including carbonaceous materials, metal oxides, phosphides, and alloy-based materials. Transition metal sulfides have received much interests as promising SIB anode materials because of their high theoretical capacity and good electrical conductivity. Numerous researches have been reported about iron sulfide, cobalt sulfide, and many others with good electrochemical properties. Among them, nickel sulfides have great advantages such as high theoretical capacity, low cost, and environmental friendliness. Especially, nickel disulfide (NiS2) delivers a theoretical capacity of 873 mAh/g, according to conversion reaction (NiS2 + 4Na = Ni + 2Na2S). However, like other conversion-type transition metal sulfides, NiS2 suffers from large volume changes which cause structural pulverization problem. To overcome this hindrance, synthesizing the composite with carbon or forming 3D network has been generally adopted. Such modifications help the active material to buffer volume changes and ensure its structural integrity. Herein, we report the electrochemical properties of NiS2 nanospheres synthesized by hydrothermal process as an anode for SIB. Compared to micro sized particles, nanospheres have superior rate capability due to shorter Na ion and electron diffusion path during the electrochemical process by offering large contact areas between electrode and electrolyte. Also, it is well known that nanoscale particles prevent the accumulation of internal stresses during volume changes. Therefore, they show the improved cyclability by additional inhibition of crack formation within the particles. NiS2 powders were synthesized via a simple hydrothermal method. Ni nitrate hexahydrate (Ni(NO)36H2O) and L-cysteine (C3H7NO2S) were used for nickel and sulfur source respectively. First, they were dispersed in DI water and hexadecyltrimethylammonium bromide (CTAB, C19H42BrN) was added as surfactant. Then the mixture solution was transferred to stainless steel autoclaves and maintained at 160 °C for 12 h. After they were cooled to room temperature, the mixture was filtrated and the separated black precipitate was dried at 50 °C under vacuum. The resulting powder was confirmed to be NiS2 by XRD with particle size of ~120 nm. The first discharge and charge curves are shown in Fig. 1. The first discharge capacity achieved was 837 mAh/g, which is 96 % of the theoretical value. The first charge capacity was 696 mAh/g, corresponding to the coulombic efficiency of 83%. Based on these results, we tried various methods such as carbon coating, to improve electrochemical properties of NiS2 nanospheres. Figure 1

Lithium ion batteries (LIBs) has been the main energy storage medium for portable electronics since the commercialization by Sony Corporation since 1991. Ever growing demand for large-scale energy storage devices such as electrical vehicles requires the high energy density and long cycle life LIBs that could not be attained by the currently used battery. Graphite is the most common anode material in commercial LIBs, but its specific capacity is relatively low (372 mAh g-1) with a poor rate capability, which does not meet the high demand for large-scale applications. Silicon (Si) is one of the most promising anode candidates due to its high theoretical specific capacity (3579 mAh g-1 for Li15Si4), relatively low discharge potential (~0.4V vs Li+/Li), and abundance in nature. However, Si goes through a dramatic volume change during cycling and thus undergoes a drastic structural deformation, which induces loss of electrical contact between Si and current collector, breakdown of solid electrolyte interphase (SEI) layer, and Si aggregation during cycling, eventually resulting in failure of cyclic performance. Although design a various nanostructure forms or introduction of secondary phase layers has been realized as a method to achieve high-performance Si anode, these methods require complex reactions such as hydrothermal or template-assisted synthesis and usually involve hazardous reagents like SiH4 or HF, which eventually result in cost and barrier to scale up. From the practical view, use of commercial Si is the most promising, where the commercial production of Si has been benefitted from the development in semi-conductor industry. Conventionally, battery is prepared by mixing active materials and binder with conducting agent in organic solvent to produce viscous slurry and blading onto copper current collector. Recently, the selection of binder has turned out to play critical role in the battery performance as maintaining the structural integrity of electrode film. It has been revealed that carboxylic acid or hydroxyl functional groups terminated binders which is commercially available, such as polyacrylic acid (PAA), carboxymethyl cellulose (CMC or Na-CMC) or alginate (Alg or Na-Alg) binder, can result in enhanced cycling performance utilizing the hydrogen bonding interactions with the native oxide on Si, compared to that of conventional PVDF binder which has no functional group and bonds weekly with Si through a week Van der Waals interaction. Nonetheless, due to the linear chain characteristic of these binders, susceptible sliding upon the continual volume change of Si results in the contact loss between binder and Si, which eventually results in the irreversible capacity failure. Herein, we propose a novel concept that can achieve stable Si anode by transitioning the bonding nature between binder and Si from hydrogen bond to mechanically robust covalent bond, which can effectively restrain any large movement of Si, and eventually prevent the destruction of the electrical network during cycling. Inducing the esterification reaction between binder and Si can be an efficient method to form a covalent bond between those two materials. (eq. (1)) R-COOH+HO-R’ -> R-COO-R’+ H2O -------- (1) To induce an esterification reaction between binder and Si, three crucial points have to be addressed. First, as carboxylate (–COO-) functional group terminated binder such as Na-CMC can hardly react with the hydroxyl functional group (-OH), PAA binder which is terminated with the carboxylic acid functional group (-COOH) has been selected in our system. Second, while commercially purchased Si has a –OH functional group by a partially hydrolyzed SiO2 layer covering the Si particles, its functional group density is insufficient for an esterification reaction to take place. Therefore, terminating –OH functional group at the surface of Si is crucial factor to increase the site to react with PAA binder. Third, due to kinetically sluggish characteristic of esterification reaction, proper usage of esterification catalyst is required. Experimental procedure is as follows; firstly, as-received Si was pretreated in piranha solution to terminate –OH. Then, –OH terminated Si was prepared into slurry by mixing with Super-P and PAA binder, casted onto copper foil, dried overnight and punched for a coin-type cell. To induce the esterification reaction, punched cell was dipped into sodium hypophosphite catalyst solution and then annealed in 180 °C for 1 h. Three counter groups are denoted as HB-Cell (punched cell with no annealing process), PE-Cell (annealed cell without usage of sodium hypophosphite), and FE-Cell (annealed cell with addition of sodium hypophosphite.) The fabricated FE-Cell exhibits superior cycle stability (2200 mAh g-1 at 100 cycles) compare to HB-Cell or PE-Cell, demonstrating the effect of covalent bond on obtaining the high-performance Si anode. Figure 1

Y(P,V)O4:Eu phosphor prepared by liquid phase precursor(LPP) method was modified by planetary ball milling and nano-sized powder with spherical shape was successfully obtained. A post-annealing was conducted at 1100 ° for 1 h to enhance the crystallinity and photoluminescence property.

Mg and its alloys have attracted an extensive attention in the field of structural materials such as automobile components, aerospace components, and computer parts due to high strength/weight ratio, good electromagnetic shielding, high thermal conductivity and good recycling ability (1). Furthermore, the use of magnesium alloys with a low density in the automotive industry is predicted to be continuously expanded because of the demands for reducing environmental burden and improving energy efficiency (2). However, magnesium and its alloys are extremely susceptible to corrosion resulting in decreased mechanical stability and surface contamination, so this point greatly restricts their applications (3). To enhance the poor corrosion resistance, various physical and chemical surface treatments have been performed. Among the various techniques, chemical-conversion coating is widely used, but conventional conversion coatings are gradually restricted because it is based on chromium compounds that have been shown to be highly toxic carcinogens (1,4). Thus, micro-arc oxidation (MAO), which is an environmental friendly process and is capable of protecting the magnesium alloys from corrosion and wear condition, has been attracting a renewed interest over the last few years(5). The extensive researches have been carried out in evaluating the effect of electrolyte composition and applied potential on the properties of MAO films. However, the effect of electrolyte compositions on the corrosion behavior of MAO films has not yet been discussed in detail. Thus, the aim of this work is to develop a proper MAO films on AZ91D magnesium alloy in various electrolyte solution. Corrosion behavior of these oxide films was evaluated in terms of electrolyte composition and concentration, and we examine relation between electrolyte condition and corrosion behavior. In this study, the protective oxide coatings were formed on AZ91D magnesium alloys by micro-arc oxidation (MAO) in several aluminate electrolytes containing potassium hydroxide, potassium fluoride, and sodium hydroxide. MAO was conducted in the range of current density between 13 – 21 A/dm using a pulse power supply for 10 – 60 min. The corrosion resistance of MAO films was performed by EG&G potentiostat/galvanostat model 273 with model 352 corrosion software in 3.5 % NaCl solution at pH 7.0. The crystalline MgO and MgAl2O4 spinel phases along with amorphous phase were detected by XRD (Fig. 1). With increase of electrolyte concentrations, the content of crystalline MgO and MgAl2O4 phases decreased and coating layers became more porous (Fig. 2). While using a less conductive electrolyte raises the breakdown voltage, it also increases the arc duration. In addition, all MAO specimens exhibited superior corrosion resistance compared to untreated AZ91D. The results indicate that the phase, morphology, thickness, and corrosion resistance of MAO films were found to be strongly dependent on electrolyte concentration and surface current density. Surprisingly, MAO films composed of amorphous phase showed much better corrosion resistance than MAO films with crystalline MgO and MgAl2O4 (Fig. 3).

SnO2 porous structure was fabricated by anodic oxidation. The Sn coated SiO2/Si wafer was used as an anode and it was anodized in 0.3 M oxalic acid aqueous solution using DC power supply. The phase of formed oxide was rutile and the morphology showed a nano porous structure. The porous SnO2 with nano-channel was obtained at 6V in 0.3 M oxalic acid and the pore diameter was approximately 20 nm. A post annealing was performed at 500 ° for 3 h to enhance the crystallinity. To evaluate the gas sensing properties, a comb like Pt pattern was deposited on the anodized and annealed specimen and its gas sensing properties were measured as a function of gas concentration and working temperature

During the last decades, rare-earth (RE) ion-doped phosphors have received much attention due to their high luminescent properties. For this reason, many studies have been focused on new composition of phosphor with high luminescent properties. Eu3+ doped SrLu2O4, which is a new composition phosphor, has been reported to describe the luminescent properties. Upon excitation with ultraviolet (UV) regions, Eu3+ doped SrLu2O4 phosphor exhibited narrow red emissions due to the 4f-4f transition of Eu3+ ions. Eu3+ ions only can be excited with UV regions and the property of narrow red emission has a limitation to apply for lighting devices such as white light-emitting diodes (WLEDs) due to a low color rendering index (CRI). In this study, we synthesize the Eu2+ doped SrLu2O4 red phosphors with solid-state reaction and characterize the luminescent properties for the first time. For the synthesis of SrLu2O4 at stoichiometric condition, it is hard to synthesize the pure SrLu2O4 phase, because formation of a second phase Lu2O3 were consistently unable to avoid. The pure phase of SrLu2O4 was formed at certain ratio of starting materials and annealing temperature conditions. The mixtures were annealed at various temperatures (1400–1600 °C) for 3 hours under 5% H2/N2 atmosphere in order to reduce Eu3+ to Eu2+. Upon excitation with 450 nm, the synthesized SrLu2O4:Eu2+ phosphors exhibited a strong red emission centered at 610 nm due to the 4f-5d transition of Eu2+ ions (Figure 1). SrLu2O4:Eu2+ phosphors showed highest PL intensity at very low europium doping level, which intensity value was 85% of commercial (Sr,Ca)AlSiN3:Eu2+ (SCASN). In addition, SrLu2O4:Eu2+ phosphors also showed a strong thermal quenching property, which indicated that PL intensity measured at 200 oC was reduced to almost zero per cent of the initial value (25 oC). These high value of PL intensity and strong thermal quenching property can be used as a high potential optical temperature sensor application. Figure 1

Owing to the fast development of portable electronics and electric vehicles, the need for electrochemical energy storage has increased. Among various electrochemical energy storage devices, lithium ion batteries (LIBs) have been demonstrated as one of the most successful examples in many electric applications. Because of their distinguished features, LIBs have high energy density and good power performance. However, due to its limited resource, its price will grow high if LIBs are progressively used. In this regard, sodium ion batteries (SIBs) have been considered as a promising alternative due to its abundance source in earth crust. Due to its similar insertion chemistry, sodium can directly transform well-established electrode materials in LIBs to SIBs. Unlimited efforts have been devoted to find new anode materials for high performance SIBs, including carbonaceous materials, metal oxides and sulfides, and alloy-based materials. Recently, elemental phosphorus P has been found to be electrochemically active for sodium ion battery anode, forming sodium phosphide (Na3P). It gives a high theoretical specific capacity of 2,597 mAh/g. But, its electrochemical performance is unsatisfactory because phosphorus has a very low electrical conductivity (~10-14 S/cm) and suffer from structural pulverization problem caused by its large volume change. To overcome this problem, Sn4P3 material has been reported as a promising anode for SIBs. It has been recently reported that Sn4P3 showed a synergistic Na-storage reaction where Sn and P atoms can react with Na to form Na15Sn4 and Na3P, and that the resulting Na15Sn4 alloy acts as a conducting pathway to activate the reversible Na-storage reaction of low electrical conductive Na3P particles. Also, Sn4P3 anode material exhibits a high reversible capacity of 1,230 mAh/g. The architecture of a stable and robust protective layer on the metallic Sn anode is critically important to ensure the good electrochemical performance of SIBs. Up to now, most of SIBs anodes consisting of elemental P and Sn alloys are generally produced by ball milling, thus the morphology has not been controlled. Ball milling method have been widely used as SnxPy electrodes because their phases can be easily controlled in laboratory scale synthesis. However, ball milling method for SnxPy is usually hard to control the morphology and produce nano scale, which leads to the deterioration of an active material resulting in capacity decay by several cycles. Therefore, hydrothermal method has received significant attention because it can control the nanoscale morphology for improved electrochemical performance. Herein, we report the porous Sn4P3-C nano spheres synthesized by hydrothermal process as an anode for SIB with an ultra-long term cycle stability and a high capacity. First, SnO2 nano spheres was synthesized by hydrothermal method with glucose precursor. Glucose not only prevents the rapid precipitation of colloidal SnO2 nano spheres but also serves as a carbon precursor for SnO2-C nano spheres. Consecutively, reduction process from SnO2 to Sn was conducted. The SnO2 redox process under hydrogen atmosphere has a significant problem. The reduction of SnO2 at 600 °C generates a liquid metallic tin, which aggregates into Sn particles. To prevent this problem, we employed a thick carbon layer coating to prevent the aggregation. Finally, phosphorization process was carried out using solvothermal method. Compared with other methods, the solvothermal route is convenient, simple, mild, and the morphology can also be controlled. With suitable temperature and time, Sn nano spheres were chemically transformed into Sn4P3 nano spheres, resulting in porous Sn4P3-C nano spheres. The synthesized porous Sn4P3-C nano sphere electrode exhibited an ultra-long cycle stability (about 2,000 cycles at 2,000 mAh/g) and high reversible capacity (700 mAh/g after 100 cycles at 200 mA/g) (Fig. 1). And its original morphology is apparently retained and the characteristic sphere geometry was unchanged after cycling test. We suggest the design strategy for the next-generation SIBs, and it can be applied to other phosphorus-metal alloying composites. Figure 1

Having high energy densities, lithium ion rechargeable batteries are widely used for energy storage and still are the subject of intensive investigation. As anode materials, tin-based materials have long been considered as a promising candidate due to their twice larger theoretical specific capacity compared to commercially used graphite carbon material. Another anode candidates with extremely high electrochemical performances have been developed steadily resulting from intensive researches, but the interests on tin-based anode materials recently have been increased again since they also show great performance as an anode for next-generation sodium-ion batteries. Most of the various tin-based materials researched for high energy battery anodes can be subdivided into two groups, pure tin (Sn) metal based and tin oxide (SnOx) based compounds. Both anode materials are based on reversible alloying reaction mechanism forming LixSn alloys in lithium-ion batteries, but tin oxide undergoes additional reaction, i.e. conversion reaction, before alloying reaction occurs in the first charging process. Even though the conversion reaction, which indicates the reaction forming reduced tin metal and lithium oxide from tin oxide, is known as almost irreversible and it consumes plenty of lithium ions, it is normally considered as an advantage because the resulting lithium oxide is believed to act as mechanical buffer layers preventing from drastic volume expansion/contraction and therefore contributes capacity retention. However, there is still a lack of understanding on the reaction mechanism of tin oxide. In particular, the SnO2 anode usually shows additional specific capacity that greatly exceeds the theoretical value. On the basis of our experimental data, the extra capacity reaches 130% of its theoretical value on the first charging process. The extra capacity commonly found in transition metal oxide (TMO) anodes has also been a subject of great interest, and Hu et al. explained that reaction of lithium hydroxide from electrolyte decomposition mainly contributes to additional capacity in RuO2 anode (Nature Materials, 2013.12.). But it still does not give an explanation of SnO2 anode because they have different fundamental electrochemical reaction mechanisms that enable lithium-ion battery to be rechargeable; TMO anodes such as the RuO2 anode are operated by the reversible conversion reaction, whereas the SnO2 anode is operated by the reversible alloying reaction. Furthermore, the partial reversibility of conversion reaction has long been in debates on SnO2 anode materials. The partial reverse conversion reaction of the SnO2 anode has been commonly accepted and considered to contribute the extra capacity, but previous reports are mostly based on indirect experimental evidences. Here, we elucidated the origin of additional capacities and studied the possibility of partial reversibility of conversion reaction through ex situ transmission electron microscopy (TEM) research. We improved and optimized an ex situ TEM analysis technique to investigate electrochemical reactions inside the actual battery-operating system. Direct (dis)charging of SnO2 particles on TEM grid in a coin cell enabled us to track the same locations of nano-areas throughout the full reaction cycle and, therefore, all of the phase evolutions including solid electrolyte interphase (SEI) layers were identified. We additionally performed same experiments with pure Sn particles to draw an exact conclusion. Eliminating the conversion reaction step, pure Sn particles give us better understanding on the reaction mechanism of SnO2. Combining all of the experimental results as well as the aid of computational works, we found out that reactions of the Li2O phase contribute to the extra capacity and the reverse conversion reaction of SnO2 hardly occurs in the real battery system. We expect that this study will provide fundamental knowledge on behaviors of various tin-based materials in lithium-ion batteries.

Lithium-ion batteries (LIBs) are the most popular power source not only for portable electronics but also for upcoming electric vehicles. So far, various materials such as graphitic carbon, Si, Ge, MoO3, NiO, Fe2O3, and SnO2 have been exploited as the anode materials for LIBs. Among these candidates, SnO2 is one of the promising materials for anode electrode in LIBs due to its high theoretical capacity (782 mAh g-1). However, the main difficulties for using the alloy-based materials are their dramatic volume expansion and contraction during Li insertion and extraction. This volume change can generate a large internal stress, leading to pulverization of the electrode and electrical detachment of the active particles. Moreover, formation of Li2O, related to irreversible capacity, results in a low efficiency and waste of Li+. If the conversion reaction of Li2O, in SnO2 system, can be induced, the reversible capacity could be increased. Recently, SnO2-transition metal oxide composites, such as MoO3, Fe2O3, and NiO, etc., have been suggested to induce the synergistic effects between Li2O, from SnO2, and transition metal oxide [1-3]. However, most of current studies of these composite materials showed the poor cyclablity and the synergistic effects diminished in the long-term cycling. We believed that these results are realated to the structual instability due to the large volume change during lithium insertion/extraction. Among various nanosturcutres, hollow sphere is the most promising structure because it can accommodate the large volume change and the synthesis process is relatively simple. Thus, we try to synthesize the hollow composite structrue with SnO2 and transition metal oxides. In this study, we synthesized multi-layered hollow spheres, composed of SnO2 and transition metal oxides (Co3O4 and Fe2O3), by a simple sol-gel based process. Even though cobalt (Co) is well-known catalyst metal for the reversible reaction of Li2O, it is one of expensive materials. So, we also synthesize the SnO2@Fe2O3 hollow spheres with the similar synthesis procedure. The size of synthesized SnO2 hollow sphere is about 60 nm and the shell thickness is about 5 nm. After Co3O4 and Fe2O3 coating, the size was not significantly changed (Fig. 1). The SnO2@Co3O4 and SnO2@Fe2O3@C electrodes showed much higher reversible capacity than SnO2 hollow sphere electrode (Fig. 2) and further cycling test is also examined. The synergistic effects between SnO2/Co3O4 (Fe2O3) and the reaction mechanism observed by TEM and electrochemical analyses will be discussed in this presentation. Furthermore, we also prepared various electrodes such as commercial SnO2 nanopowder, SnO2@C hollow spheres, SnO2@ Fe2O3@C solid spheres and the electrochemical performances will be compared. We believe that our studies might suggest the design strategy for the next-generation LIBs, and it can be applied to other SnO2-metal oxides composites. Fig. 1 SEM images of (a) SnO2@Co3O4 hollow spheres and (b) SnO2@Fe2O3 hollow spheres. Fig. 2 Cycling performance of SnO2, Co3O4/SnO2, and SnO2@Fe2O3@C hollow sphere electrodes. [1] X. -Y. Xue, Z. -H. Chen, L. -L. Xing, S. Yuan, Y. -J. Chen, Chem. Commun. 47(2011) 5205-5207. [2] W. Zhou, C. Cheng, J. Liu, Y. Y. Tay, J. Jiang, X. Jia, J. Zhang, H. Gong, H. H. Hng, T. Yu, H. J. Fan, Adv. Funct. Mater. 21(2011) 2439-2445. [3] M. F. Hassan , M. M. Rahman , Z. Guo , Z. Chen, H. Liu, J. Mater. Chem., 20(2010) 9707-9712.

Electrochemical coating technologies of metal surface have been widely used for decades in various industries, because it provides the thick and anti-corrosive films with a simple and cheap process [1]. Especially, plasma electrolytic oxidation (PEO), which is a high electrical power-induced technology, has much attention in recent years due to their excellent film property. The PEO produces adherent ceramic-like coatings, which are beneficial to enhance the corrosion and wear resistance, so the oxidized film can be applied in many industrial fields [2-4]. During PEO process, a high–voltage discharge zone is generated with spark or arc plasma micro-discharge, and the thick ceramic coating is directly formed on the surface of metals together with elements in the electrolyte. At the discharge zone, the extreme environments with high temperature and pressure are generated, and estimated temperature is around 8000 K at a hot core and 1800 K at a cold circumferential area [5]. In this study, we applied the plasma discharge phenomenon in PEO process to generate the photo-luminescent oxide film by adding the rare-earth ions in the electrolytes, and the white light emitting oxide film was successfully formed on aluminum foil. So far, the luminescent film was fabricated by screen printing technique, combustion CVD, spin coating, sol-gel soft lithography, and radio-frequency magnetron sputtering, but those kinds of phosphor films showed many problems such as poor uniformity of film thickness and low adhesion to the substrate [6-8]. In case of PEO process, the rare-earth ions are directly incorporated during oxidation process, so well adhesive luminescent films can be obtained. In order to prepare photo-luminescent oxide film, the plasma electrolytic oxidation of Al foil was conducted in rare-earth ion containing base electrolyte with constant current density of 3 A/dm2 using DC pulse power supply. Various electrolytes and rare earth ions were employed and their effects on the photoluminescence properties of the obtained films were examined. To find out the correlation of photo-luminescence and micro arc generation in early stage, cathode-luminescence properties were investigated in the films formed around break-down voltage with SEM images. When europium was present in the electrolyte, a white light emitting ceramic-like film covering from NUV to visible was formed on aluminum foil (Fig. 1). The film was mainly composed of γ-Al2O3, and the emission spectrum consisted of two emission peaks centered at 420 nm and 500 nm with a broad FWHM (~197.6 nm). The origin of these emission peaks will be discussed in this presentation. In addition, the effects of electrolyte composition and rare-earth ions on the phase content and photoluminescence properties of the Al2O3films will be presented. Reference [1] G. Helen Annal Therese and P. Vishnu Kamath, Chem. Mater.,12, 1195 (2000) [2] A. Kuhn, Met. Finish, 101, 44 (2003) [3] X. Nie, E. I. Meletis, J. C. Jiang, A. Leyland, A. L. Yerokhin, and A. Matthews, Surf. Coat. Technol., 149, 245 (2002) [4] C. Blawert, W. Dietzel, E. Ghali, and G. Song, Adv. Eng. Mater., 8, 511 (2006) [5] A. L. Yerokhin, X. Nie, A. Leyland, A. Matthews, and S. J. Dowey, Surf. Coat. Technol., 122, 73 (1999) [6] K.Y. Jung, Y.C. Kang, Mater. Lett, 58, 2161 (2004) [7] Z.T. Kang, Y. Liu, B.K. Wagner, R. Gilstrap, M. Liu, C.J. Summers, J. Lumin., 121, 595 (2006) [8] W.-H. Chao, R.-J. Wu, T.-B. Wu, J. Alloys Compd., 506, 98 (2010)

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Silver-containing oxide coatings on AZ31 Mg alloys were fabricated by microarc oxidation (MAO) in AgNO 3 -containing sodium silicate (Na 2 SiO 3 )-based electrolyte, and their physical and chemical properties were investigated, particularly focusing on corrosion resistance and antibacterial activity. The porous oxide coatings consisting of Mg 2 SiO 4 and MgO formed in both AgNO 3 -containing and AgNO 3 -free electrolytes and the MAO coatings were composed of a porous outer layer and a dense inner layer. MAO in AgN0 3 -containing electrolyte resulted in a thicker oxide coating, especially a thicker fluorine (F)-rich inner layer. Fluorine (F) was rich in the dense inner layer, and Ag was preferentially located close to the coating surface. The potentiodynamic test indicated that Ag-containing MAO coating had a more positive corrosion potential (-1.42 V), lower corrosion current density (0.02 μA/cm 2 ), and thus higher corrosion resistance (1824 kΩ cm 2 ) compared to Ag-free MAO coatings (-1.53 V, 0.32 μA/cm 2 , and 131 kΩ cm 2 , respectively). The electrochemical impedance spectroscopy results revealed that the higher corrosion resistance of Ag-containing MAO coating was due to an order of magnitude higher resistance of the dense inner layer. Ag-containing MAO coating showed an excellent antibacterial activity over 99.9% against two strains of bacteria, Staphylococcus aureus and Escherichia coli.

Yellow light-emitting Eu 2+ -doped Ca-α-SiAlON phosphors with compositions of (Ca m/2―x Eu x )Si 12―(m+n) Al m+n O n N 16―n were successfully prepared by spark plasma sintering (SPS), and their luminescence properties were investigated. The Ca-α-SiAlON:Eu 2+ phosphors absorbed in the UV-blue visible light region and showed a strong yellow-orange emission band centered at 565 nm. The influences of Ca content, Eu doping concentration, synthesis temperature, and post-heat-treatment on the luminescence performance of Ca-α-SiAlON:Eu 2+ phosphors were investigated. The optimization of SPS and subsequent postannealing yields the yellow Ca-α-SiAlON:Eu 2+ phosphor with an emission intensity comparable to the commercial yellow phosphor (yttrium aluminum garnet:Ce 3+ ) under blue light excitation.

Indium tin oxide (ITO)/SnO 2 two-layer thin films were fabricated by radio-frequency magnetron sputtering and their gas sensing properties were investigated, particularly focusing on the low temperature gas detection. ITO film was an island structure of cone shape, and subsequent SnO 2 deposition produced a uniform and homogeneous film of ~25 nm thick. The phase and chemical composition analyses by X-ray diffraction, X-ray photoelectron spectroscopy, and Auger electron spectroscopy indicated that indium (In) and tin (Sn) ions were interdiffused during annealing, resulting in the ITO film with a concentration gradient from Sn-rich (surface) to In-rich (substrate). Compared to a SnO 2 thin film, the resistance of ITO/SnO 2 two-layer films was decreased by several orders of magnitude, which makes it possible to detect the gases at as low as 100°C. The two-layer gas sensor exhibited the enhanced gas response (sensitivity) and selectivity toward NO 2 against H 2 , NH 3 , and C 2 H 5 OH gases.

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Oxide coatings were formed on AZ91D Mg alloy by microarc oxidation (MAO) in a sodium aluminate (NaAlO 2 )-based electrolyte, and the effects of additive electrolytes, KF, NaOH, and KOH, on the physical and chemical properties of the MAO coatings were investigated, particularly focusing on their corrosion resistance determined by potentiodynamic and potentiostatic tests. The anodizing characteristics (breakdown voltage and ignition time) and the phase, surface morphology, and thickness of the MAO coatings were strongly dependent on the additive electrolytes. The intense and continuous sparking in the KF-NaAlO 2 electrolyte resulted in a thick MgAl 2 O 4 coating containing F - ions, whereas the MAO coating obtained in either NaOH or KOH-NaAlO 2 electrolyte was thin and poorly crystalline, resulting from the unstable and discontinuous sparking. The MAO coating obtained in the KF-NaAlO 2 electrolyte exhibited the highest corrosion potential, the lowest corrosion current density, and the highest polarization resistance, which were closely related to the crystalline MgAl 2 O 4 phase and the relatively thick dense inner barrier layer. The pitting corrosion occurred in AZ91D Mg alloy, and the pitting was significantly protected by the MAO coating obtained in the KF-NaAlO 2 electrolyte. The pitting potentials for the MAO coatings have been determined by potentiostatic tests.

Nanoporous SnO 2 films on SiO 2 /Si substrate with one-dimensional (1D) nanochannels were fabricated by anodic oxidation, and their gas sensing properties were investigated. For this, Sn films of ~600 nm thick were deposited on SiO 2 /Si substrate by thermal evaporation and anodized in an electrolyte of 0.3 M oxalic acid. Subsequent annealing at 700°C completely transformed amorphous anodic oxide into crystalline SnO 2 , which was confirmed by X-ray diffraction. During annealing, both 1D nanoporous structure and adhesion to the substrate were maintained. The pore shape was more or less spherical, and the channel diameter and wall thickness were ∼50 and ∼20 nm, respectively. The Pt-patterned nanoporous SnO 2 film sensor responded to H 2 , NH 3 , and CO gases with a relatively short response time. It showed the highest gas response (S) of ∼52 toward 1.0% H 2 /air at 400°C and exhibited the linear concentration dependence and high selectivity toward H 2 against CO or NH 3 . The sensing performance of the nanoporous SnO 2 film sensor was compared with that of the thermally oxidized SnO 2 film sensor without the anodizing step and commercial SnO 2 powder sensor.

Ca 5 (PO 4 ) 3 Cl:Eu 2+ powders were synthesized by a solid-state reaction method using CaCl 2 as a chlorine source. CaCl 2 effectively contributed to both the solid-state reaction and luminescent properties, acting as a flux and a chlorine source simultaneously. With a small amount of CaCl 2 , the β-tricalcium phosphate (β-TCP) phase coexisted with Ca-chlorapatites (CCAp), and then it decreased and finally disappeared with increasing CaCl 2 , resulting in a CCAp single phase. Photoluminescence (PL) spectra of CCAp exhibited a single blue emission at 460 nm under the excitation of 370 nm. PL intensity was correlated with the phase ratio of β-TCP/CCAp. Excess Cl evaporation at the high firing temperatures above 1100°C dominantly caused the abrupt decrease in PL intensity.

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