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Carbon monoxide (CO) is an odorless, colorless, tasteless, extremely flammable, and highly toxic gas. It is produced when there is insufficient oxygen supply during the combustion of carbon to produce carbon dioxide (CO2). CO is produced from operating engines, stoves, or furnaces. CO poisoning occurs when CO accumulates in the bloodstream and can result in severe tissue damage or even death. Many types of CO sensors have been reported, including electrochemical, semiconductor metal-oxide, catalytic combustion, thermal conductivity, and infrared absorption-type for the detection of CO. However, despite their excellent selectivity and sensitivity, issues such as complexity, power consumption, and calibration limit their applications. In this study, a fabricbased colorimetric CO sensor is proposed to address these issues. Potassium disulfitopalladate (II) (K2Pd(SO3)2) is dyed on a polyester fabric as a sensing material for selective CO detection. The sensing characteristics and performance are investigated using optical instruments such as RGB sensor and spectrometer. The sensor shows immediate color change when exposed to CO at a concentration that is even lower than 20 ppm before 2 min. The fast response time of the sensor is attributed to its high porosity to react with CO. This easy-to-fabricate and cost-effective sensor can detect and prevent the leakage of CO simultaneously with high sensitivity and selectivity toward CO.

As hydrogen (H2) gas is highly reactive and explosive in ambient atmosphere, its prompt detection in industrial areas is imperative to prevent serious accidents. In particular, high-performance H2 sensors that can promptly detect even low-concentrations of H2 gas are necessary for safety. Carbon nanotubes (CNTs) have a large surface area and a high surface-to-volume ratio, and therefore, they are suitable for use as sensing materials in gas sensors. Moreover, gold, platinum, and palladium are known to be excellent catalyst metals that increase reactivity with H2 gas through the catalytic effect referred to as spill-over mechanism. In this study, a CNT felt sensor with a palladium (Pd) layer was fabricated, and its reactivity with H2 was evaluated. The sensitivity of a CNT felt sensor to H2 gas at room temperature was found to improve when coated with Pd layer.

Palladium-coated multi-walled carbon nanotube (Pd-MWCNT) nanocomposites have been experimentally proven to show highly improved hydrogen (H2) gas detection characteristics at room temperature when compared with single MWCNTs. In this context, we develop an efficient and convenient method for forming nanocomposites by coating Pd nanoparticles on an MWCNT film. Furthermore, we test the applicability of the nanocomposites as sensing materials in detecting H2 gas at room temperature in a reliable and sensitive manner in contrast with ordinary metal-oxidebased gas sensors that operate at high temperatures. We first study the detection efficacy of the Pd-MWCNT film relative to pure MWCNT film. Subsequently, we investigate the Pd-MWCNT sensor’s sensitivity over time for different gas concentrations, the sensor response time, and sensor reproducibility and reliability under various conditions including bending tests. Our sensor exhibits stable reliable detection characteristics and excellent structural flexibility.

Powerful sunlight, a high water temperature, and stagnation in the water flow induce eutrophication in rivers and lakes, which destroys the aquatic ecosystem and threatens the downstream water supply systems. Accordingly, it is very important to perform real-time measurements of nutrients that induce algal growth, especially total phosphorus, to preserve and manage the aquatic ecosystem. To conduct quantitative analysis of the total phosphorus in the aquatic ecosystem, it is essential to perform a pretreatment process and quickly separate the phosphorus, combined with organic and inorganic materials, into a phosphate. In this study, the sandblasting process was used for the physical etching of the wafer, and photocatalytic materials were deposited on the surface with various roughness in order to improve the photocatalytic reaction surface and efficiency. The photocatalytic reaction was applied to combine the pretreated sample with the coloring agent for color development, and the absorbance of the colored sample was analyzed quantitatively to compare and evaluate the characteristics, followed by the surface increase in the photocatalytic materials. In addition, the pretreatment and measurement parts were materialized in a single chip to produce a small and light total phosphorus analysis sensor.

In this study, pristine carbon nanotubes (CNTs) and the CNTs functionalized through heat treatment were fabricated, and their hydrogen (H2) gas sensing characteristics were evaluated at room temperature. Pristine CNTs exhibited relatively low reactivity toward H2 gas, whereas functionalized CNTs demonstrated linear electrical response characteristics with an increase in the gas concentration due to the presence of functional groups (such as COOH and OH) on the CNT surface, which reduced the activation energy for the adsorption of H2 molecules and provided additional reactive sites. Thus, functionalized CNTs can be potentially utilized in various fields because their operation does not require high-temperature environments (unlike the currently used metal oxide-based H2 sensors), while the power consumption and explosion risks of these materials are easily reduced through a simple heat treatment process.

In this study, experimental variables pertaining to the formation of nano-pillar arrays using p-type silicon were optimized by controlling current density and chamber temperature. Three factors aff...

In this study, we have studied coating method using high reflective White silicon on the whole Zener diode in order to resolve the reducing the luminance of the LED problem caused by the Ze...

Comparative properties of pin-type amorphous silicon (a-Si:H) thin-film solar cells with different PH3 flows for the i-layer and the presence of a buffer layer at the p–i interface were inv...

The proposed study describes the development of a carbon nanotube (CNT)-based gas sensor capable of detecting the presence of hydrogen (H2) gas at room temperature. CNT yarn used in the proposed sensor was fabricated from synthesized CNT arrays. Subsequently, the yarn was treated by means of a simple one-step procedure, called acid treatment, to facilitate removal of impurities from the yarn surface and forming functional species. To verify the proposed sensor’s effectiveness with regard to detection of H2 gas at room temperature, acid-treated CNT and pure yarns were fabricated and tested under identical conditions. Corresponding results demonstrate that compared to the untreated CNT yarn, the acid-treated CNT yarn exhibits higher sensitivity to the presence of H2 gas at room temperature. Additionally, the acid-treated CNT yarn was observed to demonstrate excellent selectivity pertaining to H2 gas.

Si-Ti-Ni alloy (STN) is a promising active material for lithium ion batteries with high coulombic efficiency and stable cycleability since inactive matrix plays an important role in buffer action against large volume changes of Si during charge/discharge reactions. However, there still remain several challenges to apply to electric vehicles due to capacity fading and unstable cycle performances at high current density. In this study, to improve the properties of STN, we modified the surface of STN with poly(3,4-ethylenedioxythiophene) (PEDOT) by in-situ polymerization. The modified STN provides many advantages including stable cycleability, low charge transfer resistance, strong adhesion between active materials and active material and current collector, etc. Electrochemical performances are significantly improved after modification; especially under high current density conditions.

This paper proposes a simple and efficient method to develop a nanocomposite by depositing platinum (Pt) nanoparticles on a carbon nanotube (CNT) sheet, and experimentally verifies the applicability of the proposed nanocomposite as a reliable and sensitive carbon monoxide (CO) gas sensor that operates at room temperature. A Pt-CNT nanocomposite shows improved CO gas sensing properties compared with the pristine CNT sheet. Owing to its large surface area and high conductivity, a CNT sheet exhibits improved sensitivity and fast response and recovery times. Based on the Pt-CNT nanocomposite implemented by the proposed method, we fabricated a Pt-CNT sheet-based CO gas sensor operating at room temperature and experimentally verified its stable and reliable room temperature sensing properties and excellent structural flexibility.

A gadolinium (Gd) complex with carboxylic acid was synthesized by using a neutralization chemical reaction. Gd (0.5%) was doped into a liquid scintillator by using a solvent-solvent extraction under controlled pH. Linear alkyl benzene (LAB) was used as a scintillation solvent. We measured several important physical and optical properties. The preparation, the synthesis procedures and the characterization of the resulting gadolinium-loaded, LAB-based, liquid scintillator are described in this paper.

Various TiO2-coated ZnO samples were prepared by the sol−gel method for use as the anode active materials of Ni−Zn secondary batteries. At a low annealing temperature, the added titanium does not r...

LiMn 1.5 Ni 0.5 O 4 materials coated with AlPO 4 are prepared by a sol–gel method with citric acid to improve their electrochemical performance; the physical and electrochemical properties are characterized by various analytical techniques. The coated AlPO 4 layer completely covers the surfaces of the LiMn 1.5 Ni 0.5 O 4 particles and the thickness of the coated layer is ∼15 nm. 1 wt.% AlPO 4 -coated LiMn 1.5 Ni 0.5 O 4 has much lower surface and charge-transfer resistances and shows a higher lithium diffusion rate in comparison with the pristine sample. The modified material demonstrates dramatically enhanced electrochemical reversibility and stability under elevated temperature conditions. This is because the coated AlPO 4 layer reduces the contact area between the electrode and electrolyte and suppresses the formation of undesirable solid electrolyte interface films.

Polycrystalline samples of RE 0.6Ca0.4Ba1.6Sr0.4Cu3O6 (RE = Nd, Gd, Dy, Y, Yb, Lu) without oxygen in the Cu(1)O chain have been prepared by the conventional solid-state reaction method. No superconductivity appears for larger RE = Nd, Gd, Dy, while superconductivity with T c ~50 K appears for smaller RE = Y, Yb, Lu. This is presumably because holes produced by the Ca-substitution for RE are more supplied to the conductive Cu(2)O2 plane than to Cu(1) as the lattice becomes small. The maximum T c = 53 K for RE = Lu is considerably lower than 90 K for REBa2Cu3O7. This may be due to the low hole-concentration in the Cu(2)O2 plane.

The surface modified LiMn2O4 materials with Li-Fe composites were prepared by a sol-gel method to improve the elec- trochemical performance of LiMn2O4 and were characterized by X-ray diffraction (XRD), X-ray photoelectron spec- troscopy (XPS), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and transmission electron microscopy (TEM)-EDS. XRD results indicate that all the samples (modified and pristine samples) have cubic spinel structures, and XRD, XPS, and TEM-EDS data reveal the formation of Li(LixFexMn2-2x)O4 solid solution on the sur- face of particles. For the electrochemical properties, the modified material demonstrated dramatically enhanced reversibility and stability even at elevated temperature. These improvements are attributed to the formation of the solid solution, and thus-formed solid solution phase on the surface of LiMn2O4 particle reduces the dissolution of Mn ion and suppresses the Jahn-Teller effect.

Nafion is modified by incorporating poly(1-vinylimidazole)/Pd composites into the ion cluster channels of the membrane. The poly(1-vinylimidazole)/Pd-impregnated (PVI/Pd-impregnated) membranes is characterized by means of X-ray photoelectron spectroscopy (XPS), proton conductivity and methanol permeability measurements and compared with those of the untreated Nafion. The dependence of the membrane proton conductivity and methanol permeability on the poly(1-vinylimidazole) (PVI) and palladium contents in the PVI/Pd-impregnated Nafion is studied. The performance of the cells employing the PVI/Pd-impregnated Nafion is evaluated using a direct methanol fuel cell (DMFC) unit cell. It is found that the best cell performance is obtained when Nafion is impregnated with the PVI/Pd composite solution for 20 h. This result suggests that there exists an optimum content of palladium and PVI in the modified membrane to obtain a high-proton conductivity and low-methanol permeability that result in a high-cell performance.

More than 1800 hundreds of millions of beverage cans are manufactured yearly over the world, which will pollute the globe environment without recycle. The recycle and regeneration estates of used beverage cans are highly profitable enterprises. Vacuum technologies are mature on a large scale today, and therefore, the re-melting process of used beverage cans (UBCs) does not have to use flux. Furthermore, the coating on UBCs becomes the key factor causing poor product quality. The present paper concerns removing the coating of UBCs and compares two different kinds of methods to remove the coating: a thermal method and a chemical reagent method. A new kind of reagent, thick sulfuric acid, was employed in the chemical reagent de-coating process. The de-coating ratio in the thermal method reached 93% at most, but the de-coating ratio reached 100% within 30 min in the chemical reagent method by using thick sulfuric acid. Recycling the used thick sulfuric acid was also supplied. A titanium yellow product can be simultaneously obtained. The experiments show that the chemical reagent method is more available than the thermal method, which will enhance the purity of the regeneration product enormously.

Lithium ion secondary battery has been applied widely to portable devices, and has been studied for application to high power electric cell system such as power tool or hybrid electronic vehicle. The structure change of the electrodes materials occur when lithium ions move between electrodes. Neutron or X-rays can analyze the structure of electrode. The advantage of X-rays is convenient in test. However X-rays is scattered by electron cloud in atoms. Therefore, The elucidation for correct position of lithium is difficult with X-rays because lithium has small atomic weight. Neutron analysis techniques could solve this problem. In this review, We wish to discuss about structure analysis and the principle of structural characterization method using neutron beam source.

CeO 2 -coated LiMn 2 O 4 spinel cathode was synthesized using two-step synthesis method. All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. The results of the electrochemical performances on CeO 2 -coated electrode are compared to those of electrodes based on LiMn 2 O 4 spinel without CeO 2 coating. CeO 2 -coated LiMn 2 O 4 cathode improved the cycling stability of the electrode. The capacity retention of 2 wt% CeO 2 -coated LiMn 2 O 4 was more than 82% after 150 cycles between 3.0 and 4.4 V at room temperature and 82% after 40 cycles at elevated temperature of 60 °C. The amounts of dissolved manganese-ions in CeO 2 -coated LiMn 2 O 4 significantly are smaller than pristine LiMn 2 O 4 systems especially at elevated temperatures. Surface-modified LiMn 2 O 4 can suppress the dissolution reaction of manganese-ions at elevated temperature and clearly improve the cyclability of the spinel LiMn 2 O 4 cathode materials.

A novel method, a hydrothermal method, was firstly employed to prepare a catalyst of Pt supported on carbon nanotubes (Pt/CNTs) used in a proton exchange membrane fuel cell (PEMFC) in the present work. The catalyst was characterized through the IR spectrum, XRD, TEM and Image-Pro PLUS2 software. The results show that the pretreatment using a HNO 3 –H 2 O 2 redox system on CNTs opened the ports and removed a large quantity of impurities. Reaction temperature and time are important factors to determine the Pt granule size. The average size of the Pt nanoparticles is less than 1.94 nm with homogenous dispersion and narrow distribution under the optimal reaction conditions with a reaction time of 1.5 h at 140 °C. The hydrothermal method using the conventional Pt precursor H 2 PtCl 6 ·2H 2 O together with HCHO with brief operation will be a promising method to yield Pt nanoparticles for the Pt/CNTs catalyst.

LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) compounds have been synthesized by a direct molten-salt method that uses a eutectic mixture of LiNO 3 and LiOH salts. According to X-ray diffraction analysis, these materials have a well-developed layered structure (R3-m) and are an isostructure of LiNiO 2 . The LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) compounds have average particle sizes of 1–5 μm depending on the amount of Ti salt. Charge–discharge tests show that a LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) cathode prepared at 700 °C has an initial discharge capacity as high as 171 mA h g −1 and excellent capacity retention in the range 4.3–2.8 V at a current density of 0.2 mA cm −2 .

Olivine structure LiFePO 4 /C composite powders are synthesized as cathode materials for Li-ion batteries via a conventional solid-state reaction. Improvement in electrochemical performance has been achieved by using poly(vinyl alcohol) as the carbon sources for the as-prepared materials. The influence of the heat treatment on the physical and the electrochemical properties of LiFePO 4 /C materials is investigated. To examine the effect of added carbon content on the properties of materials, a one-step heat treatment has been employed with control of the PVA content in the precursor. Six samples were prepared with 0, 1, 3, 5, 10 and 30 wt.% PVA added to the raw materials. The particle size of LiFePO 4 decreases as the carbon content increases. Materials with medium carbon contents have a small charge-transfer resistance and thus exhibit superior electrochemical performance. Interestingly, for a LiFePO 4 /C composite with a low PVA content, an unusual plateau at 4.3 V is observed. It is considered that this is due to the Fe 3+ /Fe 4+ redox reaction of Fe 3+ compounds that are present as an impurity. For samples with a high PVA amount, a thicker carbon coating provides an obstacle to improve the electrochemical properties.

The dissolution of nickel oxide cathode in the electrolyte is one of the major technical obstacles to the commercialization of molten carbonate fuel cell (MCFC). To improve the MCFC cathode stability, the alternative cathode material for MCFC was prepared, which was made of Co/Ce-coated on the surface of Ni powder using a polymeric precursor based on the Pechini method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX) were employed in characterization of the alternative cathode materials. The Co/Ce-coated Ni cathode prepared by the tape-casting technique. The solubility of the Co/Ce-coated Ni cathode was about 80% lower when compare to that of pure Ni cathode under CO2:O2 (66.7:33.3%) atmosphere at 650 °C. Consequently, the fine Co/Ce-coated Ni powder could be confirmed as a new alternative cathode material for MCFC.

Investigations on alternative material for bipolar plates of PEMFC (polymer electrolyte membrane fuel cell) are becoming a research hotspot for many fuel cell researchers. In this paper, LF11 Al alloy bipolar plates via a surface plasma Au plating preparation were applied as bipolar plates. Performances and duration times of PEMFC single cells using graphite; Au-coated LF11 Al bipolar (ALABP) and Au-coated 316L stainless steel plates were compared. It was shown that ALABP exhibited preferable properties. Based on the preparations illustrated above, a kilowatt class proton exchange membrane fuel cell stack consisting of 30 cells was successfully assembled. Pure hydrogen and air were used as the fuel and oxidant, respectively, in the stack. External humidification was employed and cycle cooling water was used to remove the heat from the reaction in order to maintain a constant temperature. A Nafion 1135 membrane and Johnson-Matthy platinum on carbon with a Pt loading of 0.4 mg/cm2 were adopted as the electrolyte and catalyst, respectively. The working temperature of the stack ranged from 25 to 100°C. The stack typically worked well under conditions in which the pressure ratio of H2/air was 0.2/0.22 MPa. The output power, current and voltage were 1–1.3 kW, 40–80 A, and 26–20 V, respectively. The normal current density of the electrode was 200–800 mA/cm2, and the energy efficiency of the stack was 51%.

The properties of a new cathode material of nano-sized TiO 2 -coated Ni powder for application in molten carbonate fuel cells (MCFCs) are investigated. The material is prepared by a sol–gel method. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) with energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and Raman spectroscopy are employed to characterize the cathode material. The nano-sized TiO 2 particles are homogenously coated on the surface of the Ni powder. A stable LiTi 1− x Ni x O 2 phase is formed on the surface of the Ni powder during immersion in molten carbonate at 650 °C. The solubility of the TiO 2 -coated Ni cathode is about 50% lower compare with that of a pure Ni cathode.

Layered Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) have been prepared by the mixed hydroxide and molten-salt synthesis method. The individual particles of synthesized materials have a sub-microsize range of 200–500 nm, and LiNi0.475Mn0.475Zr0.05O2 has a rougher surface than that of LiNi0.5Mn0.5O2. The Li/Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) electrodes were cycled between 4.5 and 2.0 V at a current density of 15 mA/g, the discharge capacity of both cells increased during the first ten cycles. The discharge capacity of the Li/LiNi0.475Mn0.475Zr0.05O2 cell increased from 150 to 220 mAh/g, which is 50 mAh/g larger than that of the Li/LiNi0.5Mn0.5O2 cell. We found that the oxidation of oxygen and the Mn3+ ion concerned this phenomenon from the cyclic voltammetry (CV). Thermal stability of the charged Li[Ni0.5−xMn0.5−xZr2x]O2 (x = 0, 0.025) cathode was improved by Zr doping.

Ordinary graphite plate was impregnated by PTFE (polytetrafluoroethylene) scattering solution to make it suitable for fuel cell collector. The feasibility of impregnation process was investigated, and the process was optimized. SEM analysis showed that the depth of impregnation process was 2.50 mm. Porosity of graphite dropped from 18.20 percent to 3.29 percent after impregnation. There is no detectable leakage of H2, even at a pressure of 0.3 MPa after impregnation with PTFE. The impregnation process has no effect on graphite resistivity. Impregnation process successfully met the requirements for fuel cell graphite collector.

A high-performance LiNi 0.8 Co 0.2 O 2 cathode was successfully fabricated by a sol–gel coating of CeO 2 to the surface of the LiNi 0.8 Co 0.2 O 2 powder and subsequent heat treatment at 700 °C for 5 h. The surface-modified and pristine LiNi 0.8 Co 0.2 O 2 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), slow rate cyclic voltammogram (CV), and differential scanning calorimetry (DSC). Unlike pristine LiNi 0.8 Co 0.2 O 2 , the CeO 2 -coated LiNi 0.8 Co 0.2 O 2 cathode exhibits no decrease in its original specific capacity of 182 mAh/g (versus lithium metal) and excellent capacity retention (95% of its initial capacity) between 4.5 and 2.8 V after 55 cycles. The results indicate that the surface treatment should be an effective way to improve the comprehensive properties of the cathode materials for lithium ion batteries.

Preparation of catalyst layer in PEMFC electrodes was investigated. Toray carbon paper was used as diffusion layer, and Johnson–Matthey 20% Pt/C was employed as catalyst. Electrode contains neither PTFE nor carbon powder. The optimal catalyst layer composition was discovered by orthogonal test method, with the use of cell voltage–current curve and cyclic voltammogram curve. The optimal amount of the Nafion (ionomer) in the catalyst layer was found to be 1.4 mg / cm 2 when Pt loading was kept at 0.4 mg / cm 2 . Power density of PEMFC achieved 0.37 W / cm 2 with air and H 2 were used at the outlet pressure of 0.1 MPa.

A Li-sulfur cell with a high discharge capacity of over 1300 mAh g(-1) at a C/10 rate, and a controlled overcharge amount less than 1%, was manufactured by synthesizing a carbon-sulfur nano-composite via a wet milling process, and suppressing polysulfide dissolution using an electrolyte with a highly concentrated lithium salt.

Single phases of M-substituted lithium cobalt oxides, HT-LiCo 0.8 M 0.2 O 2 (M=Al, Ni), were prepared by molten salt synthesis (MSS) method using coprecipitated Co–M hydroxides in 0.59 LiNO 3 –0.41 LiOH. The prepared powders consisted of well-developed particles with spherical shape and the particle size was around 150 nm in diameter. Among them, HT-LiCo 0.8 Al 0.2 O 2 showed an inferior cyclic performance and a smaller discharge capacity than HT-LiCo 0.8 Ni 0.2 O 2 , even though the former is more structurally stable than the latter. Structural analysis of HT-Li x Co 0.8 Al 0.2 O 2 indicated that the Al substitution, causing an enhanced internal resistance for lithium ion diffusion, is responsible for the capacity fading. In the meanwhile, HT-Li x Co 0.8 Ni 0.2 O 2 with large c layer spacing showed as high as 146 mAh/g at the first cycle and 130 mAh/g at the twentieth cycle.

E-mail: cheolwoo@sungshin.ac.krReceived December 27, 2011, Accepted February 15, 2012Key Words : Nafion membrane, Porous membrane, Proton conductivity, Polymer electrolyte membrane, Va-por pressure of waterProton exchange membrane fuel cells (PEMFCs) havebeen paid a great attention as a clean power generator toconvert the chemical energy of hydrogen to electric energyand they have major advantages, such as the high powerdensity and energy efficiency, rapid start-up, etc., for theportable electronic devices and transportation/stationarypower systems.

Iodine-containing, cation-deficient, lithium manganese oxides (ICCD-LMO) are prepared by reaction of MnO2 with LiI. The MnO2 is completely transformed into spinel-structured compounds with a nominal composition of Li1−δMn2−2δO4Ix. A sample prepared at 800 °C, viz. Li0.99Mn1.98O4I0.02, exhibits an initial discharge capacity of 113 mA h g−1 with good cycleability and rate capability in the 4-V region. Iodine-containing, lithium-rich lithium manganese oxides (ICLR-LMO) are also prepared by reaction of LiMn2O4 with LiI, which results in a nominal composition of Li1+xMn2−xO4Ix. Li1.01Mn1.99O4I0.02 shows a discharge capacity of 124 mA h g−1 on the first cycle and 119 mA h g−1 a on the 20th cycle. Both results indicate that a small amount of iodine species helps to maintain cycle performance.

To elucidate the mechanism of gas generation during charge–discharge cycling of a lithium-ion cell, the generated gases and passive films on the carbon electrode are examined by means of gas chromatography (GC) and Fourier transform infrared (FTIR) spectroscopy. In ethyl carbonate/dimethyl carbonate and ethyl carbonate/diethyl carbonate 1 M LiPF 6 electrolytes, the detected gaseous products are CO 2 , CO, CH 4 , C 2 H 4 , C 2 H 6 , etc. The FTIR spectrum of the surface of the carbon electrode shows bands which correspond to Li 2 CO 3 , ROCO 2 Li, (ROCO 2 Li) 2 , and RCO 2 Li. These results suggest that gas evolution is caused by electrode decomposition, reactive trace impurities, and electrolyte reduction. The surface of the electrode is composed of electrolyte reduction products. When 0.05 M Li 2 CO 3 is added as an electrolyte additive, the total volume of generated gases is reduced, and the discharge capacity and the conductivity of lithium-ions are increased. These results can be explained by a more compact and thin ‘solid electrolyte interface’ film on the carbon electrode formed by Li 2 CO 3 , which effectively prevents solvent co-intercalation and carbon exfoliation.

The influences of Sr/(Ti+Nb) ratios on the electrical properties of Nb-doped SrTiO 3 ceramics have been investigated. Regardless of Sr/(Ti+Nb) ratios, the appearance of non-linearity in the current-voltage characteristics was observed. When Sr/(Ti+Nb) ratio is lower than 1.000, the results acquired from impedance analysis revealed that the activation energies for carrier conduction were determined to be 0.83 eV in grains and 1.67 eV in grain boundaries. Otherwise, the specimens with Sr/(Ti+Nb) S 1.004 showed energies of 0.80 eV in grains and 1.27 eV in grain boundaries. From these measured results, it was suggested that the activation energies, about 0.80 eV, measured in grains were originated from oxygen vacancies and the activation energies, 1.27 and 1.67 eV, measured in grain boundaries were from titanium and strontium vacancies, respectively.

The crystal structures of n =3 Dion–Jacobson phases M La 2 Ti 2 TaO 10 ( M =Cs, Rb) and NaLa 2 Ti 2 TaO 10 · x H 2 O ( x =2, 0.9, 0) have been investigated by the Rietveld analysis of their powder XRD patterns. These compounds show the new-type ordering sequence of (Ti 1/2 Ta 1/2 )O 6 –TiO 6 –(Ti 1/2 Ta 1/2 )O 6 in the tripled octahedra, corresponding to the niobium analogs of M La 2 Ti 2 NbO 10 . They crystallize in the tetragonal system P 4/ mmm with lattice constants of a =3.84733(9) and c =15.4364(4) A for CsLa 2 Ti 2 TaO 10 , and a =3.8342(2) and c =15.2776(9) A for RbLa 2 Ti 2 TaO 10 . Sodium-exchanged phase was easily hydrated to NaLa 2 Ti 2 TaO 10 ·2H 2 O, belonging to the space group I 4/ mmm with a =3.8399(3) and c =34.288(3) A. Upon firing, NaLa 2 Ti 2 TaO 10 ·2H 2 O was dehydrated to NaLa 2 Ti 2 TaO 10 ·0.9H 2 O with P 4/ mmm at around 100°C and then NaLa 2 Ti 2 TaO 10 with I 4/ mmm at above 200°C. The Na cations in two hydrates were surrounded with six oxygens, forming face-shared octahedra along (110) direction. These structural models, especially for the coordination environment of Na cations, were proposed for the first time.

The Li+/Co3+-codoped LiMn2O4 spinel was prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol–gel method, in order to investigate the changes of the electrochemical properties of the spinel LiMn2O4 on the amount of Li+/Co3+ ions. The FT-infrared spectra, chemical analysis, and Rietveld refinements of their XRD data revealed that the manganese ions in the 16d sites were replaced by both lithium and cobalt ions. Thus, the composition of obtained powders could be expressed as the new spinel formula (Li)[Mn2−xLix/4Co3x/4]O4, that is, (Li)[Mn3+1−3x/2Mn4+1+x/2Lix/4Co3+3x/4]O4. The inclusion of lithium and cobalt ions in 16d sites enhanced the electrochemical cyclability of LiMn2O4 at the expense of a reduction in the initial charge capacity. The improvement in cycling performance was mainly attributed to the suppression of Jahn–Teller distortion as shown in (Li)[Mn2−xLix]O4 and (Li)[Mn2−xCox]O4.

Lithium cobalt oxide powders have been successfully prepared by a molten-salt synthesis (MSS) method using a eutectic mixture of LiCl and Li 2 CO 3 salts. The physico-chemical properties of the lithium cobalt oxide powders are investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), particle-size analysis and charge–discharge cycling. A lower temperature and a shorter time (∼700°C and 1 h) in the Li:Co=7 system are sufficient to prepare single-phase HT-LiCoO 2 powders by the MSS method, compared with the solid-state reaction method. Charge–discharge tests show that the lithium cobalt oxide prepared at 800°C has an initial discharge capacity as high as 140 mA h g −1 , and 100 mA h g −1 after 40 cycles. The dependence of the synthetic conditions of HT-LiCoO 2 on the reaction temperature, time and amount of flux with respect to starting oxides is extensively investigated.

Lithiated NiO cathode dissolution has been a major problem for the development of molten carbonate fuel cells (MCFCs). Many studies have been contributed to find new alternative cathodes; here, lithium cobalt oxide, LiCoO2, was coated onto the commonly used NiO cathode by the electroplating method and the resulting cathode showed much reduced solubility compared with that of the common nickel oxide cathode. Thin film lithium cobalt oxide was prepared by the oxidation of Co metal deposited on a nickel plate in molten (Li,K)2CO3 at 650 °C under a CO2–O2 (2 ∶ 1 vol%) atmosphere. When this coated nickel plate was oxidized, the open circuit potential (OCP) decayed gradually, indicating two well-defined potential plateaux; the oxide films produced at each potential plateau were identified by X-ray diffraction methods. The surface product at the first plateau was CoO. LiCoO2 was formed at the second OCP plateau [around −0.47 V vs. CO2–O2 (2 ∶ 1 vol%) reference electrode]. By the same method, LiCoO2 was coated onto a porous nickel cathode in order to produce a MCFC. For 300 h steady operation of the cells, the mean voltages of the cells were 0.80 V using a NiO cathode and 0.85 V for a LC-NiO(EP) cathode at a current density of 150 mA cm−2. In addition to the cell efficiency improvement, the solubility of the LC-NiO(EP) cathode was much lower than that of the NiO cathode.

because it has high electrical conductivity, good thermal and chemical stability, high specific capacity, and the promotion of the reduction reaction of the cathode. Hence, it is expected that the use of the highly conductive PEDOT may serve as an outer layer to assist the transportation of Li ions.The pristine LiFePO

The side chain of phenolalkylamines containing a bifunctional group was derivatized as the cyclic boronate, and then the residual phenolic group was trimethylsilylated. The resulting derivatives were single reaction products in each case, with good gas chromatographic properties and informative mass spectra to afford prominent molecular ions by gas chromatography with electron impact mass spectrometry (GC/EI-MS). The cyclic boronated-trimethylsilylated derivatives yielded the isotope pattern for boron ((10)B:(11)B =-1:4.2) and characteristic ions [M](+), [M - H](+), [M - CH(3)](+), [M - RBO](+), [M - TMSO](+), and [M - TMSO - C(6)H(5)](+) ions in the mass spectra. In order to distinguish between m- and p-phenolalkylamines, the mass spectra of the cyclic phenylboronated-trimethylsilylated (PBA-TMS) derivatives were compared with those of the trimethylsilylated (TMS) derivatives. The TMS derivatives of octopamine (p-) and norfenefrine (m-) showed identical mass spectra, while the PBA-TMS derivatives had mass spectra sufficiently different from one other to distinguish between the isomers. The most prominent ion of the PBA-TMS derivative is the [M - H](+) ion (m/z 310) for octopamine and the [M](+) ion (m/z 311) for norfenefrine. Copyright 1999 John Wiley & Sons, Ltd.

The corrosion of chromium species in molten (Li/K) 2 CO 3 and (Li/Na/K) 2 CO 3 are investigated by spectrophotometry. A strong charge-transfer absorption band is observed in the ultraviolet region with λ max =372 nm, and the molar absorptivity of CrO 4 2− in molten (Li/K) 2 CO 3 is calculated. The corrosion rates are investigated by means of increasing the concentration of CrO 4 2− in the melts. Under an air atmosphere, the corrosion rate is slower in molten (Li/K) 2 CO 3 than in molten (Li/Na/K) 2 CO 3 and Cr 2 O 3 corrodes more easily in molten (Li/K) 2 CO 3 than Cr. With an atmosphere of CO 2 =1 atm, there is no increase in the CrO 4 2− concentration in the solution phase during a period of 5 h.

The aluminium pack cementation (pack aluminization) process on a porous nickel anode for molten carbonate fuel cells has been studied to improve anode creep resistance. The porous nickel substrates used in this study were fabricated by doctor blade equipment followed by sintering (850 °C). Packs surrounding the Ni anode were made by mixing Al2O3 powder, Al powder, and NaCl as activator. The pack aluminization was performed at 700 to 850 °C for 0.5–5.0 h. After pack aluminization, the principal NiAl intermetallic compounds detected were Ni3Al at 700 °C, NiAl at 750 °C and Ni3Al2 at 800 °C. The aluminum content in the aluminized Ni anode was proportional to the square root of pack aluminizing time. With increasing the Al content in the anode, the creep of the anode decreased. It was nearly constant (2.0%) when the Al content was above 5.0%. Although the exchange current density (24 mA/cm2) for the aluminized (2.5 wt.%) Ni anode was somewhat lower than that of the pure Ni anode (40 mA/cm2), the performance of a single cell using an aluminized Ni anode was similar to that of the one with pure Ni anode.

The dissolution of nickel oxide cathodes in the electrolyte is one of the major technical obstacles to the commercialization of molten carbonate fuel cells (MCFC). A novel alternative cathode material for MCFC was synthesized, which was made of nano-size Co3O4 coated on the surface of Ni powder using a polymeric precursor based on the Pechini method. X-Ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX), electron microprobe analysis (EPMA), and Raman spectrometry were employed in characterization of the novel alternative cathode materials. The Co-coated Ni cathode prepared by the tape-casting technique has a lower solubility in the molten carbonate than in the NiO cathode under CO2 ∶ O2 (67 ∶ 33) atmosphere at 650 °C. The reason is that the nano-size Co3O4-coated Ni powder can significantly retard the dissolution of NiO in molten carbonate due to the formation of the stable LiCo1−yNiyO2 phase on the surface of NiO in molten carbonate. During 300 h cell operation, the closed-circuit voltage (CCV) of unit cells using NiO and Co-coated Ni cathodes were found to be 0.80 V and 0.82 V, respectively, at a current density of 150 mA cm−2. The results show that the Co-coated Ni cathode used as an alternative cathode could resolve the problems in scale-up of the electrode and lengthen the lifetime of MCFC.