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LiNi0.8Co0.2O2 cathode powders for lithium-ion batteries were prepared by a modified sol–gel method with citric acid as chelating agent and a small amount of hydroxypropyl cellulose as dispersant agent. The structure and morphology of LiNi0.8Co0.2O2 powders calcined at various temperatures for 4 h in air were characterized by means of powder X-ray diffraction analyzer, scanning electron microscope, thermogravimetric analyzer and differential thermal analyzer, and Brunauer–Emmett–Teller specific surface area analyzer. The results show that LiNi0.8Co0.2O2 powders calcined at 800 °C exhibit the best layered structure ordering and appear to have monodispersed particulates surface. In addition, the electrochemical properties of LiNi0.8Co0.2O2 powders as cathode material were investigated by the charge–discharge and cyclic voltammetry studies in a three-electrode test cell. The initial charge–discharge studies indicate that LiNi0.8Co0.2O2 cathode material obtained from the powders calcined at 800 °C shows the largest charge capacity of 231 mAh g−1 and the largest discharge capacity of 191 mAh g−1. And, the cyclic voltammetry studies indicate that Li+ insertion and extraction in LiNi0.8Co0.2O2 powders is reversible except for the first cycle. [ABSTRACT FROM AUTHOR]

For this study, 150 clinical isolates of Klebsiella pneumoniae were collected from one hospital in Beijing, China, and assayed for minimal inhibitory concentration (MIC) of imipenem. To elucidate the mechanisms responsible for imipenem MIC variation among extended-spectrum β-lactamase (ESBL)-positive and -negative K. pneumoniae strains, a variety of β-lactamase genes ( blaTEM, blaCTX-M, blaSHV, and blaOXA) were screened by polymerase chain reaction (PCR). The outer membrane profile and expression of related genes ( ompK35 and ompK36) then were analyzed and evaluated, respectively. None of the tested isolates were clinically resistant to imipenem, but the range of MICs among ESBL-positive and -negative strains was significantly different. Deficiency in the expression of outer membrane proteins (OmpK35,36) was observed in some of both ESBL-positive(17.6%) and -negative strains (10.9%), but only the ESBL-positive strains depressed by the expression of ompK35/36 had an increased MIC of imipenem (≥0.5 mg/l). These results confirmed that the combination of SHV-1, CTX-M-3, CTX-M-14, TEM-1, or OXA-11 production and reduced expression of ompK35/36 may not result in clinical resistance to imipenem but does correlate with increasing imipenem MIC. [ABSTRACT FROM AUTHOR]

Highly sensitive CO gas sensors based on heterocontacts of ZnO:Al on La0.8Sr0.2Co0.5Ni0.5O3 (LSCNO) were fabricated successfully. La0.8Sr0.2Co0.5Ni0.5O3 thin films were coated on (100) silicon wafers by a sol-gel method including the Pechini process followed by a spin-coating procedure. Then, ZnO:Al films prepared by radiofrequency (RF) magnetron sputtering at various oxygen partial pressures and deposited on as-deposited La0.8Sr0.2Co0.5Ni0.5O3 films were investigated. The results revealed that the CO sensing ability of the film prepared with the ratio of O2/Ar = 5/5 (ratio of volume flow rate) was the worst, owing to the highest (002) plane orientation in the ZnO:Al film. In contrast, the ZnO:Al film prepared with O2/Ar = 3/7 exhibited better CO sensitivity. Furthermore, all two-layer samples showed higher CO sensitivities than single-layer samples. The CO sensitivity of ZnO:Al/La0.8Sr0.2Co0.5Ni0.5O3 thin film was 45% for 500 ppm CO at a sensing temperature of 200°C. [ABSTRACT FROM AUTHOR]

Nanometric-sized barium titanate powders were prepared by using titanium isopropoxid as the raw material and acetylacetone as a chelating agent, in a strong alkaline solution (pH > 13) through the sol-precipitation method. The preparatory variables affect the extent of cross-linking in the structure, change the mode of condensation of the gels, and even control the particle size of the powder. The reaction rate of forming powder, at a higher temperature such as 100°C and more water content (the molar ratio of water to titanium isopropoxide is 25) or fewer acetylacetone (the molar ratio of acetylacetone to titanium isopropoxide is 1), is rapid and the particle size formed is finer at 60-80 nm. On the contrary, that of forming powder, at lower temperature (40°C) and less water content (molar ratio of water/titanium isopropoxide = 5) or higher acetylacetone (acetylacetone/titanium isopropoxide = 7), is slow and the particle size of the powder is larger. The optimal preparatory conditions were obtained by using the experimental statistical method; as a result, nanometric-sized BaTiO3 powder with an average particle size of about 50 nm was prepared. [ABSTRACT FROM AUTHOR]

Solid solution Pb1-xBaxTiO3, with particular emphasis on Pb0.5 Ba0.5TiO3, was prepared using a sol-gel process incorporating lead acetate trihydrate, barium acetate, and titanium isopropoxide as precursors, acetylacetone (2,4 pentanedione) as a chelating agent, and ethylene glycol as a solvent. The synthesis procedure was optimized by systematically varying acetylacetone: Ti and H2O:Ti molar ratios and calcination temperature. The resulting effects on sol and powder properties were studied using thermogravimetric analysis/differential scanning calorimetry, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and x-ray diffraction (XRD). Crystallization of the perovskite structure occurred at a temperature as low as 450 °C. Thin films were prepared by spin coating on (100) MgO. Pyrolysis temperature and heating rate were varied, and the resultant film properties investigated using field-emission scanning electron microscopy, atomic force microscopy, and XRD. Under optimized conditions, highly oriented films were obtained at a crystallization temperature of 600 °C. [ABSTRACT FROM AUTHOR]

A Taguchi orthogonal array design was implemented to optimize the experimental conditions for the preparation of a thin strontium titanate film on a Ti substrate using a hydrothermal process. The effects of such preparatory conditions as the strontium-concentration, pH-value, reaction temperature, reaction time and the substrate surface treatment were systematically studied. Results indicate that the effects of the reaction temperature and reaction time are the key variables influencing the relative crystal intensity (intensity of (110) SrTiO3 peaks in XRD spectrum/intensity of (101) Ti peak in XRD spectrum) of the films obtained. By combining the optimal settings of the two most influential process variables, a polycrystalline, SrTiO3-films was obtained, with improved crystallinity and a grain size of 0.2–0.4 μm and a dielectric constant of 360 at I MHz. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy has been used to investigate the existence of Ti3+ on the surface of La2O3-doped strontium titanate and to determine its surface characteristics. The surfaces, having Sr/Ti ratios significantly varying from the stoichiometric ratio, revealed the presence of carbon and suggested the presence of hydroxyl groups on the surface, whose concentration largely decreased in the bulk. Ti3+ species existed as a function of the sintering conditions and were detected on the surface of (La, Sr)TiO3 sintered in air or in N2 by natural cooling. These samples had a lower electrical resistivity, especially when sintered in a N2 atmosphere. The surfaces of air oxidized SrTiO3 and quenched from high temperature contained no detectable amount of Ti3+, resulting in higher resistivity. However, the N2-sintered samples were dark blue in color and exhibited lower resistivity, semiconductivity, and lower valence oxidation state Ti existed when sintered above 1350°C. [ABSTRACT FROM AUTHOR]

Nanometric-sized nitrogen-doped titanium oxide (TiO2-xNy) powders were synthesized by the two-microemulsion technology. The dried precursor precipitate was characterized by differential thermal analysis/thermogravimetric analysis, Raman spectroscopy, transmission electron microscopy, Brunauer-Emmet-Teller surface area analyzer, and x-ray photoelectron spectrometer (XPS), and the mechanisms for the evolution of TiO2-xNy powders in this process were proposed and discussed in the context of the microstructure. It shows that a higher pH value solution results in obtaining a small size and much more homogeneous TiO2-xNy powder after calcinations. The powder prepared from a solution of pH 10-11 and calcined at 500 °C has a particle size of ~4-6 nm with a specific surface area of 160 m2/g and exhibits a pure phase of anatase containing ~5 mol% of N evidenced by XPS. However, the nanometric-sized TiO2-xNy powder shows the photocatalytic degradation of methylene blue solution effectively by exposing the powders in aqueous solution under visible light. [ABSTRACT FROM AUTHOR]