This paper examines the interaction between Eu(III) and a multiwall carbon nanotube (MWCNT)/iron oxide magnetic composite in the absence and presence of poly(acrylic acid) (PAA). PAA was used as a surrogate for natural organic matter. The effects of pH, initial Eu(III) concentration, and PAA on Eu(III) adsorption on the magnetic composite were investigated using a batch technique. Percentage adsorption of Eu(III) on the magnetic composite increased with increasing pH and decreased with initial Eu(III) concentration. PAA adsorption on the magnetic composite decreased with increasing pH and was not obviously affected bythe presence of Eu(III). The presence of PAA resulted in strong enhancement of Eu(III) adsorption below pH 4.5. However, above pH 5, an increase in soluble Eu-PAA complexes resulted in a decrease in Eu(III) adsorption on the magnetic composite. With increasing PAA concentrations, maximum adsorption of Eu(III) decreased and the adsorption "edge" shifted toward a lower pH range. Obvious difference of Eu(III)/PAA addition sequences on Eu(III) adsorption was observed above pH 4. The Freundlich model fitted Eu(III) adsorption isotherms very well in the absence and presence of PAA. These results are important for estimating and optimizing the removal of organic and inorganic pollutants by the magnetic composite.

Dielectric Ba0.6Sr0.4TiO3 thin films were epitaxially grown on (001) MgO by using pulsed laser ablation. Microstructure studies from x-ray diffraction and electron microscopy suggest that the as-grown films are c-axis oriented with an interface relationship of 〈100〉BSTO//〈100〉MgO. A room temperature coupled microwave phase shifter has been developed with a phase shift near 250° at 23.675 GHz under an electrical field of 40 V/μm and a figure of merit of ∼53°/dB. The performance of the microwave phase shifter based on the epitaxial Ba0.6Sr0.4TiO3 thin films on (001) MgO is close to that needed for practical applications in wireless communications.

High dielectric CaCu3Ti4O12 (CCTO) thin films were epitaxially grown on (001) LaAlO3 (LAO) substrates by pulsed laser deposition. Microstructural studies by x-ray diffraction, pole figure measurements, and transmission electron microscopy show that the as-grown films are good single crystalline quality with an interface relationship of (001)CCTO//(001)LAO and [100]CCTO//[100]LAO. Dielectric property measurements show that the films have an extremely high dielectric constant with value of 10 000 at 1 MHz at room temperature. It is interesting to note that the twinned substrate results in the formation of twinning or dislocations inside the CCTO film.

Giant resistance switching behavior in mixed conductive ͑LaBa͒Co 2 O 5+␦ epitaxial thin film were discovered in high temperature and reducing environments during the reduction and reoxidation process. A reproducible resistance response of over 99% was achieved in the films during a change of 4% H 2 / 96% N 2 to oxygen at temperature range of 400-780°C. The results indicate that at, low oxygen partial pressure, the extension of oxygen deficiency is an essential factor to the high temperature physical properties of ͑LaBa͒Co 2 O 5+␦ and demonstrates its potential application as a chemical sensor device for reducing environments at high temperature. © 2010 American Institute of Physics. ͓doi:10.1063/1.3484964͔Cobalt based perovskite oxides have received increasing attention in the past decade due to their high mixed ionicelectronic conductivity in chemical sensor and green energy device development.1,2 Recent studies indicate that oxygen deficient doped double perovskite cobaltates ͑LnBa͒Co 2 O 5+␦ ͑Ln= La, Pr, Gd͒ have excellent mixed ionic-electronic conductivity with a fast surface exchange coefficient. [3][4][5] In this family of compounds, the A-site cationic ordered arrangement is favored due to the large difference in Ba 2+ and rare earth ionic radii, except ͑LaBa͒Co 2 O 5+␦ ͑LBCO͒. In LBCO, the doped bivalent Ba 2+ is not only inducing plenty of oxygen deficiency but also structurally providing the capability to achieve the smallest oxygen deficiency in this family of compounds due to the very similar ionic radii between Ba 2+ and La 3+ . Therefore, LBCO provides a unique platform with the geometrical stabilized perovskite phase and a wide range of oxygen deficiency, which enables one to study the electrical conductivity, defect structures and stability at high temperature over a wide range of oxygen partial pressure.Up to now, studies on LBCO are only limited to the bulk polycrystalline samples for low temperature transport and magnetic properties.6-8 The high temperature physical properties of LBCO are rarely studied due to the structure failure of the bulk material in a reducing environment. Recently, we have fabricated epitaxial single crystalline LBCO thin films on ͑001͒ LaAlO 3 ͑LAO͒, enabling one to systematically study the electrical transport properties of LBCO under various environments. A reproducibly dramatic resistance change is observed as the LBCO film is exposed to oxidizing and reducing environment over a wide range of temperature. Especially, it is interesting to note that the re-oxidation of the LBCO film has a very short response time, suggesting that an exceedingly fast oxygen exchange rate occurs at the film surface.A KrF excimer pulsed laser deposition system with a wavelength of 248 nm was employed to deposit the ͑LaBa͒Co 2 O 5+␦ thin films on ͑001͒ LaAlO 3 substrates. An energy density of 2.0 J / cm 2 and a laser repetition rate of 5 Hz were adopted during film deposition. A high density, single phase, stoichiometric ͑LaBa͒Co 2 O 5+␦ target was purchased from Praxair Inc. The deposit...

The (LaBa)Co2O5+δ thin films were grown on (001) SrTiO3 single crystal substrates by using pulsed laser deposition. Microstructure studies from x-ray diffraction and electron microscopy show that the films have good epitaxial quality with a-axis orientation and sharp atomic interface. Transport property and isothermal magnetoresistance measurements have been used to understand the physical properties of the films with anomalous magnetic phenomena and the largest reported magnetoresistance value of 19% at 40 K.

Diffusion and sorption of U(VI) in compacted bentonite were studied using a capillary method. The experiments were carried out at room temperature in 0.1 M NaClO 4 solutions at pH 7.0 ± 0.1. Effects of contact time, solution concentration and bentonite bulk density on diffusion were also investigated. The results fit the Fick's second law very well and are in good agreement with the literature data for similar bentonite dry densities [3]. The K d values from capillary method are in most cases lower than those from batch experiments. The interlaminary space of the compacted bentonite contributes significantly to the sorption of uranium. The apparent diffusion coefficient D a of diffusion derived from the experiments are used to simulate its diffusion in compacted bentonite and the results indicate that several meters of compacted bentonite is enough to prevent the diffusion of from the repository to the environment.

Raman spectra of LCMO films grown on LAO (001), STO (001), and MgO (001) substrates were studied at different temperatures. The effect of temperature, doping level and strain on Raman spectra are discussed in detail. With decreasing temperature, the changes of Raman spectra are correlated with the disorder-order transition, shuch as: paramagnetism to ferromagnetism, and chargeordering. The strain induced by lattice-substrate mismatch affects the Raman spectra strongly. The mode induced by disorder of oxygen defects is apparently observed in La0.67Ca0.33M nO3 film on STO due to the larger tensile strain. While this mode can not be seen in the Raman spectra for the films on LAO and MgO. A strong unsigned mode at about 690 cm −1 is observed in all films except for La0.67Ca0.33M nO3 film on LAO, which is not observed in bulk sample easily. It suggests that the mode is closely related to the strain.

Single-crystalline perovskite LaBaCo2O5.5+δ thin films were grown on a (110) NdGaO3 single-crystal substrate in order to systematically investigate the effect of lattice mismatch on the electrical transport properties in comparison to the films on LaAlO3, SrTiO3, and MgO substrates. Microstructure studies reveal that all of the LaBaCo2O5.5+δ films are of excellent quality with atomically sharp interface structures. The electrical and magnetic transport property studies indicate that the resistivity, magnetoresistance, and magnetic moment of the film are very sensitive to the substrate materials because of the lattice mismatch/interface strain. The Curie temperature, however, is almost independent of the strain imposed by the substrate, probably because of the strong coupling between the nanodomain boundary and interface strain.