23 research outputs found
Effect of ion-exchange on structural, electronic, and vibrational properties of the-O-Ti-O-Ti-O-quantum wires in ETS-10
No full textThe exchange of the extra-framework Na+ ions in Engelhard titanosilicate (ETS-10) with Ag+ and Ru3+ has been investigated theoretically by means of density functional theory (DFT) and experimentally, with the aim of elucidating its effects on the structural, electronic and vibrational properties of the Ti-O-Ti quantum wire. A comparison of theoretical findings and experimental Raman data in the region of Ti-O-Ti stretching reveals that the introduction of the Ag+ ions preserves the integrity of the wire to a large extent while Ru3+ ions cause large-scale distortions along with some loss in crystallinity
Understanding the effects of ion-exchange in titanosilicate ETS-10: A joint theoretical and experimental study
No full textDensity functional theory (DFT) calculations within the gradient-corrected approximation (GGA) were carried out on two models of Engelhard titanosilicate (ETS-10) with the aim to elucidate the effect of ion exchange on the structural and electronic properties of the TiOTi quantum wire. The partial and full exchange of Na+ cations with alkaline, earth-alkaline, and transition metal ions have been investigated. The theoretical results have been complemented by experimental X-ray diffraction (XRD) and Raman data in the region of the TiOTi stretching of the wire. Overall, the experimental data support the theoretical findings where substitution of Na+ with K+, Ag+, and Ca2+ cause only minor structural changes in the wire while the inclusion of Zn2+, Ru3+, and Au3+ cause its partial or entire disruption
Secondary Growth of Microporous Vanadosilicate AM 6 Films
No full textOriented vanadosilicate AM-6 thin films with an average thickness of 1-2 mu m were prepared on the ITO coated glass substrates using secondary growth method with a partial a(b)-out-of-plane preferred crystal orientation for the first time. In secondary growth method, titanosilicate ETS-10 crystals were deposited on the substrate from a colloidal suspension to form seed layers. Then, the hydrothermal growth of the seed crystals was conducted to form AM-6 films. It was observed that the AM-6 films formed possess similar 1-D VO3 (2-) quantum wires as also observed in powder AM-6 crystals. Afterward, the effect of reaction temperature and amount of water in the secondary growth gel on crystal morphology and a(b)-out-of-plane crystallographic preferred orientation (CPO) were investigated to gain a better understanding of the secondary growth mechanism of vanadosilicate AM-6 films. The results suggested that the increased amount of water leads to increased CPO in the AM-6 films, whereas an increase in reaction temperature from 503 to 528 K leads to more c-oriented AM-6 films with a decreased CPO value. Furthermore, an increase in the reaction temperature led to a decrease in the reaction time, resulting in the formation of quartz impurity. Accordingly, well intergrown a(b)-out-of-plane oriented vanadosilicate films were grown for the first time using ETS-10 seed crystals and it is believed that this work provides an effective pathway for controlling the synthesis of AM-6 films expanding the possible range of applications of these materials possessing 1-D quantum wires
Ionic conductivity of microporous titanosilicate ETS-10 and ion-exchanged M n+ -ETS-10 (where, M n+ = Li + , Na + , Mg 2+ , Zn 2+ , Ca 2+ ) thin films prepared by secondary growth method
No full textImpedance spectroscopy was used to investigate the long-range ionic conductivity of the microporous, titanosilicate (Na,K)-ETS-10 and ion-exchanged Mn+-ETS-10 (where, Mn+ = Li+, Na+, Mg2+, Zn2+, Ca2+) thin films prepared by secondary growth method. To figure out the effect of grain boundary on ionic conduction, as-synthesized (Na,K)-ETS-10 films possessing different thicknesses of columnar grain structure (i.e., films prepared via 4h-, 6h-, 8h-, and 10h-growth) were tested. The conductivities of the films with different thicknesses at 723 K were in the range of similar to 10(-3) Omega(-1)cm(-1). However, activation energies of the films decreased from 52.8 to 47.3 kJ mol(-1) (i.e., 0.6 to 0.5 eV) for 4h-(Na,K)-ETS-10 to 10h-(Na,K)-ETS-10 films, respectively. The as-synthesized (Na,K)-ETS-10 film prepared via 6h-growth (denoted as (Na,K)-6h-ETS-10) and monovalent cation-exchanged samples Li- and Na-6h-ETS-10 films exhibit conductivities of 2.1 x 10(-3), 2.4 x 10(-4), and 2.7 x 10(-4) Omega(-1)cm(-1), respectively, at 723 K and activation energies of 50.1, 55.5, and 55.4 kJ mol(-1), respectively, in the temperature range 573-773 K. Divalent cation-exchanged samples Mg-, Zn- and Ca-6h-ETS-10 films exhibit conductivities of 2.3 x 10(-4), 2.9 x 10(-4), and 8.8 x 10(-5) Omega(-1)cm(-1), respectively, at 723 K and activation energies of 62.5, 57.9, and 65.2 kJ mol(-1), respectively, in the temperature range 573-773 K. The data shown here indicate that ionic conductivity of intergrown (Na,K)-ETS-10 films prepared by secondary growth method were significantly enhanced with respect to pressed pellets of powder zeolite and zeo-type materials which imply the importance of engineering the microstructure of the zeolite film to improve the conductivity of zeolites and zeo-type materials
CONDUCTIVITY OF MICROPOROUS TITANOSILICATE ETS 10 THIN FILMS PREPARED THROUGH SECONDARY GROWTH METHOD
No full text
CONDUCTIVITY OF MICROPOROUS TITANOSILICATE ETS 10 THIN FILMS PREPARED THROUGH SECONDARY GROWTH METHOD
No full textZeolite A coated Zn1-XCuXO MOS sensors for NO gas detection
No full textIn the current study, a novel and highly sensitive gas sensing material for the detection of NO gas was reported. Copper doped zinc oxide nanostructures (Zn1-xCuxO, where x = 0.25 steps) were grown as a semiconducting sensor material by using Successive Ionic Layer Adsorption and Reaction (SILAR) method. The structural, morphological and optical properties of nanostructures were investigated by X-Ray Diffractometer (XRD), Scanning Electron Microscope (SEM) and UV-visible spectrometer. NO gas sensing measurements were carried out as a function of temperature and gas concentrations. The sensors exhibited acceptable responses towards 50 ppb NO gas at operating temperature of 55 degrees C. The sensors were optimized and the maximum response of 8% was obtained for the Zn0.75Cu0.25O sensor. To increase sensor selectivity, zeolite A (LTA) microporous film, used as a filter, was coated on the optimized Zn0.75Cu0.25O sensor by using secondary growth method. zeolite A coated Zn0.75Cu0.25O sensor exhibited both high selectivity and high response towards NO gas. The detection limit of the zeolite coated Zn0.75Cu0.25O sensor was shifted to 20 ppb for NO gas at operating temperature of 25 degrees C
