Magnetic orientation behavior of L-type zeolite with rare-earth elements under low magnetic field.

The magnetic orientation of L-type zeolite ion-exchanged with various rare-earth elements was observed under a low magnetic field of 0.9 T. The orientation along the applied magnetic field was classified into three types: c-axis orientation for Ce3+, Pr3+, Nd3+, Tb3+, Dy3+ and Ho3+, ab-plane orientation for Er3+, Tm3+ and Yb3+, and random orientation for Eu3+ and Gd3+. The different orientation behavior was considered to originate from the electronic structures of the rare-earth ions introduced into the zeolite structure.

Direct observation of potential phase at joining interface between p-MgO and n-MgFe2O4.

Visualization of the depletion layer is a significant a guideline for the material design of gas sensors. We attempted to measure the potential barrier at the interface of core-shell microspheres composed of p-MgO/n-MgFe2O4/Fe2O3 from the inside out by means of Kelvin probe force microscopy (KPFM) as a first step to visualizing enlargement of the depletion layer. As determined by high-angle annular dark-field scanning transmission electron microscopy, ca. 70% of the microspheres were hollow with a wall thickness of ca. 200 nm. Elemental mapping revealed that the hollow particles were composed of ca. 20 nm of MgO, ca. 80 nm of MgFe2O4, and ca. 100 nm of Fe2O3. A difference of 0.2 V at the p-MgO/n-MgFe2O4 interface was clarified by KPFM measurements of the hollow particles, suggesting that this difference depends on the formation of a p-n junction. The potential barrier enlarged by the formation of a p-n junction was considered to increase the resistance in air (Ra), since the Ra of the core-shell hollow microspheres was higher than that of MgO, Fe2O3, MgO-Fe2O3, and MgO/MgFe2O4/Fe2O3 particles with irregular shapes. Measurement of the potential barrier height by KPFM is a promising potential approach to tuning the gas sensitivity of oxide semiconductors.

Selective synthesis of zeolites A and X from two industrial wastes: Crushed stone powder and aluminum ash.

Crushed stone powder and aluminum ash are industrial wastes, and effective utilization of these wastes has been highly expected. Since the main components of the two wastes are Si, Al and O, those wastes can be used as starting materials for synthesis of zeolites of which some types have been commercialized as catalysts and ion-exchangers. In this study, zeolites A and X well-known as practical materials were successfully synthesized with high purity using the two industrial wastes by a mild process based on two hydrothermal treatments with intermediate acid treatment. In the first hydrothermal treatment at 150 °C, quartz in the crushed stone powder was dissolved and acid-soluble hydroxysodalite (Na8(AlSiO4)6(H2O)2(OH)2) with Si/Al = 1 and sodium aluminosilicate (Na6(AlSiO4)6) were formed. Those compounds were dissolved with HCl aq. solution. The zeolites were successfully synthesized from the second hydrothermal treatment of the yellow dried filtrates at 80 °C in NaOH aq. solution. In the process proposed, removal of Ca from the crushed stone powder was effective to formation of zeolites A and/or X. Selective synthesis of zeolites A and X was achieved by controlling the acid treatment conditions. Furthermore, the effect of the drying condition of the filtrate obtained after the acid treatment was also investigated on the differences in the product phase.

X-ray absorption and neutron diffraction studies of (Sr(1 - x)Ce(x))MnO3: transition from coherent to incoherent static Jahn-Teller distortions.

We have carried out Ce L- and Mn K-edge x-ray absorption near edge structure (XANES) measurements to experimentally determine the oxidation states of both Ce and Mn in (Sr(1 - x)Ce(x))MnO(3) (x = 0.1-0.4). It was found that although Ce is predominantly 4 + at low doping levels (x = 0.1 and 0.15), the Ce valency decreases with increasing Ce doping (reaching a value of around 3.5 + at x = 0.4). The average Mn oxidation state decreases with the increase of Ce content, with the percentage of Jahn-Teller active Mn(3+) ions increasing from 26% (x = 0.1) to 57% (x = 0.4). Precise structural parameters were also obtained from high resolution neutron diffraction studies for samples with x = 0.1-0.3. The crystal structure remains tetragonal in I4/mcm for x ≤ 0.3. The octahedral tilt angle increases with increasing Ce content, but the distortion of the MnO(6) octahedra is reduced significantly at x ≥ 0.2 due to a transition from long-range ordered Jahn-Teller distortions to incoherent static distortions.

Recovery of rare metal compounds from nickel-metal hydride battery waste and their application to CH4 dry reforming catalyst.

The recovery of valuable components such as nickel from nickel-metal hydride (Ni-MH) battery waste by chemical processes and their applications to CH(4) dry reforming catalysts were investigated. Three types of compound, identified by XRD analysis as NiO, CeO(2) and LaCoO(3) phases, were successfully separated from the waste by a series of chemical processes at room temperature using aqueous solutions of HCl, NaOH and NH(3), and Ni component of approximately 70% in Ni-MH battery waste was recovered. The separated NiO, CeO(2) and LaCoO(3) showed catalytic activities for CH(4) dry reforming. In particular, the separated NiO easily reduced to Ni(0) at an initial stage, and exhibited excellent catalytic activity in terms of CH(4) conversion and stability. Furthermore, it was found that the resulting Ni from separated NiO exhibited an anomalous catalysis from the comparison with that from regent NiO.

Zeolite formation from coal fly ash and heavy metal ion removal characteristics of thus-obtained Zeolite X in multi-metal systems.

Zeolitic materials have been prepared from coal fly ash as well as from a SiO(2)-Al(2)O(3) system upon NaOH fusion treatment, followed by subsequent hydrothermal processing at various NaOH concentrations and reaction times. During the preparation process, the starting material initially decomposed to an amorphous form, and the nucleation process of the zeolite began. The carbon content of the starting material influenced the formation of the zeolite by providing an active surface for nucleation. Zeolite A (Na-A) was transformed into zeolite X (Na-X) with increasing NaOH concentration and reaction time. The adsorption isotherms of the obtained Na-X based on the characteristics required to remove heavy ions such as Ni(2+), Cu(2+), Cd(2+) and Pb(2+) were examined in multi-metal systems. Thus obtained experimental data suggests that the Langmuir and Freundlich models are more accurate compared to the Dubinin-Kaganer-Radushkevich (DKR) model. However, the sorption energy obtained from the DKR model was helpful in elucidating the mechanism of the sorption process. Further, in going from a single- to multi-metal system, the degree of fitting for the Freundlich model compared with the Langmuir model was favored due to its basic assumption of a heterogeneity factor. The Extended-Langmuir model may be used in multi-metal systems, but gives a lower value for equilibrium sorption compared with the Langmuir model.

Crystal structures and phase transition in (Sr(0.8)Ce(0.2))(Mn(1-y)Co(y))O(3) (y = 0 and 0.2): the influence of Jahn-Teller distortion.

We have studied the crystal structures of (Sr(0.8)Ce(0.2))(Mn(1-y)Co(y))O(3) (y = 0 and 0.2) using neutron diffraction. Both (Sr(0.8)Ce(0.2))MnO(3) and (Sr(0.8)Ce(0.2))(Mn(0.8)Co(0.2))O(3) have a tetragonal structure in space group I4/mcm at room temperature, and the octahedral tilt angle around the c-axis is nearly the same. The only significant difference is the shape of the Mn(Co)O(6) octahedron: it is elongated in (Sr(0.8)Ce(0.2))MnO(3) due to the cooperative Jahn-Teller (JT) effect, but essentially regular in (Sr(0.8)Ce(0.2))(Mn(0.8)Co(0.2))O(3) due to the absence of JT-active Mn(3+) ions. With increasing temperature, both compounds undergo a continuous phase transition at around 400 °C to a cubic structure in [Formula: see text], with no indication of a distinct transition in (Sr(0.8)Ce(0.2))MnO(3) from the removal of the static JT distortion. In addition, the temperature dependence of the octahedral tilt angle is very similar in the two samples, implying that the JT distortion has minimal effect on the octahedral tilting and the phase transition to cubic. X-ray absorption near-edge structure (XANES) analysis indicates that the Ce oxidation state is predominantly 4+ in both samples. The electrical conductivity is higher in (Sr(0.8)Ce(0.2))MnO(3) than in (Sr(0.8)Ce(0.2))(Mn(0.8)Co(0.2))O(3) in the temperature range studied (100-900 °C).

Sorption properties of the activated carbon-zeolite composite prepared from coal fly ash for Ni(2+), Cu(2+), Cd(2+) and Pb(2+).

Composite materials of activated carbon and zeolite have been prepared successfully by activating coal fly ash (CFA) by fusion with NaOH at 750 degrees C in N(2) followed by hydrothermal treatments under various conditions. Uptake experiments for Ni(2+), Cu(2+), Cd(2+) and Pb(2+) were performed with the materials thus obtained from CFA. Of the various composite materials, that were obtained by hydrothermal treatment with NaOH solution (ca. 4M) at 80 degrees C (a composite of activated carbon and zeolite X/faujasite) proved to be the most suitable for the uptake of toxic metal ions. The relative selectivity of the present sorbents for the various ions was Pb(2+)>Cu(2+)>Cd(2+)>Ni(2+), with equilibrium uptake capacities of 2.65, 1.72, 1.44 and 1.20mmol/g, respectively. The sorption isotherm was a good fit to the Langmuir isotherm and the sorption is thought to progress mainly by ion exchange with Na(+). The overall reaction is pseudo-second order with rate constants of 0.14, 0.17, 0.21 and 0.20Lg/mmol min for the uptake of Pb(2+), Cu(2+), Cd(2+) and Ni(2+), respectively.