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Selective catalytic reduction (SCR) of NO{sub x} by hydrocarbons was investigated on Pt doped MCM-41 and copper ion and/or cerium ion-exchanged Al-MCM-41 in the presence of excess oxygen. It was found that Pt/MCM-41 provided the highest specific NO reduction rates as compared with other Pt doped catalysts reported in the literature, such as Pt/Al{sub 2}O{sub 3} and Pt/ZSM-5. For different hydrocarbons, the catalytic activity decreased according to the sequence of C{sub 3}H{sub 6} {approx} C{sub 2}H{sub 4} >> C{sub 3}H{sub 8} > CH{sub 4}. This catalyst was also stable in the presence of H{sub 2}O and SO{sub 2}. Cu exchanged Al-MCM-41 and cerium promoted Cu-Al-MCM-41 (i.e., Ce-Cu-Al-MCM-41) were also found to be active in this reaction. Higher NO{sub x} conversions to N2 were obtained on the Ce-Cu-Al-MCM-41 as compared with Cu-Al-MCM-41. The activity of Ce-Cu-Al-MCM-41 was approximately the same as that of Cu-ZSM-5; but the former had a wider temperature window. TPR results indicated that only isolated Cu{sup 2+} and Cu{sup +} ions were detected in the Cu{sup 2+}-exchanged Al-MCM-41 samples, which may play an important role in the selective catalytic reduction of NO{sub x} to N{sub 2}. After some cerium ions were introduced into Cu-Al-MCM-41, Cu{sup 2+} in the molecular sieve became more easily reducible by H{sub 2}. This may be related to the increase of catalytic activity of NO{sub x} reduction by ethylene.

Various powerful oxygenation approaches were tested in order to find the limits of the oxygen-storage capability of YBaCo 4 O 7+δ . By means of extreme solid-medium high-pressure oxygenation employing KCIO 3 as an oxygen generator the phase was successfully loaded with excess oxygen up to δ ≈1.56.

Oxygen desorption from ZnO was measured by TPD technique to estimate the increase in the amount of adsorbed oxygen on ZnO by platinum loading. The total amount of adsorbed oxygen increased by platinum loading where excess oxygen adsorbed not only on platinum particles but also on ZnO. The excess adsorption on ZnO was remarkable at 400°C.

Strongly over-doped HgBa2Ca2Cu3O8+δ samples with a T c as low as 97 K were successfully obtained using highly oxidized BaCuO2+e (e ≈ 0.13) and BaO2 powders as starting materials for the high-pressure synthesis at 5 GPa and 950 °C. The over-doped state was confirmed by observing a negative value for the Seebeck coefficient at temperatures above T c in a thermoelectric power measurement. Synthesis from less oxidized BaCuO2+e (e ≈ 0.06) yielded material with a lower doping level. By subsequent annealings in O2 at 300 °C and in Ar at 400 °C optimized (T c = 134 K) and under-doped(T c = 118 K) samples, respectively, were obtained. According to the magnetization experiments, the heavier the doped hole concentration was, the better was the H irr -versus-(T/T c ) characteristics.

The Pt-Rh/Al 2 O 3 catalysts were prepared in an attempt to overcome the limitation of the narrow temperature window for NO reduction with C 3 H 6 in the presence of excess oxygen. The impregnated Pt-Rh/Al 2 O 3 catalyst by incipient wetness method did not show high NO conversion as well as high N 2 selectivity owing to the rapid oxidation of C 3 H 6 to CO 2 . But the mechanically attrited Pt-Rh/Al 2 O 3 catalyst could be an effective catalyst for NO reduction in a quite wide temperature window by preventing the spillover of the adsorbed C 3 H 6 from Rh to Pt surface.

Oxygen radial (O2−, O−)-accommodated 12CaO·7Al2O3 (C12A7) releases oxygen molecules at about 800 °C when heated in helium. The corresponding weight loss nearly accords with that calculated from an ...

The effects of interfacial fluorination on the metal/Al2O3/HfO2/SiO2/Si (MAHOS) memory structure have been investigated. By comparing MAHOS memories with and without interfacial fluorination, it was identified that the deterioration of the performance and reliability of MAHOS memories is mainly due to the formation of an interfacial layer that generates excess oxygen vacancies at the interface. Interfacial fluorination suppresses the growth of the interfacial layer, which is confirmed by X-ray photoelectron spectroscopy depth profile analysis, increases enhanced program/erase efficiency, and improves data retention characteristics. Moreover, it was observed that fluorination at the SiO–HfO interface achieves a more effective performance enhancement than that at the HfO–AlO interface.

Co3O4 as an NH3-oxidation catalyst may transform reversibly to CoO under reaction conditions, even in the presence of excess oxygen. The use of alumina may then result in the formation of cobalt aluminate rendering the catalyst inactive. The formation of cobalt aluminate can be avoided by using ZnAl2O4 as a support.

Carbonaceous deposit (denoted as C(d)) which was formed on alumina by C2H4 pyrolysis at 550 °C reacted selectively and preferentially with a mixture of NO and O2 in the presence of C2H4, suggesting that the C(d) acts as an effective intermediate during the selective reduction of NO with C2H4 too.

The activity of Pt(0.5 wt%)/AlPO4 for C3H6-SCR was found to be much higher than that of Pt(0.5 wt%)/Al2O3; although the selectivity toward N2O of both the catalysts were comparable, the maximal conversion of NO to N2 by Pt(0.5 wt%)/AlPO4 was higher than that by Pt(0.5 wt%)/Al2O3, and moreover the temperature window of the former located in lower side than that of the latter. The superiority of Pt(0.5 wt%)/AlPO4 was discussed on the basis of the results of XPS measurements.

The ceramic La 2 CuO 4+ δ with excess oxygen is found to have two superconducting phases, whose transition temperatures are 32 K (36 K) of the low T c phase and 45 K of the high T c phase, respectively. In this paper we report the normal state susceptibilities of the two kinds of almost single superconducting phases. The susceptibility of the high T c phase was found to be similar to that of optimally doped (LaSr) 2 CuO 4 . The susceptibility gradually decreased with decreasing temperature from 300 K. On the other hand, in the low T c phase, the first large susceptibility peak suggesting some antiferromagnetic ordering was observed at about 260 K, and then the second small peak at about 215 K. In the preliminary measurements, the susceptibility of the powdered low T c phase showed a Curie-type increase from about 215 K down to the superconducting transition temperature.

Highly active alumina supported silver nano-particles were evaluated for SCR of NOx using methane in an excess oxygen atmosphere. Cs promoted Ag/Al2O3 catalysts showed high NO reduction activity. In addition, the prepared materials exhibited promotional effects in the presence of SO2 and H2O. The X-ray diffraction profiles of fresh and used catalysts indicated that the prepared materials are thermally stable up to 70 h of time-on-stream reaction. Activity results well correlated with the characterization data, which revealed that the high deNOx ability was due to superior NO adsorption properties as well as the presence of an appropriate amount of Ag+ and metallic Ag particles.

Features of structural fluctuations in T-type oxides, Nd2NiO4 and La-Sr-Ni-O, have been examined by means of transmission electron microscopy. In addition to the LTO structure, a complicated modulated structure is observed in Nd2NiO4 at room temperature. In La1.8Sr0.2NiO4, on the other hand, an enhancement of a structural fluctuation in the HTT phase on cooling, which is related to the HTT to LTO transition, is detected as an increase in an intensity of diffuse scattering at the X point, although the transition does not occur. Because the existence of excess oxygens has been reported, both the appearance of the modulated structure in Nd2NiO4 and the suppression of the transition would be due to the excess oxygen involved in the T-type structure.

Recently, we discovered a catalytic process that efficiently reduces NO with CH4 in the presence of excess O2 Co exchanged ZSM-5 is an effective catalyst for this novel reaction. Complete conversion of NO to N2 was obtained over a Co-ZSM-5 catalyst at 400°C. The presence of O2 in the feed significantly enhances the NO reduction activity, and the catalytic activity for NOx reduction is proportional to the CH4 level. This discovery may provide a new, alternative approach for NOx emission control for both stationary and mobile sources. Zeolite Y is a poor support compared to ZSM-5, and CoO/AI2O3 is inactive for this reaction. Cu-ZSM-5, which is a uniquely active catalyst for the direct NO decomposition, is a poor catalyst for the NO reduction by CH4 in the presence of excess O2. In addition we describe the impact of water as an inhibitor for this reaction.

The strong dependence of Tc on oxygen content or excess oxygen is shown for many kinds of high Tcsuperconductors. From the result, it is concluded that the excess oxygen is a key to elucidate the superconduction mechanism. It is found that the plot of logarithm of conductivity vs. oxygen content has a good similarity with that of Tc vs. oxygen. This fact indicates that the normal state conduction is correlated to the superconduction and the electronic structure model is applicable to both normal and superconducting states.

This paper discusses the technical progress of a US Department of Energy Innovative Clean Coal Technology project demonstrating advanced wall-fired combustion techniques for the reduction of nitrogen oxide (NO{sub x}) emissions from coal-fired boilers. The primary objective of the demonstration is to determine the long-term performance of advanced overfire air and low NO{sub x} burners applied in a stepwise fashion to a 500 MW boiler. A 50 percent NO{sub x} reduction target has been established for the project. The focus of this paper is to present the effects of excess oxygen level and burner settings on NO{sub x} emissions and unburned carbon levels and recent results from the phase of the project when low NO{sub x} burners were used in conjunction with advanced overfire air.

The phonon-Raman spectrum of Bi2−xPbxSr2Can−1CunO2n+4+d had been studied in detail. The 630cm−1 phonon which is assigned as a z-vibration of the oxygen between the CuO2 and the BiO layers and of the oxygens of the BiO layers shows a sample dependent shoulder at 650cm−1. This shoulder is interpreted as a mode arising from different oxygen ordering in the BiO layers and from excess oxygen. Substituting Bi with Pb increases the amount of 2223 phase and the intensity of that shoulder decreases.

The formation behavior of EuSi 2 O 2 N 2 prepared with various starting compositions and different methods from the Eu 2 O 3 -SiO 2 -Si 3 N 4 -Si system was investigated to demonstrate the effect of the oxygen content in raw materials on the synthesis of MSi 2 O 2 N 2 :Eu 2+ (M = Ca, Sr, Ba) phosphors for white light-emitting diodes. It was found that Eu 2 O 3 cannot be reduced by H 2 gas but can be reduced by a reaction with Si 3 N 4 in the synthesis process of EuSi 2 O 2 N 2 ; as a result, EuSi 2 O 2 N 2 was not obtained from the starting composition containing the excess oxygen content such as 1/2Eu 2 O 3 - 1/2SiO 2 - 1/2Si 3 N 4 even in H 2 gas flow because the extra oxygen causes the formation of secondary phases. A nearly single-phase EuSi 2 O 2 N 2 was obtained from the starting composition having a stoichiometric oxygen amount. The present study indicates that the extra oxygen induced by the use of Eu 2 O 3 should be controlled to synthesize MSi 2 O 2 N 2 :Eu 2+ phosphors as a single phase when Eu 2 O 3 is used as the Eu source material.

Oxygen permeation property in Nd deficient Nd 2 NiO 4 was studied. The oxygen permeation rate increases with increasing Ga. Nd deficiency in Nd 2 NiO 4 is also useful for increasing the oxygen permeation rate. The improved oxygen permeation rate could be assigned to the increased amount of excess oxygen and stabilizing a tetragonal structure at a low temperature. The oxygen permeation rate of Nd 1.9 (Ni 0.75 Cu 0.25 ) 0.95 Ga 0.05 O 4 achieved a value of 3.6 cm 3 /min cm 2 from air to He at 1273 K with 0.5 mm thickness and this value belongs to the highest class in the reported oxygen permeation rate.

Large, homogeneous single crystals of La2-xSrxNiO4 (x=0, 0.1, 0.2, 0.3) of 7 mm in diameter and 20 mm in length have been obtained by using FZ method under 02 atmosphere. The chemical analyses reveal the presence of excess oxygen in the crystals of x=0 and 0.1. Small magnetic susceptibility and obvious deviation from the Curie-Weiss law are observed, whereas the diamagnetic signals from superconductivity are not detected on heating from 4 K to 100 K. The resistivity is semi conductive at room temperature and becomes isolative below 100 K.

We successfully synthesized nearly single-phase samples of the nominal composition of Tl2Sr2CuOz. The temperature dependence of electrical resistivity for the sample showed that this was a normal metal. On the other hand, Tl2Ba2CuOz showed a transition from a superconductor to a nonsuperconducting normal metal, as the excess oxygen content z increased from 6.0 to 6.1. The properties of Tl2Sr2CuOz are disscussed in comparison with those of Tl2Ba2CuOz.

We have studied oxygen evolution, as a function of increasing temperature, of four oxygen-doped high T c cuprates. The oxygen effusion spectra of La 2 CuO 4+δ , YBa 2 Cu 3 O 6+δ , HgBa 2 CuO 4+δ , and Bi 2 Sr 2 CaCu 2 O 8+δ share unusually similar two-peak feature. Although excess oxygen ions (δ) occupy different crystallographic sites in different systems, i.e., interstitial site in La 2 CuO 4+δ and Bi 2 Sr 2 CaCu 2 O 8+δ , CuO chain in YBa 2 Cu 3 O 6+δ , and “normal” lattice site in HgBa 2 CuO 4+δ , the oxygen atoms evolve in two distinct steps upon heating. Considering the strong coupling between excess oxygen ions and doped holes, we suggest that this two-peak feature is intrinsic to the doped holes of all high T c cuprates.

Giant isotope effect in manganites is explained by a difference in the content of the nonstoichiometric oxygen for two isotopes. It is a consequence of mass dependence for the oxygen gas chemical potential. As the excess oxygen is the acceptor, this leads to an isotope dependence of hole density determining all the magnetic and electric properties.

We have characterized the superconducting (SC) La2CuO4+δ electrochemically oxidized at 333 K. As for the sample with single high-Tc phase ( T c =45 K ), we have observed the specific heat jump at 43.5±0.1 K: Δ C=320±25 mJ / mol K , corresponding to SC transition at 45 K. We have also studied the relation between nH, determined from Hall effect measurement as nH=1/eRH and the valence of Cu 2+p, determined by iodometric titration, in highly oxidized (La1−xSrx)2CuO4+δ (x=0–0.1); this relation was found to be apparently different from that of (La1−xSrx)2CuO4.

The effect of SO2 on activity for NO reduction by methanol over Ag/Al2O3 in the presence of excess oxygen has been investigated. Selective catalytic reduction activity was not decreased but increased and most effective NO reduction temperature shifted from 200-250 °C to 300-350 °C by pre-sulfated Ag/Al2O3 or addition of SO2 to reaction mixture.

We examine the effect of H2 on the selective reduction of NO by C3H8 over Ag/Al2O3 catalysts under lean-exhaust conditions. The NO reduction activity caused by C3H8 at low temperature (590-760 K) is greatly increased by adding H2 in the presence of excess oxygen and water vapor.

Catalytic performance of Ir catalysts for reduction of nitric oxide with carbon monoxide in the presence of SO2 and excess oxygen was investigated. NO was selectively reduced with CO on Ir/silicalite in an oxidizing atmosphere containing 1% to 10% O2 in the temperature range of 300-500 °C. The catalytic activity was scarcely influenced by 150 ppm SO2.

An Fe ion-exchanged BEA zeolite (Fe-BEA), which effectively performs selective catalytic reduction of N2O with methane in the presence of excess oxygen, is much more active than Fe-MFI zeolite reported in the literature.

By coupling microwave discharge with an Fe/HZSM-5 catalyst, novel effects have been observed for the conversion of NO to N2 in the presence of excess oxygen with high efficiency.

Oxygen contents of Bi-2201, Pb substituted Bi-2201 and T1-2201 were determined by iodometric titration and the relationship between Tc and oxygen content was examined. Oxygen number of Bi-2201 series increases with La substitution for Sr and reaches 6.52 with Lanthanum content of 1.0 in air annealed specimen. Lattice parameter, a, changes with La and Pb substitution, indicating its dependence on Cu charge. La and Pb atoms act as phase stabilizer of 2201 through charge control and structural stabilization respectively.

The crystal structure of the high-TC superconductor TlBa2Ca2Cu3O8+δ with different maximum TC values (~132, 126 and 120 K) is investigated by neutron powder diffraction measurements. The refined values of occupancy for the excess oxygen(δ) located in interstitial positions on the Tl–O layer, O(4), are 0.775(6), 0.751(16) and 0.813(25) for the samples with a maximum TC of ~132, 126 and 120 K, respectively. It is found that the Cu(2)–O(3) bond lengths of samples with higher TC are shorter, and the value of this bond length for the Tl-1223 sample with a TC of ~132 K is almost equal to that for Hg-1223 with a maximum TC of ~135 K. It is also found that the flatness of the CuO2 planes increases with increasing TC. It appears that the structural features of the CuO5 pyramids are among the factors contributing to the higher value of TC in cuprate superconductors.

Annealing effect on magnetic properties of superconductivity is investigated for the crystals of Bi1.9CaySr1.9-yCuO6+δ (0≤y≤1.8) in Bi-2201 phase. It is found that carrier density is reduced with Ca doping in Ca-poor region of y≤0.8. In contrast, the excess oxygen δ is saturated with doping at about the optimal Tc in Ca-rich region of y>0.8. The results indicate possible oxygen deficiencies with Ca doping, which gives a new aspect to a model for the appearance of 80 K-class superconductivity.

The relationship between the preparation procedure and superconducting properties of La{sub 1}Ba{sub 2}Cu{sub 3}O{sub y} was studied. A series of samples was sintered in an N{sub 2}-gas atmosphere for various lengths of time ranging from 1 to 40 h, followed by a fixed annealing procedure in O{sub 2}. It was found that the shorter the sintering period, the higher was the oxygen content. The samples sintered for a period of less than 15 h contained excess oxygen compared with La{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} and exhibited poor superconducting properties. The sample sintered for 40 h had an oxygen content y equal to 6.95, and had excellent superconducting properties. The mechanism for preparing high-quality La{sub 1}Ba{sub 2}Cu{sub 3}O{sub y} is discussed.

Uranium dioxide (UO2) exists over a wide range of O: U ratios (UO2 ± x ) at elevated temperatures as shown in Fig. 15.1 (Nadeau 1969). The variation of various physical properties with the O: U ratio has considerable technological significance, as use of UO2 based nuclear fuels necessarily encompasses a large region of the T-x space of Fig. 15.1. Plastic deformation in UO2 has been of interest since the earliest uses of UO2 as a nuclear fuel, since fuel pins are subjected to large thermomechanical stresses. In this chapter, we consider the slip systems in UO2 as a function of T and x. The way in which x is accommodated, particularly in hyperstoichiometric UO2, is also of importance to the mechanical behaviour. Isolated point-defect models are clearly not appropriate when 5–10 per cent excess oxygen can be added to the basic fluorite structure (Fig. 15.2) as interstitial species. Defect clusters (Willis 1978), an example of which is shown in Fig. 15.3, are stable over a range of T and x, and by analogy with interstitial solutes in metals and alloys, could be expected to be potent hardeners. However, such is not the case!

The structural, superconducting and normal-state properties of La2MO4+δ (M=Cu, Ni, Co) were studied by neutron powder diffraction, thermogravimetric analysis and resistivity measurements. La2CuO4+δ was found to undergo phase separation near room temperature into antiferromagnetic La2CuO4 and superconducting La2CuO4.08. Single-phase, metallic, superconducting La2CuO4.08 was prepared under 25 kbar of O2 at 500 °C. The excess oxygen present as O= ions provides a doping mechanism analogous to alkaline-earth metal ion substitution.

We study structural changes in YBa2Cu3O7−δ resulting from alloying with Al, Co, Fe and Ga. For the various interatomic interactions we use a bond model. Then we find at T = 0 that the tetragonal phase seemingly observed by x-ray diffraction consists of differently oriented orthorhombic domains. The observed uptake of excess oxygen as a consequence of doping with Al, Co and Fe is explained by domain formation. In addition, we propose a model to treat the system at T > 0.

A SOx deactivation free catalytic NOx reduction system in the presence of excess oxygen has been demonstrated. This system functioned well in the periodical two steps, which consisted of a short operation in oxidizing conditions and a far shorter operation in reducing conditions. In this system, only a Rh catalyst effectively catalyzed NOx reduction. In the presence of 50 ppm SOx, this system did not deteriorate at all.

A well-mixed CoAl2O4-Al2O3 catalyst calcined at 800 °C showed higher activity for the title reaction than that calcined at 500 °C as well as a roughly-mixed CoAl2O4-Al2O3 catalyst. The results of characterization suggested that in a CoAl2O4-Al2O3 catalyst the synergy of CoAl2O4 and Al2O3 particles at their interfaces is a critical factor causing its high activity.

Mostly, the activities for NO+C2H4+O2 and its related reactions decreased with increasing calcination temperature. In NO2+C2H4, N2 was selectively formed over alumina calcined at 800 °C, while over alumina calcined at the other temperatures, not only N2 but also NO was formed. Taking into account the temperature window as well, the most advantageous calcination temperature of alumina is 800 °C as a catalyst for NO+C2H4+O2.

The synthesis of Co3O4-free CoAl2O4 was successfully achieved, and its was revealed that this oxide (CoAl2O4) was more active than Al2O3 for NO+O2 reaction, the initiation step of the selective reduction of NO over cobalt-loaded aluminas, but was less active than Co3O4-containing CoAl2O4 for C2H4+O2 reaction, a side reaction.

The direct application of a silent electrical discharge on an ammonium-loaded zeolite as catalyst to remove NO in excess oxygen results in a synergetic improvement of NOx abatement at temperatures below 373 K.

The selective removal of Co3O4 from a cobalt-loaded alumina catalyst resulted in increased activity for the title reaction, indicating that Co3O4 inhibited the reaction but that the resudual CoAl2O...

Ethene has been added as reductant of NO in excess oxygen between an oxidation (Pt-MFI) and a reduction catalysts (Zn-MFI). The efficiency of ethene, namely the ratio of the amount of NO reduced to that of ethene consumed, reached about 2 and was much higher than that of conventional reduction on Cu-MFI.

Intermediate addition of reductant (C 2 H 4 ) into an NO+O 2 stream between an oxidation catalyst for NO to NO 2 (Pt-MFI) and a reduction catalyst for NO x to N 2 (In-MFI), a so-called IAR method, is shown to be very effective in selectively reducing NO to N 2 in the presence of excess oxygen.

High-resolution time-of-flight neutron and synchrotron X-ray powder diffraction studies of the ‘orthorhombic’ form of the high-T c superconductor Tl 2 Ba 2 CuO 6+δ evidence both the orthorhombic (Fmmm) phase and a new monoclinic (F112/m) form at high excess oxygen contents δ.