A novel electrothermodynamic cycle based on temporal temperature variations (dT/dt); the pyroelectric effect was investigated for its potential role in the use of waste heat as renewable energy. Here, we present improved generating performance with relaxer ferroelectric ceramics ((1-x)Pb(Mg2/3Nb1/3)O-3-xPbTiO(3) (PMN-xPT)), which are well known for their strong dielectric and pyroelectric properties near the morphotropic phase boundary. The theoretical potential was evaluated using hysteresis loops, and the generating properties were analyzed in the laboratory using an engine dynamometer. The experiments yielded a value of 0.48mW/cm(3), which is 3times larger than that obtained previously, because of the high polarization properties.

This study addresses pyroelectric power generation through an original electrothermodynamic cycle for environmentally friendly automotive applications. Relaxor-based ternary Pb(In1/2Nb1/2)O-3-Pb(Mb(1/3)Nb(2/3)) O-3-PbTiO3 (PIN-PMN-PT) ceramics near a morphotropic phase boundary were applied as pyroelectric materials, and their electrical properties were investigated at different temperatures. Structural disordering, depending on the PIN content, influenced the diffuse phase transition between the tetragonal and cubic structures and contributed to the power-generating behavior. The net power-generating energies (P-net) were 2.43-3.01 mW/cm(3) at temperatures above 200 degrees C and were maintained at above 1 mW/cm3 over a temperature range of approximately 100 degrees C. In the PIN-PMN-PT system, the temperature dependence of the power-generating performance was improved, and disordering of the perovskite crystal structure can be controlled to achieve pyroelectric energy conversion by the electrothermodynamic cycle over a wider range of usage temperatures. (C) 2018 Elsevier B.V. All rights reserved.

In pyroelectric applications, the general figures of merit (FOMs) have been applied and reported near room temperature. We derived the modified FOMs in considering our electro-thermodynamic cycle for the usage environment of automotive applications. The relationship between the material properties and generating performance of PZTs was investigated at various temperatures. The (F) over bar (D) was suggested from F-D, a FOM for a pyroelectric sensor, based on the modified pyroelectric coefficient (p); (p) over bar. (p) over bar was calculated by the change of the spontaneous polarization (P-S) according to a given temperature variation during one cycle; Delta P-S/Delta T (T-max-T-min). It was indicated that the (F) over bar (D) could be effective as a FOM for the pyroelectric generating performance and the dielectric loss (tan delta) significantly affected the generating performance in addition to (p) over bar under high-temperature and electric field conditions. Furthermore, of the PZTs tested, C-91 sample which showed the highest generating performance resulted in a generating energy of 1.3 mW cm(-3) in the engine dynamometer assessment. This is 13 times greater than the generating energy reported in a previous study of C-6 (0.1 mW cm(-3)).

Structural change of Pd nanoparticles on aluminum oxide during hydrogen absorption reaction was directly observed by X-ray absorption fine structure with dispersive optics. Hydrogen pressure dependence of the expansion of the interatomic distance for Pd-Pd bonding in Pd nanoparticles was investigated by real-time-resolved and in situ observation with a rate of 50 Hz at room temperature. It has been revealed that the Pd nanoparticles show strong hydrogen pressure dependence of the reaction rate and the saturated interatomic distance for the hydrogen absorption. Determined reaction order implies that the rate of the hydrogen absorption reaction is limited by the surface dissociative adsorption step. (C) 2010 Elsevier B.V. All rights reserved.

For decades, wasted heat has increased, and the thermal energy conversion system has become more important, especially in automobile applications. For waste heat recovery, an innovative electrothermodynamic cycle (pyroelectric effect with an external electric field) was recently presented, which is based on temporal temperature variations in wasted heat from engine exhaust gas. Herein, for further improvement, a generating mechanism of the cycle is investigated via an Operando analysis, time-resolved synchrotron X-ray diffraction with generating assessment. Polarization changes are analyzed via simultaneous electrical and crystallographic studies. Three types of materials are prepared: soft and hard types of PZTs and lead magnesium niobate-lead titanate (PMN-PT). Among them, PMN-PT has the highest generating power. When an external electric field is applied, the PMN-PT exhibits only 180 degrees domain rotations, whereas the other materials exhibit both 90 degrees and 180 degrees rotations. A strong driving force for 180 degrees rotation depresses rotations in other angles and increases polarization changes. The results show that the material development, which has only 180 degrees switching domains, has potential for use in the establishment of a high-efficiency waste heat recovery system.

We compare the electronic properties of Cu(111) and Cu2O(111) surfaces in relation to the dissociation of NO using first principles calculations within density functional theory. We note a well-defined three-fold site on both O- and Cu-terminated Cu2O surfaces which is verified as the active site for the adsorption and dissociation of NO. The interaction of Cu with O atoms results in the forward shifting of the local density of states and formation of unoccupied states above the Fermi level, compared to the fully occupied d band of pure Cu. These results give valuable insights in the realization of a catalyst without precious metal for the dissociation of NO.

Platinum group metal-free (PGM-free) catalysts based on transition metal-nitrogen-carbon nanomaterials have been studied by a combination of ex situ and in situ synchrotron X-ray spectroscopy techniques; high-resolution Transmission Electron Microscope (TEM); Mossbauer spectroscopy combined with electrochemical methods and Density Functional Theory (DFT) modeling/theoretical approaches. The main objective of this study was to correlate the HO2- generation with the chemical nature and surface availability of active sites in iron-nitrogen-carbon (Fe-N-C) catalysts derived by sacrificial support method (SSM). These nanomaterials present a carbonaceous matrix with nitrogen-doped sites and atomically dispersed and; in some cases; iron and nanoparticles embedded in the carbonaceous matrix. Fe-N-C oxygen reduction reaction electrocatalysts were synthesized by varying several synthetic parameters to obtain nanomaterials with different composition and morphology. Combining spectroscopy, microscopy and electrochemical reactivity allowed the building of structure-to-properties correlations which demonstrate the contributions of these moieties to the catalyst activity, and mechanistically assign the active sites to individual reaction steps. Associated with Fe-N-x motive and the presence of Fe metallic particles in the electrocatalysts showed the clear differences in the variation of composition; processing and treatment conditions of SSM. From the results of material characterization; catalytic activity and theoretical studies; Fe metallic particles (coated with carbon) are main contributors into the HO2- generation.

The epitaxial growth, structural properties, and ferroelectric properties of bismuth lanthanum nickel titanate (Bi1-xLax) (Ni0.5Ti0.5)O-3 (BLNT) thin films deposited on Pt(100)/MgO(100) substrates by rf magnetron sputtering have been investigated using x-ray diffraction, transmission electron microscope, and polarization-electric field hysteresis loop measurements. The ferroelectric BLNT(00...) phase with c-axis orientation and a single-phase tetragonal perovskite structure appeared at x >= 0.3. The tetragonality (c/a) increased significantly from 1.004 to 1.028 with increasing La content. The fabricated BLNT films of x >= 0.3 indicated the apparent fourfold rotational symmetry observed for a MgO(202) substrate, a bottom Pt(202) electrode, and a BLNT(101) ferroelectric film, based on phi scan measurements. These results imply that the present La-substituted BLNT films are grown heteroepitaxially at x >= 0.3. It was confirmed that Bi in the BLNT films is in a trivalent state at A sites in the perovskite crystal, based on x-ray anomalous diffraction measurements and x-ray absorption near edge structure spectra. The sputtering technique using compacted powder targets designed by taking the bond dissociation energy of metal oxides into account provided epitaxial perovskite-structured BLNT thin films on Pt(100)/MgO(100) substrates. It is shown that the c-axis oriented epitaxial BLNT film exhibits a hysteresis loop shape with a P-r value of 12 mu C/cm(2) that is comparable to typical high-performance Bi3.25La0.75Ti3O12 (BLT) film. (c) 2007 American Institute of Physics.

A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate the pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, and Fe) without charging issues and clarified reciprocal site-correlations among these elements with nanometer resolution. We found that Cs atoms were likely to be adsorbed evenly over the entire particle; however, we identified an occupational conflict between Cs and Mg atoms, implying that Cs sorption involves ion exchange processes. Spatially resolved X-ray absorption spectra (XAS) of the Cs-4,Cs-5 M-edge region showed Cs to be present in a monocation state (Cs+) as typically observed for Cs compounds. Further pinpoint XAS measurements were also performed at the Fe L-2,L-3-edge to determine the chemical valence of the Fe atoms. The shapes of the spectra were similar to those for Fe2O3, indicating that Fe in the clay was in a 3+ oxidation state. From these observations, we infer that charge compensation facilitates Cs adsorption in the vicinity of a substitution site where Si4+ ions are replaced by Fe3+ ions in SiO4 tetrahedral sheets. Our results demonstrate the utility of SR-PEEM as a tool for spatially resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples. Published by AIP Publishing.

The self-regenerative function of precious metals in the intelligent catalyst is an epoch-making technology in the history of automotive catalysts after the 1970's. The mechanism of the self-regenerative function is studied by X-ray absorption fine-structure (XAFS) analyses. The function was realized through a cyclic movement of Pd between the outside (as Pd nanoparticles) and the inside (as Pd cations in the lattice) of the perovskite crystal in synchronization with the inherent fluctuations between reductive and oxidative (redox) atmospheres that occur in real automotive exhaust gases. As the result, the growth of Pd particles can be suppressed during the entire lifetime of the vehicle. Moreover, the speed of this function was measured at the time resolution of a 10 ms by in situ energy dispersive XAFS, and it is proved that the self-regenerative function occurs at an extremely high speed. Furthermore, the new perovskite catalysts which have the self-regenerative function of Rh and Pt, as well as Pd, are discussed here. This self-regenerative function provides a new and useful tool for designing the future catalyst technology. (C) 2006 Elsevier B.V. All rights reserved.

The behavior of halide ions on the Au(111) electrode surface in two ionic liquids (ILs), 1-buthyl-1-methylpyrrolidiniun bis(trifluoromethylsulfonyl)amide ([BMP]TFSA) and 1-buthyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([BMIM]TFSA), was investigated by monitoring the structure of the electrode surface. The potential dependences of the X-ray diffraction intensity, which originate from the Au(111)-(1 X 1) structure and the surface normal structure, were measured simultaneously with cyclic voltammograms. We considered the effects of both ion concentration and ion species. The results revealed that halide ions are coadsorbed with IL molecules on the electrode surface and increase the mobility of surface atoms. By contrast, the Au(111) surface does not reconstruct to the (p X root 3) structure, even in the IL containing 200 mM Br-. This suggests that the interaction between halide ions and surface Au atoms is weaker than that between IL molecules and surface Au atoms; that is, the surface properties are mainly governed by adsorbed IL molecules. Furthermore, a comparison of the two ILs revealed that the effect of halide ions on the structure of the Au(111) electrode surface depends on the strength of the interaction between IL molecules and surface Au atoms.