Electronic structure and correlation in β−Ti3O5 and λ−Ti3O5 studied by hard x-ray photoelectron spectroscopy

We have conducted hard x-ray photoelectron spectroscopy investigations of the electronic structure changes and electron correlation phenomena which take place upon the photoinduced reversible phase transition between β- and λ−Ti3O. From valence band spectra of β- and λ−Ti3O5, we have identified the bipolaron caused by the σ-type bonding of dxy orbitals in β−Ti3O5 and the π stacking between the dxy orbitals between different Ti sites in λ−Ti3O5, previously predicted by ab initio calculations. This indicates that the single electron band picture is valid for the description of photoinduced phase transitions. On the other hand, the Ti 2p and Ti 1s core level spectra exhibit nonlocal screening satellite features, which are typical spectroscopic signs of strong electron correlation in the coherent Tit2g states. The most striking result we obtain is that correlation in the valence band also manifests to reduce the plasmon energy, which results in an enhancement of the valence electron mass by a factor of 2.7

In situ x-ray photoelectron spectroscopy for electrochemical reactions in ordinary solvents

In situ electrochemical X-ray photoelectron spectroscopy (XPS) apparatus, which allows XPS at solid/liquid interfaces under potential control, was constructed utilizing a microcell with an ultra-thin Si membrane, which separates vacuum and a solution. Hard X-rays from a synchrotron source penetrate into the Si membrane surface exposed to the solution. Electrons emitted at the Si/solution interface can pass through the membrane and be analyzed by an analyzer placed in vacuum. Its operation was demonstrated for potential-induced Si oxide growth in water. Effect of potential and time on the thickness of Si and Si oxide layers was quantitatively determined at sub-nanometer resolution

Blow Forming of Mg Alloy Recycled by Solid-State Recycling *

Blow forming characteristics of AZ31 Mg alloy recycled by solid-state recycling were investigated. Cylindrical scraps and machined chips were recycled by hot extrusion and hot rolling in air. Oxide layers were observed in the recycled specimens by oxygen mapping with EPMA (Electron Probe Micro Analyser). The interval of the oxygen layers for the specimen from machined chips was much shorter than that for the specimen from cylindrical scraps. As a result of tensile tests, the mechanical properties of the specimen from cylindrical scraps were found to be almost the same as those of a rolled specimen from a virgin ingot. On the other hand, at elevated temperatures, the elongation of the specimens from machined chips was low, compared with those of the rolled specimens from a virgin ingot. The large amount of oxide contamination is likely to be responsible for the lower elongation of the specimens from machined chips. In blow-forming tests, the specimen from cylindrical scraps exhibited excellent formability similar to the rolled specimen from a virgin ingot. However, the specimen from machined chips showed poor formability. Thus, oxide contamination adversely affected the formability of recycled Mg alloy

Changes in Carbon Cycling during Development of Successional Agroforestry

Successional agroforestry systems (SAFS) mimic the structure of natural forests while providing economical outputs. This study clarifies how carbon cycling and carbon sequestration change during successional development of SAFS. In Brazil, three successional stages of SAFS, 6, 12, and 34 years old, were compared in terms of carbon balance. Aboveground biomass, fruit harvest, litterfall, soil respiration, and soil organic carbon were measured for two years and analyzed. Carbon sequestration expressed by net primary productivity increased with age of SAFS from 9.8 Mg·C·ha−1·year−1 in 6-year-old system to 13.5 Mg·C·ha−1·year−1 in 34-year-old system. Accumulation of plant biomass and increased internal carbon cycling in SAFS led to an intensive sequestration of carbon. SAFS can be a sustainable way of agricultural production on vulnerable tropical soils.Peer Reviewe

Tolerance of spin-Seebeck thermoelectricity against irradiation by swift heavy ions

The ion-irradiation tolerance of thermoelectric devices based on the spin Seebeck effect (SSE) was investigated by using 320 MeV gold ion (Au24+) beams modeling cumulative damages due to fission products emitted from the surface of spent nuclear fuels. For this purpose, prototypical Pt/Y3Fe5O12/Gd3Ga5O12 SSE elements were irradiated with varying the dose level at room temperature and measured the SSE voltage of them. We confirmed that the thermoelectric and magnetic properties of the SSE elements are not affected by the ion-irradiation up to 1010 ions/cm2 fluence and that the SSE signal is extinguished around 1012 ions/cm2, in which the ion tracks almost fully cover the sample surface. We also performed the hard X-ray photoemission spectroscopy (HAXPES) measurements to understand the effects atthe interface of Pt/Y3Fe5O12. The HAXPES measurements suggest that the chemical reaction that diminishes the SSE signals is enhanced with the increase of the irradiation dose. The present study demonstrates that SSE-based devicesare applicable to thermoelectric generation even in harsh environments for a long time period