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Hydrogen behavior in oxides has triggered much interest for its scientific and technological importance in a wide range of research fields from novel ion conductors to astrochemistry. Here, we report a giant conductivity enhancement in ZnFe2O4 ferrite insulators to the metallic state by over eleven orders of magnitude induced by electrochemically generated atomic hydrogen at room temperature. The conductivity and the amount of incorporated hydrogen increased in an exponential function with time. An activation energy for the atomic hydrogen chemisorption was measured to be 8.23 kJ mol−1. Quantitative kinetics correlations among the adsorption of atomic hydrogen, hydrogen incorporation and conductivity enhancement are established, based on which hydrogen incorporation process is clarified herein. We demonstrate that the hydrogen incorporation in oxides can be adjusted by manipulating the kinetic factors. These findings have implications for research into hydrogen behavior in oxides in environments containing hydrogen atoms and offer possibilities for utilizing and controlling the modifications of oxide materials induced by atomic hydrogen. [ABSTRACT FROM AUTHOR]

Hydrogen isotopes permeation barriers (HIPB) play an important role in reducing hydrogen isotopes permeation and leakage in hydrogen energy and thermonuclear fusion energy. In this study, the Al 2 O 3 -HIPB were prepared on 316L stainless steel by RF magnetron sputtering. The impacts of coating thickness and annealing temperature of as-deposited coatings on deuterium permeation reduction factor (D-PRF) are studied in detail. With increasing thickness of coatings from 0.2 μm to 1.6 μm, the D-PRF did not rise significantly, which indicated that coating surface, for thin coatings, played more important role in impeding deuterium permeation than coating interior. As a result of further crystallization and grain growth, the 700 °C-annealed Al 2 O 3 coatings had stronger ability to impede deuterium permeation than 600 °C-annealed Al 2 O 3 coatings. This further proofs that grain boundaries may be a short-cut path for deuterium diffusion in Al 2 O 3 coatings. The D-PRF drastically decreased when the annealing temperature reaches 800 °C, which might be ascribed to the new phases form and the coating cracks appearance after 800 °C annealing. [ABSTRACT FROM AUTHOR]

In hydrogen energy and thermal fusion energy, hydrogen isotopes permeation barriers (HIPB) are used to reduce hydrogen isotopes permeation, which may result in hydrogen isotopes leak and construction materials brittleness. Here, we made Er 2 O 3 HIPB by magnetron sputtering and studied the relation between deuterium-permeation reduction factor (D-PRF) and coating thickness, micro-morphology. The 0.2 μm Er 2 O 3 coatings can reduce deuterium permeation by 1/10 ∼ 1/20 at 600 °C ∼ 300 °C. However, the reduction ability decreases gradually with the increase in coating thickness when the coatings are thicker than 0.2 μm. The reason may be ascribed to the deuterium invasion in deuterium permeation test. After deuterium invasion into coatings, the coatings suffer intrinsic stress, thermal stress and expansion stress from deuterium invasion. As a result of grain size dependence on coating thickness in PVD-derived coatings, i.e. grains become coarse with increasing coating thickness, the sum of stresses in various type increases with increasing coating thickness. The coatings crack easily when they suffer more strong tensile stress. So, the damages of coatings become serious and D-PRF reduces with increasing coating thickness. [ABSTRACT FROM AUTHOR]

Composite coatings as Hydrogen Isotopes Permeation Barriers have seldom been studied. In this work, the Al 2 O 3 –Er 2 O 3 component composite HIPB were prepared on 316L stainless steel by radio frequency reactive magnetron sputtering. The deuterium permeation reduction factor (D-PRF), structure and nano-hardness of the Al 2 O 3 –Er 2 O 3 composite HIPB were investigated. The Er 4 Al 2 O 9 (012), (023) diffraction peaks appeared. The D-PRF of 1.2 μm Al 2 O 3 –Er 2 O 3 composite HIPB could reach 160 at 600 °C, the D-PRF was 210 at 450 °C and increased sharply to 1380 at 250 °C. The coatings kept dense during the deuterium permeation tests while the Er 4 Al 2 O 9 phases changed. The nano-hardness decreased from 9.55 GPa to 7.46 GPa after the deuterium permeation tests. It was inferred that the deuterium atoms invasion and formation of oxygen vacancies should be responsible for the performance and structure changes of the Al 2 O 3 –Er 2 O 3 composite HIPB during deuterium permeation tests. [ABSTRACT FROM AUTHOR]

Connections between metals and heterogeneous solid state materials form buried interfaces. These ubiquitous structures play an essential role in determining the performances of many nano- and microdevices. However, the information about the chemistry, structure, and properties of these real interfaces is intrinsically difficult to extract by traditional techniques. Therefore, approaches to efficiently discovering metalized interfaces are in high demand. Here, we demonstrate the transformation of nanoscale metal/oxide interface problems into surface problems through a novel metal-hydrogenation detaching method. We applied this technique to study the thickness dependence in Pb(Zr,Ti)O3 (PZT) ferroelectric thin films, a long-standing interface problem in a model metal/insulator device, and this allowed comprehensive surface analytical techniques to be adapted. A nonstoichiometric interfacial layer of 4.1 nm thick with low mass density, low permittivity, and weak ferroelectricity was quantified at the Pt/PZT interface and attributed to the preferential diffusions among the compositional elements. Targeted interface engineering by Pb rebalance led to a substantial recovery of ferroelectric properties. Our results therefore pave the way to a better understanding of metallized interface in ferroelectric and dielectric nanodevices. We hope that more useful information about metalized interfaces of other solid materials could, analogously, be accessed by surface analytical techniques.

Hydrogen-related defects play crucial roles in determining physical properties of their host oxides. In this work, we report our systematic experimental and theoretical (based on density functional theory) studies of the defect states formed in hydrogenated-rutile TiO2 in gaseous H2 and atomic H. In gas-hydrogenated TiO2, the incorporated hydrogen tends to occupy the oxygen vacancy site and negatively charged. The incorporated hydrogen takes the interstitial position in atom-hydrogenated TiO2, forming a weak O-H bond with the closest oxygen ion, and becomes positive. Both states of hydrogen affect the electronic structure of TiO2 mainly through changes of Ti 3d and O 2p states instead of the direct contributions of hydrogen. The resulted electronic structures of the hydrogenated TiO2 are manifested in modifications of the electrical and optical properties that will be useful for the design of new materials capable for green energy economy.