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A paramagnetic-ferromagnetic transition was observed in normal spinel zinc ferrite (ZnFe 2 O 4 ) during atomic hydrogenation at room temperature. Magnetic measurements showed enhanced ferromagnetic property with increasing hydrogenation time. The hydrogenated ZnFe 2 O 4 has normal spinel structure according to X-ray diffraction (XRD) and Raman analyses. Iron hydride was found from the XRD and X-ray absorption fine structure results. No A–B site ions exchange was observed in the x-ray absorption spectra while the atomic distances of Fe–O, Zn–O, Fe–Fe, Zn–Zn and Fe–Zn coordinations were reduced. A hybrid of Fe 2+ and Fe 3+ in hydrogenated ZnFe 2 O 4 can be further revealed through deconvolution of x-ray absorption near edge structure. The paramagnetic-ferromagnetic transition and enhanced ferromagnetic property were mainly due to the formation of iron hydride and the B-site super-exchange interactions of Fe 2+ and Fe 3+ . [ABSTRACT FROM AUTHOR]

The environmental-friendly hematite iron oxide (α-FeO) has important application prospects in the photocatalysis field owing to its narrow indirect band gap. Here, we report a band gap engineering of α-FeO by incorporation of electrochemically-generated atomic hydrogen at moderate conditions. The ultraviolet-visible spectra show the reduction of the α-FeO band gap after hydrogenation and the absorption region from 200-800 nm is enhanced, especially in the visible light region. First principles calculation reveals the mixing of the new hybrid energy level with the valence band top resulting in a decrease in the band gap of α-FeO. Further photocatalytic degradation experiments of dyes demonstrate that the photocatalytic efficiency of α-FeO can be greatly enhanced by the atomic hydrogen incorporation. The hydrogenated α-FeO can be easily recycled by magnets and has good photocatalytic stability. These findings offer possibilities for utilizing this inexpensive and earth-abundant oxide materials in the pollution controlling areas. [ABSTRACT FROM AUTHOR]

Hydrogen Isotopes permeation barriers (HIPB) are used to reduce hydrogen isotopes permeation and leakage in the fields such as thermonuclear fusion energy, hydrogen energy, petroleum industry and vacuum solar receiver. In this study, nano-crystalline Er 2 O 3 HIPB with about 5–10 nm grain size were made by sol-gel method. Their performances, including deuterium-permeation reduction factor (D-PRF), micro-structure, mechanical property and electrical property were reported. The D-PRF of 0.2 μm nano-crystalline Er 2 O 3 HIPB reached 300 at 700 °C and did not deteriorate after 128 h deuterium permeation. The bonding strength and the nano-hardness steadily remained about 13 N and 10 GPa after 128 h deuterium permeation at 700 °C, respectively. The morphology and micro-structures of the nano-crystalline Er 2 O 3 HIPB showed no measurable changes after 128 h deuterium permeation, which ensured the stable D-PRF and mechanical properties. However, the electrical resistivity of the nano-crystalline Er 2 O 3 HIPB decreased after deuterium permeation at 700 °C. The electrical resistivity decreased from 9 × 10 9 Ω cm by over three orders of magnitude and then tended to be stable, which might be attributed to oxygen loss or deuterium invasion. [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]

Hydrogen isotope permeation barriers (HIPB) have great potential applications in the fields of hydrogen energy and thermonuclear fusion. In this study, the AlN-HIPB were prepared on 316 L stainless steel by RF magnetron sputtering. The properties of AlN-HIPB were studied, including the deuterium permeation reduced factor (D-PRF), structures and nano-hardness. The D-PRF of 0.4 μm AlN-HIPB could reach 36 at 600 °C, and gradually rise with decreasing permeation temperature. The D-PRF reached 53 at 400 °C and 144 at 250 °C, respectively. The coatings remained dense and the grains were spherical after the deuterium permeation test. The AlN (1 0 0) diffraction peaks appeared and maintained stable during the deuterium permeation process. The nano-hardness of the coatings increased from 5.96 GPa to 7.41 GPa and the elasticity modulus also increased from 156.6 GPa to 210.6 GPa after the deuterium permeation. [ABSTRACT FROM AUTHOR]