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Numerous trap states and low conductivity of compact TiO2 layers are major obstacles for achieving high power conversion efficiency and high-stability perovskite solar cells. Here we report an effe...

Four kinds of well-crystallized tritium permeation barrier coatings, including γ-Al2O3, α-Al2O3, γ-Al2O3/Cr2O3 and α-Al2O3/Cr2O3, were prepared by the metal organic decomposition (MOD) method using a dipping technique. In this study, we concentrated on the preparation and properties of α-Al2O3 and α-Al2O3/Cr2O3 double-layer coatings. The results showed that the α-Al2O3 coating exhibited a pure phase structure, which was entirely and directly transformed from the γ-Al2O3 at an annealing temperature of 1000 °C, and no obvious substrate oxides were formed. An unannealed Cr2O3 MOD layer with a thickness of 0.8 μm featured higher crystallization and was taken as a buffer layer. However, the template effect of Cr2O3 was not obvious because the formation temperature of the α-Al2O3 did not decrease. The corrosion resistance (1.068 × 10−7 A/cm2) and nanohardness (18.49 GPa) of the α-Al2O3/Cr2O3 double-layer coating improved compared to those of γ-Al2O3, α-Al2O3, and γ-Al2O3/Cr2O3 coatings. In contrast, the deuterium permeation test showed that the α-Al2O3 MOD coating had the lowest deuterium ion current at temperatures of 400 ˜ 600 °C of the films considered in this study, demonstrating better resistance to deuterium permeation. Relevant mechanisms and explanations are discussed in detail.

In this paper, a laser-based directed energy deposition (DED) technique is used to fabricate FeCoNiCr and CrMnFeCoNi multi-principal-element alloys (MPEAs). Comparing the above samples, the FeCoNiCr samples with coarse columnar grains cracked, while the CrMnFeCoNi samples with equiaxed grain were crack-free. The strategy that removes cracks is to induce a columnar-grain-to-equiaxed-grain transition (CET) with Mn addition to offer more grain boundaries to withstand residual stress in the process of DED-fabricated FeCoNiCr and to help minimize hot cracking. Furthermore, the yield strength, tensile strength, and tensile ductility of the DED-fabricated CrMnFeCoNi obviously improved compared with the DED-fabricated CoCrFeNi and exhibited better isotropic mechanical properties. The present work provides a novel strategy to utilize CET for resisting crack propagation in the process DED-fabricated MPEAs and improvement in mechanical properties of MPEAs.

Surface modification of tungsten due to the cooling species nitrogen seeded in the divertor region, i.e., by nitrogen ion implantation or re-deposition, is considered to affect the permeation behavior of H isotopes. This work focuses on the effect of nitrogen ion implantation into tungsten (W-N) on the deuterium gas-driven permeation behavior. For comparison, both permeation in tungsten implanted with W ion (W-W) and without implantation (pristine W) are studied. These three samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photo-electron spectroscopy (XPS). The SEM results revealed that the W-W sample has various voids on the surface, and the W-N sample has a rough surface with pretty fine microstructures. These are different from the pristine W sample with a smooth and compact surface. The XRD patterns show the disappearance of crystallinity on both W-W and W-N sample surfaces. It indicates that the ion implantation process results in an almost complete conversion from crystalline to amorphous in the sample surfaces. The sputter-depth profiling XPS spectra show that the implanted nitrogen prefers to form a 140 nm thick tungsten nitride layer. In permeation experiments, it was found that the D permeability is temperature dependent. Interestingly, the W-N sample presented a lower D permeability than the W-W sample, but higher than the pristine W sample. Such behavior implies that tungsten nitride acts as a permeation barrier, while defects created by ions implantation can promote permeability. The possible permeation mechanism correlated with sample surface composition and microstructure is consequently discussed in this work.

This paper reports a plasma mediated nitriding method to prepare transition metal nitrides (TMNs) for efficient oxygen evolution reaction (OER). Nickel foam (NF) dipped into FeCl3 solution is treated with N2 plasma, and a composite structure of NiFeN and Ni2Fe2N is obtained with nitride nanoparticles uniformly distributed on the surface of the nickel foam (donated as NiFeNx/NF). The prepared NiFeNx/NF shows a low overpotential of 286 mV at 10 mA cm−2 and 330 mV at 100 mA cm−2, which is lower than RuO2 loaded on NF (0.5 mg cm−2). There is no obvious increase in the overpotential after 20 h stability test. The excellent performance of NiFeNx/NF is attributed to the synergistic effect of NiFe bimetallic nitrides.

A new type plasma generator based on hollow cathode discharge has been designed and installed on the linear magnetic device, for the researches on helium and hydrogen plasma interaction with plasma facing components. The hollow cathode plasmas for argon/helium/hydrogen discharges were realized. The performances of the hollow cathode source were analyzed based on argon discharges, such as the electron temperature and electron density with respect to radial position, gas flow rate and magnetic field. The plasma parameters have been measured with Langmuir probe on the linear magnetic device. It shown that this hollow cathode source could provide ion flux density up to 10 22 m −2 s −1 with high gas efficiency and energy efficiency. Typically, for argon plasmas, it could reach an electron density of 2 × 10 19 m −3 and an electron temperature of 3.5 eV in core region, with a power dissipation of 1 kW and gas flow rate of 0.25 standard liters per minute. The plasma beam with a radius of 2.5 cm was confined very well with a magnetic field around 0.05 T. By the virtue of these properties, this plasma generator is a good candidate for the fusion related plasma-surface-interaction researches.

Thermal desorption spectroscopy (TDS) measurement of tungsten (W) exposed to tritium (T2) under a series of conditions was conducted, and the peak of T2 desorption reached as high as 895 K at the heating rate of 20 K/min. The detrapping energy of T in W was then determined experimentally to be 2.18 ± 0.22 eV, suggesting that T was mainly trapped by vacancy clusters which may be formed during manufacturing and enhanced by charged T atoms.

TiO2 powder was modified by the afterglow of plasma of pure N2 or H2, and mixed N2 + H2 gas. The ion species in plasma afterglow were measured by an ion-energy analyzer. It is found that the main ion is N2+ in N2 afterglow and the yield is changed to NH4+ with a six times higher concentration, when 10% H2 was input. The modified TiO2 shows significant differences of microstructure and optical properties depending on the plasma gas used. This work enables one to find a correlation between active species in the plasma afterglow and TiO2 microstructure/optical properties.

International audience; Rare earth (RE) ions doped in Si-based materials, compatible with Si technology, are promising compounds with regards to optical communication and energy conversion. In this article, we show the emission properties of Nd-doped Si-rich Si oxynitride (Nd-SRSON) films, and their dependence on the dangling bond density and the nature of the sensitizer. These films were prepared by reactive magnetron sputtering and post-annealing. The film composition, microstructure, and emission properties were investigated as a function of deposition parameters and annealing temperatures. Both Fourier transform infrared (FTIR) and ellipsometry spectroscopy measurements have confirmed that the sample composition (Si/N ratio) can be carefully tuned by varying the ratio of reactive nitrogen to argon in the sputtering plasma. Moreover, FTIR and x-ray photoelectron spectroscopy measurements demonstrate the existence of both nitrogen and oxygen dangling bonds (N· and O·) in as-deposited samples. These dangling bonds were passivated during annealing. Under non-resonant excitation at 488 nm, the films exhibit a significant photoluminescence (PL) signal from Nd3+ ions demonstrating the occurrence of an effective sensitization of Nd$^{3+}$ ions in the host matrix. Both PL excitation and ellipsometry results (the energy band gap from new amorphous model) exclude the sensitization by an exciton with energy over the band gap, whereas the presence of Si agglomerates, at the atomic scale, have been identified as effective sensitizers towards Nd$^{3+}$ ions. This work not only provides knowledge to optimize Si-based materials for favorable emission properties, but also, presents a universal methodology to investigate the nature of sensitizers for RE emitters. This allows one to find correlations between composition, microstructure, and emission properties.