Search

α-Al 2 O 3 as a preferred material for hydrogen isotopes permeation barrier (HIPB) can effectively prevent hydrogen embrittlement in structural steel and has higher thermal stability. However, its application is limited by the issue that it is hard to prepare α-Al 2 O 3 at relatively low temperature and its formation temperature is too high (>1000 °C) to damage the mechanical properties of structural steel. To overcome this issue, this paper presents a novel method (combining Al electrodeposition, aluminizing, Cr deposition and air oxidation) for the preparation of α-Al 2 O 3 (Cr 2 O 3)/Fe–Al composite coating on 316 L stainless steel for the first time. The formation temperature of α-Al 2 O 3 was successfully reduced to 800 °C. The post-oxidation samples were characterized by SEM, XPS, XRD, EDS and TEM. The results showed that the oxide film was composed of highly crystalline α-Al 2 O 3 and Cr 2 O 3 nanoparticles, where the later were diffusely distributed in the internal α-Al 2 O 3 film. And there was an epitaxial growth relationship between α-Al 2 O 3 and Cr 2 O 3. The low-temperature formation of the α-Al 2 O 3 film was due to the fact that the Cr 2 O 3 nanoparticles formed during the oxidation process acted as templates and nucleation sites, which reduced the nucleation barrier of α-Al 2 O 3. Deuterium permeation tests showed that its deuterium permeation reduction factor (DPRF) was 8892 at 500 °C, which met the standard for practical application. [ABSTRACT FROM AUTHOR]

Developing a cost-effective material to replace Pt catalysts for hydrogen evolution reaction (HER) holds great promising for clean energy technologies. In this work, we developed a simple way to prepare nanoporous Si by argon ion irradiation at 90 keV to fluences of 0.5, 1, 2 × 10 17 ions/cm 2 . After post-irradiation annealing at 700 °C in vacuum (2 × 10 −4 pa) for 5 h, the nanoporous Si was formed which displays largely enhanced electrocatalytic water splitting compared with the unirradiated Si. We also investigated the influence of fluence on morphology and the HER performance of the electrocathodes. It was found that 1 × 10 17 Ar + ions/cm 2 irradiated Si showed the highest HER performance. The largely enhanced HER activity comes from the unique morphology which results by Ar + ions irradiation and post-irradiation annealing. We further fabricated electrocathodes by coating Ni film on the nanoporous Si, significant improvement of the HER performance compared with Ni coated planar Si was found. Using the ion irradiation technology, we developed a new method to fabricate electrocathode with large specific surface area for largely enhanced hydrogen evolution reaction activities. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fabrication of TiO2 films by ion implantation and annealing strongly depends on ion energy. [•] Best photocatalytic activity is achieved in the TiO2 nanofilm annealed at 1000°C. [•] Phase transformation of TiO2 appears under annealing temperature of 900°C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bulk nanostructured ceramic was prepared by embedding CNTs in YSZ-MgO nanocrystals. • He ion irradiation response of CNT-reinforced ceramic at 500 °C was studied. • Management of defects/He atoms via constructed ternary nanostructures was realized. • High ability in keeping microstructure stability and resisting radiation hardening. Developing long-lifetime bulk-form ceramic-based materials with high irradiation resistance is crucial for advanced nuclear systems. Here, we incorporated carbon nanotubes (CNTs) into yttria-stabilized zirconia (YSZ) and magnesia (MgO) nanocrystals to fabricate bulk YSZ-MgO-CNT nanocomposites with abundant ternary nanostructures by spark plasma sintering. To understand the role of tailored ternary nanostructure on irradiation, we investigated the microstructure and mechanical properties evolutions of the YSZ-MgO-CNT nanocomposites irradiated by multi-energy He+ ions at high temperature to different fluences. Compared with the single-phase YSZ and ultrafine-grained YSZ-MgO composites, the YSZ-MgO-CNT nanocomposites possessed higher ability to manage irradiation-induced He bubbles/defects via the defect-interface interactions of proposed "loading-unloading" and "loading-transporting-unloading" mechanisms for controlling the dynamical behaviors of He atoms/defects in the CNT-doped ternary nanostructures, thereby presenting more stable microstructure and better performance in resisting irradiation hardening. This work provides insight into the design of advanced inert matrix nuclear fuel and new nuclear waste management materials. [ABSTRACT FROM AUTHOR]

This work demonstrated a significant hydrogen isotopes permeation resistance in nitride nano-multilayer coatings. Dense and homogeneous CrN/AlTiN nano-multilayer coatings with different period-thicknesses were fabricated as hydrogen isotopes permeation barriers (HIPB) to highlight the effect of interface on hydrogen isotopes permeation resistance. Deuterium permeation measurement found that the nano-multilayer coatings had much higher permeation reduction factors (PRF) than the corresponding monolayer coatings, and more importantly there was an interface-number-dependent deuterium permeation resistance where the nano-multilayer coating containing more interfaces had higher PRF. Interfaces in the nano-multilayer coatings play a key role in the significant improved deuterium permeation resistance which was explained from three aspects. Ceramic nano-multilayer coatings offer a promising alternative for the design and preparation of HIPB in the hydrogen related fields. Image 1 • Nano-multilayer coatings had higher PRF than corresponding monolayer coatings. • An interface-number-dependent deuterium permeation resistance was discovered. • Interfaces play a key role in the improved deuterium permeation resistance. • Ceramic nano-multilayer coatings offer a promising alternative for HIPB. [ABSTRACT FROM AUTHOR]

Hematite is a prospective semiconductor in photoelectrochemical (PEC) water oxidation field due to its suitable bandgap for the solar spectrum absorption. Nevertheless, the low transfer and separation efficiency of the charge carriers are restricted by its diffusion length of hole which is 2–4 nm and further reduce the PEC performance. Here, we report an innovative method, by introducing nanocavities into the α-Fe 2 O 3 nanorod arrays photoanodes through helium ions implantation, to improve the charge carriers' transfer and separation efficiency and further to enhance water oxidation performance. The result indicates that, the photocurrent density of nanocavities embedded α-Fe 2 O 3 photoanode (S2-A sample) reaches 1.270 mA/cm2 at 1.6 V vs. RHE which is 1-fold higher than that of the pristine α-Fe 2 O 3 (0.688 mA/cm2) and the photocurrent density of S2-A sample reaches 0.652 mA/cm2 at 1.23 V vs. RHE. In this work, the ion implantation combined with post annealing method is found to be a valid method to improve the photoelectrochemical performance, and it also can be further used to modify the other semiconductor photoelectrodes materials. • The photoelectrochemical performance of α-Fe 2 O 3 photoanode was enhanced through controlled He+ ion implantation. • The size and density of nanocavities in the α-Fe 2 O 3 nanorods can be tailored by controlling the ion fluences. • Nanocavities can increase the separation efficiency of electron-hole pairs. [ABSTRACT FROM AUTHOR]

Plasma facing materials (PFMs) face one of the most serious challenges in fusion reactors, including unprecedented harsh environment such as 14.1 MeV neutron and transmutation gas irradiation at high temperature. Tungsten (W) is considered to be one of the most promising PFM, however, virtually insolubility of helium (He) in W causes new material issues such as He bubbles and W “fuzz” microstructure. In our previous studies, we presented a new strategy using nanochannel structure designed in the W film to increase the releasing of He atoms and thus to minimize the He nucleation and “fuzz” formation behavior. In this work, we report the further study on the diffusion of He atoms in the nanochannel W films irradiated at a high temperature of 600 °C. More specifically, the temperature influences on the formation and growth of He bubbles, the lattice swelling, and the mechanical properties of the nanochannel W films were investigated. Compared with the bulk W, the nanochannel W films possessed smaller bubble size and lower bubble areal density, indicating that noticeable amounts of He atoms have been released out along the nanochannels during the high temperature irradiations. Thus, with lower He concentration in the nanochannel W films, the formation of the bubble superlattice is delayed, which suppresses the lattice swelling and reduces hardening. These aspects indicate the nanochannel W films have better radiation resistance even at high temperature irradiations. [ABSTRACT FROM AUTHOR]

Here we demonstrate that the performance of TiO 2 electrodes for photoelectrochemical water oxidation can be effectively enhanced through oxygen vacancy doping. The ion irradiation is a simple method to introduce oxygen vacancies on the surface and into the interior of TiO 2 for making oxygen-deficient titania (TiO 2-x ). The TiO 2-x thin films exhibit obvious increase in the performance of photoelectrochemical water splitting under light irradiation. The photoconversion efficiency η of the TiO 2-x photoanode is 0.5-fold higher than that of the pristine TiO 2 photoanode, which benefits from the introducing of oxygen vacancies produced by ion irradiation. While the irradiation-induced titanium vacancies act as trapping centers for charge carriers and decrease the photoelectrochemical performance of the samples. Positron annihilation spectroscopy (PAS) was used to study the type of the formed vacancies. Combining experimental with theoretical study, this study demonstrates that ion irradiation technique combing with thermal annealing could be an effective way to enhance the performance of photoanode for water splitting. [ABSTRACT FROM AUTHOR]

High-performance radiation tolerance materials are crucial for the success of future advanced nuclear reactors. In this paper, we present a further investigation that the “vein-like” nanochannel films can enhance radiation tolerance under ion irradiation at high temperature and post-irradiation annealing. The chromium nitride (CrN) nanochannel films with different nanochannel densities and the compact CrN film are chosen as a model system for these studies. Microstructural evolution of these films were investigated using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Elastic Recoil Detection (ERD) and Grazing Incidence X-ray Diffraction (GIXRD). Under the high fluence He + ion irradiation at 500 °C, small He bubbles with low bubble densities are observed in the irradiated nanochannel CrN films, while the aligned large He bubbles, blistering and texture reconstruction are found in the irradiated compact CrN film. For the heavy Ar 2+ ion irradiation at 500 °C, the microstructure of the nanochannel CrN RT film is more stable than that of the compact CrN film due to the effective releasing of defects via the nanochannel structure. Under the He + ion irradiation and subsequent annealing, compared with the compact film, the nanochannel films have excellent performance for the suppression of He bubble growth and possess the strong microstructural stability. Basing on the analysis on the sizes and number densities of bubbles as well as the concentrations of He retained in the nanochannel CrN films and the compact CrN film under different experimental conditions, potential mechanism for the enhanced radiation tolerance are discussed. Nanochannels play a crucial role on the release of He/defects under ion irradiation. We conclude that the tailored “vein-like” nanochannel structure may be used as advanced radiation tolerance materials for future nuclear reactors. [ABSTRACT FROM AUTHOR]

Utilization of high density small sinks, such as voids, to collect and store helium atoms inside might be a potential new strategy for designing nanostructured materials with high radiation resistance to swelling and embrittlement. To understand the role of pre-existing nanovoids on irradiation, we investigated the evolutions of micro-structure and mechanical properties of the YSZ/Al 2 O 3 multilayered nanofilms irradiated by He + ions to different fluences. Compared to the Al 2 O 3 monolithic film and the single crystal bulk YSZ, smaller He bubbles were found in the Al 2 O 3 layers of the YSZ/Al 2 O 3 multilayered nanofilms with pre-existing nanovoids after He + ion irradiation. The growth of He bubbles was restricted inside the Al 2 O 3 layers to avoid the formation of large bubbles. In contrast to the radiation-induced hardening in traditional materials, radiation-induced softening is observed in the YSZ/Al 2 O 3 multilayered nanofilms with pre-existing nanovoids irradiated to high fluences. In addition, the hardness to Young's modulus (H/E) ratio of the YSZ/Al 2 O 3 multilayered nanofilms increases in response to irradiation, which suggests a potential improvement in the wear resistance of the irradiated YSZ/Al 2 O 3 multilayered nanofilms. A defect “loading-unloading” effect at the interfaces was proposed to explain the enhanced radiation tolerance. [ABSTRACT FROM AUTHOR]

In this study, we report a simple, effective and universal approach to fabricate homojunction structural TiO 2 nanorod array photoelectrodes through doping of gradient distributed oxygen vacancies introduced by annealing in high vacuum with controlled time. The homogeneous junction structure promotes the separation and transport of photoexcited charge carriers, and the photocurrent density of TiO 2 nanorod arrays annealed in high vacuum for 2 h was 20 times higher than that of the pristine TiO 2 nanorod arrays. The results indicate that annealing in high vacuum with controlled time could form a homojunction structure, which is an effective approach for further enhancing the performance of UV–visible light driven photocatalytic materials for water splitting. [ABSTRACT FROM AUTHOR]

Finding high performance plasma-facing materials (PFMs) is one of the most important and challenging tasks for realizing the commercial application of fusion reactors. Herein, we found the CrMoTaWV high entropy alloy (HEA) is highly resistant to low-energy and high-flux He plasma exposure. The nanochannel HEA film has 20 times higher initial fluence for the formation of fuzz and a remarkable 8.9 times slower fuzz growth rate than those of W. Combining the in-situ TEM observation and the Molecular dynamics (MD) simulation of the He bubble growth process, a new mechanism for the enhanced radiation resistance in HEA with the unusual interaction between HEA and He is found, where, differing from traditional metal, bubble growth in HEA leads to non-directional emission of interstitial atoms while HEA greatly suppress the growth of He bubbles. The special nanochannel structure further rise the radiation resistance through releasing He out of the HEA film and reducing the He concentration. This new nanochannel refractory HEA material presents a promising choice as the PFMs with excellent performance and a much longer serving lifetime for future commercial fusion reactors. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing ceramic coating with high hydrogen isotopes permeation resistance is an urgent task in many fields such as fusion reactor systems, hydrogen storage/transportation, and fuel cell. In this work, a (TiVAlCrZr)O multi-component metal oxide glass (MCMOG) coating is developed as a new type of hydrogen isotopes permeation barrier (HIPB), and the diffusion behavior of deuterium in MCMOG is studied for the first time. Compared with the deuterium permeation reduction factor (DPRF) of 51 for amorphous alumina coating (at 587 °C in 0.65 µm), the 29 nm dense MCMOG coating has around 27 times enhancement with DPRF of 1420 at 550 °C. Based on first-principles calculations, we show that the significantly suppressed deuterium permeation in MCMOGs is attributed to the sluggish diffusion of deuterium arising from the highly rugged energy landscape, which is induced by the diversity of electronic band structures near the Fermi level. In addition, oxygen vacancies strongly affect PRF, where the PRF of the fully oxidized MCMOG layer (29 nm) is around 200 times compared to that of MCMOG with the same thickness containing oxygen vacancies. Therefore, dense MCMOG is a new promising HIPB material. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, well-ordered nanorods were fabricated on the surface of TiO 2 thin films deposited on Ti sheets by an ion irradiation method using nitrogen ion irradiation with the energy of 65 keV to a fluence of 1 × 10 17 ions/cm 2 . These TiO 2 nanorods are about 120 nm in length and 20–40 nm in diameter. After post-irradiation annealing at 500 °C in O 2 , the nanorod array photoelectrode displays largely enhanced performance for photoelectrochemical (PEC) water splitting compared to that of the un-irradiated TiO 2 thin films with a planar structure. The influences of the irradiated ion energy on the morphology and photocurrent density of the nanorods were investigated. The 65 keV N + irradiated TiO 2 thin films shows a higher photocurrent density than those of the 45 and 85 keV N + irradiated TiO 2 thin films. We also discussed the influence of annealing conditions on the PEC performance of TiO 2 nanorods, and it was found that the nanorods annealed at 600 °C in vacuum produce a much higher photocurrent density of 0.6 mA/cm 2 at 0.8 V (vs. a saturated calomel electrode), which is about 7 times higher than that of the nanorods annealed in oxygen. This work proposes that ion irradiation combination with thermal annealing in vacuum could be an effective approach for developing nanostructured materials for water splitting. [ABSTRACT FROM AUTHOR]

In this work, V ions were doped into ZnO nanorod arrays via an advanced ion implantation method for photoelectrochemical water splitting under visible light. It was indicated that the V dopants were incorporated into ZnO lattice as V 4+ and V 5+ ions. V ion doping expanded the optical absorption of ZnO nanorod arrays into visible light region and led to considerable photoelectrochemical performance under visible light illumination ( λ > 420 nm). The photocurrent density of V ions doped ZnO nanorod arrays could achieve 10.5 μA/cm 2 at 0.8 V (vs. Ag/AgCl), which was about 4 times higher than that of the pure ZnO nanorod arrays. The enhancement in photoelectrochemical performances for V ions doped ZnO nanorod arrays should be attributed to the improved visible light absorption ability and the increased charge carrier density induced by V ion doping. [ABSTRACT FROM AUTHOR]

Ion implantation is a facile surface modification technology for greatly tailoring the surface electron structure of materials, which is very important for catalytic activity. Here we report a new universal synthesis of stable, large-scale N-doped carbon fiber cloth embedded with non-noble metal nanoparticles (CN@(Ni, Fe and Co)) by ion implantation for largely enhanced hydrogen evolution reaction (HER) activity under acidic (0.5 M H 2 SO 4), neutral (0.5 M phosphate buffer, PH = 7) and basic solution (1M KOH). From the polarization curves, the overpotentials of current density for CN@Ni at 10 mA/cm2 decrease obviously from 710, 838 and 717 mV to 381, 589 and 532 mV in acidic, neutral and basic solution, respectively. Density functional theory (DFT) calculations also demonstrate that the Gibbs free energy (ΔG H∗) for H∗ adsorption of CN@Ni is much closer to the optimal value of ΔG H∗ = 0.15 eV compared with 1.84 eV of C and 0.86 eV of CN. The method is general and we demonstrate it using Fe+ and Co+ ions implantation into carbon fiber cloth to fabricate metal nanoparticles embedded carbon fiber cloth. Furthermore, this controlled technique is promising for industrial production of noble-metal-free HER electrocatalysts with large scale, low cost and high efficiency. • Metal nanoparticles embedded N-doped carbon fiber cloth was fabricated by metal ions implantation. • Greatly improved hydrogen evolution reaction performance in all pH range. • A general method for large-scale fabrication. [ABSTRACT FROM AUTHOR]