Search

Ab initio calculations have been carried out to investigate the adsorption, dissociation, and diffusion of atomic and molecular hydrogen on the Fe-doped ZrCo (110) surface. It is found that the adsorption of H2 on doped surface seems thermodynamically more stable with more negative adsorption energy than that on the pure surface, and the dissociation energy of H2 on doped surface is much bigger therefore. However, compared with the pure system, there are fewer adsorption sites for spontaneous dissociation. After dissociation, the higher hydrogen adsorption strength sites would promote the H atom diffusion towards them where they can permeate into the bulk further. Furthermore, the ZrCo (110) surface possesses much higher hydrogen permeability and lower hydrogen diffusivity than its corresponding ZrCo bulk. Moreover, further comparison of the present results to analogous calculations for pure surface reveals that the Fe dopant facilitates the H2 molecule dissociation. Unfortunately, this does not improve the hydrogen storage performance of ZrCo alloy due to the H atom diffusion on the surface and into bulk are prevented with higher reaction energetic barriers by doping Fe. Consequently, ZrCo (110) surface modified with Fe atoms should not be preferred as a result of its terrible hydrogen permeability. A clear and deep comprehending of the inhibiting effect of Fe dopant on the hydrogen storage of ZrCo materials from the perspective of the surface adsorption of hydrogen are obtained from the present results.

Formic acid intercalated Mg-Al layered double hydroxide (Mg-Al Fo-LDH) was prepared by calcination reduction intercalation assembly technology. The structure of the deicing additive was characterized by fourier transform infrared (FTIR) and X-ray diffraction (XRD). The freezing point of aqueous solution with different quality of deicing additive and the surface freezing point and adhesion of asphalt mixture were tested. The results show that formic acid ion has been intercalated into the interlayer of Mg-Al layered double hydroxide by FTIR and XRD patterns. The freezing point of 5wt% Mg-Al Fo-LDH aqueous solution reaches -9.32 °C, while the surface freezing point of the asphalt mixture mixed with 5wt% Mg-Al Fo-LDH is -6.5°C. At -8 °C, the adhesion force of the surface ice layer is 78.4N, and after the asphalt mixture is soaked in water, the surface freezing point and adhesion force of the ice layer do not change.

Copper oxide is considered as a potential anode material for lithium-ion batteries (LIBs), which have attracted huge amounts of research ardor owning to the high capacity and ultrahigh theoretical ...

Hydrogel tubes as one kind of perfusable tubular materials, show promising applications in a wide spectrum of fields. However, there is still a great challenge to design a rapid, biocompatible, and straightforward strategy for one-step engineering tough hydrogel tubes, which have excellent mechanical properties, unique resilience, and multiple functions. Herein, we explore visible-light-mediated orthogonal photochemistry to achieve the fabrication of tough hydrogel tubes with double networks via a coaxial-nozzle spinning technique under short blue-light irradiation (∼20 s). The as-prepared tubes are tough (2.3 MJ m

RGAs are widely used in molecular component examination, impurity analysis, leak detection and test of vacuum system performance. However, RGAs have different sensitivities to different gases, and the sensitivities can change quickly and depend on so many parameters, which make its ability severely limited. In this work we established a new practical method to precisely measure noble gas ratio of argon -xenon gas mixture. Gaseous argon and xenon were controlled, respectively, by two mass flow controller (MFC). A variable leak valve (VLV) was used to introduce the gas mixture sample into the RGA measurement chamber. Gas mixtures with xenon concentration from 200ppm to 20000ppm (by mass) were introduced and tested by RGA. The time stability of RGA-measurement system was optimized to 2.1%. A good linearity of MFC-RGA response was achieved, verifying the reliability of RGA in measuring noble gas mixture with component concentration down to several hundred ppm level. Since the approach we used in our experiment is gas-species independent, we believe that it can be popularized to other gas species when properly applied.

As a natural abundant high-carbon resource, the use of coal to develop carbon nanomaterials is an important research topic. In recent years, a variety of carbon materials with different morphologies and nanotextures have been designed and constructed using coal and their derivatives as precursors, and their use in energy storage, catalysis, adsorption and absorption have been explored. State-of-the-art research on carbon nanomaterials derived from coals of different rank and their derivatives are summarized with specific attention to the synthesis strategies and structure control. The use of these coal-derived carbons for energy storage, such as secondary batteries and supercapacitors, is also discussed in terms of their structural features. The review aims to provide valuable insight into the present challenges and inspire new ideas for the development of advanced coal-derived carbon materials.

A novel supramolecular chiral hydrogel with enhanced emission was obtained by the co-assembly of achiral thiobarbituric acid-modified gold nanoclusters (TBA-AuNCs) with chiral histidine molecules. Chirality transfer from histidine to the supramolecular hydrogels was achieved through the π-π stacking and intermolecular H-bonding based on molecular recognition. This work gives a creative strategy for the building of chiral nanocluster-based materials.

The microstructures and mechanical properties of nanocrystalline Li2SiO3 have been investigated via molecular dynamics calculations. The results indicate that the mean atomic mass densities of nanostructured Li2SiO3 with different mean grain size are slightly lower than that of ordinary crystal Li2SiO3. Interestingly, a significant anti-Hall–Petch effect between yield stress and average grain size is observed in the tensile deformation simulation of the samples. In fact, the curve changes linearly until the strain reaches approximately 0.016–0.018. Next, when the strain is between 0.27 and 0.38, the stress of the sample has a small peak in the plastic flow region. Then, all the samples will begin to fracture at a strain of about 0.39–0.41. Moreover, due to the influence of grain boundary sliding and grain rotation, there are a few dislocations in the samples with the small average grain sizes, highlighting the strong influence of the mechanical properties on the overall tensile deformation of the samples.

Gold nanoclusters (AuNCs) have been recognized as an emerging category of inorganic–organic hybrid luminescent materials owing to their ultrasmall size, good biocompatibility, and especially the ag...

The Cu–In binary system is receiving increasing attention due to its application in the low-temperature assembly of heat-sensitive devices. Nevertheless, the fundamental behaviors of this binary system are very difficult to study because of the extreme softness of indium. This difficulty was successfully overcome in this study, and the phase stabilities and chemical reactions were established. Binary Cu–In diffusion couples were prepared by electroplating In onto a Cu substrate. During the plating process, CuIn2 formed even though this intermetallic is not present in the Cu–In binary phase diagram. It was established in this study that CuIn2 is indeed a stable phase below 100 °C, but decomposes at a temperature between 100 and 120 °C. In addition, the microstructure evolution during solid-state aging at 100, 120, and 140 °C was investigated. The hardness values and Young’s moduli for CuIn2 and Cu11In9 were measured by using nanoindentation.

Liquid noble gases are widely used as targets in low background search experiments, particularly in direct dark matter search experiments. 83mKr is an excellent low-energy internal calibration source for future larger liquid noble gas detectors. To calibrate liquid argon detector with 83mKr in different drift fields and to study the correlation between light yield and drift fields. A dual-phase LAr prototype detector was designed to study the 83mKr responses in liquid argon. 83mKr atoms are produced through the decay of 83Rb and introduced into the LAr detector through the circulating purification system. We report that the light yield reaches 7.26 ± 0.02 pe/keV for 41.5 keV from 83mKr and 7.66 ± 0.01 pe/keV for 511 keV from 22Na, as a comparison. After stopping the fill, the rate decays of 83mKr are with a fitted half-life of 1.83 ± 0.11 h, which is consistent with the reported value of 1.83 ± 0.02 h. The light yield that varies with the drift electric field from 0 to 200 V/cm has also been reported.

An exhaustive analysis based on density functional theory (DFT) simulations of the effect of Hf doping on helium behavior has been performed in ZrCo. The He impurities have been placed both at interstitial positions and substitutional positions from the first nearest neighbor (1nn) of the Hf atom to the sixth nearest neighbor (6nn). In such areas, the electronic charge density is different, and therefore the formation and diffusion of He atoms vary in the surrounding of the Hf atom. The results show that Hf doping reduces the volume of the interstitial sites nearby, resulting in the weakening ability of the interstitial sites to accommodate He atoms. According to the results of formation energy, whether it is the substitutional He or the interstitial He atom, the formation is not only related to the distance of Hf, but more importantly, it is closely related to the unit cell where the He atom is located. In addition, Hf atoms promote the capture of He atoms by vacancies nearby and the migration of He atoms between the tetrahedral positions. The result also validates the well-known knowledge of vacancies as efficient sinks for He atoms in ZrCo. From the lower and lower migration energetic barriers along 3nn → 2nn → 1nn → 1nn pathways, we can infer an increasing mobility of the He atom from 3nn to 1nn. This situation could favor their accumulation surrounding an Hf atom, improving the ability of helium retention. These findings provide really indisputable evidence that the Hf dopant makes a difference in the behavior of He atoms in bulk ZrCo. Therefore, a ZrCo system with Hf doping can be considered as a good candidate for tritium storage material in a future nuclear fusion reactor.

Due to the advantages of low electrical resistance and size miniaturization, Cu to Cu has become the important trends in microelectric interconnect fabrication. Robust Cu to Cu bonding with low temperature, ambient pressure (under N2 or air) and short processing time is strongly requested for advanced IC and substrate packaging, MEMS hermetic sealing, and flexible electronics assembly as well. Ultrasonic technique has recently be adopted in direct copper bonding, this study focuses on the influences of surface physical features on direct bonding between two copper electro-deposits. Experimental results show that joints consisting of hard bumps bonded with soft Cu surface exhibit improved bonding strength. They also indicate that the bonding temperature at 100°C with the protection of N2 and higher surface roughness both positively contribute to the joint strength.

The anode oxygen evolution reaction (OER) is known to largely limit the efficiency of electrolyzers owing to its sluggish kinetics. While crystalline metal oxides are promising as OER catalysts, their amorphous phases also show high activities. Efforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 g in one batch) is presented with homogeneous elemental distribution via a facile supersaturated co-precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes a faster surface self-reconstruction process during OER, forming a metal oxy(hydroxide) active layer with rich oxygen vacancies, leading to superior OER activity (280 mV overpotential at 10 mA cm-2 in 0.1 m KOH). This opens up the potential of fast, facile, and scale-up production of amorphous metal oxides for high-performance OER catalysts.

Density-functional-theory (DFT) calculations and molecular dynamics simulations were performed to resolve the fracture behavior in UO2 under tensile loading. By molecular dynamics simulation, potential dependence was identified on the existence of transient plastic deformation prior to intergranular fracture in polycrystalline UO2, so we further improved the Morelon interatomic potential based on GGA + U calculations to obtain reliable fracture behavior in UO2. Using the improved potential, the fracture behaviors in polycrystalline and single crystal UO2 under tensile loading were investigated. In polycrystalline UO2, brittle intergranular fracture was observed, and no phase transition was found. In single crystal, Fm 3 ¯ m - Pbcn and Fm 3 ¯ m - P 4 2 /mnm structural transitions were observed under tensile loading. The non-coherent interfaces between Pbcn and P42/mnm phases play a critical role in microcrack formation. Under tensile loading, only Fm 3 ¯ m - P 4 2 /mnm transition was detected and the interface between Fm 3 ¯ m and P42/mnm structures was coherent, so no crack was found until the end of the simulation with strain of 25% in direction.

The elastic anisotropic, band structure, optical and lattice dynamical properties of ZnGeP2 have been investigated via density functional theory and density functional perturbation theory. The calculated lattice constants and elastic constants of ZnGeP2 are in good agreement with the previous results. The anisotropy in elasticity has been visualized by three-dimensional surfaces and the planar projection contours. ZnGeP2 shows an obvious elastic anisotropy under zero pressure, and the anisotropy increases with the increase in pressure. The hybrid functional HSE06 is used to evaluate the electronic properties of ZnGeP2, and the results suggests that the HSE06 hybrid functional can obtain more reasonable band structure. ZnGeP2 shows direct band gap of 2.06 eV. In addition, the optical spectrum is derived for photon energies up to 40 eV. The phonon frequencies at the Brillouin zone center are calculated and discussed.

The ZnO micro-nanorods are controlledly synthesized by a simple chemical vapor deposition method. With different oxygen concentrations the micro-nanorods exhibit different extrinsic feature and length. Under lower oxygen concentration, the micro-nanorods are up to 1670 μm in length which can be easily operated in singlecrystalline. When the oxygen concentration up to 30 sccm, the surface of the sample is smoother. The Raman spectra reveal that ZnO micro-nanorods have an excellent hexagonal wurtzite structure. However, the micronanorods synthesized during lower oxygen concentration exhibit more oxygen defect. The morphology controlling deposition of ZnO mircro-nanorods were realized by adjust the concentration of oxygen, which has great significance for further gas sensor application.

The incorporation of defects, such as vacancies, into functional materials could substantially tailor their intrinsic properties. Progress in vacancy chemistry has enabled advances in many technological applications, but creating new type of vacancies in existing material system remains a big challenge. We show here that ionized nitrogen plasma can break bonds of iron-carbon-nitrogen-nickel units in nickel-iron Prussian blue analogues, forming unconventional carbon-nitrogen vacancies. We study oxygen evolution reaction on the carbon-nitrogen vacancy-mediated Prussian blue analogues, which exhibit a low overpotential of 283 millivolts at 10 milliamperes per square centimeter in alkali, far exceeding that of original Prussian blue analogues and previously reported oxygen evolution catalysts with vacancies. We ascribe this enhancement to the in-situ generated nickel-iron oxy(hydroxide) active layer during oxygen evolution reaction, where the Fe leaching was significantly suppressed by the unconventional carbon-nitrogen vacancies. This work opens up opportunities for producing vacancy defects in nanomaterials for broad applications., Defect-engineering offers a promising route to vary material properties and reactivities, although the achievable defect types are limited. Here, the authors introduced unusual CN-vacancies in Prussian blue analogue pre-catalysts that can limit Fe leaching and improve oxygen evolution performances.

Three new perovskite-like hybrid iodobismuthates with two quaternary ammonium cations, namely (BnNEt3)3(Bi2I9) (1) (BnNEt3)4(Bi4I16) (2) and (n-Bu4N)2n(Bi4I14)n (3) (Bn = benzyl, n-Bu = n-butyl), have been synthesized by reacting BiI3 with the quaternary ammonium iodide in molar ratio 2:3 (1), 1:1(2), and 2:1 (3), respectively. All hybrids were characterized by elemental analysis, X-ray diffraction and UV–Vis spectroscopic analysis. Single-crystal X-ray diffraction revealed that hybrids 1 and 2 are di-nuclear and tetra-nuclear cluster structures respectively, while 3 is a polymeric chain structure based on a (Bi4I14) tetra-nuclear cluster unit. Their optical band-gaps have been determined as 2.19 eV(1), 2.16 eV(2), 2.02 eV(3), respectively. The optical band gaps exhibit a structure-related decrease from 1 to 3, in agreement with their color changes and the density functional theory (DFT) calculation results. The DFT calculations also reveal that there is a inversely proportional relationship between the optical Eg and the aggregation degree of the BiI6 octahedra in the hybrid iodobismuthate clusters.

The chemical vapor deposition technique was used to prepare the Ag doped ZnO microrods, which were located on Si substrates at two different positions. The scanning electron microscopy revealed that the samples have a clear hexagonal shape. X-ray diffraction provided information about the preferential orientation along the c-axis. The Raman analysis revealed that a new Raman mode appears at 492 cm-1 due to Ag doping. As this mode has not been reported early, it could be used as a characteristic mode of Ag doping in Raman spectrum. The red shift of the E2 (high) mode proves the existence of tensile stress in the samples. DOI: http://dx.doi.org/10.5755/j01.ms.25.3.19130

The effects of silicon (Si) on the release of tritium over lithium titanate (Li2TiO3) surface (001) are investigated using periodic density functional theory (DFT) calculations. DFT results show th...

We investigated the effect of Pd and Ni dopants on the formation and desorption of tritiated water (T2O) molecules from the Li2TiO3 (001) surface using first-principles calculations coupled with the climbing-image nudged elastic band method. We calculated the energy barriers for T2O production and desorption on the pure Li2TiO3 surface to be 0.94 and 0.64 eV, respectively. The Pd and Ni dopants enhanced T2O formation by reducing the formation energy of O vacancies, and T2O generated spontaneously on the dopant surface. Moreover, we found that dopant atoms affect the charge transfer of neighboring atoms, which leads to orbital hybridization and the generation of a chemical bond between the O and T on the doped Li2TiO3 surface. In addition, desorption of T2O from the doped Li2TiO3 surface requires a relatively low energy (

The interactions of dopants with point defects such as that between vacancies and helium can affect helium evolution and ultimately the macroscopic properties of materials. Herein, the microscopic vacancy trapping mechanism for He defects and the formation of small HemVacn (consisting of m He atoms and n vacancies) clusters in pure and Ti-doped ZrCo systems are investigated by carrying out an extensive set of first-principles calculations based on density functional theory. Our results uncover the following: the helium atom can segregate from the adjacent interstitial (tetrahedral and octahedral) sites towards the vacancy center spontaneously, and therefore, a single He atom is energetically favorable to occupy a vacancy whether in the pure or in the doped system. The dopant Ti can act as a trapping center for He impurities similar to a vacancy. Moreover, it can improve the trapping ability and increase the trapping radius of the vacancies for helium. As for the effect of the Ti atom on the trapping of multiple helium atoms by the vacancy, the higher barrier in the doped systems than in the pure one implies that doping inhibits the formation of large HemVac clusters. Furthermore, in order to evaluate the effect of dopant Ti on the stability of He atoms in multiple vacancies, the binding energies of a helium atom, a vacancy (Vac), and a self-interstitial atom (SIA) to a helium–vacancy cluster (HemVacn) were obtained and compared with that of the pure system. The results suggest that the cluster growth can be inhibited by the dopant Ti, and therefore, the formation of large helium bubbles is also hindered. All the binding energies do not depend much on the cluster size but primarily on the helium-to-vacancy ratio (m/n) of the clusters. The stability of the clusters is decided by the competitive processes among the emission of He atoms, vacancies, and SIAs, and also depends on the helium-to-vacancy ratio. The present results provide an in-depth explanation for the effect of the dopant on helium behavior and could aid future tritium storage material design.

The structural parameters, mechanical, dynamic, and thermodynamic properties of WSi2 with the C11b structure under pressure were systematically explored by using first-principles calculations. The results shown that calculated lattice constants and elastic constants of WSi2 were consistent with previous experimental findings and theoretical values. Our obtained elastic constants revealed that WSi2 was mechanically stable from 0 to 100 GPa. The values of anisotropic indexes, three-dimensional surface constructions, and two-dimensional projections under pressure indicated that WSi2 showed mechanical anisotropy. Additionally, the phonon density of state and phonon dispersion curves under pressure were obtained, and all vibration modes were analyzed. Finally, thermodynamic properties were also predicted based on quasi-harmonic approximation.

The self-assembly of chiral metal nanoclusters into supramolecular chiral aggregates is of interest for developing advanced materials. Herein, we manipulated the self-assembly of Au nanoclusters modified by l-/d-cysteine (l-/d-AuNCs) into ordered microstructures featuring enhanced phosphorescence and optical activities. The formation of these aggregates was driven by synergistic effect of coordination and electrostatic interactions assisted by Cd2+/H+. Detailed structural characterization and theoretical studies confirmed that the compact aggregation structures are essential for the emission enhancement and the chirality amplification of l-/d-AuNCs. Interestingly, upon the formation of microflowers, the emission lifetime was prolonged to 3.34 ms with a switch from fluorescence to phosphorescence induced by aurophilic Au(I)···Au(I) interactions and intensive ligand-to-metal charge transfer (LMCT). Moreover, both the CD and photoluminescence (PL) signals of the microflowers exhibited pH-responsiveness. This dual-mode sensitive platform could be developed as a pH sensor with improved accuracy. Additionally, the pH-responsive photoluminescence ON/OFF switch of the microflowers could be employed for reliable information encryption and decryption. This study provides useful ideas for regulating the self-assembly of nanoclusters to generate desired photophysical properties with potential applications.

Particle detectors based on liquid argon are now recognised as an attractive technology for dark matter direct detection and coherent elastic neutrino-nucleus scattering measurement. A program using a dual-phase liquid argon detector with a fiducial mass of 200~kg to detect coherent elastic neutrino-nucleus scattering at Taishan Nuclear Power Plant has been proposed. SiPMs will be used as the photon sensor because of their high radio-purity and high photon detection efficiency. S13370-6050CN SiPM, made by Hamamatsu, is a candidate for the detector. In this paper, the characterisation of S13370-6050CN SiPM, including the cross talk and after pulse probabilities at liquid argon temperature and the temperature dependence of break down voltage, dark counting rate and relative quantum efficiency were presented., Comment: 17 pags, 15 figures

Hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy, which involves the process of harvesting renewable energy to split water into hydrogen and oxygen and then further utilization of clean hydrogen fuel. The production of hydrogen by water electrolysis is an essential prerequisite of the hydrogen economy with zero carbon emission. Among various water electrolysis technologies, alkaline water splitting has been commercialized for more than 100 years, representing the most mature and economic technology. Here, the historic development of water electrolysis is overviewed, and several critical electrochemical parameters are discussed. After that, advanced nonprecious metal electrocatalysts that emerged recently for negotiating the alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are discussed, including transition metal oxides, (oxy)hydroxides, chalcogenides, phosphides, and nitrides for the OER, as well as transition metal alloys, chalcogenides, phosphides, and carbides for the HER. In this section, particular attention is paid to the catalyst synthesis, activity and stability challenges, performance improvement, and industry-relevant developments. Some recent works about scaled-up catalyst synthesis, novel electrode designs, and alkaline seawater electrolysis are also spotlighted. Finally, an outlook on future challenges and opportunities for alkaline water splitting is offered, and potential future directions are speculated.

In the present study, carbon-dots (CDs) were derived from the thermal oxidation of an agricultural waste, bitter tea residue, to obtain different sp2/sp3 ratios and electronic structures for metal sensing. The CDs obtained from calcination at 700 °C exhibited the highest photoluminescence (PL) quantum yield (QY) of 11.8% among all the samples treated at different temperatures. These CDs had a high degree of graphitization, which resulted in a strong π-π* electron transition, and hence in a high QY. The strong photoluminescence of the CDs could be used to sense the metal ions Ag+, Sr2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, and Sn2+ by monitoring their PL intensity at an excitation wavelength of 320 nm. The metals inhibited the PL intensity in the order Ag+ > Fe2+, Fe3+, Ni2+ > Sr2+, Co2+, Cu2+, Sn2+, which demonstrated that the CDs exhibited high metal ion detection capability and selectivity. The detection of Fe3+ using CDs was performed in the range of 10–100 ppm with a LOD (limit of detection) value of 0.380 ppm. Theoretical calculations demonstrated that Ag+, Sr2+, and Sn2+ induced charge transfer excitation and that Fe2+ and Ni2+ induced d-d transitions via complexation with the sp2 clusters. The charge transfer excitation and d-d transitions hindered the π-π* transition of the sp2 clusters, leading to a quenching effect. On the other hand, Li+, Na+, and K+ ions did not alter the π-π* transition of the sp2 clusters, resulting in a negligible quenching effect. In summary, the oxidation level and electronic structure of CDs derived from bitter tea residue could be tailored, and the CDs were shown to be a facile, sustainable, and eco-friendly material for metal sensing.

Tough hydrogels that are capable of efficient mechanical energy dissipation and withstanding large strains have potential applications in diverse areas. However, most reported fabrication strategies are performed in multiple steps with long-time UV irradiation or heating at high temperatures, limiting their biological and industrial applications. Hydrogels formed with a single pair of mechanisms are unstable in harsh conditions. Here we report a one-step, biocompatible, straightforward and general strategy to prepare tough soft hydrogels in a few tens of seconds under mild conditions. With a multimechanism design, the network structures remarkably improve the mechanical properties of hydrogels and maintain their high toughness in various environments. The broad compatibility of the proposed method with a spectrum of printing technologies makes it suitable for potential applications requiring high-resolution patterns/structures. This strategy opens horizons to inspire the design and application of high-performance hydrogels in fields of material chemistry, tissue engineering, and flexible electronics., Tough hydrogels capable of efficient mechanical energy dissipation are difficult to be patterned and/or printed which limits their application. Here the authors show a one-step, biocompatible and general strategy to prepare tough soft hydrogels with high-resolution 2D/3D microstructures quickly under mild conditions.

In this work, the structural transformation, elastic behavior, phonon spectra and thermodynamic properties of CeO2 under compressive and tensile loading were investigated by first-principles calculations based on density generalized function theory (DFT). Our calculated structural parameters and transition pressure under compressive condition are in good agreement with the experimental values. Under tensile condition, the phase transitions of CeO2 from fluorite-type (space group Fm 3 ¯ m ) phase to cotunnite-type (space group Pnma), rutile-type (space group P 4 2 /mnm) and marcasite-type (space group Pnnm) phases were predicted to occur at 23.2 GPa, −7.69 GPa, and −7.75 GPa respectively. The mechanical stability criteria are verified in terms of elastic constants and shows that the cotunnite and fluorite structures of CeO2 are mechanically stable in the studied pressure range, while the rutile and marcasite structures turn out to be mechanical unstable under high pressure. The calculated phonon spectra of CeO2 polymorphs demonstrate that all phases considered in present work are dynamically stable under ambient pressure. Furthermore, the calculated heat capacity, isothermal bulk modulus, Gibbs free energy, thermally expanding coefficient of CeO2 polymorphs as a function of temperature are discussed and compared with available experimental data.

We have measured the properties of scintillation light in liquid argon doped with xenon concentrations from 165 ppm to 10,010 ppm using a $^{22}$Na source. The energy transfer processes in the xenon-doped liquid argon are discussed in detail, and a new waveform model is established and used to fit the average waveform. The time profile of the scintillation photon in the xenon-doped liquid argon and of the TPB emission are presented. The quantities of xenon-doped are controlled by a Mass Flow Controller which is calibrated via a Redusial Gas Analyzer to ensure that the xenon concentration is accurate. In addition, a successful test of $^{83{\rm m}}$Kr as a calibration source has been implemented in the xenon-doped liquid argon detector for the first time. By comparing the light yield of the $^{22}$Na and $^{83{\rm m}}$Kr, it can be concluded that the scintillation efficiency is almost same over the range of 41.5 keV to 511 keV., Comment: 17 pages, 16 figures

Economical and abundant natural biological materials provide a low-cost and scalable approach to develop next-generation flexible and wearable electronics. Herein, a universal strategy of nature-inspired and amine-promoted metallization, namely, NIAPM, is presented to make high-quality metals for electronics fabrication. The introduction of poly(ethyleneimine) (PEI) significantly shortens the time of metallization from >48 h to ≈6 h, and the phenol compounds (TP) from green tea make metals bond tightly on all demonstrated surfaces. The as-made thin metal films of Cu and Ni feature high conductivity (∼1.0 Ω/□), excellent mechanical stability and flexibility even at the bending radius of ∼1 mm. Moreover, NIAPM is compatible with typical lithography techniques for fabricating metallic patterns, showing considerable potential applications in flexible electronics. As a proof-of-concept, two devices based on melamine-templated Cu sponges are first prepared for detecting the change of external pressure with a resistance sensitivity of 18.1 kPa-1 and collecting high-viscosity crude oil, respectively. Then, a high-performance bendable solid supercapacitor is demonstrated using as-prepared Ni metallized fabrics and the activated porous carbon from the recycled waste in NIPAM as flexible electrodes, which possesses comparable areal capacitance of 45.5 F·g-1, and energy density of 7.88 Wh·g-1 at the power density of 35 W·g-1. Therefore, it is anticipated that such a time-saving, cost-effective and whole solution-processed NIAPM strategy can inspire further practical applications in the fields of surface chemistry, material science, flexible and wearable electronics, etc.

Carbon aerogels with 3D networks of interconnected nanometer-sized particles exhibit fascinating physical properties and show great application potential. Efficient and sustainable methods are required to produce high-performance carbon aerogels on a large scale to boost their practical applications. An economical and sustainable method is now developed for the synthesis of ultrathin carbon nanofiber (CNF) aerogels from the wood-based nanofibrillated cellulose (NFC) aerogels via a catalytic pyrolysis process, which guarantees high carbon residual and well maintenance of the nanofibrous morphology during thermal decomposition of the NFC aerogels. The wood-derived CNF aerogels exhibit excellent electrical conductivity, a large surface area, and potential as a binder-free electrode material for supercapacitors. The results suggest great promise in developing new families of carbon aerogels based on the controlled pyrolysis of economical and sustainable nanostructured precursors.

Preparing an autonomous self-healing supramolecular elastomer with sunlight degradability is still a challenging task in related fields. In this work, we report a supramolecular elastomer by using the classic host–guest complexation of visible-light-photolabile picolinium-containing adamantanes (Ad) and β-cyclodextrin nanogels (β-CD). The as-synthesized elastomer possesses merits of high mechanical strength, excellent stretchability (>1500% strain), efficient self-healing (>85% at 60 min), ultrastability against electrolytes, and photodegradation properties, implying versatile applications in flexible and stretchable electronics. As proofs-of-concept, self-healable strain and pressure sensors using conductive elastomers are first fabricated, which feature exceptionally high sensitivity (e.g., 0.1% in capacitance at 0.2 kPa) and fast response to detect human body motions. A degradable and flexible supercapacitor is also fabricated using the conductive elastomer as the flexible matrix. Remarkably, both the ...

The complex permittivity and return loss (RL) for the composites of silicone rubber filled with holey graphene nanosheets (HGNS, prepared by ultra-rapid heating during the step of thermal reduction/exfoliation of graphite oxide) were measured in the 3–18 GHz range. HGNS-based composites were found to have significantly higher microwave absorption than composites incorporating other types of graphene reduced at lower heating rates. Even with only 1 wt.% loading, its experimentally measured RL reached −32.1 dB at 13.2 GHz with a thickness of 2 mm, and simulation suggested that at a thickness of 3 mm its RL can be as low as −45.3 dB at 7.8 GHz. Material characterization indicated that the density of the holes increased with the temperature ramp rate, and the hole sizes ranged from 5 to 300 nm. Compared to other graphene samples, HGNS possessed significantly larger specific surface area and higher density of defects, suggesting that defect-induced losses, interfacial polarization, and multiple reflection/scattering at the interfaces are the major loss mechanisms. Our simple and low-cost process as well as the very low loading ratio of HGNS are advantageous for cost reduction in future applications.

A bio-photoelectrochemical cell (BPEC) based on a fuel-free self-circulation water-oxygen-water system was fabricated. It consists of Ni:FeOOH modified n-type bismuth vanadate (BiVO4 ) photoanode and laccase catalyzed biocathode. In this BPEC, irradiation of the photoanode generates photocurrent for photo-oxidation of water to oxygen, which is reduced to water again at the laccase biocathode. Of note, the by-products of two electrode reactions could continue to be reacted, which means the H2 O and O2 molecules are retained in an infinite loop of water-oxygen-water without any sacrificial chemical components. As a result, the assembled fuel-free BPEC exhibits good performance with an open-circuit potential of 0.97 V and a maximum power density of 205 μW cm-2 at 0.44 V. This BPEC based on a self-circulation system offers a fuel-free model to enhance multiple energy conversion and application in reality.

Co-based electrocatalysts were prepared by facilely low-temperature multi-step calcination using ordered mesoporous carbons (OMCs) and cobalt salt as the precursors. According to the chemical reaction of cobalt compound, the calcined product of each step could be used as different catalysts, which could complete the full water splitting in alkaline solution together. The introduction of ordered mesoporous carbon not only make the morphology was well inherited, but also enhanced the catalytic activity. The OMCs/CoP exhibited overpotential of 134 mV in acidic media and 143 mV in basic media with a current density of 10 mA cm−2 for hydrogen evolution reaction (HER). While, in basic solution, the OMCs/Co3O4 had an overpotential value of 350 mV at 10 mA cm−2 for oxygen evolution reaction (OER). Moreover, the different Co-based electrocatalysts were assembled into one system for the full water splitting in 1 M KOH solution. This work provided a facile and efficient candidate for water splitting.

Photo/electrochemical splitting of water to hydrogen (H2) fuel is a sustainable way of meeting our energy demands at no environmental cost, but significant challenges remain: for example, the sluggish anodic reaction imposes a considerable overpotential requirement. By contrast, urea electrolysis offers the prospect of energy-saving H2 production together with urea-rich wastewater purification, whereas the lack of inexpensive and efficient urea oxidation reaction (UOR) catalysts places constraints on the development of this technique. Here we report a porous rod-like NiMoO4 with high oxidation states of the metal elements enabling highly efficient UOR electrocatalysis, which can be readily produced through annealing solid NiMoO4·xH2O as a starting precursor in Ar. This precursor gives the derived Ni/NiO/MoOx nanocomposite when switching the shielding gas from Ar to H2/Ar, exhibiting platinum-like activity for the hydrogen evolution reaction (HER) in alkaline electrolytes. Assembling an electrolytic cell using our developed UOR and HER catalysts as the anode and cathode can provide a current density of 10 milliamperes per square centimeter at a cell voltage of mere 1.38 volts, as well as remarkable operational stability, representing the best yet reported noble-metal-free urea electrolyser. Our results demonstrate the potential of nickel–molybdenum-based materials as efficient electrode catalysts for urea electrolysers that promises cost-effective and energy-saving H2 production.

Three new perovskite-like iodobismuthate hybrids with two butylpyridinium cations, namely (BPY)3(Bi2I9) (1), (BPY)5(Bi2I11) (2) and (BMPY)3(Bi2I9) (3) (BPY ​= ​1-butylpyridinium, BMPY ​= ​1-butyl-4-methylpyridinium), were synthesized by reacting of BiI3 and butylpyridinium. Single-crystal X-ray diffraction analysis revealed that these three hybrids exhibit two types of di-nuclear cluster structures, face-sharing Bi2I93− cluster for 1 and 3, and vertex-sharing Bi2I115− cluster for 2. Their optical band gaps were determined as 2.06 ​eV(1), 2.01 ​eV(2), 1.86 ​eV(3), respectively. DFT calculation reveals that their valence band tops and conduction band bottoms are composed of the states of iodine and pyridinium cations, respectively. Therefore these materials were classified as charge-transfer salts. Compared with similar iodobismuthates, their band gaps are significantly reduced. In addition, it is found that the band gaps should be affected by supramolecular interaction between cations in 2 and also by the conformational multiplicity of cations in structure 3. Photocurrent response test showed that these charge-transfer salts have rapid and consistent photocurrent response. This result indicated their potential applications as a photocatalyst or a photovoltaic absorber.

Ceramic Matrix Composites (CMCs) are primary candidates for advanced gas turbine engine application that require intense high temperature tests and validations. Before CMCs used in engine hot sections, a lot of tests need to be done, especially thermal test. A thermal test rig has been set up to simulate the engine turbine thermal environment. Propane gas is used to simulate the practical aviation fuel and compressed air with flow regulator is used as cooling media. The capabilities and limitations of the test facility have been calibrated and discussed in this paper. A CMC turbine vane with internal cooling path was tested on this burning rig. The results showed that the CMC vane could withstand the 1200 ℃ thermal cycling test but the coating was disappeared. It has been proved that such test rig and method could simulate the thermal boundary conditions of turbine vanes and blades.

CoFe films without buffer layers were deposited at different ultra-low argon pressures ranging from 0.085 to 0.847 mTorr. This pressure range was one to two orders lower than the normal sputtering pressure. As a consequence, the static magnetic properties, including coercivity and magnetic anisotropy field, were improved with decrease argon pressure. The high-frequency permeability spectra showed that the resonance frequency and the damping factor of the films also reached optimal values at ultra-low pressure. Basing on atomic force microscopy observations, we attributed the excellent properties to the improved morphologies of the films and released internal stress.

A simple and efficient approach for selective metallization of polyimide (PI) substrate has been developed in this work. A heat curable Pd complex ink consists of Pd salt, pH sensitive monomer N, N-dimethyl-dimethylaminoethyl methacrylate (DMAEMA), trimethylolpropane triacrylate (TMPTA), and tert-butyl peroxybenzoate (TBPB) is utilized to promote the adhesion between the Cu coating and PI substrate. After heating the spin-coated ink on PI and successive electroless deposition (ELD) of copper, a layer of copper with excellent adhesion is formed on PI substrate. The effects of this ink on catalyzing the ELD of copper and the mechanism for the enhancement of the adhesion between flexible PI substrate and copper layer are investigated by XPS and FT-IR. The copper coating plated by this method has a low resistivity (about 13.6 × 10 − 6 Ω cm) and satisfied endurance of bending. Moreover, we also demonstrate that the copper patterns can be prepared easily by integration of laser-direct patterning of the spin-coated ink and electroless Cu deposition, which is fast and effective strategy for fabricating circuit patterns on the plastic substrate.

Despite the benefit of high specific capacity offered by graphene when used as the anode material in lithium-ion batteries (LIBs), its large aspect ratio could lead to long transport paths for Li ions, thereby limiting the rate capability. We demonstrate that holey graphene (HGE) prepared by a simple and low-cost method can effectively improve the rate capability of LIBs by providing shortcuts for Li-ion diffusion through the holes in fast charge/discharge processes. HGE showed a high reversible capacity of 742 mAh/g at a current density of 0.1 A/g after 80 cycles, which was 2.3 times as much as that of non-holey graphene (GE). Moreover, at a high current density of 10 A/g, HGE still possessed a reversible capacity of 141 mAh/g, while GE retained only 27 mAh/g. In addition, both the charge transfer resistance and the interfacial resistance of HGE were lower than those of GE. We believe that HGE have high potential in applications of high-power electrochemical storage devices such as plug-in hybrid electric vehicles.

In this study, three-dimensional reduced graphene oxide/Au NPs/nitrogen-doped carbon nanotubes (RGO/Au NPs/N-doped CNTs) assembly supported on nickel foam was utilized as an anode for enzymatic biofuel cells (EBFCs). 3D RGO/Au NPs was obtained by electrodepositing reduced graphene oxide on nickel foam (Ni foam), while Au NPs were co-deposited during the process. Afterwards, nitrogen doped CNTs (N-CNTs) were allowed to grow seamlessly on the surfaces of 3D RGO/Au NPs via a simple chemical vapor deposition (CVD) process. In this nanostructure, Au NPs co-deposition and nitrogen doping offer more active sites for bioelectrocatalysis. Additionally, N-CNTs were demonstrated providing high specific surface area for enzyme immobilization and facilitating the electron transfer between glucose oxidase (GOx) and electrode. The resulting bioanode achieved efficient glucose oxidation with high current densities of 7.02mAcm-2 (0.3V vs. Ag/AgCl). Coupling with a Pt cathode, the fabricated glucose/air biofuel cell exhibited an open-circuit potential of 0.32V and generated a maximum power density 235µWcm-2 at 0.15V. This novel electrode substrate achieved high performance in current density at bioelectrochemical systems and could be useful for further exploiting the application of three dimensional carbon-based nanomaterials in EBFCs.

Helium can cause segregation of solute atoms in the material, and in turn, the segregated solute atoms will have a great influence on the behavior of helium. Studying the behavior of helium in tritium storage materials is very important for the design of materials with strong helium retention capacity. In this paper, the first-principles method based on density functional theory is used to study the segregation of doped atoms Ti caused by defects (He atoms) in ZrCo system, and the effect of segregated Ti atoms on He behavior. The effect of segregated Ti atoms on the stability of He atoms was explored. The CI-NEB method was used to simulate the variance of the trapping for He atoms by vacancy in the pure and doped systems. Finally, it was found that the number of He atoms trapped by the vacancy is reduced due to the Ti cage. In addition, the Ti cage has a certain pinning effect on He atoms. In short, the segregated Ti inhibits the migration of He and hinders the flow of He to the grain boundaries, thereby suppressing the helium embrittlement effect.

The model R5912-20MOD photomultiplier tube(PMT) is made for cryogenic application by Hamamatsu. In this paper, we report on the measurement of relative quantum efficiency (QE) of this model PMT at liquid argon(LAr) temperature. Furthermore, a specially designed setup and relevant test method are introduced. The relative QE is measured in visible wavelengths with the PMT emerged in high purity nitrogen atmosphere. The results show that the change of QE at LAr temperature is within about 5% compared with room temperature around 420 nm. However, the QE increases about 10% in the shorter wavelength range and decreases significantly after 550 nm., 10 pages, 6 figures

First-principle investigations are presented based on density functional approach to calculate the elastic properties, stress-strain relations, phonon dispersion relations, electronic properties and thermodynamic properties of hexagonal and orthorhombic U 2 Mo. The calculated energies in the present work suggest that hexagonal structure is more stable than orthorhombic one. The obtained elastic constants and moduli show that both phases of U 2 Mo are ductile and elastically stable. Besides, the stress-strain relations and the corresponding theoretical tensile strengths of these two phases exhibit strong anisotropy in selected crystalline directions. The generated phonon dispersion curves without imaginary phonon mode imply these two compounds are dynamically stable. The analyzed results of the electrical properties demonstrate the electronic stability, and the hybridizations between the f -states of U and the d -states of Mo can be noted from derived band structures and partial densities of states for these two structures. Gibbs free energy and other thermodynamics quantities are also obtained and discussed in this paper.

A series of CoFe/IrMn exchange bilayers was grown by DC-sputtering at different ultra-low argon pressures ranging from 0.008 to 0.1 Pa. This pressure range was one to two orders lower than the normal sputtering pressure. Results revealed that the exchange bias increased from 140 to 250 Oe in CoFe(10 nm)/IrMn (15 nm) bilayers of fixed thickness because of the improved crystalline structure and morphological uniformity of films. Since ferromagnetic /antiferromagnetic (FM/AF) bilayers are always used in linear magnetic sensors as detection layers, the varying exchange bias can successfully achieve tunable linear range in a crossed pinning spin valve. The linear range could be adjustable from −80 Oe – +80 Oe to −150 Oe – +150 Oe on the basis of giant magnetoresistance responses. Therefore, this method provides a simple method to tune the operating range of magnetic field sensors.