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With the innovation of electronics industry and the advancement in 5G technology, the overheating problem has become an urgent obstacle to further realize the high performance and multi-function of electronic devices. Thus, it is essential to develop efficient thermal management materials to realize timely and effective heat dissipation. The thermal management systems based on phase change materials (PCMs) have received extensive attention in recent years. In this work, composite PCMs with a high phase change enthalpy of 149.56 J g−1, multiple phase change characteristics, a high thermal conductivity of 1.28 Wm−1 K−1, and excellent shape stability were fabricated by the means of cross-linked polymer swelling strategy. When the as-prepared composite PCMs were directly attached to the heating plate or served as thermal interface materials (TIMs) to dissipate heat, the temperature of heating plate can be reduced by 5.8 °C and 18.8 °C, respectively, revealing great potential in the thermal management application of electronic devices.

The induced radioactivity in accelerator components and decay characteristics of radioactive nuclei contained therein is critical for radiation safety of occupational workers as well as for the maintenance, repair, and decommissioning activities. The topic of induced radioactivity is widely reported and extensively explored in the literature by many researchers up to now. This mini-review would demonstrate the current state of the knowledge on induced radioactivity at particle accelerators. In this article, the concepts of activation-related studies and radionuclide generation in accelerator environments are reviewed. In addition, some studies on accelerator-induced radioactivity by Monte Carlo and experimental measurement methods are briefly described. The possible radiation protection problems caused by particle accelerator-induced radioactivity are briefly reviewed and analyzed. The produced radionuclides depend on the beam parameters such as particle type, energy, irradiation period, cooling time, and irradiated material. The Monte Carlo simulation method offers comparable advantages over empirical analysis method. A review of major studies in the field of induced radioactivity of particle accelerators confirmed that the extremely strong induced radioactivity generated at hot spots of accelerators means new challenges to radiation safety and deserves further investigation and discussion.

Liquids and solids are two fundamental states of matter. However, our understanding of their three-dimensional atomic structure is mostly based on physical models. Here we use atomic electron tomography to experimentally determine the three-dimensional atomic positions of monatomic amorphous solids, namely a Ta thin film and two Pd nanoparticles. We observe that pentagonal bipyramids are the most abundant atomic motifs in these amorphous materials. Instead of forming icosahedra, the majority of pentagonal bipyramids arrange into pentagonal bipyramid networks with medium-range order. Molecular dynamics simulations further reveal that pentagonal bipyramid networks are prevalent in monatomic metallic liquids, which rapidly grow in size and form more icosahedra during the quench from the liquid to the glass state. These results expand our understanding of the atomic structures of amorphous solids and will encourage future studies on amorphous–crystalline phase and glass transitions in non-crystalline materials with three-dimensional atomic resolution. Atomic electron tomography is used to determine the three-dimensional atomic structure of monatomic amorphous solids with liquid-like structure, which is characterized by the existence of pentagonal bipyramid networks with medium-range order.

Non-layered transition metal carbides (NL-TMCs) have diverse morphologies and structures, and tunable stoichiometric ratios, giving them many intriguing electrical/catalytic properties such as high gravimetric capacities, high conductivity and excellent stability. The latest progress in the use of NL-TMCs for energy conversion and storage applications is reviewed. Several routes to synthesize NL-TMCs are described, including carbothermal reduction, chemical vapor deposition, a template-assisted method and a hydro/solvothermal method. Their electrochemical performance in lithium-ion batteries, lithium-sulfur batteries and catalytic water splitting are presented. Current challenges for the rational design and fabrication of NL-TMCs for practical applications are discussed and future research suggestions are made.

The exploration of new red phosphors is important for the development of white light-emitting diodes (w-LEDs), as existing red phosphors exhibit low efficiency and low performance. This work aims to enhance the photoluminescence characteristics of a red-emitting Gd2Zr2O7:Eu3+ phosphor by co-doping with Al3+. Eu3+ single-doped and Eu3+ and Al3+ co-doped Gd2Zr2O7 nanophosphors that could be efficiently pumped by commercial near-UV LED chips were prepared by a modified liquid–solid–solution phase-transfer method. X-ray diffraction data revealed that the synthesized phosphors were well crystallized with single-phase fluorite structure. Scanning electron microscopy images showed that the particle size ranges from 15 to 25 nm. In addition, the optical performance of the samples was characterized by fluorescence spectroscopy and lifetime spectroscopy. The effect of Al3+ on the luminescence performance of the Eu3+-doped Gd2Zr2O7 phosphor was studied in detail. The emission intensity of the Gd1.93Zr1·97O7:Eu3+0.07Al3+0.03 phosphor was found to be 620% stronger than that of the single-doped Eu3+ phosphor. These results unambiguously show that the Gd1.93Zr2-xO7:Eu3+0.07Al3+x phosphors are promising candidates for application in w-LEDs.

Polyaniline (PANI) wrapped Ti2Nb10O29 (TNO) micro-spherical composites were successfully synthesized via a solvothermal approach combined with a facial post in-situ polymerization method. Effects of different amounts of the PANI coatings on the composite microspheres’ electrochemical properties were studied in detail. Results showed that the electrochemical performance of TNO@PANI anodes with 5 wt% PANI is the optimum among all the samples, giving capacity values as high as 272 mAh/g (1 C) and 190.1 mAh/g (20 C), respectively. Moreover, the electrochemical impedance measurements exhibited that 5 wt% TNO@PANI composite electrode material possess a weaker charge transfer resistance. This indicates that an appropriate amount of polyaniline coating can effectively improve the electronic conductivity of TNO microspheres and subsequently the electrochemical properties. In this work, we have demonstrated that 3D TNO@PANI composite microspheres not only deliver a higher initial Columbic efficiency but also can serve as next-generation lithium-ion battery electrode material with enhanced rate performance.

Amorphous solids such as glass, plastics and amorphous thin films are ubiquitous in our daily life and have broad applications ranging from telecommunications to electronics and solar cells1-4. However, owing to the lack of long-range order, the three-dimensional (3D) atomic structure of amorphous solids has so far eluded direct experimental determination5-15. Here we develop an atomic electron tomography reconstruction method to experimentally determine the 3D atomic positions of an amorphous solid. Using a multi-component glass-forming alloy as proof of principle, we quantitatively characterize the short- and medium-range order of the 3D atomic arrangement. We observe that, although the 3D atomic packing of the short-range order is geometrically disordered, some short-range-order structures connect with each other to form crystal-like superclusters and give rise to medium-range order. We identify four types of crystal-like medium-range order-face-centred cubic, hexagonal close-packed, body-centred cubic and simple cubic-coexisting in the amorphous sample, showing translational but not orientational order. These observations provide direct experimental evidence to support the general framework of the efficient cluster packing model for metallic glasses10,12-14,16. We expect that this work will pave the way for the determination of the 3D structure of a wide range of amorphous solids, which could transform our fundamental understanding of non-crystalline materials and related phenomena.

In this paper, Cu/SAC-15Ag/Cu 3D package solder joints were prepared by transient liquid phase (TLP) bonding technology. The effects of bonding time on the microstructure and shear property of solder joints were investigated. The results indicated that the microstructure of solder joints is coarsened with increasing bonding time. The intermetallic compounds (IMCs) in the interfacial reaction zone consist of Cu3Sn and Cu6Sn5 phase, and the IMCs in the in situ reaction zone include Ag3Sn phase, Sn-rich phase, and Ag particles. The thickness of interfacial IMCs layer initially decreases due to the volume contraction caused by the transformation from Cu6Sn5 to Cu3Sn, and then increases as a result of the coarsen of Cu3Sn. The minimum porosity of the solder joints reaches 0.24% under bonding time of 30 min. The shear strength of solder joints increases first and then declines with the extension of bonding time, and the maximum shear strength of 45.3 MPa is obtained by bonding for 30 min. The shear fracture mechanism of solder joints changes from ductile fracture to ductile–brittle mixed fracture, and then changes to brittle fracture. Cracks nucleate at the voids and propagate quickly with prolonging bonding time, and the cracks could be restrained by the voids.

Powered by renewable electricity, the electrochemical conversion of CO2 to liquid fuels and valuable chemicals is a meaningful approach to enable carbon cycling and tackle environmental issues. An ...

A nitrate–citrate combustion method combined with microwave sintering was firstly employed for the rapid fabrication of the Gd2Zr2O7 matrix immobilizing various amounts of simulated nuclear wastes. Phase evolutions, microstructure changes, element distributions, densification processes and mechanical properties of the as-prepared (1 – x)Gd2Zr2O7·xTRPO (0.0 ≤ x ≤ 0.6) at various temperatures were investigated. Compared to the reported studies, we have increased the immobilization amount of simulated TRPO waste within a crystal structure from 45 to 60 wt%. Td and Tg (the threshold temperatures to trigger accelerated densification and grain growth, respectively) were employed to divide the densification process into three stages. the mechanical properties and the densification stages of the (1 – x)Gd2Zr2O7·xTRPO (0.0 ≤ x ≤ 0.6) ceramics sintered under microwave sintering at various temperatures were finally determined. Fine-grained (1 – x)Gd2Zr2O7·xTRPO (0.0 ≤ x ≤ 0.6) ceramic waste forms with average grain size less than 200 nm and relative density higher than 90% can be obtained by microwave sintering at sintering temperature less than 1400 °C.

The rational design of Pt-based electrocatalysts is of paramount importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Pt-Co alloys and nitrogen-doped carbons have been shown to be effective in enhancing the kinetics of the oxygen reduction reaction (ORR). Herein, we reported on two kinds of Pt-Co electrocatalysts, PtCo ordered intermetallic and PtCo

Fraction-controlled Pt–Cu-based porous films were prepared using an electrochemical deposition–stripping synthetic approach, and their structure, composition, and electronic structure were characte...

We report a method combining the top-down and bottom-up approaches for the fabrication of nanocrystalline ceramic, which can break down the Y2O3 nanorods and consolidate the broken nanoparticles to 99.1% relative density. The lab-mad nanorods with a length of about 500 nm and a diameter of about 20 nm, exhibit better compressibility and sinterability than the spherical nanopowders when the compaction pressure exceeds 0.4 GPa and the sintering condition is 5 GPa/500 °C, respectively. The obtained nanocrystalline ceramic shows a maximum transmittance of 81.3% in the infrared region, hardness as high as 10.5 GPa and fracture toughness of 2.21 MPa m1/2.

An experimental study on combustion instability is presented with focus on propane-air premixed swirling flames. Swirling flames under self-excited oscillation are studied by imaging of visible light and OH* chemiluminescence filter under several typical conditions. The dynamical characteristics of swirling flames were analysed by Dynamic Mode Decomposition (DMD) method. Three types of unstable modes in the combustor system were observed, which correspond to typical acoustic resonant modes (LF mode, C1/4 mode and P1/2 mode) of the combustor system. The combustion instability is in the longitudinal mode. Furthermore, the structure of downstream hot burnt gas under stable combustion and unstable combustion is studied by imaging of visible light and near-infrared light. Results show that there is a significant difference in the downstream flow under stable combustion and unstable combustion. The DMD spectrum of the flame and the downstream hot burnt gas obtained is the same, which is close to the characteristic frequency of acoustic pressure captured by the microphone signal. The visible light and near-infrared light imaging observation method adopted in this paper provides a new imaging method for the investigation of thermo-acoustic instability.

Here, we study the effect of bonding time on the intermetallic compound (IMC) formation and shear property of Cu/In-50Ag/Cu TLP solder joints based on low-temperature transition liquid phase (TLP) bonding of In-Ag composite powder. The bonding process was carried out at a temperature of 260°C using a wafer bonding machine. The results show that the solder joints are composed of an (Ag,Cu)2In phase and a Cu2In phase in the interfacial diffusion reaction zone and an Ag2In phase and In rich phase in the in␣situ reaction zone. It was observed that the (Ag,Cu)2In phase is formed firstly in the diffusion reaction zone when the bonding time is 0.5 min, then transforms completely into the Cu2In phase when the bonding time reaches 30 min. The shear strength increased and then decreased with increasing bonding time. The observed shear fracture mode of solder joints is brittle.

A series of Cr3+ ions activated Sr2MgAl22O36 inorganic luminescence materials were successfully synthesized. The structure provides suitable crystal field for Cr3+ ions to achieve both broadband and narrowband emission simultaneously in far-red region. Cr3+ ions doped Sr2MgAl22O36 reach the maximum of luminescence intensity when the concentration is increased to 0.02. When the concentration exceeds the value, the luminescence intensity of Cr3+ ions is quenched by the dipole-dipole interaction. The fluorescence intensity ratio I2/I1 (I1 and I2 represent the intensity at 677 and 693 nm, respectively) originating from Cr3+ ions in Sr2MgAl22O36 shows good linearity in the Arrhenius plot. The relative sensitivity of Sr2MgAl22O36: Cr3+ material at 310 K (physiological temperature) reaches 1.7% K-1, which has good application potential on ratiometric thermometers. Present researches indicate that Sr2MgAl22O36: Cr3+ has great potential application value on ratiometric thermometers.

The carrier dynamics of two isomers, α-NPB and β-NPB, were investigated through impedance spectroscopy based on the PSO algorithm. Their structure differences are only the N atom substitution sites...

A 2D coordination polymer, 1, was synthesized, characterized, and investigated with single-crystal-to-single-crystal photoreaction and thermal pyrolysis. It could undergo two-step photoaddition upon UV irradiation: at the first step, the parallel polycatenated 2D topology of the structure changed into 4-fold interpenetrating 3D nets; at the second step, a new compound with an unreported 3D net topology was formed. Upon heating, the cyclobutanes in the photoreaction product underwent a ring opening reaction. The photoluminescence of 1 was determined by its structure; it emitted green fluorescence, and after photoaddition and photopolymerization, it emitted blue fluorescence. 1 may be a photo/thermo-switchable dual-color green-to-blue fluorescence material.

A modified liquid–solid–solution (LSS) phase transfer method has been applied to synthesize Gd2Zr2O7 binary oxide nanoparticles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) were employed to reveal the structural, morphological and energetic evolutions of both precursors and Gd2Zr2O7 nanoparticle products. The Gd2Zr2O7 nanoparticles synthesized using this method exhibit an average crystallite size of 1.7 nm, which have great potential to be applied in thermal barrier coatings (TBCs), solid oxide fuel cells (SOFCs) and nuclear waste immobilizations. Moreover, the method we developed in this study has a high Gd2Zr2O7 nanoparticle yield of up to 89%.

A fluorescence intensity ratio (FIR) thermometer based on inorganic luminescence materials is a new-type temperature sensor with potential and significance. However, research based on single transi...

3D porous structural materials are proved to be enticing candidates for the fabrication of high-performance organic phase change materials (PCMs), but the stringent fabrication process and poor processability greatly hampered their commercialization. Herein, flexible leakage-proof composite PCMs with pronounced comprehensive performance are fabricated by a scalable polymer swelling strategy without using any solvent, in which the paraffin wax (PW) segment is confined in a robust flexible 3D polymer network, giving rise to the composite PCMs with excellent form stability even at 160 °C, a high latent heat energy storage density of 133.6 J/g, and an outstanding thermal conductivity of up to ∼5.11 W/mK. More importantly, the mass production of the flexible composite phase change fiber, film, and bulk products can be achieved by adopting mature processing technologies. These resultant composite PCMs exhibit promising thermal management ability to solve the overheating problem of electronics and high-efficiency solar-thermal energy conversion capacity.

It is well known that liquid Al wetting on a SiC substrate is an important process, especially when manufacturing Al/SiC composite materials. Many researchers have attempted to investigate ...

In this report, a series of amorphous organic optoelectronic pyrene–fluorene derivative materials (BP1, BP2, PFP1, PFP2, OP1, OP2) were systematically investigated through a theoretical method. Their molecular structures are different due to the difference of substitution groups at C9 of the fluorene core, which include electron-rich pyrene group (PFP1 and PFP2), relatively neutral phenyl group (BP1 and BP2), and electron-withdrawing oxadiazole group (OP1 and OP2). In the beginning, through the physical model analysis, this report proposes that the concept of p-type or n-type is not flawless because there is no real doping process in these molecular organic semiconductors. To prove such a concept, the Marcus theory and first-principles were employed to calculate the intrinsic transfer mobility of these materials. Not as the common method used for the single crystal, in this report, a series of disorderly designed lattice cells were constructed to represent the disordered distribution of the amorphous pyrenyl–fluorene derivatives. Then, the reorganization energy of materials was calculated by the adiabatic potential energy surface method. The transfer integral of dimers was calculated in possible hopping pathways near the central molecule. Research results show that the six pyrene–fluorene materials all possess intrinsic bipolar transfer characteristics. In addition, it is also showed that the electron-rich group is not necessary to improve hole transfer, and that the electron-withdrawing group is also not necessary to improve electron transfer.

Hydrogen fuel cells operated in alkaline media enable the use of abundant nonprecious 3d metal oxides to replace Pt to catalyze the sluggish oxygen reduction reaction (ORR). Herein, we describe Co–...

A metal–organic framework (MOF), {[Co3(ip)3(1,3-bpeb)4]·H2O}n (1), with multiple photoreactive centers, was synthesized via hydrothermal reaction of Co(II) ion with isophthalate and 1,3-bis[2-(4-py...

In this work, Co3O4@ZnO nanocomposite photoelectrodes with a core-shell structure were prepared, enabling enhanced photoelectrochemical activity under visible light illumination. This was demonstrated by the photoinduced cathodic polarization of 304 stainless steel in 3.5 wt% NaCl solution. The morphology, composition, crystalline structure and optical absorption properties of the photoelectrodes were characterized by various analysis techniques and UV–vis diffuse reflectance absorption spectroscopy. Results show that, compared to the ZnO nanorods, the Co3O4@ZnO nanocomposite photoelectrodes have a red shift of optical absorption and enhanced photoelectrochemical cathodic polarization on stainless steel under visible light. The enhanced photoelectrochemical performance is attributed to the narrow band gap of Co3O4 and the p-n junction formed at the Co3O4/ZnO interface. The Co3O4@ZnO nanocomposite photoelectrodes fabricated in this work achieve a photocurrent density of 10.5 μA/cm2 and a cathodic polarization potential of −720 mV (saturated calomel electrode) for 304 stainless steel in 3.5 wt% NaCl solution under visible light.

Alkaline polymer electrolyte fuel cells are a class of fuel cells that enable the use of non-precious metal catalysts, particularly for the oxygen reduction reaction at the cathode. While there have been alternative materials exhibiting Pt-comparable activity in alkaline solutions, to the best of our knowledge none have outperformed Pt in fuel-cell tests. Here we report a Mn-Co spinel cathode that can deliver greater power, at high current densities, than a Pt cathode. The power density of the cell employing the Mn-Co cathode reaches 1.1 W cm−2 at 2.5 A cm−2 at 60 oC. Moreover, this catalyst outperforms Pt at low humidity. In-depth characterization reveals that the remarkable performance originates from synergistic effects where the Mn sites bind O2 and the Co sites activate H2O, so as to facilitate the proton-coupled electron transfer processes. Such an electrocatalytic synergy is pivotal to the high-rate oxygen reduction, particularly under water depletion/low humidity conditions., Alkaline polymer electrolyte fuel cells are promising power sources, but performance is limited by catalytic activity. Here the authors report a non-precious metal-based catalyst for electrocatalytic oxygen reduction that imparts outstanding fuel cell performance.

This work reports a novel Ga-based material, NiGa2O4, which is typically used as a photocatalyst for water splitting, as an anode for Li-ion battery with a long cycle life. High-surface-area reduced graphene oxide (rGO) has been used as the conductive substrate to avoid the aggregation of NiGa2O4 nanoparticles (NPs). Because the size and shape of NiGa2O4 are very sensitive to the pH of the precursor, ethylene glycol has been employed as the solvent, as well as the reduction agent to reduce GO, to avoid using extra surfactants and also to avoid the variation of pH of the precursor. The obtained NiGa2O4/rGO composite possesses high capacity and long cycle life (2000 cycles, 2 A/g), with NiGa2O4 NPs around 3-4 nm that are uniformly distributed on the rGO surface. Full cell performance with LiCoO2 as cathode has also been studied, with the average loss of 0.04% per cycle after 100 cycles (C/2 of LiCoO2). The long cycle life of the composite was ascribed to the self-healing feature of Ga0 formed during charging.

Ordered intermetallic nanoparticles are promising electrocatalysts with enhanced activity and durability for the oxygen-reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). The ordered phase is generally identified based on the existence of superlattice ordering peaks in powder X-ray diffraction (PXRD). However, after employing a widely used postsynthesis annealing treatment, we have found that claims of “ordered” catalysts were possibly/likely mixed phases of ordered intermetallics and disordered solid solutions. Here, we employed in situ heating, synchrotron-based, X-ray diffraction to quantitatively investigate the impact of a variety of annealing conditions on the degree of ordering of large ensembles of Pt(3)Co nanoparticles. Monte Carlo simulations suggest that Pt(3)Co nanoparticles have a lower order–disorder phase transition (ODPT) temperature relative to the bulk counterpart. Furthermore, we employed microscopic-level in situ heating electron microscopy to directly visualize the morphological changes and the formation of both fully and partially ordered nanoparticles at the atomic scale. In general, a higher degree of ordering leads to more active and durable electrocatalysts. The annealed Pt(3)Co/C with an optimal degree of ordering exhibited significantly enhanced durability, relative to the disordered counterpart, in practical membrane electrode assembly (MEA) measurements. The results highlight the importance of understanding the annealing process to maximize the degree of ordering in intermetallics to optimize electrocatalytic activity.

Li–S batteries have attracted great attention for their combined advantages of potentially high energy density and low cost. To tackle the capacity fade from polysulfide dissolution, we have developed a confinement approach by in situ encapsulating sulfur with a MOF-derived CoS2 in a carbon framework (S/Z-CoS2), which in turn was derived from a sulfur/ZIF-67 composite (S/ZIF-67) via heat treatment. The formation of CoS2 was confirmed by X-ray absorption spectroscopy (XAS) and its microstructure and chemical composition were examined through cryogenic scanning/transmission electron microscopy (Cryo-S/TEM) imaging with energy dispersive spectroscopy (EDX). Quantitative EDX suggests that sulfur resides inside the cages, rather than externally. S/hollow ZIF-67-derived CoS2 (S/H-CoS2) was rationally designed to serve as a control material to explore the efficiency of such hollow structures. Cryo-STEM-EDX mapping indicates that the majority of sulfur in S/H-CoS2 stays outside of the host, despite its high void volumetric fraction of ∼85%. The S/Z-CoS2 composite exhibited highly improved battery performance, when compared to both S/ZIF-67 and S/H-CoS2, due to both the efficient physical confinement of sulfur inside the host and strong chemical interactions between CoS2 and sulfur/polysulfides. Electrochemical kinetics investigations revealed that the CoS2 could serve as an electrocatalyst to accelerate the redox reactions. The composite could provide an areal capacity of 2.2 mA h cm−2 after 150 cycles at 0.2C and 1.5 mA h cm−2 at 1C. This novel material provides valuable insights for further development of high-energy, high-rate and long-life Li–S batteries.

The wetting phenomenon of Sn-37Pb alloy solder spreading on Cu substrate under different ultrasonic fields was investigated. Sn-37Pb/Cu wetting systems showed significant precursor film characteristics with the assist of ultrasonic energy. A short-time ultrasonic field evidently enhanced the wettability of Sn-37Pb/Cu compare to a common wetting field which had no introduced ultrasonic. At the temperature of 213 °C, spreading area of a Sn-37Pb solder drop in a 20 kHz, 1000 W ultrasonic field reached maximum at 2 s, and showed significant precursor film characteristics. Atomistic dynamic models showed the relevance between wettability and precursor film formation. The observed dynamic results agreed with the experimental results.

Coal tar enamel (CTE) coatings are the primary coatings used for corrosion protection of oil/gas pipelines which have been usually in service for about fifty years. The compatibility of CTE coatings with cathodic protection (CP) is critical to integrity maintenance of the pipelines. In this work, the permeability of CTE to CP current was investigated in a simulated soil solution through monitoring potential, current and solution pH. Results show that the coatings are CP-impermeable. Even at the practically minimum thickness of 2.30 mm for the coating, the CP permeability is 0.541% only. As the coating thickness increases, the CP permeability reduces rapidly. For the coatings containing defects, the CP permeation depends on their size. In this work, the threshold diameter for circular coating defects present on CTE coating is 1 mm, below which more than 70% of CP current is shielded from permeation.

Liquids and solids are two fundamental states of matter. However, due to the lack of direct experimental determination, our understanding of the 3D atomic structure of liquids and amorphous solids remained speculative. Here we advance atomic electron tomography to determine for the first time the 3D atomic positions in monatomic amorphous materials, including a Ta thin film and two Pd nanoparticles. We observe that pentagonal bipyramids are the most abundant atomic motifs in these amorphous materials. Instead of forming icosahedra, the majority of pentagonal bipyramids arrange into a novel medium-range order, named the pentagonal bipyramid network. Molecular dynamic simulations further reveal that pentagonal bipyramid networks are prevalent in monatomic amorphous liquids, which rapidly grow in size and form icosahedra during the quench from the liquid state to glass state. The experimental method and results are expected to advance the study of the amorphous-crystalline phase transition and glass transition at the single-atom level.

Three series of copper hydride clusters [Cu8H6L6]2+ (1), [Cu4HX2L4]+ where X− = Cl− (2a), Br− (2b), I− (2c), N3− (2d) and SCN− (2e), and [Cu4HX3L3] where X− = Br− (3b) and I− (3c) (L = 2-(diphenylphosphino)pyridine, dppy) were synthesized and characterized by single-crystal X-Ray crystallography and standard spectroscopic techniques. The metal core of 1, Cu8, can be described as a bicapped octahedron, while those of 2 and 3 series adopt tetrahedral structures. The hydride positions were deduced from difference electron density maps and corroborated by NMR and DFT calculations. For 1, there are two μ4-H−, one each in the two tetrahedral cavities of the two capping atoms and four μ3-H− on the six triangular faces around the waist of the octahedron. For [Cu4HX2L4]+ and [Cu4HX3L3] series, the single μ4-H− resides in the center of the Cu4 tetrahedron. It was found that these three series of copper clusters are intimately connected and can convert from one to another under specific reaction conditions. Their transformation pathways were investigated in detail. Spontaneous resolution to form optically pure enantiomeric single crystals was observed for [Cu4H(SCN)2L4]+ (2e) and [Cu4HBr3L3] (3b). Photoluminescence was observed for [Cu4HX2L4]+, as well as [Cu4HX3L3] with strong emissions from green to yellow regions.

This study proposes an optimization method for the design of planar arbitrary-geometry thermal cloaks using natural materials based on the bilayer theory in thermal-cloaking studies. Our objective is to provide a practical design method for bilayer thermal cloaks of arbitrary shapes by determining the optimal outer-layer conductivity of the bilayer yielding the best thermal-cloaking performance. The method accounts for a potentially conducting inner layer, which is deemed more realistic from a practical standpoint as opposed to an ideal bilayer having a perfectly insulated inner layer. The proposed method is applied to solve thermal-cloaking problems involving not only conventional circular and elliptical geometries but also arbitrary-geometry thermal cloaks, as well as nonlinear background temperature distributions. For the ideal circular and elliptical bilayer cloaks, the proposed method yields the same analytical results as reported in the literature. For those cases where an analytical solution is not known to exist, the results demonstrate that excellent thermal-cloaking performance can be achieved on the basis of the bilayer design using the optimal outer-layer conductivity determined from the optimization method for a given set of background, inner-layer, and cloaked-region conductivities.

To evaluate the capability of electron cyclotron emission (ECE) diagnostic in the Chinese Fusion Engineering Testing Reactor (CFETR), ECE spectra have been simulated using the code SPECE. The results indicate that measurements of the 2nd harmonic X-mode and the 1st harmonic O-mode ECE spectra combined are capable of providing the information of local electron temperature with fairly good spatial resolution and adequate radial range covering from the plasma core to the edge. Followed with the simulation results, the conceptual design of the front-end, transmission line, instrumentation, and the calibration strategy are discussed briefly. Base on the state-of-the-art techniques, no foreseen technical obstacles exist. However, it is worthy to study the relativistic down-shift effect in the high temperature plasmas in order to obtain the position of the emission layer with required precision in a timely manner.

Ag-Cu-Au ternary alloys are promising solder materials for wire bonding. Limited experimental studies on Ag-Cu-Au materials can be found due to the high cost of gold. In this study, face-centered-cubic Cu(100), Cu(111), and Cu(110) substrates wetted by molten Ag45Cu42Au13 were investigated via molecular dynamics (MD). As demonstrated by melting simulation results, the Ag45Cu42Au13 alloy has a lower melting temperature compared to the eutectic alloy, Ag60Cu40. MD methods were also used to investigate the dissolutive characteristics of Ag45Cu42Au13/Cu wetting. Density profiles and contact angles show an increase in wettability in the Ag45Cu42Au13/Cu(100) wetting system. For molten Ag60Cu40 and Ag45Cu42Au13 the spreading behavior on Cu(100) shows a promoted tendency, which contrasts with both Cu(111) and Cu(110). Solid-liquid adhesion is indicative of the comparative spreading degrees. The contact angles and PMF analysis of wetting behaviors on rough and smooth Cu substrates illustrate that solid-liquid adhesion in Wenzel states is stronger than in Cassie wetting states.

Slurry concentration and wire speed affect the yield and machining quality of ceramics (Al2O3) that are produced using wire-saw machining (WSM). This study determines the effect of slurry concentration and wire speed on the material removal rate (MRR), the machined surface roughness (SR), the kerf width, the wire wear and the flatness for swinging and non-swinging WSM. The experiments show that swinging WSM results in a higher machining efficiency than non-swinging WSM. WSM with swinging also achieves a peak MRR at a medium slurry concentration (25 wt%) and a higher wire speed (5.6 m/s) using the cutting conditions for the experimental region. However, slurry concentration and wire speed have no significant effect on the machined SR, the kerf width, the wire wear or the flatness for WSM with swinging mode.

Multi-wire saw machining (MWSM) used for slicing hard-brittle materials in semiconductor, is an important material removal process that uses free abrasives. Cutting model of single-wire saw machining (SWSM) is the basis of MWSM, and the material removal mechanism of SWSM can better understand than MWSM. Mathematical model (includes brittle fracture and plastic deformation) is presented in this paper for SWSM ceramic with abrasives. This paper determines the effect of various machining parameters on the removal of hard-brittle materials. For brittle fracture of SWSM ceramics, the minimum of the strain energy density is used as a fracture criterion. The material removed of SWSM ceramics due to plastic deformation is calculated using the equations of motion. Actual wire-sawing experiments are conducted to verify the results from the developed mathematical model. Theoretical results agree with experimental data and practical experience. The developed mathematical model shows that brittle fracture plays a major concern role in material removed of SWSM ceramics. Wire speed and working load have positively correlated with material removed of SWSM ceramics. The coefficient of friction is low, a lateral crack, which propagates almost parallel to the working surface, leads to more brittle fracture and material removed is increased on SWSM ceramics.

Atomic termination plays a key role in activating the proximity effect of antiferromagnet., This work reports the ferromagnetism of topological insulator, (Bi,Sb)2Te3 (BST), with a Curie temperature of approximately 120 K induced by magnetic proximity effect (MPE) of an antiferromagnetic CrSe. The MPE was shown to be highly dependent on the stacking order of the heterostructure, as well as the interface symmetry: Growing CrSe on top of BST results in induced ferromagnetism, while growing BST on CrSe yielded no evidence of an MPE. Cr-termination in the former case leads to double-exchange interactions between Cr3+ surface states and Cr2+ bulk states. This Cr3+-Cr2+ exchange stabilizes the ferromagnetic order localized at the interface and magnetically polarizes the BST Sb band. In contrast, Se-termination at the CrSe/BST interface yields no detectable MPE. These results directly confirm the MPE in BST films and provide critical insights into the sensitivity of the surface state.

In this study, the Cu/In–Sn–20Cu/Cu solder joints were fabricated under the bonding temperature of 260 °C, bonding stress of 3 MPa and bonding time of 0.5–60 min by transient liquid phase bonding. The influence of bonding time on the microstructure evolution and the shear strength of the solder joints was investigated. The results indicated that the intermetallic compound in the interface reaction zone was Cu3(In, Sn) phase, and its thickness was increased continuously with increasing bonding time. The scallop-type Cu6(In, Sn)5 phase was formed at the interface of Cu3(In, Sn)/In–Sn–20Cu composite solder and then gradually grew to connect the island-type Cu6(In, Sn)5 phase which formed in the in situ reaction zone. The transformation of Cu6(In, Sn)5 phase to Cu3(In, Sn) phase occurred in the in situ reaction zone after the bonding time reached 15 min. The shear strength of the Cu/In–Sn–20Cu/Cu solder joints was increased first and then decreased with increasing bonding time. The maximum shear strength was 26.54 MPa when the bonding time reached 15 min. The shear fracture mechanism of solder joints transited from brittle fracture to ductile–brittle mixed fracture with increasing bonding time.

Amorphous solids such as glass are ubiquitous in our daily life and have found broad applications ranging from window glass and solar cells to telecommunications and transformer cores1,2. However, due to the lack of long-range order, the three-dimensional (3D) atomic structure of amorphous solids have thus far defied any direct experimental determination without model fitting3-13. Here, using a multi-component metallic glass as a proof-of-principle, we advance atomic electron tomography to determine the 3D atomic positions in an amorphous solid for the first time. We quantitatively characterize the short-range order (SRO) and medium-range order (MRO) of the 3D atomic arrangement. We find that although the 3D atomic packing of the SRO is geometrically disordered, some SRO connect with each other to form crystal-like networks and give rise to MRO. We identify four crystal-like MRO networks - face-centred cubic, hexagonal close-packed, body-centered cubic and simple cubic - coexisting in the sample, which show translational but no orientational order. These observations confirm that the 3D atomic structure in some parts of the sample is consistent with the efficient cluster packing model8,10-12,20. Looking forward, we anticipate this experiment will open the door to determining the 3D atomic coordinates of various amorphous solids, whose impact on non-crystalline solids may be comparable to the first 3D crystal structure solved by x-ray crystallography over a century ago14.

An internal transport barrier (ITB) can be formed on EAST in exploring high-parameter operation. Previous studies show that safety factor (q) profiles, Shafranov shift and magnetohydrodynamic behaviors could be helpful in ITB formation by suppressing anomalous transport. Recently, electron density evolution with high resolution demonstrates that fishbone could be dominant in electron density ITB formation and sustainment. The power threshold is low in the fishbone condition and the electron density profile is determined by traits of fishbone. Simulation shows that the low-k ion mode is suppressed by fishbone. Direct measurement of turbulence in the inner region shows that the internal kink mode could sustain an electron temperature ITB by suppressing the trapped electron mode. The multi-scale interaction between the kink mode and turbulence by current could be key in sustaining high-electron-temperature long-pulse operation.

CoFeB/MgO-based magnetic tunnel junctions (MTJs) have considerable potential in magnetic random access memory (MRAM), thanks to their tunable perpendicular magnetic anisotropy (PMA). We found significant reduction of dead-layer by inserting additional MgO into the MTJ structure. Interface, electronic and transport characterizations were utilized to approach the modified magnetic properties driven by the dual-MgO structure in this work. The dual-MgO structure appeared to hinder boron (B) diffusion into the metallic layer and prevent capping-layer (Ta) penetration across the interface. This suppressed the dead-layer effect and promoted overall magnetization despite PMA degradation. A robust BOx phase that formed within the dual-MgO structure presented a superparamagnetic ground state. In the single-MgO structure, any reduction in the thickness of the CoFeB promoted PMA, albeit at the cost of spin-polarization. The dual-MgO structure could restore spin-polarization by preferentially populating spin electrons into Fe/Co minority states. X-ray magnetic spectroscopy and anomalous Hall effect suggest that, the dual-MgO differs from the single-MgO with a favorable longitudinal polarized spin-channel. This makes the dual-MgO structure applicable to applications requiring in-plane rather than out-of-plane sensing.