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International audience; The nucleation and crystallization of glass-ceramics are typically influenced by early phase separation, which can impact glass properties. However, it has been challenging to characterize the nanoscale phase separation and understand the nucleation mechanism of lithium disilicate (L2S) glass-ceramics, which has resulted in some controversy. Here, we raised the direct evidence of nanoscale clustering in the glassy phase prior to formal nucleation and crystallization by element distribution. Firstly, the amorphous Li3PO4 phase formed on the boundary between the phase separation area and residual glass matrix, and then nucleation tended to start on this phase boundary. Furthermore, the effect of phase-separation on nucleation and final crystallize products was illustrated. By sufficient phase-separation, the formation of desired Li2Si2O5 and LiAlSi4O10 microcrystals was effectively motivated, which is prerequisite for high mechanical properties and transparency. We hope this work provides guidance to rationally understand the early phase separation in glass for subsequent controlling crystallization.

International audience; Glass scintillators have several benefits compared to the currently used single or polycrystalline scintillators, including non-hygroscopicity, mechanical ruggedness, ease of producing customizable shapes, and low-cost synthesis. The combination of the inert glass matrix and the embedded highly scintillating center render them significant materials for medical imaging and therapy, non-destructive probing, nuclear monitoring, and high-energy physics. Recently, great progress has been made in exploring new kinds of glass scintillator materials, improving imaging resolution for radiation detection, and developing an enormous range of commercial products. However, the majority of efforts have been devoted to the variation of materials, while rationally designing this new family of scintillators toward expected properties and applications is still lacking. In this review, the focus is specifically on advances in glass scintillators, including the scintillation fundamentals, material designing rule, and current application status, as well as future challenges and future directions.

International audience; 2D Ruddlesden-Popper (RP) perovskites have demonstrated highperformance emitters, and large-sized perovskite single crystals have always been pursued for efficient optoelectronic devices. However, large-sized 2D RP perovskite single crystals with high quality are still difficult to achieve due to the weak interaction between layers and strong anisotropy. Here, we show a rational design strategy to synthesize centimeter-sized 2D BM2PbBr4 (BM = benzimidazole) perovskite single crystals by intermediate-phase engineering (IPE). 1D (DMF)2BMPbBr3 intermediate-phase single crystals were structurally decoupled and transformed to perfect 2D BM2PbBr4 seed crystals with a certain thickness, presenting a huge advantage over the extrathin crystal sheets in random stacking by natural crystallization. Furthermore, the new BM with conjugated structures we obtained as the A-site of the 2D RP perovskite enhances the exciton confinement, resulting in a surprisingly large excitonic binding energy of 368.2 meV. The emitting decay time is shortened to 0.98 ns, which is the smallest among all the perovskite materials. Tailoring of the X-site components for 2D RP BM2PbBr4 - xClx (x = 1, 2, 3, and 4) series with tunable luminescence and decay time was also synthesized by IPE. We believe IPE provides a new way for synthesizing large-sized perovskite single crystals with fine-tunable properties to satisfy the target applications.

International audience; Lead-free double perovskites (DPs) have outstanding luminescent properties, which make them excellent candidates for wide use in optoelectronics. Herein, a solvent-free melting-crystallization technique, which can produce kilogram-scale DP microcrystals (DP-MCs) in one batch, is invented to synthesize the Cs(2)Na(x)Ag(1-x)InCl(6): Bi (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) DP-MCs. The structure and composition analysis confirmed the products are pure Cs(2)Na(x)Ag(1-x)InCl(6) DP-MCs. Affected by Jahn-Teller distortion of AgCl(6) octahedra, self-trapped excitons appear in the excited state, resulting in the broadband emission (400-850 nm) of Cs(2)Ag(1-x)Na(x)InCl(6): Bi DP-MCs. The enhancement of the photoluminescence quantum yield can be realized by introducing Na(+) to break the parity-forbidden transition in the Cs(2)AgInCl(6) DP. Optimized Cs(2)Na(0.4)Ag(0.6)InCl(6): Bi DP-MC phosphors combined with commercial blue and green phosphors were coated on ultraviolet chips (365 nm) to fabricate white light-emitting diodes (WLEDs) from warm white (2930 K) to cold white (6957 K). An ultrahigh color rendering index of 97.1 and a CCT of 5548 K as well as Commission Internationale de l’Eclairage color coordinates of (0.331, 0.339) have been demonstrated. This kilogram-scale synthesis technique could stimulate the industrial development of WLEDs for general lighting based on DP-MC phosphors.

Chalcohalide glasses with a gradient refractive index (GRIN) microstructure were imprinted by microthermal poling for realizing diffractive optical elements covering the visible to middle-infrared wavelength range. The effect of halogen ions on the saturation poling voltage (U), surface profile, diffraction pattern, optical transmittance, GRIN microstructure, and structural rearrangement of poled glass is investigated. An effective imprinting formation region for a GRIN microstructure based on the U and glass composition is observed under fixed poling time and temperature. The onset U (60 V–150 V) and activation energy of mobile cations (0.449 eV–0.533 eV) decreases with the atomic number of the halogen from F to I, but the saturation diffractive order (8th to 11th levels) and phase difference (~0.08λ to 0.18λ) increases accordingly. The onset U and activation energy decrease with the deformability of the glass network and radius of the halogen ions. The phase difference and saturation diffractive orders decrease with the proportion and electronegativity of interval halogen atoms in the glass network. Thus, chalcohalide glasses with GRIN microstructures can be tailored by adjusting the type of halogen ions for realizing various diffraction optical elements.

International audience; Due to the high transparency, high Verdet constant, as well as easy processing properties, rare-earth ion-doped glasses have demonstrated great potential in magneto-optical (MO) applications. However, the variation in the valence state of rare-earth ions (Tb(3+) to Tb(4+)) resulted in the decreased effective concentration of the paramagnetic ions and thus degraded MO performance. Here, a strategy was proposed to inhibit the oxidation of Tb(3+) into Tb(4+) as well as improve the thermal stability by tuning the optical basicity of glass networks. Moreover, the depolymerization of the glass network was modulated to accommodate more Tb ions. Thus, a record high effective concentration (14.19 × 10(21)/cm(3)) of Tb ions in glass was achieved, generating a high Verdet constant of 113 rad/(T·m) at 650 nm. Lastly, the first application of MO glass for magnetic field sensors was demonstrated, achieving a sensitivity of 0.139 rad/T. We hope our work provides guidance for the fabrication of MO glass with high performance and thermal stability and could push MO glass one step further for magnetic sensing applications.

International audience; Glass-ceramic, which has negligible dielectric loss, high mechanical strength, excellent drop resistance, low CTE, and low density for lightweight design, is the best option for the back cover of mobile devices in the 5 G era. Herein, the effect of P2O5 on the phase separation and crystallization of MgO-Al2O3-SiO2-TiO2 glass-ceramics is studied. The incorporation of P2O5 in the glass structure leads to phase separation, in which the P and Mgenriched phase was formed in the glass matrix, and promotes the increase of Tg. With the increase of P2O5 content, the precipitated crystals change significantly. First, the silicate crystals (Mg2SiO4) disappear, whereas the phosphate crystals (LiMgPO4) emerge when 2 mol% P2O5 is introduced. Second, titanate crystal (MgTi2O5) can not be observed when 4 mol% P2O5 is introduced. The Ti5O9 crystals appear simultaneously with LiMgPO4 crystals and transform to rutile TiO2 crystals at high temperature. Interestingly, the needle-like rutile TiO2 crystals, which is 300 nm long and 20 nm wide, have been found in a glass with 4 mol% P2O5. The large L/D ratio of needle-like crystals increases the hardness significantly from 6.08 GPa to 7.14 GPa. Similar to other fiber reinforced composites, this needle-like crystals provide a new strategy to improve the mechanical properties of glass ceramics.

Soft exosuits are an emerging class of robots that have been shown to significantly reduce the metabolic cost of daily human movement. However, most soft exosuits are currently being studied for walking and running, and relatively minor research has been carried out on exosuits for stair climbing. Numerous exoskeletons used for stair climbing have a more rigid structure and are heavier, which may result in a greater force required by the wearer to overcome the weight from the exoskeleton when ascending stairs, which can result in metabolic costs. As a result, a reduction in rigid structures can reduce the weight of the exoskeleton and further reduce metabolic costs during stair climbing. In this paper, a waist-wearable soft exosuit was designed that assists hip flexion to aid stair climbing in older adults, in order to demonstrate the importance of choosing to assist hip flexion during stair climbing. An admittance delayed feedback control method was also proposed to use the angular information measured by the IMUs to enable the exosuit to adapt to different staircases. Metabolic experiments have shown that people who use soft exosuits have an average decrease of 6.9% in metabolism when they climb stairs than those who do not. The muscle fatigue experiments demonstrated a reduction in muscle fatigue of approximately 9.35%, 38.75% and 9.65% for the rectus femoris, lateral femoris and gastrocnemius muscles, respectively, when compared to cases without the soft exosuit. The results show that assisted hip flexion during stair climbing is a reasonable approach to effectively reduce metabolic consumption and muscle fatigue.

Purpose: To study the difference in retinal vascular morphology and the developmental dynamics between preterm infants with and without Retinopathy of Prematurity (ROP).Methods: 226 preterm infants with ROP and 928 preterm infants without ROP were studied. We developed a deep learning-based method to evaluate the vascular morphological features automatically. Stepwise regression analysis was applied to analyze the differences in the retinal vascular morphology between the two groups. Furthermore, analysis of covariance was used to analyze the differences in vascular development dynamics between preterm infants with ROP and without ROP.Results: Vascular tortuosity, caliber, and branch angle in preterm infants with ROP were significantly higher than those without ROP. Furthermore, preterm infants' vascular density with ROP increased significantly slower with gestational age than preterm infants without ROP.Conclusion: ROP is a disease closely associated with the vessels in the posterior pole region of retinal. Vascular morphology of preterm infants with ROP is significantly different from that of preterm infants without ROP. The density, which could reflect the proliferation of the vessels, develops significantly slower in preterm infants with ROP. The findings could provide insights into the pathogenesis of ROP.

Vanadate as intercalation compounds are attracting considerable interest for use in electrochemical energy storage devices, such as lithium-ion batteries, sodium-ion batteries, and zinc-ion batteries. However, the ion transport mechanism in vanadate compounds has never been clearly elucidated despite its overwhelming influence on electrochemical performance. Unlike previous reports, in this work, new insights into Li+ diffusion mechanisms for LiV3O8 are proposed, and the key points are as follows. First, Li+ tended to be transported along the b-axis direction via a knock-off mechanism rather than direct hopping along the c-axis direction, as argued by traditional views. Second, the lattice lithium ions in LiV3O8, which were previously thought to function via pillar effects, were proven to be electrochemically active by computational calculations. Moreover, further studies revealed that our conclusions were universal and could be widely applied to many other vanadate compounds. This work has provided a new understanding of ion diffusion in vanadate compounds, which enables researchers to develop more efficient strategies for performance optimization.

A water-soluble Eu(III) hybrid composite based-on DPA and Phen as ligands, graphene oxide sheets (GOSs) as inorganic matrix, and Eu3+ as luminescence center has been synthesized, namely, Eu–DPA–Phen/GOSs. Compared with single Eu(III) complexes named Eu–DPA–Phen, Eu–DPA–Phen/GOSs not only retains the high luminescence intensity but also shows better solubility, higher stability, and longer fluorescence lifetime. It can be used as a fluorescent probe to detect Cu2+ ions in liquid medium and mixed with polyvinyl alcohol (PVA) to produce a self-supporting film with high luminescence intensity, good stability, mechanical properties. This film is also sensitive to Cu2+ ions and convenient to carry. Thus, it has a great potential in the field of flexible and foldable luminescent devices and fluorescence sensing.

In the absence of long-range order, the electrochemical performance of multicomponent γ-MnO2 is highly dependent on the local structural properties. However, early studies, generally based on traditional bulk phase characterization, tended to reveal average structural information and were less sensitive to the local environment. This thus led to unclear structure–property relationships for γ-MnO2. Different from traditional one-dimensional tunnel diffusion, in this work, a multidimensional Li+ diffusion mechanism is proposed after clarifying the special local structural properties. The individual one-dimensional diffusion channels of the tunnel structure were connected and developed into continuous multidimensional diffusion paths via a unique interface structure at which Li+ diffusion was dynamically favorable. From one-dimensional to multidimensional Li-ion diffusion, the optimized MnO2 exhibited high power and high energy density due to the unconventional diffusion properties. This study provides further understanding of Li+ solid-state diffusion and potentially provides a way to improve the electrochemical performance of γ-MnO2 and other intercalation compound materials.

Composite sucker rods are becoming increasingly popular in oil fields owing to their light weight and corrosion resistance. However, various defects may appear in the manufacturing and service of sucker rods. Unfortunately, research on defect detection is still insufficient for composite sucker rods. This study explores a surface crack detection technique for composite sucker rods based on low-power vibrothermography (LVT). First, an improved low-power piezoceramic actuator with a curved bottom is designed for rod-like structure. Second, the entire processes of LVT-based surface crack detection, including excitation signal generation, mechanical wave propagation, and heat generation at defects, are simulated and analyzed using the finite element method. The heat generation mechanism and characteristic at cracks are revealed by coupled thermo-electro-mechanical analysis. The superiority of the improved actuator is reflected by comparison with the conventional actuator. In addition, the simulation investigates the optimal excitation signal amplitude and circumferential angle between the actuator and the crack. Finally, a series of LVT detection experiments were conducted on a composite sucker rod with surface cracks, which not only proved the effectiveness of the LVT, but also validated the conclusions of the numerical simulations. The maximum temperature rise at the crack is 5.54 °C by using the improved actuator. Numerical simulation and experimental results demonstrate that the surface cracks of the composite sucker rod can be effectively detected using LVT with an improved piezoceramic actuator. This study provides a new direction for extending vibrothermography to the non-destructive testing of composite rod-like structures.

Metal–organic frameworks (MOFs) are a platform with multiple luminescent centers resulting from the multifaceted nature of their structure. Herein, via a facile postsynthetic modification method ap...

A diffractive optical element (DOE) covering visible to middle-infrared regions is imprinted in chalcohalide glass by microthermal poling under ultralow voltages (~125 V). The effect of the poling voltage on the surface profiling, optical diffraction, optical transmittance, and anode-side structural rearrangement is investigated. Deformation of the surface profiling and diffraction order increase with increasing poling voltage, showing a saturation voltage of 125 V and a decrease in the transmittance within 10%. In addition to the normal vertical migration of silver ions, an obvious and unexpected transverse migration of silver ions and mutual structural transformation occur between homopolar bonds Ge–Ge (Ga–Ga) and S–S and the heteropolar bond Ge–S (Ga–S), which are key to forming the surface profiling and subsurface structures. Formation of the DOE mainly depends on the periodic subsurface microstructure rather than surface profiling. Thus, simple and inexpensive processes can fabricate broadband wavelength-based DOEs for military, medical and biological applications.

The phase transition of LiV3O8 from an α phase to a β phase during the discharge/charge process leads to drastic structural change and rapid capacity decay, and the consequent sluggish Li+ solid-state diffusion results in a serious concentration polarization. Herein, Ca-doped LiV3O8 was rationally designed and synthesized to address these issues. The electrochemical behaviors of Ca-doped and undoped LiV3O8, together with their structural evolution and changes in the ion solid diffusion paths, are studied in detail. Calculations at the atomic scale have revealed that Ca doping effectively suppresses the undesired α–β phase transition and stabilizes the structure of LiV3O8 during cycling. Moreover, the calcium dopant preferentially situated at lithium sites in LiV3O8 serves as a pillar to increase the interlayer distance and extend the electrochemically active (001) plane, and thus facilitates anisotropic Li+ diffusion. More importantly, the variable-cell Nudged-Elastic-Band (VCNEB) calculations indicate that the phase transformation was hindered by kinetic factors, not by thermodynamics. The dominant factors for the electrochemical performance of LiV3O8 were clarified, and valuable insights for LiV3O8 commercialization in lithium-ion batteries were provided.

International audience; Radiation detectors require scintillator materials combining high light yield, short light decay time and high stability. Metal halide perovskite nanocrystals (PNC) with heavy atoms have demonstrated excellent luminescent efficiency and short emission lifetime, which perfectly match the requirements of X-ray scintillators. However, the poor stability of PNC restricts its applications. Here we report stable CsPbBr3 NCs generated in an all-inorganic glass matrix by controlled crystallization. The transparent composite materials demonstrated good luminescence centered at similar to 520 nm as well as excellent stability towards water and heat (250 degrees C in the air) due to the protection role of inorganic glass. The high refractive index of the inorganic glass matrix enhanced the radiative transition rates. With all these features, the PNC glass-ceramic demonstrated good X-ray response and fast decay. The emission intensity of PNC glass-ceramic was half that of the commercial scintillating material Bi4Ge3O12 (BGO) under X-ray irradiation (50 kV) and the decay time (15.2 ns) was one twentieth that of BGO. The excellent performance and the high stability as well as the easily processable nature of glass samples make these composite materials promising candidates for various X-ray detection scenarios such as remote X-ray detection using scintillating glass fibers.