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The topotactic connection style of oxygen octahedron/tetrahedron in transition metal oxides (TMOs) is an important feature that modulates their corresponding physical properties. Using a simple chemical doping technique, we obtained Sr1−xNdxCoO3-δ with a crystal structure transition from face-shared octahedron to corner-shared octahedron/tetrahedron. The Rietveld analyses of the X-ray diffraction (XRD) patterns show that the crystal structure changes from rhombohedral to cubic and the connection style transforms from face-shared to corner-shared with the increase neodymium (Nd) content. During this process, the ferromagnetic behavior is greatly improved due to the larger amount of the corner-shared cubic SrCoO3-δ phase. The synchrotron radiation X-ray absorption spectroscopies of the Co L-edge and O K-edge show that Nd-doping mainly affects the electronic structure of oxygen rather than the valence state of Co. Thereby, the Nd changes the connection style of oxygen octahedron/tetrahedron, which then alters the magnetic interactions.

Oxygen electrocatalysis at transition metal oxides is one of the key challenges underpinning electrochemical energy conversion systems, involving a delicate interplay of the bulk electronic structure and surface coordination of the active sites. In this work, we investigate for the first time the structure-activity relationship of A2RuMnO7 (A = Dy3+, Ho3+, and Er3+) nanoparticles, demonstrating how orbital mixing of Ru, Mn, and O promotes high density of states at the appropriate energy range for oxygen electrocatalysis. The bulk structure and surface composition of these multicomponent pyrochlores are investigated by high-resolution transmission electron microscopy, X-ray diffraction, X-ray absorption spectroscopy, X-ray emission spectroscopy (XES), and X-ray photoemission spectroscopy (XPS). The materials exhibit high phase purity (cubic fcc with a space group Fd3¯ m) in which variations in M-O bonds length are less than 1% upon replacing the A-site lanthanide. XES and XPS show that the mean oxidation state at the Mn-site as well as the nanoparticle surface composition was slightly affected by the lanthanide. The pyrochlore nanoparticles are significantly more active than the binary RuO2 and MnO2 toward the 4-electron oxygen reduction reaction in alkaline solutions. Interestingly, normalization of kinetic parameters by the number density of electroactive sites concludes that Dy2RuMnO7 shows twice higher activity than benchmark materials such as LaMnO3. Analysis of the electrochemical profiles supported by density functional theory calculations reveals that the origin of the enhanced catalytic activity is linked to the mixing of Ru and Mn d-orbitals and O p-orbitals at the conduction band which strongly overlap with the formal redox energy of O2 in solution. The activity enhancement strongly manifests in the case of Dy2RuMnO7 where the Ru/Mn ratio is closer to 1 in comparison with the Ho3+ and Er3+ analogs. These electronic effects are discussed in the context of the Gerischer formalism for electron transfer at the semiconductor/electrolyte junctions.

Understanding the surface structure of bimetallic nanoparticles is crucial for heterogeneous catalysis. Although surface contraction has been established in monometallic systems, less is known for bimetallic systems, especially of nanoparticles. In this work, the bond length contraction on the surface of bimetallic nanoparticles is revealed by XAS in H2at room temperature on dealloyed Pt-Sn nanoparticles, where most Sn atoms were oxidized and segregated to the surface when measured in air. The average Sn-Pt bond length is found to be ∼0.09 Å shorter than observed in the bulk. To ascertain the effect of the Sn location on the decrease of the average bond length, Pt-Sn samples with lower surface-to-bulk Sn ratios than the dealloyed Pt-Sn were studied. The structural information specifically from the surface was extracted from the averaged XAS results using an improved fitting model combining the data measured in H2and in air. Two samples prepared so as to ensure the absence of Sn in the bulk were also studied in the same fashion. The bond length of surface Sn-Pt and the corresponding coordination number obtained in this study show a nearly linear correlation, the origin of which is discussed and attributed to the poor overlap between the Sn 5p orbitals and the available orbitals of the Pt surface atoms.

Sr2RuO4 has recently attracted intense attentions for its intriguing physical properties. However, the ultra-high growth temperature (≥1000 °C) poses a major challenge for fabricating high-quality Sr2RuO4 films. In sharp contrast to effort previously attempted in traditional oxygen atmosphere, herein, a nitrogen gas is employed to grow ruthenium oxide films during pulsed laser depositions (PLD). It is shown that the present method facilitates a successive SrRuO3–Sr2RuO4 structural transformation via increasing growth temperatures from 700 °C to 900 °C. The high-quality Sr2RuO4 film grown at a relative low deposition temperature exhibits a comparable electrical resistivity, in comparison with counterparts deposited at oxygen atmosphere. Combined X-ray photoelectron and X-ray absorption measurements suggest that the nonreactive nitrogen atmosphere involved during the deposition yields a relative lower kinetic energy of laser ablated plume reaching to substrates, and effectively regulates structural and electronic properties of ruthenium oxide films. These findings may offer a new route for synthesizing other oxide functional films with high deposition-temperature.

The electrochemical performance of supercapacitors is suppressed by a large number of defects in the interface of heterostructure due to lattice mismatch. In this paper, the (001) oriented rutile M...

Hydrogenation plays a critical role in tuning the material structural phase that fundamentally determines their electronic, optical, magnetic, and catalytic properties. However, prevailing hydrogen...

Rectifying semiconductor junctions are crucial to electronic devices. They convert alternating current into a direct one by allowing unidirectional charge flows. Analogous to the current-flow rectification for itinerary electrons, here, a polar rectification that is based on the localized oxygen vacancies (OVs) in a Ti/fatigued-SrTiO3 (fSTO) Schottky junction is first demonstrated. The fSTO with OVs is produced by an electrodegradation process. The different movabilities of localized OVs and itinerary electrons in the fSTO yield a unidirectional electric polarization at the interface of the junction under the coaction of external and built-in electric fields. Moreover, the fSTO displays a pre-ferroelectric state located between paraelectric and ferroelectric phases. The pre-ferroelectric state has three sub-states and can be easily driven into a ferroelectric state by an external electric field. These observations open up opportunities for potential polar devices and may underpin many useful polar-triggered electronic phenomena.

The manipulation of two-dimensional (2D) ferromagnetic materials by spin current is emerging as the central theme of 2D spintronics research. A paradigm of spintronic devices, the spin Hall magneto...

The synthesis of perovskite (ABO3) films with mixed anions has enabled us to constitute a novel class of materials exhibiting intriguing functionalities. In contrast to traditional metallic cation doping, anion doping within easy-to-prepare conditions usually gives rise to tremendous modulations of physical properties with tunable crystal structures. Here, oxyfluoride BaFeO3-xFy (BFO–F) thin films were successfully synthesized via a low-temperature reaction with polyvinylidene fluoride, which exhibit extremely structural stability over time. The existence of fluorine was confirmed by the combination of X-ray photoelectron depth profile and soft X-ray absorption spectroscopy. The oxyfluoride BFO–F films demonstrate a sequence of structural evolutions with reduced out-of-plane lattices, by means of elevating fluorination temperatures. The valence state of iron in BFO–F is gradually changed from 3+ to 4+ for higher fluorination temperatures. Moreover, the resistivity of BFO–F dramatically decreases, compared to that of pristine oxygen-deficient BaFeO3-δ film. Our results provide insight into the modulations on the structures and physical properties of perovskite oxyfluorides through the facile fluorination process and contribute to the fundamental understanding of fluorination.

寻找一种性能良好的磁性绝缘材料是发展新型多功能量子自旋电子器件至关重要的基础, 但是大多数已知的磁性绝缘材料具有居里温度低( 300 K), 铁磁性和结构对称性差的特点. 本工作中, 我们成功设计并制备了一种新型的磁性绝缘体: Bi8Fe2.8Co0.2-Ti2O20Cl, 它具有包含五层钙钛矿层的层状Sillen-Aurivillius结构. 令人惊讶的是, 此种化合物的居里温度达到了约 804 K, 比未掺杂的奈耳温度提高超过 300 K. 此外, 由于Sillen层的存在, Bi8Fe2.8-Co0.2Ti2O20Cl具有比所有已知相同Co摩尔比掺杂的Aurivillius氧化物更大的剩余磁化强度. X射线吸收光谱(XAS)和X-光磁性圆二色性(XMCD)光谱分析表明, Bi8Fe2.8Co0.2Ti2O20Cl的铁磁性主要是由Co掺杂引起的FeO6八面体的形变和Fe−O−Co的Dzyaloshinskii-Moriya(D-M)相互作用所致.

Spintronic terahertz (THz) emitters based on ferromagnetic (FM)-nonmagnetic (NM) heterostructures are the focus of many experimental endeavors for THz sources. However, existing spintronic THz sources control emission by changing the external magnetic field, which is inconvenient for compact integration. Therefore, various modulated mechanisms are in high demand. Here, we present an electric-field-controlled spintronic THz emitter based on the ferroelectric (FE)-FM/NM structure that can emit THz radiation with voltage-modulated amplitude and polarization angle. The modulation depth of the THz amplitude is up to 69%, and the maximum rotation of the THz polarization angle is 28\ifmmode^\circ\else\textdegree\fi{}. In addition, after removing the electric field, two different THz-emission states can remain unchanged, demonstrating nonvolatile behavior. Modulation is attributed to magnetoelectric coupling between the FM and FE layers, which modifies magnetization of the FM layer by the electric-field-induced strain in the FE layer, and thus, modulates THz emission. Furthermore, the possibility of a programmable array-type THz source with varied bias voltage is theoretically demonstrated, allowing a spatially modulated THz light to be generated directly without the use of additional spatial light modulators. We believe that this electric-field-controlled THz emitter has the potential to be used in next-generation on-chip THz sources, THz memory devices, and THz ghost imaging.

Antiferromagnets have attracted considerable interest in the field of spintronics due to their attractive characteristics such as ultrafast spin dynamics and robustness against external magnetic field perturbations. Sr2IrO4 is a rare example of antiferromagnetic semiconductor oxide and has been extensively studied in anisotropic magnetoresistance-based spintronics. However, the anisotropic magnetoresistance of Sr2IrO4 films is usually very small. Herein, we have prepared a (Sr2IrO4)4/(La2/3Sr1/3MnO3)5 superlattice which shows an enhanced anisotropic magnetoresistance compared to Sr2IrO4 film or La2/3Sr1/3MnO3/Sr2IrO4 heterostructure and an obvious nonvolatile memory effect that is comparable to Sr2IrO4 single crystals. Through magnetic measurements, the increased coercivity and the exchange bias at low temperatures reveal the interfacial magnetic coupling between Sr2IrO4 and La2/3Sr1/3MnO3. Additionally, the remarkable anisotropic magnetoresistance and clear hysteresis of anisotropic magnetoresistance with distinct fourfold symmetry can be controlled by temperature and magnetic field. These findings demonstrate that the superlattices of heavy transition metal oxide Sr2IrO4 are excellent platforms for antiferromagnetic spintronics.

Heterostructures composed of superconductor and ferroelectrics (SC/FE) are very important for manipulating the superconducting property and applications. However, growth of high-quality superconducting iron chalcogenide films is challenging because of their volatility and FE substrate with rough surface and large lattice mismatch. Here, we report a two-step growth approach to get high-quality FeSe0.5Te0.5 (FST) films on FE Pb(Mg1/3Nb2/3)0.7Ti0.3O3 with large lattice mismatch, which show superconductivity at only around 10 nm. Through a systematic study of structural and electric transport properties of samples with different thicknesses, a mechanism to grow high-quality FST is discovered. Moreover, electric-field-induced remarkable change of Tc (superconducting transition temperature) is demonstrated in a 20 nm FST film. This work paves the way to grow high-quality films which contain volatile element and have large lattice mismatch with the substrate. It is also helpful for manipulating the superconducting property in SC/FE heterostructures.

(K,Na)NbO3-based lead-free ferroelectric materials are highly desired in modern electronic applications and have long been considered as a strong candidate for replacing (Pb,Zr)TiO3, but most of them are deficient in large remnant polarization and decent thermal stability. Here, a unique lead-free 0.95(K0.49Na0.49Li0.02)(Nb0.8Ta0.2)O3-0.05CaZrO3 with 2 wt % MnO2 addition (KNNLT-CZ-M) ferroelectric film with special nanocomposite structures grown on La0.7Sr0.3MnO3-coated SrTiO3(001) substrate is demonstrated. The KNNLT-CZ-M films display excellent ferroelectricity with a large twice remnant polarization of 64.91 μC/cm2, a superior thermal stability of ferroelectricity from -196 to 300 °C, and a high Curie temperature of 400 °C. These robust performances could be attributed to the densely arranged self-assembled nanocolumns (∼10 nm in diameter) in the films, which can vertically strain the matrix and enhance its b/a ratio. The formation of the nanocolumns critically depends on the CaZrO3 component. Our results may help the design of a new type of lead-free ferroelectric films and promote their potential applications in microelectronic devices.

Rationally designing bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with high activity and long term stability remains to be a big challenge. Herein, we report in situ synthesized uniform Ru-doped FeCoP (FeCoRuP) nanoarrays as a bifunctional electrocatalyst for highly efficient overall water splitting. The introduction of Ru modifies the electronic interaction between cation active sites due to the electronegativity difference, which also introduces more active sites by creating lattice defects and distortion. Benefiting from the rich active sites and the strong electronic interaction, the optimized Ru-doped FeCoP exhibits excellent HER activities (45 mV at 10 mA cm−2) and OER activity (214 mV at 20 mA cm−2), together with excellent long-term durability (110 h) in alkaline media. An overall water splitting cell in which both anode and cathode are composed of the FeCoRuP catalyst exhibits an ultralow voltage of 1.47 V at 10 mA cm−2, which is superior to the benchmark 20% Pt/C‖IrO2 electrodes (1.68 V at 10 mA cm−2). The present work offers a simple but effective approach to promote the overall water splitting performance of transition metal phosphides by modulating the electronic structure of active sites.

Perpendicularly magnetized layers are essential for information storage to increase the storage density. Modulating perpendicular magnetization by an electric field offers a promising solution to lower energy consumption. Here, we demonstrate a remarkable electric field modulation of perpendicular magnetization in perpendicularly magnetized Pt/Co/Ta ultrathin films on a ferroelectric substrate. By measuring the anomalous Hall effect under in situ electric fields, we observe a giant magnetoelectric effect with the large converse magnetoelectric coefficient of −2.1 × 10−6 s m−1 at H⊥ = −20 Oe and −0.9 × 10−6 s m−1 at H⊥ = 0 Oe, which is comparable to that in multiferroic heterostructures with in-plane magnetization. Additionally, Kerr imaging shows that electric fields observably affect magnetic domain structures of the Pt/Co/Ta ultrathin films indicating a giant magnetoelectric effect. We further measure in situ X-ray diffraction and X-ray reflectivity with electric fields, which suggests that this giant magnetoelectric effect is attributed to strain-mediated magnetoelectric coupling and is closely related to electric-field-varied interface roughness. Our findings highlight the role of interface roughness in exploring electrical control of perpendicular magnetization.

Perpendicular magnetic anisotropy is important for increasing the information storage density in the perpendicular magnetic recording media, and for rare-earth–transition-metal alloys with bulk per...

A new Sillen-Aurivillius oxide Bi7Fe2Ti2O17Cl (BFTOCl), in which four perovskite layers are sandwiched by Sillen slabs, is designed and prepared by the solid-state reaction. Compared with pure Aurivilius structure, the Sillen slab requires one less positive charge for charge compensation due to the intercalation of Cl anions between two (Bi2O2)2+, which increases the concentration of magnetic Fe3+ ions in perovskite slab, and may depress the interaction of Fe3+ ions existing in neighboring perovskite slabs. This unique natural superlattice structure and the highly orientated texture of the ceramic result in a complex spin structure and an interesting magnetic anisotropy. The magnetism in in-plane direction (0.00487 emu/g at 100 K) is about 2.5 times larger than that in out-of-plane direction. Remarkably, exchange bias anisotropy has been observed in the BFTOCl ceramic, of which the exchange bias fields in in-plane and out-of-plane directions are 345 and 174 Oe at 100 K, respectively.

Electric-field control of magnetism (EFCM) is very important for the exploration of high-density, fast, and nonvolatile random-access memory with ultralow energy consumption. Here, we report the electric-field-induced ferroelectric phase transitions in Pb(Mg1/3Nb2/3)0.82Ti0.18O3 (PMN-0.18PT) and symmetry breaking of EFCM behaviors for corresponding directions in multiferroic heterostructures composed of amorphous ferromagnetic Co40Fe40B20 (CoFeB) and PMN-0.18PT. We uncover a new mechanism behind the unusual phenomena, involving coupling between CoFeB and PMN-0.18PT via complex cooperation of electric-field-induced ferroelectric phase transitions, competition of different ferroelectric domains, and internal electric field in PMN-0.18PT. The deterministic EFCM with reversible and nonvolatile nature opens up a new avenue for exploring EFCM in multiferroic heterostructures and is also significant for applications.

The coupled effects of external multi-ions and wet-dry cycles in sea water on the evolution of autogenous self-healing in cement paste were investigated. It was found that Mg2+, rather than Cl− and SO42−, in sea water plays a primary role in the healing process. The percentage of brucite in the reaction products of self-healing was more than 50%. The closure ratio of a 400-μm-wide crack after healing in sea water for 56 days was 2.6 times that of a crack healed in tap water. Furthermore, wet-dry cycles with wetting and drying periods that are each 12 h can significantly increase the healing efficiency by promoting the formation of brucite and calcite. Moreover, the promotional effect of external ions and wet-dry cycles on self-healing was more obvious in a crack with a larger width that facilitates the entrance of external ions during immersion and the evaporation of water in wet-dry cycles.

Safer human-robot interactions mandate the adoption of proprioceptive actuation. Strain sensors can detect the deformation of tools and devices in unstructured and capricious environments. However, such sensor integration in surgical/clinical settings is challenging due to confined spaces, structural complexity, and performance losses of tools and devices. Herein, we report a highly stretchable skin-like strain sensor based on a silver nanowire (AgNW) layer and hydrogel substrate. Our facile fabrication method utilizes thermal annealing to modulate the gauge factor (GF) by forming multidimensional wrinkles and a layered conductive network. The developed AgNW-hydrogel (AGel) sensors sustain and exhibit a strain-sensitive profile (max. GF = ∼70) with high stretchability (200%). Due to its conformability, the sensor demonstrates efficacy in integration and motion monitoring with minimal mechanical constraints. We provide contextual cognizance of tooltip during a transoral procedure by incorporating AGel sensors and showing the fabrication methodology's versatility by developing a hybrid self-sensing actuator with real-time performance feedback.

The autogenous healing potential of cement-based materials is affected by multiple factors, such as mix composition, crack width, pre-cracking age and external environmental conditions. In this study, the effects of curing conditions and supplementary cementitious materials (SCMs) on autogenous self-healing of early age cracks in cement mortar were investigated. Three curing conditions, i.e., standard curing, wet–dry cycles and incubated in water, and two SCMs, i.e., fly ash (FA) and blast furnace slag (BFS) with various contents (cement replacement ratio at 0%, 20%, and 40%) were examined. A single early age crack (pre-cracking age of 3 days) with a width of 200~300 μm was generated in cylindrical mortar specimens. Autogenous crack self-healing efficiency of mortar specimens was evaluated by performing a visual observation and a water permeability test. Moreover, microstructure analysis (XRD, SEM and TG/DTG) was utilized to characterize the healing products. The results indicated that the presence of water was essential for the autogenous self-healing of early age cracks in cement mortar. The efficiency of self-healing cracks was highest in specimens incubated in water. However, no significant self-healing occurred in specimens exposed to standard curing. For wet–dry cycles, a longer healing time was needed to obtain good self-healing compared to samples incubated in water. SCMs type and content significantly affected the autogenous self-healing ability of early age cracks. The self-healing efficiency of early age cracks decreased with increases in FA and BFS content. BFS mortars exhibited greater recovery in relation to water penetration resistance compared to the reference and FA mortars. Almost the same regain of water tightness and a lower crack-healing ratio after healing of 28 days in FA mortars were observed compared to the reference. The major healing product in the surface cracks of specimens with and without SCMs was micron-sized calcite crystals with a typical rhombohedral morphology.

The two-dimensional counterpart of diamond, diamane, has attracted increasing interest due to its potentially distinctive properties. In this paper, diamanes anchored with different anion groups have been systematically studied with density functional theory (DFT) for the first time. Among them 12 conformers are confirmed to be stable and present direct semiconductor features with bandgaps ranging from 2.527 eV to 4.153 eV, and the in-plane stiffness is larger than that of graphene. Moreover, the electron carrier mobility of chair2-F is exceptionally high at 16546.713 cm2 V−1 s−1 along the y-direction, which is remarkably larger than that of diamond; and N-, B-doped boat2-H can be doped to have n-, p-type conductivity with a moderate activation energy of 0.34 and 0.37 eV, respectively. This work suggests that functionalized diamanes are promising for electronic devices and engineering materials.

Intra-abdominal pressure (IAP) is closely correlated with intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) diagnoses, indicating the need for continuous monitoring. Early intervention for IAH and ACS has been proven to reduce the rate of morbidity. However, the current IAP monitoring method is a tedious process with a long calibration time for a single time point measurement. Thus, there is the need for an efficient and continuous way of measuring IAP. Herein, a stretchable capacitive pressure sensor with controlled microstructures embedded into a cylindrical elastomeric mold, fabricated as a pressure sensing sleeve, is presented. The sensing sleeve can be readily deployed onto intrabody catheter balloons for pressure measurement at the site. The thin and highly conformable nature of the pressure sensing sleeve captures the pressure change without hindering the functionality of the foley catheter balloon.

To improve the durability of cracked concrete structures in a marine environment by self-healing of cracks, the efficiency and speed of self-healing need to be increased. In this study, the...

Excessive heat accumulation in backfill materials causes thermal fatigue damage in underground power cable systems that significantly affects the cable carrying capacity. To improve the thermal conditions of the system, two types of composite phase change materials (CPCMs) were prepared by incorporating paraffin into porous ceramsite (CS)/expanded graphite (EG) in this study. EG and CS can carry 90 and 40 wt.% paraffin, respectively. The phase change temperature of paraffin/CS and paraffin/EG CPCMs was approximately 65 °C, and the corresponding latent heats were 63.38 J/g and 156.4 J/g, respectively. Furthermore, the temperature regulation by CPCMs was evaluated experimentally by designing a setup to simulate the underground power cable system. The reduction in the maximum temperature of the backfill materials with paraffin/CS CPCM and paraffin/EG CPCM was approximately 7.1 °C and 17.1 °C, respectively, compared to reference samples. A similar conclusion was drawn from the heat flux curves. Therefore, the prepared CPCMs could significantly alleviate temperature fluctuations, where the paraffin/EG CPCM provided better temperature regulation than paraffin/CS CPCM. Both materials have potential applications for use in backfill materials for underground power cable systems.

Non-uniform stresses, strains and microcracking of the concretes with three coarse aggregate sizes (5–10 mm, 10–16 mm, 16–20 mm) dried under 40% relative humidity (RH) for 60 days were quantified using digital image correlation and lattice fracture modelling. The influencing mechanism of coarse aggregate size on the drying-induced microcracking of concrete was clarified: (1) As the coarse aggregate size decreases, propagation paths of microcracking are increased, which increase the number of small microcracks and release the drying shrinkage force from mortar phase. (2) Tensile stress shells surrounding the coarse aggregates become thinner, thereby decreasing the area of large microcracks. As the coarse aggregate size decreased from 16-20 mm to 5–10 mm, the average thickness of tensile stress shells decreased from 2.13 mm to 1.09 mm at the beginning of drying, and the area of the microcracks >5 μm in width decreased from 796.6 mm2/m2 to 340.2 mm2/m2 at 60 days since drying.

A polymer electrolyte fuel cell has been designed to allow operando x-ray absorption spectroscopy (XAS) measurements of catalysts. The cell has been developed to operate under standard fuel cell conditions, with elevated temperatures and humidification of the gas-phase reactants, both of which greatly impact the catalyst utilisation. X-ray windows in the endplates of the cell facilitate collection of XAS spectra during fuel cell operation while maintaining good compression in the area of measurement. Results of polarisation curves and cyclic voltammograms showed that the operando cell performs well as a fuel cell, while also providing XAS data of suitable quality for robust XANES analysis. The cell has produced comparable XAS results when performing a cyclic voltammogram to an established in situ cell when measuring the Pt LIII edge. Similar trends of Pt oxidation, and reduction of the formed Pt oxide, have been presented with a time resolution of 5 s for each spectrum, paving the way for time-resolved spectral measurements of fuel cell catalysts in a fully-operating fuel cell.

We demonstrate a broadband and polarization selective terahertz modulator with ultrafast modulation speed, based on the Si grating metasurface on the Sapphire substrate. The Si layer is implanted with B+ and subsequently annealed, which significantly reduces the lifetime of carriers and increases the carrier density, and thus realizes ultrafast and efficient modulation. Our modulator achieves modulation depth up to 60% for the x-polarized THz wave and less than 1% for the y-polarized THz wave in the frequency ranging from 0.5 to 2.5 THz, with switch-on and switch-off time of modulation in 20 ps and around 300 ps, respectively. The carrier dynamics of the fabricated Si grating is also studied to illustrate the ultrafast modulated mechanism. Our results pave the way for ultrafast manipulation of terahertz spectrum and shows great potential in terahertz communication.

We systematically studied the magnetization reversal (MR) and exchange bias (EB) properties of Mn-doped CuCrO2 compounds. Single-phase ceramic samples of CuCr1−xMnxO2 (x = 0–0.2) were synthesized with the sol-gel method. Synchrotron radiation X-ray absorption spectroscopy of the Mn 2p, Cr 2p core levels showed that the Cr ion is trivalent and the Mn ion is in a mixed valence state of Mn3+/4+. All the Mn-doped samples, due to the double-exchange interaction between Cr3+–O–Mn3+ and Mn3+–O–Mn4+, showed a ferromagnetic transition in field-cooling magnetization. Interestingly, zero-field-cooling magnetization reversed from positive to negative as temperature decreased below the compensation temperature. The x = 0.05 sample also showed exchange bias. The coexistence of MR and EB in the system can be explained by the competition between ferromagnetic and antiferromagnetic order.

A characteristic of a Fermi liquid is the ${T}^{2}$ dependence of its resistivity, sometimes referred to as the Baber law. However, for most metals, this behavior is only restricted to very low temperatures, usually below 20 K. Here, we experimentally demonstrate that for the single-crystal van der Waals layered material $\mathrm{MoOC}{\mathrm{l}}_{2}$, the Baber law holds in a wide temperature range up to \ensuremath{\sim}120 K, indicating that the electron-electron scattering plays a dominant role in this material. Combining with the specific heat measurement, we find that the modified Kadowaki-Woods ratio of the material agrees well with many other strongly correlated metals. Furthermore, in the magnetotransport measurement, a colossal magnetoresistance is observed, which reaches \ensuremath{\sim}350% at 9 T and displays no sign of saturation. With the help of first-principles calculations, we attribute this behavior to the presence of open orbits on the Fermi surface. We also suggest that the dominance of electron-electron scattering is related to an incipient charge density wave state of the material. Our results establish $\mathrm{MoOC}{\mathrm{l}}_{2}$ as a strongly correlated metal and shed light on the underlying physical mechanism, which may open a new path for exploring the effects of electron-electron interaction in van der Waals layered structures.

Metal-organic frameworks (MOFs) can be potentially applied as corrosion inhibitors for reinforced concrete due to their supramolecular structure. In this study, zeolitic imidazolate framework (ZIF-8) was prepared by facile and eco-friendly solvent method. The inhibition effect of the prepared ZIF-8 corrosion inhibitor on the reinforcement in cement extract was investigated by electrochemical measurements (electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization (PD)) combined with surface analysis (field emission scanning electron microscope (FESEM) and Raman spectroscopy); the adsorption behavior of ZIF-8 corrosion inhibitor on the steel surface was analyzed by UV–vis spectrophotometer and atomic force microscope (AFM). The results indicated that ZIF-8 corrosion inhibitor with the diameter of about 75 nm was successfully synthesized. In chloride-containing cement extract, ZIF-8 corrosion inhibitor was efficiently adsorbed on the reinforcement surface and mainly reduced the anodic reaction rate by halting the dissolution of the reinforcement, thus significantly increasing the charge transfer resistance and polarization resistance of the reinforcement and exhibiting high inhibition efficiency (>95 %) during the initial 24 h. The pH drop caused by pitting propagation at the local corrosion sites resulted in the decomposition of ZIF-8 and Fe-N coordination bond formed between the released 2-MeIm ligands and reinforcement. As a result, the accumulation of corrosion products was pronounced prohibited, thus corrosion initiation of the reinforcement was significantly delayed and the inhibition efficiency was still maintained at 87.8 % after 168 h with ZIF-8 concentration of 0.04 wt%.

Heterostructure between layered ferroelectric oxide Bi4Ti3O12 and perovskite (La, Sr)Mn1−xO3 is highly interesting due to the need to explore new types of functional heterostructures. However, fabricating such heterostructures with high quality is challenging because of the non-isostructural crystalline symmetry of the two constituents. In this work, we constructed two different heterostructures, in which the Bi4Ti3O12 layers with precisely controlled thicknesses were deposited on insulating La0.7Sr0.3Mn0.81O3 and conducting La0.7Sr0.3MnO3 bottom layers, respectively. Results of cross section transmission electron microscopy identified rough interfaces between insulating (La, Sr)Mn1−xO3 and Bi4Ti3O12, while sharp interfaces between metallic (La, Sr)Mn1−xO3 and Bi4Ti3O12. In the former, levels of intermixing and charge leaking are strongly dependent on the thickness of the Bi4Ti3O12 capping layer, which induces a capping-layer-thickness-dependent magnetoresistance. These results demonstrated that the interfacial defect is a critical factor for designing functional heterostructures composed of layered oxide and perovskite oxide.

To elucidate the effect of aggregate size and volume on the non-uniform strain distribution in concrete, drying shrinkage of mortar and concretes were determined with 3D digital image correlation (3D-DIC). The distribution of shrinkage displacements and strains in mortar and concrete were analyzed. The results show that 3D-DIC makes it possible to measure non-uniform displacement distributions initiated by shrinkage in mortar and concrete. The non-uniformity became more remarkable with drying time. The presence of aggregates larger than 5 mm in concrete have locally changed the displacement and strain fields. Aggregates within 5–25 mm make non-uniform strain of concrete more fluctuant, especially when the aggregate size is larger than 10 mm. The maximum and minimum principal strain distributions became more heterogeneous with decreasing volume of aggregates.

A new iron-based superconductor Lix(C3H10N2)yFe2Se2 was successfully synthesized via the novel ammonothermal technique. After post-annealing, the superconducting transition temperature T c changes from 36 K to 45 K, which is confirmed by measurements of the magnetic susceptibility and the electrical resistivity. The powder X-ray diffraction (XRD) measurements have revealed that the crystal structure keeps the same after post-annealing at 130 °C for 10 h. Hall coefficient and magnetoresistance (MR) have been measured on the annealed samples, indicating the role of electrons as the dominant charge carriers.

Surface morphological control of the metal-insulator transition behaviors of VO 2 epitaxial thin films is achieved by annealing substrates of (0001)-Al 2 O 3 single crystals. The well-defined terraces of the (0001)-Al 2 O 3 substrates are formed by annealing in air at 1200 °C. Correspondingly, the surface roughness dramatically decreases in the VO 2 epitaxial thin films on the annealed substrates, compared with that on the unannealed substrates. The order of magnitude of the resistivity change ratio (~ 10 2 ) of annealed samples across the metal-insulator transition (MIT) decreases by a factor of one, compared with that (~ 10 3 ) in unannealed samples. This result is ascribed to grain size effect in the VO 2 epitaxial thin films. Moreover, the MIT temperature is reduced in the annealed samples with various thickness, compared with the unannealed ones. A reduction of 14.4 K of the MIT temperature is observed in the thinnest VO 2 films on the annealed substrates, compared with the unannealed samples. This behavior results from a compressive strain along the V-V atom chains in the annealed samples, which modifies the orbital occupancy of the V 4+ ions. While increasing the film thickness, the MIT change ratio keeps on the order of magnitude 10 2 , and the MIT temperatures of the VO 2 films on the annealed substrates becomes closer and closer to those of the unannealed samples due to the weakened substrate effect. This work suggests a promising approach to decrease the MIT temperature and still maintain a moderate change ratio for the MIT, potentially enabling room-temperature electronic devices based on VO 2 thin films.

Aurivillius compounds have many fascinating properties such as ferroelectricity, magnetism, dielectricity, and piezoelectricity. Their structures and properties can be tuned flexibly, thus they have broad applications in FeRAM, spintronics, photocatalysts, capacitors, etc. We synthesized layer-inserted Aurivillius phase semiconducting Bi4Ti3O12–La0.5Sr0.5MnO3 (BIT–LSMO) nanoparticles by the hydrothermal method and subsequently obtained highly grain-oriented ceramics (Lotgering factor LF = 98.69% for muffle calcined samples and 99.87% for hot-pressed samples) by calcination. Significant electrical anisotropy at room temperature (the resistivity magnitude of the out-of-plane direction is about an order larger than that of the in-plane direction) and magnetic anisotropy at low temperature in the oriented ceramics were observed. Through the grain boundary conductivity estimation with the “brick layer” mode, we concluded that the anisotropy originates from the anisotropy within grain interiors for the Aurivillius layered structure rather than the contribution of grain boundary density difference. The transport path is “blocked” to some extent along the c-direction since hole hopping through the Mn4+–O2−–Mn3+ double exchange effect is the main conducting mechanism in our samples. The oxygen vacancies and element valence states of samples using different synthesis processes were investigated. The oxygen vacancies increase and the lattice shrinks during the sintering process due to the volatilization of bismuth element. The valence state of Ti is less than but near to +4, and the valence state of Mn is about +3.4. The electrical and magnetic anisotropies in BIT–LSMO provide an additional freedom in functional applications for layered complex oxides.

The magnetic anisotropy manipulation in the Sm3Fe5O12 (SmIG) films and its effect on the interfacial spin coupling in the CoFe/SmIG heterostructures were studied carefully. By switching the orientation of the Gd3Ga5O12 substrates from (111) to (001), the magnetic anisotropy of obtained SmIG films shifts from in-plane to out-of-plane. Similar results can also be obtained in the films on Gd3Sc2Ga3O12 substrates, which identifies the universality of such orientation-induced magnetic anisotropy switching. Additionally, the interfacial spin coupling and magnetic anisotropy switching effect on the spin wave in CoFe/SmIG magnetic heterojunctions have also been explored by utilizing the time-resolved magneto–optical Kerr effect technique. It is intriguing to find that both the frequency and effective damping factor of spin precession in CoFe/SmIG heterojunctions can be manipulated by the magnetic anisotropy switching of SmIG films. These findings not only provide a route for the perpendicular magnetic anisotropy acquisition but also give a further path for spin manipulation in magnetic films and heterojunctions.

Corrosion performance of the reinforcement was dramatically affected by chemical compositions of pore solution in alkali-activated fly ash. In this study, the electrochemical behavior and surface properties of reinforcement were characterized in chloride-contaminated simulated alkali-activated fly ash pore (SAFP) solution. The results indicated that due to the high alkalinity and formation of zeolite-like adsorption layer (about 20 nm), the reinforcement was still in passive state and exhibited high corrosion resistance in chloride-contaminated SAFP solution. However, the protective effect of passivation film (consisted of mainly FeOOH outer film and FeO inner film) and corrosion resistance of the reinforcement were reduced by chlorides. Further, the chloride threshold in SAFP solution was 10 times larger than simulated cement pore solution, due to the competitive adsorption between OH−/silicates and chlorides.

In this study, acrylic resin coating for concrete was modified at molecular scale and nano scale, respectively. In order to reduce the surface energy and subsequently increase the bacteriostatic and antifouling performance, acrylic resin was modified with silicone and fluorine. Moreover, GO nanosheets was incorporated to improve the mechanical properties and erosion resistance of the coating. For improving the dispersion, GO was modified with Vinyl triethyl silane when adding into the resin. The results showed that after the modification with silicone and fluorine, the water contact angle of acrylic resin increased from 82.0° to 93.7° and the surface energy decreased from 33.8 mJ/m2 to 24.0 mJ/m2. The bacteriostatic ratio of the modified acrylic resin coating was as high as 99.9%. Based on the morphology of the fracture surfaces of the coating, GO with a dosage of 1.5 wt% improved the mechanical properties of the coating and its bonding strength with concrete substrate. Moreover, after modification at multiscale, the acrylic resin coating exhibited better UV resistance and protection effects on concrete. No chloride penetration was found and the chemical composition on the surface of concrete specimens with acrylic resin/GO coating hardly changed although the specimens were immersed in seawater for 90 days and in organic acid for 30 days.

The catalytic activity for the oxygen evolution reaction (OER) in electrocatalytic water splitting strongly depends on the adsorption energy of intermediates. For the generally proposed adsorbate evolution route, the universal scaling relation between the adsorption energies of *OOH and *OH leads to an OER efficiency limitation based on the “volcano curve”. A possible solution to bypass the scaling relation is to avoid the formation of the *OOH intermediate in the OER with the participation of lattice oxygen from catalysts. In this work, the lattice oxygen in (Bi0.5Co0.5)2O3 is activated through adjusting the Fermi energy level and the strong overlap between Co 3d and O 2p, by means of increasing the oxygen vacancy concentration. Compared to oxygen-vacancy-poor (Bi0.5Co0.5)2O3, the oxygen-vacancy-rich (Bi0.5Co0.5)2O3 exhibits a significantly lower Tafel slope (43 mV dec−1), 15 times higher mass activity, 18 times higher turnover frequency, and excellent long-term stability in alkaline media, superior to those of the benchmark OER electrocatalyst IrO2. This work provides a feasible strategy to activate lattice oxygen with fast OER kinetics and puts forward the development of efficient and stable catalysts towards water oxidation.

Strain engineering is a popular approach for manipulating material properties through modifying crystal structures and/or electron-lattice interactions. In this work, we used a phase transition material, vanadium dioxide (VO2) as an active and reconfigurable substrate to generate a controllable strain. Amorphous ferromagnetic Ni thin films were deposited on the (010)-VO2/(0001)-Al2O3 substrates. It is observed that the magnetic moments of the Ni thin film were modulated by interfacing it with the VO2 thin film. We observed a hysteresis in the magnetic moment-temperature curves in the vicinity of the metal–insulator transition of the VO2 thin films at a low magnetic field bias (

As one of the most promising Pt alternatives for cost-effective hydrogen production, molybdenum disulfide (MoS2), although has been studied extensively to improve its electrocatalytic activity, suffers from scarce active sites, low conductivity, and lack of interaction with substrates. To this end, we anchor ultradispersed and single-layered MoS2 nanoflakes on graphene sheets via a hybrid intermediate (MoOx-cysteine-graphene oxide), which not only confines the subsequent growth of MoS2 on the graphene surface but also ensures the intimate interaction between Mo species and graphene at the initial stage. Mo-O-C bond and a possible residual MoO3-x layer are proposed to comprise the interface bridging the two inherent incompatible phases, MoS2 and graphene. This strongly coupled structure together with the highly exposed MoS2 morphology accelerates the electron injection from graphene to the active sites of MoS2, and thus the hydrogen evolution reaction (HER) can achieve an overpotential of ∼275 mV at ∼-740 mA cm-2, and a Pt-like Tafel slope of ∼35 mV dec-1. Our results shed light on the indispensable role of interfacial interaction within semiconducting material-nanocarbon composites and provide a new insight into the actual activity of MoS2 toward the HER.

Development of novel electrode materials with unique architectural designs is necessary to attain high power and energy density lithium-ion batteries (LIBs). SnO2, with high theoretical capacity of 1494 mAh g−1, is a promising candidate anode material, which has been explored with various strategies, such as dimensional reduction, morphological modifications and composite formation. Unfortunately, most of the SnO2-based electrodes are prepared by using complex chemical synthesis methods, which are not feasible to scale up for practical applications. In addition, concomitant irrecoverable initial capacity loss and consequently poor initial Coulombic efficiency still persistently plagued these SnO2-based anodes. To overcome hitherto conceived irreversible formation of Li2O by conversion reaction, to fully harness its theoretical capacity, this work demonstrates that a hierarchical structured SnO2-C nanocomposite with 68.5% initial Coulombic efficiency and reversible capacity of 725 mAh g−1 can be derived from the mixtures of SnO2 and graphite, by using low cost industrial compatible high energy ball milling activation.

To assess the effect of relative humidity (RH) on drying-induced damage in concrete, the non-uniform strains and microcracks in concrete under different RH conditions were obtained using the digital image correlation (DIC) technique and lattice fracture model. The simulated non-uniform displacements were consistent with those captured using DIC. A new damage index was proposed by considering all the subsets with equivalent strain larger than the threshold tensile strength. The calculated damage index showed good correlation with the microcracks' total area and indicated that RH equal or lower than 55% could cause relatively high cracking risk. This work provides an attractive method for quantifying drying-induced damage in concrete using the DIC technique.