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The incorporation of boron into carbon material can significantly enhance its capacity performances. However, the origin of the promotion effect of boron doping on electrochemical performances is still unclear, in part due to the inadequate exposure of boron configurations resulting from the complexity of traditional carbon materials. To overcome this issue, herein, a series of boron-doped graphene with highly-exposed boron configurations are prepared by tuning annealing temperature. Then the correlation between boron configurations and the electrochemical performances is investigated. The combination of density-functional theory (DFT) computation and NH3-TPD/Py-FTIR indicates that the BCO2 configuration formed on the surface of graphene is easier to accept lone-pair electrons than BC2O and BC3 configurations due to the stronger Lewis acidity. Such an electronic structure can effectively reduce the number of unstable electron donors and stabilize the electrochemical interface, which is proved by NMR, and critical for improving the electrochemical performances. Further experiments confirm that the optimized BG800 with the largest amount of BCO2 configuration presents ultralow leak current, improved cyclic stability, and better rate performance in SBPBF4/PC. This work would provide an insight into the design of high-performance boron-doped carbon materials towards energy storage.

The SiC whiskers/hollow carbon microspheres (SiCw/HCMS) were successfully synthesized by a combination of the spray drying technology and the carbothermal reduction method. The anchoring of SiCw on HCMS shells improves the thermostability of composites and induces the formation of new heterointerfaces between SiC whiskers and HCMS. Experimental characterizations together with DFT calculations show that compared to intrinsic defects and functional groups in SiCw/HCMS, the formed heterointerfaces trigger the separation of positive and negative charges and induce large dipole moments, resulting in the intensive dielectric polarization loss. Consequently, SiCw/HCMS samples achieve an excellent electromagnetic wave absorption, where the reflection loss value of SiCw/HCMS-1450 reaches to −48.60 dB at 8.0 GHz with a thickness of 2.6 mm and the maximum effective absorbing bandwidth is 4.34 GHz. This work investigates a deep insight into the relationship between interfacial polarization loss and the electromagnetic wave attenuation and designs a novel absorbent that exhibits great potential for electromagnetic wave absorption at high-temperature environments.

High-entropy alloys (HEAs) are proposed as potential structural materials for advanced nuclear systems, but little is known about the response of matrix chemistry in HEAs upon irradiation. Here, we reveal a substantial change of matrix chemical concentration as a function of irradiation damage (depth) in equiatomic NiCoFeCr HEA irradiated by 3 MeV Ni ions. After ion irradiation, the matrix contains more Fe/Cr in depth shallower than ~900–1000 nm but more Ni/Co from ~900–1000 nm to the end of the ion-damaged region due to the preferential diffusion of vacancies through Fe/Cr. Preferential diffusion also facilitates migration of vacancies from high radiation damage region to low radiation damage region, leading to no void formation below ~900–1000 nm and void formation around the end of the ion-damaged region at a fluence of 5 × 1016 cm−2 (~123 dpa, displacements per atom, peak dose under full cascade mode). As voids grow significantly at an increased fluence (8 × 1016 cm−2, 196 dpa), the matrix concentration does not change dramatically due to new voids formed below ~900–1000 nm.

The detection of post-earthquake damage inside concrete dams has recently attracted great interest in academia and industry. A novel electromechanical impedance (EMI) method using embedded EMI sensors (EMISs) is proposed in this paper to detect earthquake-induced damage within concrete dams. The basic concept of the proposed EMI method is to use high-frequency excitations to monitor local changes in the monitored dams caused by damage. Based on the effective impedance, a three-dimensional (3D) EMI model for embedded EMISs is proposed. Then, a new damage-sensitive feature factor is derived based on the proposed 3D EMI model. A high arch dam model with embedded EMISs is studied experimentally. Moreover, shaking table tests are conducted on the dam model. The proposed 3D EMI method is used to monitor the evolution of earthquake-induced damage inside the dam model. The experimental results demonstrate the efficiency and feasibility of the proposed EMI method for detecting earthquake-induced damage in concrete dams.

Nanostructured metals and alloys are generally strong but lack strain hardening due to enhanced grain boundary diffusion and sliding. Here, equal nanograined (ENG) and gradient nanograined (GNG) layered Cu/Ta architectures were acquired by introducing a hard and stable “artificial” interphase boundary zone (IBZ). The ENG architecture produced uniform plastic strain reaching 70% and high yield strength exceeding 1 GPa, which is attributed to the constraint effect of the tough IBZ on dislocation slip mediated co-deformation. The GNG architecture exhibited a remarkable linear strain hardening with hardening exponent of 1 due to the strong strain partitioning between soft and hard layers. The dominant deformation mechanism of the GNG nanocomposite evolves from partial dislocation emission to dislocation accumulation at interface with increasing strain based on the results from experiments and molecular dynamics simulations. This finding demonstrates that heterostructure with “artificial” IBZ may offer an alternative approach to design strong and tough materials.

Purpose The buried pipe element method can be used to calculate the temperature of mass concrete through highly efficient computing. However, in this method, temperatures along cooling pipes and the convection coefficient of the cooling pipe boundary should be improved to achieve higher accuracy. Thus, there is a need to propose a method for improvement. Design/methodology/approach According to the principle of heat balance and the temperature gradient characteristics of concrete around cooling pipes, a method to calculate the water temperature along cooling pipes using the buried pipe element method is proposed in this study. By comparing the results of a discrete algorithm and the buried pipe element method, it was discovered that the convection coefficient of the cooling pipe boundary for the buried pipe element method is only related to the thermal conductivity of concrete; therefore, it can be calculated by inverse analysis. Findings The results show that the buried pipe element method can achieve the same accuracy as the discrete method and simulate the temperature field of mass concrete with cooling pipes efficiently and accurately. Originality/value This new method can improve the calculation accuracy of the embedded element method and make the calculation results more reasonable and reliable.

Quantifying chemical compositions around nanovoids is a fundamental task for research and development of various materials. Atom probe tomography (APT) and scanning transmission electron microscopy (STEM) are currently the most suitable tools because of their ability to probe materials at the nanoscale. Both techniques have limitations, particularly APT, because of insufficient understanding of void imaging. Here, we employ a correlative APT and STEM approach to investigate the APT imaging process and reveal that voids can lead to either an increase or a decrease in local atomic densities in the APT reconstruction. Simulated APT experiments demonstrate the local density variations near voids are controlled by the unique ring structures as voids open and the different evaporation fields of the surrounding atoms. We provide a general approach for quantifying chemical segregations near voids within an APT dataset, in which the composition can be directly determined with a higher accuracy than STEM-based techniques., Atom probe tomography can image chemical composition at the nanoscale, but our understanding of how it images voids, or empty spaces, is still lacking. Here, the authors combine atom probe tomography, scanning transmission electron microscopy, and field-evaporation theory to show how voids are imaged and subsequently measured.

Hypothesis High temperatures can reduce the colloidal stability and rheological properties of nonpolar organoclay suspensions. The desorption of surfactants from organoclay has been proposed to explain this effect, but the mechanism remains unclear. In this work, it was hypothesized that the high-temperature-induced desorption of ion-exchanged surfactants is the main factor affecting the stabilization of suspensions. Experiments Using the cationic surfactant dimethyldioctadecylammonium chloride (DODMAC) and Na-montmorillonite (Na-MMT), the high-temperature-induced reestablishment of the adsorption–desorption equilibrium of DODMAC in organoclay suspensions was studied. Thermogravimetric analysis combined with infrared spectroscopy and gas chromatography/mass spectrometry experiments were performed to determine the thermal decomposition products and, ultimately, infer the adsorption modes and locations of DODMAC on Na-MMT. Thermal analysis and rheology were utilized to demonstrate the high-temperature-induced desorption and transfer of DODMAC in organoclay suspensions. Findings High temperatures induced the complete desorption of physically adsorbed DODMAC molecules from particle surfaces, the partial desorption of ion-exchanged dimethyldioctadecylammonium ions (DODMA+ ions) from particle surfaces, and the partial transfer of ion-exchanged DODMA+ ions from the surfaces to the interlayers. Importantly, desorption of ion-exchanged DODMA+ ions resulted in destabilization of the organoclay suspensions at high temperatures.

Temperature significantly affects defect migration and evolution in irradiated materials. However, the effects of temperature on defect evolution in concentrated solid-solution alloys (CSAs), including high entropy alloys, are not well understood, despite their potential as structural materials in advanced nuclear reactors. As an important model system of these CSAs, equiatomic Ni50Fe50 (NiFe) was selected to understand the effects of temperature on defect evolution during irradiation and subsequent thermal annealing. Specifically, defect accumulation and evolution in NiFe alloy under Ni-ion irradiation at 150, 300, and 500 K were studied, and the irradiated specimens were subsequently annealed at higher temperatures. Rutherford backscattering spectrometry along the channeling direction was employed to study damage accumulation and evolution before and after each irradiation and annealing experiment. Here we show that more defects survive and accumulate at 150 K, but more importantly defects can migrate to deeper depths at this low irradiation temperature. Irradiation-induced damage at 150 and 300 K does not recover substantially after post-irradiation annealing at 500 K, but dramatic recovery is observed after post-irradiation annealing at 700 K, indicating an onset temperature of defect recovery between 500 and 700 K. The migration of irradiation-induced defects upon annealing is closely related to the mobility and stress state arising from the surviving defects. With the consideration of five stages of defect recovery in conventional dilute alloys, the underlying mechanisms for temperature-dependent defect accumulation and evolution in NiFe CSA are discussed.

Nanocrystalline and nanolaminated materials show enhanced radiation tolerance compared with their coarse-grained counterparts, since grain boundaries and layer interfaces act as effective defect sinks. Although the effects of layer interface and layer thickness on radiation tolerance of crystalline nanolaminates have been systematically studied, radiation response of crystalline/amorphous nanolaminates is rarely investigated. In this study, we show that irradiation can lead to formation of nanocrystals and nanotwins in amorphous CuNb layers in Cu/amorphous-CuNb nanolaminates. Substantial element segregation is observed in amorphous CuNb layers after irradiation. In Cu layers, both stationary and migrating grain boundaries effectively interact with defects. Furthermore, there is a clear size effect on irradiation-induced crystallization and grain coarsening. In situ studies also show that crystalline/amorphous interfaces can effectively absorb defects without drastic microstructural change, and defect absorption by grain boundary and crystalline/amorphous interface is compared and discussed. Our results show that tailoring layer thickness can enhance radiation tolerance of crystalline/amorphous nanolaminates and can provide insights for constructing crystalline/amorphous nanolaminates under radiation environment.

Binary single-phase concentrated solid solution alloys (SP CSAs), including Ni80Co20, Ni80Fe20, Ni80Cr20, Ni80Pd20, and Ni80Mn20 (in atomic percentage), were irradiated with 200 keV He+ ions at 500 °C. He cavity size and density distribution were systematically investigated using transmission electron microscope. Here we show that alloying elements have a clear impact on He cavity formation. Cavity size is the smallest in Ni80Mn20 but the largest in Ni80Co20. Alloying elements could also substantially affect cavity density profile. In-depth examination of cavities at peak damage region (∼500 nm) and at low damage region (∼300 nm) demonstrates that cavity size is depth (damage) dependent. Competition between consumption and production of vacancies and He atoms could lead to varied cavity size. Density functional theory (DFT) calculations were performed to obtain the formation and migration energies of interstitials and vacancies. Combined experimental and simulation results show that smaller energy gap between interstitial and vacancy migration energies may lead to smaller cavity size and narrower size distribution observed in Ni80Mn20, comparing with Ni80Co20. The results of this study call attention to alloying effects of specific element on cavity formation and defect energetics in SP CSAs, and could provide fundamental understanding to predict radiation effects in more complexed SP CSAs, such as high entropy alloys.

Serrated flow is one important characteristic of shear bands through which metallic glasses (MGs) accommodate plastic deformation. Serrated flow can be affected by intrinsic properties such as elastic modulus or extrinsic variables such as strain rate. However, the influences of pre-deformation and interfaces on serrated flow are less well understood. In this study, by using in situ micropillar compression inside a scanning electron microscope, we show that pre-deformation (consisting of cyclic loading/unloading below the nominal elastic limit) suppresses serrated flows in amorphous-CuNb but enhances serrated flows in amorphous-CuZr at both high and low strain rates. Moreover, layer interfaces in Cu/amorphous-CuNb multilayers mitigate serrated flows, and the average stress drop and strain duration associated with shear banding process can be tailored. Strain accommodation and energy dissipation via shear banding have clear impact on serrated flows. This study provides new perspectives on tailoring serrated flows and enhancing plastic deformation of MGs.

The high concentration of glutathione (GSH), a feature of solid tumors, can reduce the reactive oxygen species (ROS) damage to cancer cells, which seriously weakens the efficacy of photodynamic therapy in cancer treatment. Herein, we designed and synthesized two kinds of GSH responsive pyrrolopyrrolidone (DPP) derivatives that conjugated with 2-(diphenylmethylene) malononitrile (DPPBPh) and 2,3,3-triphenylacrylonitrile (DPPTPh), respectively. DPPTPh with two –CN groups shows higher singlet oxygen quantum yield and photothermal conversion efficiency than DPPBPh with four –CN groups. These two DPP derivatives can not only be used as colorimetric GSH probes to avoid the fluorescence quenching caused by aggregation, but also enhance the photodynamic/photothermal therapeutic efficacy of their corresponding nanoparticles (NPs). Moreover, DPPTPh NPs exhibit better therapeutic efficacy than DPPBPh NPs even at a low dose (0.2 mg kg−1). This work presents DPP derivative-based theranostic nanomedicines for GSH responsive fluorescence “turn on” imaging and enhanced photodynamic/photothermal synergistic therapy.

This study investigated the feasibility of combining targeted sequencing and ultra-low-pass whole-genome sequencing (ULP-WGS) for improved somatic copy number alteration (SCNA) detection, due to its role in tumorigenesis and prognosis. Cerebrospinal fluid and matched blood samples were obtained from 29 patients with brain metastasis derived from lung cancer. Samples were subjected to targeted sequencing (genomic coverage: 300 kb) and 2×ULP-WGS. The SCNA was detected by the CTLW_CNV, Control-FreeC, and CNVkit methods and their accuracy was analyzed. Eighteen tumor samples showed consistent SCNA results between the three methods, while a small fraction of samples resulted in different SCNA estimations. Further analysis indicated that consistency of SCNA highly correlated with the difference of baseline depth (normalized depth of regions without SCNA events) estimation between methods. Conflict Index showed that CTLW_CNV significantly improved the accuracy of SCNA detection through precise baseline depth estimation. CTLW_CNV combines targeted sequencing and ULP-WGS for improved SCNA detection. The improvement in detection accuracy is mainly due to a refined baseline depth estimation, guided by single-nucleotide polymorphism allele frequencies within the deeply sequenced region (targeted sequencing). This method is especially suitable for tumor samples with biased aneuploidy, a previously under-estimated genomic characteristic across different cancer types.

Precast concrete segmental bridges (PCSBs) have been widely used in bridge engineering due to their numerous competitive advantages. The structural behavior and health status of PCSBs largely depend on the performance of the joint between the assembled segments. However, due to construction errors and dynamic loading conditions, some cracks and leakages have been found at the epoxy joints of PCSBs during the construction or operation stage. These defects will affect the joint quality, negatively impacting the safety and durability of the bridge. A structural health monitoring (SHM) method using active sensing with a piezoceramic-based smart aggregate (SA) to detect the crack and leakage in the epoxy joint of PCSBs was proposed and the feasibility was studied by experiment in the present work. Two concrete prisms were prefabricated with installed SAs and assembled with epoxy joint. An initial defect was simulated by leaving a 3-cm crack at the center of the joint without epoxy. With a total of 13 test cases and the different lengths of cracks without water and filled with water were simulated and tested. Time-domain analysis, frequency-domain analysis and wavelet-packet-based energy index (WPEI) analysis were conducted to evaluate the health condition of the structure. By comparing the collected voltage signals, Power Spectrum Density (PSD) energy and WPEIs under different healthy states, it is shown that the test results are closely related to the length of the crack and the leakage in the epoxy joint. It is demonstrated that the devised approach has certain application value in detecting the crack and leakage in the joint of PCSBs.

Hypothesis The viscosity of water-in-oil Pickering emulsions may dramatically increase upon cooling. The solvation of the long-chain alkyl groups grafted on the particles stabilizer is the likely cause of the strong dependence of rheological property on temperature. Thus, we hypothesize that silica nanoparticles (NPs) grafted with short-chain alkyl groups can stabilize Pickering emulsions, yielding weakly temperature-dependent rheological property. Experiments Using alkyl-grafted (methyl, octyl, and octadecyl) silica NPs as emulsifiers, the rheological properties and microstructure of the water-in-oil Pickering, as well as the solvation of the silica NPs, were studied using diffusing-wave spectroscopy microrheology measurements, confocal laser scanning microscopy, and low-field nuclear magnetic resonance measurements. Findings The use of methyl- and octadecyl-grafted silica NPs, which have almost identical optimum contact angles, to stabilize emulsions dramatically reduced the effect of cooling on the viscosity. Moreover, the emulsions stabilized by these methyl-grafted silica NPs exhibited nearly constant rheological properties as the temperature decreased from 75 to 5 °C. The nearly constant rheological properties are attributed to the nearly constant solvation in this temperature range. These materials have potential applications in the cosmetics and petroleum industries.

In this study, phenolic compounds that graded prepared from Pleurotus citrinopileatus using different solvents were obtained. The total content of phenolic and flavonoid, the phenolic profiles, the antioxidant activities, the tyrosinase, and α-glucosidase inhibitory activities of different extracts were determined. The results showed the phenolic and flavonoid content in different extracts ranging from 0.188 to 2.677 mg GAE/g DW and 0.137 to 0.445 mg QE/g DW, respectively. Six phenolic compounds were identified in different extracts by HPLC and the content range from 0.48 to 5778.59 μg/g DW. The water extracts showed strong scavenging activity of radicals and tyrosinase inhibitory activity, whereas acetone extracts showed obvious reducing power and high α-glucosidase inhibitory activity. These findings confirm that the P. citrinopileatus mushroom is a potential natural source of antioxidants for use in food and medicine industries along with their possible applications in ant-melanin and antidiabetic applications.

AlMg alloys have widespread industrial applications. Grain refinement techniques have been frequently used to achieve high strength in these alloys. Here, we report on the fabrication of epitaxial co-sputtered AlMg thin films with high-density growth twins. The microstructure evolution with varying Mg composition has been characterized. Nanoindentation and in-situ micropillar compression tests show that the strength of AlMg alloys increases with increasing Mg composition. The flow stress of epitaxial nanotwinned Al–10 at.% Mg thin film exceeds 800 MPa. The modified Hall–Petch plots incorporating the solid solution strengthening effect suggest that, compared to high angle grain boundaries, incoherent twin boundaries are equivalent barriers to the transmission of dislocations in nanotwinned AlMg alloys.

It has been known that twin boundaries dominate the plasticity of nanotwinned metals. However, the role of stacking faults on the deformation mechanisms in face-centered-cubic (FCC) metals is less well understood. Here we investigate the deformation mechanisms of FCC Co with high-density stacking faults using in situ micropillar compression and atomistic simulations. In situ compression tests show a prominent strain rate dependence, with either strain softening or strain hardening observed at different strain rates. Molecular dynamics simulations reveal that the stacking faults and partial dislocations dominate the plastic deformation of FCC Co. Abundant dislocation junctions form at high strain rate, leading to strengthening.

High-density growth nanotwins enable high-strength and good ductility in metallic materials. However, twinning propensity is greatly reduced in metals with high stacking fault energy. Here we adopted a hybrid technique coupled with template-directed heteroepitaxial growth method to fabricate single-crystal-like, nanotwinned (nt) Ni. The nt Ni primarily contains hierarchical twin structures that consist of coherent and incoherent twin boundary segments with few conventional grain boundaries. In situ compression studies show the nt Ni has a high flow strength of ∼2 GPa and good deformability. Moreover, the nt Ni has superb corrosion behavior due to the unique twin structure in comparison to coarse grained and nanocrystalline counterparts. The hybrid technique opens the door for the fabrication of a wide variety of single-crystal-like nt metals with unique mechanical and chemical properties.

The loess-palaeosol deposits at the Beglitsa section in the East European Plain play an important role in the understanding of climate and environmental changes in Eurasia. However, the absence of absolute geochronology has restricted the interpretation of the loess sedimentation process and its relevance to palaeoenvironmental change. In this paper, a detailed chronology was obtained from the Beglitsa section using a quartz optically stimulated luminescence (OSL) dating technique in the southern area of the East European Plain. Grains with a diameter of 38–63 μm extracted from 8 samples and a single-aliquot regenerative-dose (SAR) protocol were applied for equivalent dose (De) determination. The results showed that the OSL ages are generally in agreement with the field-observed stratigraphic order and no age inversions were apparent. Compared with magnetic susceptibility and previously published radiocarbon ages, the OSL dating results showed great potential to provide a reliable chronology sequence for loess sediments in the Sea of Azov. With a span ranging from 5.4 ± 0.4 to 203.8 ± 18.0 ka, deposition of the Azov loess may have begun during the penultimate glaciation. Based on a comparative analysis of the stratigraphic composite, the sedimentary thickness differences between sections around the Azov region were likely affected by the local topography and the location.

Certain structurally gradient metallic materials have shown a combination of high strength and work hardening capability. The fundamental mechanisms behind such a unique mechanical behavior remain less well understood. Here we processed NiCrMo based C-22HS alloys by surface mechanical grinding treatment to achieve a gradient microstructure consisting of surface nanolaminated layer, deformation twinned layer and severely deformed layers. In situ micropillar compression tests performed inside a scanning electron microscope reveal different mechanical behaviors of each layer. This study suggests that the increase of intergranular back stress may have contributed to the high strain hardening behavior of the gradient material.

Enzymes-microwave-ultrasound assisted extraction (EMUE) method had been used to extract Lentinus edodes polysaccharides (LEPs). The enzymatic temperature, enzymatic pH, microwave power and microwave time were optimized by response surface methodology. The yields, properties and antioxidant activities of LEPs from EMUE and other extraction methods including hot-water extraction, enzymes-assisted extraction, microwave-assisted extraction and ultrasound-assisted extraction were evaluated. The results showed that the highest LEPs yield of 9.38% was achieved with enzymatic temperature of 48°C, enzymatic pH of 5.0, microwave power of 440W and microwave time of 10min, which correlated well with the predicted value of 9.79%. Additionally, LEPs from different extraction methods possessed typical absorption peak of polysaccharides, which meant different extraction methods had no significant effects on type of glycosidic bonds and sugar ring of LEPs. However, SEM images of LEPs from different extraction methods were significantly different. Moreover, the different LEPs all showed antioxidant activities, but LEPs from EMUE showed the highest reducing power when compared to other LEPs. The results indicated LEPs from EMUE can be used as natural antioxidant component in the pharmaceutical and functional food industries.

Due to the variation of road conditions and motor characteristics of vehicle, great root-mean-square (rms) error and outliers would be caused. Application of Kalman filter in laser Doppler velocimetry(LDV) is important to improve the velocity measurement accuracy. In this paper, the state-space model is built by using current statistical model. A strategy containing two steps is adopted to make the filter adaptive and robust. First, the acceleration variance is adaptively adjusted by using the difference of predictive observation and measured observation. Second, the outliers would be identified and the measured noise variance would be adjusted according to the orthogonal property of innovation to reduce the impaction of outliers. The laboratory rotating table experiments show that adaptive Kalman filter greatly reduces the rms error from 0.59 cm/s to 0.22 cm/s and has eliminated all the outliers. Road experiments compared with a microwave radar show that the rms error of LDV is 0.0218 m/s, and it proves that the adaptive Kalman filtering is suitable for vehicle speed signal processing.

Laser Doppler velocimetry (LDV) is a high precision instrument based on the Doppler effect of a laser, and it would greatly improve the performance of vehicle navigation and vehicle velocity metrology for its advantages. To reduce the measurement error produced by a jolt of a vehicle, a novel Janus-configured all fibre LDV is designed. The system comprising two independent interferometers is connected by 1.55 μm single mode fibre devices. Road experiments are carried out to compare the performances of the microwave radar, single beam LDV and Janus-configured LDV. The Janus-configured LDV is reliable to measure the velocity of the vehicle and its root-mean-square error is 0.0222 m/s, while it is 0.0284 m/s for the single beam LDV. The results validate that the designed LDV can achieve improved performance of vehicle velocity measurement.

Twin boundaries can enhance the strength and preserve the ductility of a variety of metallic materials with face centered cubic structures. However, twin boundaries are rare in aluminum due to its high stacking fault energy. There are limited successes for the formation of nanotwins in Al. Here, we show that twin morphology and twin density in Al can be altered by tailoring the textures of films. Transmission Kikuchi diffraction and transmission electron microscopy studies on (111), (110) and (112) textured Al films indicate that Al (112) film has the highest twin density. Two design criteria are identified for the introduction of a high density of growth twins into Al.

In this work, we have systematically investigated the effect of cyclic deformation on the strength and rate sensitivity of Cu/Ru multilayers with different individual layer thickness ( h ) by nanoindentation tests. It was found that cyclic deformation remarkably enhances the hardness of Cu/Ru multilayers comparing with the specimens by monotonic loading. The rate sensitivity ( m ) of multilayer exhibits an anomalous size dependence after nanoscale cyclic deformation. When h > 10 nm, the m linearly increases with increasing cycle number of loading-unloading ( s ). However, the m sharply decreases with increasing s when h m . An obvious Bauschinger effect is observed during cyclic loading, where the evolution of effective stress is consistent with the m . Cyclic deformation induced dislocation accumulation and arrays at the heterogeneous interface are the intrinsic plastic mechanism for the enhanced rate sensitivity. The formation of amorphous layers at the critical h is mainly responsible for the inverse size m .

SiC whisker (SiCw) anchoring on reduced graphene oxide (rGO) is a promising thermal conductive filler, which not only constructs the high-effective phonon transmission pathway but also resolves the agglomeration phenomenon of rGO. However, how to quantificationally anchor SiCw on rGO to build a phonon transmission pathway is incompletely understood. That is, the nucleation mechanism of SiCw requires a full investigation. Here, SiCw@rGO was synthesized by stacking bed method using rGO and rice husk ash as materials, in which SiCw is bridged on the rGO sheets through SiC crystal nucleus (C-Si covalent bonds). The experimental and density functional theoretical results reveal that the oxygen-containing defects (C-O groups) of rGO provide favorable sites for SiC nucleation and promote the yield of SiCw. Additionally, some specific defects of rGO induce the unpaired electrons of the surrounding carbon atoms, which is the prerequisite of the formation of C-Si covalent bonds. The construction of C-Si bonds between SiCw and rGO serves to enhance phonon accessibility, making SiCw@rGO composites achieve good thermal conductivity property and electrical insulation performance. The combination of experimental and theoretical research provides guides for the design of high-efficient thermal conductive materials.

Modern industrial requirements are continuously demanding better performance, smaller clearance, higher rotational speed and higher load from hydraulic generating set, under this circumstance, vibration mitigation is of considerable importance for safe and efficient functioning of rotor-bearing system. The overall goal of this research is to reveal the mechanism for unexpected nonlinear vibration induced by combined action of machine and charge load from hydraulic generating set. At first, a coupled bending-torsional rotor-bearing system with rub-impact under electromagnetic excitation for hydraulic generating set is established, meanwhile, a general model of unbalanced magnetic pull, considering both dynamic and static eccentricities between stator and rotor, is introduced to the system, and corresponding equations of motion are obtained according to Lagrange equation. Secondly, the effects from excitation current, mass eccentricity, radial stiffness of stator, dynamic and static eccentricities on vibration response of system are investigated thoroughly, by means of numerical method. And nonlinear dynamic behavior of system is illustrated through bifurcation diagrams, Poincare maps, trajectories, time domains and frequency spectrums. Finally, comparisons that with and without mixed eccentricities is conducted in term of nonlinear performance, disclosing that dynamic characteristic of system changes dramatically when composited eccentricities are taken into account. The analysis contributes to a deep understanding of complex nonlinear dynamic phenomena with benefit for forecasting and diagnosing system vibration due to electromechanical excitation in hydraulic generating rotor system.

Polycrystalline Cu films with nanoscale annealing twins are subjected to in situ Kr++ ion irradiation at room temperature inside a transmission electron microscope up to a dose of 1 displacement-per-atom. Radiation induces prominent migration of incoherent twin boundaries. Depending on twin thickness, three types of twin boundary evolutions are observed, including rapid detwinning, gradual detwinning, and self-healing. The mechanism of twin thickness-dependent evolution of microstructures is discussed. This study provides further evidence on twin boundary-defect interactions and may assist the design of radiation-tolerant twinned metallic materials.

Metallic glasses (MGs) are known to have high strength, but poor ductility. Prior studies have shown that plasticity in MG can be enhanced by significantly reducing their dimension to nanoscale. Here we show that, via the introduction of certain types of crystalline/amorphous interfaces, plasticity of MG can be prominently enhanced as manifested by the formation of ductile “dimples” in a 2 μm thick amorphous CuNb film. By tailoring the volume fraction and architecture of crystalline/amorphous multilayers, tensile fracture surface of MG can evolve from brittle featureless morphology to containing ductile dimples. In situ micropillar compression studies performed inside a scanning electron microscope show that shear instability in amorphous layers can be inhibited by interfaces. The mechanisms for improving plasticity and fracture resistance of MG via interface and size effect are discussed.

Twinned silicon carbide (SiC) nanowires (NWs) reinforced Si3N4–SiOC composites were successfully fabricated through a joint process of three-dimensional printing (3DP), direct nitridation, and polymer infiltration and pyrolysis (PIP). 3DP and PIP were both addictive manufacturing processes, enabling the near net shape fabrication and microstructure designing of Si3N4–SiOC. With the increase of the PIP cycle number, the pores of Si3N4 were mostly filled with polymer-derived ceramics-silicon oxycarbide (containing SiC NWs and free carbons), which led to the increase of electrical conductivity of Si3N4–SiOC composites. With the increase of SiOC ceramics, the electromagnetic interference shielding effectiveness of Si3N4–SiOC composites increased from 2 dB to 35 dB, in which the absorption shielding effectiveness increased to 27 dB. The flexural strength of Si3N4–SiOC composites reached 63 MPa when the content of SiOC ceramics was 50.1 wt%. It is indicated that Si3N4–SiOC ceramics are a promising electromagnetic shielding and structural material.

Flash sintering has received wide attention lately due to its ultrafast densification process at low sintering temperature. However, the deformability of flash-sintered ceramics remains poorly understood. Yttria-stabilized zirconia (YSZ) was processed by flash sintering to study deformation mechanism. Transmission electron microscopy studies show that the flash-sintered YSZ contains ultrafine grains and dislocations. Strain rate jump tests at elevated temperature by in-situ microcompression indicate the existence of a large threshold stress. The activation energy of deformation is ∼145 kJ/mol, similar to the activation energy for oxygen vacancy migration. The deformation mechanisms of the flash-sintered YSZ at elevated temperatures are discussed.

To raise mechanical strength of metallic materials, methods such as grain refinement and amorphization are usually utilized but sacrifice plasticity. Strength and plasticity are largely dictated by dislocation-defect interactions in crystalline materials and by shear banding in metallic glasses, depending significantly on the length scales of microstructural features. Here we report on the evolution of microstructures and multistage phase transformations from micro/nanocrystalline to an entirely amorphous structure, realized by tailoring the composition of Cr in co-sputtered Al100-xCrx (x = 0–25 at%) alloys. The associated Cr segregation caused the formations of different dual-phase nanocomposites. In-situ micromechanical experiments revealed that the flow stress of Al–Cr alloys can reach 2.4 GPa and the deformation behaviors varied drastically with Cr composition. This study established the mechanistic connection between the Cr composition-dependent evolution of microstructure and ultrahigh strength as well as plasticity, and revealed the benefits of building nanocomposites through a multistage phase transformation to improve the plasticity of nanocrystalline and amorphous materials.

Nanostructured crystalline/amorphous metallic multilayers have been increasingly studied due to their high strength and potential enhancement of plasticity in amorphous metals. Here we report on mechanical behaviors of Cu/amorphous CuNb multilayers that were prepared by magnetron sputtering with equal individual layer thickness (h) varying from 1 to 200 nm. A medium-range-order amorphous CuNb layer formed between Cu and amorphous CuNb layers. This intermediate layer facilitates transmission of plasticity from Cu to amorphous layers by preventing the smear of dislocation core on the interface. The maximum hardness of Cu/amorphous CuNb multilayers is achieved when h ≤ 50 nm, and is much lower than the hardness of single-layer amorphous CuNb films. Molecular dynamics simulations show that, comparing with single-layer amorphous CuNb, the pile-up of dislocations in Cu layers lowers the stress for the activation of shear transformation zones in amorphous CuNb layers in multilayers.

Four Ln(III) complexes based on a new nitronyl nitroxide radical have been synthesized and structurally characterized: {Ln(hfac)3[NITPh(OMe)2]2} (Ln = Eu(1), Gd(2), Tb(3), Dy(4); NITPh(OMe)2 = 2-(3΄,4΄-dimethoxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate;). The single-crystal X-ray diffraction analysis shows that these complexes have similar mononuclear tri-spin structures, in which central Ln(III) ion is eight-coordinated by two oxygen atoms from two nitroxide groups and six oxygen atoms from three hfac anions. The variable-temperature magnetic susceptibility study reveals that there exist ferromagnetic interactions between Gd(III) and the radicals, and antiferromagnetic interactions between two radicals (JGd-Rad = 3.40 cm−1, JRad-Rad = -9.99 cm−1) in complex 2. Meanwhile antiferromagnetic interactions are estimated between Eu(III) (or Dy(III)) and radicals in complexes 1 and 4, and ferromagnetic interaction between Tb(III) and radicals in complex 3, respectively. This article is protected by copyright. All rights reserved.

Ferritic/martensitic (F/M) steels with high strength and excellent ductility are important candidate materials for the life extension of the current nuclear reactors and the design of next generation nuclear reactors. Recent studies show that equal channel angular extrusion (ECAE) was able to improve mechanical strength of ferritic T91 steels moderately. Here, we examine several strategies to further enhance the mechanical strength of T91 while maintaining its ductility. Certain thermo-mechanical treatment (TMT) processes enabled by combinations of ECAE, water quench, and tempering may lead to “ductile martensite” with exceptionally high strength in T91 steel. The evolution of microstructures and mechanical properties of T91 steel were investigated in detail, and transition carbides were identified in water quenched T91 steel. This study provides guidelines for tailoring the microstructure and mechanical properties of T91 steel via ECAE enabled TMT for an improved combination of strength and ductility.

Five rare earth heterospin complexes [Ln(hfac)3(NITptBuPh)2], [LnIII = Eu (1), Tb (2), Dy (3), Ho (4), Er (5)] (hfac = hexafluoroacetylacetonate), were synthesized with the radical ligand NITptBuPh [2-(4′-tert-butylphenyl)-4, 4,5, 5-tetramethylimidazoline-1-oxyl-3-oxide]. These complexes exhibit similar structures. All of them crystallize in the monoclinic space group P21/c, and consist of discrete mononuclear molecules. The central LnIII ion is eight-coordinate with a distorted dodecahedral environment. The NITptBuPh radical acts as monodentate ligand towards LnIII ion through the NO group. The magnetic studies suggested weak antiferromagnetic interactions between LnIII ion and radicals in 1, 3, 4, and 5, but weak ferromagnetic interaction in 2.

The damage evolution in equiatomic NiCoCr single crystals irradiated at 138 and 500 K with 1.5 MeV Ni+ ions has been investigated using ion channeling analysis and compared with previous results obtained at 300 K under identical irradiation conditions. As expected, irradiation temperature has a major influence on damage evolution and long-range effects in ion-irradiated NiCoCr. A change in relative irradiation resistance as a function of temperature is revealed when the ion channeling data are compared with previous ion channeling results from Ni-irradiated NiFe at 150, 300 and 500 K. NiCoCr has superior irradiation resistance than NiFe under ion irradiation at ≤ 300 K; surprisingly, the relative irradiation resistance is reversed under ion irradiation performed at > 300 K (i.e., 500 K), which may be attributed to local chemical ordering. These observations indicate that the NiFe alloy exhibits a more favorable chemical environment for suppressing deleterious microstructural degradation under high temperature irradiation than the NiCoCr alloy.

Void swelling can result in dimensional instability and undermine the safe operation of nuclear reactors. Current strategies to inhibit void swelling mainly focus on enhancing defect absorption and recombination by introducing high-density defect sinks. Complex concentrated solid-solution alloys (CSAs), including high-entropy alloys, can withstand severe radiation damage due to their inherent chemical complexity without interfaces. However, the underlying mechanisms for void suppression in CSAs are far from clear. In this research, we studied the void evolution with respect to irradiation depths, doses, and temperatures in equiatomic NiCoFeCr under 3 MeV Ni ion irradiations. At relatively low doses (16 and 54 displacements per atom, dpa), voids form mainly outside of the ion-damaged region, and void formation in the peak damage region is suppressed, leading to negligible swelling. However, with further increase of dose (86 up to 250 dpa), significant void growth occurs in the peak damage region and extended dislocation lines dominate instead of short dislocation lines and loops formed at lower doses. From 500 to 700 °C, the dislocation density decreases while dislocations grow. Although the overall void swelling increases dramatically from 500 to 580 °C at 54 dpa, void growth in the peak damage region is still suppressed. The transition from suppressed void growth to significant void swelling is attributed to dislocation evolution and local chemical inhomogeneity (enrichment of Fe/Cr in the matrix) at higher doses. Our study shows that controlling element diffusion and defect evolution through tuning chemical complexity can further enhance the swelling resistance of CSAs.

Lidar has been widely used in military and civilian applications. This passage mainly introduces a type of lidar used in autonomous vehicle: TOF lidar. The working principle of TOF lidar was introduced in detail. Then based on the TOF lidar, there are two types of lidar to be introduced: scanning lidar and non-scanning lidar. Scanning lidar includes single-line scanning lidar and multi-line scanning lidar. 3D-flash lidar was taken as example to introduce non-scanning lidar. The contents of each type of lidar are system structure, working principle, the development around the world and some problems existing currently. Introduction of lidar development direction is made, including MEMS technology and ZOL technology.

Flash sintering has attracted significant attention as its remarkably rapid densification process at low sintering furnace temperature leads to the retention of fine grains and enhanced dielectric properties. However, high-temperature mechanical behaviors of flash-sintered ceramics remain poorly understood. Here, we present high-temperature (up to 600 °C) in situ compression studies on flash-sintered yttria-stabilized zirconia (YSZ). Below 400 °C, the YSZ exhibits high ultimate compressive strength exceeding 3.5 GPa and high inelastic strain (~8%) due primarily to phase transformation toughening. At higher temperatures, crack nucleation and propagation are significantly retarded, and prominent plasticity arises mainly from dislocation activity. The high dislocation density induced in flash-sintered ceramics may have general implications for improving the plasticity of sintered ceramic materials., Flash sintering allows for rapid ceramic processing, but the mechanical behavior of such ceramics remains poorly understood. Here, the authors compress micropillars of yttria stabilized zirconia to show flash sintering promotes outstanding plasticity.

Traffic speed meters are important legal measuring instruments specially used for traffic speed enforcement and must be tested and verified in the field every year using a vehicular mobile standard speed-measuring instrument to ensure speed-measuring performances. The non-contact optical speed sensor and the GPS speed sensor are the two most common types of standard speed-measuring instruments. The non-contact optical speed sensor requires extremely high installation accuracy, and its speed-measuring error is nonlinear and uncorrectable. The speed-measuring accuracy of the GPS speed sensor is rapidly reduced if the amount of received satellites is insufficient enough, which often occurs in urban high-rise regions, tunnels, and mountainous regions. In this paper, a new standard speed-measuring instrument using a dual-antenna Doppler radar sensor is proposed based on a tradeoff between the installation accuracy requirement and the usage region limitation, which has no specified requirements for its mounting distance and no limitation on usage regions and can automatically compensate for the effect of an inclined installation angle on its speed-measuring accuracy. Theoretical model analysis, simulated speed measurement results, and field experimental results compared with a GPS speed sensor with high accuracy showed that the dual-antenna Doppler radar sensor is effective and reliable as a new standard speed-measuring instrument.

Nanoscale metamaterials exhibit extraordinary optical properties and are proposed for various technological applications. Here, a new class of novel nanoscale two‐phase hybrid metamaterials is achieved by combining two major classes of traditional plasmonic materials, metals (e.g., Au) and transition metal nitrides (e.g., TaN, TiN, and ZrN) in an epitaxial thin film form via the vertically aligned nanocomposite platform. By properly controlling the nucleation of the two phases, the nanoscale artificial plasmonic lattices (APLs) consisting of highly ordered hexagonal close packed Au nanopillars in a TaN matrix are demonstrated. More specifically, uniform Au nanopillars with an average diameter of 3 nm are embedded in epitaxial TaN platform and thus form highly 3D ordered APL nanoscale metamaterials. Novel optical properties include highly anisotropic reflectance, obvious nonlinear optical properties indicating inversion symmetry breaking of the hybrid material, large permittivity tuning and negative permittivity response over a broad wavelength regime, and superior mechanical strength and ductility. The study demonstrates the novelty of the new hybrid plasmonic scheme with great potentials in versatile material selection, and, tunable APL spacing and pillar dimension, all important steps toward future designable hybrid plasmonic materials.

Light-weight aluminum (Al) alloys have widespread applications. However, most Al alloys have inherently low mechanical strength. Nanotwins can induce high strength and ductility in metallic materials. Yet, introducing high-density growth twins into Al remains difficult due to its ultrahigh stacking-fault energy. In this study, it is shown that incorporating merely several atomic percent of Fe solutes into Al enables the formation of nanotwinned (nt) columnar grains with high-density 9R phase in Al(Fe) solid solutions. The nt Al-Fe alloy coatings reach a maximum hardness of ≈5.5 GPa, one of the strongest binary Al alloys ever created. In situ uniaxial compressions show that the nt Al-Fe alloys populated with 9R phase have flow stress exceeding 1.5 GPa, comparable to high-strength steels. Molecular dynamics simulations reveal that high strength and hardening ability of Al-Fe alloys arise mainly from the high-density 9R phase and nanoscale grain sizes.

Aluminium typically deforms via full dislocations due to its high stacking fault energy. Twinning in aluminium, although difficult, may occur at low temperature and high strain rate. However, the 9R phase rarely occurs in aluminium simply because of its giant stacking fault energy. Here, by using a laser-induced projectile impact testing technique, we discover a deformation-induced 9R phase with tens of nm in width in ultrafine-grained aluminium with an average grain size of 140 nm, as confirmed by extensive post-impact microscopy analyses. The stability of the 9R phase is related to the existence of sessile Frank loops. Molecular dynamics simulations reveal the formation mechanisms of the 9R phase in aluminium. This study sheds lights on a deformation mechanism in metals with high stacking fault energies., Deformation-induced defects with high formation energy are difficult to nucleate in aluminium. Here, the authors use a miniaturized projectile impact to nucleate the high stacking fault energy 9R phase in a thin film of ultrafine-grained aluminium, and show sessile Frank loops stabilize it.

The strain rate sensitivity (SRS) and dislocation activation volume are two inter-related material properties for understanding thermally-activated plastic deformation, such as creep. For face-centered-cubic metals, SRS normally increases with decreasing grain size, whereas the opposite holds for body-center-cubic metals. However, these findings are applicable to metals with average grain sizes greater than tens of nanometers. Recent studies on mechanical behaviors presented distinct deformation mechanisms in multilayers with individual layer thickness of 20 nanometers or less. It is necessary to estimate the SRS and plastic deformation mechanisms in this regime. Here, we review a new nanoindentation test method that renders reliable hardness measurement insensitive to thermal drift, and its application on SRS of Cu/amorphous-CuNb nanolayers. The new technique is applied to Cu films and returns expected SRS values when compared to conventional tensile test results. The SRS of Cu/amorphous-CuNb nanolayers demonstrates two distinct deformation mechanisms depending on layer thickness: dislocation pileup-dominated and interface-mediated deformation mechanisms.

Most metallic glasses are brittle as deformation induces low-density sporadic shear bands and severe shear localization proceeding catastrophic failure. Here, it is demonstrated that the introduction of crystalline nanolayers with appropriate dimension can substantially suppress shear localization in metallic glasses, as manifested by ubiquitous ductile dimples in amorphous phase. Furthermore, dimple sizes can be tailored by tuning the dimension of layer thickness. Additionally unlike instantaneous crack propagation occurring in most metallic glasses, crack propagation occurs in a highly periodic and “zigzag” fashion, and shows clear size dependence for metallic glass nanolaminates. Thus, it is a promising approach to promote ductility in metallic glasses while maintaining high strength by synthesizing metallic glass nanolaminates with certain layer thickness. Molecular dynamics simulations demonstrate that crystalline/amorphous interfaces can block crack propagation in crystalline layers and delocalize strain in amorphous layers, and suggest that “zigzag” crack propagation could be achieved through dislocation slips in crystalline layers.

Strain rate sensitivity of crystalline materials is closely related to dislocation activity. In the absence of dislocations, amorphous alloys are usually considered to be strain rate insensitive. However, the strain rate sensitivity of crystalline/amorphous composites is rarely studied, especially at nanoscale. In this study, we show that the strain rate sensitivity of Cu/amorphous CuNb multilayers is layer thickness dependent. At small layer thickness (below 50 nm), the multilayers demonstrate limited strain rate sensitivity; at relatively large layer thickness (above 100 nm), the strain rate sensitivity of multilayers is close to that of the single layer Cu film. Mechanisms that lead to size dependent variation of strain rate sensitivity in these multilayers are discussed.

The phase relation of harmonics in high-intensity focused ultrasound is investigated numerically and experimentally. The nonlinear Westervelt equation is solved to model nonlinear focused sound field by using the finite difference time domain method. Experimental waveforms are measured by a robust needle hydrophone. Then the relative phase quantity is introduced and obtained by using the zero-phase filter. The results show that the nth harmonic relative phase quantity is approximately (n — 1)π/3 at geometric center and increases along the axial direction. Moreover, the relative phase quantity decreases with the increase of source amplitude. This phase relation gives an explanation of some nonlinear phenomena such as the discrepancy of positive and negative pressure.