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Group IV elements and their oxides, such as Si, Ge, Sn and SiO have much higher theoretical capacity than commercial graphite anode. However, these materials undergo large volume change during cycling, resulting in severe structural degradation and capacity fading. Al2O3 coating is considered an approach to improve the mechanical stability of high-capacity anode materials. To understand the effect of Al2O3 coating directly, we monitored the morphology change of coated/uncoated Sn particles during cycling using operando focused ion beam–scanning electron microscopy. The results indicate that the Al2O3 coating provides local protection and reduces crack formation at the early stage of volume expansion. The 3 nm Al2O3 coating layer provides better protection than the 10 and 30 nm coating layer. Nevertheless, the Al2O3 coating is unable to prevent the pulverization at the later stage of cycling because of large volume expansion.

As a promising alternative to the market-leading lithiumion batteries, low-cost sodium-ion batteries (SIBs) are attractive for applications such as large-scale electrical energy storage systems. The energy density, cycling life, and rate performance of SIBs are fundamentally dependent on dynamic physiochemical reactions, structural change, and morphological evolution. Therefore, it is essential to holistically understand SIBs reaction processes, degradation mechanisms, and thermal/mechanical behaviors in complex working environments. The recent developments of advanced in situ and operando characterization enable the establishment of the structure-processing-property- performance relationship in SIBs under operating conditions. This Review summarizes significant recent progress in SIBs exploiting in situ and operando techniques based on X-ray and electron analyses at different time and length scales. Through the combination of spectroscopy, imaging, and diffraction, local and global changes in SIBs can be elucidated for improving materials design. The fundamental principles and state-of-the-art capabilities of different techniques are presented, followed by elaborative discussions of major challenges and perspectives. U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences program [DE-SC0019121]; National Science Foundation [CBET 1912885]; USDA AFRI Foundational and Applied Program [2020-67021-31139]; U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]; U.S. DOE [DE-AC02-06CH11357]; Canadian Light Source Published version D.H., E.G., J.R., K.G., Y.L., and H.X. acknowledge the funding support by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences program under Award Number DE-SC0019121. The work at Virginia Tech was supported by the National Science Foundation under no. CBET 1912885 and the USDA AFRI Foundational and Applied Program (grant number 2020-67021-31139). Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357, and the Canadian Light Source, and its funding partners.

Nanoscale oxide-based negative electrodes are of great interest for lithium ion batteries due to their high energy density, power density and enhanced safety. In this work, we conducted a case study on mesoporous TiO2 nanoparticle negative electrodes with uniform size and varying crystallinity in order to investigate the trend in the electrochemical properties of oxide-based nanoscale negative electrodes with varying crystallinity. Mesoporous solid spherical TiO2 nanoparticles with a uniform particle size and varying crystallinity, i.e., amorphous TiO2 (A-TiO2), partially crystalline TiO2 (PC-TiO2) and fully crystalline TiO2 (FC-TiO2) nanoparticles were studied. At low current rate (quasi steady-state), the specific capacity of the samples drops with the decrease of crystallinity. Ex situ synchrotron pair distribution function analysis reveals that the 1D zigzag Li ion diffusion pathway becomes expanded with the increase of crystallinity, which promotes ion mobility and charge storage. At high current rates (away from equilibrium states), however, the A-TiO2 sample demonstrates slightly larger capacity than the FC-TiO2 sample, both of which show larger capacities than that of the PC-TiO2 sample. Both A-TiO2 and FC-TiO2 samples exhibit higher capacitive contribution to the charge storage and larger Li+ diffusivity than those of the PC-TiO2 sample, which explains their better rate capability. Moreover, the larger Li+ diffusivity of the A-TiO2 sample leads to the slightly larger specific capacity than the FC-TiO2 sample at the highest current rate.

A fiber microfluidic velocity sensor based on a bare fiber adapter (BFA) was proposed and demonstrated. Ceramic end face in BFA was covered by polyethylene (PE) film, in which the inserted single mode fiber (SMF) can be moved freely. The end face of the SMF and the PE film composed a Fabry-Perot (F-P) construction. Due to PE film sustaining different press with different microfluidic velocity, the F-P cavity length was changed. The velocity can be measured by monitoring the reflection spectrum. In our experiment, three cavity lengths were measured. The experimental results showed that the achieved maximum sensitivity to microfluidic velocity is 0.048 dB/(µL/min) or 0.0059 nm/(µL/min). Also, responses of PE film thickness and microfluidic concentration to the proposed sensor have been measured in the experiment. The sensor can be used for low velocity with high sensitivity, especially in micro-channels such as biological blood vessels.

Twinning process and dislocation characteristics were determined by means of quasi in-situ electron backscatter diffraction and high-resolution transmission electron microscopy techniques in a rolled AZ31 magnesium alloy under different strain paths (compression along rolling direction and tension along normal direction). It is demonstrated that the activation of different twin variants depends on the strain path, and thus these twin variants can further induce different texture characteristics. In addition, two independent slip systems were activated during deformation of both strain paths. However, the dislocation slip modes of the two kinds of deformation are different, resulting in different stress-strain response.

The twinning and slip modes of a rolled magnesium alloy sheet were investigated through quasi-in-situ tensile tests that were carried out along the rolling direction at room temperature with a constant strain rate. Scanning electron microscopy and electron backscattered diffraction observations were used to identify activated twinning and slip systems. Schmid factors were calculated to analyze different deformation modes. The analyses show that a small number of {10-12} tensile twins were present during deformation, and these twins resulted from the accommodation of compression along the tensile direction. Post-deformation examination revealed the dominance of prismatic slip.

The compressive mechanical properties, microstructural evolution and fracture behaviors of AZ31 alloys with equiaxed grains (E-grain) or bimodal grains (B-grain) were investigated using optical microscopy, scanning electron microscopy and electron backscattered diffraction. The results indicate that the ratio of twinned grains to all grains increases for both E-grain and B-grain samples with increasing strain levels during compression deformation along the extruded direction. The average Schmid factor for {10–12} twins of B-grain samples is higher than that of E-grain samples, which lowers required activating stress for {10–12} twins in B-grain samples. This causes a higher quantity of twins in B-grain samples than that of E-grain samples at the same pre-compression level. The E-grain samples mainly exhibit parallel twins regardless of pre-compression levels, whereas the twins in coarse grains of B-grain samples are parallel to each other at low compressive strain level and then transform to crossed twins at high compressive strain level with parallel twins in fine grains. Additionally, the peak strength, strain hardening rate and fracture strain of E-grain samples are lower than those of B-grain samples, and they possess similar yield strength. The coarse grains in the B-grain samples effectively resist crack growth by deflecting and branching crack tips, bridging of the cracks and forming the secondary cracks. Meanwhile, the fine grains in B-grain samples accommodate plastic strain and mediate multiple grains’ deformation. The concurrent effect of coarse grains and fine grains results in the improvement of plasticity.

Metal ions pre-intercalated layered structure materials are considered as potential high performance cathodes for Mg-ion batteries (MIBs). Herein, metal ions pre-intercalation strategy of layered cathode for MIBs by using Li, Na, Al pre-intercalated V2O5 cathode as a carrier has been investigated and proposed based on first principle calculations. The pre-intercalation process is energetically favorable and metal ion pre-intercalation improves the electronic conductivity of V2O5. The bondings of Li-V2O5, Na-V2O5 and Al-V2O5 all exhibit ionic characters, and the interaction between Al ion and V2O5 is the strongest. The interlayer distance expansion of Na pre-intercalated V2O5 is more trivial than that of Li, Al pre-intercalated V2O5. The open circuit voltage of the V2O5 cathode is dropped by pre-intercalated metal ions, and the voltage of Li and Na pre-intercalated V2O5 is higher than that of Al pre-intercalated V2O5. The diffusion barriers of Mg in the V2O5 matrix are reduced by pre-intercalation. Overall, metal ion pre-intercalation with a large atomic radius and small atomic charges holds great potentials to expand interlayer distance, enhance electronic conductivity, maintain high discharge voltage and improve diffusion ability of layered cathode. We hope our work could provide a significant guidance to the practical design of layered cathodes for MIBs.

Building a gradient structure can achieve overall improvement of multiple properties of metal materials. However, the investigation on hydrogen embrittlement (HE) behavior of gradient structure alloys has not been reported so far. This study investigated HE of pure iron with gradient microstructure induced by pre-torsion. The results reveal that with an increase in pre-torsion angle, the resistance to HE of alloys decreases. Fracture surface observation demonstrates that hydrogen uncharged samples present ductile cup-shape fracture, whereas hydrogen charged samples exhibit brittle spiral patterns, mainly depending on pre-torsion level. Additionally, microscopical hydrogen-assisted cracking mechanism of gradient structured pure iron has been proposed.

The microstructure and texture evolution of an AZ31 magnesium rolled sheet during quasi-static compression at strain rates of 10 − 3 s − 1 has been investigated by in situ electron backscattered diffraction. The influence of the initial and pre-deformed texture on the predominant deformation mechanisms during compression has been examined. It has been found that extensive grain reorientation due to {10 − 12} tensile twinning appeared when compressed along transverse direction. Tensile twin variants were observed under this loading condition, and different variants will cause an effect to the following deformation. Several twinning modes occurred with continuative loading along rolling direction.

Twinning process involving reversible motion of twin boundaries was examined and quantified in a rolled Mg-3Al-1Zn magnesium alloy compressed along two perpendicular directions. The evolution of twinning is analyzed by quasi in-situ electron backscatter diffraction technique, and the detailed structure of the twin boundary is analyzed using high-resolution transmission electron microscopy technique. The results suggest that both twinning and detwinning are attributed to the mobility of twin boundaries. Low-angle boundaries were identified at the prior twin boundaries after detwinning due to the effect of alloying elements, and these low-angle boundaries will affect subsequent deformation. Twin boundary is serrated and consists of 10 1 ¯ 2 coherent twin boundaries and prism-basal boundaries that control twin boundary migration.

Bulk metallic glasses (BMGs) are usually brittle, and show serious negative strain rate sensitivity upon dynamic loading due to no sufficient time for generation of the shear bands, which fatally limit their practical applications. Investigations have been done on BMGs dynamic deformation behaviors, but in which yielding phenomenon was hardly reported before. In this work, by raising stored energy which appears as an exothermic heat of relaxation on heating the glass, the dynamic and quasi-static deformation behaviors of Cu45.75Zr46.75Al6.5Co1 BMG were explored. We found that, compared the BMG at higher energy state with the as-cast BMG, its quasi-static compressive plasticity is improved from 0.9% to 3.3%. Additionally, more meaningfully, under dynamic compression, an evident yield plateau appears on the stress–strain curves of all the treated specimens at different strain rates, also the typical negative strain rate sensitivity of BMG ultimate strength weakens significantly. Other results reveal that raising BMGs stored energy can bring their spatial heterogeneity enhancement which distinctly proliferates shear bands in deformation, thus avoids rapid spread of limited shear bands catastrophically. This work provides an efficient way to improve BMGs dynamic properties and may shed light on their dynamic behaviors. Keywords: Bulk metallic glasses, Dynamic loading, High stored energy, Microstructural heterogeneity

Hydrogen blister (HB) and hydrogen-induced cracking (HIC) of pure iron at various charging times were investigated. The results show that an increase in charging time leads to the increased HB height/width and HIC length/depth, and a change in hydrogen damage morphology. Subsurface HIC initiates and propagates along the grain boundaries, which makes the surface bend outwards to form blister on blister features, suggesting grain boundary cracking-induced blister-blister interaction mechanism. Crystallographic analysis demonstrates that adjacent grain boundary oriented-{100}//ND and {110}//ND exhibits the highest susceptibility to HIC, which offers a pathway to design hydrogen-resistant structural steels through the control of grain boundary.

Herein, by means of first-principle calculations based on density functional theory (DFT), the electrochemical properties of monolayer VS2 (M-VS2), double-layer VS2 (D-VS2) and bulk VS2 (B-VS2) as electrode materials for Mg-ion batteries (MIBs) were comprehensively explored. The computation results reveal that Mg atom can strongly bind with the three different forms of VS2. All of the Mg adsorbed VS2 systems demonstrate metallic characteristics, which indicates a good electronic conductivity. In addition, crystal orbital hamiltonian population shows that the stability of V-S bond is weakened after adsorption of Mg atom. The low diffusion barriers of Mg give rise to the high rate performance of VS2 in MIBs. More interestingly, the three types of VS2 display same storage ability for Mg cations, which can adsorb 0.5 Mg atoms for VS2, producing maximum theoretical capacity 233 mA h g−1 for MIBs. The average working voltages results suggest that M-VS2 can be employed as anode materials, while D-VS2, B-VS2 can be used as cathode materials for MIBs.

In AZ31 magnesium alloy, {10–12} twin pair generated at grain boundary is easy to be observed. In current study, we trace the process of twins impacting grain boundaries and stimulating the nucleation of new twins in neighbouring grains by in situ electron backscatter diffraction (EBSD) technique. Multiple twin variants (caused by twin pair) inside one grain is found in EBSD map, which is considered as the cause of strain hardening for it significantly retard the rate of propagation and growth of twinning during subsequent deformation.

Nickel-manganese oxide film with unique morphology was synthesized and its electrochemical performances were also investigated. The addition of nickel element affects significantly capacitive behaviors of the as-obtained powder. As an electrode material in supercapacitor, nickel-manganese oxide exhibited high specific capacitance of 407 F g−1 at 1 A g−1 and excellent cycling stability of 98.4% retention after 1000 cycles. Its outstanding electrochemical properties are mainly attributed to the synergistic effect between nickel and manganese elements and its novel architecture.

Manganese dioxide (MnO2) with mesoporous framework self-assembled by ultrathin nanosheets was synthesized via a facile hydrothermal strategy without any binders and substrates. The wall-like structure of this electrode material for supercapacitors can provide more attaching points for active material and shorten the diffusion paths of electrons and ions, leading to a high specific capacitance (SC) of 400 F g−1 at current density of 1 A g−1 and the good cyclic stability up to 3000 cycles. Meanwhile, the relationships among structure, specific surface area, pore size and electrochemical properties have been discussed. It indicated that three-dimensional (3D) wall-like δ-MnO2 is a promising electrochemical electrode candidate for supercapacitors.

Electron backscattered diffraction serial image analyses on AZ31 magnesium alloy compressed along RD at different strain levels revealed that twin–twin interactions are found to correlate with mechanical hardening. Four typical twin–twin structures are investigated: (1) Parallel twins with single variant; (2) Interacting twins with single variant; (3) Parallel twins with double variants; (4) Interacting twins with double variants. We studied twin–twin interactions by combining experimental observations and Schmid factor analysis. Due to twins intersecting with each other, the limited growth rate of twins was observed in EBSD maps. The intersection between different twin variant pairs was found to retard the twin growth and promote the nucleation of new twins near intersection region. Besides, “Apparent crossing” twin structure is a limiting case, in which the twin is crossed by a couple of twins, and the interaction region grow slowly. Twin–twin boundary migration is also observed during deformation in this paper, which is considered as an important cause to prohibit twins for further propagate and growth. All these features can be related to twinning-induced hardening.

Nanostructured spinel NiMn 2 O 4 arrays have been fabricated by a facile hydrothermal approach and further investigated as binder-free electrode for high-performance supercapacitors. Compared with Mn 3 O 4 , NiMn 2 O 4 exhibited higher specific capacitances (662.5 F g −1 and 370.5 F g −1 in different electrolytes at the current density of 1 A g −1 ) and excellent cycling stability (~96% capacitance retention after 1000 cycles) in a three-electrode system. Such a novel microstructure grown directly on the conductive substrate provided sufficient active sites for redox reaction resulting in their enhanced electrochemical behaviors. Their improved performances suggested that ultrathin sheet-like NiMn 2 O 4 arrays on Ni foam substrate were a promising electrode material for supercapacitors.

The strengthening mechanisms of hot-extruded AZ31 magnesium alloy by { 10 1 ¯ 2 } extension twinning lamellas during multi-pass compression are investigated in present study. The numbers of { 10 1 ¯ 2 } twinning lamellas increased dramatically with the ED-TD orthogonal compression. Grain refinement induced by { 10 1 ¯ 2 } twinning lamellas greatly improved the mechanical properties of reloading along ED and TD direction. In addition, the primary { 10 1 ¯ 2 } twinning lamella can be an effective way to strengthen material via twin-twin interaction during secondary twin growing and propagating.

Ag 2 O-loaded NiO ball-flowers were synthesized via a simple one-step hydrothermal method. The ball-flower architecture is constructed by porous nanosheets modified by Ag 2 O. During the charge-discharge processes Ag 2 O can convert to metallic Ag to enhance the conductivity of electrode materials. The unique hierarchical ball-flower architectures can provide more active sites and diffusion paths for ions, increasing the utilization rate of electrode materials. Electrochemical measurements reveal that electrode materials based on Ag 2 O/NiO nanocomposites exhibited high specific capacitance value (556 F g −1 ) at a current density (1 A g −1 ), as well as an excellent capacitance retention of 103% after 1000 cycles.

In this study, the effects of torsion strain and strain rate on microstructure and hardening behavior of extruded AZ31 Mg alloy rods are investigated. Torsion deformation can generate abundant extension twins and dislocations and cause the rotation of c-axis toward extrusion direction. These microstructures exhibit gradient distributions along the radial direction of torsion-deformed rods. Torsion deformation can effectively enhance the hardness of AZ31 rods. The gradient microstructure leads to a gradient hardness distribution in torsion-deformed rods. High strain rates can enhance the hardening effect via torsion deformation by promoting increment of dislocation density.

A novel finding of this study is that localised de-twining caused by shear banding induced by uniaxial compression deformation was first found through in situ EBSD observation. The twinning deformation process showed in this paper consists of the following three steps: twinning, de-twinning and re-twinning, which needs more energy and larger load than the process of twin growth and coalescence and complete consumption. It is believed that localised de-twining deformation mechanism is one of the strengthening mechanisms in magnesium alloy. More interestingly, twinning and de-twinning deformation operate simultaneously in a single twinning system, which was not in good agreement with the prediction of previous reports [1] . It is the first time that such unusual deformation mechanism has been found in experimental results. According to the results and combining with theoretical analysis, uncertain local stress states in individual grains is the cause of unusual experimental phenomena. The back stress induced in a twin by the surrounding matrix plays an important role in localised de-twining during uniaxial compression.

Continuous { 10 1 2 } twin bands across neighboring grains was observed in a hot rolled AZ31 during the interrupted compression along the rolling direction. The variant selection in paired twins was studied by Schmid factor (SF) and geometric misorientation relationship. The results show that most mated twins possess high rank Schmid factors (SFs), however, they does not share the same twin variant. Furthermore, EBSD analysis indicates that the formation of paired twins is correlated with the orientation relationship between adjacent grains. Based on these observation and analysis, the mechanism of “sequential twinning” nucleation and synergetic growth during deformation are proposed. Above all, this twinning behavior is capable of transmitting the localized shear and releasing stress at the former twin-termination interfaces, which plays an important role in accommodating plastic strain and mediating multiple grains' deformation

Hollow NiO ball-flowers closely assembled by porous nanosheets have been synthesized via a simple and template-free hydrothermal method. When applied to supercapacitor as electrode materials, the as-prepared NiO ball-flowers with hierarchical, porous, and hollow structures exhibited high specific capacitance value (734 F g−1) at a current density (1 A g−1), as well as good cycling stability. The outstanding electrochemical performance may be attributed to the morphology and structure of the nanosheet-assembled hollow ball-flowers which have the advantages of increasing specific surface area, facilitating the contact between the electrode and electrolyte, and accommodating the volume changes during faradaic reaction.

The twinning and slipping modes of a rolled AZ31 magnesium alloy sheet were investigated through in situ compressive tests. A method based on scanning electron microscopy and electron backscattered diffraction measurements was used to identify activated twinning and slip systems. {10-12} tensile twins were present, but only occasionally. Contraction twins were not observed. Post deformation examination revealed the dominance of pyramidal slip.

We present an unusual and unique bismuth oxychloride (BiClO) hollow nanotube fabricated by a facile and simple hydrothermal method without using any surfactant and template, such research are rarely reported to the public. Morphology analysis (SEM, TEM) revealed that the synthesized nanotube had a typical one-dimensional hollow nanostructure with a diameter of 45 nm. XRD result showed that the nanotube was pure BiClO phase without any impurity. Moreover, KMnO 4 served as an effective oxidizing and etching agent in this process, which contributed to the novel and regular hollow structure. The specific growth mechanism is also proposed and discussed systematically and scrupulously.

The evolution of ZnO nanostructures was achieved successfully. At the initial stage, bud-shaped ZnO nanorods were prepared using sodium acetate, and then assembly of nanorods was aggregated into bulbous nanostructures.. Finally, the oval-like bulbous nanostructures were turned into ZnO nanorods and nanoflowers under the same hydrothermal reaction conditions. The as-prepared nanostructures were characterized by XRD, SEM, and HRTEM. The gas-sensing properties of both bulbous nanostructures were accounted for formaldehyde, acetone, ethanol methanol, ammonia and benzene at different concentrations and temperatures. A higher response (82, 70) and greater selectivity toward formaldehyde than other gases was observed at 75 ppm. A sharp response with the best recovery time was achieved at an optimum temperature of 200 °C.

Sodium ion batteries (SIBs) are attractive alternative energy storage technology to lithium-ion batteries due to its low-cost. There has been growing attention in developing new electrode materials for sodium ion batteries. Compared to lithium ion batteries, SIBs suffer from more issues in long-term stability, resulted from the sluggish kinetics, large volume change due to the much larger Na+ ion (~ two times the size of Li+) as well as multiple phase transitions upon cycling. Several approaches to enhance the electrode performance have been explored such as doping, nanostructuring, and carbon coating. Here, we will discuss our recent work on developing advanced electrode materials for SIBs through interfacial engineering. We have developed a coaxial core-shell nanostructured negative composite electrode composed of carbon nanotube (CNT) as the core and TiO2@MoO2@C as shells. The 1D tubular nanostructure can effectively reduce ion diffusion path, increase electrical conductivity, accommodate the stress due to volume change upon cycling, and provide additional interfacial active sites for enhanced charge storage and transport properties. Significantly, a synergistic effect between TiO2 and MoO2 nanostructures is investigated through ex-situ solid state nuclear magnetic resonance. We also developed multi-phased transition metel oxide positive electrodes, which exhibits enhanced capacity and cycling stability.

A low liquid velocity sensor composed by a capillary vertically inserted in PTFE (Polytetrafluoroethylene) tube has been proposed and realized with high sensitivity. The achieved sensitivity to liquid velocity is 0.0016nm/(μL/min ).

This study aims to investigate the tension and compression properties and precipitation behavior of pre-twinned ZK60 alloys. It was found that aging treatment can effectively reduce the tension–compression yield asymmetry of pre-twinned ZK60 alloy. For the pre-twinned sample with 10 h aging treatment, the yield asymmetry ratio is nearly equal to 1. Precipitate behavior in {10–12} extension twins of ZK60 Mg alloy were characterized by TEM. Three different morphologies of precipitates, [0001] twin rods, (0001) twin plates and [11–20] twin laths were observed in {10–12} extension twins. The precipitates constituted Mg 4 Zn 7 or MgZn 2 phases. The Mg 4 Zn 7 phases have two variant orientations of the [010] zone axis, [010] Mg4Zn7 ‖ [0001] twin and (−201) Mg4Zn7 ‖ (‐12‐10) twin or (−201) Mg4Zn7 ‖ (10–10) twin , while the MgZn 2 phases have an orientation of [‐12‐10] MgZn2 ‖ [0001] twin and (10–12) MgZn2 ‖ (10–10) twin . [11–20] twin laths as a new morphology of the precipitates have been found in ZK60 alloy, which have an orientation relationship of [010] Mg4Zn7 ‖ [0001] twin and (−201) Mg4Zn7 ‖ (‐12‐10) twin . Finally, the influences of aging treatment on yield asymmetry of pre-twinned ZK60 alloy are addressed and discussed.

In this paper rolled AZ31 magnesium alloy was deformed by interrupted in situ compressive tests. Compressive and re-compressive tests were conducted along rolling direction (RD). It is discovered that the yield strength of re-compression is enhanced due to grain refinement by {10–12} tensile twins. Twinning activation and evolution are evidenced by electron backscatter diffraction. Correlations with grain orientation and boundary misorientation are observed in the region of twins that arise at grain boundaries. The distributions of grain boundary misorientation associated with twin nucleation are mapped. It is found that nucleation of twin is mainly controlled by the initial texture, and is more easy at low misorientation grain boundaries. The growth of twins depend on two modes: the thickening of the existing twin lamellae and new twins is nucleated at grain boundary. With increasing compressive strain, the growth and coalescence of twins eventually encompassed the whole grain. Meanwhile, the basal texture is weaker after compression due to the propagation and coalescence of tensile twins.

Cr-doped MnO2 nanostructure has been fabricated via a facile hydrothermal method and its morphology and electrochemical properties was discussed systematically. In this process, flower-like MnO2 transforms into the self-assembled orchid structure under the influence of Cr-doped. Moreover, electrochemical behaviors of the Cr-doped MnO2 nanostructure electrode were clarified by cyclic voltammograms, galvanostatic charge/discharge tests and electrochemical impedance spectroscopy, which shows a high specific capacitance of 202.5 F g−1 and superior cycling stability (6.8 % capacitance decay after 1000 cycling test). These remarkable and excellent results prove it has a great potential of application in future energy storage device.

Birnessite-type MnO 2 nanoflowers assembled by hierarchical nanosheets were successfully synthesized via a facile and simple hydrothermal process. The ration of reactants is a critical factor affects formation process of MnO 2 nanoflowers. The electrochemical test of the as-synthesized birnessite-type MnO 2 exhibits excellent electrochemical property with ideal voltammetry behavior, high specific capacitance (197.3 F g −1 at 1 A g −1 ) and superior cycling stability (only 5.4% capacitance loss after 1000 cycling test). The distinct hierarchical nanostructure and impressive electrochemical performances suggest the birnessite-type MnO 2 is a promising material for supercapacitor applications.

A tadpole-shape fiber sensor, with S-bend fiber cascading spherical shape, has been proposed and experimentally realized in this work. In our experiments, the output spectrum of the proposed sensor was found to be shifted with the changing of the refractive index and the temperature. Experiments results showed that the highest sensitivity of the refractive index was up to −114.845nm/RIU with a wide range from 1.347 to 1.458. Meanwhile, the temperature sensitivity of the sensor was measured to be 0.15nm/oC with the range from 20 oC to 80 oC. The proposed sensor has the merits of compactness, high sensitivity, wide sensing range and low-cost.

In this paper, a polarization maintaining fiber (PMF) is used as the sensing element for microfluidic velocity measurement. The proposed fiber microfluidic velocity sensor adopts the Sagnac loop structure, where the PMF is incorporated in the fiber loop. The microfluidic velocity measurement is realized by monitoring the output spectrum of the Sagnac loop. Different microfluidic velocity causes different pressure on the side of the PMF, which leads to the wavelength shift of the output spectrum of the Sagnac loop. Experimental results show that a quadratic relationship between the microfluidic velocity and the dip shift of the output spectrum has been observed with the microfluidic velocity range from 0∼900um/min. The proposed microfluidic velocity fiber sensor owns significant behavior in various applications such as chemical engineering and medical equipment technology.

In order to improving the sensing length of the Distributed Optical Fiber Temperature Testing System (DTS), a broadband pulsed source at 1.66um was proposed and demonstrated. A Raman frequency shifter, composed of a certain length single mode fiber (SMF) and a fiber band-pass filter was used as a key device to obtain the proposed light source. By changing the output power of the pump laser, the proposed broadband light source at 1.66um can be achieved with a bandwidth of ∼30nm, a pulse peak power of 18 W, pulse duration and repetition rate are, at all the same with the pump laser, 5ns∼1000ns and 1Hz∼100kHz respectively. In addition, relationships among output power of pump laser, fiber length in frequency shifter and output power at 1.66um were discussed. These characters facilitate a longer range DTS sensing with the spatial resolution maintaining.

A fiber sphere-embedded long-period fiber grating (LPFG) sensor has been proposed and fabricated for curvature measurement with high sensitivity. Compared with the normal LPFG, the embedded fiber sphere excites cladding modes and two dips of the output spectrum have been observed. The curvature measurement can be realized by monitoring the shift of the two dips. Experimental results show that the highest curvature sensitivity is up to −104.642 nm/m − 1 with the curvature ranging from 0 to 0.71 m − 1. The temperature response of the sensor has also been studied and a quadratic linear relationship between the dip shift and the temperature has been observed. The highest temperature sensitivity is 0.36 nm / ° C with the temperature range between 20°C and 90°C.