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Bi2Sr2Ca2Cu3O10+δ (Bi-2223) precursors for the fabrication of high temperature superconducting tapes were prepared by spray pyrolysis technique followed by a calcination process. The influences of precursor powder phase composition on the phase evolution dynamics and final current capacity of Bi-2223 superconducting tapes were systematically studied. It was interesting to notice that slight increase of Cu content in chemical composition could cause obvious variations of both the phase composition and the morphology of CuO particles in precursors. Therefore, the Bi-2223 phase formation process during the sintering process of tapes could be affected, and the current capacity changed accordingly. On the other hand, during the calcination temperature optimization process, the Bi-2223 phase content in precursors changed accordingly, thus the Bi-2223 phase formation dynamics were also studied. More Bi-2223 nuclei were formed due to the pre-existed Bi-2223 grains, which worked as inhomogeneous nuclei centers. Thus, although the final Bi-2223 phase contents were similar in all the tapes, the particle size and texture structure of Bi-2223 varied greatly, which caused a dramatic decrease of critical current in Bi-2223 tapes with the formation of Bi-2223 in precursors. Therefore, it could be concluded that both the morphology of CuO particles and the Bi-2223 phase content in precursors were the factors controlling the phase evolution dynamics during Bi-2223 tape sintering process.

FeSe superconducting bulks with different Fe contents were prepared by high energy ball milling aided sintering process followed by a post annealing process in low oxygen atmosphere. The influences of Fe content, annealing temperature and oxygen partial pressure have been systematically studied. It was found that both the critical temperature and superconducting phase volume ratio have been obviously improved with annealing. However, the effect of oxygen annealing process on FeSe polycrystalline bulks was different with that on FeSe single crystals. In polycrystalline bulks, the annealing process could further promote the phase transition from nonsuperconducting hexagonal δ-FeSe phase to superconducting tetragonal β-FeSe phase. Meanwhile, the chemical composition uniformity has also been enhanced with no obvious FeOδ phase detected by X-Ray Diffraction. With optimized annealing process under the oxygen partial pressure of 5% at 400 °C for 10 h, FeSe superconducting bulks have reached the critical temperature of 9.1 K.

Combined therapeutic strategies for bacterial infection have attracted worldwide attention owing to their faster and more effective therapy with fewer side effects compared with monotherapy. In this work, gold-platinum nanodots (AuPtNDs) are simply and quickly synthesized by a one-step method. They not only exhibit powerful peroxidase-like activity but also confer a higher affinity for hydrogen peroxide (H2O2), which is 3.4 times that of horseradish peroxidase. Under 808 nm laser irradiation, AuPtNDs also have excellent photothermal conversion efficiency (50.53%) and strong photothermal stability. Excitingly, they can combat bacterial infection through the combination of chemodynamic and photothermal therapy. In vitro antibacterial results show that the combined antibacterial strategy has a broad-spectrum antibacterial property against both Escherichia coli (Gram negative, 97.1%) and Staphylococcus aureus (Gram positive, 99.3%). Animal experiments further show that nanodots can effectively promote the healing of bacterial infection wounds. In addition, owing to good biocompatibility and low toxicity, they are hardly traceable in the main organs of mice, which indicates that they can be well excreted through metabolism. These results reveal the application potential of AuPtNDs as a simple and magic multifunctional nanoparticle in antibacterial therapy and open up new applications for clinical anti-infective therapy in the near future.

Fluorine doping Fe1.2Se polycrystalline were prepared by solid-state sintering method. The influences of fluorine doping content and sintering temperatures on phase composition, lattice parameters, microstructure as well as superconducting properties were discussed in detail. It was found that fluorine doping could effectively reduce the content of non-superconducting hexagonal δ-FeSe phase. Besides, the content of hexagonal δ-FeSe phase and grain size of superconducting tetragonal β-FeSe phase were decreased with the sintering temperature increasing. Scanning electron microscopes (SEM) images indicated that the morphology of β-FeSe phase was a typical lamellar structure with the small particles of hexagonal δ-FeSe phase. Meanwhile, a higher critical temperature Tc of 8.3 K and larger shield volume fraction were obtained with high sintering temperature of 950 °C and proper F doping content.

The Bi-2212 round wire has a multifilamentary structure, and the use of numerical method to study ac loss of such multifilamentary superconducting wire requires a long calculation time and large memory. Adopting a homogenization method at low frequency to study the ac loss of multifilamentary structural wire/tape has been proven to have high enough accuracy and can save a lot of calculation time. With the expansion of the application range of superconducting materials, however, superconducting power devices exceeding the frequency of tens of kHz have huge potential applications in the future such as wireless power transfer. Therefore, it is necessary to study the applicability of the homogenization model at high frequencies. This article mainly presents an ac loss numerical study of Bi-2212 round wire at wider frequency (50 Hz–500 kHz) by homogenization method. The homogenization is achieved by two different methods. The first method is to treat the superconducting bundle and the Ag matrix between the bundles as a superconducting domain (bundle-matrix homogenized model, BHM). The second method is to regard the Ag matrix between the superconducting filaments and the filaments as a superconducting domain (filament-matrix homogenized model, FHM). In order to evaluate the feasibility of the two different homogenization methods, we compare the calculation results of the two different homogenization models with the original model, OM. The results show that the FHM can effectively improve the calculation speed while satisfying the high calculation accuracy. This conclusion can be used to quickly evaluate the ac energy loss of large-scale superconducting devices at wider frequencies.

To realize the high-efficiency acquisition of environmental mechanical energy, traditional triboelectric nanogenerators (TENGs) based on contact-separation consist of two separate triboelectric layers. Their large contact-separation gap increases the overall volume of the device, making it difficult to realize miniaturization and flexibility. This work, therefore, presents a fully enclosed all-in-one-shaped flexible TENG (FEAST) with an air cavity using rubber mixing and high-temperature vulcanization. The air pressure inside the enclosed air cavity facilitates effective contact-separation of the FEAST. The homogeneous integration between the triboelectric layer and the electrode layer enhances structural firmness without using extra spacer materials. The developed FEAST presents excellent mechanical durability even after 10000 cycles. By increasing the active contact area between the triboelectric materials, a maximum peak-peak output voltage, current, and power density of 130 V, 1.1 µA, and 277 mW/m2, respectively, were obtained with an effective stress area of 1 cm2. Moreover, the fully enclosed structure ensures that the output performance is not affected by the external environment. The FEAST was fixed onto the sole of a shoe to demonstrate its applicability in harvesting mechanical energy from human motions. Overall, the developed method provides a simple approach for optimizing the structure of TENGs and is compatible with large-scale manufacturing.

Bi2Sr2CaCu2O8+δ (Bi-2212)/Ag round wires were fabricated by imposing ultrasonic-vibration drawing (UVD) technique during both the single-filament and multi-filament cold-drawing processes. The frequency of ultrasonic-vibration was set fixed at 20 kHz and different output power density levels had been altered by varied amplitudes. The influence of ultrasonic-vibration on the deformation process of Ag metal sheath, filament density, Ag/superconductor ratio, wire dimension, drawing force reduction, and the superconducting properties of final wires has been systematically studied. Softening effect of ultrasonic-vibration on the Ag metal can be deduced with the decreasing drawing flow stress and drawing force under certain amplitude. It was found that powder densification could be promoted and higher filament volume fraction as well as high wire diameter uniformity had been reached with the introduction of UVD process, leading to the enhancement of Jc and JE after proper heat treatment. Such technique could be considered in fabrication of Bi-2212 long wires as well as other superconducting materials.

A nanocomposite pour point depressant (NPPD), as a new type of wax additive or flow improver for waxy oil, has raised wide attention. Recent advances have been made in the modification of the cryst...

Organic conjugated carbonyl materials have attracted considerable attention in the field of high-capacity and green energy storage technologies. However, the high solubility in organic electrolyte restrains their further application. In this work, an organic terephthalate compound (Li

Purpose The purpose of this paper is to establish a transient contact position prediction method of gears at the meshing point based on the equivalent contact model. Design/methodology/approach In this method, the contacting surface profiles are constantly updated by changing the pressure angle and the chord tooth thickness, which has a direct connection with the equivalent base circle radius. According to the equivalent base circle radius, the equivalent pressure angle at the pitch circle and equivalent pitch point can be calculated. The equivalent contacting surface profile is determined by the equivalent pressure angle at the pitch circle; for each meshing point, there is one equivalent pressure angle at the pitch circle. Therefore, each meshing point can be regarded as a point on the equivalent contacting surface profile. Findings The model is applicable to find out the contact position after a series of meshing cycles through the law of pressure angle change and intentionally kept as simple as possible with the aim to be used in further study of gear flanks at the point of the actual contact. Practical implications The results of the experiment are applied to the equivalent contact model to describe the transient contact position and assess the model accuracy. Originality/value The determination of the contact position of the worn tooth profile provides the action points of the force for the study of the contact fatigue.

Precursor powders of Bi2Sr2Ca2Cu3O10+δ (Bi-2223) high temperature superconducting tapes were prepared with spray pyrolysis technique. By tuning the oxygen partial pressure in calcination atmosphere as 1.0%, 7.5%, and 10.0%, respectively, the influences of calcination atmosphere on the phase evolution dynamics during the precursor powders calcination process have been discussed. Then the optimal calcination temperatures have been obtained correspondingly. Moreover, Bi-2223 multi-filament tapes have been fabricated with the precursor powders calcinated under different atmosphere. The effects of precursor powder calcination parameters on the phase composition, microstructures as well as the current capacity of final tapes have been systematically studied. Due to the proper secondary phase content and enhanced Bi-2223 texture structures, the maximum critical current of 109 A at 77 K, self-field, corresponding to the critical current density of 23.3 kA cm−2 has been obtained with the oxygen partial pressure of 7.5% in calcination atmosphere and the calcination temperature of 790 °C.

The interplay between excitons and point defects in semiconductors play a critical role in optical and optoelectronics properties, especially within the reduced dimensional system. Recently, it has...

Bi 1.76 Pb 0.34 Sr 1.93 Ca 2.02 Cu 3.06 O 10+δ (Bi-2223) high temperature superconducting tapes were fabricated with Powder in tube (PIT) process. The traditional drawing process was partially replaced by groove rolling. The influence of cold working method on the filament density, the phase evolution mechanism as well as superconducting properties has been systematically studied. The groove rolling process could obviously enhance the filament density of Bi-2223 green wires, which thus led to the change of Bi-2223 formation rate. Meanwhile, although the heat treatment process has not been thoroughly optimized, the residual secondary phase content was still high, the critical current has been improved for more than 20% with groove rolling process, which should be attributed to the improved intergrain connections. On the other hand, the groove rolling process was also effective on the fabrication of Bi-2223 tapes with larger filament number, such as 85 or 121 to maintain the uniformity of filament deformation.

Multifilamentary Bi2Sr2Ca2Cu3O10+δ (Bi-2223) high temperature superconducting tapes were fabricated by powder-in-tube process. During the precursor powder packing process, environment atmosphere was changed from pure oxygen to dry air and 7.5% O2 balanced with N2, with the oxygen partial pressure decreasing from 100% to 25% and 7.5%, respectively. The change of packing atmosphere obviously influenced the phase assemblage in the early stage of Bi-2223 phase formation process. Therefore, the chemical composition of obtained Bi-2223 phase as well as the content and distribution of secondary phases changed accordingly. Meanwhile, the changes of intergrain connections and the flux pinning properties were investigated based on the in-field critical current, $I_{c}$ – B measurements. Finally, attributed to the decreased oxygen partial pressure in packing atmosphere, the $I_{c}$ improvements of 25% at self-field and 0.6 T were obtained comparing with the tapes packed under pure oxygen. With further optimization of sintering process, the final $I_{c}$ of 116 A was achieved, which corresponded to the critical current density, $J_{c}$ of ∼21 kAcm−2.

In addition to having significant effects on the service life of machined parts, residual stress can cause large deformations during machining of thin-walled parts in aerospace field. The residual stress in machined part surface layer is induced by mechanical and thermal stress in the machining process of parts. Therefore, it is essential to accurately predict the generated residual stress due to the machining process. To address this issue, an improved prediction model of the residual stress for orthogonal cutting process based on analytical method is presented by taking the mechanical and thermal stress into consideration. Oxley’s cutting force model and Waldorf’s plowing force model are used to calculate the chip formation force and plowing force based on the contact mechanics, Johnson-Cook constitutive model, and slip line theory. The cutting temperature is predicted according to our previous work based on the Huang-Liang model and the Komanduri-Hou model. The final residual stress is predicted by calculating the loading and relaxation of mechanical and thermal stress. The presented prediction method of residual stress is validated by orthogonal cutting of a Ti6Al4V pipe. It is found that the prediction values of the presented model show a good agreement with the experimental results, which indicates that the presented model can be adopted to predict the residual stress of Ti6Al4V during orthogonal cutting.

Superionic thermoelectric Cu2Se bulks are successfully acquired via an identical gas reinforced eutectic transformation (gasar) process based on its melting-congruent nature. The gasar synthesis process introduces tubular pores to Cu2Se matrix, which have hierarchical size and corrugated surface, and are distributed homogeneously and isotopically. The Cu2Se bulk with such a unique porous structure shows enhanced thermoelectric figure-of-merit up to ∼2.1 at 873 K owing to the conspicuously reduced thermal conductivity, which can be attributed to the increased phonon scattering. Moreover, the porous Cu2Se bulk also possesses higher mechanical robustness compared with traditional porous-structured material because of the corrugated surface, which is promising for making thermoelectric modules.

During the sintering process of Ag-alloy sheathed Bi-2223 tapes, post-annealing (PA) played an important role on the final current capacity by forming a Pb-rich phase named (Pb,Bi)3Sr2Ca2CuOx (3221) and healing the cracks. Due to the different oxygen penetration rate between AgAu alloy and pure Ag, which is traditionally used in other Bi-2223 tapes, the influence of PA parameters on the 3221 phase content, microstructures, and current capacity of AgAu tapes should be systematically studied. In this study, PA processes with different temperatures of 770–800 °C have been performed on fully reacted 37-filamentary (Bi, Pb)-2223/AgAu tapes in the atmosphere of 7.5% O2 balanced with Ar. It is found that the 3221 phase appeared after PA with its amount first increasing then decreasing with increasing PA temperature. The critical temperature Tc and peak temperature (Tp) obtained with AC susceptibility measurement both increased with increasing PA temperature, and reached the maximum value at 780 °C then decreased with increasing PA temperature. Due to the improvement of Tc and intergrain connectivity, the critical current density (Jc) increased by 24% after PA at 780 °C. Meanwhile, the 3221 phase formation mechanism has also been systematically discussed by varying the amount of remnant liquid in tapes in HT1 process.

In this work, we demonstrated the growth of high-quality GaN epilayers and InGaN/GaN multiple quantum wells (MQWs) with 400 nm emission on a (100) β-Ga2O3 substrate. The dislocation density of GaN epilayers may be obviously reduced by pulsed-growth, attributed to the enhanced three-dimensional to two-dimensional transformation process. A three-stage growth model had been proposed to clarify the underlying mechanism. Furthermore, pulsed-flow growth also enabled the relatively low-stress state (0.12 GPa) of GaN on (100) β-Ga2O3. Due to the decreased quantum confined Stark effect (QCSE), the MQWs on pulsed-GaN exhibited a lower blue-shift with increased excitation power densities and showed an increased recombination rate. Additionally, a tendency for GaN separation was also observed, beneficial to heat dissipation of devices on (100) β-Ga2O3. This work may provide a prospective way to fabricate high-performance vertical structure ultraviolet light emitting diodes (LEDs) on (100) β-Ga2O3 substrates.

This paper focuses on strong magneto-optical thin films that closely match a Si substrate. The orthorhombic perovskite crystal structure of CeFeO3 was optimized to a cubic perovskite structure by introducing strontium and vanadium ions into lattice. The cubic Ce1-xSrxFe1-xVxO3 (x = 0.3, 0.5, 0.7) thin films with high quality and high growth orientation were prepared on a Si substrate by using the RF magnetron sputtering method. Moreover, the birefringence effect, which may weaken the magneto-optical effect, should not occur in the cubic thin film. The calculation results based on density functional theory show that the increased electronic transition probability is attributed to the strong spin-coupling between the hybrid Ce3+ 4f and Fe3+/V4+ 3d states. The magnetic circular dichroism ellipticity |ΨF| of the Ce0.7Sr0.3Fe0.7V0.3O3 thin film is up to 4300 deg. cm-1, which indicates a strong magneto-optical effect. Therefore, the cubic Ce1-xSrxFe1-xVxO3/Si film with high Ce3+ concentration is expected to be a new candidate for integrated magneto-optical devices.

Crystalline defects can modify quantum interactions in solids, causing unintuitive, even favourable, properties such as quantum Hall effect or superconducting vortex pinning. Here we present another example of this notion - an unexpected unidirectional Kondo scattering in single crystals of 2H-NbS2. This manifests as a pronounced low-temperature enhancement in the out-of-plane resistivity and thermopower below 40 K, hidden for the in-plane charge transport. The anomaly can be suppressed by the c-axis-oriented magnetic field, but is unaffected by field applied along the planes. The magnetic moments originate from layers of 1T-NbS2, which inevitably form during the growth, undergoing a charge-density-wave reconstruction with each superlattice cell (David-star-shaped cluster of Nb atoms) hosting a localised spin. Our results demonstrate the unique and highly anisotropic response of a spontaneously formed Kondo lattice heterostructure, intercalated in a layered conductor., 44 pages, including the article, 5 figures, and Supplementary Information (6 notes, 9 figures, and 1 table)

We have fabricated a tubular whispering gallery mode laser based on InGaN/GaN quantum wells and transferred it onto a flexible substrate. Compared with those without the transferring processes, the threshold energy density was reduced by 60%, at about 25.55 µJ/cm2, while a high-quality factor of &gt, 15,000 was obtained. Finite-difference time-domain simulation demonstrated that such a low threshold energy density can be attributed to the decreased mode volume, from 1.32 × 10−3 μm3 to 6.92 × 10−4 μm3. The wavelength dependences on strain were found to be 5.83 nm, 1.38 nm, and 2.39 nm per stretching unit ε in the X, Y, and Z directions, respectively. Such strain sensitivity was attributed to the deformation of the GaN microtube and the change in the refractive index of the PDMS.

As a promising alternative to lithium-ion batteries (LIBs), the state-of-art potassium-ion batteries (PIBs) are attracting increasing attentions owing to the abundance and low cost of potassium. However, development of practical electrode materials for PIBs is still in its early stage and the related mechanisms are still unclear. In this work, hierarchically porous carbon supported Sn4P3@C composite prepared through a low temperature solvothermal method is firstly reported as anode material for PIBs. The electrode delivers a high discharge capacity of 473.3 mAh g−1 at 50 mA g−1 and superior rate capability of 183.6 mAh g−1 at 2.0 A g−1, surpassing most of the reported anode materials. Besides, the Sn4P3@C electrode can maintain a high reversible capacity of 181.5 mAh g−1 after 800 cycles at a high current density of 500 mA g−1. Moreover, in-depth characterizations such as GITT (Galvanostatic Intermittent Titration Technique), ex-situ XRD/HRTEM and consecutive CV (Cyclic Voltammetry) measurements are conducted to reveal the mechanisms involved in the potassiation/de-potassiation repeats.

A Weibull liner parallel bond model (WLPBM) implemented into the two-dimensional particle flow code (PFC2D) is proposed to simulate the mechanical properties of heterogeneous rocks. A continuous parameter calibration strategy associated with the Hoek–Brown strength criterion is performed to determine a series of micro-contact parameters matched with the macro responses observed in laboratory experiments (e.g., uniaxial compression test, direct tension test, and the biaxial compression test). The stress–strain responses, strength characteristics as well as the failure modes under the uniaxial and biaxial compression test are modeled and discussed detailly. The simulation results indicate that the proposed WLPBM provides a promising approach for efficiently studying nonlinear mechanical behaviors, strength characteristics and the corresponding failure modes.

The results of structure and phase composition change in tungsten after compression plasma flow and high-intensive pulsed ion beams impacts are discussed. The compression plasma flows with the absorbed energy in range 35–70 J/cm2 were used for the sub-surface modification. The preliminary Ti coating deposition on the tungsten surface allowed us to form W-Ti alloys by plasma flows treatment. The layer of the W-Ti alloy consists of solid solutions W(Ti) and β-Ti(W) as well as nitride phase (Ti,W)N. The high-intensive pulsed ion beam impact provides the tungsten carbide W2C formation in the sub-surface layer. When forming the W-Ti alloy the carbon ions implanted into the tungsten take part in the carbo-nitride (Ti,W)(N,C) formation without brittle W2C phase.

Fluorine-doped Fe(Se, Te) has been successfully synthesized using the melting method. A dual-oscillation effect was found in the F-doped sample, which combined both microstructural oscillation and chemical compositional oscillation. The microstructural oscillation could be attributed to alternate growth of tetragonal β-Fe(Se, Te) and hexagonal δ-Fe(Se, Te), which formed a pearlite-like structure and led to the enhancement of δ l flux pinning due to the alternating distributed nonsuperconducting δ-Fe(Se, Te) phase. The chemical compositional oscillations in β-Fe(Se, Te) phase were because of the inhomogeneously distributed Se and Te, which changes the pinning mechanism from surface pinning in the undoped sample to Δκ pinning in the 5% F-doped one. As a result, the critical current, upper critical field, and thermally activated flux-flow activation energy of FeSe0.45Te0.5F0.05 were enhanced by 7, 2, and 3 times, respectively. Our work revealed the physical insights into F-doping resulting in high-performance Fe(Se, Te) superconductors and inspired a new approach to optimize superconductivities in iron-based superconductors through phase and element manipulations.

Two series of benzoxazines are synthesized from a set of isomeric monofluorophenols (o-, m-, and p-fluorophenols), two polyetheramines (Jeffamine D230 and D400), and formaldehyde. The chemical structures of the benzoxazines are confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy. For m-fluorophenol-based benzoxazines, the two sets of data appeared in the 13C, DEPT-135, and 19F NMR spectra indicate that each product obtained is a mixture of two isomers. The ring-opening polymerization temperatures for ortho, meta, and para isomers in the two series of benzoxazines are in descending order para > ortho > meta. The glass transition temperatures (Tgs) of the resultant polybenzoxazines are in ascending order ortho

Oxygen partial pressure was the key factor to tune the phase evolution mechanism of Bi-2223 system. In order to investigate the influence of packing atmosphere on the phase formation rate of Bi-2223, microstructures‚ and the current capacity of final tapes‚ 37-filamentary Bi-2223/AgAu tapes were fabricated by powder-in-tube (PIT) process, and the powder packing process operated in the glove box under different atmosphere of pure O2‚ air, and N2–7.5%O2, with the oxygen partial pressure of 100%‚ 25%, and 7.5%, respectively. With different packing atmosphere, the phase formation rate of Bi-2223 increased obviously during the first heat treatment process (HT1). While, based on the same HT1 process, the maximum Bi-2223 phase content was obtained in the tapes with packing atmosphere of N2–7.5%O2‚ which should be attributed to the suitable Bi-2223 content and distribution. Due to the improvement of superconducting phase content and better texture structure, the critical current density increased with decreasing oxygen partial pressure of packing atmosphere and the maximum value of 19.9 kA/cm2 was reached. Moreover‚ the in-field current capacities of these Bi-2223/AgAu tapes have also been enhanced with low oxygen partial pressure in packing atmosphere, attributed to the improvements of intergrain connectivity.

Polycrystalline bulks Bi2.1Sr1.96CaKxCu2.0O8+δ + yAg (Bi-2212) with different K incorporation content of x = 0, 0.02, 0.05 and 0.10 and addition of Ag nanoparticles with weight ratio of y = 0.10 wt% were fabricated by a hot-pressing (HP) process. The influences of K+ ions and Ag nanoparticles on the lattice parameters, phase composition, microstructures and related superconducting properties were systematically investigated. The introductions of K+ and Ag both obviously affected the thermodynamic parameters of Bi-2212 system. Accordingly the sintering temperature during HP process changed dramatically. After the HP process, increases of average grain size were obtained with Ag incorporation, based on both XRD and SEM analysis, which implied the formation of better texture alignment structure. Slight decrease of critical temperature was observed corresponding to the changing valence of Cu2+ ions on superconducting layer. Increase of superconducting phase volume was achieved on the K and Ag co-incorporated bulk. And the enhancement of current capacity was also achieved on the very same sample, under the magnetic field higher than 1 T. The different flux pinning mechanism between K and K/Ag incorporated sample from point pinning to surface pinning could be related to the microstructure change, which can be recognized as a solid evidence for the different effects of K and Ag.

The Fe 1.1 Se 0.5 Te 0.5 polycrystalline superconductors were prepared by a high-energy ball-milling (HEBM) technique. Ball-milling times of 0, 2, 4, 6, and 8 h were adopted to optimize this technique. The influences of ball-milling time on the phase distributions of milled powders and sintered bulks, the morphology of ball-milled powders, and superconducting properties of final sintered bulks were systematically studied. It was found that with increasing ball-milling time, the ball-milled powders changed from a crystal to a noncrystalline and then to an alloy. At the same time, the main phases in ball-milled powders changed from original mixed powders of Fe, Se, and Te to (Se, Te) solid solution, and then to the two phases of β-Fe(Se, Te) and δ -Fe(Se, Te), accordingly. Due to the reduction in diffusion length, it was more likely for HEBM powders to form FeSeTe ternary alloys. Thus, the obtained Fe(Se, Te) bulk with HEBM time of 4 h exhibited the highest T c of 14.3 K and the largest content of superconducting phase. However, in the samples achieved by longer HEBM time, phase segregation and oxidation were observed. Therefore, the HEBM time of 4 h is the most suitable for the fabrication of high-quality precursor powders according to these experiments.

Bacterial infection is a common phenomenon in the process of postoperative wound healing. In severe cases, it may even lead to life-threatening, which brings a heavy burden to the clinical treatment and causes huge losses to the society and economy. As one of the most commonly applied medical materials for wound treatment, hydrogel dressings are mainly used to cover and protect wounds and provide a favorable environment to facilitate wound healing. In this work, we developed an antibacterial hydrogel dressing (Fc-PAAM) with high adhesion, which is consisted of polyacrylamide (PAM) hydrogel framework and polyacrylic acid-functionalized (PAA) with ferrocene (Fc). Morphology, adhesion and pressure resistance of PAAM hydrogel were confirmed by using scanning electron microscope (SEM) and universal testing machine, and Fc decoration in the hydrogel network was well demonstrated by using Fourier transform infrared spectroscopy (FT-IR). Ultraviolet-visible spectroscopy (UV-vis) displayed that the Fc-PAAM hydrogel had excellent peroxidase-like activity as well. It not only exhibited prominent antimicrobial activity against Gram (+/-) bacteria, but also performed high efficiency in preventing the formation of biofilms. In addition, in vivo experiments indicated that this adhesive dressing could significantly prevent bacterial infections. Compared with other clinical treatment methods, this kind of hydrogel is not easy to cause bacterial resistance, and the used raw materials are easy to obtain and low in price, which can amplify the antibacterial properties of H2O2 and provide a new opportunity for the treatment of clinical bacterial infections.

Triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) present excellent performances in harvesting multivariant mechanical energy. However, the conductivity of electrode has become one of the important factors restricting the mechanical energy acquisition under the large deformation and multiple freedom degrees. In this work, a highly conductive stretchable electrode based piezoelectric-enhanced triboelectric nanogenerator (P-TENG) with outstanding performance is reported. Ultra-flexible silicone rubber based triboelectric part with surface modification and piezoelectric part with BaTiO3 dispersed possess excellent electrical and mechanical property, at the same time, the stretchable electrode based on liquid metal could maintain low resistance even under large deformation. The peak to peak open-circuit voltage (VOC) and short-circuit current (ISC) of P-TENG could reach 1.38 kV and 36.13 μA, respectively. The instantaneous power density can reach 1.1 mW/cm2 and the charge quantity in single capacitor charging circle is approximately 0.30 μC. It also has the surpassing force-electrical linearity that the output voltage positively correlating to stretching speeds and stretching rates. The resistance increments of electrode below 0.32 Ω under stretching rate more than 200% and the percentage of breaking elongation could reach 645%. In applying experiments, the P-TENG could directly light 16 LEDs and effectively identify the motion signals. This work provides a new thought for nanogenerator (NG) with high stretchability and applied to collect irregular mechanical energy.

We experimentally observed the resolved Zeeman spectroscopy of the ${}^{3}{\mathrm{P}_{0^{-}}}^{3}\mathrm{D}_{1}$ transition using the cold 88Sr atoms, and measured the Lande $g$ factor of 3D 1 on the basis of the observable spectroscopy under different magnetic fields, which indicates the measured value is 0.4997(91) in good agreement with the calculated value of 0.4988. The detailed experimental scheme is presented here. Benefitting from the scheme, Sr atoms can be trapped in a mageto-optical trap (MOT) at a low temperature and a high density. The measurement of g J of 3D 1 is beneficial to investigate the long range dipolar interaction on the ${}^{3}{\mathrm{P}_{0^{-}}}^{3}\mathrm{D}_{1}$ transition of 88Sr.

To reduce the threshold and achieve unidirectional lasing emission in a whispering gallery mode microcavity, we propose and demonstrate a GaN-based eccentric microring with an inner hole located off the center. Compared to microdisk with the same outer diameter, the eccentric microring structure exhibits a remarkable reduction of lasing threshold by up to 53%. The introduction of the hole disturbs and eventually suppresses the field distribution of the higher order modes. Laser emission with high unidirectionality with a far-field divergence angle of about 40° has been achieved, meanwhile the Q factor of the whispering gallery modesis remains high as 6388. Finite-difference time-domain numerical simulation is carried out to prove that the far-field profile of the eccentric microring structure can be controlled by the position and the size of the hole. The properties of the whispering gallery mode microcavities are improved greatly through a simple structure and process, which has an important guiding significance to the research and development of the microcavity lasers.

We report recent progress in sub-kHz-linewidth operation of AlGaInP-based SDL systems designed for neutral Strontium optical clocks. Overall system performance is presented, including intensity, frequency and phase noise characterisation. Two almost identical SDLs, each with >150 mW output at 689 nm, were frequency locked and an optical beat note measurement produced a linewidth of 160 Hz with fractional frequency stability reaching below 2×〖10〗^(-15) for averaging times from 60-400 s. Spectroscopic measurements of a blue magneto-optical trap (MOT) of Strontium with one SDL resulted in a reduction of the atomic sample fluorescence and revealed Zeeman splitting of the 3P1 electronic level.

Phase offset locking between two 689 nm diode lasers is performed. The frequency variation of the beat note is suppressed within 0.2 Hz when it’s offset locked, which is approximately 8 orders of magnitude smaller than that of free running case. The phase noise within 400 kHz has been reduced with a maximum value of 30 dB at 100 Hz. The locked laser has been successfully applied for the red MOT of Sr.

Over the past decades, investigations of the anomalous low-energy electronic properties of ZrTe$_5$ have reached a wide array of conclusions. An open question is the growth method's impact on the stoichiometry of ZrTe$_5$ samples, especially given the very small density of states near its chemical potential. Here we report on high resolution scanning tunneling microscopy and spectroscopy measurements performed on samples grown via different methods. Using density functional theory calculations, we identify the most prevalent types of atomic defects on the surface of ZrTe$_5$, namely Te vacancies and intercalated Zr atoms. Finally, we precisely quantify their density and outline their role as ionized defects in the anomalous resistivity of this material., Comment: 12 pages, 10 figures; Accepted for publication in Physical Review Materials

A novel micro-mechanical modeling approach is developed to predict the partially debonding of a Z-pin reinforced composite laminates after the cure process. Cohesive zone model (CZM) is employed to represent the interphase between Z-pin and resin. The quadratic stress criterion and the Benzeggagh-Kenane propagation criterion are coupled to determine the failure mechanism of the interphase. Numerical simulation results indicate that residual stress concentration mainly occurs in the interphase due to thermal expansion and chemical shrinkage mismatch between Z-pin and resin regions. The ultimate residual stresses could result in the interfacial cracking around the Z-pin which coincides well with the microstructural investigations. Furthermore, the influences of curing parameters on the residual stresses and cracking area are both discussed.

Owing to their excellent high-temperature resistance, Carbon/Carbon (C/C) composites have broad application prospects in the aerospace and nuclear thermostructure fields. However, their anisotropic nature makes it difficult to guarantee their surface quality during cutting. Therefore, a detailed understanding of the cutting process is required. This study adopts a macro-orthogonal cutting model of unidirectional C/C (UD-C/C) composites to investigate their cutting forces and cutting defects using the finite element method. First, the nonlinear stress–strain relationship of the UD-C/C composites is determined by considering the fibre orientations in tension, compression, and shear experiments. Second, based on the Jones–Nelson theory, an improved constitutive model that accounts for different moduli in tension and compression is established through a weighted compliance matrix (WCM). Third, a macro-mechanical finite element (FE) model of the orthogonal cutting of the UD-C/C composites is developed based on the Jones–Nelson theory and Hashin–Chang failure criteria. The simulated cutting forces show good agreement with the experimental results for different fibre orientations (0°, 45°, and 90°).

Ge50-xSb x Te50 and Ge50-xBi x Te50 ternary alloys were synthesized by vacuum melting at 1273 K with the starting materials of Ge, Bi, Sb, and Te. The lattice structures were analyzed based on X-ray diffraction patterns, which could all be indexed to R3m rhombic structure. Electrical properties measurements revealed that the Ge-Sb-Te ternary alloys were p-type semiconductors with high electrical conductivity of 4.5×105 S∙m-1 near room temperature. And the maximum electrical property was obtained at Ge45Sb5Te50, with the power factor of 2.49×10-3 W∙m-1K-2 at 640 K. Due to the existence of secondary phases, the electrical conductivity of Ge-Bi-Te system was lower and Seebeck coefficient was higher comparing with those of Ge-Sb-Te system.

The voids in Bi2Sr2CaCu2Ox (Bi-2212) long-length wire should be eliminated as far as possible in order to improve its current-carrying capacity. There are several reasons for the void formation in Bi-2212 wire, mainly including the gas adsorbed on powder and existed in the gaps among the powder particles. We have found that the high-temperature vacuum degassing, which can eliminate the gases in wire and suppress the void formation, is an effective method to manufacture the Bi-2212 long wire with high-performance. Moreover, the high-temperature vacuum degassing is beneficial for the arrangement of Bi-2212 grains and the improvement of the texture of filaments. The engineering critical current density (Je) of Bi-2212 wire made by this method reaches to 440 A/mm2 at 4.2 K and 5 T.

Ag-sheathed Fe1.05Se superconducting wires were fabricated with ex-situ powder in tube (PIT) process. Fe and Se powders with molar ratio of 1.05 were firstly mixed and sintered under 600 °C for 12 h to form precursor powders. Owing to the complex Fe–Se binary phase diagram, both superconducting tetragonal FeSe and non-superconducting hexagonal FeSe could be formed simultaneously during sintering. Aiming at the reduction of hexagonal FeSe phase content and higher superconducting phase volume, the influences of key parameters, including sintering time, cooling rate and heating rate, on the phase composition of sintered wires were systematically studied. Optimal sintering parameters are obtained, and the maximum tetragonal FeSe phase content of ~ 97% is achieved. Meanwhile, the effects of packing density of precursor powders on the phase composition of final wires were also discussed. Owing to the shorter length of diffusion path, more tetragonal FeSe was formed with higher packing density. The superconducting transition signal with critical temperature of ~ 7.5 K was obtained, which proved the effectiveness of our optimal sintering process.

Thirty-seven-filamentary AgAu-sheathed Bi-2223 tapes were fabricated by a powder-in-tube (PIT) process. And, the round wires (ϕ 1.86 mm) were rolled to 0.35-mm tapes with 12, 7, 5, and 4 rolling passes through flat rolling, respectively. The influences of different rolling passes on the core density, deformation, and transport properties of Bi-2223/AgAu tapes were systematically investigated. It was noticed that after rolling, the Vickers microhardness of the superconducting core and deform homogeneity along both the horizontal and vertical directions on the cross section of seven-pass rolled tape were better than those on the tapes with other passes, which proved the larger core density and uniform deformation with the seven-pass rolling process. Meanwhile for the wires with 12 and 7 passes, the AgAu/superconducting core interfaces were much flatter. With the rolling passes decreasing from 12 to 4, the critical current density (Jc) first increased and then decreased. Due to the better homogeneity and flatter interfaces, Jc reached the maximum value of 17.3 kA/cm2 on the seven-pass sample. Meanwhile, the enhancement of current capacities in magnetic field applied parallel to the Bi-2223/AgAu tape surface could also be recognized as the evidence of improving intergrain connections due to the higher density in seven-pass rolled tapes.

FeSe superconducting tapes with different sheath materials of Nb/Cu composite, Ag, and Fe have been fabricated with a traditional in situ powder-in-tube (PIT) process, respectively. With the same cold working process and heat treatment, the influences of different sheath materials on the phase composition and microstructures of FeSe filaments have been analyzed. Due to the reaction between Nb-Se and Ag-Se, Nb2Se and Ag2Se particles can be clearly observed embedded in the filaments. Therefore, it is necessary to introduce a new method for the fabrication of Ag or Nb sheath FeSe wires in order to avoid the introduction of metal Fe in magnet system during practical applications. Based on our previous study, a high-energy ball milling process has been performed to achieve precursor powders with amorphous FeSe binary compound instead of elemental Se. The formation of Ag-Se compounds has been successfully avoided and the superconducting tapes with high superconducting FeSe critical temperature of 9.0 K have been obtained.

Ion doping technology with precise control of doping concentration and configuration can optimize the performance of β-phase gallium oxide (β-Ga2O3) high-power electronic and optoelectronic devices. In this work, shallow-donor Si and deep-acceptor Mg impurities are doped in β-Ga2O3 separately using edge-defined film-fed growth (EFG) method. Laser scanning confocal microscopy and X-ray diffraction analyses show that the as-grown un/Si/Mg-doped β-Ga2O3 substrates have superior qualities such as smooth surface, homogenous phase, and high crystallinity. Raman spectroscopy analysis indicate that the Raman shift and full width at half-maximum (FWHM) has a linear relationship with temperature in the range of 77–297 K. The temperature-variable photoluminescence (PL) spectroscopy suggests that the Si doping introduces less damage to the β-Ga2O3 lattice structure and the Si-doped sample has higher stability at different temperatures, however, the local atomic configurations of Mg impurities can be more easily/significantly affected by temperature. The work can offer an insightful reference to applications of ion-doped β-Ga2O3 optoelectronic devices.

A Schottky barrier diode solar-blind photodetector was fabricated on single crystal β -Ga2O3. Optoelectronic tests at 254 nm have shown that the detector has the maximum ratio (nearly 1 × 104) of light to dark current at zero voltage bias, indicating that the detector can work without any external energy (self-powered action). A fast response speed of the detector has also been found, while the rise and decay time are only 65 ms and 15 ms at self-powered mode, respectively. With increasing the illumination intensity, the photocurrent of the device is enhanced linearly, maintaining the fast response speed. Under a large fixed bias, the photoresponse time turns to be longer comparing with that at zero voltage, which can be attributed to the electrons and holes captured by the oxygen vacancies being released gradually under an applied bias. In addition, the mechanism of this self-powered photodetector has been explained by understanding the motion of photo-generated carrier.

The wear and contact fatigue of involute modified gears under minimum quantity lubrication were investigated through updated contact path and measurement of the updated profiles. The results indicated that the wear depth of pitch line was not the minimum, there was relative sliding on the pitch line during the wear process and the surface damage had a great influence on it. Continuous wear moves the point of minimum sliding in direction of the addendum/dedendum and the wear minimum is at the point with minimum sliding. Due to repeated contact occurred on the tooth surface near the root of wheel, the maximum wear depth of wheel was at a position between the dedendum and the pitch line, and its surface roughness was the lowest.

Final heat treatment involving partial melting and recrystallization under a high pressure of 50–100 bar is not conducive to the preparation of Bi2Sr2CaCu2O x (Bi2212) magnets; it also greatly increases the cost of research into Bi2212 wires. To solve these problems, in this work a final heat treatment under 10 bar was used to prepare Bi2212 wires with a high bulk density and high critical current density (J c). The ambient pressure of the final heat treatment in this paper is only one-fifth of that of the traditional overpressure for final heat treatment of Bi2212 wires. The J c of the wires is more than 2.4 times higher than that of Bi2212 wires with a final heat treatment at 1 bar and is consistent with that of samples having a final heat treatment at the traditional 50–100 bar. The reason why the ambient pressure of the final heat treatment can be greatly reduced in this work is: (a) vacuum degassing of the precursor powder eliminated the adsorption and interstitial impurity gases in the long Bi2212 wires, and reduced the internal gas pressure of the wires; (b) pre-treatment at 800 °C and 250 bar compressed the Bi2212 wires to their full density. Thus, during the subsequent final heat treatment, the low ambient pressure of 10 bar can overcome the difference between the residual gas pressure inside the wires and the yield strength or creep strength of the Ag sheath, and prevent expansion of the internal gas in the wires, so that the Bi2212 wires are always close to full density. The ambient pressure of the final heat treatment in this paper needs to prevent the expansion of the Bi2212 wires not compress them, so the pressure can be very low. The 10 bar low pressure final heat treatment will solve the problems of the high cost of research into Bi2212 wires and the difficult overpressure heat treatment of Bi2212 magnets.

In this work, the microstructure evolution and slip mechanism of TC21 titanium alloy in grind hardening (GH) and grind hardening and aging treatment (GHAG) were comparatively investigated. The experimental results showed that the hardened layer formed in both GH and GHAG is mainly composed of TiN, while their internal microstructure is quite different. Compared with as-received alloy, the tensile strength and elongation after GH process increased by 110 MPa and 1.5%, respectively. The tensile strength after GH process increased by 50 MPa but the elongation decreased by 0.2%. Moreover, A method to deduce slip systems by using interior crystall misorientation axis (ICMA) was demonstrated in this paper. The distribution of ICMA indicated that three major slip systems were activated which was verified by texture components in ODF sections. The slipping results in two kinds of crystal orientation distribution: (a) the activated slip plane parallel to loading stress; (b) the slip direction parallel to loading stress, but existing a deviation angle between slip plane and loading stress.