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Seeking an efficient and non-precious co-catalyst for g-C3N4 (CN) remains a great demanding to achieve high photocatalytic hydrogen generation performance. Herein, a composite photocatalyst with high efficiency was prepared by modifying CN with coral-like NiSe2. The optimal hydrogen evolution rate of 643.16 μmol g−1 h−1 is from NiSe2/CN-5 under visible light. Superior light absorption and interfacial charge transfer properties including suppressed photogenerated carrier recombination and efficient separation of photogenerated electron-hole pairs have been observed, which account for the enhanced photocatalytic performance of CN.

In the present work, 316L stainless steel specimens are fabricated by selective laser melting (SLM) via optimized laser process parameters. The effects of two extrinsic factors, i.e., strain rate and annealing temperature, on the mechanical performance of SLM-processed parts are studied. The two intrinsic factors, namely strain rate sensitivity m and work hardening exponent n, which control the tensile properties of the as-built samples, are quantified. Microstructure characterizations show that cellular structure and crystalline grain exhibit apparently different thermal stability at 873 K. Tensile testing reveals that the yield strength decreases from 584 ± 16 MPa to 323 ± 2 MPa, while the elongation to failure increases from (46 ± 1)% to (65 ± 2)% when annealing temperature varies from 298 K to 1328 K. The n value increases from 0.13 to 0.33 with the increase in annealing temperature. Due to the presence of fine cellular structures and high relative density achieved in as-printed 316L samples, a strong dependence between tensile yield strength and strain rate is observed. In addition, the strain rate sensitivity of the SLM-produced 316L part (m = 0.017) is much larger than that of conventional coarse-grained part (m = 0.006), whereas the n value increases slightly from 0.097 to 0.14 with increasing strain rate.

For the fatigue failure and tribological property of a rolling element bearing, the contact load variation plays a significant role while the most loaded position of the bearing outer raceway takes the greatest risk of failure. This paper focuses on the variation in contact load on the most loaded position of the outer raceway of a gearbox bearing in high-speed train. Under operation conditions of different input speeds and torques, the dynamic contact load distribution in a gearbox bearing of high-speed train was measured by instrumenting the bearing with strain gauges. The most loaded position was identified accordingly and the features and reasons of the variation in contact load on this position were suggested. Three factors were found to have varying degrees of impact on the contact load variation under different gear meshing conditions: modal vibration of the cage or shaft, radial geometrical differences among the rollers and vibration of the gearbox housing.

Mould casting and drop-tube techniques were used to solidify a AlCoCrFeNi2.1 eutectic high-entropy alloy under conditions of high cooling rate. The samples obtained from two different methods present the same phase constituent, FCC and B2 phases. During mould casting experiments the alloy almost solidified into the eutectic structure consisting of lamellar and anomalous morphology, with a tiny fraction of cellular and dendrite morphology being observed at certain sites of the sample surface due to the corresponding high cooling rate. Instead, during drop-tube experiments a typical, coarse dendrite structure of FCC single phase was formed across the entire 106-150 μm particle. The cellular structure can also be formed directly from the melt. The rest region solidified into the general eutectic morphology as was observed in the casting rods. The results clearly indicate the transition from coupled eutectic growth to single-phase dendrite growth with increasing departures from equilibrium for the multi-component AlCoCrFeNi2.1 eutectic high-entropy alloy.

The properties of a ferroelectric ceramic reported by different research groups often vary substantially. The “grain size effect” is one such theory promising to explain this issue, but few ceramics except BaTiO3 conform well to it. The common deviations are that with the decreasing grain size, the content of tetragonal and rhombohedral structures, and polar–nonpolar transition temperature (or depolarization temperature Td) increase, while the dielectric and piezoelectric responses decrease. Here, we demonstrate that for Na0.5Bi0.5TiO3 (NBT)-based ceramics, the deviations from the “grain size effect” were mainly caused by the density inhomogeneity in green body. By modifying the parameters in green body preparation, the piezoelectric properties of NBT-based ceramics sintered at the same temperature (1100 °C) can be easily tuned: for the piezoelectric response d33 from 108 pC/N to 160 pC/N and the Td from 129 to 177 °C. However, the changes were comparable to the improvements for NBT-based ceramics that were reported from special designs, for example quenching the ceramic or forming ceramic composite. This work reveals the significance of long neglected processing-related inhomogeneity on the properties of ferroelectric ceramics and demonstrates the feasibility of improving the piezoelectric properties of lead-free ceramics by the optimization of ceramic fabrication parameters.

Dye-sensitized solar cells (DSSCs) are expected to be a powerful competitor of conventional silicon devices due to their simple, low-cost, and pollution-free processing. Platinum (Pt) as commonly used counter electrode (CE) material is, however, limited to its expensive cost and undesired reverses. The development of an efficient Pt-free CE material with high electrical conductivity and excellent electrocatalytic activity is a feasible strategy to solve the above limitations. Herein, we have proposed a simple two-step strategy to synthesize hierarchical Co3O4/graphene oxide composite catalysts. The as-prepared nanoporous Co3O4 cubes with hierarchical architecture may provide a mass of electrocatalytic activity sites. The combination of hierarchical structures and graphene oxide may enable the electrons to rapidly transfer on the submicron-sized graphene oxide. As a novel and low-cost CE material, DSSCs based on hierarchical Co3O4/graphene oxide composite exhibit photovoltaic performance comparable to the traditional Pt CE. This is due to the ideal combination of excellent electrocatalytic activity and high conductivity. Our finding provides a judicious strategy for nanoscale synthesis of hierarchical composites and may facilitate the preparation of efficient and low-cost CE materials for DSSCs.

A controllable crystallization is of practical importance to produce high-quality perovskite thin films with reduced structural defects. Lewis bases as electron-pair donor chemicals can strongly coordinate to lead ions and have been extensively employed to manipulate the growth of perovskite crystals. In this work, we demonstrate a series of Lewis-base amides, for morphological regulation of methylammonium lead triiodide (MAPbI3) thin films. The screened acetamide was demonstrated to decently improve the grain size, along with a spatial distribution at grain boundaries (GBs). The mesostructured solar cells of acetamide-modified absorbers yielded an optimized power conversion efficiency (PCE) of 20.04% with a mitigated open-circuit voltage (VOC) deficit of 0.39 V. This work provides a facile and cost-effective strategy toward controllable fabrication of high-performance MAPbI3 solar cells.

The mesoporous Pd–Fe magnetic nanoparticles immobilized on the reduced graphene oxide were employed in the present work for the decolorization of toxic brilliant green in aqueous phase. The decolorization process was modeled using backpropagation artificial neural network and optimized by genetic algorithm and particle swarm optimization. These magnetic nanocomposites were synthesized by the two-step reaction in aqueous phase method and then characterized with various methods. According to response surface methodology, the effect of operating parameters on the decolorization of brilliant green in aqueous solution was studied through batch experiments. On the basis of these experiments, the prediction ability of response surface methodology and backpropagation neural network method was assessed. The decolorization process follows Freundlich isotherm and pseudo-second-order kinetics. Furthermore, thermodynamics studies demonstrate that the adsorption of brilliant green onto the nanocomposites was endothermic and spontaneous. Overall, these mesoporous nanomaterials have the advantages of strong adsorption capacity and fast decolorization for brilliant green, and modeling of the removal process with artificial neural network was successful.

Foil bearing is considered to be a promising supporting technology in high-speed centrifugal machinery. Due to the high-speed shearing effect in the viscous lubricant film, heat generation could not be ignored. In this paper, a thermo-elastic model of the multi-leaf foil thrust bearing is proposed to predict its thermal and static characteristics. In the model, modified Reynolds equation, energy equation, and Kirchhoff equation are solved in a coupling way. The contact area between the foil and welding plate is taken into account. Besides, the effect of cooling air on the bearing temperature is investigated. The ultimate load capacity and transient overload failure process of the bearing is analyzed and discussed. The effect of rotation speed on the bearing temperature is more obvious than that of the bearing load. The bearing temperature drops obviously by introducing the cooling air, and the cooling effect is improved with the supply pressure. The transient overload failure of the bearing occurs when the bearing load exceeds the ultimate value.

Inorganic perovskite absorbers are promising candidates for next-generation photovoltaics due to their good thermal and light stabilities. Halide-mixed CsPbIxBr3−x reach a compromise between its structural tolerance and absorption edge, yet the power conversion efficiencies (PCEs) of the asfabricated cells can be considerably limited by the nonideal quality of solution-processed films. Here we demonstrated a fumigation strategy on colloidal perovskite films using dual-O-donor ethyl acetate (EA). By in-situ monitoring this stage with grazing-incidence wide-angle X-ray scattering technology, we reveal that EA fumigation would impose ripening barrier on colloidal inorganic perovskites and hence slow down the nucleation rate, leading to an intermediate state for processing high-crystallinity and oriented perovskite films with improved photophysical properties. An optimized PCE of 16.6% was finally yielded upon wide-bandgap (1.9 eV) perovskite absorber.

A designed type-II heterojunction photocatalyst, NiSe2/Cd0.5Zn0.5S (NiSe2/CZS), was successfully synthesized and it exhibits outstanding photocatalytic hydrogen evolution performance. The optimal loading amount of NiSe2 on Cd0.5Zn0.5S is 13 wt %, and the corresponding hydrogen production rate is approximately 121.01 mmol g−1 h−1 under visible light. The heterojunction structure between Cd0.5Zn0.5S and NiSe2 promoted the separation of photogenerated electron-hole pairs, effectively suppressed the photogenerated carrier recombination and endowed the material with excellent interfacial charge transfer properties, thus improving the photocatalytic performance.

The mechanical characteristics of the unlocking force of the landing gear finger lock were studied in this paper, the influence of its diameter, fingertip angle, wear, and other factors on the unlocking force in one complete working cycle was analyzed, and the sensitive parameters that affect the unlocking force were obtained. Firstly, the unlocking force and wear of finger lock were calculated theoretically, and the changing rule of the unlocking force and wear with each parameter was obtained. Then, the validity of the correlation coefficient and model was verified by experiment. Finally, combined with the effective coefficient obtained from the experiment, the Archard wear model was used to simulate the change rule of lock force. The results show that in one complete working cycle, the inner surface diameter is negatively related to the unlocking force, fingertip diameter has little effect on the unlocking force, fingertip angle is negatively related to the unlocking force, and wear is positively related to the unlocking force; friction coefficient and fingertip angle are high sensitive parameters that affect the unlocking force, which have obvious effect on the unlocking force. The inner surface diameter, fingertip diameter of finger lock, and wear are the low sensitive parameters that affect the unlocking force, and the influence on the unlocking force is weak.

Perovskite solar cells (PSCs) have been attracting increasing attention in recent years because of their exceptional high efficiency with incredible developments. However, the poor contact between the hole transport layer (HTL) and perovskite layer still limits the further development of power conversion efficiency (PCE) for inverted solar cells, particularly for inorganic HTL based devices. Herein, potassium salt (KI, KSCN and KNO3) modified nickel oxides are selected as HTLs to improve the photovoltaic performance of an inverted device. We found that all potassium salts play positive roles in optimizing the photovoltaic parameters. Through the modification of potassium salts, higher charge recombination impedance and strong photoluminescence quenching were achieved, which means retarded carrier nonradiative recombination and quick charge transfer at the interface. Besides, KI modified NiOX could improve the perovskite film coverage and reduce trap densities. Thus, the champion device based on a KI modified NiOX film attained a PCE of 20.10% with an enhanced fill factor of 0.812. The findings demonstrate that potassium doping is an effective route to improve the performance of inverted planar PSCs.

In order to maintain the cryogenic environment of cryogenic wind tunnel in service, heat transfer of insulation structure is investigated in this work. Firstly, the design and material selection of insulation structure is conducted. Afterwards, theoretical calculation on heat transfer of insulation structure is carried out based on 1-D heat conduction model. Subsequently, the finite element model of insulation structure is established, on this basis, involving the actual work condition of cryogenic wind tunnel, heat transfer of the insulation structure is numerically calculated. Finally, the testing platform able to simulate the work environment of cryogenic wind tunnel is built and the temperature measurement experiments at the cryogenic condition and at the cryogenic pressure condition are carried out, respectively. The obtained results show that the designed insulation structure is in possession of great insulation characteristics to ensure the cryogenic environment of cryogenic wind tunnel. Additionally, the established testing platform can provide a testing method to investigate the heat transfer character of other materials or structures in cryogenic environment.

Metal halide perovskites (MHP) are an emerging class of semiconducting materials with superior optoelectronic properties, which have achieved notable success in photoelectric device applications. As a classical technique in the semiconductor industry, epitaxy has indeed advanced the perovskite technology in the recent years by enabling the material combinations with a coherent interfacial lattice as well as combined complementary functionalities, which are not available in the single-phase constituents. In this review, we start with the basic principles and chemical techniques for the epitaxial growth of MHP-based materials. We summarize the epitaxial structures of perovskite solids, which are categorized by the combined materials and compare their performance in photoelectric devices including solar cells, photodetectors, and light-emitting diodes (LEDs). The impact of lattice strain and band structure at the substrate/perovskite interface, which can affect the energy conversion process, are then discussed after the epitaxial cases. We finally outline the future directions for perovskite epitaxy, targeting the in situ monitoring of the surface atomic kinetics during the growth, precise interfacial structure characterization, and the upscaling fabrications, which might further benefit the performance and application of perovskite-based devices.

Organic–inorganic hybrid perovskite materials have attracted enormous attention owing to their extraordinary progress in both power conversion efficiency and stability. However, nonradiative carrier recombination occurring in the perovskite films and interface hinders its commercial viability as the next-generation photovoltaics. Doping with metal cations has been demonstrated to be efficacious for controlling charge transport and reducing charge recombination for perovskite solar cells. Herein, we report the homogeneous doping of entire perovskite solar cells by alkali cations via a dopant diffusion strategy from the hole transport layer. It was found that Rb+ ions enhanced the conductivity and optimized the energy level alignment. The diffused Rb+ ions within the perovskite layer could further reach the bulk films with modulated electronic states. The power conversion efficiency of the perovskite solar cell based on 1.0% Rb+-doped NiOx boosts to 21.80% with a high fill factor of 0.824. Unencapsulated Rb+-doped NiOx photovoltaic devices maintained 93.3% of their initial efficiency after storage in air for 1200 h.

Recently, heterogeneous nanomaterials have a wide range of applications because of their various combined functions. As a promising material for photocatalysis and gas sensing, Au@ZnO core–shell na...

Ni/porous g-C3N4 was prepared by high temperature thermal polymerization process using carbon dots as soft template and photodeposition. With nickel nanoparticles supported as co-catalyst, the hydrogen evolution reaction (HER) activity of the photocatalyst has been significantly enhanced under visible light, which is up to 1273.58 μmol g−1 h−1, superior to pristine g-C3N4 (4.12 μmol g−1 h−1). This is attributed to the inhibited recombination of photogenerated electron-hole pairs and the much better electron transport efficiency. The formed porous structure of carbon nitride could facilitate light utilization and together with nickel nanoparticles, better charge separation can be realized which are proved by the photoluminescence, time-resolved photoluminescence spectra, transient photocurrent measurements and electrochemical impendence spectroscopy. This work provides a useful route to obtain less expensive and efficient photocatalyst containing no noble metals for hydrogen production.

Previous studies have revealed that laser power and energy density are significant factors affecting the quality of parts manufactured by selective laser melting (SLM). The normalized equivalent density E0* and dimensionless laser power q*, which can be regarded as a progress on the understanding of the corresponding dimensional quantities, are adopted in this study to examine the defects, melt pool shape, and primary dendrite spacing of the SLM-manufactured 316L stainless steel, because it reflects the combined effect of process parameters and material features. It is found that the number of large defects decreases with increasing E0* due to enough heat input during the SLM process, but it will show an increasing trend when excessive heat input (i.e., utilizing a high E0*) is imported into the powder bed. The q* plays an important role in controlling maximum temperature rising in the SLM process, and in turn, it affects the number of large defects. A large q* value results in a low value of absolute frequency of large defects, whereas a maximum value of absolute frequency of large defects is achieved at a low q* even if E0* is very high. The density of the built parts is greater at a higher q* when E0* remains constant. Increasing the melt pool depth at relatively low value of E0* enhances the relative density of the parts. A narrow, deep melt pool can be easily generated at a high q* when E0* is sufficiently high, but it may increase melt pool instability and cause keyhole defects. It is revealed that a low E0* can lead to a high cooling rate, which results in a refined primary dendrite spacing. Relatively low E0* is emphasized in selecting the process parameters for the tensile test sample fabrication. It shows that excellent tensile properties, namely ultimate tensile strength, yield strength, and elongation to failure of 773 MPa, 584 MPa, and 46%, respectively, can be achieved at a relatively low E0* without heat treatment.

Cryo-compressed hydrogen storage has potential applications in fuel-cell vehicles due to its large storing density and thermal endurance. The dormancy of storage can be extended when considering the endothermic conversion of para-to-ortho hydrogen. In present study, a thermodynamic model is established to analyze the effect of the conversion in a cryogenic pressure vessel. The influence of the parameters such as the filling density, initial temperature and initial ortho hydrogen fraction is studied. It is demonstrated that different “transition pressures” for the vessels exist for different filling densities. The conversion can carry out sufficiently and the dormancy can be extended significantly when the designed release pressure of the vessel matches with the transition pressure. The heat of absorption increases with the initial o-H2 fraction, whereas the peak of conversion rate occurs earlier for the vessel with a large initial o-H2 fraction. The dormancy can be extended by 163% for the vessel with filling density of 70 kg/m3. The investigations on the effect of the para-to-ortho hydrogen conversion can provide useful guideline for the design of cryo-compressed hydrogen vessels.

Surface engineering has been shown critical for the success of perovskite solar cells by passivating the surface enriched defects and mobile species. The discovery of surface modulators with superior interaction strength to perovskite is of paramount importance since they can retain reliable passivation under various environments. Here, we report a chelation strategy for surface engineering of CsPbI2Br perovskite, in which dithiocarbamate molecules can be coordinate to surface Pb sites via strong bidentate chelating bonding. Such chelated CsPbI2Br perovskite can realize excellent passivation of surface under-coordinated defects, reaching a champion power conversion efficiency of 17.03% and an open-circuit voltage of 1.37 V of CsPbI2Br solar cells. More importantly, our chelation strategy enabled excellent device stability by maintaining 98% of their initial efficiency for over 1400 h in ambient condition. Our findings provide scientific insights on the surface engineering of perovskite that can facilitate the further development and application of perovskite optoelectronics., Surface engineering is a known strategy to optimize the perovskite solar cells but it is usually based on weak bondings, such as Van der Waals, or coorordiating interacterions. Here He et al. report a chelation strategy using strongly adsorbed dithiocarbamate molecules and achieve high efficiency of 17.03% with excellent stability for CsPbI2Br based solar cells.

We design and integrate four optical phased arrays (OPAs) in a single chip. Each OPA possesses different output grating period. Furthermore, we use optical switches to select one or more OPAs for beam scanning. We demonstrate the longitudinal scanning by tuning the laser wavelength. The experimental results show that the scanning range of the four-lines chip reaches 28.54° when the wavelength ranges from 1520 nm to 1570 nm, and the eight-lines one reaches 19.04° with wavelength range of 1520 nm-1540 nm. We greatly improve the wavelength tuning efficiency for longitudinal scanning.

The measured flexoelectric response of ferroelectric ceramics is usually several orders of magnitude larger than the theoretically calculated response, causing the controversy about the magnitude of the intrinsic response of flexoelectricity in the materials. In order to understand this issue, the temperature-dependent flexoelectric response of (1-x)BaTiO3-xSrTiO3 (BST) ceramics were measured. We show that near the Curie temperature (Tc), BST ceramics exhibit the highest flexoelectric response, which is much larger than the intrinsic response calculated theoretically. The response becomes lower at the temperature above or below Tc. The flexoelectric response that is consistent with the theoretical value can only be measured at a temperature much above Tc. Below Tc, the flexoelectric response is also much higher than the theoretical value because of the effect of some extrinsic mechanisms including the surface effect. Our study provides important experimental results to understand the mechanisms of flexoelectric response of ferroelectric ceramics and resolve the controversy about the magnitude of the intrinsic flexoelectric response of the materials.

The efficiency, stability, and scalability of perovskite devices still require further enhancement for real-world application. Defect passivation has been recognized as one prominent strategy that ...

Increasing attention has been paid to layered high-Ni oxides with high capacity as a promising cathode for high-energy lithium-ion batteries. However, the undesirable microcracks in secondary particles usually occur due to the volume changes of anisotropic primary grains during cycles, which lead to the decay of electrochemical performance. Here, for the first time, a functional electrolyte with di-sec-butoxyaluminoxytriethoxysilane additive integrating the functions of silane and aluminate is proposed to in situ form the binder-like filler between anisotropic primary grains for mitigating the microcracks of high-Ni oxides. It is demonstrated that Li-containing aluminosilicate as a glue layer between the gaps of grains and as a coating layer on the surface of the grains is generated, and these features further enhance the interfacial bonding and surface stability of anisotropic primary grains. Consequently, the microcracks along with side reactions and phase transitions of high-Ni oxides are mitigated. As anticipated, the electrochemical performance and thermal stability of high-Ni oxides are improved, and there is also a capacity retention of 75.4% even after 300 cycles and large reversible capacity of ∼160 mA h g-1 at 5 C. The functional electrolyte offers a simple, efficient, and scalable method to promote the electrochemical properties and applicability of high-Ni oxide cathodes in high-energy lithium-ion batteries.

We report a facil and robust strategy for fabricating flexible piezoelectric nanogenerator based on free-standing polydimethylsiloxane (PDMS) / ZnO nanowire (NW) hybrid film. Free-standing hybrid film was fabricated by mechanical exfoliation of ZnO NWs grown on a FR4 substrate. The free-standing ZnO/PDMS hybrid film is robust enough to be transferred into a flexible substrate of polyimide (Kapton) with Au sputtered. The nanogenerator based on the free-standing hybrid film exhibits stable output voltage about 0.7 V and current of 7 nA under pressing conditions. This facil and robust method should hold significant promise applications in efficient energy harvesting.

Cesium lead halide perovskites are promising alternatives as light-absorbing materials for achieving perovskite solar cells with excellent thermal stability, but their inferior power conversion efficiency (PCE) and ambient instability are impeding their application. In this work, we show that liquid water can assist the formation of CsPbI2Br perovskites under the synergetic adsorption of H2O and dimethylsulfoxide (DMSO), which enabled uniform, [100] oriented CsPbI2Br films with a grain size up to 4.4 μm. It was found that a suitable amount of H2O helps desorb the DMSO molecules, and thus favours the formation of a cubic perovskite phase from DMSO complexed intermediates. Perovskite solar cells based on our strategy delivered an optimized PCE of 16.47% with a high open-voltage of 1.33 V, as well as good device stability against humidity, light and heat.

The pneumatic hammer phenomenon and pneumatic stability of a single-pad aerostatic thrust bearing with pocked orifice were investigated numerically. A time-dependent dynamic model for pneumatic stability analysis of the bearing was established with taking the pocket volume and the mass flow difference between the pocket inlet and outlet into account. The numerical prediction indicates that the delay effect is an important reason for the pneumatic hammer phenomenon. With considering the delay effect, an in-depth explanation for the pneumatic hammer phenomenon is proposed in this paper. The air compressibility combined with the volume effect in the aerostatic bearing could lead to the delay of pocket pressure change, then resulting in the delay of bearing force change at larger film thickness region. The delay of the bearing force change at larger film thickness region causes the bearing damping to become negative at larger film thickness. The negative damping provides some energy into the aerostatic bearing system at larger film thickness and maintains vibration, which leads to the pneumatic hammer phenomenon.

Despite many cationic nanomaterials that have been developed for efficient adsorption of anionic pollutants, tailoring a stable shape with denser cations on the surface for advanced removal capability remains challenging. Here, a new strategy is presented for fabricating two-dimensional (2D) cationic laminas and their curvature based on cross-linking of 2D supramolecular networks from hydrogen-bonded trimesic amide derivatives. Owing to the distribution of most cations on the surface, two cationic nanostructures from cross-linking of supramolecular networks show fast sorption kinetics for anionic pollutants. Notably, the removal capacity of the capsule-like curvature adsorbent is more than twice that of lamina adsorbent for sufficient space around cationic sites in hollow aperture. Moreover, the capsule-like adsorbent is triggered to open and spontaneously release the adsorbed pollutants upon the addition of halogen anions, which can be recovered by subsequent dialysis. Strategy of a capsule-like pocket with tunable opening-closing will provide a new insight for storage and adsorption.

The bypass of subway tunnels in soft soil areas is usually constructed by the artificial freezing method due to the waterproof property and high strength of frozen soil. The thawing settle...

The optical power handling of an OPA scanning beam determines its targeted detection distance. So far, a limited number of investigations have been conducted on the restriction of the beam power. To the best of our knowledge, we for the first time in this paper explore the ability of the silicon photonics based OPA circuit for the high power application. A 64-channel SiN-Si based one-dimensional (1D) OPA chip has been designed to handle high beam power to achieve large scanning range. The chip was fabricated on the standard silicon photonics platform. The main lobe power of our chip can reach 720 mW and its peak side-lobe level (PSLL) is -10.33 dB. We obtain a wide scanning range of 110° in the horizontal direction at 1550 nm wavelength, with a compressed longitudinal divergence angle of each scanning beam of 0.02°.

Highlights Oxyacid anions (NO3−, SO42−, CO32−, PO43− and SiO32−) were investigated both theoretically and experimentally about their passivation effect on CsPbI2Br perovskite interface.Adjustment of oxysalt layer thickness can optimize the surface band position that could be beneficial for electronic band alignment at perovskite/transport layer interface.Using silicate as a passivator, the CsPbI2Br solar cells achieved a PCE of 17.26% with an open-circuit voltage of 1.36 V. This strategy is also effective for organic-inorganic perovskite solar cells. Electronic supplementary material The online version of this article (10.1007/s40820-021-00683-7) contains supplementary material, which is available to authorized users., Passivation, as a classical surface treatment technique, has been widely accepted in start-of-the-art perovskite solar cells (PSCs) that can effectively modulate the electronic and chemical property of defective perovskite surface. The discovery of inorganic passivation compounds, such as oxysalts, has largely advanced the efficiency and lifetime of PSCs on account of its favorable electrical property and remarkable inherent stability, but a lack of deep understanding of how its local configuration affects the passivation effectiveness is a huge impediment for future interfacial molecular engineering. Here, we demonstrate the central-atom-dependent-passivation of oxysalt on perovskite surface, in which the central atoms of oxyacid anions dominate the interfacial oxygen-bridge strength. We revealed that the balance of local interactions between the central atoms of oxyacid anions (e.g., N, C, S, P, Si) and the metal cations on perovskite surface (e.g., Pb) generally determines the bond formation at oxysalt/perovskite interface, which can be understood by the bond order conservation principle. Silicate with less electronegative Si central atoms provides strong O-Pb motif and improved passivation effect, delivering a champion efficiency of 17.26% for CsPbI2Br solar cells. Our strategy is also universally effective in improving the device performance of several commonly used perovskite compositions. Electronic supplementary material The online version of this article (10.1007/s40820-021-00683-7) contains supplementary material, which is available to authorized users.

Two novel waveguide gratings for optical phased array transmitters are investigated. By offsetting the grating structures along the waveguide on the upper and lower surfaces of the silicon nitride (Si3N4) waveguide, the dual-level chain and dual-level fishbone structures can achieve 95% of unidirectional radiation with a single Si3N4 layer by design. With apodized perturbation along the gratings, both structures can achieve uniform radiation without compromising the unidirectional radiation performance. In experiment, both demonstrate ∼ 80-90% unidirectionality. With further analysis, it is found that the dual-level fishbone structure is more feasible and robust to process variations in uniform radiation.

Cesium-based all-inorganic perovskite absorbers have attracted increasing attention due to their superior thermal stability, compared to their organic–inorganic counterparts. Up to now, it is a challenge to fabricate high-efficiency all-inorganic perovskite solar cells (PSCs) with low defect densities. Herein, we used bivalent metal chloride salts (SrCl2 and NiCl2) to optimize CsPbI2Br films. The experimental results indicate that this method could deliver high-quality films with improved electronic property. As a result, the champion device based on the 0.01 M SrCl2–doped CsPbI2Br film achieved a power conversion efficiency (PCE) of 16.07% with a high open voltage (VOC) of 1,322 mV, which is about 18% higher than that of the pristine device.

SThe present paper investigates the nanoscale thermal transport at diamond/copper (dCu) interfaces using the density functional theory (DFT) and the atomistic Green's function method. The DFT calculations show the boundary scattering become negligible for diamond particles larger than 10 μm. The temperature-dependent thermal conductivity of the dCu composite is predicted according to the thermal boundary conductance and thermal conductivity from DFT calculations. The results show a low thermal boundary conductance (18.5–26.9 MW/m2K at 300 K) at dCu interfaces causes the reduction in the thermal conductivity of dCu composites with small diamond particles or at low temperatures. Due to the dominant effects of interfacial resistance, adding small diamond particles (

Although the cage slip of cylindrical roller bearings has been measured and studied experimentally, it is difficult to use current experimental measurement to detect the cage slip of the bearing in actual service or engineering environment. The problem is attributed to the limit on the space for current test instruments that can be installed arbitrarily in laboratory, but not in actual environment. A novel measurement based on strain detection is presented. This measurement can be used to obtain the cage slip of the bearing in service or large bench test. The technique is demonstrated and validated in principle by an experimental system. The system is developed to obtain the strain signal of the outer ring in loaded zone as well as the speed signal of the cage and the inner ring at the same time. Under given test load–speed conditions, the cage slip based on strain detection was compared with the cage slip based on speed detection. Experimental results showed that cage slip ratio curves based on strain responses agreed very well with those based on speed signals. In this way, it is revealed that frequency characteristics of strain signals can be used to obtain internal cage slip of cylindrical roller bearings.

Organometal halide perovskites have recently emerged with a huge potential for photovoltaic applications. Moreover, preparation of high-quality perovskite crystals with controlled morphology is of great significance for the fundamental studies such as optical and electrical properties, as well as the applications. Here, we report a one-pot solvothermal process to synthesize sheet-shaped CH3NH3PbBr3 single crystals with the lateral size of 100 µm and the thickness of 3–8 µm. Furthermore, a controlled etching behavior on the crystalline surface was demonstrated, which could be the irregular collapse of the crystalline surface caused by the local accumulation of methylammonium cations. Using this technique, CH3NH3PbBr3 single crystal sheets could be used in the various optoelectronic devices, such as nanolaser, optical sensors, photodetectors and field effect transistors.

An accurate condensation model plays an important role in the development of high-efficiency turbine. Many efforts have been devoted into the research on steam non-equilibrium condensation. However, aiming at the cryogenic gas at high-speed flow the studies on the condensation model are still inadequate and incomprehensive. In present paper, different condensation models, established via the alternations of nucleation model and droplet growth model are compiled into commercial CFD software to simulate the non-equilibrium condensation flow within a cryogenic radial-inflow turbo-expander. Firstly, the rotation effect on droplets diameter and distribution within the impeller passage are analyzed. The results point out the region where large droplets are prone to form and gather. Furthermore, the influence mechanism of heat and mass transfer in varying condensation models on the flow fields, including rapid nucleation, supercooled degree, liquid mass fraction, droplet diameter, are revealed based on the analysis of Nusselt number and Knudsen number. The results imply that the predicted location of condensation onset is little sensitive to the droplet growth model. At last, the effect of modifications for nucleation rate and droplet growth rate on the thermodynamic losses in turbo-expander are quantificationally discussed.

Strength is usually compromised with toughness of polymer blends. We report a new way to synchronously strengthen and toughen a typical blend of epoxy resin/nitrile-butadiene rubber (EP/LNBR) with ...

In a modern cryogenic liquefaction system, the turbo-expander is used to operate in the two-phase region so that a high cooling capacity can be provided. Compared with the expansion process in a conventional over-heated turbo-expander, non-equilibrium condensation occurs in the duct when the turbo-expander operates in the two-phase region, which varies the expansion process. In our previous works, the simulation by CFX can predict the nucleation process controlled by gaseous sub-cooling well, and the outlet liquid fraction has a good agreement with our experimental data. As the non-equilibrium condensation simulated by using CFX consumes much time and massive computing resource, it is not feasible to simulate the two-phase expansion in the turbo-expander in a wide off-design range. In this study, we investigate the non-equilibrium spontaneous condensation along the mean streamline of a cryogenic turbo-expander passage by using an off-design computational code compiled by Matlab. The two-phase off-design computational code is developed from our previous overheated off-design code. The calculation function of thermodynamic parameters on the mean streamline and non-equilibrium condensation module are integrated with this code. The variations of thermodynamic parameters on the mean streamline in a non-equilibrium condensation process are simulated. Nucleation onset, droplet growth/vaporization process, liquid fraction distribution are revealed. Droplet developing region is divided according to the droplet critical and mean radius. Simulation results of five two-phase cases are compared and analyzed, and different non-equilibrium condensation features and liquid fraction distributions are found. At last, isentropic efficiency and outlet liquid fraction are used to evaluate two-phase expansion performance, and it is found that the performance results from the simulation in five cases agree with experimental data well.

Hot dip aluminizing of mild steel at different temperatures was conducted to reveal the influence of reaction temperature and time on interfacial intermetallic compounds (IMCs). Scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray diffraction were employed to investigate the interfacial microstructures. The IMCs of the dipping interface consisted of a thick layer of η-Fe2Al5 between 4.2–132.2 μm next to the steel and a thin layer of θ-Fe4Al13 between 0–5.5 μm close to the aluminum. With increasing dipping temperature and time, the total thickness of IMCs (Fe2Al5 plus Fe4Al13) increased. Specifically, the growth of the Fe2Al5 layer can be described by parabolic rate laws. An activation energy of 93 kJ mol−1 was obtained, combining both the results from the present work and previous studies in the temperature range of 675–900°C. The change in Fe4Al13 thickness is not significant compared with the Fe2Al5. However, the decrease in IMC thickness of the Fe4Al13 with dipping temperature was observed for the first time and had never been reported before. Moreover, it can be clearly observed that the thickness of the Fe4Al13 decreased with dipping time based on the linear fitting results by excluding the result of the initial 1 s. A possible mechanism is that interfacial dynamics and thermodynamics work for the dissolution and decomposition of the Fe4Al13 layer. Higher temperature accelerates the dissolution of the θ layer.

Accurate calculation of the transient cooling performance is crucial for the operation and control of a reverse Brayton refrigerator. Components of the refrigerator have complex working characteristics individually and interact each other mutually. To solve the problem easily, the turboexpander matching characteristics were usually ignored and relations among components were simplified. In this study, a cryogenic reverse Brayton air refrigerator equipped with gas bearing turboexpander and plate-fin heat regenerator was presented. The ultimate refrigerating temperature was proposed through analysis. The transient cooling characteristics of the cryogenic part in refrigerator were resolved into the turboexpander matching performance and the regenerator transient cooling characteristics. The regenerator was simulated through numerical heat transfer and computational fluid dynamics by considering the axial conduction and cold loss. The matching model was improved by adopting a significant method of constant rotating speed. Using the dual non-steady time steps, a transient cooling model of the cryogenic part was explored via C++ code, and verified by experiment. Through the model, the refrigerator cooling performances were evaluated under different operation modes, and the energy utilization efficiency was determined. It can be used to evaluate the operation strategy of refrigerators and help to promote energy efficiency.

Organic–inorganic hybrid perovskite solar cells (PSCs) have been rapidly evolving as a promising candidate for next-generation photovoltaic technologies. P-type organics or polymers are generally used as hole transport materials (HTMs), which are expensive and non-sustainable for long-term applications. Herein, we demonstrate an inorganic Ni–Co–O hole conductor that displayed fast hole extraction and transport by the presence of gap states and relative high hole conductivity. Detailed structural inspection reveals that Co3+ and Ni2+ ions would reform into Co2+ and Ni3+ sites with the incorporation of Co, which contributes to greatly enhanced hole concentration. Inverted heterojunction devices based on NiCoOx hole transport layers yielded a maximum power conversion efficiency (PCE) of 20.03%, with 16.9% improvement compared with those based on NiOx layers (17.14%). This novel HTM with a facile synthesis process provides a new strategy for designing efficient carrier transport materials such that efficient charge collection and transport are achieved.

To determine the influence of design parameters on droplet evaporation and distribution of liquid nitrogen (LN2) spray cooling, experimental and numerical studies are performed by varying the mass flow rate, flow velocity, droplet diameter, injection orientation, and droplet velocity. The results demonstrate that backward injection yields the highest droplet evaporation ratio, which is 40% and 10% higher than the evaporation ratios obtained through forward and transverse injections, respectively. Counter-rotating vortex pairs are observed in the transverse injection, which improves the temperature distribution via convective mixing. Reducing the droplet diameter provides a more effective means of enhancing the evaporation than increasing the droplet velocity, and a linear increase in the droplet evaporation is observed by reducing the droplet diameter from 0.6 to 0.2 mm. The results and findings provide guidelines for the design of LN2 spray cooling systems for cryogenic wind tunnels.

SrTiO3 is a promising thermoelectric material for high temperature application of waste heat electrical generation. However, its dimensionless figure of merit (zT) is restricted by its high thermal conductivity, which results from the simple perovskite structure and light elements of SrTiO3. In this paper, we successfully obtained complex structured bulk SrTiO3 with a TiO2 second phase and a porous structure by tuning the doping ratios of the heavy elements La and Nb, resulting in a low thermal conductivity of 1.97 W m−1 K−1 and a high zT value of 0.31 at 1050 K. The first-principles calculation was utilized to calculate the formation energy, effective mass and electron band structure of La–Nb co-doped SrTiO3, and the effects of the parameters on the thermoelectric properties were also discussed. We found that the doping ratio of La to Nb changed the electron band structure and controlled the formation of the TiO2 second phase, which affected the electrical transport and thermal transport properties, respectively. The formation of the in situ TiO2 second phase was related to the high formation energy derived from the high Nb concentration. These results offer an approach for the design of other thermoelectric materials with low thermal conductivity and a high power factor.