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Three-dimensional (3D) graphene networks have aroused great interest because it can effectively avoid the agglomeration problem of graphene powder and improve its utilization efficiency. Such a structure also has the advantages of lightweight, high thermal conductivity and superior electrical conductivity, and is widely used in thermal management and electromagnetic interference shielding. To fully recognize 3D graphene networks, we summarize the different preparation strategies and properties of isotropic and anisotropic 3D graphene networks. The latest research progress of thermal interface materials, phase change materials, electromagnetic interference shielding materials and microwave absorbing materials is reviewed. Finally, the challenges and outlook for 3D graphene networks are proposed. This review provides new perspectives and research directions for the future development of 3D graphene networks in heat dissipation and electromagnetic protection for 5G electronic devices.

A surface-enhanced infrared absorption spectroscopic chalcogenide waveguide sensor based on the silver island film was proposed for the first time to enhance the sensing performance in both liquid and gas phases. The chalcogenide waveguide sensor was fabricated by the lift-off and oblique angle deposition methods. The surface morphology of the silver island film with different thicknesses was characterized. The absorption of ethanol (liquid) at a wavelength of 1654 nm and that of methane (gas) at 3291 nm were measured using the fabricated chalcogenide waveguide sensor. The chalcogenide waveguide sensor integrated with the 1.8 nm-thick silver island film revealed the best sensing performance. With an acceptable increased waveguide loss resulting from the fabrication of the film, the absorbance enhancement factors for ethanol and methane were experimentally obtained to be >1.5 and >2.3, respectively. The 1σ limit of detection of methane for the sensor integrated with the 1.8 nm-thick silver island film was ∼4.11% for an averaging time of 0.2 s. The mathematic relation between the absorbance enhancement factor and the waveguide loss was derived for sensing performance improvement. Also, the proposed rectangular waveguide sensor provides an idea for the design of a sensor-on-a-chip instead of other waveguide sensors with a high requirement of fabrication accuracy, for example, a slot waveguide or a photonic crystal waveguide.

We demonstrate a distributed feedback (DFB) semiconductor laser based on i-line lithography and surface periodic current injection technologies with a lasing wavelength of 795 nm, which corresponds to the D1 spectrum of Rb and has many applications with respect to alkali vapor lasers and atomic clocks. The maximum output power, side mode suppression ratio (SMSR), and single-longitudinal-mode tunable range of our device are 50.89 mW (at 20 °C), 34.56 dB, and 12.792 nm, respectively. The rate of change in wavelength with temperature of the laser is 0.401 nm/°C, which is equivalent to that of a Fabry-Perot (FP) laser and much better than that of a general DFB device. This device has a cavity the same as an FP laser without any etching gratings, meanwhile the lasing spectrum behaves a single longitudinal mode characteristic as a DFB laser.

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

A high-sensitivity and small-size pressure sensor based on dual fiber Bragg grating (FBG), a diaphragm and hinge-lever structure is proposed. Its measurement principle is described and simulation analysis is conducted. We compensate for temperature cross-sensitivity by using an additional FBG to accurately measure the ambient temperature. Sensing experiments indicate that the pressure sensitivity is 5.227 pm/kPa within the range of 0–1.0 MPa, which is three times greater than that of a single-diaphragm pressure sensor without a flexible hinge lever. The sensor is suitable for accurate and stable pressure measurement in oil and gas pipelines and similar environments.

The microstructural evolution and mechanism of grain refinement during rapid solidification of Ni–Cu alloys were studied by molten glass purification and cyclic superheating. The maximum undercooling has achieved 320 K for Ni65Cu35, 295 K for Ni55Cu45 and 280 K for Ni50Cu50 alloys. Two mechanisms were found to be responsible for the grain refinements under small undercooling and large undercooling, respectively. The grain refinement at small undercooling is mainly caused by dendrite superheating and remelting, whereas that for large undercooling is mainly due to recrystallization occurred at high angle grain boundary and high proportion of twin boundaries. Meanwhile, almost no dislocations and other defects were observed in the substructure of the alloy with large undercooling.The average microhardness was found a sharp decrease in the alloy with large undercooling, which indicates that the plastic strain accumulated in the microstructure formed under large undercooling is completely dissipated in post-recalescence, and the deformation energy can offer the driving force for recrystallization in the microstructure.

In order to monitoring vibration-reduction and vibration-isolation effects of subway floating slab, an FBG displacement sensor was developed to monitor the deformation of the subway floating slab. The proposed sensor mainly consists of an FBG, a thin-walled ring, a steel-spring, connecting rod probe, linear bearing, sleeve, and other auxiliary unit. The connecting rod probe transmits the external displacement to the steel-spring and elastic thin-walled ring, and then leads to the wavelength shift of the FBG pasted in the reserved groove of the thin-walled ring. Meanwhile, the linear bearing can reduce the friction loss and increase the sensor stability. Lots of sensing tests showed that, the sensor has a sensitivity of 36.36 pm/mm and a precision of $8.25\times 10$ -2 mm in the displacement range of 0 - 20 mm, and also has good micro-displacement measurement capabilities. The theoretically calculated data for the vertical displacement of the floating slab are consistent with the actual measured data, which verifies the feasibility of the proposed displacement sensor in the monitoring of the subway floating slab.

The exploration of high-efficient, environment-stable, and cost-effective microwave absorption (MA) materials is of great significance for commercial application, and the main challenge lies in how to integrate these fascinating features using facile strategies. Herein, a one-step synergistic catalytic pyrolysis strategy was developed to construct bamboo-like N-doped carbon tube encapsulated cobalt-nickel alloy. As for a bamboo-like N-doped carbon tube, it not only provides abundant cavities for the generation of the induced current, but also induces uneven distribution of local charges from the N-doping, which results in the enhanced conduction loss and polarization relaxation. More importantly, the confinement of CoNi alloy into carbon tube effectively prevents the agglomeration of magnetic CoNi nanoparticles and simultaneously protects the CoNi alloy from corrosion, which is favorable for preserving its original magnetic properties and achieving stable MA performance in extreme chemical environment. On the basis of the combined effect, the optimized CoNi–N/C-700 achieves strong absorption of −55.62 dB and broad bandwidth of 4.25 GHz with an ultrathin thickness of 1.45 mm and low filler loading of 10 wt%, outperforming most bimetal-based microwave absorbers. This one-step synthetic strategy may pave a new way to design and construct high-efficient and anti-corrosion microwave absorbers for future large-scale applications.

Spacecraft materials are a key limiting factor for the rapid development of the aerospace exploration field. In an advanced spacecraft, superior multi-functional material with thermal management and electromagnetic shielding can ensure the normal operation of its equipment in space. Currently, graphene thin film can’t satisfy a high heat flux and excellent through-plane thermal conduction. In this contribution, a full-carbon dual-functional graphene/carbon nanotubes (CNTs) thick film with high heat flux was successfully prepared, and the structure and composition evolution was investigated after hot-pressing carbonization and graphitization of 2800 °C, which indicates the existence of a compact defects-free and high crystalline carbon structure. Molecular dynamics simulations further confirm the formation of C–C covalent bonds between graphene sheets and CNTs after 2800 °C graphitization, enhancing the phonons transfer in through-plane. Simultaneously, the axially adjacent graphene sheets are connected by the CNTs, which endow excellent thermal conductive properties. The in-plane and through-plane thermal diffusivity are as high as 1188.2 mm2/s and 8.0 mm2/s, respectively. Moreover, the electrical conductivity up to 1819.17 S/cm and EMI SE reach 75 dB in Ku-band. The results provide a bright prospect for spacecraft materials preparation and application.

Supercritical carbon dioxide (SC-CO2) fracturing technology has the characteristics of a large amount of fixed CO2 and anhydrous fracturing. It has great application potential for developing unconventional oil and gas resources and mitigating the greenhouse effect. However, the low viscosity of SC-CO2 limits the development of this technology. In this work, HS series thickeners were prepared via a ring-opening polymerization and hydrosilylation reaction by a molecular simulation-aided design method. The simulation results of cohesive energy density, interaction energy, and radial distribution function are consistent with the visualization experimental results, which proves that HS (hyperbranched siloxane) series thickeners have excellent solubility in SC-CO2. HS-3 is the best thickener in the HS series. At 305.15 K and 10 MPa, 5 wt% HS-3 (60 s−1) increases the viscosity of SC-CO2 by 151 times, and the apparent viscosity is 3.024 mPa s. The apparent viscosity of SC-CO2 was positively correlated with the pressure and concentration but negatively correlated with the temperature and shear rate. The results indicate that it is feasible to introduce an aliphatic group and polysiloxane into a SC-CO2 thickener by hydrosilylation.

Semiconductor optical amplifiers (SOAs) offer direct electrical injection, power consumption, integration, and anti-radiation advantages over optical fiber amplifiers. However, saturation output power and gain bandwidth have been limited in traditional structure SOAs. We demonstrate a monolithic integrated SOA with broad spectrum, high power, high gain, and small spectral linewidth expansion. The device adopts a two-stage amplified large optical cavity structure, and a lower optical field confinement factor is obtained by adjusting the thickness of the waveguide layer. The lower optical field confinement factor is conducive to improving the coupling efficiency and the maximum output power. Our device, fabricated only by standard i-line lithography with micron-scale precision, obtains excellent and stable performance. When the input power is set to 1 mW, the output power is 419 mW with a gain of 26.23 dB. When the input power is set to 25 mW at 25 °C, the output power increases to 600 mW with a gain of 13.8 dB. The corresponding gain bandwidth of 3 dB measures at least 70 nm. The spectral linewidth after the SOA is 1.15 times wider than that of the seed laser.

Metal germanium (Ge) with a high theoretical capacity of 590 mA h g−1 is regarded as a promising anode material for sodium ion batteries, but it suffers from a fast capacity decay problem due to the serious agglomeration of Ge particles caused by the drastic volume change during the sodiation/desodiation process. Constructing highly dispersed ultrafine Ge nanoparticles is a possible way to address this problem. However, reported methods to obtain highly dispersed metal nanoparticles encountered problems of poor electrochemical activity or non-uniform particle size. In this work, we proposed a new in situ confined polymerization method for preparing highly dispersed Ge quantum dots (QDs). Due to the high dispersion of Ge QDs in carbon frameworks derived from poly(ionic liquid) networks, the obtained Ge@C nanocomposite could effectively avoid the agglomeration of Ge particles. When applied as the anode material for sodium ion batteries, the Ge@C nanocomposite shows ultra-long cycle life and high rate capability. At a current density of 1500 mA g−1, the Ge@C electrode could display a high capacity of 201 mA h g−1 after 5000 cycles. This method could be extended to prepare other highly dispersed metal nanoparticles and achieve fairly efficient electrode materials for new-type secondary batteries.

Uncontrollable growth of lithium (Li) dendrite has severely hindered the development of Li metal anodes, while separator modification is regarded as a simple and effective way to mitigate the growth of Li dendrite. However, the "drop-dregs" phenomenon of coating layer desquamated from polyolefin separator due to their different Young's modulus would induce a nonuniform Li ionic flux, finally resulting in deteriorative electrochemical performance and even thermal runaway of the battery. Herein, we introduce a novel nanopile mechanical interlocking strategy to create delamination-free separator modification, which could stably generate a homogeneous Li ionic flux to guide long-term uniform Li deposition. Both experimental and simulation results demonstrate a strong bonding strength between the coating layer and membrane matrix based on this physical interlocking mechanism. Consequently, with a nearly dendrite-free Li deposition and a largely reduced interface impedance, 1000 h stable cycling of Li/Li half cells enrolled this modified separator is successfully achieved. Also, a significant improvement in Li/LiFePO4 full cells in long-term cycling stability to 500 cycles further indicates its promising practical potential. Moreover, this presented approach without any binding agents or surface activation procedures could be facilely scaled up, providing an applicable and durable separator modification solution toward stable Li metal anodes.

Abundant engineering practice shows that coal and rock dynamic disasters often occur in fault zones; hence, the detection of faults in coal mines is important. As an essential branch of seismic tomographic application, research shows that ultrasonic P-wave velocity can detect mine faults and provide technical support for dynamic disaster prewarning systems. Traditional P-wave testing mostly takes rock or raw coal as the research object, which has some shortcomings in controllability, homogeneity and comparability. This paper compares the difference in ultrasonic P-wave propagation velocity in jointless and jointed briquettes through laboratory research, focuses on the effect of macro-joints on P-wave velocity and makes a preliminary theoretical analysis. The results show that: (i) the three-dimensional P-wave velocity throughout a jointless briquette specimen is similar, which reflects the high homogeneity of this medium and avoids the influence of the random distribution of primary bedding, joints and structural planes; (ii) the P-wave velocity in jointless and jointed briquettes is positively correlated with density and forming pressure, and is negatively correlated with the angle between the ultrasonic wave and the joint surface in a sample and (iii) when the P-wave encounters the macroscopic joint surface, it may reflect and refract, changing the propagation direction and inducing wave mode conversion. This study provides the necessary technical support and a theoretical guide to optimise acoustic property analysis of coal and rock as well as a field application for seismic tomography technology.

Assembling Ti3C2Tx MXene nanosheets into three-dimensional (3D) architecture with controllable alignment is of great importance for electromagnetic wave absorption (EMA) application. However, it is...

Lightweight, low-cost electromagnetic (EM) wave absorption materials are in urgent need, as EM interference pollution is increasingly serious. Carbon material as EM absorber has attracted ever increasing attention. However, their absorption property is still limited. Herein, we propose a very simple strategy to prepare hierarchical carbon fiber coated with Co/C nano-dodecahedron particles where CNTs were anchored (HCF@CZ-CNTs), using cotton and metal-organic-framework (MOF) as raw materials. One of MOF, ZIF-67 particles were in-situ grown onto the surface of cotton fibers. Lightweight HCF@CZ-CNTs samples were obtained by direct carbonization, the apparent density of which is only 0.0198 g/cm3. The minimum reflection loss (RLmin) of hierarchical HCF@CZ-CNTs was dramatically enhanced to −53.5 dB at 7.8 GHz, compared with pure carbonized cotton fiber (RLmin = −18.9 dB at 16 GHz). Meanwhile the effectively absorption bandwidth was also remarkably enlarged to 8.02 GHz. The excellent EM wave absorption performance is attributed to the micro-to-nano hierarchical hollow fibrous structure, as well as the synergetic effect of polarization relaxation and magnetic loss. These results illuminate a low-cost and sustainable strategy to prepare ultra-lightweight microwave absorbers with excellent EM wave absorbing ability utilizing biomass precursor and MOF.

In this study, nitrogen defect (cyano-group and N vacancy)-modified mesoporous g-C3N4 (CNMCN) was synthesized via a new in situ silica gel strategy. Resultant CNMCN was analyzed via numerous techniques such as TEM, BET, XRD, FTIR, XPS, PL and DRS. The results revealed that the introduced mesoporous structure, cyano-group and N vacancy, could increase surface area, improve the separation of photoinduced charge and heighten light response capacity. These positive factors promoted CNMCN exhibiting better photocatalytic ability for splitting water, its H2 evolution rate was around 14.7-fold more than that of bulk g-C3N4, and excellent continuous service capacity was also showed. Moreover, CNMCN had better performance than mesoporous g-C3N4, cyano-group modified g-C3N4 and N vacancy modified g-C3N4. Apparently, this present study provides a new thought for preparing mesoporous structure N defect-modified g-C3N4, which might be applied in clean energy production and environmental restoration.

The rolling path for a radial-axial ring rolling (RARR) process defines the matched motions of all the rolls including the main roll, mandrel, guide rolls and axial rolls. Materials with low thermal conductivity such as titanium alloys show an overheating in the local region of the ring due to the concentration of forming energy. The temperature sensitivity of these materials leads to severe microstructure and forming defects. Therefore, for the RARR process of titanium alloy rings, it is a core industrial technology to plan a rolling path by which the temperature in the whole ring can be maintained within a desired range (a designed control objective of ring temperature) to improve the mechanical properties. In this work, an intelligent real-time temperature-controlled finite element (FE) model for the RARR process of TA15 titanium alloy rings has been developed under ABAQUS/Explicit software. In the intelligent simulation, by establishing a ring growth velocity model relating to the ring temperature, the motions of various rolls could be driven in real time by the control objective of the ring temperature. Without definition of rolling path prior to the simulation, the new intelligent simulation realizes the self-adaptive control of rolling process to maintain the ring temperature within a desired range. By only one calculation, the rolling path satisfying the control objective of temperature can be obtained. This work achieves quick planning of the rolling path for real-time temperature-controlled RARR process.

The low sand-carrying problem caused by the low viscosity of supercritical carbon dioxide (SC-CO2) limits the development of supercritical CO2 fracturing technology. In this study, a molecular simulation method was used to design a fluorine-free solvent-free SC-CO2 thickener 1,3,5,7-tetramethylcyclotetrasiloxane (HBD). Simulations and experiments mutually confirm that HBD-1 and HBD-2 have excellent solubility in SC-CO2. The apparent viscosity of SC-CO2 after thickening was evaluated with a self-designed and assembled capillary viscometer. The results show that when the concentration of HBD-2 is 5 wt.% (305.15 K, 10 MPa), the viscosity of SC-CO2 increases to 4.48 mPa&middot, s. Combined with the capillary viscometer and core displacement device, the low damage of SC-CO2 fracturing fluid to the formation was studied. This work solves the pollution problems of fluoropolymers and co-solvents to organisms and the environment and provides new ideas for the molecular design and research of SC-CO2 thickeners.

Recently, as a two-dimensional (2D) material, black phosphorous (BP) has attracted more and more attention. However, few efforts have been made to investigate the BP/polyaniline (PANI) nanocomposite for ammonia (NH3) gas sensors. In this work, the BP/PANI nanocomposite as a novel sensing material for NH3 detection, has been synthesized via in situ chemical oxidative polymerization, which is then fabricated onto the interdigitated transducer (IDTs). The electrical properties of the BP/PANI thin film are studied in a large detection range from 1 to 4000 ppm, such as conduction mechanism, response, reproducibility, and selectivity. The experimental result indicates that the BP/PANI sensor shows higher sensitivity and larger detection range than that of PANI. The BP added into PANI, that may enlarge the specific surface area, obtain the special trough structure for gas channels, and form the p–π conjugation system and p–p isotype heterojunctions, which are beneficial to increase the response of BP/PANI to NH3 sensing. Meanwhile, in order to support the discussion result, the structure and morphology of the BP/PANI are respectively measured by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV−vis), transmission electron microscopy (TEM), and field emissions scanning electron microscopy (SEM). Moreover, the sensor shows good reproducibility, and fast response and recovery behavior, on NH3 sensing. In addition, this route may offer the advantages of an NH3 sensor, which are of simple structure, low cost, easy to assemble, and operate at room temperature.

Mediumfrequency fiber Bragg grating (FBG) acceleration sensors are used in important applications in mechanical, aerospace and weapon equipment, and have strict requirements in terms of resonance frequency and sensitivity. A novel medium-frequency accelerometer, based on fiber Bragg grating and flexible hinges, is proposed in this paper. The differential structure doubles the sensitivity of the sensor while avoiding temperature effects. The structure model and principle for the sensor are introduced, the sensor’s sensing characteristics are theoretically analyzed, and the structure parameters for the sensor are determined through numerical analysis. The sensing experiments show that the resonance frequency of the sensor is approximately 2800 Hz, the sensitivity is 21.8 pm/g in the flat frequency range of 50–1000 Hz, and the proposed sensor has a good temperature self-compensation function and lateral anti-interference capability.

Reservoir wettability is an important factor in the process of reservoir reconstruction. Especially in hydrophilic formation, it is easy to cause a water-locked phenomenon. A new type of fluoropolymer microemulsion was prepared by emulsion polymerization, and its structure and properties were characterized. The average particle size in the prepared emulsion was about 2.0 μm. The emulsion had good stability and wettability reversal performance for the storage of 30 days. After the treatment of 2.0 wt % emulsion, the contact angle between the core and water changed from 26 to 128°, the core surface free energy decreased from 66 to 2.6 mN/m, and the saturated water imbibition amount of the core decreased from 1.38 to 0.15 g. The ability of the fluoropolymer microemulsion to enhance oil recovery was evaluated by the visual displacement experiment. The fluoropolymer microemulsion can increase the displacement efficiency by more than 10%. The wettability of the core changed from hydrophilicity to hydrophobicity, and wettability reversal was achieved.

Bistable electrowetting display (EWD) is a promising low-power electronic paper technology, where power is consumed only during the switching between two stable states; however, it is not required for state maintenance once switched. In this paper, a bistable electrowetting device with non-planar designed controlling electrodes is fabricated by a fully conventional photolithography process. The device has potential for video display applications with a controllable gray scale. The novel electrode design realizes a lower driving voltage and a higher contrast between two stable states than the EWDs with planar electrodes reported previously.

In spite of rapid progress in cesium lead halide (CsPbX3) perovskites solar cells (PSCs), their power conversion efficiencies (PCEs) achieved to date leave much space for further improvement, princ...

In this paper, we demonstrate a regrowth-free double-tapered gain-coupled distributed feedback semiconductor laser. It is designed based on periodic surface current injection to reach a high-power and single-longitudinal mode. A continuous-wave output power of over 1.2 W/facet is achieved at 4 A. High single-longitudinal-mode output power reaches up to 0.9 W/facet at 3 A at each uncoated facet. The side mode suppression ratio is nearly 30 dB at 980 nm. The 3 dB spectral width is less than 2.7 pm. The lateral far field divergence angle is only 14.5°, the beam quality factor M2 is 1.7, achieving a near-diffraction-limit emission. Our device, produced by standard i-line lithography, enhances the output power while obtaining the pleasurable spectral and spatial properties. It has great potential in widespread commercial applications such as high efficiency pumping sources for its low-cost, easy fabrication technique and excellent performance.

Alloyed-type anode materials with high-energy density for lithium and sodium ion batteries attracted much attention of the researchers. However, substantial volume expansion of these materials in the devices during repeated electrochemical process leads to fast capacity fading and hinders their further practical application. Nanotechnology could act as a useful tool to effectively address the issue. Herein, lotus-stalk Bi4Ge3O12 nanosheets vertically grown on the nickel foam (denoted as Bi4Ge3O12 NSs@NF) were prepared via a straight-forward solvothermal method. Benefiting from their three dimensional (3D) conductive framework and two dimensional (2D) lotus-stalk Bi4Ge3O12 nanosheet structure, as anode materials of lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs), the electrochemical performances of Bi4Ge3O12 NSs@NF were greatly enhanced as a result of mitigating the huge volume variations during cycles. The Bi4Ge3O12 NSs@NF electrodes delivered a high reversible capacity of 1033.1 mAh/g for the first cycle and exhibited 68.6% capacity retention of after 88 cycles at 0.10 A/g in the voltage window of 0.01∼3.0 V versus Li/Li+. In the test of NIBs, the lotus-stalk Bi4Ge3O12 composite electrodes still stored Na+ as high as 332.3 mAh/g at 0.10 A/g over 100 sodiation/desodiation repeating cycles.

Different density nitrogen vacancy modified g-C3N4 photocatalysts were successfully prepared, and investigated their photocatalytic performance for H2 evolution and pollutant degradation. In this system, the increase of nitrogen vacancy density could enable the conduction band position of resultant g-C3N4 to negative shift compared to previous g-C3N4. Meanwhile, various positive factors were also introduced in this system, such as larger surface areas, the improvement of light response capacity, effective separation of photogenerated charge, resulting in resultant g-C3N4 photocatalysts exhibiting evident improvement of photocatalytic performance for H2 evolution and pollutant degradation. Obviously, this work provides physico-chemical insights for the nature of the promotion effect of nitrogen vacancies.

Hybrid polyimide (PI)-polytetrafluoroethylene (PTFE)/Nomex fabric composites and Nomex-PTFE/Nomex fabric composites were prepared with benzoxazine (BOZ) as the resin binder. The tribological properties and wear mechanisms of the two composites at different temperatures were investigated using a ball-on-disk wear tester. Before sliding wear tests, a thermo-aging test, thermogravimetric analysis and dynamic mechanical analysis of PI and Nomex fibers were performed to evaluate the thermal properties of the two reinforcing fibers. After each wear test, scanning electron microscopy was employed to analyze the morphologies of the worn surfaces of the composite. The results of sliding wear tests show that the difference between the tribological properties of the two composites is small at room temperature. However, the hybrid PI-PTFE/Nomex fabric composite achieves better tribological properties at high temperatures compared with the hybrid Nomex-PTFE/Nomex fabric composite, which suffered wear failure at 240℃. It is proposed that the excellent thermal mechanical property and thermal stability of PI fibers is the main factor that endows the PI-PTFE/Nomex/BOZ composite with a more favorable tribological property at high temperatures. Moreover, the influence of the increasing temperature on the tribological properties of the two composites was also investigated.

Although the solar cells based on the α-CsPbI3 presents very impressive power conversion efficiency, it suffers from insufficient crystalline structure stability even in ambient condition. Herein, the black orthorhombic γ phase based CsPbI3 is successfully fabricated with its performance further optimized by doping chlorine ions. It is found that the chlorine incorporation improves crystallization dynamics for favorable surface morphology and crystalline orientation. In particular by doping 3 mol% chlorine into the γ-CsPbI3 film, its trap density is minimized with enhanced black phase stability and much improved thin film characteristics, including conductivities, electron and hole mobilities. Consequently, the solar cell efficiency is increased to as high as 16.07%. More importantly, the PCE of the optimized device shows only 0.45% degradation after continuous light soaking for 200 h. It retains as much as 94% of its initial PCE even after being exposed in air (relative humidity of 20–30% at 25 °C) for 60 days.

Similar to carbon, germanium exists in various structures such as three-dimensional crystalline germanium and germanene, a two-dimensional germanium atomic layer. Regarding the electronic properties, they are either semiconductors or Dirac semimetals. Here, we report a highly conductive metallic state in thermally annealed germanane (hydrogen-terminated germanene, GeH), which shows a resistivity of similar to 10(-7) Omega.m that is orders of magnitude lower than any other allotrope of germanium. By comparing the resistivity, Raman spectra, and thickness change measured by AFM, we suggest the highly conductive metallic state is associated with the dehydrogenation during heating, which likely transforms germanane thin flakes to multilayer germanene. In addition, weak antilocalization is observed, serving as solid evidence for strong spin-orbit interaction (SOI) in germanane/germanene. Our study opens a possible new route to investigate the electrical transport properties of germanane/germanene, and the large SOI might provide the essential ingredients to access their topological states predicted theoretically.

Recently, γ-CsPbI3 perovskite solar cells (PSCs) have shown potential applications in optoelectronic devices, due to their high thermal stability. However, the incomplete utilization of the solar s...

The insufficient utilization of sunlight has been a big obstacle preventing inorganic perovskite solar cells (PSCs) from achieving high power conversion efficiency (PCE). Herein, nitrogen-doped graphene quantum dots (N-GQDs) are developed to achieve a photoluminescence quantum yield (PLQY) as high as 80% to effectively convert harmful UV light into useful visible photons for improved solar cell efficiency. It is found that the N-GQD material is very stable against humidity and under high temperature stress. When it is deposited on the top of the γ-CsPbI3 PSCs, it serves as an energy-down-shift (EDS) layer to harvest light in the short wavelength range

In this work, nitrogen vacancy modified graphitic carbon nitride (g-C3N4) with large surface area was synthesized and analyzed by a series of instruments, including XRD, FTIR, XPS, EPR SEM, TEM, DRS and PL, etc. and the photocatalytic H2-evolution activity was investigated. The results indicated that the as-synthesized g-C3N4 with nitrogen vacancy exhibited stronger visible light response capability, enlarged specific surface area and notably separated rate of photoinduced charge carriers, which caused the as-synthesized photocatalyst possessing the higher hydrogen evolution rate (5250 μmol h−1 g−1) and excellent recycle stability. Evidently, this work could provide a new insight for preparing highly efficient photocatalyst.

Recently, CsPbI3 perovskite solar cells (PSCs) have shown a breakthrough in photovoltaic performance due to their constantly improving power conversion efficiencies (PCEs) because of their admirable photoelectric properties and enhanced thermal stability. However, most fabrication processes take place inside a nitrogen glove box because CsPbI3 is notoriously sensitive to moisture. These tedious and rigorous operational conditions restrict CsPbI3 PSCs' commercialization. In our research, in order to solve the awkward situation of fabricating CsPbI3 PSCs without ambient moisture, we successfully developed an easy, one-step anti-solvent hot substrate (Anti-hot) spin-coating method to fabricate CsPbI3 film. Pre-heating the substrate could change the saturated vapor pressure of the mixed solvents and accelerate the precursor concentrations up to the supersaturation limit. Meanwhile, the anti-solvent method could induce heterogeneous nucleation. As a result, we could efficaciously control nucleation generation and grain growth under ambient moisture conditions and resist erosion and damage by molecular water. Finally, uniform and compact CsPbI3 film could be achieved and the corresponding PSCs reached up to 15.91% in a high humidity environment (RH, ∼50%). We hope that our exploration can provide a synthetic approach for producing high-quality CsPbI3 film for PSCs under ambient conditions.

High-power single-longitudinal-mode regrowth-free gain-coupled distributed feedback laser diode based on ridge waveguide with periodic current injection is achieved at 990 nm. Our device is fabricated only by standard i-line lithography with micron-scale precision, obtains an excellent performance at high injection current. A continuous-wave power of over 0.681 W is achieved at 3 A. The maximum continuous-wave power at single-longitudinal-mode operation is up to 0.303 W at 1.4 A. Narrow linewidth emission has been reached with a 3 dB spectrum width less than 1.41 pm. The high side mode suppression ratio is over 35 dB. The lateral far field divergence angle is only 15.05°, the beam quality factor M2 is 1.245, achieving a laterally near-diffraction-limit emission. It is more beneficial for single-mode fiber coupling as pumping sources and other applications which require high beam quality at high power with easy fabrication technique.

With the increase of operating frequency of electronic devices, electromagnetic interference (EMI) radiation in the 20 GHz and higher frequency is becoming an increasingly difficult problem to solve, especially in the integrated circuit (IC) package with heat sink where the radiation from the chip will leak out through the gap between the heat sink and the ground plane of PCB. In this paper, the electromagnetic radiation mechanism of the package with heat sink in the frequency range up to 40 GHz is proposed from plenty of full-wave simulations using different absorbing materials, which is beneficial to the selection of package structural parameters and the suppression of radiation. According to the proposed mechanism, the methods to improve the EMI radiation suppression effect in the frequency range from 20 GHz to 30 GHz are designed.

So far, most techniques for modifying perovskite solar cells (PSCs) focus on either the perovskite or electron transport layer (ETL). For the sake of comprehensively improving device performance, a dual‐functional method of simultaneously passivating trap defects in both the perovskite and ETL films is proposed that utilizes guidable transfer of Eu3+ in SnO2 to perovskite. Europium ions are distributed throughout the SnO2 film during the formation process of SnO2, and they can diffuse directionally through the SnO2/perovskite interface into the perovskite, while most of the europium ions remain at the interface. Under the synergistic effect of distributed Eu3+ in the SnO2 and aggregated Eu3+ at the interface, the electron mobilities of ETLs are evidently improved. Meanwhile, diffused Eu3+ ions passivate the perovskite to reduce trap densities at the grain boundaries, which can dramatically elevate the open‐circuit voltage (V oc) of PSCs. Finally, the mainly PSCs coated on SnO2:Eu3+ ETL achieve a power conversion efficiency of 20.14%. Moreover, an unsealed device degrades by only 13% after exposure to ambient atmosphere for 84 days., A dual‐functional method of simultaneously passivating trap defects in both perovskite and electron transport layer (ETL) films is proposed. Europium ions distribute throughout SnO2 film and diffuse into perovskite, while most of Eu3+ remain at the interface. Under the synergistic effect of distributed Eu3+, the electron mobility of ETL is improved and the trap density of perovskite is also reduced.

A tri-component (3-C) fiber-optic interferometric accelerometer using weak fiber Bragg grating array is proposed and tested. Experimental results showed that the axis sensitivity was about 55 dB and the suppression effect of cross-axil sensitivity is 30 dB in the frequency range of 5 Hz ~ 120 Hz.

The semiconductor laser array with single-mode emission is presented in this paper. The 6-μm-wide ridge waveguides (RWGs) are fabricated to select the lateral mode. Thus the fundamental mode of laser array can be obtained by the RWGs. And the maximum output power of single-mode emission can reach 36 W at an injection current of 43 A, after that, a kink will appear. The slow axis (SA) far-field divergence angle of the unit is 13.65°. The beam quality factor M 2 of the units determined by the second-order moment (SOM) method, is 1.2. This single-mode emission laser array can be used for laser processing.

As the helical gear is widely used as transmission part in the planetary gear train system, a six-degree-of-freedom bending-torsion-axis coupling dynamic model is established for the helical gear. In order to analyze the influence of the tooth profile modification on the gear meshing transmission, the tooth profile modification model is established, and the modification curve equation is analyzed by different curves. The results are substituted into the dynamic model of the original helical gear transmission, and a five-degree-of-freedom dynamic equation systematically considering tooth profile modification is obtained. The numerical simulation results show that the external stimulation, the tooth side gap and other factors have great influence on the vibration of the gear transmission, and the reasonable tooth profile curve can effectively reduce the system amplitude.

A chalcogenide (ChG) vertical slot waveguide and a ChG horizontal slot waveguide racetrack resonator were proposed for gas sensing. The vertical slot waveguide and the upper strip waveguide of the horizontal slot waveguide are suspended to enhance light-gas interaction. The waveguide sensors were optimized and the sensing performances were studied numerically.

In this paper, we proposed and experimentally demonstrated a high-sensitivity optical fiber relative humidity (RH) sensor, which consists of a tapered fiber and a silica microsphere resonator, for excitation of Whispering Gallery Modes (WGMs). Whispering gallery modes in the microsphere (200 µm) resonator are excited by evanescent coupling using the tapered fiber with ∼2.1 µm waist diameter. The variation of surrounding RH will induce the effective refractive index and coupling efficiency of the microsphere change, and result in transmission spectra change finally. Studies of the RH response sensitivity, the repeatability, long-term stability and temperature dependence of the proposed sensor are carried out. The sensitivity achieved in our experiments was 0.11 dB/%RH in the RH range from 20% to 70%, and 0.21 dB/% RH in the RH range from 70% to 90%. The proposed sensor with the advantages of compact size, high sensitivity, low hysteresis, good repeatability, and low cross sensitivity to temperature has good application prospects.

As the black cesium lead iodide (CsPbI3) tends to transit into a yellow δ-phase at ambient, it is imperative to develop a stabilized black phase for photovoltaic applications. Herein, we report a distorted black CsPbI3 film by exploiting the synergistic effect of hydroiodic acid (HI) and phenylethylammonium iodide (PEAI) additives. It is found that the HI induces formation of hydrogen lead iodide (HPbI3+x), an intermediate to the distorted black phase with appropriate band gap of 1.69 eV; while PEAI provides nucleation for optimized crystallization. More importantly, it stabilizes the distorted black phase by hindering phase transition via its steric effects. Upon optimization, we have attained solar cell efficiency as high as 15.07%. Specifically, the bare cell without any encapsulation shows negligible efficiency loss after 300 h of light soaking. The device keeps 92% of its initial cell efficiency after being stored for 2 months under ambient conditions., Black phase cesium lead iodide perovskite is regarded as a promising candidate for solar cells, but it easily transits to undesired yellow phase. Herein, Wang et al. stabilized the black phase using molecular additives to achieve device efficiency beyond 15% with high light soaking stability.

Hydrogel is a kind of functional cross-linked polymer material with 3-D network structure. When hydrogel is exposed to water environment, a mass of hydrophobic groups and hydrophilic residues existing in the cross linked netlike nano-structure is willing to combine with water molecules and expand, respectively. In this paper, a novel optical fiber probe based on hollow-core fiber and calcium alginate (CaAlg) hydrogel film is proposed and experimentally demonstrated. The experimental results of relative humidity (RH) and temperature sensing characteristics show that the proposed probe has a binomial response to RH in the range of 20%~90% RH and a linear response to temperature with the sensitivity of 121pm/°C. CaAlg is considered as an effective and potential as the humidity-sensitive material to optical fiber RH sensors.

Summary All-inorganic perovskite shows great potential for photovoltaic applications due to its excellent solar cell performance and atmospheric stability. Here, a CsPbI2+xBr1−x perovskite solar cell with a graded bandgap is explored using CsPbBrI2 and CsPbI3 quantum dots as component cells. Four strategies were pursued to boost the device performance. First, CsPbI2Br film was fabricated as the main absorber, with the component cell showing remarkable power conversion efficiency (PCE) as high as 13.45%. Second, by Mn2+ substitution, SCN− capping, and [(NH2)2CH]+ treatment, stable and high-mobility CsPbI3 quantum dot (QD) film was attained. Third, a halide-ion-profiled heterojunction was designed at the CsPbBrI2/CsPbI3 QD interface to achieve proper band-edge bending as graded bandgap for improved carrier collection. Finally, the CsPbI3 QD layer was optimized in the graded bandgap structure to achieve maximum overall light harvesting. As a result, the device achieved a PCE of 14.45%. This is the highest efficiency ever reported for inorganic perovskite solar cells.

High-resolution grating areas with none stitching error are in demanding needs but usually expensive and hard to prepare. In this paper, we present a method of making refined grating areas from coarse photolithography mask using Displacement Talbot Lithography (DTL). DTL is relatively simple and low-cost system based on mask photolithography for high-resolution periodic structures over large areas. The grating periods on the ordinary coarse photolithography mask was designed as 3.552 μm. By patterning gratings on Si3N4 film deposited on fused silica as intervening phase masks, the final prepared grating periods shrinks 8 times, down to 444 nm. This technology is suitable for producing large area high resolution gratings to reduce the research cost, and can be applied to applications such as DFB laser production, LED substrates preparation and other relative fields.

It is imperative to develop a large-aspect-ratio grain-based thin film with low trap density for high-performance inorganic perovskite CsPbI2Br solar cells. Herein, by using Mn2+ ion doping to modulate film growth, we achieved CsPbI2Br grains with aspect ratios as high as 8. It is found that Mn2+ ions insert into the interstices of the CsPbI2Br lattice during the growth process, leading to suppressed nucleation and a decreased growth rate. The combination aids in the achievement of larger CsPbI2Br crystalline grains for increased JSC values as high as 14.37 mA/cm2 and FFs as large as 80.0%. Moreover, excess Mn2+ ions passivate the grain boundary and surface defects, resulting in effectively decreased recombination loss with improved hole extraction efficiency, which enhances the built-in electric field and hence increases VOC to 1.172 V. As a result, the champion device achieves stabilized efficiency as high as 13.47%, improved by 13% compared with only 11.88% for the reference device.

Single-longitudinal-mode, gain-coupled distributed feedback (DFB) lasers based on high order surface gain-coupled gratings are achieved. Periodic surface metal p-contacts with insulated grooves realize gain-coupled mechanism. To enhance gain contrast in the quantum wells without the introduction of effective index-coupled effect, groove length and depth were well designed. Our devices provided a single longitudinal mode with the maximum CW output power up to 48.8 mW/facet at 971.31 nm at 250 mA without facet coating, 3dB linewidth ( 3.2 pm) and SMSR ( > 39 dB). Optical bistable characteristic was observed with a threshold current difference. Experimentally, devices with different cavity lengths were contrasted on power–current and spectrum characteristics. Due to easy fabrication technique and stable performance, it provides a method of fabricating practical gain-coupled distributed feedback lasers for commercial applications.