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Near-equiaxed β grain was achieved in the near-α Ti60 (Ti-5.7Al-4.0Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C) titanium alloy via laser directed energy deposition (LDED). The microstructural evolution along the building direction and the room-temperature tensile properties along the horizontal and vertical directions (building direction) were systematically studied through SEM and OM. EBSD and XRD were utilized to accurately demonstrate the texture of the α and β phases. The results showed that the α phase presented a low texture intensity, which was ascribed to the weak textured β grain with near-equiaxed morphology, since there are Burgers orientation relationships during the β→α transition. In addition, numerical simulation, combined with the CET curve of Ti60 alloy considering the effect of multi-composition, was utilized to elucidate the formation mechanism of the near-equiaxed β grains. Furthermore, according to the solidification theory, we proposed that the solidification temperature range Δ T f was more accurate than the growth restriction factor Q in predicting the formation tendency of equiaxed β grain in different titanium alloys. Tensile results showed that the horizontal and vertical samples had similar strength, while the former exhibited larger elongation than the latter. The effect of the near-equiaxed β grain and the internal α phase on mechanical properties were revealed at last.

We demonstrate the fabrication of a flexible and conductive bioelectrode via the electrodeposition of IrO2 nanoparticles on a metalized polypropylene micromembrane (PPMM). The metalized PPMM is prepared by carrying out conformal electroless deposition of Au on individual polypropylene (PP) fibers of PPMM using both polydopamine and polyvinyl alcohol as the surface–modifying agents to improve the hydrophilicity of PPMM. Images from scanning and transmission electron microscopes, as well as analysis from energy dispersive X–ray spectrometer and X–ray photoelectron spectroscopy confirm the successful formation of IrO2 nanoparticles on individual PP fibers of metalized PPMM. For bio–stimulating purpose, the IrO2–coated PPMM reveals an impressive charge–storage–capacity of 54.6 mC/cm2 in cyclic voltammetry, In addition, under a symmetric bi–phasic current pulse, its charge–injection–capacity reaches 466 μC/cm2. Since the entire constituents for the IrO2–coated PPMM are bio−compatible, we envision its potential use as a bioelectrode in implantable biomedical devices.

Although TiO2 is a wide band gap semiconductor, it demonstrates photodegradation activity under visible light irradiation after dye sensitization. Compared with esterification between the surface hydroxyl group of TiO2 and the carboxylic group of dyes, electrostatic interaction between TiO2 and dye shows better photosensitized performance. In this work, Bi/Al co-doping anatase titania (Ti1-xBi2x/3Al2x/3O2 (0 ≤ x ≤ 0.3)) is designed to enhance the electrostatic interaction. The effect of Al ions is to enhance the solubility of Bi3+ into titania nanocrystals. A new band gap is generated after high concentration of Bi element doping, which not only promotes the absorption of visible light, but also improves the utilization of photogenerated carriers. Based on the results of transmission electron microscopy, light absorption, photodegradation activity and density functional theory calculations, it is found that bismuth dopant is the electron capture site. It first accumulates electrons through photocatalytic degradation reaction to enhance electrostatic adsorption between the catalyst and the positively charged dye molecules, and finally realizes high-efficiency photosensitization degradation of Rhodamine B. In addition, the sensitized titania has excellent photodegradation recyclability.

Crude oil pretreatment using flow improver or pour point depressants has been accepted considerably owing to its simplicity and economy. We prepared herein new allyl 4-(dodecyloxy) benzoate I12 and...

The detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial for preventing and controlling infectious diseases and disease treatment. In this work, a Au@Ti3C2@PEI-Ru(dcbpy)32+ nanocomposite-based electrochemiluminescence (ECL) biosensor was rationally designed, which realized sensitive detection of the RNA-dependent RNA polymerase (RdRp) gene of SARS-CoV-2. In addition, a DNA walker was also used to excise the hairpin DNAs under the action of Nb.BbvCI endonuclease. Furthermore, model DNA–Ag nanoclusters (model DNA–AgNCs) were used to quench the initial ECL signal. As a result, the ECL biosensor was used to sensitively detect the SARS-CoV-2 RdRp gene with a detection range of 1 fM to 100 pM and a limit of detection of 0.21 fM. It was indicated that the ECL biosensor had a great application potential for clinical medical detection. Furthermore, the DNA walker amplification also played a reliable candidate strategy for other detection methods.

This letter proposes a testing method to emulate realistic stress conditions of DC and AC capacitors, with minimum required power supply and robust operation at the presence of capacitor degradation. It is especially suitable for parameter characterization and accelerated degradation testing of high-voltage and high-ripple current power electronic capacitors. The circuit architecture of the proposed testing method and the constraints of the testing samples under given designs are discussed. Proof-of-concept experiments on both DC and AC capacitors verify the feasibility.

In current work, the impact of ammonium sulfide (NH4)2S solution passivation with varied pH value on the Yb2O3/n-GaSb interface has been investigated comparatively. Compared with control samples, the neutral (NH4)2S solution passivation can effectively reduce oxides layer on GaSb surface and gate leakage via X-ray photoelectron spectroscopy (XPS) measurements and electrical characterization. High-low frequency capacitance method was used to evaluate interface-state density ${D}_{{\text {it}}}$ , it was found that capping with Yb2O3 can delay the interface-state generation and the lowest $D_{{\text {it}}}$ value of ${5.18}\times {10} ^{{12}}$ cm−2 eV−1 for Yb2O3/GaSb capacitor with neutral (NH4)2S was achieved. Moreover, the possible leakage current conduction mechanisms for capacitors measured at room temperature and low temperature have also been discussed systematically.

We demonstrate a facile and seedless wet chemical process to deposit RuO2 thin film on a glass slide. The process entails the use of dopamine and its oxidized form, polydopamine (PDA), as the reducing and chelating agent, as well as the adhesive agent bonding the RuO2 and glass slide. The formula starts with the oxidation of K2RuCl5 to prepare RuO4 solution, followed by its reduction by dopamine to form chelated RuO2 colloids for the deposition of amorphous RuO2 thin film containing 26.5 at% hydrous RuO2 and 73.5 at% RuO2. After a mild Ar annealing, the RuO2 thin film exhibits a rutile phase with (110) preferred orientation. Elemental analysis indicates incomplete pyrolysis of PDA. Results from X-ray absorption spectroscopy confirm the presence of RuO4 and its transformation to RuO2. Electrochemical analysis of the adsorbed dopamine molecules on an ITO substrate validates the oxidative behavior of dopamine. The bonding strength of RuO2 thin film is determined by a tape-peeling test in which both the as-deposited and annealed RuO2 thin films show robust adhesion to the glass substrate.

Esterification reaction of lactic acid with butanol to produce butyl lactate and its optimal conditions were investigated. Cyclohexane was used as entrainer to remove water to promote reaction yield. Catalyst of NaHSO4 was also used to increase reaction rate. Reaction parameters of butanol/lactic acid ratio, cyclohexane/lactic acid ratio, catalyst amount, and reaction time were optimized using Response Surface Methodology (RSM). Results showed that the butanol/lactic acid ratio was the most significant factor for esterification yield while interactions between butanol/lactic acid ratio and cyclohexane/lactic acid ratio, butanol/lactic acid ratio, and reaction time were less significant. The correlation coefficient between predicted values and experiment values was 0.985. The optimal conditions for the experiment are: ethanol/lactic acid ratio 5:1, cyclohexane/lactic acid ratio 1:1, catalyst loading 1.5%, and incubation period 3 hours. The esterification yield reaches 99.8% under these conditions.

The precipitation of wax crystals in water-in-crude-oil emulsion impairs the safety and economy of multiphase transportation in oil fields. At present, there are different opinions on the precipita...

In this paper, a novel ethylene-vinyl acetate copolymer (EVA)/amino-functionalized polymethylsilsesquioxane (PAMSQ) composite wax inhibitor (WI) was prepared through melt blending, and the rheological and wax depositing properties of the doped crude oil were studied. The EVA/PAMSQ composite can strongly crystallize with wax molecules and trigger the formation of compact wax flocs, which greatly improve the rheological properties of crude: compared to the pure EVA at the same dosage, the composite can further decrease the gel point and apparent viscosity (25 °C) by 14.6 °C and 92.0%, respectively. The wax deposition can also be inhibited by adding the composite: adding EVA inhibits the mass of the wax deposit at 24 h by 62.3%, and this number is suppressed by 77.9% after adding the EVA/PAMSQ composite, but the wax molecule diffusion is accelerated and the wax content in the wax deposit rises because of the improved crude oil rheological characteristics. Here, we develop the gel structure theory to consider the wax deposition process affected by the WI. Adding the WI contributes little to the wax precipitation temperature but decreases the gel structural strength of the oil a lot, and thus, the oil near the pipe wall can only form the wax deposit with a higher wax content to resist the pipe wall shearing. Therefore, the crude oil added EVA/PAMSQ composite possesses not only the lowest wax deposit rate and the highest aging rate but also the highest wax content in the wax deposit.

We propose and demonstrate a cladding-pumped, erbium-ytterbium co-doped fiber amplifier (EYDFA) scheme based on dual wavelength auxiliary signal injection technique to solve the issue of the backward Yb-ASE self-lasing under strong pumping for the high-power fiber amplification of 1.5-μm kHz-linewidth linearly-polarized laser signal. With the dual wavelength auxiliary signal of 1030 and 1040 nm injection, the allowable maximum pump power without triggering the backward Yb-ASE self-lasing can be greatly increased due to the relieving effect on the inhomogeneous gain broadening. For an EYDFA with 3.8-m erbium-ytterbium co-doped double-clad fiber, the net output power is improved to 13.8 W, while the linewidth of the amplified single-transverse-mode linearly-polarized 1560 nm laser signal is still only 3.5 kHz. The SBS effect is observed to be trivial during the fiber amplification.

Two-dimensional atomic layers composed of metallic atoms with a high principal quantum number in valence shells are promising materials for applications in state-of-the-art magnetic devices due to the presence of a strong spin-orbit coupling. In this work we experimentally explored the effects of triggering perpendicular magnetic anisotropy (PMA) of ferromagnetic (FM) films by applying a series of $6p$-Pb, Bi and $4d$-Pd (reference) atomic layers with high-level atomic orbital and low-level lattice strain. Our research indicates that, compared with Pd atoms, Pb and Bi atoms can produce higher-strength PMA on adjacent FM films through orbital hybridization at the interface. Moreover, we demonstrate that the PMA induced by Pb and Bi atoms is highly sensitive to the ordering degree of the wetting layer which is determined by the interplay of surface free, cohesive, and strain energies within the grown materials; the Pb(Bi) atoms added on the wetting layer can enhance the PMA of the adjacent FM film only when the wetting layer maintains an ordered structure. This work clarifies the critical interface effects of $6p$-HMs on the FM layer, thus providing important clues to increase control over the spin-orbit interaction engendered by HMs through the interface.

In this paper, we study the limitations of decreasing the repetition rate for the narrowband dissipative soliton picosecond (ps) pulsed Figure-9 fiber laser with periodically saturable absorber (SA), and demonstrate how to decrease the repetition rate of this kind of fiber laser. By asymmetrically increasing the passive fiber length of nonlinear amplifying loop mirror (NALM) to lower SA saturation power, Q-switching instability can be avoided, thus effectively reducing the repetition rate of ps pulses. To combat noise-like pulse caused by excessive reduction of SA saturation power, we invoke the non-reciprocal output characteristics of periodic SA, and combined with increasing the intracavity fiber length outside the SA, we further reduce the laser repetition rate. Repetition rates for ∼10 and ∼20 ps pulses are reduced to 1.7 MHz and 848 kHz, respectively, which are, to the best of our knowledge, the lowest repetition rates of Figure-9 lasers reported thus far.

Antiferromagnetic (AFM) thin films are promising materials for engineering the magnetic anisotropy of adjacent ferromagnetic (FM) films. In this work, we explored the effects of triggering perpendicular magnetic anisotropy (PMA) of FM films by applying a series of NiMn-based AFM films with in-plane-oriented spin structures. The vertically expanded face-centered tetragonal ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50}$ films alone could not induce PMA in Co/Ni films. By contrast, PMA was triggered through the application of Mn-rich NiMn alloy films or ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50}/1$-monolayer Mn $(\mathrm{Mn}/1\text{\ensuremath{-}}\mathrm{ML} {\mathrm{Ni}}_{50}{\mathrm{Mn}}_{50})$ heterostructures. Detailed analyses of a series of samples indicated that two criteria must be met for a NiMn-based AFM film to trigger PMA in a neighboring FM film: (1) perpendicular interface crystalline anisotropy of interfacial uncompensated Mn moments must be established, and (2) strengthened lateral exchange coupling to volume AFM moments must be made. This paper clarifies how NiMn-based AFM films with in-plane-oriented AFM spin structures trigger the PMA of FM films, thus identifying a pathway to increase control over antiferromagnet-induced PMA through the interface/volume magnetic engineering of AFM layers.

Asphaltenes are natural pour point depressants, and the effect of asphaltene polarity on the low-temperature rheology of waxy oils has been well studied. In this paper, the influence of asphaltene ...

Among various processing methods for growing perovskite thin layers, dual-source vacuum deposition was once regarded as the most economical and high throughput method. However, co-evaporation of MAI and PbI2 often leads to an inevitable PbI2 interfacial layer formed by the initial growth of evaporation resulting in a compromised efficiency of vacuum deposited MAPbI3 solar cell. Here, two modified growth methods based on vacuum co-evaporation, namely solution-vacuum hybrid method (SVHM) and soaking-assistant fully-vacuum method (SAFVM), are developed to grow a completely converted MAPbI3 perovskite layer at the interface prior to the co-evaporation of MAPbI3 perovskite layer. Upon these two methods, the unwanted PbI2 layer can be removed from the interface resulting in much improved power conversion efficiency up to 14.35%. Our result shows that, while unwanted interfacial PbI2 layer is the main cause of low performing co-evaporated perovskite solar cell devices, by removing the PbI2 interfacial layer we can unlock the full potential of vacuum-based perovskite solar cells to industrial mass production.

For the pipeline transportation of waxy crude oil, pour point depressants (PPDs) have been developed and used to improve its flowability at low temperature. As supercritical CO2 (scCO2) flooding becomes a common technique to improve oilfield recovery, how the sensitivity of PPD changes due to the degassed crude oil treated by CO2 should be studied. In this work, the effect of scCO2 extraction on the performance of EVA in improving the flowability of Changqing degassed crude oil is investigated by means of a self-developed scCO2 treating equipment, SARA/HTGC analysis, SEM analysis, pour point test, rheological measurement, asphaltene precipitation test, particle size analysis, DSC test, and microscopic observation. The results show that without EVA addition, scCO2 extraction aggravates the flowability of the crude oil at low temperature. The scCO2 extraction extracts light components from asphaltene aggregates causing asphaltenes to precipitate, which inhibits the asphaltenes on playing a role as the natur...

Formamidinium lead iodide (FAPbI3) is a promising candidate as the solar cell absorption layer with a suitable band gap of 1.45 eV and excellent optoelectronic properties. In this work, we report a new vacuum flash evaporation method to deposit phase-pure black α-FAPbI3 films in situ on low-temperature substrates without post-annealing, and the area of deposited films can be up to 36 cm2 (6 cm × 6 cm). Besides, the unique relationship between substrate temperature and phases in films is demonstrated for the further development of the method. With the α-FAPbI3 films as the active layer, perovskite solar cells with power conversion efficiency of 12.55% are fabricated.

This paper reports a low-cost and versatile micro-basin array fabrication approach for single mammalian cell and single bacterial analysis. This approach is based on optical lithography, material sputtering, and lift off. The pitch, size, height, thickness, inclination angle and material type of the micro-basins can be adjusted controllably. The whole fabrication process does not require any strong chemical etching process and is environmentally friendly and cost-effective. Finite element analysis was applied to obtain optimal dimensions of micro-basins. Preliminary results show successful isolation of single bacterium within micro-basins. Ongoing work focuses on improving the isolation efficiency through hydrophobic and hydrophilic patterning.

We report the recent progress on the Shanghai Superintense Ultrafast Laser Facility (SULF) project. The schematic design of SULF is described. The upgrade information from SULF laser prototype to SULF 10 PW laser user facility is presented in detail. A high contrast front is developed to generate high-quality clean seed pulses which are then stretched to about 2 ns by a new double-grating Offner stretcher. A Dazzler is used to control the high-order phase distortions and shape the spectrum of the laser pulses simultaneously. The laser pulses are amplified to 7 J energy in the 1 Hz pre-amplifiers system before injected into the three stages large aperture main amplifiers system. The first two main amplifiers are pumped by five commercial lasers which can be operated at 1 shot/min. The final main amplifier is pumped by six home-built high energy frequency doubled Nd:glass lasers at a repetition rate of 1 shot/3 min. The final amplifier output energy is ~408 J with high stability under a pump energy of ~530 J. Compressed pulse duration of the amplified laser and the total transport efficiency for compression is measured to be 22.4 fs and 70.52% respectively. The experimental results demonstrate that SULF user facility has the capacity to deliver 10 PW peak power femtosecond pulses.

We demonstrate a facile fabrication scheme for Co3O4@CoO@Co (gradient core@shell) nanoparticles on graphene and explore their electrocatalytic potentials for an oxygen evolution reaction (OER) and an oxygen reduction reaction (ORR) in alkaline electrolytes. The synthetic approach begins with the preparation of Co3O4 nanoparticles via a hydrothermal process, which is followed by a controlled hydrogen reduction treatment to render nanoparticles with radial constituents of Co3O4/CoO/Co (inside/outside). X-ray diffraction patterns confirm the formation of crystalline Co3O4 nanoparticles, and their gradual transformation to cubic CoO and fcc Co on the surface. Images from transmission electron microscope reveal a core@shell microstructure. These Co3O4@CoO@Co nanoparticles show impressive activities and durability for OER. For ORR electrocatalysis, the Co3O4@CoO@Co nanoparticles are subjected to a galvanic displacement reaction in which the surface Co atoms undergo oxidative dissolution for the reduction of Pt ions from the electrolyte to form Co3O4@Pt nanoparticles. With commercial Pt/C as a benchmark, we determine the ORR activities in sequence of Pt/C &gt, Co3O4@Pt &gt, Co3O4. Measurements from a rotation disk electrode at various rotation speeds indicate a 4-electron transfer path for Co3O4@Pt. In addition, the specific activity of Co3O4@Pt is more than two times greater than that of Pt/C.

A long-term stable single-longitudinal-mode (SLM) all polarization-maintaining (PM) compound-ring cavity fiber laser is reported. The results show that the PM fiber's strong ability to resist the environment disturbance allows finely designing the length of each secondary cavity in real time according to the main cavity under the laboratory environment, and then the effective longitudinal mode spacing can be sufficiently increased by accurately using the Vernier effect, so that the mode-hopping can be effectively suppressed. Furthermore, the temperature compensation is used for asynchronously fine-adjusting each cavity length to follow the Vernier effect requirement more strictly. The mode-hopping-free SLM operation time of the packaged laser reaches 11 h. As far as we know, this is the longest SLM free running time of ring cavity fiber laser to date. The optical signal to noise ratio of the laser reaches 77 dB and the linewidth is less than 850 Hz with up to 50 mW maximum output power.

Generation of topological defect that has a particular type (topological charge) and specific shape (radial, spiral, or circular) on a designed position is a crucial step in producing q plates and defect-mediated self-assembled micro structures. Shaping and positioning of topological defects can be achieved by applying delicately designed electric field on nematic liquid crystal (NLC). The guidelines for the electrode design are provided in this paper. The following are the three frequently asked questions: 1) What kinds of defects can exist in NLC? Points, lines, or walls? 2) How to generate a defect with a particular topological charge by setting proper boundary condition? 3) How to control the orientation of liquid crystal to have a defect with desired vorticity? The three questions can be answered by the three theories in physics: 1) Symmetry breaking in ordered material, 2) Euler characteristic and vectors in closed confinement, and 3) Minimization of free energy of NLC in electric field. Topological defects in spherical and toroidal confinements were generated in NLC cell and examined under polarized microscope. Radial and circular hedgehog defects were successfully created by fishbone- and coil-shaped patterned electrodes, respectively. By applying the three physical theories in NLC cell design, topological defects were successfully arranged in square and hexagonal arrays. They are large, stable, and re-configurable, and the applications in optics are demonstrated.

The influence of thermal treatment temperature on the flowability and wax deposition characteristics of Changqing waxy crude oil was researched in detail through pour point/rheological tests, a cylindrical Couette wax deposition experimental device, DSC analyses, asphaltenes stability tests, and microscopic observations. It is found that the flowability of the crude oil can be greatly improved through increasing the thermal treatment temperature. Meanwhile, the wax deposition rate of the crude oil can be outstandingly inhibited with the increase of thermal treatment temperature from 50 to 70 °C. Moreover, the flow regime can also influence the wax deposition characteristics. Under cold flow regime (22 °C/12 °C), the structure of formed wax deposits is homogeneous while the aging of the wax deposits is not obvious. Under hot flow regime (30 °C/20 °C), the aging of the wax deposits is obvious, but a heterogeneous two-layer structure exists in the formed wax deposits at the thermal treatment temperatures 50 ...

Epoxy asphalt is a thermosetting paving material that can provide higher strength, stiffness, adhesion, high-temperature stability, and service life compared to conventional asphalt; howeve...

In CO2 flooding, the dissolution of CO2 in produced fluid may change the stability of crude oil emulsion, thereby affecting the design/operation of the gathering pipeline and oil–water separation. The purpose of this study is to investigate the stability change of crude oil emulsion and its mechanisms after the dissolution of CO2. The stability of the CO2-dissolved crude oil emulsions is determined with a self-made apparatus. The mechanisms of the stability change are uncovered from interfacial properties and bulk viscosity. It is found that the stability of the crude oil emulsions is visibly reduced with an increasing dissolved quantity of CO2. This is partly attributed to the fact that dissolved-state CO2 can lessen the interfacial dilational modulus and increase the loss angle markedly, thus lowering the structural strength and elasticity of the interface. Meanwhile, the dissolution of CO2 in crude oil can reduce its viscosity, resulting in easier collision of droplets. In view of these experimental re...

The direct shear tests were conducted to study the shear performance of steel-asphalt interface by taking epoxy asphalt (EA) as waterproofing adhesive layer (WAL) material when considering temperature and relative humidity (RH) coupling. The temperatures of 30 and 60 °C and RH of 30, 50, 70 and 95% for each temperature were chosen and the steel-WAL interface, WAL-pavement interface and composite structure specimens were cured under specified temperature and RH. The research results show that the influence of RH on the shear strength of the steel-asphalt composite structure without considering the effects of temperature and RH on interfaces is negligible and the traditional shear test method should be updated. However, the interface shear strength decreases with increased RH when it exceeds 70% by considering the effects of temperature and RH on interfaces.

The aging fracture of bonding wire is one of the main reasons for failure of insulated gate bipolar transistor (IGBT). This paper proposes an online monitoring method for IGBT bonding wire aging that does not interfere with the normal operation of the IGBT module. A quantitative analysis of aging degree was first performed, and the results of multivariate and univariate monitoring were compared. Based on the relationship between the monitoring parameters and the aging of the IGBT bonding wire, gradual damage of the IGBT bond wire was implemented to simulate aging failure and obtain the aging data. Moreover, the change of junction temperature was considered to regulate monitoring parameters. Then, the aging degree was evaluated by an artificial neural network (ANN) algorithm. The experimental results showed the effectiveness of the proposed method.

Hydrogenation has recently been proposed for use in modulating the magnetic properties of Pd-rich ferromagnetic (FM) alloy films. This study successfully fabricated Pd-rich Mn/MnPd/Fe antiferromagnetic/FM films with an established exchange bias field at RT, and determined that hydrogenation can enhance the exchange bias coupling in such films. Specifically, magnetic hysteresis loops revealed that the magnetic state of the Pd-rich Mn/MnPd/Fe films was gradually changed from an unbiased state to an exchange-biased state upon exposure to a hydrogen environment; moreover, hydrogenation engendered a larger magnitude of the exchange bias field than conventional field cooling. This phenomenon can be attributed to the enhanced long-range antiferromagnetic ordering of the Pd-rich MnPd film upon uptake of hydrogen atoms.

Recently, studies on the use of polymer nanomaterial composites as pour-point depressants (PPD) have drawn much attention, but the crystallization properties and improved rheological performance of waxy crude oils using nanoclay-based composite PPDs have rarely been reported. In this paper, montmorillonite (Mnt) was first organically modified using octadecyltrimethylammonium chloride (C21H46NCl, or stearyltrimethylammonium chloride) in aqueous solution. Then, the organically modified Mnt (OMnt) material was dispersed into a polyoctadecylacrylate (POA) matrix to prepare a POA/OMnt composite PPD by melt blending. The composition, structure, and morphology of Mnt, OMnt, and the POA/OMnt composite PPDs were investigated. The results showed that the OMnt and POA were compatible and that the OMnt was exfoliated into several sheets in the POA matrix. Subsequently, the isothermal crystallization kinetics of the POA/OMnt composite PPDs showed that small amounts of OMnt had a dramatic impact on POA chain motion during crystallization and facilitated POA crystallization. After it was added to a waxy crude oil, the POA/OMnt composite PPDs produced better rheological properties and performance than identical concentrations of the neat POA. The POA/OMnt composite PPDs can act as wax nucleation sites for wax molecule precipitation and result in larger and more compact wax crystal flocs, which adversely affect the formation of a wax crystal network and, thus, favor the improvement of waxy crude oil rheology.

In the previous work, we have reported that small dosages of the polymethylsilsesquioxane (PMSQ) microsphere can effectively improve the performance of the EVA pour point depressant (PPD) and the amount of EVA PPD adsorbed on the microsphere evidently influences the efficiency of the EVA/PMSQ composite particle. To further promote the adsorption of EVA on the microsphere and enhance the efficiency of the composite particle, here, the amino-functionalized PMSQ microspheres with different amino molar ratios (PAMSQ) are first synthesized and characterized. The flow behavior, exothermic crystallization and microstructure of the waxy crude oil undoped/doped with EVA, EVA/PMSQ and EVA/PAMSQ are systemically investigated. Results show that 50 ppm EVA PPD can greatly improve the flow behavior of the oil and small dosages (2.5 ppm) of PMSQ microsphere can significantly improve the performance of the EVA PPD. After the amino-functionalization, the flow improving efficiency of EVA/PAMSQ is further enhanced: the gelation point, G′, G″, apparent viscosity and yield stress of the oil sample decrease to a lower value. The best performance is found at adding 50 ppm EVA + 2.5 ppm PAMSQ-2 (with amino molar ratios at 15%). Compared to EVA/PMSQ, the EVA/PAMSQ exhibits a stronger nucleation effect to increase the WAT of the oil sample slightly, and outstandingly modifies the morphology of the precipitated wax crystals into larger and more compact flocs. The amino-functionalization facilitates more EVA PPDs adsorbing and concentrating on the PAMSQ microsphere, causing the formation of the EVA/PAMSQ composite particles. The composite particles provide stronger nucleation effect for the wax precipitation, resulting in larger and more compact wax microstructures and then further improving the flow behavior of the oil. The rheological improving performance of EVA/PAMSQ for the waxy crude oil increases with the increase of amino molar ratio and the efficiency of EVA/PAMSQ-2 reaches the best. When the amino molar ratio is too high (PMASQ-3), the PAMSQ-3 microsphere is unstable in oil phase and aggregates into large particle flocs, which inhibits the EVA adsorption on the PAMSQ-3 microsphere and then weakens the rheological improving efficiency of the EVA/PAMSQ-3 composite particle.

Here, we reported that by adjusting the stirring speed, condensation pH value, precursor concentration and reaction temperature, the morphologies of the polymethylsilsesquioxane (PMSQ) microsphere could be well controlled through the two-step sol-gel synthesis. Because of the specific structural property and strong hydrophobicity, the obtained PMSQ microsphere dispersed well in the ethylene-vinyl acetate copolymer (EVA) matrix to form EVA/PMSQ hybrid. Subsequently, the thermal properties of both EVA and EVA/PMSQ hybrid were investigated through the TGA and DSC tests. The presence of PMSQ microsphere generates a significant delay in the thermal degradation processes of EVA, thus improving the thermal stability of EVA. The PMSQ microsphere also obviously increases the onset crystallization temperature and the crystallization rate of EVA, meaning that adding PMSQ microsphere enhances the crystallization ability of EVA. Finally, by applying rheological tests and microscopic observation, EVA/PMSQ hybrid was found to further improve the flow behavior of Qinghai waxy crude oil than the neat EVA did. The EVA/PMSQ hybrid can act as heterogeneous nucleation templates of wax crystals, and favor the formation of wax crystal flocs with increased size and compactness, thus inhibiting the continuous wax crystal network structure and further improving the flow behavior of the waxy crude oil.

In this paper, the effect of POA PPD together with resin-stabilized asphaltenes on the flow behavior of model waxy oils was investigated through rheological test, DSC, microscopic observation and a...

In real crude-oil pipelines, the formed wax deposits could be heterogeneous along the radial or axial directions. However, studies on this aspect are scarce. In this paper, the effect of the polyoctadecyl acrylate (POA) wax inhibitor on the wax deposition of 10 wt % model waxy oil was investigated with the aid of an in-house wax deposition device, differential scanning calorimetry test, high-temperature gas chromatography–Fourier transform infrared analysis, and microscopic observation. The results showed that adding POA in the model waxy oil greatly modifies the morphology of precipitated wax crystals, thus greatly changing the wax deposition behavior of the oil. For oil sample 1 (without POA), the precipitated wax crystals (needle-like) more easily form porous network structures, causing the formation of a thick and porous wax deposit with relatively low WAT, wax conten,t and critical carbon number (CCN). With the increase of POA concentration (oil samples 2–5), the precipitated wax crystals become more...

A mixture of polydopamine (PDA) and polyethyleneimine (PEI) are used as the adhesive, wetting, and reducing agent simultaneously to fabricate a conductive silver membrane. The conformal coating of PDA/PEI on individual polypropylene fibers of polypropylene micromembrane (PPMM) renders the latter to be hydrophilic for subsequent electroless silver deposition. The resulting conductive silver membrane demonstrates impressive electric conductivity in both X and Z directions. The thickness of conformal silver overcoat is 250 nm and the effective loading is 2.4 mg/cm2. The mechanical strength of conducive silver membrane is similar to that of pristine PPMM. Both cyclic voltammetry and impedance spectroscopy on the conductive silver membrane reveal a large electrochemical active surface area. To validate its usefulness as a robust soft electrode, the conductive silver membrane is evaluated for the detection of chlorine in aqueous solution in which a low detection limit of 0.07 ppm and a wide detection range of 0.1–20 ppm are validated.

A new scheme is proposed to improve the electron beam quality of ionization-induced injection by tailoring gas profile in laser wakefield acceleration. Two-dimensional particle-in-cell simulations show that the ionization-induced injection mainly occurs in high-density stage and automatically truncates in low-density stage due to the decrease of wakefield potential difference. The beam loading can be compensated by the elongated beam resulting from the density transition stage. The beam quality can be improved by shorter injection distance and beam loading effect. A quasi-monoenergetic electron beam with a central energy of 258 MeV and an energy spread of 5.1% is obtained under certain laser-plasma conditions.

It has been reported that the oil dispersible polymethylsilsesquioxane (PMSQ) microsphere can effectively improve the flow behavior of the waxy crude oil through the spacial hindrance effect. Because of the complex composition of the crude oil, in this work, model waxy oil is used to further investigate the effects and mechanisms of PMSQ microspheres on influencing the rheology of the waxy oil. The effects of PMSQ microspheres with sizes from 200 nm to 10 μm on the formation and breakage of the waxy oil gel are first studied based on the rheological measurements. Results show that adding PMSQ microsphere effectively inhibits the formation of the waxy oil gel and weakens the gel structure of the waxy oil formed at 20 °C under static cooling condition. The gelation point, the G ′, G ″ value at 20 °C/25 °C and the yield stress at 20 °C of the doped waxy oil are found to first decrease and then increase with the increase of the PMSQ microsphere size, and the PMSQ-3 (2 μm) has the best improving performance. Under static isothermal condition, the formation of waxy oil gel is delayed after adding the PMSQ microsphere. However, under dynamic cooling condition, adding PMSQ microsphere slightly increases the losing flow point and apparent viscosity of the waxy oil. DSC results show that PMSQ microsphere can act as the heterogeneous nucleation sites favoring slight increase of the WAT but have no apparent influence on the precipitated wax crystals’ amount of the waxy oil at each temperature. Associated with the microstructure observation, the mechanism of the PMSQ microsphere influencing the formation and breakage of waxy oil gel is deduced. Under static cooling condition and static isothermal condition, PMSQ microsphere occupies a certain space in oil phase and impedes the interactions of the precipitated wax crystals around the microsphere through spacial hindrance effect, thus effectively inhibiting the formation of wax crystal network under static cooling and weakening the strength of the formed waxy oil gel. Under dynamic cooling condition, the interactions among the precipitated wax crystals are greatly weakened by shearing, the PMSQ microsphere cannot further weaken the interactions among the precipitated wax crystals, but act as a dispersed phase in the waxy oil to increase the concentration of the dispersed phases (wax crystals and PMSQ) at each temperature, resulting in the slightly higher losing flow point and apparent viscosity for the doped waxy oil.

In a previous work, the addition of the polymethylsilsesquioxane (PMSQ) microsphere (50–400 ppm) can improve the flow behavior of waxy crude oil through the spacial hindrance effect. However, the flow improving efficiency of the neat PMSQ microsphere is not as good as the traditional polymeric pour point depressants (PPDs). In this paper, the effect of the ethylene-vinyl acetate copolymer (EVA2806) PPD together with the PMSQ microsphere (with the size around 2 µm) on the flow behavior of a typical waxy crude oil was investigated. The results show that adding 50 ppm EVA PPD can greatly improve the flow behavior of the oil. The neat PMSQ microsphere cannot improve the flow behavior of the oil at small dosages (≤10 ppm), but can significantly improve the performance of the EVA PPD. The gelation point, G′, G″, transient apparent viscosity and yield stress of the oil decrease further after adding both 50 ppm EVA and a small amount of the PMSQ microsphere (≤10 ppm). The best flow improving efficiency is found at 50 ppm EVA + 2.5 ppm PMSQ. The addition of the PMSQ microsphere has little influence on the WAT and precipitated wax crystal amount of the oil doped with EVA, but outstandingly changes the morphology of the precipitated wax crystals into larger and more compact flocs. The adsorption tests show that the EVA molecules can adsorb and concentrate on the PMSQ microsphere, thus causing the formation of the EVA/PMSQ composite particles. The composite particles can act as nucleation templates for the wax precipitation, resulting in larger and more compact wax microstructures and then further improving the flow behavior of the oil. The PMSQ microsphere dosage and the amount of EVA PPD adsorbed on the microsphere obviously influence the performance of the composite particle with the best performance at 50 ppm EVA + 2.5 ppm PMSQ. The findings mentioned above provide a new way to improve the performance of polymeric PPDs efficiently.

This study is specifically concerned with the effect and mechanism of asphaltenes and wax inhibitors on the wax deposition characteristics of model waxy oil. According to the rheological and wax deposition test, the pure model waxy oil has a pour point higher than the pipe wall temperature, and the formed wax deposit exhibits the slowest aging rate and homogeneous wax deposit structure. Based on the DSC and rheological experiments, the solubility of wax crystals is hardly influenced by asphaltenes or wax inhibitors, but the decrease of oil viscosity and the weakened low-temperature gel structure induced by asphaltenes and wax inhibitors would increase the wax molecular diffusion coefficient and wax content in the wax deposit, which ultimately leads to a thinner and harder wax deposit. Moreover, based on the molecular dynamic simulation, the EVA molecules can be adsorbed on the asphaltene surface thus forming EVA-asphaltene composite particles, which can change the crystallization habit of wax molecules and the wax crystal micromorphology, thereby dramatically improving the crude oil rheology at low temperatures and inhibiting wax deposition. This work provides a comprehensive understanding of the wax deposition mechanism induced by asphaltenes and wax inhibitors, which helps to the well or pipeline operation safety and efficiency.

Application of nanocomposite pour point depressants to improve the rheology of waxy crude oil is a novel and efficient technique and receives much attention. However, the effects of nano and microparticles alone on the rheology of waxy crude oil are unclear up to now. In this paper, monodispersed PMSQ microspheres with different sizes (200 nm–10 µm) were successfully synthesized through a two-step sol-gel route. Then the effect of the PMSQ microspheres on the flow behavior of two typical waxy crude oils was studied. The results showed that the PMSQ microspheres disperse well in oil phase as single spheres. A small dosage of the PMSQ microspheres significantly decreases the gelation point, elastic modulus G′, viscous modulus G″, apparent viscosity and yield stress of the two oil samples, indicating that the PMSQ microspheres improve the flow behavior of waxy crude oil at temperatures below the wax appearance temperature. The flow improving efficiency of the PMSQ microspheres is greatly influenced by the size and dosage of the microspheres. Moreover, adding PMSQ microspheres in the oil samples also inhibits asphaltenes precipitation because the PMSQ microspheres are capable of adsorbing part of the asphaltenes. However, the PMSQ microspheres have little influence on the exothermic character and microstructure of the two oil samples. Similar tests on a model waxy oil further confirmed that the PMSQ microspheres cannot participate in wax precipitation process and change the morphology of precipitated wax crystals, but can impede the interactions of the precipitated wax crystals through spacial hindrance effect, which inhibits the development of wax crystal network structure and thus improves the flow behavior of the oil. This mechanism brings a new way to improve the flow behavior of waxy crude oil and favors the development of new-generation flow improvers based on nano or microparticles.

With a fiber pigtailed electro-optic modulator as the active Q-switch, mode-hopping-free single-longitudinal-mode pulses are generated by a ring cavity fiber laser based on the injection seeding technique. The experimental results show that the single-longitudinal-mode oscillating properties of the laser may be determined by the power and the center frequency of the injection seed rather than the Q-switch waveform and modulation frequency. With the injected seed power of 200 μW, single-longitudinal-mode Q-switched pulses with the repetition rate and the pulse width from 1 to 100 kHz, and 50 to 400 ns are achieved with the laser. The output pulse linewidth can be narrowed effectively by reducing the coupling ratio of the output coupler of the laser. A stable single-longitudinal-mode pulse stream with a linewidth of 1.5 MHz is obtained with our laser, which may be the narrowest linewidth for a Q-switched fiber laser so far to our best knowledge.

The novel and effective nanocomposite PPD has garnered attention for its potential application in pipelines transporting waxy crude oil. In this paper, melt blending method was used here to prepare the poly(octadecyl acrylate) (POA)/clay nanocomposite PPD, which shows much better performance on waxy crude oil. The effects of the POA and POA/clay nanocomposite PPDs on the structural properties of gelled Changqing waxy crude oil were well studied through rheological tests, DSC analyses and microscopic observation. The precipitated wax crystal amount of the crude oil at low temperatures does not change with the addition of POA and nanocomposite PPDs, but the addition greatly weakens the structure of the gelled crude oil. Compared with the same dosage of POA, the addition of nanocomposite PPD further inhibits the formation of wax crystal’s network and further weakens the structural strength and viscoelasticity of the gelled crude oil. Increasing the dosage of nanocomposite PPD favors the weakening of the gelled crude oil structure. The nanocomposite PPD particles can act as nucleation templates of wax crystals and further weaken the gelled structure of waxy crude oil. In addition, we deduce that controlling the dispersed state of polymeric PPDs in oil phase could control the performance of the polymeric PPDs. The decrease of the mean nanocomposite PPD particle size from 6 μm (prepared by solvent blending) to 2 μm (prepared by melt blending) changes the dispersed state of POA molecules in oil phase and thus greatly enhances the performance of nanocomposite PPD.

We have demonstrated a nonlinear behavior for the bandgap opening of doped graphene by controlling the concentration of B and N co-dopants. X-ray absorption and emission spectra reveal that the ban ...

Rapid, portable, and efficient detection of lead cations (Pb2+) is of great significance for monitoring and evaluating environmental toxicity and human healthcare. In this work, we developed a simple and low-cost homogenous fluorescence DNAzyme assay for Pb2+ determination based on Pb2+-dependent cleaving and rolling circle amplification (RCA). DNAzyme and its substrate (5′-biotin) formed double-stranded hybrids in solution which could thoroughly react with Pb2+ in aqueous phase. Then, the unreacted DNAzyme/substrate hybrids as well as cleaved parts with biotin labeling of substrate strand would be captured by magnetic beads through biotin-streptavidin interactions and removed from the reaction solution. Meanwhile, the other parts of the substrate strand remained in solution and subsequently acted as the primer and triggered RCA. The concentration of the cleaved substrate strand correlated to that of Pb2+ and non-specific amplification was effectively minimized through biotin-streptavidin isolation. With a smartphone camera, the fluorescence intensity was recorded and quantified after 30–90 min amplification, making it a portable method with minimum instrumentation. A dynamic range of 1–100 nM of Pb2+ was achieved under optimized conditions and it was successfully employed for Pb2+ detection in spiked lake water.

Graphene oxide (GO) is often quantified via its UV absorption, typically at around 230 nm. This is convenient but the effect of the size of GO on the accuracy of this method has been ignored so far. The authors report that the molar absorbance of GO is size-dependent. Data are presented on the absorbance of small (hydrodynamic diameter 1 μm), medium sized (1.5 μm), and large (2.2 μm) GO particles at wavelengths of 210, 230 and 250 nm. In general, linear relationship and good regression fits are obtained, but with different slope depending on size even at the same wavelength. This implies that using the UV absorption-based calibration may cause significant errors in GO quantification. Ultimately, this leads to incorrect dosages and faulty conclusions. This may also explain a variety of inconsistent results obtained in previous biological applications of GO. Graphical abstract The size of graphene oxide (GO) determines its UV absorption and the UV absorption-based calibration (GO-s, GO-m and GO-l represent the GO with small, medium and large size).

Polyethylene vinyl acetate (EVA) has been widely investigated and employed as polymeric wax inhibitor (PWI). In this paper, the wax deposition characteristics of synthetic oils with different concentrations of EVA PWI were investigated. The obtained surface and bottom wax deposits were analyzed through differential scanning calorimeter (DSC), polarizing microscope, Fourier transform-infrared spectroscopy (FT-IR) and high-temperature gas chromatography (HTGC). It is found that the EVA PWI could obviously decrease the wax deposition rate and accelerate the aging of wax deposits. Adding the EVA PWI can trigger a novel heterogeneous wax deposit structure, in which the wax appearance temperature and wax content increases continuously from the bottom to the surface layer. Compared to the bottom wax deposit, the surface wax deposit has higher concentrations of both EVA and high carbon number wax molecules (Cn > C25). The formation mechanism of the novel heterogeneous wax deposit structure was explained from two aspects. Firstly, the wax crystal morphology of surface layer is significantly changed from needlelike to diamond-like due to higher temperature and the accumulation of EVA and high carbon number wax molecules in the surface wax deposit, therefore, higher solid wax content is needed for the building of a continuous three-dimensional network structure to resist shearing of pipe flow. Secondly, the lower temperature and larger aspect ratio of wax crystals in the bottom wax deposit are adverse for the diffusion of wax molecules into the bottom wax deposit, thus the aging rate of bottom wax deposit is lower than that of surface layer.

We report on the laser pulse output of 339 J centered at 800 nm from a chirped-pulse amplification (CPA) Ti:sapphire laser system at the Shanghai Superintense Ultrafast Laser Facility. The experimental results demonstrated that the parasitic lasing as well as the transverse amplified spontaneous emission of the homemade 235-mm-diameter Ti:sapphire final amplifier were suppressed successfully via the temporal dual-pulse pumped scheme and the index-matching liquid cladding technique. The maximum pump-to-signal conversion efficiency of 32.1% was measured for the final amplifier. With a compressor transmission efficiency of 64% and a compressed pulse duration of 21 fs obtained for the sample light at a lower energy level, this laser system could potentially generate a compressed laser pulse with a peak power of 10.3 PW. The experimental results represent significant progress with respect to the CPA laser.

In recent years, due to their unique physical, chemical and electronic properties, two-dimensional materials have received more and more researchers’ attention. In particular, the excellent optoelectronic properties and transport properties of two-dimensional materials such as graphene, black phosphorous and transition metal sulfide materials make them have broad application prospects in the field of next-generation optoelectronic devices. In this article, we will mainly introduce the advantages of two-dimensional materials in the field of photodetection, outline the basic principles and parameters of photodetectors, focus on the difference between the grating effect and the traditional photoconductive effect, and the reasons and characteristics of improving optical gain and optical responsivity. Then we review the latest developments and applications of grating local control in photodetectors, and finally summarize the problems faced by the photodetectors of this kind and their prospects for the future.

Metal nanostructures exhibit distinct physical properties from macroscopic objects, which have been widely applied to organic optoelectronic device. N, N'-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) is one of the few air-stable, high mobility n-type semiconductor, which is usually used to fabricate green or white light detectors due to its main absorption concentrated in the range 450 - 600 nm. In this paper, a high performance red light sensor was achieved by PTCDI-C8 based organic phototransistor (OPT) with the optimized gold nanoparticles (AuNPs) modified layer, the photosensitivity, photoresponsivity, specific detectivity and the external quantum efficiency (EQE) of which can reach 6.21 × 105, 24.12 A/W, 2.85 × 1011 Jones and 453.58% at 660 nm, respectively. Additionally, the AuNPs-modified OPT also gained a significant improvement in EQE under green light illumination at 532 nm compared with single PTCDI-C8 layer OPT. The photophysical mechanisms of introducing AuNPs to improve device performance were explored.