Coaxial heterogeneous graphene quantum dot-sensitized TiO2 nanotube arrays (GQDs/TNTs) are prepared by a coupling technique of linker molecule binding and electrophoretic deposition (EPD). The silane ...linker molecules act as a superb medium for integrating GQDs and TNTs by covalent amide linkage, thus preventing GQDs from clogging the tube entrances and forming a uniform GQD layer tightly attached to the inside tube walls during the following EPD process. By adjusting the time of EPD, appropriate thickness of the deposited GQDs in the internal tube walls of TNTs can be controlled. Compared to the pristine TNTs and GQDs/TNTs prepared by the conventional impregnation–precipitation method, the hybrids fabricated by EPD exhibit significantly enhanced photoelectrochemical water-splitting activity and photocatalytic organic dye decomposition performance for their broad photo-absorption range, fast separation of photogenerated charge, and stability.
•The gas-liquid characteristics are systematically investigated in jet-flow HSM.•The structural improvement can significantly intensify the mass transfer performance.•The operating conditions affect ...the mass transfer performance while exist limitation.•The dimensionless correlations of Pog and kLa in jet-flow HSM are established.
Experimental measurements were performed to systematically investigate the effects of operating conditions and structural configurations of the rotor-stator head on gas-liquid characteristics (volumetric mass transfer coefficient, gas hold-up and bubble dispersion) and power consumption of the jet-flow high shear mixer (HSM). Gas hold-up distribution, bubble dispersion and flow fields under different structural configurations were also analyzed and verified by the computational fluid dynamics (CFD). The results indicated that the gas-liquid mass transfer performance and power consumption in jet-flow HSM were significantly impacted by the structural parameters involving blade angle, blade arc and stator bottom opening. Increasing gas flow rate or reducing surface tension could enhance the gas-liquid mass transfer performance to some extent. In addition, gas hold-up distribution and bubble dispersion in the gas-liquid system were more uniform with the modified configuration of the rotor-stator head. The dimensionless correlations were established based on the experimental data to predict Pog and kLa in gas-liquid operation of the jet-flow HSM: Pog = 0.958⋅(sinθ)1.567(D/(Ds – Db))-0.164 with the standard deviation (σ) of 16%; ShL = 7.92 × 104⋅FlQ0.38Fr0.69Pog0.29 with σ of 17%. This work can provide useful guidance on scaleup design and optimization of the jet-flow HSM to intensify the transfer properties for gas-liquid operation systems.
Developing efficient, durable, and earth‐abundant electrocatalysts for both hydrogen and oxygen evolution reactions is important for realizing large‐scale water splitting. The authors report that ...FeB2 nanoparticles, prepared by a facile chemical reduction of Fe2+ using LiBH4 in an organic solvent, are a superb bifunctional electrocatalyst for overall water splitting. The FeB2 electrode delivers a current density of 10 mA cm−2 at overpotentials of 61 mV for hydrogen evolution reaction (HER) and 296 mV for oxygen evolution reaction (OER) in alkaline electrolyte with Tafel slopes of 87.5 and 52.4 mV dec−1, respectively. The electrode can sustain the HER at an overpotential of 100 mV for 24 h and OER for 1000 cyclic voltammetry cycles with negligible degradation. Density function theory calculations demonstrate that the boron‐rich surface possesses appropriate binding energy for chemisorption and desorption of hydrogen‐containing intermediates, thus favoring the HER process. The excellent OER activity of FeB2 is ascribed to the formation of a FeOOH/FeB2 heterojunction during water oxidation. An alkaline electrolyzer is constructed using two identical FeB2‐NF electrodes as both anode and cathode, which can achieve a current density of 10 mA cm−2 at 1.57 V for overall water splitting with a faradaic efficiency of nearly 100%, rivalling the integrated state‐of‐the‐art Pt/C and RuO2/C.
Iron diboride (FeB2) nanoparticles, prepared by a facile chemical reduction of Fe2+ using LiBH4 in an organic solvent, deliver a current density of 10 mA cm−2 (j10) at overpotentials of 61 mV for hydrogen evolution reaction and 296 mV for oxygen evolution reaction in alkaline electrolyte. A full alkaline electrolyzer using two identical FeB2/NF electrodes can achieve j10 at a voltage of 1.57 V for overall water splitting, rivalling the integrated state‐of‐the‐art Pt/C and RuO2/C.
Two‐dimensional (2D) monometallic pnictogens (antimony or Sb, and bismuth or Bi) nanosheets demonstrate potential in a variety of fields, including quantum devices, catalysis, biomedicine and energy, ...because of their unique physical, chemical, electronic and optical properties. However, the development of general and high‐efficiency preparative routes toward high‐quality pnictogen nanosheets is challenging. A general method involving a molten‐salt‐assisted aluminothermic reduction process is reported for the synthesis of Sb and Bi nanosheets in high yields (>90 %). Electrocatalytic CO2 reduction was investigated on the Bi nanosheets, and high catalytic selectively to formate was demonstrated with a considerable current density at a low overpotential and an impressive stability. Bi nanosheets continuously convert CO2 into formate in a flow cell operating for one month, with a yield rate of 787.5 mmol cm−2 h−1. Theoretical results suggest that the edge sites of Bi are far more active than the terrace sites.
A low‐temperature molten‐salt‐assisted method to synthesize nanosheet‐like monometallic antimony or bismuth with high‐yield has been developed. The obtained bismuth nanosheets can effectively and continuously electrocatalyze the reduction of CO2 to formate with a stability of more than one month.
Display omitted
•The influence of the wettability of modified cement pastes on the film-forming property was investigated.•The modified cement paste was redistributed during the film formation ...process.•The reduction of wettability can improve the adhesion ability between cement paste and aggregate in wet environment.
The film-forming property of cement paste is an important factor affecting the compressive strength and water permeability of permeable concrete. In this paper, the influence of the wettability on the film-forming property of stearic acid modified cement paste was investigated by using surface free energy theory and film-forming experiments. The results show that the wettability of the cement paste decreased with the addition of stearic acid. The decrease of the wettability caused the formation of a hydrophobic film on the surface of the cement paste. It is found that the hydrophobic film caused the redistribution of the cement paste. The change of cement paste wettability has a strong impact on the formation of cement paste film on the surface of aggregate other than the surface of plastic rods. In addition, the reduced wettability of the cement paste improved the adhesion energy between cement paste and aggregate in wet environment. It is expected that the proposed method may pave a new way for preparing cement-based materials with good film-forming property by varying its wettability.
Seismic data noise processing is an important part of seismic exploration data processing, and the effect of noise elimination is directly related to the follow-up processing of data. In response to ...this problem, many authors have proposed methods based on rank reduction, sparse transformation, domain transformation, and deep learning (DL). However, such methods are often not ideal when faced with strong noise. Therefore, we propose to use diffusion model theory for noise removal. The Bayesian equation is used to reverse the noise addition process, and the noise reduction work is divided into multiple steps to effectively deal with high-noise situations. Furthermore, we propose to evaluate the noise level of blind Gaussian seismic data using principal component analysis (PCA) to determine the number of steps for noise reduction processing of seismic data. We train the model on synthetic data and validate it on field data through transfer learning. Experiments show that the proposed method can identify most of the noise with less signal leakage. This has positive significance for high-precision seismic exploration and future seismic data signal processing research.
Display omitted
•Hyperbranched phosphorus-containing polysiloxane functionalized halloysite nanotubes (HBPPSi@HNTs) were successfully synthesized.•HBPPSi@HNTs exhibited highly efficient flame ...retardancy and smoke suppression for epoxy composites, which passed the UL-94V-0 rating and showed a high LOI of 42.6 %.•HBPPSi@HNTs significantly improved the strength and toughness of epoxy composites.
Development of high-performance thermosets with simultaneously improved flame retardancy, toughness and strength but unaffected glass transition temperature (Tg) has been a great challenge. In this work, hyperbranched phosphorus-containing polysiloxane functionalized halloysite nanotubes (HBPPSi-HNTs) were synthesized to prepare flame-retarding, mechanically-strong and tough epoxy composites. The tensile and impact strengths of the composites with 5.0phr HBPPSi-HNTs were improved by 23.7 % and 48.8 % respectively compared with the neat epoxy resin. The epoxy composites also exhibited excellent flame-retardancy due to the instantaneous gas-phase and condensed-phase flame retardant behavior of HBPPSi-HNTs. The composite with 10.0phr HBPPSi-HNTs passed UL-94V-0 rating, with an LOI value as high as 42.6 %. And compared with neat epoxy resin, the peak of heat release rate (PHRR), total heat release (THR), total smoke production (TSP) and CO generated per second (COY) were reduced by 50.1 %, 32.6 %, 30.1 % and 39.5 %, respectively. This work presented a general approach to prepare epoxy composites with simultaneously improved flame retardancy and mechanical properties without sacrificing the glass transition temperature.
The jet-flow high shear mixer (JF-HSM) is a new type of intensified equipment with special configurations of the rotor and the stator. The mass transfer property and power consumption were studied in ...the solid-liquid system for a series of JF-HSMs involving different configuration parameters, such as rotor diameter, rotor blade inclination, rotor blade bending direction, stator diameter, and stator bottom opening diameter. The flow characteristics were examined by computational fluid dynamic simulations. Results indicate that the turbulent power consumption of the JF-HSM is affected by the change in rotor blade inclination and stator bottom opening. With the increase in the shear head size and the change in the rotor into a backward-curved blade, the solid-liquid mass transfer rate can be remarkably increased under the same input power. Dimensionless correlations for the mass transfer coefficient and power consumption were obtained to guide the scale-up design and selection of such a new type of equipment to intensify the overall mixing efficiency.
Abstract The regulation of topological structure of covalent adaptable networks (CANs) remains a challenge for epoxy CANs. Here, we report a strategy to develop strong and tough epoxy supramolecular ...thermosets with rapid reprocessability and room-temperature closed-loop recyclability. These thermosets were constructed from vanillin-based hyperbranched epoxy resin (VanEHBP) through the introduction of intermolecular hydrogen bonds and dual dynamic covalent bonds, as well as the formation of intramolecular and intermolecular cavities. The supramolecular structures confer remarkable energy dissipation capability of thermosets, leading to high toughness and strength. Due to the dynamic imine exchange and reversible noncovalent crosslinks, the thermosets can be rapidly and effectively reprocessed at 120 °C within 30 s. Importantly, the thermosets can be efficiently depolymerized at room temperature, and the recovered materials retain the structural integrity and mechanical properties of the original samples. This strategy may be employed to design tough, closed-loop recyclable epoxy thermosets for practical applications.
PDF
