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To develop efficient ionic liquid (IL)-based separation processes like extractive distillation, the knowledge of IL-involved vapor–liquid equilibria (VLE) is necessary. Since experimental measureme...

Synergistic flame-retardant effect of aluminum diethyl phosphinate (AlPi) in intumescent flame retardant polypropylene (PP/IFR) system and the flame-retardant mechanism were investigated. The flame retardancy of PP/IFR/AlPi (the mass ratio of IFR to AlPi is 2 : 1) was the best, which was proved by the results of the limiting oxygen index (LOI) test, UL-94 test, and cone calorimeter test ( CCT) test. Here, the LOI value of the sample was as high as 34% and passed the V–0 rating in UL–94 test. The peak heat release rate (PHRR) decreased by 92.57%, the total heat release (THR) reduced by 90.52%. Thermogravimetric (TGA) data showed that the introduction of AlPi improved thermal stability and changed the thermal degradation behavior of PP/IFR composites. Interestingly, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS) and laser Raman spectroscopy (LRS) proved that PP/IFR/AlPi had formed more residual carbon, but the flame retardancy was worse than PP/IFR/AlPi. This is because when the mass ratio of IFR to AlPi is 2 : 1, the synergy between IFR and AlPi was significant, gas-phase flame retardant and condensed-phase flame retardant reached a balance and obtained the best flame retardant effect.

2-Ethylhexyl acrylate (2-EHA) is one of the most widely used acrylates in the polymer industry, which is synthesized via Fisher esterification that is limited by chemical equilibrium. To intensify the esterification process, in this work, reactive extraction concept is proposed, with halogen-free deep eutectic solvent (DES [Im:2PTSA]) as dual solvent-catalyst that consists of imidazole (Im) and p-toluenesulfonamide (PTSA). The bifunctional effects of the DES [Im:2PTSA] are evaluated by thermodynamic analysis and experimental study. Favorable phase splitting is verified by σ-potential analysis predicted by COSMO-RS theory, combined with experiments, and the optimal acid-to-alcohol molar ratio is set to 1.2. The esterification kinetics is then experimentally determined and fitted using the molar-based and activity-based pseudo-homogeneous (PH) models, respectively. The activity-based PH model, that considers the bifunctional roles of the DES, proves to be more accurate with small RMSD of 0.0344. The stability of DES after recycling is validated to further confirm the industrial prospects of DES [Im:2PTSA] in 2-EHA production.

In this paper, a thermal inkjet printing simulation model is established in the CFD simulation platform, and the influence of inkjet driver parameters and ink physical parameters on the printing process is studied by numerical simulation. The evaporation-condensation model is coupled with the VOF multiphase flow model in Fluent software to establish a thermal inkjet printing process simulation model. Based on the orthogonal test method, we investigate the influence of fluid physical parameters (ink viscosity, surface tension) and inkjet driver parameters (heater temperature value) on droplet formation by changing the physical parameters of the material and the boundary conditions of the model. Through the comparison of the results, exploring the adjustment rules of thermal inkjet technology and obtaining the optimal combination of material and process parameters for high-quality ink drop formation.

The effects of pressure oscillation on aerodynamic characteristics in an aero-engine combustor are investigated. A combustor test rig is designed to simulate the pressure drop characteristics of a practical annular combustor. The pressure drop characteristics are firstly measured under atmosphere condition with non-reacting flow (or cold flow), and the air mass flow proportion of each component (dome/liner) are obtained; these properties are base lines for comparison with combustion state. The combustion tests are then carried out under conditions of inlet temperature 340–450 K, fuel air ratio 0.010–0.028. The stability map and the oscillation frequencies are obtained in the tests, the results show that pressure oscillation amplitude increases with the increase of fuel air ratio. Phase trajectory reconstruction is applied to classify the pressure oscillation motion; there are three motions captured in the tests including: “disk”, “ring” and “cluster”. The pressure drops across the dome under strong pressure oscillation are distinctly divergent from the cold flow, and the changes of pressure drops are mainly affected by pressure oscillation amplitude, but is less influenced by pressure oscillation motion nor oscillation frequencies. Based on the mass flow conservation, the reduction of effective flow area of combustor under strong pressure oscillation is demonstrated. Liner wall temperatures are analyzed through Multiple Linear Regression (MLR) method to estimate the reduction of the air mass flow proportion of the liner cooling under strong pressure oscillation. Finally, the air mass flow proportions of each component under strong pressure oscillation are estimated, the results show that the pressure oscillation motion also has influence on air mass flow proportion.

The solid-state redox couple is a vital charge transfer medium for electrochemical water splitting. In this Frontiers article, we summarize the versatile application of redox couples in promoting OER kinetics, in decoupling the HER and OER, and in combined electrochemical-thermochemical water splitting. These new ideas unlock vast potential for applying redox-couple-mediated water splitting to the storage of the intermittent and fluctuating energy derived from renewable sources.

The photoelectrochemical (PEC) water splitting determines by the light absorption and charge extraction/injection. Here, we dispersedly modified the core-shell structured Ni@Niy Fe1-y (OH)2 on Si photoanodes and in-situ electrochemically converted it to Ni@Niy Fe1-y OOH to form a Si/SiOx /Ni@Niy Fe1-y OOH assembly, exhibiting the adjustable band bending and catalytic ability in water oxidation depending closely on the composition of Niy Fe1-y OOH. Combining with the island-like dispersed distribution to maximize the light absorption and the Ni@Niy Fe1-y shell as a high work function and a catalytic layer to simultaneously enlarge charge extraction and injection, the Si/SiOx /Ni@Ni0.7 Fe0.3 OOH assembly achieved an onset potential of 1.0 VRHE , a saturated current density of 35.4 mA cm-2 and a more than 50 h stability in an electrolyte with pH 9 under AM1.5G simulated sunlight irradiation. Our findings suggested that regulating the charge energetics at Si-electrolyte interface by discontinuously modifying a composition-adjustable core-shell structure is a potential route to develop highly efficient PEC devices.

Interface engineering has been regarded as a promising strategy for enhancing the catalytic activities of heterojunction photocatalysts. Herein, we have adopted an in situ etching sulfurization method to construct a Zn2GeO4−x/ZnS intimate heterojunction, which exhibited excellent photocatalytic H2 production in the absence of a Pt co-catalyst. Distinctively, TEM and HRTEM measurements showed that the interface of the Zn2GeO4−x/ZnS heterojunction became rough (topologically) due to in situ etching sulfurization, and etching was found to be strongly dependent on the crystal orientation. Moreover, the surface of the Zn2GeO4 nanorods from flat (100) planes evolved into an irregular coastline-like structure topologized with (110) and (113) high-index planes. ICP and elemental distribution measurements indicated that during the precipitation of ZnS via in situ etching sulfurization, the migration and dissolution of Zn and Ge ions on the Zn2GeO4(100) plane led to the roughening of the interface and the evolution of crystal planes. XPS and EPR analyses showed that Zn2GeO4−x/ZnS contained more oxygen vacancies with structural evolution. The theoretical calculations demonstrated that oxygen defects were prone to be generated on the Zn2GeO4(113) plane and formed the Ge3c3+–VO complexes. Compared to the inactive (100) plane, etching caused the Zn2GeO4(110) planes to have a higher number of threefold coordinated germanium (Ge3c4+) and (113) high-index planes that possessed abundant active sites (Ge3c3+–VO complexes), which dramatically decreased the barrier and reaction energy of H2O dissociation. This work not only provides fundamental insights into the topological interface evolution and facet-dependent defect distribution but also offers a strategy for the design of efficient photocatalysts for H2 production without the use of Pt as a co-catalyst based on a multifunctional interface.

In this work, the effect of (NH4)2CO3 additive on the combustion behavior and NOx emission properties during the combustion process of semi-coke was investigated. The combustion characteristics of ...

Currently, it is still a huge challenge to prepare flame-retardant polymeric materials with excellent fire safety, high strength, good durability and processability. We here propose a H-bonding cross-linking strategy that can simultaneously endow polymers with excellent flame retardancy, non-dripping behavior and enhanced strength. In this work, a novel benzimidazole monomer, 2-(4-methoxycarbonyl-phenyl)-1H-benzimidazole-5-carboxylic acid methyl ester (PBM) has been designed as a H-bonding cross-linking monomer to prepare poly(ethylene terephthalate)-based copolyesters (PET-co-PBMs). Interestingly, along with the hydrogen bonding, the π-π stacking interactions from the benzimidazole groups also exist. Due to the formation of physical crosslinking network via hydrogen bonding and π-π stacking, the melt strength of copolyesters are greatly improved. Combining with char forming ability of benzimidazole, PET-co-PBMs display excellent fire safety. Moreover, PET-co-PBMs also exhibit higher glass transition temperature, higher mechanical strength and good processability. This work provides a promising strategy to design polymers with high strength, good processability, excellent flame retardance and anti-dripping performance.

The MoS2/TiO2 heterojunction composites photocatalysts exhibits excellent photocatalytic performance, and they were resoundingly synthesized by a one-step hydrothermal experimental method combined with mild calcination (300 °C) under an argon atmosphere. Under the visible light irradiation, the photocatalytic activity of MoS2/TiO2 heterojunction composites were tested for photocatalytic reduction of CO2 and it exhibited superior performance and stability. The consequences show that the pure MoS2 demonstrates a poor photocatalytic activity because of its high electron-hole recombination, and the maximum yields of CO and CH4 on 10% MoS2/TiO2 heterojunction composite are 268.97 μmol/g.cat and 49.93μmol/g.cat, respectively, which are about 5.33 times and 16.26 times of pure TiO2 (P25). The improved photocatalytic activity of 10% MoS2/TiO2 heterojunction composite could be put down to the high-efficiency separation of photogenerated electron-hole pairs, strong response to visible light and the narrowed band gap.

Air, water, and DINCH (Di-isononyl-cyclohexane-1,2-dicarboxylate) were selected as the cooling media to prepare polypropylene hollow fiber membranes by melt spinning. The effects of various cooling ways with different cooling rates on the row-nucleated lamellar crystallization were investigated. The crystallinity, orientation and arrangement of the crystals were examined by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). Membrane morphology was observed by SEM. The less uniform pores, a layer of amorphous phase, and only a small part of slit-shaped pores were observed on the surface of samples when water and DINCH were used as the heat transfer medium because the fast cooling rate froze the surface molecules and decreased the crystallinity and orientation. However, when air was used as the cooling medium, the higher crystallinity and the better orientation of the annealed hollow fibers were obtained mainly due to the slow cooling rate. Corresponding hollow fiber membranes prepared by stretching had better interconnectivity of pores and larger pure water flux. Thus this study explains why air was selected as the cooling medium to prepare polypropylene hollow fiber membranes which can have larger pure water flux. Also, it provides new insights into the structure control of polypropylene hollow fiber membranes by stretching in order to prepare membranes with high strength.

Polypropylene (PP)/poly(ethylene-co-vinyl alcohol) (EVOH) blends were prepared by melt blending using PP-g-MAH as a compatabilizer. The microstructure and rheological behavior of PP/EVOH blends were studied. The results showed the that EVOH particles were uniformly dispersed in the PP matrix and inhibited the mobility of PP chains. The isothermal crystallization kinetics and morphology development of PP/EVOH blends were compared with that of pure PP. It was found that the EVOH essentially acted as an effective nucleating agent for PP, which could significantly increase the nucleation rate because the EVOH molecules in PP/EVOH blends aggregated together to form interface. Therefore, the introduction of EVOH increased the overall rate of isothermal crystallization compared with pure PP, although the PP molecular chains would be hindered seriously if excessive amounts of EVOH were added. X-ray diffraction showed that pure PP and PP/EVOH blends exhibited an identical crystal structure, and the crystallinity of the PP phase in the blends was not significantly different from that of pure PP.

Binary composite with heterostructure have received intense concerns in gas sensing domains. In this paper, we describe the design, fabrication, and gas-sensing tests of 1-D decorated-type ZnO/ZnCo2O4 nanocomposite, which is synthesized through a facile and eco-friendly solution-based process. A series of characterization methods are employed to evaluate the as-synthesized products, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and BET technique. The acetone gas-sensing properties of ZnO/ZnCo2O4 nanorods are evaluated with different acetone vapor concentrations at the working temperature of 240 °C. Among, the response of 1:1 ZnO/ZnCo2O4 nanorod based sensor displays a fascinating value ca. 15.3, which is superior to the sensor based on original ZnO nanorods. Gas test results also reveal that the sensor has fast response kinetics and good selectivity to acetone gas. A plausible sensing mechanism is also illustrated hereinafter, which we believe it can provide theoretical guidance for the further development of novel and advanced gas-sensitive materials with p-n heterojunction. As such, this binary nanocomposite (ZnO/ZnCo2O4) is a rather promising candidate to be applied into gas detection field.

The nonrenewable nature of fossil energy has led to a gradual decrease in reserves. Meanwhile, as society becomes increasingly aware of the severe pollution caused by fossil energy, the demand for clean energy, such as solar energy, is rising. Moreover, in recent years, electronic devices with screens, such as mobile phones and computers, have had increasingly higher requirements for light transmittance. Whether in solar cells or in the display elements of electronic devices, transparent conductive films directly affect the performance of these devices as a cover layer. In this context, the development of transparent electrodes with low sheet resistance and high light transmittance has become one of the most urgent issues in related fields. At the same time, conventional electrodes can no longer meet the needs of some of the current flexible devices. Because of the high sheet resistance, poor light transmittance, and poor bending stability of the conventional tin-doped indium tin oxide conductive film and fluorine-doped tin oxide transparent conductive glass, there is a need to find alternatives with better performance. In this article, the progress of research on transparent electrode materials with sandwich structures and their advantages is reviewed according to the classification of conductive materials to provide reference for research in related fields.

Tool edge preparation can improve the tool life, as well as cutting performance and machined surface quality, meeting the requirements of high-speed and high-efficiency cutting. In general, prepared tool edges could be divided into symmetric or asymmetric edges. In the present study, the cemented carbide tools were initially edge prepared through drag finishing. The simulation model of the carbide cemented tool milling steel was established through Deform software. Effects of edge form factor, spindle speed, feed per tooth, axial, and radial cutting depth on the cutting force, the tool wear, the cutting temperature, and the surface quality were investigated through the orthogonal cutting simulation. The simulated cutting force results were compared to the results obtained from the orthogonal milling experiment through the dynamometer Kistler, which verified the simulation model correctness. The obtained results provided a basis for edge preparation effect along with high-speed and high effective cutting machining comprehension.

The limited availability of studies on the natural convection heat transfer characteristics of fluoride salt has hindered progress in the design of passive residual heat removal systems (PRHRS) for molten salt reactors. This paper presents results from a numerical investigation of natural convection heat transfer characteristics of fluoride salt and heat pipes in the drain tank of a PRHRS. Simulation results are compared with experimental data, demonstrating the accuracy of the calculation methodology. Temperature distribution of fluoride salt and heat transfer characteristics are obtained and analyzed. The radial temperature of liquid fluoride salt in the drain tank shows a uniform distribution, while temperatures increase with increase in axial height from the bottom to the top of the drain tank. In addition, natural convection intensity increases with increase in height of the heat pipes in the tank. Spacing between heat pipes has no obvious effect on the natural convection heat transfer coefficient. This study will contribute to the design of passive heat removal systems for advanced nuclear reactors.

The one dimension (1D) TiO2 nanotubes and nanorods were successfully prepared via a one-step hydrothermal method. The structure and properties of the catalysts were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), N2 adsorption-desorption, UV–vis diffuse reflectance and photoluminescence (PL) spectroscopy. Meanwhile, the photoelectrochemical properties were recorded through Mott-Schottky, transient photo-current responses and electrochemical impedance spectroscopy curves (EIS). The results showed that 1D TiO2 nanostructures catalysts had a high specific surface area, enhanced visible light response and superior electron transport properties. The photocatalytic activities of catalysts for reduction CO2 were investigated under 9 h irradiation of a 300 W Xe arc lamp equipped with UV 420 nm bandpass filter. The maximum yields of CH4 over the TiO2 nanotubes (TNT) and TiO2 nanorods (TNR) were 19.16 μmol/g.cat and 12.71 μmol/g.cat, respectively, which were approximately 2.33 folds and 1.48 folds higher than TiO2 nanoparticles (TNP). The enhanced photocatalytic activity of TiO2 nanotubes and nanorods could be ascribed to the presence of oxygen vacancies and defects formed during the calcination process and its special structures, which accelerates the transfer of electrons. Besides, the better activity of TNT than TNR may be ascribed to its unique hollow tubular structure and larger surface area.

Constructing p-n junctions is an efficient strategy to resolve the narrow light absorption range and rapid electron-hole recombination problems of single photocatalysts. However, the promotion effect is greatly limited by poor interfacial contact between the p-type and n-type semiconductors. Herein, a facile surface charge-induced electrostatic self-assembly strategy is developed to construct BiOI/TiO2 heterostructures, in which the positively charged TiO2 nanosheets are spontaneously and uniformly assembled on the negatively charged BiOI nanosheets under pronounced electrostatic interaction in formic acid, acetic acid, or aminopropyltriethoxysilane (APTES) aqueous dispersion. Though featuring identical sufficient interfacial contact, BiOI/TiO2 heterostructures obtained in each dispersion medium, show extraordinary different visible light photocatalytic performance for methyl orange (MO) and phenol. Using multiple characterization techniques, the superior photocatalytic activity of BiOI/TiO2 heterostructures obtained in formic acid or acetic acid aqueous dispersion, can be ascribed to the enhanced photogenerated charge transportation and separation efficiency, which is attributed to the synergistic effects between the internal electric field induced by the formation of p-n junctions and sufficient interfacial contact. However, due to the remaining APTES goes against the formation of p-n junctions, BiOI/TiO2 heterostructure obtained in an APTES aqueous dispersion, shows fairly low photogenerated carriers separation efficiency and rather poor visible-light photocatalytic performance. This work may provide a rational and facile strategy to construct highly efficient p-n heterojunction photocatalysts toward environmental purification and solar energy conversion.

Tritium control is one of the most key issues for the development of Molten Salt Reactor (MSR). The tritium transport characteristics in 2MWth Thorium Molten Salt Reactor-Solid Fuel (TMSR-SF) proposed by Shanghai INstitute of Applied Physics (SINAP) is studied in this paper. Three works are conducted: Firstly, an integrated numerical model is established, including tritium production, adsorption, diffusion, corrosion and permeation. Secondly, the Tritium trAnsPort chAracteristics analysiS code (TAPAS) for TMSR-SF is developed and benchmarked. The results prove the fidelity and accuracy of TAPAS. Finally, the distributions of the key variables including TF, T2 and Cr2+ in TMSR-SF system at both steady and transient state are obtained. In addition, some methods for tritium mitigation are evaluated by TAPAS. Numerical results show that tritium can be efficiently removed from the molten salt via graphite absorption. The amount of T2 at steady state is two orders of magnitude more than TF. Tritium permeation can be prevented by increasing 7Li enrichment and reducing redox potential. Tungsten or similar low-permeability material is a candidate for tritium barrier when covered on the surface of the heat exchanger wall. This work provides some valuable considerations for the tritium control in the MSR.

The Eu-doped TiO2 nanoparticles were successfully prepared by a simple sol-gel method. The properties of the catalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer (EDS), N2 adsorption-desorption, UV–vis diffuse reflectance and photoluminescence (PL) spectroscopy. The results indicated that Eu-TiO2 catalysts had a high specific surface area, enhanced visible light response and low recombination rate of electron-hole pairs. The photocatalytic performances of Eu-TiO2 catalysts for CO2 reduction were investigated under 9 h irradiation of a 300 W Xe arc lamp. The maximum yields of CH4 and CO over the optimized Eu-TiO2 catalyst were 65.53 μmol/g.cat and 42.91 μmol /g.cat, respectively, which were approximately 13 times and 1 times higher than that of pure TiO2. The enhanced photocatalytic performance could be ascribed to the high-efficiency separation of photo-generated electron-hole pairs.

The CuO polyhedrons functionalized with different amounts of PtO 2 nanoparticles were synthesized by simple two-step method. The gas sensing properties of the sensors prepared by PtO 2 functionalized CuO polyhedron were studied and compared with pure CuO sensors. The electrical sensitivity values show that the response of S2-CuO (3.5% wt PtO 2 -CuO) polyhedron is higher than that of pure CuO polyhedron in n-butanol/air atmosphere. The sensor showed excellent reproducibility and good selectivity to n-butanol gas, and its working temperature was relatively low (180 °C), and the reaction time quickly reached 2.4 s. The enhanced properties are attributed to the structure of the CuO polyhedron and the synergistic effect of CuO and PtO 2.

A series of polypropylene hollow fiber membranes was fabricated by melt-spinning and stretching. The crystalline behavior and hard elasticity of precursor hollow fibers were studied by differential scanning calorimetry (DSC), elastic recovery and strain-stress curves. The structure and properties of membranes were investigated in detail by scanning electron microscopy (SEM), optical microscopy, pure water flux, and so on. The results showed that membranes with excellent structure and properties can be obtained at a spin-draw rate of 350 m/min and a stretching ratio of 200 %. The evolution of crystal structure was explored during the annealing and stretching processes by two-dimensional small-angle X-ray scattering (2D-SAXS). Shish-kebab structure was obtained during annealing for hollow fibers at a spin-draw rate of 350 m/min. The crystalline lamellae were destroyed and micropores were formed during the fabrication of membranes by stretching.

CO2 activation is a vital knot for CO2-mediated energy conversion and storage. Frustrated Lewis pairs (FLPs) are well confirmed to be highly efficient in CO2 activation. Here, we synthesized the single-crystal ZnSn(OH)6 cube with exposed (100) facet (Sc) and ZnSn(OH)6 octahedra with exposed (111) facet (So) and created FLPs with different acid-base distance on these exposed facets by vacuum irradiation, resulting from the light unstability of terminal hydroxyls. Our results demonstrated that the FLPs with short acid-base distance on So are more efficient activation centers due to the strong orbital interactions, well exemplifying that shortening the Lewis acid-base distance is a potential route to develop highly efficient FLPs catalysts. In addition, as an initial attempt, the combination effects between facet junction separating charges and FLPs activating molecules were proposed to accelerate CO2 reduction. Our findings may provide new insights into designing photocatalysts with highly catalytic performances.

Z-Scheme MoS2/g-C3N4 heterojunction photocatalysts were fabricated using a hydrothermal deposition procedure together with a calcination route, and then applied for CO2 photoreduction. Experimental results indicated that the 10% MoS2/g-C3N4 heterojunction displayed the best photocatalytic performance. Furthermore, the maximum CO yields of 58.59 μmol (g-cat)-1 under 7 h-visible light irradiation was up to 2.94 times that of the unadulterated g-C3N4. The enhanced photocatalytic performance of 10% MoS2/g-C3N4 catalyst was due to the favored visible light response, the efficient separation of photogenerated electron-hole pairs as well as its larger specific surface area.

Poor durability prominently limits the application of superhydrophobic coatings. In this study, a super-hard superhydrophobic Fe-based amorphous alloy coating was prepared on Q235 steel substrate via plasma spraying and further surface modification with heptadecafluoro-1,1,2,2-tetrahydro-decyl-1-trimethoxysilane (FAS17). The SEM observation showed that the coating surface feature varied with plasma spray power. The coating with a spray power of 30 kW has a triple-level hierarchical surface feature with no-flattening particles in dozens of micron size, adherent splashing particles in several micron size, and wool-like oxides with nano size. The corresponding water contact angle and sliding angle were 154° ± 2° and 4° ± 1°, respectively. The X-ray diffraction results revealed that the coatings have amorphous structure; however, the crystallization and oxidation may occur with increasing spray power. The energy dispersive spectroscopy result confirmed that the nano wool-like oxides comprise multi metal oxides, in which Fe, C, and Mo dominated. The adherent splashing particles were rarely found at 15 kW, whereas the wool-like oxides were not at all observed at 15 and 22.5 kW. Thus, the hydrophobicity decreased when the spray power increased. The X-ray phosphorescence spectroscopy test verified the chemical bonding of FAS17 and coatings. In addition, in virtue of super-high microhardness of 884 ± 61HV0.1, the superhydrophobic coating at 30 kW spray power displayed excellent anti-wear property under a pressure as high as 10 kPa.

Nuclear thermal propulsion (NTP) is one of the most promising approaches for deep space exploration and manned interstellar voyage. As the propellant and coolant of NTP reactors, hydrogen provides higher specific impulse. In this paper, the thermohydraulic performance of high temperature hydrogen flowing through the twisted rod bundles were investigated numerically by contrasting with the cruciform rod bundles and the circular rod bundles. The heat transfer models were validated by literature data and the relative errors are within 20%. Twisted rods could enhance lateral mixing and heat transfer since the twisted lobes and valleys could enhance radial heat transfer and produce a strong rotational flow near the walls disturbing boundary layer, which reduces hot spot factors and assures the thermal safety. The largest relative difference of the JF factor between the twisted and other non-twisted channels are 28.0% and 6.1% respectively in this model.

The development of the space vehicles puts forward higher requirements on the energy supply, and the megawatt gas-cooled space nuclear reactors are promising to satisfy the demand. The energy allocation optimization on the space nuclear reactors takes critical part in the system design. The optimization between the energy conversion efficiency and radiator mass of the gas-cooled space nuclear reactor is conducted and analyzed. The models of direct Brayton cycle, heat pipe radiator, and liquid droplet radiator are established. The working performance of the thermodynamic cycle coupled with heat pipe radiator (HPR) and liquid droplet radiator (LDR) are obtained respectively, and compared. The area and weight of the HPR increases linearly with the radiant power. The calculation results show that, for space nuclear reactors adopting HPR, decreasing the coolant temperature at the reactor core outlet (T1) from 1500 K to 1200 K will increase the specific surface area from 1200 m2/MW to about 3000 m2/MW with the same energy conversion efficiency. The radiant power of the LDR can be regulated by operation mode with the radiator weight remains unchanged. The mass of LDR is only about 10% of HPR for case with electricity power Pe = 0.5 MW, T1 = 1500 K, showing significant advantage in the mass optimization. This paper may contribute to the energy management and allocation optimization of the gas-cooled space nuclear reactor.

Grain refinement is a critical approach to improve the strength of materials without damaging the toughness. The grains of deformation-induced ferrite are considerably smaller than those of proeutectoid ferrite. Grain refinement is crucial to the application of deformation-induced ferrite. The composition of ferrite and bainite or martensite is important in controlling the performance of X70HD pipeline steel, and cooling significantly influences the control of their ratio and grain size. By analyzing the static and dynamic phase-transition points using Gleeble-3800 thermal simulator, thermal simulations were performed through two-stage deformations in the austenite zone. Ferrite transformation rules were studied with thermal simulation tests under different deformation and cooling parameters based on the actual production of cumulative deformation. The influence of deformation parameters on the microstructure transformation was analyzed. Numerous fine-grain deformation-induced ferrites were obtained by regulating various parameters, including deformation temperature, strain rate, cooling rate, final cooling temperature and other parameters. Results of metallographic observation and microtensile testing revealed that the selection of appropriate parameters can refine the grains and improve the performance of the X70HD pipeline steel.

Co 3 O 4 nanoparticle-decorated hierarchical flower-like α-Fe 2 O 3 microspheres were prepared via a facile two-step method and subsequent annealing. The structure, morphology and surface characteristics of the as-prepared products were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). Considering the potential applications, the gas sensing performances of the sensor based on α-Fe 2 O 3 /Co 3 O 4 composites and pure α-Fe 2 O 3 microspheres were investigated towards a series of volatile organic compounds. The response of hierarchical α-Fe 2 O 3 /Co 3 O 4 composites sensor to 100 ppm ethanol at operating temperature of 170 °C is about 16.1, which is twice as much as the pure α-Fe 2 O 3 microspheres sensor at 300 °C. Moreover, a dramatic reduction of response/recovery time (3.3 s/5.4 s) has been achieved at different operating temperature. The enhanced sensitivity performance is mainly due to its unique hierarchical structure, which provides high surface area, a large number of active sites, and the synergistic effect between n-type α-Fe 2 O 3 and p-type Co 3 O 4.

In this communication, efficient reinforcement of cement matrix was obtained by graphene-oxide (GO) doping and curing treatments. The compressive strength of plain cement is 14.3±0.2 MPa. When the cement contained 0.5 wt% GO, its strength reached 19.4±0.9 MPa. The strength can be further enhanced by curing, which follows the sequence: Microwave-cured GO-cement > Microwave and water-cured GO-cement > Water-cured GO-cement > GO-cement without curing. The highest compressive strength (32.4±0.7 MPa), which was achieved by combining GO-doping and microwave curing, is 126.6±8.1% higher than that without GO-doping and microwave curing. This demonstrates a synergistic effect of GO doping and microwave-curing on the strength of cement composite materials. Furthermore, X-ray diffraction (XRD), Fourier transform Infrared Spectroscopy (FTIR), and field emission scanning electron microscope (FESEM) characterizations revealed that the combination of GO doping and microwave-curing remarkably accelerated cement hydration, leading to the regular and compact structure and thus a high compressive strength. This work provides a new way to improve the mechanical properties of cement composites.

In order to design the structure combination of semi-rigid base asphalt pavements based on the Dynamic Stability(DS) of asphalt surface course and asphalt mixture, the Wheel Tracking Test(WTT) on three-layers asphalt mixture specimens and its each layer specimen was carried out. Based on these laboratory test data, a formula to calculate full-thickness specimen’s DS from its each layer’s DS and thickness was developed firstly. Secondly, some full-thickness specimens were cut from the asphalt surface of an expressway which had served for many years. WTT was also carried out on these field specimens. Based on analyzing the relationship between the field specimens’ DS and the corresponding rut depth at the cutting location of the expressway pavement, a DS controlling standard of the asphalt surface was suggested to suit the traffic volume of the expressway. Lastly, various asphalt surface structure combination schemes were obtained according to each layer’s DS control standard decomposing from the DS control standard of asphalt surface as mentioned above. Then the optimal structure combination scheme was suggested.

Recently the concept of "no external gas hydrate control measures" has been proposed, whereby gas hydrate formation can occur in oil and gas subsea pipelines during steady state and transient operations, with the operational window defined by predictive analytic tools. Flow assurance engineers routinely use computer programs, including transient multiphase flow simulators coupled to a gas hydrate kinetics model to simulate gas hydrate formation and transportability. Given the complexity in multiphase flow modeling, modern machine learning technologies, especially artificial intelligence, could be applied to solve high-level, non-linear problems, such as evaluating gas hydrate risk based on measurable process parameters. In this work, several machine learning techniques, such as regression, classification, feature learning with an algorithm/framework like support vector machine (SVM) and neural networks (NN), are applied to analyze the data sets on: 1) hydrate tests conducted at pilot-scale flowloop facilities (4,500 data points), as well as 2) transient operation field data. The classification/regression model based on flowloop test data uses several independent input variables (features), such as water cut, gas-oil ratio, hydrate particle cohesive force, fluid velocity, oil viscosity, specific gravity, interfacial tension, and time in the hydrate stable zone, to output the hydrate fraction and probability of hydrate plugging in the pipeline. The semi-supervised learning model was applied based on the field data use as input, including water cut, shut-down time (where applicable), and gas-oil ratio to determine the level of hydrate resistance to flow during restart or dead oil displacement after production shut-down. The flowloop based machine learning model exhibited good prediction accuracies in test and validation processes, and was used to assess the hydrate risks in an actual field. The field data based machine learning model demonstrated the ability to construct field risk maps. The machine learning technique could be potentially applied in hydrate management to evaluate hydrate risks in subsea oil/gas pipelines. As a complement to more complex transient multiphase flow simulations, this machine learning approach can aid in the development of advanced hydrate management strategies.

4140 steel and 4150 steel are different only in their carbon content. A comparison between the kinetics and microstructure of the bainite transformation of both steels has been carried out under a wide range of isothermal temperatures, in which four bainite phase matrices were generated. The four phases are upper bainite, mixed upper and lower bainite, lower bainite and mixed martensite and lower bainite (lower bainite transformed under Ms temperature). The bainite transformation kinetics-morphology characteristics of the four phases were studied and compared. Kinetics behavior patterns are shown with the developed TTT diagrams and kinetics plots- (bainite volume fraction vs isothermal holding time). The upper bainite and lower bainite transition temperatures are different and the bainite reaction time span is shorter when carbon content is higher. The n values in the Johnson-Mehl- Kolmogorov-Avrami (JMKA) equation have a wider deviation when carbon content is higher, indicating more bainite reaction variation. The activation energy required for the bainite phase transformations were compared and it was found that higher activation energy is needed when carbon content is higher. The subtle microstructure morphology differences are illustrated. This work will aid future development of 4140/4150 steels with bainitic microstructures having improved mechanical properties.

This paper focuses on transient aerodynamic performances and pressure oscillations of a practical core-engine annular combustor during start up core-engine test article and its measurement systems are introduced at first. Then the test results. The transient evolutions of pressure drops which represent basic aerodynamic characteristics of combustor are discussed. A new and special aerodynamic “swing” phenomenon of static pressure (or pressure drops across combustor liner) and low frequency pressure oscillations (50 Hz∼180 Hz) were observed in the tests and are discussed in detail. The variations of pressure drops and pressure oscillation magnitudes are affected by compressor outlet flow conditions with different core-engine acceleration rates. With elaborate analysis on “waterfall” maps and Campbell maps of transient pressure oscillations, the driving of low frequency pressure oscillations in combustor is confirmed to be unsteady flow originating from pre-diffuser flow passage. Combined with analysis on dynamic pressures monitored in compressor passage, the aerodynamic “swing” phenomenon is confirmed to be a resonance process between unsteady flow produced by upstream stages rotation of compressor and acoustic field of compressor (with natural frequency bands 97 Hz ± 10 Hz and 152 Hz ± 15 Hz). Results also infer that low frequency pressure oscillations will amplify magnitude of swing under certain conditions.

Constructed wetland coupled with microbial fuel cells (CW-MFCs) are a promising technology for sustainable wastewater treatment. However, the performance of CW-MFCs has long been constrained by the limited size of its anode. In this study, we developed an alternative CW-MFC configuration that uses inexpensive natural conductive pyrite as an anodic filling material (PyAno) to extend the electroactive scope of the anode. As a result, the PyAno configuration significantly facilitated the removal of chemical oxygen demand, ammonium nitrogen, total nitrogen, and total phosphorus. Meanwhile, the PyAno increased the maximum power density by 52.7% as compared to that of the quartz sand control. Further, a typical exoelectrogen Geobacter was found enriched in the anodic zone of PyAno, indicating that the electroactive scope was extended by conductive pyrite. In addition, a substantial electron donating potential was observed for the anodic filling material of PyAno, which explained the higher electricity output. Meanwhile, a higher dissimilatory iron reducing potential was observed for the anodic sediment of PyAno, demonstrating the integrity of an iron redox cycling in the system and its promotive effect for the wastewater treatment. Together, these results implied that the PyAno CW-MFCs can be a competitive technology to enhance wastewater treatment and energy recovery simultaneously.

Liquid droplet radiator (LDR) is the frameless space radiator designed for heat dissipation of large-power space nuclear reactors. This paper analyzes the radiative heat transfer and evaporative characteristics of liquid metals adopted in LDR including lithium, aluminum and tin. Firstly, the cooling process of different working fluids is simulated and the temperature distribution at the droplet collector is obtained. The radiant energy of per unit mass fluid with different optical thicknesses and temperatures is calculated. Secondly, the evaporative characteristics of the working fluid are studied. Finally, the system operation performances are evaluated including the system life and radiant energy with different optical thicknesses and temperatures. Results show that liquid lithium is appropriate for heat dissipation system working under 600 K, while liquid aluminum and tin are more appropriate for working under 1200 K and 1500 K, respectively. This work provides the theoretical support for liquid droplet radiator thermal design.

The health of contact sets is one of the most critical factors for the breaking capacity of the high voltage circuit breaker. Dynamic resistance measurement is considered to be an effective method to assess the erosion degree of the contact sets. However, the electrical resistance may be influenced by many other mechanical faults which will cause the misdiagnosis of the contact sets. At present, the influence mechanism has not been clarified. Therefore, the influence mechanism and degree of mechanical faults (stress relaxation, fatigue, friction) of contact sets is studied in the present paper. Firstly, the accelerated stress relaxation experiments of CuW alloy, the fatigue experiments of contact sets, and the mechanical friction experiments are carried out to obtain the relationship between the fault degree and the electrical resistance. Secondly, the fatigue fracture, micromorphology, energy dispersive spectroscopy, and metal loss of the contact sets are investigated. Thirdly, the stress distribution and fatigue fracture of the contact finger is analyzed by the finite element method. Based on the above works, the fatigue damage, and the partial loss of the contact fingers are considered to be the most distinct influence on the electrical resistance curves.

Due to their ability to elicit a potent immune reaction with low systemic toxicity, cancer vaccines represent a promising strategy for treating tumors. Considerable effort has been directed toward improving the in vivo efficacy of cancer vaccines, with direct lymph node (LN) targeting being the most promising approach. Here, a click-chemistry-based active LN accumulation system (ALAS) is developed by surface modification of lymphatic endothelial cells with an azide group, which provide targets for dibenzocyclooctyne (DBCO)-modified liposomes, to improve the delivery of encapsulated antigen and adjuvant to LNs. When loading with OVA257-264 peptide and poly(I:C), the formulation elicits an enhanced CD8+ T cell response in vivo, resulting in a much more efficient therapeutic effect and prolonged median survival of mice. Compared to treatment with DBCO-conjugated liposomes (DL)-Ag/Ad without the azide targeting, the percent survival of ALAS-vaccine-treated mice improves by 100% over 60 days. Altogether, the findings indicate that the novel ALAS approach is a powerful strategy to deliver vaccine components to LNs for enhanced antitumor immunity.

Capture of CO2 with high efficiency is essential to tackle the global warming issue that has aroused widespread attention. Herein we employed the halogen-free deep eutectic solvents (DESs) consisting of imidazole (Im) and p-toluenesulfonic acid (PTSA) to absorb CO2. The CO2 solubility in [3Im:PTSA], [3.5Im:PTSA], and [4Im:PTSA] is measured in the range of temperature from 303.15 to 333.15 K and pressure from 110 to 1500 kPa. Henry's constants of Hx and Hm and thermodynamic properties of∆solG, ∆solH, and ∆solS are correlated from the experimental data. The comparison between the studied DESs and the reported solvents is performed based on Hm. Afterwards, the experiment-dependent Jou and Mather empirical model and fully predictive COSMO-RS model are used to calculate the CO2 solubility, which are compared with the experimental results. Finally, the interaction energies between CO2 and DESs, as indicated by misfit, hydrogen bond, and van der Waals energies, are calculated by COSMO-RS to illustrate the absorption mechanism.

Polystyrene-block-polybutadiene-block-polystyrene triblock copolymer (SBS) has the potential to be used as a dielectric elastomer for actuator, sensor, energy harvesting, and so on, but its low dielectric constant and thermal conductivity seriously limit this application. In this study, novel exfoliated graphite nanoplates (xGNPs)/SBS composites were prepared by a solution-blending method using N,N-dimethylformamide and tetrahydrofuran as co-solvents. Wide-angle X-ray diffraction measurement confirms that xGNPs have been incorporated into SBS. Furthermore, the result of scanning electron microscopy shows that xGNPs disperse well in the SBS matrix. The effects of xGNPs on the dielectric constant and thermal conductivity of the resultant xGNPs/SBS composites were investigated. The dielectric constant at 1,000 Hz significantly increased from 2.72 for pure SBS to 15.96 and 40.94 for xGNPs/SBS composite containing 1.19 and 1.27 vol.% of xGNPs, respectively. Moreover, the thermal conductivity of the xGNPs/SBS composite containing 1.27 vol.% of xGNPs has been improved from 0.18 to 0.41 W/m·K in comparison with that of pure SBS.

The liquid droplet radiator (LDR) as a frameless heat removal system is considered as a promising solution for the waste heat dissipation of megawatt aerospace applications. The radiation heat transfer and evaporation characteristics of the LDR working fluid are tightly coupled with the operational performance of the liquid droplet generator. In this paper, the effects of operational parameters of droplet generator on the radiative heat transfer and evaporation loss rate are clarified, including the pressure disturbance frequency, pressure difference between the inside and outside of the droplet generator. It is observed that higher coolant mass flow rate does not assure higher heat transfer power for the LDR. For cases with higher pressure difference, where the coolant flow rate is higher consequently, the evaporation loss rate increases continually with pressure difference while the heat transfer power does not increase any more. The disturbance frequency has inconspicuous impact on the evaporation characteristics. Besides, cases with higher pressure differences have wider suitable frequency ranges according to the droplet formation restriction. Generally, a relatively higher pressure difference coupled with a higher disturbance frequency (such as 0.3 MPa and 12 kHz) is suggested to achieve a higher heat transfer power and low evaporation loss rate. This paper may provide favorable reference for determining the operational parameters of the droplet generator in consideration of radiation heat transfer and evaporation characteristics.

As the breaking capacity of circuit breaker depends in part on the state of contact sets, and the states can be described by the electrical resistance. However, the electrical resistance shows great differences when the closing or opening speed changes due to the fault or degradation of operating mechanism, and the differences will cause trouble to the diagnosis results inevitably. In order to achieve accurate diagnosis of the contact condition, the mechanism of resistance changing with speeds has to be studied. In the present paper, the contact resistance under different speeds is measured by DRM experimental platform, and the characteristic parameters of resistance curves are extracted to show the positive correlation between contact resistance and speeds. What follows is a finite model of contact sets used to simulate the deformation and strain under different speeds. After the simulation, the influence mechanism is discussed, and a mathematical model is proposed.

Photoreduction carbon dioxide to hydrocarbons has been recognized as one of the most promising and sustainable solutions to realize solar-to-chemical energy conversion and alleviate environmental pollution. Herein, we prepared g-C3N4 photocatalyst modified by NiS2 quantum dots as co-catalyst based on a seed-mediated hydrothermal process. The composite showed superior activity and stability in photocatalytic CO2 reduction. The highest CO evolution rate of 10.68 μmol h−1 g−1 was obtained on NSQD/CN-25 catalyst, which was 3.88-fold as high as unadulterated g-C3N4, and its apparent quantum efficiency (AQE) was 2.03% at 420 nm. During the photoconversion process, the possible intermediate products (such as C O O - , C O 2 - and H C O 3 - ) were detected by in situ FTIR analysis. Notably, the electron transfer from g-C3N4 to NiS2 QDs could effectively accelerate the separation of photoexcited electron–hole pairs. This work paves a new strategy toward designing cost-effective photocatalyst with high performance for photocatalytic CO2 reduction.

A rock mass structure has the risk of being subjected to both chemical corrosion and impact loading, which significantly affects the stability of the rock mass structure. In this study, the influence of corrosion on the dynamic fracture toughness of limestone was studied. NaCl and KHSO4 mixed solutions with different pH values (pH = 2, 4, and 6) were used to corrode nicked semicircle bending (NSCB) specimans in three groups and then tested with a split Hopkinson pressure bar (SHPB) device. Before performing the dynamic fracture tests, the porosity of the corroded specimens were obtained using the Nuclear magnetic resonance (NMR) system, and the damage variables were applied to describe the corrosion damage of the limestone. In addition, a high-speed camera, the JR 3D scanning system, scanning electron microscope (SEM) and X-ray fluorescence (XRF) technology were also carried out to examine the fractal dimensions, fracture roughness, micro-fracture morphology, and mineral composition and content. With the increase in the damage variable, the dynamic fracture toughness and fracture energy gradually decrease, while the fractal dimension of the fracture increases. The standard deviation of the 3D spatial distribution parameters, including the asperity height, slope angle, and aspect direction of the fracture surface mesh element planes, all increase, indicating a gradual increase in the fracture surface roughness due to the defects of the corrosion damage. The SEM and XRF results show that the chemical actions had a significant impact on the microstructure and mineral elements of the limestone. Finally, the relationship between the macroscopic mechanical parameters of the limestone specimens and the mechanism of the chemical corrosion damage was discussed.

Tritium management is a vital factor that needs to be considered before a molten salt reactor (MSR) or fluoride-salt-cooled high-temperature reactor (FHR) is constructed. The analysis of tritium transport characteristics under steady and transient conditions is essential in the conceptual design of MSRs and FHRs. In this study, tritium transport characteristics analysis is conducted for a fluoride-salt-cooled pebble bed reactor, i.e., thorium molten salt reactor with solid fuel (TMSR-SF) under accident conditions. The tritium transport characteristics analysis (TAPAS) code is improved with a power model and heat-and-mass transfer model to adapt to TMSR-SF. The transient responses of the tritium transport characteristics of TMSR-SF under the unprotected reactivity insertion accident (URIA) and unprotected overcooling accident (UOC) are determined. It is found that the amount of tritium fluoride (TF) adsorbed on graphite varies, indicating the dynamic equilibrium between the TF adsorption and desorption on graphite. Due to the nuclear density variations of Li-6 and Be-9 in the fluoride salt under the accident conditions, the tritium production rate increases and decreases under the UOC and URIA conditions, respectively. Generally, under these two accident conditions, the tritium permeation rates are lower than that of the normal operation condition. In these cases, it is unnecessary to develop extra safety facilities for tritium control. This study contributes to the tritium management of TMSR-SF.