Search

We reported the fracture behavior of multimodal AA7075-B4C composites with three types of coarse grains (CG, AA7075 powder-1 μm, AA7075 powder-10 μm, and as-cryomilled AA7075 powder) synthesized via cryomilling and plasma activated sintering. Our results indicated that the type (particle size) and weight fraction could affect the distribution of CGs, which in turn significantly affect the fracture behavior of multi-modal composites. Multiple voids were found in the vicinity of AA7075 powder-1 μm, leading to a limited plasticity even with a lower yield strength. AA7075 powder-10 μm (25%) could distribute homogeneously in the composites, resulting in a high yield strength (712 ± 24 MPa) with the plasticity of ~7.7%. The localized grain growth occurred during consolidation with addition of as-cryomilled AA7075 powder. Noted that once the continuous distribution of CGs were detected in the composites, the yield strength decrease dramatically. The CGs could enhance the plasticity by retarding the propagation of micro-cracks during deformation.

Rate-dependent hysteresis nonlinearity in piezoelectric actuators severely limits micro- and nanoscale system performance. It is necessary to establish a dynamic model to describe the full behavior of rate-dependent hysteresis. In this article, the Elman neural network–based hysteresis model is developed for piezoelectric actuators. An improved dynamic hysteretic operator is proposed to transform the multi-valued mapping of hysteresis into one-to-one mapping on a newly constructed expanded input space. Then, Elman neural network incorporated with the improved dynamic hysteretic operator is utilized to approximate the behavior of rate-dependent hysteresis. The combination of Elman neural network and the improved dynamic hysteretic operator can dually embody the dynamic property and is capable of fully extracting the characteristics of rate-dependent hysteresis. The experimental results are presented to illustrate the potential of the proposed modeling technique.

1-Dodecanol has good extraction efficiency of cresols from aqueous solution. The liquid-liquid equilibrium (LLE) data of ternary system 1-dodecanol-(o-/m-/p-)-cresol-water were determined at 298.15 K, 313.15 K, 323.15 K, 333.15 K and 343.15 K under atmospheric pressure. The Hand and Othmer-Tobias equations were used to test the reliability of the experimental tie-line results. The results show that the measurement data has high consistency. The LLE data were correlated by non-random two-liquid (NRTL) and universal chemical activity coefficient (UNIQUAC) models. The experimental results show that the correlation coefficients of both models exceed 0.995. All root mean square deviations (RMSDs) between the calculated values from the single temperature NRTL model, the UNIQUAC model and the multiple temperatures NRTL model and the experimental data are

To improve the interaction between cells and scaffolds, the appropriate surface chemical property is very important for tissue engineering scaffolds. In this study, the thermoplastic polyurethane (TPU) nanofibers was firstly fabricated by electrospinning technique, and then its surface was modified with cellulose nanofibrils (CNF) particles by ultrasonic-assisted to obtain TPU/CNF nanofibers. Subsequently, the TPU/CNF-polydopamine (PDA) composite nanofibers with core/shell structure were fabricated by PDA coating method. In comparison with TPU nanofibers, the uniformization of PDA coating layer on the surface of TPU/CNF composite nanofibers significantly increased due to the addition of CNF, which used as the active sites to guide the PDA particles accumulated along with the fiber direction. The water absorption and hydrophilicity of TPU/CNF-PDA composite nanofibers were significantly increased in comparison with those of TPU and TPU/CNF nanofibers. The mechanical properties of the TPU/CNF-PDA composite nanofibers were higher than those of the TPU and TPU/CNF nanofibers due to the formation of strong hydrogen bonds between PDA and TPU/CNF, making TPU, CNF and PDA strongly adhere to each other. The attachment and viability of mouse embryonic osteoblasts cells (MC3T3-E1) cultured on TPU/CNF-PDA composite nanofibers were obviously enhanced compared with TPU and TPU/CNF nanofibers. Those results suggested that the modified TPU/CNF-PDA composite nanofibers have excellent mechanical and biological properties, which promoting them potentially useful for tissue engineering scaffolds. The presented strategy represents a general route to modify the surface of scaffolds, which are promising for tissue engineering applications.

To explore the mechanical failure and permeability characteristics of porous gas-bearing coal under triaxial stress, the triaxial compression experiment was carried out for porous and conventional gas-bearing coal samples based on the triaxial creep-seepage experiment system and sound emission signal acquisition system. Acoustic emission testing was carried out at the same time of loading failure. The experimental results showed that (1) under fixed gas pressure but changing confining pressure, the porous gas-bearing coal sample had higher peak strength and elastic modulus but lower peak strain; under changing gas pressure but fixed confining pressure, the porous gas-bearing coal sample had lower peak strength and peak strain but higher elastic modulus. When either confining pressure or gas pressure was changed, the mechanical properties of the two kinds of gas-bearing coal samples showed a good consistency, but the mechanical parameters differed greatly, with the peak strength, peak strain, and elastic modulus of porous coal samples are reduced by 1/4, 2/3, and 3/4, respectively. (2) When either the confining pressure or gas pressure was changed, the permeability of the porous gas-bearing coal sample was larger than that of the conventional gas-bearing coal sample. However, the change rules of permeability characteristics of the two were basically the same, except that there was a large difference in permeability value that the porous gas-bearing coal sample increases nearly twice as much as that of the conventional gas-bearing coal sample. (3) In the whole stress-strain process, the acoustic emission characteristics of the porous gas-bearing coal sample differed significantly from those of the conventional gas-bearing coal sample. The maximum ringdown count of the porous gas-bearing coal sample can be reduced by one-third at most, the maximum energy can be reduced by nearly half at most, and the maximum amplitude changes little with only 1–3 dB reduction. The research results have important guiding significance for the prediction of failure and instability of coal tunnel and the development of relevant protective techniques.

Aqueous nickel-zinc (Ni-Zn) batteries hold great promise for large-scale energy storage systems. However, traditional Ni-based cathode electrodes are generally consist of none capacity contribution additives and heavy current collectors, resulting in a low percentage of the active materials. In this regard, developing lightweight, flexible and binder-free cathode electrodes for aqueous Ni-Zn batteries is highly desirable. Herein, for the first time, we develop a simple electrospinning technique to synthesize the one-dimensional (1D) electrospun carbon nanofibers functionalized with ternary NiCo2S4 nanoparticles (denoted as CNF@NiCo2S4) as a lightweight, flexible and binder-free electrode for aqueous Ni-Zn batteries. Based on the self-standing CNF@NiCo2S4 film as cathode, the as-fabricated aqueous CNF@NiCo2S4//Zn battery exhibits a high capacity of 0.32 mAh cm−2 and 35.9 mAh cm−3 at a current density of 2 mA cm−2, and good rate performance (0.21 mAh cm−2 at 20 mA cm−2) and long-term cycling stability (83% capacity retention at 10 mA cm−2 after 2000 cycles). More importantly, a quasi-solid-state CNF@NiCo2S4//Zn battery is also fabricated, which also displays an impressive energy density of 362.3 Wh kg−1, indicating the potential towards practical applications. Impressively, the volumetric energy density of CNF@NiCo2S4//Zn battery are 58.2 mWh cm−3 (liquid) and 45.4 mWh cm−3 (quasi-solid-state), which are much larger than the values of other reported Ni-Zn batteries. Theses results indicate the self-standing CNF@NiCo2S4 film is promising for for next generation electronic applications.

In a pulse detonation engine, filling fresh reactive mixtures into the detonation chamber is an indispensable process. The fill flow rate would significantly influence the subsequent flame acceleration and detonation initiation processes. Nevertheless, the existing works regarding the flame acceleration and detonation initiation are mostly performed on the quiescent mixtures. This work, therefore, investigates the effect of fill flow rate on the flame acceleration process in a square cross-section, obstructed detonation channel. Ethylene was utilized as the fuel, and oxygen-enriched air with an oxygen volume fraction of 40% as the oxidizer. The flame acceleration processes of quiescent and moving mixtures were observed by high-speed Schlieren and chemiluminescence techniques. It was found in this work that the fill flow rate dominates the flame propagation in the early stage of the flame acceleration (i.e., to the sound velocity of reactants). The initial flame structures vary from smooth (quiescent) to wrinkled (50 g/min) and cellular (100 g/min and 150 g/min), and to turbulent (200 g/min) with the increase of the fill flow rate. The Schlieren measurements of the filling processes show that the flow instabilities and the shear layer shedding from the obstacle surfaces into the mainstream are responsible for the promoted flame acceleration in high fill flow rate cases.

Junctions are an important structure that allows charge separation in solar cells and photocatalysts. Here, we studied the charge transfer at an anatase/rutile TiO 2 phase junction using time-resolved photoluminescence spectroscopy. Visible (~500 nm) and near-infrared (NIR, ~830 nm) emissions were monitored to give insight into the photoinduced charges of anatase and rutile in the junction, respectively. New fast photoluminescence decay components appeared in the visible emission of rutile-phase dominated TiO 2 and in the NIR emission of many mixed phase TiO 2 samples. The fast decays confirmed that the charge separation occurred at the phase junction. The visible emission intensity from the mixed phase TiO 2 increased, revealing that charge transfer from rutile to anatase was the main pathway. The charge separation slowed the microsecond time scale photoluminescence decay rate for charge carriers in both anatase and rutile. However, the millisecond decay of the charge carriers in anatase TiO 2 was accelerated, while there was almost no change in the charge carrier dynamics of rutile TiO 2 . Thus, charge separation at the anatase/rutile phase junction caused an increase in the charge carrier concentration on a microsecond time scale, because of slower electron-hole recombination. The enhanced photocatalytic activity previously observed at anatase/rutile phase junctions is likely caused by the improved charge carrier dynamics we report here. These findings may contribute to the development of improved photocatalytic materials.

Due to the charge leakage during the touch sensing period and the threshold voltage shift of the driving thin-film transistors (TFTs), the conventional gate driver circuits suffer from poor stability for in-cell touch displays with an increased touch reporting rate. This paper shows a new gate driver circuit, consisting of a two-stage pre-charge structure, which can reduce the charge leakage during the touch sensing period and suppress the threshold voltage shift of the driving TFTs. Simulation results demonstrate that, the rising and falling time differences between adjacent stages are 9.3% and 1.6% for the conventional and the proposed gate driver circuit, respectively. In the case that the threshold voltage of key TFT shifts by +10 V, the rising and falling time degradation ratios are 120% and 2.4% for the conventional and the proposed gate driver circuit, respectively. Therefore, the proposed gate driver circuit is stable for in-cell touch panels with a high touch reporting rate.

Steam curing has an adverse effect on the long-term performance of concrete, which is inseparable from the early hygro-thermal coupling action. The temperature-humidity field and performance of steam-cured concrete with different surface covering methods were characterized under the treatment temperature ranging from 45 to 75 ℃ by water permeability along with hydration characteristics, porosity, microhardness, and microstructure. The results show that steam-curing regimes directly affect the long-term performance of steam-cured concrete by changing internal temperature-humidity field. During the steam curing process, a higher treatment temperature often corresponds to a more complex temperature-humidity gradient, so that the steam-cured concrete exhibits low compactness and high permeability. In addition, the surface covering methods can reduce the surface porosity and interface transition zone width of steam-cured concrete. Meanwhile, with the increase of treatment temperature, the improvement effect of the surface covering methods on the impermeability of steam-cured concrete is more obvious.

Steam curing is a common method of producing prefabricated elements, achieving high early strength to meet economic benefits. However, this rapid curing method is extremely detrimental to the microstructure and long-term performance of concrete. Therefore, choosing an appropriate measure to remission this adverse effect is critical to the development of long-term performances of steam-cured concrete. In this study, two steam-curing regime and four subsequent curing conditions were employed on the curing of concrete. The long-term compressive strength, surface permeability and microstructure were measured to analyze the effects of curing condition on performance of steam-cured concrete. The results indicate that step-curing is beneficial to the formation of pre-structures, thereby improving the long-term mechanical properties and impermeability of steam-cured concrete. Among the four subsequent curing conditions, saturated limestone immersion is most beneficial to the long-term performance of steam-cured concrete, while water immersion is the most unfavorable.

The accelerated hardening of concrete caused by steam curing has adverse effects on the microstructure and properties of concrete, so it is necessary to adopt appropriate curing method to reduce the damage caused by steam curing. The effects of curing methods on the properties of concrete after steam curing are worth studying. The compressive strength, non-evaporable water content and permeability (air, water and ion) of steam-cured concrete were tested under different subsequent curing conditions. Meanwhile, the internal microstructure was also investigated by image processing and SEM. The results show that the compressive strength of steam-cured concrete with four curing methods increases with the curing time, but the growth rates are different. The permeability of the concretes cured in the air decreased first and then increased with the curing time, while other curing methods decreased with curing time. The microstructure also shows that adequate subsequent wet curing can effectively reduce the adverse effects of steam curing on concrete.

Effects of steam curing parameters on the capillary water absorption (CWA) of concrete are investigated, and the models related to steam curing parameters for predicting the sorptivity coefficient of concrete are developed using extensive experimental database. The results show that the CWA and sorptivity coefficient of steam-cured concrete is closely related to the steam curing regimes and the surface condition of concrete. Longer precuring time or lower heating rate can reduce the CWA and sorptivity coefficient of steam-cured concrete. When the treatment time is 8 h, higher and lower treatment temperature can increase the CWA and sorptivity coefficient of concrete. When the treatment temperature is 60 ℃, the CWA and sorptivity coefficient of concrete increase with the treatment time. Highest cooling rate will lead to highest sorptivity coefficient of steam-cured concrete. The CWA and sorptivity coefficient of top surface are higher than that of side surface, and the CWA and sorptivity coefficient of surface concrete are higher than that of the interior concrete. In addition, the surface treatment methods of quadric-plastering and covering film can reduce the CWA and sorptivity coefficient of concrete. Finally, linear regression analysis and multiple nonlinear regression are employed to simulate the sorptivity coefficient of steam-cured concrete. The multivariable regression analysis method gives an explicit formula that achieves a good predictive result.

Steam curing is commonly used in the production of prefabricated elements in China. However, this curing regime has proven to have an adverse effect on the long-term performance of concrete due to heat damage effects. Steam curing (60 ℃) were compared with standard curing (20 ℃ and 90% RH), and the temperature field inside the cement pastes under two curing regimes was tested by a temperature sensor. The effects of the precuring time, water-binder ratio, surface treatment methods, mineral admixtures, forming process, and subsequent curing conditions on heat damage of steam-cured concrete were examined by capillary water absorption, pore structure and microstructure. The results indicate that there are obvious pore gradients and microstructure differences of hydration products in the surface and interior of steam-cured concrete, and the sorptivity coefficient of the surface is also higher than the internal. Prolonging the precuring time can achieve high early resistance, and surface treatment can reduce the interconnected porosity of the exposed surface. Moreover, concrete mixed with mineral admixtures can delay the hydration process of the cementitious component, which is also beneficial to reduce heat damage. The higher stiffness of the steel mold can offset part of the internal stress, which reduces the sorptivity coefficient of the steam-cured concrete. In addition, appropriate subsequent curing conditions are necessary for steam-cured concrete.

The applicability of 2-octanone as solvent for the liquid phase extraction of phenol from aqueous solution was investigated in this work. The liquid liquid equilibrium (LLE) for the ternary systems {2-octanone + phenol + water} was experimentally determined at 298.15 K, 318.15 K and 338.15 K under atmospheric pressure. Distribution coefficients and separate factors calculated from the experimental LLE data were used to judge if 2-octanone can be used as potential solvent to extract phenol from aqueous solution. Distribution coefficients and separation factors of 2-octanone were also compared with other extractants and results show that 2-octanone has excellent extraction performance. Binary interaction parameters were regressed by the NRTL and UNIQUAC methods, and related physical meaning is explained by interaction forces. The root mean squared deviations (RMSDs) show that both models can well describe phase equilibrium behavior of ternary system {2-octanone + phenol + water}. In order to predict ternary LLE data at other temperatures, the NRTL model was used to simultaneously regress ternary experimental data at all temperatures and the largest RMSD is 0.49%.

In situ transmission infrared spectroscopy was used to study the role of pt cocatalyst in pt/tio2 using co as a probe molecule. an 11 cm(-1) redshift of co adsorbed on pt/tio2 was observed under irradiation in the absence of changes in the co coverage or sample temperature. in contrast, no co shift was detected on pt/al2o3. this indicates that the redshift of the co adsorption peak is due to the photogenerated electron transfer from tio2 to pt, and this accounts for the increased photocatalytic activity by the loaded pt cocatalyst. (c) 2014, dalian institute of chemical physics, chinese academy of sciences. published by elsevier b.v. all rights reserved.

The kinetics of photogenerated electrons in SrTiO3(La,Cr) pretreated with either H2 or O2 were studied using time-resolved infrared spectroscopy. The X-ray photoelectron and Raman spectra showed that the Cr cations in the sample reduced with H2 were all in Cr3+, whereas those oxidized with O2 were in mixed of Cr3+ and Cr6+. Electrons excited with 355 and 532 nm light pulses showed the absorption of mid-IR light, and this was traced as a function of the time delay in a microsecond domain. The time-resolved results revealed that the decay rate of the photoinduced electrons with Cr3+ was slower than that with Cr6+, implying that trivalent Cr contributed more to retarding recombination of photoinduced electrons and holes, and enhanced photocatalytic H2 production activity.

Copper nanoparticles dispersed rod-shaped La2O2CO3 efficiently catalyzed transfer dehydrogenation of primary aliphatic alcohols with an aldehyde yield of up to 97%. This high efficiency was achieved by creating a catalytically active nanoenvironment for effective reaction coupling between alcohol dehydrogenation and styrene hydrogenation via hydrogen transfer. The {110} planes on the La2O2CO3 nanorods not only provided substantial amounts of medium-strength basic sites for the activation of alcohol but also directed the selective dispersion of hemispherical Cu particles of about 4.5 nm on their surfaces, which abstracted and transferred hydrogen atoms for styrene hydrogenation. This finding provides a new strategy for developing highly active alcohol-dehydrogenation catalysts by tuning the shape of the oxide support and consequently the metal-oxide interfacial nanostructure.

When Alpha met Beta: a tuneable α-β surface phase junction on Ga(2)O(3) can significantly improve photocatalytic overall water splitting into H(2) and O(2) over individual α-Ga(2)O(3) or β-Ga(2)O(3) surface phases. This enhanced photocatalytic performance is mainly attributed to the efficient charge separation and transfer across the α-β phase junction.

Cocatalysts have been extensively used to promote water oxidation efficiency in solar-to-chemical energy conversion, but the influence of interface compatibility between semiconductor and cocatalyst has been rarely addressed. Here we demonstrate a feasible strategy of interface wettability modification to enhance water oxidation efficiency of the state-of-the-art CoO(x)/Ta3N5 system. When the hydrophobic feature of a Ta3N5 semiconductor was modulated to a hydrophilic one by in situ or ex situ surface coating with a magnesia nanolayer (2-5 nm), the interfacial contact between the hydrophilic CoO(x) cocatalyst and the modified hydrophilic Ta3N5 semiconductor was greatly improved. Consequently, the visible-light-driven photocatalytic oxygen evolution rate of the resulting CoO(x)/MgO(in)-Ta3N5 photocatalyst is ca. 23 times that of the pristine Ta3N5 sample, with a new record (11.3%) of apparent quantum efficiency (AQE) under 500-600 nm illumination.

The effects of nonlinearity on sub-500 fs pulse transmission over dispersion compensated fiber links using dispersion compensating fiber technique are investigated numerically and experimentally. The pulse broadening and recompression ratio of the 2.5-km transmission link is over 300. The postcompensated and precompensated links are compared when the input pulse energy ranges from 15 to 159 pJ. At high powers, self-phase modulation (SPM) degrades the pulse recompression process and provides an upper bound on the transmitted pulse energy. The SPM effect is stronger in the postcompensated link than in the precompensated link. A dramatic spectral narrowing effect was observed in the postcompensated link. Pulse energies up to tens of pJ, consistent with high quality communication, should be possible for a sub-500 fs pulse in such dispersion compensated links.

A composite Sr2TiO4/SrTiO3(La,Cr) heterojunction photocatalyst has been prepared by a simple in situ polymerized complex method. Upon Pt cocatalyst loading, this catalyst shows higher photocatalytic activity towards hydrogen production than individual SrTiO3(La,Cr) and Sr2TiO4(La,Cr) in the presence of methanol sacrificial reagent. Microscopic morphology studies show that well defined heterojunctions are formed by matching the lattice fringes of SrTiO3(La,Cr) and Sr2TiO4(La,Cr), and Pt was preferentially loaded on the surface of the Sr2TiO4(La,Cr) component in the composite Sr2TiO4/SrTiO3(La,Cr) photocatalyst. XPS and EPR analyses show that the composite photocatalyst also has the lowest amount of Cr6+ electron trapping sites. Band structure analysis by combining absorption spectroscopy and Mott–Schottky plots shows that, in the composite photocatalyst, the photogenerated electrons and holes tend to migrate from SrTiO3(La,Cr) to Sr2TiO4(La,Cr) and from Sr2TiO4(La,Cr) to SrTiO3(La,Cr), respectively. This kind of band structure can facilitate charge transfer and separation driven by the minor potential difference between the two components, which is further confirmed by the observation of long lived electrons in the time resolved FT-IR spectroscopic study. It is concluded that the superior photocatalytic activity of the composite heterojunction photocatalyst is due to efficient charge transfer and separation by well defined heterojunctions formed between SrTiO3(La,Cr) and Sr2TiO4(La,Cr), preferential loading of Pt nanoparticles on the Sr2TiO4(La,Cr) component, and the lowest amount of Cr6+ in the composite photocatalyst. The tailored design and synthesis of the composite heterojunction structure is a promising approach for the improvement of the photocatalytic activity of a photocatalyst.

A novel optical method for high-resolution angle measure- ment based on surface plasmon resonance (SPR) is presented. The phase difference between p and s polarization states when SPR takes place is very sensitive to the angle of incidence. Heterodyne interferom- etry is employed to measure this phase difference and thus to measure small angles. The feasibility of this method is demonstrated. The mea- surement resolution of 2310 25 deg can be achieved by this method.