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The properties of the combustion and deflagration to detonation transition (DDT) of Al/Fe2O3/RDX hybrid nanocomposites, a type of potentially novel lead-free primary explosives, were tested in weakly confined conditions, and the interaction of Al/Fe2O3 nanothermite and RDX in the DDT process was studied in detail. Results show that the amount of the Al/Fe2O3 nanothermite has a great effect on the DDT properties of Al/Fe2O3/RDX nanocomposites. The addition of Al/Fe2O3 nanothermite to RDX apparently improves the firing properties of RDX. A small amount of Al/Fe2O3 nanothermite greatly increases the initial combustion velocity of Al/Fe2O3/RDX nanocomposites, accelerating their DDT process. When the contents of Al/Fe2O3 nanothermite are less than 20 wt%, the DDT mechanisms of Al/Fe2O3/RDX nanocomposites follow the distinct abrupt mode, and are consistent with that of RDX, though their DDT processes are different. The RDX added into the Al/Fe2O3 nanothermite increases the latter's peak combustion velocity and makes it generate the DDT when the RDX content is at least 10 wt%. RDX plays a key role in the shock compressive combustion, the formation and the properties of the DDT in the flame propagation of nanocomposites. Compared with RDX, the fast DDT of Al/Fe2O3/RDX nanocomposites could be obtained by adjusting the chemical constituents of nanocomposites.

Fabrication of highly crystalline covalent organic framework (COF) films with tunable thickness and good substrate adaptability remains a substantial challenge. Here, we have developed an effective...

In view of the difficulty of kerosene-air detonation faced by the application of rotating detonation to aviation engines, in order to improve the kerosene detonation activity, the atmospheric pressure gliding arc plasma is used to conduct secondary adjustment of the pre-combustion cracking products. The results show that the components with larger molecular weight in the pre-combustion cracking products, such as ethylene and methane, can be cracked into highly active species of hydrogen and acetylene by gliding arc plasma. With the increase of the fuel ratio of pre-combustion cracking, the plasma has a more significant effect on the adjustment of high active components. However, as the flow rate of the cracking gas treated by plasma increases, the adjustment effect is obviously reduced.

Cold-formed steel members are usually used as purlins in buildings to support roof cladding and thus they can be treated as beams restrained fully or partially in the lateral and torsional directions. However, when these beams are subjected to wind suction loading, their free flange is in compression, which may cause web–flange distortional buckling (WFDB). This paper presents an analytical study on the WFDB of zed-section purlins when subjected to uplift bending. A simplified model is proposed to describe the WFDB of partially restrained purlins, from which the formula for calculating the critical stress of the WFDB is derived. The present model is validated by the results obtained from the finite strip analysis.

Background: The thermal bubble-driven micro actuators have advantages of simple structure and low working voltage, which have broad prospects in the field of micro-fluidic systems. Methods: This paper presents a new type of micro-planar induction heater which can realize the fixed-point growth of thermal bubbles by adding some active cavities. The micro-planar induction heater is composed of a metal heating plate, a glass substrate, and a planar coil. Results: In the experiments, an alternating current of 80 kHz was applied to the micro-planar induction heater; both the heating time and the interruption time were 1 s controlled by a PLC. A CCD camera was used to record the generation process of thermal bubbles, including nucleation, growth, and shrinkage. The experimental results show that thermal bubbles can grow and contract periodically at the position of the cavities when the cavities diameter is 50 μm and 90 μm, respectively. The ideal thickness of the heating plate is between 6 μm and 13 μm. Conclusion:: Here, the fixed-point growth of the thermal bubble with a micro-planar induction heater has been studied. This kind of fixed-point growth of thermal bubbles can be used in micro actuators, such as micro ejectors, micro mixers, and micro pumps.

The laser welding (LW) process of highly reflective materials presents low thermal efficiency and poor stability. To solve the problem, the effects of subatmospheric environment on LW process, technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored. The AZ31 magnesium (Mg) alloy was used as the test materials. The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure. After the keyhole depth greatly rises, significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth. Eventually, the hump-shaped surface morphology of the welded seam is formed; moreover, the weld width in local zones in the lower part of the welded seam remarkably grows. During LW in subatmospheric environment, the weld penetration can be further greatly increased through power modulation. Besides, power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment, thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams. Finally, the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated. This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.

The structure stability of the diameter-expanded conductor with fewer inner wires is the principal limitation in its large-scale use at present. As the traditional design method cannot be adopted to solve this problem, the instability properties of the diameter-expanded conductors were studied in this paper. To perform this analysis, different typical diameter-expanded conductors with fewer inner wires were chosen for the sheave tests under different working conditions at first. Then the simulation model as well as the instability criterion was established to analyze the influence factors of the structure stability. Finally, the synchronous stringing tests were carried out to assess the correctness of the model proposed. The results showed that the weakened support of the inner layer(s) and the local buckling of the external wires are the main causes of the wire jumping phenomenon. Therefore, a reasonable increase in the outmost wires gap and decrease in the inner wires gap are feasible to improve the load-carrying ability of the diameter-expanded conductor.

Ionic liquids (ILs) have attracted increasing attention since last few decades due to their high molecular design abilities and wide applications in different fields. In this study, four novel fluorescent isoquinolino [2,1-a]quinoxalin-5-ium ILs were designed and synthesized via a two-step process including a simple dual Schiff's base formation and a subsequent [RhCp∗Cl2]2-catalyzed oxidative C–H activation/annulation reaction. The as-synthesized ILs were extensively characterized using FT-IR, 1H-NMR, 13C-NMR, 19F-NMR, HSQC-NMR, HMBC-NMR and HR-MS. Their photophysical properties were determined by steady-state fluorescence spectroscopy. The results demonstrate that all these ILs showed dual or triple emissions, large stokes shift (90 nm) and mechanochromic behaviors. Basing on solvatochromism and titration experiments, it is thought that the emission bands of the ILs are raised from their local excited states, charge transfer states or excited state proton transfer of cations, while the substitute effect of these quinoxaline derived ILs on their stokes shifts is negligible.

Designing highly active and selective metal nanocatalysts for use in liquid chemical hydrides is highly attractive but remains a critical challenge. Herein, bimetallic NiPt nanoparticles (NPs) immobilized on lanthanum oxycarbonate (NiPt/La2O2CO3) have been facilely synthesized via an alkali-assisted reduction method. The introduction of NaOH is the key factor to the formation of the well-dispersed and ultrafine NiPt NPs (2.8 nm). The obtained Ni0.6Pt0.4/La2O2CO3 exhibits an extraordinarily high catalytic activity and 100% H2 selectivity for hydrous hydrazine dehydrogenation, providing a turnover frequency value (TOF) high up to 490 h-1 at 298 K. Additionally, the NiPt/La2O2CO3 prepared with NaOH demonstrates higher catalytic performance and lower activation energy than that of NiPt/La2O2CO3_N prepared without NaOH. Moreover, the NiPt/La2O2CO3 also shows an outstanding catalytic efficiency (TOF = 1200 h-1) for dehydrogenation of hydrazine borane at 298 K. The efficient catalytic performance may be attributed to the small size effect, the strong metal-support interaction, and the NaOH promotion effect. This alkali-assisted reduction method provides a new perspective for preparing of highly efficient catalysts in clean energy application.

Supported palladium is the most promising catalyst for catalytic combustion/oxidation of unburned methane generated in vehicles and thermal power generation. The development of a stable catalyst in the presence of high concentrations of water vapor is a challenging task. Herein, core–shell Pd@silicalite-1 catalysts were synthesized with a two-step seed-directed hydrothermal growth method. Firstly, we demonstrate that Fourier transform infrared spectroscopy of CO adsorption (CO-FTIR) is a facile, sensitive, and definite method to probe the completeness of the zeolite shell for metal@zeolite materials. CO-FTIR method is based on the CO access to metal surface because the structure directing agent (SDA) retained in the pores of zeolite shell in the fresh metal@zeolite materials will block the transport of CO. More importantly, for catalysts with complete shell, Pd@S-x (x = 1.5, 2.0) catalyst show no deactivation for 200 h in practical wet conditions (10% H2O, 500 °C). To the best of our knowledge, this is one of the scare Pd catalysts which show 200 h stability in these practical conditions. Pd@S-2.0 shows negligible low temperature water absorption which lead to its high catalytic stability in wet conditions.

Poly(arylene sulfide sulfone)/graphene nanoplate (PASS/GNP) composites with segregated structure based on continuous polymer fiber skeletons were fabricated by coating a thin conductive layer on the PASS fibers and then performing compression molding. The formation of a unique segregated conductive network endowed the PASS/GNP composites with high electrical conductivity and excellent electromagnetic interference (EMI) shielding effectiveness (SE), reaching 17.8 ​S/m and 30.1 ​dB, respectively, when the content of the GNPs in the conductive layer was 20 ​wt%. The PASS/GNP composites also exhibited outstanding mechanical properties, which was attributed to the continuous PASS fiber skeletons that could withstand large loads and the strong interfacial interaction between the conductive layers and the PASS fibers that could provide good stress transfer. This approach is suitable for most soluble polymers.

Singlet fission (SF) has attracted much attention on account of its great potential for applications in high efficiency solar energy conversion. The major roadblock to realize this potential is roo...

Due to its high theoretical capacity and appropriate potential platform, tin-based alloy materials are expected to be a competitive candidate for the next-generation high performance anodes of lithium-ion batteries. Nevertheless, the immense volume change during the lithium-ion insert process leads to severe disadvantages of structural damage and capacity fade, which limits its practical application. In this work, a three-dimensional (3D) multicore-shell hollow nanobox encapsulated by carbon layer is obtained via a three-step method of hydrothermal reaction, annealing and alkali etching. During the electrochemical reactions, the CoSn@void@C nanoboxes provide internal space to compensate the volumetric change upon the lithiation of Sn, while the inactive component of Co acts as chemical buffers to withstand the anisotropic expansion of nanoparticles. Owing to the above-mentioned advantages, the elaborated anode delivers an excellent capacity of 788.2 mAh/g at 100 mA/g after 100 cycles and considerable capacity retention of 519.2 mAh/g even at a high current density of 1 A/g after 300 cycles. The superior stability and high performance indicate its capability as promising anodes for lithium-ion batteries.

In this paper, the nonlinear bending behavior of functionally graded porous (FGP) plates under uniformly distributed transverse loads is studied based on the neutral surface concept within the framework of first-order shear deformation theory (FSDT) including geometrical nonlinearity. The FGP materials with three porosity distribution patterns namely uniform, non-uniform symmetric and non-uniform asymmetric are considered. Using the stress function and Galerkin method, the analytical solutions are obtained to examine the load vs deflection and load vs bending moment curves for various edges boundary conditions. The present results are compared with reference solutions to show the accuracy and the effectiveness of the proposed approach. The effects of the geometric, material parameters, elastic foundations and in-plane constraints on the nonlinear bending behavior of FGP plates are studied in detail through numerical investigations.

Extensive use of selective catalytic reduction denitrogenation technology leads to the generation of a large amount of hazardous waste vanadium–tungsten–titanium catalysts. To valorize these waste ...

Tin sulfide semiconductor nanowires (NWs) have been widely investigated for photodetection applications because of their good optical and electrical properties. Herein, we synthesized n-type SnS2 NWs and then fabricated SnS2 NW photodetectors with a ferroelectric polymer side-gate. The strong electric field induced by ferroelectric polymer can effectively suppress the dark current and improve the detectivity in SnS2 NW photodetectors. The photodetectors after polarization depletion exhibit a high photoconductive gain of 4.0 × 105 and a high responsivity of 2.1 × 105 A W−1. Compared with devices without polarization depletion, the detectivity of polarization-depleted photodetectors is improved by at least two orders of magnitude, and the highest detectivity is 1.3 × 1016 Jones. Further, the rise and fall time are 56 and 91 ms respectively, which are about tens of times faster than those without polarization depletion. The device also shows a good spectral response from ultraviolet to near-infrared. This study demonstrates that ferroelectric materials can enhance optoelectronic properties of low-dimensional semiconductors for high-performance photodetectors.

With the rapid development of wireless power transfer (WPT), the self-resonant WPT system without using additional compensation capacitors has attracted attention. However, most of reported self-resonant WPT systems have low power transfer (less than 100 W) and high operating frequencies at megahertz. In this article, four multilayer, self-resonant WPT coil pads with different dielectrics are designed and experimentally validated. The aim of this article is to increase the power rating and decrease the operating frequency for capacitor-free WPT system compared to reported systems used in consumer electronics. Analysis of integrated compensation capacitance, inductance, and parasitic capacitance of the coil is provided. Finite-element analysis is used to evaluate four dielectric materials, mica, polypropylene, polyimide, and fiberglass. An experimental setup has been developed, which can achieve more than 360-W power transfer for a 120 mm air gap with an efficiency of 82% and an operating frequency of near 80 kHz.

Aggregation plays a critical role in modulating the photophysical process of organic molecules. However, the rational control of the construction of a function-oriented stacking mode for efficient ...

Complex biological environments and multiple physiological barriers significantly impede efficient accumulation and penetration of nanomaterials within tumor tissue for therapy. In situ energy conv...

In this paper, the effect of Ba2+ ions A-site doping LaFeO3 on structure, magnetic properties and microwave absorption properties was investigated by the sol-gel method. According to the TEM and FullProf refinement results, the structure of LaFeO3 changes from orthogonal (SG: Pnma) to cubic (SG: Pm-3m) when the Ba doping amount is x = 0.4. The SEM image shows that the particles size tends to decrease with the increase of Ba content. The production of weak ferromagnetism indicates that Ba doping has a significant effect on the magnetic properties of LaFeO3. The Neel temperature (TN) decreases significantly with the increase of Ba doping amount. An appropriate amount of Ba doping can effectively increase the dielectric and magnetic loss of LaFeO3 ceramics powders. The increase permittivity (e′) may have been attributed to the hopping spin of the electrons between the Fe3+ and Fe4+ ions with the Ba2+ ions doping. The minimum reflection loss (RL) of La0.9Ba0.1FeO3 at 6.72 GHz reached –30.04 dB, its effective bandwidth (RL ≤ –10 dB) is 2.1 GHz, and the matching thickness is only 3.2 mm. These results indicate that Ba doping can effectively control the microwave absorption properties of LaFeO3, especially in the C-band.

The distribution of abrasive particles in fluids is an important research topic in the study of abrasive waterjet cutting processes. However, it is impossible to obtain the accurate distribution law and influencing factors by performing only experiments; therefore, it is necessary to study abrasive waterjet cutting processes with the help of numerical models. The existing numerical models usually adopt the form of artificial settings for the distribution of abrasive particles in fluid. This method cannot accurately simulate the random distribution of particles. In this paper, the random algorithm method is used to simulate the impact azimuth and the random distribution of abrasive particles in water. The smoothed particle hydrodynamics (SPH) method is used to simulate the distribution of abrasive particles and the process of jet impingement. The influence of the particle distribution on the simulation results is studied. Comparisons show that the dent formed by the jet impinging on the target with random abrasive particles is similar to the dent from the actual cut, and the contour distribution of the dent is more uniform than that of the cut. The simulation results obtained by the SPH method are accurate.

Thermodynamic calculation is the theoretical basis for the study of initiation and detonation, as well as the prerequisite for forecasting the detonation performance of unknown explosives. Based on the VLWR(Virial-Wu) thermodynamic code, this paper introduced the universal solid equation of state (EOS) VINET. In order to truly reflect the compressibility of nanocarbon under the extremely high-temperature and high-pressure environment in detonation, an SVM (support vector machine) was utilized to optimize the input parameters of carbon. The detonation performance of several explosives with different densities was calculated by the optimized universal EOS, and the results show that the thermodynamic code coupled with the universal solid EOS VINET can predict the detonation performance parameters of explosives well. To investigate the application of the thermodynamic code with the improved VINET EOS in the working capacity of explosives, the interrelationship between pressure P-particle velocity u and pressure P-volume V were computed for the detonation products of TNT and HMX-based PBX (HMX: binder: insensitive agent = 95:4.3:0.7) in the CJ isentropic state. A universal curve proposed by Cooper was used to compared the computed isentropic state, where the ratio of pressure to CJ state were plotted against the ratio of velocity to CJ state. The parameters of the JWL(Jones-Wilkins-Lee) EOS for detonation products were obtained by fitting the P–V curve. The cylinder tests of TNT and HMX-based PBX were numerically simulated using the LS-DYNA, it is verified that, within a certain range, the improved algorithm has superiority in describing the working capacity of explosives.