成型温度对PBX装药内部质量及性能的影响

针对压制成型的PBX炸药装药，选择CT无损检测、巴西实验和扫描电镜检测等技术，对比研究了室温和加热两种温度下压制成型的炸药装药内部质量、静态力学性能和细观破坏形式。结果表明，加热压制有利于改善炸药装药的内部质量，可避免产生初始损伤，且提高了装药的力学性能。细观尺度上，室温压制成型的装药主要发生界面脱黏破坏，加热压制成型装药的主要破坏形式是穿晶断裂。     

复杂环境下氧化铝储槽定向爆破拆除

在较为复杂的环境下,爆破拆除钢筋混凝土氧化铝储槽。该储槽自重大、呈圆形,内有4根立柱支撑下料漏斗。为使储槽顺利定向倒塌,通过爆破方案选择、参数确定,采取梯形切口和预处理以及安全防护和减振措施,使储槽爆破拆除获圆满成功。     

Ni2P(O)–Fe2P(O)/CeOx as high effective bifunctional catalyst for overall water splitting

The development of cost-effective bifunctional catalysts with excellent performance and good stability is of great significance for overall water splitting. In this work, NiFe layered double hydroxides (LDHs) nanosheets are prepared on nickel foam by hydrothermal method, and then Ni₂P(O)–Fe₂P(O)/CeO_x nanosheets are in situ synthesized by electrodeposition and phosphating on NiFe LDHs. The obtained self-supporting Ni₂P(O)–Fe₂P(O)/CeO_x exhibit excellent catalytic performances in alkaline solution due to more active sites and fast electron transport. When the current density is 10 mA cm^?2, the overpotential of hydrogen evolution reaction and oxygen evolution reaction are 75 mV and 268 mV, respectively. In addition, driven by two Ni₂P(O)–Fe₂P(O)/CeO_x electrodes, the alkaline battery can reach 1.45 V at 10 mA cm^?2.     

Enhancing the dehydrogenation properties of LiAlH4 using K2NiF6 as additive

Lithium alanate (LiAlH₄) is a material that can be potentially used for solid-state hydrogen storage due to its high hydrogen content (10.5 wt%). Nevertheless, a high desorption temperature, slow desorption kinetic, and irreversibility have restricted the application of LiAlH₄ as a solid-state hydrogen storage material. Hence, to lower the decomposition temperature and to boost the dehydrogenation kinetic, in this study, we applied K₂NiF₆ as an additive to LiAlH₄. The addition of K₂NiF₆ showed an excellent improvement of the LiAlH₄ dehydrogenation properties. After adding 10 wt% K₂NiF₆, the initial decomposition temperature of LiAlH₄ within the first two dehydrogenation steps was lowered to 90 °C and 156 °C, respectively, that is 50 °C and 27 °C lower than that of the аs-milled LiAlH₄. In terms of dehydrogenation kinetics, the dehydrogenation rate of K₂NiF₆-doped LiAlH₄ sample was significantly higher as compared to аs-milled LiAlH₄. The K₂NiF₆-doped LiAlH₄ sample can release 3.07 wt% hydrogen within 90 min, while the milled LiAlH₄ merely release 0.19 wt% hydrogen during the same period. According to the Arrhenius plot, the apparent activation energies for the desorption process of K₂NiF₆-doped LiAlH₄ are 75.0 kJ/mol for the first stage and 88.0 kJ/mol for the second stage. These activation energies are lower compared to the undoped LiAlH₄. The morphology study showed that the LiAlH₄ particles become smaller and less agglomerated when K₂NiF₆ is added. The in situ formation of new phases of AlNi and LiF during the dehydrogenation process, as well as a reduction in particle size, is believed to be essential contributors in improving the LiAlH₄ dehydrogenation characteristics.     

Swapping catalytic active sites from cationic Ni to anionic F in Fe–F–Ni3S2 enables more efficient alkaline oxygen evolution reaction and urea oxidation reaction

Electrolysis of water for producing hydrogen instead of traditional fossil fuels is one of the most promising methods to alleviate environmental pollution and energy crisis. In this work, Fe and F ion co-doped Ni₃S₂ nanoarrays grown on Ni foam substrate were prepared by typical hydrothermal and sulfuration processes for the first time. Density functional theory (DFT) calculation demonstrate that the adsorption energy of the material to water is greatly enhanced due to the doping of F and Fe, which is conducive to the formation of intermediate species and the improvement of electrochemical performance of the electrode. The adsorption energy of anions (F and S) and cations (Fe and Ni) to water in each material was also calculated, and the results showed that F ion showed the most optimal adsorption energy of water, which proved that the doping of F and Fe was beneficial to improve the electrochemical performance of the electrode. It is worth noting that the surface of Fe–F–Ni₃S₂ material will undergo reconstruction during the process of water oxidation reaction and urea oxidation reaction, and amorphous oxides or hydroxides in situ would be formed on the surface of electrode, which are the real active species.     

Enhanced oxygen evolution reaction kinetics through biochar-based nickel-iron phosphides nanocages in water electrolysis for hydrogen production

Highly-efficient and stable non-noble metal electrocatalysts for overcoming the sluggish kinetics of oxygen evolution reaction (OER) is urgent for water electrolysis. Biomass-derived biochar has been considered as promising carbon material because of its advantages such as low-cost, renewable, simple preparation, rich structure, and easy to obtain heteroatom by in-situ doping. Herein, Ni₂P–Fe₂P bimetallic phosphide spherical nanocages encapsulated in N/P-doped pine needles biochar is prepared via a simple two-step pyrolysis method. Benefiting from the maximum synergistic effects of bimetallic phosphide and biochar, high conductivity of biochar encapsulation, highly exposed active sites of Ni₂P–Fe₂P spherical nanocages, rapid mass transfer in porous channels with large specific surface area, and the promotion in adsorption of reaction intermediates by high-level heteroatom doping, the (Ni_0.75Fe_0.25)₂P@NP/C demonstrates excellent OER activity with an overpotential of 250 mV and a Tafel slope of 48 mV/dec at 10 mA/cm² in 1 M KOH. Also it exhibits a long-term durability in 10 h electrolysis and its activity even improves during the electrocatalytic process. The present work provides a favorable strategy for the inexpensive synthesis of biochar-based transition metal electrocatalysts toward OER, and improves the water electrolysis for hydrogen production.     

Impact of viscous dissipation and Dufour on MHD natural convective flow past an accelerated vertical plate with Hall current

The present research work concentrates on viscous dissipation, Dufour, and heat source on an unsteady magnetohydrodynamics natural convective flow of a viscous, incompressible, and electrically conducting fluid past an exponentially accelerated infinite vertical plate in the existence of a strong magnetic field. The presence of the Hall current induces a secondary flow in the problem. The distinguishing features of viscous dissipation and heat flux produced due to gradient of concentration included in the model along with heat source as they are known to arise in thermal-magnetic polymeric processing. The flow equations are discretized implicitly using the finite difference method and solved using MATLAB fsolve routine. Numerical values of the primary and secondary velocities, temperature, concentration, skin friction, Nusselt number, and Sherwood number are illustrated and presented via graphs and tables for various pertinent parametric values. The Dufour effect was observed to strengthen the velocity and temperature profile in the flow domain. In contrast, due to the impact of viscous dissipation, the local Nusselt number reduces. The study also reveals that the inclusion of the chemical reaction term augments the mass transfer rate and diminishes the heat transfer rate at the plate.     

CNT-interconnected iron-doped NiP2/Ni2P heterostructural nanoflowers as high-efficiency electrocatalyst for oxygen evolution reaction

Oxygen evolution reaction (OER) plays a decisive role in electrolytic water splitting. However, it is still challengeable to develop low-cost and efficient OER electrocatalysts. Herein, we present a combination strategy via heteroatom doping, hetero-interface engineering and introducing conductive skeleton to synthesize a hybrid OER catalyst of CNT-interconnected iron-doped NiP₂/Ni₂P (Fe-(NiP₂/Ni₂P)@CNT) heterostructural nanoflowers by a simple hydrothermal reaction and subsequent phosphorization process. The optimized Fe-(NiP₂/Ni₂P)@CNT catalyst delivers an ultralow Tafel slope of 46.1 mV dec^?1 and overpotential of 254 mV to obtain 10 mA cm^?2, which are even better than those of commercial OER catalyst RuO₂. The excellent OER performance is mainly attributed to its unique nanoarchitecture and the synergistic effects: the nanoflowers constructed by a 2D-like nanosheets guarantee large specific area and abundant active sites; the highly conductive CNT skeleton and the electronic modulation by the heterostructural NiP₂/Ni₂P interface and the hetero-atom doping can improve the catalytic activity; porous nanostructure benefits electrolyte penetration and gas release; most importantly, the rough surface and rich defects caused by phosphorization process can further enhance the OER performance. This work provides a deep insight to boost catalytic performance by heteroatom doping and interface engineering for water splitting.     

Self-construction of pea-like Cu/Cu2S Mott-Schottky electrocatalyst for the oxygen evolution reaction

The speed of the oxygen evolution reaction seriously affects the hydrogen production efficiency of water electrolysis. Hence it is crucial to develop efficient and durable OER electrocatalysts. Construction of heterojunction catalysts is also one of the strategies to develop efficient catalysts. In this paper, a pea-like Cu/Cu₂S–C3 Mott?Schottky electrocatalyst was self-constructed by vapor deposition, while CF (copper foam) was used as substrate material and copper source, and thiourea was served as sulfur source. The built-in electric field is formed at the metal-semiconductor interface, which endows it with promising electrocatalytic performance. As the working electrode, the overpotentials of Cu/Cu₂S–C3 required to reach the current density of 10 and 50 mA cm^?2 were about 170 and 335 mV. The impact of the Mott-Schottky structure on the catalyst was also reflected in stability. The i-t tests of the sample Cu/Cu₂S–C3 were carried out under 10 and 60 mA cm^?2 and performed well.     

Impedance matching optimization of SiCf/Si3N4–SiOC composites for excellent microwave absorption properties

SiC fiber reinforced ceramic matrix composites (SiC_f-CMCs) are considered to be one of the most promising materials in the electromagnetic (EM) stealth of aero-engines, which is expected to achieve strong absorption and broad-band performance. Multiscale structural design was applied to SiC_f/Si₃N₄–SiOC composites by construction of micro/nanoscale heterogeneous interfaces and macro double-layer impedance matching structure. SiC_f/Si₃N₄–SiOC composites were fabricated by using SiC fibers with different conductivities and SiOC–Si₃N₄ matrices with gradient impedance structures to improve impedance matching effectively. Owing to its unique structure, SiC_f/Si₃N₄–SiOC composites (A3-composites) achieved excellent EM wave absorption performance with a minimum reflection coefficient (RC_min) of ?25.1 dB at 2.45 mm and an effective absorption bandwidth (EAB) of 4.0 GHz at 2.85 mm in X-band. Moreover, double-layer SiC_f/Si₃N₄–SiOC with an improved impedance matching structure obtained an RC_min of ?56.9 dB and an EAB of 4.2 GHz at 3.00 mm, which means it can absorb more than 90% of the EM waves in the whole X-band. The RC is less than ?8 dB at 2.6–2.8 mm from RT to 600 °C in the whole X-band, displaying excellent high-temperature absorption performance. The results provide a new design opinion for broad-band EM absorbing SiC_f-CMCs at high temperatures.