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。     

Molecular dynamics study of interfacial load transfer capability in amorphous SiOx films deposited on alumina surfaces

Effective adhesion between AlO_x and SiO_x is important for protective coatings and high-k films under extreme operating conditions. Here, we study the chemo-mechanical behavior of the AlO_x/SiO_x interface and its delamination mechanism using all-atom reactive molecular dynamics simulations. The structure of the interface is examined by the formation of bridge oxygen and the distribution of nanopores. The cleavage of ionic bonds during delamination and the resulting adhesion strength of the system are quantified using pull-out simulations. The results reveal the dependence of the nanopores and ionic bond formation on the oxide structure. The ionic bond density at the interface increases as the oxidation of the aluminum surface proceeds, which directly increases the adhesion strength with SiO_x. In particular, the global coordination distribution in the homogeneously grown oxide inhibits the formation of nanopores inside the aluminum substrate and contributes to extremely high adhesion strength. This reveals a fundamental relationship between physicochemical parameters and engineering mechanics for hetero-oxide structure design.     

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.     

Metal chlorides-promoted ammonia absorption of deep eutectic solvent

Ammonia is considered as a promising hydrogen or energy carrier. Ammonia absorption or adsorption is an important aspect for both ammonia removal, storage and separation applications. To these ends, a wide range of solid and liquid sorbents have been investigated. Among these, the deep eutectic solvent (DES) is emerging as a promising class of ammonia absorbers. Herein, we report a novel type of DES, i.e., metal-containing DESs for ammonia absorption. Specifically, the NH₃ absorption capacity is enhanced by ca. 18.1–36.9% when a small amount of metal chlorides, such as MgCl₂, MnCl₂ etc., are added into a DES composed of resorcinol (Res) and ethylene glycol (EG). To our knowledge, the MgCl₂/Res/EG (0.1:1:2) DES outperforms most of the reported DESs. The excellent NH₃ absorption performances of metal–containing DESs have been attributed to the synergy of Lewis acid–base and hydrogen bonding interactions. Additionally, good reversibility and high NH₃/CO₂ selectivity are achieved over the MgCl₂/Res/EG (0.1:1:2) DES, which enables it to be a potential NH₃ absorber for further investigations.     

Synergistic regulation of hydrogen adsorption/desorption via dual interfaces of Cu/Ni/Ni(OH)2 toward efficient hydrogen evolution reaction

Nickel-based catalysts have attracted tremendous attention as alternatives to precious metal-based catalysts for electrocatalytic hydrogen evolution reaction (HER) in virtue of their conspicuous advantages such as abundant reserves and high electrochemical activity. Nevertheless, a great challenge for Ni-based electrocatalyst is that nickel sites possess too strong adsorption for key intermediates H1, which severely suppresses the hydrogen-production activities. Herein, we report a hierarchical architecture Cu/Ni/Ni(OH)₂ consisting of dual interfaces as a high-efficient electrocatalyst for HER. The Cu nanowire backbone could provide geometric spaces for loading plenty of Ni sites and the formed Ni/Cu interface could effectively weakened the adsorption intensity of H1 intermediates on the catalyst surface. Moreover, the H1 adsorption could be further controlled to appropriate states by in-situ formed Ni(OH)₂/Ni interface, which simultaneously promotes water adsorption and activation, thus both Heyrovsky and Volmer steps in HER could be obviously accelerated. Experimental and theoretical results confirm that this interface structure can promote water dissociation and optimize H1 adsorption. Consequently, the Cu/Ni/Ni(OH)₂ electrocatalyst exhibits a low overpotential of 20 mV at 10 mA cm^?2 and an ultralow Tafel slope of 30 mV dec^?1 in 1.0 M KOH, surpassing those of reported transition-metal-based electrocatalysts and even the prevailing commercial Pt/C.     

Fluid sloshing thermo-mechanical characteristic in a cryogenic fuel storage tank under different gravity acceleration levels

Fluid sloshing usually causes serious safety issues on the dynamic stability and propellant thermal management during the powered-flight phase of launch vehicle. With the wide using of cryogenic propellants, the coupled thermo-mechanical performance during fluid sloshing becomes more prominent. In the present study, one numerical model is established to simulate fluid sloshing by using the VOF method coupled with the mesh motion treatment. The phase change occurring within the tank is considered. Both the experimental validation and mesh sensitivity analysis are made. It shows that present numerical model is acceptable. Based on the developed numerical model, the effect of different super gravity accelerations on fluid sloshing hydrodynamic characteristic is numerically researched. The fluid pressure variation, the sloshing force and sloshing moment, the interface dynamic response and the interface shape variation are investigated, respectively. It shows that the gravity acceleration has caused obvious influences on fluid sloshing characteristic. When the gravity acceleration is higher than 4g₀, fluid sloshing becomes more obvious and must be paid enough attention. With some valuable conclusions obtained, the present work is of great significance for in-depth understanding of fluid sloshing mechanism.     

Effect of MnOx phase on Pt-based catalyst for enhancing CO/C3H6/NO oxidation performance

To improve the fuel economy, it is crucial to promote the low-temperature performance in eliminating diesel emissions. The work investigates the impact of different MnO₂/Mn₂O₃ phase ratio on the low-temperature performance of Pt-based monolithic diesel oxidation catalyst. Near equal ratio of MnO_x phase could form the three-phase (platinum, MnO₂, Mn₂O₃) interfacial structure, leading to the smaller platinum particle size and exhibiting the higher interface rate (1.6–11.1 times) than other mono-manganese oxide with platinum. Besides, the higher oxygen mobility and more active oxygen species could be contributed to the positive effect of Pt/MnO_x interface, which are prevalent to activate the reactant and greatly enhance the TOF value (1.4–20.8 times). The results imply that the modification of multi-phase metal/oxide interface is potential in dispersing platinum for greatly enhancing the catalytic efficiency.     

Adenine-functionalized conjugated polymer as an efficient photocatalyst for hydrogen evolution from water

Conjugated polymers have emerged as a promising class of organic photocatalysts for photocatalytic hydrogen evolution from water splitting due to their adjustable chemical structures and electronic properties. However, developing highly efficient organic polymer photocatalysts with high photocatalytic activity for hydrogen evolution remains a significant challenge. Herein, we present an efficient approach to enhance the photocatalytic performance of linear conjugated polymers by modifying the surface chemistry via introducing a hydrophilic adenine group into the side chain. The adenine unit with five nitrogen atoms could enhance the interaction between the surface of polymer photocatalyst and water molecules through the formation of hydrogen bonding, which improves the hydrophilicity and dispersity of the resulting polymer photocatalyst in the photocatalytic reaction solution. In addition, the strong electron-donating ability of adenine group with plentiful nitrogen atoms could promote the separation of light-induced electrons and holes. As a result, the adenine-functionalized conjugated polymer PF6A-DBTO2 shows a high photocatalytic activity with a hydrogen evolution rate (HER) of 25.21 mmol g^?1 h^?1 under UV-Vis light irradiation, which is much higher than that of its counterpart polymer PF6-DBTO2 without the adenine group (6.53 mmol g^?1 h^?1). More importantly, PF6A-DBTO2 without addition of a Pt co-catalyst also exhibits an impressive HER of 21.93 mmol g^?1 h^?1 under visible light (λ > 420 nm). This work highlights that it is an efficient strategy to improve the photocatalytic activity of conjugated polymer photocatalysts by the modification of surface chemistry.     

Effect of geotextile ageing and geomembrane surface roughness on the geomembrane-geotextile interfaces for heap leaching applications

A series of large scale direct shear experiments is used to investigate the effect of the geomembrane (GMB) surface roughness, geotextile (GTX) properties, and GTX ageing, on the GMB-GTX interface shear behaviour. Interfaces involving smooth, coextruded textured, and structured surface GMBs underlying four different nonwoven needle-punched staple fibres (GTXs) with mass per unit areas between 200 and 2400 g/m², and a geocomposite drain (GCD) are examined at normal stresses between 250 and 1000 kPa. The results showed that the interlocking between the GMB and GTX increased with increasing the GMB asperity height and/or decreasing the mass per unit area of the GTX. For the interfaces that involved GTXs preaged prior to the shear box experiments for up to 2 years at 85 °C, it was found that the 2400 g/m² heat bonded two-layered GTX exhibited internal shear failure at low shear displacements. However, all the highly aged single layered GTXs showed an increase in the peak interface friction angles with the increase in their ageing. For these single layered GTX, the results suggest that assessing the interface friction angles using unaged GTXs for the stability analysis is conservative as long as the GTX remains intact in the field.     

Role of particle shape on the shear strength of sand-GCL interfaces under dry and wet conditions

Interface shear strength of geosynthetic clay liners (GCL) with the sand particles is predominantly influenced by the surface characteristics of the GCL, size and shape of the sand particles and their interaction mechanisms. This study brings out the quantitative effects of particle shape on the interaction mechanisms and shear strength of GCL-sand interfaces. Interface direct shear tests are conducted on GCL in contact with a natural sand and a manufactured sand of identical gradation, eliminating the particle size effects. Results showed that manufactured sand provides effective particle-fiber interlocking compared to river sand, due to the favorable shape of its grains. Further, the role of particle shape on the hydration of GCL is investigated through interface shear tests on GCL-sand interfaces at different water contents. Bentonite hydration is found to be less in tests with manufactured sand, leading to better interface shear strength. Grain shape parameters of sands, surface changes related to hydration and particle entrapment in GCL are quantified through image analysis on sands and tested GCL surfaces. It is observed that the manufactured sand provides higher interface shear strength and causes lesser hydration related damages to GCL, owing to its angular particles and low permeability.