Behaviors of oxide film at the ultrasonic aided interaction interface of Zn–Al alloy and Al2O3p/6061Al composites in air

Ultrasonic aided interactions between Zn–Al alloy and Al₂O_3p/6061Al composites were investigated. Ultrasonic vibration imposed on the composite plate can cause high cavitation intensity in the liquid Zn–Al alloy which disrupts and flakes off surface oxides, thereby allowing the Zn–Al alloy to wet the bare composite surfaces and form a metallurgical bond. Whether the undermining phenomena occurred or not, the spreading of Zn–Al liquid over the composite did not occur until the ultrasonic vibration amplitude reached 10 μm. The Zn–Al liquid spread quickly over the composite despite that the surface oxide had not been fully disrupted when the ultrasonic vibration higher than 10 μm was applied. When undermining phenomena occurred during interaction, the oxide layer at the interaction interface was firstly lifted up by the undermining alloy, suspending in the Zn–Al liquid, and subsequently broke up by the ultrasonic excitation. Gas escaping from the base metal was observed to be helpful in decohesion of the oxide layer from the composite. When undermining phenomena did not occur during interaction, the removal of the oxide layer was based upon the melting of the nether base metal. The disruption of oxide initiated from the composite surface where the drop center located and the surface oxide layer near the drop edge was lastly removed.     

预应力撑杆柱整体稳定性能的数值分析

在正确定义单元类型、实常数和边界条件等基础上,采用有限元分析软件ANSYS建立预应力撑杆柱的有限元模型,对单横隔预应力撑杆柱在平面内的对称和反对称的2种屈曲模态进行数值分析。采用有限元软件ANSYS对预应力撑杆柱和无预应力柱进行弹性屈曲分析并与已有文献的分析结果进行对比以验证有限元模型的正确性;对预应力撑杆柱进行扩展参数分析,分析预应力撑杆柱的横撑杆长度h、预应力T及横撑杆直径D_s等主要影响参数对其弹性屈曲荷载的影响。研究表明:当预应力撑杆柱发生对称屈曲时,其弹性屈曲荷载N_cr随着横撑杆长度h的增大而增大,与横撑杆直径D_s无关;当预应力撑杆柱发生反对称屈曲时,其弹性屈曲荷载N_cr随着横撑杆直径D_s的增大而增大,而横撑杆长度h对其影响较小;预应力撑杆柱的2种屈曲模态的弹性屈曲荷载N_cr随着预应力T的增大而增大,当预应力T超过某个临界最优值T_opt时,弹性屈曲荷载N_cr随着预应力T的增大而减小。     

钢-混组合截面外包薄钢组合管梁抗弯性能研究

为了对不同夹层混凝土强度的钢-混组合截面外包薄钢组合管梁抗弯性能进行分析,通过试验和有限元软件模拟相结合的方法,选用外层为薄壁不锈钢管,内层为钢管,双壁管中间分别喷注混凝土强度等级为C20、C40、C60的三种试件,采用分级加载方式对试件进行加载,试验结果与有限元软件模拟的结果相吻合。研究结果表明:随着混凝土强度的提高,试件的抗弯承载力提高、延性增大,能发生较大的塑性变形以吸收能量。     

混凝土强度影响GFRP板-混凝土组合梁力学性能研究

为研究GFRP板-混凝土组合梁的力学性能,利用ABAQUS有限元软件建立玻璃纤维增强复合材料(GFRP)加固混凝土梁模型,通过组合梁的荷载-跨中挠度曲线和承载力两个方面验证了建立模型方法的合理性。设计了C25、C30和C40三个不同强度等级混凝土的构件模型,分析并得出关于GFRP板-混凝土组合梁的力学性能的结论。结果表明:(1)在相同荷载下,组合梁的极限承载力随着混凝土强度等级增大而增大,延性随着混凝土强度等级增大而减小;(2)增大混凝土强度等级可以有效增大组合梁的极限承载力;(3)GFRP板可以提高组合梁的抗弯承载力;(4)GFRP板-混凝土组合梁主要分为弹性阶段和带裂缝工作两个阶段。     

纳米氧化锌光催化剂制备方法

介绍了纳米氧化锌的制备方法。包括物理法和化学方法,其中物理法有喷雾热解法、高能球磨法和深度塑性变形法;化学方法有固相法、气相法和液相法,液相法又可分为沉淀法、溶胶-凝胶法、微乳液法、水热法等。并对纳米氧化锌今后的研究方向进行了展望。     

Corrosion of high‐velocity oxy‐fuel (HVOF) sprayed iron‐based amorphous metallic coatings for marine pump in sodium chloride solutions

FeCrMoMnWBCSi amorphous metallic coatings (AMCs) were deposited onto the 304 stainless steel (base material of pump impeller operated in sand‐containing seawater) by high‐velocity oxygen‐fuel (HVOF) thermal spray. The preparation, microstructural characteristics, and static corrosion behavior of the AMCs were presented. The microstructure and corrosion behavior of the AMCs were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and electrochemical methods. Melt‐spun ribbon and 304 stainless steel were also used for comparison purposes. The results indicated that the AMCs can spontaneously passivate with a wide passive region, and much higher ability to withstand pitting corrosion than that of the 304 stainless steel for the high pitting resistance equivalent value. The passive current density of the AMCs was at least two orders of magnitude higher than the counterpart ribbon, which showed a slightly decreased uniform corrosion resistance of the AMCs due to the incompact structure and porosity. The corrosion resistance of the AMCs increased with the coating thickness and decreased with the concentration of NaCl solution. A stable passivation ability held in the AMCs endowed them suitably used in marine environments.     

Two new Keggin-type polyoxometalate-based entangled coordination networks constructed from metal-organic chains with dangling arms

Two new polyoxometalate(POM)-based entangled coordination networks with chemical formula of [Mn₂(H₂O)₂(BBPTZ)₅][SiW₁₂O₄₀] (1) and [Ni₂(H₂O)₂(BBPTZ)₅][SiMo₁₂O₄₀]·6H₂O (2) (BBPTZ = 4.4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl), were prepared in a hydrothermal reaction system. Compounds 1–2 were characterized by elemental analyses, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. In compound 1, dangling arms thread in quadrangular window of the adjacent 2-D layers, thus resulting in a rare 2-D → 3-D polythreading motif. Compound 2 exhibits a rare 2-D → 3-D zipper-closing motif. Using the degradation of methylene blue (MB) as the model, the photocatalytic activities of compounds 1–2 were investigated. Both compounds show efficient catalytic activity for the degradation of MB with the order of 2 > 1. It is found that the POM species of compounds 1–2 play the main role in the photocatalytic degradation process.     

Soft-templated mesoporous carbons as potential materials for oral drug delivery

Template-synthesized mesoporous carbons were successfully used in in vitro investigations of controlled delivery of three model drugs, captopril, furosemide, and ranitidine hydrochloride (HCl). Captopril and furosemide exhibited desorption kinetics over 30–40 h, and ranitidine. HCl had a complete release time of 5–10 h. As evident from the slow release kinetics, the mesoporous carbons have excellent potential for the controlled-release media of the specific drugs targeted towards oral delivery. The mesoporous carbons, synthesized from phloroglucinol and lignin, a synthetic and a sustainable precursor, respectively, exhibit BET surface area of 200–400 m² g⁻¹ and pore volume of 0.2–0.6 cm³ g⁻¹. The synthetic carbon has narrower pore widths and higher pore volume than the renewable counterpart and maintains a longer release time. The release kinetics reveals that the diffusivities of the drugs from carbon media are of equivalent magnitude (10⁻²² to 10⁻²⁴ m² s⁻¹). However, a tailored reduction of pore width in the sorbent reduces the diffusivity of smaller drug molecule by an order of magnitude. Thus, engineered pore morphology, along with its functionalization potential for specific interaction, can be exploited for optimal delivery system of a preferred drug.     

Improvement of sediment microbial fuel cell performances by design and application of power management systems

One of the ways to generate clean and non-destructive energy is to use the energy stored in the biomass resources by the microbial fuel cells (MFCs). Sediment Microbial Fuel Cells (SMFCs) are a special type of MFCs that use organic materials in aquifers sediment to generate electricity. In this research, the effects of an increase in the electrode surface are investigated. The results showed that the increase in cathode electrode surface had better efficiency than the multi-cathode mode (maximum power generated for a 3-cathode electrode (27 cm³) and 1-cathode electrode (27 cm³) was 526 mW/cm² and 800 mW/cm², respectively. Another parameter affecting the performance of these systems is temperature. In the next step, the power generation rate was measured in different step currents and at different sample times. In the final stage, a power management system (PMS) was designed to optimally utilize the output energy of the improved SMFC, leading to an increase in the output voltage to 3.3 V.