具有良好可再生性的新型二氧化硅磁性氧化石墨烯纳米复合材料

Graphene oxide (GO) wrapped Fe₃O₄ nanoparticles (NPs) were prepared by coating the Fe₃O₄ NPs with a SiO₂ layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO₂ coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO₂ on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO₂ layer can effectively induce the GO nanosheets to completely wrap the Fe₃O₄ NPs, forming a core-shell Fe₃O₄@SiO₂@GO composite where Fe₃O₄@SiO₂ NPs are firmly encapsulated by GO nanosheets. The optimized Fe₃O₄@SiO₂@GO sample exhibits a high saturated adsorption capacity of 253 mg·g?1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.     

微波预处理对复杂铜矿磨矿及浮选动力学的影响

The effect of CaCO₃, Na₂CO₃, and CaF₂ on the reduction roasting and magnetic separation of high-phosphorus iron ore containing phosphorus in the form of Fe₃PO₇ and apatite was investigated. The results revealed that Na₂CO₃ had the most significant effect on iron recovery and dephosphorization, followed by CaCO₃, the effect of CaF₂ was negligible. The mechanisms of CaCO₃, Na₂CO₃, and CaF₂ were investigated using X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS). Without additives, Fe₃PO₇ was reduced to elemental phosphorus and formed an iron–phosphorus alloy with metallic iron. The addition of CaCO₃ reacted with Fe₃PO₇ to generate an enormous amount of Ca₃(PO₄)₂ and promoted the reduction of iron oxides. However, the growth of iron particles was inhibited. With the addition of Na₂CO₃, the phosphorus in Fe₃PO₇ migrated to nepheline and Na₂CO₃ improved the reduction of iron oxides and growth of iron particles. Therefore, the recovery of iron and the separation of iron and phosphorus were the best. In contrast, CaF₂ reacted with Fe₃PO₇ to form fine Ca₃(PO₄)₂ particles scattered around the iron particles, making the separation of iron and phosphorus difficult.     

不同硅饱和系数水榴石的碳酸化分解动力学

Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method, which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method. In this study, the effect of the silica saturation coefficient (x) on the carbonation of hydrogarnet was investigated from the kinetic perspective. The results indicated that the carbonation of hydrogarnets with different x values (x = 0.27, 0.36, 0.70, and 0.73) underwent two stages with significantly different rates, and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3. The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and 14.80–34.84 kJ/mol, respectively. Moreover, the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion.     

一种超重力燃烧合成制备高性能高熵合金的新方法

A new method of high-gravity combustion synthesis (HGCS) followed by post-treatment (PT) is reported for preparing high-performance high-entropy alloys (HEAs), Cr_0.9FeNi_2.5V_0.2Al_0.5 alloy, whereby cheap thermite powder is used as the raw material. In this process, the HEA melt and the ceramic melt are rapidly formed by a strong exothermic combustion synthesis reaction and completely separated under a high-gravity field. Then, the master alloy is obtained after cooling. Subsequently, the master alloy is sequentially subjected to conventional vacuum arc melting (VAM), homogenization treatment, cold rolling, and annealing treatment to realize a tensile strength, yield strength, and elongation of 1250 MPa, 1075 MPa, and 2.9%, respectively. The present method is increasingly attractive due to its low cost of raw materials and the intermediate product obtained without high-temperature heating. Based on the calculation of phase separation kinetics in the high-temperature melt, it is expected that the final alloys with high performance can be prepared directly across master alloys with higher high-gravity coefficients.     

利用皮秒激光烧蚀制备非球形铝纳米颗粒

We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid (chloroform, CHCl₃) with ~2 ps laser pulses at an input energy of ~350 μJ. The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at ~340 nm. Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of (27 ± 3.6) nm. The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles. In addition to spherical aluminum nanoparticles, triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution. Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures (LIPSSs), which were the high spatial frequency LIPSSs (HSF-LIPSSs) since their grating period was ~280 nm. Additionally, coarse structures with a period of ~700 nm were observed.     

窄板坯结晶器内连铸工艺参数对钢液流场的影响

Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting (CC) molds with narrow widths for the production of automobile exposed panels. Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process. The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold. Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone. The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min?1 and casting speed of 1.7 m·min?1. Under the present experimental conditions, the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm.     

电渣重熔脱硫技术研究进展

Electroslag remelting (ESR) gives a combination of liquid metal refining and solidification structure control. One of the typical aspects of liquid metal refining during ESR for the advanced steel and alloy production is desulfurization. It involves two patterns, i.e., slag–metal reaction and gas–slag reaction (gasifying desulfurization). In this paper, the advances in desulfurization practices of ESR are reviewed. The effects of processing parameters, including the initial sulfur level of consumable electrode, remelting atmosphere, deoxidation schemes of ESR, slag composition, melting rate, and electrical parameters on the desulfurization in ESR are assessed. The interrelation between desulfurization and sulfide inclusion evolution during ESR is discussed, and advancements in the production of sulfur-bearing steel at a high-sulfur level during ESR are described. The remaining challenges for future work are also proposed.     

Mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al2O3?Na2O system during high-temperature sintering

The mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al₂O₃?Na₂O system during the high-temperature sintering process were systematically investigated using DSC?TG, XRD, SEM?EDS, FTIR, and Raman spectra, and the crystal structure of Na₄Ca₃(AlO₂)₁₀ was also simulated by Material Studio software. The results indicated that the minerals formed during the sintering process included Na₄Ca₃(AlO₂)₁₀, CaO·Al₂O₃, and 12CaO·7Al₂O₃, and the content of Na₄Ca₃(AlO₂)₁₀ could reach 92wt% when sintered at 1200°C for 30 min. The main formation stage of Na₄Ca₃(AlO₂)₁₀ occurred at temperatures from 970 to 1100°C, and the content could reach 82wt% when the reaction temperature increased to 1100°C. The crystal system of Na₄Ca₃(AlO₂)₁₀ was tetragonal, and the cells preferred to grow along crystal planes (110) and (210). The formation of Na₄Ca₃(AlO₂)₁₀ was an exothermic reaction that followed a secondary reaction model, and its activation energy was 223.97 kJ/mol.     

含细夹层的分矿充填层中流动特性的可视化

Ore particles, especially fine interlayers, commonly segregate in heap stacking, leading to undesirable flow paths and changeable flow velocity fields of packed beds. Computed tomography (CT), COMSOL Multiphysics, and MATLAB were utilized to quantify pore structures and visualize flow behavior inside packed beds with segregated fine interlayers. The formation of fine interlayers was accompanied with the segregation of particles in packed beds. Fine particles reached the upper position of the packed beds during stacking. CT revealed that the average porosity of fine interlayers (24.21%) was significantly lower than that of the heap packed by coarse ores (37.42%), which directly affected the formation of flow paths. Specifically, the potential flow paths in the internal regions of fine interlayers were undeveloped. Fluid flowed and bypassed the fine interlayers and along the sides of the packed beds. Flow velocity also indicated that the flow paths easily gathered in the pore throat where flow velocity (1.8 × 10?5 m/s) suddenly increased. Fluid stagnant regions with a flow velocity lower than 0.2 × 10?5 m/s appeared in flow paths with a large diameter.     

高等农业院校基础力学实验教学质量优化与实践

高等农业院校基础力学课程是重要的专业基础课,是工程应用性较强的课程,基础力学实验是工科教学中的重要环节。针对实验教学在高等教育中的重要地位,分析了实验教学质量管理的复杂性和力学实验教学质量管理中的不足,提出了基础力学实验教学质量的优化措施。通过建立合理的实验教学质量监控体系等措施,有利于优化实验教学管理,提高实验教学质量,有利于培养具有实践能力和创新精神的高素质人才。     

湖北农村“技、信、物”综合服务模式探索

围绕农民在生产过程中的科技需求、农业生产资料流通过程中的信息化管理需求,提出了整合科研机构的科技信息资源、镇村信息服务站、农资经营加盟店等网点资源的"技、信、物"综合服务新模式;通过技术流动、信息流动、物质流动,实现面向农户、农业生产资料物流体系、农资经营加盟店和政府监管部门等主体的科技、标准、市场、监管等全方位的信息化管理与服务,并对模式的运行保障措施进行了分析。     

圆管分层层流的流动规律

从流体力学中NOS 方程出发,建立了圆管两相分层层流流动的数学模型。通过两相分层层流的相互作用的流体力学分析,提出了两相流动界面的耦合条件,从而得到了一组完整描述两相圆管分层流的数学方程,再通过数值求解分层流的数学方程,得到了对工程实际应用有重要价值的流动规律。应用圆管两相分层层流的流动规律,可以实现高粘流体的高效率输送, ,其节能效果十分明显。     

试论农业工程中的力学问题及主要研究方向

综述了农业工程中所存在的主要力学问题或现象，如：应力与植物的生长、种子损伤与激活、土壤粒子(泥沙)在雨水和江河中的流动、农作物体内水分、矿质元素和光合产物的运输、农作物种植、农产品运输和土壤耕作过程中所存在的力学问题或现象，并在概述了相关研究现状的同时，着重探讨了今后农业生物力学研究的主要方向，强调了加强生物力学研究的重要性．     

椭圆柱绕流的理论研究

现有的椭圆柱绕流理论给出了椭圆柱周边流场分布示意图,但流场分布图的数学分析计算过程并不完善,给进一步研究椭圆柱绕流问题增加了难度。首先利用保角变换的方法求得攻角为零时的椭圆柱绕流复势,然后利用复变函数理论将椭圆柱绕流复势分离,得到了椭圆柱绕流的势函数和流函数,随后利用MATLAB软件绘制出了流线和等势线分布图,进而基于求得的绕流势函数和流函数,应用理想流体力学相关理论,讨论了椭圆柱面的流体压力分布规律。     

承压含水层非稳定渗流耦合问题的研究

基于岩石力学与渗流力学理论,建立了承压含水层中应力与渗流耦合问题的力学模型, 研究了渗流与应力的耦合规律,对承压含水层中孔隙压力分布在耦合与非耦合气相的条件下分布规律进行数值模拟,并给出了实现耦合分析有限元方法,最后通过算例检验了耦合分析的有效性和实用性。     

可动凝胶体系非线性渗流数学模型

为进一步研究油田开发渗流中可动凝胶驱的力学行为特征,在实验研究基础上,通过对渗流机理、渗流规律的分析,研究可动凝胶体系非线性渗流力学行为,揭示可动凝胶体系的渗流特征。结合实验,对可动凝胶流动机理和物理化学性质的研究,根据质量传输流体力学、化学动力学的深入研究,系统地建立了可动凝胶体系驱油渗流数学模型。从而,系统的刻画了可动凝胶体系驱油这一复杂渗流流动数学描述难题,完善可动凝胶体系渗流的理论,为今后可动凝胶体系驱油数值模拟研究和现场应用提供了理论基础。     

解决因油液离心力造成齿轮泵容积效率低的方法

利用流体力学和理论力学原理,在外啮合齿轮泵中新设计出一进油槽,能及时补充齿轮泵高速旋转时因油液离心力而使齿间充油不足的现象,提高容积效率明显。该进油槽结构简单,制造容易。可为解决外啮合齿轮泵容积效率低提供一条新的途径。     

高压水射流切割流场的数值模拟研究

利用计算流体动力学(CFD)的方法对高压水射流切割进行了多相流的数值模拟,研究并分析了淹没流与非淹没流的影响、压力的影响、喷嘴直径的影响、喷嘴对射流的影响以及淹没与非淹没流下磨料的流动特性关系,其结果可为高压水切割工具的设计提供参考依据.