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.     

混凝土构件裂纹损伤的分析与评价

混凝土构件难免会出现裂缝、损伤,裂缝等出现以后判断裂缝的类型,了解其是否在允许范围之内,评价和预测裂缝的危险性和涉及范围,是结构安全和正常使用的重要保证。文章对一些常见的混凝土构件裂缝作了分类研究和损伤定位分析,介绍一种评价方法,旨在为混凝土结构的养护、管理提供参考。     

突破“排列与组合”难点探讨

排列和组合是概率论、统计学、经济管理学等学科的必备知识。本文针对学习、研究应用"排列与组合"的理论难点,归纳了相应的突破方法:判定是"排列"还是"组合"问题其关键看对象与顺序是否有关;判断是应用加法原理还是乘法原理其关键看"依次"还是"任选";分析了"排列"、"组合"问题的基本类型及解析。为经济管理、统计研究、概率论学习提供一些理解和探究的路径。     

京沪大学生创业素质能力现状调查及对策建议

通过对北京和上海10所高校大学生进行调查分析,了解京沪大学生的创业意识、创业精神和创业能力.调查显示,京沪大学生整体创业素质能力较高,但也存在影响大学生创业素质能力提升的问题:创业课程培训的普及率不高,大学生缺少创业激情,创业的"坚持不懈精神"不足,创业能力中"设定目标能力"和"产融互动能力"较弱等问题.对此建议如下:高校要完善创新创业教育生态体系;提升大学生创业心理资本水平;建立产学助创协同育人机制;培育基于地域文化的创新创业文化.     

中美社会力量设立科学技术奖比较研究

对中美两国社会力量设奖的历史与现状进行了系统考察,通过对比分析,认为二者在4个方面有相似之处,包括设奖者以专业学会为主、奖励范围以单个学科为主、奖励对象以个人为主、物质奖励和精神奖励相结合等;同时也存在5个方面的主要区别,包括社会力量设奖的影响力、国际奖的数量、对社会力量设奖的管理、资金来源、评审机制等。在此基础上,对如何推动中国社会力量设奖的健康发展提出了看法。     

科学技术指标体系设计及评价

 国际上关于国家科技活动投入产出的评价指标体系建设及其评价研究已有较长历史,产生了一些具有重要影响力的代表性研究成果。通过对世界主要科学技术指标体系进行梳理与分析,总结其研究共识与特征,分析存在问题与不足,并基于中国现有的科学技术指标研究框架,针对跻身创新型国家前列、建设世界科技强国的战略目标,提出指标体系设计、数据采集分析以及国际交流合作等方面的发展建议。     

高校思想政治教育工作实效性提升探析

通过分析目前高校思想政治教育存在的主要问题,认为造成当前高校思想政治教育效果弱化、实效性不强的主要原因是思想政治教育理论脱离实际,内容不贴近生活,方法不贴近学生。因此,必须深化思想政治教育的改革,在教育理念、教育内容、教育方法等方面进行革新,才能增强思想政治教育的针对性和实效性。     

论影响日韩影视剧在中国传播的政治与文化因素

在中国,日韩影视剧能够成功传播有着很多因素的影响,如中日和中韩外交关系的发展、日韩影视文本内含的儒家文化在中国的寻根等等。中国与日本、中国与韩国之间外交关系的发展、中日韩文化的接近性与差异性,分别构成了日韩影视剧能在中国成功开展跨国文化传播的政治与文化因素。     

中国铁线莲属植物研究现状及展望

中国有丰富的野生铁线莲属植物资源,文中综述了中国铁线莲属植物资源的现状、保护和利用情况,简单介绍了国外开发利用铁线莲属植物的情况,并就中国铁线莲属植物资源存在的问题和发展前景提出了自己的建议。     

卜辞所见殷人心目中的鬼神世界

殷墟甲骨卜辞是殷人卜祭诸神的实录,祭祀对象涉及殷代所有神灵。殷人所构筑的天神系统、地祇系统和人鬼系统,生动呈现了上古社会精神世界的一个侧面,奠定了中国传统宗教鬼神世界的基本模式,其造神特征和对自然神祇的尊卑态度也对后世产生了深远影响。     

建筑物沉降裂缝产生的原因及防治措施

沉降裂缝是1个普遍存在且难以解决的工程问题,本文着重分析裂缝形成原因,提出设计和施工2个阶段的预防措施,以及裂缝的治理方法。