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.     

利用网络环境培养特色信息技术人才的教学模式探讨

阐述了网络技术与信息处理专业课程的特点及其教学模式改革的必要性．通过对课程结构的调整、教学手段的创新以及教学资源的优化控制等手段，探讨了更符合信息技术专业特点的人才培养方式。     

数学课堂教学改革与发展研究重点及基本思路探讨

2007年5月底在重庆师范大学召开了"海峡两岸数学课程与教学第三届学术研讨会",会议对数学课堂教学改革与发展研究的重点及基本思路进行了深入的讨论,讨论重点集中在对数学本质的认识、对学生的数学学习的本质的认识、数学课堂教学设计、数学课堂教学策略的实施、数学课堂教学的研究方法等5个方面,达成了一些新的观点和共识。     

网络环境下文献检索课教学改革的探讨

结合当前文献检索课教学的现状，探讨了网络环境下文献检索课教学改革的几个问题。并结合实际提出了改革的内容与方案。     

谈多媒体教学课件的制作过程

多媒体教学是课堂教学优化的重要途径,也是课堂教学的发展趋势,多媒体课件的制作是实施课堂多媒体教学的基本条件 本文试图介绍多媒体教学课件的涵义和制作过程．     

线性代数中突出行最简形相关内容的教学设计

从线性代数的教学经验出发,针对非数学专业线性代数教学的实际情况,初步探讨了线性代数教学中以Gauss消元法为根本,突出行最简形及其相关内容的教学设计.     

机能学实验的发展

计算机辅助教学系统以人机交互方式为传统教学注入了新的生机，多媒体教学系统对教学内容体系的改革起到了促进作用。文章简要叙述了计算机辅助教学系统及多媒体教学系统在机能学实验中的应用及发展。     

《现代教育技术》网络课程的设计

在对《现代教育技术》课程教学的现状进行分析的基础上,提出设计和开发《现代教育技术》网络课程的必要性,并结合实际分析该网络课程的设计原则、教学设计过程和系统设计过程。     

改革实验教学,提高高校学生综合实践能力

通过国内外高校实验教学对比 ,分析国内高校学生实践动手能力薄弱的原因 ,试图从设计实验教学纵向总体 ,建立完整实验教学评估体系 ,完善实验教学的横向联系等方面建立有利于培养学生综合能力的新实验教学模式 ,达到改革传统实验教学 ,提高学生综合实践能力的目的     

基于探究性的数学教学

数学课程改革特别强调“数学探究”,它已经成为数学教学改革的主流方向。要打破传统数学教学观的束缚 ,以建构主义理论为基础 ,建立探究性数学教学观。教师为学生创设铺垫式问题情境 ,使学生在“做数学中学数学”;加强师生之间的合作 ,学生要学会收集资料、筛选资料 ,学会利用信息技术开展探究性数学课题学习。     

对高校教材科学管理的思考和认识

通过分析教材在教学管理中的地位以及高校“学分制”教学管理形势下教材管理工作呈现出的新特点,阐述了科学管理高校教材的必要性,并提出了搞好高校教材管理工作的几点设想。