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1.
《矿物冶金与材料学报》2021,28(12):2001-2007
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.  相似文献   

2.
《矿物冶金与材料学报》2021,28(12):1908-1916
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.  相似文献   

3.
4.
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.  相似文献   

5.
《矿物冶金与材料学报》2020,27(10):1347-1352
A new method of high-gravity combustion synthesis (HGCS) followed by post-treatment (PT) is reported for preparing high-performance high-entropy alloys (HEAs), Cr0.9FeNi2.5V0.2Al0.5 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.  相似文献   

6.
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.  相似文献   

7.
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.  相似文献   

8.
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.  相似文献   

9.
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.  相似文献   

10.
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.  相似文献   

11.
文化教学是英语教学不可缺少的组成部分,在大学英语教学中导入文化教学势在必行。本文从四个方面论述文化教学在大学英语教学中的重要作用,并探讨教师在文化教学中的作用。  相似文献   

12.
目前我国高校教师普遍轻视传授知识的学问,教师教学能力发展滞后已成为影响高校教学质量的首要因素。博耶的教学学术理念为高校教师教学发展提供了理论新视角,高校应当大兴崇尚教学学术之风,立足本校教学实践,提高教师教学能力,建立以激励教师潜心教学、钻研教学为导向的教学评价机制,让善于教学的教师以一种乐于教学的心态追求教学卓越。  相似文献   

13.
探讨阶段性分级教学改革措施及其必备的实施条件。即通过实施大学英语的深化教改,实行按等级分班教学和精读、听说一体化教学,将培养学生自我提高的能力纳入分级教学目标中,将文化品位渗透到教学过程中,将完善教学体制、完善考核手段和提高师资素质列入教改实施的基本条件中,为进一步构筑具有建设性和趋势化意义的双语教学平台奠定基础。  相似文献   

14.
通过对某所地方院校的部分学生进行问卷调查,发现学生在肯定网络教学模式的优势时并没有否定传统教学有利的一面。他们希望能将“网络教学和课堂面授”相结合,大多数学生认为网络教学能大大提高他们的学习兴趣和主动性、自我调控学习方法、增强自信心,同时,有利于他们分享最优化的学习资源。另一方面,课堂面授能弥补网络教学的不足,增加师生间的亲和力,避免“机灌”代替“人灌”。此外,调查也发现地方院校的网络教学基础设施存在的问题。网络自主学习室的建立、多媒体教室和语音室的修缮和改进、教学资源的丰富和教学形式的多样化等方面亟待解决。由此,进一步提出将课堂面授和网络教学进行有机整合,实现教学手段和教学模式的多样化。要实现教学模式的整合,教师必须转变教学理念、学院要改进教学设备、增强师资力量。  相似文献   

15.
课堂教学作为学生获取知识的主战场,如何发挥课堂50分钟教学的作用?让学生在课堂教学中随着教师不同时段教学内容的设计、教学方法的调整,使学生的兴奋点和主要精力集中在一堂课程教学内容的重点与难点上,从而发挥课堂教学的最大效用。笔者提出了将课堂教学分为"5个时段7种方式"的教学模式来达到课堂教学效用的最大化。  相似文献   

16.
课堂教学的目标指向必须是满足社会需求和学生个体发展的需要,教学方法上必须教与学相结合.教学内容上,必须与现代科技相结合,教学手段上,必须突出实践教学.考试时,需围绕教学目标,考出水平.  相似文献   

17.
唐瑭 《实验科学与技术》2012,10(1):103-103,109
生物化学及实验是生物工程专业最重要的基础课程。生物化学实验技术不仅是后续专业课学习的基础,也是一切从事生命科学的工作者所必备的知识与技能。因此,建立先进的生物化学实验教学体系是生物学教学改革与建设的重要内容之一。笔者结合近几年的教学实践,对生物工程专业生物化学实验教学内容、教学方法和手段进行了一些改革探索,取得了较好的教学效果。  相似文献   

18.
新时期实践教学扩展性内容探讨   总被引:1,自引:0,他引:1  
实践教学是大学教学的基本环节,是课堂理论教学的延伸和检验,也是增强课堂理论教学针对性、实效性的有效途径。本文结合实践教学理论,总结多年实践教学的经验,来论述实践教学扩展性内容,提出了实践教学要同课堂教学、科学研究、师资队伍建设、学科建设、校园文化建设、“教书育人”、制度建设相结合、相统一的观点,并分析了实践教学与这几者之间的互动性关系。  相似文献   

19.
通过多年的物理实验教学实践,主要介绍中学物理课堂演示实验教学的方式、方法和技巧。给出了演示实验教学的参考教学模式及教学设计流程,希望能在中学物理教学中得以启发或借鉴。  相似文献   

20.
基础英语教学在复合型外语人才的培养中的作用举足轻重,如何提高教学质量,如何适应新形势的发展和21世纪的外语教学,自然成为教师们研究的热点问题,事实证明,有效的教学取决于理想的教材、科学的教学模式和灵活的教学技巧。  相似文献   

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