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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
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《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
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《矿物冶金与材料学报》2020,27(4):472-482
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
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《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
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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
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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
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《矿物冶金与材料学报》2020,27(7):980-986
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
9.
Mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al2O3?Na2O system during high-temperature sintering
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《矿物冶金与材料学报》2020,27(7):924-932
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
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《矿物冶金与材料学报》2020,27(7):900-909
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.
王文明 《首都师范大学学报(自然科学版)》1987,(3)
图集的统一协调,对图集质量有很大影响。本文是作者在编制北京市农业区划地图集的实践基础上,根据地图信息传输论的观点,对农业区划地图集的统一协调的内容及方法进行了探讨。试图总结编制这类图集的统一协调模式,以供读者编图时参考。 相似文献
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李川 《沈阳大学学报:自然科学版》2008,20(6):63-67
研究了国家法的抽象正义观与民间法的情理正义观,认为西方国家法的抽象正义观与东方民间法的情理正义观存在实质的不同,原因在于思维方式、超验与经验传统、政治结构的差别。在现代法治理念下,传统民间法所代表的正义观将向混合正义观转型,西方法治所代表的国家法抽象正义观是其骨架。 相似文献
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给出了一维非自治时滞系统点态退化的一个例子,拓宽了该领域的研究。 相似文献
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利用对位异构体的对称性由核磁共振氢谱测定了工业十二烷基苯在硝硫混酸中的硝化选择性,发现一硝化产物中对位异构体的比例为75% ̄80%。以月桂酸和苯为原料,经氯化、酰化和还原合成了正十二烷基苯。在同样条件下研究了正十二烷基苯的硝化,由核磁共振氢谱和气相色谱分析,发现一硝化产物中对位异构体的比例仅为60%。根据空间位阻效应,对结果进行了讨论,并与甲苯,乙苯,异丙苯等短链烷基苯的硝化结果进行了比较。 相似文献
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YBCO掺杂效应研究 总被引:3,自引:0,他引:3
张莉 《兰州理工大学学报》2004,30(1):130-133
介绍了YBCO掺杂的基础知识,总结了YBCO各个位置采用典型元素掺杂而导致的超导电性和结构的变化,阐述了掺杂对YBCO的重要影响,并简介了当前YBCO掺杂效应研究中的几个热点问题. 相似文献
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由于有限群的Lagrange定理的逆不成立,因此,n较大时要确定n次交代群An的所有子群或对An阶数的每一个正因数,确定是否存在这个阶数的子群是较困难的问题.文章通过对5-循环置换各次方幂的计算及其研究,构造出了A5的5个12阶子集,并证明了每一个子集都是A5的12阶子群,最后对A5的部分阶的子群做了总结. 相似文献
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为了找出诱发高频机组基础不良振动的原因,从基础计算模型方面对基础激励与响应进行了分析,以两个高频机组基础为动测实例,经模态分析得出钢筋混凝土构架式基础竖向1阶振动与电机产生共振;应用功率谱法对动力机组及基础平台进行动测,得出平台异常响应频率66Hz为水泵工作频率,调整机器的工作频率可避开不良振源影响,达到明显的减振效果。由此而知,动力机器基础出现不良振动时,不可盲目改变结构的动力特性,应在机器不同工况比如:停机、起机及正常转速下,对机器及基础进行动测并对振动信号进行比较分析,以制定出行之有效的减振方法。 相似文献
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冯爱芬 《河南科技大学学报(自然科学版)》2005,26(1):91-93
基于“前沿分支”的观点研究了圈幂补图的树宽,首先确定了它的树宽下界,又给出了达到此下界的标号,从而得到了它的树宽表达式。 相似文献