In the continuous casting of medium-carbon steel, highly crystalline mold fluxes are employed to suppress surface longitudinal cracks; however, the lubrication performance of such mold fluxes is generally poor. One hypothesis is that the composition segregation of the remaining liquid slag after crystallization in the mold fluxes leads to the deterioration of lubrication performance, but no direct experimental data currently confirm this hypothesis. Thus, remaining liquid slag in the glassy state after crystallization was obtained by rapidly cooling samples. The composition of original slag, crystals, and remaining liquid slag was analyzed using an electron probe microanalysis system. The performance changes caused by the compositional changes in the remaining liquid slag at 200 μm away from the crystals were calculated using FactSage. The results indicated that the crystalline phase of all mold fluxes is cuspidine (3CaO·2SiO2·CaF2). After the mold fluxes precipitate crystals, the content of non-cuspidine components in the remaining slag increases. As for the cuspidine component, the CaO content has significantly decreased. Overall, the content of SiO2 in the remaining slag decreases, while the content of F increases. The experimental results confirmed that there is obvious segregation in the remaining liquid slag after the mold flux selectively crystallizes. Compared with the original slag, the liquidus temperature of the remaining liquid slag is significantly reduced, and the maximum crystallization ratio of cuspidine also decreases. The poor lubricity of the mold fluxes for medium-carbon steel is its nature, rather than caused by segregation.

With the increasing demand for high-quality continuous casting slab, electromagnetic devices are widely used to control the flow field in the mold. The new generation electromagnetic device FC Mold G3 with the combined function of electromagnetic braking (EMBr) and electromagnetic stirring (EMS) has received extensive attention. Herein, a 3D multiphysics numerical model coupling the electromagnetic, turbulence, heat transfer in the continuously cast slab mold with the FC Mold G3 is established, and the effects of different electromagnetic flow control methods of the FC Mold G3 on the flow and initial solidification behavior in the mold are investigated. The simulation results indicate that the velocity and temperature distribution at the top surface are more uniform when the EMS current is 150 A, but it does not improve the uniformity of the solidified shell. The initial solidified shell growth becomes more uniform after the EMBr is applied, but the local velocity of the steel-slag interface increases. When the current intensities of EMS and EMBr of FC Mold G3 are, respectively, 150 and 600 A, the velocity near the meniscus and the uniformity of the solidified shell become more reasonable and the impact depth is suppressed.

Final electromagnetic stirring (F-EMS) effectively improves macrosegregation and central porosity in round bloom continuous casting, while the flow and solidification of molten steel under F-EMS have a direct impact on metallurgical properties. Fluid flow and solidification behavior in a 600 mm round bloom continuous casting process with F-EMS were simulated. The influence of the liquid fraction model on strand temperature distribution was investigated. The flow of molten steel was analyzed under both continuous and alternate stirring modes. The results indicated that in continuous stirring mode, the stirring velocity fluctuates between peaks and troughs over a specific period. The closer the F-EMS is to the meniscus, the larger the mushy zone area and the higher the stirring velocity. Due to the 10+ s rise time for current intensity, a 25 s forward and reverse stirring duration is recommended for Φ600 mm round bloom continuous casting with F-EMS.

The mold level is an important factor for high-quality slab. In this paper, the analysis method and the relationship between the argon blowing rate and the maximum mold level were proposed. The experimental data were collected from continuous caster in Meishan steel plant at first. Then, the maximum ten values of mold level data were taken the average value to represent the maximum mold level. After that, the Pearson correlation coefficient and Spearman correlation coefficient were used as standards to compare the correlation between different process parameters and the maximum mold level. And the results showed that there is a strong relationship between the argon blowing rate at submerged entry nozzle (SEN) and the maximum mold level. When the SEN is clogged, the Pearson correlation coefficient and Spearman correlation coefficient values between argon blowing rate and maximum mold level are the largest, 0.91 and 0.94, respectively. After the clog fragmentation, the coefficient values are 0.90 and 0.92, respectively. And the maximum mold level, (Ml, mm), is formulated as a function of argon blowing rate, (r, L/min). When the SEN is clogged, it can be determined by M_l=5.82r-28.42 . After the clog fragmentation, it can be determined by M_l=0.61r+1.12 . Besides, the numerical simulation also showed that the argon blowing rate could affect the molten steel velocity change rate at the SEN, which in turn affects the mold level. And when the SEN is clogged, the difference between the numerical value and field data of maximum mold level is 0.18 mm. After the clog fragmentation, the difference is 0.41 mm.

Heavy metal ions (HMIs) threaten ecosystems and human health due to their carcinogenicity, bioaccumulativity, and persistence, demanding highly sensitive, low-cost real-time detection. Electrochemical sensing technology has gained significant attention owing to its rapid response, high sensitivity, and low cost. Molybdenum disulfide (MoS2), with its layered structure, tunable bandgap, and abundant edge active sites, demonstrates significant potential in the electrochemical detection of heavy metals. This review systematically summarizes the crystal structure characteristics of MoS2, various preparation strategies, and their mechanisms for regulating electrochemical sensing performance. It particularly explores the cooperative effects of MoS2 composites with other materials, which effectively enhance the sensitivity, selectivity, and detection limits of electrochemical sensors. Although MoS2-based materials have made significant progress in theoretical and applied research, practical challenges remain, including fabrication process optimization, interference from complex-matrix ions, slow trace-metal enrichment kinetics, and stability issues in flexible devices. Future work should focus on developing efficient, low-cost synthesis methods, enhancing interference resistance through microfluidic and biomimetic recognition technologies, optimizing composite designs, resolving interfacial reaction dynamics via in situ characterization, and establishing structure–property relationship models using machine learning, ultimately promoting practical applications in environmental monitoring, food safety, and biomedical fields.

Exploring the mechanism of the α-ferrite precipitation process on high-temperature properties plays an important guiding role in avoiding slab cracks and effectively regulating quality. In this work, in situ observation of the α-ferrite sustained precipitation behavior for peritectic steel during the austenitic phase transition process has been investigated using high-temperature confocal scanning laser microscopy. Meanwhile, the high-temperature evolution of the phase fractions during the phase transition process was quantitatively analyzed based on the high-temperature expansion experiment using the peak separation method. Furthermore, the high-temperature properties variations of the casting slab during the α-ferrite sustained precipitation process were investigated with the Gleeble thermomechanical simulator. The results show that the film-like ferrite precipitated along the austenite grain boundaries at the initial stage of phase transition, then needle-like ferrite initiates rapid precipitation on film-like ferrite when the average thickness reaches 15~20 μm. Hot ductility reached a minimum at the ferrite phase fraction fα = 10~15%, while high-temperature properties returned to a higher level after fα > 40~45%. The appearance of a considerable amount of needle-like ferrite and grain refinement effectively improves the high-temperature properties with the α-ferrite precipitation process advances.

Rare earth elements have excellent catalytic effects on improving hydrogen storage properties of the Mg2Ni-based alloys. This study used a small amount of Y to substitute Mg partially in Mg2Ni0.9Co0.1 and characterized and discussed the effects of Y on the solidification and de-/hydrogenation behaviors. The Mg2−xYxNi0.9Co0.1 (x = 0, 0.2, 0.3, and 0.4) hydrogen storage alloys were prepared using a metallurgy method. The phase composition of the alloys was studied using X-ray diffraction (XRD). Additionally, their microstructure and chemical composition were studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The hydrogen absorption and desorption properties of the alloys were studied using pressure-composition isotherms and differential scanning calorimetric (DSC) measurements. The structure of the as-cast Mg2Ni0.9Co0.1 alloy was composed of the peritectic Mg2Ni, eutectic Mg–Mg2Ni, and a small amount of pre-precipitated Mg–Ni–Co ternary phases, and was converted into the Mg2NiH4, Mg2Ni0.9Co0.1H4, and MgH2 phases after hydrogen absorption. Furthermore, the XRD patterns of the alloys showed the MgYNi4 phase and a trace amount of the Y2O3 phase along with the Mg and Mg2Ni phases after the addition of Y. After hydrogen absorption, the phase of the alloys was composed of the Mg2NiH4, MgH2, MgYNi4, YH3, Y2O3, and Mg2NiH0.3 phases. With the increase of Y addition, the area ratios of the peritectic Mg2Ni matrix phase in the Mg2−xYxNi0.9Co0.1 (x = 0, 0.2, 0.3, and 0.4) alloys gradually decreased until they disappeared. However, the eutectic structure gradually increased, and the microstructures of the alloys were obviously refined. The addition of Y improves the activation performance of the alloys. The alloy only needed one cycle of de-/hydrogenation to complete the activation for x = 0.4. The DSC curves showed that the initial dehydrogenation temperatures of Mg2Ni0.9Co0.1 and Mg1.8Y0.2Ni0.9Co0.1 were 200 and 156 °C, respectively. The desorption activation energies of the hydrides of the Mg2Ni0.9Co0.1 and Mg1.8Y0.2Ni0.9Co0.1 alloys calculated using the Kissinger method were 94.7 and 56.5 kJ/mol, respectively. Moreover, the addition of Y reduced the initial desorption temperature of the alloys and improved their kinetic properties.

Various efficient strategies have been developed to overcome the anodic electrocatalyst issue of methanol-based fuel cells owing to their complicated methanol electrooxidation mechanism. In this work, PtCo nanoparticles with adjustable compositions supported on multiwalled carbon nanotubes (Pt1Cox/MWCNTs) through the adsorbing-coating-annealing-etching route were synthesized. Compared with the Pt/C catalyst, Pt1Co3/MWCNTs exhibit better electrocatalytic MOR activity in both activity and durability. Notably, the electrochemical mass and specific activity of the as-prepared catalyst are 1.04 mA mu g(Pt)(-1) and 2.18 mA cm(-2), respectively, which are higher than those of the Pt/C catalyst. Moreover, the as-prepared sample revealed lower onset potential during the CO stripping test. Furthermore, the Pt1Co3/MWCNTs possess a lower current density decrease rate in chronoamperometry and cyclic durability tests. The enhancement of activity and stability of Pt1Co3/MWCNTs could be ascribed to their ordered morphological structure, the electronic interaction between MWCNTs and PtCo nanoparticles, and the suitable electronic structure effect between Pt/Co ratios. The concept of the catalyst design in this study offers a different guideline for constructing the novel methanol electrooxidation catalyst, which will accelerate the widespread fuel cell practical application.

The Mg _1.8 Y _0.2 Ni _1−y Co _y (y = 0, 0.05, 0.1, 0.15, 0.2) hydrogen storage alloys were prepared following the principles of metallurgy, the phase composition and microstructure of the alloys were studied using XRD and SEM/EDS techniques, and the hydrogen absorption and desorption properties of the alloys were studied using PCT and DSC techniques. The results showed that the addition of Co did not affect the phase composition of Mg _1.8 Y _0.2 Ni _1−y Co _y alloys in the as-cast state and after hydrogen absorption. The Co addition could help refine the microstructure of the alloys to a certain extent. The de-/hydrogenation kinetics of Mg _1.8 Y _0.2 Ni _1−y Co _y (y = 0, 0.1, and 0.2) alloys were improved by adding Co, and the best results were obtained at y = 0.1. The onset decomposition temperature of Mg _1.8 Y _0.2 Ni _1−y Co _y (y = 0, 0.1, and 0.2) alloys were recorded to be 180 °C, 156 °C, and 210 °C, respectively, which were significantly lower than that of Mg _2 Ni (253 °C). The results revealed that the addition Co could improve the thermodynamic performance of the dehydrogenation process.

利用Ansys APDL软件建立了计算长度2 200 mm和宽度500 mm的超声速氧枪的二维轴对称数学模型,并采用Ansys Fluent软件的标准k-ε模型对单孔超声速氧枪内外的射流特性进行了数值模拟,分析了在不同操作压力(0.8,1.0,1.2 MPa)条件下,基于特征线法设计的曲线氧枪与传统锥线氧枪的内部流场的分布特征.模拟结果表明,曲线氧枪能够改善氧枪内部流场稳定性,减少激波或膨胀波等复杂现象波系的发生,延长氧气射流的超声速段长度,提高氧气射流区域宽度,从而增加了氧气射流与熔池的冲击面积,改善了氧气在熔池内的传质效果.

文中总结了异型坯连铸主要缺陷的形成机理与应对措施.就腹板纵裂纹、圆角处裂纹和表面夹渣方面分析了表面缺陷产生的原因;以中心裂纹、翼缘顶端角部裂纹和气泡的特征说明了内部缺陷的发生机理.对于表面质量缺陷,主要是对钢水成分、冷却方式、保护渣性能等进行优化;对于内部质量缺陷,主要通过调整钢水过热度、拉速、浸入式水口位置等方案进行改良.最后,阐明了异型坯连铸过程需要重点关注的事项.

为了进一步提高课堂教学质量,文章通过CiteSpace软件对21世纪以来发表在中文核心期刊上关于高校课堂教学研究的1080篇论文进行了可视化分析,结果显示,课堂教学、教学评价和教学模式是词频最高的3个关键词;高校教师、翻转课堂、对分课堂、互联网+、思想政治教育是近年来突然增加的5个关键词.

A cylindrical electrochemical cell is designed. The mean residence time and volume fraction of stagnant zone under perpendicular inflow (PI) and tangential inflow (TI) are studied by hydraulics experiments. Fine copper powders are prepared by galvanostatic regime of electrolysis of copper scrap. The effects of current density on current efficiency, cell voltage, power consumption, and the particle size of copper powder (D50) are investigated both under PI and TI. The results show the residence time of fluid particles is prolonged with decreasing flow rate, which is beneficial to the reaction of substances, and volume fraction of stagnant zone decrease. Maximum current efficiency and minimum power consumption are obtained under PI, which corresponds to the maximum D50 particle size. According to SEM figures, deposits on the surface of cathode are honeycomb-like forms. There are more arborous secondary dendrites under PI, but more compact and stout dendrites under TI in comparison.

本科教育中，学生的学业成绩是衡量学生学业水平和素质水平的重要标准，但是由于教育体制和文化背景等的不同，导致中美本科生学业成绩评价体系有明显的不同。本文对比了中国大学和美国亚利桑那州立大学(ASU)的学业成绩评价内容、评定方式、权重、评定标准和反馈机制等，为我国本科教育的学生学业成绩评价体系改革提供思路。

Bi-functional effect, elevated mass transport and increased durability have been combined within one catalyst for electrochemical methanol oxidation reaction. It has niobium (Nb) doped titanium dioxides (TiO2) nanosized half-sphere shell (HSS) as the substrate material deposited with small amount of Pt nanoparticles. These specially designed HSS nanostructure has significantly increased surface areas which are suitable for Pt nanoparticles to be deposited onto them to form the catalyst denoted as Pt/Nb-TiO2 HSS. It exhibits a remarkably high methanol oxidation activity of 0.21 V vs. RHE which is 0.05 V lower than HiSPEC10000 PtRu/C catalyst, due to the substrate's strong metal support interactions effect, bi-functional effect and the special structure. These HSS nanostructures have also increased the methanol diffusion and mass transport within the anode to give a maximum power output of 0.0931 W of cathode polarization in miniature direct methanol fuel cell (DMFC). It also acts as protection shells, which minimises the dissolution of Pt metal nanoparticles to prevent its diffusion through the membrane.

在锰电解工业的发展中,存在着能耗高、污染大等问题.针对这些问题,本文对相关研究进行了总结,包括电解液的净化、新阳极板的研制、添加剂在电解锰过程的使用和节能技术等,为工业电解锰生产提供理论指导.

以冶金工程设计课程为切入点,根据冶金工程专业工程教育认证毕业要求指标点的要求,分析教学过程中存在的问题,从优化教学大纲、加强质量监控和改革考核方式等方面进行教学改革与实践,达到了工程教育认证的教学要求.

Electrolytic production of copper powders is a process with a high power consumption. This study establishes a power consumption model for copper powder electrolysis using the response surface methodology (RSM) under laboratory conditions, which provides the basis for reducing power consumption. First, seven process parameters were screened out using the Plackett–Burman design (PBD) experiments. The results show that the factors that have a significant effect on the power consumption of copper powder electrolysis are electrolyte temperature, Cu2+ concentration, H2SO4 concentration, inter-electrode spacing, and current density. A quadratic mathematical model of significant factors and power consumption was then developed using the Box–Behnken design (BBD) of RSM. Finally, the model was used to optimize the most energy-efficient process conditions. In addition, scanning electron microscopy (SEM) analysis indicates that the morphologies of electrolytic copper powders deposited under the optimized conditions generally have dendritic structure and the agglomerated copper particles are almost globular.

在铜电解精炼过程中,最主要的能耗是直流电耗,而槽电压对直流电耗的影响最大.针对铜电解精炼过程,首先采用Plackett-Burman实验设计法筛选出对铜电解精炼槽电压具有显著影响的4个因素,其显著性次序为:电解液温度＞电流密度＞阴阳极间隙＞硫酸浓度;然后根据中心复合实验设计(Central composite design,CCD)原理设计的4因素5水平实验及响应面法(Response surface methodology,RSM)对影响铜电解精炼槽电压的显著因素做进一步优化,建立了多元二次回归方程拟合模型.在电流密度为280 A/m2的前提下,得到槽电压最低的工艺条件为:电解液温度60℃、硫酸浓度210 g/L、阴阳极间隙20 mm.实验表明,基于响应面法建立的预测模型是准确可靠的,对降低铜电解精炼能耗具有良好的指导作用.

Electrolysis is one of the main methods for producing copper powder, but has the disadvantage of high power consumption. This paper describes an experimental study of a process for electrolytic production of copper powder in which a jet flow of fresh electrolyte is introduced between anode-cathode pairs. The effects of electrolyte inlet mode and circulation rate on the direct current (DC) power consumption and on the morphology and apparent density of the copper powder produced are investigated. The results show that in the conventional bottom-inlet/top-outlet mode, the electrolyte circulation rate has little influence on DC power consumption. In contrast, when a jet flow is used, an increase in electrolyte circulation rate leads to an increase in current efficiency and a decrease in cell voltage, resulting in a significant reduction in DC power consumption, which drops by as much as 37%. In addition, as a result of agitation by the jet flow, the copper powder deposited at the cathode becomes denser, the powder particles become coarser and less dendritic on the microscale, and their apparent density increases from 0.33 g cm(-3) to 1.90 g cm(-3). (C) 2018 Published by Elsevier B.V.