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.     

微生物浸矿技术在我国的研究现状及发展前景

As the world’s second largest economy experiencing rapid economic growth, China has a huge demand for metals and energy. In recent years, China ranks first, among all the countries in the world, in the production and consumption of several metals such as copper, gold, and rare earth elements. Bioleaching, which is an approach for mining low grade and refractory ores, has been applied in industrial production, and bioleaching has made great contributions to the development of the Chinese mining industry. The exploration and application of bioleaching in China are reviewed in this study. Production and consumption trends of several metals in China over the past decade are reviewed. Technological processes at key bioleaching operations in China, such as at the Zijinshan Copper Mine and Mianhuakeng Uranium Mine, are presented. Also, the current challenges faced by bioleaching operations in China are introduced. Moreover, prospects such as efficiency improvement and environmental protection are proposed based on the current situation in the Chinese bioleaching industry.     

不同结构和形态的天然镁硅酸盐:与K反应制备生物柴油的K2MgSiO4催化剂

In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile (which have the same general formula Mg₃Si₂O₅(OH)₄), and talc (Mg₃Si₄O₁₀(OH)₂) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20wt% K and treatment at 700–900°C led to a solid-state reaction to mainly form the K₂MgSiO₄ phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K₂MgSiO₄ formation. All the materials showed catalytic activity for the transesterification of soybean oil (1:6 of oil : methanol molar ratio, 5wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K₂MgSiO₄.     

烧结铁矿中FeO含量对其在富氢高炉中还原行为的影响

Japan started the national project “COURSE 50” for CO₂ reduction in the 2000s. This project aimed to establish novel technologies to reduce CO₂ emissions with partially utilization of hydrogen in blast furnace-based ironmaking by 30% by around 2030 and use it for practical applications by 2050. The idea is that instead of coke, hydrogen is used as the reducing agent, leading to lower fossil fuel consumption in the process. It has been reported that the reduction behavior of hematite, magnetite, calcium ferrite, and slag in the sinter is different, and it is also considerably influenced by the sinter morphology. This study aimed to investigate the reduction behavior of sinters in hydrogen enriched blast furnace with different mineral morphologies in CO–CO₂–H₂ mixed gas. As an experimental sample, two sinter samples with significantly different hematite and magnetite ratios were prepared to compare their reduction behaviors. The reduction of wustite to iron was carried out at 1000, 900, and 800°C in a CO–CO₂–H₂ atmosphere for the mineral morphology-controlled sinter, and the following findings were obtained. The reduction rate of smaller amount of FeO led to faster increase of the reduction rate curve at the initial stage of reduction. Macro-observations of reduced samples showed that the reaction proceeded from the outer periphery of the sample toward the inside, and a reaction interface was observed where reduced iron and wustite coexisted. Micro-observations revealed three layers, namely, wustite single phase in the center zone of the sample, iron single phase in the outer periphery zone of the sample, and iron oxide-derived wustite FeO and iron, or calcium ferrite-derived wustite 'FeO' and iron in the reaction interface zone. A two-interface unreacted core model was successfully applied for the kinetic analysis of the reduction reaction, and obtained temperature dependent expressions of the chemical reaction coefficients from each mineral phases.     

Mg和La对Ca–Ti 处理钢中夹杂物演变和组织的影响

The evolution of inclusions and the formation of acicular ferrite (AF) in Ca–Ti treated steel was systematically investigated after Mg and La addition. The inclusions in the molten steel were Ca–Al–O, Ca–Al–Mg–O, and La–Mg–Ca–Al–O after Ca, Mg, and La addition, respectively. The type of oxide inclusion in the final quenched samples was the same as that in the molten steel. However, unlike those in molten steel, the inclusions were Ca–Al–Ti–O + MnS, Ca–Mg–Al–Ti–O + MnS, and La–Ca–Mg–Al–Ti–O + MnS in Mg-free, Mg-containing, and La-containing samples, respectively. The inclusions distributed dispersedly in the La-containing sample. In addition, the average size of the inclusions in the La-containing sample was the smallest, while the number density of inclusions was the highest. The size of effective inclusions (nucleus of AF formation) was mainly in the range of 1–3 μm. In addition, the content of ferrite side plates (FSP) decreased, while the percentage of AF increased by 16.2% due to the increase in the number of effective inclusions in the La-containing sample in this study.     

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.     

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.     

项目管理与项目组织研究结构与分析

项目与项目管理的研究目前在国外有了很大发展,其研究方向从传统的项目管理拓展到项目组织。项目型组织及项目型企业是最新研究热点。Sderlund以及Young和Frank的通过对国外顶级杂志与项目管理相关文献的回顾,分别运用＂项目-企业＂研究框架、项目管理研究主题定量分析方法对项目管理的研究发展及趋势,说明项目管理研究方向。在他们的研究基础上,将项目的研究分为项目管理与项目组织两个方向,并分别对项目管理与项目组织的研究的演变及其核心内容进行了概括和总结。     

浅谈工程建设项目的档案资料管理

工程建设项目档案作为项目知识形态的建设成果,对于项目的建设、管理、维护、改造具有不可替代的作用。本文结合西江二期工程建设实际,浅谈如何做好工程建设项目的档案管理工作。     

项目经理服务型领导行为对项目绩效的影响

构建以项目经理服务型领导行为为自变量、项目绩效为因变量、团队情感承诺为中介变量和领导团队代表性为调节变量的一个被调节的中介模型,探讨项目经理服务型领导行为对项目绩效的作用机理.通过对64个工程项目团队的316份有效调查样本进行研究,发现项目经理服务型领导行为对团队情感承诺和项目绩效都具有正向的影响;团队情感承诺在项目经理服务型领导行为与项目绩效的关系中发挥完全中介效应;领导团队代表性调节了团队情感承诺在项目经理服务型领导行为和项目绩效关系中的中介作用.     

项目管理理论在研究生课题中的应用

通过项目管理方法的项目启动、项目计划、项目执行与监控、项目收尾与评估四过程实践,阐述项目管理理论在研究生课题中的实践应用。     

石油勘探开发建设项目评价系统探讨

石油勘探开发建设项目评价是石油勘探开发建设项目管理的重要内容之一,也是提高项目决策科学性的一个重要环节。首先分析了石油勘探开发建设项目评价的理论和方法,然后从项目前评价、项目中评价、项目后评价、技改项目评价四部分讨论了项目评价的基本内容,并在此基础上构建出了新的项目评价系统。指出:新的项目评价系统与传统的评价系统[1]的最大区别在于增加了项目中评价内容,并且对其它大、中型建设项目也是适用的。     

国内外对项目成功评价标准的研究回顾

随着项目管理在更广泛领域的应用，如何评价项目成功已经成为国际项目管理研究领域的一个重要题目．笔在讨论美国项目管理协会对项目和管理的定义的基础上，分析国内外研究项目成功评价标准的有关献。总结国内外对项目成功评价标准的研究现状和趋势，提出国内在相应领域的改进建议，以便促进项目管理在中国的更加有效的应用和推广．     

工程质量、进度、成本控制是施工项目管理的关键

工程质量是施工企业的生命,是企业立足市场的基石,是企业竞争举足轻重的筹码;施工进度控制是保证施工项目按期完工,合理安排资源供应,节约工程成本的主要措施;项目成本管理反映施工项目管理的核心内容,体现施工项目管理的本质特征,提供了衡量施工项目管理绩效的客观标尺。文章结合工程实际探讨了施工项目管理的有关问题。     

我省国际科技合作项目管理中存在的问题及对策

为使我省国际科技合作项目管理更加科学公正,通过对我省国际科技合作项目管理流程中的项目申报、项目评审、项目实施和项目验收4个不同阶段中存在的问题的分析,提出了在国际科技合作项目管理中尽可能的减少人的主观判断,借助先进的计算机技术建立公平公正科学的项目管理系统。     

项目经理制在工程造价咨询中的实施

从建设项目的管理、项目经理制成立的条件、项目经理制的关键、项目经理制的实施方法等方面阐述了项目经理制在工程造价咨询中的实施。     

项目计划管理在软件研发中的应用研究

针对软件项目经常延期的问题,应用项目计划管理的理论,对如何保障项目按期完成进行了系统的研究.以某企业PDM项目的工期估计和项目时间表制定过程为中心,讨论了在项目计划阶段如何合理分配资源、优化工作秩序等问题,为软件项目的科学管理和控制提供了借鉴.