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.     

氧化锌矿物浸出渣中铅、锶的提取及动力学分析

NH₄HCO₃ conversion followed by HCl leaching was performed and proven to be effective in extracting Pb and Sr from zinc extracted residual. The mechanism and operating conditions of NH₄HCO₃ conversion, including molar ratio of NH₄HCO₃ to zinc extracted residual, NH₄HCO₃ concentration, conversion temperature, conversion time, and stirring velocity, were discussed, and operating conditions were optimized by the orthogonal test. Experimental results indicate that NH₄HCO₃ conversion at temperatures ranging from 25 to 85°C follows the shrinking unreacted core model and is controlled by inner diffusion through the product layer. The extraction ratios of Pb and Sr under optimized conditions reached 85.15% and 87.08%, respectively. Moreover, the apparent activation energies of Pb and Sr were 13.85 and 13.67 kJ·mol?1, respectively.     

摩擦焊接碳钢（EN24）和镍基高温合金（IN718）的显微组织和力学性能

Continuous-drive rotary friction welding was performed to join cylindrical specimens of carbon steel (EN24) and nickel-based superalloy (IN718), and the microstructures of three distinct weld zones—the weld interface (WI)/thermo-mechanically affected zone (TMAZ), the heat-affected zone (HAZ), and the base metal—were examined. The joint was observed to be free of defects but featured uneven flash formation. Electron backscatter diffraction (EBSD) analysis showed substantial changes in high-angle grain boundaries, low-angle grain boundaries, and twin boundaries in the TMAZ and HAZ. Moreover, significant refinement in grain size (2–5 μm) was observed at the WI/TMAZ with reference to the base metal. The possible causes of these are discussed. The microhardness profile across the welded joint shows variation in hardness. The changes in hardness are ascribed to grain refinement, phase transformation, and the dissolution of strengthening precipitates. The tensile test results reveal that a joint efficiency of 100% can be achieved using this method.     

汽车暴露面板带有表面条状缺陷的夹杂物分布特征分析:一种定量电解方法

The specific distribution characteristics of inclusions along with the sliver defect were analyzed in detail to explain the formation mechanism of the sliver defect on the automobile exposed panel surface. A quantitative electrolysis method was used to compare and evaluate the three-dimensional morphology, size, composition, quantity, and distribution of inclusions in the defect and non-defect zone of automobile exposed panel. The Al₂O₃ inclusions were observed to be aggregated or chain-like shape along with the sliver defect of about 3–10 μm. The aggregation sections of the Al₂O₃ inclusions are distributed discretely along the rolling direction, with a spacing of 3–7 mm, a length of 6–7 mm, and a width of about 3 mm. The inclusion area part is 0.04%–0.16% with an average value of 0.08%, the inclusion number density is 40 mm?2 and the inclusion average spacing is 25.13 μm. The inclusion spacing is approximately 40–160 μm, with an average value of 68.76 μm in chain-like inclusion parts. The average area fraction and number density of inclusions in the non-defect region were reduced to about 0.002% and 1–2 mm?2, respectively, with the inclusion spacing of 400 μm and the size of Al₂O₃ being 1–3 μm.     

在酸性溶液中加压氧化三价砷离子和二价铁离子

The co-oxidation of As(III) and Fe(II) in acidic solutions by pressured oxygen was studied under an oxygen pressure between 0.5 and 2.0 MPa at a temperature of 150°C. It was confirmed that without Fe(II) ions, As(III) ions in the solutions are virtually non-oxidizable by pressured oxygen even at a temperature as high as 200°C and an oxygen pressure up to 2.0 MPa. Fe(II) ions in the solutions did have a catalysis effect on the oxidation of As(III), possibly attributable to the production of such strong oxidants as hydroxyl free radicals (OH·) and Fe(IV) in the oxidation process of Fe(II). The effects of such factors as the initial molar ratio of Fe(II)/As(III), initial pH value of the solution, oxygen pressure, and the addition of radical scavengers on the oxidation efficiencies of As(III) and Fe(II) were studied. It was found that the oxidation of As(III) was limited in the co-oxidation process due to the accumulation of the As(III) oxidation product, As(V), in the solutions.     

采用超声组装与滚压工艺制备铝–碳纳米管复合材料

This study introduced a novel fabrication of aluminum–carbon nanotube (CNT) composites by employing bulk acoustic waves and accumulative roll bonding (ARB). In this method, CNT particles were aligned using ultrasonic standing wave in an aqueous media, and the arrayed particles were precipitated on the aluminum plate substrate. Then, the plates rolled on each other through the ARB process with four passes. Optical and scanning electron micrographs demonstrated the effective aligning of CNTs on the aluminum substrate with a negligible deviation of arrayed CNTs through the ARB process. The X-ray diffraction pattern of the developed composites showed no peaks for carbon and aluminum carbide. In addition, tensile tests showed that the longitudinal strength of the specimens processed with aligned CNTs was significantly greater than that of the specimens with common randomly dispersed particles. The proposed technique is beneficial for the fabrication of Al–CNT composites with directional mechanical strength.     

活化天然矿石选择性还原二氧化碳为无定形碳

Natural magnetite formed by the isomorphism substitutions of transition metals, including Fe, Ti, Co, etc., was activated by mechanical grinding followed by H₂ reduction. The temperature-programmed reduction of hydrogen (H₂-TPR) and temperature-programmed surface reaction of carbon dioxide (CO₂-TPSR) were carried out to investigate the processes of oxygen loss and CO₂ reduction. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that the stability of spinel phases and oxygen-deficient degree significantly increased after natural magnetite was mechanically milled and reduced in H₂ atmosphere. Meanwhile, the activity and selectivity of CO₂ reduction into carbon were enhanced. The deposited carbon on the activated natural magnetite was confirmed as amorphous. The amount of carbon after CO₂ reduction at 300°C for 90 min over the activated natural magnetite was 2.87wt% higher than that over the natural magnetite.     

约化框架下带有信用风险的永久可转债定价

将信用风险引入到可转债的定价中,通过修改股票价格的运动过程,得到了一个具有违约风险的股票价格运动过程,然后将其转化为风险中性测度下的运动过程.通过将回收率直接引入到贴现现金流中,得到了可违约永久可转债价格的变分不等方程,并求出了该变分不等方程的显式解,同时对于可回购的可转债,根据息票率的范围.可转债的定价分为3大类,并分别求出每类可转债的价格,最后指出,无论是否具有回购条款,可违约可转债的价格和无违约可转债的价格是相容的.     

随机利率下可转换债券定价

假定股票遵循分数布朗运动驱动的随机微分方程,利率满足由分数布朗运动驱动的Hull-White模型.利用分数布朗运动随机分析理论与方法,建立了随机利率下可转换债券定价数学模型,得到了可转换债券的定价公式.     

可转换债券的最优发行策略设计

综合考虑可转换债券发行条件中所涉及的相关因素,以公司总价值最大化为目标,建立了转换速率与公司资产变化量之间的关系模型.运用泛函变分原理,求出最优转换速率,并且进一步得到可转换债券的最优发行策略,为可转换债券发行条件的设计提供了一种新的方法.以首钢转债为例,利用该方法分析了票面利率和最优转股期限对初始转股溢价率的影响,得出的结论与发行公司对可转换债券发行条款的实际运用一致,证明了该方法的有效性.     

发展可转换公司债券完善资本市场

介绍了可转换公司债券的内涵及1997-2003年中国境内发行的可转换公司债券的发展概况。指出2003年我国可转换公司债券市场活跃，各方当事人应在现有的市场基础上总结经验吸取教训，进一步发展可转换公司债券，完善我国的资本市场。     

我国可转换债券条款设计研究

作为一种混合型金融工具，可转债以其独特的性质越来越为我国上市公司和投资者们所接受，而如何设计合理的条款是可转债发行成功的基础。文章在分析可转债条款设计目的和思路的基础上，分别对可转债各主要条款的设计进行研究，并结合我国的实际情况提出了发行人在条款设计过程中应注意的几个问题。     

二叉树模型在可转换债券定价中的应用

可转换债券在我国是一种比较新的兼具债券和期权特征的混合型金融衍生产品,具有筹资和避险双重功能．无论对于发行者还是投资者,对可转换债券的定价研究都有其理论和实际意义．文中运用二叉树期权定价模型,考虑赎回和回售条款,并结合上市的24只可转换债券,对可转换债券的定价理论和应用模型做了系统研究．结果表明,可转换债券价值被明显低估．     

可转债价值的非参数估计

目的在传统的可转换债券定价理论的基础上分析可转债的价值,给出了其价值确定公式。方法采用非参数核密度估计推断方法。结果对华菱转债进行了实证分析,考虑了该转债转股获利的可能性,并就该转债回售风波做出了理论解释。结论可转债由于其隐含期权的复杂性,加之转换条款的多样性,定价比较复杂,本文从数据出发利用统计分析方法分析其价值不失为一种较好的方法。     

随机利率下附有赎回条款的可转换债券的鞅定价

从定量的角度分析了随机利率下有赎回条款的可转换债券的价值构成,并在股价服从广义O-U过程的条件下,利用鞅定价方法推导出可转换债券的定价公式．     

对可转换公司债券财务特性的研究

在对可转换公司债券本质属性分析的基础上,运用期权定价方法对可转换债券的“可赎回性”价值特征进行深入解析;提出了可转换债券融资的资金成本是由筹资费用、票面利息和隐性成本三项构成,并给出了成本计量的方法;阐述了可转换债券的运作在企业内部可形成调节资本结构的内生机制,有助于改善公司的治理结构。     

股价服从跳－扩散模型的可转换债券的定价

研究了在股价服从跳－扩散模型下可转换债券的定价问题,并在随机利率下,利用Martingale Pricing方法推导出其定价公式．