石英与蛇纹石异相凝聚及其对黄铁矿浮选的影响

通过单矿物和人工混合矿的浮选试验、Zeta电位测试、吸附量测试,研究了蛇纹石和石英异相凝聚的机理,以及对黄铁矿浮选的影响,以进一步探索多种矿物的体系中,蛇纹石对硫化矿物浮选影响的主要原因。结果表明:通过添加石英,可以恢复黄铁矿对捕收剂的吸附量,减弱蛇纹石的不良影响,不同粒级的石英与蛇纹石的异相凝聚作用强弱不同,粒级越细的石英,与蛇纹石的异相凝聚作用越强。     

蛇形防护布线设计

高速电路中蛇形线可作为传统防护布线的替代方案，但其提出过程未曾考虑如何进行合理的设计。文中基于蛇形防护布线的外形特征影响耦合参数的原理，通过全波求解器建立蛇形防护布线模型，分析了其端接策略以及特征变化对应的远端串扰变化规律，得出了蛇形防护布线的合理设计方法。结果表明，短路策略作为最佳策略，且在信号边沿变化较快的情况下，应采用线宽小、高度高和长度短的蛇形线作为防护布线。     

Hydrothermal synthesis (200 °C) of Co–kaolinite and Al–Co–serpentine

In the systems CoO–Al₂O₃–SiO₂–H₂O and CoO–Al₂O₃–SiO₂–HCl–H₂O, at initial pH between 5.5 and 8.1 and temperature of 200 °C, kaolinite is unstable and the following phases form through a dissolution-precipitation process: a) kaolinite and Co-bearing kaolinite; b) Al–Co–serpentine; and c) poorly crystalline phases. Identification of the several phases was carried out from a combination of X-ray diffraction and transmission/analytical electron microscopy.Co–kaolinite shows variable morphologies: a) Platy lath-shaped particles with very low Co content; b) Spherical particles, with relatively constant Co contents (in the order of 0.10 apfu); c) Kaolinite stacks with very variable Co contents (up to 0.25 apfu). Analytical data indicate that the presence of Co(OH)₂ in the system favors the dissolution process as well as serpentine formation but it leads to the parallel formation of abundant poorly crystalline phases. The Co-content in kaolinite increased as a function of the Co(OH)₂/CoCl₂ ratio in the initial systems, and it is reflected by a parallel increase of the b-cell parameter of kaolinite. The average composition of the coexisting Al–Co–serpentine is: (Al_1.20Fe_0.11Co_1.27)(Si_1.64Al_0.36)O₅(OH,Cl)₂, with Cl contents in the order of 0.14 apfu.The assemblage Co–kaolinite + Al–Co–serpentine, which appears to be stable at 200 °C, has not been described in natural environments, probably because it requires unusual Al- and Co-rich chemical systems.     

Multi-pass serpentine flow-fields to enhance under-rib convection in polymer electrolyte membrane fuel cells: Design and geometrical characterization

The flow-field for reactant distribution is an important design factor that influences the performance of polymer electrolyte membrane fuel cells (PEMFCs). Under-rib convection between neighboring channels has been recognized to enhance the performance of PEMFCs with serpentine flow-fields. This study presents a simple design method to generate multi-pass serpentine flow-fields (MPSFFs) that can maximize under-rib convection in a given cell area. Geometrical characterization indicates that MPSFFs lead to significantly higher under-rib convection intensities and more uniform conditions, such as reactant concentrations, temperature, and liquid water saturation, compared with conventional serpentine flow-fields. The implications of the enhanced under-rib convection due to MPSFFs on the performance of PEMFCs are discussed.     

蛇纹石酸浸提镁残渣制备硅酸锂及其性能研究

以蛇纹石酸浸提镁残渣为硅源,碳酸锂为锂源,通过高温固相反应合成了硅酸锂高温固碳材料,探究了煅烧时间、气氛以及物料配比对合成材料高温固碳性能的影响。采用热重-差热综合热分析仪(TG-DTG)研究了蛇纹石酸浸提镁残渣型硅酸锂的CO2吸收性能,并通过扫描电子显微镜(SEM)与X射线衍射仪(XRD)对合成材料的微观形貌与结构特征进行了表征。结果表明:蛇纹石酸浸提镁残渣型硅酸锂具有较好的CO2吸收性能,吸收量可达26.66%;与市售Si O2为硅源相比,蛇纹石酸浸提镁残渣型硅酸锂材料煅烧合成时间缩短,高温固碳性能更优。     

柠檬酸在蛇纹石/镍黄铁矿浮选分离中的作用

通过浮选实验、沉降实验、吸附量实验、Zeta电位测试和DLVO理论计算,考察柠檬酸在蛇纹石/镍黄铁矿浮选分离中的作用,分析柠檬酸的作用机理。结果表明：在弱碱性pH条件下,蛇纹石的加入降低了镍黄铁矿的回收率,而柠檬酸处理后的蛇纹石不会影响镍黄铁矿的浮选。机理分析表明：蛇纹石与镍黄铁矿表面带有相反电荷,能通过静电作用罩盖在黄镍铁矿表面,影响其浮选;柠檬酸能够溶解蛇纹石表面荷正电的镁离子,使蛇纹石表面电位发生变化,此时,蛇纹石与镍黄铁矿之间存在较强的排斥作用,从而减弱蛇纹石在镍黄铁矿表面的附着,消除其对镍黄铁矿的抑制作用。     

蛇纹石尾矿固体废弃物资源化的途径

蛇纹石尾矿是蛇纹石开采、利用过程中产生的固体废弃物,是我国排放量较大的矿业固体废弃物之一,也是可回收利用的二次资源。本文介绍了蛇纹石尾矿对环境的危害,分析了蛇纹石尾矿的物理化学性质,总结出资源化利用的途径。     

冬瓜山铜矿深部矿石工艺矿物学研究

冬瓜山铜矿属于复杂难选矿石,具有铜磁黄铁矿、层状滑石、蛇纹石类型矿石占比高的特点,该性质对铜的选别过程具有不利影响,影响铜精矿品位和铜回收率。因此,开展该矿石的矿物学特性研究,对指导选矿生产具有重要的现实意义。研究的主要内容包括:矿石化学成分分析、矿物组成及含量、主要矿物的粒度及嵌布特征分析、不同磨矿细度下重要矿物的解离度分析,并对影响选别指标的工艺矿物学因素进行总结。工艺矿物学研究表明,冬瓜山深部矿石中铜矿物绝大部分为黄铜矿,墨铜矿占8.46%,且含有24.26%的滑石、蛇纹石易浮层状脉石矿物;黄铜矿、墨铜矿、磁黄铁矿、磁铁矿和黄铁矿的嵌布粒度不均匀,尤其是20μm以下部分占11.04%,在磨矿细度-0.074 mm粒级含量占75%时,仍有26.06%与脉石连生。以上性质都是铜选矿的重要影响因素,对指导选矿厂生产具有重要的意义。     

Numerical investigation into transient response of proton exchange membrane fuel cell with serpentine flow field

The transient response of a proton exchange membrane fuel cell (PEMFC) with a serpentine flow field design is investigated using a three‐dimensional numerical model. The simulations consider three different flow field designs with 7, 11, and 15 bends, respectively. For the flow field design with 11 bends, three different channel width ratios are considered, namely 25%, 50%, and 75%. The channel width ratio is defined as the ratio of the channel width to the total channel/rib width. The simulation results show that for all of the flow field designs, an overshoot in the local current density occurs when the voltage is reduced instantaneously from 0.7 to 0.5 V because of the high and uniform oxygen mass fraction. Conversely, a significant undershoot occurs when the voltage is increased instantaneously from 0.5 to 0.7 V because of the low and nonuniform oxygen mass fraction. The overshoot and undershoot phenomena are particularly evident in the PEMFC with a 15‐bend flow field. For the flow field design with 11 bends, the channel width ratio has little effect on the current density at an operating voltage of 0.7 V. However, at an operating voltage of 0.5 V, the oxygen concentration into the catalyst and diffusion layers increases with the increasing channel width ratio, which leads to higher current density. As a result, a more significant overshoot phenomenon is observed in the flow field with a width ratio of 75%. Copyright © 2012 John Wiley & Sons, Ltd.     

The impact of flow field pattern on concentration and performance in PEMFC

In this study, we present a rigorous mathematical model, to treat prediction and analysis of proton exchange membrane fuel cells gas concentration and current density distribution in mass transfer area and chemical reaction area performed in 3‐D geometry. The model is based on the solution of the conservation equations of mass, momentum, species, and electric current in a fully integrated finite‐volume solver using the CFDRC commercial code. The influences of fuel cell performance with two kinds of flow channel pattern design are studied. The gas concentration of the straight flow pattern appears excessively non‐uniform, resulting in a local concentration polarization. On the other hand, the gas concentration is well distributed for the serpentine flow pattern, creating a better mass transfer phenomena. The performance curves (polarization curves) are also well correlated with experimental data. Copyright © 2005 John Wiley & Sons, Ltd.