陈化温度对LiNi0.5Co0.2Mn0.3O2型正极 材料电化学性能的影响

以简单的球磨-干燥-煅烧法,制备了具有稳定α-NaFeO2型层状结构（R-3m空间群）的LiNi0.5Co0.2Mn0.3O2 型的三元正极材料。通过X射线衍射分析、傅里叶红外光谱、扫描电子显微镜、充放电循环、循环伏安、交流阻抗谱等手段测试了样品的理化性能。研究表明：球磨浆料的陈化温度对样品性能有明显的影响。在0.1C、1C、2C、3C、5C、6C、8C和10C倍率电流和连续充放电下,经过50 ℃陈化浆料制备的亚微米样品的放电容量分别为172.3、161.4、151.5、145.2、136.9、133.2、126.3、121.4 mA·h/g,表现出较好的大倍率电流放电性能。随着循环次数的增加,该样品的锂离子扩散系数和电荷传递阻抗均发生变化。该样品的未循环、充放电循环1次及循环40次样品的锂离子扩散速率分别为1.45×10-16、6.60×10-16、7.92×10-15 cm/s。     

Thermal properties of La2Zr2O7 double-layer thermal barrier coatings

La₂Zr₂O₇ is a promising thermal barrier coating (TBC) material. In this work, La₂Zr₂O₇ and 8YSZ-layered TBC systems were fabricated. Thermal properties such as thermal conductivity and coefficient of thermal expansion were investigated. Furnace heat treatment and jet engine thermal shock (JETS) tests were also conducted. The thermal conductivities of porous La₂Zr₂O₇ single-layer coatings are 0.50–0.66?W?m^?1?°C^?1 at the temperature range from 100 to 900°C, which are 30–40% lower than the 8YSZ coatings. The coefficients of thermal expansion of La₂Zr₂O₇ coatings are about 9–10?×?10^?6?°C^?1 at the temperature range from 200 to 1200°C, which are close to those of 8YSZ at low temperature range and about 10% lower than 8YSZ at high temperature range. Double-layer porous 8YSZ plus La₂Zr₂O₇ coatings show a better performance in thermal cycling experiments. It is likely because porous 8YSZ serves as a buffer layer to release stress.     

时效及冷热循环对Al2O3增强2A12铝合金尺寸稳定性的影响

采用压铸方法制备了体积分数为30%的Al₂O₃/2A12复合材料,对其残余应力松弛及尺寸变化进行了研究,分析了时效和冷热循环处理对复合材料尺寸稳定性的影响规律。结果表明,复合材料的残余应力松弛量随时效时间的延长而增加;冷热循环处理不仅能导致高密度位错的形成,还能够促进时效析出,并能够降低复合材料中的残余应力,从而提高了复合材料在交变温度场下的尺寸稳定性。伴随着冷热循环处理循环下限温度的降低,即上下限温差越大,复合材料中的残余应力持续减小,微变形抗力提高,对基体析出的加速作用增大,复合材料的尺寸稳定性获得明显改善。本文提出的3种工艺中,160℃×10 h时效+（-196～160℃）冷热循环4次是提高Al₂O₃/2A12复合材料尺寸稳定性的最佳工艺。      

Impact of Thermal Cycling on Sn-Ag-Cu Solder Joints and Board-Level Drop Reliability

The electronic packaging industry uses electroless nickel immersion gold (ENIG) or Cu-organic solderability preservative (Cu-OSP) as a bonding pad surface finish for solder joints. In portable electronic products, drop impact tests induce solder joint failures via the interfacial intermetallic, which is a serious reliability concern. The intermetallic compound (IMC) is subjected to thermal cycling, which negatively affects the drop impact reliability. In this work, the reliability of lead-free Sn-3.0Ag-0.5Cu (SAC) soldered fine-pitch ball grid array assemblies were investigated after being subjected to a combination of thermal cycling followed by board level drop tests. Drop impact tests conducted before and after thermal aging cycles (500, 1000, and 1500 thermal cycles) show a transition of failure modes and a significant reduction in drop durability for both SAC/ENIG and SAC/Cu-OSP soldered assemblies. Without thermal cycling aging, the boards with the Cu-OSP surface finish exhibit better drop impact reliability than those with ENIG. However, the reverse is true if thermal cycle (TC) aging is performed. For SAC/Cu-OSP soldered assemblies, a large number of Kirkendall voids were observed at the interface between the intermetallic and Cu pad after thermal cycling aging. The void formation resulted in weak bonding between the solder and Cu, leading to brittle interface fracture in the drop impact test, which resulted in significantly lower drop test lifetimes. For SAC/ENIG soldered assemblies, the consumption of Ni in the formation of NiCuSn intermetallics induced vertical voids in the Ni(P) layer.     

烧结生产节能潜力解析

由于烧结过程中热量沿料层厚度方向分布的不合理,导致烧结矿成品率低,返矿量高,导致设备磨损,能耗大。烧结生产有巨大的节能潜力,节能措施就是开发新的工艺技术,最大限度地改变或减小焙烧过程的非均匀性,提高烧结生产的成品率,如进行热量补偿与保温的复合焙烧技术、改变燃料的配加工艺等。     

对我国硫铁矿资源开发及利用的思考

在分析我国硫铁矿开发利用的历史和现状的基础上,针对硫铁矿资源的特点,提出了硫铁矿综合开发利用循环产业链,并给出了产业链建设的原则方法和措施建议。本文的研究观点和结论,将对拥有丰富硫铁矿等矿产资源的地区,研究规划可持续利用资源,发展当地工业经济,具有一定的参考价值。     

热机械循环对B/Al复合材料拉伸性能及显微结构的影响

热机械循环是复合材料所面临的苛刻空间环境因素.对B/Al复合材料进行温度变化范围为-125～125℃,外加拉伸载荷为30MPa的热机械循环试验,通过室温拉伸试验测量了B/Al复合材料的拉伸性能,利用SEM及TEM分析了复合材料的拉伸断口形貌及显微结构,研究了热机械循环对B/Al复合材料拉伸性能及显微结构的影响.研究表明,热机械循环造成了B纤维与Al基体之间界面的弱化,产生了可测的弹性模量的降低;同时,引起基体塑性应变,造成基体内位错密度增加.在热机械循环初期,B/Al复合材料的抗拉强度是增加的,但随即随热机械循环周次的增加而下降.     

Durability study of Pt–Pd/C as PEMFC cathode catalyst

In this paper, Pt–Pd/C and Pt/C catalysts were evaluated and compared. The catalysts were evaluated as oxygen reduction reaction (ORR) catalysts in half cell test under potential cycling, and cathode catalysts in single cell test under dynamic loading simulating the vehicle operation. Physical and electrochemical techniques were applied to investigate the structure, performance and durability of those catalysts. The electrochemical active surface area (ECA) loss, particle size distribution, polarization behavior and electrochemistry impedance spectroscopy (EIS) suggested that the Pt–Pd/C showed a better durability than Pt/C.     

Synergistic effects of novel battery manufacturing processes for lead–acid batteries. Part I: Charge/discharge cycling of batteries

The present research aimed to ascertain if the merging of novel battery manufacturing processes could achieve an enhancement in the improvement of battery cycle-life. We found that the melding of novel battery manufacturing processes leads to synergistic effects with regard to the cycling performance of lead–acid batteries. The novel battery manufacturing processes employed in this study include: (i) grid cleaning; (ii) positive active material compression; and (iii) conductive additives in the positive paste. It was found that a combination of positive active material compression and grid cleaning approximately doubles the durability of batteries and is consistent with the additive effects of the individual treatments, while a combination of positive active material compression and conductive additives yields an approximate 30% boost in performance compared to the additive effects of the isolated treatments. Synergistic effects were not noted for other combinations of the aforementioned battery manufacturing practices.     

Thermomechanical failures in microelectronic interconnects

Thermomechanical fatigue failures are an important class of failures in microelectronic interconnect structures. Thermomechanical stresses arise from differences in the coefficients of thermal expansion of the various materials comprising a microelectronics circuit. Polymer dielectrics and adhesives have larger coefficients of expansion than metal conductors. Dielectrics and adhesives may also exhibit large anisotropy in the coefficient of expansion, producing significant thermomechanical stresses in vias or other metal interconnect structures. During ambient thermal cycling or operational power dissipation, cyclic stresses are induced, which cause fatigue failures. The basic elements of thermomechanical fatigue behavior of microelectronic interconnect structures, such as lines and vias, are presented in this paper. In addition, a case study illustrating many of the concepts is presented for a complex 3-D interconnect.