The effects of Ni and Li doping on the performance of lithium manganese oxide material for lithium secondary batteries

Layered Li_0.7[M_1/6Mn_5/6]O₂ (M=Li, Ni) was synthesized using a sol-gel method. P2-Na_0.7[M_1/6Mn_5/6]O₂ precursor was first synthesized by a sol-gel method, and then O2-Li_0.7[M_1/6Mn_5/6]O₂ was prepared by an ion exchange of Li for Na in P2-Na_0.7[M_1/6Mn_5/6]O₂ precursor. From charge/discharge curves, it was seen that Li_0.7[Li_1/6Mn_5/6]O₂ has two plateaus similar to those observed from a spinel structure, but Li_0.7[Ni_1/6Mn_5/6]O₂ holds a single plateau as observed from a typical layered structure. It was considered that Li_0.7[Li_1/6Mn_5/6]O₂ undergoes a phase transformation from layered to spinel structure during the charge/discharge cycle, but Li_0.7[Ni_1/6Mn_5/6]O₂ maintains O2-layered structure after the cycles. Li_0.7[Ni_1/6Mn_5/6]O₂ was higher in discharge capacity and retention rate than Li_0.7[Li_1/6Mn_5/6]O₂.     

A porous mixed-valent iron MOF exhibiting the acs net: Synthesis, characterization and sorption behavior of Fe3O(F4BDC)3(H2O)3·(DMF)3.5

A new mixed-valent iron MOF, formulated as Fe₃O(F₄BDC)₃(H₂O)₃·(DMF)_3.5 (1), has been synthesized by using a perfluorinated linear dicarboxylate to link trigonal prismatic Fe₃(μ³-O)(O₂C–)₆ clusters. The structure refinement based on single crystal X-ray diffraction data collected from 1 reveals the material exhibits the acs topology with large channels along the crystallographic c-axis. Due to the presence of fluorine atoms the organic link, 2,3,5,6-tetrafluorobenzene-1,4-dicarboxylate (F₄BDC), has a 63° torsion angle between the carboxylate and aromatic planes, resulting in larger channels compared to those in the isoreticular material MOF-235. While few iron-based MOFs have demonstrated porosity, nitrogen and hydrogen sorption experiments carried out at 77 K proved the porosity of outgassed 1, which has a Langmuir surface are of 635 m²/g and a gravimetric capacity of 0.9 wt% of hydrogen at 1 bar.     

Effects of melt‐extension and annealing on row‐nucleated lamellar crystalline structure of HDPE films

The row‐nucleated lamellar crystalline structure of high‐density polyethylene (HDPE) films was prepared by applying elongation stress to HDPE melt during T‐die cast film extrusion and subsequently annealing the extruded films. This unusual crystalline structure was analyzed in terms of lamellar crystalline orientation, long‐period lamellar spacing, crystallite size, and degree of crystallinity. The contribution of melt‐extension represented by draw‐down‐ratio (DDR) to the overall orientation was found to be most noticeable than other processing variables. Meanwhile, the long‐period lamellar spacing, the crystallite size, and the degree of crystallinity were influenced predominantly by the annealing temperature. Finally, the processing (melt extension and annealing temperature) – structure (lamellar crystalline structure) – property (hard elasticity) relationship of HDPE films was investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3326–3333, 2007     

The removal of hydrogen sulfide with manganic sorbent in a high-temperature fluidized-bed reactor

The removal of hydrogen sulfide (H₂S) from simulated gas was carried out in a batch type fluidized-bed reactor using natural manganese ore (NMO), which consists of several metal oxides (MnO_x: 51.85%, FeO_y: 3.86%, CaO: 0.11%). The H₂S breakthrough curves were obtained by changing temperature, gas velocity, initial H₂S concentration, and aspect ratio. Moreover, the effects of the particle size and the particle-mixing fraction on H₂S removal were investigated in a binary system of different particle size. From this study, H₂S removal efficiency increased with increasing temperature but decreased with increasing excess gas velocity. The breakthrough time for H₂S decreased as the gas velocity increased, which leads to reducing gas-solid contacting due to gas bypassing in a fluidized bed reactor. Improvement of H₂S removal efficiency in continuous process can be expected from the results of the binary particle system with different size in a batch experiment. The NMO could be considered as a potential sorbent in H₂S removal.     

Advanced underfill for high thermal reliability

The key to the success of flip‐chip technology lies in the availability of sucessful underfill materials. However, the reliability of flip‐chip technology using current underfill materials is generally found to be lower than that of conventional wire‐bond connection packaging materials such as epoxy molding compound (EMC) because of the high coefficients of thermal expansion (CTE) and moisture absorption of cured underfill material. In this study desbimide (DBMI), which has a low melting point (about 80°C), was used in the underfill materials as a cohardener. As a result, DBMI‐added underfill can show excellent thermal reliability, which is due to the superior properties of the CTE, the elastic modulus, and water resistance. When the properties of a 2 wt % DBMI‐added underfill were compared with those of a typical underfill (epoxy/anhydride), the CTE value was reduced to less than one‐half at the solder reflow temperature (about 200°C), the elastic modulus was reduced to less than one‐half in the temperature region below the glass‐transition temperature, and the water resistance was improved twofold. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2617–2624, 2002     

构筑中控系统网络安全体系探析

中控系统网络化给广播电台提供了更灵活、功能更强大的中控传输系统,使得安全备份系统完善可靠,节目通道任意调配,状态信息实时掌握和控制处理手段多样灵活。本文着重阐述了中控系统网络化的基础框架、系统网络化的技术实现及功能特点。     

Characterization and preparation of new multiwall carbon nanotube/conducting polymer composites by in situ polymerization

Composites based on poly(diphenyl amine) (PDPA) and multiwall carbon nanotubes (MWNTs) were prepared by chemical oxidative polymerization through two different approaches: in situ polymerization and intimate mixing. In in situ polymerization, DPA was polymerized in the presence of dispersed MWNTs in sulfuric acid medium for different molar composition ratios of MWNT and DPA. Intimate mixing of synthesized PDPA with MWNT was also used for the preparation of PDPA/MWNT composites. Transmission electron microscopy revealed that the diameter of the tubular structure for the composite was 10–20 nm higher than the diameter of pure MWNT. Scanning electron microscopy provided evidence for the differences in the morphology between the MWNTs and the composites. Raman and Fourier transform IR (FTIR) spectroscopy, thermogravimetric analysis, X‐ray diffraction, and UV–visible spectroscopy were used to characterize the composites and reveal the differences in the molecular level interactions between the components in the composites. The Raman and FTIR spectral results revealed doping‐type molecular interactions and coordinate covalent‐type interactions between MWNT and PDPA in the composite prepared by in situ polymerization and intimate mixing, respectively. The backbone structure of PDPA in the composite decomposed at a higher temperature (>340°C) than the pristine PDPA (～300°C). This behavior also favored the molecular level interactions between MWNT and PDPA in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3721–3729, 2006     

Synthesis of polystyrene/poly(butyl acrylate) core–shell latex and its surface morphology

A polystyrene (PS)/poly(butyl acrylate) (PBA) composite emulsion was produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles which were prepared by emulsifier‐free polymerization of styrene with potassium persulfate (KPS) under a nitrogen atmosphere at 70°C for 24 h with stirring at 60 rpm and swelled with the BA monomer in an ethanol/water medium. The structure of the PS/PBA composite particles was confirmed by the presence of the characteristic absorption band attributed to PS and PBA from FTIR spectra. The particles for pure PS and PS/PBA with a low content of the BA monomer were almost spherical and regular. As the BA monomer content was increased, the particle size of the PS/PBA composite particles became larger, and more golf ball‐like particles were produced. The surface morphology of the PS/PBA composite particles was investigated by AFM and SEM. The T_g's attributed to PS and PBA in the PS/PBA composite particles were found at 110 and ?49°C, respectively. The thermal degradation of the pure PS and PS/PBA composite particles occurred in one and two steps, respectively. With an increasing amount of PBA, the initial thermal decomposition temperature increased. On the contrary the residual weight at 450°C decreased with an increasing amount of PBA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 595–601, 2003     

Thermal runaway prevention in catalytic packed bed reactor by solid temperature measurement and Control

Magnetic crystallite thermometry has been used to measure the average nickel crystallite temperature in packed bed reactors during ethane hydrogenolysis, an exothermic reaction. The technique is based on the temperature dependence of the magnetic moment of dispersed nickel catalysts. Measurement of the average catalyst temperature is very useful for reactor control because of its shorter time constant compared with exit fluid temperature. Bed temperature control based on the exit fluid temperature, which has often been used as a control variable, is too slow to protect thermal runaway of the bed. The advantage of short time constant by measuring the average catalyst temperature has been incorporated with enhanced feedback control system to control the bed temperature and prevent the thermal runaway of the catalyst bed. An enhanced feedback control structure with supervisory action performed better than the classical proportional-integral control in runaway prevention when the two control schemes were compared with each other on the basis of the trippoint (incipient thermal runaway).     

GNSS接收机多径抑制性能检测技术

多径干扰信号会导致GNSS接收机伪距、载波相位和多普勒等测量精度降低,多径信号对GNSS接收机观测数据的影响与多径信号的延迟、幅度、相位等特性参数有关,造成的伪距测量误差高于载波相位测量误差2个数量级。多径抑制是GNSS接收机关键性能指标之一,GNSS接收机主要从试验室模拟环境和实际工作环境两方面检测多径抑制性能,多径误差包络检测技术利用模拟导航信号源完成多径抑制性能检测,码减载波和多径误差分析都是通过接收观测卫星导航信号并进行数据分析完成多径抑制性能的检测。