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排序方式: 共有229条查询结果,搜索用时 93 毫秒
191.
Junting Xu Linxian Feng Shilin Yang Yinan Wu Yiqing Yang Xiangming Kong 《Macromolecular rapid communications》1996,17(9):645-651
Poly(propylene) samples produced by heterogeneous Ziegler-Natta catalysts containing different internal electron donors were fractionated by using temperature rising elution fractionation; some key fractions were analyzed with 13C NMR. It was found that internal electron donors with different structures can convert aspecific active sites into different isospectrific ones. The employment of bis(2-ethylhexyl) phthalate as internal electron donor leads to chemically inverted structures in the atactic fraction. This suggests that an internal electron donor may also exist in the environment of aspecific active sites. 相似文献
192.
锂离子电池锡基合金体系负极研究 总被引:1,自引:0,他引:1
综述了锂离子电池锡基金属间化合物和复合物负极的研究进展。介绍了锡基合金体系作锂离子电池负极的优势, 指出了锡金属负极的不足,提出了采用锡基合金及其复合物是克服锡金属负极主体材料尺寸稳定问题的解决办法。概述了各种锡基合金和其复合物的结构、电化学性能、相应的加工方法和某些反应机理,总结了这些材料的优点和缺点,提出了改进这些材料性能的一些建议,如采用分散形态的纳米颗粒结构或用非晶合金并控制形态结构的转变,着重指出多相锡基锂合金复合物是最有前景的负极材料。 相似文献
193.
高效液相色谱荧光测定及质谱鉴定土壤和苔藓中的脂肪酸 总被引:1,自引:0,他引:1
以吖啶酮-9-乙基对甲苯磺酸酯(AETS)作荧光衍生化试剂,建立了灵敏、简单的游离脂肪酸反相高效液相色谱测定方法。在Ec lipse XDB-C8色谱柱上,实现了19种游离脂肪酸(FFA)衍生物的完全基线分离。选取AETS摩尔数为脂肪酸的6倍,以DMF作溶剂,在85℃条件下以K2CO3作催化剂可获得稳定的荧光产物,条件温和、衍生产率高。利用柱后在线串联质谱以APC I大气压化学电离源正离子模式实现了各组分的质谱定性。对土壤和3种苔藓植物中(树藓、狭叶绢藓、曲尾藓)FFA组分定量结果表明,苔藓植物从土壤中富集了大量的游离脂肪酸。荧光检测的激发和发射波长分别为404 nm和440 nm。绝大多数脂肪酸的线性相关系数大于0.9996,检出限为12.3~43.7 fmol。本方法具有良好的重现性,用于实际样品测定,结果满意。 相似文献
194.
Electrolyte is essentially important for electrochemical and safety performance of batteries. The pseudoconcentrated electrolyte, with lean solvent but anion-involved solvation sheath and heterogeneous long-range structure, endows the electrolyte with superior interfacial properties and the bulk properties, enabling the high-voltage lithium-ion battery, lithium-metal battery, and sodium battery with outstanding electrochemical performances. Nonflammable solvents as diluent in the pseudoconcentrated electrolyte can reach 30–60% by volume share, making the electrolyte nonflammable and then showing great possibility in mitigating the thermal runaway of the battery. As a new family of liquid electrolyte, nonflammable pseudoconcentrated electrolyte is promising for high safety and high energy density secondary batteries. 相似文献
195.
Delayed crosslinking polymer gel systems are widely used in-depth profile control technology for water production control. In this paper, an amphiphilic polymer P(AM-NaA-DDAM) was synthesized by a free radical micellar polymerization method and a delayed crosslinking amphiphilic polymer gel system was prepared based on multiple emulsion of W1/O/W2 emulsion which was prepared by a two-step emulsification method. The optimized formulation of amphiphilic polymer gel systems is: 0.15% P(AM-NaA-DDAM), 0.3% methenamine, 0.02% resorcinol, and 0.3% citric acid. The delayed gelation time of the delayed crosslinking amphiphilic polymer gel system is closely related to the stability of the W1/O emulsion. By using multiple emulsion delayed crosslinking method, the delayed crosslinking amphiphilic polymer gel system with diesel as the oil phase can delay the gelation time up to 168 hours. 相似文献
196.
In an effort to reduce thermal shrinkage and improve electrochemical performance of porous polypropylene (PP) separators for lithium-ion batteries, a new composite separator is developed by introducing ceramic coated layers on both sides of PP separator through a dip-coating process. The coated layers are comprised of heat-resistant and hydrophilic silica nanoparticles and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) binders. Highly porous honeycomb structure is formed and the thickness of the layer is only about 700 nm. In comparison to the pristine PP separator, the composite separator shows significant reduction in thermal shrinkage and improvement in liquid electrolyte uptake and ionic conduction, which play an important role in improving cell performance such as discharge capacity, C-rate capability, cycle performance and coulombic efficiency. 相似文献
197.
Xiuyi Zhu Shenshen Jin Shuxin Wang Dr. Xiangming Meng Changwei Zhu Prof. Dr. Manzhou Zhu Prof. Dr. Rongchao Jin 《化学:亚洲杂志》2013,8(11):2739-2745
We report two synthetic routes for concurrent formation of phenylmethanethiolate (‐SCH2Ph)‐protected Au20(SR)16 and Au24(SR)24 nanoclusters in one‐pot by kinetic control. Unlike the previously reported methods for thiolate‐protected gold nanoclusters, which typically involve rapid reduction of the gold precursor by excess NaBH4 and subsequent size focusing into atomically monodisperse clusters of a specific size, the present work reveals some insight into the kinetic control in gold–thiolate cluster synthesis. We demonstrate that the synthesis of ‐SCH2Ph‐protected Au20 and Au24 nanoclusters can be obtained through two different, kinetically controlled methods. Specifically, route 1 employs slow addition of a relatively large amount of NaBH4 under slow stirring of the reaction mixture, while route 2 employs rapid addition of a small amount of NaBH4 under rapid stirring of the reaction mixture. At first glance, these two methods apparently possess quite different reaction kinetics, but interestingly they give rise to exactly the same product (i.e., the coproduction of Au20(SCH2Ph)16 and Au24(SCH2Ph)20 clusters). Our results explicitly demonstrate the complex interplay between the kinetic factors that include the addition speed and amount of NaBH4 solution as well as the stirring speed of the reaction mixture. Such insight is important for devising synthetic routes for different sized nanoclusters. We also compared the photoluminescence and electrochemical properties of PhCH2S‐protected Au20 and Au24 nanoclusters with the PhC2H4S‐protected counterparts. A surprising 2.5 times photoluminescence enhancement was observed for the PhCH2S‐capped nanoclusters when compared to the PhC2H4S‐capped analogues, thereby indicating a drastic effect of the ligand that is merely one carbon shorter. 相似文献
198.
Zhang Xiangming Niu Guodong Ma Nianke Fan Hualin Zhao Yong Yang Wei 《Acta Mechanica Solida Sinica》2007,20(3):189-197
In vivo experiments of screwing the electrode of canine hearts and assigning external excitation on the lead-myocardium interface was carried out to evaluate the lead/myocardium adherence safety.The electrode is specially designed to host a measurement unit of strain gauges. We obtained the lead/heart interactions data from 12 dogs under natural heart beating and beating with external excitations.The data recorded from the acute phase and the chronic phase of pulling out pacing leads were compared with each other.The electrode/heart interaction is caused by the heart beat and influenced by the lung breath.This process induced tolerable damage to the lead or myocardium.The interaction decreases as the frequency of external excitations increases.The lead is more likely to be detached from myocardium under higher excitation frequency.At the same implanting sites,safer pacing lead/myocardium attachment can be realized in the chronic tests than in the acute tests. 相似文献
199.
Shuxin Wang Xiangming Meng Anindita Das Tao Li Yongbo Song Tiantian Cao Xiuyi Zhu Manzhou Zhu Rongchao Jin 《ChemInform》2014,45(22):no-no
Two series of Ag‐doped AgxAu25‐x nanoclusters are prepared by two different routes. 相似文献
200.
Jiangang Li Xiangming He Maosong Fan Chunrong Wan Changin Jiang Shichao Zhang 《Ionics》2006,12(2):153-157
Capacity fading of LiCr0.1Mn1.9O4 /MPCF (mesophase pitch-based carbon fiber) cells was investigated at elevated temperature (55 °C). The cells showed very fast capacity fading, keeping only 60% of capacity retention at the 100th cycle at 55 °C. The cycled electrodes and the electrolyte were analyzed using electrochemical test, inductively coupled plasma, and X-ray diffraction. Results of the analyses indicated that LiCr0.1Mn1.9O4 exhibited good effects on restraint of Mn dissolution and stabilization of structure at 55 °C. The cycled LiCr0.1Mn1.9O4 electrode and the cycled MPCF electrode presented good electrochemical performance again with fresh electrolyte. Therefore, it was proposed that the cycling fading of LiCr0.1Mn1.9O4/MPCF cells was mainly caused by decomposition of electrolyte upon LiCr0.1Mn1.9O4 electrode during cycling. It was found that the decomposition of electrolyte led to the formation of a surface layer comprised of Li2CO3, Li
x
PF
y
, CH3OCO2Li or (CH2OCO2Li)2, polymeric ether etc. The formation of this film consumed active lithium ions, leading to fast capacity fading of LiCr0.1Mn1.9O4/MPCF cell at elevated temperature. 相似文献