锂离子电池正极材料LiMn2-xSrxO4的制备与电化学性能研究

采用固相分段煅烧的方法合成了具有尖晶石结构的锂离子电池正极材料LiMn2-xSrxO4（x=0.0、0.05、0.1）,并利用X射线衍射、IR光谱、SEM、充放电、交流阻抗测试对材料进行了表征.结果表明,所合成的锶掺杂改性材料仍具有标准的尖晶石结构,但结晶度有所下降,晶格发生收缩.当x=0.05时,掺杂锶的改性材料LiMn2-xSrxO4具有优异的循环性能,在0.2 C放电速率下,其首次放电容量为116.4 mAh/g,循环20次后,容量保持率超过98%.少量锶的掺杂能使材料循环性能得到大副提高,与锶掺杂引起的结构稳定性提高有关,这说明改善材料结构稳定性对抑制循环过程中容量衰减有重要作用.     

LiMn1.8Co0.2O3.95F0.05的络合燃烧法合成及其性质研究

以醋酸锂、醋酸锰、醋酸钴、氟化锂、柠檬酸及乙二醇为原料，采用燃烧辅助有机酸络合法合成LiMn1．8Co0．2O3．95F0．05，用X射线衍射检测和分析产物的物相及晶格常数，用循环伏安、交流阻抗技术研究产物的氧化-还原及界面过程，用恒流充放电测试产物的容量及循环性能。研究表明，各条件下合成的LiMn1．8Co0．2O3．95F0．05粉末的X射线衍射峰强度大、峰尖锐，粉末具有良好的结晶性LiMn1．8Co0．2O3．95F0．05容量随热处理温度的升高而增大，即由750℃热处理4h的92mAh／g升高到850℃热处理4h的105mAh／g。相对LiMn2O4而言，LiMn1．8Co0．2O3．95F0．05的初始容量虽略有下降，但双掺杂后的循环性能得到了显著提高。     

超声辅助TiO2包覆尖晶石LiMn2O4及电化学性能研究

采用超声辅助溶液法在尖晶石LiMn2O4表面包覆TiO2.通过X射线衍射、扫描电子显微镜、恒电流充放电、交流阻抗技术分析合成材料的结构、形貌及电化学性能.结果表明:TiO2包覆LiMn2O4与LiMn2O4具有相似的X射线衍射结果,衍射峰尖锐,样品颗粒大小均匀,无明显团聚.室温下0.2C充放电时,表面包覆1％TiO2的LiMn2O4首次放电比容量为123.51 mAh·g-1,略低于未包覆LiMn2O4的124.02 mAh·g-1,但在2C和4C高倍率时,表面包覆1％TiO2的LiMn2O4比容量分别为105.54和80.73 mAh·g-1,远高于未包覆的79.76和66.37 mAh·g -1.室温及55℃下以0.2C倍率循环50后,表面包覆1％ TiO2的LiMn2O4容量保持率分别为91.69％和87.36％,远高于未包覆LiMn2O4的86.58％和78.02％.室温下以1C倍率循环100次后,表面包覆1％ TiO2的容量保持率比未包覆LiMn2O4高出3.75％.表面包覆TiO2后LiMn2O4的循环性能得到了大大的提高,尤其是高温循环性能.     

微波法制备锂离子电池正极材料LiFePO4的研究

采用微波法制备锂离子电池正极材料LiFePO4，通过X射线衍射（XRD）、扫描电镜（SEM）、循环伏安和恒电流充放电测试等方法对材料的结构、表观形貌及电化学性能进行表征，考察了葡萄糖、导电碳黑等不同碳源对目标材料性能的影响。结果表明，采用微波法能快速简便地制备出均相LiFePO4；于0．1C倍率下，以葡萄糖作为碳源的正极材料首次放电比容量可达131．1mA·h／g，充放电30次循环后，容量损失率为2．1％；以导电炭黑作为碳源的正极材料首次放电比容量为118．3mA·h／g，充放电30次循环后，容量损失率为5．2％。     

尖晶石LiMn2O4表面包覆氧化钴的研究

采用高温固相法合成尖晶石LiMn2O4,并以化学沉积方式对其进行包覆氧化钴的表面处理。通过X射线衍射（XRD）、扫描电镜（SEM）等技术对表面处理前后的LiMn2O4进行表征,分析了表面处理后LiMn2O4物理特性的变化,并结合电化学性能测试,研究了表面处理及其工艺和条件对LiMn2O4电化学容量与循环性能的影响。结果表明,表面处理后LiMn2O4循环性能显著提高。随氧化物含量的增加,循环性能提高,容量降低。未经表面包覆的LiMn2O4首次充放电容量为108．13mAh／g,50次循环充放电后容量衰减26．3％。500℃加热处理的表面包覆0．5％、2％氧化钴的LiMn2O4首次循环放电容量各为118．38mAh／g、115mAh／g,经过50次充放电循环后,容量分别降低8％、7％。     

Co掺杂对锂离子电池材料LiMn_2O_4性能的影响

采用高温固相法和溶胶-凝胶法制备LiCoXMn2-XO4(x=0,0.05,0.1,0.2),研究了掺杂Co后,材料的相结构和充放电性能,并与LiMn2O4相对比.结果表明:掺杂Co后材料的充放电性能相对LiMn2O4均有所提高;两种方法制备的LiCoXMn2-XO4循环40次后,容量保持率、放电比容量均优于LiMn2O4;且当x=0.05时,两种方法制备的LiCoXMn2-XO4的充放电性能均明显优于x=0.1和x=0.2时.     

锂离子电池正极材料LiMn2O4的改性研究

为改善尖晶石LiMn2O4的循环性能，采用高温固相法合成了由Li2CO3改性的尖晶石锂锰氧化物，研究了Li2CO3添加量对LiMn2O4性能的影响。通过XRD，Rietveld精细XRD分析和模拟电池等方法对产物的结构和电化学性能进行了表征与测试。结果表明，部分Li进入到尖晶石LiMn2O4的晶格中，增强了材料充放电循环过程中的结构稳定性。随着Li2CO3量的增加，产物的循环稳定性增加。当Li2CO3的加入量为0．06摩尔比时，10次循环后的高温容量衰减由改性前的15％降低到6．8％。     

Co掺杂对锂离子电池材料LiMn2O4性能的影响

采用高温固相法和溶胶-凝胶法制备LiCoXMn2-XO4（x=0,0.05,0.1,0.2）,研究了掺杂Co后,材料的相结构和充放电性能,并与LiMn2O4相对比.结果表明：掺杂Co后材料的充放电性能相对LiMn2O4均有所提高;两种方法制备的LiCoXMn2-XO4循环40次后,容量保持率、放电比容量均优于LiMn2O4;且当x=0.05时,两种方法制备的LiCoXMn2-XO4的充放电性能均明显优于x=0.1和x=0.2时.     

S-Y复合掺杂LiMn2O4的电化学性能研究

用高温固相反应法合成了锂离子电池正极材料锂锰氧化物，并对其进行了硫、钇掺杂厦硫和钇的复合掺杂修饰。对材料进行了X射线衍射、恒电流充放电、交流阻抗等测试。实验结果表明：固相反应法合成的硫和钇复合掺杂的材料具有标准尖晶石结构；掺杂硫其首次放电容量达196．1mAh／g，但容量衰减较快；掺杂钇后正极材料在0．2C充放电速率下，循环20次后容量保持率为98．6％，但是初始容量较低；而硫钇复合掺杂综合了硫掺杂效应和钇掺杂效应，有较好的电化学性能。     

锂离子电池正极材料LiMn2-xNdxO4的性能研究

采用高温固相反应法,合成了具有尖晶石结构的锂离子电池正极材料LiMn2O4,并对其掺杂不同量的Nd,得到LiMn2-xNdxO4(x=0～0.03).对材料进行了XRD、粒度分析及恒电流充放电测试.试验结果表明,掺杂微量稀土元素Nd合成的正极材料具有标准尖晶石结构,较好的循环稳定性.其中LiMn0.995Nd0.005O4具有较好的电化学性能和循环稳定性,最高容量达到132mAh·g-1.     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

Results of treatment of cancer of the cardia

Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients.     

焦炭热性能指标意义浅析

通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of rates of infection of two methods of emergency ventricular drainage

The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.     

浅析《野草》的版画特征

鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美".     

四辊破碎机车刀架的改造

针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。     

Effect of antibiotics of chemotaxis of human leukocytes

The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed.