Decoding Li+/Na+ Exchange Route Toward High-Performance Mn-Based Layered Cathodes for Li-Ion Batteries

Li⁺/Na⁺ exchange has been extensively explored as an effective method to prepare high-performance Mn-based layered cathodes for Li-ion batteries, since the first report in 1996 by P. G. Bruce (Nature, 1996. 381, 499–500). Understanding the detailed structural changes during the ion-exchange process is crucial to implement the synthetic control of high-performance layered Mn-based cathodes, but less studied. Herein, in situ synchrotron X-ray diffraction, density functional theory calculations, and electrochemical tests are combined to conduct the systemic studies into the structural changes during the ion-exchange process of an Mn-only layered cathode O3-type Li_0.67[Li_0.22Mn_0.78]O₂ (LLMO) from the corresponding counterpart P3-type Na_0.67[Li_0.22Mn_0.78]O₂ (NLMO). The temperature-resolved observations combined with theoretical calculations reveal that the Li⁺/Na⁺ exchange is favorable thermodynamically and composited with two tandem topotactic phase transitions: 1) from NLMO to a layered intermediate through ≈60% of Li⁺/Na⁺ exchange. 2) then to the final layered product LLMO through further Li insertion. Moreover, the intermediate-dominate composite is obtained by slowing down the exchange kinetics below room temperature, showing better electrochemical performance than LLMO obtained by the traditional molten-salt method. The findings provide guides for the synthetic control of high-performance Mn-based cathodes under mild conditions.     

模型毒物急性毒性尿液核磁共振氢谱标记物的二阶段聚类分析

采用现代核磁共振技术,通过分析给药肝、肾损伤模型化合物异硫氰酸α-萘酯(灌胃150 mg/kg体重)和二溴乙胺氢溴酸盐(腹腔注射250 mg/kg体重)24 h内W istar大鼠尿液的1H NMR谱,由尿液中内源性代谢物浓度变化研究了肝、肾模型毒物在大鼠体内的急性毒性。首次利用模式识别技术中的二阶段聚类分析方法解析大鼠尿液1H NMR谱确定了模型化合物尿液1H NMR标记物。结果表明,应用核磁共振和二阶段聚类分析相结合的方法,可提供模型化合物毒性比较清楚的认识。该方法也可用于金属化合物、中药及其它药物的毒性分类和预测研究以及建议各类靶向毒性的NMR标记物。     

CVD两步法生长ZnO薄膜及其光致发光特性

用CVD两步法在常压下于p型Si(100)衬底上沉积出具有较好择优取向的多晶ZnO薄膜。在325nm波长的光激发下,室温下可观察到显著的紫外光发射(峰值波长381nm)。高温退火后氧空位缺陷浓度增加,出现了一个450~600nm的绿光发光带,发光峰值在510nm。作为比较,用一步法生长的ZnO薄膜结晶质量稍差。在其PL谱中不仅有峰值波长389nm的紫外发射而且还出现了一个很强的蓝光发光中心(峰值波长437nm),退火后同样产生绿光发光带。对这两种绿光发光带的发光机制进行了研究,认为前者源于VO,而后者与O_Zn有密切的关系。     

硫化亚锡有序纳米孔道阵列薄膜的制备与表征

以阳极氧化铝为模板,采用两步复型技术首次制备了一种SnS有序纳米孔道阵列薄膜。SEM和TEM测试结果显示此SnS有序多孔薄膜具有几乎均一的、紧密堆积的、直形的纳米孔道阵列结构,孔道直径约200mm,长度约1μm。EDS,XPS和XRD分析结果表明此SnS有序多孔薄膜的SnS骨架具有正交SnS的晶体结构,薄膜中锡与硫的原子比接近化学计量比1:1。     

分步晶化法合成ZSM-5/SAPO-5复合材料

通过分步晶化水热处理的方式合成了ZSM-5/SAPO-5复合材料。研究了两种分子筛凝胶的混合方式、调节ZSM-5母液的酸类型、SAPO-5凝胶组成以及晶化时间对复合材料形成的影响。实验结果表明,简单将两种分子筛的合成凝胶混合不能得到复合材料。采用H₂SO₄调节ZSM-5合成母液的pH值,在ZSM-5与SAPO-5理论质量比为3.5、SAPO-5凝胶中P₂O₅与Al₂O₃摩尔比为1.2的条件下可以得到ZSM-5/SAPO-5复合材料。但样品中含有少量无定形物质,这些无定形通过延长晶化时间并不能完全消除。     

模型毒物急性毒性尿液核磁共振氨谱标记物的二阶段聚类分析

采用现代核磁共振技术，通过分析给药肝、肾损伤模型化合物异硫氰酸α-萘酯（灌胃150mg／kg体重）和二溴乙胺氢溴酸盐（腹腔注射250mg／kg体重）24h内Wistar大鼠尿液的^1H NMR谱，由尿液中内源性代谢物浓度变化研究了肝、肾模型毒物在大鼠体内的急性毒性。首次利用模式识别技术中的二阶段聚类分析方法解析大鼠尿液^1H NMR谱确定了模型化合物尿液^1H NMR标记物。结果表明，应用核磁共振和二阶段聚类分析相结合的方法，可提供模型化合物毒性比较清楚的认识。该方法也可用于金属化合物、中药及其它药物的毒性分类和预测研究以及建议各类靶向毒性的NMR标记物。     

On Occupation Times for Compound Poisson Risk Model with Two-Step Premium Rate

In this paper, we consider the classical compound Poisson risk model with two-step premium rate. Using an alternative approach, we find the explicit expressions for the Laplace transforms of joint occupation times over disjoint intervals for this model. The Laplace transforms are expressed in terms of scale functions of L\'{e}vy processes.     

A data optimization test technique for characterizing embedded ADCs

A novel data optimization test technique is presented which utilizes a BIST structure, an ADC model and histogram data to characterize embedded ADCs. A practical 8 bit ADC is modeled and then characterized using 20% less data points then conventional analysis with a 78% reduction in the amount of data required to be shifted off-chip. Comparisons between theoretical, modeled and practical results are also made in the paper.     

LiYF4:Nd3+中脉冲光泵浦的上转换蓝光

本文报道利用578.4nm的脉冲光泵浦,在室温和77K下,观察到LiYF4:Nd3+单晶中的上转换蓝光。由发光强度与泵浦光强度平方的直线关系,确定此上转换过程是双光子过程.通过对吸收谱和激发谱以及衰减曲线的研究,确定其上转换激发机制为两步激发和能量传递上转换。     

两步投影对变分不等方程组解的迭代逼近

本文研究Hilbert空间中两步投影方法及其对变分不等方程组解具误差的迭代序列的收敛性.本文结果发展和改进了Verma等人的最新结果.