ETEM公司改造铝挤压机

苏兰奥托昆普公司宣布采用其直接浸出工艺取代挪威Odda锌冶炼厂的焙烧工艺,投资为 8800万澳元,该改造将会立即开工并于2004年下半年完成,在此期间对生产影响不会太大。

Multiscale strain alleviation of Ni-rich cathode guided by in situ environmental transmission electron microscopy during the solid-state synthesis

Ni-rich layered oxides are one of the most promising cathode materials for Li-ion batteries due to their high energy density.However,the chemomechanical breakdown and capacity degradation associated with the anisotropic lattice evolution during lithiation/delithiation hinders its practical application.Herein,by utilizing the in situ environmental transmission electron microscopy(ETEM),we provide a real time nanoscale characterization of high temperature solid-state synthesis of LiNi_(0.8)CO_(0.1)Mn_(0.1)O_(2)(NCM811) cathode,and unprecedentedly reveal the strain/stress formation and morphological evolution mechanism of primary/second ary particles,as well as their influence on electrochemical performance.We show that stress inhomogeneity during solid-state synthesis will lead to both primary/secondary particle pulverization and new grain boundary initiation,which are detrimental to cathode cycling stability and rate performance.Aiming to alleviate this multiscale strain during solid-state synthesis,we introduced a calcination scheme that effectively relieves the stress during the synthesis,thus mitigating the primary/secondary particle crack and the detrimental grain boundaries formation,which in turn improves the cathode structural integrity and Li-ion transport kinetics for long-life and high-rate electrochemical performance.This work remarkably advances the fundamental understanding on mechanochemical properties of transition metal oxide cathode with solid-state synthesis and provides a unified guide for optimization the Ni-rich oxide cathode.

文学的永恒——论消费社会语境中文学的命运

消费社会中文学的命运是备受学界关注的问题,文学终结的声音不绝于耳。本文尝试分析了消费社会语境中出现此种现象的根本原因在于外部环境、受众群体、创作主体心态三个方面的变化,并进一步论证文学得以永恒的原因在于文学的内视特性及其人的本性需求两个方面,得出文学不仅不会终结而且在新的社会语境中将有更大发展的可能。

原位透射电镜在金属纳米颗粒氧化研究中的应用

原子尺度原位研究金属纳米颗粒的氧化过程,对理解金属氧化反应机理和合理设计金属纳米材料有重要意义。长期以来,研究人员通过热重分析、X射线衍射、X射线光电子能谱等手段对金属块体材料和薄膜材料的氧化行为和反应机理开展了广泛研究。但当金属的尺寸缩小到纳米尺度时,其比表面积、电子结构都与块体材料显著不同,从而导致其氧化行为和反应机理也与块体材料产生差异。由于纳米颗粒体积小,氧化速率快,传统方法很难对其微观的氧化机理进行原位研究。受益于环境控制的电子显微镜技术(atmosphere controlled TEM technologies)的发展,人们有机会在原子尺度对金属纳米颗粒的氧化行为进行系统研究,包括柯肯达尔效应、氧化动力学过程等。然而目前对金属纳米颗粒氧化的研究仍然处于初期阶段,其氧化初期的形核过程仍有待揭示,温度、氧气分压、载体作用对金属纳米颗粒氧化的影响仍有待进一步研究。本文主要以近几年利用原位TEM研究金属纳米颗粒氧化的工作为例,简要介绍这些工作在认识金属氧化理论和推进反应机理的理解方面的最新进展,并探讨了未来研究的机遇和挑战。

基于改进的FP-Growth算法提取客户关系图

利用客户关系图可以很清晰地看出企业与客户之间的各类关系,便于企业决策者采取针对性的措施来改善客户关系。该文提出了一种基于改进的FP-Growth算法进行客户关系图提取的方法,通过最小支持度寻找到所有的频繁项集,然后结合最小置信度,筛选出所需要的关联规则来提高算法的效率。本方法已应用于浙江中烟CRM系统,结果证明该改进算法有比较好的效果。

Direct observation of oxygen vacancy formation and migration over ceria surface by in situ environmental transmission electron microscopy

The extremely high structural tolerance of ceria to oxygen vacancies(Ov)has made it a desirable catalytic material for the hydrocarbon oxidation to chemicals and pharmaceuticals and the reduction of gaseous pollutants.It is proposed that the formation and diffusion of Ov originate from its outstanding reduction property.However,the formation and diffusion process of Ov over the surface of ceria at the atomic level is still unknown.Herein,the structural and valence evolution of CeO_(2)(111)surfaces in reductive,oxidative and vacuum environments from room temperature up to 700℃was studied with in situ aberration-corrected environmental transmission electron microscopy(ETEM)experiments.Ov is found to form under a high vacuum at elevated temperatures;however,the surface can recover to the initial state through the adsorption of oxygen atoms in an oxygen-contained environment.Furthermore,in hydrogen environment,the step-CeO_(2)(111)surface is not stable at elevated temperatures;thus,the steps tend to be eliminated with increasing temperature.Combined with first-principles density function calculations(DFT),it is proposed that O-terminated surfaces would develop in a hypoxic environment due to the dynamic diffusion of Ov from the outer surface to the subsurface.Furthermore,in a reductive environment,H2 facilitates the formation and diffusion of Ov while Ce-terminated surfaces develope.These results reveal dynamic atomic-scale interplay between the nanoceria surface and gas,thereby providing fundamental insights into the Ov-dependent reaction of nano-CeO_(2) during catalytic processes.

Revealing the dynamics of the alloying and segregation of Pt-Co nanoparticles via in-situ environmental transmission electron microscopy

Thermal treatment is a general and efficient way to synthesize intermetallic catalysts and may involve complicated physical processes.So far,the mechanisms leading to the size and composition heterogeneity,as well as the phase segregation behavior in Pt-Co nanoparticles(NPs)are still not well understood.Via in-situ environmental transmission electron microscopy,the formation dynamics and segregation behaviors of Pt-Co alloyed NPs during the thermal treatment were investigated.It is found that Pt-Co NPs on zeolitic imidazolate frameworks-67-derived nanocarbon(NC)are formed consecutively through both particle migration coalescence and the Ostwald ripening process.The existence of Pt NPs is found to affect the movement of Co NPs during their migration.With the help of theoretical calculations,the correlations between the composition and migration of the Pt and Co during the ripening process were uncovered.These complex alloying processes are revealed as key factors leading to the heterogeneity of the synthesized Pt-Co alloyed NPs.Under oxidation environment,the Pt-Co NPs become surface faceted gradually,which can be attributed to the oxygen facilitated relatively higher segregation rate of Co from the(111)surface.This work advances the fundamental understanding of design,synthesis,and durability of the Pt-based nanocatalysts.

热敏灸得气灸感量表的研制与初步评价

建立基于热敏灸理论的、广泛适用的、反映艾灸得气的量表。通过文献法和访谈法,对灸感词汇条目进行收集,建立备选条目池;再通过专家问卷、患者问卷以及核心小组专家讨论,采用主观评价法对条目进行筛选并量化,建立热敏灸得气灸感量表初稿。量表初稿对121例患者预调查,通过探索性因子分析(主要成分)检测量表的结构效度,使用克朗巴赫系数评估量表的内部一致性。热敏灸得气灸感量表条目池由最初的36条削减为9条;回收有效调查量表110份进行统计分析,最终热敏灸得气灸感量表V 1.0包含9个条目,4个维度。其中,全身舒适情感体验3个条目,自主神经反应3个条目,热感传2个条目,非热觉1个条目。热敏灸得气灸感量表具有较好的内容和结构效度,符合目前对热敏得气灸感的临床认识,临床操作性强,具有广泛的适应性。

In situ TEM observation of dissolution and regrowth dynamics of MoO2 nanowires under oxygen

Direct observation of the dissolution behavior of nanomaterials could provide fundamental insight to understanding their anisotropic properties and stability. The dissolution mechanism in solution and vacuum has been well documented. However, the gas-involved dissolution and regrowth have seldom been explored and the mechanisms remain elusive. We report herein, an in situ TEM study of the dissolution and regrowth dynamics of MoO2 nanowires under oxygen using environmental transmission electron microscopy （ETEM）. For the first time, oscillatory dissolution on the nanowire tip is revealed, and, intriguingly, simultaneous layer-by-layer regrowth on the sidewall facets is observed, leading to a shorter and wider nanowire. Combined with first-principles calculations, we found that electron beam irradiation caused oxygen loss in the tip facets, which resulted in changing the preferential growth facets and drove the morphology reshaping.

贵金属-过渡金属化合物复合纳米材料的界面调控及原子尺度原位表征

由贵金属纳米晶或单原子与过渡金属化合物(包括氧化物、磷化物、硫化物等)形成的复合纳米材料,在能源、催化、信息等诸多领域有重要的基础研究价值和广泛的应用前景。贵金属与过渡金属化合物间界面结构的尺寸、电子结构和缺陷态分布等对纳米复合材料的性能起决定性作用,从可控合成、原子水平表征、构效关系一体化研究贵金属-过渡金属化合物间的界面结构是推进其在相关领域应用的关键。本文综述了贵金属-过渡金属化合物复合纳米材料界面结构的可控合成和原子水平原位表征。重点介绍了通过原位转换和吸附方法制备界面结构可控的纳米复合材料,以及利用先进的环境气氛透射电子显微镜(ETEM)表征平台结合多种谱学手段,在原子水平研究其界面结构信息和其在模拟使役条件下的演变过程。并结合该领域面临的问题与挑战,展望了贵金属-过渡金属化合物复合纳米材料的发展前景。

Oxidation behavior of cobalt nanoparticles studied by in situ environmental transmission electron microscopy

The dynamics of oxidation of cobalt nanoparticles were directly revealed by in situ environmental transmission electron microscopy.Firstly,cobalt nanoparticles were oxidized to polycrystalline cobalt monoxide,then to polycrystalline tricobalt tetroxide,in the presence of oxygen with a low partial pressure.Numerous cavities(or voids) were formed during the oxidation,owing to the Kirkendall effect.Analysis of the oxides growth suggested that the oxidation of cobalt nanoparticles followed a parabolic rate law,which was consistent with diffusion-limited kinetics.In situ transmission electron microscopy allowed potential atomic oxidation pathways to be considered.The outward diffusion of cobalt atoms inside the oxide layer controlled the oxidation,and formed the hollow structure.Irradiation by the electron beam,which destroyed the sealing effect of graphite layer coated on the cobalt surface and resulted in fast oxidation rate,played an important role in activating and promoting the oxidations.These findings further our understanding on the microscopic kinetics of metal nanocrystal oxidation and knowledge of energetic electrons promoting oxidation reaction.

In Situ TEM Observation of the Gasification and Growth of Carbon Nanotubes Using Iron Catalysts

We report the in situ transmission electron microscope (TEM) observation of the catalytic gasification and growth of carbon nanotubes (CNTs). It was found that iron catalysts can consume the CNTs when pumping out the precursor gas, acetylene, at the growth temperature, and reinitiate the growth when acetylene is re-introduced. The switching between gasification and growth of CNTs can be repeated many times with the same catalyst. To understand the phenomenon, thermogravimetric analysis (TGA) coupled with mass spectroscopy was used to study the mechanism involved. It was shown that the residual water molecules in the growth chamber of the TEM react with and remove carbon atoms of CNTs as carbon monoxide vapor under the action of the catalyst, when the precursor gas is pumped out. This result contributes to a better understanding of the water-assisted and oxygen-assisted synthesis of CNT arrays, and provides useful clues on how to extend the lifetime and improve the activity of the catalysts.

永恒的美感——莫兰迪

意大利画家乔治·莫兰迪一生专注于画瓶子,并通过对这些瓶子反复的观察和组合,抛弃客观属性与主观喜好,探寻物与物之间最和谐的状态。在他的作品中一切物体平凡而自然的存在。这些作品历经岁月,依然充满生命,散发着美感。