(Pb0.85Sm0.10)(Ti0.98Mn0.02)O3压电陶瓷超高各向异性机电耦合性能的X射线衍射研究

本文用X射线衍射技术研究了具有典型超高各向异性机电耦合性能的Sm改性PbTiO₃压电陶瓷。通过引入面网取向密度指数ρ_(hkl)和建立90°电畴转向畴壁平移模型,就改性PbTiO₃陶瓷圆片经不同电压极化后材料内部电畴结构变化作了定量的分析与讨论。结果表明,在改性PbTiO₃陶瓷结构中,90°畴壁空间取向分布具有高度的择优性;极化处理使材料中90°电畴壁显著平移,但其取向分布变化甚少;材料的纵向机电耦合系数K_t与(002)面网取向密度指数增量△ρ₍₀₀₂₎具有基本平行的电场依赖关系。关键词：     

La0.8Ca0.2MnO3/SrTiO3薄膜厚度对其结构及磁学性能的影响

采用多种X射线衍射技术和磁电阻测量技术研究了不同厚度的La_0.8Ca_0.2MnO₃/SrTiO₃ (LCMO/STO)薄膜的应变状态及其对磁电阻性能的影响.结果表明,在STO(001)单晶衬底上生长的LCMO薄膜沿［00l］取向生长.LCMO薄膜具有伪立方钙钛矿结构,随着薄膜厚度的增加,面内晶格参数增加,垂直于面内的晶格参数减小,晶格参数a和b相近,略小于c.LC关键词：X射线衍射微结构应变物理性能     

用SAXS和XRD方法研究TiO2纳米颗粒微观结构

用溶胶-凝胶方法制备了TiO₂纳米样品,并对该样品在300℃到800℃温度区域进行了退火处理.应用同步辐射X射线粉末衍射(XRD)方法研究了经不同热处理温度的TiO₂纳米颗粒的结构相变.应用同步辐射小角X射线散射(SAXS)方法研究了TiO₂纳米颗粒的表面分形与界面特性.得到纳米颗粒粒度与退火温度的变化规律,讨论了表面界面特征与相变的关系.关键词：X射线小角散射X射线衍射2纳米颗粒')\" href=\"#\">TiO₂纳米颗粒     

Mn3O4包覆对LiNi0.5Mn1.5O4正极材料界面电化学性能的提高

本文采用化学湿磨法,首次将金属氧化物Mn₃O₄包覆于LiNi_0.5Mn_1.5O₄颗粒表面,使得电极材料的电子电导率从1.53×10^-7 S/cm 提高到3.15×10^-5 S/cm. 电化学测试结果表明Mn₃O₄包覆大大提高LiNi_0.5Mn_1.5O₄正极材料的倍率性能和高温循环稳定性. 最佳包覆样品为2.6wt% Mn₃O₄包覆的LiNi_0.5Mn_1.5O₄,在10 C倍率下具有108 mAh/g的高放电容并且在55 °C下100次循环后仍有78%的容量保持率,远大于未包覆样品67%的容量保持率.     

电极活性材料精细结构与MH-Ni电池性能关系研究的一些进展

为了更深入地研究正负极活性材料精细结构与MH-Ni电池性能之间的关系,本文在介绍了简单而较适用的处理X射线衍射数据的方法之后,系统综述了电池活化前后、循环过程中正负极活性物质结构和微结构与电池性能之间关系研究的一些进展。主要包括:(1)具有适当晶粒大小和较大层错几率的β-Ni(OH)2物质,能获得较大的充放电容量;(2)没有观测到MH/Ni电池在充放电过程中有β-Ni(OH)2β-NiOOH的相变,只有满充和过充电时才发生部份β-Ni(OH)2γ-NiOOH的相变;MH/Ni电池的物理导电机制是在正负极活性物质中嵌入和脱嵌的氢离子形成固相质子在电极间定向运动。(3)循环性能的衰减、内阻、容量的变化与正负极活性物质的微结构变化有良好对应关系。微结构变化消耗电解液,并改变电解液的性能。正极、负极和电解液三者的共同作用是循环性能衰减的主导原因。(4)正极添加剂与电池性能之间的关系。由于正极添加剂Lu2O3和CaF2能抑制正极活性物质的微晶细化、减缓总的层错几率降低,对于储氢合金能抑制晶粒增大,特别能抑制A(OH)3和B的析出,故能提高了电池的循环性能和寿命。(5)电池储存前后的容量衰减和内阻增加是其在储存过程中CoOOH析出和晶粒细化双重作用的结果。     

电极活性材料精细结构与MH-Ni电池性能关系研究的一些进展

为了更深入地研究正负极活性材料精细结构与MH-Ni电池性能之间的关系,本文在介绍了简单而较适用的处理X射线衍射数据的方法之后,系统综述了电池活化前后、循环过程中正负极活性物质结构和微结构与电池性能之间关系研究的一些进展.主要包括:(1)具有适当晶粒大小和较大层错几率的βNi(OH)2物质,能获得较大的充放电容量;(2)没有观测到MH/Ni电池在充放电过程中有β-Ni(OH)2 β-NiOOH的相变,只有满充和过充电时才发生部份β-Ni(OH)2 γNiOOH的相变;MH/Ni电池的物理导电机制是在正负极活性物质中嵌入和脱嵌的氢离子形成固相质子在电极间定向运动.(3)循环性能的衰减、内阻、容量的变化与正负极活性物质的微结构变化有良好对应关系.微结构变化消耗电解液,并改变电解液的性能.正极、负极和电解液三者的共同作用是循环性能衰减的主导原因.(4)正极添加剂与电池性能之间的关系.由于正极添加剂Lu2O3和CaF2能抑制正极活性物质的微晶细化、减缓总的层错几率降低,对于储氢合金能抑制品粒增大,特别能抑制A(0H)3和B的析出,故能提高了电池的循环性能和寿命.(5)电池储存前后的容量衰减和内阻增加是其在储存过程中CoOOH析出和晶粒细化双重作用的结果.     

纯Cr2O3包覆Li4Ti5O12微球的制备及其储锂性能研究

The pure Cr₂O₃ coated Li₄Ti₅O₁₂ microspheres were prepared by a facile and cheap solutionbased method with basic chromium(III) nitrate solution (pH=11.9). And their Li-storage properties were investigated as anode materials for lithium rechargeable batteries. The pure Cr₂O₃ works as an adhesive interface to strengthen the connections between Li₄Ti₅O₁₂ particles, providing more electric conduction channels, and reduce the inter-particle resistance. Moreover, LixCr₂O₃, formed by the lithiation of Cr₂O₃, can further stabilize Li₇Ti₅O₁₂ with high electric conductivity on the surface of particles. While in the acid chromium solution (pH=3.2) modification, besides Cr₂O₃, Li₂CrO₄ and TiO₂ phases were also found in the final product. Li₂CrO₄ is toxic and the presence of TiO₂ is not welcome to improve the electrochemical performance of Li₄Ti₅O₁₂ microspheres. The reversible capacity of 1% Cr₂O₃-coated sample with the basic chromium solution modification was 180 mAh/g at 0.1 C, and 134 mAh/g at 10 C. Moreover, it was even as high as 127 mAh/g at 5 C after 600 cycles. At-20℃, its reversible specific capacity was still as high as 118 mAh/g.     

Bi2Sr2CaCu2-xSnxO8+δ系列 超导体的XRD和XPS研究

实验研究了Bi₂Sr₂CaCu_2-xSn_xO_8+δ 的X射线衍射(XRD)和光电子能谱(XPS).实验发现随着掺杂(Sn)量的增加,晶格参数a 和c都有所变化,O1s和Cu2p芯能级谱也发生了变化.实验结果表明： 在低掺杂量时,Sn主要 呈二价态;而在高掺杂浓度时呈四价态;掺Sn对超导电性的影响与其他元素的掺杂不同.这 些实验结果支持化学环境在高温超导样品的电子结构中起着重要作用的结论.关键词：Bi系超导体掺杂X射线衍射光电子能谱     

LiMn2O4掺杂金属调控的XRD研究

近年来随着新能源汽车的迅速发展,锂资源发挥越来越重要的作用。我国的盐湖资源丰富,盐湖中蕴含大量的锂资源亟待提取。锰系锂离子筛对锂离子具有优越的选择性,其高吸附容量、环境友好及高稳定性也使其成为从盐湖卤水中直接提取锂的最有潜力的吸附剂之一。但锰系离子筛溶损问题阻碍了其工业化应用,通过掺杂Al、 Mg、 Fe、 Cu元素进改性,使溶损降低,稳定性提高。通过XRD分析表明我们成功制备了LiMn₂O₄锰系离子筛前驱体,通过0.5 mol·L^-1盐酸酸洗获得相应的锰系离子筛,并将其用于盐湖卤水提锂,通过ICP OES测得吸附容量为12.16 mg·g^-1,表明我们合成的锂离子筛可以成功用于盐湖原卤锂的提取。     

通过Mo掺杂诱导低Li/Ni混排程度增强Li1.2Ni0.13Fe0.13Mn0.54O2可逆容量与循环稳定性

富锂层状氧化物因能量密度高和成本低,有望成为下一代锂离子电池正极的重要候选材料.然而,富锂正极材料中阴离子氧化还原反应使晶格氧不稳定,导致电压衰减和不可逆容量损失.尽管铁代无钴富锂材料可以实现较少的电压衰减,但存在严重的阳离子混排和较差的动力学.采用一种简单易行的高价离子掺杂策略,在Li_1.2Ni_0.13Fe_0.13Mn_0.54O₂ （LNFMO）中掺入Mo元素,拓宽了锂层间距,为Li⁺的传输提供了更宽的通道,改善了Li⁺的扩散动力学,有效抑制了阳离子混排,进一步稳定了层状结构.得益于此,Mo掺杂后的富锂材料表现出显著增强的电化学性能,在0.2 C电流密度下表现出209.48 mAh/g的初始放电比容量.1C下的初始放电比容量从137.02 mAh/g提高到165.15 mAh/g;循环300次后,仍有117.49 mAh/g的放电比容量,电压衰减由2.09 mV/cycle降低为1.66 mV/cycle.本文对Mo掺杂后的正极材料进行了系统表征并揭示了循环稳定的机理,为高性能富锂正极材料的设计提供了重要参考.     

4A碳纳米管及相关结构的嵌锂特性(英文)

碳纳米管独特的一维结构和强烈的卷曲效应为外来原子提供了理想的嵌入通道。本文全面总结了近年来我们对直径仅为4A的三种单壁碳纳米管嵌锂特性的密度泛函研究工作。我们具体讨论了体系嵌锂后的结构、能量、电子、电化学等特性。由于这些超小直径的碳纳米管最初合成于沸石晶体的纳米管道,我们也讨论了碳纳米管?沸石晶体复合体系的嵌锂特性。另外,我们还研究了由(5,0)和(14,0)碳纳米管组成的双壁碳纳米管体系的嵌锂特性。我们的理论计算表明,超小直径碳纳米管及相关结构作为锂离子电池负极材料具有很好的应用前景。     

Conversion reactions: a new pathway to realise energy in lithium-ion battery—review

Rechargeable lithium-ion batteries of today operate by an electrochemical process that involves intercalation reactions that warrants the use of electrode materials having very specific structures and properties. Further, they are limited to the insertion of one Li per 3D metal. One way to circumvent this intrinsic limitation and achieve higher capacities would be the use of electrode materials in which the metal-redox oxidation state could reversibly change by more than one unit. Through the discovery of conversion or displacement reactions, it is possible to reversibly change by more than one unit. Further, the need for materials with open structures or good electronic ionic conductivity is eliminated, thus leading to a new area in materials for lithium ion battery. In this paper, we present a review enlightens new reaction schemes and their potential impact on applications.     

Dielectric and impedance spectroscopy of rare earth-based tungsten bronze ceramic

The ceramic oxide Na₂Pb₂Gd₂W₂Ti₄Ta₄O₃₀ (NPGWT) was synthesized by the solid solution route. The formation of compound was checked by using X-ray diffraction and scanning electron microscope study. It is observed from both the studies that the material is a single phase and highly dense. The preliminary temperature variation of the dielectric study reveals ferroelectric to paraelectric phase transition much above the room temperature. The polarization study of the material further confirms the presence of ferroelectricity in the studied compound. The transport property of the material was carried out by using the impedance spectroscopy technique. From both impedance and modulus analysis, it is confirmed that conduction mechanism in the material is due to the hopping motion of charge carrier. To strengthen the hopping motion of charge carrier in the material frequency dependence, ac conductivity is carried out.     

Vibrational Spectroscopy of Intercalated Kaolinites. Part I.

Abstract

The industrial application of kaolinite is closely related to its reactivity and surface properties. The reactivity of kaolinite can be tested by intercalation; that is, via the insertion of low-molecular-weight organic compounds between the kaolinite layers resulting in the formation of a nano-layered organo-complex. Although intercalation of kaolinite is an old and ongoing research topic, there is limited knowledge available on the reactivity of different kaolinites and the mechanism of complex formation, as well as on the structure of the complexes formed. Grafting and incorporation of exfoliated kaolinite in polymer matrices and other potential applications can open new horizons in the study of kaolinite intercalation. This article attempts to summarize (without completion) the most recent achievements in the study of kaolinite organo-complexes obtained with the most common intercalating compounds such as urea, potassium acetate, dimethyl sulphoxide, formamide, and hydrazine using vibrational spectroscopy combined with X-ray powder diffraction and thermal analysis.     

X射线衍射进展简介

100年前,劳厄等证明X射线对硫酸铜晶体具有衍射能力,揭开了X射线衍射分析晶体结构的序幕.100年的发展,X射线衍射已经成为自然科学乃至医学、考古、历史学等众多学科发展的必备技术.文章介绍了X射线衍射现象的发现历史,X射线运动学和动力学理论的发展概况,并举例说明了X射线衍射在粉末多晶体、单晶体和人工功能晶体以及人工薄膜材料中的具体应用情况,最后简要展望了X射线衍射技术的发展前景.     

锂电池发展简史

由于具有很高的能量密度,锂金属在1958年被引入电池领域,1970年进入锂一次电池的商业研发阶段。自1990年以来,随着正极材料、负极材料与电解质的革新,可充放二次锂电池不断发展并实现商品化。如今锂电池技术仍在继续发展并将进一步改善人类生活。文章对40多年来锂电池技术发展历程进行了简单的回顾。     

锂电池发展简史

由于具有很高的能量密度，锂金属在1958年被引入电池领域，1970年进入锂一次电池的商业研发阶段。自1990年以来，随着正极材料、负极材料与电解质的革新，可充放二次锂电池不断发展并实现商品化。如今锂电池技术仍在继续发展并将进一步改善人类生活。文章对40多年来锂电池技术发展历程进行了简单的回顾。     

Structures,microstructures, physical and chemical properties of different rice grains

Herein, we demonstrated a well-rounded exploration of the universal structures, microstructures and physical properties of different rice grains. We show that these rice grains are nanocrystalline in nature, have the standard pattern of type A rice crystalline, and can be attributed to the hexagonal crystal structure with space group of P6. These rice grains have uneven surfaces, clusters of the granules, or schistose structure. Carbon, nitrogen and oxygen elements are presented in the rice grains. No significant difference is observed in FTIR spectra in these rice grains, indicating the fundamental chemical structures of these rice grains are analogical. Their microstructural and physical properties were investigated in detail. Moreover, chemical properties (e.g. thermal stability) of the rice grains were explored. This research provides an in-depth understanding on the physical and structural properties on the atomic and molecular level, as well as guidance for food and industry applications.