LixNi0.8-yCo0.2ZnyOp的合成及电化学性能研究

A series of single-phase Li_xNi_0.8-yCo_0.2Zn_yO_p(0.96 ≤x≤ 1.10， 0 ≤y≤ 0.05， 2 ≤p≤ 2(1+y) ) (different in the y values) were synthesized by a two-step solid state reaction method， in which LiOH·H₂O， Zn-doped spherical Ni(OH)₂ and Co₂O₃ were used as the precursors. The ICP-AES analyses proved that the Zn-doped compounds synthesized had the nonstoichiometric form. The results of the XRD， SEM identified that the uniform particles of the as-prepared materials having a good layered structure were fine， narrowly distributed and well crystallized. The electrochemical performance test was carried out and the results showed that the as-prepared Zn-doped materials had not only a high capacity， but also a better cycling stability characterization than the un-doped one. The Li_1.06Ni_0.75Co_0.22Zn_0.03O_2.03 material has an initial reversible capacity as high as 160.5mAh·g^-1; and a first discharge efficiency 89.2%， and exhibits satisfactory cyclic stability with 90% retainable capacity after 50 cycles.     

掺镍型层状LixNiyMn1-yO2正极材料的合成与电性能研究

A kind of cathode material of layered Li_xNi_yMn_1-yO₂ characterized with the O2 type has been synthesized by a simple method. Its precursor Na_xNi_yMn_1-yO₂ has been prepared from manganese dioxide， nickel hydroxide and sodium carbonate at high temperature in air and quickly cooled in cold water， then it has been exchanged by the melted LiNO₃ at 300～400℃ in air. The effects of calcine-temperature for the precursors and its compositions (the content of Na and Ni) on the electrochemical properties of the material Li_xNi_yMn_1-yO₂ have been investingated by XRD and electrochemical tests. The results show that the sample Li_0.7Ni_0.3Mn_0.7O₂， has the best electrochemical properties which shows only one charge-discharge potential stage of 2.8～3.0V and has a high specific capacity over 180mAh·g^-1 cycled between 2.0～4.20V. A significant structure transformation to the spinal-type phase has not been found in the charge-discharge cycling and the discharge specific capacity around 165mAh·g^-1 has re-mained after the 20th cyclings for the material.     

层状O2结构锂锰氧化物Li0.60[MgxCoyMn1-x-y]O2的制备及结构表征

本文采用离子交换法分别制备了双复合锂锰氧化物Li_0.60[Mg_xMn_1-x]O₂(0.05 ≤ x ≤ 0.15)和三复合锂锰氧化物Li_0.60[Mg_xCo_yMn_1-x-y]O₂(x=0.05，0.05 ≤      

Li1.02Cr0.1Mn1.9O4表面包覆的热稳定性研究

Improvement of elevated-temperature performance of Li_1.02Cr_0.1Mn_1.9O₄ cathode material by silicious surface modification was studied. The Li_1.02Cr_0.1Mn_1.9O₄ cathode material was treated by silanes coupling agent and then heated at 580 ℃ to remove organic material. The structures of the modified and unmodified Li_1.02Cr_0.1Mn_1.9O₄ were characterized by SpectraPlus, SEM and XRD. The results show that the surface layer of Li_1.02Cr_0.1Mn_1.9O₄ material is found to be rich in silicious compound. X-ray diffraction show that all the samples have perfect spinel structure. The electrochemical characterization of modified Li_1.02Cr_0.1Mn_1.9O₄ cathode material was tested. The cycle stability of charge/discharge at 55℃ is improved. The results of the charge/discharge curves show that the modified Li_1.02Cr_0.1Mn_1.9O₄ has better performance than those unmodified according to the inhibition of decline of reversible capacity of spinel Li_1.02Cr_0.1Mn_1.9O₄. Therefore, cycle performance is improved so obviously that 86.03% of the initial capacity is preserved after 100 cycles.     

凝胶自燃法合成LaxSr1-x CoyFe1-y O3-α纳米粉体

用凝胶自燃法制备了La_xSr_1-x Co_yFe_1-y O_3-α纳米粉体，研究了粉体的元素组成和掺杂性能，表征了粉体的晶相结构，测试了其粒度和形貌。结果表明应用凝胶自燃工艺合成的La_xSr_1-x Co_yFe_1-y O_3-α粉体材料粒子大小非常均匀，元素掺杂性能好，晶相单一，不需经高温热处理便能直接形成钙钛矿型结构。     

纳米钙钛矿LaxSr1-xFe1-yCoyO3复合氧化物的制备和表征

用甘氨酸-硝酸盐燃烧合成法，制备La_xSr_1-xFe_1-yCo_yO₃复合氧化物的陶瓷粉末，对该钙钛矿型氧化物进行了XRD、IR、紫外漫反射光谱及循环伏安曲线分析。结果表明：该复合氧化物粉体平均晶粒为15.3～29.8 nm,为立方和正交晶系。该氧电极具有双功能催化特性，但不完全可逆。对水溶液染料进行光解实验，利用紫外-可见、人工神经网络光度法研究La_xSr_1-xFe_1-yCo_yO₃的催化性能。结果表明：CO²⁺的加入可使La_xSr_1-xFeO₃的光催化活性有所提高，B位离子(Fe³⁺，CO²⁺)改变与加入，使La_xSr_1-xFe_1-yCo_yO₃(x=0.7，0.3；y=0.3，0.9，1)光催化活性高于La_xSr_1-xFeO₃。同时，对5种染料进行紫外光解，在0.75 h，脱色率大于91%，并为动力学一级反应。     

阴阳离子复合掺杂对尖晶石型正极材料的影响

采用高温固相法合成了复合离子掺杂的尖晶石型锰酸锂Li_1.02CraCobLacMn₂－a－b－cFyO₄－y(a，b，c＝0，0.01，0.02；y＝0，0.02)正极材料. XRD表征合成物均具有良好的尖晶石型结构. 充放电表明多元复合掺杂产物Li_1.02Cr_0.01Co_0.02La_0.01Mn_1.96F_0.02O_3.98作为锂离子电池正极材料较未掺杂或仅掺杂阳离子的材料能够更好地抑制可逆容量在充放电循环中的衰减，80次循环充放电比容量（120.1～113.5 mAh•g-1）仍保持94.5％以上. 高温(55 ℃)循环性能也有较大的改善. 交流阻抗测试结果表明该材料在充放电平台附近有较小的阻抗和良好的充放电可逆性.     

纳米尖晶石LixMn2O4的制备与电化学性能表征

Nano-spinel Li_xMn₂O₄(0.6 ≤x≤ 1.0) was synthesized by two steps of coprecipitation and calcination. The influences of calcination temperature, time and Li/Mn ratio on the crystal structure and the particle size of Li_xMn₂O₄ were investigated. It was shown that the higher the calcination temperature, the more complete the crystal structure, and the larger the particle size. Moreover, the influence of calcination time on the crystal structure was insignificant when it was more than 3h at 700℃. With the increase of x in Li_xMn₂O₄ in the range of 0.6～1.0, the d111 and lattice parameter a increased first and then decreased. The electrochemical properties of nano-spinel LiMn₂O₄ using as cathode material of lithium-ion battery were studied. The low discharge capacity might be due to the irreversible capacity loss brought by the large surface area and lattice vacancies of the nano-spinel.     

纳米Ce1-xLaxO2-δ的微波引诱燃烧合成及其性能表征

Nanometer Ce_1-xLa_xO_2-δ solid solutions were synthesized by microwave-induced combustion process us-ing cerium nitrate hexahydrate， lanthanum nitrate hexahydrate and urea as raw materials. The process took only six minutes to obtain La₂O₃-doped CeO₂ nanopowders. The nanopowders were characterized by XRD， Laser Raman spectrum ， UV-Vis spectroscopy，field-emission scanning electron micrograph(FE-SEM)and TEM. The results revealed that the grain size of Ce_1-xLa_xO_2-δ varied from 20 to 40 nm calculated by Scherer formula through the plane of (111)， that oxygen vacancy was produced in the crystal lattices and the concentration of oxygen vacancy was increased with La doping， therefore the covalence of Ce-O bond was strenthened， which results in more intensive UV-C(200～280 nm)absorption. It can be seen from SEM that the porous appearance was obtained. Grain size is no more than 40nm observed from TEM.     

(Ag0.9Li0.1)(Nb1-yTay)O3纳米瓷粉的制备与表征

A series of (Ag_0.9Li_0.1)(Nb_1-yTa_y)O₃ ceramic powders were prepared by an aque-chemical method. The optimized calcination temperature, time and crystal lattice were studied by TG-DTA, IR, XRD and TEM. The results show that the optimized conditions were calcination of the precursor at 800 ℃ for 2 h. The ceramic powder thus prepared was rhombohedral with the average grain size of 48 nm.     

LixZryOz三元化合物的制备及表征

采用高温固相法制备了4种高纯度晶相组成的LixZryOz三元化合物,研究了焙烧温度、时间、反应物的种类和初始反应物物质的量比对产物组成的影响,进一步用XRD、SEM及BET分析方法对产物的晶相结构、表面形貌及比表面积进行了表征.实验结果表明,Li2CO3与ZrO2在适当条件下可以合成得到单斜相Li3ZrO3;以LiOH替代Li2CO3,在适当条件下可以分别合成得到四方相Li2ZrO3和三斜/单斜相Li6Zr2O7;进一步以Zr(NO3)4·5H2O代替Zr02,可将单斜相Li6Zr2O7的制备时间由96 h缩短至24 h.SEM照片显示产物硬团聚明显,粒径分布在1～10μm间,BET分析表明样品比表面积处于1.0～9.0 m2·g-1间分布,反应过程中锂的过量以及长时间高温焙烧是引起产物粒径长大和产生硬团聚的主要原因.     

Synthesis and characterization of the La1−xSrxFeO3−δ system and the fluorinated phases La1−xSrxFeO3−xFx

The oxyfluorides La_1−xSr_xFeO_3−xF_x have been prepared by fluorination of the precursor oxides La_1−xSr_xFeO_3−δ via a low temperature route using poly(vinylidene fluoride) (PVDF). The structures of the oxides and oxyfluorides were investigated in detail by the Rietveld analysis of powder diffraction data. The oxyfluorides crystallize in the space group Pnma for 0<x≤0.9 (SrFeO₂F itself is cubic, space group Pm-3m) and show a sort of two-step structural distortion for decreasing x. Furthermore, a structural comparison of the oxyfluorides with the oxides is given, revealing an increase of the volume per La_1−xSr_xFeX₃ unit during fluorination, of which the magnitude highly depends on the value of x.     

Ce4+和Eu3+共掺杂的Ca2SnO4发光材料的合成与光谱特性

利用高温固相反应法合成了Ce4 和Eu3 共掺杂的Ca2-xEuxSn1-yCeyO4样品,并对其结构和发光特性进行了研究。X射线衍射结果显示,在Ca2SnO4中同时掺入Ce4 和Eu3 离子没有改变其晶体结构。Ca2-xEuxSn1-yCeyO4样品的发射光谱随Eu3 掺杂浓度产生很大变化,当Eu3 掺杂浓度低时,样品中同时存在着Ce4 -O2-的蓝光发射和Eu3 的红光发射;当Eu3 掺杂浓度较高时,样品呈现出Eu3 离子的红光发射。Ce4 -O2-蓝色发光的寿命约为81μs,其能量来源于O2-和Ce4 离子间的电荷迁移吸收;而Eu3 红色发光的寿命约为830μs,其能量来源于O2-和Eu3 离子间的电荷迁移吸收。Eu3 -O2-键比Ce4 -O2-键更容易吸收紫外光,两者之间没有能量传递现象。     

Analysis of nonvalent interactions in the crystals of conformational polymorphs of the composition CaHbNcOdSe by means of molecular voronoi-dirichlet polyhedra

Nonvalent interactions in crystals of compounds of the composition C _a H _b N _c O _d S _e that exhibit conformational polymorphism and have no fewer than four structurally characterized modifications are analyzed using molecular Voronoi-Dirichlet polyhedrals. A unique combination of the types of occurring intra- and intermolecular nonvalent contacts is shown to correspond to each conformational polymorph. Nonvalent interactions involving hydrogen atoms are found to occur most often in crystal structures, and least often those involving S, N, and O atoms.     

直接Z型Zn2SnO4-xNx/ZnO1-yNy异质结光催化剂的制备及机理

采用微波溶剂热法成功制备直接Z型Zn_2SnO_(4-x)N_x/ZnO_(1-y)N_y核壳结构异质结光催化剂。2种物质不同的功函数改变了其表面电荷密度,并在界面处形成内建电场,导致其从传统的Ⅰ型镶嵌异质结转变为Ⅱ型异质结,再转变为Z型异质结构。N杂质原子替代O原子进入Zn_2SnO_4和ZnO的晶格,在两者的价带(VB)顶部形成双杂质能级。核壳结构的Z型异质结光催化剂对罗丹明B的降解速率为纯相Zn_2SnO_(4-x)N_x的1.40～1.43倍,同时具有良好的循环稳定性,且可以降解亚甲基蓝、甲基橙、水杨酸等污染物。Z型异质结的形成使其光生电子-空穴对具有较强的氧化还原能力,而双杂质能级的存在可以拓宽其光响应范围并提高载流子的分离效率。因此,Zn_2SnO_(4-x)N_x/ZnO_(1-y)N_y异质结光催化剂高的光催化活性归因于Z型异质结和双杂质能级的协同作用。     

Ce1-XMnXO2-a复合氧化物催化剂甲烷催化燃烧性能的研究

采用水热法合成了系列Ce_1-XMn_XO_2-a-T(X=0.0，0.1，0.2，0.3，0.5，0.7，0.9，1.0；T表示焙烧温度)，T=500，650，800 ℃)复合氧化物催化剂用于甲烷的催化燃烧。通过XRD、N₂吸/脱附、TG-DSC、UV-Vis-DRS和TPR表征手段研究了不同组成催化剂的物理化学性质及其对甲烷催化燃烧活性。结果表明，在500 ℃焙烧的情况下Mn进入CeO₂晶格形成均相固溶体催化剂的最大取代值为0.7，而当Mn继续增加时则出现Mn₂O₃晶相偏析，同时各催化剂具有较高的比表面积；随着焙烧温度的升高，进入CeO₂晶格的Mn最大取代值逐渐减少，650和800 ℃时分别为0.5和0.3，且比表面积相应降低。Ce_1-XMn_XO_2-a-800催化剂的还原行为大致呈现三阶段，即为Mn₂O₃ → Mn₃O₄的还原(340～420 ℃)，Mn₃O₄ → MnO的还原(420～480 ℃)和体相氧化铈的还原(700～900 ℃)，且Mn的引入整体上提高了催化剂的可还原能力。甲烷催化燃烧活性评价结果表明，比表面积并非影响催化剂活性的主要因素，影响催化剂甲烷催化活性的主要因素为催化剂的组成、可还原能力和焙烧温度；而其中以Ce_0.3Mn_0.7O_2-a-800催化剂表现出较高的甲烷催化燃烧活性，在甲烷转化率为10%和90%时的温度分别为430 和613 ℃。进一步考察Ce_0.3Mn_0.7O_2-a在不同温度(500、650、800和1 000 ℃)焙烧后的催化活性表明，随着焙烧温度的提高催化剂催化活性降低。     

X-ray study of the PbCl2−xIx and PbBr2−xIx systems

Compounds from the systems PbCl₂/PbI₂ and PbBr₂/PbI₂ were examined by x-ray diffraction. The lattice parameters of these phases are presented and the refined crystal structures of the intermediate compounds PbClI and PbBr_1.2I_0.8 are reported. Both structures have Pbnm symmetry, are isostructural with PbCl₂, and have the different halogens ordered in the two Cl sites. Phase studies showed that PbCl₂ and PbClI have practically no mutual solubility, while PbBr₂ and PbBr_1.2I_0.8 have appreciable solubility ranges, particularly for PbBr₂-rich concentrations. At least 17% Br is present in the I site of PbBr_1.2I_0.8. Nevertheless, it is a distinct phase with miscibility gaps toward PbBr₂ and PbI₂. This behavior is explained by the size disparity between the halogens. The intermediate phases do not form solid solutions with hexagonal PbI₂.     

溶剂热法合成CdSxSe1-x棒状纳米材料

以乙二胺为溶剂，制备了直径为10～20 nm、长度100～150 nm的棒状CdS_xSe_1-x纳米晶体，并对其形成过程及机理进行了探讨。研究发现CdS_xSe_1-x纳米晶体在120 ℃下就可形成且纳米棒的形貌不受温度及反应物配比的影响。紫外-可见光谱表明得到的CdS_xSe_1-x纳米晶体的光学性质可通过简单改变反应物中S与Se的配比进行调控。