α-PbO纳米粉体的固相合成及其对MnO2电极材料的改性作用

固相反应;放电容量;α-PbO纳米粉体的固相合成及其对MnO2电极材料的改性作用     

PbO~2纳米粉体的固相合成及其对MnO~2电极材料的改性作用

利用固相氧化反应制备了PbO~2纳米粉体样品，借助XRD，TEM以及循环伏安测试对其性质进行了表征。同时，对反应条件的选择进行了讨论。将所得样品用于改性MnO~2电极，恒流放电测试结果表明，样品掺杂量在1.25%～5.00%间对MnO~2有良好的改性效果，可使改性MnO~2的放电容量得到极大提高。循环伏安测试结果表明，铅的掺入改变了MnO~2的放电机理。在循环扫描过程中，掺杂物与MnO~2均不再以单纯氧化物的形式存在，而是形成了一系列Pb(X)(X=0,Ⅱ)Mn(Y)(Y=Ⅳ，Ⅲ，Ⅱ)复合物的共氧化与共还原，抑制了电化学惰性物质Mn~3O~4的生成和积累，从而有望改善MnO~2的可充性能。纳米PbO~2与常粒径PbO~2与常粒径PbO~2(标记为S)对MnO~2的改性机理类似。但前者对MnO~2的改性效果明显优于后者，当恒流放电至-1.0V时，其放电容量较S样改性MnO~2的放电容量平均高出约30%。     

纳米α-PbO粉体改性MnO2的循环伏安行为

探讨了固相合成的纳米α-PbO粉体样品及其改性MnO2电极的循环伏安行为。结果表明,纳米α-PbO在碱性电解液中具有优良化学活性。铅的掺入改变了MnO2的充放电机理。在其循环扫描过程中,掺杂物与MnO2均不再以单纯氧化物的形式存在,而是形成了一系列Pb(X)(X=0,Ⅱ）Mn（Y）（Y=Ⅳ,Ⅲ,Ⅱ）复合物的共氧化与共还原,抑制了电化学惰性物质Mn3O4的生成和积累,使MnO2的可逆性得到了明显改复合物的共氧化与共还原,抑制了电化学惰性物质Mn3O4的生成和积累,使MnO2的可逆性得到了明显改善。纳米α-PbO样品与普通粒径的α-PbO样品对MnO2的改性机理类似。但前以MnO2的改性效果明显优于后。     

纳米MnO2的固相合成及其电化学性能的研究（Ⅰ）：纳米γ—MnO2 …

用醋酸锰分别与柠檬酸、草酸和８－羟基喹啉在室温及低 相反应生成锰配合物,经热分解和酸处理等手段最终制备出纳米γ－ＭｎＯ２,用元素分析,化学分析、Ｘ射线衍射、热重／差热分析和透射电等测试手段对固相反应的可行性作了讨论,地合成的样品进行了表征,从ＴＥＭ照片上看,产物粒子呈球形,粒径多为２０－３０ｎｍ,酸处理可大大提高样品的氧化度,但酸化过程中粒子出现团聚现象,粒子形貌也有所改变,似有取向生长的趋势,文     

纳米PbTiO3改性MnO2电极

改性添加剂;放电容量;纳米PbTiO3改性MnO2电极     

纳米MnO2的固相合成及其电化学性能研究(Ⅱ)--纳米γ-MnO2的电化学性能

用循环伏安(CV)和恒流放电及充放电技术测试了固相方法合成的纳米γ-MnO2的电化学性能.结果表明,纳米γ-MnO2在碱性电解液中具有优良的电化学活性.纳米样品在-0.2 V之后极化程度变小,电位下降的趋势明显减慢.重负荷放电时,纳米微粒样品显示出更大的优势,放电容量大幅度增加.CV图中显示,纳米MnO2的峰电流明显大于国际1号电解二氧化锰样品(记为S)的峰电流,表明在纳米样品中,质子、电子的嵌入和脱出以及Mn(Ⅲ)、Mn(Ⅱ)的溶解和沉积比S样中更易进行.     

锂离子固相扩散控制下的材料放电过程

从理论上分析了在锂离子相扩散控制条件下,电极材料的恒流放电过程,数值计算的结果表明,Q值（放电时率和扩散时间常数之比）对材料的放电容量有非常重要的影响,模拟了LiMn2O4正极材料和石墨负极材料的恒流放电曲线,分析了颗粒粒径对这两种材料放电容量的影响。     

CoTiO3纳米粉体的合成及其对MnO2电极材料的改性作用

采用溶胶-凝胶法制得钙钛矿型CoTiO₃纳米粉体，借助XRD、TEM以及循环伏安测试对其性质进行了表征。不同量的所制样品用于MnO₂电极的物理掺杂，进行了深度恒流放电、循环伏安和充放电测试。结果表明在40%KOH电解质溶液中，样品掺杂量为5%时改性效果较好。纳米CoTiO₃参与了电极反应，抑制了电化学惰性物质Mn₃O₄的生成，从而有效地改善MnO₂的放电性能，放电容量较I.C     

锂离子固相扩散控制下的材料放电过程

从理论上分析了在锂离子固相扩散控制条件下,电极材料的恒流放电过程.数值计算的结果表明,Q值（放电时率和扩散时间常数之比）对材料的放电容量有非常重要的影响.模拟了LiMn2O4正极材料和石墨负极材料的恒流放电曲线,分析了颗粒粒径对这两种材料放电容量的影响.     

Synthesis and Characterization of Novel Nanophase Hexagonal Poly(2,5‐dimethoxyaniline)

Novel nanophase hexagonal structured polyaniline (PANI) and poly(2,5‐dimethoxyanilines) (PDMA) were synthesized by oxidative polymerization involving the respective anilines and a mixture of ferric chloride and ammonium persulfate. The morphological, spectral and electrochemical characteristics of the polymers were determined from the results of SEM, FTIR, UV‐vis, TGA and cyclic voltammetry experiments. The hexagonal PANI and PDMA nanorods (15–200 nm diameter) exhibited very good thermal stabilities, losing only 10% of their weight on heating to 400 °C. Electrochemical data indicated a pernigraniline state of the polymers with formal potential, E°′, values of 394±6 mV and 400±1 mV, for PANI (conductance, C=0.37×10^?3 S) and PDMA (conductance, C=2.02×10^?3 S), respectively. The pernigraniline state was confirmed by sharp FTIR pernigraniline quinoidic peaks (PANI: 1414 cm^?1; PDMA: 1157 cm^?1), and UV‐vis absorption maxima at 340–370 nm (PANI) and 450–650 nm (PDMA) which are characteristic of charge transfer excitons of the quinoid structures of pernigraniline.     

Study on Synthesis and Electrochemical Properties of Nanophase Li-Mo-spinel

Li-Mn-spinel was synthesized using the rheological phase recation method,First,the precursor was prepared by rheological phase reaction.The it was decomposed to form Li-Mn-spine,which was characterized by X-ray diffraction analysis and IR spectra.The particle size of Li-Mn-spinel was determined by the method of the transmission electron microscopy.The synthesized materials are of nanometer size with 30-100nm in the average diameter.The electrochemical properties of the Li-Mn-spinel were also studied.It proved that this method not only provided a simple practicable and effective route for the synthesis of Li-Mn-spinel,but also had many advantages such as lower sintering temperature,shorter sintering time,fine particles and particularly excellent electrochemical performances.     

纳米MnO2超级电容器的研究

用固相合成法制备纳米MnO2，作为超级电容器材料，通过循环伏安、交流阻抗与恒电流充放电等测试手段对MnO2电极进行分析.结果表明,以1 mol•L－1 KOH为电解液， MnO2电极在－0.1～0.6 V(vs. Hg/HgO)的电压范围内具有良好的法拉第电容性能.在不同电流密度下，电极比容量达240.25到325.21 F•g－1.恒电流充放电5000次后，电极容量衰减不超过10％.     

纳米钙钛矿型Ca1-xBixMnO3-δ的合成及其作为可充碱性电池阴极材料的可行性研究

采用共沉淀合成法制备了Bi不同取代量的纳米Ca1-xBixMnO3-δ,其中烧结温度由TG-DTA测试确定.用原子吸收对其进行了分组分析,采用XRD, TEM对其结构和晶粒的大小及形貌进行了分析,并与高温固相法和硬脂酸法制备样品进行比较.结果表明,Bi取代量的不同,所得样品的物相也随之发生变化.但不同制备方法所得样品的物相相同,晶粒的平均粒径不同,但均属纳米级.当在碱性溶液(9 mol/L KOH)中进行充放电性能测试时发现,取代量x=0.l时Ca1-xBixMnO3-δ的放电容量为380 mAh/g,与同等条件下国际一号样(MnO2)的放电容量248 mAh/g相比,提高了53%.在充放电实验中,电极的可充性能比国际一号样及无取代的CaMnO3-δ有很大的提高.因此有希望作为可充电池阴极的活性材料.本文还利用循环伏安方法对其充放电机理进行了初步讨论.     

New Nanophase Separated Intelligent Amphiphilic Conetworks and Gels

Amphiphilic conetworks (APCN) are new materials composed of covalently bonded otherwise immiscible hydrophilic and hydrophobic polymer chains. The amphiphilic nature of these new crosslinked polymers is indicated by their swelling ability in both hydrophilic and hydrophobic solvents. Special synthetic techniques have been developed for the preparation of these new unique materials, such as poly(2-hydroxyethyl methacrylate)-l-polyisobutylene (PHEMA-l-PIB), poly(methacrylic acid)-l-polyisobutylene (PMAA-l-PIB) and poly(N,N-dimethylaminoethyl methacrylate)-l-polyisobutylene (PDMAEMA-l-PIB) (-l- stands for linked by). Due to their unique architecture, macrophase separation of the immiscible components is prevented by the chemical bonding in the conetworks. As a results, phase separation leads to nanodomains with usually 2-20 nm domain sizes as shown by AFM measurements. The nanophase separated morphology may also lead to smart temperature responsive gels with high mechanical stability, such as in the case of poly(N,N-dimethylaminoethyl methacrylate)-l-polyisobutylene APCNs as discovered during these studies. In another approach, poly(2-hydroxyethyl methacrylate)-l-polyisobutylene and poly(methacrylic acid)-l-polyisobutylene APCNs were prepared by a special two-step process. The new PMAA-l-PIB polyelectrolyte APCNs possess smart (intelligent) reversible pH-responsive properties in aqueous media. These unique conetwork structures and properties of these new emerging materials may lead to numerous new potential applications, such as smart materialk products, sustained drug release matrices, biomaterials, nanohybrids, nanotemplates etc.     

High Temperature Reaction Calorimetry Applied to Metastable and Nanophase Materials

Materials with high surface areas and small particle size (nanophases), metastable polymorphs, and hydrated oxides are increasingly important in both materials and environmental science. Using modifications of oxide melt solution calorimetry, we have developed techniques to study the energetics of such oxides and oxyhydroxides, and to separate the effects of polymorphism, chemical variation, high surface area, and hydration. Several generalizations begin to emerge from these studies. The energy differences among different polymorphs (e.g., various zeolite frameworks, the - and -alumina polymorphs, manganese and iron oxides and oxyhydroxides) tend to be small, often barely more than thermal energy under conditions of synthesis. Much larger contributions to the energetics come from oxidation-reduction reactions and charge-coupled substitutions involving the ions of basic oxides (e.g., K and Ba). The thermodynamics of hydration involve closely balanced negative enthalpies and negative entropies and are very dependent on the particular framework and cage or tunnel geometry.This revised version was published online in November 2005 with corrections to the Cover Date.