导电聚合物聚醚聚氨酯的结构与导电性能的正电子湮没研究

用正电子湮设方法研究了高分子固体电解质聚醚聚氨酯（ＰＥＵ）在与ＬｉＣlＯ₄络合前后的结构变化及导电性能．实验结果表明，当ＰＥＵ与ＬｉＣlＯ₄络合后，正电子素（o－Ｐｓ）的寿命及其强度均减少，而中间寿命分量的湮没参数基本不变．这表明Ｌｉ杂质主要扩散在无序的非晶区．掺杂前后样品的温度实验表明，在玻璃化转变温度Ｔ_g之下，络合前后的自由体积分数的变化很小，这与自由体积理论预言的结果一致．在Ｔ_g之上，络合后的自由体积空洞的浓度和自由体积分数均减小．此外，ＰＥＵ－ＬｉＣlＯ₄络合物的电导率随温度和Ｌｉ杂质浓度的变化可以用自由体积理论解释． 关键词：     

LiF-LiCl-B2O3系统非晶态快离子导体结构的研究

本文通过对¹¹B核磁共振(¹¹B-NMR)、红外光谱等实验方法,研究了LiF-LiCl-B₂O₃三元系统玻璃的结构和离子导电性,着重于F^-离子在玻璃网络中所起的作用,以及F^-,Cl^-和Li⁺离子对导电率的影响。LiF-LiCl-B₂O₃三元系统玻璃,随LiF含量的增加,B由三角体向四面体变化,从而F^-离子进入网络,使玻璃结构由[B₂O₃]三角体层状结构向三维空间延展,形成了含有[BO₃F]基团的三维空间网络,Cl^-离子以游离的离子存在于网络中,起着松散网络的作用,对提高电导率有利,而Li⁺离子作为传导离子,对电导率的贡献是主要的。本系统玻璃的电导率是随LiF,LiCl含量的增加而增大,在300℃时测得电导率σ=6.12×10^-4Ω^-1·cm^-1。 关键词：     

SMMA/SMA共聚物共混物的自由体积的热动态特性与相分离行为的PALS研究

基于自由体积理论，利用正电子湮灭寿命谱仪(PALS)分别研究在不同升温速率条件下，聚苯乙烯-甲基丙烯酸甲酯共聚物(SMMA)和聚苯乙烯-马来酸酐共聚物(SMA)混合物(30/70)的自由体积参数的温度依赖性，探索相容共混物相行为的热动态特性.在PALS实验中，在玻璃化转变温度T_g以上，当结构松弛的弛豫时间与等温停留时间相当，发现在某一段温度范围内，共混物的自由体积参数随着温度的变化明显地偏离线性关系.从自由体积孔的浓度I₃值在该段的变化趋势，初步推断共混物在该温 关键词： 正电子湮没 正电子素 聚合物共混物 相分离     

纳米Fe3 O4 颗粒的正电子湮没谱学研究

测量了磁性纳米Fe₃O₄颗粒的X射线衍射谱(XRD)、正电子湮没寿命谱(PALS)和符合多普勒展宽谱(CDBS),研究了不同压力和退火温度对磁性纳米Fe₃O₄颗粒物相、电子结构、缺陷及电子动量分布等的影响. XRD,PALS,CDBS测量结果表明:纳米Fe₃O₄颗粒的缺陷浓度随压力的增加而增大,但物相和缺陷类型并未发生变化;磁性纳米Fe₃O_{4< 关键词： 正电子 3}O₄')" href="#">Fe₃O₄ 寿命谱 多普勒展宽谱     

La1.6(MoO4)3:Eu0.43+纳米晶合成及发光特性

采用燃烧法合成了La_1.6(MoO₄)₃:Eu_0.4³⁺纳米晶末,研究了其声子-掺杂-晶格相互作用和发光性质.X射线粉末衍射(XRD)分析表明,在500~900 ℃退火后,La_1.6(MoO₄)₃:Eu_0.4³⁺样品为单一晶相.对样品进行了光致发光(PL)测量,激发Mo⁶⁺-O^2-电荷迁移带,观察到Eu³⁺的系列发光,表明Mo⁶⁺-O^2-带和Eu³⁺间存在能量传递,中心波长分别在λ₁=469 nm和λ₂=426 nm处的两个one-phonon边带,相应的声子能量分别为767和1202 cm^-1,分别对应于 Mo=O 和Mo-O-Mo伸缩振动.同时,计算了两个局域模电子-声子耦合强度的黄昆因子分别为S₁=0.055和S₂=0.037,为揭示其三价离子高传导特性及其负热膨胀物理特性提供了实验基础.     

三嵌段共聚物SEBS中自由体积行为的温度及e+辐照时间依赖性的研究

利用正电子湮没寿命谱实验手段研究了²²Na放射源的e⁺自辐射对三 嵌段共聚物SEBS的正电子湮没参数的影响，而后结合Eldrup的经典模型，研究了SEBS的自由体积孔尺寸和自由体积分数随着温度的变化关系，给出了自由体积分数在T_g以上和在Tg以下各自区域内分别与温度呈线性关系，最后结合Williams-Landel-Ferry(WLF)自由体积理论和Eldrup的经典模型讨论了热膨胀系数和自由体积分数中的A常数. 关键词： 正电子湮没技术 嵌段共聚物 自辐射 热膨胀     

Na+替位掺杂对Li2MnSiO4的电子结构以及Li+迁移过程的影响

在锂二次电池中, 硅酸锰锂作为正极材料得到广泛研究, 但其固有的电子和离子电导率较低, 直接影响着电池的功率密度和充放电速率. 本文建立了不同浓度的Na⁺离子替位掺杂Li⁺离子形成的Li_1-xNa_xMnSiO₄(x=0, 0.125, 0.25, 0.5)结构, 采用第一性原理的方法, 研究了掺杂前后硅酸锰锂的电子结构以及Li⁺离子的跃迁势垒. 发现在Li⁺位替代掺杂Na⁺, 导带底的能级向低能方向发生移动, 降低了Li₂MnSiO₄ 材料的禁带宽度, 有利于提升材料的电子导电性能. 随着掺杂浓度的升高, 禁带宽度逐渐变窄. CI-NEB结果表明, 在Li₂MnSiO₄体系中具有两条有效的Li⁺离子迁移通道, 掺杂Na⁺以后扩大了Li⁺ 离子在[100]晶向上的迁移通道, Li⁺离子的跃迁势垒由0.64 eV降低为0.48, 0.52和0.55 eV. 掺杂浓度为 x=0.125时, 离子迁移效果最佳. 研究表明Na⁺掺杂有利于提高Li₂MnSiO₄材料的离子和电子电导率.     

Co掺杂纳米ZnO微结构的正电子湮没研究

利用正电子湮没技术研究了10 at.% Co掺杂的Co₃O₄/ZnO纳米复合物中退火对缺陷的影响. 利用X射线衍射(XRD)测量了Co₃O₄/ZnO纳米复合物的结构和晶粒尺寸. 随着退火温度升高,Co₃O₄相逐步消失,ZnO晶粒尺寸也有显著增加. 经过1000 ℃以上退火后,Co₃O₄相完全消失,并出现了CoO的岩盐结构. 正电子湮没寿命测量显示出Co₃O₄ /ZnO纳米复合物中存在大量的Zn空位和空位团. 这些空位缺陷可能存在于纳米复合物的界面区域. 当退火温度达到700 ℃后Zn空位开始恢复,空位团也开始收缩. 900 ℃以上退火后,所有空位缺陷基本消失,正电子寿命接近ZnO完整晶格中的体态寿命值. 符合多普勒展宽谱测量也显示Co₃O₄ /ZnO纳米复合物经过900 ℃以上退火后电子动量分布与单晶ZnO基本一致,表明界面缺陷经过退火后得到消除. 关键词： ZnO 界面缺陷 正电子湮没     

过渡族元素掺杂BaTiO3-Tb1-xDyxFe2-y层状复合材料中的磁电效应

用溶胶-凝胶法制备1.0%mol Mn,Cr,Co掺杂 BaTiO₃(BTO)粉体,在1350℃下烧结成多晶陶瓷样品.X射线衍射和差示扫描量热分析表明,室温下掺杂BaTiO₃具有四方钙钛矿结构;居里点和相变潜热随Cr,Mn,Co掺杂逐渐降低.将掺杂BaTiO₃与Tb_1-xDy_xFe_2-y(TDF)胶合制成双层磁电复合材料,并研究了Cr:BTO-TDF,Mn∶BTO-TDF,Co:BTO-TDF层状复合材料中的磁电效应.实验表明,在340×80 A·m^-1偏置磁场下, Cr:BTO-TDF的横向磁电电压系数达到最大值586 mV·cm^-1·(80 A·m^-1)^-1.在400×80 A·m^-1偏置磁场下,Mn∶BTO-TDF和Co:BTO-TDF的横向磁电电压系数的最大值分别为480 mV·cm^-1·(80 A·m^-1)^-1和445mV·cm^-1·(80 A·m^-1)^-1.研究表明掺杂BaTiO₃-TDF层状复合材料中具有较强的磁电耦合.作为无铅压电材料,掺杂BaTiO₃制备的磁电效应器件颇具应用前景. 关键词： 磁电效应 双层复合材料 3')" href="#">掺杂BaTiO₃ 1-xDy_xFe_2-y')" href="#">Tb_1-xDy_xFe_2-y     

Eu3+掺杂Bi2O3-PbO-B2O3-ZnO玻璃光谱性质

用高温融熔法制备了Eu³⁺掺杂浓度为1%的(60-x)Bi₂O₃xPbO30B₂O₃10ZnO(x=0,10,30,摩尔分数)玻璃.测定了玻璃的差热分析曲线、吸收光谱、声子边带谱、发射光谱与激发光谱.由发射光谱与稀土Eu³⁺离子光学跃迁矩阵元的特点,计算了Eu³⁺光学跃迁的J-O参数Ω₂与Ω₄.结果显示强度参数Ω₂随着PbO量的增加而略减少,表明材料的对称性略增加,Eu—O键强减弱,共价性降低.PbO组分的增加,使玻璃的结晶起始温度与软化温度差降低,导致玻璃的热温度性变差.随着PbO的增加,电-声子耦合减弱.     

Ionic conductivity of PVdF-co-HFP/LiClO4 in terms of free volume defects probed by positron annihilation lifetime spectroscopy

ABSTRACT

Polymers based on ionic conducting materials have important interest because of their potential applications in polymer electrolytes and membranes for fuel cell application. PVdF-co-HFP poly(viniliden-co-hexafluoropropylene) was chosen as a polymer matrix because of its high ionic conductivity and better mechanical properties. Polymer matrix composites were prepared with various amounts of LiClO₄ salt by a solution casting method. The sample-ionic conductivity measurements were recorded by AC impedance analyzer at different frequencies from 0.1?Hz to 20?MHz and at different temperatures from 273 to 373?K.

The changes of nanoscopic free volume and free volume fraction in these materials were investigated in terms of temperature from 273 to 373?K using Positron Annihilation Lifetime Spectroscopy (PALS) and Simha-Somcynsky (SS) Hole Theory. The free volume had a bump at about 3% in weight percentage of the salt and there is a slight increase after 10%. The effects of weight percentages of LiClO₄ and temperature were investigated. The mechanism of the ac ionic conductivity was presented in terms of the free volume models, however thermo-occupancy function justifies the best accurate representation of the data.     

非晶态离子导体Li2B2O4晶化前期的离子导电性

本文研究了非晶态离子导体Li₂B₂O₄的离子电导率与温度的关系,特别着重于晶化前期的离子迁移特性。当温度低于T_K(≈310℃)时,离子电导率遵从Arrhenius关系。当高于晶化温度(≈411℃)时,以晶态中的离子迁移为主。在T_kc时,电导率偏离热激活机制呈反常增高。我们把这一过程称为晶化前期过程。可以用自由体积模型进行描述。晶化前期又可分为两部分:当温度低于、T_p(≈380℃)时,由于自由体积的重新分布,导致了电导率的增高;当T>T_p时,出现了少量微晶,但晶化量小于5%,由于非晶母体与微晶之间的界面效应使得离子导电性显著增强。可以通过室温淬火,把晶化前期非晶态的状态保持到室温,从而有可能制备出离子电导率高于纯非晶态的材料。 关键词：     

Conduction in ionic organic plastic crystals: The role of defects

This paper describes the relationship between the ionic conduction and the characteristics of defects in plastic crystalline phases of N,N-dimethylpyrrolidinium bis(trifluoromethanesulfonyl)amide (P₁₁TFSA). Positron annihilation lifetime spectroscopy (PALS) shows that the phase III to phase II transition involves the generation and expansion of vacancies, which is confirmed by measurement of volumetric expansion. The vacancies expand to match the cation size in phase II and this gives rise to an increase in the conductivity. The relationship between the vacancy volume and the conductivity obeys a Cohen–Turnbull free volume conduction model. The critical volume matches the volume of a cation–anion pair in phase III, which indicates a Schottky mechanism. The critical volume shows a greater value in phase II, which is probably indicative of a pipe diffusion mechanism.     

高聚物(PEO)n-CuBr2薄膜在流体静高压下的离子导电性

用混溶蒸发法制备出高聚物（ＰＥＯ）_n－ＣｕＢｒ₂（ｎ＝４，８，１２，１６，２４）薄膜。并详细测量它们在０．１－３５０ＭＰａ静水压范围的复阻抗谱，以及在０．１－２４００ＭＰａ静水压范围的交流电导率。结果表明：离子电导率与压力的依赖关系可分解为四段相迭加的线性关系。根据Ｘ射线衍射物相分析，它们分别归于ＰＥＯ非晶相的压力效应，ＰＥＯ结晶相的压力效应和析出新相ＣｕＢｒ₂的压力效应。最后给出克服办法——添加少量增塑剂碳酸乙烯酯可增加（ＰＥＯ）_n－ＣｕＢｒ₂薄膜的弹性，使压力下的离子电导率提高一至两个数量级。 关键词：     

Effect of hot pressing on the ionic conductivity of the PEO/LiCF3SO3 based electrolyte membranes

PEO/LiCF₃SO₃ (LiTFS) /Ethylene carbonate (EC) polymer electrolyte membranes were prepared with a solution casting method followed by a hot pressing process. The effect of the hot pressing process on the in-plane conductivity of the PEO electrolyte membranes was evaluated using a four-electrode AC impedance method. The composition, morphology, and microstructure of the composite polymer electrolyte were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The AC impedance measurement results indicate that the hot pressing process can increase the room temperature conductivity of the membranes 14 times to 1.7 × 10^− 3 S cm^− 1 depending upon the duration of the hot pressing process. The SEM, FTIR, XRD, and DSC results indicate that the hot pressing process could increase the amorphous part of the polymer electrolyte membrane or convert large spherulite crystals into nano-sized crystals.     

Effects of Al2O3 nanofiller and EC plasticizer on the ionic conductivity enhancement of solid PEO-LiCF3SO3 solid polymer electrolyte

A solid polymer electrolyte (SPE) is synthesized by solution casting technique. The SPE uses poly(ethylene oxide) PEO as a host matrix doped with lithium triflate (LiCF₃SO₃), ethylene carbonate (EC) as plasticizer and nano alumina (Al₂O₃) as filler. The polymer electrolytes are characterized by Impedance Spectroscopy (IS) to determine the composition of the additive which gives the highest conductivity for each system. At room temperature, the highest conductivity is obtained for the composition PEO-LiCF₃SO₃-EC-15%Al₂O₃ with a value of 5.07 10^− 4 S/cm. The ionic conductivity of the polymer electrolytes increases with temperature and obeys the Arrhenius law. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) studies indicate that the conductivity increase is due to an increase in amorphous content which enhances the segmental flexibility of polymeric chains and the disordered structure of the electrolyte. Fourier transform infrared spectroscopy (FTIR) spectra show the occurrence of complexation and interaction among the components. Scanning electron microscopy (SEM) images show the changes morphology of solid polymer electrolyte.     

Properties of nano-ZnO/poly(vinyl alcohol)/poly(ethylene oxide) composite thin films

A series of poly(vinyl alcohol)/nano-ZnO composites were prepared by dispersing nano-ZnO in aqueous solutions containing mixtures of the biodegradable polymers poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEO), and composite thin films were prepared by casting. The introduction of nano-ZnO into PVA/PEO mixed solutions significantly decreased the resistivity of the solutions. Ultraviolet absorption, thermal behaviour and visco-elastic properties of the thin films were determined as a function of nano-ZnO content up to 15 wt%. Optimum film properties were obtained with 1 wt% nano-ZnO, higher proportions of nano-ZnO resulting in agglomeration of ZnO particles and deterioration in film properties. The Forouhi and Bloomer model was used for the modelling of ZnO thin films.     

New nanocomposite polymer electrolyte comprising nanosized ZnAl2O4 with a mesopore network and PEO-LiClO4

A novel poly(ethylene oxide) (PEO)-based nanocomposite polymer electrolyte (NCPE) has been developed by using nanosized, high surface area ZnAl₂O₄ with a mesopore network as the filler. X-ray diffraction (XRD), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM) were used to characterize the NCPE. The results showed that the presence of the nanosized ZnAl₂O₄ powder leads to a reduction in the crystallinity of the PEO phase. The ionic conductivity and lithium ion transference number of the PEO-based polymer electrolyte were enhanced by the addition of the nanosized ZnAl₂O₄ powder. A broad electrochemical stability window suggests that the PEO-LiClO₄-ZnAl₂O₄ NCPE is a viable candidate for the electrolyte material in lithium polymer batteries.     

Field enhanced Li ion conduction in nanoferroelectric modified polymer electrolyte systems

Nanocomposite polymer electrolyte (NCPE) films based on polyethylene oxide (PEO) complexed with lithium perchlorate (LiClO₄) and nanosized ferroelectric ceramic fillers such as BaTiO₃, SrTiO3 have been prepared using solution cast technique. The films showed very good mechanical stability when exposed to ambient atmospheres for prolonged periods. Lithium ion transport studies revealed that the conductivity is predominantly ionic. The effect of electric field on ionic conductivity of NCPE films was investigated. One order enhancement in conductivity due to the field was observed at 323 K. NCPE films exhibited conductivity of 3.46?×?10^?5 Scm^?1 at 323 K. NCPE films were characterized using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) technique. The DSC and XRD studies revealed reduced crystallinity which confirmed the higher amorphous phase and hence the improved ionic conductivity.     

The effect of alumina addition on the conductivity, microstructure and mechanical strength of zirconia — yttria electrolytes

The effect of alumina additions on the ionic conductivity and mechanical properties of 3 and 8 mol% Y₂O₃ - ZrO₂ compositions has been investigated. Such materials are of interest for use in fuel cells and other similar applications. Sintered specimens were characterised by XRD, SEM, impedance spectroscopy, four — probe DC conductivity and mechanical strength measurements. Alumina additions had no affect on the conductivity degradation behaviour at 1000 °C and the activation energy but resulted in an increase in the strength of 8 mol% Y₂O₃ - ZrO₂ composition by about 25%. However, a significant drop in the ionic conductivity well above what could be accounted for by the decrease in the volume fraction of the conducting phase, was observed.