共沉淀法制备球形磷酸亚铁铵

以FeSO4·7H2O、NH4H2PO4、NH3·H2O为原料,用共沉淀法合成了用于制备磷酸铁锂正极材料的前驱体磷酸亚铁铵(NH4FePO4),通过XRD、SEM、FTIR等测试手段对材料进行了表征.通过正交实验得到了最佳工艺条件.在该工艺条件下材料振实密度达到1.73g/cm3.     

高密度LiFePO4/C正极材料的合成其及电化学性能研究

以Li2CO3为锂源,葡萄糖为C源,与高密度前驱体FePO4混合,采用高温固相反应法合成高密度的锂离子电池正极材料LiFePO4/C复合材料.采用X射线衍射、电子扫描显微镜和恒电流充放电对制得的LiFPO4进行了研究.结果表明,合成材料结晶完整,为均一的橄榄石型结构.C的含量在很大程度上影响LiFePO4的密度,当C的含量为3.0%(质量分数)时,所制正极材料LiFePO4/C的振实密度可达到2.14g/cm3,0.1C放电容量为121.5mAh/g,体积比容量达到260.OmAh/V.     

球磨时间对LiFePO4/C性能的影响

以碳酸锂、磷酸铁、单水葡萄糖为主要原料,选用高效的立式搅拌磨做球磨设备,采用湿法球磨混料和高温固相反应法合成锂离子电池正极材料LiFePO4/C。研究了不同球磨时间对LiFePO4/C的物理性能和电化学性能的影响。通过粒度分布、振实密度、比表面积、扫描电子显微镜、充放电测试对材料性能进行表征。结果表明,控制球磨时间为3h,在热处理温度为700℃的条件下,合成的LiFePO4/C正极材料具有较好的性能,振实密度为1.41g/cm3,比表面积为13.9m2/g,以0.2C倍率充放电时的首次充放电效率为95.2%、首次放电容量为151.4mAh·g-1,1C充放循环100次的容量保持率为99.3%。     

LiFePO4/C复合正极材料的固相法合成

以LiOH·H2O、FeC2O4·2H2O、NH4H2PO4和C6H12 O6·H2O为原料,采用一步固相法在氮气氛下合成了LiFePO4/C复合正极材料.采用XRD、SEM和电池性能测试仪对合成产物进行了表征.研究了煅烧温度、煅烧时间、葡萄糖用量和锂过量对合成产物结构和电化学性能的影响.实验结果表明,采用一步固相法合成LiFePO4/C的最佳务件为:将经过高能球磨的前驱体在氮气氛下于650℃煅烧18h,葡萄糖用量为其它原料总质量的10％,锂过量10％(摩尔分数).在此条件下合成的LiFeP(4/C具有单一的橄榄石型结构和良好的电化学性能,0.1C的首次放电容量达到154.87mAh/g,30次循环后放电容量仍保持138.97mAh/g.     

锂离子电池正极材料LiNi0.5Mn1.5O4的固相法制备及性能研究

以Ni(CH3COO)2·4H2O和Mn(CH3COO)2·4H2O为原料,分别在400、500℃分解3、7h得到镍锰复合氧化物前驱体,再与锂源Li2CO3混匀,在800℃煅烧12h,600℃退火24h得到LiNi0.5Mn1.5O4正极材料。XRD、SEM、EIS和恒流充放电测试结果表明,在400℃、7h制备的前驱体与Li2CO3合成的LiNi0.5Mn1.5O4性能最佳。室温下以0.1C倍率充放电,首次放电比容量达到141.5mAh/g,循环30次后容量保持率为98.55%;以1C倍率充放电,首次放电比容量为120.34mAh/g,循环30次后放电比容量为112.09mAh/g。     

不同粒径球形LiFePO4的制备及其性能研究

利用控制结晶法制备了粒径约为1、5、10μm球形FePO4,以此为前驱体通过碳热还原法合成不同粒径的球形LiFePO4正极材料.采用XRD、SEM以及恒流充放电测试等手段对材料的结构、形貌和电化学性能进行表征,并比较了不同粒径产物的振实密度.合成的材料较好地保持了球形形貌,大粒径的样品振实密度高达2.03 g/cm3,...     

锂源对LiFePO4组织结构及电化学性能的影响

利用不同的锂化合物Li2CO3、LiOH.H2O、LiNO3、LiF作为锂源,采用二步固相法合成了LiFePO4/C,研究了不同锂源对LiFePO4组织结构和电化学性能的影响。结果表明,在相同的合成工艺条件下,采用4种不同锂源合成的LiFePO4的电化学性能表现出明显差异。采用LiOH.H2O合成的LiFe-PO4的电化学性能最佳,0.1C下的放电比容量为161mAh/g,1C下的放电比容量达117mAh/g,且0.5C下循环容量无衰减。采用不同锂源合成的LiFePO4电化学性能差异的原因与LiFePO4的颗粒大小、粒径分布、团聚程度及是否存在杂相有直接关系。     

锂离子电池复合正极材料xLiFePO4·yLi3V2(PO4)3的制备与性能研究

以FePO4·xH2O、V2O5、NH4H2PO4和Li2CO3为原料,以乙二酸为还原剂,在常温常压下经机械活化并还原嵌锂,形成无定形的5LiFePO4·Li3V2(PO4)3前驱体混合物,然后低温热处理合成出晶态的复合正极材料5LiFePO4·Li3V2(PO4)3.分别研究了复合材料的物相结构、形貌、电化学性能.SEM图像表明合成的材料粒径小、分布均匀,一次粒径为100～200nm.充放电测试结果表明,650℃烧结12h制得的复合正极材料5LiFePO4·Li3V2(PO4)3电化学性能优良,1C放电比容量高达158mAh/g,达到该复合材料的理论比容量(156.8mAh/g).复合材料具有良好的倍率性能和循环性能,在10C放电比容量高达114mAh/g,100次循环后容量几乎无衰减.循环伏安测试表明,复合材料的脱嵌锂性能优良,且明显优于单一的LiFePO4和Li3V2(PO4)3.     

用自制FePO4为铁源研究合成温度对LiFePO4/C电化学性能的影响

以FeSO4·7H2O,H3PO4,H2O2和NH3·H2O为原料合成纳米化的FePO4·1.5H2O,并将Li2CO3、FePO4·1.5H2O和葡萄糖混合球磨,在不同的温度下通过碳热还原合成LiFePO4/C.采用X射线衍射(XRD)、扫描电镜(SEM)、循环伏安(CV)和恒电流充放电测试研究了不同温度下合成的Li...     

纳米LiFePO4/C复合材料的制备和性能

以Fe(NO3)3·9H2O、H3PO4和稀氨水为原料,用控制结晶法制备FePO4·x H2O,研究了表面活性剂CTAB和PEG对FePO4·x H2O材料的影响。再以Li2CO3、蔗糖和高温烧结后的FePO4为原料用碳热还原法制备了纳米LiFePO4/C复合材料。用SEM、XRD、充放电测试、循环伏安测试等手段对该复合材料进行表征,研究其电化学性能。结果表明:添加表面活性剂制备的LiFePO4/C复合材料纳米颗粒呈球形且团聚减少,提高了材料的倍率性能和循环性能,其中添加CTAB制备的LiFePO4/C材料的颗粒最小、分散性较好,0.1C时的首次放电比容量为159.8 m Ah·g-1,10C倍率下比容量仍达到132.4 m Ah·g-1。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.