三元系ZrO2—Y2O3—Yb2O3材料的低温电性能

采用复阻抗技术对三元系ＺｒＯ２－Ｙ２Ｏ３－Ｙｂ２Ｏ３材料在５７３－８７３Ｋ内的离子电导率随组成的变化关系进行了研究,发现该材料的低温电导率随Ｙｂ２Ｏ２含量的增加而降低。用Ａｒｒｈｅｎｉｕｓ公式对实验数据进行的分析表明,电导率降低的原因在于Ｙｂ＾２＋与结构中氧空位之间的缔合比Ｙ＾３＋与氧空位之间的缔合更甚,阻碍了氧空位在低温下的定向迁移。     

掺入Al2O3对固体氧化物电解质材料YSZ性能影响的研究

在立方相的钇稳定化氧化锆〖（ＺｒＯ２）０．９２（Ｙ２Ｏ３）０．０８〗（ＹＳＺ）中,掺入少许不同量的Ｚｌ２Ｏ３,研究其对基体材料ＹＳＺ的烧结性能、机械强度和导电性能的影响,并对其机理进行了分析。实验结果表明,掺入Ａｌ２Ｏ３能够明显降低电解质烧结温度,改善烧结性能。在１３００℃烧结１ｈ后,少量掺杂Ａｌ２Ｏ３的样品晶粒尺寸明显比纯ＹＳＺ样品的小;从阻抗谱图上可以看出,随着Ａｌ２Ｏ３含量的增加,晶界电阻不     

SiC晶须增韧Al_2O_3及ZrO_2（Y_2O_3）基陶瓷复合材料的抗热震行

采用三点弯曲及扫描电镜等方法研究了ＳｉＣｗ／Ａｌ２Ｏ３、ＳｉＣｗ／ＺｒＯ３（Ｙ２Ｏ３）及ＳｉＣｗ／Ａｌ２Ｏ３＋ＺｒＯ２（Ｙ２Ｏ３）陶瓷复合材料的抗热震性．结果表现ＳｉＣｗ的加入使Ａｌ２Ｏ３、ＺｒＯ２（Ｙ２Ｏ３）以及Ａｌ２Ｏ３＋ＺｒＯ２（Ｙ２Ｏ３）基体的抗热震性显著提高，Ａｌ２Ｏ３陶瓷基复合材料的抗热震性明显优于ＺｒＯ２（Ｙ２Ｏ３）陶瓷基复复合材料．同时发现在Ａｌ２Ｏ３十ＳｉＣｗ材料基础上再加入少量ＺｒＯ２（２Ｙ）颗粒（１０Ｖｏ１％），也可进一步提高Ａｌ２Ｏ３＋ＳｉＣｗ材料的抗热震性．     

金属／YSZ多晶陶瓷电极交流阻抗特性

本文测量了以Ｙ２Ｏ３稳定的ＺｒＯ２（ＹＳＺ）电池：Ａｉｒ，Ｍ（ｐｔ、Ａｕ、Ｐｄ－Ａｇ）｜ＹＳＺ）｜Ｍ（ｐｔ、Ａｕ、Ｐｄ－Ａｇ），Ａｉｒ在２５０～５００°Ｃ、１２Ｈｚ～１００ＫＨｚ之间的交流阻抗．从作出阻抗谱分析，计算了ＹＳＺ多品陶瓷的晶内、晶界电阻及其对温度的依从性．晶界阻抗半圆的特征频率和温度的关系同样服从于Ａｒｒｈｅｎｉｕｓ公式．比较了Ｐｔ、Ａｕ和Ｐｄ－Ａｇ电极在ＹＳＺ氧化物电解质上的极化特性，并对氧通过各个电极扩散的电极过程中氧浓度－扩散率的积ＣＯ作了计算．     

共沉淀法制备Al_2O_3-YAG复相陶瓷及其显微结构研究

用共沉淀法制备了Ａｌ２Ｏ３－ＹＡＧ复合粉体,ＹＡＧ的结晶温度在１０００℃左右．共沉淀法 制备的Ａｌ２Ｏ３－ＹＡＧ复合粉体经１５５０℃热压烧结,获得致密烧结体,ＹＡＧ的加入量对烧结温度 的影响不大． Ａｌ２Ｏ３－５ｖｏｌ％ＹＡＧ复合材料的抗弯强度为６０４ＭＰａ,断裂韧性为５．０ＭＰａｍ１／２; Ａｌ２Ｏ３－２５ｖｏｌ％ＹＡＧ复合材料的抗弯强度为６１１ＭＰａ,断裂韧性为４５ＭＰａｍ１／２．所有这些数据 都高于单相Ａｌ２Ｏ３陶瓷的力学性能,说明ＹＡＧ的加入有利于Ａ１２Ｏ３陶瓷力学性能的提高． 通过显微结构观察发现：大的ＹＡＧ颗粒位于Ａｌ２Ｏ３晶界上,小的ＹＡＧ颗粒位于Ａｌ２Ｏ３晶粒 内．在 Ａｌ２Ｏ３－５ｖｏｌ％ＹＡＧ复合材料中,许多小的白色区域存在于 Ａｌ２Ｏ３晶粒内,这可能和较低 的Ｙ２Ｏ３含量有关．     

燃烧合成AlN/ Y2O3陶瓷及致密化机理分析

采用ＳＨＳ工艺,在１００ＭＰａ的高压氮气下,制备了具有较高致密度的ＡｌＮ／Ｙ２Ｏ３陶瓷,结果显示,Ａｌ－Ｎ２－Ｙ２Ｏ３体系的ＳＨＳ过程中,当反应温度升至１７６０Ｃ时,Ｙ２Ｏ３与Ａｌ２Ｏ３形成共晶液相Ｙ３ＡＩ３Ｏ１２,发生液相烧结。随着Ｙ２Ｏ３含量的增加,上烧结作用增强２,产物致密度显著提高,抗弯强度及断裂韧性。Ａｌ－Ｎ２－Ｙ２Ｏ３主要发生在燃烧波蔓延方向,具有明显的方向性。     

热处理对ZrO2（8mol%Y2O3）固体电解质电性能的影响

采用化学共沉淀法制备ＺｒＯ２（Ｙ２Ｏ３）超微粉。利用热膨胀法，Ｘ射线衍射分析及复阻抗分析研究热处理温度及升降温速度对ＺｒＯ２（８ｍｏｌ％Ｙ２Ｏ３）固体电解质四方相（ｔ）向单斜相（ｍ）的转变以及晶界偏析的影响。结果表明：降温速度可以改变ｔ－ＺｒＯ２相含量，热处理还会使ｍ相的含量增加，晶粒长大及晶界偏析，从而导致ＺｒＯ２（８ｍｏｌ％Ｙ２Ｏ３）固体电解质电导率下降。     

SiC晶须增韧Al2O3及ZrO2（Y2O3）基陶瓷复合材料的抗热震行为

采用三点弯曲及扫描电镜等方法研究了ＳｉＣｗ／Ａｌ２Ｏ３，ＳｉＣｗ／ＺｒＯ２）及ＳｉＣｗ／Ａｌ２Ｏ３＋ＺｒＯ２（Ｙ２Ｏ３）陶瓷复合材料的抗热震性。结果表明ＳｉＣｗ的加入使Ａｌ２Ｏ３，ＺｒＯ２（Ｙ２Ｏ３）以及Ａｌ２Ｏ３＋ＺｒＯ２（Ｙ２Ｏ３）基体的抗热震性显著提高，Ａｌ２Ｏ３陶瓷基复合材料的抗热震性明显优于ＺｒＯ２（Ｙ２Ｏ３）陶瓷基复合材料。同时发现在Ａｌ２Ｏ３＋ＳｉＣｗ材料基础上再加入少量ＺｒＯ２９２     

ZrO2-Y2O3(CaO)固体电解质的致密化烧结及电性能研究

研究了Ｙ２Ｏ３、ＣａＯ稳定剂及Ａｌ２Ｏ３、ＳｉＯ２（ＡＳ）添加剂对ＺｒＯ２固体电解质的烧结性能和电特性的影响。结果表明,加入ＡＳ的样品微观结构致密,其相对密度达到９７％。ＡＳ添加剂导致ＺｒＯ２固体电解质的粒界偏析和电导率下降,但是在ＡＳ含量很少时,对ＺｒＯ２的电特性影响不大。     

氧化钇含量对Al2O3／Y—TZP复相陶瓷的影响

本文以ＺｒＯＣｌ２．８Ｈ２Ｏ、Ａｌ２Ｏ３及Ｙ（ＮＯ３）３为原料，用共沉淀法合成Ｙ２Ｏ３含量不同的ＺｒＯ２－Ａｌ２Ｏ３复合粉体，并采用热压工艺制备复相陶瓷。研究了氧化钇含量对复相陶瓷力学性能及应力诱导下氧化锆相变能力的影响。     

四氯苯醌/三苯磷可控掺杂四取代酞菁铜薄膜材料的导电性能研究

本文通过电化学沉积方法制备了一种四氯苯醌/三苯磷可控掺杂四取代酞菁铜薄膜材料体系,研究了该可控掺杂有机薄膜材料的导电性能.研究结果表明,四取代酞菁铜可控掺杂薄膜材料的电导率,随着温度的升高或掺杂剂浓度的增加而显著增加,其原因是酞菁铜给体与四氯苯醌和三苯基磷等小分子电子受体之间发生了较强的氧化还原作用.     

Cu-3.0Ni-0.75Si合金时效析出动力学分析

为研究Cu-3.0Ni-0.75Si合金时效过程中沉淀相的析出与长大规律,及其对合金硬度的影响,采用涡流电导仪和布氏硬度计分别测量合金的电导率和硬度,根据导电率与新相析出量之间的关系分析合金的时效析出动力学过程.结果表明,在350℃下时效,合金硬度随时效时间的延长,先升高后趋于平缓;在450℃、550℃下时效,合金硬度随时效时间的增加快速上升,到达峰值后缓慢下降;时效温度越高,合金硬度峰值越低,但硬度达到峰值所需的时间越短.温度一定,随时效时间的增加,合金电导率在时效初期快速升高,至峰值后趋于平缓.根据Cu-3.0Ni-0.75Si合金在450℃时效过程中电导率的变化,通过Avrami方程推导出相应的相变动力学方程及电导率方程分别为f=1-exp(-0.052 2t0.717 61)和σ=15.2+16.3[1-exp(-0.052 2t0.717 61)],采用相关系数检验法及F检验法对电导率方程的可信性进行检验,结果说明时效析出动力学方程和电导率方程具有一定的可靠性.对比由电导率经验方程得出的电导率理论值与测量得出的实验值,该理论值与实验值有良好的吻合度.     

The effects of impurity doping on the optical properties of biased bilayer graphene

We address the optical conductivity of doped AA-stacked bilayer graphene in the presence of a finite bias voltage at finite temperature. The effect of scattering by dilute charged impurities is discussed in terms of the self-consistent Born approximation. Green's function approach has been implemented to find the behavior of optical conductivity of bilayer graphene within linear response theory. We have found the frequency dependence of optical conductivity for different values of concentration and scattering strength of dopant impurity. Also the dependence of optical conductivity on the impurity concentration and bias voltage has been investigated in details. A peak appears in the plot of optical conductivity versus impurity concentration for different values of chemical potential. Furthermore we find optical conductivity reduces with frequency for any impurity concentration and scattering strength.     

Thermal conductivity by a pulse-heating method: Theory and experimental apparatus

A new dynamic technique for the measurement of thermal conductivity at high temperatures has been developed at the IMGC. The specimen is brought to high temperatures with a current pulse; during cooling the heat content is dissipated by radiation and by conduction. The differential equation describing this process contains terms related to the heat capacity, the hemispherical total emittance, and the thermal conductivity of the material. If the first two properties are determined using the same specimen during subsecond pulse heating experiments, thermal conductivity may be evaluated by accurate measurements of the round-shaped temperature profiles established on the specimen during cooling. High-speed scanning pyrometry makes possible accurate measurements of temperatures and of temperature derivatives (with respect to space and time), which enables the differential equation describing the power balance at each point of the specimen to be transformed into a linear equation of the unknown thermal conductivity. A large overdetermined system of linear equations is solved by least-squares techniques to obtain thermal conductivity as a function of temperature. The theory underlying the technique is outlined, the experimental apparatus is described, and details of the measurement technique are given.Paper presented at the First Workshop on Subsecond Thermophysics, June 20–21, 1988, Gaithersburg, Maryland, U.S.A.     

Polar Side Chains Enhance Processability,Electrical Conductivity,and Thermal Stability of a Molecularly p‐Doped Polythiophene

Molecular doping of organic semiconductors is critical for optimizing a range of optoelectronic devices such as field‐effect transistors, solar cells, and thermoelectric generators. However, many dopant:polymer pairs suffer from poor solubility in common organic solvents, which leads to a suboptimal solid‐state nanostructure and hence low electrical conductivity. A further drawback is the poor thermal stability through sublimation of the dopant. The use of oligo ethylene glycol side chains is demonstrated to significantly improve the processability of the conjugated polymer p(g₄2T‐T)—a polythiophene—in polar aprotic solvents, which facilitates coprocessing of dopant:polymer pairs from the same solution at room temperature. The use of common molecular dopants such as 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) is explored. Doping of p(g₄2T‐T) with F4TCNQ results in an electrical conductivity of up to 100 S cm^?1. Moreover, the increased compatibility of the polar dopant F4TCNQ with the oligo ethylene glycol functionalized polythiophene results in a high degree of thermal stability at up to 150 °C.     

The thermal conductivity of commercial brines and seawater in the freezing rangeLa conductivité thermique des saumures du commerce et de l'eau de mer en régime de congélation

This study refers to the thermal conductivity of the slush formed by NaCl and CaCl₂ brines and seawater between their freezing and eutectic temperatures. Based on equations of state relating freezing temperature and salinity, the variation of density and conductivity of the liquid brines between 0°C and their freezing points is shown on diagrams for various parameters of salinity. Their conductivity and that of ice at the respective low temperatures are introduced into a modified Maxwell-Eucken equation for calculating the conductivity of the slush. The results are given in diagrams and in empirical equations.     

双组元掺杂钛硅再结晶石墨传导性能的研究

用煅烧石油焦作填料,煤沥青作粘结剂,钛粉和硅粉作添加剂,采用热压工艺制备了一系列双组元掺杂再结晶石墨.考察了不同质量配比的添加剂对再结晶石墨的热导率、电阻率和抗弯强度的影响以及微观结构的变化.实验结果表明,与相同工艺条件下制备的纯石墨材料相比较,掺杂15wt％钛粉再结晶石墨的传导以及力学性能有较大幅度的提高.在掺杂钛粉15wt％、硅粉<2wt％时,双组元再结晶石墨的常温热导率随着硅粉的掺杂量的增加有所提高.当掺杂钛粉及硅粉分别为15wt％和2wt％时,再结晶石墨RG-TiSi-152的常温热导率可达494W/m·K.但是当掺杂钛粉15wt％、硅粉>2wt％时,随着硅粉的继续增加,再结晶石墨的常温热导率反而降低.而双组元掺杂钛硅再结晶石墨的导电以及力学性能却随着硅粉的掺杂量的增加而降低.XRD分析表明,对于双组元掺杂钛硅再结晶石墨而言,钛元素最终在材料中以碳化钛形式存在,而硅元素则大都以气态形式被逸出,XRD物相图谱中未发现硅及其碳化物的存在.材料RG-TiSi-152的微晶尺寸La以及晶面层间距d002分别为864和0.3355nm.     

Thermal conductivity and diffusivity measurements at cryogenic temperatures by double specimen technique

A double specimen technique is used in measuring the thermal conductivity and diffusivity of low thermal conductivity materials. In this technique good thermal contact is maintained between the heat source and sink and two geometrically similar specimens. A thin-copper heater plate is compressed between the two specimens and the temperature difference is measured between the heat source and the temperature controlled heat sink. Thermal conductivity is determined at steady state conditions by the differential method while the diffusivity is determined from transient measurements combined with an analytical solution to the one dimensional solution of the diffusion equation.     

自由体积理论在聚氨酯/掺杂盐体系中的应用与矫正

利用交流阻抗谱仪，FT－IR，DSC研究了聚氨酯／盐体系的离子状态和电导率，通过自由体积理论推导了聚合物固体电解质电导率的计算公式，为使公式更符合实际离子的存在状态，用变温红外光谱首次对离子状态随温度的变化进行跟踪研究，对公式进行了改进，并从电导率数据计算出了VTF公式应用于聚氨酯／LiCF3SO4体系的各种参数，讨论了盐浓度对参数的影响。     

N‐Type Organic Thermoelectrics: Improved Power Factor by Tailoring Host–Dopant Miscibility

In this contribution, for the first time, the polarity of fullerene derivatives is tailored to enhance the miscibility between the host and dopant molecules. A fullerene derivative with a hydrophilic triethylene glycol type side chain (PTEG‐1) is used as the host and (4‐(1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol‐2‐yl)phenyl)dimethylamine n ‐DMBI) as the dopant. Thereby, the doping efficiency can be greatly improved to around 18% (<1% for a nonpolar reference sample) with optimized electrical conductivity of 2.05 S cm^?1, which represents the best result for solution‐processed fullerene derivatives. An in‐depth microstructural study indicates that the PTEG‐1 molecules readily form layered structures parallel to the substrate after solution processing. The fullerene cage plane is alternated by the triethylene glycol side chain plane; the n ‐DMBI dopants are mainly incorporated in the side chain plane without disturbing the π–π packing of PTEG‐1. This new microstructure, which is rarely observed for codeposited thin films from solution, formed by PTEG‐1 and n ‐DMBI molecules explains the increased miscibility of the host/dopant system at a nanoscale level and the high electrical conductivity. Finally, a power factor of 16.7 µW m^?1 K^?2 is achieved at 40% dopant concentration. This work introduces a new strategy for improving the conductivity of solution‐processed n‐type organic thermoelectrics.