柔性聚苯胺电极体积电容的提高:溶液浇铸法以及还原氧化石墨烯的影响

高体积比电容是柔性超级电容器的关键.在本文中,我们设计并制备了一种具有超高体积比电容和良好倍率性能的柔性复合电极.该膜电极以无孔且致密的聚苯胺作为基质,少量的还原氧化石墨烯片作为填料,通过一种新开发的溶液浇铸法制备而成.用于浇铸的溶液是由聚苯胺和氧化石墨烯的混合溶液自组装制备得到.关于还原氧化石墨烯作用的系统研究结果表...     

固体氧化物燃料电池封接玻璃的研究:成分与性能

固体氧化物燃料电池封接玻璃在初期必须具备一定的流动性以便有效形成封接,进而保持足够的机械强度。它的热膨胀系数必须与燃料电池的其它部件相匹配,还需要具有化学稳定性。通过对研制的80多个逆性硅酸盐玻璃成分的分析,获得了成分-性能的一些规律:B2O3能够降低玻璃的软化温度和玻璃转变温度;ZnO通过拓宽玻璃转变温度和结晶温度之间的温度范围而改善封接性能,如Zn/Si比为0.7的成分可以获得230℃的温度范围;逆性玻璃的热膨胀系数取决于网络配体的平均势场强度,如加入BaO因为其较小的势场强度而提高玻璃的热膨胀系数,而加入势场强度较大的ZnO则呈现相反趋势。     

La2Cu04＋δ在加热过程中氧的逸出与电导率的变化

研究了La2Cu04 δ试样在加热过程中氧的逸出及其对试样电导率的影响。结果表明La2Cu04 δ试样的电导率与其所逸出的氧分子数密切相关。未经电化学充氧、即间隙氧含量较低的试样,在673K和1073K附近有两个氧逸出过程,前者为间隙氧的逸出,其导致CuO2平面空穴载流子浓度的降低而使试样的电导率显著下降;后者系晶格中的氧逸出,使晶格中产生氧空位,但对试样电导率影响较小。经电化学充氧的间隙氧含量较高的试样,在533K和673K附近有两个脱氧过程,分别对应处于两种状态的间隙氧的逸出,两者均导致空穴载流子浓度的降低而使试样的电导率显著下降。     

电导率与溶液浓度函数之间直线关系的经验公式研究

本文通过对有代表性的不同价型的几种强电解质溶液电导率的测定,得出了溶液的电导率和其浓度之间,以及电导率与溶液的离子强度之间均呈现出直线关系,其回归方程的相关系数都达到了两个9以上,属于极显著相关,获得了比较满意的结果.     

WO_(3)敏感电极的制备及其性能研究北大核心CSCD

迈向微型化、集成化及具有高选择性和灵敏度的固体电解质气体传感器已成为未来的发展趋势。文章采用磁控溅射法成功制备了WO_(3)气体传感器敏感电极材料,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)等表征手段研究了WO_(3)的结构、成分和形貌并测试了该气体传感器对NO_(2)的气敏性能。XRD结果表明,当退火温度大于400℃时,WO_(3)出现(200)衍射峰,且该衍射峰随退火温度增加而显著增强,表明WO_(3)结晶质量增加。SEM测试结果表明,随着退火温度的升高,薄膜的晶粒尺寸逐渐增大。当退火温度达到500℃时,采用谢乐公式计算其晶粒尺寸达到23 nm。EDS结果表明,退火温度对薄膜的成分也有较大影响,O:W原子比例呈现增大趋势,由2.7增加到3.2,这与XPS结果相符合。通过高温气敏性能测试表明,所制得的WO_(3)敏感电极对NO_(2)表现出了明显的气体响应。本研究为制备微型化、高选择性和灵敏性的固体电解质气体传感器提供了一定的研究基础。     

堇青石微晶玻璃与银电极的共烧兼容性

通过在MgO-Al2O3-SiO2(MAS)凝胶玻璃中引入少量银,研究了共烧过程中银对凝胶玻璃的析晶过程、烧结特性和介电性能的影响,以及微晶玻璃与银电极的共烧匹配性。结果表明,银的引入可促进α-堇青石析晶,并使微晶玻璃的烧结温度和介电常数降低。微晶玻璃和电极存在明显共烧失配,从而导致界面缺陷。     

WC-Co硬质合金的性能与成分和显微结构的关系

通过XRD相分析,SEM显微结构参数和磁性、密度与力学性能测试,探讨了两相WC－Co硬质合金的断裂韧性KIC、抗弯强度σTRS、维氏硬度HV、比矫顽磁力HSC间及其同γ粘结相平均自由程λγ间的定量实验关系。结果表明,随λγ改变,KIC和σTRS与HIV和HSC间具有反向相关的变化规律。提出了用磁性和密度测定值无损鉴定WC－Co硬质合金的成分和显微结构参数及评估合金力学性能的实验原理。     

与标准平均海水同位素成分相近的石英水三相点瓶的研制

介绍了与标准平均海水同位素(VSMOW)成分相近的石英水三相点瓶的研制过程和试验分析结果.利用新的制作工艺,所有水三相点瓶的同位素成分δD和δ18O可被分别控制在±10‰和±1.5‰之内,这样即使没有进行同位素修正,由同位素成分与VSMOW的偏离对温度的影响仍可控制在±8μK之内.如果对某个水三相点容器的同位素成分单独分析,并用分析结果对水三相点温度值进行修正,则由上述因素对温度的影响可控制在±3μK之内.实验结果表明,硼硅玻璃水三相点瓶的年漂移约为-13μK,而石英水三相点瓶年漂移约为-2μK,因此,石英水三相点瓶比硼硅玻璃水三相点瓶的性能更加优越.     

基于分形理论的玻璃纤维真空绝热热工特性研究

基于分形理论,描述了玻璃纤维多孔介质材料微尺度空间结构,建立分形等效单元体模型,分析了影响其真空下有效导热系数关键因素为固体基质导热系数、空隙率、纤维丝空间结构、分形直径、残余气体压力及导热系数、玻璃纤维材料厚度、使用环境等,并导出了气相、固相热传导计算公式和热辐射等效导热系数计算公式及材料总有效导热系数计算公式.研究表明,玻璃纤维有效导热系数随着分形直径、分形维数、残余气体压力的增大而增大,随着空隙率的增大而减小.同时,模型计算值与实验测量值比较,具有较好的一致性.文章的分析方法对新型真空绝热材料的研制和绝热性能的提高具有实用价值.     

Effect of Pb Ions on the Ionic Conductivity of Some Silicate Glass Systems

Conductivity of glasses in the systems SiO2.PbO.RO, (where R=Ca, Sr or Ba) was investigated between room temperature and 530 K. The dependence of log resistivity as well as the activation energy on the PbO content has been studied. Based on the present experimental results, the possible different conduction mechanisms in such glasses are discussed. It was postulated that Pb2+ ions may represent the major charge carrying species in these glasses. This assumption was confirmed by the calculations of the mean distance between the interstitial Pb2+ ions and the effective center of the O2- ions in the glass networks. The variation in the values of the density and the molar volume with PbO content is also discussed in view of the obtained activation energies for the studied glass-systems.     

电导率在确定水中总放射性检测项目取样体积的应用

在检测水中总α放射性和总β放射性的时候,对于一些蒸发残渣较少的水样,为了得到足够的固体残渣用于铺样,需要预先知道所需蒸干的水样体积。本文通过试验研究了水样的电导率数值与蒸发残渣数值之间的对应关系。试验结果表明,西江、北江水系水样的电导率数值和残渣含量之间的平均关联系数(电导率/残渣含量)为1.8,该系数不受季节变化的影响。东江水系水样的平均关联系数为2.0。通过测定水样的电导率值,再根据水样的电导率数值与蒸发残渣数值之间的对应关系计算得出取样体积,从而提高总放射性项目检测结果的准确度。     

相对湿度对泡沫玻璃导热系数的影响

采用瞬态平面热源法在不同的环境相对湿度下对3对泡沫玻璃的导热系数进行了测量。实验结果表明,在相对湿度较低的情况下,试样的导热系数受湿度影响较小,几乎不随环境湿度变化;在相对湿度较高的情况下,试样的导热系数随湿度的增大而增大,与低湿度时相比导热系数最多增大了近1.5%;此外,实验结果还表明泡沫玻璃的导热系数存在不均匀性,不同区域的导热系数值存在较大差别,最大可相差8.8%。     

Thermal Conductivity of Polymethyl Methacrylate (PMMA) and Borosilicate Crown Glass BK7

The thermal conductivity of polymethyl methacrylate (PMMA) and borosilicate crown glass BK7 has been studied. The transient hot-wire technique has been employed, and measurements cover a temperature range from room temperature up to 350 K for PMMA and up to 500 K for BK7. The technique is applied here in a novel way that minimizes all remaining thermal-contact resistances. This allows the apparatus to operate in an absolute way and with very low uncertainty. The method makes use of a soft silicone paste material between the hot wires and the solid under test. Measurements of the transient temperature rise of the wires in response to an electrical heating step over a period of 20 μs up to 5 s allow an absolute determination of the thermal conductivity of the solid, as well as of the silicone paste. The method is based on a full theoretical model with equations solved by a two-dimensional finite-element method applied to the exact geometry. At the 95% confidence level, the standard deviations of the thermal conductivity measurements are 0.09% for PMMA and 0.16% for BK7, whereas the standard uncertainty of the technique is less than 1.5%.     

Modulating Ion Diffusivity and Electrode Conductivity of Carbon Nanotube@Mesoporous Carbon Fibers for High Performance Aluminum–Selenium Batteries

Selenium (Se)‐based rechargeable aluminum batteries (RABs), known as aluminum–selenium (Al–Se) batteries, are an appealing new battery design that holds great promise for addressing the low‐capacity problem of current RAB technology. However, their applications are hindered by mediocre high‐rate capacity (≈100 mAh g^?1 at 0.5 A g^?1) and insufficient cycling life (50 cycles). Herein, the synthesis of mesoporous carbon fibers (MCFs) by coating mesoporous carbon with short‐length mesopores and tunable mesopore sizes (2.7 to 8.9 nm) coaxially on carbon nanotubes (CNT) is reported. When compositing MCFs with Se for Al–Se batteries, a positive correlation between mesopore size and electrolyte ion diffusivity is observed, however when pore size is increased to 8.9 nm, large voids are created at the interface of CNT core and mesoporous carbon shell, leading to decreased electrode conductivity. The trade‐off between ion diffusivity and interfacial connectivity/conductivity determines MCF with pore size of 7.1 nm as the best host material for Al–Se batteries. The composite cathode delivers high specific capacities (366 and 230 mAh g^?1 at 0.5 and 1 A g^?1), good rate performance, and excellent cycling stability (152 mAh g^?1 after 500 cycles at 2 A g^?1), superior over previously reported Se cathodes and other cathodes for RABs.     

Stability of Standard Electrolytic Conductivity Solutions in Glass Containers

The stability of solutions having an electrolytic conductivity, κ, of 5 μS/cm to 100 000 μS/cm packaged in glass screw-cap bottles, glass serum bottles, and glass ampoules was monitored for 1 year to 2 years. The conductivity was determined by measuring the ac resistance of the solution. Mass loss was also monitored for solutions packaged in bottles. The solutions were prepared using KCl in water (κ ≥100 μS/cm) or KCl in 30 % (by mass) n-propanol 70 % (by mass) water (κ ≤ 15 μS/cm). The conductivity changes were compared by packaging type and by nominal κ. The main causes of the κ changes are evaporation (screw-cap bottles) and leaching (screw-cap bottles, serum bottles, and ampoules). Evaporation is determined from mass loss data; leaching occurs from the glass container with no change in mass. The choice of optimal packaging, which depends on the conductivity level, is the packaging in which κ changes the least with time. Ampoules are the most suitable packaging for standards having nominal κ values of 500 μS/cm to 100 000 μS/cm. Screw-cap bottles are most suitable for standards having a nominal κ of 5 μS/cm to 100 μS/cm.     

玻璃池窑保温设计中隔热度与外表面温度关系探讨

本文针对玻璃池窑内壁温度、窑体部位以及环境温度之间的各种不同关系,利用分步逐次拟合的数值计算方法,推导出隔热度与外表面温度关系的显性经验公式,并由此得出隔热度与表面散热热流的相应关系式,方便了保温设计计算,为进一步实现窑体保温优化设计提供了条件     

复相陶瓷导电性与其粒径级配的关系研究

通过对无序渗流模型的修正，建立了具有不同特征尺寸的两相无序体系的导电模型，推导了相关关系式，将其结果与相复合导电陶瓷的实验结果进行了比较，结论相当一致。由此揭示了陶瓷生料的两相粒径分布对复合导电陶瓷导电性的影响。