利用卫星探测研究地下结构

介绍了国外利用卫星上观测的电子流量和磁场资料进行地下结构探测研究的一些成果.研究表明,卫星上记录到的不同能量电子流量脉冲突变与地下结构、深大岩石圈断裂带有密切的对应关系.卫星磁场观测具有覆盖全球的优势,随着卫星磁场数据观测精度的提高,卫星磁测在全球磁变模型的建立、研究大陆内部结构、大陆和海洋边界带、地幔过渡带等方面的将发挥越来越重要的作用.卫星观测将成为全面、整体探测研究地球内部结构有效的手段之一.

SOFC阳极原始粉末制备工艺对阳极片微结构和电性能的影响

固体氧化物燃料电池(SOFC)的阳极是燃料氧化反应的场所,是SOFC的重要组成部分。然而具有较好催化活性的Ni-SDC阳极的制备目前普遍采用的是NiO与Ce0.8Sm0.2O1.9(SDC)混合的方法,即外加法,很少有用内加法同时制备出包含有NiO与SDC的NiO-SDC粉体。阳极材料的加工方法有可能会对Ni-SDC阳极性能产生大的影响,很有研究的必要。采用柠檬酸-硝酸盐溶胶-凝胶低温自蔓延燃烧法分别制备了NiO、SDC、NiO-SDC(质量比NiO∶SDC=1∶1)和Co3O4-NiO-SDC(质量比Co3O4∶NiO∶SDC=1∶1∶2)粉末,采用X射线衍射仪(XRD)检测了粉体的成相情况。将单独制备的NiO与SDC粉末按质量比为1∶1制成阳极片a,NiO-SDC粉末和Co3O4-NiO-SDC粉末也分别制成了阳极片b和阳极片c。并采用四端子法测量了其电导率值。分析了电导率与原始粉体制备工艺及阳极片的微结构之间的关系。结果显示,用上述方法合成的粉体成相很好,阳极片的电导率与微结构有极强的联系,微结构则受其原始粉末制备工艺和组成的强烈影响。

2013年3月3日洱源M_S5.5地震前地磁谐波振幅比异常研究

本文首先使用滇西北地磁台阵8个测点2012年6月1日—2013年5月31日记录的短周期地磁数据,计算得到各测点的谐波振幅比时间序列变化曲线.该曲线显示:各测点的谐波振幅比YZHy和YHD在2013年3月3日普洱MS5.5地震前均呈显著高值,发震前则刚好是由高转低再上升的一个转折点;而谐波振幅比YZHx没有出现类似的异常变化.其次通过对台阵区地下电导率结构的定性分析,对该计算结果予以解释.对于地磁短周期垂直分量反相现象和威斯矢量分布的分析结果表明,地下存在着近似南北走向的电导率异常带.由于台阵区域YZHy和YHD的异常变化代表南北向地下电导率变化和地下电导率不均匀,因此谐波振幅比的变化与电导率异常带的分布一致,表明谐波振幅比的变化与地下电性结构密切相关.

二维对称各向异性介质大地电磁反演

考虑一种二维构造走向与一水平各向异性主方向一致的对称各向异性介质.在这种特殊情况下,若假设电导率沿垂向和倾向表现相同的各向异性,即σzz=σyy,则得到形式完全等同于各向同性情形TE和TM极化方程的微分方程.因此,就可用各向同性完全相同的反演方法,获得二维各向异性介质的电导率.亦即各向同性介质的TE和TM极化反演结果,可以解释为对称各向异性介质两主方向上的电阻率.这为MT解释提供了新的解释途径及其理论依据.最后用由此发展起来的各向异性介质反演方法,对甘肃天祝永登一带大地电磁资料进行了反演试验。

天祝—永登地区大地电磁资料的一维各向异性反演

对分布在甘肃天祝、永登一带的10个大地电磁测点资料进行了一维各向异性介质反演研究,并与二维对称各向异性介质反演结果进行了对比。结果表明在大多数情况下一维各向异性反演有可能揭示出地壳介质电导率各向异性结构的主要特征;同时利用某些平均阻抗和特征阻抗的一维各向同性介质反演亦可获得较为可信的电性分层界面。反演所获得之介质电导率可能为各主方向电导率主值的某种平均。

Ambient electrical conductivity of carbon cathode materials for aluminum reduction cells

The ambient electrical conductivity (AEC) of carbon cathode materials was investigated in respect to their open porosity, crystal structure and graphite content using hydrostatic method, four-probe technique and X-ray diffraction (XRD), respectively. The AEC is proportional to the specific conductivity (σ0) and the exponential of (1?ε) (ε is porosity) by a quasi-uniform formula based on the percolation theory. Theσ0 can reflect the intrinsic conductivity of the carbon cathodes free of pores, and it depends on the mean crystallite size parallel to the layer (002). The exponentn is dependent on the materials nature of the cathode aggregates, while an averaged value, 4.65, can practically work well with 5 types of cathode materials. The calculation ofσ0 can be extended to the graphitic cathodes containing different aggregates using the simple rule of mixture.

Comparative experiments on electro-osmotic treatment effect of polluted soil using EKG and iron electrodes

This study presents a comprehensive comparison of the electro-osmosis treatments of heavy metal contaminated soil using electrokinetic geosynthetics(EKG)and iron electrodes in terms of both theoretical analysis and experimental research.The variation in the electrical parameters was analyzed,and the results show linear relationships between temperature and conductivity and between the soil and pore water conductivities.The average cathode contact resistance of iron is60%smaller than that of EKG,whereas the average anode contact resistance of EKG is56%smaller than that of iron.The values of the power consumption per unit mass of contaminants for EKG and iron are1.895and1.989kJ/g,respectively.After electro-osmosis,the number of soil pores increased,but the average area decreased,with an average area of0.9100–1.0504μm^2.Based on microstructure analysis,we obtained higher electroosmotic efficiency and realized the effective analysis and utilization between macroscopic and microscopic parameters.

Thermal conductivity of PVDF/PANI-nanofiber composite membrane aligned in an electric field

Poly(vinylidene fluoride)(PVDF) is a semi-crystalline thermoplastic polymer with excellent thermal stability,electrochemical stability and corrosion resistance, which has been widely studied and applied in industrial nonmetallic heat exchanger and piezoelectric-film sensor. In this study, polyaniline(PANI) nanofibers were synthesized using dodecylbenzene sulfonic acid as the surfactant. The obtained PANI nanofibers were blended in PVDF matrix to enhance thermal conductivity and tensile strength of composite materials. Electric field was applied for the orientation of membrane structure during membrane formation. Scanning electron microscope(SEM) images exhibited that the PANI nanofibers were well-dispersed in the composite membranes. The structure of composite membranes was more orderly after alignment. X-ray diffraction(XRD) and differential scanning calorimetry(DSC) indicated that the content of PANI nanofibers contributed to the transformation of PVDF from α-phase to β-phase. Both the tensile strength and thermal conductivity of composite membranes were significantly improved. This tendency was further enhanced by the application of electric field. The maximum tensile strength was obtained when the content of PANI nanofibers was 3 wt%, which was 46.44% higher than that of pure PVDF membrane. The maximum thermal conductivity of composite membranes after alignment was 84.5% greater than that of pure PVDF membrane when the content of PANI nanofibers was 50 wt%. The composite membrane is a promising new potential material in heat transfer field and the mechanism explored in this study would be informative for further development of similar thermal conductive polymeric materials.

Structure, Energy Band Gap and Electrical Conductivity of Tapioca/Metal Oxide Composite

A natural polymer composite is the main choice to replace composites from petroleum derivatives. A composite is formed in two or more phases （i.e., organic and inorganic phases）. A composite that has specified energy band gap, electrical conductivity, and tensile strength can be used as semiconductor material. The objective of this research was to study the effect of production methods, concentration and type of metal oxide filler （TiO2, A1203, Fe203, and ZnO） on structure, energy band gap, and electrical conductivity of composites. Composites were prepared using a melt intercalation process with tapioca as a matrix and addition of 1%, 3%, 5o and 7% filler concentrations, and sonication processing time in interval of 40, 50, and 60 min. Structure and morphology of the composite were analyzed using FT-IR, XRD, SEM, and TEM. UV-vis was used to measure the energy band gap while electrical conductivity was measured using a potentiostat through determination of resistivity. In addition, tensile strength and elongation were measured by ASTM 822-02. The energy band gap of the tapioca/metal oxide composite was between 4.9-1.62 eV. Electrical conductivity showed a percolation thresholds for concentrations of 3%-5% TiO2, A1203, and Fe203 and 7% ZnO. The tapioca/ZnO composite with 5% ZnO and 50 min of processing time showed a maximum tensile strength of 74.84 kgf/cm2, 6% elongation, 1.27 - 10^-7ohm^-1cm^-1 electrical conductivity and energy band gap of 3.27 eV. The characteristics described show that the tapioca/metal oxide composite can be used as a semiconductor material.

Reconstruction of solid oxide fuel cell electrode microstructure and analysis of its effective conductivity

The effective conductivity （aeff） of solid oxide fuel cell （SOFC） electrode is an important parameter for predicting the ohmic loss in SOFC. This paper investigates the effective conductivity of SOFC electrodes recon- structed numerically by packing spherical particles in a computational domain, followed by a dilation process to simulate the sintering procedure. The effects of various parameters on the effective conductivity of the electrodes are investigated, including material composition, porosity, particle size and contact angle. Results show that the effective conductivity ratio （aeff/ao） of the computed con- ducting phase is mainly affected by its total volume frac- tion （VF） in electrode （including the porosity）. The effective conductivity can be improved by increasing the VF, electrode particle size or the contact angle between electrode particles. Based on the numerical results, the conventional percolation model for the calculation of O＇eft is improved by adjusting the Bruggeman factor from 1.5 to 2.7. The results are useful for understanding the microstructure properties of SOFC composite electrode and for subsequent electrode optimization.

Biomimetic brain-like nanostructures for solid polymer electrolytes with fast ion transport

The intrinsic drawbacks of electrolytes and the growth of lithium dendrites limit the development of commercial lithium batteries.To address the aforementioned challenges,a novel biomimetic brain-like nanostructure(BBLN)solid polymer electrolyte was created by manipulating the shape of the incorporated nanoparticles.Our designed BBLN solid polymer electrolyte was created by incorporating spherical core-shell(UIO-66@67)fillers into polymer electrolyte,which is significantly different from traditional polymer-based composite electrolytes.UIO-66@67 spherical nanoparticles are highly favorable to eliminating polymer electrolyte stress and deformation during solidification,indicating a great potential for fabricating highly uniform BBLN solid polymer electrolytes with a substantial number of continuous convolutions.Furthermore,spherical nanoparticles can significantly reduce the crystalline structure of polymer electrolytes,improving polymer chain segmental movement and providing continuous pathways for rapid ion transfer.As a result,BBLN solid polymer electrolyte shows excellent ionic conductivity(9.2×10^(−4)S cm^(−1)),a high lithium transference number(0.74),and outstanding cycle stability against lithium electrodes over 6500 h at room temperature.The concept of biomimetic brain-like nanostructures in this work demonstrates a novel strategy to enhance ion transport in polymerbased electrolytes for solid-state batteries.

“Phonon” scattering beyond perturbation theory

Searching and designing materials with intrinsically low lattice thermal conductivity （LTC） have attracted extensive considera- tion in thermoelectrics and thermal management community. The concept of part-crystalline part-liquid state, or even part-crystalline part-amorphous state, has recently been proposed to describe the exotic structure of materials with chemical-bond hierarchy, in which a set of atoms is weakly bonded to the rest species while the other sublattices retain relatively strong rigidity. The whole system inherently manifests the coexistence of rigid crystalline sublattices and fluctuating noncrystalline substructures. Representative materials in the unusual state can be classified into two categories, i.e., caged and non-caged ones. LTCs in both systems deviate from the traditional 7-1 relationship （T, the absolute temperature）, which can hardly be described by small-parameter-based perturbation approaches. Beyond the classical perturbation theory, an extra rattling-like scattering should be considered to interpret the liquid-like and sublattice-amorphization-induced heat transport. Such a kind of compounds could be promising high-performance thermoelectric materials, due to the extremely low LTCs. Other physical properties for these part-crystalline substances should also exhibit certain novelty and deserve further exploration.