BaFe0.4 Sn0.6 O3 /BaBiO3负温度系数复合热敏陶瓷阻抗分析

以BaBiO₃为导电相,BaFe_0.4Sn_0.6O₃为高阻相,采用固态反应法制备了不同BaBiO₃含量的BaFe_0.4Sn_0.6O₃/BaBiO₃负温度系数(NTC)热敏复合陶瓷.为获得在渗流阈值(即BaBiO₃含量为12 mol%)前后复合陶瓷的内部导电机理,对复合陶瓷进行了阻抗分析.分     

Sb2 Te3 纳米结构的制备与表征

以室温热电性能优异的传统热电材料Sb₂Te₃为研究对象,利用化学气相沉积法制备Sb₂Te₃单晶纳米结构,并研究其生长机理.实验结果表明,不加催化剂时Sb₂Te₃易生长成六方纳米盘,在金催化剂条件下定向生长成纳米线.Sb₂Te₃的形貌与其晶体结构和生长机理有关.Sb₂Te₃为三角结构,Sb和     

Bi2 Te3 合金低温热电性能及冷能发电研究

利用机械合金化和冷压烧结法制备得到n型和p型Bi₂Te₃基热电材料,在80—300 K温度范围测量了电导率、Seebeck系数,结果表明其具有良好的低温热电性能.采用Bi₂Te₃基热电材料制备出半导体热电器件,并配合附属设备搭建出一套半导体温差发电装置.利用液氮汽化时释放的冷能,对半导体热电器件的发电性能进行实验研究,得出这种半导体热电器件输出电压、输出功率与电流关系式,测得最大的输出功率达到1.33 W,从而证明了冷     

氧化钒晶体的半导体至金属相变的理论研究

本文利用第一性原理方法研究了金红石相和单斜相VO₂晶体的电子结构和热力学性质.在计算中采用局域密度近似结合Hubbard U模型(LDA+U)描述电子的局域强关联效应,同时也利用微扰密度泛函方法计算了两种相结构的声子谱.计算结果表明V原子3d电子轨道中x²-y²轨道能级分裂决定了VO₂晶体在不同相结构下的金属和绝缘体特性.零温状态方程计算揭示了在68 GPa时可以发生从单斜结构     

In掺杂对n型方钴矿化合物的微结构及热电性能的影响规律

用熔融退火法结合放电等离子烧结(SPS)技术成功制备了具有不同 In含量的In_xCo₄Sb₁₂(x=0.1—0.4)方钴矿化合物.X射线衍射分析和扫描电镜分析结果表明,当In的掺杂量超过一定值时,化合物中会原位析出纳米InSb的第二相,且其含量会随In掺杂量的增加而增大.研究结果表明,InSb第二相的存在增大了化合物的功率因子,降低了化合物的晶格热导率,显著提高了化合物的热电性能.在温度为800 K时,In相似文献   

相变存储材料Ge1Sb2Te4和Ge2Sb2Te5薄膜的结构和电学特性研究

采用射频磁控溅射方法制备了两种用于相变存储器的Ge₁Sb₂Te₄和Ge₂Sb₂Te₅相变薄膜材料,对其结构、电学输运性质和恒温下电阻随时间的变化关系进行了比较和分析.X射线衍射(XRD)和原子力显微镜(AFM)的结果表明:随着退火温度的升高,Ge₁Sb₂Te₄薄膜逐步晶化,由非晶态转变为多晶态,表面出现均匀的、     

氧掺杂碳气体扩散电极用于电催化产活性氧抗菌防污研究

过氧化氢(H₂O₂)等活性氧(ROS)物质因具有绿色高效的特点,在废水处理、杀菌消毒等领域受到研究者广泛关注。利用电催化生成H₂O₂是一种实时提供活性氧物质的有用方法。然而,目前报道的大多数高性能催化材料都是粉体形式,不便于在实际场景中的应用。因此,制备可直接应用的电极材料显得尤为重要。本研究利用喷涂-热解的制备方法,制备了高活性氧催化活性的氧化炭黑(O−CB)/多孔碳毡电极,通过聚四氟乙烯(PTFE)的修饰优化电极表面的氧气传质,成功制备氧掺杂碳气体扩散电极。研究结果表明,O−CB/PTFE-5 wt%电极具有最高的催化性能,其合成H₂O₂的速率达27.19 mg·L^-1(mg catalyst)^-1·cm^-1·h^-1。海洋典型污损微生物假单胞菌(Pseudomonas sp.)的抗菌实验表明,该电极电催化作用60 min产生的活性氧对Pseudomonas sp.的杀菌率可达到97.69%,作用120 min的杀菌率可达到99.99%。     

锰掺杂对Ba(Zr,Ti)O3陶瓷压电与介电性能的影响

采用氧化物固相反应法制备了锰掺杂改性的Ba(Zr_0.06Ti_0.94)O₃陶瓷.研究了锰的掺杂量对Ba(Zr_0.06Ti_0.94)Mn_xO₃ (BZTM)陶瓷的结构、介电和压电性能的影响.实验发现,当锰含量x<0.5 mol%时进入晶格,使材料压电性能提高,损耗减小,表现出受主掺杂的特性;当锰含量x>0.5 mo     

Cu3 N弹性和热力学性质的第一性原理研究

利用基于密度泛函理论的第一性原理全势线性缀加平面波方法,研究了立方反ReO₃结构Cu₃N在零温(0 K)零压下的平衡晶格常数、体弹模量及其对压强的一阶导数,计算结果与其他实验及理论结果基本相符. 同时得出Cu₃N的弹性常数,Poisson比等,并分析出Cu₃N在零温零压下是稳定的. 通过准谐Debye模型计算Cu₃N的热力学性质,得到了Cu₃N的晶格常数、等压比热容、等容比热     

基于反转法的O2 -CO2 输运性质预测

采用反转法计算得到了O₂-CO₂混合气体新的势能参数.在此基础上,根据分子动力学理论,计算了混合气体在零密度下的输运性质,包括黏度系数、热扩散系数和热扩散因子,计算的温度范围为273.15—3273.15 K.与实验值比较表明,计算结果可以满足实际工程应用.     

Thermal conductivity and permeability assessment by electrical resistivity measurements in marine sediments

Abstract

The problem of radioactive waste containment, the modeling of hydrocarbon formation processes, and the proposed laying of fiber‐optic communication cables on the seafloor have recently focused attention on the thermal and fluid flow properties of porous media. Both properties are difficult to determine accurately for large volumes of material, particularly where disturbance is inevitable either on sampling or penetration of the measuring device. Both properties, however, have been tentatively identified as bearing some form of analogy with electrical flow, and evaluation of these relationships with electrical measurements may provide practical means of obtaining rapid coverage of the sediment from a semi‐remote position. Using a variety of laboratory cells, an attempt has been made to evaluate useful relationships between electrical formation factor and thermal conductivity and/or permeability for both sands and clays. Formation factor exhibits a close relationship with permeability, and the capability of predicting permeability to within an order of magnitude is shown providing the grade of sediment is identified (e.g., sand or clay). Formation factor is related to porosity and while any one sample is best represented by Archie's (sands) or Winsauer's (clays) empirical law, the overall trend is a third‐degree polynomial; particle shape appears to dominate both porosity and permeability relationships with electrical formation factor. Thermal conductivity shows a clear dependence on the porosity of a saturated sediment. The successful prediction of thermal conductivity using a geometrical model requiring volume and thermal conductivity values for the components has been demonstrated for a variety of particle shapes and sizes. Thermal conductivity may be related to formation factor through the porosity of the sample for both sands and clays.     

室内海底沉积物热导率测量的原理与方法——以TK04热导率测量系统为例

沉积物热导率是计算海底热流的一个重要参数。文中以TK04热导率测量系统为例,详细介绍了实验室内热导率测量原理、样品热导率测量的各个环节,包括样品准备、测量流程、测量数据质量评估与校正等,以及沉积物原位热导率的计算,以为油气资源评价、天然气水合物评价及地球动力学研究提供高精度的海底热流数据。     

悬浮泥沙含量与电导率关系及其影响因素的实验研究

为了寻求一种简单、快速、连续测定悬浮泥沙含量的方法,以高含沙量海区黄河口泥沙为研究对象,利用电导率仪测定了不同悬浮泥沙含量水体的电导率。前期实验结果已经证明悬浮泥沙含量与电导率之间有很好的线性关系。在此基础上扩大研究范围,并对影响悬浮泥沙含量与电导率关系的因素进行定量分析,结果表明,盐度、温度、颗粒粒径对电导率具有一定的影响,其中盐度的影响最大,颗粒粒径的影响最小,几乎可以忽略。在此基础上通过大量的实验数据初步建立起在盐度、温度较大变化范围内电导率与泥沙含量的一般函数关系,为实现海水悬浮泥沙含量的现场电导率原位监测系统提供可靠的数据支持。     

悬浮泥沙含量与电导率关系及其影响因素的实验研究

为了寻求一种简单、快速、连续测定悬浮泥沙含量的方法,以高含沙量海区黄河口泥沙为研究对象,利用电导率仪测定了不同悬浮泥沙含量水体的电导率.前期实验结果已经证明悬浮泥沙含量与电导率之间有很好的线性关系.在此基础上扩大研究范围,并对影响悬浮泥沙含量与电导率关系的因素进行定量分析,结果表明,盐度、温度、颗粒粒径对电导率具有一定...     

Incidence de la cinetique de decroissance de la temperature apres le choc thermique sur les modifications d'activite des esterases et les possibilites de survie de Scolelepis (malacoceros) fuliginosa (annelide polychete)

Scolelepis fuliginosa reared in the laboratory at 13°C were put through 10-min thermal shocks at 16°C and 18°C and were then submitted to either a slow or a rapid temperature reduction. After the thermal shock, a posterior fragment of each specimen was cut off at intervals, until six days. Samples were submitted to electrophoresis on polyacrylamide gel, esterase activity being determined with α-naphthyl acetate.Enzymograms show that thermal shocks act on esterases in decreasing the activity of the main fractions. Immediate effects result in a very precocious enzymic response; more long-term effects depend on the maximum temperature, the animal's sex and the kinetics of the post-shock thermal reduction.Females are more sensitive than males. For a given Δt, esterase changes are greater and more long-lasting. After a 16°C Δt, a rapid decrease in temperature prevents the loss of activity of the middle and fast fractions in males and delays, by about 10 h, the alteration of female esterases. After 18°C ΔT, loss of activity of the middle and fast fractions occurs in less than 1 h, independently of the thermal kinetics, but survival is only possible—solely for males—with a rapid decrease in temperature which also delays females' deaths by between 24 and 48 h.In conclusion, a rapid decrease in temperature gives organisms a better resistance to thermal shock, as determined by esterase activity and controls the lethality of a high Δt.     

“海翼号”水下滑翔机盐度数据的热滞后效应偏差订正方法探讨

水下滑翔机可以高效地观测海水的温度、盐度和压强等海洋参数,但由于热滞后效应,盐度数据,特别是在温度梯度较大的温跃层,会出现一定程度的偏差。本研究选取了3种目前常用的盐度热滞后订正方法,对带泵的“海翼号”水下滑翔机,于2019年8月在中北太平洋所观测的盐度数据因热滞后效应引起的偏差进行订正处理,与船载911型温盐深测量仪(Instrument for Measuring Conductivity Temperature and Depth,CTD)观测盐度进行对比,在比较了3种方法对滑翔机盐度订正前后下降和上升剖面偏差的减少程度、订正后剖面与船载CTD观测剖面的偏差大小和下降上升温盐曲线(T-S曲线)的一致程度后,得出了水下滑翔机盐度订正的最优方法,即在订正电导池中实际温度的前提下,采用计算机图形分割方法,最小化滑翔机机载CTD测得的下降和上升两个剖面T-S曲线围成面积所确定的目标函数,来确定合适的热滞后修正振幅和时间常数,从而修正下降和上升两个剖面之间盐度偏差。     

我国东海陆架地区新生代地层的热导率

对东海陆架区的浅表层柱状岩芯样品和多口钻井岩心样品的热导率数据按岩性、深度、年龄和孔隙度进行了统计分析。发现泥岩、粉砂岩和砂岩的热导率有所不同。在3000m以上，泥岩的热导率大于砂岩的热导率；而在3000m以下砂岩的热导率则大于泥岩的热导率。粉砂岩的热导率基本介于泥岩和砂岩之间。岩石的热导率和岩石样品所处的深度密切相关，随着深度的增大热导率数值增大。岩石的年龄影响岩石的热导率。在同等深度的情况下，年龄越老，热导率数值越高，但埋深浅的老地层热导率会小于埋深大的新地层的热导率。孔隙度和含水对岩石样品的热导率有很大的影响，岩石会因孔隙中含水而使热导率有非常大的变化。本文给出了饱和水热导率和干样热导率之差和孔隙度的回归方程。     

Effect of electrode contact impedance on A.C. electrical properties of a wet hematite sample

Electrode polarization is a major problem in the determination of dielectric properties of samples, particularly at low frequencies. Understanding of these interfacial phenomena is essential in order to measure correctly the electrical properties of a sample of interest. This paper presents a comparative study of the effect of electrode contact impedance on A.C. electrical properties of a partially and fully saturated hematitic sandstone sample. The electrical properties of the sample were first measured using stainless steel electrodes with high contact impedance, and measured again with a four terminal Cu–CuSO₄ electrode of low contact impedance. Complex impedance measurements at room temperature (~16°C) were performed in the frequency range from 1 Hz to 100 kHz. Measured electrical spectra vary strongly with the electrode type. The difference in the electrical properties between the two electrode types (stainless steel and Cu–CuSO₄) may be attributed to the surface contact impedance between the sample and the electrode. Experimental data indicate that the electrical properties vary strongly with water saturation. The dielectric constant decreases with frequency and increases with saturation up to a certain saturation limit then decreases. Charge transport can occur either through the bulk of the solid matrix (hematite or sand) or along the grain boundaries of aggregates (water). When soil minerals are exposed to water, exchangeable ions go into solution. Most of the ionic or covalent bonded rock forming minerals such as quartz, mica, and feldspars are nonconductors. When the surfaces of these minerals come into contact with liquid water, electrolytes are formed and ionic drift associated with the electrical field causes electrical conduction. The anomalous dielectric properties of partially saturated rocks can be interpreted using percolation theory. This theory predicts that when the conductive fraction (water) increases, clustering of conductive inclusions develops, and the thickness of insulating gaps between conductive clusters decreases, causing a large increment in the capacitance of the sample. Further increases in the conductive component causes the shunting of insulating capacitive gaps.     

EMRIDGE: The electromagnetic investigation of the Juan de Fuca Ridge

From July to November 1988, a major electromagnetic (EM) experiment, known as EMRIDGE, took place over the southern end of the Juan de Fuca Ridge in the northeast Pacific. It was designed to complement the previous EMSLAB experiment which covered the entire Juan de Fuca Plate, from the spreading ridge to subduction zone. The principal objective of EMRIDGE was to use natural sources of EM induction to investigate the processes of ridge accretion. Magnetotelluric (MT) sounding and Geomagnetic Depth Sounding (GDS) are well suited to the study of the migration and accumulation of melt, hydrothermal circulation, and the thermal evolution of dry lithosphere. Eleven magnetometers and two electrometers were deployed on the seafloor for a period of three months. Simultaneous land-based data were made available from the Victoria Magnetic Observatory, B.C., Canada and from a magnetometer sited in Oregon, U.S.A.Changes in seafloor bathymetry have a major influence on seafloor EM observations as shown by the orientation of the real GDS induction arrows away from the ridge axis and towards the deep ocean. Three-dimensional (3D) modelling, using a thin-sheet algorithm, shows that the observed EM signature of the Juan de Fuca Ridge and Blanco Fracture Zone is primarily due to nonuniform EM induction within the ocean, associated with changes in ocean depth. Furthermore, if the influence of the bathymetry is removed from the observations, then no significant conductivity anomaly is required at the ridge axis. The lack of a major anomaly is significant in the light of evidence for almost continuous hydrothermal venting along the neo-volcanic zone of the southern Juan de Fuca Ridge: such magmatic activity may be expected to have a distinct electrical conductivity signature, from high temperatures, hydrothermal fluids and possible melt accumulation in the crust.Estimates of seafloor electrical conductivity are made by the MT method, using electric field records at a site 35 km east of the ridge axis, on lithosphere of age 1.2 Ma, and magnetic field records at other seafloor sites. On rotating the MT impedance tensor to the principal axis orientation, significant anisotropy between the major (TE) and minor (TM) apparent resistivities is evident. Phase angles also differ between the principal axis polarisations, and TM phase are greater than 90° at short periods. Thin-sheet modelling suggests that bathymetric changes accounts for some of the observed 3D induction, but two-dimensional (2D) electrical conductivity structure in the crust and upper mantle, aligned with the ridge axis, may also be present. A one-dimensional (1D) inversion of the MT data suggests that the top 50 km of Earth is electrically resistive, and that there is a rise in conductivity at approximately 300 km. A high conductivity layer at 100 km depth is also a feature of the 1D inversion, but its presence is less well constrained.     

基于电导率测定海水悬沙含量试验研究

为了寻求一种简单、快速、连续确定悬浮泥沙含量的方法,以高含沙量海区黄河口泥沙为研究对象,利用电导率仪测定了不同悬浮泥沙含量水体的电导率,建立起了悬浮泥沙含量与电导率之间的关系,并对影响上述关系的因素进行了分析,结果表明,悬浮泥沙含量与电导率之间有很好的线性关系;盐度、颗粒粒径对电导率具有一定的影响,其中盐度的影响最大,颗粒粒径的影响较小。在盐度变化范围有限的高悬沙含量海区,用电导率的方法来实现现场监测悬浮泥沙含量是可行的。