Anomaly Effects of Arrays for 3d Geoelectrical Resistivity Imaging using Orthogonal or Parallel 2d Profiles

The effectiveness of using a net of orthogonal or parallel sets of two-dimensional (2D) profiles for threedimensional (3D) geoelectrical resistivity imaging has been evaluated. A series of 2D apparent resistivity data were generated over two synthetic models which represent geological or environmental conditions for a typical weathered profile and waste dump site, respectively, commonly associated with geophysical applications for hydrogeological, environmental and engineering investigations. Several minimum electrode separations and inter-line spacing were used to generate the apparent resistivity data for each electrode array with a view to determining the optimum inter-line spacing relative to the minimum electrode separation. The 2D apparent resistivity data for each array were collated to 3D data sets. The effectiveness and efficiency of the arrays in 3D geoelectrical resistivity imaging were evaluated by determining the mean absolute anomaly effects of the electrodes arrays on the synthetic models. The anomaly effects observed in dipole-dipole (DDP), pole-dipole (PDP) and Wenner- Schlumberger (WSC) arrays were generally larger than that observed in other arrays considered. The least anomaly effect on the synthetic models was observed in pole-pole (PP) array. This indicates that DDP, PDP and WSC arrays are more sensitive to 3D features. In all the arrays, the anomaly effects observed in the data set generated using the conventional square grids were slightly larger than those from parallel or orthogonal 2D profiles. This slight increase is attributed to the increased data density and is insignificant when compared with those of parallel and orthogonal 2D profiles. Hence, the use of parallel or orthogonal 2D profiles for 3D geoelectrical resistivity survey is effective

Effectiveness of 3D Geoelectrical Resistivity Imaging using Parallel 2D Profiles

Acquisition geometry for 3D geoelectrical resistivity imaging in which apparent resistivity data of a set of parallel 2D profiles are collated to 3D dataset was evaluated. A set of parallel 2D apparent resistivity data was generated over two model structures. The models, horst and trough, simulate the geological environment of a weathered profile and refuse dump site in a crystalline basement complex respectively. The apparent resistivity data were generated for Wenner–alpha, Wenner–beta, Wenner–Schlumberger, dipole–dipole, pole–dipole and pole–pole arrays with minimum electrode separation, a (a = 2, 4, 5 and 10 m) and inter-line spacing, L (L = a, 2a, 2.5a, 4a, 5a and 10a). The 2D apparent resistivity data for each of the arrays were collated to 3D dataset and inverted using a full 3D inversion code. The 3D imaging capability and resolution of the arrays for the set of parallel 2D profiles are presented. Grid orientation effects are observed in the inversion images produced. Inter-line spacing of not greater than four times the minimum electrode separation gives reasonable inverse models. The resolution of the inverse models can be greatly improved if the 3D dataset is built by collating sets of orthogonal 2D profile

3D lithium ion batteries—from fundamentals to fabrication

3D microbatteries are proposed as a step change in the energy and power per footprint of surface mountable rechargeable batteries for microelectromechanical systems (MEMS) and other small electronic devices. Within a battery electrode, a 3D nanoarchitecture gives mesoporosity, increasing power by reducing the length of the diffusion path; in the separator region it can form the basis of a robust but porous solid, isolating the electrodes and immobilising an otherwise fluid electrolyte. 3D microarchitecture of the whole cell allows fabrication of interdigitated or interpenetrating networks that minimise the ionic path length between the electrodes in a thick cell. This article outlines the design principles for 3D microbatteries and estimates the geometrical and physical requirements of the materials. It then gives selected examples of recent progress in the techniques available for fabrication of 3D battery structures by successive deposition of electrodes, electrolytes and current collectors onto microstructured substrates by self-assembly methods

Electrochemical activation of molecular nitrogen at the Ir/YSZ interface.

Nitrogen is often used as an inert background atmosphere in solid state studies of electrode and reaction kinetics, of solid state studies of transport phenomena, and in applications e.g. solid oxide fuel cells (SOFC), sensors and membranes. Thus, chemical and electrochemical reactions of oxides related to or with dinitrogen are not supposed and in general not considered. We demonstrate by a steady state electrochemical polarisation experiments complemented with in situphotoelectron spectroscopy (XPS) that at a temperature of 450 °C dinitrogen can be electrochemically activated at the three phase boundary between N2, a metal microelectrode and one of the most widely used solid oxide electrolytes—yttria stabilized zirconia (YSZ)—at potentials more negative than E = −1.25 V. The process is neither related to a reduction of the electrolyte nor to an adsorption process or a purely chemical reaction but is electrochemical in nature. Only at potentials more negative than E = −2 V did new components of Zr 3d and Y 3d signals with a lower formal charge appear, thus indicating electrochemical reduction of the electrolyte matrix. Theoretical model calculations suggest the presence of anionic intermediates with delocalized electrons at the electrode/electrolyte reaction interface. The ex situSIMS analysis confirmed that nitrogen is incorporated and migrates into the electrolyte beneath the electrode

Development of EHD Ion-Drag Micropump for Microscale Electronics Cooling Systems

In this investigation, the numerical simulation of electrohydrodynamic (EHD) ion-drag micropumps with micropillar electrode geometries have been performed. The effect of micropillar height and electrode spacing on the performance of the micropumps was investigated. The performance of the EHD micropump improved with increased applied voltage and decreased electrode spacing. The optimum micropillar height for the micropump with electrode spacing of 40$\mu$m and channel height of 100$\mu$m at 200V was 40$\mu$m, where a maximum mass flow rate of 0.18g/min was predicted. Compared to that of planar electrodes, the 3D micropillar electrode geometry enhanced the overall performance of the EHD micropumps.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Synergistic effects of micro/nano modifications on electrodes for microfluidic electrochemical ELISA

Microfluidic electrochemical sensing has been considered to be highly efficient. However, we showed, by using numerical simulations in this study, that a planar electrode formed on the bottom of a microchannel is exposed to only a small fraction of analytes in amperometric detection. We also showed that three-dimensional (3D) micropillar electrodes significantly improve the detection current. The practical performance was evaluated using 3D micropillar electrodes fabricated by photolithography. The output current increased as the diameters of the micropillars decreased, as predicted by the simulations. It is noteworthy that the current enhancements obtained with the 3D electrodes were larger than those expected from an increase in the surface area. Further increase in current was achieved by electrical deposition of nanoporous gold-black onto the surface of the 3D electrode: when a 3D electrode with micropillars 30 μm in diameter was used, the output current was approximately 20 times that obtained with a 2D electrode without modification. The applicability of the micropillar electrodes was demonstrated in electrochemical enzyme-linked immunosorbent assay (ELISA) of bone metabolic marker proteins. Although an increase in the surface area of the electrode leads to more noise in general, there is no significant difference in the signal-to-noise ratio between the modified 3D electrode and the 2D electrode without modification in the ELISA experiments. This nanoporous micropillar electrode could potentially be a useful component for the development of on-site diagnosis systems

MULTIBAT: Unified workflow for fast electrochemical 3D simulations of lithium-ion cells combining virtual stochastic microstructures, electrochemical degradation models and model order reduction

We present a simulation workflow for efficient investigations of the interplay between 3D lithium-ion electrode microstructures and electrochemical performance, with emphasis on lithium plating. Our approach addresses several challenges. First, the 3D microstructures of porous electrodes are generated by a parametric stochastic model, in order to significantly reduce the necessity of tomographic imaging. Secondly, we integrate a consistent microscopic, 3D spatially-resolved physical model for the electrochemical behavior of the lithium-ion cells taking lithium plating and stripping into account. This highly non-linear mathematical model is solved numerically on the complex 3D microstructures to compute the transient cell behavior. Due to the complexity of the model and the considerable size of realistic microstructures even a single charging cycle of the battery requires several hours computing time. This renders large scale parameter studies extremely time consuming. Hence, we develop a mathematical model order reduction scheme. We demonstrate how these aspects are integrated into one unified workflow, which is a step towards computer aided engineering for the development of more efficient lithium-ion cells

Mechanical rolling formation of interpenetrated lithium metal/lithium tin alloy foil for ultrahigh-rate battery anode

To achieve good rate capability of lithium metal anodes for high-energy-density batteries, one fundamental challenge is the slow lithium diffusion at the interface. Here we report an interpenetrated, three-dimensional lithium metal/lithium tin alloy nanocomposite foil realized by a simple calendering and folding process of lithium and tin foils, and spontaneous alloying reactions. The strong affinity between the metallic lithium and lithium tin alloy as mixed electronic and ionic conducting networks, and their abundant interfaces enable ultrafast charger diffusion across the entire electrode. We demonstrate that a lithium/lithium tin alloy foil electrode sustains stable lithium stripping/plating under 30mAcm(-2) and 5mAhcm(-2) with a very low overpotential of 20mV for 200 cycles in a commercial carbonate electrolyte. Cycled under 6C (6.6mAcm(-2)), a 1.0mAhcm(-2) LiNi0.6Co0.2Mn0.2O2 electrode maintains a substantial 74% of its capacity by pairing with such anode

Precision scans of the pixel cell response of double sided 3D pixel detectors to pion and x-ray beams

hree-dimensional (3D) silicon sensors offer potential advantages over standard planar sensors for radiation hardness in future high energy physics experiments and reduced charge-sharing for X-ray applications, but may introduce inefficiencies due to the columnar electrodes. These inefficiencies are probed by studying variations in response across a unit pixel cell in a 55μm pitch double-sided 3D pixel sensor bump bonded to TimePix and Medipix2 readout ASICs. Two complementary characterisation techniques are discussed: the first uses a custom built telescope and a 120GeV pion beam from the Super Proton Synchrotron (SPS) at CERN; the second employs a novel technique to illuminate the sensor with a micro-focused synchrotron X-ray beam at the Diamond Light Source, UK. For a pion beam incident perpendicular to the sensor plane an overall pixel efficiency of 93.0±0.5% is measured. After a 10o rotation of the device the effect of the columnar region becomes negligible and the overall efficiency rises to 99.8±0.5%. The double-sided 3D sensor shows significantly reduced charge sharing to neighbouring pixels compared to the planar device. The charge sharing results obtained from the X-ray beam study of the 3D sensor are shown to agree with a simple simulation in which charge diffusion is neglected. The devices tested are found to be compatible with having a region in which no charge is collected centred on the electrode columns and of radius 7.6±0.6μm. Charge collection above and below the columnar electrodes in the double-sided 3D sensor is observed