Collector Electrode Research Articles

Sb2S3/TiO2 Heterojunction Solar Cells Based on Carbon Electrode with Higher Photocurrent

In Sb2S3 thin film solar cells, an organic material is typically used as the hole transport layer (HTL), while a noble metal grid is used for hole collection. However, the organic HTL often has poor stability during long-term operation and requires expensive materials. In this work, a carbon electrode is used as both the HTL and collection electrode in Sb2S3 solar cells. Electrochemical impedance spectroscopy showed that the carbon-electrode-containing device exhibited a smaller transfer resistance Rtr of 5.05 × 103 Ω compared with1.41 × 104 Ω in a device based on poly(3-hexylthiophene-2,5-diyl)(P3HT) and Ag. This indicated that carbon has a better hole transfer from Sb2S3 to the cathode. Intensity-modulated photocurrent spectroscopy showed that the electron-hole transit time was reduced by almost half from the time of excitation to collection, which suggests that holes are more easily transferred from Sb2S3 to HTL. Moreover, hole transfer kinetics were investigated by transient absorption spectroscopy, which showed that the estimated hole transfer rate, kht, was 1.8 × 109 s−1at the Sb2S3/carbon interface, which is 2.43 times faster than 7.4 × 108 s−1at the Sb2S3/P3HT interface. These results indicate that the carbon electrode displays superior hole extraction from Sb2S3 compared to the P3HT/Ag electrode.

Driving Fatigue Classification Based on Fusion Entropy Analysis Combining EOG and EEG

The rising number of traffic accidents has become a major issue in our daily life, which has attracted the concern of society and governments. To deal with this issue, in our previous study, we have designed a real-time driving fatigue detection system using power spectrum density and sample entropy. By using the wireless technology and dry electrodes for EEG collection, we further integrated virtual reality simulated driving environment, which made our study more applicable to realistic settings. However, the high accuracy of classification for driving fatigue has not been obtained. To measure the time series complexity of the EEG signal, we proposed a fusion entropy (sample entropy, approximate entropy, and spectral entropy) analysis method of EEG and EOG. First, a sample entropy was applied for feature extraction from the horizontal and vertical EOG. Second, an approximate entropy, sample entropy, and spectral entropy features of each sub-band of EEG are extracted. Third, feature fusion for sub-band is performed by canonical correlation analysis (CCA). Finally, the features of EOG and EEG are classified using a relevant vector machine (RVM). Twenty-two subjects participated in the driving fatigue experiments for a duration of 90 min. The results demonstrated that the fusion entropy analysis combining EOG and EEG could provide an alternative method for driving fatigue detection, and the average accuracy rate was up to 99.1 ± 1.2%. The authors further analyzed the effect of feature fusion in four sub-bands (δ, α, β and θ) and compared with every single sub-band on classification performance, it is proved that the former is superior to the latter presenting the proposed method can provide effective indicators for driving fatigue detection.

Sensitivity-Selectivity Trade-Offs in Surface Ionization Gas Detection.

Surface ionization (SI) provides a simple, sensitive, and selective method for the detection of high-proton affinity substances, such as organic decay products, medical and illicit drugs as well as a range of other hazardous materials. Tests on different kinds of SI sensors showed that the sensitivity and selectivity of such devices is not only dependent on the stoichiometry and nanomorphology of the emitter materials, but also on the shape of the electrode configurations that are used to read out the SI signals. Whereas, in parallel-plate capacitor devices, different kinds of emitter materials exhibit a high level of amine-selectivity, MEMS (micro-electro-mechanical-systems) and NEMS (nanowire) versions of SI sensors employing the same kinds of emitter materials provide significantly higher sensitivity, however, at the expense of a reduced chemical selectivity. In this paper, it is argued that such sensitivity-selectivity trade-offs arise from unselective physical ionization phenomena that occur in the high-field regions immediately adjacent to the surfaces of sharply curved MEMS (NEMS) emitter and collector electrodes.

Electrodes based on cellulose nanofibers/carbon nanotubes networks, polyaniline nanowires and carbon cloth for supercapacitors

Supercapacitors (SCs) are promising devices for meeting the future demand of sustainable energy conversion and storage. Here, cellulose nanofibers (CNFs), carbon nanotubes (CNTs), polyaniline (PANI) and carbon cloth (CC) were used to fabricate SCs electrodes. CNFs and CNTs were constructed into networks and served as the skeleton for depositing polyaniline nanowires (PANI-NWs). The vacuum filtration method contributed to the construction of a three-dimensional network structure for CNFs and CNTs. CC was used as a flexible current collector in the electrode. In-situ polymerization was performed to polymerize PANI on the surface of CNFs, CNTs and CC to form a three-dimensional porous film-current collector structure (CCPC electrodes). Electrochemical measurements showed that the CCPC electrode exhibited a low charge transfer resistance of 1.50 Ω, as well as excellent specific capacitance of 318 F g−1 at a scan rate of 10 mA s−1. In addition, it exhibited 72.09% retention of the initial value after 1000 cycles of testing. Overall, this work provides a strategy for the fabrication of a porous network film-soft current collector electrode for supercapacitors.

Velocity field of EHD flow during back corona discharge in electrostatic precipitator

Particle Image Velocimetry studies of velocity field of the EHD flow during the back corona discharge at atmospheric pressure in an electrode system comprising a needle discharge electrode at negative potential and a grounded plate collection electrode covered with fly ash layer are presented in this paper. It was found that the magnitude of velocity vector of the EHD flow starting from the crater formed in fly ash layer after the onset of back corona discharge is of the same order of magnitude as for the flow generated by the corona discharge from the needle electrode. The measurements have shown that both these flows do not mix, but deflect each other off the axis of the needle electrode. The conclusion from this research is that the EHD deflection of the trajectories of particles flowing towards the collection electrode by the particles erupted from the crater at the collection electrode probably prevents those particles from the precipitation on the collection electrode that can result in a decreased collection efficiency of electrostatic precipitator during back corona discharge. This new mechanism has been called the “dynamic” process of the collection efficiency reduction.

Increase of power conversion efficiency in dye-sensitized solar cells through ferroelectric substrate induced charge transport enhancement

Ferroelectric functionalized dye-sensitized solar cells were fabricated by using a positively-poled LiNbO3 substrate coated with ITO (ITO-LiNbO3) as a collector electrode and demonstrated enhanced power conversion efficiency. Surface potential properties of TiO2 nanoparticle film coated on the ITO-LiNbO3 (TiO2/ITO-LiNbO3) examined by Kelvin probe force microscopy (KPFM) confirmed that a large electric field (a few 10 V/µm) generated from LiNbO3 can penetrate through the ITO layer and is applied to TiO2 film. This polarization-induced electric field leads to an increased photocurrent density by attracting and promoting electrons to direct transport through the mesoporous TiO2 network toward the collector electrode and a decreased charge recombination by facilitating electrons to pass through fewer boundaries of nanoparticles, resulting in high power conversion efficiency. The power conversion efficiency was enhanced by more than 40% in comparison with that without polarization-induced electric field. Incorporating functional ferroelectrics into photovoltaic cells would be a good strategy in improving photovoltaic performance and is applicable to other types of photovoltaic devices, such as perovskite solar cells.

Synergistic Effect of Innovating Electrode Technology and Eddy-Current Electromagnetic Impedance for Non-Destructive Testing are Resulting in Increasing Battery Power

The value of contact resistance between metallic current lead and electrode mass composite is one of the key parameters for determination of performance of energy storage devices, such as batteries, supercapacitors, etc. During discharge process of batteries the resistance of interface between electrode mass layer & the current collector influences on the battery voltage The surface of the aluminum foil, which used as a current collector for positive electrodes in lithium batteries is passivated by Al2O3 film that has a low electric conductivity. As result the energy and power battery are decreased. Our article is connected with technology for Li electrode production that insures the low interface resistance between electrode collector and electrode mass, the increasing the power of batteries, and stability the cycling. We have the strong opinion that the success of technology must be supported by nondestructive testing the initial materials, semi- and final product during batteries production.

Ultra‐Lightweight and Flexible Current Collector Based on Freestanding Carbon Nanotube Sheets for Lithium‐Ion Capacitors

AbstractA new and simple strategy for the fabrication of an ultra‐lightweight and flexible current collector based on freestanding carbon nanotube (CNT) sheets for lithium‐ion capacitors (LICs) with excellent electrochemical performance is reported. A novel lightweight current collector is fabricated using CNT sheets (≈0.05 mg cm−2) which are prepared by a direct spinning method. LICs are assembled using prelithiated graphite/CNT sheets as anodes, and activated carbon/CNT sheets as cathodes. The electrochemical performances of anode and cathode are investigated through coin‐type half‐cell tests, demonstrating the high discharge capacities of about 350 and 40 mAh g−1, respectively. These discharge capacities based on the total mass of electrode exhibit about 73% and 75% of capacities based on the mass of active materials. However, in the case of fabricating metallic current collector electrode, discharge capacities are reduced to about 6.5% and 20%, respectively. LICs demonstrate the maximum energy density of ≈26.4 Wh kg−1 and the maximum power density of ≈672 W kg−1, showing comparable energy and power densities when values are evaluated on the basis of the total mass of electrode. These features make the collector a potential candidate for the energy storage systems, which require large‐scale and lightweight power sources.

Enhancement of heat transfer via corona discharge by using needle-mesh and needle-fin electrodes

As a potential alternative of traditional heat transfer enhancement technology, ionic wind has drawn great attention. In this study, a direct comparison of the ionic wind devices with needle-mesh and needle-fin electrodes is carried out experimentally. The ionic characteristics and cooling performances of two electrode types here are tested and quantitatively analyzed by calculating the empirical correlations defining the relationship between electrohydrodynamics and heat transfer. The results indicate that the electrode gap d and the number of needle electrodes N are the main factors of ionic characteristics such as current, velocity and efficiency. And the results of heat transfer show that the needle-fin configuration has a superior performance, which has made a temperature drop from 54.5 °C to 39.1 °C with the low power consumption of 0.85 W. An empirical correlation for calculating the Nu-Re relation in the case is developed, which reflects that the ionic wind is a fluid with thinner boundary layer and stronger convection. In addition, the heat transferred by the fins in the ionic wind device is more than twice that of the convection on the plate surface. Finally, the feasibility and advantages of using fins as collector electrodes are confirmed.

A primed current collector for high performance carbon-coated LiFePO4 electrodes with no carbon additive

This work shows that newly developed primed aluminum current collector for positive electrodes allows to vastly improve the electrochemical performance compared to bare aluminum foil for full cells assembled with a C-coated LiFePO4 positive electrode, a graphite negative electrode and a standard carbonate/LiPF6 based electrolyte. Moreover, it is discovered that using a primed collector allows to drastically reduce the carbon additive content in the C-LiFePO4 electrode down to zero, while maintaining a very low impedance and excellent rate capability (80 mAh/g at 5C rate) and cyclability (60% capacity retention after 200 cycles at 2C rate). Comparatively, the same electrode shows no cyclability in the same testing conditions if a bare aluminum foil is used as the collector. Improving the energy density while maintaining good power capability of a Li-ion cell was thus achieved by using an adapted primed current collector. Such performance originates from a significant reduction of the contact resistance at the current collector – electrode interface through the multiplication of electrical contact points and/or the modification of their nature. In complement, this work shows that the carbon coating of the C-LiFePO4 particles is sufficient to ensure a good electrical conductivity within the electrode.

Ultrafast Broadband Charge Collection from Clean Graphene/CH3NH3PbI3 Interface.

Photocarrier generation in a material, transportation to the material surface, and collection at the electrode interface are of paramount importance in any optoelectronic and photovoltaic device. In the last collection process, ideal performance comprises ultrafast charge collection to enhance current conversion efficiency and broadband collection to enhance energy conversion efficiency. Here, for the first time, we demonstrate ultrafast broadband charge collection achieved simultaneously at the clean graphene/organic-inorganic halide perovskite interface. The clean interface is realized by directly growing perovskite on graphene surface without polymer contamination. The tunable two-color pump-probe spectroscopy, time-resolved photoluminescence spectroscopy, and time-dependent density functional theory all reveal that the clean-interfacial graphene collects band-edge photocarriers of perovskite in an ultrashort time of ∼100 fs, with a current collection efficiency close to 99%. In addition, graphene can extract deep-band hot carriers of perovskite within only ∼50 fs, several orders faster than hot carrier relaxation and cooling in perovskite itself, due to the unique Dirac linear band structure of graphene, indicating a potential high energy conversion efficiency exceeding the Shockley-Queisser limit. Adding other graphene superiority of good transparency, high carrier mobility, and extreme flexibility, clean-interfacial graphene provides an ideal charge collection layer and electrode candidate for future optoelectronic and photovoltaic applications in two dimensions.

Synthesis of nanoporous copper foam-applied current collector electrode for supercapacitor

Through electrodeposition at a high current density and controlling the produced hydrogen gas, nanostructured copper foams were fabricated on copper as high-performance electrodes for supercapacitors. The structure and morphology of copper foams were controlled by adjusting deposition parameters and addition of acid acetic as bubble stabilizer addition. Acid acetic reduced the hydrophobic force between individual bubbles, and thus allowed controlling the porosity of the thin foam. Electrochemical impedance spectroscopy (EIS) measurements, galvanostatic charge/discharge (GCD) and cyclic voltammetry were carried out to study the electrochemical behavior of copper foams. EIS results showed that thin copper foams deposited from 0.4 M CuSO4 and 0.1 M CH3COOH, at 3 A/cm2 for 20 s present the highest specific capacitance that was 102.68 F/g. GCD data for the same foam showed a capacitance of 95 F/g at 1 mA/cm2. Cycle life study exhibited 90% capacitance retention after 6000 cycles at high current density (20 mA/cm2).

CMOS monolithic pixel sensors based on the column-drain architecture for the HL-LHC upgrade

Depleted Monolithic Active Pixel Sensors (DMAPS) constitute a promising low cost alternative for the outer layers of the ATLAS experiment Inner Tracker (ITk). Realizations in modern, high resistivity CMOS technologies enhance their radiation tolerance by achieving substantial depletion of the sensing volume. Two DMAPS prototypes that use the same "column-drain" readout architecture and are based on different sensor implementation concepts named LF-Monopix and TJ-Monopix have been developed for the High Luminosity upgrade of the Large Hardon Collider (HL-LHC). LF-Monopix was fabricated in the LFoundry 150 nm technology and features pixel size of $50x250~\mu m^{2}$ and large collection electrode opted for high radiation tolerance. Detection efficiency up to 99\% has been measured after irradiation to $1\cdot10^{15}~n_{eq}/cm^{2}$. TJ-Monopix is a large scale $(1x2~cm^{2})$ prototype featuring pixels of $36x40~\mu m^{2}$ size. It was fabricated in a novel TowerJazz 180 nm modified process that enables full depletion of the sensitive layer, while employing a small collection electrode that is less sensitive to crosstalk. The resulting small sensor capacitance ($<=3~fF$) is exploited by a compact, low power front end optimized to meet the 25ns timing requirement. Measurement results demonstrate the sensor performance in terms of Equivalent Noise Charge (ENC) $\approx11e^{-}$, threshold $\approx300~e^-$, threshold dispersion $\approx30~e^-$ and total power consumption lower than $120~mW/cm^2$.

Nanogap-Based Electrochemical Measurements at Double-Carbon-Fiber Ultramicroelectrodes.

Electrochemical measurements with unprecedentedly high sensitivity, selectivity, and kinetic resolution have been enabled by a pair of electrodes separated by a nanometer-wide gap. The fabrication of nanogap electrodes, however, requires extensive nanolithography or nanoscale electrode positioning, thereby preventing the full exploration of this powerful method in electrode design and application. Herein, we report the simple fabrication of double-carbon-fiber ultramicroelectrodes (UMEs) with nanometer-wide gaps not only to facilitate nanogap-based electrochemical measurements but also to gain high time resolution, signal-to-background ratio, and kinetic selectivity for dopamine against ascorbic acid. Specifically, ∼7 μm-diameter carbon fibers are inserted into a double-bore glass capillary, heat-pulled, and milled by focused ion-beam technology to yield ∼50 μm-long double-cylinder UMEs. The redox cycling of the Ru(NH3)63+/2+ couple across a nanogap between voltammetric generator and amperometric collector electrodes reaches quasi-steady states at fast scan rates of 100 V/s as demonstrated experimentally and even 1000 V/s as predicted theoretically. The transient background of the amperometric collector response is suppressed ∼100 times in comparison with that of the voltammetric generator response. Nanogap voltammograms based on the collector response against the cycled generator potential are quantitatively analyzed without background subtraction to reproducibly yield nanogap widths of ∼0.18 μm and a standard electron-transfer rate constant of 0.9 cm/s. Moreover, nanogap-mediated redox cycling can be initiated by dopamine oxidation at the generator electrode to largely improve the dopamine selectivity of the collector response against ascorbic acid, which is also oxidized at the generator electrode to immediately and irreversibly produce a redox-inactive species.

RAPID VISUALIZATION OF THE MASS DISTRIBUTION PROFILE OF ELECTROSPUN LAYERS

Nanofibrous materials are currently widely used in many different areas. One of the technologies commonly used for their production is electrospinning. The mass distribution in a produced nanofibrous layer is a crucial factor especially for filtration applications and active ingredients or drug release applications. Image analysis is an efficient non-destructive method of a mass distribution determination, which has already been used in the evaluation of textiles and melt-blown webs, but so far only a few publications have dealt with its use in the field of electrospun materials. To facilitate the process of image analysis of deposited nanofibers, we developed a new collector electrode, which makes it possible to determine the optical mass distribution profile of the produced layer. A series of experiments proved that the developed collector allows an easy evaluation of the appearance of nanofibrous layers as well as the effects of many associated factors such as emitter configuration on the resulting sample. The results showed how the properties of nanofibrous layers (such as deposition zone dimensions, location of these zones, mass distribution profiles produced by different spinning nozzles) can change during the electrospinning process. The advantages of the method described in the present article are that it allows a contactless and non-destructive determination of mass distribution, detection of macroscopic defects, and investigation of causes behind layer thickness inhomogeneities. All in all, the presented method is a useful research and development tool for the field of electrospinning.

Current Collector-Free Asymmetric Capacitive Deionization System for Energy-Efficient Brackish Water Desalination

Capacitive deionization, CDI, is considered as a versatile and promising electrochemical technology useful for both water desalination and remediation.1 CDI works under operational conditions equivalent to the charging/discharging steps in a generic electric double-layer capacitor (EDLC). Thus, it allows reducing ion concentration of an aqueous stream by the electrosorption of ions in porous electrodes and formation of the EDL, resulting in simultaneous salt withdrawal and energy accumulation. Once the deionization (charging) step is completed, the ions can be desorbed in regeneration (discharging) step. This leads to energy release and leaves the electrode surface available for the next deionization cycle. Accordingly, CDI is considered a simple, non-energy intensive method to produce clean water.2 In this work, a novel current collector-free electrode for CDI devices is designed based on electrodes consisting of a porous metal oxide (MOx) network interpenetrated into porous fibres of carbon nanotubes (CNTf). The fabrication of electrodes is based on the continuous impregnation of CNTf with MOx precursors in-line as they are spun from the chemical vapour deposition reaction. SiO2 and γ-Al2O3 were chosen, which have the following main benefits: i) developing an electrostatic EDL surface potential in the pH range of seawater and drinking water; ii) increasing specific surface area; iii) enabling wetting of electrodes by aqueous electrolytes.3 The content of MOx can be varied by adjusting the concentration of sol in the dispersion. γ-Al2O3/CNTf and SiO2/CNTf electrodes from 6 wt.% to 60 wt.% of MOx have been manufactured and characterized (TG-analysis, electrical conductivity, N2 adsorption isotherms, SEM and TEM images and RAMAN spectroscopy). The hybrid structure consisting of two interconnected porous networks with a uniform distribution of MOx on the supporting CNTf (see Fig 1a and Fig 1b) leads to high capacitance while reducing internal resistance (see Fig 1c), as confirmed by the electrochemical characterization (cyclic voltammetry, charge-discharge and electrochemical impedance spectroscopy). The use of a relatively simple fabrication process, particularly the infiltration of fabrics with sol particles in-line during fibre spinning, enables fabrication of large electrode samples and testing of a full CDI flow cell for brackish water desalination, 2.0 gNaCl L-1 (see Fig 1d). The full current collector-free CDI cell (see Fig 1e and Fig 1f), comprising a stack of γ-Al2O3/CNTf and SiO2/CNTf anodes and cathodes, respectively, has a large salt adsorption capacity of 6.5 mg g-1 and very high efficiency of 86%, which translates into a low energy consumption per gram of salt removed, 0.26 W h g-1. This is an 80% improvement compared with reference devices based on activated carbon and titanium foil current collector electrodes. The exceptional desalination properties (see Fig 1g) are directly linked to the interconnected nanoparticle MOx/CNTf hybrid network. Accordingly, we believe that these CNTf-based electrodes fabricated in a large scale could contribute to a significant improvement in the engineering manufacturing process of desalination reactors through more energy-efficient systems. Considering the high flexibility in bending of these hybrid electrodes, the possibility to build current collector-free desalination devices with complex non-planar shapes has also been opened up. References M. A. Anderson et al. Capacitive deionization as an electrochemical means of saving energy and delivering clean water. Comparison to present desalination practices: Will it compete?, Electrochim. Acta, 55, 3845–3856 (2010). http://dx.doi.org/10.1016/j.electacta.2010.02.012.M. E. Suss et al., Water desalination via capacitive deionization: what is it and what can we expect from it?, Energy Environ. Sci., 8, 2296–2319 (2015).http://dx.doi.org/10.1149/2.0271805jes.J. J. Wouters et al., Influence of Metal Oxide Coatings, Carbon Materials and Potentials on Ion Removal in Capacitive Deionization J. Electrochem.Soc., 165, 148–161 (2018). http://dx.doi.org/10.1149/2.0271805jes. Figure 1

Electrohydrodynamic drying of multiple food products: Evaluating the potential of emitter-collector electrode configurations for upscaling

Electrohydrodynamic (EHD) drying is a promising, non-thermal drying technology, based on ionic wind generation between an emitter and a collector electrode. This simulation-based study evaluates impact of various emitter-collector configurations for EHD drying in order to assess their potential towards industrial upscaling. The conventional wire-to-plate configuration, which creates impinging flow, is found not to be an optimal solution for EHD drying of multiple food products in a fast and uniform way. With a single wire (emitter), it is found that the products placed more downstream dry slower due to the progressive loading of the air with water vapor. With multiple emitters, up to a threefold increase in drying time of the food products is found, compared to a single wire. This increase is caused by the recirculation of most air. To avoid water vapor accumulation in the drying zone, a wire-to-mesh configuration is proposed. The mesh collector minimizes interference of neighboring airflows and avoids recirculation of moist air in the drying zone. As such, the wire-to mesh configuration provides more uniform drying between adjacent products, but also within a product, as it can dry from all its surfaces. An increase in emitter density for the wire-to-mesh configuration leads to an overall increase in air speed, but, surprisingly, not to increased product drying rates. The reason is that the high-speed EHD airflow is always generated very locally in the vicinity of the emitter and collector. Thereby the convective drying process is not affected so much by the emitter density.

Influence of Temperature on the Pressure Distribution Within Press Pack IGBTs

Press pack (PP) packaging technology has been applied to insulated-gate bipolar transistors (IGBTs) for high-voltage and high power density applications in recent years. The pressure distribution within PP IGBTs is very important because it affects both the electrical and thermal contact resistances, thermal cycling capability, and short-circuit current rating. Too much pressure will mechanically damage the chip and too little pressure will increase the thermal contact resistance, which eventually leads to chip thermal damage. In this paper, a finite-element multiphysics model cocoupled with an electrical field, thermal field, and mechanical field is proposed to analyze the collector current distribution, pressure distribution, and junction temperature distribution within PP IGBTs. The most important coupling variables, such as electrical and thermal contact resistances, for this cocoupled multiphysics model are calculated or measured by experiment through a single IGBT/fast-recovery diode chip submodule. Based on this multiphysics model, the influence of the high temperature generated by the chip's power dissipation on the pressure distribution within PP IGBTs (in the heating phase) is discussed, and then, compared with the pressure distribution in the clamping phase. The results show that the pressure distribution within PP IGBTs in the heating phase is extremely uneven and different from the value in the clamping phase. Furthermore, the mechanical model and its boundary conditions are verified through the pressure distribution experimental results in the clamping phase, which is measured based on the Fuji prescale film and the clamping test bench. Based on the simulation and experimental results, an optimization of the collector electrode and pedestal is proposed to improve the pressure distribution within PP IGBTs in the heating phase.

Designs and electric properties studied of 3D trench electrode Si detector with adjustable central collection electrode

In order to improve the radiation resistance of semiconductor detector, 3D trench electrode Si detector structures have been proposed by the Brookhaven National Laboratory (BNL) in 2009. In this paper, we propose a 3D trench electrode Si detector with adjustable central collection electrode, which integrates advantages of cylindrical units and parallel units. For those combined units, we use 1D Poisson equation as the first order approximation to study the changing of depletion in different regions. These results have been compared to those obtained from the full 3D simulation using a 3D-TCAD tool. According to calculations, we design a 3D trench electrode Si detector with adjustable central collection electrode. Furthermore, electrical characteristics of this type of detectors with different lengths of central collection electrode (lp+) have been simulated using the 3D-TCAD. Regarded as the main factor of signal-noise ratio, the geometric capacitance obtained from Silvaco TCAD simulations is compared with which is calculated by physical models when detectors size varies. Finally, the physic model of charge collection is established using Ramo theorem. The CCE (Charge Collection Efficiency) of detector unit is studied with this model (after Φ=1016 neq/cm2, average CCE is 38%).

Electrohydrodynamic drying of food: New insights from conjugate modeling

Abstract Electrohydrodynamic (EHD) drying is a non-thermal technology with promising perspectives to dehydrate heat-sensitive materials such as foods. With EHD drying, corona discharge is used to generate airflow, which enhances convective drying of the food product. Further development and upscaling of this technology are hindered by a lack of insight in both the airflow and the dehydration process inside the material during drying. This study is the first to develop a conjugate continuum model which couples EHD-generated airflow directly to the convective heat transfer and moisture removal from the food. For the wire-to-plate configuration with impinging flow, the impact of different geometrical and operational parameters (wire radius, distance to collector electrode, emitter voltage) on the EHD-driven airflow and resulting drying kinetics is quantified. The fruit drying time is found to increase linearly with increasing distance between electrodes or increasing emitter electrode radius, but decreases in a non-linear way with increasing voltage between the electrodes. For other emitter-collector configurations, where airflow passes around the fruit, such as wire-to-mesh, wire-to-plate, wire-to-wires and wire-to-parallel plates, significant differences in drying kinetics were quantified. Such configurations provide better perspectives towards upscaling to dry large amounts of products uniformly. Of all tested configurations, the wire-to-mesh configuration provided the highest drying rate. Placing the fruit on a mesh also showed to be advantageous since the fruit can be dried more uniformly. The developed conjugate approach has the distinct advantage that the impact of EHD process parameters and geometrical configurations on the drying rate can be quantified very swiftly. Such modeling approach is thereby a valuable tool for further optimization of EHD drying technology towards industrial implementation.