Cold Electrodes Research Articles

A cold-electrode metal–oxide resistive random access memory

To reduce the leakage and power consumption of metal–oxide resistive random access memory (RRAM), we propose and fabricate a cold-electrode (CE) RRAM (CE-RRAM) by extending the mechanism of cold-source FETs. First-principles calculations show that the n-Si/TiN composite CE can filter electrons with energy within the Si bandgap, which contribute to leakage current. A n-Si/TiN/HfOx/Pt CE-RRAM with low leakage current and large on/off current ratio was designed and fabricated. Comparative analysis with conventional RRAM demonstrates over a 100-fold reduction in leakage current in a high resistance state and a tenfold improvement in the Ion/Ioff ratio. Additionally, the CE-RRAM effectively suppresses the overshoot effect in terminal I–V characteristics and exhibits good endurance, maintaining a 100 Ion/Ioff ratio after 104 cycles. Furthermore, even after 104 s at 100 °C, the state remains unchanged. Moreover, the CE-RRAM demonstrates its multi-level storage capability.

Water, Not Salt, Causes Most of the Seebeck Effect of Nonisothermal Aqueous Electrolytes.

A temperature difference between two electrolyte-immersed electrodes often yields a voltage Δψ between them. This electrolyte Seebeck effect is usually explained by cations and anions flowing differently in thermal gradients. However, using molecular simulations, we found almost the same Δψ for cells filled with pure water as with aqueous alkali halides. Water layering and orientation near polarizable electrodes cause a large temperature-dependent potential drop χ there. The difference in χ of hot and cold electrodes captures most of the thermovoltage, Δψ≈χ_{hot}-χ_{cold}.

The Behavior and Removal of Condensable Particulate Matter in Flue Gas in a Multi-Field Force: A Modeling and Experimental Study

Condensable particulate matter (CPM) is different from filterable particulate matter (FPM), which could escape from air pollution control devices (APCDs) and pose a great threat to the environment and human health. Thus, modeling and experimental studies were conducted on CPM particle behavior and removal, in a cold electrode electrostatic precipitator (CE−ESP) coupled with a electric field, temperature field and concentration field. A multi−field force coupling model was then established that was based on the mechanical behavior of particles inside the CE−ESP. The results showed that temperature field was beneficial to depositing small size particles and that, the greater the temperature gradient, the higher CPM’s removal efficiency. While the electric field tended to gather larger size particles, the greater the voltage provided, the higher the removal efficiency for CPM and FPM. In the multi−field, the augmented coagulation and the removal efficiencies of both CPM and FPM increased significantly, reaching 89% and 98%, respectively. Subsequently, experiments were conducted by a self−made CE−ESP device, which showed the removal efficiencies of CE−ESP of a CPM in a multi−field were 91% and 81% for a coal−fired power plant and a waste incineration plant, respectively. This research could make a great contribution to CPM condensation, aggregation and removal.

Experimental demonstration of scalability in a cavity-free planar silicon-integrated thermoelectric device

We demonstrate the scalability of cavity-free planar integrated thermoelectric (TE) devices using silicon nanowires (Si-NWs), where miniaturizing the thermoelement by shortening the Si-NWs improves the areal power density. Shortening the Si-NW length decreases the temperature difference between the Si-NW ends and the open-circuit voltage. Meanwhile, the integrated number density of the thermoelement is increased by shortening the Si-NW length, thereby preserving the total electrical resistance. Bileg devices comprising both n- and p-type Si-NWs exhibited superior performance compared to unileg devices comprising only n-type Si-NWs. In unileg devices, the hot and cold electrodes in the adjacent thermoelements are interconnected through metal wiring, which leaks heat, resulting in a lowering of the temperature difference between the Si-NW ends. This study yields structural design guidelines for planar-integrated TE devices using Si-NWs.

Emission characteristics and removal of heavy metals in flue gas: a case study in waste incineration and coal-fired power plants.

Heavy metal pollutants such as Hg, As, Pb, Cr, and Cd emitted from coal and waste combustion have received widespread attention. In this study, we systematically investigated the emission characteristics of heavy metals in waste incineration and coal-fired flue gases, focused on testing the removal effect of self-made cold electrode electrostatic precipitator (CE-ESP) on heavy metals in flue gas, and made a comparative analysis with the existing air pollution control devices (APCDs). Test results from waste incineration power plant showed that each APCD showed a certain effect on the removal of heavy metals in condensable particulate matter (CPM), with an average removal efficiency of bag filter was 86%, but its effect on Hg removal was slightly worse. Under the coupled field with electrified cold electrode plate operation mode, the average removal efficiency of CE-ESP on heavy metals in CPM was as high as 93%, including 76% for Hg. The removal efficiency of heavy metals (especially Hg) in CPM increased with the increase of flue gas temperature difference between inlet and outlet of CE-ESP. Test results from this coal-fired power plant showed that heavy metals were enriched in fly ash to a higher degree than in slag, the synergistic control of heavy metals in submicron particulate matter by the dust remover was not obvious, and there was a significant correlation between each heavy metal emission factor and its content in coal. Under the temperature field with non-electric cold electrode plate operation mode, the overall effect of CE-ESP on the removal of gaseous heavy metals was better than that of particulate heavy metals. Under the conventional electric field operation mode, CE-ESP was less effective in removing particulate Cr and gaseous Hg0. Under the coupled field with electrified cold electrode plate operation mode, the average removal efficiencies of CE-ESP for particulate and gaseous heavy metals were 82.37% and 76.16%, respectively.

Concentration gradient effect in liquid thermoelectric device composed of organic-solvent-added aqueous solution containing K4[Fe(CN)6]/K3[Fe(CN)6

A liquid thermoelectric conversion device (LTE), which has a simple device structure composed of low-cost materials, is attracting attention. Here, we investigated the additive effect of methanol (MeOH), acetone, and tetrahydrofuran (THF) on an LTE composed of a K4[Fe(CN)6]/K3[Fe(CN)6] aqueous solution. We ascribed to the enhancement of the thermal voltage V and electrochemical Seebeck coefficient α to precipitation of K4[Fe(CN)6] and resultant concentration gradient of [Fe(CN)6]3− between the hot and cold electrodes. The enhancement of V and α is quantitatively reproduced by the concentration gradient model incorporating experimentally-obtained solubility s(T) of K4[Fe(CN)6]. We further demonstrated that precipitation enhances the maximum power by as much as 152% in a MeOH-added LTE composed of 0.35 M K4[Fe(CN)6]/K3[Fe(CN)6] aqueous solution at ΔT = 10 K.

Characterization and Removal of Condensable Particulate Matter in Flue Gas Studied with Cold Electrode Electrostatic Precipitator

Characterization and Removal of Condensable Particulate Matter in Flue Gas Studied with Cold Electrode Electrostatic Precipitator

Designing a professional burnout correction program based on life-purpose orientations in wartime conditions

The work is devoted to substantiation of possibility of reduction of failure rate of thermal mode support system when operating with variable load by control of reliability indicators of thermoelectric cooler. A mathematical model for evaluating the effect of variable thermal load on reliability indicators of a single-cascade thermoelectric cooler at a given temperature level of cooling, medium temperature, geometry of thermocouple branches for various current modes of operation is considered. The relationship between the cooler steady-state operation time and mass and heat capacity of the structure, relative operating current and temperature difference is presented. The results of thermal load relation with operating current, refrigerating factor, time to steady-state mode, energy input, heat dissipation capacity of the radiator, and relative failure rate are presented. Calculations have been made at a given cooling temperature level, medium temperature, temperature differential, and thermocouple branch geometry for various characteristic current operating modes. It is shown that with decreasing thermal load at a given design of thermoelectric cooler, the value of operating current decreases, thus increasing the probability of no-failure operation. The obtained relationship of thermal load with operating current and relative failure rate serves as primary information for design of thermoelectric system for providing thermal modes of thermally loaded elements with variable thermal load. Using the rate of change of temperature difference between the thermally loaded element and the cold electrode of the cooler as a control feature, it is possible to reduce the failure rate when the thermal load decreases, which contributes to increasing the average probability of no-failure operation

Controlling the reliability performance of a thermoelectric cooler under variable heat load

The work is devoted to substantiation of possibility of reduction of failure rate of thermal mode support system when operating with variable load by control of reliability indicators of thermoelectric cooler. A mathematical model for evaluating the effect of variable thermal load on reliability indicators of a single-cascade thermoelectric cooler at a given temperature level of cooling, medium temperature, geometry of thermocouple branches for various current modes of operation is considered. The relationship between the cooler steady-state operation time and mass and heat capacity of the structure, relative operating current and temperature difference is presented. The results of thermal load relation with operating current, refrigerating factor, time to steady-state mode, energy input, heat dissipation capacity of the radiator, and relative failure rate are presented. Calculations have been made at a given cooling temperature level, medium temperature, temperature differential, and thermocouple branch geometry for various characteristic current operating modes. It is shown that with decreasing thermal load at a given design of thermoelectric cooler, the value of operating current decreases, thus increasing the probability of no-failure operation. The obtained relationship of thermal load with operating current and relative failure rate serves as primary information for design of thermoelectric system for providing thermal modes of thermally loaded elements with variable thermal load. Using the rate of change of temperature difference between the thermally loaded element and the cold electrode of the cooler as a control feature, it is possible to reduce the failure rate when the thermal load decreases, which contributes to increasing the average probability of no-failure operation

The Manufacture of Cold Storage with 10 Kg Capacity

Indonesia is one of the maritime countries so that most of Indonesia's territory is the sea, which is rich in marine product; fish is one of the marine products. Fish is a commodity that is not durable and easily damaged if placed in open place. The main causes of fish damage include the activity of microorganisms and bacteria in the fish meat, where at room temperature bacteria and microorganisms can multiply rapidly. Therefore, the author makes a cold storage cooling system with a 10 kg capacity, which can be used to cool the fish caught by fishermen so that the quality and quality of the fish is still fresh to consumers or buyers so that can increase the selling price of fish caught by fishermen in South Aceh Regency. The cold storage manufacturing method is carried out with the initial process of measuring, cutting, welding, drilling, joining, vacuuming and electrical installation. The tools used in the process of making cold storage are welding machines, acetylene welders, cutting grinders, rubbing grinders, measuring elbows, meter tubing cutters, vacuum pumps, digital scales and clam meters. The materials used are angle iron, cold storage boxes, electrodes, relays, MCBs, elbows, and thermostats. The benefits generated by the manufacture of cold storage are to cool fish and increase knowledge of how the system works in cold storage for students of the South Aceh Polytechnic. The results of the cold storage trial for 30 minutes operate with an outside cold storage temperature of 270C and a cold storage temperature of -200C.

Study on cathode spot expansion process in vacuum arc with high di/dt

The study on cathode spot under high di/dt condition promotes the application of vacuum circuit breaker in DC transmission and aerospace technology. Cathode spot, as a source of microscopic particles, directly affects the breaking capacity of vacuum circuit breaker. In this paper, vacuum arc with high di/dt was generated in L-C oscillating circuit. The cathode spot behavior was obtained by a high-speed camera. There are two types of cathode spots with different size, different expansion velocity and brightness. The difference in the size of different types of cathode spots leads to the difference in the thermal diffusion velocity of the spots, which is also the main reason for the difference in the expansion velocity of the two types of spots. The influence of spot current density on temperature and electric field is discussed. With the increase of di/dt, the phenomenon of unstable expansion of cathode spots is observed. A new cathode spot is generated in the cold electrode area far away from the previous cathode spot area, resulting in a significant increase in the arc voltage. The expansion characteristics of cathode spot under different current amplitude, frequency and di/dt conditions are obtained.

Theoretical Prediction of Semiconductor-Free Negative Differential Resistance Tunnel Diodes with High Peak-to-Valley Current Ratios Based on Two-Dimensional Cold Metals

The negative differential resistance (NDR) tunnel diodes are promising alternative devices for beyond-CMOS (complementary metal oxide semiconductor) computing because they offer several potential applications when integrated with transistors. We propose a semiconductor-free NDR tunnel diode concept that exhibits an ultrahigh peak-to-valley current ratio (PVCR) value. Our proposed NDR diode consists of two cold metal electrodes separated by a thin insulating tunnel barrier. The NDR effect stems from the unique electronic band structure of the cold metal electrodes; i.e., the width of the isolated metallic bands around the Fermi level as well as the energy gaps separating higher- and lower-lying bands determine the current–voltage (I–V) characteristics and the PVCR value of the tunnel diode. By proper choice of the cold metal electrode materials, either a conventional N-type or Λ-type NDR effect can be obtained. Two-dimensional (2D) nanomaterials offer a unique platform for the realization of proposed NDR tunnel diodes. To demonstrate the proof of concept, we employ the nonequilibrium Green function method combined with density functional theory to calculate the I–V characteristic of the lateral (AlI2/MgI2/AlI2) and vertical (NbS2/h-BN/NbS2) heterojunction tunnel diodes based on 2D cold metals. For the lateral tunnel diode, we obtain a Λ-type NDR effect with an ultrahigh PVCR value of 1016 at room temperature, while the vertical tunnel diode exhibits a conventional N-type NDR effect with a smaller PVCR value of about 104. The proposed concept provides a semiconductor-free solution for NDR devices to achieve the desired I–V characteristics with ultrahigh PVCR values for memory and logic applications.

Synergistic Effect of Multi-field Force on Condensable Particulate Matter Properties and Behavior in Flue Gas: A Case Study in a Municipal Solid Waste Incineration Plant

At present, filterable particulate matter (FPM) emissions from stable source flue gases are well controlled, and the more difficult to remove condensable particulate matter (CPM) has received much attention due to its environmental hazards. In this study, we built a cold electrode electrostatic precipitator (CE-ESP) and systematically investigated the removal efficiency of CPM from municipal solid waste incineration plant flue gas by CE-ESP under three different operating modes. The results showed that hydrocarbons, esters and aromatic compounds were the main organic substances in CPM. The CE-ESP had a significant contribution to the removal of SO42–, F–, Al, Ni, Cr, and Pb from CPM. In contrast, it had a less effective removal of NO3– and Ca in CPM. The CE-ESP was effective for removing esters in CPM. The removal efficiency of CE-ESP for CPM could reach 76%, and the removal efficiency of organic substance was higher than that of inorganic substance. It is demonstrated that the combination of thermophoretic force and electric field in CE-ESP intensifies the turbulent agglomeration process, and the diffusion force generated by the concentration field synergistically enhances the interparticle coagulation and agglomeration. This promotes the homogeneous condensation process of CPM and the heterogeneous condensation of CPM and FPM, which is conducive to the reduction of condensable particulate matter in flue gas and can provide a theoretical basis for practical application in engineering.

A Novel Gel Thermoelectric Chemical Cell for Harvesting Low-Grade Heat Energy.

The use of gel thermoelectric chemical cells to capture low-grade heat for conversion to electricity is an attractive approach. However, there are few studies on whether the distribution of redox species in the electrolyte has an effect on the performance of cells. Herein, this concern was discussed by constructing a novel gel thermoelectric chemical cell (Cu-C-cg). Using cellulose-like rice paper as a separator, a concentration gradient of electrolyte was carefully constructed, so that the concentration of potassium ferrocyanide gradually decreased from the hot electrode to the cold electrode while the concentration of potassium ferricyanide gradually increased. Through electrochemical measurement and analysis, it was found that the thermoelectric performance of this cell outperformed the cell without electrolyte concentration gradients. Meanwhile, this performance could be enhanced by the use of asymmetric electrodes composed of copper foil and carbon electrodes. After optimizing the conditions, the open-circuit voltage, output power, and Seebeck coefficient of the Cu-C-cg cell at 12 K temperature difference were 0.450 V, 183 μW, and 7.82 mV K-1 , respectively. This work not only provides a novel idea in gel-based cell design but also an excellent thermoelectric chemical cell.

Dynamic characteristics of cathode spots during expansion process in a vacuum arc

Cathode spot is the source of plasma and metal vapor which affects the breaking capacity of vacuum circuit breakers. In this paper, the cup-shaped axial magnetic field contacts were used and the images of cathode spots were obtained by an ultra high-speed camera in the experiment. The dynamic characteristics of cathode spots during expansion process in vacuum arc were investigated. Under the conditions of different current amplitudes, different distributions of cathode spots were observed. During the expansion process of cathode spot, there are group spots and individual spots. The group spot only occurs in the cold electrode. The electrons emission characteristics of cathode spot as a function of temperature and electric field was calculated. The formation of group spot is related to the current and electron emission of cathode spot. The cathode spots were identified by Matlab. It was found that the variation of number of cathode spots is consistent with the current. However, at different stages, the reasons for the increase in the number of cathode spots are different, such as the increase in the area of cathode spots in the initial arcing stage and the splitting of cathode spot. It was observed that the cathode spots are not completely evenly distributed on the cathode surface. The farther away from the center of the contact, the longer the distance between the cathode spots. It is mainly effected by the transverse magnetic field (TMF) which is generated by the arc column. The closer to the contact edge, the higher the TMF at the cathode spot and the higher the expansion velocity of cathode spot.

Effects of electrodes and imposed flow on forced ignition in laminar premixed hydrogen/air mixtures with large Lewis number

Compared to quiescent premixed reactants, forced ignition of flowing/turbulent premixed reactants is expected to be more difficult because of increased dissipation of the deposited energy. However, the counterintuitive turbulence-facilitated ignition (TFI) has been observed in recent experiments for mixtures with large Lewis number, Le. The mechanisms behind TFI are still not well understood and this study aims to interpret a part of the TFI mechanisms through considering electrodes and imposed flow in the simulations of forced ignition in hydrogen/air mixtures. The imposed flow emulates the local turbulent effects around the electrodes which might blow the ignition kernel away from the electrodes. Since TFI occurs only for mixtures with large Le (e.g., lean hydrocarbon/air or rich H2/air mixture), a fuel-rich (ϕ=5.1) H2/air mixture with Le≈2.3 is investigated to reduce computational cost and consider more factors that may lead to TFI. Similar to TFI observed in experiments, the flow-facilitated ignition is observed for H2/air with ϕ=5.1 and Le≈2.3 when the electrodes have a small gap distance. The detailed effects of including electrodes on forced ignition of quiescent and flowing mixtures are explored. It is found that the existence of electrodes not only induces heat loss but also affects the shape and global curvature/stretch of the ignition kernel. The heat loss to the electrodes is demonstrated to play an important role for the ignition of mixtures with large Le. Compared to quiescent mixtures, considering an imposed flow normal to the electrodes can blow the flame kernel away from the cold electrodes. Such movement of the ignition kernel can greatly reduce both the heat loss to the electrodes and flame curvature/stretch, and thereby promote the ignition in mixtures with large Le. These results help to understand the underlying mechanisms for the TFI observed in experiments.

Thermally Chargeable Ammonium‐Ion Capacitor for Energy Storage and Low‐Grade Heat Harvesting

AbstractHarvesting heat from the low‐grade heat (below 100 °C) into electricity has the signification to enhance the utilization of energy and lower carbon emissions by a simple device. Herein we demonstrate a thermally chargeable ammonium ion capacitor (TAIC) by employing graphene‐polyimide (rGO‐PI) synthesized through polycondensation of 1,4,5,8‐naphthalenetetracarboxylic dianhydride and ethylenediamine as cold electrode, N‐doped hollow carbon nanofibers as hot electrode to directly convert waste heat into electricity. Combining thermodiffusion effect of electrolyte with thermogalvanic effect of a redox couple (−C=O/−C−O−NH4+), as‐assembled TAIC can deliver a high output voltage of 624 mV, power density of 82 μW cm−2 and average Seebeck coefficient of 9.07 mV K−1 at temperature difference of 45 K. Meanwhile, with the introduction of polyacrylamide‐polyacrylic acid‐based gel electrolyte, the assembled flexible device can well serve in various bending states, and the power density can attain a satisfying value of 1.92 μW cm−2. This quasi‐solid‐state TAIC shows great potential as one promising candidate for high value‐added conversion from low‐grade heat into electricity as well as wearable applications.

Trade-off in perpendicular electric field control using negatively biased emissive end-electrodes

The benefits of thermionic emission from negatively biased electrodes for perpendicular electric field control in a magnetized plasma are examined through its combined effects on the sheath and on the plasma potential variation along magnetic field lines. By increasing the radial current flowing through the plasma thermionic emission is confirmed to improve control over the plasma potential at the sheath edge compared to the case of a cold electrode. Conversely, thermionic emission is shown to be responsible for an increase of the plasma potential drop along magnetic field lines in the quasi-neutral plasma. These results suggest that there exists a trade-off between electric field longitudinal uniformity and amplitude when using negatively biased emissive electrodes to control the perpendicular electric field in a magnetized plasma.

Real-Time Tunable Dynamic Range for Calibration-Free Biomolecular Measurements with a Temperature-Modulated Electrochemical Aptamer-Based Sensor in an Unprocessed Actual Sample.

The sensing technologies for monitoring molecular analytes in biological fluids with high frequency and in real time could enable a broad range of applications in personalized healthcare and clinical diagnosis. However, due to the limited dynamic range (less than 81-fold), real-time analysis of biomolecular concentration varying over multiple orders of magnitude is a severe challenge faced by this class of analytical platforms. For the first time, we describe here that temperature-modulated electrochemical aptamer-based sensors with a dynamically adjustable calibration-free detection window could enable continuous, real-time, and accurate response for the several-hundredfold target concentration changes in unprocessed actual samples. Specifically, we could regulate the electrode surface temperature of sensors to obtain the corresponding dynamic range because of the temperature-dependent affinity variations. This temperature modulation method relies on an alternate hot and cold electrode reported by our group, whose surface could actively be heated and cooled without the need for altering ambient temperature, thus likewise applying for the flowing system. We then performed dual-frequency calibration-free measurements at different interface temperatures, thus achieving an extended detection window from 25 to 2500 μM for procaine in undiluted urine, 1-500 μM for adenosine triphosphate, and 5-2000 μM for adenosine in undiluted serum. The resulting sensor architecture could drastically expand the real-time response range accessible to these continuous, reagent-less biosensors.

Investigation of Si-based thermoelectrochemical cells (TECs) towards semiconductor fabrication and processing

Thermoelectrochemical cells (TECs) are an alternative with potential for micro-power generator applications but is rarely fabricated using semiconductor processes or micro-fabrication technology. This study initiates fabrication of a Si-based TEC cell device using micro-fabrication technology. The iodide/triiodide poly(vinyl alcohol) hydrogel polymer electrolyte, and citric acid as supporting electrolyte, is selected as the TEC material. A platinum electrode sputtered on a silicon substrate is used as the hot and cold electrode. The TEC voltage generation that is based on Soret diffusion and the Seebeck effect shows good repeatability and stability. The magnitude of the power density shows dependence on the device electrode separation and temperature difference. At 10 mm electrode separation and a temperature difference of 30 K, the Si substrate TEC is able to produce 310 µW m−2; thus, it shows high potential as a low heat waste Si-based TEC power generator.