Cathode Region Research Articles

Opto-Electronic Properties Modulation Through Iodine Doping of Imine- and Triphenylamine-Based Oligomers

Conjugated imine derivatives are of particular interest for the opto-electronic field since their opto-electronic properties can be finely tailored by protonation or doping of the imine unit, e.g. by iodine doping. In this context, four triphenylamine-based oligoimines were subjected to iodine doping in the solid state and thoroughly investigated with respect to the electronic structure modulation induced by doping. The iodine doping process was analyzed by several methods, such as cyclic voltammetry, ultraviolet–visible absorption and Fourier-transform infrared (FTIR) spectroscopy. In addition, a four-point probe technique was applied to measure the electrical conductivities of both the doped and undoped oligoimines. We have noticed changes of the electronic absorption spectra that consisted of the appearance of a new absorption band due to dopant-induced states within the highest occupied molecular orbital (HOMO)—lowest unoccupied molecular orbital (LUMO) gap. Due to the p-type doping process, a distinct reduction of the energy bandgap occurred, being contingent on the formation of imine polaron states, according to the proposed mechanisms. This was confirmed by FTIR spectroscopy, which indicated the presence of the quinoid skeleton in polaronic species formed by doping. Nevertheless, the iodine doping process of oligoimines was accompanied by new redox processes in both the anodic and cathodic regions. Electrochemical data indicated that iodine-doped oligoimines exhibit a higher electronic affinity (LUMO) and a slightly lower energy bandgap compared to pristine forms. The electrical conductivity values of the undoped oligoimines were found in the range of 6.4 × 10−7–8.14 × 10−8 S/cm and increased eight times after oligoimine iodine-doping only in the case of two oligomers. Since doped oligoimine films display better features compared to their pristine forms, they could find applications in opto-electronic devices.

Doping-Less SiC p-i-n Diode: Design and Investigation

We introduce a novel high-voltage SiC p-i-n diode considering a charge plasma approach. This technique facilitates the formation of the anode and the cathode regions within the silicon carbide without requiring any impurity doping by taking advantage of the work-function difference between silicon carbide and metal electrodes. Utilizing the 2-D TCAD simulation, we represent the performance of the proposed doping-less silicon carbide p-i-n diode is analogous to the silicon carbide Schottky diode in terms of forward and reverse characteristics as well as temperature dependency. As opposed to the conventional (doped) silicon carbide p-i-n diode, the doping-less silicon carbide p-i-n diode holds a lower ON-state voltage drop and higher reverse saturation current. Although the doping-less silicon carbide p-i-n diode has the merits of the silicon carbide Schottky diode, but it has leverage over the corresponding counterparts by eliminating the doping and the high thermal budget fabrication processes.

ОБ ЭКСТРЕМУМАХ НА ЗАВИСИМОСТИ СОПРОТИВЛЕНИЯ ПЕРЕНОСА ЗАРЯДА В РЕАКЦИИ ВЫДЕЛЕНИЯ ВОДОРОДА ОТ ПОТЕНЦИАЛА ЭЛЕКТРОДА

The shape of the charge transfer resistance Rct versus overpotentialh curves for the hydrogen evolution reaction (Volmer – Heyrovsky mechanism, Langmuir isotherm for adsorbed hydrogen) was analyzed. It was shown that, depending on the kinetic parameters of reaction steps, three cases are possible: (i) there are no extrema on these curves; (ii) there is one maximum; (iii) there are a minimum and a maximum. Some ways for obtaining kinetic parameters from the curves with extrema are discussed. It was shown that the rate constants and transfer coefficients of all steps can be determined from logRct–h curve alone if there are a minimum and maximum of Rct in cathodic region. In the absence of the extrema, the amount of kinetic information gained from logRct–h plots is considerably reduced.

New copper(II) µ-Alkoxo-µ-Carboxylato Double Bridged Complexes As Models for Active Site of Catechol Oxidase: Synthesis, Spectral Characterization and DFT Calculations

A series of four copper(II) µ-alkoxo-µ-carboxylato double bridged complexes, [{Cu 2 (L)} 2 ][(µ-O 2 C-CO 2 ] 1 , [{Cu 2 (L)} 2 (µ-O 2 C-(CH 2 )CO 2 ] 2 , [{Cu 2 (L)} 2 (µ-O 2 C-CH 2 -CO 2 ] 3 and [{Cu 2 (L)} 2 (µ-O 2 C-C 6 H 4 -CO 2 ] 4 (H 3 L = 4-bromo-2-((E)-((3-(((E)-5-chloro-2-hydroxybenzylidene) amino)-2-hydroxypropyl) imino) methyl)-6-methoxyphenol and µ-dicarboxylate ions = oxalate, malonate, succinate and terephthalate) have been synthesized and characterized using several physicochemical technique. The tridentate nature of H 3 L is interpreted from IR spectra. The Epr spectra of these complexes are characteristic of the quintet state (S = 2) in central features and the triplet state (S = 1) of the tetranuclear complexes. The electrochemical potential of these complexes was investigated using cyclic Voltammetry (CV) and differential pulse Voltammetry (DPV). All complexes exhibited quasi-reversible reduction peaks in the cathodic region. To explore the stability of these complexes, quantum chemical parameters like electronegativity, ionization potential, electron affinity, global hardness and softness and electrophilicity were estimated and discussed. The synthesized complexes have been designed as structural and functional models of the catechol oxidase enzymes to investigate the catecholase activity. Additionally, superoxide dismutase activity data of all complexes have also been evaluated and compared with known SOD mimics.

ИССЛЕДОВАНИЕ РЯДА КОМПОЗИЦИЙ МАРКИ «СОЛИНГ» В КАЧЕСТВЕ ИНГИБИТОРОВ КОРРОЗИИ МАЛОУГЛЕРОДИСТОЙ СТАЛИ В КИСЛЫХ СРЕДАХ

The inhibiting effect of some compositions of «Soling» series on low-carbon steel St3 in solutions of 5% and 15% HCl and 5% H2SO4 has been studied by the methods of polarization and gravimetric measurements. The protective action and the coefficient of inhibition of the corrosion process are calculated, the slopes of the Tafel sections in the cathode and anode regions of the polarization curves have been calculated. The influence of inhibitors on the kinetics of partial electrochemical reactions has been determined. The state of the surface of the samples has been estimated using micrographs. The high efficiency of inhibitors in acidic media has been shown.

МОДЕЛЮВАННЯ КОЛИВАЛЬНИХ І ПОВОРОТНИХ ТРАЄКТОРІЙ ЕЛЕКТРОНІВ В ГРАДІЄНТНОМУ МАГНІТНОМУ ПОЛІ МАГНЕТРОННОЇ ГАРМАТИ

Розглянуто рух електронів в циліндричному магнітному полі зі змінною напруженістю вздовж осі поля. Використано математичні та чисельні моделі перетворення експеримегтальних даних аналітичними функціями. З метою отримання прецизійних характеристик вивчено формування пучка з енергією 55 кеВ в повздовжньому і радіальному напрямках при його транспортуванні в магнітному полі соленоїда. Показано, що руху електронів можна зіставити оптичну модель проходження світлових променів в середовищі з градієнтним коефіцієнтом, що залежить від радіуса. Побудовано програмний засіб, використання якого дало можливість промоделювати основні залежності руху електронного пучка в заданому соленоїдальному магнітному полі. Представлено результати чисельного моделювання траєкторій електронів в градієнтному магнітному полі магнетронній гармати з вторінноемісійним катодом. Розглянуто формування пучка з енергією 55 кеВ в радіальному і поздовжньому напрямках при його транспортуванні в соленоїдальному магнітному полі з великим градієнтом. Отримано режими роботи гармати, при яких частка відчуває ефект "пляшкового горлечка" і завершує свій рух поверненням в прикатодну область. Таким чином, отримані біфуркаційні режими динаміки часток при їх русі вздовж осі транспортування як вперед на мішень, так і назад в прикатодну область. Вивчено вплив початкових умов при емісії на виникнення зворотного ефекту. Показано, що при заданій енергії електрона і фіксованому магнітному полі параметром, що визначає відображення частки, є полярний кут вльоту щодо осі циліндричного магнітного поля. Досліджено залежність формування підсумкового розподілу від амплітуди і градієнта магнітного поля вздовж осі системи. Наводяться результати чисельного моделювання по руху трубчастого електронного потоку. Вивчено можливість управління поздовжньої координати точки повернення електрона. На основі моделі руху електронного потоку розглянуті характеристики результуючого електронного пучка.

Effect of electric field on push-out strength of cemented steel pipes

<abstract> Cement-steel interfacial strength is an important measure for estimating the robustness and hydraulic sealing ability of wells. In this paper, laboratory experiments were performed in which small steel pipes (10 mm in diameter) were cemented in place within a Portland cement slurry under application of constant electrical potential difference between the pipes. The objective was to investigate whether there might be an observable difference between push-out strengths obtained with the pipes of different polarity (anode vs. cathode vs. reference nonpolarized pipe). The duration of the potential application and the magnitude of the potential difference were varied between the tests. The experiments demonstrated that at the higher potential difference (4 V), the duration of potential application had a noticeable effect on interfacial bonding. Application of 4 V for 24 h resulted in loss of bonding at cement-cathode interface, which could be attributed to massive water transportation to the cathode region by small radii cations. At the lower applied potential difference (1 V), there is an improvement in push-out strength at anode at short duration of potential application. This could be due to pore filling by precipitation of expansive minerals in pores and cement particles migration toward anode. The effect of potential on push-out strength in a hardened cement suggests that low potential difference applied for a short period of time might improve cement-steel interfacial strength. </abstract>

Acidophilic Microorganisms Leptospirillum sp., Acidithiobacillus sp., Ferroplasma sp. As a Cathodic Bioagents in a MFC

Reducing fuel cells electrical losses is achieved by the use of a catalyst. Being inexpensive and renewable, biocathodes have an advantage over synthetic and chemical ones. Here the microbial fuel cell (MFC)-utilizing biocathode based on the acidophilic chemolythotrophic microorganisms (ACM) mixed culture has been studied. The Leptospirillum sp., Acidithiobacillus sp., Ferroplasma sp. consortium has been used as a cathode biocatalyst. Pyrite enrichment tails of a mining and processing enterprise served as the catholyte substrates. It is experimentally demonstrated that ACM mixed culture Leptospirillum sp., Acidithiobacillus sp., Ferroplasma sp. introduced into the catholyte leads to MFC electrical characteristics increase by approximately two times. With the selected external load (30 Ω) Cathodic bioagents increased the MFC electric power four-fold (from 137 to 579 µW). Catholyte redox potential increased from 431 to 581 mV during 11 d in the presence of acidophilic iron-oxidizing microorganisms. At 33 d, this value increased up to 695 mV. This is an indirect evidence for active processes of iron oxidation. The analysis results for the Fe3+ content in the medium also support this assumption. Thus, in a course of a 33-d experiment Fe3+ concentration increased from 0 to 1.5 g/l. The redox processes intensification in the studied systems also confirmed by the cyclic voltammetry (CV). Under pyrite utilization conditions in the presence of ACM mixed culture cyclic voltammograms show an increase in the reduction current at the cathodic potentials region. The results obtained herein suggest that the studied biochemical system is a perspective catholyte for MFC capable to reduce a cathodic overpotential.

A novel approach towards crown-ether modified polyimides with affinity for alkali metal ions recognition

In the attempt to enlarge the family of imide-based materials suitable for sensor applications, novel five- and six-membered thermostable polyimides functionalized with benzo-15-crown-5 ether side chains were synthesized and thoroughly investigated with regard to their affinity for alkali metal ions recognition. For this purpose, a new diamine monomer containing as receptor triphenylmethane modified with 15-crown-5 ether (called by us crowned TPM) has been synthesized and structurally characterized. For the first time, we brought evidence for the occurrence of a ground-state intermolecular charge transfer (CT) complex between the donor crowned TPM diamine and the acceptor diimide segment which is actually responsible for the polyimides strong light emission in the green to yellow spectral range. All polyimides were electrochemically active in both anodic and cathodic regions, their voltammetric response being consistent with the coplanarity and electron accepting strength of the diimide segment. In the presence of alkali metal ions some changes appeared in the electronic absorption signals, although quite diffuse. Instead, these cations significantly altered the fluorescence response of polyimides in dependence on the excitation wavelength, cation type and polymer structure. These mostly caused the occurrence of a new emission band, when the green or yellow fluorescence turned in blue, thus proving the capability of our polyimides to detect alkali metal ions.

Enhanced Adsorption of Polysulfides on Carbon Nanotubes/Boron Nitride Fibers for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are one of the most promising high-energy-density storage systems. However, serious capacity attenuation and poor cycling stability induced by the shuttle effect of polysulfide intermediates can impede the practical application of Li-S batteries. Herein we report a novel sulfur cathode by intertwining multi-walled carbon nanotubes (CNTs) and porous boron nitride fibers (BNFs) for the subsequent loading of sulfur. This structural design enables trapping of active sulfur and serves to localize the soluble polysulfide within the cathode region, leading to low active material loss. Compared with CNTs/S, CNTs/BNFs/S cathodes deliver a high initial capacity of 1222 mAh g-1 at 0.1 C. Upon increasing the current density to 4 C, the cell retained a capacity of 482 mAh g-1 after 500 cycles with a capacity decay of only 0.044 % per cycle. The design of CNTs/BNFs/S gives new insight on how to optimize cathodes for Li-S batteries.

Microstructure and Electrochemistry of Al-Rich Primer

Al-rich primer (AlRP) is designed to be anodic relative to high strength Al alloys, so that it drives the mixed potential of Al alloy substrates (e.g. AA2024) into the cathodic region below the breakdown potentials of the Al alloys, preventing localized corrosion. The Al-rich primer (AlRP) under study is composed of spherical Al-Zn-In pigments in an epoxy binder. The 2D and 3D microstructure of the AlRP was studied using a combination of X-ray microscopy, plasma focus ion beam/scanning electron microscopy, and transmission electron microscopy techniques. The primer contained Al-Zn-In particles with various sizes ranging from tens of nanometers to microns, epoxy binder and a significant volume of voids. Potentiodynamic polarization testing was performed to measure the electrochemistry of the Al-Zn-In bulk alloy under neat primer in NaCl solution to simulate the environment which Al-Zn-In pigments are exposed to in the real primer. The bulk alloy under neat primer exhibited higher breakdown potential than the bare bulk alloy exposed to NaCl solution. The polarization curves of the bulk alloy under neat primer provide more accurate boundary conditions for modeling of the galvanic interaction between the AlRP and an alloy substrate. Galvanic corrosion between an AA2024 sample and Al-Zn-In bulk alloy was also studied using a zero resistance ammeter. A trivalent chromium process treatment on galvanic couples can protect AA2024 substrate from cathodic corrosion.Acknowledgements: this project is funded by the Office of Naval Research through the Small Business Innovation Research (SBIR) program. We thank Naval Air Systems Command (NAVAIR) for providing Al-rich primer samples. We acknowledge Dr. Mansoureh Norouzi Rad at Zeiss for 3D microstructure reconstruction on Al-rich primer using X-ray microscope, and Thermo Fisher Scientific for 3D microstructure reconstruction on Al-rich primer using Helios Plasma FIB/SEM. We appreciate Dr. Babu Viswanathan at OSU for STEM characterization, and Swagelok Center for Surface Analysis of Materials (SCSAM) at Case Western Reserve University for Ar ion polishing.

Tuning the Electrochromic Properties of Fluorinated Benzochalcogenodiazole Based Donor‐Acceptor Polymers

AbstractIn this study, a series of benzochalcogenodiazole based donor acceptor monomers namely 4,7‐bis(4‐hexyl‐2‐thienyl)‐2,1,3‐benzothiadiazole (TST), 5,6‐difluoro‐4,7‐bis(4‐hexyl‐2‐thienyl)‐2,1,3‐benzothiadiazole (TST2) and 4,7‐bis(4‐hexyl‐2‐thienyl)‐2,1,3‐benzoselenadiazole (TSeT) were synthesized by Stille reaction and then directly polymerized on to Indium Tin Oxide coated glass (ITO/Glass) surface by electrochemical polymerization process. According to UV‐Vis measurements, a 20 nm blue shift was detected at low energy band after fluorination of TST (TST2). Besides, a 40 nm red shift was observed by changing S to Se on the benzochalcogenodiazole moiety (TSeT). Thus, the optical band gaps were varied as 2.32, 2.45 and 2.16 eV for TST, TST2 and TSeT, respectively. According to AFM results, rougher surface was observed in the PTSeT thin film than that of PTST and PTST2. Thin films of electrodeposited polymers onto ITO/glass surface displayed ambipolar multi‐electrochromic behavior both anodic and cathodic region. The ambipolar charge distribution was also observed in the theoretical DFT calculations. When the electrochromic performance of the polymer films was compared to each other, it was seen that the PTST2 has a better stability and higher the percentage transmittance change (ΔT%) at near‐IR regime between neutral and oxidized states.

A Full Li-S Battery with Ultralow Excessive Li Enabled via Lithiophilic and Sulfilic W2 C Modulation.

The practical application of Li-S batteries demands low cell balance (Licapacity /Scapacity ), which involves uniform Li growth, restrained shuttle effect, and fast redox reaction kinetics of S species simultaneously. Herein, with the aid of W2 C nanocrystals, a freestanding 3D current collector is applied as both Li and S hosts owing to its lithiophilic and sulfilic property. On the one hand, the highly conductive W2 C can reduce Li nucleation overpotentials, thus guiding uniform Li nucleation and deposition to suppress Li dendrite growth. On the other hand, the polar W2 C with catalytic effect can enhance the chemisorption affinity to lithium polysulfides (LiPSs) and guarantee fast redox kinetics to restrain S species in cathode region and promote the utilization of S. Surprisingly, a full Li-S battery with ultralow cell balance of 1.5:1 and high sulfur loading of 6.06 mg cm-2 shows obvious redox plateaus of S and maintains high reversible specific capacity of 1020 mAh g-1 (6.2 mAh cm-2 ) after 200 cycles. This work may shed new sights on the facile design of full Li-S battery with low excessive Li supply.

Local Electrochemical Behavior of Friction Stir Welded Mg-Al-Mn Alloy Joints

Local scanning electrochemical microscopy (SECM), along with a scanning vibrating electrode technique (SVET), were used to spatially map anodic and cathodic regions in a complex assembly including a friction stir lap welded joint between two Mg-Al-Mn alloys, namely AM60 and AM30. The assembly investigated herein was comprised of the two base materials (AM60 and AM30) and a stir zone (SZ). The transitory electrochemical characteristics of the three regions were perceived from different electrochemical tests and have been correlated to their respective microstructures. Potentiometric and voltametric SECM performed on the assembly in 0.01 M NaCl revealed that during the first few minutes of exposure, AM60 and SZ regions act as dominant anodic regions in the assembly while after 2 h of exposure these regions transition to become cathodic relative to the AM30 region. Galvanic interaction between the different weld regions immersed in a significantly more conductive NaCl electrolyte was investigated by SVET. Under such conditions, filiform-like corrosion initiated, and propagated exclusively within the AM30 region, resulting in cathodic activation of the corroded surface. However, after approximately 5 h of exposure, the AM60 region preferentially dissolves following sufficient cathodic activation of the AM30 region.

Experimental and mechanistic research on modifying the mechanic properties of the high water backfill material by electrochemical treatment

To promote the engineering applications of high water backfill materials (HWBM) in mining, a series of experiments are performed to investigate the effects of the direct current (DC) electric field on the mechanic properties and electrical resistivity of HWBMs. Based on X-ray diffraction (XRD) and scanning electron microscopy (SEM) investigations, the influence of electrochemical treatment on the hydration products and the microstructure of the HWBM was studied. The results show that the peak strength, elastic modulus, deformation modulus and electrical resistivity of the HWBM samples all first increased and then decreased with the increasing of the potential gradient, and the peak points appeared when the potential gradient was 0.2 V/cm. The anisotropy of content of ettringite and calcium silicate hydrates (C–S–H) increased betweent the anodic and cathodic regions of samples. Meanwhile, microstructure in the anodic region of the samples was more stable after electrochemical treatment, which indicates that the different variation of mineralogical compositions and microstructures in different regions of the samples are the primary factors affecting the mechanic properties and electrical resistivity of the HWBM. Therefore, the electrochemical method is a potential technology to modify the engineering properties of the HWBM.

Recycling lithium cobalt oxide from its spent batteries: An electrochemical approach combining extraction and synthesis

LiCoO2 is still the most extensively used cathode material in Li-ion battery for portable electronics currently. The increasing usage of electronics has resulted in the growing discard of LiCoO2 with the stream of its spent battery. Current recycling approaches for LiCoO2 from spent batteries are dominantly based on hydrometallurgy and pyrometallurgy, which usually require multiple complicated steps and involve the use of high temperature or harmful chemicals, like acids and alkalis. There remains an urgent need for green and simple processes. Here we report a single step approach based on suspension electrolysis to directly recycle LiCoO2 in one reactor at atmospheric condition without any usage of acid and alkalis. The electrolyte of the suspension electrolysis system is only comprised of NH4HCO3, NH42SO3 and NaF. The reaction system of LiCoO2 leaching in the anode region and simultaneously re-synthesizing in the cathode region in the electrochemical system is established. Mechanism analysis indicates that NH4+ only serves as a provider for complexing agent of NH3 and is virtually not consumed. This work provides potentially meaningful strategies for recovering LiCoO2 in a shorter procedure and an environmentally friendly manner.

Features of the secondary runaway electron flow formed in an elongated, atmospheric pressure air gap

We investigate the formation of a secondary flow of runaway electrons with energies on the order of 100 keV in an air gap after the passage of a primary picosecond flow of similar fast particles, arising in the cathode region where the distribution of the electric field is very inhomogeneous. The dependence of the secondary flow onset delay on the gap length and the field strength is demonstrated. The reasons for the discrimination of the two flows in time are considered analytically. The occurrence of fast secondary electrons in an anode-located part of the gap is demonstrated under conditions when the ionization wave generated in the cathode region by the primary runaway electrons is cutoff. For this, an intermediate aluminum foil electrode under a floating potential has been used. This third electrode, which divides the gap into two sections, is partially transparent for the runaway electrons. It has been also shown that runaway electrons demonstrate the earliest arrival to the anode if they arise due to the photoionization of the gas by bremsstrahlung of the primary particles bombarding an intermediate electrode made of tantalum foil.

Stress corrosion cracking in pipelines

Stress corrosion is viewed as cracking of a pipe metal in cathodic protection regions of gas transmission pipelines, which are simultaneously affected by various unrelated, at first glance, factors. Stress corrosion is otherwise referred to as stress corrosion cracking or SCC. Stress corrosion cracking of pipelines is the main cause of emergencies in gas transmission pipelines. Currently, this type of corrosion is widespread and very dangerous. The reliability and safety of modern pipelines is of great national importance. Despite being significant, multiple efforts to address this problem have not yet identified the causes and algorithms for handling stress corrosion.

Simulation studies on the RF gun saturated emission

The emission of a short high charged electron bunch in a radiofrequency gun was simulated. The numerical model is supplemented by a positive charge arising and dynamically changing during emission in the cathode region The numerical results are compared with experimental data.

Electron Groups in Solar Wind and Gas Discharge Plasmas

The formation of electron groups is a common phenomenon in gas discharges and space plasmas. We describe similarities between electron kinetics in solar wind, cathode region of glow discharges, and magnetic nozzles. Remarkable resemblances between adiabatic focusing of magnetized electrons and spherical geometry effects for neutral particles escaping planet’s atmosphere are pointed out. The previously developed kinetic solvers for electrons coupled to Poisson equation for self-consistent simulations of the electric field are used to analyse the formation of electron groups in the cathode region of glow discharges and solar wind plasma.