Possibility of High Phosphorus Pig Iron as Sacrificial Anode

NASA Astrophysics Data System (ADS)

Prasad, Nisheeth Kr.; Pathak, A. S.; Kundu, S.; Mondal, K.

2018-05-01

Cathodic protection is an effective method to control the corrosion of underground pipelines and submerged structures. In the present work, high phosphorus containing pig iron was utilized as sacrificial anode for cathodic protection of underground mild steel plates and the results were compared with that of a commercially pure magnesium sacrificial anode. Driving potential and current between the galvanically coupled sacrificial anodes and mild steel plates were continuously monitored in real time for one month. Microstructure and morphology of the corrosion products formed on the surface of pig iron, magnesium sacrificial anodes and mild steel plates were observed with the help of optical microscope and scanning electron microscopy, and phase identification were performed using x-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. The distribution of phosphorus in the pig iron matrix and soluble rust formation on the surface of pig iron under buried condition were critical from the point of sacrificial effect, indicating the possible scientific reasons for high phosphorous pig iron to be used as sacrificial anode.

Fabrication of porous anodic alumina using normal anodization and pulse anodization

NASA Astrophysics Data System (ADS)

Chin, I. K.; Yam, F. K.; Hassan, Z.

2015-05-01

This article reports on the fabrication of porous anodic alumina (PAA) by two-step anodizing the low purity commercial aluminum sheets at room temperature. Different variations of the second-step anodization were conducted: normal anodization (NA) with direct current potential difference; pulse anodization (PA) alternate between potential differences of 10 V and 0 V; hybrid pulse anodization (HPA) alternate between potential differences of 10 V and -2 V. The method influenced the film homogeneity of the PAA and the most homogeneous structure was obtained via PA. The morphological properties are further elucidated using measured current-transient profiles. The absent of current rise profile in PA indicates the anodization temperature and dissolution of the PAA structure were greatly reduced by alternating potential differences.

Carbon and Carbon Hybrid Materials as Anodes for Sodium-Ion Batteries.

PubMed

Zhong, Xiongwu; Wu, Ying; Zeng, Sifan; Yu, Yan

2018-02-12

Sodium-ion batteries (SIBs) have attracted much attention for application in large-scale grid energy storage owing to the abundance and low cost of sodium sources. However, low energy density and poor cycling life hinder practical application of SIBs. Recently, substantial efforts have been made to develop electrode materials to push forward large-scale practical applications. Carbon materials can be directly used as anode materials, and they show excellent sodium storage performance. Additionally, designing and constructing carbon hybrid materials is an effective strategy to obtain high-performance anodes for SIBs. In this review, we summarize recent research progress on carbon and carbon hybrid materials as anodes for SIBs. Nanostructural design to enhance the sodium storage performance of anode materials is discussed, and we offer some insight into the potential directions of and future high-performance anode materials for SIBs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improving carbon dioxide yields and cell efficiencies for ethanol oxidation by potential scanning

NASA Astrophysics Data System (ADS)

Majidi, Pasha; Pickup, Peter G.

2014-12-01

An ethanol electrolysis cell with aqueous ethanol supplied to the anode and nitrogen at the cathode has been operated under potential cycling conditions in order to increase the yield of carbon dioxide and thereby increase cell efficiency relative to operation at a fixed potential. At ambient temperature, faradaic yields of CO2 as high as 26% have been achieved, while only transient CO2 production was observed at constant potential. Yields increased substantially at higher temperatures, with maximum values at Pt anodes reaching 45% at constant potential and 65% under potential cycling conditions. Use of a PtRu anode increased the cell efficiency by decreasing the anode potential, but this was offset by decreased CO2 yields. Nonetheless, cycling increased the efficiency relative to constant potential. The maximum yields at PtRu and 80 °C were 13% at constant potential and 32% under potential cycling. The increased yields under cycling conditions have been attributed to periodic oxidative stripping of adsorbed CO, which occurs at lower potentials on PtRu than on Pt. These results will be important in the optimization of operating conditions for direct ethanol fuel cells and for the electrolysis of ethanol to produce clean hydrogen.

[Effect of the initial anode potential on electricity generation in microbial fuel cell].

PubMed

Fan, Ming-Zhi; Liang, Peng; Cao, Xiao-Xin; Huang, Xia

2008-01-01

The initial anode potential of the microbial fuel cell (MFC) was changed by additional circuit in the anode chamber, and the influence of the initial anode potential on the electricigens was studied. When the initial anode potential was 350 mV (vs Hg/Hg2 Cl2), the growth of microorganisms was much slower than that of the microorganisms which grew on the anode with an initial potential of -200 mV or 200 mV (vs Hg/Hg2 Cl2). After stable electricity generation, the anode resistances of the three MFCs, which had initial anode potentials of 350 mV, 200 mV and -200 mV respectively, were 71 Omega, 43 Omega and 80 Omega. The community structures in MFCs, before and after the electricity generation, were also studied by denaturing gradient gel electrophoresis (DGGE). Clostridium sticklandii, Pseudomonas mendocina and Paenibacillus taejonensis were the three most enriched strains on the anode.

Self-Ordered Nanoporous Alumina Templates Formed by Anodization of Aluminum in Oxalic Acid

NASA Astrophysics Data System (ADS)

Vida-Simiti, Ioan; Nemes, Dorel; Jumate, Nicolaie; Thalmaier, Gyorgy; Sechel, Niculina

2012-10-01

Anodic aluminum oxide (AAO) membranes with highly ordered nanopores serve as ideal templates for the formation of various nanostructured materials. The procedure of the template preparation is based on a two-step self-organized anodization of aluminum. In the current study, AAO templates were fabricated in 0.3 M oxalic acid under the anodizing potential range of 30-60 V at an electrolyte temperature of ~5°C. The AAO templates were analyzed using scanning electron microscopy, x-ray diffraction, Fourier-transform infrared spectroscopy, and differential thermal analysis. The as obtained layers are amorphous; the mean pore size is between 40 nm and 75 nm and increases with the increase of the anodization potential. Well-defined pores across the whole aluminum template, a pore density of ~1010 pores/cm2, and a tendency to form a porous structure with hexagonal symmetry were observed.

Quasi-perpetual discharge behaviour in p-type Ge-air batteries.

PubMed

Ocon, Joey D; Kim, Jin Won; Abrenica, Graniel Harne A; Lee, Jae Kwang; Lee, Jaeyoung

2014-11-07

Metal-air batteries continue to become attractive energy storage and conversion systems due to their high energy and power densities, safer chemistries, and economic viability. Semiconductor-air batteries - a term we first define here as metal-air batteries that use semiconductor anodes such as silicon (Si) and germanium (Ge) - have been introduced in recent years as new high-energy battery chemistries. In this paper, we describe the excellent doping-dependent discharge kinetics of p-type Ge anodes in a semiconductor-air cell employing a gelled KOH electrolyte. Owing to its Fermi level, n-type Ge is expected to have lower redox potential and better electronic conductivity, which could potentially lead to a higher operating voltage and better discharge kinetics. Nonetheless, discharge measurements demonstrated that this prediction is only valid at the low current regime and breaks down at the high current density region. The p-type Ge behaves extremely better at elevated currents, evident from the higher voltage, more power available, and larger practical energy density from a very long discharge time, possibly arising from the high overpotential for surface passivation. A primary semiconductor-air battery, powered by a flat p-type Ge as a multi-electron anode, exhibited an unprecedented full discharge capacity of 1302.5 mA h gGe(-1) (88% anode utilization efficiency), the highest among semiconductor-air cells, notably better than new metal-air cells with three-dimensional and nanostructured anodes, and at least two folds higher than commercial Zn-air and Al-air cells. We therefore suggest that this study be extended to doped-Si anodes, in order to pave the way for a deeper understanding on the discharge phenomena in alkaline metal-air conversion cells with semiconductor anodes for specific niche applications in the future.

Yolk-shell structured Sb@C anodes for high energy Na-ion batteries

DOE PAGES

Song, Junhua; Yan, Pengfei; Luo, Langli; ...

2017-09-04

Despite great advances in sodium-ion battery developments, the search for high energy and stable anode materials remains a challenge. Alloy or conversion-typed anode materials are attractive candidates of high specific capacity and low voltage potential, yet their applications are hampered by the large volume expansion and hence poor electrochemical reversibility and fast capacity fade. Here in this paper, we use antimony (Sb) as an example to demonstrate the use of yolk-shell structured anodes for high energy Na-ion batteries. The Sb@C yolk-shell structure prepared by controlled reduction and selective removal of Sb 2O 3 from carbon coated Sb 2O 3 nanoparticlesmore » can accommodate the Sb swelling upon sodiation and improve the structural/electrical integrity against pulverization. It delivers a high specific capacity of ~ 554 mAh g -1, good rate capability (315 mhA g-1 at 10 C rate) and long cyclability (92% capacity retention over 200 cycles). Full-cells of O3-Na 0.9[Cu0.22Fe 0.30Mn 0.48]O 2 cathodes and Sb@C-hard carbon composite anodes demonstrate a high specific energy of ~ 130 Wh kg-1 (based on the total mass of cathode and anode) in the voltage range of 2.0–4.0 V, ~ 1.5 times energy of full-cells with similar design using hard carbon anodes.« less

Yolk-shell structured Sb@C anodes for high energy Na-ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Junhua; Yan, Pengfei; Luo, Langli

Despite great advances in sodium-ion battery developments, the search for high energy and stable anode materials remains a challenge. Alloy or conversion-typed anode materials are attractive candidates of high specific capacity and low voltage potential, yet their applications are hampered by the large volume expansion and hence poor electrochemical reversibility and fast capacity fade. Here, we use antimony (Sb) as an example to demonstrate the use of yolk-shell structured anodes for high energy Na-ion batteries. The Sb@C yolk-shell structure prepared by controlled reduction and selective removal of Sb2O3 from carbon coated Sb2O3 nanoparticles can accommodate the Sb swelling upon sodiationmore » and improve the structural/electrical integrity against pulverization. It delivers a high specific capacity of ~554 mAh•g-1, good rate capability (315 mhA•g-1 at 10C rate) and long cyclability (92% capacity retention over 200 cycles). Full-cells of O3-Na0.9[Cu0.22Fe0.30Mn0.48]O2 cathodes and Sb@C-hard carbon composite anodes demonstrate a high specific energy of ~130 Wh•kg-1 (based on the total mass of cathode and anode) in the voltage range of 2.0-4.0 V, ~1.5 times energy of full-cells with similar design using hard carbon anodes.« less

Yolk-shell structured Sb@C anodes for high energy Na-ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Junhua; Yan, Pengfei; Luo, Langli

Despite great advances in sodium-ion battery developments, the search for high energy and stable anode materials remains a challenge. Alloy or conversion-typed anode materials are attractive candidates of high specific capacity and low voltage potential, yet their applications are hampered by the large volume expansion and hence poor electrochemical reversibility and fast capacity fade. Here in this paper, we use antimony (Sb) as an example to demonstrate the use of yolk-shell structured anodes for high energy Na-ion batteries. The Sb@C yolk-shell structure prepared by controlled reduction and selective removal of Sb 2O 3 from carbon coated Sb 2O 3 nanoparticlesmore » can accommodate the Sb swelling upon sodiation and improve the structural/electrical integrity against pulverization. It delivers a high specific capacity of ~ 554 mAh g -1, good rate capability (315 mhA g-1 at 10 C rate) and long cyclability (92% capacity retention over 200 cycles). Full-cells of O3-Na 0.9[Cu0.22Fe 0.30Mn 0.48]O 2 cathodes and Sb@C-hard carbon composite anodes demonstrate a high specific energy of ~ 130 Wh kg-1 (based on the total mass of cathode and anode) in the voltage range of 2.0–4.0 V, ~ 1.5 times energy of full-cells with similar design using hard carbon anodes.« less

High field CdS detector for infrared radiation

NASA Technical Reports Server (NTRS)

Tyagi, R. C.; Robertson, J. B.; Boer, K. W.; Hadley, H. C., Jr. (Inventor)

1974-01-01

An infrared radiation detector including a cadmium sulfide platelet having a cathode formed on one of its ends and an anode formed on its other end is presented. The platelet is suitably doped such that stationary high-field domains are formed adjacent the cathode when based in the negative differential conductivity region. A negative potential is applied to the cathode such that a high-field domain is formed adjacent to the cathode. A potential measuring probe is located between the cathode and the anode at the edge of the high-field domain and means are provided for measuring the potential at the probe whereby this measurement is indicative of the infrared radiation striking the platelet.

Conductor of high electrical current at high temperature in oxygen and liquid metal environment

DOEpatents

Powell, IV, Adam Clayton; Pati, Soobhankar; Derezinski, Stephen Joseph; Lau, Garrett; Pal, Uday B.; Guan, Xiaofei; Gopalan, Srikanth

2016-01-12

In one aspect, the present invention is directed to apparatuses for and methods of conducting electrical current in an oxygen and liquid metal environment. In another aspect, the invention relates to methods for production of metals from their oxides comprising providing a cathode in electrical contact with a molten electrolyte, providing a liquid metal anode separated from the cathode and the molten electrolyte by a solid oxygen ion conducting membrane, providing a current collector at the anode, and establishing a potential between the cathode and the anode.

Experimental Studies of the Effects of Anode Composition and Process Parameters on Anode Slime Adhesion and Cathode Copper Purity by Performing Copper Electrorefining in a Pilot-Scale Cell

NASA Astrophysics Data System (ADS)

Zeng, Weizhi; Wang, Shijie; Free, Michael L.

2016-10-01

Copper electrorefining tests were conducted in a pilot-scale cell under commercial tankhouse environment to study the effects of anode compositions, current density, cathode blank width, and flow rate on anode slime behavior and cathode copper purity. Three different types of anodes (high, mid, and low impurity levels) were used in the tests and were analyzed under SEM/EDS. The harvested copper cathodes were weighed and analyzed for impurities concentrations using DC Arc. The adhered slimes and released slimes were collected, weighed, and analyzed for compositions using ICP. It was shown that the lead-to-arsenic ratio in the anodes affects the sintering and coalescence of slime particles. High current density condition can improve anode slime adhesion and cathode purity by intensifying slime particles' coalescence and dissolving part of the particles. Wide cathode blanks can raise the anodic current densities significantly and result in massive release of large slime particle aggregates, which are not likely to contaminate the cathode copper. Low flow rate can cause anode passivation and increase local temperatures in front of the anode, which leads to very intense sintering and coalescence of slime particles. The results and analyses of the tests present potential solutions for industrial copper electrorefining process.

Engineering of Nanoscale Antifouling and Hydrophobic Surfaces on Naval Structural Steel HY-80 by Anodizing

DTIC Science & Technology

2015-06-01

examination of the morphologies of the nanoporous structures and the evaluation of the anodization parameters such as anodization potential, time... sponges , anemones, tunicates, and hydroids, whilst hard fouling comprises invertebrates such as barnacles, mussels, and tubeworms. The specific...of metals by making them more stable and highly resistant, but also to modify the surface by giving it a desired morphology . Ferrous alloys such as

Study of the highly ordered TiO2 nanotubes physical properties prepared with two-step anodization

NASA Astrophysics Data System (ADS)

Pishkar, Negin; Ghoranneviss, Mahmood; Ghorannevis, Zohreh; Akbari, Hossein

2018-06-01

Highly ordered hexagonal closely packed titanium dioxide nanotubes (TiO2 NTs) were successfully grown by a two-step anodization process. The TiO2 NTs were synthesized by electrochemical anodization of titanium foils in an ethylene glycol based electrolyte solution containing 0.3 wt% NH4F and 2 vol% deionized (DI) water at constant potential (50 V) for 1 h at room temperature. Physical properties of the TiO2 NTs, which were prepared via one and two-step anodization, were investigated. Atomic Force Microscopy (AFM) analysis revealed that anodization and subsequently peeled off the TiO2 NTs caused to the periodic pattern on the Ti surface. In order To study the nanotubes morphology, Field Emission Scanning Electron Microscopy (FESEM) was used, which was revealed that the two-step anodization resulted highly ordered hexagonal TiO2 NTs. Crystal structures of the TiO2 NTs were mainly anatase, determined by X-ray diffraction analysis. Optical studies were performed by Diffuse Reflection Spectra (DRS) and Photoluminescence (PL) analysis showed that the band gap of TiO2 NTs prepared via two-step anodization was lower than the band gap of samples prepared by one-step anodization process.

Importance of Electrode Material in the Electrochemical Treatment of Wastewater Containing Organic Pollutants

NASA Astrophysics Data System (ADS)

Panizza, Marco

Electrochemical oxidation is a promising method for the treatment of wastewaters containing organic compounds. As a general rule, the electrochemical incineration of organics at a given electrode can take place at satisfactory rates and without electrode deactivation only at high anodic potentials in the region of the water discharge due to the participation of the intermediates of oxygen evolution. The nature of the electrode material strongly influences both the selectivity and the efficiency of the process. In particular, anodes with low oxygen evolution overpotential (i.e., good catalysts for oxygen evolution reactions), such as graphite, IrO2, RuO2, and Pt only permit the partial oxidation of organics, while anodes with high oxygen evolution overpotential (i.e., anodes that are poor catalysts for oxygen evolution reactions), such as SnO2, PbO2, and boron-doped diamond (BDD) favor the complete oxidation of organics to CO2 and so are ideal electrodes for wastewater treatment.However, the application of SnO2 and PbO2 anodes may be limited by their short service life and the risk of lead contamination, while BDD electrodes exhibit good chemical and electrochemical stability, a long life, and a wide potential window for water discharge, and are thus promising anodes for industrial-scale wastewater treatment.

Anode sheath transition in an anodic arc for synthesis of nanomaterials

NASA Astrophysics Data System (ADS)

Nemchinsky, V. A.; Raitses, Y.

2016-06-01

The arc discharge with ablating anode or so-called anodic arc is widely used for synthesis of nanomaterials, including carbon nanotubes and fullerens, metal nanoparticles etc. We present the model of this arc, which confirms the existence of the two different modes of the arc operation with two different anode sheath regimes, namely, with negative anode sheath and with positive anode sheath. It was previously suggested that these regimes are associated with two different anode ablating modes—low ablation mode with constant ablation rate and the enhanced ablation mode (Fetterman et al 2008 Carbon 46 1322). The transition of the arc operation from low ablation mode to high ablation mode is determined by the current density at the anode. The model can be used to self-consistently determine the distribution of the electric field, electron density and electron temperature in the near-anode region of the arc discharge. Simulations of the carbon arc predict that for low arc ablating modes, the current is driven mainly by the electron diffusion to the anode. For positive anode sheath, the anode voltage is close to the ionization potential of anode material, while for negative anode sheath, the anode voltage is an order of magnitude smaller. It is also shown that the near-anode plasma, is far from the ionization equilibrium.

A type of cylindrical Hall thruster with a magnetically insulated anode

NASA Astrophysics Data System (ADS)

Yongjie, Ding; Yu, Xu; Wuji, Peng; Liqiu, Wei; Hongbo, Su; Hezhi, Sun; Peng, Li; Hong, Li; Daren, Yu

2017-04-01

In this paper, a type of magnetically insulated anode structure is proposed for the design of a low-power cylindrical Hall thruster. The magnetic field distribution in the channel is guided by the magnetically insulated anode, altering the intersection status of the magnetic field line passing through the anode and wall. Experimental and simulation results show that a high potential is formed near the wall by the magnetically insulated anode. As the ionization moves towards the outlet, the energy and flux of the ions bombarding the channel wall can be reduced effectively. Due to the reduction in the bombardment of the wall from high-energy ions, the thrust and specific impulse greatly increase compared with those of the non-magnetically insulated anode. For anode mass flow rates of 0.3 and 0.35 mg s-1 and discharge voltages in the 100-200 V range, the thrust can be increased by more than 33% and the anode efficiency can be improved by more than 7%. Meanwhile, the length of the sputtering area is clearly reduced. The starting position of the sputtering area is in front of the magnetic pole, which can effectively prolong the service life of the thruster.

Advancing Lithium Metal Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Bin; Zhang, Ji-Guang; Xu, Wu

Considering the unsatisfied energy density of traditional graphite anode-based lithium (Li)-ion batteries, any alterative high capacity anodes will be highly expected to be practically applied in future high energy battery systems. Li metal is regarded as one of the most promising anodes due to its ultrahigh capacity (3860 mAh g-1), the lowest standard negative electrochemical potential (-3.040 V) and the very low gravimetric density (0.534 g cm-3). However, dendrite growth and high reactivity of Li metal result in low cycling efficiency and severe safety concerns. The revival of research and development on Li metal anode in recent years has broughtmore » new in-depth understandings and key experimental achievements regarding Li metal protection and enhanced performances of Li-metal batteries. In this perspective article, we first concisely review the recent discoveries and then offer possible research directions for further development of Li metal batteries.« less

Free-standing hierarchically sandwich-type tungsten disulfide nanotubes/graphene anode for lithium-ion batteries.

PubMed

Chen, Renjie; Zhao, Teng; Wu, Weiping; Wu, Feng; Li, Li; Qian, Ji; Xu, Rui; Wu, Huiming; Albishri, Hassan M; Al-Bogami, A S; El-Hady, Deia Abd; Lu, Jun; Amine, Khalil

2014-10-08

Transition metal dichalcogenides (TMD), analogue of graphene, could form various dimensionalities. Similar to carbon, one-dimensional (1D) nanotube of TMD materials has wide application in hydrogen storage, Li-ion batteries, and supercapacitors due to their unique structure and properties. Here we demonstrate the feasibility of tungsten disulfide nanotubes (WS2-NTs)/graphene (GS) sandwich-type architecture as anode for lithium-ion batteries for the first time. The graphene-based hierarchical architecture plays vital roles in achieving fast electron/ion transfer, thus leading to good electrochemical performance. When evaluated as anode, WS2-NTs/GS hybrid could maintain a capacity of 318.6 mA/g over 500 cycles at a current density of 1A/g. Besides, the hybrid anode does not require any additional polymetric binder, conductive additives, or a separate metal current-collector. The relatively high density of this hybrid is beneficial for high capacity per unit volume. Those characteristics make it a potential anode material for light and high-performance lithium-ion batteries.

Effect of the anode feeding composition on the performance of a continuous-flow methane-producing microbial electrolysis cell.

PubMed

Zeppilli, Marco; Villano, Marianna; Aulenta, Federico; Lampis, Silvia; Vallini, Giovanni; Majone, Mauro

2015-05-01

A methane-producing microbial electrolysis cell (MEC) was continuously fed at the anode with a synthetic solution of soluble organic compounds simulating the composition of the soluble fraction of a municipal wastewater. The MEC performance was assessed at different anode potentials in terms of chemical oxygen demand (COD) removal efficiency, methane production, and energy efficiency. As a main result, about 72-80% of the removed substrate was converted into current at the anode, and about 84-86% of the current was converted into methane at the cathode. Moreover, even though both COD removed and methane production slightly decreased as the applied anode potential decreased, the energy efficiency (i.e., the energy recovered as methane with respect to the energy input into the system) increased from 54 to 63%. Denaturing gradient gel electrophoresis (DGGE) analyses revealed a high diversity in the anodic bacterial community with the presence of both fermentative (Proteiniphilum acetatigenes and Petrimonas sulphurifila) and aerobic (Rhodococcus qingshengii) microorganisms, whereas only two microorganisms (Methanobrevibacter arboriphilus and Methanosarcina mazei), both assignable to methanogens, were observed in the cathodic community.

Plasma properties and heating at the anode of a 1 kW arcjet using electrostatic probes

NASA Astrophysics Data System (ADS)

Tiliakos, Nicholas

A 1 kW hydrazine arcjet thruster has been modified for internal probing of the near-anode boundary layer with an array of fourteen electrostatic micro-probes. The main objectives of this experimental investigation were to: (1) obtain axial and azimuthal distributions of floating potential phisbf, anode sheath potential phisbs, probe current density at zero volts jsba, electron number density nsbes, electron temperature Tsbes, and anode heating due to electrons qsbe for arc currents Isbarc, between 7.8 and 10.6 A, propellant flow rates m = 40-60 mg/s, and specific energies, 18.8 MJ/kg ≤ P/m ≤ 27.4 MJ/kg; (2) probe the anode boundary layer using flush-mounted and cylindrical micro-probes; (3) verify azimuthal current symmetry; (4) understand what affects anode heating, a critical thruster lifetime issue; and (5) provide experimental data for validation of the Megli-Krier-Burton (MKB) model. All of the above objectives were met through the design, fabrication and implementation of fourteen electrostatic micro-probes, of sizes ranging from 0.170 mm to 0.43 mm in diameter. A technique for cleaning and implementing these probes was developed. Two configurations were used: flush-mounted planar probes and cylindrical probes extended 0.10-0.30 mm into the plasma flow. The main results of this investigation are: (1) electrostatic micro-probes can successfully be used in the harsh environment of an arcjet; (2) under all conditions tested the plasma is highly non-equilibrium in the near-anode region; (3) azimuthal current symmetry exists for most operating conditions; (4) the propellant flow rate affects the location of maximum anode sheath potential, current density, and anode heating more than the arc current; (5) the weighted anode sheath potential is always positive and varies from 8-17 V depending on thruster operating conditions; (6) the fraction of anode heating varies from 18-24% of the total input power over the range of specific energies tested; and (7) based on an energy loss factor of delta = 1200, reasonable correlation between the experimental data and the MKB model was found.

Metallurgically lithiated SiOx anode with high capacity and ambient air compatibility

PubMed Central

Zhao, Jie; Lee, Hyun-Wook; Sun, Jie; Yan, Kai; Liu, Yayuan; Liu, Wei; Lu, Zhenda; Lin, Dingchang; Zhou, Guangmin; Cui, Yi

2016-01-01

A common issue plaguing battery anodes is the large consumption of lithium in the initial cycle as a result of the formation of a solid electrolyte interphase followed by gradual loss in subsequent cycles. It presents a need for prelithiation to compensate for the loss. However, anode prelithiation faces the challenge of high chemical reactivity because of the low anode potential. Previous efforts have produced prelithiated Si nanoparticles with dry air stability, which cannot be stabilized under ambient air. Here, we developed a one-pot metallurgical process to synthesize LixSi/Li2O composites by using low-cost SiO or SiO2 as the starting material. The resulting composites consist of homogeneously dispersed LixSi nanodomains embedded in a highly crystalline Li2O matrix, providing the composite excellent stability even in ambient air with 40% relative humidity. The composites are readily mixed with various anode materials to achieve high first cycle Coulombic efficiency (CE) of >100% or serve as an excellent anode material by itself with stable cyclability and consistently high CEs (99.81% at the seventh cycle and ∼99.87% for subsequent cycles). Therefore, LixSi/Li2O composites achieved balanced reactivity and stability, promising a significant boost to lithium ion batteries. PMID:27313206

Effects of the voltage and time of anodization on modulation of the pore dimensions of AAO films for nanomaterials synthesis

NASA Astrophysics Data System (ADS)

Chahrour, Khaled M.; Ahmed, Naser M.; Hashim, M. R.; Elfadill, Nezar G.; Maryam, W.; Ahmad, M. A.; Bououdina, M.

2015-12-01

Highly-ordered and hexagonal-shaped nanoporous anodic aluminum oxide (AAO) of 1 μm thickness of Al pre-deposited onto Si substrate using two-step anodization was successfully fabricated. The growth mechanism of the porous AAO film was investigated by anodization current-time behavior for different anodizing voltages and by visualizing the microstructural procedure of the fabrication of AAO film by two-step anodization using cross-sectional and top view of FESEM imaging. Optimum conditions of the process variables such as annealing time of the as-deposited Al thin film and pore widening time of porous AAO film were experimentally determined to obtain AAO films with uniformly distributed and vertically aligned porous microstructure. Pores with diameter ranging from 50 nm to 110 nm and thicknesses between 250 nm and 1400 nm, were obtained by controlling two main influential anodization parameters: the anodizing voltage and time of the second-step anodization. X-ray diffraction analysis reveals amorphous-to-crystalline phase transformation after annealing at temperatures above 800 °C. AFM images show optimum ordering of the porous AAO film anodized under low voltage condition. AAO films may be exploited as templates with desired size distribution for the fabrication of CuO nanorod arrays. Such nanostructured materials exhibit unique properties and hold high potential for nanotechnology devices.

Nanostructural characterization of large-scale porous alumina fabricated via anodizing in arsenic acid solution

NASA Astrophysics Data System (ADS)

Akiya, Shunta; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

2017-05-01

Anodizing of aluminum in an arsenic acid solution is reported for the fabrication of anodic porous alumina. The highest potential difference (voltage) without oxide burning increased as the temperature and the concentration of the arsenic acid solution decreased, and a high anodizing potential difference of 340 V was achieved. An ordered porous alumina with several tens of cells was formed in 0.1-0.5 M arsenic acid solutions at 310-340 V for 20 h. However, the regularity of the porous alumina was not improved via anodizing for 72 h. No pore sealing behavior of the porous alumina was observed upon immersion in boiling distilled water, and it may be due to the formation of an insoluble complex on the oxide surface. The porous alumina consisted of two different layers: a hexagonal alumina layer that contained arsenic from the electrolyte and a pure alumina honeycomb skeleton. The porous alumina exhibited a white photoluminescence emission at approximately 515 nm under UV irradiation at 254 nm.

Using sewage sludge pyrolytic gas to modify titanium alloy to obtain high-performance anodes in bio-electrochemical systems

NASA Astrophysics Data System (ADS)

Gu, Yuan; Ying, Kang; Shen, Dongsheng; Huang, Lijie; Ying, Xianbin; Huang, Haoqian; Cheng, Kun; Chen, Jiazheng; Zhou, Yuyang; Chen, Ting; Feng, Huajun

2017-12-01

Titanium is under consideration as a potential stable bio-anode because of its high conductivity, suitable mechanical properties, and electrochemical inertness in the operating potential window of bio-electrochemical systems; however, its application is limited by its poor electron-transfer capacity with electroactive bacteria and weak ability to form biofilms on its hydrophobic surface. This study reports an effective and low-cost way to convert a hydrophobic titanium alloy surface into a hydrophilic surface that can be used as a bio-electrode with higher electron-transfer rates. Pyrolytic gas of sewage sludge is used to modify the titanium alloy. The current generation, anodic biofilm formation surface, and hydrophobicity are systematically investigated by comparing bare electrodes with three modified electrodes. Maximum current density (15.80 A/m2), achieved using a modified electrode, is 316-fold higher than that of the bare titanium alloy electrode (0.05 A/m2) and that achieved by titanium alloy electrodes modified by other methods (12.70 A/m2). The pyrolytic gas-modified titanium alloy electrode can be used as a high-performance and scalable bio-anode for bio-electrochemical systems because of its high electron-transfer rates, hydrophilic nature, and ability to achieve high current density.

Stabilizing the baseline current of a microbial fuel cell-based biosensor through overpotential control under non-toxic conditions.

PubMed

Stein, Nienke E; Hamelers, Hubertus V M; Buisman, Cees N J

2010-04-01

A MFC-based biosensor can act as online toxicity sensor. Electrical current is a direct linear measure for metabolic activity of electrochemically active microorganisms. Microorganisms gain energy from anodic overpotential and current strongly depends on anodic overpotential. Therefore control of anodic overpotential is necessary to detect toxic events and prevent false positive alarms. Anodic overpotential and thus current is influenced by anode potential, pH, substrate and bicarbonate concentrations. In terms of overpotential all factor showed a comparable effect, anode potential 1.2% change in current density per mV, pH 0.43%/mV, bicarbonate 0.75%/mV and acetate 0.8%/mV. At acetate saturation the maximum acetate conversion rate is reached and with that a constant bicarbonate concentration. Control of acetate and bicarbonate concentration can be less strict than control of anode potential and pH. Current density changes due to changing anode potential and pH are in the same order of magnitude as changes due to toxicity. Strict control of pH and anode potential in a small range is required. The importance of anodic overpotential control for detection of toxic compounds is shown. To reach a stable baseline current under nontoxic conditions a MFC-based biosensor should be operated at controlled anode potential, controlled pH and saturated substrate concentrations. 2009 Elsevier B.V. All rights reserved.

Double-sided anodic titania nanotube arrays: a lopsided growth process.

PubMed

Sun, Lidong; Zhang, Sam; Sun, Xiao Wei; Wang, Xiaoyan; Cai, Yanli

2010-12-07

In the past decade, the pore diameter of anodic titania nanotubes was reported to be influenced by a number of factors in organic electrolyte, for example, applied potential, working distance, water content, and temperature. All these were closely related to potential drop in the organic electrolyte. In this work, the essential role of electric field originating from the potential drop was directly revealed for the first time using a simple two-electrode anodizing method. Anodic titania nanotube arrays were grown simultaneously at both sides of a titanium foil, with tube length being longer at the front side than that at the back side. This lopsided growth was attributed to the higher ionic flux induced by electric field at the front side. Accordingly, the nanotube length was further tailored to be comparable at both sides by modulating the electric field. These results are promising to be used in parallel configuration dye-sensitized solar cells, water splitting, and gas sensors, as a result of high surface area produced by the double-sided architecture.

Characteristics of the NASA Lewis bumpy-torus plasma generated with positive applied potentials

NASA Technical Reports Server (NTRS)

Roth, J. R.; Gerdin, G. A.; Richardson, R. W.

1976-01-01

Experimental observations were made during steady-state operation of a bumpy-torus plasma at input powers up to 150 kW in deuterium and helium gas and with positive potentials applied to the midplane electrodes. In this steady-state ion heating method a modified Penning discharge is operated such that the plasma is acted upon by a combination of strong electric and magnetic fields. Experimental investigation of a deuterium plasma revealed electron temperatures from 14 to 140 eV and ion kinetic temperatures from 160 to 1785 eV. At least two distinct modes of operation exist. Experimental data shows that the average ion residence time in the plasma is virtually independent of the magnetic field strength. Data was taken when all 12 anode rings were at high voltage, and in other symmetric configurations in which the toroidal plasma was generated by applying positive potentials to six anode rings, three anode rings, and a single anode ring.

Enhancing Near Zero Volt Storage Tolerance of Lithium-ion Batteries

NASA Astrophysics Data System (ADS)

Crompton, Kyle R.

There are inherent safety risks associated with inactive lithium ion batteries leading to greater restrictions and regulations on shipping and storage. Maintaining all cells of a lithium ion battery at near zero voltage with an applied fixed resistive load is one promising approach which can lessen (and potentially eliminate) the risk of a lithium ion battery entering thermal runaway when in an inactive state. However, in a conventional lithium ion cell, a near zero cell voltage can be damaging if the anode electrochemical potential increases to greater than the potential where dissolution of the standard copper current collector occurs (i.e. 3.1 V vs. Li/Li+ at room temperature). Past approaches to yield lithium ion cells that are resilient to a near zero volt state of charge involve use of secondary active materials or alternative current collectors which have anticipated tradeoffs in terms of cell performance and cost. In the the present dissertation work the approach of managing the amount of reversible lithium in a cell during construction to prevent the anode potential from increasing to greater than 3.1 V vs. Li/Li+ during near zero volt storage is introduced. Anode pre-lithiation was used in LiCoO 2/MCMB pouch cells to appropriately manage the amount of reversible lithium so that there is excess reversible lithium compared to the cathodes intercalation capacity (reversible lithium excess cell or RLE cell). RLE LiCoO 2/MCMB cells maintained 99% of their original capacity after three, 3-day and three, 7-day storage periods at near zero volts under fixed load. A LiCoO2/MCMB pouch cell fabricated with a pre-lithiated anode also maintained its original discharge performance after three, 3-day storage periods under fixed load at 45°C. The strong recharge performance after near zero volt storage is attributed to the anode potential remaining below the copper dissolution potential during near zero volt storage as informed by reference electrode measurements. Pulse discharge measurements were performed and show that double layer capacitance likely plays a major role in determining the behavior of electrode potentials during near zero volt storage. To further the viability of the anode pre-lithiation method in LiCoO2/MCMB cells, stabilization coatings on the cathode materials are being investigated to increase the tolerance of the cathode to the low potentials it may experience during near zero volt storage of an RLE lithium ion cell. Results show that an AlPO4 coating prevents cation exhange in the cathode crystal structure and substantially increases the cathode's resilience to low electrochemical potentials. Investigations into applying anode pre-lithiation to cells utilizing LiNiCoAlO2 (NCA) cathodes have also been initiated and found to maintain the anode potential below the copper dissolution potential during near zero volt storage. RLE NCA/MCMB cells showed strong recharge performance and improved rate capability retention over a conventional NCA/MCMB cell after ten, 3-day near zero volt storage periods. Scale up of reversible lithium management to NCA/MCMB x3450 pouch cells was achieved using bath lithium addition and rendered a cell that retained 100% of its discharge performance after a 14 day period at near zero volts under fixed load. The near zero volt storage tolerance of lithium ion cells utilizing an advanced, high energy density lithium rich cathode material (0.49Li2MnO3˙0.51LiNi 0.37Co0.24Mn0.39O2 or HE5050) has also been studied and found to be high at room temperature without the need for anode pre-lithiation. HE5050/MCMB cells maintained 100% of their discharge capacity after five, 3-day and five, 7-day near zero volt storage periods at room temperature. HE5050/MCMB also maintained 99% of their discharge capacity after two, 3-day near zero volt storage periods at 40°C. The high first cycle loss and lower intercalation potential of the HE5050 cathode lead to the anode potential remaining <2.8 V vs. Li/Li+ during near zero volt storage and as such, no copper dissolution is expected to be occurring. Finally, Carbon Nanotube (CNT) papers have been shown to be stable up to high potentials vs. Li/Li+ and thus, using them as an anode current collector in place of standard copper can generate lithium ion cells that can tolerate near zero volt storage. However, CNT papers suffer from significant irreversible loss due to their high surface area. An Al2O3 coating deposited by atomic layer deposition is investigated for its effect in reducing the irreversible losses of a CNT paper. The Al2O3 coating was found to reduce irreversible loss by 55% over 50 cycles and still serve as an effective current collector for a graphitic anode composite.

Active control of methanol carbonylation selectivity over Au/carbon anode by electrochemical potential.

PubMed

Funakawa, Akiyasu; Yamanaka, Ichiro; Otsuka, Kiyoshi

2005-05-12

Electrochemical oxidative carbonylation of methanol was studied over Au supported carbon anode in CO. The major carbonylation products were dimethyl oxalate (DMO) and dimethyl carbonate (DMC). The minor oxidation products were dimethoxy methane (DMM) and methyl formate (MF) from methanol and CO(2). Influences of various reaction conditions were studied on carbonylation activities and selectivities. The selectivities to DMO and DMC can be controlled by the electrochemical potential. Electrocatalysis of Au/carbon anode was studied by cyclic voltammetry (CV), stoichiometric reactions among Au(3+), methanol, and CO, and UV-vis spectra. The Au/carbon anode was characterized by XRD, SEM, and BE images before and after the carbonylation. These experimental facts strongly suggest that transition of oxidation states of Au affects changing of the carbonylation selectivities to DMO and DMC. Au(0) is the active species for the selective DMO formation by direct electrochemical carbonylation at low potentials (<+1.2 V (Ag/AgCl)). On the other hand, Au(3+) is the active spices for the selective DMC formation by indirect electrochemical carbonylation through Au(3+)/Au(+) redox at high potentials (>+1.3 V).

Scalable Production of the Silicon-Tin Yin-Yang Hybrid Structure with Graphene Coating for High Performance Lithium-Ion Battery Anodes.

PubMed

Jin, Yan; Tan, Yingling; Hu, Xiaozhen; Zhu, Bin; Zheng, Qinghui; Zhang, Zijiao; Zhu, Guoying; Yu, Qian; Jin, Zhong; Zhu, Jia

2017-05-10

Alloy anodes possessed of high theoretical capacity show great potential for next-generation advanced lithium-ion battery. Even though huge volume change during lithium insertion and extraction leads to severe problems, such as pulverization and an unstable solid-electrolyte interphase (SEI), various nanostructures including nanoparticles, nanowires, and porous networks can address related challenges to improve electrochemical performance. However, the complex and expensive fabrication process hinders the widespread application of nanostructured alloy anodes, which generate an urgent demand of low-cost and scalable processes to fabricate building blocks with fine controls of size, morphology, and porosity. Here, we demonstrate a scalable and low-cost process to produce a porous yin-yang hybrid composite anode with graphene coating through high energy ball-milling and selective chemical etching. With void space to buffer the expansion, the produced functional electrodes demonstrate stable cycling performance of 910 mAh g -1 over 600 cycles at a rate of 0.5C for Si-graphene "yin" particles and 750 mAh g -1 over 300 cycles at 0.2C for Sn-graphene "yang" particles. Therefore, we open up a new approach to fabricate alloy anode materials at low-cost, low-energy consumption, and large scale. This type of porous silicon or tin composite with graphene coating can also potentially play a significant role in thermoelectrics and optoelectronics applications.

Facile Fabrication of Ordered Anodized Aluminum Oxide Membranes with Controlled Pore Size by Improved Hard Anodization.

PubMed

Fan, Jiangxia; Zhu, Xinxin; Wang, Kunzhou; Chen, Xiaoyuan; Wang, Xinqing; Yan, Minhao; Ren, Yong

2018-05-01

We have fabricated highly ordered anodized aluminum oxide (AAO) membranes with different diameter through improved hard anodization (HA) at high temperature. This process can generate thick AAO membranes (30 μm) in a short anodizing time with high growth rate 20-60 μm h-1 which is much faster than that in traditional mild two-step anodization. We enlarged the AAO pore diameter by adjusting the voltage rise rate at the same time, which has a great influence on current density and temperature. The AAO pore diameter varies from 60-110 nm to 160-190 nm. The pore diameter (Dp) of the AAO prepared by this improved process is much larger than that prepared by HA (40-60 nm) when H2C2O4 as electrolyte. It can expand potential use of the AAO membranes such as for the template-based synthesis of nanowires or nanotubes with modulated diameters and also for practical separation technology. We also has used the AAO with different diameters prepared by this improved HA to fabricate Co nanowires and γ-Fe2O3 superparamagnetic nanorods.

Properties of nanostructures obtained by anodization of aluminum in phosphoric acid at moderate potentials

NASA Astrophysics Data System (ADS)

Zaraska, L.; Sulka, G. D.; Jaskuła, M.

2009-01-01

The influence of the process duration, anodizing potential and methanol addition on the structural features of porous anodic alumina formed in a 0.3 M H3PO4 solutions by twostep self-organized anodizing was investigated for potentials ranging from 100 to 170 V. The structural features of porous structures including pore diameter and interpore distance were evaluated from FE-SEM top-view images for samples anodized in the presence and absence of methanol. For the highest studied anodizing time and methanol volume fraction, an excellent agreement between experimental values of the interpore distance and theoretical predictions was observed. The pore arrangement regularity was analyzed for various electrolyte compositions and anodizing potentials. It was found that the regularity ratio of porous alumina increases linearly with increasing anodizing potential and time. The addition of methanol improves the quality of nanostructures and especially better uniformity of pore sizes is observed in the presence of the highest studied methanol content.

Plasma-anode electron gun

NASA Astrophysics Data System (ADS)

Santoru, Joseph; Schumacher, Robert W.; Gregoire, Daniel J.

1994-11-01

The plasma-anode electron gun (PAG) is an electron source in which the thermionic cathode is replaced with a cold, secondary-electron-emitting electrode. Electron emission is stimulated by bombarding the cathode with high-energy ions. Ions are injected into the high-voltage gap through a gridded structure from a plasma source (gas pressure less than or equal to 50 mTorr) that is embedded in the anode electrode. The gridded structure serves as both a cathode for the plasma discharge and as an anode for the PAG. The beam current is modulated at near ground potential by modulating the plasma source, eliminating the need for a high-voltage modulator system. During laboratory tests, the PAG has demonstrated square-wave, 17-microsecond-long beam pulses at 100 kV and 10 A, and it has operated stably at 70 kV and 2.5 A for 210 microsecond pulse lengths without gap closure.

Alloy-Based Anode Materials toward Advanced Sodium-Ion Batteries.

PubMed

Lao, Mengmeng; Zhang, Yu; Luo, Wenbin; Yan, Qingyu; Sun, Wenping; Dou, Shi Xue

2017-12-01

Sodium-ion batteries (SIBs) are considered as promising alternatives to lithium-ion batteries owing to the abundant sodium resources. However, the limited energy density, moderate cycling life, and immature manufacture technology of SIBs are the major challenges hindering their practical application. Recently, numerous efforts are devoted to developing novel electrode materials with high specific capacities and long durability. In comparison with carbonaceous materials (e.g., hard carbon), partial Group IVA and VA elements, such as Sn, Sb, and P, possess high theoretical specific capacities for sodium storage based on the alloying reaction mechanism, demonstrating great potential for high-energy SIBs. In this review, the recent research progress of alloy-type anodes and their compounds for sodium storage is summarized. Specific efforts to enhance the electrochemical performance of the alloy-based anode materials are discussed, and the challenges and perspectives regarding these anode materials are proposed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Novel and Generalized Lithium-Ion-Battery Configuration utilizing Al Foil as Both Anode and Current Collector for Enhanced Energy Density.

PubMed

Ji, Bifa; Zhang, Fan; Sheng, Maohua; Tong, Xuefeng; Tang, Yongbing

2017-02-01

A novel battery configuration based on an aluminum foil anode and a conventional cathode is developed. The aluminum foil plays a dual role as both the active anode material and the current collector, which enhances the energy density of the packaged battery, and reduces the production cost. This generalized battery configuration has high potential for application in next-generation lithium-ion batteries. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sulfur poisoning of Ni/Gadolinium-doped ceria anodes: A long-term study outlining stable solid oxide fuel cell operation

NASA Astrophysics Data System (ADS)

Riegraf, Matthias; Zekri, Atef; Knipper, Martin; Costa, Rémi; Schiller, Günter; Friedrich, K. Andreas

2018-03-01

This work presents an analysis of the long-term behavior of nickel/gadolinium-doped ceria (CGO) anode-based solid oxide fuel cells (SOFC) under sulfur poisoning conditions. A parameter study of sulfur-induced irreversible long-term degradation of commercial, high-performance single cells was carried out at 900 °C for different H2/N2/H2S fuel gas atmospheres, current densities and Ni/CGO anodes. The poisoning periods of the cells varied from 200 to 1500 h. The possibility of stable long-term Ni/CGO anode operation under sulfur exposure is established and the critical operating regime is outlined. Depending on the operating conditions, two degradation phenomena can be observed. Small degradation of the ohmic resistance was witnessed for sulfur exposure times of approximately 1000 h. Moreover, degradation of the anode charge transfer resistance was observed to be triggered by the combination of a small anodic potential step and high sulfur coverage on Ni. The microstructural evolution of altered Ni/CGO anodes was examined post-mortem by means of SEM and FIB/SEM, and is correlated to the anode performance degradation under critical operating conditions, establishing Ni depletion, porosity increase and a tripe phase boundary density decrease in the anode functional layer. It is shown that short-term sulfur poisoning behavior can be used to assess long-term stability.

In situ fabrication of green reduced graphene-based biocompatible anode for efficient energy recycle.

PubMed

Cheng, Ying; Mallavarapu, Megharaj; Naidu, Ravi; Chen, Zuliang

2018-02-01

Improving the anode configuration to enhance biocompatibility and accelerate electron shuttling is critical for efficient energy recovery in microbial fuel cells (MFCs). In this paper, green reduced graphene nanocomposite was successfully coated using layer-by-layer assembly technique onto carbon brush anode. The modified anode achieved a 3.2-fold higher power density of 33.7 W m -3 at a current density of 69.4 A m -3 with a 75% shorter start period. As revealed in the characterization, the green synthesized nanocomposite film affords larger surface roughness for microbial colonization. Besides, gold nanoparticles, which anchored on graphene sheets, promise the relatively high electroactive sites and facilitate electron transfer from electricigens to the anode. The reduction-oxidation peaks in cyclic voltammograms indicated the mechanism of surface cytochromes facilitated current generation while the electrochemical impedance spectroscopy confirmed the enhanced electron transfer from surface cytochrome to electrode. The green synthesis process has the potential to generate a high performing anode in further applications of MFCs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrostatic spray deposition of porous SnO₂/graphene anode films and their enhanced lithium-storage properties.

PubMed

Jiang, Yinzhu; Yuan, Tianzhi; Sun, Wenping; Yan, Mi

2012-11-01

Porous SnO₂/graphene composite thin films are prepared as anodes for lithium ion batteries by the electrostatic spray deposition technique. Reticular-structured SnO₂ is formed on both the nickel foam substrate and the surface of graphene sheets according to the scanning electron microscopy (SEM) results. Such an assembly mode of graphene and SnO₂ is highly beneficial to the electrochemical performance improvement by increasing the electrical conductivity and releasing the volume change of the anode. The novel engineered anode possesses 2134.3 mA h g⁻¹ of initial discharge capacity and good capacity retention of 551.0 mA h g⁻¹ up to the 100th cycle at a current density of 200 mA g⁻¹. This anode also exhibits excellent rate capability, with a reversible capacity of 507.7 mA h g⁻¹ after 100 cycles at a current density of 800 mA g⁻¹. The results demonstrate that such a film-type hybrid anode shows great potential for application in high-energy lithium-ion batteries.

Nanopatterning of steel by one-step anodization for anti-adhesion of bacteria.

PubMed

Chen, Shiqiang; Li, Yuan; Cheng, Y Frank

2017-07-13

Surface nanopatterning of metals has been an effective technique for improved performance and functionalization. However, it is of great challenge to fabricate nanostructure on carbon steels despite their extensive use and urgent needs to maintain the performance reliability and durability. Here, we report a one-step anodization technique to nanopattern a carbon steel in 50 wt.% NaOH solution for highly effective anti-adhesion by sulphate reducing bacteria (SRB), i.e., Desulfovibrio desulfuricans subsp. desulfuricans (Beijerinck) Kluyver and van Niel. We characterize the morphology, structure, composition, and surface roughness of the nanostructured film formed on the steel as a function of anodizing potential. We quantify the surface hydrophobicity by contact angle measurements, and the SRB adhesion by fluorescent analysis. The optimal anodization potential of 2.0 V is determined for the best performance of anti-adhesion of SRB to the steel, resulting in a 23.5 times of reduction of SRB adhesion compared to bare steel. We discuss the mechanisms for the film formation on the steel during anodization, and the high-performance anti-adhesion of bacteria to nanopatterned steels. Our technique is simple, cost-effective and environment-friendly, providing a promising alternative for industry-scale surface nanopatterning of carbon steels for effective controlling of bacterial adhesion.

Current collection by high voltage anodes in near ionospheric conditions

NASA Technical Reports Server (NTRS)

Antoniades, John A.; Greaves, Rod G.; Boyd, D. A.; Ellis, R.

1990-01-01

The authors experimentally identified three distinct regimes with large differences in current collection in the presence of neutrals and weak magnetic fields. In magnetic field/anode voltage space the three regions are separated by very sharp transition boundaries. The authors performed a series of laboratory experiments to study the dependence of the region boundaries on several parameters, such as the ambient neutral density, plasma density, magnetic field strength, applied anode voltage, voltage pulsewidth, chamber material, chamber size and anode radius. The three observed regimes are: classical magnetic field limited collection; stable medium current toroidal discharge; and large scale, high current space glow discharge. There is as much as several orders of magnitude of difference in the amount of collected current upon any boundary crossing, particularly if one enters the space glow regime. They measured some of the properties of the plasma generated by the breakdown that is present in regimes II and III in the vicinity of the anode including the sheath modified electrostatic potential, I-V characteristics at high voltage as well as the local plasma density.

An Overview of the VHITAL Program: A Two-Stage Bismuth Fed Very High Specific Impulse Thruster with Anode Layer

NASA Technical Reports Server (NTRS)

Sengupta, Anita; Marrese-Reading, Colleen; Capelli, Mark; Scharfe, David; Tverdokhlebov, Sergey; Semenkin, Sasha; Tverdokhlebov, Oleg; Boyd, Ian; Keidar, Michael; Yalin, Azer;

Improving startup performance with carbon mesh anodes in separator electrode assembly microbial fuel cells.

PubMed

Zhang, Fang; Xia, Xue; Luo, Yong; Sun, Dan; Call, Douglas F; Logan, Bruce E

2013-04-01

In a separator electrode assembly microbial fuel cell, oxygen crossover from the cathode inhibits current generation by exoelectrogenic bacteria, resulting in poor reactor startup and performance. To determine the best approach for improving startup performance, the effect of acclimation to a low set potential (-0.2V, versus standard hydrogen electrode) was compared to startup at a higher potential (+0.2 V) or no set potential, and inoculation with wastewater or pre-acclimated cultures. Anodes acclimated to -0.2 V produced the highest power of 1330±60 mW m(-2) for these different anode conditions, but unacclimated wastewater inocula produced inconsistent results despite the use of this set potential. By inoculating reactors with transferred cell suspensions, however, startup time was reduced and high power was consistently produced. These results show that pre-acclimation at -0.2 V consistently improves power production compared to use of a more positive potential or the lack of a set potential. Copyright © 2013 Elsevier Ltd. All rights reserved.

SiC Nanofibers as Long-Life Lithium-Ion Battery Anode Materials.

PubMed

Sun, Xuejiao; Shao, Changzhen; Zhang, Feng; Li, Yi; Wu, Qi-Hui; Yang, Yonggang

2018-01-01

The development of high energy lithium-ion batteries (LIBs) has spurred the designing and production of novel anode materials to substitute currently commercial using graphitic materials. Herein, twisted SiC nanofibers toward LIBs anode materials, containing 92.5 wt% cubic β-SiC and 7.5 wt% amorphous C, were successfully synthesized from resin-silica composites. The electrochemical measurements showed that the SiC-based electrode delivered a stable reversible capacity of 254.5 mAh g -1 after 250 cycles at a current density of 0.1 A g -1 . It is interesting that a high discharge capacity of 540.1 mAh g -1 was achieved after 500 cycles at an even higher current density of 0.3 A g -1 , which is higher than the theoretical capacity of graphite. The results imply that SiC nanomaterials are potential anode candidate for LIBs with high stability due to their high structure stability as supported with the transmission electron microscopy images.

Single chamber microbial fuel cell with spiral anode for dairy wastewater treatment.

PubMed

Mardanpour, Mohammad Mahdi; Nasr Esfahany, Mohsen; Behzad, Tayebeh; Sedaqatvand, Ramin

2012-01-01

This study reports on the fabrication of a novel annular single chamber microbial fuel cell (ASCMFC) with spiral anode. The stainless steel mesh anode with graphite coating was used as anode. Dairy wastewater, containing complex organic matter, was used as substrate. ASCMFC had been operated for 450 h and results indicated a high open circuit voltage (about 810 mV) compared with previously published results. The maximum power density of 20.2 W/m(3) obtained in this study is significantly greater than the power densities reported in previous studies. Besides, a maximum coulombic efficiency of 26.87% with 91% COD removal was achieved. Good bacterial adhesion on the spiral anode is clearly shown in SEM micrographs. High power density and a successful performance in wastewater treatment in ASCMFC suggest it as a promising alternative to conventional MFCs for power generation and wastewater treatment. ASCMFC performance as a power generator was characterized based on polarization behavior and cell potentials. Copyright © 2012 Elsevier B.V. All rights reserved.

Inorganic-Organic Coating via Molecular Layer Deposition Enables Long Life Sodium Metal Anode.

PubMed

Zhao, Yang; Goncharova, Lyudmila V; Zhang, Qian; Kaghazchi, Payam; Sun, Qian; Lushington, Andrew; Wang, Biqiong; Li, Ruying; Sun, Xueliang

2017-09-13

Metallic Na anode is considered as a promising alternative candidate for Na ion batteries (NIBs) and Na metal batteries (NMBs) due to its high specific capacity, and low potential. However, the unstable solid electrolyte interphase layer caused by serious corrosion and reaction in electrolyte will lead to big challenges, including dendrite growth, low Coulombic efficiency and even safety issues. In this paper, we first demonstrate the inorganic-organic coating via advanced molecular layer deposition (alucone) as a protective layer for metallic Na anode. By protecting Na anode with controllable alucone layer, the dendrites and mossy Na formation have been effectively suppressed and the lifetime has been significantly improved. Moreover, the molecular layer deposition alucone coating shows better performances than the atomic layer deposition Al 2 O 3 coating. The novel design of molecular layer deposition protected Na metal anode may bring in new opportunities to the realization of the next-generation high energy-density NIBs and NMBs.

A novel strategy to prepare Ge@C/rGO hybrids as high-rate anode materials for lithium ion batteries

NASA Astrophysics Data System (ADS)

Wang, Bangrun; Wen, Zhaoyin; Jin, Jun; Hong, Xiaoheng; Zhang, Sanpei; Rui, Kun

2017-02-01

Germanium is considered as a promising anode material for lithium ion batteries (LIBs) due to its high-capacity. However, owing to the huge volume variation during cycling, the batteries based on germanium anodes usually show poor cyclability and inferior rate capability. Herein, we demonstrated a novel strategy to uniformly anchor the core-shell structured germanium@carbon (Ge@C) on the reduced graphene oxide (rGO) nanosheets by the strong adhesion of dopamine. In the resulting Ge@C/rGO hybrid, the amorphous carbon layer and rGO nanosheets can effectively reduce the agglomeration of germanium and provide buffer matrix for the volume change in electrochemical lithium reactions. When used as anode materials for LIBs, Ge@C/rGO hybrids deliver a reversible capacity of 1074.4 mA h g-1 at 2C after 600 cycles (with capacity retention of 96.5%) and high rate capability of 436 mA h g-1 at 20C after 200 cycles. The encouraging electrochemical performance clearly demonstrates that Ge@C/rGO hybrids could be a potential anode material with high capacity, excellent rate capability, and good cycling stability for LIBs.

A lithium-ion sulfur battery based on a carbon-coated lithium-sulfide cathode and an electrodeposited silicon-based anode.

PubMed

Agostini, Marco; Hassoun, Jusef; Liu, Jun; Jeong, Moongook; Nara, Hiroki; Momma, Toshiyuki; Osaka, Tetsuya; Sun, Yang-Kook; Scrosati, Bruno

2014-07-23

In this paper, we report a lithium-ion battery employing a lithium sulfide cathode and a silicon-based anode. The high capacity of the silicon anode and the high efficiency and cycling rate of the lithium sulfide cathode allowed optimal full cell balance. We show in fact that the battery operates with a very stable capacity of about 280 mAh g(-1) at an average voltage of 1.4 V. To the best of our knowledge, this battery is one of the rare examples of lithium-metal-free sulfur battery. Considering the high theoretical capacity of the employed electrodes, we believe that the battery here reported may be of potential interest as high-energy, safe, and low-cost power source for electric vehicles.

Electrochemical separation of hydrogen from reformate using PEM fuel cell technology

NASA Astrophysics Data System (ADS)

Gardner, C. L.; Ternan, M.

This article is an examination of the feasibility of electrochemically separating hydrogen obtained by steam reforming a hydrocarbon or alcohol source. A potential advantage of this process is that the carbon dioxide rich exhaust stream should be able to be captured and stored thereby reducing greenhouse gas emissions. Results are presented for the performance of the anode of proton exchange membrane (PEM) electrochemical cell for the separation of hydrogen from a H 2-CO 2 gas mixture and from a H 2-CO 2-CO gas mixture. Experiments were carried out using a single cell state-of-the-art PEM fuel cell. The anode was fed with either a H 2-CO 2 gas mixture or a H 2-CO 2-CO gas mixture and hydrogen was evolved at the cathode. All experiments were performed at room temperature and atmospheric pressure. With the H 2-CO 2 gas mixture the hydrogen extraction efficiency is quite high. When the gas mixture included CO, however, the hydrogen extraction efficiency is relatively poor. To improve the efficiency for the separation of the gas mixture containing CO, the effect of periodic pulsing on the anode potential was examined. Results show that pulsing can substantially reduce the anode potential thereby improving the overall efficiency of the separation process although the anode potential of the CO poisoned and pulsed cell still lies above that of an unpoisoned cell.

Challenges in Accommodating Volume Change of Si Anodes for Li-Ion Batteries

PubMed Central

Ko, Minseong; Chae, Sujong; Cho, Jaephil

2015-01-01

Si has been considered as a promising alternative anode for next-generation Li-ion batteries (LIBs) because of its high theoretical energy density, relatively low working potential, and abundance in nature. However, Si anodes exhibit rapid capacity decay and an increase in the internal resistance, which are caused by the large volume changes upon Li insertion and extraction. This unfortunately limits their practical applications. Therefore, managing the total volume change remains a critical challenge for effectively alleviating the mechanical fractures and instability of solid-electrolyte-interphase products. In this regard, we review the recent progress in volume-change-accommodating Si electrodes and investigate their ingenious structures with significant improvements in the battery performance, including size-controlled materials, patterned thin films, porous structures, shape-preserving shell designs, and graphene composites. These representative approaches potentially overcome the large morphologic changes in the volume of Si anodes by securing the strain relaxation and structural integrity in the entire electrode. Finally, we propose perspectives and future challenges to realize the practical application of Si anodes in LIB systems. PMID:27525208

Facile and cost effective synthesis of mesoporous spinel NiCo2O4 as an anode for high lithium storage capacity

NASA Astrophysics Data System (ADS)

Jadhav, Harsharaj S.; Kalubarme, Ramchandra S.; Park, Choong-Nyeon; Kim, Jaekook; Park, Chan-Jin

2014-08-01

To fulfill the high power and high energy density demands for Li-ion batteries (LIBs) new anode materials need to be explored to replace conventional graphite. Herein, we report the urea assisted facile co-precipitation synthesis of spinel NiCo2O4 and its application as an anode material for LIBs. The synthesized NiCo2O4 exhibited an urchin-like microstructure and polycrystalline and mesoporous nature. In addition, the mesoporous NiCo2O4 electrode exhibited an initial discharge capacity of 1095 mA h g-1 and maintained a reversible capacity of 1000 mA h g-1 for 400 cycles at 0.5 C-rate. The reversible capacity of NiCo2O4 could still be maintained at 718 mA h g-1, even at 10 C. The mesoporous NiCo2O4 exhibits great potential as an anode material for LIBs with the advantages of unique performance and facile preparation.To fulfill the high power and high energy density demands for Li-ion batteries (LIBs) new anode materials need to be explored to replace conventional graphite. Herein, we report the urea assisted facile co-precipitation synthesis of spinel NiCo2O4 and its application as an anode material for LIBs. The synthesized NiCo2O4 exhibited an urchin-like microstructure and polycrystalline and mesoporous nature. In addition, the mesoporous NiCo2O4 electrode exhibited an initial discharge capacity of 1095 mA h g-1 and maintained a reversible capacity of 1000 mA h g-1 for 400 cycles at 0.5 C-rate. The reversible capacity of NiCo2O4 could still be maintained at 718 mA h g-1, even at 10 C. The mesoporous NiCo2O4 exhibits great potential as an anode material for LIBs with the advantages of unique performance and facile preparation. Electronic supplementary information (ESI) available: Experimental details and additional experimental results. See DOI: 10.1039/c4nr02183e

Formation of crack-free nanoporous tin oxide layers via simple one-step anodic oxidation in NaOH at low applied voltages

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Gilek, Dominika; Gawlak, Karolina; Jaskuła, Marian; Sulka, Grzegorz D.

2016-12-01

A simple anodic oxidation of metallic tin in fluoride-free alkaline electrolyte at low potentials was proposed as a new and effective strategy for fabrication of crack-free nanoporous tin oxide layers. A low-purity Sn foil (98.8%) was used as a starting material, and a series of anodizations were performed in 1 M NaOH at different conditions such as anodizing potential, and duration of the process. It was proved for the first time that nanostructured tin oxides with ultra-small nanochannels having diameters of <15 nm can be synthesized by simple anodization of metallic tin at a potential of 2 V in 1 M NaOH electrolyte. Increasing anodizing potential to 3 and 4 V allowed for formation of tin oxide layers with much larger pores (40-50 nm in diameter) which were still free from internal cracks and transversal pores. Applying such low potentials significantly reduces the oxide growth rate and suppresses vigorous oxygen evolution at the anode. As a result mechanical deterioration of the oxide structure is prevented while strongly alkaline electrolyte is responsible for formation of the porous layer with completely open pores even at such low potentials. On the contrary, when anodization was carried out at potentials of 5 and 6 V, much faster formation of anodic layer, accompanied by vigorous oxygen gas formation, was observed. In consequence, as grown oxide layers exhibited typical cracked or even stacked internal structure. Finally, we demonstrated for the first time that nanoporous tin oxide layers with segments of different channel sizes can be successfully obtained by simple altering potential during anodization.

Penta-graphene: A Promising Anode Material as the Li/Na-Ion Battery with Both Extremely High Theoretical Capacity and Fast Charge/Discharge Rate.

PubMed

Xiao, Bo; Li, Yan-Chun; Yu, Xue-Fang; Cheng, Jian-Bo

2016-12-28

Recently, a new two-dimensional (2D) carbon allotrope named penta-graphene was theoretically proposed ( Zhang , S. ; et al. Proc. Natl. Acad. Sci. U.S.A. 2015 , 112 , 2372 ) and has been predicted to be the promising candidate for broad applications due to its intriguing properties. In this work, by using first-principles simulation, we have further extended the potential application of penta-graphene as the anode material for a Li/Na-ion battery. Our results show that the theoretical capacity of Li/Na ions on penta-graphene reaches up to 1489 mAh·g -1 , which is much higher than that of most of the previously reported 2D anode materials. Meanwhile, the calculated low open-circuit voltages (from 0.24 to 0.60 V), in combination with the low diffusion barriers (≤0.33 eV) and the high electronic conductivity during the whole Li/Na ions intercalation processes, further show the advantages of penta-graphene as the anode material. Particularly, molecular dynamics simulation (300 K) reveals that Li ion could freely diffuse on the surface of penta-graphene, and thus the ultrafast Li ion diffusivity is expected. Superior performance of penta-graphene is further confirmed by comparing with the other 2D anode materials. The light weight and unique atomic arrangement (with isotropic furrow paths on the surface) of penta-graphene are found to be mainly responsible for the high Li/Na ions storage capacity and fast diffusivity. In this regard, except penta-graphene, many other recently proposed 2D metal-free materials with pentagonal Cairo-tiled structures may be the potential candidates as the Li/Na-ion battery anodes.

Tin phosphide-based anodes for sodium-ion batteries: synthesis via solvothermal transformation of Sn metal and phase-dependent Na storage performance

PubMed Central

Shin, Hyun-Seop; Jung, Kyu-Nam; Jo, Yong Nam; Park, Min-Sik; Kim, Hansung; Lee, Jong-Won

2016-01-01

There is a great deal of current interest in the development of rechargeable sodium (Na)-ion batteries (SIBs) for low-cost, large-scale stationary energy storage systems. For the commercial success of this technology, significant progress should be made in developing robust anode (negative electrode) materials with high capacity and long cycle life. Sn-P compounds are considered promising anode materials that have considerable potential to meet the required performance of SIBs, and they have been typically prepared by high-energy mechanical milling. Here, we report Sn-P-based anodes synthesised through solvothermal transformation of Sn metal and their electrochemical Na storage properties. The temperature and time period used for solvothermal treatment play a crucial role in determining the phase, microstructure, and composition of the Sn-P compound and thus its electrochemical performance. The Sn-P compound prepared under an optimised solvothermal condition shows excellent electrochemical performance as an SIB anode, as evidenced by a high reversible capacity of ~560 mAh g−1 at a current density of 100 mA g−1 and cycling stability for 100 cycles. The solvothermal route provides an effective approach to synthesising Sn-P anodes with controlled phases and compositions, thus tailoring their Na storage behaviour. PMID:27189834

Photocatalytic effect of anodic titanium oxide nanotubes on various cell culture media

NASA Astrophysics Data System (ADS)

Yu, Chun-Kang; Hu, Kan-Hung; Wang, Shing-Hoa; Hsu, Todd; Tsai, Huei-Ting; Chen, Chien-Chon; Liu, Shiu-Mei; Lin, Tai-Yuan; Chen, Chin-Hsing

2011-02-01

The use of titanium dioxide (TiO2) in photodynamic therapy for the treatment of cancer cells has been proposed following studies of cultured cancer cells. In this work, an ordered channel array of anodic titanium oxide (ATO) was fabricated by anodizing titanium foil. The ATO layer of nanotubes with diameters of 100 nm was made in NH4F electrolyte by anodization. The photocatalytic effect of ATO was examined on various culture media by ultraviolet A (UV-A) (366 nm) irradiation. After UV-A irradiation of the ATO layer, redox potential of Tris-HCl buffer (pH 7.5) and dilute acrylamide solution increased instantaneously. The redox potential of the serum-containing RPMI1640 medium also increased dramatically, while that of serum-containing MEM and DMEM media increased slightly. The UVA-induced high redox potential was correlated with the greater ability to break down plasmid DNA strands. These phenomena suggest that a culture medium, such as RPMI1640, with a greater ability to produce free radical may be associated with a stronger photocatalytic effect of ATO on cultured cancer cells reported previously.

Process Developed for Fabricating Engineered Pore Structures for High- Fuel-Utilization Solid Oxide Fuel Cells

NASA Technical Reports Server (NTRS)

Sofie, Stephen W.; Cable, Thomas L.; Salamone, Sam M.

2005-01-01

Solid oxide fuel cells (SOFCs) have tremendous commercial potential because of their high efficiency, high energy density, and flexible fuel capability (ability to use fossil fuels). The drive for high-power-utilizing, ultrathin electrolytes (less than 10 microns), has placed an increased demand on the anode to provide structural support, yet allow sufficient fuel entry for sustained power generation. Concentration polarization, a condition where the fuel demand exceeds the supply, is evident in all commercial-based anode-supported cells, and it presents a significant roadblock to SOFC commercialization.

High-rate capability of three-dimensionally ordered macroporous T-Nb2O5 through Li+ intercalation pseudocapacitance

NASA Astrophysics Data System (ADS)

Lou, Shuaifeng; Cheng, Xinqun; Wang, Long; Gao, Jinlong; Li, Qin; Ma, Yulin; Gao, Yunzhi; Zuo, Pengjian; Du, Chunyu; Yin, Geping

2017-09-01

Orthorhombic Niobium oxide (T-Nb2O5) has been regarded as a promising anode material for high-rate lithium ion batteries (LIBs) due to its potential to operate at high rates with improved safety and high theoretical capacity of 200 mA h g-1. Herein, three-dimensionally ordered macroporous (3DOM) T-Nb2O5, with mesoporous hierarchical structure, was firstly prepared by a simple approach employing self-assembly polystyrene (PS) microspheres as hard templates. The obtained T-Nb2O5 anode material presents obvious and highly-efficiency pseudocapacitive Li+ intercalation behaviour, which plays a dominant role in the kinetics of electrode process. As a result, rapid Li+ intercalation/de-intercalation are achieved, leading to excellent rate capability and long cycle life. The 3DOM T-Nb2O5 shows a remarkable high capacity of 106 and 77 mA h g-1 at the rate of 20C and 50C. The work presented herein holds great promise for future design of material structure, and demonstrates the great potential of T-Nb2O5 as a practical high-rate anode material for LIBs.

Analysis of nanopore arrangement and structural features of anodic alumina layers formed by two-step anodizing in oxalic acid using the dedicated executable software

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Stępniowski, Wojciech J.; Sulka, Grzegorz D.; Ciepiela, Eryk; Jaskuła, Marian

2014-02-01

Anodic porous alumina layers were fabricated by a two-step self-organized anodization in 0.3 M oxalic acid under various anodizing potentials ranging from 30 to 60 V at two different temperatures (10 and 17 ∘C). The effect of anodizing conditions on structural features and pore arrangement of AAO was investigated in detail by using the dedicated executable publication combined with ImageJ software. With increasing anodizing potential, a linear increase of the average pore diameter, interpore distance, wall thickness and barrier layer thickness, as well as a decrease of the pore density, were observed. In addition, the higher pore diameter and porosity values were obtained for samples anodized at the elevated temperature, independently of the anodizing potential. A degree of pore order was investigated on the basis of Delaunay triangulations (defect maps) and calculation of pair distribution or angle distribution functions (PDF or ADF), respectively. All methods confirmed that in order to obtain nanoporous alumina with the best, hexagonal pore arrangement, the potential of 40 V should be applied during anodization. It was confirmed that the dedicated executable publication can be used to a fast and complex analysis of nanopore arrangement and structural features of nanoporous oxide layers.

Advanced Nanostructured Anode Materials for Sodium-Ion Batteries.

PubMed

Wang, Qidi; Zhao, Chenglong; Lu, Yaxiang; Li, Yunming; Zheng, Yuheng; Qi, Yuruo; Rong, Xiaohui; Jiang, Liwei; Qi, Xinguo; Shao, Yuanjun; Pan, Du; Li, Baohua; Hu, Yong-Sheng; Chen, Liquan

2017-11-01

Sodium-ion batteries (NIBs), due to the advantages of low cost and relatively high safety, have attracted widespread attention all over the world, making them a promising candidate for large-scale energy storage systems. However, the inherent lower energy density to lithium-ion batteries is the issue that should be further investigated and optimized. Toward the grid-level energy storage applications, designing and discovering appropriate anode materials for NIBs are of great concern. Although many efforts on the improvements and innovations are achieved, several challenges still limit the current requirements of the large-scale application, including low energy/power densities, moderate cycle performance, and the low initial Coulombic efficiency. Advanced nanostructured strategies for anode materials can significantly improve ion or electron transport kinetic performance enhancing the electrochemical properties of battery systems. Herein, this Review intends to provide a comprehensive summary on the progress of nanostructured anode materials for NIBs, where representative examples and corresponding storage mechanisms are discussed. Meanwhile, the potential directions to obtain high-performance anode materials of NIBs are also proposed, which provide references for the further development of advanced anode materials for NIBs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Protected Lithium-Metal Anodes in Batteries: From Liquid to Solid.

PubMed

Yang, Chunpeng; Fu, Kun; Zhang, Ying; Hitz, Emily; Hu, Liangbing

2017-09-01

High-energy lithium-metal batteries are among the most promising candidates for next-generation energy storage systems. With a high specific capacity and a low reduction potential, the Li-metal anode has attracted extensive interest for decades. Dendritic Li formation, uncontrolled interfacial reactions, and huge volume effect are major hurdles to the commercial application of Li-metal anodes. Recent studies have shown that the performance and safety of Li-metal anodes can be significantly improved via organic electrolyte modification, Li-metal interface protection, Li-electrode framework design, separator coating, and so on. Superior to the liquid electrolytes, solid-state electrolytes are considered able to inhibit problematic Li dendrites and build safe solid Li-metal batteries. Inspired by the bright prospects of solid Li-metal batteries, increasing efforts have been devoted to overcoming the obstacles of solid Li-metal batteries, such as low ionic conductivity of the electrolyte and Li-electrolyte interfacial problems. Here, the approaches to protect Li-metal anodes from liquid batteries to solid-state batteries are outlined and analyzed in detail. Perspectives regarding the strategies for developing Li-metal anodes are discussed to facilitate the practical application of Li-metal batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lithium-ion diffusion mechanisms in the battery anode material Li(1+x)V(1-x)O₂.

PubMed

Panchmatia, Pooja M; Armstrong, A Robert; Bruce, Peter G; Islam, M Saiful

2014-10-21

Layered Li(1+x)V(1-x)O2 has attracted recent interest as a potential low voltage and high energy density anode material for lithium-ion batteries. A greater understanding of the lithium-ion transport mechanisms is important in optimising such oxide anodes. Here, stoichiometric LiVO2 and Li-rich Li1.07V0.93O2 are investigated using atomistic modelling techniques. Lithium-ion migration is not found in LiVO2, which has also previously shown to be resistant to lithium intercalation. Molecular dynamics simulations of lithiated non-stoichiometric Li(1.07+y)V0.93O2 suggest cooperative interstitial Li(+) diffusion with favourable migration barriers and diffusion coefficients (D(Li)), which are facilitated by the presence of lithium in the transition metal layers; such transport behaviour is important for high rate performance as a battery anode.

Advanced electrolyte/additive for lithium-ion batteries with silicon anode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Shuo; He, Meinan; Su, Chi-Cheung

State-of-the-art lithium-ion batteries (LIBs) are based on a lithium transition metal oxide cathode, a graphite anode and a nonaqueous carbonate electrolyte. To further increase the energy and power density of LIBs, silicon anodes have been intensively explored due to their high theoretical capacity, low operation potential, and low cost. However, the main challenges for Si anode are the large volume change during lithiation/delithiation process and the instability of the solid-electrolyte-interphase associated with this process. Recently, significant progress has been achieved via advanced material fabrication technologies and rational electrolyte design in terms of improving the Coulombic efficiency and capacity retention. Inmore » this paper, new developments in advanced electrolyte and additive for LIBs with Si anode were systematically reviewed, and perspectives over future research were suggested.« less

Nanosheets of earth-abundant jarosite as novel anodes for high-rate and long-life lithium-ion batteries.

PubMed

Ding, Yuan-Li; Wen, Yuren; Chen, Chia-Chin; van Aken, Peter A; Maier, Joachim; Yu, Yan

2015-05-20

Nanosheets of earth-abundant jarosite were fabricated via a facile template-engaged redox coprecipitation strategy at room temperature and employed as novel anode materials for lithium-ion batteries (LIBs) for the first time. These 2D materials exhibit high capacities, excellent rate capability, and prolonged cycling performance. As for KFe3(SO4)2(OH)6 jarosite nanosheets (KNSs), the reversible capacities of above 1300 mAh g(-1) at 100 mA g(-1) and 620 mAh g(-1) after 4000 cycles at a very high current density of 10 A g(-1) were achieved, respectively. Moreover, the resulting 2D nanomaterials retain good structural integrity upon cycling. These results reveal great potential of jarosite nanosheets as low-cost and high-performance anode materials for next-generation LIBs.

Enhancing Sulfur Tolerance of Ni-Based Cermet Anodes of Solid Oxide Fuel Cells by Ytterbium-Doped Barium Cerate Infiltration.

PubMed

Li, Meng; Hua, Bin; Luo, Jing-Li; Jiang, San Ping; Pu, Jian; Chi, Bo; Li, Jian

2016-04-27

Conventional anode materials for solid oxide fuel cells (SOFCs) are Ni-based cermets, which are highly susceptible to deactivation by contaminants in hydrocarbon fuels. Hydrogen sulfide is one of the commonly existed contaminants in readily available natural gas and gasification product gases of pyrolysis of biomasses. Development of sulfur tolerant anode materials is thus one of the critical challenges for commercial viability and practical application of SOFC technologies. Here we report a viable approach to enhance substantially the sulfur poisoning resistance of a Ni-gadolinia-doped ceria (Ni-GDC) anode through impregnation of proton conducting perovskite BaCe0.9Yb0.1O3-δ (BCYb). The impregnation of BCYb nanoparticles improves the electrochemical performance of the Ni-GDC anode in both H2 and H2S containing fuels. Moreover, more importantly, the enhanced stability is observed in 500 ppm of H2S/H2. The SEM and XPS analysis indicate that the infiltrated BCYb fine particles inhibit the adsorption of sulfur and facilitate sulfur removal from active sites, thus preventing the detrimental interaction between sulfur and Ni-GDC and the formation of cerium sulfide. The preliminary results of the cell with the BCYb+Ni-GDC anode in methane fuel containing 5000 ppm of H2S show the promising potential of the BCYb infiltration approach in the development of highly active and stable Ni-GDC-based anodes fed with hydrocarbon fuels containing a high concentration of sulfur compounds.

Integrated anode structure for passive direct methanol fuel cells with neat methanol operation

NASA Astrophysics Data System (ADS)

Wu, Huijuan; Zhang, Haifeng; Chen, Peng; Guo, Jing; Yuan, Ting; Zheng, Junwei; Yang, Hui

2014-02-01

A microporous titanium plate based integrated anode structure (Ti-IAS) suitable for passive direct methanol fuel cells (DMFCs) fueled with neat methanol is reported. This anode structure incorporates a porous titanium plate as a methanol mass transfer barrier and current collector, pervaporation film for passively vaporizing methanol, vaporous methanol cavity for evenly distributing fuel, and channels for carbon dioxide venting. With the effective control of methanol delivery rate, the Ti-IAS based DMFC allows the direct use of neat methanol as the fuel source. In the meantime, the required water for methanol-oxidation reaction at the anode can also be fully recovered from the cathode with the help of the highly hydrophobic microporous layer in the cathode. DMFCs incorporating this new anode structure exhibit a power density as high as 40 mW cm-2 and a high volumetric energy density of 489 Wh L-1 operating with neat methanol and at 25 °C. Importantly, no obvious performance degradation of the passive DMFC system is observed after more than 90 h of continuous operation. The experimental results reveal that the compact DMFC based on the Ti-IAS exhibits a substantial potential as power sources for portable applications.

Mesoporous Germanium Anode Materials for Lithium-Ion Battery with Exceptional Cycling Stability in Wide Temperature Range.

PubMed

Choi, Sinho; Cho, Yoon-Gyo; Kim, Jieun; Choi, Nam-Soon; Song, Hyun-Kon; Wang, Guoxiu; Park, Soojin

2017-04-01

Porous structured materials have unique architectures and are promising for lithium-ion batteries to enhance performances. In particular, mesoporous materials have many advantages including a high surface area and large void spaces which can increase reactivity and accessibility of lithium ions. This study reports a synthesis of newly developed mesoporous germanium (Ge) particles prepared by a zincothermic reduction at a mild temperature for high performance lithium-ion batteries which can operate in a wide temperature range. The optimized Ge battery anodes with the mesoporous structure exhibit outstanding electrochemical properties in a wide temperature ranging from -20 to 60 °C. Ge anodes exhibit a stable cycling retention at various temperatures (capacity retention of 99% after 100 cycles at 25 °C, 84% after 300 cycles at 60 °C, and 50% after 50 cycles at -20 °C). Furthermore, full cells consisting of the mesoporous Ge anode and an LiFePO 4 cathode show an excellent cyclability at -20 and 25 °C. Mesoporous Ge materials synthesized by the zincothermic reduction can be potentially applied as high performance anode materials for practical lithium-ion batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemically Bonded Phosphorus/Graphene Hybrid as a High Performance Anode for Sodium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Jiangxuan; Yu, Zhaoxin; Gordin, Mikhail

2014-11-12

Room temperature sodium-ion batteries are of great interest for high-energy-density energy storage systems because of low-cost, natural abundance of sodium. Here, we report a novel graphene nanosheets-wrapped phosphorus composite as an anode for high performance sodium-ion batteries though a facile ball-milling of red phosphorus and graphene nanosheets. Not only can the graphene nanosheets significantly improve the electrical conductivity, but they also serve as a buffer layer to accommodate the large volume change of phosphorus in the charge-discharge process. As a result, the graphene wrapped phosphorus composite anode delivers a high reversible capacity of 2077 mAh/g with excellent cycling stability (1700more » mAh/g after 60 cycles) and high Coulombic efficiency (>98%). This simple synthesis approach and unique nanostructure can potentially extend to other electrode materials with unstable solid electrolyte interphases in sodium-ion batteries.« less

An artificial interphase enables reversible magnesium chemistry in carbonate electrolytes.

PubMed

Son, Seoung-Bum; Gao, Tao; Harvey, Steve P; Steirer, K Xerxes; Stokes, Adam; Norman, Andrew; Wang, Chunsheng; Cresce, Arthur; Xu, Kang; Ban, Chunmei

2018-05-01

Magnesium-based batteries possess potential advantages over their lithium counterparts. However, reversible Mg chemistry requires a thermodynamically stable electrolyte at low potential, which is usually achieved with corrosive components and at the expense of stability against oxidation. In lithium-ion batteries the conflict between the cathodic and anodic stabilities of the electrolytes is resolved by forming an anode interphase that shields the electrolyte from being reduced. This strategy cannot be applied to Mg batteries because divalent Mg 2+ cannot penetrate such interphases. Here, we engineer an artificial Mg 2+ -conductive interphase on the Mg anode surface, which successfully decouples the anodic and cathodic requirements for electrolytes and demonstrate highly reversible Mg chemistry in oxidation-resistant electrolytes. The artificial interphase enables the reversible cycling of a Mg/V 2 O 5 full-cell in the water-containing, carbonate-based electrolyte. This approach provides a new avenue not only for Mg but also for other multivalent-cation batteries facing the same problems, taking a step towards their use in energy-storage applications.

An artificial interphase enables reversible magnesium chemistry in carbonate electrolytes

NASA Astrophysics Data System (ADS)

Son, Seoung-Bum; Gao, Tao; Harvey, Steve P.; Steirer, K. Xerxes; Stokes, Adam; Norman, Andrew; Wang, Chunsheng; Cresce, Arthur; Xu, Kang; Ban, Chunmei

2018-05-01

Magnesium-based batteries possess potential advantages over their lithium counterparts. However, reversible Mg chemistry requires a thermodynamically stable electrolyte at low potential, which is usually achieved with corrosive components and at the expense of stability against oxidation. In lithium-ion batteries the conflict between the cathodic and anodic stabilities of the electrolytes is resolved by forming an anode interphase that shields the electrolyte from being reduced. This strategy cannot be applied to Mg batteries because divalent Mg2+ cannot penetrate such interphases. Here, we engineer an artificial Mg2+-conductive interphase on the Mg anode surface, which successfully decouples the anodic and cathodic requirements for electrolytes and demonstrate highly reversible Mg chemistry in oxidation-resistant electrolytes. The artificial interphase enables the reversible cycling of a Mg/V2O5 full-cell in the water-containing, carbonate-based electrolyte. This approach provides a new avenue not only for Mg but also for other multivalent-cation batteries facing the same problems, taking a step towards their use in energy-storage applications.

One-Dimensional Porous Silicon Nanowires with Large Surface Area for Fast Charge⁻Discharge Lithium-Ion Batteries.

PubMed

Chen, Xu; Bi, Qinsong; Sajjad, Muhammad; Wang, Xu; Ren, Yang; Zhou, Xiaowei; Xu, Wen; Liu, Zhu

2018-04-27

In this study, one-dimensional porous silicon nanowire (1D⁻PSiNW) arrays were fabricated by one-step metal-assisted chemical etching (MACE) to etch phosphorus-doped silicon wafers. The as-prepared mesoporous 1D⁻PSiNW arrays here had especially high specific surface areas of 323.47 m²·g -1 and were applied as anodes to achieve fast charge⁻discharge performance for lithium ion batteries (LIBs). The 1D⁻PSiNWs anodes with feature size of ~7 nm exhibited reversible specific capacity of 2061.1 mAh·g -1 after 1000 cycles at a high current density of 1.5 A·g -1 . Moreover, under the ultrafast charge⁻discharge current rate of 16.0 A·g -1 , the 1D⁻PSiNWs anodes still maintained 586.7 mAh·g -1 capacity even after 5000 cycles. This nanoporous 1D⁻PSiNW with high surface area is a potential anode candidate for the ultrafast charge⁻discharge in LIBs with high specific capacity and superior cycling performance.

Enhancing the energy density of safer Li-ion batteries by combining high-voltage lithium cobalt fluorophosphate cathodes and nanostructured titania anodes

PubMed Central

Ortiz, Gregorio F.; López, María C.; Li, Yixiao; McDonald, Matthew J.; Cabello, Marta; Tirado, José L.; Yang, Yong

2016-01-01

Recently, Li-ion batteries have been heavily scrutinized because of the apparent incompatibility between safety and high energy density. This work report a high voltage full battery made with TiO2/Li3PO4/Li2CoPO4F. The Li2CoPO4F cathode and TiO2 anode materials are synthesized by a sol–gel and anodization methods, respectively. X-ray diffraction (XRD) analysis confirmed that Li2CoPO4F is well-crystallized in orthorhombic crystal structure with Pnma space group. The Li3PO4-coated anode was successfully deposited as shown by the (011) lattice fringes of anatase TiO2 and (200) of γ-Li3PO4, as detected by HRTEM. The charge profile of Li2CoPO4F versus lithium shows a plateau at 5.0 V, revealing its importance as potentially high-voltage cathode and could perfectly fit with the plateau of anatase anode (1.8–1.9 V). The full cell made with TiO2/Li3PO4/Li2CoPO4F delivered an initial reversible capacity of 150 mA h g−1 at C rate with good cyclic performance at an average potential of 3.1–3.2 V. Thus, the full cell provides an energy density of 472 W h kg−1. This full battery behaves better than TiO2/Li2CoPO4F. The introduction of Li3PO4 as buffer layer is expected to help the cyclability of the electrodes as it allows a rapid Li-ion transport. PMID:26879916

Optimization of Semitransparent Anode Electrode for Flexible Green and Red Phosphorescent Organic Light-Emitting Diodes.

PubMed

Lee, Ho Won; Park, Jaehoon; Yang, Hyung Jin; Lee, Song Eun; Lee, Seok Jae; Koo, Ja Ryong; Kim, Hye Jeong; Yoon, Seung Soo; Kim, Young Kwan

2015-03-01

In this paper, we demonstrated thin film semitransparent anode electrode using Ni/Ag/Ni (3/6/3 nm) on green and red phosphorescent OLEDs, which have basically high efficiency and good optical characteristics. Moreover, we applied this semitransparent anode on flexible green and red phosphorescent OLEDs, which were then optimized for possible applications on flexible substrates. First, we studied optimization using various conditions of Ni/Ag/Ni electrodes via transmittance and sheet resistance. We then fabricated the devices on a glass substrate with ITO or Ni/Ag/Ni electrodes as well as on a flexible substrate with a Ni/Ag/Ni electrode for green and red phosphorescent OLEDs. Consequently, we could be proposed that the potential of our semitransparent anode electrode is demonstrated. Green phosphorescent OLEDs characteristics using ITO or Ni/Ag/Ni anode electrodes were coincided and those of the red phosphorescent OLEDs were improved by semitransparent electrodes at 10,000 cd/m2 criterion. Therefore, this research suggests for additional studies to be conducted on flexible and high-performance phosphorescent OLED displays and light applications for ITO-free processes.

Electrochemical anodizing treatment to enhance localized corrosion resistance of pure titanium.

PubMed

Prando, Davide; Brenna, Andrea; Bolzoni, Fabio M; Diamanti, Maria V; Pedeferri, Mariapia; Ormellese, Marco

2017-01-26

Titanium has outstanding corrosion resistance due to the thin protective oxide layer that is formed on its surface. Nevertheless, in harsh and severe environments, pure titanium may suffer localized corrosion. In those conditions, costly titanium alloys containing palladium, nickel and molybdenum are used. This purpose investigated how it is possible to control corrosion, at lower cost, by electrochemical surface treatment on pure titanium, increasing the thickness of the natural oxide layer. Anodic oxidation was performed on titanium by immersion in H2SO4 solution and applying voltages ranging from 10 to 80 V. Different anodic current densities were considered. Potentiodynamic tests in chloride- and fluoride-containing solutions were carried out on anodized titanium to determine the pitting potential. All tested anodizing treatments increased corrosion resistance of pure titanium, but never reached the performance of titanium alloys. The best corrosion behavior was obtained on titanium anodized at voltages lower than 40 V at 20 mA/cm2. Titanium samples anodized at low cell voltage were seen to give high corrosion resistance in chloride- and fluoride-containing solutions. Electrolyte bath and anodic current density have little effect on the corrosion behavior.

Performance comparison of tin oxide anodes to commercially available dimensionally stable anodes.

PubMed

Watts, Richard J; Finn, Dennis D; Wyeth, Megan S; Teel, Amy L

2008-06-01

Dimensionally stable anodes (DSAs) demonstrate potential for the electrochemical treatment of industrial waste streams and disinfection of effluent. Oxidation by laboratory-prepared tin oxide DSAs was compared with that of commercially available ruthenium oxide, iridium oxide, and mixed metal oxide DSAs, using hexanol as a probe molecule. The performance of the four anodes was similar in two-chamber reactors, in which the anode cell was separated from the cathode cell by a Nafion membrane, which allows transmission of current between the chambers, but not passage of chemical constituents. The anodes were then evaluated in single-cell reactors, which are more representative of potential treatment and disinfection applications. However, in the single-cell reactors, the tin oxide anodes were significantly more effective at oxidation and generated higher quality cyclic voltammograms than the other DSAs. These results suggest that tin oxide anodes have greater potential than the three commercially available DSAs tested for industrial waste stream treatment and effluent disinfection.

Nickel-based anode with water storage capability to mitigate carbon deposition for direct ethanol solid oxide fuel cells.

PubMed

Wang, Wei; Su, Chao; Ran, Ran; Zhao, Bote; Shao, Zongping; Tade, Moses O; Liu, Shaomin

2014-06-01

The potential to use ethanol as a fuel places solid oxide fuel cells (SOFCs) as a sustainable technology for clean energy delivery because of the renewable features of ethanol versus hydrogen. In this work, we developed a new class of anode catalyst exemplified by Ni+BaZr0.4Ce0.4Y0.2O3 (Ni+BZCY) with a water storage capability to overcome the persistent problem of carbon deposition. Ni+BZCY performed very well in catalytic efficiency, water storage capability and coking resistance tests. A stable and high power output was well maintained with a peak power density of 750 mW cm(-2) at 750 °C. The SOFC with the new robust anode performed for seven days without any sign of performance decay, whereas SOFCs with conventional anodes failed in less than 2 h because of significant carbon deposition. Our findings indicate the potential applications of these water storage cermets as catalysts in hydrocarbon reforming and as anodes for SOFCs that operate directly on hydrocarbons. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of Self-Ordered Alumina Films with Large Interpore Distance by Janus Anodization in Citric Acid

NASA Astrophysics Data System (ADS)

Ma, Yingjun; Wen, Yihao; Li, Juan; Li, Yuxin; Zhang, Zhiying; Feng, Chenchen; Sun, Runguang

2016-12-01

Self-organized porous anodic alumina (PAA) formed by electrochemical anodization have become a fundamental tool to develop various functional nanomaterials. However, it is still a great challenge to break the interpore distance (Dint) limit (500 nm) by using current anodization technologies of mild anodization (MA) and hard anodization (HA). Here, we reported a new anodization mode named “Janus anodization” (JA) to controllably fabricate self-ordered PAA with large Dint at high voltage of 350-400 V. JA naturally occurs as anodizing Al foils in citric acid solution, which possessing both the characteristics of MA and HA. The process can be divided into two stages: I, slow pore nucleation stage similar to MA; II, unequilibrium self-organization process similar to HA. The as-prepared films had the highest modulus (7.0 GPa) and hardness (127.2 GPa) values compared with the alumina obtained by MA and HA. The optical studies showed that the black films have low reflectance (<10 %) in the wavelength range of 250-1500 nm and photoluminescence property. Dint can be tuned between 645-884 nm by controlling citric acid concentration or anodization voltage. JA is a potential technology to efficiently and controllably fabricate microstructured or hybrid micro- and nanostructured materials with novel properties.

Fabrication of Self-Ordered Alumina Films with Large Interpore Distance by Janus Anodization in Citric Acid

PubMed Central

Ma, Yingjun; Wen, Yihao; Li, Juan; Li, Yuxin; Zhang, Zhiying; Feng, Chenchen; Sun, Runguang

2016-01-01

Self-organized porous anodic alumina (PAA) formed by electrochemical anodization have become a fundamental tool to develop various functional nanomaterials. However, it is still a great challenge to break the interpore distance (Dint) limit (500 nm) by using current anodization technologies of mild anodization (MA) and hard anodization (HA). Here, we reported a new anodization mode named “Janus anodization” (JA) to controllably fabricate self-ordered PAA with large Dint at high voltage of 350–400 V. JA naturally occurs as anodizing Al foils in citric acid solution, which possessing both the characteristics of MA and HA. The process can be divided into two stages: I, slow pore nucleation stage similar to MA; II, unequilibrium self-organization process similar to HA. The as-prepared films had the highest modulus (7.0 GPa) and hardness (127.2 GPa) values compared with the alumina obtained by MA and HA. The optical studies showed that the black films have low reflectance (<10 %) in the wavelength range of 250–1500 nm and photoluminescence property. Dint can be tuned between 645–884 nm by controlling citric acid concentration or anodization voltage. JA is a potential technology to efficiently and controllably fabricate microstructured or hybrid micro- and nanostructured materials with novel properties. PMID:27958365

The study of aluminium anodes for high power density Al/air batteries with brine electrolytes

NASA Astrophysics Data System (ADS)

Nestoridi, Maria; Pletcher, Derek; Wood, Robert J. K.; Wang, Shuncai; Jones, Richard L.; Stokes, Keith R.; Wilcock, Ian

Aluminium alloys containing small additions of both tin (∼0.1 wt%) and gallium (∼0.05 wt%) are shown to dissolve anodically at high rates in sodium chloride media at room temperatures; current densities >0.2 A cm -2 can be obtained at potentials close to the open circuit potential, ∼-1500 mV versus SCE. The tin exists in the alloys as a second phase, typically as ∼1 μm inclusions (precipitates) distributed throughout the aluminium structure, and anodic dissolution occurs to form pits around the tin inclusions. Although the distribution of the gallium in the alloy could not be established, it is also shown to be critical in the formation of these pits as well as maintaining their activity. The stability of the alloys to open circuit corrosion and the overpotential for high rate dissolution, both critical to battery performance, are shown to depend on factors in addition to elemental composition; both heat treatment and mechanical working influence the performance of the alloy. The correlation between alloy performance and their microstructure has been investigated.

Sn-Based Nanocomposite for Li-Ion Battery Anode with High Energy Density, Rate Capability, and Reversibility.

PubMed

Park, Min-Gu; Lee, Dong-Hun; Jung, Heechul; Choi, Jeong-Hee; Park, Cheol-Min

2018-03-27

To design an easily manufactured, large energy density, highly reversible, and fast rate-capable Li-ion battery (LIB) anode, Co-Sn intermetallics (CoSn 2 , CoSn, and Co 3 Sn 2 ) were synthesized, and their potential as anode materials for LIBs was investigated. Based on their electrochemical performances, CoSn 2 was selected, and its C-modified nanocomposite (CoSn 2 /C) as well as Ti- and C-modified nanocomposite (CoSn 2 / a-TiC/C) was straightforwardly prepared. Interestingly, the CoSn 2 , CoSn 2 /C, and CoSn 2 / a-TiC/C showed conversion/nonrecombination, conversion/partial recombination, and conversion/full recombination during Li insertion/extraction, respectively, which were thoroughly investigated using ex situ X-ray diffraction and extended X-ray absorption fine structure analyses. As a result of the interesting conversion/full recombination mechanism, the easily manufactured CoSn 2 / a-TiC/C nanocomposite for the Sn-based Li-ion battery anode showed large energy density (first reversible capacity of 1399 mAh cm -3 ), high reversibility (first Coulombic efficiency of 83.2%), long cycling behavior (100% capacity retention after 180 cycles), and fast rate capability (appoximately 1110 mAh cm -3 at 3 C rate). In addition, degradation/enhancement mechanisms for high-capacity and high-performance Li-alloy-based anode materials for next-generation LIBs were also suggested.

Lanthanum doped strontium titanate - ceria anodes: deconvolution of impedance spectra and relationship with composition and microstructure

NASA Astrophysics Data System (ADS)

Burnat, Dariusz; Nasdaurk, Gunnar; Holzer, Lorenz; Kopecki, Michal; Heel, Andre

2018-05-01

Electrochemical performance of ceramic (Ni-free) SOFC anodes based on La0.2Sr0.7TiO3-δ (LST) and Gd0.1Ce0.9O1.95-δ (CGO) is thoroughly investigated. Microstructures and compositions are systematically varied around the percolation thresholds of both phases by modification of phase volume fractions, particle size distributions and firing temperature. Differential impedance spectroscopy was performed while varying gas composition, electrical potential and operating temperature, which allows determining four distinct electrode processes. Significant anode impedances are measured at low frequencies, which in contrast to the literature cannot be linked with gas concentration impedance. The dominant low frequency process (∼1 Hz) is attributed to the chemical capacitance. Combined EIS and microstructure investigations show that the chemical capacitance correlates inversely with the available surface area of CGO, indicating CGO surface reactions as the kinetic limitation for the dominant anode process and for the associated chemical capacitance. In anodes with a fine-grained microstructure this limitation is significantly smaller, which results in an impressive power output as high as 0.34 Wcm-2. The anodes show high redox stability by not only withstanding 30 isothermal redox cycles, but even improving the performance. Hence, compared to conventional Ni-cermet anodes the new LST-CGO material represents an interesting alternative with much improved redox-stability.

Enrichment of extremophilic exoelectrogens in microbial electrolysis cells using Red Sea brine pools as inocula.

PubMed

Shehab, Noura A; Ortiz-Medina, Juan F; Katuri, Krishna P; Hari, Ananda Rao; Amy, Gary; Logan, Bruce E; Saikaly, Pascal E

2017-09-01

Applying microbial electrochemical technologies for the treatment of highly saline or thermophilic solutions is challenging due to the lack of proper inocula to enrich for efficient exoelectrogens. Brine pools from three different locations (Valdivia, Atlantis II and Kebrit) in the Red Sea were investigated as potential inocula sources for enriching exoelectrogens in microbial electrolysis cells (MECs) under thermophilic (70°C) and hypersaline (25% salinity) conditions. Of these, only the Valdivia brine pool produced high and consistent current 6.8±2.1A/m 2 -anode in MECs operated at a set anode potential of +0.2V vs. Ag/AgCl (+0.405V vs. standard hydrogen electrode). These results show that exoelectrogens are present in these extreme environments and can be used to startup MEC under thermophilic and hypersaline conditions. Bacteroides was enriched on the anode of the Valdivia MEC, but it was not detected in the open circuit voltage reactor seeded with the Valdivia brine pool. Copyright © 2017 Elsevier Ltd. All rights reserved.

The effect of zinc (Zn) content to cell potential value and efficiency aluminium sacrificial anode in 0.2 M sulphuric acid environment

NASA Astrophysics Data System (ADS)

Akranata, Ahmad Ridho; Sulistijono, Awali, Jatmoko

2018-04-01

Sacrificial anode is sacirifial component that used to protect steel from corrosion. Generally, the component are made of aluminium and zinc in water environment. Sacrificial anode change the protected metal structure become cathodic with giving current. The advantages of aluminium is corrosion resistance, non toxicity and easy forming. Zinc generally used for coating in steel to prevent steel from corrosion. This research was conducted to analyze the effect of zinc content to the value of cell potential and efficiency aluminium sacrificial anode with sand casting method in 0.2 M sulphuric acid environment. The sacrificial anode fabrication made with alloying aluminium and zinc metals with variation composition of alloy with pure Al, Al-3Zn, Al-6Zn, and Al-9Zn with open die sand casting process. The component installed with ASTM A36 steel. After the research has been done the result showed that addition of zinc content increase the cell potential, protection efficiency, and anode efficiency from steel plate. Cell potential value measurement and weight loss measurement showed that addition of zinc content increase the cell potential value into more positive that can protected the ASTM A36 steel more efficiently that showed in weight loss measurement where the protection efficiency and anodic efficiency of Al-9Zn sacrificial anode is better than protection efficiency and anodic efficiency of pure Al. The highest protection efficiency gotten by Al-9Zn alloy

In vivo assessment of a new multifunctional coating architecture for improved Mg alloy biocompatibility.

PubMed

Gomes, Pedro S; Zomorodian, Amir; Kwiatkowski, Lech; Lutze, Rafal; Balkowiec, Alicja; Colaço, Bruno; Pinheiro, Vitor; Fernandes, João C S; Montemor, Maria F; Fernandes, Maria H

2016-08-10

Magnesium alloys are regarded as potential biodegradable load-bearing biomaterials for orthopedic applications due to their physico-chemical and biomechanical properties. However, their clinical applicability is restricted by their high degradation rate, which limits the physiological reconstruction of the neighbouring tissues. In this work, a multifunctional coating architecture was developed on an AZ31 alloy by conjoining an anodization process with the deposition of a polymeric-based layer consisting of polyether imine reinforced with hydroxyapatite nanoparticles, aiming at improved control of the corrosion activity and biological performance of the Mg substrate. Anodization and coating protocols were evaluated either independently or combined for corrosion resistance and biological behaviour, i.e. the irritation potential and angiogenic capability within a chicken chorioallantoic membrane assay, and bone tissue response following tibia implantation within a rabbit model. Electrochemical impedance spectroscopy (EIS) analysis showed that coated Mg constructs, particularly anodized plus coated with AZ31, exhibited excellent stability compared to the anodized alloy and, particularly, to the bare AZ31. Microtomographic evaluation of the implanted samples correlated with these degradation results. Mg constructs displayed a non-irritating behaviour, and were associated with high levels of vascular ingrowth. Bone ingrowth neighbouring the implanted constructs was observed for all samples, with coated and anodized plus coated samples presenting the highest bone formation. Gene expression analysis suggested that the enhanced bone tissue formation was associated with the boost in osteogenic activity through Runx2 upregulation, following the activation of PGC-1α/ERRα signaling. Overall, the developed multifunctional coatings appear to be a promising strategy to obtain safe and bioactive biodegradable Mg-based implants with potential applications within bone tissue.

Anode power in quasisteady magnetoplasmadynamic accelerators

NASA Technical Reports Server (NTRS)

Saber, A. J.; Jahn, R. G.

1978-01-01

Anode heat flux in a quasi-steady MPD accelerator has been measured directly and locally by thermocouples attached to the inside surface of a shell anode. These measurements show that over a range of arc current from 5.5 to 44 kA, and argon mass flow from 1 to 48 g/s, the fraction of the total arc power deposited in the anode decreases from 50% at 200 kW to 10% at 20 MW. A theoretical model of the anode heat transfer asserts that energy exchange between electrons and heavy particles in the plasma near the anode occurs over distances greater than the anode sheath thickness, and hence the usual anode fall voltage, electron temperature, and work function contributions to the anode heat flux are supplemented by a contribution from the interelectrode potential. Calculations of anode heat flux using the measured current density, plasma potential, and electron temperature in the plasma adjacent to the anode agree with the direct measurements and indicate that the decrease in anode power fraction at higher arc powers can be attributed to the smaller mean free paths in the interelectrode plasma.

Li3PO4 Matrix Enables a Long Cycle Life and High Energy Efficiency Bismuth-Based Battery.

PubMed

Sun, Chuan-Fu; Hu, Junkai; Wang, Peng; Cheng, Xi-Yuan; Lee, Sang Bok; Wang, YuHuang

2016-09-14

Bismuth is a lithium-ion battery anode material that can operate at an equilibrium potential higher than graphite and provide a capacity twice as high as that of Li4Ti5O12, making it intrinsically free from lithium plating that may cause catastrophic battery failure. However, the potential of bismuth is hampered by its inferior cyclability (limited to tens of cycles). Here, we propose an "ion conductive solid-state matrix" approach to address this issue. By homogeneously confining bismuth nanoparticles in a solid-state γ-Li3PO4 matrix that is electrochemically formed in situ, the resulting composite anode exhibits a reversible capacity of 280 mA hours per gram (mA h/g) at a rate of 100 mA/g and a record cyclability among bismuth-based anodes up to 500 cycles with a capacity decay rate of merely 0.071% per cycle. We further show that full-cell batteries fabricated from this composite anode and commercial LiFePO4 cathode deliver a stable cell voltage of ∼2.5 V and remarkable energy efficiency up to 86.3%, on par with practical batteries (80-90%). This work paves a way for harnessing bismuth-based battery chemistry for the design of high capacity, safer lithium-ion batteries to meet demanding applications such as electric vehicles.

Na-Ion Battery Anodes: Materials and Electrochemistry.

PubMed

Luo, Wei; Shen, Fei; Bommier, Clement; Zhu, Hongli; Ji, Xiulei; Hu, Liangbing

2016-02-16

The intermittent nature of renewable energy sources, such as solar and wind, calls for sustainable electrical energy storage (EES) technologies for stationary applications. Li will be simply too rare for Li-ion batteries (LIBs) to be used for large-scale storage purposes. In contrast, Na-ion batteries (NIBs) are highly promising to meet the demand of grid-level storage because Na is truly earth abundant and ubiquitous around the globe. Furthermore, NIBs share a similar rocking-chair operation mechanism with LIBs, which potentially provides high reversibility and long cycling life. It would be most efficient to transfer knowledge learned on LIBs during the last three decades to the development of NIBs. Following this logic, rapid progress has been made in NIB cathode materials, where layered metal oxides and polyanionic compounds exhibit encouraging results. On the anode side, pure graphite as the standard anode for LIBs can only form NaC64 in NIBs if solvent co-intercalation does not occur due to the unfavorable thermodynamics. In fact, it was the utilization of a carbon anode in LIBs that enabled the commercial successes. Anodes of metal-ion batteries determine key characteristics, such as safety and cycling life; thus, it is indispensable to identify suitable anode materials for NIBs. In this Account, we review recent development on anode materials for NIBs. Due to the limited space, we will mainly discuss carbon-based and alloy-based anodes and highlight progress made in our groups in this field. We first present what is known about the failure mechanism of graphite anode in NIBs. We then go on to discuss studies on hard carbon anodes, alloy-type anodes, and organic anodes. Especially, the multiple functions of natural cellulose that is used as a low-cost carbon precursor for mass production and as a soft substrate for tin anodes are highlighted. The strategies of minimizing the surface area of carbon anodes for improving the first-cycle Coulombic efficiency are also outlined, where graphene oxide was employed as dehydration agent and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was used to unzip wood fiber. Furthermore, surface modification by atomic layer deposition technology is introduced, where we discover that a thin layer of Al2O3 can function to encapsulate Sn nanoparticles, leading to a much enhanced cycling performance. We also highlight recent work about the phosphorene/graphene anode, which outperformed other anodes in terms of capacity. The aromatic organic anode is also studied as anode with very high initial sodiation capacity. Furthermore, electrochemical intercalation of Na ions into reduced graphene oxide is applied for fabricating transparent conductors, demonstrating the great feasibility of Na ion intercalation for optical applications.

Thylakoid-Deposited Micro-Pillar Electrodes for Enhanced Direct Extraction of Photosynthetic Electrons

PubMed Central

Ryu, DongHyun; Kim, Yong Jae; Kim, Seon Il; Hong, Hyeonaug; Ahn, Hyun S.

2018-01-01

Photosynthesis converts solar energy to electricity in a highly efficient manner. Since only water is needed as fuel for energy conversion, this highly efficient energy conversion process has been rigorously investigated. In particular, photosynthetic apparatus, such as photosystem II (PSII), photosystem I (PSI), or thylakoids, have been isolated from various plants to construct bio-hybrid anodes. Although PSII or PSI decorated anodes have shown potentials, there still remain challenges, such as poor stability of PSII-based systems or need for electron donors other than water molecules of PSI-based systems. Thylakoid membranes are relatively stable after isolation and they contain all the necessary photosynthetic apparatus including the PSII and PSI. To increase electrical connections between thylakoids and anodes, nanomaterials such as carbon nanotubes, nanowires, nanoparticles, or graphene have been employed. However, since they rely on the secondary electrical connections between thylakoids and anodes; it is desired to achieve larger direct contacts between them. Here, we aimed to develop micro-pillar (MP) array anodes to maximize direct contact with thylakoids. The thylakoid morphology was analyzed and the MP array was designed to maximize direct contact with thylakoids. The performance of MP anodes and a photosynthetic fuel cell based on MP electrodes was demonstrated and analyzed. PMID:29587387

Auger electron spectroscopy and Rutherford backscattering studies of copper in 2024-T3 aluminum following electrochemical anodization in phosphoric acid

NASA Astrophysics Data System (ADS)

Solomon, J. S.

1981-05-01

The effects of the electrochemical anodization of dioxidized 2024-T3 aluminum on copper were characterized by Auger electron spectroscopy and Rutherford backscattering. Anodization was performed in phosphoric acid at constant potential. Data is presented which shows that constant potential anodization of 2024-T3 is more efficient than aluminum in terms of oxide growth rates for short anodization times. However the maximum anodic oxide thickness achievable on the alloy is less than the pure metal. Copper is shown to be enriched at the oxide metal interface because of its diffusion from the bulk during anodization. The presence of copper at the oxide-metal interface is shown to affect oxide morphology.

Life cycle environmental impact of high-capacity lithium ion battery with silicon nanowires anode for electric vehicles.

PubMed

Li, Bingbing; Gao, Xianfeng; Li, Jianyang; Yuan, Chris

2014-01-01

Although silicon nanowires (SiNW) have been widely studied as an ideal material for developing high-capacity lithium ion batteries (LIBs) for electric vehicles (EVs), little is known about the environmental impacts of such a new EV battery pack during its whole life cycle. This paper reports a life cycle assessment (LCA) of a high-capacity LIB pack using SiNW prepared via metal-assisted chemical etching as anode material. The LCA study is conducted based on the average U.S. driving and electricity supply conditions. Nanowastes and nanoparticle emissions from the SiNW synthesis are also characterized and reported. The LCA results show that over 50% of most characterized impacts are generated from the battery operations, while the battery anode with SiNW material contributes to around 15% of global warming potential and 10% of human toxicity potential. Overall the life cycle impacts of this new battery pack are moderately higher than those of conventional LIBs but could be actually comparable when considering the uncertainties and scale-up potential of the technology. These results are encouraging because they not only provide a solid base for sustainable development of next generation LIBs but also confirm that appropriate nanomanufacturing technologies could be used in sustainable product development.

Ultra-thick, Low-Tortuosity, and Mesoporous Wood Carbon Anode for High-Performance Sodium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Fei; Luo, Wei; Dai, Jiaqi

Sodium-ion batteries (SIBs) have attracted extensive interest in the past few years because of the low cost and abundance of sodium resources and hence the potential for grid scale energy storage. Developing low cost electrode materials, particularly anode materials, is the key for further promoting the application of SIBs. Here, we for the first time report a self-standing porous carbon anode directly from natural wood for SIBs, which processes following advantages: (i) ultra-thick carbon anode with a high areal capacity, for example a capacity of 13.6 mAh cm-2 was delivered when the thickness reached 0.85 mm; (ii) low tortuosity, wheremore » numerous inherited aligned channels in the wood carbon provide a rapid ion transport path; (iii) porous nature enables a fast ion transfer between the carbon electrode and the electrolyte; (iv) 100% utilization of the wood carbon that conductive additives, binders, and current-collectors are not needed; v) when coupling a Na3V2(PO4)3 cathode with the wood carbon anode, a high capacity of 80 mAh g-1 was obtained at 0.5 C rate (base on cathode) and excellent cycling stability of 300 cycles was also achieved, which demonstrated the promising performance of earth-abundant wood derived carbon material.« less

Leakage current and charging/discharging processes in barrier-type anodic alumina thin films for use in metal-insulator-metal capacitors

NASA Astrophysics Data System (ADS)

Hourdakis, E.; Koutsoureli, M.; Papaioannou, G.; Nassiopoulou, A. G.

2018-06-01

Barrier-type anodic alumina thin films are interesting for use in high capacitance density metal-insulator-metal capacitors due to their excellent dielectric properties at small thickness. This thickness is easily controlled by the anodization voltage. In previous papers we studied the main parameters of interest of the Al/barrier-type anodic alumina/Al structure for use in RF applications and showed the great potential of barrier-type anodic alumina in this respect. In this paper, we investigated in detail charging/discharging processes and leakage current of the above dielectric material. Two different sets of metal-insulator-metal capacitors were studied, namely, with the top Al electrode being either e-gun deposited or sputtered. The dielectric constant of the barrier-type anodic alumina was found at 9.3. Low leakage current was observed in all samples studied. Furthermore, depending on the film thickness, field emission following the Fowler-Nordheim mechanism was observed above an applied electric field. Charging of the anodic dielectric was observed, occurring in the bulk of the anodic layer. The stored charge was of the order of few μC/cm2 and the calculated trap density ˜2 × 1018 states/cm3, the most probable origin of charge traps being, in our opinion, positive electrolyte ions trapped in the dielectric during anodization. We do not think that oxygen vacancies play an important role, since their existence would have a more important impact on the leakage current characteristics, such as resistive memory effects or significant changes during annealing, which were not observed. Finally, discharging characteristic times as high as 5 × 109 s were measured.

Developing High-Performance Lithium Metal Anode in Liquid Electrolytes: Challenges and Progress.

PubMed

Li, Sa; Jiang, Mengwen; Xie, Yong; Xu, Hui; Jia, Junyao; Li, Ju

2018-04-01

Lithium metal anodes are potentially key for next-generation energy-dense batteries because of the extremely high capacity and the ultralow redox potential. However, notorious safety concerns of Li metal in liquid electrolytes have significantly retarded its commercialization: on one hand, lithium metal morphological instabilities (LMI) can cause cell shorting and even explosion; on the other hand, breaking of the grown Li arms induces the so-called "dead Li"; furthermore, the continuous consumption of the liquid electrolyte and cycleable lithium also shortens cell life. The research community has been seeking new strategies to protect Li metal anodes and significant progress has been made in the last decade. Here, an overview of the fundamental understandings of solid electrolyte interphase (SEI) formation, conceptual models, and advanced real-time characterizations of LMI are presented. Instructed by the conceptual models, strategies including increasing the donatable fluorine concentration (DFC) in liquid to enrich LiF component in SEI, increasing salt concentration (ionic strength) and sacrificial electrolyte additives, building artificial SEI to boost self-healing of natural SEI, and 3D electrode frameworks to reduce current density and delay Sand's extinction are summarized. Practical challenges in competing with graphite and silicon anodes are outlined. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of mass and charge transport speed and direction in porous anodes on microbial electrolysis cell performance.

PubMed

Sleutels, Tom H J A; Hamelers, Hubertus V M; Buisman, Cees J N

2011-01-01

The use of porous electrodes like graphite felt as anode material has the potential of achieving high volumetric current densities. High volumetric current densities, however, may also lead to mass transport limitations within these porous materials. Therefore, in this study we investigated the mass and charge transport limitations by increasing the speed of the forced flow and changing the flow direction through the porous anode. Increase of the flow speed led to a decrease in current density when the flow was directed towards the membrane caused by an increase in anode resistance. Current density increased at higher flow speed when the flow was directed away from the membrane. This was caused by a decrease in transport resistance of ions through the membrane which increased the buffering effect of the system. Furthermore, the increase in flow speed led to an increase of the coulombic efficiency by 306%. Copyright © 2010 Elsevier Ltd. All rights reserved.

Building one-dimensional oxide nanostructure arrays on conductive metal substrates for lithium-ion battery anodes.

PubMed

Jiang, Jian; Li, Yuanyuan; Liu, Jinping; Huang, Xintang

2011-01-01

Lithium ion battery (LIB) is potentially one of the most attractive energy storage devices. To meet the demands of future high-power and high-energy density requirements in both thin-film microbatteries and conventional batteries, it is challenging to explore novel nanostructured anode materials instead of conventional graphite. Compared to traditional electrodes based on nanostructure powder paste, directly grown ordered nanostructure array electrodes not only simplify the electrode processing, but also offer remarkable advantages such as fast electron transport/collection and ion diffusion, sufficient electrochemical reaction of individual nanostructures, enhanced material-electrolyte contact area and facile accommodation of the strains caused by lithium intercalation and de-intercalation. This article provides a brief overview of the present status in the area of LIB anodes based on one-dimensional nanostructure arrays growing directly on conductive inert metal substrates, with particular attention to metal oxides synthesized by an anodized alumina membrane (AAM)-free solution-based or hydrothermal methods. Both the scientific developments and the techniques and challenges are critically analyzed.

Building one-dimensional oxidenanostructure arrays on conductive metal substrates for lithium-ion battery anodes

NASA Astrophysics Data System (ADS)

Jiang, Jian; Li, Yuanyuan; Liu, Jinping; Huang, Xintang

2011-01-01

Lithium ion battery (LIB) is potentially one of the most attractive energy storage devices. To meet the demands of future high-power and high-energy density requirements in both thin-film microbatteries and conventional batteries, it is challenging to explore novel nanostructured anode materials instead of conventional graphite. Compared to traditional electrodes based on nanostructure powder paste, directly grown ordered nanostructure array electrodes not only simplify the electrode processing, but also offer remarkable advantages such as fast electron transport/collection and ion diffusion, sufficient electrochemical reaction of individual nanostructures, enhanced material-electrolyte contact area and facile accommodation of the strains caused by lithium intercalation and de-intercalation. This article provides a brief overview of the present status in the area of LIB anodes based on one-dimensional nanostructure arrays growing directly on conductive inert metal substrates, with particular attention to metal oxides synthesized by an anodized aluminamembrane (AAM)-free solution-based or hydrothermal methods. Both the scientific developments and the techniques and challenges are critically analyzed.

The alkaline zinc electrode as a mixed potential system

NASA Technical Reports Server (NTRS)

Fielder, W. L.

1979-01-01

Cathodic and anodic processes for the alkaline zinc electrode in 0.01 molar zincate electrolyte (9 molar hydroxide) were investigated. Cyclic voltammograms and current-voltage curves were obtained by supplying pulses through a potentiostat to a zinc rotating disk electrode. The data are interpreted by treating the system as one with a mixed potential; the processes are termed The zincate and corrosion reactions. The relative proportions of the two processes vary with the supplied potential. For the cathodic region, the cathodic corrosion process predominates at higher potentials while both processes occur simultaneously at a lower potential (i.e., 50 mV). For the anodic region, the anodic zincate process predominates at higher potentials while the anodic corrosion process is dominant at lower potential (i.e., 50 mV) if H2 is present.

Alternative Anodes for the Electrolytic Reduction of Uranium Dioxide

NASA Astrophysics Data System (ADS)

Merwin, Augustus

Reprocessing of spent nuclear fuel is an essential step in closing the nuclear fuel cycle. In order to consume current stockpiles, ceramic uranium dioxide spent nuclear fuel will be subjected to an electrolytic reduction process. The current reduction process employs a platinum anode and a stainless steel alloy 316 cathode in a molten salt bath consisting of LiCl-2wt% Li 2O and occurs at 700°C. A major shortcoming of the existing process is the degradation of the platinum anode under the severely oxidizing conditions encountered during electrolytic reduction. This work investigates alternative anode materials for the electrolytic reduction of uranium oxide. The high temperature and extreme oxidizing conditions encountered in these studies necessitated a unique set of design constraints on the system. Thus, a customized experimental apparatus was designed and constructed. The electrochemical experiments were performed in an electrochemical reactor placed inside a furnace. This entire setup was housed inside a glove box, in order to maintain an inert atmosphere. This study investigates alternative anode materials through accelerated corrosion testing. Surface morphology was studied using scanning electron microscopy. Surface chemistry was characterized using energy dispersive spectroscopy and Raman spectroscopy. Electrochemical behavior of candidate materials was evaluated using potentiodynamic polarization characteristics. After narrowing the number of candidate electrode materials, ferrous stainless steel alloy 316, nickel based Inconel 718 and elemental tungsten were chosen for further investigation. Of these materials only tungsten was found to be sufficiently stable at the anodic potential required for electrolysis of uranium dioxide in molten salt. The tungsten anode and stainless steel alloy 316 cathode electrode system was studied at the required reduction potential for UO2 with varying lithium oxide concentrations. Electrochemical impedance spectroscopy showed mixed (kinetic and diffusion) control and an overall low impedance due to extreme corrosion. It was observed that tungsten is sufficiently stable in LiCl - 2wt% Li 2O at 700°C at the required anodic potential for the reduction of uranium oxide. This study identifies tungsten to be a superior anode material to platinum for the electrolytic reduction of uranium oxide, both in terms of superior corrosion behavior and reduced cost, and thus recommends that tungsten be further investigated as an alternative anode for the electrolytic reduction of uranium dioxide.

Effect of Copper and Silicon on Al-5%Zn Alloy as a Candidate Low Voltage Sacrificial Anode

NASA Astrophysics Data System (ADS)

Pratesa, Yudha; Ferdian, Deni; Togina, Inez

2017-05-01

One common method used for corrosion protection is a sacrificial anode. Sacrificial anodes that usually employed in the marine environment are an aluminum alloy sacrificial anode, especially Al-Zn-In. However, the electronegativity of these alloys can cause corrosion overprotection and stress cracking (SCC) on a high-strength steel. Therefore, there is a development of the sacrificial anode aluminum low voltage to reduce the risk of overprotection. The addition of alloying elements such as Cu, Si, and Ge will minimize the possibility of overprotection. This study was conducted to analyze the effect of silicon and copper addition in Al-5Zn. The experiment started from casting the sacrificial anode aluminum uses electrical resistance furnace in a graphite crucible in 800°C. The results alloy was analyzed using Optical emission spectroscopy (OES), Differential scanning calorimetry, electrochemical impedance spectroscopy, and metallography. Aluminum alloy with the addition of a copper alloy is the most suitable and efficient to serve as a low-voltage sacrificial anode aluminum. Charge transfer resistivity of copper is smaller than silicon which indicates that the charge transfer between the metal and the electrolyte is easier t to occur. Also, the current potential values in coupling with steel are also in the criteria range of low-voltage aluminum sacrificial anodes.

Highly efficient lithium composite anode with hydrophobic molten salt in seawater

NASA Astrophysics Data System (ADS)

Zhang, Yancheng; Urquidi-Macdonald, Mirna

A lithium composite anode (lithium/1-butyl-3-methyl-imidazoleum hexafluorophosphate (BMI +PF 6-)/4-VLZ) for primary lithium/seawater semi-fuel-cells is proposed to reduce lithium-water parasitic reaction and, hence, increase the lithium anodic efficiency up to 100%. The lithium composite anode was activated when in contact with artificial seawater (3% NaCl solution) and the output was a stable anodic current density at 0.2 mA/cm 2, which lasted about 10 h under potentiostatic polarization at +0.5 V versus open circuit potential (OCP); the anodic efficiency was indirectly measured to be 100%. With time, a small traces of water diffused through the hydrophobic molten salt, BMI +PF 6-, reached the lithium interface and formed a double layer film (LiH/LiOH). Accordingly, the current density decreased and the anodic efficiency was estimated to be 90%. The hypothesis of small traces of water penetrating the molten salt and reaching the lithium anode—after several hours of operation—is supported by the collected experimental current density and hydrogen evolution, electrochemical impedance spectrum analysis, and non-mechanistic interface film modeling of lithium/BMI +PF 6-.

Back-gated graphene anode for more efficient thermionic energy converters

DOE PAGES

Yuan, Hongyuan; Riley, Daniel C.; Shen, Zhi-Xun; ...

2016-12-15

Thermionic energy converters (TECs) are a direct heat-to-electricity conversion technology with great potential for high efficiency and scalability. However, space charge barrier in the inter-electrode gap and high anode work function are major obstacles toward realizing high efficiency. Here, we demonstrate for the first time a prototype TEC using a back-gated graphene anode, a barium dispenser cathode, and a controllable inter-electrode gap as small as 17 µm, which simultaneously addresses these two obstacles. This leads to an electronic conversion efficiency of 9.8% at cathode temperature of 1000 °C, the highest reported by far. We first demonstrate that electrostatic gating ofmore » graphene by a 20 nm HfO 2 dielectric layer changes the graphene anode work function by 0.63 eV, as observed from the current-voltage characteristics of the TEC. Next, we show that the efficiency increases by a factor of 30.6 by reducing the gap from 1 mm down to 17 µm, after a mono-layer of Ba is deposited on graphene by the dispenser cathode. Lastlu, we show that electrostatic gating of graphene further reduces the graphene work function from 1.85 to 1.69 eV, leading to an additional 67% enhancement in TEC efficiency. Note that the overall efficiency using the back-gated graphene anode is 6.7 times higher compared with that of a TEC with a tungsten anode and the same inter-electrode gap.« less

Back-gated graphene anode for more efficient thermionic energy converters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Hongyuan; Riley, Daniel C.; Shen, Zhi-Xun

Thermionic energy converters (TECs) are a direct heat-to-electricity conversion technology with great potential for high efficiency and scalability. However, space charge barrier in the inter-electrode gap and high anode work function are major obstacles toward realizing high efficiency. Here, we demonstrate for the first time a prototype TEC using a back-gated graphene anode, a barium dispenser cathode, and a controllable inter-electrode gap as small as 17 µm, which simultaneously addresses these two obstacles. This leads to an electronic conversion efficiency of 9.8% at cathode temperature of 1000 °C, the highest reported by far. We first demonstrate that electrostatic gating ofmore » graphene by a 20 nm HfO 2 dielectric layer changes the graphene anode work function by 0.63 eV, as observed from the current-voltage characteristics of the TEC. Next, we show that the efficiency increases by a factor of 30.6 by reducing the gap from 1 mm down to 17 µm, after a mono-layer of Ba is deposited on graphene by the dispenser cathode. Lastlu, we show that electrostatic gating of graphene further reduces the graphene work function from 1.85 to 1.69 eV, leading to an additional 67% enhancement in TEC efficiency. Note that the overall efficiency using the back-gated graphene anode is 6.7 times higher compared with that of a TEC with a tungsten anode and the same inter-electrode gap.« less

Nanoporous Mo2C functionalized 3D carbon architecture anode for boosting flavins mediated interfacial bioelectrocatalysis in microbial fuel cells

NASA Astrophysics Data System (ADS)

Zou, Long; Lu, Zhisong; Huang, Yunhong; Long, Zhong-er; Qiao, Yan

2017-08-01

An efficient microbial electrocatalysis in microbial fuel cells (MFCs) needs both high loading of microbes (biocatalysts) and robust interfacial electron transfer from microbes to electrode. Herein a nanoporous molybdenum carbide (Mo2C) functionalized carbon felt electrode with rich 3D hierarchical porous architecture is applied as MFC anode to achieve superior electrocatalytic performance. The nanoporous Mo2C functionalized anode exhibits strikingly improved microbial electrocatalysis in MFCs with 5-fold higher power density and long-term stability of electricity production. The great enhancement is attributed to the introduction of rough Mo2C nanostructural interface into macroporous carbon architecture for promoting microbial growth with great excretion of endogenous electron shuttles (flavins) and rich available nanopores for enlarging electrochemically active surface area. Importantly, the nanoporous Mo2C functionalized anode is revealed for the first time to have unique electrocatalytic activity towards redox reaction of flavins with more negative redox potential, indicating a more favourable thermodynamic driving force for anodic electron transfer. This work not only provides a promising electrode for high performance MFCs but also brings up a new insight into the effect of nanostructured materials on interfacial bioelectrocatalysis.

After-effects of anodal transcranial direct current stimulation on the excitability of the motor cortex in rats.

PubMed

Koo, Ho; Kim, Min Sun; Han, Sang Who; Paulus, Walter; Nitche, Michael A; Kim, Yun-Hee; Kim, Hyoung-Ihl; Ko, Sung-Hwa; Shin, Yong-Il

2016-09-21

Transcranial direct current stimulation (tDCS) is increasingly seen as a useful tool for noninvasive cortical neuromodulation. A number of studies in humans have shown that when tDCS is applied to the motor cortex it can modulate cortical excitability. It is especially interesting to note that when applied with sufficient duration and intensity, tDCS can enable long-lasting neuroplastic effects. However, the mechanism by which tDCS exerts its effects on the cortex is not fully understood. We investigated the effects of anodal tDCS under urethane anesthesia on field potentials in in vivo rats. These were measured on the skull over the right motor cortex of rats immediately after stimulating the left corpus callosum. Evoked field potentials in the motor cortex were gradually increased for more than one hour after anodal tDCS. To induce these long-lasting effects, a sufficient duration of stimulation (20 minutes or more) was found to may be required rather than high stimulation intensity. We propose that anodal tDCS with a sufficient duration of stimulation may modulate transcallosal plasticity.

An artificial interphase enables reversible magnesium chemistry in carbonate electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Son, Seoung-Bum; Gao, Tao; Harvey, Steve P.

Magnesium-based batteries possess potential advantages over their lithium counterparts. However, reversible Mg chemistry requires a thermodynamically stable electrolyte at low potential, which is usually achieved with corrosive components and at the expense of stability against oxidation. In lithium-ion batteries the conflict between the cathodic and anodic stabilities of the electrolytes is resolved by forming an anode interphase that shields the electrolyte from being reduced. This strategy cannot be applied to Mg batteries because divalent Mg2+ cannot penetrate such interphases. Here, we engineer an artificial Mg2+-conductive interphase on the Mg anode surface, which successfully decouples the anodic and cathodic requirements formore » electrolytes and demonstrate highly reversible Mg chemistry in oxidation-resistant electrolytes. The artificial interphase enables the reversible cycling of a Mg/V2O5 full-cell in the water-containing, carbonate-based electrolyte. This approach provides a new avenue not only for Mg but also for other multivalent-cation batteries facing the same problems, taking a step towards their use in energy-storage applications.« less

Tunneled Mesoporous Carbon Nanofibers with Embedded ZnO Nanoparticles for Ultrafast Lithium Storage.

PubMed

An, Geon-Hyoung; Lee, Do-Young; Ahn, Hyo-Jin

2017-04-12

Carbon and metal oxide composites have received considerable attention as anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stability and high specific capacity based on the chemical and physical stability of carbon and the high theoretical specific capacity of metal oxides. However, efforts to obtain ultrafast cycling stability in carbon and metal oxide composites at high current density for practical applications still face important challenges because of the longer Li-ion diffusion pathway, which leads to poor ultrafast performance during cycling. Here, tunneled mesoporous carbon nanofibers with embedded ZnO nanoparticles (TMCNF/ZnO) are synthesized by electrospinning, carbonization, and postcalcination. The optimized TMCNF/ZnO shows improved electrochemical performance, delivering outstanding ultrafast cycling stability, indicating a higher specific capacity than previously reported ZnO-based anode materials in LIBs. Therefore, the unique architecture of TMCNF/ZnO has potential for use as an anode material in ultrafast LIBs.

High Voltage Magnesium-ion Battery Enabled by Nanocluster Mg3Bi2 Alloy Anode in Noncorrosive Electrolyte.

PubMed

Tan, Yi-Hong; Yao, Wei-Tang; Zhang, Tianwen; Ma, Tao; Lu, Lei-Lei; Zhou, Fei; Yao, Hong-Bin; Yu, Shu-Hong

2018-05-03

Currently, developing high voltage (beyond 2 V) rechargeable Mg-ion batteries still remains a great challenge owing to the limit of corrosive electrolyte and low compatibility of anode material. Here we report a facile one step solid state alloying route to synthesize nanoclustered Mg 3 Bi 2 alloy as a high-performance anode to build up a 2 V Mg-ion battery using noncorrosive electrolyte. The fabricated nanoclustered Mg 3 Bi 2 anode delivers a high reversible specific capacity (360 mAh g -1 ) with excellent stability (90.7% capacity retention over 200 cycles) and high Coulombic efficiency (average 98%) at 0.1 A g -1 . The good performance is attributed to the stable nanostructures, which effectively accommodate the reversible Mg 2+ ion insertion/deinsertion without losing electric contact among clusters. Significantly, the nanoclustered Mg 3 Bi 2 anode can be coupled with high voltage cathode Prussian Blue to assemble a full cell using noncorrosive electrolyte, showing a stable cycling (88% capacity retention over 200 cycles at 0.2 A g -1 ) and good rate capability (103 mAh g -1 at 0.1 A g -1 and 58 mAh g -1 at 2 A g -1 ). The energy and power density of the as-fabricated full cell can reach up to 81 Wh kg -1 and 2850 W kg -1 , respectively, which are both the highest values among the reported Mg-ion batteries using noncorrosive electrolytes. This study demonstrates a cost-effective route to fabricate stable and high voltage rechargeable Mg-ion battery potentially for grid-scale energy storage.

Influence of Fluoride Ion on the Performance of Pb-Ag Anode During Long-Term Galvanostatic Electrolysis

NASA Astrophysics Data System (ADS)

Zhong, Xiaocong; Yu, Xiaoying; Jiang, Liangxing; Lv, Xiaojun; Liu, Fangyang; Lai, Yanqing; Li, Jie

2015-09-01

Anodic potential, morphology and phase composition of the anodic layer, corrosion morphology of the metallic substrate, and oxygen evolution behavior of Pb-Ag anode in H2SO4 solution without/with fluoride ion were investigated and compared. The results showed that the presence of fluoride ions contributed to a smoother anodic layer with lower PbO2 concentration, which resulted in lower double layer capacity and higher charge transfer resistance for the oxygen evolution reaction. Consequently, the Pb-Ag anode showed a higher anodic potential (about 35 mV) in the fluoride-containing electrolyte. In addition, the fluoride ions accelerated the detachment of loose flakes on the anodic layer. It was demonstrated that the anodic layer formed in the fluoride-containing H2SO4 solution was thinner. Furthermore, fluoride ions aggravated the corrosion of the metallic substrate at interdendritic boundary regions. Hence, the presence of fluoride ions is detrimental to oxygen evolution reactivity and increases the corrosion of the Pb-Ag anode, which may further increase the energy consumption and capital cost of zinc plants.

Fabrication of Ni-Ti-O nanotube arrays by anodization of NiTi alloy and their potential applications

PubMed Central

Hang, Ruiqiang; Liu, Yanlian; Zhao, Lingzhou; Gao, Ang; Bai, Long; Huang, Xiaobo; Zhang, Xiangyu; Tang, Bin; Chu, Paul K.

2014-01-01

Nickel-titanium-oxide (Ni-Ti-O) nanotube arrays (NTAs) prepared on nearly equiatomic NiTi alloy shall have broad application potential such as for energy storage and biomedicine, but their precise structure control is a great challenge because of the high content of alloying element of Ni, a non-valve metal that cannot form a compact electronic insulating passive layer when anodized. In the present work, we systemically investigated the influence of various anodization parameters on the formation and structure of Ni-Ti-O NTAs and their potential applications. Our results show that well controlled NTAs can be fabricated during relatively wide ranges of the anodization voltage (5–90 V), electrolyte temperature (10–50°C) and electrolyte NH4F content (0.025–0.8 wt%) but within a narrow window of the electrolyte H2O content (0.0–1.0 vol%). Through modulating these parameters, the Ni-Ti-O NTAs with different diameter (15–70 nm) and length (45–1320 nm) can be produced in a controlled manner. Regarding potential applications, the Ni-Ti-O NTAs may be used as electrodes for electrochemical energy storage and non-enzymic glucose detection, and may constitute nanoscaled biofunctional coating to improve the biological performance of NiTi based biomedical implants. PMID:25520180

Electrode effects on temporal changes in electrolyte pH and redox potential for water treatment

PubMed Central

Ciblak, Ali; Mao, Xuhui; Padilla, Ingrid; Vesper, Dorothy; Alshawabkeh, Iyad; Alshawabkeh, Akram N.

2012-01-01

The performance of electrochemical remediation methods could be optimized by controlling the physicochemical conditions of the electrochemical redox system. The effects of anode type (reactive or inert), current density and electrolyte composition on the temporal changes in pH and redox potential of the electrolyte were evaluated in divided and mixed electrolytes. Two types of electrodes were used: iron as a reactive electrode and mixed metal oxide coated titanium (MMO) as an inert electrode. Electric currents of 15, 30, 45 and 60 mA (37.5 mA L−1, 75 mA L−1, 112.5 mA L−1 and 150 mA L−1) were applied. Solutions of NaCl, Na2SO4 and NaHCO3 were selected to mimic different wastewater or groundwater composition. Iron anodes resulted in highly reducing electrolyte conditions compared to inert anodes. Electrolyte pH was dependent on electrode type, electrolyte composition and current density. The pH of mixed-electrolyte was stable when MMO electrodes were used. When iron electrodes were used, the pH of electrolyte with relatively low current density (37.5 mA L−1) did not show significant changes but the pH increased sharply for relatively high current density (150 mA L−1). Sulfate solution showed more basic and relatively more reducing electrolyte condition compared to bicarbonate and chloride solution. The study shows that a highly reducing environment could be achieved using iron anodes in divided or mixed electrolytes and the pH and redox potential could be optimized by using appropriate current and polarity reversal. PMID:22416866

Varying Radii of On-Axis Anode Hollows For kJ-Class Dense Plasma Focus

NASA Astrophysics Data System (ADS)

Shaw, Brian; Chapman, Steven; Falabella, Steven; Pankin, Alexei; Liu, Jason; Link, Anthony; Schmidt, Andréa

2017-10-01

A dense plasma focus (DPF) is a compact plasma gun that produces high energy ion beams, up to several MeV, through strong potential gradients. Motivated by particle-in-cell simulations, we have tried a series of hollow anodes on our kJ-class DPF. Each anode has varying hollow sizes, and has been studied to optimize ion beam production in Helium, reduce anode sputter, and increase neutron yields in deuterium. We diagnose the rate at which electrode material is ablated and deposited onto nearby surfaces. This is of interest in the case of solid targets, which perform poorly in the presence of sputter. We have found that the larger the hollow radius produces more energetic ion beams, higher neutron yield, and sputter less than a flat top anode. A complete comparison is presented. This work was prepared by LLNL under Contract DE-AC52-07NA27344 and supported by Office of Defense Nuclear Nonproliferation Research and Development within U.S. Department of Energy's National Nuclear Security Administration.

Tailored Organic Electrode Material Compatible with Sulfide Electrolyte for Stable All-Solid-State Sodium Batteries.

PubMed

Chi, Xiaowei; Liang, Yanliang; Hao, Fang; Zhang, Ye; Whiteley, Justin; Dong, Hui; Hu, Pu; Lee, Sehee; Yao, Yan

2018-03-01

All-solid-state sodium batteries (ASSSBs) with nonflammable electrolytes and ubiquitous sodium resource are a promising solution to the safety and cost concerns for lithium-ion batteries. However, the intrinsic mismatch between low anodic decomposition potential of superionic sulfide electrolytes and high operating potentials of sodium-ion cathodes leads to a volatile cathode-electrolyte interface and undesirable cell performance. Here we report a high-capacity organic cathode, Na 4 C 6 O 6 , that is chemically and electrochemically compatible with sulfide electrolytes. A bulk-type ASSSB shows high specific capacity (184 mAh g -1 ) and one of the highest specific energies (395 Wh kg -1 ) among intercalation compound-based ASSSBs. The capacity retentions of 76 % after 100 cycles at 0.1 C and 70 % after 400 cycles at 0.2 C represent the record stability for ASSSBs. Additionally, Na 4 C 6 O 6 functions as a capable anode material, enabling a symmetric all-organic ASSSB with Na 4 C 6 O 6 as both cathode and anode materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

MoTe2, A novel anode material for sodium ion battery

NASA Astrophysics Data System (ADS)

Panda, Manas Ranjan; Anish Raj, K.; Bao, Qiaoliang; Mitra, Sagar

2018-04-01

2D layered transition metal dichalcogenides are considered as a potential anode for sodium-ion batteries due to their high specific capacity, structural stability and its well-developed two-dimensional layers. 2D layered structure Molybdenum ditelluride (MoTe2) provides a superior Na-ion storage properties in sodium ion battery due to its comparative more interlayer spacing (0.699 nm). In the current study MoTe2 polycrystalline powder sample has been prepared by solid state reaction process, the structural and morphological studies have been carried out by XRD, FE-SEM and EDS etc. XRD study revealsthe well crystalline structure of the material having hexagonal structure. FE-SEM and EDS studies depict the uniformflakes like structure of the material. When it is tested as sodium-ion battery anode by applying a potential window 0.1-2.5 V, the material demonstrates a high capacity and high power performances. The as prepared MoTe2 shows an initial discharge capacity of 376 mA h g-1 and a corresponding discharge capacity of 303 mA h g-1 after the 50th cycle at a current density of 500 mA g-1.

Diversity of microbes and potential exoelectrogenic bacteria on anode surface in microbial fuel cells.

PubMed

Sun, Yujiao; Zuo, Jiane; Cui, Longtao; Deng, Qian; Dang, Yan

2010-02-01

Single-chamber microbial fuel cells (MFCs), inoculated with anaerobic sludge and continuously run with two kinds of organic wastewater influents, were systemically investigated. The diversity of microbes, determined by 16S rDNA analysis, was analyzed on three anodes under different conditions. One anode was in a closed circuit in synthetic wastewater containing glucose. The other two anodes, in open or closed circuits, were fed effluent from an anaerobic reactor treating starch wastewater. The chemical oxygen demand (COD) removal efficiency was about 70%, and the exported voltages were about 450 mV. The 16S rDNA molecular clones of microbes on anode surfaces showed significant changes in Eubacterial structure under different conditions. gamma-Proteobacteria and the high G+C gram-positive groups were predominant in the synthetic wastewater, while epsilon-Proteobacteria predominated in the anaerobic reactor effluent. Known exoelectrogenic bacterial species composition also changed greatly depending on substrate. On the artificial substrate, 28% of the bacterial sequences were affiliated with Aeromonas, Pseudomonas, Geobacter, and Desulfobulbus. On the anaerobic effluent, only 6% were affiliated with Geobacter or Clostridium. Because only a few exoelectrogenic bacteria from MFCs have been directly isolated and studied, we compared the community structures of two bacterial anodes, in open and closed circuits, under the same substrate of anaerobic effluent in order to identify additional exoelectrogenic bacterial strains. Alcaligenes monasteriensis, Comamonas denitrificans, and Dechloromonas sp. were found to be potential exoelectrogenic bacteria worthy of further research.

Particle-In-Cell Simulations of a Thermionic Converter

NASA Astrophysics Data System (ADS)

Clark, S. E.

2017-12-01

Simulations of thermionic converters are presented where cesium is used as a work function reducing agent in a nano-fabricated triode configuration. The cathode and anode are spaced on the order of 100 μm, and the grid structure has features on the micron scale near the anode. The hot side is operated near 1600 K, the cold side near 600 K, and the converter has the potential to convert heat to DC electrical current upwards of 20% efficiency. Affordable and robust thermionic converters have the potential to displace century old mechanical engines and turbines as a primary means of electrical power generation in the near future. High efficiency converters that operate at a small scale could be used to generate power locally and alleviate the need for large scale power transmission systems. Electron and negative cesium ion back emission from the anode are considered, as well as device longevity and fabrication feasibility.

Particle-In-Cell Simulations of a Thermionic Converter

NASA Astrophysics Data System (ADS)

Clark, Stephen

2017-10-01

Simulations of thermionic converters are presented where cesium is used as a work function reducing agent in a nano-fabricated triode configuration. The cathode and anode are spaced on the order of 100 μm, and the grid structure has features on the micron scale near the anode. The hot side is operated near 1600 K, the cold side near 600 K, and the converter has the potential to convert heat to DC electrical current upwards of 20% efficiency. Affordable and robust thermionic converters have the potential to displace century old mechanical engines and turbines as a primary means of electrical power generation in the near future. High efficiency converters that operate at a small scale could be used to generate power locally and alleviate the need for large scale power transmission systems. Electron and negative cesium ion back emission from the anode are considered, as well as device longevity and fabrication feasibility.

Uniform Li deposition regulated via three-dimensional polyvinyl alcohol nanofiber networks for effective Li metal anodes.

PubMed

Wang, Gang; Xiong, Xunhui; Lin, Zhihua; Zheng, Jie; Fenghua, Zheng; Li, Youpeng; Liu, Yanzhen; Yang, Chenghao; Tang, Yiwei; Liu, Meilin

2018-05-31

Lithium metal anodes are considered to be the most promising anode material for next-generation advanced energy storage devices due to their high reversible capacity and extremely low anode potential. Nevertheless, the formation of dendritic Li, induced by the repeated breaking and repairing of solid electrolyte interphase layers, always causes poor cycling performance and low coulombic efficiency, as well as serious safety problems, which have hindered the practical application of Li anodes for a long time. Herein, we design an electrode by covering a polyvinyl alcohol layer with a three-dimensional nanofiber network structure through an electrospinning technique. The polar functional groups on the surface of the polymer nanofibers can restrict the deposition of Li along the fibers and regulate the deposition of Li uniformly in the voids between the nanofibers. Owing to the structural features of the polymer, the modified Li|Cu electrode displays excellent cycle stability, with a high coulombic efficiency of 98.6% after 200 cycles at a current density of 1 mA cm-2 under a deposition capacity of 1 mA h cm-2, whilst the symmetric cell using the polymer modified Li anode shows stable cycling with a low hysteresis voltage of ∼80 mV over 600 h at a current density of 5 mA cm-2.

ELECTROCHEMICAL DEGRADATION OF ORGANIC CONTAMINANTS IN WATER AND SEDIMENTS

EPA Science Inventory

Electrochemical degradation (ECD) utilizes high redox potential at the anode and low redox potential at the cathode to oxidize and/or reduce organic and inorganic contaminants. EDC of Trichloroethylene (TCE), although theoretically possible, has not been experimentally proven. Th...

Probing anode degradation in automotive Li-ion batteries

NASA Astrophysics Data System (ADS)

Kwon, Ou Jung

The lithium-ion battery is drawing attention as a power source for future clean and fuel-efficient vehicles. Although the Li-ion battery presently shows best performance for energy density and power density compared to other rechargeable batteries, some degradation problems still remain as key challenges for long-term durability in automotive applications. Among those problems, Li deposition is well known for causing permanent capacity loss. Fundamental mechanisms of Li deposition in the carbon anode are, however, not fully understood, especially at subzero temperature and/or under high rate charge. This dissertation introduces comprehensive study of Li deposition using automotive 18650 Li-ion cells. The mechanism and relevant diagnostic methods as well as preventive charging protocol are discussed. In part one, a new diagnostic tool is introduced utilizing 3-electrode cell system, which measures thermodynamic and kinetic parameters of cathode and anode, respectively, as a function of temperature and SOC (state of charge): open circuit potential (OCP); Li diffusion coefficient in active particles; and internal resistance. These data are employed to understand electrochemical reaction and its thermal interaction under charging conditions that result in Li deposition. Part two provides a threshold parameter for the onset of Li deposition, which is not commonly used anode potential but charge capacity, or more specifically the amount of Li+ ions participating in intercalation reaction without Li deposition at given charging circumstances. This is called the critical charge capacity in this thesis, beyond which capacity loss at normal operating condition is observed, which becomes more serious as temperature is lowered and/or charge C-rate increases. Based on these experimental results, the mechanism of Li deposition is proposed as the concept of anode particle surface saturation, meaning that once the anode particle surface is saturated with Li in any charging circumstances, no more Li+ ions can be intercalated but should be reduced to metallic form on the anode particle surface. This is validated by calculating the distribution of Li concentration inside the anode particle with electrochemical modeling. In part three, a novel pulse charge protocol is developed, which consists of two steps. First high current charge/discharge pulses increase the cell temperature from a subzero temperature up to above room temperature in a short time, and next, high current charge provides the net charge capacity. Sluggish Li diffusion at low temperature becomes fast thanks to cell temperature elevation by high current pulses (1st step), which plays a role of preventing surface saturation during high current charge (2nd step). Thus, this charge protocol is not only Li deposition-free but also leads to rapid charge at subzero temperatures.

Mechanism of p-substituted phenol oxidation at a Ti4O7 reactive electrochemical membrane.

PubMed

Zaky, Amr M; Chaplin, Brian P

2014-05-20

This research investigated the removal mechanisms of p-nitrophenol, p-methoxyphenol, and p-benzoquinone at a porous Ti4O7 reactive electrochemical membrane (REM) under anodic polarization. Cross-flow filtration experiments and density functional theory (DFT) calculations indicated that p-benzoquinone removal was primarily due to reaction with electrochemically formed OH(•), while the dominant removal mechanism of p-nitrophenol and p-methoxyphenol was a function of the anodic potential. At low anodic potentials (1.7-1.8 V/SHE), p-nitrophenol and p-methoxyphenol were removed primarily by an electrochemical adsorption/polymerization mechanism on the REM. Increasing anodic potentials (1.9-3.2 V/SHE) resulted in the electroassisted adsorption mechanism contributing far less to p-methoxyphenol removal compared to p-nitrophenol. DFT calculations indicated that an increase in anodic potential resulted in a shift in p-methoxyphenol removal from a 1e(-) direct electron transfer (DET) reaction that resulted in radical formation and significant adsorption/polymerization, to a 2e(-) DET reaction that formed nonadsorbing products (i.e., p-benzoquinone). However, the anodic potentials were too low for the 2e(-) DET reaction to be thermodynamically favorable for p-nitrophenol. The decreased COD adsorption for p-nitrophenol at higher anodic potentials was attributed to reaction of soluble/adsorbed organics with OH(•). These results provide the first mechanistic explanation for p-substituted phenolic compound removal during advanced electrochemical oxidation processes.

Nernst-ping-pong model for evaluating the effects of the substrate concentration and anode potential on the kinetic characteristics of bioanode.

PubMed

Peng, Sikan; Liang, Da-Wei; Diao, Peng; Liu, Yanyan; Lan, Fei; Yang, Yuhan; Lu, Shanfu; Xiang, Yan

2013-05-01

Understanding the electron-transfer mechanism and kinetic characteristics of bioanodes is greatly significant to enhance the electron-generating efficiencies in bioelectrochemical systems (BESs). A Nernst-ping-pong model is proposed here to investigate the kinetics and biochemical processes of bioanodes in a microbial electrolysis cell. This model can accurately describe the effects of the substrate (including substrate inhibition) and the anode potential on the current of bioanodes. Results show that the half-wave potential positively shifts as the substrate concentration increases, indicating that the rate-determining steps of anodic processes change from substrate oxidation to intracellular electron transport reaction. The anode potential has negligible effects on the enzymatic catalysis of anodic microbes in the range of -0.25 V to +0.1 V vs. a saturated calomel electrode. It turns out that to reduce the anodic energy loss caused by overpotential, higher substrate concentrations are preferred, if the substrate do not significantly and adversely affect the output current. Copyright © 2013 Elsevier Ltd. All rights reserved.

High-speed MCP anodes for high time resolution low-energy charged particle spectrometers

NASA Astrophysics Data System (ADS)

Saito, Yoshifumi; Yokota, Shoichiro; Asamura, Kazushi; Krieger, Amanda

2017-02-01

The time resolution of low-energy charged particle measurements is becoming higher and higher. In order to realize high time resolution measurements, a 1-D circular delay line anode has been developed as a high-speed microchannel plate (MCP) anode. The maximum count rate of the 1-D circular delay line anode is around 1 × 107/s/360°, which is much higher than the widely used resistive anode, whose maximum count rate is around 1 × 106/s/360°. In order to achieve much higher speeds, an MCP anode with application-specific integrated circuit (ASIC) has been developed. We have decided to adopt an anode configuration in which a discrete anode is formed on a ceramic substrate, and a bare ASIC chip is installed on the back of the ceramic. It has been found that the anode can detect at a high count rate of 2 × 108/s/360°. Developments in both delay line and discrete anodes, as well as readout electronics, will be reviewed.

Microgap x-ray detector

DOEpatents

Wuest, Craig R.; Bionta, Richard M.; Ables, Elden

1994-01-01

An x-ray detector which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope.

Detector arrays for photometric measurements at soft X-ray, ultraviolet and visible wavelengths

NASA Technical Reports Server (NTRS)

Timothy, J. G.; Mount, G. H.; Bybee, R. L.

1979-01-01

The construction and modes of operation of the Multi-Anode Microchannel Array (MAMA) detectors are described, and the designs of spectrometers utilizing them are outlined. MAMA consists of a curved microchannel array plate, an opaque photocathode (peak quantum efficiency of 19% at 1216 A), and a multi-anode (either discrete- or coincidence-anode) readout array. Designed for use in instruments on spaceborne telescopes, MAMA can be operated in a windowless configuration in extreme-ultraviolet and soft X-ray wavelengths, or in a sealed configuration at UV and visible wavelengths. Advantages of MAMA include low applied potential (less than 3.0 kV), high gain (greater than 10 to the 6th electrons/pulse), low sensitivity to high-energy charged particles, and immunity to external magnetic fields of less than 500 Gauss

Microgap x-ray detector

DOEpatents

Wuest, C.R.; Bionta, R.M.; Ables, E.

1994-05-03

An x-ray detector is disclosed which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope. 3 figures.

Three-dimensional graphene foam supported Fe₃O₄ lithium battery anodes with long cycle life and high rate capability.

PubMed

Luo, Jingshan; Liu, Jilei; Zeng, Zhiyuan; Ng, Chi Fan; Ma, Lingjie; Zhang, Hua; Lin, Jianyi; Shen, Zexiang; Fan, Hong Jin

2013-01-01

Fe3O4 has long been regarded as a promising anode material for lithium ion battery due to its high theoretical capacity, earth abundance, low cost, and nontoxic properties. However, up to now no effective and scalable method has been realized to overcome the bottleneck of poor cyclability and low rate capability. In this article, we report a bottom-up strategy assisted by atomic layer deposition to graft bicontinuous mesoporous nanostructure Fe3O4 onto three-dimensional graphene foams and directly use the composite as the lithium ion battery anode. This electrode exhibits high reversible capacity and fast charging and discharging capability. A high capacity of 785 mAh/g is achieved at 1C rate and is maintained without decay up to 500 cycles. Moreover, the rate of up to 60C is also demonstrated, rendering a fast discharge potential. To our knowledge, this is the best reported rate performance for Fe3O4 in lithium ion battery to date.

High capacity and stable all-solid-state Li ion battery using SnO2-embedded nanoporous carbon.

PubMed

Notohara, Hiroo; Urita, Koki; Yamamura, Hideyuki; Moriguchi, Isamu

2018-06-08

Extensive research efforts are devoted to development of high performance all-solid-state lithium ion batteries owing to their potential in not only improving safety but also achieving high stability and high capacity. However, conventional approaches based on a fabrication of highly dense electrode and solid electrolyte layers and their close contact interface is not always applicable to high capacity alloy- and/or conversion-based active materials such as SnO 2 accompanied with large volume change in charging-discharging. The present work demonstrates that SnO 2 -embedded nanoporous carbons without solid electrolyte inside the nanopores are a promising candidate for high capacity and stable anode material of all-solid-state battery, in which the volume change reactions are restricted in the nanopores to keep the constant electrode volume. A prototype all-solid-state full cell consisting of the SnO 2 -based anode and a LiNi 1/3 Co 1 / 3 Mn 1/3 O 2 -based cathode shows a good performance of 2040 Wh/kg at 268.6 W/kg based on the anode material weight.

Thin film integrated capacitors with sputtered-anodized niobium pentoxide dielectric for decoupling applications

NASA Astrophysics Data System (ADS)

Jacob, Susan

Electronics system miniaturization is a major driver for high-k materials. High-k materials in capacitors allow for high capacitance, enabling system miniaturization. Ta2O5 (k˜24) has been the dominant high-k material in the electronic industry for decoupling capacitors, filter capacitors, etc. In order to facilitate further system miniaturization, this project has investigated thin film integrated capacitors with Nb2O5 dielectric. Nb2O 5 has k˜41 and is a potential candidate for replacing Ta2O5. But, the presence of suboxides (NbO2 and NbO) in the dielectric deteriorates the electrical properties (leakage current, thermal instability of capacitance, etc.). Also, the high oxygen solubility of niobium results in oxygen diffusion from the dielectric to niobium metal, if any is present. The major purpose of this project was to check the ability of NbN as a diffusion barrier and fabricate thermally stable niobium capacitors. As a first step to produce niobium capacitors, the material characterizations of reactively sputtered Nb2O5 and NbN were done. Thickness and film composition, and crystal structures of the sputtered films were obtained and the deposition parameters for the desired stoichiometry were found. Also, anodized Nb2O5 was characterized for its stoichiometry and thickness. To study the effect of nitrides on capacitance and thermal stability, Ta2O5 capacitors were initially fabricated with and without TaN. The results showed that the nitride does not affect the capacitance, and that capacitors with TaN are stable up to 150°C. In the next step, niobium capacitors were first fabricated with anodized dielectric and the oxygen diffusion issues associated with capacitor processing were studied. Reactively sputtered Nb2O5 was anodized to form complete Nb2O5 (with few oxygen vacancies) and NbN was used to sandwich the dielectric. The capacitor fabrication was not successful due to the difficulties in anodizing the sputtered dielectric. Another method, anodizing reactively sputtered Nb2O5 and a thin layer of sputtered niobium metal yielded high yield (99%) capacitors. Capacitors were fabricated with and without NbN and the results showed 93% decrease in leakage for a capacitor with ˜2000 A dielectric when NbN was present in the structure. These capacitors could withstand 20 V and showed 2.7 muA leakage current at 5 V. These results were obtained after thermal storage at 100°C and 150°C in air for 168 hours at each temperature. Two set of experiments were performed using Ta2O5 dielectric: one to determine the effect of anodization end point on the thickness (capacitance) and the second to determine the effect of boiling the dielectric on functional yield. The anodization end point experiment showed that the final current of anodization along with the anodizing voltage determines the anodic oxide thickness. The lower the current, the thicker the films produced by anodization. Therefore, it was important to specify the final current along with the anodization voltage for oxide growth rate. The capacitors formed with boiled wafers showed better functional yield 3 out of 5 times compared with the unboiled wafer. Niobium anodization was studied for the Nb--->Nb 2O5 conversion ratio and the effect of anodization bath temperature on the oxide film; a color chart was prepared for thicknesses ranging from 1900 A - 5000 A. The niobium metal to oxide conversion ratio was found to change with temperature.

Influence of anodizing conditions on generation of internal cracks in anodic porous tin oxide films grown in NaOH electrolyte

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Gawlak, Karolina; Gurgul, Magdalena; Dziurka, Magdalena; Nowak, Marlena; Gilek, Dominika; Sulka, Grzegorz D.

2018-05-01

Nanoporous tin oxide layers were synthesized via simple one-step anodic oxidation of a low-purity Sn foil (98.8%) in sodium hydroxide electrolyte. The process of pore formation at the early stage of anodization was discussed on the basis of concepts of oxygen bubble mould effect and viscous flow of oxide. The effect of anodizing conditions on the generation of internal cracks and fractures within the anodic film was investigated in detail. It was confirmed that crack-free tin oxide films can be obtained if the anodization is carried out at the potential of 4 V independently of the electrolyte concentration. On the other hand, the porous anodic film with a totally stacked internal morphology is obtained at the potential of 5 V in 0.1 M NaOH electrolyte. The generation of internal cracks and voids can be attributed to a much lower surface porosity and local trapping of O2 inside the pores of the oxide layer. However, increasing electrolyte concentration allows for obtaining less cracked porous films due to effective and uniform liberation of oxygen bubbles from the channels through completely open pore mouths. Furthermore, it was confirmed that uniformity of the anodic tin oxide layers can be significantly improved by vigorous electrolyte stirring. Finally, we observed that the addition of ethanol to the electrolyte can reduce anodic current density and the oxide growth rate. In consequence, less cracked anodic film can be formed even at the potential of 6 V. The generation of oxygen at the pore bottoms, together with the open pore mouths were found to be critical factors responsible for the anodic formation of crack-free porous tin oxide films.

A miniature microbial fuel cell with conducting nanofibers-based 3D porous biofilm

NASA Astrophysics Data System (ADS)

Jiang, Huawei; Halverson, Larry J.; Dong, Liang

2015-12-01

Miniature microbial fuel cell (MFC) technology has received growing interest due to its potential applications in high-throughput screening of bacteria and mutants to elucidate mechanisms of electricity generation. This paper reports a novel miniature MFC with an improved output power density and short startup time, utilizing electrospun conducting poly(3,4-ethylenedioxythiophene) (PEDOT) nanofibers as a 3D porous anode within a 12 μl anolyte chamber. This device results in 423 μW cm-3 power density based on the volume of the anolyte chamber, using Shewanella oneidensis MR-1 as a model biocatalyst without any optimization of bacterial culture. The device also excels in a startup time of only 1hr. The high conductivity of the electrospun nanofibers makes them suitable for efficient electron transfer. The mean pore size of the conducting nanofibers is several micrometers, which is favorable for bacterial penetration and colonization of surfaces of the nanofibers. We demonstrate that S. oneidensis can fully colonize the interior region of this nanofibers-based porous anode. This work represents a new attempt to explore the use of electrospun PEDOT nanofibers as a 3D anode material for MFCs. The presented miniature MFC potentially will provide a high-sensitivity, high-throughput tool to screen suitable bacterial species and mutant strains for use in large-size MFCs.

Lithium rich cathode/graphite anode combination for lithium ion cells with high tolerance to near zero volt storage

NASA Astrophysics Data System (ADS)

Crompton, K. R.; Staub, J. W.; Hladky, M. P.; Landi, B. J.

2017-03-01

Management of reversible lithium is an advantageous approach to design lithium ion cells that are tolerant to near zero volt (NZV) storage under fixed resistive load towards highly controllable, enhanced user-inactive safety. Presently, the first cycle loss from a high energy density Li-rich HE5050 cathode is used to provide excess reversible lithium when paired with an appropriately capacity matched mesocarbon microbead (MCMB) anode. Cells utilizing 1.2 M LiPF6 3:7 v/v ethylene carbonate:ethyl methyl carbonate electrolyte and a lithium reference were used for 3-electrode testing. After conditioning, a fixed resistive load was applied to 3-electrode cells for 72 or 168-h during which the anode potential and electrode asymptotic potential (EAP) remained less than the copper dissolution potential. After multiple storage cycles (room temperature or 40 °C), the NZV coulombic efficiency (cell reversibility) exceeded 97% and the discharge capacity retention was >98%. Conventional 2-electrode HE5050/MCMB pouch cells stored at NZV or open circuit for 3 days had nearly identical rate capability (up to 5C) and discharge performance stability (for 500 cycles under a 30% depth of discharge low-earth-orbit regime). Thus, lithium ion cells with appropriately capacity matched HE5050/MCMB electrodes have excellent tolerance to prolonged NZV storage, which can lead to enhanced user-inactive safety.

X-ray reflectivity study of formation of multilayer porous anodic oxides of silicon.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, Y.; Fenollosa, R.; Parkhutik, V.

1999-07-21

The paper reports data on the kinetics of anodic oxide films growth on silicon in aqueous solutions of phosphoric acids as well as a study of the morphology of the oxides grown in a special regime of the oscillating anodic potential. X-ray reflectivity measurements were performed on the samples of anodic oxides using an intense synchrotron radiation source. They have a multilayer structure as revealed by theoretical fitting of the reflectivity data. The oscillations of the anodic potential are explained in terms of synchronized oxidation/dissolution reactions at the silicon surface and accumulation of mechanic stress in the oxide film.

Optimization and Domestic Sourcing of Lithium Ion Battery Anode Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, III, D. L.; Yoon, S.

2012-10-25

The purpose of this Cooperative Research and Development Agreement (CRADA) between ORNL and A123Systems, Inc. was to develop a low-temperature heat treatment process for natural graphite based anode materials for high-capacity and long-cycle-life lithium ion batteries. Three major problems currently plague state-of-the-art lithium ion battery anode materials. The first is the cost of the artificial graphite, which is heat-treated well in excess of 2000°C. Because of this high-temperature heat treatment, the anode active material significantly contributes to the cost of a lithium ion battery. The second problem is the limited specific capacity of state-of-the-art anodes based on artificial graphites, whichmore » is only about 200-350 mAh/g. This value needs to be increased to achieve high energy density when used with the low cell-voltage nanoparticle LiFePO4 cathode. Thirdly, the rate capability under cycling conditions of natural graphite based materials must be improved to match that of the nanoparticle LiFePO4. Natural graphite materials contain inherent crystallinity and lithium intercalation activity. They hold particular appeal, as they offer huge potential for industrial energy savings with the energy costs essentially subsidized by geological processes. Natural graphites have been heat-treated to a substantially lower temperature (as low as 1000-1500°C) and used as anode active materials to address the problems described above. Finally, corresponding graphitization and post-treatment processes were developed that are amenable to scaling to automotive quantities.« less

Measurement of the surface charge accumulation using anodic aluminum oxide(AAO) structure in an inductively coupled plasma

NASA Astrophysics Data System (ADS)

Park, Ji-Hwan; Oh, Seung-Ju; Lee, Hyo-Chang; Kim, Yu-Sin; Kim, Young-Cheol; Kim, June Young; Ha, Chang-Seoung; Kwon, Soon-Ho; Lee, Jung-Joong; Chung, Chin-Wook

2014-10-01

As the critical dimension of the nano-device shrinks, an undesired etch profile occurs during plasma etch process. One of the reasons is the local electric field due to the surface charge accumulation. To demonstrate the surface charge accumulation, an anodic aluminum oxide (AAO) membrane which has high aspect ratio is used. The potential difference between top electrode and bottom electrode in an anodic aluminum oxide contact structure is measured during inductively coupled plasma exposure. The voltage difference is changed with external discharge conditions, such as gas pressure, input power, and gas species and the result is analyzed with the measured plasma parameters.

Anode property of carbon coated LiFePO4 nanocrystals

NASA Astrophysics Data System (ADS)

Ni, Jiangfeng; Jiang, Jiaxing; Savilov, S. V.; Aldoshin, S. M.

2016-10-01

Nanostructured LiFePO4 is appealing cathode material for rechargeable lithium batteries. Herein, however, we report the intriguing anode properties of carbon coated LiFePO4 nanocrystals. In the potential range of 0-3.0 V, the LiFePO4 nanocrystal electrodes afford high reversible capacity of 373 mAhg-1 at a current rate of 0.05 Ag-1 and retains 239 mAhg-1 at a much higher rate of 1.25 Ag-1. In addition, it is capable of sustaining 1000 cycles at 1.25 Ag-1 without any capacity fading. Such superior properties indicate that nanostructured LiFePO4 could also be promising anode for rechargeable battery applications.

Simulation study on AlGaN/GaN diode with Γ-shaped anode for ultra-low turn-on voltage

NASA Astrophysics Data System (ADS)

Wang, Zeheng; Chen, Wanjun; Wang, Fangzhou; Cao, Jun; Sun, Ruize; Ren, Kailin; Luo, Yi; Guo, Songnan; Wang, Zirui; Jin, Xiaosheng; Yang, Lei; Zhang, Bo

2018-05-01

An ultra-low turn-on voltage (VT) Γ-shaped anode AlGaN/GaN Schottky barrier diode (GA-SBD) is proposed via modeling and simulation for the first time, in which a Γ-shaped anode consists of a metal-2DEG junction together with a metal-AlGaN junction beside a shallowly recessed MIS field plate (MFP). An analytic forward current-voltage model matching the simulation results well is presented where an ultra-low VT of 0.08 V is obtained. The turn-on and blocking mechanisms are investigated to reveal the GA-SBD's great potential for applications of highly efficient power ICs.

Contribution of the backstreaming ions to the Self-Magnetic pinch (SMP) diode current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazarakis, Michael G.; Cuneo, Michael E.; Fournier, Sean D.

2016-08-08

Summary form only given. The results presented here were obtained with an SMP diode mounted at the front high voltage end of the RITS accelerator. RITS is a Self-Magnetically Insulated Transmission Line (MITL) voltage adder that adds the voltage pulses of six 1.3 MV inductively insulated cavities. Our experiments had two objectives: first to measure the contribution of the back-streaming ion currents emitted from the anode target to the diode beam current, and second to try to evaluate the energy of those ions and hence the actual Anode-Cathode (A-K) gap actual voltage. In any very high voltage inductive voltage addermore » (IVA) utilizing MITLs to transmit the power to the diode load, the precise knowledge of the accelerating voltage applied on the anode-cathode (A-K) gap is problematic. The accelerating voltage quoted in the literature is from estimates based on measurements of the anode and cathode currents of the MITL far upstream from the diode and utilizing the para-potential flow theories and inductive corrections. Thus it would be interesting to have another independent measurement to evaluate the A-K voltage. The diode's anode is made of a number of high Z metals in order to produce copious and energetic flash x-rays. The backstreaming currents are a strong fraction of the anode materials and their stage of cleanness and gas adsorption. We have measured the back-streaming ion currents emitted from the anode and propagating through a hollow cathode tip for various diode configurations and different techniques of target cleaning treatments, such as heating to very high temperatures with DC and pulsed current, with RF plasma cleaning and with both plasma cleaning and heating. Finally, we have also evaluated the A-K gap voltage by ion filtering techniques.« less

Novel iron oxide nanotube arrays as high-performance anodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Zhong, Yuan; Fan, Huiqing; Chang, Ling; Shao, Haibo; Wang, Jianming; Zhang, Jianqing; Cao, Chu-nan

2015-11-01

Nanostructured iron oxides can be promising anode materials for lithium ion batteries (LIBs). However, improvement on the rate capability and/or electrochemical cycling stability of iron oxide anode materials remains a key challenge because of their poor electrical conductivities and large volume expansion during cycling. Herein, the vertically aligned arrays of one-dimensional (1D) iron oxide nanotubes with 5.8 wt% carbon have been fabricated by a novel surfactant-free self-corrosion process and subsequent thermal treatment. The as-fabricated nanotube array electrode delivers a reversible capacity of 932 mAh g-1 after 50 charge-discharge cycles at a current of 0.6 A g-1. The electrode still shows a reversible capacity of 610 mAh g-1 even at a very high rate (8.0 A g-1), demonstrating its prominent rate capability. Furthermore, the nanotube array electrode also exhibits the excellent electrochemical cycling stability with a reversible capacity of 880 mAh g-1 after 500 cycles at a current of 4 A g-1. The nanotube array electrode with superior lithium storage performance reveals the promising potential as a high-performance anode for LIBs.

Characteristics from Recycled of Zinc Anode used as a Corrosion Preventing Material on Board Ship

NASA Astrophysics Data System (ADS)

Barokah, B.; Semin, S.; Kaligis, D. D.; Huwae, J.; Fanani, M. Z.; Rompas, P. T. D.

2018-02-01

The objective of this research is to obtain the values of chemical composition, electrochemical potential and electrochemical efficiency. Methods used were experiment with physical tests conducted in metallurgical laboratory and DNV-RP-B401 cathode protection design DNV (Det Norske Veritas) standard. The results showed that the composition of chemical as Zinc (Zn), Aluminium, Cadmium, Plumbumb, Copper and Indium is suitable of standard. The values of electrochemical potential and electrochemical efficiency were respectively. However it can be concluded that the normal meaning of recycled zinc anode with increasing melting temperature can produce zinc anode better than original zinc anode and can be used as cathode protection on board ships. This research can assist in the management of used zinc anode waste, the supply of zinc anodes for consumers at relatively low prices, and recommendations of using zinc anodes for the prevention of corrosion on board ship.

Nanostructured silicon anodes for lithium ion rechargeable batteries.

PubMed

Teki, Ranganath; Datta, Moni K; Krishnan, Rahul; Parker, Thomas C; Lu, Toh-Ming; Kumta, Prashant N; Koratkar, Nikhil

2009-10-01

Rechargeable lithium ion batteries are integral to today's information-rich, mobile society. Currently they are one of the most popular types of battery used in portable electronics because of their high energy density and flexible design. Despite their increasing use at the present time, there is great continued commercial interest in developing new and improved electrode materials for lithium ion batteries that would lead to dramatically higher energy capacity and longer cycle life. Silicon is one of the most promising anode materials because it has the highest known theoretical charge capacity and is the second most abundant element on earth. However, silicon anodes have limited applications because of the huge volume change associated with the insertion and extraction of lithium. This causes cracking and pulverization of the anode, which leads to a loss of electrical contact and eventual fading of capacity. Nanostructured silicon anodes, as compared to the previously tested silicon film anodes, can help overcome the above issues. As arrays of silicon nanowires or nanorods, which help accommodate the volume changes, or as nanoscale compliant layers, which increase the stress resilience of silicon films, nanoengineered silicon anodes show potential to enable a new generation of lithium ion batteries with significantly higher reversible charge capacity and longer cycle life.

Generalized alternating stimulation: a novel method to reduce stimulus artifact in electrically evoked compound action potentials.

PubMed

Alvarez, Isaac; de la Torre, Angel; Sainz, Manuel; Roldan, Cristina; Schoesser, Hansjoerg; Spitzer, Philipp

2007-09-15

Stimulus artifact is one of the main limitations when considering electrically evoked compound action potential for clinical applications. Alternating stimulation (average of recordings obtained with anodic-cathodic and cathodic-anodic bipolar stimulation pulses) is an effective method to reduce stimulus artifact when evoked potentials are recorded. In this paper we extend the concept of alternating stimulation by combining anodic-cathodic and cathodic-anodic recordings with a weight in general different to 0.5. We also provide an automatic method to obtain an estimation of the optimal weights. Comparison with conventional alternating, triphasic stimulation and masker-probe paradigm shows that the generalized alternating method improves the quality of electrically evoked compound action potential responses.

Sustainable Interfaces between Si Anodes and Garnet Electrolytes for Room-Temperature Solid-State Batteries.

PubMed

Chen, Cheng; Li, Quan; Li, Yiqiu; Cui, Zhonghui; Guo, Xiangxin; Li, Hong

2018-01-17

Solid-state batteries (SSBs) have seen a resurgence of research interests in recent years for their potential to offer high energy density and excellent safety far beyond current commercialized lithium-ion batteries. The compatibility of Si anodes and Ta-doped Li 7 La 3 Zr 2 O 12 (Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 , LLZTO) solid electrolytes and the stability of the Si anode have been investigated. It is found that Si layer anodes thinner than 180 nm can maintain good contact with the LLZTO plate electrolytes, leading the Li/LLZTO/Si cells to exhibit excellent cycling performance with a capacity retention over 85% after 100 cycles. As the Si layer thickness is increased to larger than 300 nm, the capacity retention of Li/LLZTO/Si cells becomes 77% after 100 cycles. When the thickness is close to 900 nm, the cells can cycle only for a limited number of times because of the destructive volume change at the interfaces. Because of the sustainable Si/LLZTO interfaces with the Si layer anodes with a thickness of 180 nm, full cells with the LiFePO 4 cathodes show discharge capacities of 120 mA h g -1 for LiFePO 4 and 2200 mA h g -1 for the Si anodes at room temperature. They cycle 100 times with a capacity retention of 72%. These results indicate that the combination between the Si anodes and the garnet electrolytes is a promising strategy for constructing high-performance SSBs.

Center-iodized graphene as an advanced anode material to significantly boost the performance of lithium-ion batteries.

PubMed

Chen, Jie; Xu, Mao-Wen; Wu, Jinggao; Li, Chang Ming

2018-05-17

Iodine edge-doped graphene can improve the capacity and stability of lithium-ion batteries (LIBs). Our theoretical calculations indicate that center-iodization can further significantly enhance the anode catalytic process. To experimentally prove the theoretical prediction, iodine-doped graphene materials were prepared by one-pot hydrothermal and ball-milling approaches to realize different doping-sites. Results show that the center-iodinated graphene (CIG) anode exhibits a remarkably high reversible capacity (1121 mA h g-1 after 180 cycles at 0.5 A g-1), long-cycle life (0.01% decay per cycle over 300 cycles at 1 A g-1) and high-rate capacity (374 mA h g-1 after 800 cycles at 8 A g-1), which greatly improves the performance of the edge-iodinated graphene anode and these results are in good agreement with the theoretical analysis. More importantly, the CIG anode also delivers a high-rate capacity and excellent cycling stability (279 mA h g-1 after 500 cycles at 10 A g-1) in full-cells. Both the theoretical analysis and experimental investigation reveal the enhancement mechanism, in which the center-iodization increases the surface charge for fast electron transfer rate, improves the conductivity for charge transport and rationalizes the pore structure for enhanced mass transport and ion insertion/desertion, thus resulting in a high rate capacity and long cycle life. This work not only discloses the critical role of catalytic sites including both amounts and site positions but also offers great potential for high-power rechargeable LIB applications.

Carbon-Confined SnO2-Electrodeposited Porous Carbon Nanofiber Composite as High-Capacity Sodium-Ion Battery Anode Material.

PubMed

Dirican, Mahmut; Lu, Yao; Ge, Yeqian; Yildiz, Ozkan; Zhang, Xiangwu

2015-08-26

Sodium resources are inexpensive and abundant, and hence, sodium-ion batteries are promising alternative to lithium-ion batteries. However, lower energy density and poor cycling stability of current sodium-ion batteries prevent their practical implementation for future smart power grid and stationary storage applications. Tin oxides (SnO2) can be potentially used as a high-capacity anode material for future sodium-ion batteries, and they have the advantages of high sodium storage capacity, high abundance, and low toxicity. However, SnO2-based anodes still cannot be used in practical sodium-ion batteries because they experience large volume changes during repetitive charge and discharge cycles. Such large volume changes lead to severe pulverization of the active material and loss of electrical contact between the SnO2 and carbon conductor, which in turn result in rapid capacity loss during cycling. Here, we introduce a new amorphous carbon-coated SnO2-electrodeposited porous carbon nanofiber (PCNF@SnO2@C) composite that not only has high sodium storage capability, but also maintains its structural integrity while ongoing repetitive cycles. Electrochemical results revealed that this SnO2-containing nanofiber composite anode had excellent electrochemical performance including high-capacity (374 mAh g(-1)), good capacity retention (82.7%), and large Coulombic efficiency (98.9% after 100th cycle).

Scalable 2D Mesoporous Silicon Nanosheets for High-Performance Lithium-Ion Battery Anode.

PubMed

Chen, Song; Chen, Zhuo; Xu, Xingyan; Cao, Chuanbao; Xia, Min; Luo, Yunjun

2018-03-01

Constructing unique mesoporous 2D Si nanostructures to shorten the lithium-ion diffusion pathway, facilitate interfacial charge transfer, and enlarge the electrode-electrolyte interface offers exciting opportunities in future high-performance lithium-ion batteries. However, simultaneous realization of 2D and mesoporous structures for Si material is quite difficult due to its non-van der Waals structure. Here, the coexistence of both mesoporous and 2D ultrathin nanosheets in the Si anodes and considerably high surface area (381.6 m 2 g -1 ) are successfully achieved by a scalable and cost-efficient method. After being encapsulated with the homogeneous carbon layer, the Si/C nanocomposite anodes achieve outstanding reversible capacity, high cycle stability, and excellent rate capability. In particular, the reversible capacity reaches 1072.2 mA h g -1 at 4 A g -1 even after 500 cycles. The obvious enhancements can be attributed to the synergistic effect between the unique 2D mesoporous nanostructure and carbon capsulation. Furthermore, full-cell evaluations indicate that the unique Si/C nanostructures have a great potential in the next-generation lithium-ion battery. These findings not only greatly improve the electrochemical performances of Si anode, but also shine some light on designing the unique nanomaterials for various energy devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sodium storage mechanisms of bismuth in sodium ion batteries: An operando X-ray diffraction study

NASA Astrophysics Data System (ADS)

Gao, Hui; Ma, Wensheng; Yang, Wanfeng; Wang, Jiawei; Niu, Jiazheng; Luo, Fakui; Peng, Zhangquan; Zhang, Zhonghua

2018-03-01

Understanding the sodium (Na) chemistry is crucial for development of high-performance sodium ion batteries (SIBs). Nanostructured bismuth (Bi) has shown great potentials as an anode in SIBs, however, the Na storage mechanisms of Bi are still unclear. Herein, the operando X-ray diffraction (XRD) technique was utilized to probe the Na storage mechanisms of three Bi anodes (sputtered Bi film, nanoporous Bi and commercial Bi). Despite different morphologies and sizes, all the Bi anodes follow the same two-step reversible alloying/dealloying mechanisms (Bi ↔ NaBi ↔ Na3Bi) during the discharge/charge processes, associated with two voltage plateaus. As for the intercalation/deintercalation mechanism proposed for nanostructured Bi anodes in SIBs, we rationalize the reason why only the Bi phase is detected in the discharged/charged samples under ex-situ XRD conditions through addressing the stability issue of the Na-Bi system (NaBi and Na3Bi).

Heat treatment condition of EN AW-7075 influencing the anodic oxidation process and coating properties

NASA Astrophysics Data System (ADS)

Morgenstern, R.; Scharf, I.; Lampke, T.

2018-06-01

The age-hardenable aluminium alloy EN AW-7075 exhibits outstanding specific mechanical properties and therefore offers a high potential for lightweight construction. Anodising in aqueous oxalic acid solutions is suitable to produce a protective oxide ceramic conversion layer on this alloy. This study examines the influence of the precipitation state of the substrate alloy on microstructure and properties of anodic oxide layers. Therefore, EN AW-7075 sheets in the heat treatment conditions T4, T6 and T73 were anodized in 0.8 M oxalic acid solution at constant voltage. The current efficiency was determined on the basis of the electrical charge quantity, coating thickness and coating mass. Instrumented indentation tests were applied in order to evaluate the coating hardness. The microstructure of the anodic oxide layer was illustrated using field emission electron microscopy. It was shown that the current efficiency strongly depends on the heat treatment condition.

Polarization-Induced Interfacial Reactions between Nickel and Selenium in Ni/Zirconia SOFC Anodes and Comparison with Sulfur Poisoning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marina, Olga A.; Pederson, Larry R.; Coyle, Christopher A.

2011-01-10

Three distinctly different characteristic responses of a nickel/yttria-stabilized zirconia (Ni/YSZ) cermet anode to the presence of hydrogen selenide in synthetic coal gas were observed, depending on temperature (650-800oC), H2Se concentration (0-40 ppm), and especially on the extent of anodic polarization (0 to ~0.5 V). The first level of response was characterized by a rapid but modest decrease in power density to a new steady state, with no further degradation observed in tests up to 700 hours in duration. Mostly observed at high temperatures, low H2Se concentrations, and low anodic polarizations, this response level was similar to effects caused by themore » presence of H2S, but with slower onset and lower reversibility. Higher anodic polarization at a constant current could trigger a second level of response characterized by oscillatory behavior involving cycles of rapid performance loss followed by rapid recovery. Oscillations at the constant current density were accompanied by the appearance and disappearance of a new feature in the electrochemical impedance spectrum with a summit frequency of ~100 Hz. Oscillatory behavior ceased when the current density was lowered. Such behavior was not observed for cells operated at a constant potential of similar magnitude, though. A third level of response, irreversible cell failure, could be induced by further increases in anodic polarization, additionally favored by low temperature and high H2Se concentration. Post-test analyses of failed cells by electron microscopy revealed the extensive microstructural changes including the appearance of nickel oxide and nickel selenide alteration phases, only at the anode/electrolyte interface. From bulk thermochemical considerations the formation of nickel selenides could not be expected. Local chemical conditions created at the anode/electrolyte interface appear to be of overriding importance with respect to the extent of Ni/YSZ anode interactions with H2Se in coal gas.« less

High-absorptance high-emittance anodic coating

NASA Technical Reports Server (NTRS)

Le, Huong Giang (Inventor); Chesterfield, John L. (Inventor)

1998-01-01

A colored anodic coating for use on surfaces of substrates, e.g. aluminum substrates in which it is desirable to maintain a high solar absorptance (a) and a high infrared emittance (e), particularly in low earth orbit space environments. This anodic coating is preferably a dark colored coating, and even more preferably a black coating. This coating allows a touch temperature within an acceptable design range to preclude burning of an astronaut in case of contact, but also allows a solar radiation absorption in an amount such that an a/e ratio of unity is achieved. The coating of the invention comprises a first layer in the form of an acid anodized colored anodic layer for achieving a high solar absorptance and a second or high emittance layer in the form of a clear acid anodized layer for achieving a high emittance. The entire coating is quite thin, e.g. 1-2 mils and is quite stable in a hostile space environment of the type encountered in a low earth orbit. The coating is obtained by first creating the high emittance clear anodized coating on the metal surface followed by anodizing using a colored anodizing process.

High-absorptance high-emittance anodic coating

NASA Technical Reports Server (NTRS)

Le, Huong Giang (Inventor); Chesterfield, John L. (Inventor)

1999-01-01

A colored anodic coating for use on surfaces of substrates, e.g. aluminum substrates in which it is desirable to maintain a high solar absorptance (.alpha.) and a high infrared emittance (.epsilon.), particularly in low earth orbit space environments. This anodic coating is preferably a dark colored coating, and even more preferably a black coating. This coating allows a touch temperature within an acceptable design range to preclude burning of an astronaut in case of contact, but also allows a solar radiation absorption in an amount such that an .alpha./.epsilon. ratio of unity is achieved. The coating of the invention comprises a first layer in the form of an acid anodized colored anodic layer for achieving a high solar absorptance and a second or high emittance layer in the form of a clear acid anodized layer for achieving a high emittance. The entire coating is quite thin, e.g. 1-2 mils and is quite stable in a hostile space environment of the type encountered in a low earth orbit. The coating is obtained by first creating the high emittance clear anodized coating on the metal surface followed by anodizing using a colored anodizing process.

ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES: IDENTIFICATION AND QUANTIFICATION OF DECHLORINATION PRODUCTS

EPA Science Inventory

Electrochemical degradation (ECD) utilizes high redox potential at the anode and low redox potential at the cathode to oxidize and/or reduce organic and inorganic contaminants. ECD of Trichloroethylene (TCE), although theoretically possible, has not been experimentally proven. Th...

Organic hydrogen peroxide-driven low charge potentials for high-performance lithium-oxygen batteries with carbon cathodes

PubMed Central

Wu, Shichao; Qiao, Yu; Yang, Sixie; Ishida, Masayoshi; He, Ping; Zhou, Haoshen

2017-01-01

Reducing the high charge potential is a crucial concern in advancing the performance of lithium-oxygen batteries. Here, for water-containing lithium-oxygen batteries with lithium hydroxide products, we find that a hydrogen peroxide aqueous solution added in the electrolyte can effectively promote the decomposition of lithium hydroxide compounds at the ultralow charge potential on a catalyst-free Ketjen Black-based cathode. Furthermore, for non-aqueous lithium-oxygen batteries with lithium peroxide products, we introduce a urea hydrogen peroxide, chelating hydrogen peroxide without any water in the organic, as an electrolyte additive in lithium-oxygen batteries with a lithium metal anode and succeed in the realization of the low charge potential of ∼3.26 V, which is among the best levels reported. In addition, the undesired water generally accompanying hydrogen peroxide solutions is circumvented to protect the lithium metal anode and ensure good battery cycling stability. Our results should provide illuminating insights into approaches to enhancing lithium-oxygen batteries. PMID:28585527

Organic hydrogen peroxide-driven low charge potentials for high-performance lithium-oxygen batteries with carbon cathodes

NASA Astrophysics Data System (ADS)

Wu, Shichao; Qiao, Yu; Yang, Sixie; Ishida, Masayoshi; He, Ping; Zhou, Haoshen

2017-06-01

Reducing the high charge potential is a crucial concern in advancing the performance of lithium-oxygen batteries. Here, for water-containing lithium-oxygen batteries with lithium hydroxide products, we find that a hydrogen peroxide aqueous solution added in the electrolyte can effectively promote the decomposition of lithium hydroxide compounds at the ultralow charge potential on a catalyst-free Ketjen Black-based cathode. Furthermore, for non-aqueous lithium-oxygen batteries with lithium peroxide products, we introduce a urea hydrogen peroxide, chelating hydrogen peroxide without any water in the organic, as an electrolyte additive in lithium-oxygen batteries with a lithium metal anode and succeed in the realization of the low charge potential of ~3.26 V, which is among the best levels reported. In addition, the undesired water generally accompanying hydrogen peroxide solutions is circumvented to protect the lithium metal anode and ensure good battery cycling stability. Our results should provide illuminating insights into approaches to enhancing lithium-oxygen batteries.

Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries.

PubMed

Badi, Nacer; Erra, Abhinay Reddy; Hernandez, Francisco C Robles; Okonkwo, Anderson O; Hobosyan, Mkhitar; Martirosyan, Karen S

2014-01-01

The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about $15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about $1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization.

Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries

PubMed Central

2014-01-01

The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about $15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about $1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization. PMID:25114651

Optimizing membrane electrode assembly of direct methanol fuel cells for portable power

NASA Astrophysics Data System (ADS)

Liu, Fuqiang

Direct methanol fuel cells (DMFCs) for portable power applications require high power density, high-energy conversion efficiency and compactness. These requirements translate to fundamental properties of high methanol oxidation and oxygen reduction kinetics, as well as low methanol and water crossover. In this thesis a novel membrane electrode assembly (MEA) for direct methanol fuel cells has been developed, aiming to improve these fundamental properties. Firstly, methanol oxidation kinetics has been enhanced and methanol crossover has been minimized by proper control of ionomer crystallinity and its swelling in the anode catalyst layer through heat-treatment. Heat-treatment has a major impact on anode characteristics. The short-cured anode has low ionomer crystallinity, and thus swells easily when in contact with methanol solution to create a much denser anode structure, giving rise to higher methanol transport resistance than the long-cured anode. Variations in interfacial properties in the anode catalyst layer (CL) during cell conditioning were also characterized, and enhanced kinetics of methanol oxidation and severe limiting current phenomenon were found to be caused by a combination of interfacial property variations and swelling of ionomer over time. Secondly, much effort has been expended to develop a cathode CL suitable for operation under low air stoichiometry. The effects of fabrication procedure, ionomer content, and porosity distribution on the microstructure and cathode performance under low air stoichiometry are investigated using electrochemical and surface morphology characterizations to reveal the correlation between microstructure and electrochemical behavior. At the same time, computational fluid dynamics (CFD) models of DMFC cathodes have been developed to theoretically interpret the experimental results, to investigate two-phase transport, and to elucidate mechanism of cathode mixed potential due to methanol crossover. Thirdly, a MEA with low water crossover has been developed by employing a highly-hydrophobic microporous layer (MPL) to build up hydraulic pressure at the cathode, promoting product water permeation from the cathode to anode to offset water dragged by electro-osmosis. Water crossover through the MEA is further reduced by an anode hydrophobic MPL through facilitating water back diffusion. Under different current densities, the MEA with hydrophobic MPL has consistently low alpha, several times smaller than those with hydrophilic or without MPL. A simulation study of anode water transport by a two-phase model shows that anode MPL wettability strongly determines liquid saturation in the anode, and thus is identified as playing a crucial role in promoting water back diffusion. Finally, direct feed of highly-concentrated methanol using the optimized MEA has been successfully demonstrated by a face-feed anode plate, which minimizes methanol crossover by controlling the fuel delivery rate. Using 10 M methanol, a steady-state power density of ˜67mW/cm2 is reached at 60°C and 175mA/cm2, which is almost identical to that with 2M methanol.

Ultra-High Density Single Nanometer-Scale Anodic Alumina Nanofibers Fabricated by Pyrophosphoric Acid Anodizing

NASA Astrophysics Data System (ADS)

Kikuchi, Tatsuya; Nishinaga, Osamu; Nakajima, Daiki; Kawashima, Jun; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

2014-12-01

Anodic oxide fabricated by anodizing has been widely used for nanostructural engineering, but the nanomorphology is limited to only two oxides: anodic barrier and porous oxides. Therefore, the discovery of an additional anodic oxide with a unique nanofeature would expand the applicability of anodizing. Here we demonstrate the fabrication of a third-generation anodic oxide, specifically, anodic alumina nanofibers, by anodizing in a new electrolyte, pyrophosphoric acid. Ultra-high density single nanometer-scale anodic alumina nanofibers (1010 nanofibers/cm2) consisting of an amorphous, pure aluminum oxide were successfully fabricated via pyrophosphoric acid anodizing. The nanomorphologies of the anodic nanofibers can be controlled by the electrochemical conditions. Anodic tungsten oxide nanofibers can also be fabricated by pyrophosphoric acid anodizing. The aluminum surface covered by the anodic alumina nanofibers exhibited ultra-fast superhydrophilic behavior, with a contact angle of less than 1°, within 1 second. Such ultra-narrow nanofibers can be used for various nanoapplications including catalysts, wettability control, and electronic devices.

Ultra-High Density Single Nanometer-Scale Anodic Alumina Nanofibers Fabricated by Pyrophosphoric Acid Anodizing

PubMed Central

Kikuchi, Tatsuya; Nishinaga, Osamu; Nakajima, Daiki; Kawashima, Jun; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

2014-01-01

Anodic oxide fabricated by anodizing has been widely used for nanostructural engineering, but the nanomorphology is limited to only two oxides: anodic barrier and porous oxides. Therefore, the discovery of an additional anodic oxide with a unique nanofeature would expand the applicability of anodizing. Here we demonstrate the fabrication of a third-generation anodic oxide, specifically, anodic alumina nanofibers, by anodizing in a new electrolyte, pyrophosphoric acid. Ultra-high density single nanometer-scale anodic alumina nanofibers (1010 nanofibers/cm2) consisting of an amorphous, pure aluminum oxide were successfully fabricated via pyrophosphoric acid anodizing. The nanomorphologies of the anodic nanofibers can be controlled by the electrochemical conditions. Anodic tungsten oxide nanofibers can also be fabricated by pyrophosphoric acid anodizing. The aluminum surface covered by the anodic alumina nanofibers exhibited ultra-fast superhydrophilic behavior, with a contact angle of less than 1°, within 1 second. Such ultra-narrow nanofibers can be used for various nanoapplications including catalysts, wettability control, and electronic devices. PMID:25491282

Fluidized bed reaction towards crystalline embedded amorphous Si anode with much enhanced cycling stability.

PubMed

Zhou, Yu; Guo, Huajun; Yan, Guochun; Wang, Zhixing; Li, Xinhai; Yang, Zhewei; Zheng, Anxiong; Wang, Jiexi

2018-04-10

A facile and large-scale fluidized bed reaction route was introduced for the first time to prepare crystalline embedded amorphous silicon nanoparticles with an average size of 50 nm as anode materials for lithium-ion batteries. By increasing the operating potential to control the electrochemically active degree, the resulting sample showed excellent cycle stability with a high capacity retention of 94.7% after 200 cycles at 1 A g-1 in the voltage range of 0.12-2.00 V.

Tape Casting of High-Performance Low-Temperature Solid Oxide Cells with Thin La0.8Sr0.2Ga0.8Mg0.2O3-δ Electrolytes and Impregnated Nano Anodes.

PubMed

Gao, Zhan; Wang, Hongqian; Miller, Elizabeth; Liu, Qinyuan; Senn, Daniel; Barnett, Scott

2017-03-01

Low-temperature solid oxide cells (LT-SOCs), operating at 400 to 650 °C, have great potential for commercialization since they can provide lower cost and improved long-term durability. Low operating temperature can also enable high round-trip efficiency of SOCs as reversible energy storage devices. This paper describes Sr 0.8 La 0.2 TiO 3-α (SLT) anode supported LT-SOC with thin La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ (LSGM) electrolyte made by tape casting, with screen printed La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3-δ (LSCF) cathode and impregnated Ni anode. Optimization of the anode functional layers is described; the best anodes had 68 vol % LSGM and 12.3 vol % Ni and yielded maximum power density of 1.6 Wcm -2 with a cell area specific resistance (ASR) of 0.21 Ωcm 2 at 650 °C. Most of the cell ASR was associated with the cathode. Reversible electrolysis and fuel cell operation yielded similar characteristics with both 50% H 2 -50% H 2 O and syngas fuel. Life testing over 500 h showed that the cathode impedance stabilized after an initial break-in period; the ohmic and anode resistances, though relatively small, increased slightly with time.

Engineering Hollow Carbon Architecture for High-Performance K-Ion Battery Anode.

PubMed

Bin, De-Shan; Lin, Xi-Jie; Sun, Yong-Gang; Xu, Yan-Song; Zhang, Ke; Cao, An-Min; Wan, Li-Jun

2018-05-31

K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K + , stable electrode materials capable of sustaining the repeated K + intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extraordinary capacity (340 mAh g -1 at 0.1 C) together with a superior cycling stability (no obvious fading over 150 cycles at 0.5 C).

Facile synthesis of Fe4N/Fe2O3/Fe/porous N-doped carbon nanosheet as high-performance anode for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Dan; Li, Guangshe; Yu, Meijie; Fan, Jianming; Li, Baoyun; Li, Liping

2018-04-01

Iron nitrides are considered as highly promising anode materials for lithium-ion batteries because of their nontoxicity, high abundance, low cost, and higher electrical conductivity. Unfortunately, their limited synthesis routes are available and practical application is still hindered by their fast capacity decay. Herein, a facile and green route is developed to synthesize Fe4N/Fe2O3/Fe/porous N-doped carbon nanosheet composite. The size of Fe4N/Fe2O3/Fe particles is small (10-40 nm) and they are confined in porous N-doped carbon nanosheet. These features are conducive to accommodate volume change well, shorten the diffusion distance and further elevate electrical conductivity. When tested as anode material for lithium-ion batteries, a high discharge capacity of 554 mA h g-1 after 100 cycles at 100 mA g-1 and 389 mA h g-1 after 300 cycles at 1000 mA g-1 are retained. Even at 2000 mA g-1, a high capacity of 330 mA h g-1 can be achieved, demonstrating superior cycling stability and rate performance. New prospects will be brought by this work for the synthesis and the potential application of iron nitrides materials as an anode for LIBs.

°Enhancing High Temperature Anode Performance with 2° Anchoring Phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Robert A.; Sofie, Stephen W.; Amendola, Roberta

2015-10-01

Project accomplishments included developing and optimizing strength testing of aluminum titanate (ALT)-doped Ni-YSZ materials and identified the dopant levels that optimized mechanical strength and enhanced electrochemical performance. We also optimized our ability to fabricate electrolyte supported button cells with anodes consisting of powders provided by Fuel Cell Energy. In several instances, those anodes were infiltrated with ALT and tested with hydrogen for 30 hours at 800°C at an applied potential of 0.4 V. Our research activities were focused in three areas: 1) mechanical strength testing on as prepared and reducced nickel-YSZ structures that were either free of a dopant ormore » prepared by mechanically mixing in ALT at various weight percents (up to 10 wt%); 2) 24-hour electrochemical testing of electroylte supported cells having anodes made from Ni/YSZ and Ni/YSZ/ALT anodes with specific attention focused on modeling degradation rates; and 3) operando EIS and optical testing of both in-house fabricated devices as well as membrane electrode assemblies that were acquired from commercial vendors.« less

GASEOUS DISCHARGE DEVICE

DOEpatents

Gow, J.D.

1961-01-10

An extremely compact two-terminal gaseous discharge device is described that is capable of producing neutrons in copious quantities, relatively high energy ions, intense x rays, and the like. Principal novelty resides in the provision of a crossed electric-magnetic field region in the discharge envelope that traps electrons and accelerates them to very high energies to provide an intense ionizing medium adjacent the anode of the device for ionizing gas therein with extremely high efficiency. In addition, the crossed-field trapping region holds the electrons close to the anode whereby the acceleration of ions to the cathode is not materially effected by the electron sheath and the ions assume substantially the full energy of the anodecathode potential drop. (auth)

Synthesis and electrochemical performances of amorphous carbon-coated Sn Sb particles as anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wang, Zhong; Tian, Wenhuai; Liu, Xiaohe; Yang, Rong; Li, Xingguo

2007-12-01

The amorphous carbon coating on the Sn-Sb particles was prepared from aqueous glucose solutions using a hydrothermal method. Because the outer layer carbon of composite materials is loose cotton-like and porous-like, it can accommodate the expansion and contraction of active materials to maintain the stability of the structure, and hinder effectively the aggregation of nano-sized alloy particles. The as-prepared composite materials show much improved electrochemical performances as anode materials for lithium-ion batteries compared with Sn-Sb alloy and carbon alone. This amorphous carbon-coated Sn-Sb particle is extremely promising anode materials for lithium secondary batteries and has a high potentiality in the future use.

All 2D materials as electrodes for high power hybrid energy storage applications

NASA Astrophysics Data System (ADS)

Kato, Keiko; Sayed, Farheen N.; Babu, Ganguli; Ajayan, Pulickel M.

2018-04-01

Achieving both high energy and power densities from energy storage devices is a core strategy to meet the increasing demands of high performance portable electronics and electric transportation systems. Li-ion capacitor is a promising hybrid technology that strategically exploits high energy density from a Li-ion battery electrode and high power density from a supercapacitor electrode. However, the performance and safety of hybrid devices are still major concerns due to the use of graphite anodes which form passivation layers with organic electrolytes at lower potentials. Here, we explore 2D nanosheets as both anode and cathode electrodes to build a high power system without compromising energy density. Owing to the high electrical conductivity and multivalent redox activity at higher potentials, the Li-ion intercalation electrode is capable of maintaining large energy density at higher current rates with less safety risk than conventional systems. Hybrid devices consisting of all in all 2D electrodes deliver energy density as high as 121 Wh g-1 (at 240 W kg-1) and retains 29 Wh g-1 at high power density of 3600 W kg-1.

The Weinstein conjecture with multiplicities on spherizations

NASA Astrophysics Data System (ADS)

Hertzberg, Benjamin J.

2011-07-01

Si-based anodes have recently received considerable attention for use in Li-ion batteries, due to their extremely high specific capacity---an order of magnitude beyond that offered by conventional graphite anode materials. However, during the lithiation process, Si-based anodes undergo extreme increases in volume, potentially by more than 300 %. The stresses produced within the electrode by these volume changes can damage the electrode binder, the active Si particles and the solid electrolyte interphase (SEI), causing the electrode to rapidly fail and lose capacity. These problems can be overcome by producing new anode materials incorporating both Si and C, which may offer a favorable combination of the best properties of both materials, and which can be designed with internal porosity, thereby buffering the high strains produced during battery charge and discharge with minimal overall volume changes. However, in order to develop useful anode materials, we must gain a thorough understanding of the structural, microstructural and chemical changes occurring within the electrode during the lithiation and delithiation process, and we must develop new processes for synthesizing composite anode particles which can survive the extreme strains produced during lithium intercalation of Si and exhibit no volume changes in spite of the volume changes in Si. In this work we have developed several novel synthesis processes for producing internally porous Si-C nanocomposite anode materials for Li-ion batteries. These nanocomposites possess excellent specific capacity, Coulombic efficiency, cycle lifetime, and rate capability. We have also investigated the influence of a range of different parameters on the electrochemical performance of these materials, including pore size and shape, carbon and silicon film thickness and microstructure, and binder chemistry.

Hydrothermal synthesis and potential applicability of rhombohedral siderite as a high-capacity anode material for lithium ion batteries

NASA Astrophysics Data System (ADS)

Zhao, Shiqiang; Yu, Yue; Wei, Shanshan; Wang, Yuxi; Zhao, Chenhao; Liu, Rui; Shen, Qiang

2014-05-01

Natural siderite is a valuable iron mineral composed of ferrous carbonate (FeCO3), which is commonly found in hydrothermal veins and contains no sulfur or phosphorus. In this paper, micro-sized FeCO3 crystallites are synthesized via a facile hydrothermal route, and almost all of them possess a rhombohedral shape similar to that of natural products. When applied as an anode material for lithium ion batteries, the synthetic siderite can deliver an initial specific discharge capacity of ∼1587 mAh g-1 with a coulombic efficiency of 68% at 200 mA g-1, remaining a reversible value of 1018 mAh g-1 over 120 cycles. Even at a high current density of 1000 mA g-1, after 120 cycles the residual specific capacity (812 mAh g-1) is still higher than the theoretical capacity of FeCO3 (463 mAh g-1). Moreover, a novel reversible conversion mechanism accounts for the excellent electrochemical performances of rhombohedral FeCO3 to a great extent, implying the potential applicability of synthetic siderite as lithium ion battery anodes.

Electrostatic spray deposition of porous Fe 2O 3 thin films as anode material with improved electrochemical performance for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wang, L.; Xu, H. W.; Chen, P. C.; Zhang, D. W.; Ding, C. X.; Chen, C. H.

Iron oxide materials are attractive anode materials for lithium-ion batteries for their high capacity and low cost compared with graphite and most of other transition metal oxides. Porous carbon-free α-Fe 2O 3 films with two types of pore size distribution were prepared by electrostatic spray deposition, and they were characterized by X-ray diffraction, scanning electron microscopy and X-ray absorption near-edge spectroscopy. The 200 °C-deposited thin film exhibits a high reversible capacity of up to 1080 mAh g -1, while the initial capacity loss is at a remarkable low level (19.8%). Besides, the energy efficiency and energy specific average potential (E av) of the Fe 2O 3 films during charge/discharge process were also investigated. The results indicate that the porous α-Fe 2O 3 films have significantly higher energy density than Li 4Ti 5O 12 while it has a similar E av of about 1.5 V. Due to the porous structure that can buffer the volume changes during lithium intercalation/de-intercalation, the films exhibit stable cycling performance. As a potential anode material for high performance lithium-ion batteries that can be applied on electric vehicle and energy storage, rate capability and electrochemical performance under high-low temperatures were also investigated.

Automatic control and monitoring equipment for cathodic protection of offshore structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgan, J.H.

1979-10-01

The preferred cathodic-protection systems for offshore structures are (1) the sacrificial-anode form for areas where the anode's weight or wave resistance is not a serious handicap and (2) a combined anode/impressed-current system that reduces the anode mass. Problems associated with controlling and monitoring the equipment are related to the anode locations, suitability of the reference electrodes, instrumentation requirements, interpretation of the measured potentials, and influence of water depth.

The influence of electrolyte additives on the anodic dissolution of aluminum in alkaline solutions

NASA Astrophysics Data System (ADS)

Boehnstedt, W.

1980-09-01

The paper describes the effect of electrolyte additives on the anodic dissolution of aluminum in alkaline solutions. The dissolution is accelerated by the addition of small quantities of gallium or indium ions to the electrolyte indicated by the shift of the zero current potential by about 250 mV on the current-potential curve. Scanning electron microscope studies showed that gallium ions produce many small cracks in the aluminum electrode and collect at the grain boundary areas, increasing the electrode surface; this enlargement, in combination with increased electrolyte agitation due to greater hydrogen evolution, provides higher current densities at the same potential. It is concluded that this process will widen the possibilities of using aluminum and its alloys in high-rate batteries.

Direct electrochemical reduction of metal-oxides

DOEpatents

Redey, Laszlo I.; Gourishankar, Karthick

2003-01-01

A method of controlling the direct electrolytic reduction of a metal oxide or mixtures of metal oxides to the corresponding metal or metals. A non-consumable anode and a cathode and a salt electrolyte with a first reference electrode near the non-consumable anode and a second reference electrode near the cathode are used. Oxygen gas is produced and removed from the cell. The anode potential is compared to the first reference electrode to prevent anode dissolution and gas evolution other than oxygen, and the cathode potential is compared to the second reference electrode to prevent production of reductant metal from ions in the electrolyte.

Investigation of platinum and palladium as potential anodic catalysts for direct borohydride and ammonia borane fuel cells

NASA Astrophysics Data System (ADS)

Olu, Pierre-Yves; Deschamps, Fabien; Caldarella, Giuseppe; Chatenet, Marian; Job, Nathalie

2015-11-01

Platinum and palladium are investigated as anodic catalysts for direct borohydride and direct ammonia borane fuel cells (DBFC and DABFC). Half-cell characterizations performed at 25 °C using NH3BH3 or NaBH4 alkaline electrolytes demonstrate the lowest open-circuit potential and highest electrocatalytic activity for the NH3BH3 alkaline electrolyte for Pd and Pt rotating disk electrodes, respectively. Voltammograms performed in fuel cell configuration at 25 °C confirm this trend: the highest open circuit voltage (1.05 V) and peak power density (181 mW·cm-2) are monitored for DABFC using Pd/C and Pt/C anodes, respectively. Increasing the temperature heightens the peak power density (that reaches 420 mW·cm-2 at 60 °C for DBFC using Pt/C anodes), but strongly generates gas from the fuel hydrolysis, hindering the overall fuel cells performances. The anode texture strongly influences the fuel cell performances, highlighting: (i) that an open anode texture is required to efficiently circulate the anolyte and (ii) the difficulty to compare potential anodic catalysts characterized using different fuel cell setups within the literature. Furthermore, TEM imaging of Pt/C and Pd/C catalysts prior/post DBFC and DABFC operation shows fast degradation of the carbon-supported nanoparticles.

Growth behavior of anodic oxide formed by aluminum anodizing in glutaric and its derivative acid electrolytes

NASA Astrophysics Data System (ADS)

Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

2014-12-01

The growth behavior of anodic oxide films formed via anodizing in glutaric and its derivative acid solutions was investigated based on the acid dissociation constants of electrolytes. High-purity aluminum foils were anodized in glutaric, ketoglutaric, and acetonedicarboxylic acid solutions under various electrochemical conditions. A thin barrier anodic oxide film grew uniformly on the aluminum substrate by glutaric acid anodizing, and further anodizing caused the film to breakdown due to a high electric field. In contrast, an anodic porous alumina film with a submicrometer-scale cell diameter was successfully formed by ketoglutaric acid anodizing at 293 K. However, the increase and decrease in the temperature of the ketoglutaric acid resulted in non-uniform oxide growth and localized pitting corrosion of the aluminum substrate. An anodic porous alumina film could also be fabricated by acetonedicarboxylic acid anodizing due to the relatively low dissociation constants associated with the acid. Acid dissociation constants are an important factor for the fabrication of anodic porous alumina films.

Highly Stable Operation of Lithium Metal Batteries Enabled by the Formation of a Transient High Concentration Electrolyte Layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jianming; Yan, Pengfei; Mei, Donghai

2016-02-08

Lithium (Li) metal has been extensively investigated as an anode for rechargeable battery applications due to its ultrahigh specific capacity and the lowest redox potential. However, significant challenges including dendrite growth and low Coulombic efficiency are still hindering the practical applications of rechargeable Li metal batteries. Here, we demonstrate that long-term cycling of Li metal batteries can be realized by the formation of a transient high concentration electrolyte layer near the surface of Li metal anode during high rate discharge process. The highly concentrated Li+ ions in this transient layer will immediately solvate with the available solvent molecules and facilitatemore » the formation of a stable and flexible SEI layer composed of a poly(ethylene carbonate) framework integrated with other organic/inorganic lithium salts. This SEI layer largely suppresses the corrosion of Li metal anode by free organic solvents and enables the long-term operation of Li metal batteries. The fundamental findings in this work provide a new direction for the development and operation of Li metal batteries that could be operated at high current densities for a wide range of applications.« less

Evolution of Multiple Double Layer in Glow discharge and its inherent Properties

NASA Astrophysics Data System (ADS)

Alex, Prince; A, Saravanan; Sinha, Suraj

2016-10-01

Formation and evolution of multiple anodic double layers (MADLs) were experimentally studied in glow discharge plasma. The boundary condition for the existence of MADL was identified in terms of threshold bias and ambient working pressure. The MADL formation is accompanied by an explosive growth in anode current and consequent current-voltage characteristics follows a hysteresis loop. The analysis yield that stable MADLs is only observed when the control voltage V2 is between a certain critical values (Vq > νte MADL completely transforms to an intense high current carrying unstable anode glow. The floating potential analysis carried out using three axially positioned electrostatic probes shows a bipolar signature of DL with as the control parameter is varied. The floating potential analysis also shows that hysteresis arises due to the difference in magnitude of electric field required to align the space charges in the DL sheet at the control voltage changes forward and backward. The effect of pressure on MADL indicates that the MADL structure advances towards anode surface as the pressure is increases. The power dumped (W) in the MADL is estimated to decrease with increase in pressure while the same increase in the anode glow.

Miniature x-ray source

DOEpatents

Trebes, James E.; Stone, Gary F.; Bell, Perry M.; Robinson, Ronald B.; Chornenky, Victor I.

2002-01-01

A miniature x-ray source capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature x-ray source comprises a compact vacuum tube assembly containing a cathode, an anode, a high voltage feedthru for delivering high voltage to the anode, a getter for maintaining high vacuum, a connection for an initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is highly x-ray transparent and made, for example, from boron nitride. The compact size and potential for remote operation allows the x-ray source, for example, to be placed adjacent to a material sample undergoing analysis or in proximity to the region to be treated for medical applications.

Carbon foam anode modified by urea and its higher electrochemical performance in marine benthic microbial fuel cell

NASA Astrophysics Data System (ADS)

Fu, Yubin; Lu, Zhikai; Zai, Xuerong; Wang, Jian

2015-08-01

Electrode materials have an important effect on the property of microbial fuel cell (MFC). Carbon foam is utilized as an anode and further modified by urea to improve its performance in marine benthic microbial fuel cell (BMFC) with higher voltage and output power. The electrochemical properties of plain carbon foam (PC) and urea-modified carbon foam (UC) are measured respectively. Results show that the UC obtains better wettability after its modification and higher anti-polarization ability than the PC. A novel phenomenon has been found that the electrical potential of the modified UC anode is nearly 100 mV lower than that of the PC, reaching -570 ±10 mV ( vs. SCE), and that it also has a much higher electron transfer kinetic activity, reaching 9399.4 mW m-2, which is 566.2-fold higher than that from plain graphite anode (PG). The fuel cell containing the UC anode has the maximum power density (256.0 mW m-2) among the three different BMFCs. Urea would enhance the bacteria biofilm formation with a more diverse microbial community and maintain more electrons, leading to a lower anodic redox potential and higher power output. The paper primarily analyzes why the electrical potential of the modified anode becomes much lower than that of others after urea modification. These results can be utilized to construct a novel BMFC with higher output power and to design the conditioner of voltage booster with a higher conversion ratio. Finally, the carbon foam with a bigger pore size would be a potential anodic material in conventional MFC.

Circuit for high resolution decoding of multi-anode microchannel array detectors

NASA Technical Reports Server (NTRS)

Kasle, David B. (Inventor)

1995-01-01

A circuit for high resolution decoding of multi-anode microchannel array detectors consisting of input registers accepting transient inputs from the anode array; anode encoding logic circuits connected to the input registers; midpoint pipeline registers connected to the anode encoding logic circuits; and pixel decoding logic circuits connected to the midpoint pipeline registers is described. A high resolution algorithm circuit operates in parallel with the pixel decoding logic circuit and computes a high resolution least significant bit to enhance the multianode microchannel array detector's spatial resolution by halving the pixel size and doubling the number of pixels in each axis of the anode array. A multiplexer is connected to the pixel decoding logic circuit and allows a user selectable pixel address output according to the actual multi-anode microchannel array detector anode array size. An output register concatenates the high resolution least significant bit onto the standard ten bit pixel address location to provide an eleven bit pixel address, and also stores the full eleven bit pixel address. A timing and control state machine is connected to the input registers, the anode encoding logic circuits, and the output register for managing the overall operation of the circuit.

Novel Potassium-Ion Hybrid Capacitor Based on an Anode of K2Ti6O13 Microscaffolds.

PubMed

Dong, Shengyang; Li, Zhifei; Xing, Zhenyu; Wu, Xianyong; Ji, Xiulei; Zhang, Xiaogang

2018-05-09

To fill the gap between batteries and supercapacitors requires integration of the following features in a single system: energy density well above that of supercapacitors, cycle life much longer than Li-ion batteries, and low cost. Along this line, we report a novel nonaqueous potassium-ion hybrid capacitor (KIC) that employs an anode of K 2 Ti 6 O 13 (KTO) microscaffolds constructed by nanorods and a cathode of N-doped nanoporous graphenic carbon (NGC). K 2 Ti 6 O 13 microscaffolds are studied for potential applications as the anode material in potassium-ion storage for the first time. This material exhibits an excellent capacity retention of 85% after 1000 cycles. In addition, the NGC//KTO KIC delivers a high energy density of 58.2 Wh kg -1 based on the active mass in both electrodes, high power density of 7200 W kg -1 , and outstanding cycling stability over 5000 cycles. The usage of K ions as the anode charge carrier instead of Li ions and the amenable performance of this device suggest that hybrid capacitor devices may welcome a new era of beyond lithium.

General One-Pot Synthesis of Transition-Metal Phosphide/Nitrogen-Doped Carbon Hybrid Nanosheets as Ultrastable Anodes for Sodium-Ion Batteries.

PubMed

Li, Jingjing; Shi, Liang; Gao, Jingyu; Zhang, Genqiang

2018-01-26

Sodium-ion batteries (SIBs) have been considered as promising energy storage devices in grid-level applications, owing to their largely reduced cost compared with that of lithium-ion batteries. However, the practical application of SIBs has been seriously hindered because of the lack of appropriate anode materials, limited by the thermodynamics perspective, which is one of the central task at current stage. Herein, we have developed a general one-pot strategy for the synthesis of transition-metal phosphide (TMP) based hybrid nanosheets composed of carbon-coated TMP nanoparticles anchored to the surface of nitrogen-doped carbon nanosheets. This facile and cost-effective method is quite universal and holds potential to be further extended to other metal phosphide materials. Significantly, the hybrid nanosheet electrode possesses excellent sodium storage properties as anodes for SIBs, including high specific capacity, an ultra-long cycle life and a remarkable rate performance. This work makes a significant contribution to not only the synthetic methodology of TMP-carbon two-dimensional hybrid nanostructures, but also the application of TMP-based anodes for high-energy SIBs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic anodes and sulfur/selenium cathodes for advanced Li and Na batteries

NASA Astrophysics Data System (ADS)

Luo, Chao

To address energy crisis and environmental pollution induced by fossil fuels, there is an urgent demand to develop sustainable, renewable, environmental benign, low cost and high capacity energy storage devices to power electric vehicles and enhance clean energy approaches such as solar energy, wind energy and hydroenergy. However, the commercial Li-ion batteries cannot satisfy the critical requirements for next generation rechargeable batteries. The commercial electrode materials (graphite anode and LiCoO 2 cathode) are unsustainable, unrenewable and environmental harmful. Organic materials derived from biomasses are promising candidates for next generation rechargeable battery anodes due to their sustainability, renewability, environmental benignity and low cost. Driven by the high potential of organic materials for next generation batteries, I initiated a new research direction on exploring advanced organic compounds for Li-ion and Na-ion battery anodes. In my work, I employed croconic acid disodium salt and 2,5-Dihydroxy-1,4-benzoquinone disodium salt as models to investigate the effects of size and carbon coating on electrochemical performance for Li-ion and Na-ion batteries. The results demonstrate that the minimization of organic particle size into nano-scale and wrapping organic materials with graphene oxide can remarkably enhance the rate capability and cycling stability of organic anodes in both Li-ion and Na-ion batteries. To match with organic anodes, high capacity sulfur and selenium cathodes were also investigated. However, sulfur and selenium cathodes suffer from low electrical conductivity and shuttle reaction, which result in capacity fading and poor lifetime. To circumvent the drawbacks of sulfur and selenium, carbon matrixes such as mesoporous carbon, carbonized polyacrylonitrile and carbonized perylene-3, 4, 9, 10-tetracarboxylic dianhydride are employed to encapsulate sulfur, selenium and selenium sulfide. The resulting composites exhibit exceptional electrochemical performance owing to the high conductivity of carbon and effective restriction of polysulfides and polyselenides in carbon matrix, which avoids shuttle reaction.

Mesoporous Amorphous Silicon: A Simple Synthesis of a High-Rate and Long-Life Anode Material for Lithium-Ion Batteries.

PubMed

Lin, Liangdong; Xu, Xuena; Chu, Chenxiao; Majeed, Muhammad K; Yang, Jian

2016-11-02

Amorphous Si (a-Si) shows potential advantages over crystalline Si (c-Si) in lithium-ion batteries, owing to its high lithiation potential and good tolerance to intrinsic strain/stress. Herein, porous a-Si has been synthesized by a simple process, without the uses of dangerous or expensive reagents, sophisticated equipment, and strong acids that potential cause environment risks. These porous a-Si particles exhibit excellent electrochemical performances, owing to their porous structure, amorphous nature, and surface modification. They deliver a capacity of 1025 mAh g -1 at 3 A g -1 after 700 cycles. Moreover, the reversible capacity after electrochemical activation, is quite stable throughout the cycling, resulting in a capacity retention about around 88 %. The direct comparison between a-Si and c-Si anodes clearly supports the advantages of a-Si in lithium-ion batteries. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Assessment of the performance of SMFCs in the bioremediation of PAHs in contaminated marine sediments under different redox conditions and analysis of the associated microbial communities.

PubMed

Hamdan, Hamdan Z; Salam, Darine A; Hari, Ananda Rao; Semerjian, Lucy; Saikaly, Pascal

2017-01-01

The biodegradation of naphthalene, 2-methylnaphthalene and phenanthrene was evaluated in marine sediment microbial fuel cells (SMFCs) under different biodegradation conditions, including sulfate reduction as a major biodegradation pathway, employment of anode as terminal electron acceptor (TEA) under inhibited sulfate reducing bacteria activity, and combined sulfate and anode usage as electron acceptors. A significant removal of naphthalene and 2-methylnaphthalene was observed at early stages of incubation in all treatments and was attributed to their high volatility. In the case of phenanthrene, a significant removal (93.83±1.68%) was measured in the closed circuit SMFCs with the anode acting as the main TEA and under combined anode and sulfate reduction conditions (88.51±1.3%). A much lower removal (40.37±3.24%) was achieved in the open circuit SMFCs operating with sulfate reduction as a major biodegradation pathway. Analysis of the anodic bacterial community using 16S rRNA gene pyrosequencing revealed the enrichment of genera with potential exoelectrogenic capability, namely Geoalkalibacter and Desulfuromonas, on the anode of the closed circuit SMFCs under inhibited SRB activity, while they were not detected on the anode of open circuit SMFCs. These results demonstrate the role of the anode in enhancing PAHs biodegradation in contaminated marine sediments and suggest a higher system efficiency in the absence of competition between microbial redox processes (under SRB inhibition), namely due to the anode enrichment with exoelectrogenic bacteria, which is a more energetically favorable mechanism for PAHs oxidation than sulfate. Copyright © 2016. Published by Elsevier B.V.

Formation of titanium diboride coatings during the anodic polarization of titanium in a chloride melt with a low boron oxide content

NASA Astrophysics Data System (ADS)

Elshina, L. A.; Malkov, V. B.; Molchanova, N. G.

2015-02-01

The corrosion-electrochemical behavior of titanium in a molten eutectic mixture of cesium and sodium chlorides containing up to 1 wt % boron oxide is studied in the temperature range 810-870 K in an argon atmosphere. The potential, the current, and the rate of titanium corrosion are determined. The optimum conditions of forming a dense continuous titanium diboride coating on titanium with high adhesion to the metallic base are found for the anodic activation of titanium in the molten electrolyte under study.

Measuring Hydrogen Concentrations in Metals

NASA Technical Reports Server (NTRS)

Danford, M. D.

1985-01-01

Commercial corrosion-measurement system adapted to electrochemical determination of hydrogen concentrations in metals. New technique based on diffusion of hydrogen through foil specimen of metal. In sample holder, hydrogen produced on one side of foil, either by corrosion reaction or by cathodic current. Hydrogen diffused through foil removed on other side by constant anode potential, which leads to oxidation of hydrogen to water. Anode current is measure of concentration of hydrogen diffusing through foil. System used to study hydrogen uptake, hydrogen elimination by baking, effect of heat treatment, and effect of electroplating on high-strength steels.

Recycled tire crumb rubber anodes for sustainable power production in microbial fuel cells

NASA Astrophysics Data System (ADS)

Wang, Heming; Davidson, Matthew; Zuo, Yi; Ren, Zhiyong

One of the greatest challenges facing microbial fuel cells (MFCs) in large scale applications is the high cost of electrode material. We demonstrate here that recycled tire crumb rubber coated with graphite paint can be used instead of fine carbon materials as the MFC anode. The tire particles showed satisfactory conductivity after 2-4 layers of coating. The specific surface area of the coated rubber was over an order of magnitude greater than similar sized graphite granules. Power production in single chamber tire-anode air-cathode MFCs reached a maximum power density of 421 mW m -2, with a coulombic efficiency (CE) of 25.1%. The control graphite granule MFC achieved higher power density (528 mW m -2) but lower CE (15.6%). The light weight of tire particle could reduce clogging and maintenance cost but posts challenges in conductive connection. The use of recycled material as the MFC anodes brings a new perspective to MFC design and application and carries significant economic and environmental benefit potentials.

Generation of High Pressure Oxygen via Electrochemical Pumping in a Multi-stage Electrolysis Stack

NASA Technical Reports Server (NTRS)

Setlock, John A (Inventor); Green, Robert D (Inventor); Farmer, Serene (Inventor)

2016-01-01

An oxygen pump can produce high-purity high-pressure oxygen. Oxygen ions (O.sup.2-) are electrochemically pumped through a multi-stage electrolysis stack of cells. Each cell includes an oxygen-ion conducting solid-state electrolyte between cathode and anode sides. Oxygen dissociates into the ions at the cathode side. The ions migrate across the electrolyte and recombine at the anode side. An insulator is between adjacent cells to electrically isolate each individual cell. Each cell receives a similar volt potential. Recombined oxygen from a previous stage can diffuse through the insulator to reach the cathode side of the next stage. Each successive stage similarly incrementally pressurizes the oxygen to produce a final elevated pressure.

Generation of High Pressure Oxygen via Electrochemical Pumping in a Multi-Stage Electrolysis Stack

NASA Technical Reports Server (NTRS)

Setlock, John A (Inventor); Green, Robert D (Inventor); Farmer, Serene (Inventor)

2017-01-01

An oxygen pump can produce high-purity high-pressure oxygen. Oxygen ions (O(2-)) are electrochemically pumped through a multi-stage electrolysis stack of cells. Each cell includes an oxygen-ion conducting solid-state electrolyte between cathode and anode sides. Oxygen dissociates into the ions at the cathode side. The ions migrate across the electrolyte and recombine at the anode side. An insulator is between adjacent cells to electrically isolate each individual cell. Each cell receives a similar volt potential. Recombined oxygen from a previous stage can diffuse through the insulator to reach the cathode side of the next stage. Each successive stage similarly incrementally pressurizes the oxygen to produce a final elevated pressure.

Ion source with improved primary arc collimation

DOEpatents

Dagenhart, William K.

1985-01-01

An improved negative ion source is provided in which a self-biasing, molybdenum collimator is used to define the primary electron stream arc discharge from a filament operated at a negative potential. The collimator is located between the anode and the filament. It is electrically connected to the anode by means of an appropriate size resistor such that the collimator is biased at essentially the filament voltage during operation. Initially, the full arc voltage appears across the filament to collimator until the arc discharge strikes. Then the collimator biases itself to essentially filament potential due to current flow through the resistor thus defining the primary electron stream without intercepting any appreciable arc power. The collimator aperture is slightly smaller than the anode aperture to shield the anode from the arc power, thereby preventing the exposure of the anode to the full arc power which, in the past, has caused overheating and erosion of the anode collimator during extended time pulsed-beam operation of the source. With the self-biasing collimator of this invention, the ion source may be operated from short pulse periods to steady-state without destroying the anode.

High areal capacity, micrometer-scale amorphous Si film anode based on nanostructured Cu foil for Li-ion batteries

NASA Astrophysics Data System (ADS)

Si, Wenping; Sun, Xiaolei; Liu, Xianghong; Xi, Lixia; Jia, Yandong; Yan, Chenglin; Schmidt, Oliver G.

2014-12-01

We report a feasible design to fabricate micrometer-scale Si films deposited on nanostructured Cu foil as high areal capacity anodes for Li-ion batteries with excellent cycling performance. Nanostructured copper oxides are prepared by anodic oxidation of Cu foil in alkaline solution. The resultant copper oxide nanofibers function as matrix for thick Si films (1-2 μm) loading. Metallic Cu nanofibers are obtained by in-situ electrochemical reduction at low potentials, which work as electrical highways for fast electron transport and a reliable mechanical matrix to accommodate volume changes during lithium-silicon alloy/dealloy processes. The engineered thick Si film anode exhibit both high areal capacity (0.48 mAh cm-2 for 1 μm Si film and 0.6 mAh cm-2 for 2 μm Si film after 200 cycles at 0.225 mA cm-2) and excellent rate capability (0.52 mAh cm-2 at 1.05 mA cm-2 for 2 μm Si film). The 2 μm silicon film electrode is able to recover to the initial value of 1 mAh cm-2 when the current rate is set back to 0.15 mA cm-2 even after cycling at high current rates. The reported concept can be a general method for high-loading-film electrodes, which is industrial scalable and compatible with current battery manufacturing processes.

Fast fabrication of long TiO2 nanotube array with high photoelectrochemical property on flexible stainless steel.

PubMed

Tao, Jie; Wu, Tao; Gao, Peng

2012-03-01

Oriented highly ordered long TiO2 nanotube array films with nanopore structure and high photoelectrochemical property were fabricated on flexible stainless steel substrate (50 microm) by anodization treatment of titanium thin films in a short time. The samples were characterized by means of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and photoelectrochemical methods, respectively. The results showed that Ti films deposited at the condition of 0.7 Pa Ar pressure and 96 W sputtering power at room temperature was uniform and dense with good homogeneity and high crystallinity. The voltage and the anodization time both played significant roles in the formation of TiO2 nanopore-nanotube array film. The optimal voltage was 60 V and the anodization time is less than 30 min by anodizing Ti films in ethylene glycerol containing 0.5% (w) NH4F and 3% (w) H2O. The growth rate of TiO2 nanotube array was as high as 340 nm/min. Moreover, the photocurrent-potential curves, photocurrent response curves and electrochemical impedance spectra results indicated that the TiO2 nanotube array film with the nanoporous structure exhibited a better photo-response ability and photoelectrochemical performance than the ordinary TiO2 nanotube array film. The reason is that the nanoporous structure on the surface of the nanotube array can separate the photo electron-hole pairs more efficiently and completely than the tubular structure.

Physicochemical effects on uncontaminated kaolinite due to electrokinetic treatment using inert electrodes.

PubMed

Liaki, Christina; Rogers, Christopher D F; Boardman, David I

2008-07-01

To determine the consequences of applying electrokinetics to clay soils, in terms of mechanisms acting and resulting effects on the clay, tests were conducted in which an electrical gradient was applied across controlled specimens of English China Clay (ECC) using 'inert' electrodes and a 'Reverse Osmosis' water feed to the electrodes (i.e., to mimic electrokinetic stabilisation without the stabiliser added or electrokinetic remediation without the contaminant being present). The specimens in which electromigration was induced over time periods of 3, 7, 14 and 28 days were subsequently tested for Atterberg Limits, undrained shear strength using a hand shear vane, water content, pH, conductivity and zeta potential. Water flowed through the system from anode to cathode and directly affected the undrained shear strength of the clay. Acid and alkali fronts were created around the anode and cathode, respectively, causing changes in the pH, conductivity and zeta potential of the soil. Variations in zeta potential were linked to flocculation and dispersion of the soil particles, thus raising or depressing the Liquid Limit and Plastic Limit, and influencing the undrained shear strength. Initial weakening around the anode and cathode was replaced by a regain of strength at the anode once acidic conditions had been created, while highly alkaline conditions at the cathode induced a marked improvement in strength. A novel means of indicating strength improvement by chemical means, i.e., free from water content effects, is presented to assist in interpretation of the results.

Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

NASA Astrophysics Data System (ADS)

Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

2015-11-01

The formation behavior of anodic alumina nanofibers via anodizing in a concentrated pyrophosphoric acid under various conditions was investigated using electrochemical measurements and SEM/TEM observations. Pyrophosphoric acid anodizing at 293 K resulted in the formation of numerous anodic alumina nanofibers on an aluminum substrate through a thin barrier oxide and honeycomb oxide with narrow walls. However, long-term anodizing led to the chemical dissolution of the alumina nanofibers. The density of the anodic alumina nanofibers decreased as the applied voltage increased in the 10-75 V range. However, active electrochemical dissolution of the aluminum substrate occurred at a higher voltage of 90 V. Low temperature anodizing at 273 K resulted in the formation of long alumina nanofibers measuring several micrometers in length, even though a long processing time was required due to the low current density during the low temperature anodizing. In contrast, high temperature anodizing easily resulted in the formation and chemical dissolution of alumina nanofibers. The structural nanofeatures of the anodic alumina nanofibers were controlled by choosing of the appropriate electrochemical conditions, and numerous high-aspect-ratio alumina nanofibers (>100) can be successfully fabricated. The anodic alumina nanofibers consisted of a pure amorphous aluminum oxide without anions from the employed electrolyte.

Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

NASA Technical Reports Server (NTRS)

Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

2010-01-01

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600?C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form? process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Development and Testing of High Surface Area Iridium Anodes for Molten Oxide Electrolysis

NASA Technical Reports Server (NTRS)

Shchetkovskiy, Anatoliy; McKechnie, Timothy; Sadoway, Donald R.; Paramore, James; Melendez, Orlando; Curreri, Peter A.

2010-01-01

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400-1600 C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Integrated structure vacuum tube: A Concept

NASA Technical Reports Server (NTRS)

Dimeff, J.; Kerwin, W. J.

1974-01-01

Cathode emission is made to occur by heating entire structure to 600 C, and positive potential is applied to anode with negative potential on grids. Electron flow takes place from ring to circular anode through electric field produced by grids.

Flagellar filament bio-templated inorganic oxide materials - towards an efficient lithium battery anode.

PubMed

Beznosov, Sergei N; Veluri, Pavan S; Pyatibratov, Mikhail G; Chatterjee, Abhijit; MacFarlane, Douglas R; Fedorov, Oleg V; Mitra, Sagar

2015-01-13

Designing a new generation of energy-intensive and sustainable electrode materials for batteries to power a variety of applications is an imperative task. The use of biomaterials as a nanosized structural template for these materials has the potential to produce hitherto unachievable structures. In this report, we have used genetically modified flagellar filaments of the extremely halophilic archaea species Halobacterium salinarum to synthesize nanostructured iron oxide composites for use as a lithium-ion battery anode. The electrode demonstrated a superior electrochemical performance compared to existing literature results, with good capacity retention of 1032 mAh g(-1) after 50 cycles and with high rate capability, delivering 770 mAh g(-1) at 5 A g(-1) (~5 C) discharge rate. This unique flagellar filament based template has the potential to provide access to other highly structured advanced energy materials in the future.

Flagellar filament bio-templated inorganic oxide materials – towards an efficient lithium battery anode

PubMed Central

Beznosov, Sergei N.; Veluri, Pavan S.; Pyatibratov, Mikhail G.; Chatterjee, Abhijit; MacFarlane, Douglas R.; Fedorov, Oleg V.; Mitra, Sagar

2015-01-01

Designing a new generation of energy-intensive and sustainable electrode materials for batteries to power a variety of applications is an imperative task. The use of biomaterials as a nanosized structural template for these materials has the potential to produce hitherto unachievable structures. In this report, we have used genetically modified flagellar filaments of the extremely halophilic archaea species Halobacterium salinarum to synthesize nanostructured iron oxide composites for use as a lithium-ion battery anode. The electrode demonstrated a superior electrochemical performance compared to existing literature results, with good capacity retention of 1032 mAh g−1 after 50 cycles and with high rate capability, delivering 770 mAh g−1 at 5 A g−1 (~5 C) discharge rate. This unique flagellar filament based template has the potential to provide access to other highly structured advanced energy materials in the future. PMID:25583370

Flagellar filament bio-templated inorganic oxide materials - towards an efficient lithium battery anode

NASA Astrophysics Data System (ADS)

Beznosov, Sergei N.; Veluri, Pavan S.; Pyatibratov, Mikhail G.; Chatterjee, Abhijit; Macfarlane, Douglas R.; Fedorov, Oleg V.; Mitra, Sagar

2015-01-01

Designing a new generation of energy-intensive and sustainable electrode materials for batteries to power a variety of applications is an imperative task. The use of biomaterials as a nanosized structural template for these materials has the potential to produce hitherto unachievable structures. In this report, we have used genetically modified flagellar filaments of the extremely halophilic archaea species Halobacterium salinarum to synthesize nanostructured iron oxide composites for use as a lithium-ion battery anode. The electrode demonstrated a superior electrochemical performance compared to existing literature results, with good capacity retention of 1032 mAh g-1 after 50 cycles and with high rate capability, delivering 770 mAh g-1 at 5 A g-1 (~5 C) discharge rate. This unique flagellar filament based template has the potential to provide access to other highly structured advanced energy materials in the future.

Microbial fuel cell as a biocapacitor by using pseudo-capacitive anode materials

NASA Astrophysics Data System (ADS)

Lv, Zhisheng; Xie, Daohai; Li, Fusheng; Hu, Yun; Wei, Chaohai; Feng, Chunhua

2014-01-01

Here, we report that the microbial fuel cell (MFC) containing pseudo-capacitive anode materials such as polypyrrole (PPy)/9,10-anthraquinone-2-sulfonic acid sodium salt (AQS) composite films and RuO2 nanoparticles can function as a biocapacitor, able to store bioelectrons generated from microbial oxidation of substrate and release the accumulated charge upon requirement. Influences of the specific capacitance of the PPy/AQS- and RuO2-modified carbon felt anodes on the extent of accumulated charge are examined. Results show that increasing anode capacitance is responsible for the increases in the amount of electrons stored and released, and thereby leading to more energy stored and average power dissipated. The long-term charging-discharging tests indicate that the RuO2-modified biocapacitor with a specific capacitance of 3.74 F cm-2 exhibits 6% loss in the amount of released charge over 10 cycles for one-month operation, and 40% loss over 60 cycles for six-month operation. Our findings suggest that the MFC anode incorporating pseudo-capacitive materials shows potential for storing energy from waste organic matter and releasing in a short time of high power to the electronic device.

Low Substrate Loading Limits Methanogenesis and Leads to High Coulombic Efficiency in Bioelectrochemical Systems

PubMed Central

Sleutels, Tom H. J. A.; Molenaar, Sam D.; Heijne, Annemiek Ter; Buisman, Cees J. N.

2016-01-01

A crucial aspect for the application of bioelectrochemical systems (BESs) as a wastewater treatment technology is the efficient oxidation of complex substrates by the bioanode, which is reflected in high Coulombic efficiency (CE). To achieve high CE, it is essential to give a competitive advantage to electrogens over methanogens. Factors that affect CE in bioanodes are, amongst others, the type of wastewater, anode potential, substrate concentration and pH. In this paper, we focus on acetate as a substrate and analyze the competition between methanogens and electrogens from a thermodynamic and kinetic point of view. We reviewed experimental data from earlier studies and propose that low substrate loading in combination with a sufficiently high anode overpotential plays a key-role in achieving high CE. Low substrate loading is a proven strategy against methanogenic activity in large-scale reactors for sulfate reduction. The combination of low substrate loading with sufficiently high overpotential is essential because it results in favorable growth kinetics of electrogens compared to methanogens. To achieve high current density in combination with low substrate concentrations, it is essential to have a high specific anode surface area. New reactor designs with these features are essential for BESs to be successful in wastewater treatment in the future. PMID:27681899

Low Substrate Loading Limits Methanogenesis and Leads to High Coulombic Efficiency in Bioelectrochemical Systems.

PubMed

Sleutels, Tom H J A; Molenaar, Sam D; Heijne, Annemiek Ter; Buisman, Cees J N

2016-01-05

A crucial aspect for the application of bioelectrochemical systems (BESs) as a wastewater treatment technology is the efficient oxidation of complex substrates by the bioanode, which is reflected in high Coulombic efficiency (CE). To achieve high CE, it is essential to give a competitive advantage to electrogens over methanogens. Factors that affect CE in bioanodes are, amongst others, the type of wastewater, anode potential, substrate concentration and pH. In this paper, we focus on acetate as a substrate and analyze the competition between methanogens and electrogens from a thermodynamic and kinetic point of view. We reviewed experimental data from earlier studies and propose that low substrate loading in combination with a sufficiently high anode overpotential plays a key-role in achieving high CE. Low substrate loading is a proven strategy against methanogenic activity in large-scale reactors for sulfate reduction. The combination of low substrate loading with sufficiently high overpotential is essential because it results in favorable growth kinetics of electrogens compared to methanogens. To achieve high current density in combination with low substrate concentrations, it is essential to have a high specific anode surface area. New reactor designs with these features are essential for BESs to be successful in wastewater treatment in the future.

Elaborate strategy for preparing Li4Ti5O12-based anode materials with significantly improved lithium storage: TiO2 nanodots in-situ decoration and hierarchical structure construction

NASA Astrophysics Data System (ADS)

Xu, Hui; Tian, Qinghua; Huang, Jun; Bao, Dongmei; Zhang, Zhengxi; Yang, Li

2017-11-01

Spinel Li4Ti5O12 (LTO) has attracted extensive attention as potential anode materials for power lithium-ion batteries due to its outstanding structural stability and remarkable safety. However, it's practical application yet be limited by such disadvantages of dissatisfied specific capacity, poor electron conductivity and low lithium-ion diffusion coefficient. Thus, design and preparation of LTO anodes with desirable performance is still a challenge. Herein, we have successfully and greatly improved the performance of LTO anodes, in terms of rate capability, life and specific capacity in particular via dot-to-face anatase TiO2in-situ decoration and hierarchical structure construction under a facile approach (directly using the tetrabutyl titanate as titanium source instead of specially prepared titanium oxide precursors). The as-prepared LTO-based anode (denoted as T-LTO) delivers an ultra-high reversible specific capacity of 196.5 mAh g-1 after 300 cycles at 20 mA g-1, and superior rate performance and even ultra-long life of more than 145.8 mAh g-1 at 28.5C between 1.0 and 3.0 V. The achieved outstanding electrochemical performance largely surpasses that of reportedly state-of-the-art LTO-based anode materials. This work may open up a broader vision into developing advanced LTO-based anode materials for lithium-ion batteries.

Microwave beamed power technology improvement. [magnetrons and slotted waveguide arrays

NASA Technical Reports Server (NTRS)

Brown, W. C.

1980-01-01

The magnetron directional amplifier was tested for (1) phase shift and power output as a function of gain, anode current, and anode voltage, (2) background noise and harmonics in the output, (3) long life potential of the magnetron cathode, and (4) high operational efficiency. Examples of results were an adequate range of current and voltage over which 20 dB of amplification could be obtained, spectral noise density 155 dB below the carrier, 81.7% overall efficiency, and potential cathode life of 50 years in a design for solar power satellite use. A fabrication method was used to fabricate a 64 slot, 30 in square slotted waveguide array module from 0.020 in thick aluminum sheet. The test results on the array are discussed.

New insight into the discharge mechanism of silicon-air batteries using electrochemical impedance spectroscopy.

PubMed

Cohn, Gil; Eichel, Rüdiger A; Ein-Eli, Yair

2013-03-07

The mechanism of discharge termination in silicon-air batteries, employing a silicon wafer anode, a room-temperature fluorohydrogenate ionic liquid electrolyte and an air cathode membrane, is investigated using a wide range of tools. EIS studies indicate that the interfacial impedance between the electrolyte and the silicon wafer increases upon continuous discharge. In addition, it is shown that the impedance of the air cathode-electrolyte interface is several orders of magnitude lower than that of the anode. Equivalent circuit fitting parameters indicate the difference in the anode-electrolyte interface characteristics for different types of silicon wafers. Evolution of porous silicon surfaces at the anode and their properties, by means of estimated circuit parameters, is also presented. Moreover, it is found that the silicon anode potential has the highest negative impact on the battery discharge voltage, while the air cathode potential is actually stable and invariable along the whole discharge period. The discharge capacity of the battery can be increased significantly by mechanically replacing the silicon anode.

High efficiency aqueous and hybrid lithium-air batteries enabled by Li1.5Al0.5Ge1.5(PO4)3 ceramic anode-protecting membranes

NASA Astrophysics Data System (ADS)

Safanama, Dorsasadat; Adams, Stefan

2017-02-01

Due to their extremely high specific energy, rechargeable Li-air batteries could meet the demand for large-scale storage systems to integrate renewable sources into the power grid. Li-air batteries with aqueous catholytes with high solubility of discharge products have a higher potential to reach their slightly lower theoretical limits in practical devices. In this work, we demonstrate aqueous and hybrid Li-air batteries with NASICON-type Li1+xAxGe2-x(PO4)3 ceramic as anode-protecting membrane. The LAGP ceramic pellets with room temperature conductivity >10-4 S cm-1 are synthesized by melt quenching and subsequently annealed based on our optimized heat treatment cycle. Hybrid Li-air batteries are assembled by sandwiching LAGP membranes between Li-anode chamber and catholyte solutions (of various pH values) with CNT/Pt as air-cathode. When the two electron reduction mechanism prevails, overpotentials below 0.2 V are achieved for currents up to 0.07 mA cm-2 leading to energy efficiencies exceeding 98%.

Corrosion behavior of high-nickel and chromium alloys in natural Baltic seawater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birn, J.; Janik-Czachor, M.; Wolowik, A.

Effect of Cl{sup {minus}} ion concentration (O M sodium chloride [NaCl] to 2 M NaCl) and temperature (25 C to 75 C) on stability of the passive state of high-Ni and Cr alloys: NI-1 ({approximately} 16% Mo), CR-2 ({approximately} 6.2% Mo), and NI-3 (3.5% Mo) were investigated in acidic and neutral electrolytes in strictly controlled electrochemical conditions. The anodic behavior of the alloys appeared to depend mostly upon Mo content in the alloy. Thus, the NI-1 was the most stable alloy under the applied experimental conditions. The other alloys were also quite resistant, undergoing pitting only at elevated temperatures, atmore » high anodic potentials, and at a chloride concentration not lower than 1 M. In natural Baltic seawater, these alloys did not exhibit any tendency to pitting, in qualitative agreement with the accelerated electrochemical tests. Complementary microscopic and surface analytical (AES) investigations were carried out to correlate the anodic and corrosion behavior of these materials with their composition and structure, and the composition of the passivating films formed at their surfaces.« less

Advanced Sodium Ion Battery Anode Constructed via Chemical Bonding between Phosphorus, Carbon Nanotube, and Cross-Linked Polymer Binder.

PubMed

Song, Jiangxuan; Yu, Zhaoxin; Gordin, Mikhail L; Li, Xiaolin; Peng, Huisheng; Wang, Donghai

2015-12-22

Maintaining structural stability is a great challenge for high-capacity conversion electrodes with large volume change but is necessary for the development of high-energy-density, long-cycling batteries. Here, we report a stable phosphorus anode for sodium ion batteries by the synergistic use of chemically bonded phosphorus-carbon nanotube (P-CNT) hybrid and cross-linked polymer binder. The P-CNT hybrid was synthesized through ball-milling of red phosphorus and carboxylic group functionalized carbon nanotubes. The P-O-C bonds formed in this process help maintain contact between phosphorus and CNTs, leading to a durable hybrid. In addition, cross-linked carboxymethyl cellulose-citric acid binder was used to form a robust electrode. As a result, this anode delivers a stable cycling capacity of 1586.2 mAh/g after 100 cycles, along with high initial Coulombic efficiency of 84.7% and subsequent cycling efficiency of ∼99%. The unique electrode framework through chemical bonding strategy reported here is potentially inspirable for other electrode materials with large volume change in use.

High-speed microstrip multi-anode multichannel plate detector system

NASA Astrophysics Data System (ADS)

Riedo, Andreas; Tulej, Marek; Rohner, Urs; Wurz, Peter

2017-04-01

High-speed detector systems with high dynamic range and pulse width characteristics in the sub-nanosecond regime are mandatory for high resolution and highly sensitive time-of-flight mass spectrometers. Typically, for a reasonable detector area, an impedance-matched anode design is necessary to transmit the registered signal fast and distortion-free from the anode to the signal acquisition system. In this report, a high-speed microstrip multi-anode multichannel plate detector is presented and discussed. The anode consists of four separate active concentric anode segments allowing a simultaneous readout of signal with a dynamic range of about eight orders of magnitude. The impedance matched anode segments show pulse width of about 250 ps, measured at full width at half maximum, and rise time of ˜170 ps, measured with an oscilloscope with a sampling rate of 20 GS/s and 4 GHz analogue bandwidth. The usage of multichannel plates as signal amplifier allowed the design of a lightweight, low power consuming, and compact detector system, suitable, e.g., for the integration into space instrumentation or portable systems where size, weight, and power consumption are limited parameters.

Effects of High and Low Salt Concentration in Electrolytes at Lithium–Metal Anode Surfaces

DOE PAGES

Camacho-Forero, Luis E.; Smith, Taylor W.; Balbuena, Perla B.

2016-12-16

The use of high concentration salts in electrolyte solutions of lithium-sulfur (Li-S) batteries has been shown beneficial for mitigating some effects such as polysulfide shuttle and dendrite growth at the Li metal anode. Such complex solutions have structural, dynamical, and reactivity associated issues that need to be analyzed for a better understanding of the reasons behind such beneficial effects. A passivation interfacial layer known as solid-electrolyte interphase (SEI) is generated during battery cycling as a result of electron transfer from the metal anode causing electrolyte decomposition. Here in this work, we investigate using density functional theory and ab initio molecularmore » dynamics simulations the salt decomposition, solvation effects, interactions among intermediate products and other species, and potential components of the SEI layer as a function of chemical nature and concentration of the salt, for lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI) at 1M and 4M concentrations in dimethoxyethane. It is found that LiTFSI undergoes a less complete reduction and facilitates charge transfer from the anode, whereas LiFSI shows a more complete decomposition forming LiF as one of the main SEI products. In addition, the specific decomposition mechanisms of each salt clearly point to the initial SEI components and the potential main products derived from them. Finally, very complex networks are found among the salt and solvent molecules in their attempt to maximize Li ion solvation that is quantified through the determination of coordination numbers.« less

Potential Dependence of Pt and Co Dissolution from Platinum-Cobalt Alloy PEFC Catalysts Using Time-Resolved Measurements

DOE PAGES

Ahluwalia, Rajesh K.; Papadias, Dionissios D.; Kariuki, Nancy N.; ...

2018-02-09

An electrochemical flow cell system with catalyst-ionomer ink deposited on glassy carbon is used to investigate the aqueous stability of commercial PtCo alloys under cyclic potentials. An on-line inductively coupled plasma-mass spectrometer, capable of real-time measurements, is used to resolve the anodic and cathodic dissolution of Pt and Co during square-wave and triangle-wave potential cycles. We observe Co dissolution at all potentials, distinct peaks in anodic and cathodic Pt dissolution rates above 0.9 V, and potential-dependent Pt and Co dissolution rates. The amount of Pt that dissolves cathodically is smaller than the amount that dissolves anodically if the upper potentialmore » limit (UPL) is lower than 0.9 V. At the highest UPL investigated, 1.0 V, the cathodic dissolution greatly exceeds the anodic dissolution. A non-ideal solid solution model indicates that the anodic dissolution can be associated with the electrochemical oxidation of Pt and PtOH to Pt 2+, and the cathodic dissolution to electrochemical reduction of a higher Pt oxide, PtO x (x > 1), to Pt 2+. Pt also dissolves oxidatively during the cathodic scans but in smaller amounts than due to the reductive dissolution of PtO x. The relative amounts Pt dissolving oxidatively as Pt and PtOH depend on the potential cycle and UPL.« less

Potential Dependence of Pt and Co Dissolution from Platinum-Cobalt Alloy PEFC Catalysts Using Time-Resolved Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahluwalia, Rajesh K.; Papadias, Dionissios D.; Kariuki, Nancy N.

An electrochemical flow cell system with catalyst-ionomer ink deposited on glassy carbon is used to investigate the aqueous stability of commercial PtCo alloys under cyclic potentials. An on-line inductively coupled plasma-mass spectrometer, capable of real-time measurements, is used to resolve the anodic and cathodic dissolution of Pt and Co during square-wave and triangle-wave potential cycles. We observe Co dissolution at all potentials, distinct peaks in anodic and cathodic Pt dissolution rates above 0.9 V, and potential-dependent Pt and Co dissolution rates. The amount of Pt that dissolves cathodically is smaller than the amount that dissolves anodically if the upper potentialmore » limit (UPL) is lower than 0.9 V. At the highest UPL investigated, 1.0 V, the cathodic dissolution greatly exceeds the anodic dissolution. A non-ideal solid solution model indicates that the anodic dissolution can be associated with the electrochemical oxidation of Pt and PtOH to Pt 2+, and the cathodic dissolution to electrochemical reduction of a higher Pt oxide, PtO x (x > 1), to Pt 2+. Pt also dissolves oxidatively during the cathodic scans but in smaller amounts than due to the reductive dissolution of PtO x. The relative amounts Pt dissolving oxidatively as Pt and PtOH depend on the potential cycle and UPL.« less

Bio-derived hierarchically macro-meso-micro porous carbon anode for lithium/sodium ion batteries

NASA Astrophysics Data System (ADS)

Elizabeth, Indu; Singh, Bhanu Pratap; Trikha, Sunil; Gopukumar, Sukumaran

2016-10-01

Nitrogen doped hierarchically porous carbon derived from prawn shells have been efficiently synthesized through a simple, economically viable and environmentally benign approach. The prawn shell derived carbon (PSC) has high inherent nitrogen content (5.3%) and possesses a unique porous structure with the co-existence of macro, meso and micropores which can afford facile storage and transport channels for both Li and Na ions. PSC is well characterized using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission electron Microscopy (TEM), High resolution TEM (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Electron Paramagnetic Resonance (EPR) and Solid state-Nuclear Magnetic Resonance (NMR) studies have been conducted on pristine PSC and Li/Na interacted PSC. PSC as anode for Lithium ion batteries (LIBs) delivers superior electrochemical reversible specific capacity (740 mAh g-1 at 0.1 Ag-1 current density for 150 cycles) and high rate capability. When used as anode material for Sodium ion batteries (SIBs), PSC exhibits excellent reversible specific capacity of 325 mAh g-1 at 0.1 Ag-1 for 200 cycles and rate capability of 107 mAh g-1 at 2 Ag-1. Furthermore, this study demonstrates the employment of natural waste material as a potential anode for both LIB and SIB, which will definitively make a strike in the energy storage field.

Toward better Li-ion batteries: hard x-ray photoelectron spectroscopy investigation of binder materials for Si-based anodes

NASA Astrophysics Data System (ADS)

Young, Benjamin; Heskett, David; Nguyen, Cao Cuong; Woicik, Joseph; Lucht, Brett

From portable electronics to space exploration, the desire for more capable rechargeable batteries is driving a search for high capacity anodes. There is much interest in incorporating silicon as a partial or full replacement for the current graphite material in the most popular batteries because it could potentially hold much more charge. There is a significant challenge, however, in that storing so much more lithium in either electrode as the battery is charged and discharged as this causes an accompanying increase in the physical size fluctuation of the electrodes. Specifically, in the anode where this investigation focuses, the active material may experience a 300% volume change between the charged and discharged state. This makes a long lifetime difficult to achieve because the passivation layer protecting the electrolyte material from decomposition is compromised upon each cycle. One approach to accommodating the large volumetric fluctuation without sacrificing lifetime is to find a better material to include in the anode substrate to act as a binder. Ideally, such a material would permit the anode to fluctuate without breaking. Polyvinylidene fluoride (PVdF) is not successful for silicon-based anodes and we present Hard X-ray photoelectron spectroscopy studies of batteries incorporating three alternatives. The alternative binders outperform the PVdF and we present possible explanations. DOE EPSCoR and RI College Faculty Research Fund.

Microsized Porous SiOx@C Composites Synthesized through Aluminothermic Reduction from Rice Husks and Used as Anode for Lithium-Ion Batteries.

PubMed

Cui, Jinlong; Cui, Yongfu; Li, Shaohui; Sun, Hongliang; Wen, Zhongsheng; Sun, Juncai

2016-11-09

Microsized porous SiO x @C composites used as anode for lithium-ion batteries (LIBs) are synthesized from rice husks (RHs) through low-temperature (700 °C) aluminothermic reduction. The resulting SiO x @C composite shows mesoporous irregular particle morphology with a high specific surface area of 597.06 m 2 /g under the optimized reduction time. This porous SiO x @C composite is constructed by SiO x nanoparticles uniformly dispersed in the C matrix. When tested as anode material for LIBs, it displays considerable specific capacity (1230 mAh/g at a current density of 0.1 A/g) and excellent cyclic stability with capacity fading of less than 0.5% after 200 cycles at 0.8 A/g. The dramatic volume change for the Si anode during lithium-ion (Li + ) insertion and extraction can be successfully buffered because of the formation of Li 2 O and Li 4 SiO 4 during initial lithiation process and carbon coating layer on the surface of SiO x . The porous structure could also mitigate the volume change and mechanical strains and shorten the Li + diffusion path length. These characteristics improve the cyclic stability of the electrode. This low-cost and environment-friendly SiO x @C composite anode material exhibits great potential as an alternative for traditional graphite anodes.

Graphene/blue-phosphorus heterostructure as potential anode materials for sodium-ion batteries

NASA Astrophysics Data System (ADS)

Fan, Kaimin; Tang, Ting; Wu, Shiyun; Zhang, Zhiyuan

2018-01-01

The first-principles calculations based on density functional theory (DFT) have been implemented to investigate the graphene/blue-phosphorus (G/BP) heterostructure as potential anode material for SIBs. The adsorption and diffusion behaviors of sodium (Na) in G/BP heterostructure and the effect of external electric field on Na adsorption have been investigated. The results indicate that G/BP heterostructure with Na adsorption is metallic due to Na incorporation, which is of benefit for electronic conductivity as anode material. The results show that the design of G/BP heterostructure is an efficient scheme to enhance the Na adsorption in G/BP without affecting the high mobility of Na in the G/BP heterostructure surface. The present work demonstrates that the external electric field can effectively modulate the adsorption of Na, and the adsorption behavior of Na is more sensitive to the external electric field when E > 0.10 V Å-1 in G/BP heterostructure. The Mulliken population analysis and DOS calculations have been performed to explore the charge transfer and the interaction between Na and G/BP.

Mesostructured niobium-doped titanium oxide-carbon (Nb-TiO2-C) composite as an anode for high-performance lithium-ion batteries

NASA Astrophysics Data System (ADS)

Hwang, Keebum; Sohn, Hiesang; Yoon, Songhun

2018-02-01

Mesostructured niobium (Nb)-doped TiO2-carbon (Nb-TiO2-C) composites are synthesized by a hydrothermal process for application as anode materials in Li-ion batteries. The composites have a hierarchical porous structure with the Nb-TiO2 nanoparticles homogenously distributed throughout the porous carbon matrix. The Nb content is controlled (0-10 wt%) to investigate its effect on the physico-chemical properties and electrochemical performance of the composite. While the crystalline/surface structure varied with the addition of Nb (d-spacing of TiO2: 0.34-0.36 nm), the morphology of the composite remained unaffected. The electrochemical performance (cycle stability and rate capability) of the Nb-TiO2-C composite anode with 1 wt% Nb doping improved significantly. First, a full cut-off potential (0-2.5 V vs. Li/Li+) of Nb-doped composite anode (1 wt%) provides a higher energy utilization than that of the un-doped TiO2-C anode. Second, Nb-TiO2-C composite anode (1 wt%) exhibits an excellent long-term cycle stability (100% capacity retention, 297 mAh/g at 0.5 C after 100 cycles and 221 mAh/g at 2 C after 500 cycles) and improved rate-capability (192 mAh/g at 5 C), respectively (1 C: 150 mA/g). The superior electrochemical performance of Nb-TiO2-C (1 wt%) could be attributed to the synergistic effect of improved electronic conductivity induced by optimal Nb doping (1 wt%) and lithium-ion penetration (high diffusion kinetics) through unique pore structures.

Studies on sulfur poisoning and development of advanced anodic materials for waste-to-energy fuel cells applications

NASA Astrophysics Data System (ADS)

Zaza, Fabio; Paoletti, Claudia; LoPresti, Roberto; Simonetti, Elisabetta; Pasquali, Mauro

Biomass is the renewable energy source with the most potential penetration in energy market for its positive environmental and socio-economic consequences: biomass live cycles for energy production is carbon neutral; energy crops promote alternative and productive utilizations of rural sites creating new economic opportunities; bioenergy productions promote local energy independence and global energy security defined as availability of energy resource supply. Different technologies are currently available for energy production from biomass, but a key role is played by fuel cells which have both low environmental impacts and high efficiencies. High temperature fuel cells, such as molten carbonate fuel cells (MCFC), are particularly suitable for bioenergy production because it can be directly fed with biogas: in fact, among its principal constituents, methane can be transformed to hydrogen by internal reforming; carbon dioxide is a safe diluent; carbon monoxide is not a poison, but both a fuel, because it can be discharged at the anode, and a hydrogen supplier, because it can produce hydrogen via the water-gas shift reaction. However, the utilization of biomass derived fuels in MCFC presents different problems not yet solved, such as the poisoning of the anode due to byproducts of biofuel chemical processing. The chemical compound with the major negative effects on cell performances is hydrogen sulfide. It reacts with nickel, the main anodic constituent, forming sulfides and blocking catalytic sites for electrode reactions. The aim of this work is to study the hydrogen sulfide effects on MCFC performances for defining the poisoning mechanisms of conventional nickel-based anode, recommending selection criteria of sulfur-tolerant materials, and selecting advanced anodes for MCFC fed with biogas.

Reactant gas composition for fuel cell potential control

DOEpatents

Bushnell, Calvin L.; Davis, Christopher L.

1991-01-01

A fuel cell (10) system in which a nitrogen (N.sub.2) gas is used on the anode section (11) and a nitrogen/oxygen (N.sub.2 /O.sub.2) gaseous mix is used on the cathode section (12) to maintain the cathode at an acceptable voltage potential during adverse conditions occurring particularly during off-power conditions, for example, during power plant shutdown, start-up and hot holds. During power plant shutdown, the cathode section is purged with a gaseous mixture of, for example, one-half percent (0.5%) oxygen (O.sub.2) and ninety-nine and a half percent (99.5%) nitrogen (N.sub.2) supplied from an ejector (21) bleeding in air (24/28) into a high pressure stream (27) of nitrogen (N.sub.2) as the primary or majority gas. Thereafter the fuel gas in the fuel processor (31) and the anode section (11) is purged with nitrogen gas to prevent nickel (Ni) carbonyl from forming from the shift catalyst. A switched dummy electrical load (30) is used to bring the cathode potential down rapidly during the start of the purges. The 0.5%/99.5% O.sub.2 /N.sub.2 mixture maintains the cathode potential between 0.3 and 0.7 volts, and this is sufficient to maintain the cathode potential at 0.3 volts for the case of H.sub.2 diffusing to the cathode through a 2 mil thick electrolyte filled matrix and below 0.8 volts for no diffusion at open circuit conditions. The same high pressure gas source (20) is used via a "T" juncture ("T") to purge the anode section and its associated fuel processor (31).

Thermally oxidized titania nanotubes enhance the corrosion resistance of Ti6Al4V.

PubMed

Grotberg, John; Hamlekhan, Azhang; Butt, Arman; Patel, Sweetu; Royhman, Dmitry; Shokuhfar, Tolou; Sukotjo, Cortino; Takoudis, Christos; Mathew, Mathew T

2016-02-01

The negative impact of in vivo corrosion of metallic biomedical implants remains a complex problem in the medical field. We aimed to determine the effects of electrochemical anodization (60V, 2h) and thermal oxidation (600°C) on the corrosive behavior of Ti-6Al-4V, with serum proteins, at physiological temperature. Anodization produced a mixture of anatase and amorphous TiO2 nanopores and nanotubes, while the annealing process yielded an anatase/rutile mixture of TiO2 nanopores and nanotubes. The surface area was analyzed by the Brunauer-Emmett-Teller method and was estimated to be 3 orders of magnitude higher than that of polished control samples. Corrosion resistance was evaluated on the parameters of open circuit potential, corrosion potential, corrosion current density, passivation current density, polarization resistance and equivalent circuit modeling. Samples both anodized and thermally oxidized exhibited shifts of open circuit potential and corrosion potential in the noble direction, indicating a more stable nanoporous/nanotube layer, as well as lower corrosion current densities and passivation current densities than the smooth control. They also showed increased polarization resistance and diffusion limited charge transfer within the bulk oxide layer. The treatment groups studied can be ordered from greatest corrosion resistance to least as Anodized+Thermally Oxidized > Anodized > Smooth > Thermally Oxidized for the conditions investigated. This study concludes that anodized surface has a potential to prevent long term implant failure due to corrosion in a complex in-vivo environment. Copyright © 2015 Elsevier B.V. All rights reserved.

A flat microbial fuel cell for decentralized wastewater valorization: process performance and optimization potential.

PubMed

Peixoto, Luciana; Rodrigues, Alexandrina L; Martins, Gilberto; Nicolau, Ana; Brito, António G; Silva, M Manuela; Parpot, Pier; Nogueira, Regina

2013-01-01

A very compact flat microbial fuel cell (MFC), with 64 cm2 each for the anode surface and the cathode surface and 1 cm3 each for the anode and cathode chambers, was tested for wastewater treatment with simultaneous electricity production with the ultimate goal of implementing an autonomous service in decentralized wastewater treatment systems. The MFC was operated with municipal wastewater in sequencing batch reactor mode with re-circulation. Current densities up to 407 W/m3 and a carbon removal of 83% were obtained. Interruption in the operation slightly decreased power density, while the re-circulation ratio did not influence power generation. The anode biofilm presented high conductivity, activity and diversity. The denaturing gradient gel electrophoresis band-pattern of the DNA showed the presence of several ribotypes with different species of Shewanellaceae and Geobacteraceae families.

Copper Silicate Hydrate Hollow Spheres Constructed by Nanotubes Encapsulated in Reduced Graphene Oxide as Long-Life Lithium-Ion Battery Anode.

PubMed

Wei, Xiujuan; Tang, Chunjuan; Wang, Xuanpeng; Zhou, Liang; Wei, Qiulong; Yan, Mengyu; Sheng, Jinzhi; Hu, Ping; Wang, Bolun; Mai, Liqiang

2015-12-09

Hierarchical copper silicate hydrate hollow spheres-reduced graphene oxide (RGO) composite is successfully fabricated by a facile hydrothermal method using silica as in situ sacrificing template. The electrochemical performance of the composite as lithium-ion battery anode was studied for the first time. Benefiting from the synergistic effect of the hierarchical hollow structure and conductive RGO matrix, the composite exhibits excellent long-life performance and rate capability. A capacity of 890 mAh/g is achieved after 200 cycles at 200 mA/g and a capacity of 429 mAh/g is retained after 800 cycles at 1000 mA/g. The results indicate that the strategy of combining hierarchical hollow structures with conductive RGO holds the potential in addressing the volume expansion issue of high capacity anode materials.

Thermal investigation of an electrical high-current arc with porous gas-cooled anode

NASA Technical Reports Server (NTRS)

Eckert, E. R. G.; Schoeck, P. A.; Winter, E. R. F.

1984-01-01

The following guantities were measured on a high-intensity electric arc with tungsten cathode and transpiration-cooled graphite anode burning in argon: electric current and voltage, cooling gas flow rate (argon), surface temperature of the anode and of the anode holder, and temperature profile in three cross-sections of the arc are column. The last mentioned values were obtained from spectroscopic photographs. From the measured quantities, the following values were calculated: the heat flux into the anode surface, the heat loss of the anode by radiation and conduction, and the heat which was regeneratively transported by the cooling gas back into the arc space. Heat balances for the anode were also obtained. The anode losses (which are approximately 80% of the total arc power for free burning arcs) were reduced by transpiration cooling to 20%. The physical processes of the energy transfer from the arc to the anode are discussed qualitatively.

Theoretical Limits of Energy Density in Silicon-Carbon Composite Anode Based Lithium Ion Batteries.

PubMed

Dash, Ranjan; Pannala, Sreekanth

2016-06-17

Silicon (Si) is under consideration as a potential next-generation anode material for the lithium ion battery (LIB). Experimental reports of up to 40% increase in energy density of Si anode based LIBs (Si-LIBs) have been reported in literature. However, this increase in energy density is achieved when the Si-LIB is allowed to swell (volumetrically expand) more than graphite based LIB (graphite-LIB) and beyond practical limits. The volume expansion of LIB electrodes should be negligible for applications such as automotive or mobile devices. We determine the theoretical bounds of Si composition in a Si-carbon composite (SCC) based anode to maximize the volumetric energy density of a LIB by constraining the external dimensions of the anode during charging. The porosity of the SCC anode is adjusted to accommodate the volume expansion during lithiation. The calculated threshold value of Si was then used to determine the possible volumetric energy densities of LIBs with SCC anode (SCC-LIBs) and the potential improvement over graphite-LIBs. The level of improvement in volumetric and gravimetric energy density of SCC-LIBs with constrained volume is predicted to be less than 10% to ensure the battery has similar power characteristics of graphite-LIBs.

Reduction of Carbon Footprint and Energy Efficiency Improvement in Aluminum Production by Use of Novel Wireless Instrumentation Integrated with Mathematical Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

James W. Evans

2012-04-11

The work addressed the greenhouse gas emission and electrical energy consumption of the aluminum industry. The objective was to provide a means for reducing both through the application of wireless instrumentation, coupled to mathematical modeling. Worldwide the aluminum industry consumes more electrical energy than all activities in many major countries (e.g. the UK) and emits more greenhouse gasses (e.g. than France). Most of these excesses are in the 'primary production' of aluminum; that is the conversion of aluminum oxide to metal in large electrolytic cells operating at hundreds of thousands of amps. An industry-specific GHG emission has been the focusmore » of the work. The electrolytic cells periodically, but at irregular intervals, experience an upset condition known as an 'anode effect'. During such anode effects the cells emit fluorinated hydrocarbons (PFCs, which have a high global warming potential) at a rate far greater than in normal operation. Therefore curbing anode effects will reduce GHG emissions. Prior work had indicated that the distribution of electrical current within the cell experiences significant shifts in the minutes before an anode effect. The thrust of the present work was to develop technology that could detect and report this early warning of an anode effect so that the control computer could minimize GHG emissions. A system was developed to achieve this goal and, in collaboration with Alcoa, was tested on two cells at an Alcoa plant in Malaga, Washington. The project has also pointed to the possibility of additional improvements that could result from the work. Notable among these is an improvement in efficiency that could result in an increase in cell output at little extra operating cost. Prospects for commercialization have emerged in the form of purchase orders for further installations. The work has demonstrated that a system for monitoring the current of individual anodes in an aluminum cell is practical. Furthermore the system has been installed twice on a smelter in the US without exposing workers to hazards usually associated with running signal wires in aluminum plants. The results display the early warning of an anode effect that potentially can be used to minimize such anode effects with their excessive GHG emissions. They also point to a possible, but substantial, economic benefit that could result in improved current efficiency by anode adjustment based on individual anode current measurements.« less

Anode initiated surface flashover switch

DOEpatents

Brainard, John P.; Koss, Robert J.

2003-04-29

A high voltage surface flashover switch has a pair of electrodes spaced by an insulator. A high voltage is applied to an anode, which is smaller than the opposing, grounded, cathode. When a controllable source of electrons near the cathode is energized, the electrons are attracted to the anode where they reflect to the insulator and initiate anode to cathode breakdown.

MULTI-ELECTRODE TUBE PULSE MEMORY CIRCUIT

DOEpatents

Gundlach, J.C.; Reeves, J.B.

1958-05-20

Control circuits are described for pulse memory devices for scalers and the like, and more particularly to a driving or energizing circuit for a polycathode gaseous discharge tube having an elongated anode and a successive series of cathodes spaced opposite the anode along its length. The circuit is so arranged as to utilize an arc discharge between the anode and a cathode to count a series of pulses. Upon application of an input pulse the discharge is made to occur between the anode and the next successive cathode, and an output pulse is produced when a particular subsequent cathode is reached. The circuit means for transfering the discharge by altering the anode potential and potential of the cathodes and interconnecting the cathodes constitutes the novel aspects of the invention. A low response time and reduced number of circuit components are the practical advantages of the described circuit.

Self-standing silicon-carbon nanotube/graphene by a scalable in situ approach from low-cost Al-Si alloy powder for lithium ion batteries

NASA Astrophysics Data System (ADS)

Cai, Hongyan; Han, Kai; Jiang, Heng; Wang, Jingwen; Liu, Hui

2017-10-01

Silicon/carbon (Si/C) composite shows great potential to replace graphite as lithium-ion battery (LIB) anode owing to its high theoretical capacity. Exploring low-cost scalable approach for synthesizing Si/C composites with excellent electrochemical performance is critical for practical application of Si/C anodes. In this study, we rationally applied a scalable in situ approach to produce Si-carbon nanotube (Si-CNT) composite via acid etching of commercial inexpensive micro-sized Al-Si alloy powder and CNT mixture. In the Si-CNT composite, ∼10 nm Si particles were uniformly deposited on the CNT surface. After combining with graphene sheets, a flexible self-standing Si-CNT/graphene paper was fabricated with three-dimensional (3D) sandwich-like structure. The in situ presence of CNT during acid-etching process shows remarkable two advantages: providing deposition sites for Si atoms to restrain agglomeration of Si nanoparticles after Al removal from Al-Si alloy powder, increasing the cross-layer conductivity of the paper anode to provide excellent conductive contact sites for each Si nanoparticles. When used as binder-free anode for LIBs without any further treatment, in situ addition of CNT especially plays important role to improve the initial electrochemical activity of Si nanoparticles synthesized from low-cost Al-Si alloy powder, thus resulting in about twice higher capacity than Si/G paper anode. The self-standing Si-CNT/graphene paper anode exhibited a high specific capacity of 1100 mAh g-1 even after 100 cycles at 200 mA g-1 current density with a Coulombic efficiency of >99%. It also showed remarkable rate capability improvement compared to Si/G paper without CNT. The present work demonstrates a low-cost scalable in situ approach from commercial micro-sized Al-Si alloy powder for Si-based composites with specific nanostructure. The Si-CNT/graphene paper is a promising anode candidate with high capacity and cycling stability for LIBs, especially for the flexible batteries application.

Electric thruster research

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.

1981-01-01

The multipole discharge chamber of an electrostatic ion thruster is discussed. No reductions in discharge losses were obtained, despite repeated demonstration of anode potentials more positive than the bulk of the discharge plasma. The penalty associated with biased anode operation was reduced as the magnetic integral above the biased anodes was increased. The hollow cathode is discussed. The experimental configuration of the Hall current thruster had a uniform field throughout the ion generation and acceleration regions. To obtain reliable ion generation, it was necessary to reduce the magnetic field strength, to the point where excessive electron backflow was required to establish ion acceleration. The theoretical study of ion acceleration with closed electron drift paths resulted in two classes of solutions. One class has the continuous potential variation in the acceleration region that is normally associated with a Hall current accelerator. The other class has an almost discontinuous potential step near the anode end of the acceleration region. This step includes a significant fraction of the total acceleration potential difference.

Facile Synthesis of Layer Structured GeP3/C with Stable Chemical Bonding for Enhanced Lithium-Ion Storage

NASA Astrophysics Data System (ADS)

Qi, Wen; Zhao, Haihua; Wu, Ying; Zeng, Hong; Tao, Tao; Chen, Chao; Kuang, Chunjiang; Zhou, Shaoxiong; Huang, Yunhui

2017-02-01

Recently, metal phosphides have been investigated as potential anode materials because of higher specific capacity compared with those of carbonaceous materials. However, the rapid capacity fade upon cycling leads to poor durability and short cycle life, which cannot meet the need of lithium-ion batteries with high energy density. Herein, we report a layer-structured GeP3/C nanocomposite anode material with high performance prepared by a facial and large-scale ball milling method via in-situ mechanical reaction. The P-O-C bonds are formed in the composite, leading to close contact between GeP3 and carbon. As a result, the GeP3/C anode displays excellent lithium storage performance with a high reversible capacity up to 1109 mA h g-1 after 130 cycles at a current density of 0.1 A g-1. Even at high current densities of 2 and 5 A g-1, the reversible capacities are still as high as 590 and 425 mA h g-1, respectively. This suggests that the GeP3/C composite is promising to achieve high-energy lithium-ion batteries and the mechanical milling is an efficient method to fabricate such composite electrode materials especially for large-scale application.

A facile synthesis of zinc oxide/multiwalled carbon nanotube nanocomposite lithium ion battery anodes by sol-gel method

NASA Astrophysics Data System (ADS)

Köse, Hilal; Karaal, Şeyma; Aydın, Ali Osman; Akbulut, Hatem

2015-11-01

Free standing zinc oxide (ZnO) and multiwalled carbon nanotube (MWCNT) nanocomposite materials are prepared by a sol gel technique giving a new high capacity anode material for lithium ion batteries. Free-standing ZnO/MWCNT nanocomposite anodes with two different chelating agent additives, triethanolamine (TEA) and glycerin (GLY), yield different electrochemical performances. Field emission gun scanning electron microscopy (FEG-SEM), energy dispersive X-ray spectrometer (EDS), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analyses reveal the produced anode electrodes exhibit a unique structure of ZnO coating on the MWCNT surfaces. Li-ion cell assembly using a ZnO/MWCNT/GLY free-standing anode and Li metal cathode possesses the best discharge capacity, remaining as high as 460 mAh g-1 after 100 cycles. This core-shell structured anode can offer increased energy storage and performance over conventional anodes in Li-ion batteries.

Controllable Self-Assembly of Micro-Nanostructured Si-Embedded Graphite/Graphene Composite Anode for High-Performance Li-Ion Batteries.

PubMed

Lin, Ning; Xu, Tianjun; Li, Tieqiang; Han, Ying; Qian, Yitai

2017-11-15

Si-containing graphite-based composites are considered as promising high-capacity anodes for lithium-ion batteries (LIBs). Here, a controllable and scalable self-assembly strategy is developed to produce micro-nanostructured graphite/Si/reduced graphene oxides composite (SGG). The self-assembly procedure is realized by the hydrogen bond interaction between acylamino-modified graphite and graphene oxides (GO); Si nanoparticles are in situ embedded between graphite and GO sheets uniformly. This architecture is able to overcome the incompatibility between Si nanoparticles and microsized graphite. Accordingly, the as-prepared SGG anode (Si 8 wt %) delivers a reversible Li-storage capacity of 572 mAh g -1 at 0.2 C, 502.2 mAh g -1 after 600 cycles at 0.8 C with a retention of 92%, and a capacity retention of 64% even at 10 C. The impressive electrochemical properties are ascribed to the stable architecture and three-dimensional conductive network constructed by graphite and graphene sheets, which can accommodate the huge volume change of Si, keep the conductive contact and structural integrity, and suppress side reactions with electrolyte. Additionally, the full-cell (LiFePO 4 cathode/SGG anode) delivers a specific capacity of 550 mAh g -1 with a working potential beyond 3.0 V.

Porous carbon-free SnSb anodes for high-performance Na-ion batteries

NASA Astrophysics Data System (ADS)

Choi, Jeong-Hee; Ha, Choong-Wan; Choi, Hae-Young; Seong, Jae-Wook; Park, Cheol-Min; Lee, Sang-Min

2018-05-01

A simple melt-spinning/chemical-etching process is developed to create porous carbon-free SnSb anodes. Sodium ion batteries (SIBs) incorporating these anodes exhibit excellent electrochemical performances by accomodating large volume changes during repeated cycling. The porous carbon-free SnSb anode produced by the melt-spinning/chemical-etching process shows a high reversible capacity of 481 mAh g-1, high ICE of 80%, stable cyclability with a high capacity retention of 99% after 100 cycles, and a fast rate capability of 327 mAh g-1 at 4C-rate. Ex-situ X-ray diffraction and high resolution-transmission electron microscopy analyses demonstrate that the synthesized porous carbon-free SnSb anodes involve the highly reversible reaction with sodium through the conversion and recombination reactions during sodiation/desodiation process. The novel and simple melt-spinning/chemical-etching synthetic process represents a technological breakthrough in the commercialization of Na alloy-able anodes for SIBs.

High-speed growth of TiO2 nanotube arrays with gradient pore diameter and ultrathin tube wall under high-field anodization

NASA Astrophysics Data System (ADS)

Yuan, Xiaoliang; Zheng, Maojun; Ma, Li; Shen, Wenzhong

2010-10-01

Highly ordered TiO2 nanotubular arrays have been prepared by two-step anodization under high field. The high anodizing current densities lead to a high-speed film growth (0.40-1.00 µm min - 1), which is nearly 16 times faster than traditional fabrication of TiO2 at low field. It was found that an annealing process of Ti foil is an effective approach to get a monodisperse and double-pass TiO2 nanotubular layer with a gradient pore diameter and ultrathin tube wall (nearly 10 nm). A higher anodic voltage and longer anodization time are beneficial to the formation of ultrathin tube walls. This approach is simple and cost-effective in fabricating high-quality ordered TiO2 nanotubular arrays for practical applications.

High-speed growth of TiO2 nanotube arrays with gradient pore diameter and ultrathin tube wall under high-field anodization.

PubMed

Yuan, Xiaoliang; Zheng, Maojun; Ma, Li; Shen, Wenzhong

2010-10-08

Highly ordered TiO(2) nanotubular arrays have been prepared by two-step anodization under high field. The high anodizing current densities lead to a high-speed film growth (0.40-1.00 microm min(-1)), which is nearly 16 times faster than traditional fabrication of TiO(2) at low field. It was found that an annealing process of Ti foil is an effective approach to get a monodisperse and double-pass TiO(2) nanotubular layer with a gradient pore diameter and ultrathin tube wall (nearly 10 nm). A higher anodic voltage and longer anodization time are beneficial to the formation of ultrathin tube walls. This approach is simple and cost-effective in fabricating high-quality ordered TiO(2) nanotubular arrays for practical applications.

Hybrid phosphorene/graphene nanocomposite as an anode material for Na-ion batteries: a first-principles study

NASA Astrophysics Data System (ADS)

Wang, Linxia; Jiang, Zhiqiang; Li, Wei; Gu, Xiao; Huang, Li

2017-04-01

The potential application of the hybrid phosphorene/graphene (P/G) composites as an anode material in Na-ion batteries (NIBs) has been explored based on first-principles calculations. The calculated elastic constants reveal that the P/G has an ultrahigh stiffness, which can effectively suppress the undesirable structural deformation during the sodiation and desodiation cycles. Na atoms can strongly bind with the phosphorene single-layer (SP), double-layer (DP), and their composites with graphene (SP/G, DP/G, G/DP/G), and can even cause a sliding between the layers when the DP/G accommodate more Na atoms. The migration of Na in P/G is anisotropic with the minimum energy path along the zigzag channel. The low diffusion barriers of only about several tens of meV ensure the high mobility of Na within the layers, and thus lead to rapid charge/discharge capacity of P/G. The electronic structures show that the hybrid P/G becomes metallic with the Na incorporation, which contributes to the good electric conductivity in P/G. We further demonstrate that the average open circuit voltage (OCV) of DP/G is 0.53 V, which is comparable to other anode materials. These results suggest that P/G composites hold great potential to be a good anode material in NIBs.

The onset of plasma potential locking

DOE PAGES

Hopkins, Matthew M.; Yee, Benjamin T.; Baalrud, Scott D.; ...

2016-06-22

In this study, we provide insight into the role and impact that a positively biased electrode (anode) has on bulk plasma potential. Using two-dimensional Particle-in-Cell simulations, we investigate the plasma potential as an anode transitions from very small (“probe” mode) to large (“locking” mode). Prior theory provides some guidance on when and how this transition takes place. Initial experimental results are also compared. The simulations demonstrate that as the surface area of the anode is increased transitions in plasma potential and sheath polarity occur, consistent with experimental observations and theoretical predictions. It is expected that understanding this basic plasma behaviormore » will be of interest to basic plasma physics communities, diagnostic developers, and plasma processing devices where control of bulk plasma potential is important.« less

Effect of friction on anodic polarization properties of metallic biomaterials.

PubMed

Okazaki, Yoshimitsu

2002-05-01

The effect of friction on the anodic polarization properties of metallic biomaterials in a physiological saline solution was investigated. The current density during friction becomes higher than during the static condition. The fluctuation range of the current density caused by the destruction and formation of passive film was observed. For SUS316L stainless steel and Co-Cr-Mo casting alloy, the fluctuation range was observed in the passivity zone. Otherwise, for Ti alloys, the fluctuation range was observed in both the activity and passivity zones. The decrease of the corrosion potential for Ti alloys due to friction was much larger than that of SUS316L stainless steel and Co-Cr-Mo casting alloy. From this result, it was considered that in a the frictional environment, the stressing zone turned anodic and its periphery cathodic, and corrosion tended to progress more than in the static environment. The effect of wear on the anodic polarization curves also changed depending on the frictional load, potential zone and the pH of the solution. A rapid increase in current density due to corrosion starting from the frictional area was found in the Ti-6Al-4V and Ti-15Mo-5Zr-3Al alloys containing Al. However, for the new Ti-15Zr-4Nb-4Ta alloy, this rapid increase was not seen in the high-potential region. The effect of the lateral reciprocal speed was also negligible for the new Ti alloy. It was found that the new Ti-15Zr-4Nb-4Ta alloy exhibited excellent corrosion resistance under friction.

Recent advances in the development and utilization of modern anode materials for high performance microbial fuel cells.

PubMed

Sonawane, Jayesh M; Yadav, Abhishek; Ghosh, Prakash C; Adeloju, Samuel B

2017-04-15

Microbial fuel cells (MFCs) are novel bio-electrochemical device for spontaneous or single step conversion of biomass into electricity, based on the use of metabolic activity of bacteria. The design and use of MFCs has attracted considerable interests because of the potential new opportunities they offer for sustainable production of energy from biodegradable and reused waste materials. However, the associated slow microbial kinetics and costly construction materials has limited a much wider commercial use of the technology. In the past ten years, there has been significant new developments in MFCs which has resulted in several-fold increase in achievable power density. Yet, there is still considerable possibility for further improvement in performance and development of new cost effective materials. This paper comprehensively reviews recent advances in the construction and utilization of novel anodes for MFCs. In particular, it highlights some of the critical roles and functions of anodes in MFCs, strategies available for improving surface areas of anodes, dominant performance of stainless-steel based anode materials, and the emerging benefits of inclusion of nanomaterials. The review also demonstrates that some of the materials are very promising for large scale MFC applications and are likely to replace conventional anodes for the development of next generation MFC systems. The hurdles to the development of commercial MFC technology are also discussed. Furthermore, the future directions in the design and selection of materials for construction and utilization of MFC anodes are highlighted. Copyright © 2016 Elsevier B.V. All rights reserved.

Efficient organic photovoltaic cells on a single layer graphene transparent conductive electrode using MoOx as an interfacial layer.

PubMed

Du, J H; Jin, H; Zhang, Z K; Zhang, D D; Jia, S; Ma, L P; Ren, W C; Cheng, H M; Burn, P L

2017-01-07

The large surface roughness, low work function and high cost of transparent electrodes using multilayer graphene films can limit their application in organic photovoltaic (OPV) cells. Here, we develop single layer graphene (SLG) films as transparent anodes for OPV cells that contain light-absorbing layers comprised of the evaporable molecular organic semiconductor materials, zinc phthalocyanine (ZnPc)/fullerene (C60), as well as a molybdenum oxide (MoO x ) interfacial layer. In addition to an increase in the optical transmittance, the SLG anodes had a significant decrease in surface roughness compared to two and four layer graphene (TLG and FLG) anodes fabricated by multiple transfer and stacking of SLGs. Importantly, the introduction of a MoO x interfacial layer not only reduced the energy barrier between the graphene anode and the active layer, but also decreased the resistance of the SLG by nearly ten times. The OPV cells with the structure of polyethylene terephthalate/SLG/MoO x /CuI/ZnPc/C60/bathocuproine/Al were flexible, and had a power conversion efficiency of up to 0.84%, which was only 17.6% lower than the devices with an equivalent structure but prepared on commercial indium tin oxide anodes. Furthermore, the devices with the SLG anode were 50% and 86.7% higher in efficiency than the cells with the TLG and FLG anodes. These results show the potential of SLG electrodes for flexible and wearable OPV cells as well as other organic optoelectronic devices.

Ion source with improved primary arc collimation

DOEpatents

Dagenhart, W.K.

1983-12-16

An improved negative ion source is provided in which a self-biasing, molybdenum collimator is used to define the primary electron stream arc discharge from a filament operated at a negative potential. The collimator is located between the anode and the filament. It is electrically connected to the anode by means of an appropriate size resistor such that the collimator is biased at essentially the filament voltage during operation. Initially, the full arc voltage appears across the filament to collimator until the arc discharge strikes. Then the collimator biases itself to essentially filament potential due to current flow through the resistor thus defining the primary electron stream without intercepting any appreciable arc power. The collimator aperture is slightly smaller than the anode aperture to shield the anode from the arc power which, in the past, has caused overheating and erosion of the anode collimator during extended time pulsed-beam operation of the source. With the self-biasing collimator of this invention, the ion source may be operated from short pulse periods to steady-state without destroying the anode.

Cyclic performance tests of Sn/MWCNT composite lithium ion battery anodes at different temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tocoglu, U., E-mail: utocoglu@sakarya.edu.tr; Cevher, O.; Akbulut, H.

In this study tin-multi walled carbon nanotube (Sn-MWCNT) lithium ion battery anodes were produced and their electrochemical galvanostatic charge/discharge tests were conducted at various (25 °C, 35 °C, 50 °C) temperatures to determine the cyclic behaviors of anode at different temperatures. Anodes were produced via vacuum filtration and DC magnetron sputtering technique. Tin was sputtered onto buckypapers to form composite structure of anodes. SEM analysis was conducted to determine morphology of buckypapers and Sn-MWCNT composite anodes. Structural and phase analyses were conducted via X-ray diffraction and Raman Spectroscopy technique. CR2016 coin cells were assembled for electrochemical tests. Cyclic voltammetry testmore » were carried out to determine the reversibility of reactions between anodes and reference electrode between 0.01-2.0 V potential window. Galvanostatic charge/discharge tests were performed to determine cycle performance of anodes at different temperatures.« less

First principles calculations of stability and lithium intercalation potentials of ZnCo2O4

NASA Astrophysics Data System (ADS)

Yu, L. C.; Wu, J.; Liu, H.; Zhang, Y. N.

2015-03-01

Among the metal oxides, which are the most widely investigated alternative anodes for use in lithium ion batteries (LIBs), binary and ternary tin oxides have received special attention due to their high capacity values. ZnCo2O4 is a promising candidate as the anode material for LIB, and one can expect a total capacity corresponding to 7.0 - 8.33 mol of recyclable Li per mole of ZnCo2O4. Here we studied the structural stability, electronic properties, diffusion barrier and lithium intercalation potentials of ZnCo2O4 through density functional calculations. The calculated structural and energetic parameters are comparable with experiments. Our DFT studies provide insights in understanding the mechanism of lithium ion displacement reactions in this ternary metal oxide.

Anodic oxidation of commercially pure titanium for purification of polluted water

NASA Astrophysics Data System (ADS)

Benkafada, Faouzia; Kerdoud, Djahida; Bouchoucha, Ali

2018-05-01

Anodisation of pure titanium has been carried out in sulphuric acid solution at potentials ranging from 40 V to 5 days. We studied the parameters influencing the anodic deposition such as acid concentration and anodic periods. Anodic oxides thin films were characterized by X-ray diffraction, cyclic polarization and electrochemical impedance spectroscopy. The I-V curves and electrochemical impedance measurements were carried out in 0.1 N NaOH solution. The results indicated that although the thin films obtained by anodic oxidation are nonstoichiometric, they have an electric behaviour like n-type semiconducting material.

Promotion of water-mediated carbon removal by nanostructured barium oxide/nickel interfaces in solid oxide fuel cells.

PubMed

Yang, Lei; Choi, YongMan; Qin, Wentao; Chen, Haiyan; Blinn, Kevin; Liu, Mingfei; Liu, Ping; Bai, Jianming; Tyson, Trevor A; Liu, Meilin

2011-06-21

The existing Ni-yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) perform poorly in carbon-containing fuels because of coking and deactivation at desired operating temperatures. Here we report a new anode with nanostructured barium oxide/nickel (BaO/Ni) interfaces for low-cost SOFCs, demonstrating high power density and stability in C(3)H(8), CO and gasified carbon fuels at 750°C. Synchrotron-based X-ray analyses and microscopy reveal that nanosized BaO islands grow on the Ni surface, creating numerous nanostructured BaO/Ni interfaces that readily adsorb water and facilitate water-mediated carbon removal reactions. Density functional theory calculations predict that the dissociated OH from H(2)O on BaO reacts with C on Ni near the BaO/Ni interface to produce CO and H species, which are then electrochemically oxidized at the triple-phase boundaries of the anode. This anode offers potential for ushering in a new generation of SOFCs for efficient, low-emission conversion of readily available fuels to electricity.

Flavins contained in yeast extract are exploited for anodic electron transfer by Lactococcus lactis.

PubMed

Masuda, Masaki; Freguia, Stefano; Wang, Yung-Fu; Tsujimura, Seiya; Kano, Kenji

2010-06-01

Cyclic voltammograms of yeast extract-containing medium exhibit a clear redox peak around -0.4V vs. Ag|AgCl. Fermentative bacterium Lactococcus lactis was hereby shown to exploit this redox compound for extracellular electron transfer towards a graphite anode using glucose as an electron donor. High performance liquid chromatography revealed that this may be a flavin-type compound. The ability of L. lactis to exploit exogenous flavins for anodic glucose oxidation was confirmed by tests where flavin-type compounds were supplied to the bacterium in well defined media. Based on its mid-point potential, riboflavin can be regarded as a near-optimal mediator for microbially catalyzed anodic electron transfer. Riboflavin derivative flavin mononucleotide (FMN) was also exploited by L. lactis as a redox shuttle, unlike flavin adenine dinucleotide (FAD), possibly due to the absence of a specific transporter for the latter. The use of yeast extract in microbial fuel cell media is herein discouraged based on the related unwanted artificial addition of redox mediators which may distort experimental results. Copyright 2009 Elsevier B.V. All rights reserved.

Low-crystalline iron oxide hydroxide nanoparticle anode for high-performance supercapacitors

PubMed Central

Owusu, Kwadwo Asare; Qu, Longbing; Li, Jiantao; Wang, Zhaoyang; Zhao, Kangning; Yang, Chao; Hercule, Kalele Mulonda; Lin, Chao; Shi, Changwei; Wei, Qiulong; Zhou, Liang; Mai, Liqiang

2017-01-01

Carbon materials are generally preferred as anodes in supercapacitors; however, their low capacitance limits the attained energy density of supercapacitor devices with aqueous electrolytes. Here, we report a low-crystalline iron oxide hydroxide nanoparticle anode with comprehensive electrochemical performance at a wide potential window. The iron oxide hydroxide nanoparticles present capacitances of 1,066 and 716 F g−1 at mass loadings of 1.6 and 9.1 mg cm−2, respectively, a rate capability with 74.6% of capacitance retention at 30 A g−1, and cycling stability retaining 91% of capacitance after 10,000 cycles. The performance is attributed to a dominant capacitive charge-storage mechanism. An aqueous hybrid supercapacitor based on the iron oxide hydroxide anode shows stability during float voltage test for 450 h and an energy density of 104 Wh kg−1 at a power density of 1.27 kW kg−1. A packaged device delivers gravimetric and volumetric energy densities of 33.14 Wh kg−1 and 17.24 Wh l−1, respectively. PMID:28262797

Promotion of water-mediated carbon removal by nanostructured barium oxide/nickel interfaces in solid oxide fuel cells

PubMed Central

Yang, Lei; Choi, YongMan; Qin, Wentao; Chen, Haiyan; Blinn, Kevin; Liu, Mingfei; Liu, Ping; Bai, Jianming; Tyson, Trevor A.; Liu, Meilin

2011-01-01

The existing Ni-yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) perform poorly in carbon-containing fuels because of coking and deactivation at desired operating temperatures. Here we report a new anode with nanostructured barium oxide/nickel (BaO/Ni) interfaces for low-cost SOFCs, demonstrating high power density and stability in C3H8, CO and gasified carbon fuels at 750°C. Synchrotron-based X-ray analyses and microscopy reveal that nanosized BaO islands grow on the Ni surface, creating numerous nanostructured BaO/Ni interfaces that readily adsorb water and facilitate water-mediated carbon removal reactions. Density functional theory calculations predict that the dissociated OH from H2O on BaO reacts with C on Ni near the BaO/Ni interface to produce CO and H species, which are then electrochemically oxidized at the triple-phase boundaries of the anode. This anode offers potential for ushering in a new generation of SOFCs for efficient, low-emission conversion of readily available fuels to electricity. PMID:21694705

Effects of a common transcranial direct current stimulation (tDCS) protocol on motor evoked potentials found to be highly variable within individuals over 9 testing sessions.

PubMed

Horvath, Jared Cooney; Vogrin, Simon J; Carter, Olivia; Cook, Mark J; Forte, Jason D

2016-09-01

Transcranial direct current stimulation (tDCS) uses a weak electric current to modulate neuronal activity. A neurophysiologic outcome measure to demonstrate reliable tDCS modulation at the group level is transcranial magnetic stimulation engendered motor evoked potentials (MEPs). Here, we conduct a study testing the reliability of individual MEP response patterns following a common tDCS protocol. Fourteen participants (7m/7f) each underwent nine randomized sessions of 1 mA, 10 min tDCS (3 anode; 3 cathode; 3 sham) delivered using an M1/orbito-frontal electrode montage (sessions separated by an average of ~5.5 days). Fifteen MEPs were obtained prior to, immediately following and in 5 min intervals for 30 min following tDCS. TMS was delivered at 130 % resting motor threshold using neuronavigation to ensure consistent coil localization. A number of non-experimental variables were collected during each session. At the individual level, considerable variability was seen among different testing sessions. No participant demonstrated an excitatory response ≥20 % to all three anodal sessions, and no participant demonstrated an inhibitory response ≥20 % to all three cathodal sessions. Intra-class correlation revealed poor anodal and cathodal test-retest reliability [anode: ICC(2,1) = 0.062; cathode: ICC(2,1) = 0.055] and moderate sham test-retest reliability [ICC(2,1) = 0.433]. Results also revealed no significant effect of tDCS at the group level. Using this common protocol, we found the effects of tDCS on MEP amplitudes to be highly variable at the individual level. In addition, no significant effects of tDCS on MEP amplitude were found at the group level. Future studies should consider utilizing a more strict experimental protocol to potentially account for intra-individual response variations.

Anode power in a quasi-steady MPD thruster. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Saber, A. J.

1974-01-01

Local anode heat flux in a quasi-steady MPD thruster is measured by thermocouples attached to the inside surface of a shell anode. Over a range of arc currents J from 5.5 to 44 kiloamperes and argon propellant mass flows m from 1 to 48 g/sec, with the ratio J2/m held constant, the fraction of arc power deposited in the anode is found to decrease with increasing arc power. Specifically, this anode power fraction decreases from 50% at 200 kW arc power, to 10% at 20 MW. In an effort to account for this functional behavior, the current density, plasma potential, and electron temperature in the plasma adjacent to the anode are measured with probes, and the results are used in a theoretical anode heat flux model. The model asserts that energy exchange between electrons and heavy particles in the plasma near the anode occur over distances greater than the anode sheath thickness.

Electrochemical mineral scale prevention and removal on electrically conducting carbon nanotube--polyamide reverse osmosis membranes.

PubMed

Duan, Wenyan; Dudchenko, Alexander; Mende, Elizabeth; Flyer, Celeste; Zhu, Xiaobo; Jassby, David

2014-05-01

The electrochemical prevention and removal of CaSO4 and CaCO3 mineral scales on electrically conducting carbon nanotube - polyamide reverse osmosis membrane was investigated. Different electrical potentials were applied to the membrane surface while filtering model scaling solutions with high saturation indices. Scaling progression was monitored through flux measurements. CaCO3 scale was efficiently removed from the membrane surface through the intermittent application of a 2.5 V potential to the membrane surface, when the membrane acted as an anode. Water oxidation at the anode, which led to proton formation, resulted in the dissolution of deposited CaCO3 crystals. CaSO4 scale formation was significantly retarded through the continuous application of 1.5 V DC to the membrane surface, when the membrane was operated as an anode. The continuous application of a sufficient electrical potential to the membrane surface leads to the formation of a thick layer of counter-ions along the membrane surface that pushed CaSO4 crystal formation away from the membrane surface, allowing the formed crystals to be carried away by the cross-flow. We developed a simple model, based on a modified Poisson-Boltzmann equation, which qualitatively explained our observed experimental results.

High-velocity DC-VPS for diffusion and protecting barrier layers in solid oxide fuel cells (SOFCs)

NASA Astrophysics Data System (ADS)

Henne, R. H.; Franco, T.; Ruckdäschel, R.

2006-12-01

High-temperature fuel cells of the solid oxide fuel cell (SOFC) type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced lightweight planar cells for electricity supply units in cars and other mobile systems. Such cells, in one new design, consist mainly of metallic parts, for example, of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of chromium species from the interconnect or the cell containment into the electrolyte/cathode interface forming insulating phases and by the mutual diffusion of substrate and anode material, for example, iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite, which in both cases reduces performance and system lifetime. Additional intermediate layers of perovskite-type material, (e.g., doped LaCrO3) applied with high-velocity direct-current vacuum plasma spraying (DC-VPS) can reduce such effects considerably if they are stable and of high electronic conductivity.

Electricity generation from acetate and glucose by sedimentary bacterium attached to electrode in microbial-anode fuel cells

NASA Astrophysics Data System (ADS)

Zhang, Enren; Xu, Wei; Diao, Guowang; Shuang, Chendong

Microbial-anode fuel cells (MAFCs) with high electron recovery (>50%) from acetate and glucose have been constructed in this study. By inoculating fresh sedimentary microorganisms into anaerobic anode compartments, a stable current (∼0.42 mA for acetate-fed MAFCs; ∼0.35 mA for glucose-fed MAFCs) is generated from the oxidation of the added organic matter until its concentration decreases to a low level. SEM micrographs indicate that thick biofilms of microbial communities (coccoid cells with a diameter of ∼0.5 μm in acetate-fed MAFCs; rod-shaped cells with a length of 2.0-4.0 μm and a width of 0.5-0.7 μm in glucose-fed MAFCs) completely cover the anode electrodes. These anodophillic biofilms are thought to be responsible for the current generation, and make these microbial-anode fuel cells exhibit good performance even when the growth medium is replaced by a salt buffer without any growth factor. In comparison with those microbial fuel cells that require the addition of artificial electron transfer-mediating compounds, the findings in this study imply a potential way to develop excellent mediator-less MAFCs for electricity generation from organic matter by using substrate-induced anodophillic microbial species.

Electrochemical studies on the performance of SS316L electrode in electrokinetics

NASA Astrophysics Data System (ADS)

Choi, Jeong-Hee; Maruthamuthu, Sundaram; Lee, Hyun-Goo; Ha, Tae-Hyun; Bae, Jeong-Hyo

2009-10-01

Organic and trace metal pollutants are removed by employing various electrodes in an electrokinetic (EK) process. Stainless steel was used either as an anode or a cathode by various investigators in electroremediation systems. In the present study, the role of SS316L as an anode and cathode in EK system was studied by the measurements of pH, conductivity of electrolyte, and potential of the anode and cathode at different current densities. The weight loss of the anode and cathode and the leaching of chromium, iron, and nickel at different current densities were measured and discussed with an electroosmosis process. The electrochemical behavior of SS316L electrode in neutral, acidic and alkaline pH in soil environment was studied by an electrochemical technique viz. polarization study. Surface analysis of SS316L after EK was done by XPS and SEM. The higher conductivity was noticed at anolyte when compared to catholyte. The weight loss of the anode was in the following order 0.615 > 0.307 > 0.123 mA/cm2 and the cathode corrosion rate was vice versa. Peroxide production was also noticed at the anolyte, which may encourage the degradation of the total organic content (TOC) in the soil. The OCP (open circuit potential) of SS316L was about +75 mV vs SCE in the soil extract; while adding acetic acid, the potential shifted to the positive side, to about +380 mV vs SCE. The breakdown potential and the range of passivation potential were higher in acetic acid added system when compared to other systems. Pitting was observed on both the anode and cathode within 48 h during the EK process. The present study concludes that SS is not a proper electrode material for the EK process.

MEMBRANE POTENTIAL OF THE SQUID GIANT AXON DURING CURRENT FLOW

PubMed Central

Cole, Kenneth S.; Curtis, Howard J.

1941-01-01

The squid giant axon was placed in a shallow narrow trough and current was sent in at two electrodes in opposite sides of the trough and out at a third electrode several centimeters away. The potential difference across the membrane was measured between an inside fine capillary electrode with its tip in the axoplasm between the pair of polarizing electrodes, and an outside capillary electrode with its tip flush with the surface of one polarizing electrode. The initial transient was roughly exponential at the anode make and damped oscillatory at the sub-threshold cathode make with the action potential arising from the first maximum when threshold was reached. The constant change of membrane potential, after the initial transient, was measured as a function of the total polarizing current and from these data the membrane potential is obtained as a function of the membrane current density. The absolute value of the resting membrane resistance approached at low polarizing currents is about 23 ohm cm.2. This low value is considered to be a result of the puncture of the axon. The membrane was found to be an excellent rectifier with a ratio of about one hundred between the high resistance at the anode and the low resistance at the cathode for the current range investigated. On the assumption that the membrane conductance is a measure of its ion permeability, these experiments show an increase of ion permeability under a cathode and a decrease under an anode. PMID:19873234

Fabrication of Highly Ordered Anodic Aluminium Oxide Templates on Silicon Substrates

DTIC Science & Technology

2007-01-01

highly ordered anodic aluminium oxide ( AAO ) templates of unprecedented pore uniformity directly on Si, enabled by new advances on two fronts – direct...field emitter, sensors, oscillators and photodetectors. 15. SUBJECT TERMS Anodic aluminum oxide , template-assisted nanofabrication, carbon nanotube...Fabrication of the aligned and patterned carbon nanotube field emitters using the anodic aluminum oxide nano-template on a Si wafer’, Synth. Met

Structural and characteristic variation of anodic oxide on pure Ti with anodization duration

NASA Astrophysics Data System (ADS)

Mizukoshi, Yoshiteru; Ohtsu, Naofhumi; Masahashi, Naoya

2013-10-01

Change in the structural and characteristic of the anodic oxide on pure Ti with the duration of anodization time was investigated. With the progress of the anodization, the phase of the formed TiO2 successively changed from anatase phase to rutile phase. In the transition process, peak intensities of rutile TiO2 1 0 1, 1 1 1 and 2 1 1 planes of X-ray diffraction characteristically increased. The contact angles of water droplets on the anodize TiO2 were monotonously decreased with the progress of the anodization except on the characteristically oriented rutile surface. In the evaluations of acetaldehyde photocatalysis under UV illumination, the anatase TiO2 anodized for short period exhibited high activities. On the other hand, when illuminated with visible light (>422 nm), rutile-structured TiO2 formed by anodization with a long duration exhibited superior photocatalytic activities probably due to high rutile fraction and sulfur incorporation from the electrolyte.

Novel structure formation at the bottom surface of porous anodic alumina fabricated by single step anodization process.

PubMed

Ali, Ghafar; Ahmad, Maqsood; Akhter, Javed Iqbal; Maqbool, Muhammad; Cho, Sung Oh

2010-08-01

A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H(2)SO(4) electrolyte through a single step anodization without any additional pre-anodizing procedure is reported. Free-standing porous anodic alumina film of 180 microm thickness with through hole morphology was obtained. A simple and single step process was used for the detachment of alumina from aluminum substrate. The effect of anodizing conditions, such as anodizing voltage and time on the pore diameter and pore ordering is discussed. The metal/oxide and oxide/electrolyte interfaces were examined by high resolution scanning transmission electron microscope. The arrangement of pores on metal/oxide interface was well ordered with smaller diameters than that of the oxide/electrolyte interface. The inter-pore distance was larger in metal/oxide interface as compared to the oxide/electrolyte interface. The size of the ordered domain was found to depend strongly upon anodizing voltage and time. (c) 2010 Elsevier Ltd. All rights reserved.

CdZnTe Image Detectors for Hard-X-Ray Telescopes

NASA Technical Reports Server (NTRS)

Chen, C. M. Hubert; Cook, Walter R.; Harrison, Fiona A.; Lin, Jiao Y. Y.; Mao, Peter H.; Schindler, Stephen M.

2005-01-01

Arrays of CdZnTe photodetectors and associated electronic circuitry have been built and tested in a continuing effort to develop focal-plane image sensor systems for hard-x-ray telescopes. Each array contains 24 by 44 pixels at a pitch of 498 m. The detector designs are optimized to obtain low power demand with high spectral resolution in the photon- energy range of 5 to 100 keV. More precisely, each detector array is a hybrid of a CdZnTe photodetector array and an application-specific integrated circuit (ASIC) containing an array of amplifiers in the same pixel pattern as that of the detectors. The array is fabricated on a single crystal of CdZnTe having dimensions of 23.6 by 12.9 by 2 mm. The detector-array cathode is a monolithic platinum contact. On the anode plane, the contact metal is patterned into the aforementioned pixel array, surrounded by a guard ring that is 1 mm wide on three sides and is 0.1 mm wide on the fourth side so that two such detector arrays can be placed side-by-side to form a roughly square sensor area with minimal dead area between them. Figure 1 shows two anode patterns. One pattern features larger pixel anode contacts, with a 30-m gap between them. The other pattern features smaller pixel anode contacts plus a contact for a shaping electrode in the form of a grid that separates all the pixels. In operation, the grid is held at a potential intermediate between the cathode and anode potentials to steer electric charges toward the anode in order to reduce the loss of charges in the inter-anode gaps. The CdZnTe photodetector array is mechanically and electrically connected to the ASIC (see Figure 2), either by use of indium bump bonds or by use of conductive epoxy bumps on the CdZnTe array joined to gold bumps on the ASIC. Hence, the output of each pixel detector is fed to its own amplifier chain.

Degradation Mechanisms of Magnesium Metal Anodes in Electrolytes Based on (CF 3SO 2) 2N – at High Current Densities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Hyun Deog; Han, Sang-Don; Bolotin, Igor L.

The energy density of rechargeable batteries utilizing metals as anodes surpasses that of Li ion batteries, which employ carbon instead. Among possible metals, magnesium represents a potential alternative to the conventional choice, lithium, in terms of storage density, safety,stability, and cost. However, a major obstacle for metal-based batteries is the identification of electrolytes that show reversible deposition/dissolution of the metal anode and support reversible intercalation of ions into a cathode. Traditional Grignard-based Mg electrolytes are excellent with respect to the reversible deposition of Mg, but their limited anodic stability and compatibility with oxide cathodes hinder their applicability in Mg batteriesmore » with higher voltage. Non-Grignard electrolytes, which consist of ethereal solutions of magnesium(II) bis(trifluoromethanesulfonyl)imide (Mg(TFSI) 2), remain fairly stable near the potential of Mg deposition. The slight reactivity of these electrolytes toward Mg metal can be remedied by the addition of surface-protecting agents, such as MgCl 2. Hence, ethereal solutions of Mg(TFSI) 2 salt with MgCl 2 as an additive have been suggested as a representative non-Grignard Mg electrolyte. In this work, the degradation mechanisms of a Mg metal anode in the TFSI-based electrolyte were studied using a current density of 1 mA cm -2 and an areal capacity of ~0.4 mAh cm -2, which is close to those used in practical applications. The degradation mechanisms identified include the corrosion of Mg metal, which causes the loss of electronic pathways and mechanical integrity, the nonuniform deposition of Mg, and the decomposition of TFSI - anions. This study not only represents an assessment of the behavior of Mg metal anodes at practical current density and areal capacity but also details the outcomes of interfacial passivation, which was detected by simple cyclic voltammetry experiments. This study also points out the absolute absence of any passivation at the electrode-electrolyte interface for the premise of developing electrolytes compatible with a metal anode.« less

Degradation Mechanisms of Magnesium Metal Anodes in Electrolytes Based on (CF 3SO 2) 2N – at High Current Densities

DOE PAGES

Yoo, Hyun Deog; Han, Sang-Don; Bolotin, Igor L.; ...

2017-06-21

The energy density of rechargeable batteries utilizing metals as anodes surpasses that of Li ion batteries, which employ carbon instead. Among possible metals, magnesium represents a potential alternative to the conventional choice, lithium, in terms of storage density, safety,stability, and cost. However, a major obstacle for metal-based batteries is the identification of electrolytes that show reversible deposition/dissolution of the metal anode and support reversible intercalation of ions into a cathode. Traditional Grignard-based Mg electrolytes are excellent with respect to the reversible deposition of Mg, but their limited anodic stability and compatibility with oxide cathodes hinder their applicability in Mg batteriesmore » with higher voltage. Non-Grignard electrolytes, which consist of ethereal solutions of magnesium(II) bis(trifluoromethanesulfonyl)imide (Mg(TFSI) 2), remain fairly stable near the potential of Mg deposition. The slight reactivity of these electrolytes toward Mg metal can be remedied by the addition of surface-protecting agents, such as MgCl 2. Hence, ethereal solutions of Mg(TFSI) 2 salt with MgCl 2 as an additive have been suggested as a representative non-Grignard Mg electrolyte. In this work, the degradation mechanisms of a Mg metal anode in the TFSI-based electrolyte were studied using a current density of 1 mA cm -2 and an areal capacity of ~0.4 mAh cm -2, which is close to those used in practical applications. The degradation mechanisms identified include the corrosion of Mg metal, which causes the loss of electronic pathways and mechanical integrity, the nonuniform deposition of Mg, and the decomposition of TFSI - anions. This study not only represents an assessment of the behavior of Mg metal anodes at practical current density and areal capacity but also details the outcomes of interfacial passivation, which was detected by simple cyclic voltammetry experiments. This study also points out the absolute absence of any passivation at the electrode-electrolyte interface for the premise of developing electrolytes compatible with a metal anode.« less

Electrochemical double layers at the interface between glassy electrolytes and platinum: Differentiating between the anode and the cathode capacitance

NASA Astrophysics Data System (ADS)

Kruempelmann, J.; Mariappan, C. R.; Schober, C.; Roling, B.

2010-12-01

We have measured potential-dependent interfacial capacitances of two Na-Ca-phosphosilicate glasses and of an AgI-doped silver borate glass between ion-blocking Pt electrodes. An asymmetric electrode configuration with highly dissimilar electrode areas on both faces of the glass samples allowed us to determine the capacitance at the small-area electrode. Using equivalent circuit fitting we extract potential-dependent double-layer capacitances. The potential-dependent anodic capacitance exhibits a weak maximum and drops strongly at higher potentials. The cathodic capacitance exhibits a more pronounced maximum, this maximum being responsible for the maximum in the total capacitance observed in measurements in a symmetrical electrode configuration. The capacitance maxima of the Na-Ca phosphosilicate glasses show up at higher electrode potentials than the maxima of the AgI-doped silver borate glass. Remarkably, for both types of glasses, the potential of the cathodic capacitance maximum is closely related to the activation energy of the bulk ion transport. We compare our results to recent theoretical predictions by Shklovskii and co-workers.

Currents between tethered electrodes in a magnetized laboratory plasma

NASA Technical Reports Server (NTRS)

Stenzel, R. L.; Urrutia, J. M.

1989-01-01

Laboratory experiments on important plasma physics issues of electrodynamic tethers were performed. These included current propagation, formation of wave wings, limits of current collection, nonlinear effects and instabilities, charging phenomena, and characteristics of transmission lines in plasmas. The experiments were conducted in a large afterglow plasma. The current system was established with a small electron-emitting hot cathode tethered to an electron-collecting anode, both movable across the magnetic field and energized by potential difference up to V approx.=100 T(sub e). The total current density in space and time was obtained from complete measurements of the perturbed magnetic field. The fast spacecraft motion was reproduced in the laboratory by moving the tethered electrodes in small increments, applying delayed current pulses, and reconstructing the net field by a linear superposition of locally emitted wavelets. With this technique, the small-amplitude dc current pattern is shown to form whistler wings at each electrode instead of the generally accepted Alfven wings. For the beam electrode, the whistler wing separates from the field-aligned beam which carries no net current. Large amplitude return currents to a stationary anode generate current-driven microinstabilities, parallel electric fields, ion depletions, current disruptions and time-varying electrode charging. At appropriately high potentials and neutral densities, excess neutrals are ionized near the anode. The anode sheath emits high-frequency electron transit-time oscillations at the sheath-plasma resonance. The beam generates Langmuir turbulence, ion sound turbulence, electron heating, space charge fields, and Hall currents. An insulated, perfectly conducting transmission line embedded in the plasma becomes lossy due to excitation of whistler waves and magnetic field diffusion effects. The implications of the laboratory observations on electrodynamic tethers in space are discussed.

Local potential evolutions during proton exchange membrane fuel cell operation with dead-ended anode - Part I: Impact of water diffusion and nitrogen crossover

NASA Astrophysics Data System (ADS)

Abbou, S.; Dillet, J.; Maranzana, G.; Didierjean, S.; Lottin, O.

2017-02-01

Operating a PEMFC with a dead-ended anode may lead to local fuel-starvation because of water and possibly nitrogen accumulation in the anode compartment. In previous works, we used a segmented linear cell with reference electrodes to monitor simultaneously the local potentials and current densities during dead-ended anode operation. The results indicated that water transport as well as nitrogen crossover through the membrane were most probably the two key factors governing fuel starvation. In this first from a set of two papers, we evaluated with more details the contributions of nitrogen crossover and water transport to hydrogen starvation. To assess nitrogen contribution, the fuel cell cathode compartment was first supplied with pure oxygen instead of air. The results showed that in the absence of nitrogen (in the cathode side) the fuel starvation was much slower than with air, suggesting that nitrogen contribution cannot be neglected. On the other hand, the contribution of water flooding to hydrogen starvation was investigated by using different cooling temperature on the cathode and anode sides in order to drive water toward the colder plate. The results showed that with a colder anode side, fuel starvation was faster. In the opposite case of a hotter anode plate, water accumulation in the anode compartment was limited, nitrogen crossover through the membrane was the main reason for hydrogen starvation in this case. To fully assess the impact of the thermal configurations on membrane-electrode assembly (MEA) degradation, aging protocols with a dead-ended anode and a fixed closing time were also performed. The results showed that operation with a hotter anode could help to limit significantly cathode ElectroChemical Surface Area (ECSA) losses along the cell area and performance degradation induced by hydrogen starvation.

Theoretical Limits of Energy Density in Silicon-Carbon Composite Anode Based Lithium Ion Batteries

PubMed Central

Dash, Ranjan; Pannala, Sreekanth

2016-01-01

Silicon (Si) is under consideration as a potential next-generation anode material for the lithium ion battery (LIB). Experimental reports of up to 40% increase in energy density of Si anode based LIBs (Si-LIBs) have been reported in literature. However, this increase in energy density is achieved when the Si-LIB is allowed to swell (volumetrically expand) more than graphite based LIB (graphite-LIB) and beyond practical limits. The volume expansion of LIB electrodes should be negligible for applications such as automotive or mobile devices. We determine the theoretical bounds of Si composition in a Si–carbon composite (SCC) based anode to maximize the volumetric energy density of a LIB by constraining the external dimensions of the anode during charging. The porosity of the SCC anode is adjusted to accommodate the volume expansion during lithiation. The calculated threshold value of Si was then used to determine the possible volumetric energy densities of LIBs with SCC anode (SCC-LIBs) and the potential improvement over graphite-LIBs. The level of improvement in volumetric and gravimetric energy density of SCC-LIBs with constrained volume is predicted to be less than 10% to ensure the battery has similar power characteristics of graphite-LIBs. PMID:27311811

Method and apparatus for measuring purity of noble gases

DOEpatents

Austin, Robert

2008-04-01

A device for detecting impurities in a noble gas includes a detection chamber and a source of pulsed ultraviolet light. The pulse of the ultraviolet light is transferred into the detection chamber and onto a photocathode, thereby emitting a cloud of free electrons into the noble gas within the detection chamber. The cloud of electrons is attracted to the opposite end of the detection chamber by a high positive voltage potential at that end and focused onto a sensing anode. If there are impurities in the noble gas, some or all of the electrons within the cloud will bond with the impurity molecules and not reach the sensing anode. Therefore, measuring a lower signal at the sensing anode indicates a higher level of impurities while sensing a higher signal indicates fewer impurities. Impurities in the range of one part per billion can be measured by this device.

Lithium metal protection enabled by in-situ olefin polymerization for high-performance secondary lithium sulfur batteries

NASA Astrophysics Data System (ADS)

An, Yongling; Zhang, Zhen; Fei, Huifang; Xu, Xiaoyan; Xiong, Shenglin; Feng, Jinkui; Ci, Lijie

2017-09-01

Lithium metal is considered to be the optimal choice of next-generation anode materials due to its ultrahigh theoretical capacity and the lowest redox potential. However, the growth of dendritic and mossy lithium for rechargeable Li metal batteries lead to the possible short circuiting and subsequently serious safety issues during charge/discharge cycles. For the further practical applications of Li anode, here we report a facile method for fabricating robust interfacial layer via in-situ olefin polymerization. The resulting polymer layer effectively suppresses the formation of Li dendrites and enables the long-term operation of Li metal batteries. Using Li-S cells as a test system, we also demonstrate an improved capacity retention with the protection of tetramethylethylene-polymer. Our results indicate that this method could be a promising strategy to tackle the intrinsic problems of lithium metal anodes and promote the development of Li metal batteries.

Microscale Digital Vacuum Electronic Gates

NASA Technical Reports Server (NTRS)

Manohara, Harish (Inventor); Mojarradi, Mohammed M. (Inventor)

2014-01-01

Systems and methods in accordance with embodiments of the invention implement microscale digital vacuum electronic gates. In one embodiment, a microscale digital vacuum electronic gate includes: a microscale field emitter that can emit electrons and that is a microscale cathode; and a microscale anode; where the microscale field emitter and the microscale anode are disposed within at least a partial vacuum; where the microscale field emitter and the microscale anode are separated by a gap; and where the potential difference between the microscale field emitter and the microscale anode is controllable such that the flow of electrons between the microscale field emitter and the microscale anode is thereby controllable; where when the microscale anode receives a flow of electrons, a first logic state is defined; and where when the microscale anode does not receive a flow of electrons, a second logic state is defined.

Natural gas anodes for aluminium electrolysis in molten fluorides.

PubMed

Haarberg, Geir Martin; Khalaghi, Babak; Mokkelbost, Tommy

2016-08-15

Industrial primary production of aluminium has been developed and improved over more than 100 years. The molten salt electrolysis process is still suffering from low energy efficiency and considerable emissions of greenhouse gases (CO2 and PFC). A new concept has been suggested where methane is supplied through the anode so that the CO2 emissions may be reduced significantly, the PFC emissions may be eliminated and the energy consumption may decrease significantly. Porous carbon anodes made from different graphite grades were studied in controlled laboratory experiments. The anode potential, the anode carbon consumption and the level of HF gas above the electrolyte were measured during electrolysis. In some cases it was found that the methane oxidation was effectively participating in the anode process.

Direct electrochemical oxidation of ammonia on graphite as a treatment option for stored source-separated urine.

PubMed

Zöllig, Hanspeter; Fritzsche, Cristina; Morgenroth, Eberhard; Udert, Kai M

2015-02-01

Electrolysis can be a viable technology for ammonia removal from source-separated urine. Compared to biological nitrogen removal, electrolysis is more robust and is highly amenable to automation, which makes it especially attractive for on-site reactors. In electrolytic wastewater treatment, ammonia is usually removed by indirect oxidation through active chlorine which is produced in-situ at elevated anode potentials. However, the evolution of chlorine can lead to the formation of chlorate, perchlorate, chlorinated organic by-products and chloramines that are toxic. This study focuses on using direct ammonia oxidation on graphite at low anode potentials in order to overcome the formation of toxic by-products. With the aid of cyclic voltammetry, we demonstrated that graphite is active for direct ammonia oxidation without concomitant chlorine formation if the anode potential is between 1.1 and 1.6 V vs. SHE (standard hydrogen electrode). A comparison of potentiostatic bulk electrolysis experiments in synthetic stored urine with and without chloride confirmed that ammonia was removed exclusively by continuous direct oxidation. Direct oxidation required high pH values (pH > 9) because free ammonia was the actual reactant. In real stored urine (pH = 9.0), an ammonia removal rate of 2.9 ± 0.3 gN·m(-2)·d(-1) was achieved and the specific energy demand was 42 Wh·gN(-1) at an anode potential of 1.31 V vs. SHE. The measurements of chlorate and perchlorate as well as selected chlorinated organic by-products confirmed that no chlorinated by-products were formed in real urine. Electrode corrosion through graphite exfoliation was prevented and the surface was not poisoned by intermediate oxidation products. We conclude that direct ammonia oxidation on graphite electrodes is a treatment option for source-separated urine with three major advantages: The formation of chlorinated by-products is prevented, less energy is consumed than in indirect ammonia oxidation and readily available and cheap graphite can be used as the electrode material. Copyright © 2014 Elsevier Ltd. All rights reserved.

Strong texturing of lithium metal in batteries

DOE PAGES

Shi, Feifei; Pei, Allen; Vailionis, Arturas; ...

2017-10-30

Lithium, with its high theoretical specific capacity and lowest electrochemical potential, has been recognized as the ultimate negative electrode material for next-generation lithium-based high-energy-density batteries. However, a key challenge that has yet to be overcome is the inferior reversibility of Li plating and stripping, typically thought to be related to the uncontrollable morphology evolution of the Li anode during cycling. Here we show that Li-metal texturing (preferential crystallographic orientation) occurs during electrochemical deposition, which governs the morphological change of the Li anode. X-ray diffraction pole-figure analysis demonstrates that the texture of Li deposits is primarily dependent on the type ofmore » additive or cross-over molecule from the cathode side. With adsorbed additives, like LiNO 3 and polysulfide, the lithium deposits are strongly textured, with Li (110) planes parallel to the substrate, and thus exhibit uniform, rounded morphology. A growth diagram of lithium deposits is given to connect various texture and morphology scenarios for different battery electrolytes. In conclusion, this understanding of lithium electrocrystallization from the crystallographic point of view provides significant insight for future lithium anode materials design in high-energy-density batteries.« less

Influence of the heat treatment condition of alloy AlCu4Mg1 on the microstructure and properties of anodic oxide layers

NASA Astrophysics Data System (ADS)

Morgenstern, R.; Dietrich, D.; Sieber, M.; Lampke, T.

2017-03-01

Due to their outstanding specific mechanical properties, high-strength, age-hardenable aluminum alloys offer a high potential for lightweight security-related applications. However, the use of copper-alloyed aluminum is limited because of their susceptibility to selective corrosion and their low wear resistance. These restrictions can be overcome and new applications can be opened up by the generation of protective anodic aluminum oxide layers. In contrast to the anodic oxidation of unalloyed aluminum, oxide layers produced on copper-rich alloys exhibit a significantly more complex pore structure. It is the aim of the investigation to identify the influence of microstructural parameters such as size and distribution of the strengthening precipitations on the coating microstructure. The aluminum alloy EN AW-2024 (AlCu4Mg1) in different heat treatment conditions serves as substrate material. The influence of the strengthening precipitations’ size and distribution on the development of the pore structure is investigated by the use of high-resolution scanning electron microscopy. Integral coating properties are characterized by non-destructive and light-microscopic thickness measurements and instrumented indentation tests.

Strong texturing of lithium metal in batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Feifei; Pei, Allen; Vailionis, Arturas

Lithium, with its high theoretical specific capacity and lowest electrochemical potential, has been recognized as the ultimate negative electrode material for next-generation lithium-based high-energy-density batteries. However, a key challenge that has yet to be overcome is the inferior reversibility of Li plating and stripping, typically thought to be related to the uncontrollable morphology evolution of the Li anode during cycling. Here we show that Li-metal texturing (preferential crystallographic orientation) occurs during electrochemical deposition, which governs the morphological change of the Li anode. X-ray diffraction pole-figure analysis demonstrates that the texture of Li deposits is primarily dependent on the type ofmore » additive or cross-over molecule from the cathode side. With adsorbed additives, like LiNO 3 and polysulfide, the lithium deposits are strongly textured, with Li (110) planes parallel to the substrate, and thus exhibit uniform, rounded morphology. A growth diagram of lithium deposits is given to connect various texture and morphology scenarios for different battery electrolytes. In conclusion, this understanding of lithium electrocrystallization from the crystallographic point of view provides significant insight for future lithium anode materials design in high-energy-density batteries.« less

High performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte. I. Ni-SDC cermet anode

NASA Astrophysics Data System (ADS)

Ohara, S.; Maric, R.; Zhang, X.; Mukai, K.; Fukui, T.; Yoshida, H.; Inagaki, T.; Miura, K.

A Ni-samaria-doped ceria (SDC) cermet was selected as the anode material for reduced temperature (800°C) solid oxide fuel cells. The NiO-SDC composite powder, synthesized by spray pyrolysis, was employed as the starting anode powder in this study. The influence of Ni content in Ni-SDC cermets on the electrode performance was investigated in order to create the most suitable microstructures. It was found that anodic polarization was strongly influenced by the Ni content in Ni-SDC cermets. The best results were obtained for anode cermets with Ni content of around 50 vol.%; anodic polarization was about 30 mV at a current density of 300 mA/cm 2. This high performance seems to be attributable to the microstructure, in which Ni grains form a skeleton with well-connected SDC grains finely distributed over the Ni grains surfaces; such microstructure was also conducive to high stability of the anode.

Cu-SnO2 nanostructures obtained via galvanic replacement control as high performance anodes for lithium-ion storage

NASA Astrophysics Data System (ADS)

Nguyen, Tuan Loi; Park, Duckshin; Hur, Jaehyun; Son, Hyung Bin; Park, Min Sang; Lee, Seung Geol; Kim, Ji Hyeon; Kim, Il Tae

2018-01-01

SnO2 has been considered as a promising anode material for lithium ion batteries (LIBs) because of its high theoretical capacity (782 mAh g-1). However, the reaction between lithium ions and Sn causes a large volume change, resulting in the pulverization of the anode, a loss of contact with the current collector, and a deterioration in electrochemical performance. Several strategies have been proposed to mitigate the drastic volume changes to extend the cyclic life of SnO2 materials. Herein, novel composites consisting of Cu and SnO2 were developed via the galvanic replacement reaction. The reaction was carried out at 180 °C for different durations and triethylene glycol was used as the medium solvent. The structure, morphology, and composition of the composites were analyzed by X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The reaction time affected the particle size, which in turn affected the reaction kinetics. Furthermore, the novel nanostructures contained an inactive metal phase (Cu), which acted both as the buffer space against the volume change of Sn during the alloying reaction and as the electron conductor, resulting in a lower impedance of the composites. When evaluated as potential anodes for LIBs, the composite electrodes displayed extraordinary electrochemical performance with a high capacity and Coulombic efficiency, an excellent cycling stability, and a superior rate capability compared to a Sn electrode.

Potassium vanadate K0.23V2O5 as anode materials for lithium-ion and potassium-ion batteries

NASA Astrophysics Data System (ADS)

Liu, Cailing; Luo, Shaohua; Huang, Hongbo; Wang, Zhiyuan; Wang, Qing; Zhang, Yahui; Liu, Yanguo; Zhai, Yuchun; Wang, Zhaowen

2018-06-01

A layered potassium vanadate K0.23V2O5 has been successfully prepared by the hydrothermal method and evaluated as an anode material for lithium-ion and potassium-ion batteries. High structural stability is demonstrated by the ex situ X-ray diffraction (XRD) and ex situ scanning electron microscopy (SEM). When used as an anode material for lithium-ion batteries, the K0.23V2O5 exhibits a reversible capacity of 480.4 mAh g-1 at 20 mA g-1 after 100 cycles and 439.7 mAh g-1 at 200 mA g-1 after 300 cycles as well as good cycling stability. Even at a high current density of 800 mA g-1, a high reversible capacity of 202.5 mAh g-1 can be retained, indicating excellent rate performance. Whereas in potassium-ion batteries, it retains a capacity of 121.6 mAh g-1 after 150 cycles at 20 mA g-1 and 97.6 mAh g-1 at 100 mA g-1 after 100 cycles. Such superior electrochemical performance of K0.23V2O5 can be ascribed to the special flower-like morphology and structure. Overall, the results highlight the great potential of K0.23V2O5 as an anode material for both lithium-ion and potassium-ion batteries.

Local potential evolutions during proton exchange membrane fuel cell operation with dead-ended anode - Part II: Aging mitigation strategies based on water management and nitrogen crossover

NASA Astrophysics Data System (ADS)

Abbou, S.; Dillet, J.; Maranzana, G.; Didierjean, S.; Lottin, O.

2017-02-01

Proton exchange membrane (PEM) fuel cells operate with dead-ended anode in order to reduce system cost and complexity when compared with hydrogen re-circulation systems. In the first part of this work, we showed that localized fuel starvation events may occur, because of water and nitrogen accumulation in the anode side, which could be particularly damaging to the cell performance. To prevent these degradations, the anode compartment must be purged which may lead to an overall system efficiency decrease because of significant hydrogen waste. In the second part, we present several purge strategies in order to minimize both hydrogen waste and membrane-electrode assembly degradations during dead-ended anode operation. A linear segmented cell with reference electrodes was used to monitor simultaneously the current density distribution along the gas channel and the time evolution of local anode and cathode potentials. To asses MEA damages, Platinum ElectroChemical Surface Area (ECSA) and cell performance were periodically measured. The results showed that dead-end mode operation with an anode plate maintained at a temperature 5 °C hotter than the cathode plate limits water accumulation in the anode side, reducing significantly purge frequency (and thus hydrogen losses) as well as MEA damages. As nitrogen contribution to hydrogen starvation is predominant in this thermal configuration, we also tested a microleakage solution to discharge continuously most the nitrogen accumulating in the anode side while ensuring low hydrogen losses and minimum ECSA losses provided the right microleakage flow rate is chosen.

Development of a Nanomaterial Anode for a Low-Voltage Proportional Counter for Neutron Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craps, Matthew Greg

NanoTechLabs (NTL) in collaboration with the Savannah River National Laboratory (SRNL) and Clemson University have continued development of a next generation proportional counter (PC) for neutron detection utilizing robust, inexpensive nanostructured anodes while maximizing neutron capture. Neutron detectors are vital to national security as they can be used to detect illicit trafficking of radioactive materials, which could mean the presence of or planning of a dirty bomb attack. Typical PCs operate with high bias potentials that create electronic noise. Incorporating nanomaterials into the anode of PCs can theoretically operate at low voltages (eg. 10-300V) due to an increase in themore » electric field associated with a smaller diameter nano-scale anode. In addition to the lower operating voltage, typical high PC voltages (500-1200V) could be used to generate a larger electric field resulting in more electrons being collected, thus increasing the sensitivity of the PC. Other advantages of nano-PC include reduced platform size, weight, cost, and improved ruggedness. Clemson modeled the electric field around the CNT array tips. NTL grew many ordered CNT arrays as well as control samples and densified the arrays to improve the performance. The primary objective for this work is to provide evidence of a commercially viable technique for reducing the voltage of a parallel plate proportional counter using nanosized anodes. The parallel plate geometry has advantages over the typical cylindrical design based on more feasible placement of solid neutron absorbers and more geometrically practical windows for radiation capture and directional detection.« less

A comparison of bioelectricity in microbial fuel cells with aerobic and anaerobic anodes.

PubMed

Chen, Chih-Yu; Chen, Tzu-Yu; Chung, Ying-Chien

2014-01-01

Microbial fuel cells (MFCs) can, besides running on wastewater, also derive energy directly from certain aquatic plants. However, few studies have focussed on electricity generation using aerobic anodes. This study presents a comparison of the MFC performances of an anaerobic-anode MFC (ana-MFC) and an aerobic-anode MFC (aa-MFC), and shows their individual conditions for optimal operation. Results show that the maximum power density of 7.07 +/- 0.45 mW/m2 for the ana-MFC occurred at 500 omega, whereas the aa-MFC had a maximum power density of 2.34 +/- 0.16 mW/m2 at 2200 omega. The ana-MFC generally achieved high electricity generation, and the aa-MFC achieved relatively high electricity generation when fed with a diluted substrate. In the ana-MFC, the optimal substrate for electricity generation was glucose (fermentable substrate); however, glucose and acetic acid (non-fermentable substrate) were both suitable substrates for the aa-MFC. The optimal gas retention times of the ana-MFC and the aa-MFC were 9 and 120 s, respectively. This retention time is an important limiting factor of electricity generation for the ana-MFC. The aa-MFCs fed with different substrates exhibited non-significant differences between bacterial communities. We observed the relative diversities of bacterial communities in the ana-MFC fed with various substrates. The results of denaturing gradient gel electrophoresis analysis suggest that Ochrobactrum intermedium, Delftia acidovorans, and Citrobacterfreundii may be potential electrogenic bacteria. To our knowledge, this is the first study comparing the MFC performances of anaerobic and aerobic anodes.

Hollow Nanostructured Anode Materials for Li-Ion Batteries

PubMed Central

2010-01-01

Hollow nanostructured anode materials lie at the heart of research relating to Li-ion batteries, which require high capacity, high rate capability, and high safety. The higher capacity and higher rate capability for hollow nanostructured anode materials than that for the bulk counterparts can be attributed to their higher surface area, shorter path length for Li+ transport, and more freedom for volume change, which can reduce the overpotential and allow better reaction kinetics at the electrode surface. In this article, we review recent research activities on hollow nanostructured anode materials for Li-ion batteries, including carbon materials, metals, metal oxides, and their hybrid materials. The major goal of this review is to highlight some recent progresses in using these hollow nanomaterials as anode materials to develop Li-ion batteries with high capacity, high rate capability, and excellent cycling stability. PMID:21076674

Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating.

PubMed

Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

2016-03-15

Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium-scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with "lithiophilic" coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm(2) over 80 cycles.

Synthesis of Fe3O4 cluster microspheres/graphene aerogels composite as anode for high-performance lithium ion battery

NASA Astrophysics Data System (ADS)

Zhou, Shuai; Zhou, Yu; Jiang, Wei; Guo, Huajun; Wang, Zhixing; Li, Xinhai

2018-05-01

Iron oxides are considered as attractive electrode materials because of their capability of lithium storage, but their poor conductivity and large volume expansion lead to unsatisfactory cycling stability. We designed and synthesized a novel Fe3O4 cluster microspheres/Graphene aerogels composite (Fe3O4/GAs), where Fe3O4 nanoparticles were assembled into cluster microspheres and then embedded in 3D graphene aerogels framework. In the spheres, the sufficient free space between Fe3O4 nanoparticles could accommodate the volume change during cycling process. Graphene aerogel works as flexible and conductive matrix, which can not only significantly increase the mechanical stress, but also further improve the storage properties. The Fe3O4/GAs composite as an anode material exhibits high reversible capability and excellent cyclic capacity for lithium ion batteries (LIBs). A reversible capability of 650 mAh g-1 after 500 cycles at a current density of 1 A g-1 can be maintained. The superior storage capabilities of the composites make them potential anode materials for LIBs.

Reversible calcium alloying enables a practical room-temperature rechargeable calcium-ion battery with a high discharge voltage

NASA Astrophysics Data System (ADS)

Wang, Meng; Jiang, Chunlei; Zhang, Songquan; Song, Xiaohe; Tang, Yongbing; Cheng, Hui-Ming

2018-06-01

Calcium-ion batteries (CIBs) are attractive candidates for energy storage because Ca2+ has low polarization and a reduction potential (-2.87 V versus standard hydrogen electrode, SHE) close to that of Li+ (-3.04 V versus SHE), promising a wide voltage window for a full battery. However, their development is limited by difficulties such as the lack of proper cathode/anode materials for reversible Ca2+ intercalation/de-intercalation, low working voltages (<2 V), low cycling stability, and especially poor room-temperature performance. Here, we report a CIB that can work stably at room temperature in a new cell configuration using graphite as the cathode and tin foils as the anode as well as the current collector. This CIB operates on a highly reversible electrochemical reaction that combines hexafluorophosphate intercalation/de-intercalation at the cathode and a Ca-involved alloying/de-alloying reaction at the anode. An optimized CIB exhibits a working voltage of up to 4.45 V with capacity retention of 95% after 350 cycles.

Rechargeable LiNiO2/carbon cells

NASA Astrophysics Data System (ADS)

Dahn, J. R.; von Sacken, U.; Juzkow, M. W.; Al-Janaby, H.

1991-08-01

Rechargeable cells can be made using two different intercalation compounds, in which the chemical potential of the intercalant differs by several eV, for the electrodes. The factors that play a role in the selection of appropriate lithium intercalation compounds for such cells are discussed. For the ease of cell assembly, the cathode should be stable in air when it is fully intercalated, like LiNiO2. For the anode, the chemical potential of the intercalated Li should be close to that of Li metal, like it is in Li(x)C6. The intercalation of Li in LiNiO2 is discussed, and then in petroleum coke. Then, it is shown that LiNiO2/coke cells have high energy density, long cycle life, excellent high-temperature performance, low self-discharge rates, can be repeatedly discharged to zero volts without damage, and are easily fabricated. It is considered that this type of cell shows far more promise for widespread applications than traditional secondary Li cells using metallic Li anodes.

Experimental breakdown of selected anodized aluminum samples in dilute plasmas

NASA Technical Reports Server (NTRS)

Grier, Norman T.; Domitz, Stanley

1992-01-01

Anodized aluminum samples representative of Space Station Freedom structural material were tested for electrical breakdown under space plasma conditions. In space, this potential arises across the insulating anodized coating when the spacecraft structure is driven to a negative bias relative to the external plasma potential due to plasma-surface interaction phenomena. For anodized materials used in the tests, it was found that breakdown voltage varied from 100 to 2000 volts depending on the sample. The current in the arcs depended on the sample, the capacitor, and the voltage. The level of the arc currents varied from 60 to 1000 amperes. The plasma number density varied from 3 x 10 exp 6 to 10 exp 3 ions per cc. The time between arcs increased as the number density was lowered. Corona testing of anodized samples revealed that samples with higher corona inception voltage had higher arcing inception voltages. From this it is concluded that corona testing may provide a method of screening the samples.

Synthesis and photo-electrochemical properties of spinel-ferrite-coated hematite for solar water splitting

NASA Astrophysics Data System (ADS)

Selvaraj, Seenivasan; Moon, Hee; Kim, Do-Heyoung

2018-01-01

Photo-electrochemical water splitting with hematite photo-anodes under solar irradiation has attracted considerable attention as regards the production of renewable hydrogen energy. However, many challenges remain unresolved, as the full contribution of the catalytic over-layers has not been fully realized. Herein, we incorporate uniform spinel nickel-ferrite over-layers in hematite photo-anodes to obtain an improved understanding of the associated intrinsic changes. We achieve a 1.5-mA/cm2 photo-current density at 1.23 VRHE (RHE: reversible hydrogen electrode) under one-sun illumination conditions, along with a negative shift of 200 mV in the onset potential, for NiFe2O4-coated Sn-doped hematite photo-anodes. Fundamental electrochemical analyses clearly show that the shift in the onset potential is predominantly due to the enhanced photo-voltage development inside the hematite, rather than being purely caused by the interfacial kinetics. These insights reveal a new direction for fundamental research on photo-anodes towards fabrication of more efficient photo-anode systems.

Te/C nanocomposites for Li-Te Secondary Batteries

NASA Astrophysics Data System (ADS)

Seo, Jeong-Uk; Seong, Gun-Kyu; Park, Cheol-Min

2015-01-01

New battery systems having high energy density are actively being researched in order to satisfy the rapidly developing market for longer-lasting mobile electronics and hybrid electric vehicles. Here, we report a new Li-Te secondary battery system with a redox potential of ~1.7 V (vs. Li+/Li) adapted on a Li metal anode and an advanced Te/C nanocomposite cathode. Using a simple concept of transforming TeO2 into nanocrystalline Te by mechanical reduction, we designed an advanced, mechanically reduced Te/C nanocomposite electrode material with high energy density (initial discharge/charge: 1088/740 mA h cm-3), excellent cyclability (ca. 705 mA h cm-3 over 100 cycles), and fast rate capability (ca. 550 mA h cm-3 at 5C rate). The mechanically reduced Te/C nanocomposite electrodes were found to be suitable for use as either the cathode in Li-Te secondary batteries or a high-potential anode in rechargeable Li-ion batteries. We firmly believe that the mechanically reduced Te/C nanocomposite constitutes a breakthrough for the realization and mass production of excellent energy storage systems.

Sustainable design of high-performance microsized microbial fuel cell with carbon nanotube anode and air cathode.

PubMed

Mink, Justine E; Hussain, Muhammad Mustafa

2013-08-27

Microbial fuel cells (MFCs) are a promising alternative energy source that both generates electricity and cleans water. Fueled by liquid wastes such as wastewater or industrial wastes, the microbial fuel cell converts waste into energy. Microsized MFCs are essentially miniature energy harvesters that can be used to power on-chip electronics, lab-on-a-chip devices, and/or sensors. As MFCs are a relatively new technology, microsized MFCs are also an important rapid testing platform for the comparison and introduction of new conditions or materials into macroscale MFCs, especially nanoscale materials that have high potential for enhanced power production. Here we report a 75 μL microsized MFC on silicon using CMOS-compatible processes and employ a novel nanomaterial with exceptional electrochemical properties, multiwalled carbon nanotubes (MWCNTs), as the on-chip anode. We used this device to compare the usage of the more commonly used but highly expensive anode material gold, as well as a more inexpensive substitute, nickel. This is the first anode material study done using the most sustainably designed microsized MFC to date, which utilizes ambient oxygen as the electron acceptor with an air cathode instead of the chemical ferricyanide and without a membrane. Ferricyanide is unsustainable, as the chemical must be continuously refilled, while using oxygen, naturally found in air, makes the device mobile and is a key step in commercializing this for portable technology such as lab-on-a-chip for point-of-care diagnostics. At 880 mA/m(2) and 19 mW/m(2) the MWCNT anode outperformed the others in both current and power densities with between 6 and 20 times better performance. All devices were run for over 15 days, indicating a stable and high-endurance energy harvester already capable of producing enough power for ultra-low-power electronics and able to consistently power them over time.

Engineering of highly ordered TiO2 nanopore arrays by anodization

NASA Astrophysics Data System (ADS)

Wang, Huijie; Huang, Zhennan; Zhang, Li; Ding, Jie; Ma, Zhaoxia; Liu, Yong; Kou, Shengzhong; Yang, Hangsheng

2016-07-01

Finite element analysis was used to simulate the current density distributions in the TiO2 barrier layer formed at the initial stage of Ti anodization. The morphology modification of the barrier layer was found to induce current density distribution change. By starting the anodization with proper TiO2 barrier layer morphology, the current density distribution can be adjusted to favor the formation of either nanotube arrays or nanopore arrays of anodic TiO2. We also found that the addition of sodium acetate into the electrolyte suppressed both the field-assisted chemical dissolution of TiO2 and the TiF62- hydrolysis induced TiO2 deposition during anodization, and thus further favored the nanopore formation. Accordingly, highly ordered anodic TiO2 nanopore arrays, similar to anodic aluminum oxide nanopore arrays, were successfully prepared.

Efficiency arcjet thruster with controlled arc startup and steady state attachment

NASA Technical Reports Server (NTRS)

Smith, William W. (Inventor); Knowles, Steven C. (Inventor)

1989-01-01

An improved efficiency arcjet thruster has a constrictor and electrically-conductive nozzle anode defining an arc chamber, and an electrically-conductive rod having a tip spaced upstream from the constrictor and defining a cathode spaced from the anode by a gap generally coextensive with the arc chamber. An electrical potential is applied to the anode and cathode to generate an electrical arc in the arc chamber from the cathode to anode. Catalytically decomposed hydrazine is supplied to the arc chamber with generation of the arc so as to produce thermal heating and expansion thereof through the nozzle. The constrictor can have a electrically insulative portion disposed between the cathode tip and the nozzle anode, and an electrically-conductive anode extension disposed along the insulative portion so as to define an auxiliary gap with the cathode tip substantially smaller than the gap defined between the cathode and nozzle anode for facilitating startup of arc generation. The constrictor can also include an electrically-conductive electrode with a variable electrical potential to vary the shape of the arc generated in the arc chamber. Also, the cathode is mounted for axial movement such that the gap between its tip and the nozzle anode can be varied to facilitate a generally nonerosive generation of the electrical arc at startup and reliable steady state operation. Further, the arc chamber can have a nonparallel subsonic-to-supersonic transition configuration, or alternatively solely a nonparallel supersonic configuration, for improved arc attachment.

Titanium dental implant surfaces obtained by anodic spark deposition - From the past to the future.

PubMed

Kaluđerović, Milena R; Schreckenbach, Joachim P; Graf, Hans-Ludwig

2016-12-01

Commercial titanium-based dental implants are obtained applying various methods such as machining, acid etching, anodization, plasma spraying, grit blasting or combination techniques yielding materials with smooth or micro-roughened surfaces. Those techniques are used to optimize the surface properties and to maximize biocompatibility and bioactivity with bone tissue. Present review is focused on the material surfaces obtained by anodic spark deposition (ASD). From the early 1980s till present, the results of numerous studies have shown that anodically oxidized surfaces with different dopants express a positive effect on osteoblasts behavior in vitro and osseointegration in vivo. Those surfaces demonstrated a high biocompatibility and rapid osseointegration in clinical application. This paper provides an overview of the preparation of implant surfaces by employing ASD process. Moreover, reviewed are clinically used ASD implant surfaces (Ticer, TiUnite, Osstem, etc.). The electrolyte variations in ASD process and their influence on surface properties are given herein. Using different electrolytes, anode voltages and temperatures, the above fabrication process can yield various surface morphologies from smooth to rough, porous surfaces. Furthermore, ASD enables thickening of oxide layers and enrichment with different dopands from used electrolyte, which hinder release of potentially toxic titanium ions in surrounding tissue. Particularly exciting results were achieved by calcium and phosphorus doping of the oxide layer (Ticer, ZL Microdent; TiUnite, Nobel Biocare Holding AB) which significantly increased the osteocompatibility. Ticer, a dental implant with anodically oxidized surface and the first among similar materials employed in clinical practice, was found to promote fast osteoblast cell differentiation and mineralization processes. Moreover, Ticer accelerate the integration with the bone, increase the bone/implant contact and improve primary and secondary stability of the implants. Additionally, potential innovations in this field such as fabrication of nanotubes on the implant surfaces as well as novel approaches (e.g. coating with proteins, nanostructured topography; combining implant body and surface derived from titanium and zirconia) are elaborated in this review. Besides, biochemical aspects on implant surface cell/tissue interaction are summarized. From the clinical point of view implant surfaces fabricated by ASD technology possess fast and improved osseointegration, high healing rates and long term prognosis. Copyright © 2016 Elsevier B.V. All rights reserved.

A Model of Anode Sheath Potential Evolution in a Transverse Magnetic Field

NASA Astrophysics Data System (ADS)

Foster, John E.; Gallimore, Alec D.

1996-11-01

It has been conjectured that the growth in the magnitude of the anode fall voltage with changing transverse magnetic field is a function of the ratio of available transverse current to the discharge current. It has been postulated that at small values of this ratio, the anode fall voltage and thus the near-anode electric field increases in order to assure that the prescribed discharge is maintained.footnote H. Hugel, IEEE Tran. Plas. Sci., PS-8,4, 1980 In this present work, a model is presented which predicts the behavior of the anode fall voltage as a function of transverse magnetic field. The model attempts to explain why the anode fall voltage depends so strongly on this ratio. In addition, it is further shown that because of the current ratio's strong dependence on local electron number density, ultimately it is the changes in near-anode ionization processes with varying transverse magnetic field that control the anode fall voltage.

Optimization of Aluminum Anodization Conditions for the Fabrication of Nanowires by Electrodeposition

NASA Technical Reports Server (NTRS)

Fucsko, Viola

2005-01-01

Anodized alumina nanotemplates have a variety of potential applications in the development of nanotechnology. Alumina nanotemplates are formed by oxidizing aluminum film in an electrolyte solution.During anodization, aluminum oxidizes, and, under the proper conditions, nanometer-sized pores develop. A series of experiments was conducted to determine the optimal conditions for anodization. Three-micrometer thick aluminum films on silicon and silicon oxide substrates were anodized using constant voltages of 13-25 V. 0.1-0.3M oxalic acid was used as the electrolyte. The anodization time was found to increase and the overshooting current decreased as both the voltage and the electrolyte concentrations were decreased. The samples were observed under a scanning electron microscope. Anodizing with 25V in 0.3M oxalic acid appears to be the best process conditions. The alumina nanotemplates are being used to fabricate nanowires by electrodeposition. The current-voltage characteristics of copper nanowires have also been studied.

Dependence of CO2 Reactivity of Carbon Anodes on Pore Structure

NASA Astrophysics Data System (ADS)

Chen, Tong; Xue, Jilai; Lang, Guanghui; Liu, Rui; Gao, Shoulei; Wang, Zengjie

2017-09-01

The correlation between the CO2 reactivity and pore structure of carbon anodes was experimentally investigated. The pore structures of the anodes before and after CO2 oxidation were characterized using image analysis. The porosity, mean pore diameter, and the number of micro-cracks decreased with increasing anode forming pressure, while they increased with over-compaction. With prolonged CO2 oxidation time, the porosity, pore density, mean pore diameter, pore aspect ratio, and the number of micro-cracks increased due to the merging of small pores, increased pore connectivity, and generation of new pores. The activation energy decreased with increasing porosity of the anodes' pitch phase due to easier CO2 penetration and reaction within the anodes. The results confirm that the fine pitch-coke phase of anodes is preferentially consumed, a cause of carbon dusting. Optimization of the pore structures to balance the pitch, coke, and butt phases may potentially further reduce carbon dusting.

Anomalous acceleration of ions in a plasma accelerator with an anodic layer

NASA Astrophysics Data System (ADS)

V, M. BARDAKOV; S, D. IVANOV; A, V. KAZANTSEV; N, A. STROKIN; A, N. STUPIN; Binhao, JIANG; Zhenyu, WANG

2018-03-01

In a plasma accelerator with an anodic layer (PAAL), we discovered experimentally the effect of ‘super-acceleration’ of the bulk of the ions to energies W exceeding the energy equivalent to the discharge voltage V d. The E × B discharge was ignited in an environment of atomic argon and helium and molecular nitrogen. Singly charged argon ions were accelerated most effectively in the case of the largest discharge currents and pressure P of the working gas. Helium ions with W > eV d (e being the electron charge) were only recorded at maximum pressures. Molecular nitrogen was not accelerated to energies W > eV d. Anomalous acceleration is realized in the range of radial magnetic fields on the anode 2.8 × 10 -2 ≤ B rA ≤ 4 × 10 -2 T. It was also found analytically that the cathode of the accelerator can receive anomalously accelerated ions. In this case, the value of the potential in the anodic layer becomes higher than the anode potential, and the anode current exceeds some critical value. Numerical modeling in terms of the developed theory showed qualitative agreement between modeling data and measurements.

Light-driven OR and XOR programmable chemical logic gates.

PubMed

Szaciłowski, Konrad; Macyk, Wojciech; Stochel, Grazyna

2006-04-12

Photoelectrodes made of nanocrystalline titanium dioxide modified with various pentacyanoferrates exhibit unique photoelectrochemical properties; photocurrent direction can be switched from anodic to cathodic and vice versa upon changes in photoelectrode potential and incident light wavelength (PhotoElectrochemical Photocurrent Switching, PEPS effect). At certain potentials, anodic photocurrent generated upon UV irradiation has the same intensity as the cathodic photocurrent generated upon visible irradiation. Under these conditions, simultaneous irradiation with UV and visible light results in compensation of anodic and cathodic photocurrents, and zero net photocurrent is observed. This process can be used for construction of unique light-driven chemical logic gates.

Modelling potential/current distribution in microbial electrochemical systems shows how the optimal bioanode architecture depends on electrolyte conductivity.

PubMed

Lacroix, Rémy; Da Silva, Serge; Gaig, Monica Viaplana; Rousseau, Raphael; Délia, Marie-Line; Bergel, Alain

2014-11-07

The theoretical bases for modelling the distribution of the electrostatic potential in microbial electrochemical systems are described. The secondary potential distribution (i.e. without mass transport limitation of the substrate) is shown to be sufficient to validly address microbial electrolysis cells (MECs). MECs are modelled with two different ionic conductivities of the solution (1 and 5.3 S m(-1)) and two bioanode kinetics (jmax = 5.8 or 34 A m(-2)). A conventional reactor configuration, with the anode and the cathode face to face, is compared with a configuration where the bioanode perpendicular to the cathode implements the electrochemical reaction on its two sides. The low solution conductivity is shown to have a crucial impact, which cancels out the advantages obtained by setting the bioanode perpendicular to the cathode. For the same reason, when the surface area of the anode is increased by multiplying the number of plates, care must be taken not to create too dense anode architecture. Actually, the advantages of increasing the surface area by multiplying the number of plates can be lost through worsening of the electrochemical conditions in the multi-layered anode, because of the increase of the electrostatic potential of the solution inside the anode structure. The model gives the first theoretical bases for scaling up MECs in a rather simple but rigorous way.

Miniature Lightweight Ion Pump

NASA Technical Reports Server (NTRS)

Sinha, Mahadeva P.

2010-01-01

This design offers a larger surface area for pumping of active gases and reduces the mass of the pump by eliminating the additional vacuum enclosure. There are three main components to this ion pump: the cathode and anode pumping elements assembly, the vacuum enclosure (made completely of titanium and used as the cathode and maintained at ground potential) containing the assembly, and the external magnet. These components are generally put in a noble diode (or differential) configuration of the ion pump technology. In the present state of the art, there are two cathodes, one made of titanium and the other of tantalum. The anodes are made up of an array of stainless steel cylinders positioned between the two cathodes. All the elements of the pump are in a vacuum enclosure. After the reduction of pressure in this enclosure to a few microns, a voltage is applied between the cathode and the anode elements. Electrons generated by the ionization are accelerated toward the anodes that are confined in the anode space by the axial magnetic field. For the generation of the axial field along the anode elements, the magnet is designed in a C-configuration and is fabricated from rare earth magnetic materials (Nd-B-Fe or Sm-Co) possessing high energy product values, and the yoke is fabricated from the high permeability material (Hiperco-50A composed of Fe-Co-V). The electrons in this region collide with the gas molecules and generate their positive ions. These ions are accelerated into the cathode and eject cathode material (Ti). The neutral atoms deposit on the anode surfaces. Because of the chemical activity of Ti, the atoms combine with chemically active gas molecules (e.g. N2, O2, etc.) and remove them. New layers of Ti are continually deposited, and the pumping of active gases is thus accomplished. Pumping of the inert gases is accomplished by their burial several atomic layers deep into the cathode. However, they tend to re-emit if the entrapping lattice atoms are sputtered away. For stable pumping of inert gases, one side of the cathode is made of Ta. Impaction on Ta produces energetic, neutral atoms that pump the inert gases on the anode structure at the peripheral areas of the cathodes (between anode rings). For inert gases stability, a post design has been implemented. Here, posts of cathode material (Ti) are mounted on the cathode. These protrude into the initial part of the anode elements. Materials sputtered from the posts condense on the anode assembly and on the cathode plane at higher rates than in the normal diodes due to enhanced sputtering at glancing angles from geometrical considerations. This increases pumping by burial. This post design has enhanced pumping rates for both active and inert gases, compared with conventional designs.

Preparations, Properties, and Applications of Periodic Nano Arrays using Anodized Aluminum Oxide and Di-block Copolymer

NASA Astrophysics Data System (ADS)

Noh, Kunbae

2011-12-01

Self-ordered arrangements observed in various materials systems such as anodic aluminum oxide, polystyrene nanoparticles, and block copolymer are of great interest in terms of providing new opportunities in nanofabrication field where lithographic techniques are broadly used in general. Investigations on self-assembled nano arrays to understand how to obtain periodic nano arrays in an efficient yet inexpensive way, and how to realize advanced material and device systems thereof, can lead to significant impacts on science and technology for many forefront device applications. In this thesis, various aspects of periodic nano-arrays have been discussed including novel preparations, properties and applications of anodized aluminum oxide (AAO) and PS-b-P4VP (S4VP) di-block copolymer self-assembly. First, long-range ordered AAO arrays have been demonstrated. Nanoimprint lithography (NIL) process allowed a faithful pattern transfer of the imprint mold pattern onto Al thin film, and interesting self-healing and pattern tripling phenomena were observed, which could be applicable towards fabrication of the NIL master mold having highly dense pattern over large area, useful for fabrication of a large-area substrate for predictable positioning of arrayed devices. Second, S4VP diblock copolymer self-assembly and S4VP directed AAO self-assembly have been demonstrated in the Al thin film on Si substrate. Such a novel combination of two dissimilar self-assembly techniques demonstrated a potential as a versatile tool for nanopatterning formation on a Si substrate, capable of being integrated into Si process technology. As exemplary applications, vertically aligned Ni nanowires have been synthesized into an S4VP-guided AAO membrane on a Si substrate in addition to anti-dot structured [Co/Pd]n magnetic multilayer using S4VP self assembly. Third, a highly hexagonally ordered, vertically parallel aluminum oxide nanotube array was successfully fabricated via hard anodization technique. The Al2O3 nanotube arrays so fabricated exhibit a uniform and reproducible dimension, and a quite high aspect ratio of greater than ˜1,000. Such high-aspect-ratio, mechanically robust, large-surface-area nanotube array structure can be useful for many technical applications. As a potential application in biomedical research, drug storage/controlled drug release from such AAO nanotubes was investigated, and the advantageous potential of using AAO nanotubes for biological implant surface coatings alternative to TiO2 nanotubes has been discussed.

Incorporation of Ca and P on anodized titanium surface: Effect of high current density.

PubMed

Laurindo, Carlos A H; Torres, Ricardo D; Mali, Sachin A; Gilbert, Jeremy L; Soares, Paulo

2014-04-01

This study systematically evaluated the surface and corrosion characteristics of commercially pure titanium (grade 2) modified by plasma electrolytic oxidation (PEO) with high current density. The anodization process was carried out galvanostatically (constant current density) using a solution containing calcium glycerophosphate (0.02mol/L) and calcium acetate (0.15mol/L). The current densities applied were 400, 700, 1000 and 1200mA/cm(2) for a period of 15s. Composition, crystalline structure, morphology, roughness, wettability and "in-vitro" bioactivity test in SBF of the anodized layer were evaluated by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, profilometry and contact angle measurements. Corrosion properties were evaluated by open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that the TiO2 oxide layers present an increase of thickness, porosity, roughness, wettability, Ca/P ratio, and bioactivity, with the applied current density up to 1000mA/cm(2). Corrosion resistance also increases with applied current density. It is observed that for 1200mA/cm(2), there is a degradation of the oxide layer. In general, the results suggest that the anodized TiO2 layer with better properties is formed with an applied current of 1000mA/cm(2). Copyright © 2014 Elsevier B.V. All rights reserved.

Hydroxyapatite electrodeposition on anodized titanium nanotubes for orthopedic applications

NASA Astrophysics Data System (ADS)

Parcharoen, Yardnapar; Kajitvichyanukul, Puangrat; Sirivisoot, Sirinrath; Termsuksawad, Preecha

2014-08-01

Nanotubes modification for orthopedic implants has shown interesting biological performances (such as improving cell adhesion, cell differentiation, and enhancing osseointegration). The purpose of this study is to investigate effect of titanium dioxide (TiO2) nanotube feature on performance of hydroxyapatite-coated titanium (Ti) bone implants. TiO2 nanotubes were prepared by anodization using ammonium fluoride electrolyte (NH4F) with and without modifiers (PEG400 and Glycerol) at various potential forms, and times. After anodization, the nanotubes were subsequently annealed. TiO2 nanotubes were characterized by scanning electron microscope and X-ray diffractometer. The amorphous to anatase transformation due to annealing was observed. Smooth and highly organized TiO2 nanotubes were found when high viscous electrolyte, NH4F in glycerol, was used. Negative voltage (-4 V) during anodization was confirmed to increase nanotube thickness. Length of the TiO2 nanotubes was significantly increased by times. The TiO2 nanotube was electrodeposited with hydroxyapatite (HA) and its adhesion was estimated by adhesive tape test. The result showed that nanotubes with the tube length of 560 nm showed excellent adhesion. The coated HA were tested for biological test by live/dead cell straining. HA coated on TiO2 nanotubes showed higher cells density, higher live cells, and more spreading of MC3T3-E1 cells than that growing on titanium plate surface.

Multi-Phase Field Models and Microstructural Evolution with Applications in Fuel Cell Technology

NASA Astrophysics Data System (ADS)

Davis, Ryan Scott

The solid oxide fuel cell (SOFC) has shown tremendous potential as an efficient energy conversion device that may be instrumental in the transition to renewable resources. However, commercialization is hindered by many degradation mechanisms that plague long term stability. In this dissertation, computation methods are used to explore the relationship between the microstructure of the fuel cell anode and performance critical metrics. The phase field method and standard modeling procedures are introduced using a classic model of spinodal decomposition. This is further developed into a complete, multi-phase modeling framework designed for the complex microstructural evolution of SOFC anode systems. High-temperature coarsening of the metallic phase in the state-of-the-art SOFC cermet anode is investigated using our phase field model. A systematic study into the effects of interface properties on microstructural evolution is accomplished by altering the contact angle between constituent phases. It is found that metrics of catalytic activity and conductivity display undesirable minima near the contact angle of conventional SOFC materials. These results suggest that tailoring the interface properties of the constituent phases could lead to a significant increase in the performance and lifetime of SOFCs. Supported-metal catalyst systems are investigated in the first detailed study of their long-term stability and application to SOFC anode design. Porous support structures are numerically sintered to mimic specific fabrication techniques, and these structures are then infiltrated with a nanoscale catalyst phase ranging from 2% to 21% loading. Initially, these systems exhibit enhanced potential for catalytic activity relative to conventional cells. However, extended evolution results in severe degradation, and we show that Ostwald ripening and particle migration are key kinetic processes. Strong geometric heterogeneity in the support structure via a novel approach to nanopore formation is proposed as a potential solution for catalyst stabilization.

Surface treatments for aluminium alloys

NASA Astrophysics Data System (ADS)

Ardelean, M.; Lascău, S.; Ardelean, E.; Josan, A.

2018-01-01

Typically, in contact with the atmosphere, the aluminium surface is covered with an aluminium oxide layer, with a thickness of less than 1-2μm. Due to its low thickness, high porosity and low mechanical strength, this layer does not protect the metal from corrosion. Anodizing for protective and decorative purposes is the most common method of superficial oxidation processes and is carried out through anodic oxidation. The oxide films, resulted from anodizing, are porous, have a thickness of 20-50μm, and are heat-resistant, stable to water vapour and other corrosion agents. Hard anodizing complies with the same obtains principles as well as decorative and protective anodization. The difference is in that hard anodizing is achieved at low temperatures and high intensity of electric current. In the paper are presented the results of decorative and hard anodization for specimens made from several aluminium alloys in terms of the appearance of the specimens and of the thickness of the anodized.

Exploring As-Cast PbCaSn-Mg Anodes for Improved Performance in Copper Electrowinning

NASA Astrophysics Data System (ADS)

Yuwono, Jodie A.; Clancy, Marie; Chen, Xiaobo; Birbilis, Nick

2018-06-01

Lead calcium tin (PbCaSn) alloys are the common anodes used in copper electrowinning (Cu EW). Given a large amount of energy consumed in Cu EW process, anodes with controlled oxygen evolution reaction (OER) kinetics and a lower OER overpotential are advantageous for reducing the energy consumption. To date, magnesium (Mg) has never been studied as an alloying element for EW anodes. As-cast PbCaSn anodes with the addition of Mg were examined herein, revealing an improved performance compared to that of the industrial standard PbCaSn anode. The alloy performances in the early stages of anode life and passivation were established from electrochemical studies which were designed to simulate industrial Cu EW process. The 24-hour polarization testing revealed that the Mg alloying depolarizes the anode potential up to 80 mV; thus, resulting in a higher Cu EW efficiency. In addition, scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the alteration of the alloy microstructure and the corresponding interfacial reactions contribute to the changes of the anode electrochemical performances. The present study reveals for the first time the potency of Mg alloying in reducing the overpotential of PbCaSn anode.

Transient desorption of water vapor - A potential source of error in upper atmosphere rocket experiments

NASA Technical Reports Server (NTRS)

Kendall, B. R. F.; Weeks, J. O.

1974-01-01

Results of measurements of the outgassing rates of samples of materials and surface finishes used on the outer skins of rocket-borne experiment packages in simulated rocket ascents. The results showed outgassing rates for anodized aluminum in the second minute of flight which are two to three orders of magnitude higher than those given in typical tables of outgassing rates. The measured rates for aluminum with chromate conversion surface coatings were also abnormally high. These abnormally high initial rates fell quickly after about five to ten minutes to values comparable with those in the published literature. It is concluded that anodized and chromate conversion coatings on the aluminum outer surfaces of a sounding rocket experiment package will cause gross distortion of the true water vapor environment.

Anodic Oxidation of Carbon Steel at High Current Densities and Investigation of Its Corrosion Behavior

NASA Astrophysics Data System (ADS)

Fattah-Alhosseini, Arash; Khan, Hamid Yazdani

2017-06-01

This work aims at studying the influence of high current densities on the anodization of carbon steel. Anodic protective coatings were prepared on carbon steel at current densities of 100, 125, and 150 A/dm2 followed by a final heat treatment. Coatings microstructures and morphologies were analyzed using X-ray diffraction (XRD) and scanning electron microscope (SEM). The corrosion resistance of the uncoated carbon steel substrate and the anodic coatings were evaluated in 3.5 wt pct NaCl solution through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results showed that the anodic oxide coatings which were prepared at higher current densities had thicker coatings as a result of a higher anodic forming voltage. Therefore, the anodized coatings showed better anti-corrosion properties compared to those obtained at lower current densities and the base metal.

Synthesis of highly ordered TiO2 nanotube in malonic acid solution by anodization.

PubMed

Ryu, Won Hee; Park, Chan Jin; Kwon, Hyuk Sang

2008-10-01

We synthesized TiO2 nanotube array by anodizing in a solution of malonic acid (HOOCCH2COOH) and NH4F, and analyzed the morphology of the nanotube using scanning electron microscopy (SEM). The morphology of TiO2 nanotube was largely affected by anodizing time, anodizing voltage, and malonic acid concentration. With increasing the anodizing voltage from 5 V to 20 V, the diameter of TiO2 nanotube was increased from about 20 nm to 110 nm and its length from about 10 nm to 700 nm. In addition, the length of TiO2 nanotube was increased with increasing anodizing time up to 6 h at 20 V. We obtained the longest and the most highly ordered nanotube structure when anodizing Ti in a solution of 0.5 wt% NH4F and 1 M malonic acid at 20 V for 6 h.

Facile synthesis of a SiOx/asphalt membrane for high performance lithium-ion battery anodes.

PubMed

Xu, Quan; Sun, Jian-Kun; Li, Ge; Li, Jin-Yi; Yin, Ya-Xia; Guo, Yu-Guo

2017-11-07

Herein, a novel SiO x /asphalt membrane was facilely synthesized via demulsification of porous SiO x microspheres. After high temperature pyrolysis, SiO x /carbon composites not only could function as binder-free anodes, but could also exhibit excellent cycling stability and high initial Coulombic efficiency as anodes for practical application.

Halogen effect for improving high temperature oxidation resistance of Ti-50Al by anodization

NASA Astrophysics Data System (ADS)

Mo, Min-Hua; Wu, Lian-Kui; Cao, Hua-Zhen; Lin, Jun-Pin; Zheng, Guo-Qu

2017-06-01

The high temperature oxidation resistance of Ti-50Al was significantly improved via halogen effect which was achieved by anodizing in an ethylene glycol solution containing with fluorine ion. The anodized Ti-50Al with holes and micro-cracks could be self-repaired during oxidation at 1000 °C. The thickness of the oxide scale increases with the prolonging of oxidation time. On the basis of halogen effect for improving the high temperature oxidation resistance of Ti-50Al by anodization, only fluorine addition into the electrolyte can effectively improve the high temperature oxidation resistance of Ti-50Al.

Influence of an electric probe on the anode layer of a glow discharge in nitrogen

NASA Astrophysics Data System (ADS)

Taran, M. D.; Dyatko, N. A.; Kochetov, I. V.; Napartovich, A. P.; Akishev, Yu S.

2018-05-01

A two-dimensional (2D) numerical model of a DC glow discharge in nitrogen is developed for the case when the electric probe is mounted in the discharge gap. Within this model, calculations are performed for the gas pressure of 50 Torr and discharge current densities of 22 and 90 mA cm‑2. A cylindrical probe 1 mm in diameter is located parallel to the anode at a distance of 5 or 10 mm. The probe potential is varied in a wide range relative to the floating potential. Numerical simulations predict the 2D plasma perturbation pattern induced by the electric probe and the influence of the probe on anode layer characteristics. In particular, conditions are determined under which a region with no glow forms in the anode layer.

Process for producing a high emittance coating and resulting article

NASA Technical Reports Server (NTRS)

Le, Huong G. (Inventor); O'Brien, Dudley L. (Inventor)

1993-01-01

Process for anodizing aluminum or its alloys to obtain a surface particularly having high infrared emittance by anodizing an aluminum or aluminum alloy substrate surface in an aqueous sulfuric acid solution at elevated temperature and by a step-wise current density procedure, followed by sealing the resulting anodized surface. In a preferred embodiment the aluminum or aluminum alloy substrate is first alkaline cleaned and then chemically brightened in an acid bath The resulting cleaned substrate is anodized in a 15% by weight sulfuric acid bath maintained at a temperature of 30.degree. C. Anodizing is carried out by a step-wise current density procedure at 19 amperes per square ft. (ASF) for 20 minutes, 15 ASF for 20 minutes and 10 ASF for 20 minutes. After anodizing the sample is sealed by immersion in water at 200.degree. F. and then air dried. The resulting coating has a high infrared emissivity of about 0.92 and a solar absorptivity of about 0.2, for a 5657 aluminum alloy, and a relatively thick anodic coating of about 1 mil.

Theory of plasma contactors in ground-based experiments and low Earth orbit

NASA Technical Reports Server (NTRS)

Gerver, M. J.; Hastings, Daniel E.; Oberhardt, M. R.

1990-01-01

Previous theoretical work on plasma contactors as current collectors has fallen into two categories: collisionless double layer theory (describing space charge limited contactor clouds) and collisional quasineutral theory. Ground based experiments at low current are well explained by double layer theory, but this theory does not scale well to power generation by electrodynamic tethers in space, since very high anode potentials are needed to draw a substantial ambient electron current across the magnetic field in the absence of collisions (or effective collisions due to turbulence). Isotropic quasineutral models of contactor clouds, extending over a region where the effective collision frequency upsilon sub e exceeds the electron cyclotron frequency omega sub ce, have low anode potentials, but would collect very little ambient electron current, much less than the emitted ion current. A new model is presented, for an anisotropic contactor cloud oriented along the magnetic field, with upsilon sub e less than omega sub ce. The electron motion along the magnetic field is nearly collisionless, forming double layers in that direction, while across the magnetic field the electrons diffuse collisionally and the potential profile is determined by quasineutrality. Using a simplified expression for upsilon sub e due to ion acoustic turbulence, an analytic solution has been found for this model, which should be applicable to current collection in space. The anode potential is low and the collected ambient electron current can be several times the emitted ion current.

Development of 10×10 Matrix-anode MCP-PMT

NASA Astrophysics Data System (ADS)

Yang, Jie; Li, Yongbin; Xu, Pengxiao; Zhao, Wenjin

2018-02-01

10×10 matrix-anode is developed by high-temperature co-fired ceramics (HTCC) technology. Based on the new matrix-anode, a new kind of photon counting imaging detector - 10×10 matrix-anode MCP-PMT is developed, and its performance parameters are tested. HTCC technology is suitable for the MCP-PMT's air impermeability and its baking process. Its response uniformity is better than the metal-ceramic or metal-glass sealing anode, and it is also a promising method to realize a higher density matrix-anode.

Preparation of Aluminum Nanomesh Thin Films from an Anodic Aluminum Oxide Template as Transparent Conductive Electrodes

NASA Astrophysics Data System (ADS)

Li, Yiwen; Chen, Yulong; Qiu, Mingxia; Yu, Hongyu; Zhang, Xinhai; Sun, Xiao Wei; Chen, Rui

2016-02-01

We have employed anodic aluminum oxide as a template to prepare ultrathin, transparent, and conducting Al films with a unique nanomesh structure for transparent conductive electrodes. The anodic aluminum oxide template is obtained through direct anodization of a sputtered Al layer on a glass substrate, and subsequent wet etching creates the nanomesh metallic film. The optical and conductive properties are greatly influenced by experimental conditions. By tuning the anodizing time, transparent electrodes with appropriate optical transmittance and sheet resistance have been obtained. The results demonstrate that our proposed strategy can serve as a potential method to fabricate low-cost TCEs to replace conventional indium tin oxide materials.

Gamma-insensitive optical sensor

DOEpatents

Kruger, Hans W.

1994-01-01

An ultra-violet/visible/infra-red gamma-insensitive gas avalanche focal plane array comprising a planar photocathode and a planar anode pad array separated by a gas-filled gap and across which is applied an electric potential. Electrons ejected from the photocathode are accelerated sufficiently between collisions with the gas molecules to ionize them, forming an electron avalanche. The gap acts like a proportional counter. The array of anode pad are mounted on the front of an anode plate and are connected to matching contact pads on the back of the anode via feed through wires. Connection of the anode to signal processing electronics is made from the contact pads using standard indium bump techniques, for example.

Preparation of Aluminum Nanomesh Thin Films from an Anodic Aluminum Oxide Template as Transparent Conductive Electrodes

PubMed Central

Li, Yiwen; Chen, Yulong; Qiu, Mingxia; Yu, Hongyu; Zhang, Xinhai; Sun, Xiao Wei; Chen, Rui

2016-01-01

We have employed anodic aluminum oxide as a template to prepare ultrathin, transparent, and conducting Al films with a unique nanomesh structure for transparent conductive electrodes. The anodic aluminum oxide template is obtained through direct anodization of a sputtered Al layer on a glass substrate, and subsequent wet etching creates the nanomesh metallic film. The optical and conductive properties are greatly influenced by experimental conditions. By tuning the anodizing time, transparent electrodes with appropriate optical transmittance and sheet resistance have been obtained. The results demonstrate that our proposed strategy can serve as a potential method to fabricate low-cost TCEs to replace conventional indium tin oxide materials. PMID:26831759

Preparation of Aluminum Nanomesh Thin Films from an Anodic Aluminum Oxide Template as Transparent Conductive Electrodes.

PubMed

Li, Yiwen; Chen, Yulong; Qiu, Mingxia; Yu, Hongyu; Zhang, Xinhai; Sun, Xiao Wei; Chen, Rui

2016-02-02

We have employed anodic aluminum oxide as a template to prepare ultrathin, transparent, and conducting Al films with a unique nanomesh structure for transparent conductive electrodes. The anodic aluminum oxide template is obtained through direct anodization of a sputtered Al layer on a glass substrate, and subsequent wet etching creates the nanomesh metallic film. The optical and conductive properties are greatly influenced by experimental conditions. By tuning the anodizing time, transparent electrodes with appropriate optical transmittance and sheet resistance have been obtained. The results demonstrate that our proposed strategy can serve as a potential method to fabricate low-cost TCEs to replace conventional indium tin oxide materials.

The effects of anode material type on the optoelectronic properties of electroplated CdTe thin films and the implications for photovoltaic application

NASA Astrophysics Data System (ADS)

Echendu, O. K.; Dejene, B. F.; Dharmadasa, I. M.

2018-03-01

The effects of the type of anode material on the properties of electrodeposited CdTe thin films for photovoltaic application have been studied. Cathodic electrodeposition of two sets of CdTe thin films on glass/fluorine-doped tin oxide (FTO) was carried out in two-electrode configuration using graphite and platinum anodes. Optical absorption spectra of films grown with graphite anode displayed significant spread across the deposition potentials compared to those grown with platinum anode. Photoelectrochemical cell result shows that the CdTe grown with graphite anode became p-type after post-deposition annealing with prior CdCl2 treatment, as a result of carbon incorporation into the films, while those grown with platinum anode remained n-type after annealing. A review of recent photoluminescence characterization of some of these CdTe films reveals the persistence of a defect level at (0.97-0.99) eV below the conduction band in the bandgap of CdTe grown with graphite anode after annealing while films grown with platinum anode showed the absence of this defect level. This confirms the impact of carbon incorporation into CdTe. Solar cell made with CdTe grown with platinum anode produced better conversion efficiency compared to that made with CdTe grown using graphite anode, underlining the impact of anode type in electrodeposition.

Development of Ni-Ba(Zr,Y)O3 cermet anodes for direct ammonia-fueled solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Miyazaki, Kazunari; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

2017-10-01

In this study, the availability of Ni-Ba(Zr,Y)O3-δ (BZY) cermet for the anode of direct ammonia-fueled solid oxide fuel cells (SOFCs) is evaluated. In this device, the anodes need to be active for the catalytic ammonia decomposition as well as the electrochemical hydrogen oxidation. In the catalytic activity test, ammonia decomposes completely over Ni-BZY at ca. 600 °C, while higher temperature is required to accomplish the complete decomposition over the conventional SOFC anode of Ni-yttria-stabilized zirconia cermet. The high activity of Ni-BZY is attributed to the high basicity of BZY and the high resistance to hydrogen poisoning effect. The electrochemical property of Ni-BZY anode is also evaluated with the anode-supported cell of Ni-BZY|BZY|Pt at 600-700 °C with feeding ammonia or hydrogen as a fuel. Since the residence time of ammonia fuel in the thick Ni-BZY anode is long, the difference in the cell performance between two fuels is relatively small. Furthermore, it is proved that the steam concentration in the fuel strongly affects the cell performance. We find that this factor is important to satisfy the above mentioned requirements for the anode of direct ammonia-fueled SOFCs. Throughout this study, it is concluded that Ni-BZY cermet will be a promising anode.

Application of infiltrated LSCM-GDC oxide anode in direct carbon/coal fuel cells.

PubMed

Yue, Xiangling; Arenillas, Ana; Irvine, John T S

2016-08-15

Hybrid direct carbon/coal fuel cells (HDCFCs) utilise an anode based upon a molten carbonate salt with an oxide conducting solid electrolyte for direct carbon/coal conversion. They can be fuelled by a wide range of carbon sources, and offer higher potential chemical to electrical energy conversion efficiency and have the potential to decrease CO2 emissions compared to coal-fired power plants. In this study, the application of (La, Sr)(Cr, Mn)O3 (LSCM) and (Gd, Ce)O2 (GDC) oxide anodes was explored in a HDCFC system running with two different carbon fuels, an organic xerogel and a raw bituminous coal. The electrochemical performance of the HDCFC based on a 1-2 mm thick 8 mol% yttria stabilised zirconia (YSZ) electrolyte and the GDC-LSCM anode fabricated by wet impregnation procedures was characterized and discussed. The infiltrated oxide anode showed a significantly higher performance than the conventional Ni-YSZ anode, without suffering from impurity formation under HDCFC operation conditions. Total polarisation resistance (Rp) reached 0.8-0.9 Ω cm(2) from DCFC with an oxide anode on xerogel and bituminous coal at 750 °C, with open circuit voltage (OCV) values in the range 1.1-1.2 V on both carbon forms. These indicated the potential application of LSCM-GDC oxide anode in HDCFCs. The chemical compatibility of LSCM/GDC with carbon/carbonate investigation revealed the emergence of an A2BO4 type oxide in place of an ABO3 perovskite structure in the LSCM in a reducing environment, due to Li attack as a result of intimate contact between the LSCM and Li2CO3, with GDC being stable under identical conditions. Such reaction between LSCM and Li2CO3 was not observed on a LSCM-YSZ pellet treated with Li-K carbonate in 5% H2/Ar at 700 °C, nor on a GDC-LSCM anode after HDCFC operation. The HDCFC durability tests of GDC-LSCM oxide on a xerogel and on raw bituminous coal were performed under potentiostatic operation at 0.7 V at 750 °C. The degradation mechanisms were addressed, especially on raw coal.

Nb-doped rutile TiO₂: a potential anode material for Na-ion battery.

PubMed

Usui, Hiroyuki; Yoshioka, Sho; Wasada, Kuniaki; Shimizu, Masahiro; Sakaguchi, Hiroki

2015-04-01

The electrochemical properties of the rutile-type TiO2 and Nb-doped TiO2 were investigated for the first time as Na-ion battery anodes. Ti(1-x)Nb(x)O2 thick-film electrodes without a binder and a conductive additive were prepared using a sol-gel method followed by a gas-deposition method. The TiO2 electrode showed reversible reactions of Na insertion/extraction accompanied by expansion/contraction of the TiO2 lattice. Among the Ti(1-x)Nb(x)O2 electrodes with x = 0-0.18, the Ti(0.94)Nb(0.06)O2 electrode exhibited the best cycling performance, with a reversible capacity of 160 mA h g(-1) at the 50th cycle. As the Li-ion battery anode, this electrode also attained an excellent rate capability, with a capacity of 120 mA h g(-1) even at the high current density of 16.75 A g(-1) (50C). The improvements in the performances are attributed to a 3 orders of magnitude higher electronic conductivity of Ti(0.94)Nb(0.06)O2 compared to that of TiO2. This offers the possibility of Nb-doped rutile TiO2 as a Na-ion battery anode as well as a Li-ion battery anode.

Red Phosphorus Nanodots on Reduced Graphene Oxide as a Flexible and Ultra-Fast Anode for Sodium-Ion Batteries.

PubMed

Liu, Yihang; Zhang, Anyi; Shen, Chenfei; Liu, Qingzhou; Cao, Xuan; Ma, Yuqiang; Chen, Liang; Lau, Christian; Chen, Tian-Chi; Wei, Fei; Zhou, Chongwu

2017-06-27

Sodium-ion batteries offer an attractive option for potential low cost and large scale energy storage due to the earth abundance of sodium. Red phosphorus is considered as a high capacity anode for sodium-ion batteries with a theoretical capacity of 2596 mAh/g. However, similar to silicon in lithium-ion batteries, several limitations, such as large volume expansion upon sodiation/desodiation and low electronic conductance, have severely limited the performance of red phosphorus anodes. In order to address the above challenges, we have developed a method to deposit red phosphorus nanodots densely and uniformly onto reduced graphene oxide sheets (P@RGO) to minimize the sodium ion diffusion length and the sodiation/desodiation stresses, and the RGO network also serves as electron pathway and creates free space to accommodate the volume variation of phosphorus particles. The resulted P@RGO flexible anode achieved 1165.4, 510.6, and 135.3 mAh/g specific charge capacity at 159.4, 31878.9, and 47818.3 mA/g charge/discharge current density in rate capability test, and a 914 mAh/g capacity after 300 deep cycles in cycling stability test at 1593.9 mA/g current density, which marks a significant performance improvement for red phosphorus anodes for sodium-ion chemistry and flexible power sources for wearable electronics.

Direct anodic hydrochloric acid and cathodic caustic production during water electrolysis

NASA Astrophysics Data System (ADS)

Lin, Hui-Wen; Cejudo-Marín, Rocío; Jeremiasse, Adriaan W.; Rabaey, Korneel; Yuan, Zhiguo; Pikaar, Ilje

2016-02-01

Hydrochloric acid (HCl) and caustic (NaOH) are among the most widely used chemicals by the water industry. Direct anodic electrochemical HCl production by water electrolysis has not been successful as current commercially available electrodes are prone to chlorine formation. This study presents an innovative technology simultaneously generating HCl and NaOH from NaCl using a Mn0.84Mo0.16O2.23 oxygen evolution electrode during water electrolysis. The results showed that protons could be anodically generated at a high Coulombic efficiency (i.e. ≥ 95%) with chlorine formation accounting for 3 ~ 5% of the charge supplied. HCl was anodically produced at moderate strengths at a CE of 65 ± 4% together with a CE of 89 ± 1% for cathodic caustic production. The reduction in CE for HCl generation was caused by proton cross-over from the anode to the middle compartment. Overall, this study showed the potential of simultaneous HCl and NaOH generation from NaCl and represents a major step forward for the water industry towards on-site production of HCl and NaOH. In this study, artificial brine was used as a source of sodium and chloride ions. In theory, artificial brine could be replaced by saline waste streams such as Reverse Osmosis Concentrate (ROC), turning ROC into a valuable resource.

Enhanced ablation of small anodes in a carbon nanotube arc discharge

NASA Astrophysics Data System (ADS)

Raitses, Yevgeny; Fetterman, Abraham; Keidar, Michael

2008-11-01

An atmospheric pressure helium arc discharge is used for carbon nanotube synthesis. The arc discharge operates in an anodic mode with the ablating anode made from a graphite material. For such conditions, models predict the electron-repelling (negative) anode sheath. In the present experiments, the anode ablation rate is investigated as a function of the anode diameter. It is found that anomalously high ablation occurs for small anode diameters (< 0.4 cm). This result is explained by the formation of an electron-attracting (positive) anode sheath leading to increased power losses on small anodes as compared to larger anodes [1]. The suggested mechanism for the positive anode sheath formation is plasma convergence. The increased ablation rate due to this positive sheath could imply a greater yield of carbon nanotube production. [1] A. J. Fetterman, Y. Raitses and M. Keidar, Carbon (2008).

Supercapacitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Donghai; Yi, Ran; Chen, Shuru

Embodiments provide a hybrid supercapacitor exhibiting high energy and power densities enabled by a high-performance lithium-alloy anode coupled with a porous carbon cathode in an electrolyte containing lithium salt. Embodiments include a size reduced silicon oxide anode, a boron-doped silicon oxide anode, and/or a carbon coated silicon oxide anode, which may improve cycling stability and rate performance. Further embodiments include a hybrid supercapacitor system using a Li-active anode in an electrolyte including LiPF6 in a mixture of ethylene carbonate, diethyl carbonate, and dimethyl carbonate (EC:DEC:DMC, 2:1:2 by vol.) and 10 wt % fluoroethylene carbonate (FEC), which may reduce the self-dischargemore » rate.« less

Alumina-coated and manganese monoxide embedded 3D carbon derived from avocado as high-performance anode for lithium-ion batteries

NASA Astrophysics Data System (ADS)

rehman, Wasif ur; Xu, Youlong; Du, Xianfeng; Sun, Xiaofei; Ullah, Inam; Zhang, Yuan; Jin, Yanling; Zhang, Baofeng; Li, Xifei

2018-07-01

Derived from avocado fruit, a three dimension (3D) carbon is prepared via a hydrothermal/pyrolysis process followed by embedding with MnO nanoparticles by a wet chemical method and coating with Al2O3 through an atomic layer deposition technique. The obtained material presents a hierarchical structure that MnO nanocrystals wrapped in 3D carbon and then encapsulated in a uniform Al2O3 layer with a thickness of about 5 nm. Benefiting from this hierarchical structure in which 3D carbon offers numerous electronic pathways to enhance the conductivity and Al2O3 nanolayer provide a shelter to keep away from dissolution of Mn4+ and volume changes during charge/discharge process. This material (marked as C/MnO@Al2O3) has exhibited high rate performance and excellent cyclability as an anode for lithium ion batteries. A high specific capacity of about 600 mA h g-1 is achieved at a current density of 1000 mA g-1 and the electrode can still deliver a high specific capacity of about 1165 mA h g-1 at 150 mA g-1 after 100 cycles. These results facilitate a green and high potential of anode materials towards promising devices for advance performance of lithium-ion batteries.

Evaluation of selected thermal control coatings for long-life space structures

NASA Technical Reports Server (NTRS)

Teichman, Louis A.; Slemp, Wayne S.; Witte, William G., Jr.

1992-01-01

Graphite-reinforced resin matrix composites are being considered for spacecraft structural applications because of their light weight, high stiffness, and lower thermal expansion. Thin protective coatings with stable optical properties and the proper ratio of solar absorption (alpha sub s) to thermal emittance (epsilon) minimize orbital thermal extremes and protect these materials against space environment degradation. Sputtered coatings applied directly to graphite/epoxy composite surfaces and anodized coatings applied to thin aluminum foil were studied for use both as an atomic oxygen barrier and as thermal control coatings. Additional effort was made to develop nickel-based coatings which could be applied directly to composites. These coating systems were selected because their inherent tenacity made them potentially more reliable than commercial white paints for long-life space missions. Results indicate that anodized aluminum foil coatings are suitable for tubular and flat composite structures on large platforms in low Earth orbit. Anodized foil provides protection against some elements of the natural space environment (atomic oxygen, ultraviolet, and particulate radiation) and offers a broad range of tailored alpha sub s/epsilon. The foil is readily available and can be produced in large quantities, while the anodizing process is a routine commercial technique.

Silicon hollow sphere anode with enhanced cycling stability by a template-free method

NASA Astrophysics Data System (ADS)

Chen, Song; Chen, Zhuo; Luo, Yunjun; Xia, Min; Cao, Chuanbao

2017-04-01

Silicon is a promising alternative anode material since it has a ten times higher theoretical specific capacity than that of a traditional graphite anode. However, the poor cycling stability due to the huge volume change of Si during charge/discharge processes has seriously hampered its widespread application. To address this challenge, we design a silicon hollow sphere nanostructure by selective etching and a subsequent magnesiothermic reduction. The Si hollow spheres exhibit enhanced electrochemical properties compared to the commercial Si nanoparticles. The initial discharge and charge capacities of the Si hollow sphere anode are 2215.8 mAh g-1 and 1615.1 mAh g-1 with a high initial coulombic efficiency (72%) at a current density of 200 mA g-1, respectively. In particular, the reversible capacity is 1534.5 mAh g-1 with a remarkable 88% capacity retention against the second cycle after 100 cycles, over four times the theoretical capacity of the traditional graphite electrode. Therefore, our work demonstrates the considerable potential of silicon structures for displacing commercial graphite, and might open up new opportunities to rationally design various nanostructured materials for lithium ion batteries.

Na-ion batteries based on the inorganic BN nanocluster anodes: DFT studies.

PubMed

Nejati, K; Hosseinian, A; Bekhradnia, A; Vessally, E; Edjlali, L

2017-06-01

It has been recently indicated that the Li-ion batteries may be replaced by Na-ion batteries because of their low safety, high cost, and low-temperature performance, and lack of the Li mineral reserves. Here, using density functional theory calculations, we studied the potential application of B 12 N 12 nanoclusters as anode in Na-ion batteries. Our calculations indicate that the adsorption energy of Na + and Na are about -23.4 and -1.4kcal/mol, respectively, and the pristine BN cage to improve suffers from a low cell voltage (∼0.92V) as an anode in Na-ion batteries. We presented a strategy to increase the cell voltage and performance of Na-ion batteries. We showed that encapsulation of different halides (X=F - , Cl - , or Br - ) into BN cage significantly increases the cell voltage. By increasing the atomic number of X, the Gibbs free energy change of cell becomes more negative and the cell voltage is increased up to 3.93V. The results are discussed based on the structural, energetic, frontier molecular orbital, charge transfer and electronic properties and compared with the performance of other nanostructured anodes. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of TiO2 Addition on Grain Growth, Anodic Bubble Evolution and Anodic Overvoltage of NiFe2O4-Based Composite Inert Anodes

NASA Astrophysics Data System (ADS)

Wang, Bin; Du, Jinjing; Liu, Yihan; Fang, Zhao; Hu, Ping

2017-11-01

A two-step powder compaction and sintering process was employed to fabricate TiO2-doped NiFe2O4 ceramic-based inert anodes. Grain growth during isothermal sintering was analyzed using Brook grain growth model. The bubble behavior of NiFe2O4 ceramic-based inert anodes was investigated in a two-compartment see-through quartz cell for aluminum electrolysis process. Anodic overvoltage and potential decay curves of the inert anodes were measured by using the steady state and current interruption technique. The results showed that the kinetic index of grain growth decreased with an increase in temperature. The average activation energy of grain growth for 1.0 wt.% TiO2-doped NiFe2O4 ceramic samples with a sintering temperature range from 1373 to 1673 K dropped from 675.30 to 183.47 kJ/mol. The diameter size of bubbles before releasing from the bottom surface of the anodes was reduced with increasing the current density, and the larger average releasing bubble size for carbon anode at the same current density could be obtained, which was compared to the NiFe2O4 inert anodes. Besides, the cell voltage of carbon anodes fluctuated much more violently under the same experimental conditions. After adding small amount of TiO2, a minor reduction in anodic overvoltage of NiFe2O4-based anodes can be observed.

Increased performance of hydrogen production in microbial electrolysis cells under alkaline conditions.

PubMed

Rago, Laura; Baeza, Juan A; Guisasola, Albert

2016-06-01

This work reports the first successful enrichment and operation of alkaline bioelectrochemical systems (microbial fuel cells, MFC, and microbial electrolysis cells, MEC). Alkaline (pH=9.3) bioelectrochemical hydrogen production presented better performance (+117%) compared to conventional neutral conditions (2.6 vs 1.2 litres of hydrogen gas per litre of reactor per day, LH2·L(-1)REACTOR·d(-1)). Pyrosequencing results of the anodic biofilm showed that while Geobacter was mainly detected under conventional neutral conditions, Geoalkalibacter sp. was highly detected in the alkaline MFC (21%) and MEC (48%). This is the first report of a high enrichment of Geoalkalibacter from an anaerobic mixed culture using alkaline conditions in an MEC. Moreover, Alkalibacter sp. was highly present in the anodic biofilm of the alkaline MFC (37%), which would indicate its potentiality as a new exoelectrogen. Copyright © 2016 Elsevier B.V. All rights reserved.

Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating

PubMed Central

Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

2016-01-01

Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium–scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with “lithiophilic” coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm2 over 80 cycles. PMID:26929378

Polyarene mediators for mediated redox flow battery

DOEpatents

Delnick, Frank M.; Ingersoll, David; Liang, Chengdu

2018-01-02

The fundamental charge storage mechanisms in a number of currently studied high energy redox couples are based on intercalation, conversion, or displacement reactions. With exception to certain metal-air chemistries, most often the active redox materials are stored physically in the electrochemical cell stack thereby lowering the practical gravimetric and volumetric energy density as a tradeoff to achieve reasonable power density. In a general embodiment, a mediated redox flow battery includes a series of secondary organic molecules that form highly reduced anionic radicals as reaction mediator pairs for the reduction and oxidation of primary high capacity redox species ex situ from the electrochemical cell stack. Arenes are reduced to stable anionic radicals that in turn reduce a primary anode to the charged state. The primary anode is then discharged using a second lower potential (more positive) arene. Compatible separators and solvents are also disclosed herein.

Unlocking the potential of SnS2: Transition metal catalyzed utilization of reversible conversion and alloying reactions

NASA Astrophysics Data System (ADS)

Huang, Zhi Xiang; Wang, Ye; Liu, Bo; Kong, Dezhi; Zhang, Jun; Chen, Tupei; Yang, Hui Ying

2017-01-01

The alloying-dealloying reactions of SnS2 proceeds with the initial conversion reaction of SnS2 with lithium that produces Li2S. Unfortunately, due to the electrochemical inactivity of Li2S, the conversion reaction of SnS2 is irreversible, which significantly limit its potential applications in lithium-ion batteries. Herein, a systematic understanding of transition metal molybdenum (Mo) as a catalyst in SnS2 anode is presented. It is found that Mo catalyst is able to efficiently promote the reversible conversion of Sn to SnS2. This leads to the utilization of both conversion and alloying reactions in SnS2 that greatly increases lithium storage capability of SnS2. Mo catalyst is introduced in the form of MoS2 grown directly onto self-assembled vertical SnS2 nanosheets that anchors on three-dimensional graphene (3DG) creating a hierarchal nanostructured named as SnS2/MoS2/3DG. The catalytic effect results in a significantly enhanced electrochemical properties of SnS2/MoS2/3DG; a high initial Coulombic efficiency (81.5%) and high discharge capacities of 960.5 and 495.6 mA h g-1 at current densities of 50 and 1000 mA g-1, respectively. Post cycling investigations using ex situ TEM and XPS analysis verifies the successful conversion reaction of SnS2 mediated by Mo. The successful integration of catalyst on alloying type metal sulfide anode creates a new avenue towards high energy density lithium anodes.

Unlocking the potential of SnS2: Transition metal catalyzed utilization of reversible conversion and alloying reactions.

PubMed

Huang, Zhi Xiang; Wang, Ye; Liu, Bo; Kong, Dezhi; Zhang, Jun; Chen, Tupei; Yang, Hui Ying

2017-01-19

The alloying-dealloying reactions of SnS 2 proceeds with the initial conversion reaction of SnS 2 with lithium that produces Li 2 S. Unfortunately, due to the electrochemical inactivity of Li 2 S, the conversion reaction of SnS 2 is irreversible, which significantly limit its potential applications in lithium-ion batteries. Herein, a systematic understanding of transition metal molybdenum (Mo) as a catalyst in SnS 2 anode is presented. It is found that Mo catalyst is able to efficiently promote the reversible conversion of Sn to SnS 2 . This leads to the utilization of both conversion and alloying reactions in SnS 2 that greatly increases lithium storage capability of SnS 2 . Mo catalyst is introduced in the form of MoS 2 grown directly onto self-assembled vertical SnS 2 nanosheets that anchors on three-dimensional graphene (3DG) creating a hierarchal nanostructured named as SnS 2 /MoS 2 /3DG. The catalytic effect results in a significantly enhanced electrochemical properties of SnS 2 /MoS 2 /3DG; a high initial Coulombic efficiency (81.5%) and high discharge capacities of 960.5 and 495.6 mA h g -1 at current densities of 50 and 1000 mA g -1 , respectively. Post cycling investigations using ex situ TEM and XPS analysis verifies the successful conversion reaction of SnS 2 mediated by Mo. The successful integration of catalyst on alloying type metal sulfide anode creates a new avenue towards high energy density lithium anodes.

Silicon oxide based high capacity anode materials for lithium ion batteries

DOEpatents

Deng, Haixia; Han, Yongbong; Masarapu, Charan; Anguchamy, Yogesh Kumar; Lopez, Herman A.; Kumar, Sujeet

2017-03-21

Silicon oxide based materials, including composites with various electrical conductive compositions, are formulated into desirable anodes. The anodes can be effectively combined into lithium ion batteries with high capacity cathode materials. In some formulations, supplemental lithium can be used to stabilize cycling as well as to reduce effects of first cycle irreversible capacity loss. Batteries are described with surprisingly good cycling properties with good specific capacities with respect to both cathode active weights and anode active weights.

Evaluation of ion release, cytotoxicity, and platelet adhesion of electrochemical anodized 316 L stainless steel cardiovascular stents.

PubMed

Díaz, M; Sevilla, P; Galán, A M; Escolar, G; Engel, E; Gil, F J

2008-11-01

316L Stainless steel is one of the most used metallic material in orthopedical prosthesis, osteosinthesis plates, and cardiovascular stents. One of the main problems this material presents is the nickel and chromium release, specially the Ni ion release that provokes allergy in a high number of patients. Recently, experimental applications in vitro and in vivo seem to indicate that the thickness of the nature oxide of the stainless steel results in very strong reinforcement of the biological response and reduce the ion release due to the thicker surface oxide. It is possible to grow the natural chromium oxide layer by electrolytic method such anodization. In this study, two main anodization methods to grow chromium oxide on the 316L stainless steel have been evaluated. Nickel and Chromium ions release in human blood at 37 degrees C were detected at times of 1, 6, 11, and 15 days by means of atomic absorption in a graphite furnace (GAAF). Moreover, cytocompatibility tests were carried out. Perfusion experiments were performed to evaluate morphometrically platelet interaction with the material and to explore the potential thrombogenicity. The results showed a good cytocompatibility between the material and the osteoblast-like cells. However, these anodization methods released between 2 and 10 times more nickel and chromium than the original stainless steel, depending on the method used. Besides, anodized samples shown an increase of the percentage of surface covered by platelets. Consequently, the anodization methods studied do not improve the long-term behavior of the stainless steel for its application as cardiovascular stents.

Electrochemically induced dual reactive barriers for transformation of TCE and mixture of contaminants in groundwater.

PubMed

Mao, Xuhui; Yuan, Songhu; Fallahpour, Noushin; Ciblak, Ali; Howard, Joniqua; Padilla, Ingrid; Loch-Caruso, Rita; Alshawabkeh, Akram N

2012-11-06

A novel reactive electrochemical flow system consisting of an iron anode and a porous cathode is proposed for the remediation of mixture of contaminants in groundwater. The system consists of a series of sequentially arranged electrodes, a perforated iron anode, a porous copper cathode followed by a mesh-type mixed metal oxide anode. The iron anode generates ferrous species and a chemically reducing environment, the porous cathode provides a reactive electrochemically reducing barrier, and the inert anode provides protons and oxygen to neutralize the system. The redox conditions of the electrolyte flowing through this system can be regulated by controlling the distribution of the electric current. Column experiments are conducted to evaluate the process and study the variables. The electrochemical reduction on a copper foam cathode produced an electrode-based reductive potential capable of reducing TCE and nitrate. Rational electrodes arrangement, longer residence time of electrolytes and higher surface area of the foam electrode improve the reductive transformation of TCE. More than 82.2% TCE removal efficiency is achieved for the case of low influent concentration (<7.5 mg/L) and high current (>45 mA). The ferrous species produced from the iron anode not only enhance the transformation of TCE on the cathode, but also facilitates transformation of other contaminants including dichromate, selenate and arsenite. Removal efficiencies greater than 80% are achieved for these contaminants in flowing contaminated water. The overall system, comprising the electrode-based and electrolyte-based barriers, can be engineered as a versatile and integrated remedial method for a relatively wide spectrum of contaminants and their mixtures.

Effect of the electronegativity on the electrosorption selectivity of anions during capacitive deionization.

PubMed

Sun, Zhumei; Chai, Liyuan; Liu, Mingshi; Shu, Yude; Li, Qingzhu; Wang, Yunyan; Qiu, Dingfan

2018-03-01

The effect of electronegativity on the electrosorption selectivity of anions during capacitive deionization was investigated via a combination of experimental and theoretical studies. A model was developed based on chemical thermodynamics and the classic Stern's model to reveal the role of the anode potential and to describe electrosorption selectivity behavior during capacitive deionization. The effects of the anode potential on the adsorption of Cl - and ReO 4 - were studied and the obtained data were used to validate the model. Using the validated model, the effects of the anode potential and electronegativity of various anions, including Cl - , ReO 4 - , SO 4 2- and NO 3 - were assessed. The experimental results for the electrosorption of Cl - and ReO 4 - corresponded well with the developed model. The electrosorption capacity demonstrates a logarithmic relationship with the anode potential. The model showed that the electronegativity significantly affects the selectivity. In a mixed Cl - , ReO 4 - , SO 4 2- and NO 3 - solution, ReO 4 - was preferentially adsorbed over the other three anions, and the following selectivity was exhibited: ReO 4 -  > NO 3 -  > Cl -  > SO 4 2- . The results showed that the effect of flow rates on the electrosorption selectivity can be considered negligible when the flow rates are higher than 112 mL min -1 . The anions selectivity can be further enhanced by increasing the anode potential, and electrosorption selectivity is no appreciable decline after 6 experiments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Template-Growth of Highly Ordered Carbon Nanotube Arrays on Silicon POSTPRINT

DTIC Science & Technology

2006-09-01

packed uni- form CNTs that are spatially isolated from each other is to use a growth template. Highly ordered anodic aluminum oxide ( AAO ) template can...process for evaporating thick aluminum of high quality and good adhesion. 15. SUBJECT TERMS Anodic Aluminum Oxide Template, Carbon Nanotubes (CNTs...within the highly ordered nanopores of an alumina oxide template, which is in turn formed on silicon through anodization of aluminum of unprecedented

Self-assembly of novel hierarchical flowers-like Sn3O4 decorated on 2D graphene nanosheets hybrid as high-performance anode materials for LIBs

NASA Astrophysics Data System (ADS)

Chen, Xuefang; Huang, Ying; Li, Tianpeng; Wei, Chao; Yan, Jing; Feng, Xuansheng

2017-05-01

Novel hierarchical flower-like Sn3O4 assembled by thin Sn3O4 nanosheets, as a kind of mixed-valence tin oxide, decorated on two-dimensional graphene nanosheets has been synthesized via a hydrothermal route and a step solution deoxidization technique. More importantly, as the anode materials for lithium ion batteries, the flower-like Sn3O4/graphene composite has not been investigated in detail. Noticeably, the nanosheets stemming from flower-like Sn3O4 and graphene have been linked together to form a specials three dimensional structure, possessing high active surface area and large enough inner spaces, which is benefit to the diffusion of liquid electrolyte into the electrode materials. In addition, the special structure could provide sufficient free volume to buffer the volume expansion appeared in the process of discharging and charging. The as-prepared flowers-like Sn3O4/graphene displayed excellent electrochemical performance with high capacity and good cycling stability as anode materials for lithium ion batteries. The discharge capacity is 1727 mAh/g in the first cycle at the current density of 60 mA/g. The obtained reversible capacity is 631mAh/g with a coulomb efficiency of 97.04% after 50 cycles. With its better electrochemical properties, the as-prepared flowers-like Sn3O4/graphene has the potential to be the next generation materials as an environmentally benign, abundant, cheap anode materials for lithium ion batteries.

Melt-Spun Fe-Sb Intermetallic Alloy Anode for Performance Enhanced Sodium-Ion Batteries.

PubMed

Edison, Eldho; Sreejith, Sivaramapanicker; Madhavi, Srinivasan

2017-11-15

Owing to the high theoretical sodiation capacities, intermetallic alloy anodes have attracted considerable interest as electrodes for next-generation sodium-ion batteries (SIBs). Here, we demonstrate the fabrication of intermetallic Fe-Sb alloy anode for SIBs via a high-throughput and industrially viable melt-spinning process. The earth-abundant and low-cost Fe-Sb-based alloy anode exhibits excellent cycling stability with nearly 466 mAh g -1 sodiation capacity at a specific current of 50 mA g -1 with 95% capacity retention after 80 cycles. Moreover, the alloy anode displayed outstanding rate performance with ∼300 mAh g -1 sodiation capacity at 1 A g -1 . The crystalline features of the melt-spun fibers aid in the exceptional electrochemical performance of the alloy anode. Further, the feasibility of the alloy anode for real-life applications was demonstrated in a sodium-ion full-cell configuration which could deliver a sodiation capacity of over 300 mAh g -1 (based on anode) at 50 mA g -1 with more than 99% Coulombic efficiency. The results further exhort the prospects of melt-spun alloy anodes to realize fully functional sodium-ion batteries.

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

NASA Astrophysics Data System (ADS)

Zhao, Jie; Zhou, Guangmin; Yan, Kai; Xie, Jin; Li, Yuzhang; Liao, Lei; Jin, Yang; Liu, Kai; Hsu, Po-Chun; Wang, Jiangyan; Cheng, Hui-Ming; Cui, Yi

2017-10-01

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed LixM (M = Si, Sn, or Al) nanoparticles encapsulated by large graphene sheets. With the protection of graphene sheets, the large and freestanding LixM/graphene foils are stable in different air conditions. With fully expanded LixSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). This foil is also paired with high-capacity Li-free V2O5 and sulfur cathodes to achieve stable full-cell cycling.

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

DOE PAGES

Zhao, Jie; Zhou, Guangmin; Yan, Kai; ...

2017-07-10

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed Li xM (M = Si, Sn, or Al) nanoparticles encapsulated by largemore » graphene sheets. With the protection of graphene sheets, the large and freestanding Li xM/graphene foils are stable in different air conditions. With fully expanded Li xSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). As a result, this foil is also paired with high-capacity Li-free V 2O 5 and sulfur cathodes to achieve stable full-cell cycling.« less

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Jie; Zhou, Guangmin; Yan, Kai

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed Li xM (M = Si, Sn, or Al) nanoparticles encapsulated by largemore » graphene sheets. With the protection of graphene sheets, the large and freestanding Li xM/graphene foils are stable in different air conditions. With fully expanded Li xSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). As a result, this foil is also paired with high-capacity Li-free V 2O 5 and sulfur cathodes to achieve stable full-cell cycling.« less

A Single-Step Hydrothermal Route to 3D Hierarchical Cu2 O/CuO/rGO Nanosheets as High-Performance Anode of Lithium-Ion Batteries.

PubMed

Wu, Songhao; Fu, Gaoliang; Lv, Weiqiang; Wei, Jiake; Chen, Wenjin; Yi, Huqiang; Gu, Meng; Bai, Xuedong; Zhu, Liang; Tan, Chao; Liang, Yachun; Zhu, Gaolong; He, Jiarui; Wang, Xinqiang; Zhang, Kelvin H L; Xiong, Jie; He, Weidong

2018-02-01

As anodes of Li-ion batteries, copper oxides (CuO) have a high theoretical specific capacity (674 mA h g -1 ) but own poor cyclic stability owing to the large volume expansion and low conductivity in charges/discharges. Incorporating reduced graphene oxide (rGO) into CuO anodes with conventional methods fails to build robust interaction between rGO and CuO to efficiently improve the overall anode performance. Here, Cu 2 O/CuO/reduced graphene oxides (Cu 2 O/CuO/rGO) with a 3D hierarchical nanostructure are synthesized with a facile, single-step hydrothermal method. The Cu 2 O/CuO/rGO anode exhibits remarkable cyclic and high-rate performances, and particularly the anode with 25 wt% rGO owns the best performance among all samples, delivering a record capacity of 550 mA h g -1 at 0.5 C after 100 cycles. The pronounced performances are attributed to the highly efficient charge transfer in CuO nanosheets encapsulated in rGO network and the mitigated volume expansion of the anode owing to its robust 3D hierarchical nanostructure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transcranial direct current stimulation in mild cognitive impairment: Behavioral effects and neural mechanisms.

PubMed

Meinzer, Marcus; Lindenberg, Robert; Phan, Mai Thy; Ulm, Lena; Volk, Carina; Flöel, Agnes

2015-09-01

The long preclinical phase of Alzheimer's disease provides opportunities for potential disease-modifying interventions in prodromal stages such as mild cognitive impairment (MCI). Anodal transcranial direct current stimulation (anodal-tDCS), with its potential to enhance neuroplasticity, may allow improving cognition in MCI. In a double-blind, cross-over, sham-controlled study, anodal-tDCS was administered to the left inferior frontal cortex during task-related and resting-state functional magnetic resonance imaging (fMRI) to assess its impact on cognition and brain functions in MCI. During sham stimulation, MCI patients produced fewer correct semantic-word-retrieval responses than matched healthy controls, which was associated with hyperactivity in bilateral prefrontal regions. Anodal-tDCS significantly improved performance to the level of controls, reduced task-related prefrontal hyperactivity and resulted in "normalization" of abnormal network configuration during resting-state fMRI. Anodal-tDCS exerts beneficial effects on cognition and brain functions in MCI, thereby providing a framework to test whether repeated stimulation sessions may yield sustained reversal of cognitive deficits. Copyright © 2015 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.

Asymmetrical electrically induced injury of rabbit ventricular myocytes.

PubMed

Knisley, S B; Grant, A O

1995-05-01

Strong defibrillation-type electric field stimulation may injure myocytes when transmembrane potentials during the pulse exceed the threshold for membrane permeabilization. The location of injury may depend on intrinsic transmembrane potential or influx of calcium by "electro-osmosis" during the stimulation pulse in addition to the transmembrane potential changes induced by the pulse. We have studied injury by examining contracture and changes in transmembrane potential-sensitive dye fluorescence induced by electric field stimulation (St) with a duration of 20 ms and strength of 16-400 V/cm in isolated rabbit ventricular myocytes. St of 100-150 V/cm produced injury in myocytes oriented parallel to the St field frequently without injuring myocytes oriented perpendicular to the field. Injury required calcium in the solution and was asymmetric, occurring first at the myocyte and facing the St anode in 100% of injured myocytes in normal Tyrode's solution. Injury depended significantly on whether the product of the electric field strength and myocyte length exceeded a threshold of 1.1 V (P < 0.05). Asymmetric injury at the end facing the anode was still present in 96% of injured myocytes for stimulation after depolarization by an action potential or 20 mM or 125 mM potassium, suggesting that intrinsic transmembrane potential is not responsible for asymmetry. In 125 mM potassium, eliminating calcium from the bathing solution during the St pulse and introducing calcium after the pulse decreased the fraction of injured myocytes in which injury occurred at the end facing the anode to 62%, suggesting that calcium influx by "electro-osmosis" at the myocyte end facing the anode contributes to asymmetry. Asymmetric injury at the end facing the anode was still present in 100% of injured myocytes after adding 1 mM tetraethylammonium chloride, indicating that asymmetry is not sensitive to the potassium channel blockade. For stimulation pulses stronger than 50 V/cm given after depolarization by an action potential, transmembrane potentials at both myocyte ends decayed after the initial deflection indicating that permeabilization occurred at both ends. In conclusion, injury depends on myocyte orientation and is asymmetric occurring first at the myocyte end facing the anode. Asymmetric injury is not explained by asymmetric permeabilization, is independent of the intrinsic transmembrane potential and may result from "electro-osmosis" during the stimulation pulse.

Carbon-Coated, Diatomite-Derived Nanosilicon as a High Rate Capable Li-ion Battery Anode.

PubMed

Campbell, Brennan; Ionescu, Robert; Tolchin, Maxwell; Ahmed, Kazi; Favors, Zachary; Bozhilov, Krassimir N; Ozkan, Cengiz S; Ozkan, Mihrimah

2016-10-07

Silicon is produced in a variety of ways as an ultra-high capacity lithium-ion battery (LIB) anode material. The traditional carbothermic reduction process required is expensive and energy-intensive; in this work, we use an efficient magnesiothermic reduction to convert the silica-based frustules within diatomaceous earth (diatomite, DE) to nanosilicon (nanoSi) for use as LIB anodes. Polyacrylic acid (PAA) was used as a binder for the DE-based nanoSi anodes for the first time, being attributed for the high silicon utilization under high current densities (up to 4C). The resulting nanoSi exhibited a high BET specific surface area of 162.6 cm 2 g -1 , compared to a value of 7.3 cm 2 g -1 for the original DE. DE contains SiO 2 architectures that make ideal bio-derived templates for nanoscaled silicon. The DE-based nanoSi anodes exhibit good cyclability, with a specific discharge capacity of 1102.1 mAh g -1 after 50 cycles at a C-rate of C/5 (0.7 A g Si -1 ) and high areal loading (2 mg cm -2 ). This work also demonstrates the fist rate capability testing for a DE-based Si anode; C-rates of C/30 - 4C were tested. At 4C (14.3 A g Si -1 ), the anode maintained a specific capacity of 654.3 mAh g -1 - nearly 2x higher than graphite's theoretical value (372 mAh g -1 ).

Structure that encapsulates lithium metal for high energy density battery anode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Yi; Yan, Kai; Chu, Steven

A battery includes 1) an anode, 2) a cathode, and 3) an electrolyte disposed between the anode and the cathode. The anode includes a current collector and an interfacial layer disposed over the current collector, and the interfacial layer includes an array of interconnected, protruding regions that define spaces.

Increasing the Thermal Stability of Aluminum Titanate for Solid Oxide Fuel Cell Anodes

NASA Technical Reports Server (NTRS)

Bender, Jeffrey B.

2004-01-01

Solid-oxide fuel cells (SOFCs) show great potential as a power source for future space exploration missions. Because SOFCs operate at temperatures significantly higher than other types of fuel cells, they can reach overall efficiencies of up to 60% and are able to utilize fossil fuels. The SOFC team at GRC is leading NASA's effort to develop a solid oxide fuel cell with a power density high enough to be used for aeronautics and space applications, which is approximately ten times higher than ground transport targets. layers must be able to operate as a single unit at temperatures upwards of 900'C for at least 40,000 hours with less than ten percent degradation. One key challenge to meeting this goal arises from the thermal expansion mismatch between different layers. The amount a material expands upon heating is expressed by its coefficient of thermal expansion (CTE). If the CTEs of adjacent layers are substantially different, thermal stresses will arise during the cell's fabrication and operation. These stresses, accompanied by thermal cycling, can fracture and destroy the cell. While this is not an issue at the electrolyte-cathode interface, it is a major concern at the electrolyte-anode interface, especially in high power anode-supported systems. electrolyte are nearly identical. Conventionally, this has been accomplished by varying the composition of the anode to match the CTE of the yittria-stabilized zirconia (YSZ) electrolyte (approx.10.8x10(exp -6/degC). A Ni/YSZ composite is typically used as a base material for the anode due to its excellent electrochemical properties, but its CTE is about 13.4x10(exp -6/degC). One potential way to lower the CTE of this anode is to add a small percentage of polycrystalline Al2TiO5, with a CTE of 0.68x10(exp -6/degC, to the Ni/YSZ base. However, Al2TiO5 is thermally unstable and loses its effectiveness as it decomposes to Al2O3 and TiO2 between 750 C and 1280 C. be used as additives to increase the thermal stability of Al2TiO5 in SOFC operating conditions without adversely affecting the electrochemical properties of the SOFC anode. Three candidate materials were chosen through an extensive literature review: MgO, Fe2O3, and ZrTiO4. Although all three have been shown to prevent Al2TiO5 decomposition under various conditions, their effectiveness in the temperature range and atmosphere of the SOFC has not yet been evaluated. Several batches of Al2TiO5 with varying amounts of additives were prepared, exposed to reducing and oxidizing atmospheres at elevated temperatures, and the resulting decomposition of Al2TiO5 was measured. The most promising additives were further evaluated with the goal of ultimately preparing low CTE anodes that are chemically compatible to current systems. Adding minor constituents to stabilize Al2TiO5 could ultimately preserve its low CTE for the life of the fuel cell and improve the cell's long-term performance without a drop in anode conductivity. Further, these low CTE filler additions could allow the use of new sulfur tolerant anode materials, improving the viability of SOFCs for future aeronautics and space applications. Every SOFC consists of a cathode and an anode separated by an electrolyte, These three One way to avoid this problem is to design the cell such that the CTEs of the anode and The objective of this summer research project was to evaluate several materials that could

Improving Efficiency of Aluminium Sacrificial Anode Using Cold Work Process

NASA Astrophysics Data System (ADS)

Asmara, Y. P.; Siregar, J. P.; Tezara, C.; Ann, Chang Tai

2016-02-01

Aluminium is one of the preferred materials to be used as sacrificial anode for carbon steel protection. The efficiency of these can be low due to the formation of oxide layer which passivate the anodes. Currently, to improve its efficiency, there are efforts using a new technique called surface modifications. The objective of this research is to study corrosion mechanism of aluminium sacrificial anode which has been processed by cold work. The cold works are applied by reducing the thickness of aluminium sacrificial anodes at 20% and 40% of thickness reduction. The cathodic protection experiments were performed by immersion of aluminium connected to carbon steel cylinder in 3% NaCl solutions. Visual inspections using SEM had been conducted during the experiments and corrosion rate data were taken in every week for 8 weeks of immersion time. Corrosion rate data were measured using weight loss and linear polarization technique (LPR). From the results, it is observed that cold worked aluminium sacrificial anode have a better corrosion performance. It shows higher corrosion rate and lower corrosion potential. The anodes also provided a long functional for sacrificial anode before it stop working. From SEM investigation, it is shown that cold works have changed the microstructure of anodes which is suspected in increasing corrosion rate and cause de-passivate of the surface anodes.

Activated microporous-mesoporous carbon derived from chestnut shell as a sustainable anode material for high performance microbial fuel cells.

PubMed

Chen, Qin; Pu, Wenhong; Hou, Huijie; Hu, Jingping; Liu, Bingchuan; Li, Jianfeng; Cheng, Kai; Huang, Long; Yuan, Xiqing; Yang, Changzhu; Yang, Jiakuan

2018-02-01

Microbial fuel cells (MFCs) are promising biotechnologies tool to harvest electricity by decomposing organic matter in waste water, and the anode material is a critical factor in determining the performance of MFCs. In this study, chestnut shell is proposed as a novel anode material with mesoporous and microporous structure prepared via a simple carbonization procedure followed by an activation process. The chemical activation process successfully modified the macroporous structure, created more mesoporous and microporous structure and decreased the O-content and pyridinic/pyrrolic N groups on the biomass anode, which were beneficial for improving charge transfer efficiency between the anode surface and microbial biofilm. The MFC with activated biomass anode achieved a maximum power density (23.6 W m -3 ) 2.3 times higher than carbon cloth anode (10.4 W m -3 ). This study introduces a promising and feasible strategy for the fabrication of high performance anodes for MFCs derived from cost-effective, sustainable natural materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of anode (electro)catalytic materials for the direct borohydride fuel cell: Methods and benchmarks

NASA Astrophysics Data System (ADS)

Olu, Pierre-Yves; Job, Nathalie; Chatenet, Marian

2016-09-01

In this paper, different methods are discussed for the evaluation of the potential of a given catalyst, in view of an application as a direct borohydride fuel cell DBFC anode material. Characterizations results in DBFC configuration are notably analyzed at the light of important experimental variables which influence the performances of the DBFC. However, in many practical DBFC-oriented studies, these various experimental variables prevent one to isolate the influence of the anode catalyst on the cell performances. Thus, the electrochemical three-electrode cell is a widely-employed and useful tool to isolate the DBFC anode catalyst and to investigate its electrocatalytic activity towards the borohydride oxidation reaction (BOR) in the absence of other limitations. This article reviews selected results for different types of catalysts in electrochemical cell containing a sodium borohydride alkaline electrolyte. In particular, propositions of common experimental conditions and benchmarks are given for practical evaluation of the electrocatalytic activity towards the BOR in three-electrode cell configuration. The major issue of gaseous hydrogen generation and escape upon DBFC operation is also addressed through a comprehensive review of various results depending on the anode composition. At last, preliminary concerns are raised about the stability of potential anode catalysts upon DBFC operation.

Reduced Graphene Oxide Anodes for Potential Application in Algae Biophotovoltaic Platforms

PubMed Central

Ng, Fong-Lee; Jaafar, Muhammad Musoddiq; Phang, Siew-Moi; Chan, Zhijian; Salleh, Nurul Anati; Azmi, Siti Zulfikriyah; Yunus, Kamran; Fisher, Adrian C.; Periasamy, Vengadesh

2014-01-01

The search for renewable energy sources has become challenging in the current era, as conventional fuel sources are of finite origins. Recent research interest has focused on various biophotovoltaic (BPV) platforms utilizing algae, which are then used to harvest solar energy and generate electrical power. The majority of BPV platforms incorporate indium tin oxide (ITO) anodes for the purpose of charge transfer due to its inherent optical and electrical properties. However, other materials such as reduced graphene oxide (RGO) could provide higher efficiency due to their intrinsic electrical properties and biological compatibility. In this work, the performance of algae biofilms grown on RGO and ITO anodes were measured and discussed. Results indicate improved peak power of 0.1481 mWm−2 using the RGO electrode and an increase in efficiency of 119%, illustrating the potential of RGO as an anode material for applications in biofilm derived devices and systems. PMID:25531093

Constructing a novel and safer energy storing system using a graphite cathode and a MoO 3 anode

NASA Astrophysics Data System (ADS)

Gunawardhana, Nanda; Park, Gum-Jae; Dimov, Nikolay; Thapa, Arjun Kumar; Nakamura, Hiroyoshi; Wang, Hongyu; Ishihara, Tatsumi; Yoshio, Masaki

A cell employing a graphite cathode and a molybdenum (VI) oxide (MoO 3) anode is investigated as a possible energy storage device. Graphite cathode allows raising the voltage well above the cathode materials of LIBs without causing safety issues. The bottom potential of this anode is 2.0 V vs. Li/Li +, which is well above the lithium plating potential. Pulse polarization experiment reveals that no lithium deposition occurs, which further enhances the safety of the graphite/MoO 3 full cell. Charge/discharge mechanism of this system results from intercalation and de-intercalation of the PF 6 - in the cathode (KS-6) and Li + in the anode (MoO 3). This mechanism is supported by in situ X-ray diffraction data of the graphite/MoO 3 cell recorded at various states of charge.

Reduced graphene oxide anodes for potential application in algae biophotovoltaic platforms.

PubMed

Ng, Fong-Lee; Jaafar, Muhammad Musoddiq; Phang, Siew-Moi; Chan, Zhijian; Salleh, Nurul Anati; Azmi, Siti Zulfikriyah; Yunus, Kamran; Fisher, Adrian C; Periasamy, Vengadesh

2014-12-22

The search for renewable energy sources has become challenging in the current era, as conventional fuel sources are of finite origins. Recent research interest has focused on various biophotovoltaic (BPV) platforms utilizing algae, which are then used to harvest solar energy and generate electrical power. The majority of BPV platforms incorporate indium tin oxide (ITO) anodes for the purpose of charge transfer due to its inherent optical and electrical properties. However, other materials such as reduced graphene oxide (RGO) could provide higher efficiency due to their intrinsic electrical properties and biological compatibility. In this work, the performance of algae biofilms grown on RGO and ITO anodes were measured and discussed. Results indicate improved peak power of 0.1481 mWm(-2) using the RGO electrode and an increase in efficiency of 119%, illustrating the potential of RGO as an anode material for applications in biofilm derived devices and systems.

Effect of anodic treatment on the electrocatalytic activity of superficial Raney nickel catalyst in cathodic hydrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korovin, N.V.; Kozlova, N.I.; Kumenko, M.V.

This work is concerned with the effect of oxidation on the activity of Raney nickel catalyst in cathodic hydrogen evolution. The superficial Raney nickel catalyst (nickel SRC) was prepared by a previously described procedure. The surface of the nickel SRC was oxidized by applying an anodic sweep over the potential range from 0.25 to 1.00 V with a potential sweep rate of 1 mV/sec. The rate of cathodic hydrogen evolution increases after pretreatment of the surface of nickel SRC by application of an anodic pulse. A significant increase in the reaction rate most probably is due to oxygen adsorption onmore » the nickel SRC surface. The largest increase in the amount of weakly bound hydrogen corresponds to the most active electrode. Oxidation of the nickel surface by an anodic pulse causes both an acceleration and a retardation of the cathodic hydrogen evolution reaction.« less

Effect of anodization on the surface characteristics and electrochemical behaviour of zirconium in artificial saliva.

PubMed

Romonti, Daniela E; Gomez Sanchez, Andrea V; Milošev, Ingrid; Demetrescu, Ioana; Ceré, Silvia

2016-05-01

The paper is focused on elaboration of ZrO2 films on pure zirconium via anodizing in phosphoric acid with and without fluoride at constant potentials of 30 V and 60 V. The structure and composition of the films were investigated using scanning electronic microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The composition of the oxides formed at both potentials can be identified as monoclinic ZrO2. In addition to Zr and O, the layers formed in phosphoric acid contain phosphorus originating from the phosphoric acid. When the phosphoric acid solution contains NaF, fluorine is also incorporated into the oxide layer. The oxides formed at a higher voltage have greater roughness than those formed at 30 V. Anodized samples exhibit smaller current densities during anodic polarization compared to the as-received zirconium covered with native oxide. Copyright © 2016 Elsevier B.V. All rights reserved.

An Overview of Electron Acceptors in Microbial Fuel Cells

PubMed Central

Ucar, Deniz; Zhang, Yifeng; Angelidaki, Irini

2017-01-01

Microbial fuel cells (MFC) have recently received increasing attention due to their promising potential in sustainable wastewater treatment and contaminant removal. In general, contaminants can be removed either as an electron donor via microbial catalyzed oxidization at the anode or removed at the cathode as electron acceptors through reduction. Some contaminants can also function as electron mediators at the anode or cathode. While previous studies have done a thorough assessment of electron donors, cathodic electron acceptors and mediators have not been as well described. Oxygen is widely used as an electron acceptor due to its high oxidation potential and ready availability. Recent studies, however, have begun to assess the use of different electron acceptors because of the (1) diversity of redox potential, (2) needs of alternative and more efficient cathode reaction, and (3) expanding of MFC based technologies in different areas. The aim of this review was to evaluate the performance and applicability of various electron acceptors and mediators used in MFCs. This review also evaluated the corresponding performance, advantages and disadvantages, and future potential applications of select electron acceptors (e.g., nitrate, iron, copper, perchlorate) and mediators. PMID:28469607

Evaluating the Passivation of Corrosion of API-X100 Steel with Cyclic Voltammetry

NASA Astrophysics Data System (ADS)

Eliyan, Faysal Fayez; Alfantazi, Akram

2017-10-01

In this research, cyclic voltammetry, in oxygen-free low bicarbonate-carbonate solutions, was used to study the corrosion reactions of a high-strength steel, API-X100. With cycles of different scan ranges, the effects of cycling, transpassivation, and cathodic reduction on the electrochemistry of the passive films were analyzed. It was found that carbonate in higher concentrations reduces the anodic activity and the cathodic reactions of the surface. Bicarbonate in small concentrations in solutions that contained low carbonate concentrations catalyzed dissolution and disrupted the formation of the passive films, in reference to the measured anodic currents. From the experiments, there was electrochemical evidence that with more cycles, the passive films were growing thicker, the transpassivation deteriorated the passive films, and during the cathodic reduction, the dissolution was occurring at lower potentials to facilitate later the passivation at higher potentials.

Field-scale observations of a transient geobattery resulting from natural attenuation of a crude oil spill

USGS Publications Warehouse

Heenan, Jeffrey; Ntarlagiannis, Dimitris; Slater, Lee; Beaver, Carol; Rossbach, S.; Revil, A.; Atekwana, E.A.; Bekins, Barbara A.

2017-01-01

We present evidence of a geobattery associated with microbial degradation of a mature crude oil spill. Self-potential measurements were collected using a vertical array of nonpolarizing electrodes, starting at the land surface and passing through the smear zone where seasonal water table fluctuations have resulted in the coating of hydrocarbons on the aquifer solids. These passive electrical potential measurements exhibit a dipolar pattern associated with a current source. The anodic and cathodic reactions of this natural battery occur below and above the smear zone, respectively. The smear zone is characterized by high magnetic susceptibility values associated with the precipitation of semiconductive magnetic iron phase minerals as a by-product of biodegradation, facilitating electron transfer between the anode and the cathode. This geobattery response appears to have a transient nature, changing on a monthly scale, probably resulting from chemical and physical changes in subsurface conditions such as water table fluctuations.

Electrodeposition of Amorphous Molybdenum Chalcogenides from Ionic Liquids and Their Activity for the Hydrogen Evolution Reaction.

PubMed

Redman, Daniel W; Rose, Michael J; Stevenson, Keith J

2017-09-19

This work reports on the general electrodeposition mechanism of tetrachalcogenmetallates from 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Both tetrathio- and tetraselenomolybdate underwent anodic electrodeposition and cathodic corrosion reactions as determined by UV-vis spectroelectrochemistry. Electrodeposition was carried out by cycling the potential between the anodic and cathodic regimes. This resulted in a film of densely packed nanoparticles of amorphous MoS x or MoSe x as determined by SEM, Raman, and XPS. The films were shown to have high activity for the hydrogen evolution reaction. The onset potential (J = 1 mA/cm 2 ) of the MoS x film was E = -0.208 V vs RHE, and that of MoSe x was E = -0.230 V vs RHE. The Tafel slope of MoS x was 42 mV/decade, and that of MoSe x was 59 mV/decade.

Nanoporous TiNb2O7/C Composite Microspheres with Three-Dimensional Conductive Network for Long-Cycle-Life and High-Rate-Capability Anode Materials for Lithium-Ion Batteries.

PubMed

Zhu, Guozhen; Li, Qing; Zhao, Yunhao; Che, Renchao

2017-11-29

On the basis of the advantages of ideal cycling stability, high discharge voltage (1.65 V), and excellent reversibility, more and more attention has been focused on TiNb 2 O 7 (marked as TNO) as an anode material candidate for lithium-ion batteries. However, the poor electronic conductivity and low ionic diffusion rate intrinsically restrict its practical use. Herein, we first synthesize the TNO/C composite microspheres with three-dimensionally (marked as 3D) electro-conductive carbon network and abundant nanoporous structure by a simple spray-drying method. The microspheres are constructed by irregularly primary cubic nanoparticle units with size of 100-200 nm. The nanopores throughout the microspheres range from 1 to 50 nm. As an anode material, the prepared TNO/C composite microspheres demonstrate a prominent charge/discharge capacity of 323.2/326 mA h g -1 after 300 cycles at 0.25 C (1 C = 388 mA g -1 ) and 259.9/262.5 mA h g -1 after 1000 long cycles at a high current density of 5 C, revealing the ideal reversible capacity and long cycling life. Meanwhile, the TNO/C composite microspheres present ideal rate performance, showing the discharge capacity of 120 mA h g -1 at 30 C after 10 cycles. The super electrochemical performance could be attributed to the 3D electro-conductive carbon network and nanoporous structure. The nanopores facilitate the permeation of electrolyte into the intercontacting regions of the anode materials. Carbon layers disperse uniformly throughout the 3D microspheres, effectively improving the electrical conductivity of the electrode. Hence, the prepared TNO/C composite microspheres have great potential to be used as an anode material for lithium-ion batteries.

Rydberg gas theory of a glow discharge plasma: I. Application to the electrical behaviour of a fast flowing glow discharge plasma.

PubMed

Mason, Rod S; Mitchell, David J; Dickinson, Paul M

2010-04-21

Current-voltage (I-V) curves have been measured, independent of the main discharge, for electricity passing through the steady state fast flowing 'afterglow' plasma of a low power dc glow discharge in Ar. Voltage profiles along the axial line of conduction have been mapped using fixed probes and potentiometry, and the mass spectra of cations emerging from the downstream sampling Cone, also acting as a probe anode, were recorded simultaneously. Floating double probe experiments were also carried out. The electrical behavior is consistent with the well established I-V characteristics of such discharges, but does not comply with classical plasma theory predictions. The plasma decays along the line of conduction, with a lifetime of approximately 1 ms, despite carrying a steady state current, and its potential is below that of the large surface area anode voltage; a situation which cannot exist in the presence of a conventional free ion-electron plasma, unless the electron temperature is super cold. Currents, large by comparison with the main discharge current, and independent of it, are induced to flow through the downstream plasma, from the Anode (acting as a cathode) to the anodic ion exit Cone, induced by electron impact ionisation at the anode, but without necessarily increasing the plasma density. It appears to be conducted by direct charge transfer between a part of the anode surface (acting as cathode to the auxiliary circuit) and the plasma, without secondary electron emission or heating, which suggests the direct involvement of Rydberg atom intermediates. The reaction energy defect (= the work function of the electrode surface) fits with the plasma potential threshold observed for the cathodic reaction to occur. A true free ion-electron plasma is readily detected by the observation of cations at the anode surface, when induced at the downstream anode, at high bias voltages, by the electron impact ionisation in the boundary region. In contrast to the classical model, the complex electrical (and mass spectrometric) behaviour fits qualitatively, but can be understood well, with the Rydberg gas model described in papers II and III (R. S. Mason, and R. S. Mason and P. Douglas, PCCP, 2010, DOI: 10.1039/b918081h and b918083d) over a wide range of probe bias voltages. The full cycle of behavior is then described for the development of a true secondary discharge within the downstream plasma.

Electrical stimulation modulates injury potentials in rats after spinal cord injury

PubMed Central

Zhang, Guanghao; Huo, Xiaolin; Wang, Aihua; Wu, Changzhe; Zhang, Cheng; Bai, Jinzhu

2013-01-01

An injury potential is the direct current potential difference between the site of spinal cord injury and the healthy nerves. Its initial amplitude is a significant indicator of the severity of spinal cord injury, and many cations, such as sodium and calcium, account for the major portion of injury potentials. This injury potential, as well as injury current, can be modulated by direct current field stimulation; however, the appropriate parameters of the electrical field are hard to define. In this paper, injury potential is used as a parameter to adjust the intensity of electrical stimulation. Injury potential could be modulated to slightly above 0 mV (as the anode-centered group) by placing the anodes at the site of the injured spinal cord and the cathodes at the rostral and caudal sections, or around –70 mV, which is resting membrane potential (as the cathode-centered group) by reversing the polarity of electrodes in the anode-centered group. In addition, rats receiving no electrical stimulation were used as the control group. Results showed that the absolute value of the injury potentials acquired after 30 minutes of electrical stimulation was higher than the control group rats and much lower than the initial absolute value, whether the anodes or the cathodes were placed at the site of injury. This phenomenon illustrates that by changing the polarity of the electrical field, electrical stimulation can effectively modulate the injury potentials in rats after spinal cord injury. This is also beneficial for the spontaneous repair of the cell membrane and the reduction of cation influx. PMID:25206563

Transpassive Dissolution of Copper and Rapid Formation of Brilliant Colored Copper Oxide Films

NASA Astrophysics Data System (ADS)

Fredj, Narjes; Burleigh, T. David; New Mexico Tech Team

2014-03-01

This investigation describes an electrochemical technique for growing adhesive copper oxide films on copper with attractive colors ranging from gold-brown to pearl with intermediate colors from red violet to gold green. The technique consists of anodically dissolving copper at transpassive potentials in hot sodium hydroxide, and then depositing brilliant color films of Cu2O onto the surface of copper after the anodic potential has been turned off. The color of the copper oxide film depends on the temperature, the anodic potential, the time t1 of polarization, and the time t2, which is the time of immersion after potential has been turned off. The brilliant colored films were characterized using glancing angle x-ray diffraction, and the film was found to be primarily Cu2O. Cyclic voltammetry, chronopotentiometry, scanning electron microscopy, and x-ray photoelectron spectroscopy were also used to characterize these films.

Growth behavior of anodic porous alumina formed in malic acid solution

NASA Astrophysics Data System (ADS)

Kikuchi, Tatsuya; Yamamoto, Tsuyoshi; Suzuki, Ryosuke O.

2013-11-01

The growth behavior of anodic porous alumina formed on aluminum by anodizing in malic acid solutions was investigated. High-purity aluminum plates were electropolished in CH3COOH/HClO4 solutions and then anodized in 0.5 M malic acid solutions at 293 K and constant cell voltages of 200-350 V. The anodic porous alumina grew on the aluminum substrate at voltages of 200-250 V, and a black, burned oxide film was formed at higher voltages. The nanopores of the anodic oxide were only formed at grain boundaries of the aluminum substrate during the initial stage of anodizing, and then the growth region extended to the entire aluminum surface as the anodizing time increased. The anodic porous alumina with several defects was formed by anodizing in malic acid solution at 250 V, and oxide cells were approximately 300-800 nm in diameter.

Ordered and Ultra-High Aspect Ratio Nanocapillary Arrays as a Model System

DTIC Science & Technology

2015-10-13

formation and deep pore growth of anodized aluminum oxide ( AAO )-based nanocapillary arrays as the basis for high density, safe and high rate gas... anodized aluminum oxide , nanocapillary arrays 16. SECURITY CLASSIFICATION OF: Unclassified 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME... Aluminum Page 7 Copyright © 2015 Mainstream Engineering Corporation CPE Mitigation Schemes  Control thermal and flow profile -> even anodization

Design, Fabrication, Characterization and Modeling of Integrated Functional Materials

DTIC Science & Technology

2014-10-01

oxide ( AAO ) membranes were fabricated from high purity aluminum foil (99.999%) by electrochemical route using a controlled two-step anodization ...deposition of Fe and Co in anodized alumina templates. We used commercially prepared AAO templates which had pore diameters of 100 nm (300 nm), an...a thermal decomposition method. The final product was suspended in high-purity hexane to create a ferrofluid. Custom highly ordered anodic aluminum

Processing Ti-25Ta-5Zr Bioalloy via Anodic Oxidation Procedure at High Voltage

NASA Astrophysics Data System (ADS)

Ionita, Daniela; Grecu, Mihaela; Dilea, Mirela; Cojocaru, Vasile Danut; Demetrescu, Ioana

2011-12-01

The current paper reports the processing of Ti-25Ta-5Zr bioalloy via anodic oxidation in NH4BF4 solution under constant potentiostatic conditions at high voltage to obtain more suitable properties for biomedical application. The maximum efficiency of the procedure is reached at highest applied voltage, when the corrosion rate in Hank's solution is decreased approxomately six times. The topography of the anodic layer has been studied using atomic force microscopy (AFM), and the results indicated that the anodic oxidation process increases the surface roughness. The AFM images indicated a different porosity for the anodized surfaces as well. After anodizing, the hydrophilic character of Ti-25Ta-5Zr samples has increased. A good correlation between corrosion rate obtained from potentiodynamic curves and corrosion rate from ions release analysis was obtained.

Preparation of Ti/IrO2 Anode with Low Iridium Content by Thermal Decomposition Process: Electrochemical removal of organic pollutants in water

NASA Astrophysics Data System (ADS)

Yaqub, Asim; Isa, Mohamed Hasnain; Ajab, Huma; Kutty, S. R. M.; Ezechi, Ezerie H.; Farooq, Robina

2018-04-01

In this study IrO2 (Iridium oxide) was coated onto a titanium plate anode from a dilute (50 mg/10 ml) IrCl3×H2O salt solution. Coating was done at high temperature (550∘C) using thermal decomposition. Surface morphology and characteristics of coated surface of Ti/IrO2 anode were examined by FESEM and XRD. The coated anode was applied for electrochemical removal of organic pollutants from synthetic water samples in 100 mL compartment of batch electrochemical cell. About 50% COD removal was obtained at anode prepared with low Ir content solution while 72% COD removal was obtained with anode prepared at high Ir content. Maximum COD removal was obtained at 10 mA/cm2 current density.

Applications of Tunable TiO2 Nanotubes as Nanotemplate and Photovoltaic Device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Dongdong; Chang, Pai-Chun; Chien, Chung-Jen

2010-10-26

Highly ordered anodic titanium oxide (ATO) TiO{sub 2} nanotube film has been synthesized via a typical two-step anodization method. Following a reductive doping approach, metallic materials (copper and nickel) can be efficiently electrodeposited into the nanotubes. This versatile process yields reproducible tubular structures in ATO membranes, because of the conductive nature of crystallized TiO{sub 2}, yielding promising potential for nanotemplate applications. In this paper, we present a dye-sensitized solar cell constructed by employing such ATO films. It is observed that the reductive doping treatment can also enhance the solar cell’s short current density and fill factor, resulting in an improvedmore » energy conversion efficiency.« less

Time and space resolved spectroscopic investigation during anode plume formation in a high-current vacuum arc

NASA Astrophysics Data System (ADS)

Khakpour, A.; Methling, R.; Uhrlandt, D.; Franke, St.; Gortschakow, S.; Popov, S.; Batrakov, A.; Weltmann, K. D.

2017-05-01

This paper presents time and space resolved results of spectroscopic measurements during the formation of an anode plume in the late current pulse phase of a high-current vacuum arc. The formation of the anode plume is investigated systematically based on the occurrence of high-current anode spots, depending on gap distance and current for AC 100 Hz and CuCr7525 butt contacts with a diameter of 10 mm. The anode plume is observed after the extinction of anode spot type 2 in which both the anode and cathode are active. It is concluded from the spatial profiles of the atomic and ionic radiation, parallel and perpendicular to anode surface, that the inner part of the plume is dominated by Cu I radiation, whereas a halo of light emitted by Cu II covers the plume. The radiation intensity of Cu III lines is quite low across the whole anode plume. Upper level excited state densities corresponding to Cu I lines at 510.55, 515.32, 521.82, 578.21 nm are determined. The temporal evolution of the resulting excitation temperature in the centre of the plume varies from 8500 K to 6000 K at 500 µs to 100 µs before current zero, respectively. The density calculated for Cu I at position in the plume is in the range of 1-5  ×  1019 m-3.

On the application of ionic liquids for rechargeable Li batteries: High voltage systems

NASA Astrophysics Data System (ADS)

Borgel, V.; Markevich, E.; Aurbach, D.; Semrau, G.; Schmidt, M.

We examined the possible use of the following ionic liquids all having the same anion, bis(trifluoromethylsulfonyl)imide (TFSI) and the following cations: 1-hexyl-3-methyl imidazolium (HMITFSI), 1-(2-methoxyethyl)-3-methyl imidazolium (MEMITFSI), N-ethyl- NN-dimethyl-2-methoxyethylammonium (EDMETFSI), 1-methyl-1-butylpyrrolidinium (BMPTFSI), and 1-methyl-1-propylpiperidinium (MPPpTFSI) solutions with LiTFSI (the source of Li ions), as electrolyte systems for 5 V, rechargeable battery systems with Li metal anodes and LiMn 1.5Ni 0.5O 4 spinel cathodes. Standard solution based on alkyl carbonates and LiPF 6 was examined in this respect for comparison. The ionic liquids (ILs) based on derivatives of piperidinium and pyrrolidinium demonstrate a very wide electrochemical window (up to 5.5 V) and they can be compatible with lithium metal anodes. At low potentials in the presence of Li ions in solutions (or on Li metal surfaces), TFSI anions are reduced to insoluble Li compounds which passivate Li, noble metal and graphite electrodes in the Li salt/IL solutions. The mechanism, kinetics and effectiveness of electrodes' passivation in these systems depend on the nature of both IL and electrode used. It was possible to demonstrate reversible behavior of Li/LiMn 1.5Ni 0.5O 4 cells (4.8 V) with solutions based on BMPTFSI and MPPpTFSI. Possible parasitic anodic reactions upon charging at the high potentials are much lower in the ILs than in standard solutions.

Nanostructured sapphire optical fiber for sensing in harsh environments

NASA Astrophysics Data System (ADS)

Chen, Hui; Liu, Kai; Ma, Yiwei; Tian, Fei; Du, Henry

2017-05-01

We describe an innovative and scalable strategy of transforming a commercial unclad sapphire optical fiber to an allalumina nanostructured sapphire optical fiber (NSOF) that overcomes decades-long challenges faced in the field of sapphire fiber optics. The strategy entails fiber coating with metal Al followed by subsequent anodization to form anodized alumina oxide (AAO) cladding of highly organized pore channel structure. We show that Ag nanoparticles entrapped in AAO show excellent structural and morphological stability and less susceptibility to oxidation for potential high-temperature surface-enhanced Raman Scattering (SERS). We reveal, with aid of numerical simulations, that the AAO cladding greatly increases the evanescent-field overlap both in power and extent and that lower porosity of AAO results in higher evanescent-field overlap. This work has opened the door to new sapphire fiber-based sensor design and sensor architecture.

A Nonaqueous Potassium-Based Battery-Supercapacitor Hybrid Device.

PubMed

Fan, Ling; Lin, Kairui; Wang, Jue; Ma, Ruifang; Lu, Bingan

2018-05-01

A low cost nonaqueous potassium-based battery-supercapacitor hybrid device (BSH) is successfully established for the first time with soft carbon as the anode, commercialized activated carbon as the cathode, and potassium bis(fluoro-slufonyl)imide in dimethyl ether as the electrolyte. This BSH reconciles the advantages of potassium ion batteries and supercapacitors, achieving a high energy density of 120 W h kg -1 , a high power density of 599 W kg -1 , a long cycle life of 1500 cycles, and an ultrafast charge/slow discharge performance (energy density and power density are calculated based on the total mass of active materials in the anode and cathode). This work demonstrates a great potential of applying the nonaqueous BSH for low cost electric energy storage systems. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of discharge parameters on the micro-hollow cathode sustained glow discharge

NASA Astrophysics Data System (ADS)

Shoujie, HE; Peng, WANG; Jing, HA; Baoming, ZHANG; Zhao, ZHANG; Qing, LI

2018-05-01

The effects of parameters such as pressure, first anode radius, and the cavity diameter on the micro-hollow cathode sustained glow discharge are investigated by using a two-dimensional self-consistent fluid model in pure argon. The results indicate that the three parameters influence the discharge in the regions inside and outside of the cavity. Under a fixed voltage on each electrode, a larger volume of high density plasma can be produced in the region between the first and the second anodes by selecting the appropriate pressure, the higher first anode, and the appropriate cavity diameter. As the pressure increases, the electron density inside the hollow cathode, the high density plasma volume between the first anode and second anodes, and the radial electric field in the cathode cavity initially increase and subsequently decrease. As the cavity diameter increases, the high-density plasma volume between the first and second anodes initially increases and subsequently decreases; whereas the electron density inside the hollow cathode decreases. As the first anode radius increases, the electron density increases both inside and outside of the cavity. Moreover, the increase of the electron density is more obvious in the microcathode sustained region than in the micro cavity region. The results reveal that the discharge inside the cavity interacts with that outside the cavity. The strong hollow cathode effect and the high-density plasma inside the cavity favor the formation of a sustained discharge between the first anode and the second anodes. Results also show that the radial boundary conditions exert a considerably weaker influence on the discharge except for a little change in the region close to the radial boundary.

Automotive assessment of carbon-silicon composite anodes and methods of fabrication

NASA Astrophysics Data System (ADS)

Karulkar, Mohan; Blaser, Rachel; Kudla, Bob

2015-01-01

To assess the potential of carbon silicon composite anodes for automotive applications, C-Si anodes were fabricated and certain improvements employed. The use of a PVDF buffer layer is demonstrated for the first time with a C-Si composite material. The buffer layer increases adhesion by 89%, and increases capacity by 50-80%. Also, a limited capacity range is employed to improve cycle life by up to 200%, and enable currents as high as 2 mA cm-1. The combined use of a buffer layer and limited capacity range has not been reported before. A model is also presented for comparing C-Si performance with real-world automotive targets from USABC, including energy density, power density, specific energy, and specific power. The analysis reveals a capacity penalty that arises from pairing C-Si with a traditional cathode (NCA), and which prevents the cell from meeting all targets. Scenarios are presented in which a higher-capacity cathode (250 mAh g-1) allows all targets to be hypothetically met.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Electrochemical properties of SnO2 nanorods as anode materials in lithium-ion battery

NASA Astrophysics Data System (ADS)

Shi, Song-Lin; Liu, Yong-Gang; Zhang, Jing-Yuan; Wang, Tai-Hong

2009-10-01

Well-dispersed SnO2 nanorods with diameter of 4-15 nm and length of 100-200 nm are synthesised through a hydrothermal route and their potential as anode materials in lithium-ion batteries is investigated. The observed initial discharge capacity is as high as 1778 mA·h/g, much higher than the theoretical value of the bulk SnO2 (1494 mA·h/g). During the following 15 cycles, the reversible capacity decreases from 929 to 576 mA·h/g with a fading rate of 3.5% per cycle. The fading mechanism is discussed. Serious capacity fading can be avoided by reducing the cycling voltages from 0.05-3.0 to 0.4-1.2 V. At the end, SnO2 nanorods with much smaller size are synthesized and their performance as anode materials is studied. The size effect on the electrochemical properties is briefly discussed.

Porous Fe2O3 Microspheres as Anode for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Noerochim, L.; Indra, M. A. T.; Purwaningsih, H.; Subhan, A.

2018-05-01

In this work, Fe2O3 was successfully synthesized by the hydrothermal process at low temperature. FeCl3.6H2O as precursor and variation of lysine as hydrolyzing agent were used to preparing Fe2O3. SEM images show that the morphology of Fe2O3 is porous microsphere with sizes in the range of (1 to 5) µm in diameter. The as-prepared Fe2O3 with the 2 M of lysine exhibits excellent cycling performance when used as the anode for lithium ion batteries, obtaining reversible discharge capacity of 172.33 mA·h·g‑1 at 0.5 C after 50 cycles. It is attributed to the unique structure of porous microspheres providing a large surface area which maintains good electronic contact between particles during charge-discharge process. This result demonstrates that Fe2O3 porous microsphere has a high potential as anode material for application of lithium-ion battery.

Pyrite (FeS2) nanocrystals as inexpensive high-performance lithium-ion cathode and sodium-ion anode materials

NASA Astrophysics Data System (ADS)

Walter, Marc; Zünd, Tanja; Kovalenko, Maksym V.

2015-05-01

In light of the impeding depletion of fossil fuels and necessity to lower carbon dioxide emissions, economically viable high-performance batteries are urgently needed for numerous applications ranging from electric cars to stationary large-scale electricity storage. Due to its low raw material cost, non-toxicity and potentially high charge-storage capacity pyrite (FeS2) is a highly promising material for such next-generation batteries. In this work we present the electrochemical performance of FeS2 nanocrystals (NCs) as lithium-ion and sodium-ion storage materials. First, we show that nanoscopic FeS2 is a promising lithium-ion cathode material, delivering a capacity of 715 mA h g-1 and average energy density of 1237 Wh kg-1 for 100 cycles, twice higher than for commonly used LiCoO2 cathodes. Then we demonstrate, for the first time, that FeS2 NCs can serve as highly reversible sodium-ion anode material with long cycling life. As sodium-ion anode material, FeS2 NCs provide capacities above 500 mA h g-1 for 400 cycles at a current rate of 1000 mA g-1. In all our tests and control experiments, the performance of chemically synthesized nanoscale FeS2 clearly surpasses bulk FeS2 as well as large number of other nanostructured metal sulfides.In light of the impeding depletion of fossil fuels and necessity to lower carbon dioxide emissions, economically viable high-performance batteries are urgently needed for numerous applications ranging from electric cars to stationary large-scale electricity storage. Due to its low raw material cost, non-toxicity and potentially high charge-storage capacity pyrite (FeS2) is a highly promising material for such next-generation batteries. In this work we present the electrochemical performance of FeS2 nanocrystals (NCs) as lithium-ion and sodium-ion storage materials. First, we show that nanoscopic FeS2 is a promising lithium-ion cathode material, delivering a capacity of 715 mA h g-1 and average energy density of 1237 Wh kg-1 for 100 cycles, twice higher than for commonly used LiCoO2 cathodes. Then we demonstrate, for the first time, that FeS2 NCs can serve as highly reversible sodium-ion anode material with long cycling life. As sodium-ion anode material, FeS2 NCs provide capacities above 500 mA h g-1 for 400 cycles at a current rate of 1000 mA g-1. In all our tests and control experiments, the performance of chemically synthesized nanoscale FeS2 clearly surpasses bulk FeS2 as well as large number of other nanostructured metal sulfides. Electronic supplementary information (ESI) available: Materials and methods, additional structural and electrochemical characterization. See DOI: 10.1039/c5nr00398a

Controlled synthesis of MnOOH multilayer nanowires as anode materials for lithium-ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Yue; Yue, Kaiqiang; Wang, Yuanxin

MnOOH multilayer nanowires have been successfully synthesized by a hydrothermal method. It is found that the uniform multilayer structure of nanowires ran through the entire nanowire, which is formed via a layer by layer. The electrochemical properties of MnOOH multilayer nanowires as an anode material for Li-ion batteries (LIB) were investigated, and excellent capacity retention, superior cycling performance, and high rate capability were achieved. Specifically, the reversible capacity of MnOOH multilayer nanowires is 521 mAh/g after 500 cycles at 0.1 C, with excellent electrochemical stability. The multilayer nanowire electrodes exhibit short electron path lengths, high internal dislocation densities and largemore » surface to volume ratio, resulting in increased specific capacity, cycling stability and rate performance in the energy storage devices, which serves as an indication of their potential application in LIBs. - Highlights: •MnOOH multilayer nanowires were synthesized by a hydrothermal method. •The uniform multilayer structure of nanowires was formed via layer by layer. •The reversible capacity of product shows 521 mAh/g after 500 cycles at 0.1 C. •MnOOH multilayer nanowires showed higher property as anode material in LIB.« less

Applications of Carbon Nanotubes for Lithium Ion Battery Anodes

PubMed Central

Xiong, Zhili; Yun, Young Soo; Jin, Hyoung-Joon

2013-01-01

Carbon nanotubes (CNTs) have displayed great potential as anode materials for lithium ion batteries (LIBs) due to their unique structural, mechanical, and electrical properties. The measured reversible lithium ion capacities of CNT-based anodes are considerably improved compared to the conventional graphite-based anodes. Additionally, the opened structure and enriched chirality of CNTs can help to improve the capacity and electrical transport in CNT-based LIBs. Therefore, the modification of CNTs and design of CNT structure provide strategies for improving the performance of CNT-based anodes. CNTs could also be assembled into free-standing electrodes without any binder or current collector, which will lead to increased specific energy density for the overall battery design. In this review, we discuss the mechanism of lithium ion intercalation and diffusion in CNTs, and the influence of different structures and morphologies on their performance as anode materials for LIBs. PMID:28809361

The capacity fading mechanism and improvement of cycling stability in MoS2-based anode materials for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Shu, Haibo; Li, Feng; Hu, Chenli; Liang, Pei; Cao, Dan; Chen, Xiaoshuang

2016-01-01

Two-dimensional (2D) layered MoS2 nanosheets possess great potential as anode materials for lithium ion batteries (LIBs), but they still suffer from poor cycling performance. Improving the cycling stability of electrode materials depends on a deep understanding of their dynamic structural evolution and reaction kinetics in the lithiation process. Herein, thermodynamic phase diagrams and the lithiation dynamics of MoS2-based nanostructures with the intercalation of lithium ions are studied by using first-principles calculations and ab initio molecular dynamics simulations. Our results demonstrate that the continuous intercalation of Li ions induces structural destruction of 2H phase MoS2 nanosheets in the discharge process that follows a layer-by-layer dissociation mechanism. Meanwhile, the intercalation of Li ions leads to a structural transition of MoS2 nanosheets from the 2H to the 1T phase due to the ultralow transition barriers (~0.1 eV). We find that the phase transition can slow down the dissociation of MoS2 nanosheets during lithiation. The result can be applied to explain extensive experimental observation of the fast capacity fading of MoS2-based anode materials between the first and the subsequent discharges. To suppress the dissociation of MoS2 nanosheets in the lithiation process, we propose a strategy by constructing a sandwich-like graphene/MoS2/graphene structure that indicates high chemical stability, superior conductivity, and high Li-ion mobility in the charge/discharge process, implying the possibility to induce an improvement in the anode cycling performance. This work opens a new route to rational design layered transition-metal disulfide (TMD) anode materials for LIBs with superior cycling stability and electrochemical performance.Two-dimensional (2D) layered MoS2 nanosheets possess great potential as anode materials for lithium ion batteries (LIBs), but they still suffer from poor cycling performance. Improving the cycling stability of electrode materials depends on a deep understanding of their dynamic structural evolution and reaction kinetics in the lithiation process. Herein, thermodynamic phase diagrams and the lithiation dynamics of MoS2-based nanostructures with the intercalation of lithium ions are studied by using first-principles calculations and ab initio molecular dynamics simulations. Our results demonstrate that the continuous intercalation of Li ions induces structural destruction of 2H phase MoS2 nanosheets in the discharge process that follows a layer-by-layer dissociation mechanism. Meanwhile, the intercalation of Li ions leads to a structural transition of MoS2 nanosheets from the 2H to the 1T phase due to the ultralow transition barriers (~0.1 eV). We find that the phase transition can slow down the dissociation of MoS2 nanosheets during lithiation. The result can be applied to explain extensive experimental observation of the fast capacity fading of MoS2-based anode materials between the first and the subsequent discharges. To suppress the dissociation of MoS2 nanosheets in the lithiation process, we propose a strategy by constructing a sandwich-like graphene/MoS2/graphene structure that indicates high chemical stability, superior conductivity, and high Li-ion mobility in the charge/discharge process, implying the possibility to induce an improvement in the anode cycling performance. This work opens a new route to rational design layered transition-metal disulfide (TMD) anode materials for LIBs with superior cycling stability and electrochemical performance. Electronic supplementary information (ESI) available: Models and energetics of Li adsorption/intercalation onto MoS2 sheets, details of the phase diagram calculations, schematic illustration for the structural evolution of lithiated MoS2 nanosheets, AIMD trajectories for lithiated silicene/MoS2/silicene composites, and movies for recording the AIMD simulation results. See DOI: 10.1039/c5nr07909h

Bacterial nanometric amorphous Fe-based oxide: a potential lithium-ion battery anode material.

PubMed

Hashimoto, Hideki; Kobayashi, Genki; Sakuma, Ryo; Fujii, Tatsuo; Hayashi, Naoaki; Suzuki, Tomoko; Kanno, Ryoji; Takano, Mikio; Takada, Jun

2014-04-23

Amorphous Fe(3+)-based oxide nanoparticles produced by Leptothrix ochracea, aquatic bacteria living worldwide, show a potential as an Fe(3+)/Fe(0) conversion anode material for lithium-ion batteries. The presence of minor components, Si and P, in the original nanoparticles leads to a specific electrode architecture with Fe-based electrochemical centers embedded in a Si, P-based amorphous matrix.

Graphene-Wrapped Anatase TiO2 Nanofibers as High-Rate and Long-Cycle-Life Anode Material for Sodium Ion Batteries

PubMed Central

Yeo, Yeolmae; Jung, Ji-Won; Park, Kyusung; Kim, Il-Doo

2015-01-01

Anatase TiO2 has been suggested as a potential sodium anode material, but the low electrical conductivity of TiO2 often limits the rate capability, resulting in poor electrochemical properties. To address this limitation, we propose graphene-wrapped anatase TiO2 nanofibers (rGO@TiO2 NFs) through an effective wrapping of reduced graphene oxide (rGO) sheets on electrospun TiO2 NFs. To provide strong electrostatic interaction between the graphene oxide (GO) sheets and the TiO2 NFs, poly(allylamine hydrochloride) (PAH) was used to induce a positively charged TiO2 surface by the immobilization of the -NH3+ group and to promote bonding with the negatively charged carboxylic acid (-COO−) and hydroxyl (-O−) groups on the GO. A sodium anode electrode using rGO@TiO2 NFs exhibited a significantly improved initial capacity of 217 mAh g−1, high capacity retention (85% after 200 cycles at 0.2C), and a high average Coulombic efficiency (99.7% from the second cycle to the 200th cycle), even at a 5C rate, compared to those of pristine TiO2 NFs. The improved electrochemical performances stem from highly conductive properties of the reduced GO which is effectively anchored to the TiO2 NFs. PMID:26355340

Polarization controlled kinetics and composition of trivalent chromium coatings on aluminum.

PubMed

Dardona, Sameh; Chen, Lei; Kryzman, Michael; Goberman, Daniel; Jaworowski, Mark

2011-08-15

Combined in situ spectroscopic ellipsometry and electrochemistry have been employed to monitor, in real-time, the formation of trivalent Cr conversion coatings on polished Al substrates at applied sample potentials. It is found that the formation kinetics and chemical composition of the film can be controlled by adjusting the anodic and cathodic reactions. The growth kinetics are accelerated at more positive anodic potentials or more negative cathodic potentials. At more negative potentials, the percentage of chromium in the coating is found to increase, while the zirconium percentage decreases.

Structural micro-porous carbon anode for rechargeable lithium-ion batteries

DOEpatents

Delnick, Frank M.; Even, Jr., William R.; Sylwester, Alan P.; Wang, James C. F.; Zifer, Thomas

1995-01-01

A secondary battery having a rechargeable lithium-containing anode, a cathode and a separator positioned between the cathode and anode with an organic electrolyte solution absorbed therein is provided. The anode comprises three-dimensional microporous carbon structures synthesized from polymeric high internal phase emulsions or materials derived from this emulsion source, i.e., granules, powders, etc.

Investigation of electrochemical phenomena related to corrosion in high temperature aqueous systems

NASA Astrophysics Data System (ADS)

Biswas, Ritwik

1999-11-01

Three separate phenomena, each related to the problem of corrosion of metals, in high temperature aqueous solutions, have been studied. These are: (1) Kinetics of the Hydrogen Oxidation Reaction (HOR), (2) Effect of solutions containing sulfur oxyanions on Stainless Steel 347 and Inconel 600, and (3) Characterization of electrochemical behavior of intermetallic compounds Ni3Nb and Ni3(TiAl). The anodic transfer coefficient and the Tafel constant, for the HOR, on platinized nickel, in 0.1 m NaOH solution, was experimentally measured over the temperature range of 25°C to 300°C. Potentiodynamic polarization experiments, under controlled hydrodynamic flow conditions, in a cell with annular flow geometry, were used for these measurements. The anodic transfer coefficient and the Tafel constant were found to increase with increase in solution temperature. At high anodic potentials (>1V vs. rest potential), passivation of the platinum electrode was observed. Electron tunneling theory was used to determine that this was the result of formation of platinum oxide (PtO) on the surface of the platinum electrode. The relative corrosion properties of Stainless Steel 347 and Inconel 600, exposed to an aqueous electrolyte containing sulfur oxyanions, at temperatures up to 285°C, was studied using electrochemical tests, mathematical modeling and surface analysis. The presence of sulfur oxyanions was found to cause the breakdown of the protective passive film on both the alloy surfaces, and increase their corrosion rates. As a result of exposure to the electrolyte, a porous layer of corrosion product was formed on both alloys. This porous layer was composed principally of Ni3S2 in the case of Inconel 600 and Fe3O4 in the case of Stainless Steel 347. The corrosive effect of sulfur oxyanions was found to be greater on Inconel 600 than Stainless Steel 347. Galvanic coupling experiments were conducted on the intermetallics Ni 3Nb and Ni3(TiAl) and a nickel rich alloy. It was determined that the intermetallics acted as the anodes when coupled with the nickel rich alloy material. At room temperature, both galvanic current and galvanic potential displayed oscillatory behavior as a function of time. These were analyzed using dynamic systems theory. It was determined from such analysis that the galvanic coupling process can be theoretically described by two coupled ordinary differential equations.

Mirror-finished superhydrophobic aluminum surfaces modified by anodic alumina nanofibers and self-assembled monolayers

NASA Astrophysics Data System (ADS)

Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

2018-05-01

We demonstrate mirror-finished superhydrophobic aluminum surfaces fabricated via the formation of anodic alumina nanofibers and subsequent modification with self-assembled monolayers (SAMs). High-density anodic alumina nanofibers were formed on the aluminum surface via anodizing in a pyrophosphoric acid solution. The alumina nanofibers became tangled and bundled by further anodizing at low temperature because of their own weight, and the aluminum surface was completely covered by the long falling nanofibers. The nanofiber-covered aluminum surface exhibited superhydrophilic behavior, with a contact angle measuring less than 10°. As the nanofiber-covered aluminum surface was modified with n-alkylphosphonic acid SAMs, the water contact angle drastically shifted to superhydrophobicity, measuring more than 150°. The contact angle increased with the applied voltage during pyrophosphoric acid anodizing, the anodizing time, and the number of carbon atoms contained in the SAM molecules modified on the alumina nanofibers. By optimizing the anodizing and SAM-modification conditions, superhydrophobic behavior could be achieved with only a brief pyrophosphoric acid anodizing period of 3 min and subsequent simple immersion in SAM solutions. The superhydrophobic aluminum surface exhibited a high reflectance, measuring approximately 99% across most of the visible spectrum, similar to that of an electropolished aluminum surface. Therefore, our mirror-finished superhydrophobic aluminum surface based on anodic alumina nanofibers and SAMs can be used as a reflective mirror in various optical applications such as concentrated solar power systems.

Conductive polymer binder for nano-silicon/graphite composite electrode in lithium-ion batteries towards a practical application

DOE PAGES

Zhao, Hui; Du, Allen; Ling, Min; ...

2016-05-10

The state-of-the-art graphite anode containing a small portion of silicon represents a promising way of applying high-capacity alloy anode in the next generation high energy density lithium-ion batteries. The conductive polymeric binders developed for Si anodes proved to be an effective binder for this graphite/nanoSi composite electrode. Without any acetylene black conductive additives in the electrode, a high areal capacity of above 2.5 mAh/cm 2 is achieved during long-term cycling over 100 cycles. Finally, this conductive polymer-enabled graphite/nanoSi composite electrode exhibits high specific capacity and high 1 st cycle efficiency, which is a significant progress toward commercial application of Simore » anodes.« less

Electrolyte additive enabled fast charging and stable cycling lithium metal batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jianming; Engelhard, Mark H.; Mei, Donghai

2017-03-01

Lithium (Li) metal battery is an attractive energy storage system owing to the ultrahigh specific capacity and the lowest redox potential of Li metal anode. However, safety concern associated with dendrite growth and limited cycle life especially at a high charge current density are two critical challenges hindering the practical applications of rechargeable Li metal batteries. Here, we report for the first time that an optimal amount (0.05 M) of LiPF6 as additive in the LiTFSI-LiBOB dual-salt/carbonate-based electrolyte can significantly enhance the charging capability and the long-term cycle life of Li metal batteries with a moderately high cathode loading ofmore » 1.75 mAh cm-2. Unprecedented stable-cycling (97.1% capacity retention after 500 cycles) along with very limited increase in electrode over-potential has been achieved at a high current density of 1.75 mA cm-2. This unparalleled fast charging and stable cycling performance is contributed from both the stabilized Al cathode current collector, and, more importantly, the robust and conductive SEI layer formed on Li metal anode in the presence of the LiPF6 additive.« less

Theoretical investigation of the use of nanocages with an adsorbed halogen atom as anode materials in metal-ion batteries.

PubMed

Razavi, Razieh; Abrishamifar, Seyyed Milad; Rajaei, Gholamreza Ebrahimzadeh; Kahkha, Mohammad Reza Rezaei; Najafi, Meysam

2018-02-21

The applicability of C 44 , B 22 N 22 , Ge 44 , and Al 22 P 22 nanocages, as well as variants of those nanocages with an adsorbed halogen atom, as high-performance anode materials in Li-ion, Na-ion, and K-ion batteries was investigated theoretically via density functional theory. The results obtained indicate that, among the nanocages with no adsorbed halogen atom, Al 22 P 22 would be the best candidate for a novel anode material for use in metal-ion batteries. Calculations also suggest that K-ion batteries which utilize these nanocages as anode materials would give better performance and would yield higher cell voltages than the corresponding Li-ion and Na-ion batteries with nanocage-based anodes. Also, the results for the nanocages with an adsorbed halogen atom imply that employing them as anode materials would lead to higher cell voltages and better metal-ion battery performance than if the nanocages with no adsorbed halogen atom were to be used as anode materials instead. Results further implied that nanocages with an adsorbed F atom would give higher cell voltages and better battery performance than nanocages with an adsorbed Cl or Br atom. We were ultimately able to conclude that a K-ion battery that utilized Al 21 P 22 with an adsorbed F atom as its anode material would afford the best metal-ion battery performance; we therefore propose this as a novel highly efficient metal-ion battery. Graphical abstract The results of a theoretical investigation indicated that Al 22 P 22 is a better candidate for a high-performance anode material in metal-ion batteries than Ge 44 is. Calculations also showed that K-ion batteries with nanocage-based anodes would produce higher cell voltages and perform better than the equivalent Li-ion and Na-ion batteries with nanocage-based anodes, and that anodes based on nanocages with an adsorbed F atom would perform better than anodes based on nanocages with an adsorbed Cl or Br atom.

A novel bio-electrochemical system with sand/activated carbon separator, Al anode and bio-anode integrated micro-electrolysis/electro-flocculation cost effectively treated high load wastewater with energy recovery.

PubMed

Gao, Changfei; Liu, Lifen; Yang, Fenglin

2018-02-01

A novel bio-electrochemical system (BES) was developed by integrating micro-electrolysis/electro-flocculation from attaching a sacrificing Al anode to the bio-anode, it effectively treated high load wastewater with energy recovery (maximum power density of 365.1 mW/m 3 and a maximum cell voltage of 0.97 V), and achieving high removals of COD (>99.4%), NH 4 + -N (>98.7%) and TP (>98.6%). The anode chamber contains microbes, activated carbon (AC)/graphite granules and Al anode. It was separated from the cathode chamber containing bifunctional catalytic and filtration membrane cathode (loaded with Fe/Mn/C/F/O catalyst) by a multi-medium chamber (MMC) filled with manganese sand and activated carbon granules, which replaced expensive PEM and reduced cost. An air contact oxidation bed for aeration was still adopted before liquid entering the cathode chamber. micro-electrolysis/electro-flocculation helps in achieving high removal efficiencies and contributes to membrane fouling migration. The increase of activated carbon in the separator MMC increased power generation and reduced system electric resistance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrochemical investigation of stainless steel corrosion in a proton exchange membrane electrolyzer cell

DOE PAGES

Mo, Jingke; Steen, Stuart M.; Zhang, Feng-Yuan; ...

2015-08-05

The lack of a fundamental understanding of the corrosion mechanisms in the electrochemical environments of proton exchange membrane (PEM) electrolyzer and/or fuel cells (ECs/FCs) has seriously hindered the improvement of performance and efficiency of PEM ECs/FCs. In this study, a stainless steel mesh was purposely used as an anode gas diffusion layer that was intentionally operated with high positive potentials under harsh oxidative environments in a PEMEC to study the corrosion mechanism of metal migration. A significant amount of iron and nickel cations were determined to transport through the anode catalyst layer, the PEM and the cathode catalyst layer duringmore » the PEMEC operation. The formation/deposition of iron oxide and nickel oxide on the carbon paper gas diffusion layer at the cathode side is first revealed by both scanning electron microscope and X-ray diffraction. The results indicate the corrosion elements of iron and nickel are transported from anode to cathode through the catalyst-coated membrane, and deposited on carbon fibers as oxides. This phenomenon could also open a new corrosion-based processing approach to potentially fabricate multifunctional oxide structures on carbon fiber devices. This study has demonstrated a new accelerated test method for investigating the corrosion and durability of metallic materials as well.« less

Electrochemical investigation of stainless steel corrosion in a proton exchange membrane electrolyzer cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mo, Jingke; Steen, Stuart M.; Zhang, Feng-Yuan

The lack of a fundamental understanding of the corrosion mechanisms in the electrochemical environments of proton exchange membrane (PEM) electrolyzer and/or fuel cells (ECs/FCs) has seriously hindered the improvement of performance and efficiency of PEM ECs/FCs. In this study, a stainless steel mesh was purposely used as an anode gas diffusion layer that was intentionally operated with high positive potentials under harsh oxidative environments in a PEMEC to study the corrosion mechanism of metal migration. A significant amount of iron and nickel cations were determined to transport through the anode catalyst layer, the PEM and the cathode catalyst layer duringmore » the PEMEC operation. The formation/deposition of iron oxide and nickel oxide on the carbon paper gas diffusion layer at the cathode side is first revealed by both scanning electron microscope and X-ray diffraction. The results indicate the corrosion elements of iron and nickel are transported from anode to cathode through the catalyst-coated membrane, and deposited on carbon fibers as oxides. This phenomenon could also open a new corrosion-based processing approach to potentially fabricate multifunctional oxide structures on carbon fiber devices. This study has demonstrated a new accelerated test method for investigating the corrosion and durability of metallic materials as well.« less

Trends in reactivity of electrodeposited 3d transition metals on gold revealed by operando soft x-ray absorption spectroscopy during water splitting

NASA Astrophysics Data System (ADS)

Velasco-Vélez, J. J.; Jones, Travis E.; Pfeifer, Verena; Dong, Chung-Li; Chen, Yu-Xun; Chen, Chieh-Ming; Chen, Hsin-Yu; Lu, Ying-Rui; Chen, Jin-Ming; Schlögl, R.; Knop-Gericke, A.; Chuang, C.-H.

2017-01-01

We activated gold electrodes for their use as electrocatalyst for water splitting by electrodepositing Cu, Ni and Co. A combination of operando x-ray absorption spectroscopy and potentiometric control under aqueous conditions revealed the trends in reactivity yielded by these electrodes, which are directly associated with the cross- and overpotentials as well as the occupancy of the 3d orbitals. It was found that under anodic polarization the materials electrodeposited on gold suffer from a lack of stability, while under cathodic polarization they exhibit stable behavior. The observed activity is strongly related to the lack of stability shown by these composites under anodic polarization revealing a dynamic process ruled by corrosion. By operando x-ray absorption, we established that the overall enhancement of the activity for the oxygen evolution reaction is directly attributable to the cross-potential and corrosion process of the electrodeposited materials. It is associated with the high potential deposition, which is the origin of the incipient oxidation-corrosion resistance of the lattice. We conclude that the observed trends in the total current are directly associated with the loss of oxygen in the metal-oxide lattice and the subsequent dissolution of metallic ions in the electrolyte under anodic polarization.

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells

PubMed Central

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-01-01

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm−1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm−2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm−2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode. PMID:26648509

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-12-01

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm-1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm-2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm-2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells.

PubMed

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-12-09

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm(-1) in 5% H2 and peak power densities of 1.72 and 0.54 W cm(-2) using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm(-2). To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

Carbon-Coated, Diatomite-Derived Nanosilicon as a High Rate Capable Li-ion Battery Anode

PubMed Central

Campbell, Brennan; Ionescu, Robert; Tolchin, Maxwell; Ahmed, Kazi; Favors, Zachary; Bozhilov, Krassimir N.; Ozkan, Cengiz S.; Ozkan, Mihrimah

2016-01-01

Silicon is produced in a variety of ways as an ultra-high capacity lithium-ion battery (LIB) anode material. The traditional carbothermic reduction process required is expensive and energy-intensive; in this work, we use an efficient magnesiothermic reduction to convert the silica-based frustules within diatomaceous earth (diatomite, DE) to nanosilicon (nanoSi) for use as LIB anodes. Polyacrylic acid (PAA) was used as a binder for the DE-based nanoSi anodes for the first time, being attributed for the high silicon utilization under high current densities (up to 4C). The resulting nanoSi exhibited a high BET specific surface area of 162.6 cm2 g−1, compared to a value of 7.3 cm2 g−1 for the original DE. DE contains SiO2 architectures that make ideal bio-derived templates for nanoscaled silicon. The DE-based nanoSi anodes exhibit good cyclability, with a specific discharge capacity of 1102.1 mAh g−1 after 50 cycles at a C-rate of C/5 (0.7 A gSi−1) and high areal loading (2 mg cm−2). This work also demonstrates the fist rate capability testing for a DE-based Si anode; C-rates of C/30 - 4C were tested. At 4C (14.3 A gSi−1), the anode maintained a specific capacity of 654.3 mAh g−1 – nearly 2x higher than graphite’s theoretical value (372 mAh g−1). PMID:27713474

Carbon-Coated, Diatomite-Derived Nanosilicon as a High Rate Capable Li-ion Battery Anode

NASA Astrophysics Data System (ADS)

Campbell, Brennan; Ionescu, Robert; Tolchin, Maxwell; Ahmed, Kazi; Favors, Zachary; Bozhilov, Krassimir N.; Ozkan, Cengiz S.; Ozkan, Mihrimah

2016-10-01

Silicon is produced in a variety of ways as an ultra-high capacity lithium-ion battery (LIB) anode material. The traditional carbothermic reduction process required is expensive and energy-intensive; in this work, we use an efficient magnesiothermic reduction to convert the silica-based frustules within diatomaceous earth (diatomite, DE) to nanosilicon (nanoSi) for use as LIB anodes. Polyacrylic acid (PAA) was used as a binder for the DE-based nanoSi anodes for the first time, being attributed for the high silicon utilization under high current densities (up to 4C). The resulting nanoSi exhibited a high BET specific surface area of 162.6 cm2 g-1, compared to a value of 7.3 cm2 g-1 for the original DE. DE contains SiO2 architectures that make ideal bio-derived templates for nanoscaled silicon. The DE-based nanoSi anodes exhibit good cyclability, with a specific discharge capacity of 1102.1 mAh g-1 after 50 cycles at a C-rate of C/5 (0.7 A gSi-1) and high areal loading (2 mg cm-2). This work also demonstrates the fist rate capability testing for a DE-based Si anode; C-rates of C/30 - 4C were tested. At 4C (14.3 A gSi-1), the anode maintained a specific capacity of 654.3 mAh g-1 - nearly 2x higher than graphite’s theoretical value (372 mAh g-1).

Mechanisms of anode power deposition in a low pressure free burning arc

NASA Technical Reports Server (NTRS)

Soulas, George C.; Myers, Roger M.

1994-01-01

Anode power deposition is a dominant power loss mechanism for arc jets and MPD thrusters. In this study, a free burning arc experiment was operated at pressures and current densities similar to those in arc jets and MPD thrusters in an attempt to identify the physics controlling this loss mechanism. Use of a free burning arc allowed for the isolation of independent variables controlling anode power deposition and provided a convenient and flexible way to cover a broad range of currents, anode surface pressures, and applied magnetic field strengths and orientations using an argon gas. Test results showed that anode power deposition decreased with increasing anode surface pressure up to 6.7 Pa (0.05 torr) and then became insensitive to pressure. Anode power increased with increasing arc current while the electron number density near the anode surface increased linearity. Anode power also increased with increasing applied magnetic field strength due to an increasing anode fall voltage. Applied magnetic field orientation had an effect only at high currents and low anode surface pressures, where anode power decreased when applied field lines intercepted the anode surface. The results demonstrated that anode power deposition was dominated by the current carrying electrons and that the anode fall voltage was the largest contributor. Furthermore, the results showed that anode power deposition can be reduced by operating at increased anode pressures, reduced arc currents, and applied magnetic field strengths and with magnetic field lines intercepting the anode.

High performance porous Si@C anodes synthesized by low temperature aluminothermic reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Kuber; Zheng, Jianming; Patel, Rajankumar

A low temperature (210°C) aluminothermic reduction reaction process has been developed to synthesis porous silicon (Si) as an anode for Li ion battery applications. An eutectic mixture of AlCl3 and ZnCl2 is used as the mediator to reduce the reaction temperature. With carbon pre-coated on the porous SiO2 precursor, porous Si@C core shell structured anodes could be obtained with structure and morphology similar to that of the porous precursor. In addition, carbon coated porous Si also exhibits superior cyclic stability, higher rate performance, and higher coulombic efficiency. The porous Si anode demonstrates a high specific capacity of ~2100 mAh/g atmore » the current density of 1.2 A/g and has a good cycling stability with ~76% capacity retention over 250 cycles. Therefore, it will be a good candidate for anode used in high energy density Li-ion batteries.« less

Model anodes and anode models for understanding the mechanism of hydrogen oxidation in solid oxide fuel cells.

PubMed

Bessler, Wolfgang G; Vogler, Marcel; Störmer, Heike; Gerthsen, Dagmar; Utz, Annika; Weber, André; Ivers-Tiffée, Ellen

2010-11-14

This article presents a literature review and new results on experimental and theoretical investigations of the electrochemistry of solid oxide fuel cell (SOFC) model anodes, focusing on the nickel/yttria-stabilized zirconia (Ni/YSZ) materials system with operation under H(2)/H(2)O atmospheres. Micropatterned model anodes were used for electrochemical characterization under well-defined operating conditions. Structural and chemical integrity was confirmed by ex situ pre-test and post-test microstructural and chemical analysis. Elementary kinetic models of reaction and transport processes were used to assess reaction pathways and rate-determining steps. The comparison of experimental and simulated electrochemical behaviors of pattern anodes shows quantitative agreement over a wide range of operating conditions (p(H(2)) = 8×10(2) - 9×10(4) Pa, p(H(2)O) = 2×10(1) - 6×10(4) Pa, T = 400-800 °C). Previously published experimental data on model anodes show a strong scatter in electrochemical performance. Furthermore, model anodes exhibit a pronounced dynamics on multiple time scales which is not reproduced in state-of-the-art models and which is also not observed in technical cermet anodes. Potential origin of these effects as well as consequences for further steps in model anode and anode model studies are discussed.

Structural micro-porous carbon anode for rechargeable lithium-ion batteries

DOEpatents

Delnick, F.M.; Even, W.R. Jr.; Sylwester, A.P.; Wang, J.C.F.; Zifer, T.

1995-06-20

A secondary battery having a rechargeable lithium-containing anode, a cathode and a separator positioned between the cathode and anode with an organic electrolyte solution absorbed therein is provided. The anode comprises three-dimensional microporous carbon structures synthesized from polymeric high internal phase emulsions or materials derived from this emulsion source, i.e., granules, powders, etc. 6 figs.

Anode macrostructures influence electricity generation in microbial fuel cells for wastewater treatment.

PubMed

Ishii, Yoshikazu; Miyahara, Morio; Watanabe, Kazuya

2017-01-01

Microbial fuel cells (MFCs) are devices that exploit microbes for generating electricity from organic substrates, including waste biomass and wastewater pollutants. MFCs have the potential to treat wastewater and simultaneously generate electricity. The present study examined how anode macrostructure influences wastewater treatment, electricity generation and microbial communities in MFCs. Cassette-electrode MFCs were equipped with graphite-felt anodes with three different macrostructures, flat-plate (FP), vertical-fin (VF), and horizontal-fin (HF) structures (these were composed of a same amount of graphite felt), and were continuously supplied with artificial wastewater containing starch as the major organic constituent. Polarization analyses revealed that MFCs equipped with VF and HF anodes generated 33% and 21% higher volumetric power densities, respectively, than that of MFCs equipped with FP anodes. Organics were also more efficiently removed from wastewater in MFCs with VF and HF anodes compared to reactors containing FP anodes. In addition, pyrosequencing of PCR-amplified 16S rRNA gene fragments from microbial samples collected from the anodes showed that the presence of fins also affected the bacterial compositions in anode biofilms. Taken together, the findings presented here suggest that the modification of anodes with fins improves organics removal and electricity generation in MFCs. The optimization of anode macrostructure therefore appears to be a promising strategy for improving MFC performance without additional material costs. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Intracellular Calcium and the Mechanism of Anodal Supernormal Excitability in Langendorff Perfused Rabbit Ventricles

PubMed Central

Joung, Boyoung; Park, Hyung-Wook; Maruyama, Mitsunori; Tang, Liang; Song, Juan; Han, Seongwook; Piccirillo, Gianfranco; Weiss, James N.; Lin, Shien-Fong; Chen, Peng-Sheng

2012-01-01

Background Anodal stimulation hyperpolarizes cell membrane and increases intracellular Ca2+ (Cai) transient. This study tested the hypothesis that The maximum slope of Cai decline (–(dCai/dt)max) corresponds to the timing of anodal dip on the strength-interval curve and the initiation of repetitive responses and ventricular fibrillation (VF) after a premature stimulus (S2). Methods and Results We simultaneously mapped membrane potential (Vm) and Cai in 23 rabbit ventricles. A dip was observed on the anodal strength-interval curve. During the anodal dip, ventricles were captured by anodal break excitation directly under the S2 electrode. The Cai following anodal stimuli is larger than that following cathodal stimuli. The S1-S2 intervals of the anodal dip (203 ± 10 ms) coincided with the -(dCai/dt)max (199 ± 10 ms, p=NS). BAPTA-AM (n=3), INCX inhibition by low extracellular Na+ (n=3), and combined ryanodine and thapsigargin infusion (n=2) eliminated the anodal supernormality. Strong S2 during the relative refractory period (n=5) induced 29 repetitive responses and 10 VF episodes. The interval between S2 and the first non-driven beat was coincidental with the time of -(dCai/dt)max. Conclusions Larger Cai transient and INCX activation induced by anodal stimulation produces anodal supernormality. Time of maximum INCX activation is coincidental to the induction of non- driven beats from the Cai sinkhole after a strong premature stimulation. PMID:21301131

In situ fabrication of high-performance Ni-GDC-nanocube core-shell anode for low-temperature solid-oxide fuel cells

PubMed Central

Yamamoto, Kazuhiro; Qiu, Nan; Ohara, Satoshi

2015-01-01

A core–shell anode consisting of nickel–gadolinium-doped-ceria (Ni–GDC) nanocubes was directly fabricated by a chemical process in a solution containing a nickel source and GDC nanocubes covered with highly reactive {001} facets. The cermet anode effectively generated a Ni metal framework even at 500 °C with the growth of the Ni spheres. Anode fabrication at such a low temperature without any sintering could insert a finely nanostructured layer close to the interface between the electrolyte and the anode. The maximum power density of the attractive anode was 97 mW cm–2, which is higher than that of a conventional NiO–GDC anode prepared by an aerosol process at 55 mW cm–2 and 600 °C, followed by sintering at 1300 °C. Furthermore, the macro- and microstructure of the Ni–GDC-nanocube anode were preserved before and after the power-generation test at 700 °C. Especially, the reactive {001} facets were stabled even after generation test, which served to reduce the activation energy for fuel oxidation successfully. PMID:26615816

Treatment of Ni-EDTA containing wastewater by electrocoagulation using iron scraps packed-bed anode.

PubMed

Ye, Xiaokun; Zhang, Junya; Zhang, Yan; Lv, Yuancai; Dou, Rongni; Wen, Shulong; Li, Lianghao; Chen, Yuancai; Hu, YongYou

2016-12-01

The unique electrocoagulator proposed in this study is highly efficient at removing Ni-EDTA, providing a potential remediation option for wastewater containing lower concentrations of Ni-EDTA (Ni ≤ 10 mg L -1 ). In the electrocoagulation (EC) system, cylindrical graphite was used as a cathode, and a packed-bed formed from iron scraps was used as an anode. The results showed that the removal of Ni-EDTA increased with the application of current and favoured acidic conditions. We also found that the iron scrap packed-bed anode was superior in its treatment ability and specific energy consumption (SECS) compared with the iron rod anode. In addition, the packed density and temperature had a large influence on the energy consumption (ECS). Over 94.3% of Ni and 95.8% of TOC were removed when conducting the EC treatment at an applied current of 0.5 A, initial pH of 3, air-purged rate 0.2 L min -1 , anode packed density of 400 kg m -3 temperature of 313 K and time of 30 min. SEM analysis of the iron scraps indicated that the specific area of the anode increased after the EC. The XRD analysis of flocs produced during EC revealed that hematite (α-Fe 2 O 3 ) and magnetite (Fe 3 O 4 ) were the main by-products under aerobic and anoxic conditions, respectively. A kinetic study demonstrated that the removal of Ni-EDTA followed a first-order model with the current parameters. Moreover, the removal efficiency of real wastewater was essentially consistent with that of synthetic wastewater. Copyright © 2016 Elsevier Ltd. All rights reserved.

Combined carbon mesh and small graphite fiber brush anodes to enhance and stabilize power generation in microbial fuel cells treating domestic wastewater

NASA Astrophysics Data System (ADS)

Wu, Shijia; He, Weihua; Yang, Wulin; Ye, Yaoli; Huang, Xia; Logan, Bruce E.

2017-07-01

Microbial fuel cells (MFCs) need to have a compact architecture, but power generation using low strength domestic wastewater is unstable for closely-spaced electrode designs using thin anodes (flat mesh or small diameter graphite fiber brushes) due to oxygen crossover from the cathode. A composite anode configuration was developed to improve performance, by joining the mesh and brushes together, with the mesh used to block oxygen crossover to the brushes, and the brushes used to stabilize mesh potentials. In small, fed-batch MFCs (28 mL), the composite anode produced 20% higher power densities than MFCs using only brushes, and 150% power densities compared to carbon mesh anodes. In continuous flow tests at short hydraulic retention times (HRTs, 2 or 4 h) using larger MFCs (100 mL), composite anodes had stable performance, while brush anode MFCs exhibited power overshoot in polarization tests. Both configurations exhibited power overshoot at a longer HRT of 8 h due to lower effluent CODs. The use of composite anodes reduced biomass growth on the cathode (1.9 ± 0.2 mg) compared to only brushes (3.1 ± 0.3 mg), and increased coulombic efficiencies, demonstrating that they successfully reduced oxygen contamination of the anode and the bio-fouling of cathode.

Contribution of the backstreaming ions to the self-magnetic pinch (SMP) diode current

NASA Astrophysics Data System (ADS)

Mazarakis, Michael G.; Bennett, Nichelle; Cuneo, Michael E.; Fournier, Sean D.; Johnston, Mark D.; Kiefer, Mark L.; Leckbee, Joshua J.; Nielsen, Dan S.; Oliver, Bryan V.; Sceiford, Matthew E.; Simpson, Sean C.; Renk, Timothy J.; Ruiz, Carlos L.; Webb, Timothy J.; Ziska, Derek; Droemer, Darryl W.; Gignac, Raymond E.; Obregon, Robert J.; Wilkins, Frank L.; Welch, Dale R.

2018-04-01

The results presented here were obtained with a self-magnetic pinch (SMP) diode mounted at the front high voltage end of the RITS accelerator. RITS is a Self-Magnetically Insulated Transmission Line (MITL) voltage adder that adds the voltage pulse of six 1.3 MV inductively insulated cavities. The RITS driver together with the SMP diode has produced x-ray spots of the order of 1 mm in diameter and doses adequate for the radiographic imaging of high area density objects. Although, through the years, a number of different types of radiographic electron diodes have been utilized with SABER, HERMES III and RITS accelerators, the SMP diode appears to be the most successful and simplest diode for the radiographic investigation of various objects. Our experiments had two objectives: first to measure the contribution of the back-streaming ion currents emitted from the anode target and second to try to evaluate the energy of those ions and hence the Anode-Cathode (A-K) gap actual voltage. In any very high voltage inductive voltage adder utilizing MITLs to transmit the power to the diode load, the precise knowledge of the accelerating voltage applied on the A-K gap is problematic. This is even more difficult in an SMP diode where the A-K gap is very small (˜1 cm) and the diode region very hostile. The accelerating voltage quoted in the literature is from estimates based on the measurements of the anode and cathode currents of the MITL far upstream from the diode and utilizing the para-potential flow theories and inductive corrections. Thus, it would be interesting to have another independent measurement to evaluate the A-K voltage. The diode's anode is made of a number of high-Z metals in order to produce copious and energetic flash x-rays. It was established experimentally that the back-streaming ion currents are a strong function of the anode materials and their stage of cleanness. We have measured the back-streaming ion currents emitted from the anode and propagating through a hollow cathode tip for various diode configurations and different techniques of target cleaning treatment: namely, heating at very high temperatures with DC and pulsed current, with RF plasma cleaning, and with both plasma cleaning and heating. We have also evaluated the A-K gap voltage by energy filtering technique. Experimental results in comparison with LSP simulations are presented.

Cobalt Oxide Porous Nanofibers Directly Grown on Conductive Substrate as a Binder/Additive-Free Lithium-Ion Battery Anode with High Capacity.

PubMed

Liu, Hao; Zheng, Zheng; Chen, Bochao; Liao, Libing; Wang, Xina

2017-12-01

In order to reduce the amount of inactive materials, such as binders and carbon additives in battery electrode, porous cobalt monoxide nanofibers were directly grown on conductive substrate as a binder/additive-free lithium-ion battery anode. This electrode exhibited very high specific discharging/charging capacities at various rates and good cycling stability. It was promising as high capacity anode materials for lithium-ion battery.

Selectivity control of carbonylation of methanol to dimethyl oxalate and dimethyl carbonate over gold anode by electrochemical potential.

PubMed

Funakawa, Akiyasu; Yamanaka, Ichiro; Takenaka, Sakae; Otsuka, Kiyoshi

2004-05-05

New and unique electrocatalysis of gold for the carbonylation of methanol to dimethyl oxalate (DMO) and dimethyl carbonate (DMC) was found. The selectivity to DMO and DMC could be controlled over gold anode by electrochemical potential, as you like. Drastic changes of gold electrocatalysis was due to changes of the oxidation state of gold, Au0 or Au3+.

Effect of alloying elements Al and Ca on corrosion resistance of plasma anodized Mg alloys

NASA Astrophysics Data System (ADS)

Anawati, Asoh, Hidetaka; Ono, Sachiko

2016-04-01

Plasma anodizing is a surface treatment used to form a ceramic-type oxide film on Mg alloys by the application of a high anodic voltage to create intense plasma near the metal surface. With proper selection of the process parameters, the technique can produce high quality oxide with superior adhesion, corrosion resistance, micro-hardness, wear resistance and strength. The effect of alloying element Al on plasma anodizing process of Mg alloys was studied by comparing the anodizing curves of pure Mg, AZ31, and AZ61 alloys while the effect of Ca were studied on AZ61 alloys containing 0, 1, and 2 wt% Ca. Anodizing was performed in 0.5 M Na3PO4 solution at a constant current density of 200 Am-2 at 25°C. Anodic oxide films with lava-like structure having mix composition of amorphous and crystal were formed on all of the alloys. The main crystal form of the oxide was Mg3(PO4)2 as analyzed by XRD. Alloying elements Al and Ca played role in modifying the plasma lifetime during anodization. Al tended to extend the strong plasma lifetime and therefore accelerated the film thickening. The effect of Ca on anodizing process was still unclear. The anodic film thickness and chemical composition were altered by the presence of Ca in the alloys. Electrochemical corrosion test in 0.9% NaCl solution showed that the corrosion behavior of the anodized specimens depend on the behavior of the substrate. Increasing Al and Ca content in the alloys tended to increase the corrosion resistance of the specimens. The corrosion resistance of the anodized specimens improved significantly about two orders of magnitude relative to the bare substrate.

Promising Cell Configuration for Next-Generation Energy Storage: Li2S/Graphite Battery Enabled by a Solvate Ionic Liquid Electrolyte.

PubMed

Li, Zhe; Zhang, Shiguo; Terada, Shoshi; Ma, Xiaofeng; Ikeda, Kohei; Kamei, Yutaro; Zhang, Ce; Dokko, Kaoru; Watanabe, Masayoshi

2016-06-29

Lithium-ion sulfur batteries with a [graphite|solvate ionic liquid electrolyte|lithium sulfide (Li2S)] structure are developed to realize high performance batteries without the issue of lithium anode. Li2S has recently emerged as a promising cathode material, due to its high theoretical specific capacity of 1166 mAh/g and its great potential in the development of lithium-ion sulfur batteries with a lithium-free anode such as graphite. Unfortunately, the electrochemical Li(+) intercalation/deintercalation in graphite is highly electrolyte-selective: whereas the process works well in the carbonate electrolytes inherited from Li-ion batteries, it cannot take place in the ether electrolytes commonly used for Li-S batteries, because the cointercalation of the solvent destroys the crystalline structure of graphite. Thus, only very few studies have focused on graphite-based Li-S full cells. In this work, simple graphite-based Li-S full cells were fabricated employing electrolytes beyond the conventional carbonates, in combination with highly loaded Li2S/graphene composite cathodes (Li2S loading: 2.2 mg/cm(2)). In particular, solvate ionic liquids can act as a single-phase electrolyte simultaneously compatible with both the Li2S cathode and the graphite anode and can further improve the battery performance by suppressing the shuttle effect. Consequently, these lithium-ion sulfur batteries show a stable and reversible charge-discharge behavior, along with a very high Coulombic efficiency.

The Identification of Cable Bacteria Attached to the Anode of a Benthic Microbial Fuel Cell: Evidence of Long Distance Extracellular Electron Transport to Electrodes

PubMed Central

Reimers, Clare E.; Li, Cheng; Graw, Michael F.; Schrader, Paul S.; Wolf, Michael

2017-01-01

Multicellular, filamentous, sulfur-oxidizing bacteria, known as cable bacteria, were discovered attached to fibers of a carbon brush electrode serving as an anode of a benthic microbial fuel cell (BMFC). The BMFC had been operated in a temperate estuarine environment for over a year before collecting anode samples for scanning electron microscopy and phylogenetic analyses. Individual filaments were attached by single terminus cells with networks of pilus-like nano-filaments radiating out from these cells, across the anode fiber surface, and between adjacent attachment locations. Current harvesting by the BMFC poised the anode at potentials of ~170–250 mV vs. SHE, and these surface potentials appear to have allowed the cable bacteria to use the anode as an electron acceptor in a completely anaerobic environment. A combination of catalyzed reporter deposition fluorescent in situ hybridization (CARD-FISH) and 16S rRNA gene sequence analysis confirmed the phylogeny of the cable bacteria and showed that filaments often occurred in bundles and in close association with members of the genera Desulfuromonas. However, the Desulfobulbaceae Operational Taxonomic Units (OTUs) from the 16S sequencing did not cluster closely with other putative cable bacteria sequences suggesting that the taxonomic delineation of cable bacteria is far from complete. PMID:29114243

Carbonate species as OH- carriers for decreasing the pH gradient between cathode and anode in biological fuel cells.

PubMed

Torres, César I; Lee, Hyung-Sool; Rittmann, Bruce E

2008-12-01

Anodes of biological fuel cells (BFCs) normally must operate at a near-neutral pH in the presence of various ionic species required for the function of the biological catalyst (e.g., substrate, nutrients, and buffers). These ionic species are in higher concentration than protons (H+) and hydroxides (OH-); slow transport of H+ and OH- equivalents between anode and cathode compartments can lead to a large pH gradient that can inhibit the function of biological components, decrease voltage efficiency in BFCs, or both. We evaluate the use of carbonate species as OH- carriers from the cathode to the anode compartment. This is achieved by adding CO2 to the influent air in the cathode. CO2 is an acid that combines with OH- in the cathode to produce bicarbonate and carbonate. These species can migrate to the anode compartment as OH- carriers at a rate much greater than can OH- itself when the pH is not extremely high in the cathode compartment We demonstrate this concept by feeding different air/CO2 mixtures to the cathode of a dual-chamber microbial fuel cell (MFC) fed with acetate as substrate. Our results show a 45% increase in power density (from 1.9 to 2.8 W/m2) by feeding air augmented with 2-10% CO2. The cell voltage increased by as much as 120 mV, indicating that the pH gradient decreased by as much as 2 pH units. Analysis of the anode effluent showed an average increase of 4.9 mM in total carbonate, indicating that mostly carbonate was transferred from the cathode compartment This process provides a simple way to minimize potential losses in BFCs due to pH gradients between anode and cathode compartments.

Using Copper Nanoparticle Additive to Improve the Performance of Silicon Anodes in Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Bachand, Gabrielle

In the foreseeable future, global energy demand is expected to rapidly increase as a result of the swelling population and higher standards of living. Current energy generation and transportation methods predominantly involve the combustion of non-renewable fossil fuels, and greenhouse gas emissions from these processes have been shown to contribute to global climate change and to be detrimental to human and environmental health. To satisfy future energy needs and to reduce greenhouse gas emissions, the advancement of renewable energy generation and electric vehicles is important. The proliferation of intermittent renewable energy sources (such as solar and wind) and electric vehicles depends upon reliable, high-capacity energy storage to serve the practical needs of society. The present-day lithium-ion battery offers excellent qualities for this purpose; however, improvements in the capacity and cost-effectiveness of these batteries are needed for further growth. As an anode material, silicon has exceptionally high theoretical capacity and is an earth-abundant, low-cost option. However, silicon also suffers from poor conductivity and long-term stability, prompting many studies to investigate the use of additive materials to mitigate these issues. This thesis focuses on the improvement of silicon anode performance by using a nanoparticulate copper additive to increase material conductivity and an inexpensive, industry-compatible anode fabrication process. Three main fabrication processes were explored using differing materials and heat treatment techniques for comparison. Anodes were tested using CR2032 type coin cells. The final anodes with the most-improved characteristics were fabricated using a high-temperature heating step for the anode material, and an additional batch was formed to test the viability of the copper additive functioning as a full substitute for carbon black, which is the traditional choice of conductive additive for electrode materials. Anodes materials were characterized using a variety of techniques including scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), inductively coupled plasma optical emission spectrometry (ICP-OES), Raman spectroscopy, and X-ray diffraction (XRD) to evaluate surface qualities and material content. Electrochemical techniques including electrochemical impedance spectroscopy (EIS) and charge/discharge cycling were also used to determine the conductivity and functional behavior of the anode materials. Anodes from the final experimental study achieved initial capacities of 309 mA/g and 957 mA/g for the silicon-only control and silicon with copper additive anodes, respectively, demonstrating an over 300% increase in specific capacity. Si-Cu (NC) anodes also showed superior performance over control anodes with an initial capacity of 775 mA/g. For all three anodes, high efficiencies of over 96% were achieved for the testing duration of 100 cycles and reached near or over 99% in final cycles. Results also show a significant decrease in the resistance of anodes with copper additive, contributing to the improved performance of these anodes.

Bone Cell–materials Interactions and Ni Ion Release of Anodized Equiatomic NiTi Alloy

PubMed Central

Bernard, Sheldon A.; Balla, Vamsi Krishna; Davies, Neal M.; Bose, Susmita; Bandyopadhyay, Amit

2011-01-01

Laser processed NiTi alloy was anodized for different durations in H2SO4 electrolyte with varying pH to create biocompatible surfaces with low Ni ion release as well as bioactive surfaces to enhance biocompatibility and bone cell-materials interactions. The anodized surfaces were assessed for their in vitro cell-materials interactions using human fetal osteoblast (hFOB) cells for 3, 7 and 11 days, and Ni ion release up to 8 weeks in simulated body fluids. The results were correlated with surface morphologies of anodized surfaces characterized using field-emission scanning electron microscopy (FESEM). The results show that the anodization creates a surface with nano/micro roughness depending on anodization conditions. The hydrophilicity of NiTi surface was found to improve after anodization due to lower contact angles in cell media, which dropped from 32° to < 5°. The improved wettability of anodized surfaces is further corroborated by their high surface energy comparable to that of cp Ti. Relatively high surface energy, especially polar component, and nano/micro surface features of anodized surfaces significantly increased the number of living cells and their adherence and growth on these surfaces. Finally, a significant drop in Ni ion release from 268 ± 11 to 136 ± 15 ppb was observed for NiTi surfaces after anodization. This work indicates that anodization of NiTi alloy has a positive influence on the surface energy and surface morphology, which in turn improve bone cell-materials interactions and reduce Ni ion release in vitro. PMID:21232641

Metallic Sn-Based Anode Materials: Application in High-Performance Lithium-Ion and Sodium-Ion Batteries.

PubMed

Ying, Hangjun; Han, Wei-Qiang

2017-11-01

With the fast-growing demand for green and safe energy sources, rechargeable ion batteries have gradually occupied the major current market of energy storage devices due to their advantages of high capacities, long cycling life, superior rate ability, and so on. Metallic Sn-based anodes are perceived as one of the most promising alternatives to the conventional graphite anode and have attracted great attention due to the high theoretical capacities of Sn in both lithium-ion batteries (LIBs) (994 mA h g -1 ) and sodium-ion batteries (847 mA h g -1 ). Though Sony has used Sn-Co-C nanocomposites as its commercial LIB anodes, to develop even better batteries using metallic Sn-based anodes there are still two main obstacles that must be overcome: poor cycling stability and low coulombic efficiency. In this review, the latest and most outstanding developments in metallic Sn-based anodes for LIBs and SIBs are summarized. And it covers the modification strategies including size control, alloying, and structure design to effectually improve the electrochemical properties. The superiorities and limitations are analyzed and discussed, aiming to provide an in-depth understanding of the theoretical works and practical developments of metallic Sn-based anode materials.

Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries

DOE PAGES

Dose, W. M.; Piernas-Munoz, M. J.; Maroni, V. A.; ...

2018-02-09

A silicon-graphite blended anode is paired with a high capacity LiFePO 4 reference/counter electrode to track irreversibility and lithium inventory. The LiFePO 4 electrode provides a reliable, flat potential for dQ dV -1 analysis of Li xSi and Li xC electrochemical reactions. We can relate this electrochemistry to the morphological and physical changes taking place.

Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dose, W. M.; Piernas-Munoz, M. J.; Maroni, V. A.

A silicon-graphite blended anode is paired with a high capacity LiFePO 4 reference/counter electrode to track irreversibility and lithium inventory. The LiFePO 4 electrode provides a reliable, flat potential for dQ dV -1 analysis of Li xSi and Li xC electrochemical reactions. We can relate this electrochemistry to the morphological and physical changes taking place.

Role of anode length in a mather-type plasma focus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beg, F.N.; Zakaullah, M.; Nisar, M.

In this paper, neutron emission from a 3 KJ Mather-type plasma focus is studied. Specifically, the behavior of system with the change in anode length is investigated. Anode lengths of high and low fluence anisotropy as well as for high neutron yield are identified. Experiment also suggest the possibility of ion beam generation leading to neutron production via beam-plasma interaction.

Position-sensitive proportional counter with low-resistance metal-wire anode

DOEpatents

Kopp, Manfred K.

1980-01-01

A position-sensitive proportional counter circuit is provided which allows the use of a conventional (low-resistance, metal-wire anode) proportional counter for spatial resolution of an ionizing event along the anode of the counter. A pair of specially designed active-capacitance preamplifiers are used to terminate the anode ends wherein the anode is treated as an RC line. The preamplifiers act as stabilized active capacitance loads and each is composed of a series-feedback, low-noise amplifier, a unity-gain, shunt-feedback amplifier whose output is connected through a feedback capacitor to the series-feedback amplifier input. The stabilized capacitance loading of the anode allows distributed RC-line position encoding and subsequent time difference decoding by sensing the difference in rise times of pulses at the anode ends where the difference is primarily in response to the distributed capacitance along the anode. This allows the use of lower resistance wire anodes for spatial radiation detection which simplifies the counter construction and handling of the anodes, and stabilizes the anode resistivity at high count rates (>10.sup.6 counts/sec).

Conceptual design and experiments of electrochemistry-flushing technology for the remediation of historically Cr(Ⅵ)-contaminated soil.

PubMed

Li, Dong; Sun, Delin; Hu, Siyang; Hu, Jing; Yuan, Xingzhong

2016-02-01

A conceptual design and experiments, electrochemistry-flushing (E-flushing), using electrochemistry to enhance flushing efficiency for the remediation of Cr(Ⅵ)-contaminated soil is presented. The rector contained three compartments vertically superposed. The upper was airtight cathode compartment containing an iron-cathode. The middle was soil layer. The bottom was anode compartment containing an iron-anode and connected to a container by circulation pumps. H2 and OH(-) ions were produced at cathode. H2 increased the gas pressure in cathode compartment and drove flushing solution into soil layer forming flushing process. OH(-) ions entered into soil layer by eletromigration and hydraulic flow to enhance the desorption of Cr(Ⅵ). High potential gradient was applied to accelerate the electromigration of desorbed Cr(Ⅵ) ions and produced joule heat to increase soil temperature to enhance Cr(Ⅵ) desorption. In anode compartment, Fe(2+) ions produced at iron-anode reduced the desorbed Cr(Ⅵ) into Cr(3+) ions, which reacted with OH(-) ions forming Cr(OH)3. Experimental results show that Cr(Ⅵ) removal efficiency of E-flushing experiments was more than double of flushing experiments and reached the maximum of removal efficiency determined by desorption kinetics. All electrochemistry processes were positively used in E-flushing technology. Copyright © 2015 Elsevier Ltd. All rights reserved.

Enhanced degradation of Orange G by permanganate with the employment of iron anode.

PubMed

Bu, Lingjun; Shi, Zhou; Zhou, Shiqing

2017-01-01

Iron anode was employed to enhance the degradation of Orange G (OG) by permanganate (EC/KMnO 4 ). Continuously generated Fe 2+ from iron anode facilitated the formation of fresh MnO 2 , which plays a role in catalyzing permanganate oxidation. The EC/KMnO 4 system also showed a better performance to remove OG than Fe 2+ /KMnO 4 , indicating the importance of in situ formed fresh MnO 2 . Besides, the effects of applied current, KMnO 4 dosage, solution pH, and natural organics were evaluated and results demonstrated that high current and oxidant dosage are favorable for OG removal. And the application of iron anode has a promoting effect on the KMnO 4 oxidation over a wide pH range (5.0-9.0), while the Fe 2+ /KMnO 4 process does not. For natural organics, its presence could inhibit OG removal due to its competitive role. And the promoting effect of OG removal by the EC/KMnO 4 process in natural water was confirmed. At last, the EC/KMnO 4 process showed a satisfying performance on the decolorization and mineralization of OG. This study provides a potential technology to enhance permanganate oxidation and broadens the knowledge of azo dye removal.

Dry-air-stable lithium silicide-lithium oxide core-shell nanoparticles as high-capacity prelithiation reagents.

PubMed

Zhao, Jie; Lu, Zhenda; Liu, Nian; Lee, Hyun-Wook; McDowell, Matthew T; Cui, Yi

2014-10-03

Rapid progress has been made in realizing battery electrode materials with high capacity and long-term cyclability in the past decade. However, low first-cycle Coulombic efficiency as a result of the formation of a solid electrolyte interphase and Li trapping at the anodes, remains unresolved. Here we report LixSi-Li2O core-shell nanoparticles as an excellent prelithiation reagent with high specific capacity to compensate the first-cycle capacity loss. These nanoparticles are produced via a one-step thermal alloying process. LixSi-Li2O core-shell nanoparticles are processible in a slurry and exhibit high capacity under dry-air conditions with the protection of a Li2O passivation shell, indicating that these nanoparticles are potentially compatible with industrial battery fabrication processes. Both Si and graphite anodes are successfully prelithiated with these nanoparticles to achieve high first-cycle Coulombic efficiencies of 94% to >100%. The LixSi-Li2O core-shell nanoparticles enable the practical implementation of high-performance electrode materials in lithium-ion batteries.

Mussel-Inspired Conductive Polymer Binder for Si-Alloy Anode in Lithium-Ion Batteries

DOE PAGES

Zhao, Hui; Wei, Yang; Wang, Cheng; ...

2018-01-15

The excessive volume changes during cell cycling of Si-based anode in lithium ion batteries impeded its application. One major reason for the cell failure is particle isolation during volume shrinkage in delithiation process, which makes strong adhesion between polymer binder and anode active material particles a highly desirable property. Here, a biomimetic side-chain conductive polymer incorporating catechol, a key adhesive component of the mussel holdfast protein, was synthesized. Atomic force microscopy-based single-molecule force measurements of mussel-inspired conductive polymer binder contacting a silica surface revealed a similar adhesion toward substrate when compared with an effective Si anode binder, homo-poly(acrylic acid), withmore » the added benefit of being electronically conductive. Electrochemical experiments showed a very stable cycling of Si-alloy anodes realized via this biomimetic conducting polymer binder, leading to a high loading Si anode with a good rate performance. We attribute the ability of the Si-based anode to tolerate the volume changes during cycling to the excellent mechanical integrity afforded by the strong interfacial adhesion of the biomimetic conducting polymer.« less

Laser pumping of thyristors for fast high current rise-times

DOEpatents

Glidden, Steven C.; Sanders, Howard D.

2013-06-11

An optically triggered semiconductor switch includes an anode metallization layer; a cathode metallization layer; a semiconductor between the anode metallization layer and the cathode metallization layer and a photon source. The semiconductor includes at least four layers of alternating doping in the form P-N-P-N, in which an outer layer adjacent to the anode metallization layer forms an anode and an outer layer adjacent the cathode metallization layer forms a cathode and in which the anode metallization layer has a window pattern of optically transparent material exposing the anode layer to light. The photon source emits light having a wavelength, with the light from the photon source being configured to match the window pattern of the anode metallization layer.

Fabrication and characterization of anode-supported micro-tubular solide oxide fuel cell by phase inversion method

NASA Astrophysics Data System (ADS)

Ren, Cong

Nowadays, the micro-tubular solid oxide fuel cells (MT-SOFCs), especially the anode supported MT-SOFCs have been extensively developed to be applied for SOFC stacks designation, which can be potentially used for portable power sources and vehicle power supply. To prepare MT-SOFCs with high electrochemical performance, one of the main strategies is to optimize the microstructure of the anode support. Recently, a novel phase inversion method has been applied to prepare the anode support with a unique asymmetrical microstructure, which can improve the electrochemical performance of the MT-SOFCs. Since several process parameters of the phase inversion method can influence the pore formation mechanism and final microstructure, it is essential and necessary to systematically investigate the relationship between phase inversion process parameters and final microstructure of the anode supports. The objective of this study is aiming at correlating the process parameters and microstructure and further preparing MT-SOFCs with enhanced electrochemical performance. Non-solvent, which is used to trigger the phase separation process, can significantly influence the microstructure of the anode support fabricated by phase inversion method. To investigate the mechanism of non-solvent affecting the microstructure, water and ethanol/water mixture were selected for the NiO-YSZ anode supports fabrication. The presence of ethanol in non-solvent can inhibit the growth of the finger-like pores in the tubes. With the increasing of the ethanol concentration in the non-solvent, a relatively dense layer can be observed both in the outside and inside of the tubes. The mechanism of pores growth and morphology obtained by using non-solvent with high concentration ethanol was explained based on the inter-diffusivity between solvent and non-solvent. Solvent and non-solvent pair with larger Dm value is benefit for the growth of finger-like pores. Three cells with different anode geometries was prepared, La0.85Sr0.15MnO 3 (LSM) was selected as the cathode. Cells were tested at 800°C using humidified H2 as fuel. Cell with anode prepared by using pure water as non-solvent shows a maximum power density up to 437mW/cm 2. By comparing the anode geometry and electrochemical performance, it indicated that microstructure with longer finger-like pores and thinner macrovoid free layer close to the inner side of the tube is benefit to cell performance. Another factor that can affect the microstructure of anode support is the ratio of solvent and polymer binder. In this research, anode-supported MT-SOFCs have been fabricated by phase inversion method. The effect of the viscosity of the casting slurry on the microstructure of YSZ-NiO anode support has been investigated. The microstructure of the YSZ-NiO support can be effectively controlled by varying the slurry composition with different solvent and polymer binder content. Gas permeation and mechanical strength of the YSZ-NiO support have been measured and four YSZ-NiO anode supports have been chosen for subsequent cell fabrication. The effective conductivity of the different anode supports has been measured at room temperature after reduced. Anode-supported single cells with YSZ electrolyte and LSM/YSZ cathode are fabricated and tested. Maximum cell power densities of 606 mWcm-2, 449 mWcm -2, 339 mWcm-2 and 253 mWcm-2 have been obtained respectively at 750 °C with humidified hydrogen as fuel and ambient air as oxidant. The correlation between the cell electrochemical performance and anode microstructures has been discussed. Adjusting the slurry composition by introducing additive is also an effective approach to tailor the microstructure of the anode support. Poly(ethylene glycol) (PEG), which is a common applied polymer additive, was selected to fabricate the YSZ-NiO anode supports. The effect of molecular weight and amount of PEG additive on the thermodynamics of the casting solutions was characterized by measuring the coagulation value. Viscosity of the casting slurries was also measured and the influence of PEG additive on viscosity was studied and discussed. The presence of PEG in the casting slurry can greatly influence the final anode support microstructure. Based on the microstructure result and the measured gas permeation value, two anode supports were selected for cell fabrication. For cell with the anode support fabricated using slurry with PEG additive, a maximum cell power density of 704 mWcm-2 is obtained at 750 oC with humidified hydrogen as fuel and ambient air as oxidant; cell fabricated without any PEG additive shows the peak cell power density of 331 mWcm-2. The relationship between anode microstructure and cell performance was discussed. Anode-supported micro-tubular solid oxide fuel cells (MT-SOFCs) based on BaZr0.1Ce0.7Y0.1Yb0.1O 3-delta (BZCYYb) proton-conducting electrolyte have been prepared using a phase inversion method. Three sulfur-free polymer binder candidates ethyl cellulose (EC), polyvinylidene fluoride (PVDF), polyetherimide (PEI) and sulfur-containing polythersulfone (PESf) were used as polymer binders to fabricate NiO-BZCYYb anode. The overall influence of polymer binder on the anode supports was evaluated. Sulfide impurity generated from PESf was revealed by XRD and X-ray photoelectron spectroscopy (XPS). The difference in the anode microstructure for samples fabricated by different polymer binders was examined by scanning electron microscope (SEM) and analyzed by measuring the gas permeation data of the reduced samples. Single cells based on different anode supports were characterized in anode-supported MT-SOFCs with the cell configuration of Ni-BZCYYb anode, BZCYYb electrolyte and La0.6Sr 0.4Co0.2Fe0.8O3-delta (LSCF)-BZCYYb cathode at 650 °C using hydrogen as fuel and ambient air as oxidant. MT-SOFCs of the anode fabricated using PEI show maximum power density of 0.45 Wcm -2 compared with 0.35 Wcm-2 for cells fabricated with PESf. The difference in cell performance was attributed to the phase purity of the anode fabricated by different polymer binders. Sulfur-free polymer binder PEI exhibits advantages over the commonly applied PESf and other sulfur-free polymer binder candidates. To eliminate the skin layer formed close to the inner side of the tubular sample when using the phase inversion method. Polyethersulfone (PESf)-polyethylenimine (PEI) blend was employed as the polymer binder to fabricate the micro-tubular solid oxide fuel cells (MT-SOFCs). The potential impurity introduced in the anode support by the polymer binder was examined by XPS and the resulting novel microstructure was analyzed based on the backscattered electron (BSE) images. Cells fabricated with blend polymer binder showed significantly enhanced power output compared with those cells only fabricated with PEI or PESf. The improved cell performance demonstrated that using blend polymer as binder is a promising and versatile approach for MT-SOFC fabrication via phase inversion method. Finally, to investigate the effect of the anode microstructure on the total cell performance, two types of anode support with different microstructure were prepared via the phase inversion method at different temperature. Cells fabricated based on these two anode supports were tested at 750 °C with hydrogen or hydrogen mixture with fuel gas. The measured current density-voltage (I-V) curves were fitted by a polarization model, and several parameters were archived through the modeling process. The influence of the anode support on the total cell performance was discussed based on the calculated result.

High-pressure-assisted design of porous topological semimetal carbon for Li-ion battery anode with high-rate performance

NASA Astrophysics Data System (ADS)

Liu, Junyi; Wang, Shuo; Qie, Yu; Zhang, Cunzhi; Sun, Qiang

2018-02-01

It has been a great challenge to develop a high-rate anode material with high-capacity, fast Li-ions diffusion and long cycling life going beyond the commercially used graphite in Li-ion battery. Here for the first time we propose a strategy combined high-pressure synthesis method with the global structure search to find a topological semimetal porous carbon as the desired anode. Our crystal-structure searching shows that we can obtain the ground state of an orthorhombic phase Li C6 with regular pores at 30 GPa, and when the Li atoms are removed, the resulting carbon structure is the recently predicted interlocked graphene network (IGN) that is a topological semimetal with an intrinsic high electronic conductivity. Based on the state-of-the-art first-principles calculations, we further find that the Li-ion migration energy barrier in the IGN is extremely low and the estimated diffusion coefficient can reach a magnitude of 10-4c m2/s at both low and high Li concentrations, which is three orders of magnitude larger than that of graphite anode. Moreover, the volume changes during the Li insertion and deinsertion are smaller than 3.2 % , while the theoretical specific capacity is the same as that of graphite anode. Our studies not only suggest a practical way of synthesizing the topological semimetal carbon but also propose a new anode material for Li-ion battery.

High-Capacity and Long-Cycle Life Aqueous Rechargeable Lithium-Ion Battery with the FePO4 Anode.

PubMed

Wang, Yuesheng; Yang, Shi-Ze; You, Ya; Feng, Zimin; Zhu, Wen; Gariépy, Vincent; Xia, Jiexiang; Commarieu, Basile; Darwiche, Ali; Guerfi, Abdelbast; Zaghib, Karim

2018-02-28

Aqueous lithium-ion batteries are emerging as strong candidates for a great variety of energy storage applications because of their low cost, high-rate capability, and high safety. Exciting progress has been made in the search for anode materials with high capacity, low toxicity, and high conductivity; yet, most of the anode materials, because of their low equilibrium voltages, facilitate hydrogen evolution. Here, we show the application of olivine FePO 4 and amorphous FePO 4 ·2H 2 O as anode materials for aqueous lithium-ion batteries. Their capacities reached 163 and 82 mA h/g at a current rate of 0.2 C, respectively. The full cell with an amorphous FePO 4 ·2H 2 O anode maintained 92% capacity after 500 cycles at a current rate of 0.2 C. The acidic aqueous electrolyte in the full cells prevented cathodic oxygen evolution, while the higher equilibrium voltage of FePO 4 avoided hydrogen evolution as well, making them highly stable. A combination of in situ X-ray diffraction analyses and computational studies revealed that olivine FePO 4 still has the biphase reaction in the aqueous electrolyte and that the intercalation pathways in FePO 4 ·2H 2 O form a 2-D mesh. The low cost, high safety, and outstanding electrochemical performance make the full cells with olivine or amorphous hydrated FePO 4 anodes commercially viable configurations for aqueous lithium-ion batteries.

High-energy lithium-ion hybrid supercapacitors composed of hierarchical urchin-like WO3/C anodes and MOF-derived polyhedral hollow carbon cathodes.

PubMed

Xu, Juan; Li, Yuanyuan; Wang, Lei; Cai, Qifa; Li, Qingwei; Gao, Biao; Zhang, Xuming; Huo, Kaifu; Chu, Paul K

2016-09-22

A lithium-ion hybrid supercapacitor (Li-HSC) comprising a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode has attracted much interest because it accomplishes a large energy density without compromising the power density. In this work, hierarchical carbon coated WO 3 (WO 3 /C) with a unique mesoporous structure and metal-organic framework derived nitrogen-doped carbon hollow polyhedra (MOF-NC) are prepared and adopted as the anode and the cathode for Li-HSCs. The hierarchical mesoporous WO 3 /C microspheres assembled by radially oriented WO 3 /C nanorods along the (001) plane enable effective Li + insertion, thus exhibit high capacity, excellent rate performance and a long cycling life due to their high Li + conductivity, electronic conductivity and structural robustness. The WO 3 /C structure shows a reversible specific capacity of 508 mA h g -1 at a 0.1 C rate (1 C = 696 mA h g -1 ) after 160 discharging-charging cycles with excellent rate capability. The MOF-NC achieved the specific capacity of 269.9 F g -1 at a current density of 0.2 A g -1 . At a high current density of 6 A g -1 , 92.4% of the initial capacity could be retained after 2000 discharging-charging cycles, suggesting excellent cycle stability. The Li-HSC comprising a WO 3 /C anode and a MOF-NC cathode boasts a large energy density of 159.97 W h kg -1 at a power density of 173.6 W kg -1 and 88.3% of the capacity is retained at a current density of 5 A g -1 after 3000 charging-discharging cycles, which are better than those previously reported for Li-HSCs. The high energy and power densities of the Li-HSCs of WO 3 /C//MOF-NC render large potential in energy storage.

Electron transfer from a carbon nanotube into vacuum under high electric fields

NASA Astrophysics Data System (ADS)

Filip, L. D.; Smith, R. C.; Carey, J. D.; Silva, S. R. P.

2009-05-01

The transfer of an electron from a carbon nanotube (CNT) tip into vacuum under a high electric field is considered beyond the usual one-dimensional semi-classical approach. A model of the potential energy outside the CNT cap is proposed in order to show the importance of the intrinsic CNT parameters such as radius, length and vacuum barrier height. This model also takes into account set-up parameters such as the shape of the anode and the anode-to-cathode distance, which are generically portable to any modelling study of electron emission from a tip emitter. Results obtained within our model compare well to experimental data. Moreover, in contrast to the usual one-dimensional Wentzel-Kramers-Brillouin description, our model retains the ability to explain non-standard features of the process of electron field emission from CNTs that arise as a result of the quantum behaviour of electrons on the surface of the CNT.

Dynamics of multiple double layers in high pressure glow discharge in a simple torus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar Paul, Manash, E-mail: manashkr@gmail.com; Sharma, P. K.; Thakur, A.

2014-06-15

Parametric characterization of multiple double layers is done during high pressure glow discharge in a toroidal vessel of small aspect ratio. Although glow discharge (without magnetic field) is known to be independent of device geometry, but the toroidal boundary conditions are conducive to plasma growth and eventually the plasma occupy the toroidal volume partially. At higher anode potential, the visibly glowing spots on the body of spatially extended anode transform into multiple intensely luminous spherical plasma blob structures attached to the tip of the positive electrode. Dynamics of multiple double layers are observed in argon glow discharge plasma in presencemore » of toroidal magnetic field. The radial profiles of plasma parameters measured at various toroidal locations show signatures of double layer formation in our system. Parametric dependence of double layer dynamics in presence of toroidal magnetic field is presented here.« less

Study of Stable Cathodes and Electrolytes for High Specific Density Lithium-Air Battery

NASA Technical Reports Server (NTRS)

Hernandez-Lugo, Dionne M.; Wu, James; Bennett, William; Ming, Yu; Zhu, Yu

2015-01-01

Future NASA missions require high specific energy battery technologies, greater than 400 Wh/kg. Current NASA missions are using "state-of-the-art" (SOA) Li-ion batteries (LIB), which consist of a metal oxide cathode, a graphite anode and an organic electrolyte. NASA Glenn Research Center is currently studying the physical and electrochemical properties of the anode-electrolyte interface for ionic liquid based Li-air batteries. The voltage-time profiles for Pyr13FSI and Pyr14TFSI ionic liquids electrolytes studies on symmetric cells show low over-potentials and no dendritic lithium morphology. Cyclic voltammetry measurements indicate that these ionic liquids have a wide electrochemical window. As a continuation of this work, sp2 carbon cathode and these low flammability electrolytes were paired and the physical and electrochemical properties were studied in a Li-air battery system under an oxygen environment.

Metal-catalyst-free carbohydrazide fuel cells with three-dimensional graphene anodes.

PubMed

Qi, Ji; Benipal, Neeva; Wang, Hui; Chadderdon, David J; Jiang, Yibo; Wei, Wei; Hu, Yun Hang; Li, Wenzhen

2015-04-13

As a potential solution to concerns on sustainable energy, the wide spread commercialization of fuel cell has long been hindered by limited reserves and relatively high costs of metal catalysts. 3D graphene, a carbon-only catalyst prepared by reduction of carbon monoxide with lithium oxide, is found to electrochemically catalyze carbohydrazide oxidation reaction efficiently. A prototype of a completely metal-catalyst-free anion exchange membrane fuel cell (AEMFC) with a 3D graphene anode catalyst and an N-doped CNT (N-CNT) cathode catalyst generate a peak power density of 24.9 mW cm(-2) . The average number of electrons electrochemically extracted from one carbohydrazide molecule is 4.9, indicating the existence of CN bond activation, which is a key factor contributing to high fuel utilization efficiency. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

How to get between the sheets: a review of recent works on the electrochemical exfoliation of graphene materials from bulk graphite

NASA Astrophysics Data System (ADS)

Abdelkader, A. M.; Cooper, A. J.; Dryfe, R. A. W.; Kinloch, I. A.

2015-04-01

Since the beginning of the `graphene era' post-2004, there has been significant interest in developing a high purity, high yield, and scalable fabrication route toward graphene materials for both primary research purposes and industrial production. One suitable approach to graphene production lies in the realm of electrochemical exfoliation, in which a potential difference is applied between a graphite anode/cathode in the presence of an electrolyte-containing medium. Herein we review various works on the electrochemical fabrication of graphene materials specifically through the use of electrochemical intercalation and exfoliation of a graphite source electrode, focusing on the quality and purity of products formed. We categorise the most significant works in terms of anodic and cathodic control, highlighting the merits of the respective approaches, as well as indicating the challenges associated with both procedures.

Time and position sensitive single photon detector for scintillator read-out

NASA Astrophysics Data System (ADS)

Schössler, S.; Bromberger, B.; Brandis, M.; Schmidt, L. Ph H.; Tittelmeier, K.; Czasch, A.; Dangendorf, V.; Jagutzki, O.

2012-02-01

We have developed a photon counting detector system for combined neutron and γ radiography which can determine position, time and intensity of a secondary photon flash created by a high-energy particle or photon within a scintillator screen. The system is based on a micro-channel plate photomultiplier concept utilizing image charge coupling to a position- and time-sensitive read-out anode placed outside the vacuum tube in air, aided by a standard photomultiplier and very fast pulse-height analyzing electronics. Due to the low dead time of all system components it can cope with the high throughput demands of a proposed combined fast neutron and dual discrete energy γ radiography method (FNDDER). We show tests with different types of delay-line read-out anodes and present a novel pulse-height-to-time converter circuit with its potential to discriminate γ energies for the projected FNDDER devices for an automated cargo container inspection system (ACCIS).

Improving Spectroscopic Performance of a Coplanar-Anode High-Pressure Xenon Gamma-Ray Spectrometer

NASA Astrophysics Data System (ADS)

Kiff, Scott Douglas; He, Zhong; Tepper, Gary C.

2007-08-01

High-pressure xenon (HPXe) gas is a desirable radiation detection medium for homeland security applications because of its good inherent room-temperature energy resolution, potential for large, efficient devices, and stability over a broad temperature range. Past work in HPXe has produced large-diameter gridded ionization chambers with energy resolution at 662 keV between 3.5 and 4% FWHM. However, one major limitation of these detectors is resolution degradation due to Frisch grid microphonics. A coplanar-anode HPXe detector has been developed as an alternative to gridded chambers. An investigation of this detector's energy resolution is reported in this submission. A simulation package is used to investigate the contributions of important physical processes to the measured photopeak broadening. Experimental data is presented for pure Xe and Xe + 0.2%H2 mixtures, including an analysis of interaction location effects on the energy spectrum.

Structure, Morphology and Optical Properties of TiO2 Films Formed by Anodizing in a Mixed Solution of Citric Acid and Sulfamic Acid

NASA Astrophysics Data System (ADS)

Choudhary, R. K.; Sarkar, P.; Biswas, A.; Mishra, P.; Abraham, G. J.; Sastry, P. U.; Kain, V.

2017-08-01

TiO2 films of 50-180 nm thickness were formed at room temperature by anodization of titanium metal in a mixture of citric acid and sulfamic acid in the potential range of 5-30 V. The films so obtained were characterized for their crystal structure, surface morphology, chemical composition and optical properties. Grazing incidence x-ray diffraction and micro-laser Raman spectroscopy measurements of the anodic films confirmed the formation of brookite phase of TiO2 at anodizing potentials of 15, 20, 25 and 30 V and amorphous structure at 5 and 10 V. Field emission scanning electron microscopy revealed non-porous microstructure of the films. Spectroscopic ellipsometry measurements evaluated the band gap of TiO2 at around 3.3 eV, whereas the refractive index of the films was found to be in the range of 2-2.35, in the visible range of spectrum.

Fault detection and isolation of high temperature proton exchange membrane fuel cell stack under the influence of degradation

NASA Astrophysics Data System (ADS)

Jeppesen, Christian; Araya, Samuel Simon; Sahlin, Simon Lennart; Thomas, Sobi; Andreasen, Søren Juhl; Kær, Søren Knudsen

2017-08-01

This study proposes a data-drive impedance-based methodology for fault detection and isolation of low and high cathode stoichiometry, high CO concentration in the anode gas, high methanol vapour concentrations in the anode gas and low anode stoichiometry, for high temperature PEM fuel cells. The fault detection and isolation algorithm is based on an artificial neural network classifier, which uses three extracted features as input. Two of the proposed features are based on angles in the impedance spectrum, and are therefore relative to specific points, and shown to be independent of degradation, contrary to other available feature extraction methods in the literature. The experimental data is based on a 35 day experiment, where 2010 unique electrochemical impedance spectroscopy measurements were recorded. The test of the algorithm resulted in a good detectability of the faults, except for high methanol vapour concentration in the anode gas fault, which was found to be difficult to distinguish from a normal operational data. The achieved accuracy for faults related to CO pollution, anode- and cathode stoichiometry is 100% success rate. Overall global accuracy on the test data is 94.6%.

Corrosion fatigue studies on a bulk glassy Zr-based alloy under three-point bending

NASA Astrophysics Data System (ADS)

Grell, Daniel; Wilkin, Yannic; Gostin, Petre F.; Gebert, Annett; Kerscher, Eberhard

2016-12-01

Corrosion fatigue (CF) tests were carried out on bulk glassy Zr52.5Cu17.9Al10Ni14.6Ti5 (Vitreloy 105) samples under load-controlled three-point bending conditions with a load ratio of R = 0.1 in 0.01 M Na2SO4 + 0.01 M NaCl electrolyte. During cyclic testing, the bar-shaped specimens were polarized in situ at constant potentials and the current was monitored. Three different anodic potentials within the interval between the pitting potential EP and the repassivation potential ER, and three different load amplitudes were applied. In some cases, in situ microscopic observations revealed the formation of black corrosion products in the vicinity of the crack tip during anodic polarization. Fractographic analysis revealed a clear distinction between two modes of crack growth characterized by smooth dissolution induced regions on the one hand and slim fast fracture areas on the other hand. Both alternating features contributed to a broad striated corrosion fatigue fracture surface. Moreover, further fatigue tests were carried out under free corrosion conditions yielding additional information on crack initiation and crack propagation period by means of the open circuit potential (OCP) changes. Thereby, a slight increase in OCP was detected after rupture of the passive layer due to bare metal exposed to the electrolyte. The electrochemical response increased continuously according to stable crack propagation until fracture occurred. Finally, the fracture surfaces of the corrosion fatigue samples were investigated by energy dispersive X-ray with the objective of analyzing the elemental distribution after anodic dissolution. Interestingly, anodic polarization at a near repassivation potential of -50 mV vs. SCE (Saturated Calomel Electrode, E = 0.241 V vs. SHE, Standard Hydrogen Electrode) led to favorable effects on the fatigue lifetime. In conclusion, all results are conflated to a corrosion fatigue model for bulk glassy Vitreloy 105 under anodic polarization in chloride-containing electrolyte and compared to the previously proposed stress corrosion mechanisms under similar conditions.

Solid state thin film battery having a high temperature lithium alloy anode

DOEpatents

Hobson, David O.

1998-01-01

An improved rechargeable thin-film lithium battery involves the provision of a higher melting temperature lithium anode. Lithium is alloyed with a suitable solute element to elevate the melting point of the anode to withstand moderately elevated temperatures.

Effectiveness of sacrificial anodes in high-resistivity shotcrete repairs.

DOT National Transportation Integrated Search

2005-01-01

This study investigated the use of discrete sacrificial anodes to improve the durability and extend the life of a shotcrete patch repair in a column. Three columns were used in the investigation. In two columns, anodes were placed around the perimete...

Preparation and Evaluation of Multi-Layer Anodes of Solid Oxide Fuel Cell

NASA Technical Reports Server (NTRS)

Santiago, Diana; Farmer, Serene C.; Setlock, John A.

2012-01-01

The development of an energy device with abundant energy generation, ultra-high specific power density, high stability and long life is critical for enabling longer missions and for reducing mission costs. Of all different types of fuel cells, the solid oxide fuel cells (SOFC) is a promising high temperature device that can generate electricity as a byproduct of a chemical reaction in a clean way and produce high quality heat that can be used for other purposes. For aerospace applications, a power-to-weight of (is) greater than 1.0 kW/kg is required. NASA has a patented fuel cell technology under development, capable of achieving the 1.0 kW/kg figure of merit. The first step toward achieving these goals is increasing anode durability. The catalyst plays an important role in the fuel cells for power generation, stability, efficiency and long life. Not only the anode composition, but its preparation and reduction are key to achieving better cell performance. In this research, multi-layer anodes were prepared varying the chemistry of each layer to optimize the performance of the cells. Microstructure analyses were done to the new anodes before and after fuel cell operation. The cells' durability and performance were evaluated in 200 hrs life tests in hydrogen at 850 C. The chemistry of the standard nickel anode was modified successfully reducing the anode degradation from 40% to 8.4% in 1000 hrs and retaining its microstructure.

Ion beam enhancement in magnetically insulated ion diodes for high-intensity pulsed ion beam generation in non-relativistic mode

NASA Astrophysics Data System (ADS)

Zhu, X. P.; Zhang, Z. C.; Pushkarev, A. I.; Lei, M. K.

2016-01-01

High-intensity pulsed ion beam (HIPIB) with ion current density above Child-Langmuir limit is achieved by extracting ion beam from anode plasma of ion diodes with suppressing electron flow under magnetic field insulation. It was theoretically estimated that with increasing the magnetic field, a maximal value of ion current density may reach nearly 3 times that of Child-Langmuir limit in a non-relativistic mode and close to 6 times in a highly relativistic mode. In this study, the behavior of ion beam enhancement by magnetic insulation is systematically investigated in three types of magnetically insulated ion diodes (MIDs) with passive anode, taking into account the anode plasma generation process on the anode surface. A maximal enhancement factor higher than 6 over the Child-Langmuir limit can be obtained in the non-relativistic mode with accelerating voltage of 200-300 kV. The MIDs differ in two anode plasma formation mechanisms, i.e., surface flashover of a dielectric coating on the anode and explosive emission of electrons from the anode, as well as in two insulation modes of external-magnetic field and self-magnetic field with either non-closed or closed drift of electrons in the anode-cathode (A-K) gap, respectively. Combined with ion current density measurement, energy density characterization is employed to resolve the spatial distribution of energy density before focusing for exploring the ion beam generation process. Consistent results are obtained on three types of MIDs concerning control of neutralizing electron flows for the space charge of ions where the high ion beam enhancement is determined by effective electron neutralization in the A-K gap, while the HIPIB composition of different ion species downstream from the diode may be considerably affected by the ion beam neutralization during propagation.

Corrosion of graphite composites in phosphoric acid fuel cells

NASA Technical Reports Server (NTRS)

Christner, L. G.; Dhar, H. P.; Farooque, M.; Kush, A. K.

1986-01-01

Polymers, polymer-graphite composites and different carbon materials are being considered for many of the fuel cell stack components. Exposure to concentrated phosphoric acid in the fuel cell environment and to high anodic potential results in corrosion. Relative corrosion rates of these materials, failure modes, plausible mechanisms of corrosion and methods for improvement of these materials are investigated.

Electrolyte and Electrode Passivation for Thin Film Batteries

NASA Technical Reports Server (NTRS)

West, W.; Whitacre, J.; Ratnakumar, B.; Brandon, E.; Blosiu, J.; Surampudi, S.

2000-01-01

Passivation films for thin film batteries have been prepared and the conductivity and voltage stability window have been measured. Thin films of Li2CO3 have a large voltage stability window of 4.8V, which facilitates the use of this film as a passivation at both the lithium anode-electrolyte interface at high cathodic potentials.

Investigation on the Oxidation and Reduction of Titanium in Molten Salt with the Soluble TiC Anode

NASA Astrophysics Data System (ADS)

Wang, Shulan; Wan, Chaopin; Liu, Xuan; Li, Li

2015-12-01

To reveal the oxidation process of titanium from TiC anode and the reduction mechanism of titanium ions in molten NaCl-KCl, the polarization curve of TiC anode in molten NaCl-KCl and cyclic voltammograms of the molten salt after polarization were studied. Investigation on the polarization curve shows that titanium can be oxidized and dissociated from the TiC anode at very low potential. The cyclic voltammograms demonstrated that the reduction reaction of titanium ions in the molten salt is a one-step process. By potentiostatic electrolysis, dendritic titanium is obtained on the steel plate. The work promotes the understanding on the process of electrochemical oxidization/dissociation of titanium from TiC anode and the reduction mechanism of titanium ions in molten salt.

Experimental study of the electrolysis of silicate melts

NASA Technical Reports Server (NTRS)

Keller, Rudolf

1992-01-01

Melting and electrolyzing lunar silicates yields oxygen gas and potentially can be practiced in situ to produce oxygen. With the present experiments conducted with simulant oxides at 1425-1480 C, it was ascertained that oxygen can be obtained anodically at feasible rates and current efficiencies. An electrolysis cell was operated with platinum anodes in a sealed vessel, and the production of gas was monitored. In these electrolysis experiments, stability of anodes remained a problem, and iron and silicon did not reduce readily into the liquid silver cathode.

Phosphorus-doped silicon nanorod anodes for high power lithium-ion batteries.

PubMed

Yan, Chao; Liu, Qianru; Gao, Jianzhi; Yang, Zhibo; He, Deyan

2017-01-01

Heavy-phosphorus-doped silicon anodes were fabricated on CuO nanorods for application in high power lithium-ion batteries. Since the conductivity of lithiated CuO is significantly better than that of CuO, after the first discharge, the voltage cut-off window was then set to the range covering only the discharge-charge range of Si. Thus, the CuO core was in situ lithiated and acts merely as the electronic conductor in the following cycles. The Si anode presented herein exhibited a capacity of 990 mAh/g at the rate of 9 A/g after 100 cycles. The anode also presented a stable rate performance even at a current density as high as 20 A/g.

Composite Li metal anode with vertical graphene host for high performance Li-S batteries

NASA Astrophysics Data System (ADS)

Zhang, Y. J.; Liu, S. F.; Wang, X. L.; Zhong, Y.; Xia, X. H.; Wu, J. B.; Tu, J. P.

2018-01-01

Efficient and stable operation of a lithium metal anode has become the enabling factor for next-generation high energy density storage system. Here, vertical graphene (VG) arrays are used as the scaffold structure for high performance Li metal batteries. The melt infusion method is employed to encapsulate Li inside the VG scaffold structure, and the lithiophilic Si layer is coated onto the array surface by magnetron sputtering to assist this melt-infusion process. The porous scaffold structure can control the volume expansion and inhibit the formation of dendritic lithium significantly, leading to the excellent electrochemical performance of the Li composite anode. In addition, the Li-S full batteries with the composite anode display enhanced cycling reversibility.

Fabrication of free standing anodic titanium oxide membranes with clean surface using recycling process.

PubMed

Meng, Xianhui; Lee, Tae-Young; Chen, Huiyu; Shin, Dong-Wook; Kwon, Kee-Won; Kwon, Sang Jik; Yoo, Ji-Beom

2010-07-01

Large area of self-organized, free standing anodic titanium oxide (ATO) nanotube membranes with clean surfaces were facilely prepared to desired lengths via electrochemical anodization of highly pure Ti sheets in an ethylene glycol electrolyte, with a small amount of NH4F and H2O at 50 V, followed by self-detachment of the ATO membrane from the Ti substrate using recycling processes. In the first anodization step, the nanowire oxide layer existed over the well-arranged ATO nanotube. After sufficiently rinsing with water, the whole ATO layer was removed from the Ti sheet by high pressure N2 gas, and a well-patterned dimple layer with a thickness of about 30 nm existed on the Ti substrate. By using these naturally formed nano-scale pits as templates, in the second and third anodization process, highly ordered, vertically aligned, and free standing ATO membranes with the anodic aluminum oxide (AAO)-like clean surface were obtained. The inter-pore distance and diameter was 154 +/- 2 nm and 91+/- 2 nm, the tube arrays lengths for 25 and 46 hours were 44 and 70 microm, respectively. The present study demonstrates a simple approach to producing high quality, length controllable, large area TiO2 membrane.

Nickel-Tin Electrode Materials for Nonaqueous Li-Ion Cells

NASA Technical Reports Server (NTRS)

Ehrlich, Grant M.; Durand, Christopher

2005-01-01

Experimental materials made from mixtures of nickel and tin powders have shown promise for use as the negative electrodes of rechargeable lithium-ion electrochemical power cells. During charging (or discharging) of a lithium-ion cell, lithium ions are absorbed into (or desorbed from, respectively) the negative electrode, typically through an intercalation or alloying process. The negative electrodes (for this purpose, designated as anodes) in state-of-the-art Li-ion cells are made of graphite, in which intercalation occurs. Alternatively, the anodes can be made from metals, in which alloying can occur. For reasons having to do with the electrochemical potential of intercalated lithium, metallic anode materials (especially materials containing tin) are regarded as safer than graphite ones; in addition, such metallic anode materials have been investigated in the hope of obtaining reversible charge/discharge capacities greater than those of graphite anodes. However, until now, each of the tin-containing metallic anode formulations tested has been found to be inadequate in some respect.

Medium-chain-length poly-3-hydroxyalkanoates-carbon nanotubes composite anode enhances the performance of microbial fuel cell.

PubMed

Hindatu, Y; Annuar, M S M; Subramaniam, R; Gumel, A M

2017-06-01

Insufficient power generation from a microbial fuel cell (MFC) hampers its progress towards utility-scale development. Electrode modification with biopolymeric materials could potentially address this issue. In this study, medium-chain-length poly-3-hydroxyalkanoates (PHA)/carbon nanotubes (C) composite (CPHA) was successfully applied to modify the surface of carbon cloth (CC) anode in MFC. Characterization of the functional groups on the anodic surface and its morphology was carried out. The CC-CPHA composite anode recorded maximum power density of 254 mW/m 2 , which was 15-53% higher than the MFC operated with CC-C (214 mW/m 2 ) and pristine CC (119 mW/m 2 ) as the anode in a double-chambered MFC operated with Escherichia coli as the biocatalyst. Electrochemical impedance spectroscopy and cyclic voltammetry showed that power enhancement was attributed to better electron transfer capability by the bacteria for the MFC setup with CC-CPHA anode.

Al-Air Batteries: Fundamental Thermodynamic Limitations from First-Principles Theory.

PubMed

Chen, Leanne D; Nørskov, Jens K; Luntz, Alan C

2015-01-02

The Al-air battery possesses high theoretical specific energy (4140 W h/kg) and is therefore an attractive candidate for vehicle propulsion. However, the experimentally observed open-circuit potential is much lower than what bulk thermodynamics predicts, and this potential loss is typically attributed to corrosion. Similarly, large Tafel slopes associated with the battery are assumed to be due to film formation. We present a detailed thermodynamic study of the Al-air battery using density functional theory. The results suggest that the maximum open-circuit potential of the Al anode is only -1.87 V versus the standard hydrogen electrode at pH 14.6 instead of the traditionally assumed -2.34 V and that large Tafel slopes are inherent in the electrochemistry. These deviations from the bulk thermodynamics are intrinsic to the electrochemical surface processes that define Al anodic dissolution. This has contributions from both asymmetry in multielectron transfers and, more importantly, a large chemical stabilization inherent to the formation of bulk Al(OH)3 from surface intermediates. These are fundamental limitations that cannot be improved even if corrosion and film effects are completely suppressed.

A Bio-Inspired, Heavy-Metal-Free, Dual-Electrolyte Liquid Battery towards Sustainable Energy Storage.

PubMed

Ding, Yu; Yu, Guihua

2016-04-04

Wide-scale exploitation of renewable energy requires low-cost efficient energy storage devices. The use of metal-free, inexpensive redox-active organic materials represents a promising direction for environmental-friendly, cost-effective sustainable energy storage. To this end, a liquid battery is designed using hydroquinone (H2BQ) aqueous solution as catholyte and graphite in aprotic electrolyte as anode. The working potential can reach 3.4 V, with specific capacity of 395 mA h g(-1) and stable capacity retention about 99.7% per cycle. Such high potential and capacity is achieved using only C, H and O atoms as building blocks for redox species, and the replacement of Li metal with graphite anode can circumvent potential safety issues. As H2BQ can be extracted from biomass directly and its redox reaction mimics the bio-electrochemical process of quinones in nature, using such a bio-inspired organic compound in batteries enables access to greener and more sustainable energy-storage technology. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Measurement and validation of benchmark-quality thick-target tungsten X-ray spectra below 150 kVp.

PubMed

Mercier, J R; Kopp, D T; McDavid, W D; Dove, S B; Lancaster, J L; Tucker, D M

2000-11-01

Pulse-height distributions of two constant potential X-ray tubes with fixed anode tungsten targets were measured and unfolded. The measurements employed quantitative alignment of the beam, the use of two different semiconductor detectors (high-purity germanium and cadmium-zinc-telluride), two different ion chamber systems with beam-specific calibration factors, and various filter and tube potential combinations. Monte Carlo response matrices were generated for each detector for unfolding the pulse-height distributions into spectra incident on the detectors. These response matrices were validated for the low error bars assigned to the data. A significant aspect of the validation of spectra, and a detailed characterization of the X-ray tubes, involved measuring filtered and unfiltered beams at multiple tube potentials (30-150 kVp). Full corrections to ion chamber readings were employed to convert normalized fluence spectra into absolute fluence spectra. The characterization of fixed anode pitting and its dominance over exit window plating and/or detector dead layer was determined. An Appendix of tabulated benchmark spectra with assigned error ranges was developed for future reference.

Effects of Coke Calcination Level on Pore Structure in Carbon Anodes

NASA Astrophysics Data System (ADS)

Fang, Ning; Xue, Jilai; Lang, Guanghui; Bao, Chongai; Gao, Shoulei

2016-02-01

Effects of coke calcination levels on pore structure of carbon anodes have been investigated. Bench anodes were prepared by 3 types of cokes with 4 calcination temperatures (800°C, 900°C, 1000°C and 1100°C). The cokes and anodes were characterized using hydrostatic method, air permeability determination, mercury porosimetry, image analysis and confocal microscopy (CSLM). The cokes with different calcination levels are almost the same in LC values (19-20 Å) and real density (1.967-1.985 g/cm3), while the anode containing coke calcined at 900°C has the lowest open porosity and air permeability. Pore size distribution (represented by Anode H sample) can be roughly divided into two ranges: small and medium pores in diameter of 10-400 μm and large pores of 400-580 μm. For the anode containing coke calcined at 800°C, a number of long, narrow pores in the pore size range of 400-580 μm are presented among cokes particles. Formation of these elongated pores may be attributed to coke shrinkages during the anode baking process, which may develop cracking in the anode under cell operations. More small or medium rounded pores with pore size range of 10-400 μm emerge in the anodes with coke calcination temperatures of 900°C, 1000°C and 1100°C, which may be generated due to release of volatiles from the carbon anode during baking. For the anode containing coke calcined at 1100°C, it is found that many rounded pores often closely surround large coke particles, which have potential to form elongated, narrow pores.

Histomorphometric and histologic evaluation of titanium-zirconium (aTiZr) implants with anodized surfaces.

PubMed

Sharma, Ajay; McQuillan, A James; Shibata, Yo; Sharma, Lavanya A; Waddell, John Neil; Duncan, Warwick John

2016-05-01

The choice of implant surface has a significant influence on osseointegration. Modification of TiZr surface by anodization is reported to have the potential to modulate the osteoblast cell behaviour favouring more rapid bone formation. The aim of this study is to investigate the effect of anodizing the surface of TiZr discs with respect to osseointegration after four weeks implantation in sheep femurs. Titanium (Ti) and TiZr discs were anodized in an electrolyte containing DL-α-glycerophosphate and calcium acetate at 300 V. The surface characteristics were analyzed by scanning electron microscopy, electron dispersive spectroscopy, atomic force microscopy and goniometry. Forty implant discs with thickness of 1.5 and 10 mm diameter (10 of each-titanium, titanium-zirconium, anodized titanium and anodized titanium-zirconium) were placed in the femoral condyles of 10 sheep. Histomorphometric and histologic analysis were performed 4 weeks after implantation. The anodized implants displayed hydrophilic, porous, nano-to-micrometer scale roughened surfaces. Energy dispersive spectroscopy analysis revealed calcium and phosphorous incorporation into the surface of both titanium and titanium-zirconium after anodization. Histologically there was new bone apposition on all implanted discs, slightly more pronounced on anodised discs. The percentage bone-to-implant contact measurements of anodized implants were higher than machined/unmodified implants but there was no significant difference between the two groups with anodized surfaces (P > 0.05, n = 10). The present histomorphometric and histological findings confirm that surface modification of titanium-zirconium by anodization is similar to anodised titanium enhances early osseointegration compared to machined implant surfaces.

A high-rate and long cycle life aqueous electrolyte battery for grid-scale energy storage.

PubMed

Pasta, Mauro; Wessells, Colin D; Huggins, Robert A; Cui, Yi

2012-01-01

New types of energy storage are needed in conjunction with the deployment of solar, wind and other volatile renewable energy sources and their integration with the electric grid. No existing energy storage technology can economically provide the power, cycle life and energy efficiency needed to respond to the costly short-term transients that arise from renewables and other aspects of grid operation. Here we demonstrate a new type of safe, fast, inexpensive, long-life aqueous electrolyte battery, which relies on the insertion of potassium ions into a copper hexacyanoferrate cathode and a novel activated carbon/polypyrrole hybrid anode. The cathode reacts rapidly with very little hysteresis. The hybrid anode uses an electrochemically active additive to tune its potential. This high-rate, high-efficiency cell has a 95% round-trip energy efficiency when cycled at a 5C rate, and a 79% energy efficiency at 50C. It also has zero-capacity loss after 1,000 deep-discharge cycles.

High-Performance Sodium Metal Anodes Enabled by a Bifunctional Potassium Salt.

PubMed

Shi, Qiuwei; Zhong, Yiren; Wu, Min; Wang, Hongzhi; Wang, Hailiang

2018-04-12

Developing Na metal anodes that can be deeply cycled with high efficiency for a long time is a prerequisite for rechargeable Na metal batteries to be practically useful despite their notable advantages in theoretical energy density and potential low cost. Their high chemical reactivity with the electrolyte and tendency for dendrite formation are two major issues limiting the reversibility of Na metal electrodes. In this work, we introduce for the first time potassium bis(trifluoromethylsulfonyl)imide (KTFSI) as a bifunctional electrolyte additive to stabilize Na metal electrodes, in which the TFSI - anions decompose into lithium nitride and oxynitrides to render a desirable solid electrolyte interphase layer while the K + cations preferentially adsorb onto Na protrusions and provide electrostatic shielding to suppress dendritic deposition. Through the cooperation of the cations and anions, we have realized Na metal electrodes that can be deeply cycled at a capacity of 10 mAh cm -2 for hundreds of hours. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrogenated TiO2 Branches Coated Mn3O4 Nanorods as an Advanced Anode Material for Lithium Ion Batteries.

PubMed

Wang, Nana; Yue, Jie; Chen, Liang; Qian, Yitai; Yang, Jian

2015-05-20

Rational design and delicate control on the component, structure, and surface of electrodes in lithium ion batteries are highly important to their performances in practical applications. Compared with various components and structures for electrodes, the choices for their surface are quite limited. The most widespread surface for numerous electrodes, a carbon shell, has its own issues, which stimulates the desire to find another alternative surface. Here, hydrogenated TiO2 is exemplified as an appealing surface for advanced anodes by the growth of ultrathin hydrogenated TiO2 branches on Mn3O4 nanorods. High theoretical capacity of Mn3O4 is well matched with low volume variation (∼4%), enhanced electrical conductivity, good cycling stability, and rate capability of hydrogenated TiO2, as demonstrated in their electrochemical performances. The proof-of-concept reveals the promising potential of hydrogenated TiO2 as a next-generation material for the surface in high-performance hybrid electrodes.

Switching on/off the chemisorption of thioctic-based self-assembled monolayers on gold by applying a moderate cathodic/anodic potential.

PubMed

Sahli, Rihab; Fave, Claire; Raouafi, Noureddine; Boujlel, Khaled; Schöllhorn, Bernd; Limoges, Benoît

2013-04-30

An in situ and real-time electrochemical method has been devised for quantitatively monitoring the self-assembly of a ferrocene-labeled cyclic disulfide derivative (i.e., a thioctic acid derivative) on a polycrystalline gold electrode under electrode polarization. Taking advantage of the high sensitivity, specificity, accuracy, and temporal resolution of this method, we were able to demonstrate an unexpectedly facilitated formation of the redox-active SAM when the electrode was held at a moderate cathodic potential (-0.4 V vs SCE in CH3CN), affording a saturated monolayer from only micromolar solutions in less than 10 min, and a totally impeded SAM growth when the electrode was polarized at a slightly anodic potential (+0.5 V vs SCE in CH3CN). This method literally allows for switching on/off the formation of SAMs under "soft" conditions. Moreover the cyclic disulfide-based SAM was completely desorbed at this potential contrary to the facilitated deposition of a ferrocene-labeled alkanethiol. Such a strikingly contrasting behavior could be explained by an energetically favored release of the thioctic-based SAM through homolytic cleavage of the Au-S bond followed by intramolecular cyclization of the generated thiyl diradicals. Moreover, the absence of a discernible transient faradaic current response during the potential-assisted adsorption/desorption of the redox-labeled cyclic disulfide led us to conclude in a potential-dependent reversible surface reaction where no electron is released or consumed. These results provide new insights into the formation of disulfide-based SAMs on gold but also raise some fundamental questions about the intimate mechanism involved in the facilitated adsorption/desorption of SAMs under electrode polarization. Finally, the possibility to easily and selectively address the formation/removal of thioctic-based SAMs on gold by applying a moderate cathodic/anodic potential offers another degree of freedom in tailoring their properties and in controlling their self-assembly, nanostructuration, and/or release.

Optimal condition for fabricating superhydrophobic Aluminum surfaces with controlled anodizing processes

NASA Astrophysics Data System (ADS)

Saffari, Hamid; Sohrabi, Beheshteh; Noori, Mohammad Reza; Bahrami, Hamid Reza Talesh

2018-03-01

A single step anodizing process is used to produce micro-nano structures on Aluminum (1050) substrates with sulfuric acid as electrolyte. Therefore, surface energy of the anodized layer is reduced using stearic acid modification. Undoubtedly, effects of different parameters including anodizing time, electrical current, and type and concentration of electrolyte on the final contact angle are systemically studied and optimized. Results show that anodizing current of 0.41 A, electrolyte (sulfuric acid) concentration of 15 wt.% and anodizing time of 90 min are optimal conditions which give contact angle as high as 159.2° and sliding angle lower than 5°. Moreover, the study reveals that adding oxalic acid to the sulfuric acid cannot enhance superhydrophobicity of the samples. Also, scanning electron microscopy images of samples show that irregular (bird's nest) structures present on the surface instead of high-ordered honeycomb structures expecting from normal anodizing process. Additionally, X-ray diffraction analysis of the samples shows that only amorphous structures present on the surface. The Brunauer-Emmett-Teller (BET) specific surface area of the anodized layer is 2.55 m2 g-1 in optimal condition. Ultimately, the surface keeps its hydrophobicity in air and deionized water (DIW) after one week and 12 weeks, respectively.

Anodizing of High Electrically Stressed Components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flores, P.; Henderson, D. J.; Good, D. E.

2013-06-01

Anodizing creates an aluminum oxide coating that penetrates into the surface as well as builds above the surface of aluminum creating a very hard ceramic-type coating with good dielectric properties. Over time and use, the electrical carrying components (or spools in this case) experience electrical breakdown, yielding undesirable x-ray dosages or failure. The spool is located in the high vacuum region of a rod pinch diode section of an x-ray producing machine. Machine operators have recorded decreases in x-ray dosages over numerous shots using the reusable spool component, and re-anodizing the interior surface of the spool does not provide themore » expected improvement. A machine operation subject matter expert coated the anodized surface with diffusion pump oil to eliminate electrical breakdown as a temporary fix. It is known that an anodized surface is very porous, and it is because of this porosity that the surface may trap air that becomes a catalyst for electrical breakdown. In this paper we present a solution of mitigating electrical breakdown by oiling. We will also present results of surface anodizing improvements achieved by surface finish preparation and surface sealing. We conclude that oiling the anodized surface and using anodized hot dip sealing processes will have similar results.« less

Methods for determining the degree of baking in anodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, C.P.

Anode baking temperature is recognized as a critical factor in determining anode quality and performance. It is difficult and costly to measure directly and an indirect method, the coke L{sub c} technique, is often used. In this technique, baking temperature is estimated from the average crystallite size in the c direction (L{sub c}) of a coke sample placed in the anode stubhole. The paper details the results of a large statistically designed experimental program in which coke L{sub c} results were compared to anode properties routinely measured by smelters. Anode thermal conductivity and air and carboxy reactivity were found tomore » correlate well with baking temperature. A direct anode L{sub c} measurement technique was also strongly associated with temperature, particularly at high baking temperatures. Recommendations are given on the usefulness and simplicity of traditional anode property measurements for assessing baking temperatures as alternatives to the coke L{sub c} method.« less

Demonstrating the potential of yttrium-doped barium zirconate electrolyte for high-performance fuel cells.

PubMed

Bae, Kiho; Jang, Dong Young; Choi, Hyung Jong; Kim, Donghwan; Hong, Jongsup; Kim, Byung-Kook; Lee, Jong-Ho; Son, Ji-Won; Shim, Joon Hyung

2017-02-23

In reducing the high operating temperatures (≥800 °C) of solid-oxide fuel cells, use of protonic ceramics as an alternative electrolyte material is attractive due to their high conductivity and low activation energy in a low-temperature regime (≤600 °C). Among many protonic ceramics, yttrium-doped barium zirconate has attracted attention due to its excellent chemical stability, which is the main issue in protonic-ceramic fuel cells. However, poor sinterability of yttrium-doped barium zirconate discourages its fabrication as a thin-film electrolyte and integration on porous anode supports, both of which are essential to achieve high performance. Here we fabricate a protonic-ceramic fuel cell using a thin-film-deposited yttrium-doped barium zirconate electrolyte with no impeding grain boundaries owing to the columnar structure tightly integrated with nanogranular cathode and nanoporous anode supports, which to the best of our knowledge exhibits a record high-power output of up to an order of magnitude higher than those of other reported barium zirconate-based fuel cells.

Bone cell-materials interactions and Ni ion release of anodized equiatomic NiTi alloy.

PubMed

Bernard, Sheldon A; Balla, Vamsi Krishna; Davies, Neal M; Bose, Susmita; Bandyopadhyay, Amit

2011-04-01

A laser processed NiTi alloy was anodized for different times in H(2)SO(4) electrolyte with varying pH to create biocompatible surfaces with low Ni ion release as well as bioactive surfaces to enhance biocompatibility and bone cell-material interactions. The anodized surfaces were assessed for their in vitro cell-material interactions using human fetal osteoblast (hFOB) cells for 3, 7 and 11 days, and Ni ion release up to 8 weeks in simulated body fluids. The results were correlated with the surface morphologies of anodized surfaces characterized using field-emission scanning electron microscopy (FESEM). The results show that anodization creates a surface with nano/micro-roughness depending on the anodization conditions. The hydrophilicity of the NiTi surface was found to improve after anodization, as shown by the lower contact angles in cell medium, which dropped from 32° to <5°. The improved wettability of anodized surfaces is further corroborated by their high surface energy, comparable with that of commercially pure Ti. Relatively high surface energies, especially the polar component, and nano/micro surface features of anodized surfaces significantly increased the number of living cells and their adherence and growth on these surfaces. Finally, a significant drop in Ni ion release from 268±11 to 136±15 ppb was observed for NiTi surfaces after anodization. This work indicates that anodization of a NiTi alloy has a positive influence on the surface energy and surface morphology, which in turn improves bone cell-material interactions and reduces Ni ion release in vitro. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Anode power deposition in a MPD thruster with a magnetically annulled Hall parameter anode

NASA Technical Reports Server (NTRS)

Gallimore, Alec D.; Kelly, Arnold J.; Jahn, Robert G.

1992-01-01

Results from previous studies indicate that the anode fall increases monotonically with the electron Hall parameter. In an attempt to reduce the anode fall by decreasing the local electron Hall parameter, a proof-of-concept test was performed in which an array of 36 permanent magnets were imbedded within the anode of a high power quasi-steady MPD thruster to decrease the local azimuthal component of the induced magnetic field. The modified thruster was operated at power levels between 150 kW and 4 MW with Ar and He propellants. Terminal voltage, triple probe, floating probe, and magnetic probe measurements were made to characterize the performance of the thruster with new anode. Incorporation of the modified anode resulted in a reduction of the anode fall by up to 15 V with Ar and 20 V with He, which corresponded to decreased anode power fractions of 40 and 45 percent with Ar and He, respectively.

Solid state thin film battery having a high temperature lithium alloy anode

DOEpatents

Hobson, D.O.

1998-01-06

An improved rechargeable thin-film lithium battery involves the provision of a higher melting temperature lithium anode. Lithium is alloyed with a suitable solute element to elevate the melting point of the anode to withstand moderately elevated temperatures. 2 figs.

A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes

NASA Astrophysics Data System (ADS)

Lin, Yuanjing; Lin, Qingfeng; Liu, Xue; Gao, Yuan; He, Jin; Wang, Wenli; Fan, Zhiyong

2015-12-01

Due to the broad applications of porous alumina nanostructures, research on fabrication of anodized aluminum oxide (AAO) with nanoporous structure has triggered enormous attention. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, it is known that its growth rate can be easily affected by the fluctuation of process conditions such as acid concentration and temperature during electrochemical anodization process. To fabricate AAO with various geometric parameters, particularly, to realize precise control over pore depth for scientific research and commercial applications, a controllable fabrication process is essential. In this work, we revealed a linear correlation between the integrated electric charge flow throughout the circuit in the stable anodization process and the growth thickness of AAO membranes. With this understanding, we developed a facile approach to precisely control the growth process of the membranes. It was found that this approach is applicable in a large voltage range, and it may be extended to anodization of other metal materials such as Ti as well.

A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes.

PubMed

Lin, Yuanjing; Lin, Qingfeng; Liu, Xue; Gao, Yuan; He, Jin; Wang, Wenli; Fan, Zhiyong

2015-12-01

Due to the broad applications of porous alumina nanostructures, research on fabrication of anodized aluminum oxide (AAO) with nanoporous structure has triggered enormous attention. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, it is known that its growth rate can be easily affected by the fluctuation of process conditions such as acid concentration and temperature during electrochemical anodization process. To fabricate AAO with various geometric parameters, particularly, to realize precise control over pore depth for scientific research and commercial applications, a controllable fabrication process is essential. In this work, we revealed a linear correlation between the integrated electric charge flow throughout the circuit in the stable anodization process and the growth thickness of AAO membranes. With this understanding, we developed a facile approach to precisely control the growth process of the membranes. It was found that this approach is applicable in a large voltage range, and it may be extended to anodization of other metal materials such as Ti as well.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Hui; Wei, Yang; Wang, Cheng

The excessive volume changes during cell cycling of Si-based anode in lithium ion batteries impeded its application. One major reason for the cell failure is particle isolation during volume shrinkage in delithiation process, which makes strong adhesion between polymer binder and anode active material particles a highly desirable property. Here, a biomimetic side-chain conductive polymer incorporating catechol, a key adhesive component of the mussel holdfast protein, was synthesized. Atomic force microscopy-based single-molecule force measurements of mussel-inspired conductive polymer binder contacting a silica surface revealed a similar adhesion toward substrate when compared with an effective Si anode binder, homo-poly(acrylic acid), withmore » the added benefit of being electronically conductive. Electrochemical experiments showed a very stable cycling of Si-alloy anodes realized via this biomimetic conducting polymer binder, leading to a high loading Si anode with a good rate performance. We attribute the ability of the Si-based anode to tolerate the volume changes during cycling to the excellent mechanical integrity afforded by the strong interfacial adhesion of the biomimetic conducting polymer.« less

Determination of sulfuric acid concentration for anti-cavitation characteristics of Al alloy by two step anodizing process to forming nano porous.

PubMed

Lee, Seung-Jun; Kim, Seong-Kweon; Jeong, Jae-Yong; Kim, Seong-Jong

2014-12-01

Al alloy is a highly active metal but forms a protective oxide film having high corrosion resistance in atmosphere environment. However, the oxide film is not suitable for practical use, since the thickness of the film is not uniform and it is severly altered with formation conditions. This study focused on developing an aluminum anodizing layer having hardness, corrosion resistance and abrasion resistance equivalent to a commercial grade protective layer. Aluminum anodizing layer was produced by two-step aluminum anodizing oxide (AAO) process with different sulfuric acid concentrations, and the cavitation characteristics of the anodized coating layer was investigated. In hardness measurement, the anodized coating layer produced with 15 vol.% of sulfuric acid condition had the highest value of hardness but exhibited poor cavitation resistance due to being more brittle than those with other conditions. The 10 vol.% of sulfuric acid condition was thus considered to be the optimum condition as it had the lowest weight loss and damage depth.

Phenol-degrading anode biofilm with high coulombic efficiency in graphite electrodes microbial fuel cell.

PubMed

Zhang, Dongdong; Li, Zhiling; Zhang, Chunfang; Zhou, Xue; Xiao, Zhixing; Awata, Takanori; Katayama, Arata

2017-03-01

A microbial fuel cell (MFC), with graphite electrodes as both the anode and cathode, was operated with a soil-free anaerobic consortium for phenol degradation. This phenol-degrading MFC showed high efficiency with a current density of 120 mA/m 2 and a coulombic efficiency of 22.7%, despite the lack of a platinum catalyst cathode and inoculation of sediment/soil. Removal of planktonic bacteria by renewing the anaerobic medium did not decrease the performance, suggesting that the phenol-degrading MFC was not maintained by the planktonic bacteria but by the microorganisms in the anode biofilm. Cyclic voltammetry analysis of the anode biofilm showed distinct oxidation and reduction peaks. Analysis of the microbial community structure of the anode biofilm and the planktonic bacteria based on 16S rRNA gene sequences suggested that Geobacter sp. was the phenol degrader in the anode biofilm and was responsible for current generation. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.